CSWIP 3.1 Study Book 2013 Rev 2 Edition
CSWIP 3.1 Study Book 2013 Rev 2 Edition
CSWIP 3.1 Study Book 2013 Rev 2 Edition
www.twitraining.com
Rev 2 April 2013
Contents
Copyright TWI Ltd 2013
7 Materials Inspection
7.1 General
7.2 Material type and weldability
7.3 Alloying elements and their effects
7.4 Material traceability
7.5 Material condition and dimensions
7.6 Summary
8 Codes and Standards
8.1 General
8.2 Definitions
8.3 Summary
9 Welding Symbols
9.1 Standards for symbolic representation of welded joints on drawings
9.2 Elementary welding symbols
9.3 Combination of elementary symbols
9.4 Supplementary symbols
9.5 Position of symbols on drawings
9.6 Relationship between the arrow and joint lines
9.7 Position of the reference line and weld symbol
9.8 Positions of the continuous and dashed lines
9.9 Dimensioning of welds
9.10 Complimentary indications
9.11 Indication of the welding process
9.12 Weld symbols in accordance with AWS 2.4
10 Introduction to Welding Processes
10.1 General
10.2 Productivity
10.3 Heat input
10.4 Welding parameters
10.5 Power source characteristics
11 Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
11.1 MMA basic equipment requirements
11.2 Power requirements
11.3 Welding variables
11.4 Summary of MMA/SMAW
12 TIG Welding
12.1 Process characteristics
12.2 Process variables
12.3 Filler wires
12.4 Tungsten inclusions
12.5 Crater cracking
12.6 Common applications
12.7 Advantages
12.8 Disadvantages
www.twitraining.com
Rev 2 April 2013
Contents
Copyright TWI Ltd 2013
13 MIG/MAG Welding
13.1 Process
13.2 Variables
13.3 MIG basic equipment requirements
13.4 Inspection when MIG/MAG welding
13.5 Flux-cored arc welding (FCAW)
13.6 Summary of solid wire MIG/MAG
14 Submerged Arc Welding
14.1 Process
14.2 Fluxes
14.3 Process variables
14.4 Storage and care of consumables
14.5 Power sources
15 Thermal Cutting Processes
15.1 Oxy-fuel cutting
15.2 Plasma arc cutting
15.3 Arc air gouging
15.4 Manual metal arc gouging
16 Welding Consumables
16.1 Consumables for MMA welding
16.2 AWS A 5.1 and AWS 5.5-
16.3 Inspection points for MMA consumables
16.4 Consumables for TIG/GTW
16.5 Consumables for MIG/MAG
16.6 Consumables for SAW welding
17 Weldability of Steels
17.1 Introduction
17.2 Factors that affect weldability
17.3 Hydrogen cracking
17.4 Solidification cracking
17.5 Lamellar tearing
17.6 Weld decay
18 Weld Repairs
18.1 Two specific areas
19 Residual Stresses and Distortions
19.1 Development of residual stresses
19.2 What causes distortion?
19.3 The main types of distortion?
19.4 Factors affecting distortion?
19.5 Prevention by pre-setting, pre-bending or use of restraint
19.6 Prevention by design
19.7 Prevention by fabrication techniques
19.8 Corrective techniques
www.twitraining.com
Rev 2 April 2013
Contents
Copyright TWI Ltd 2013
20 Heat Treatment
20.1 Introduction
20.2 Heat treatment of steel
20.3 Postweld heat treatment (PWHT)
20.4 PWHT thermal cycle
20.5 Heat treatment furnaces
21 Arc Welding Safety
21.1 General
21.2 Electric shock
21.3 Heat and light
21.4 Fumes and gases
21.5 Noise
21.6 Summary
22 Calibration
22.1 Introduction
22.2 Terminology
22.3 Calibration frequency
22.4 Instruments for calibration
22.5 Calibration methods
23 Application and Control of Preheat
23.1 General
23.2 Definitions
23.3 Application of preheat
23.4 Control of preheat and interpass temperature
23.5 Summary
24 Gauges
www.twitraining.com
Rev 2 April 2013
Contents
Copyright TWI Ltd 2013
Examination Contents
60 Technology questions
90 Min
20 Macroscopic questions
45 Min
www.twitraining.com
Section 1
Guidance and basic requirements for visual inspection are given by:
1-1
www.twitraining.com
Rev 2 April 2013
Typical Duties of Welding Inspectors
Copyright TWI Ltd 2013
ISO 17637 does not give or make any recommendation about a formal
qualification for visual inspection of welds. However, it has become industry
practice for inspectors to have practical experience of welding inspection
together with a recognised qualification in welding inspection such as a
CSWIP qualification.
Access
Access to the surface for direct inspection should enable the eye to be:
600mm (max.)
30 (min.)
1-2
www.twitraining.com
Rev 2 April 2013
Typical Duties of Welding Inspectors
Copyright TWI Ltd 2013
Welding gauges (for checking bevel angles and weld profile, fillet sizing,
measuring undercut depth).
Dedicated weld gap gauges and linear misalignment (hi-lo) gauges.
Straight edges and measuring tapes.
Magnifying lens (if a magnification lens is used it should be X2 to X5).
ISO 17637 shows a range of welding gauges together with details of what
they can be used for and the precision of the measurements.
However, ISO 17637 says that the extent of examination and the stages
when inspection activity is required should be specified by the Application
Standard or by agreement between client and fabricator.
For fabricated items that must have high integrity, such as pressure vessels
and piping or large structures inspection, activity will usually be required
throughout the fabrication process:
Before welding.
During welding.
After welding.
1-3
www.twitraining.com
Rev 2 April 2013
Typical Duties of Welding Inspectors
Copyright TWI Ltd 2013
In practice the application of the fabricated item will be the main factor that
influences what is judged to be good workmanship or the relevant client
specification will determine what the acceptable level of workmanship is.
A welding inspector should also ensure that any inspection aids that will be
needed are:
In good condition.
Calibrated as appropriate/as specified by QC procedures.
1-4
www.twitraining.com
Rev 2 April 2013
Typical Duties of Welding Inspectors
Copyright TWI Ltd 2013
Check Action
Material In accordance with drawing/WPS.
Identified and can be traced to a test certificate.
In suitable condition (free from damage and contamination).
WPSs Approved and available to welders (and inspectors).
Welding equipment In suitable condition and calibrated as appropriate.
Weld preparations In accordance with WPS (and/or drawings).
Welder qualifications Identification of welders qualified for each WPS to be used.
All welder qualification certificates are valid (in date).
Welding consumables Those to be used are as specified by the WPSs, are
stored/controlled as specified by the QC procedure.
Joint fit-ups In accordance with WPS/drawings tack welds are to good
workmanship standard and to code/WPS.
Weld faces Free from defects, contamination and damage.
Preheat (if required) Minimum temperature is in accordance with WPS.
Check Action
Site/field welding Ensure weather conditions are suitable/comply with Code
(conditions will not affect welding).
Welding process In accordance with WPS.
Preheat (if required) Minimum temperature is being maintained in accordance with
WPS.
Interpass temperature Maximum temperature is in accordance with WPS.
Welding consumables In accordance with WPS and being controlled as procedure.
Welding parameters Current, volts, travel speed are in accordance with WPS.
Root run Visually acceptable to Code before filling the joint (for single
sided welds).
Gouging/grinding By an approved method and to good workmanship standard.
Inter-run cleaning To good workmanship standard.
Welder On the approval register/qualified for the WPS being used.
1-5
www.twitraining.com
Rev 2 April 2013
Typical Duties of Welding Inspectors
Copyright TWI Ltd 2013
Check Action
Weld identification Each weld is marked with the welder's identification and is
identified in accordance with drawing/weld map.
Weld appearance Ensure welds are suitable for all NDT (profile, cleanness, etc).
Visually inspect welds and sentence in accordance with Code.
Dimensional survey Check dimensions are in accordance with drawing/Code.
Drawings Ensure any modifications are included on as-built drawings.
NDT Ensure all NDT is complete and reports are available for records.
Repairs Monitor in accordance with the procedure.
PWHT (if required) Monitor for compliance with procedure (check chart record).
Pressure/load test Ensure test equipment is calibrated.
(if required) Monitor test to ensure compliance with procedure/Code.
Ensure reports/records are available.
Documentation records Ensure all reports/records are completed and collated as
required.
The form of this record will vary, possibly a signature against an activity on
an inspection checklist or quality plan, or it may be an individual inspection
report for each item.
For individual inspection reports, ISO 17637 lists typical details for inclusion
such as:
Name of manufacturer/fabricator.
Identification of item examined.
Material type and thickness.
Type of joint.
Welding process.
Acceptance standard/criteria.
Locations and types of all imperfections not acceptable (when specified,
it may be necessary to include an accurate sketch or photograph).
Name of examiner/inspector and date of examination.
1-6
www.twitraining.com
Section 2
Brazing
A process of joining generally applied to metals in which, during or after
heating, molten filler metal is drawn into or retained in the space between
closely adjacent surfaces of the parts to be joined by capillary attraction. In
general, the melting point of the filler metal is above 450C but always below
the melting temperature of the parent material.
Braze welding
The joining of metals using a technique similar to fusion welding and a filler
metal with a lower melting point than the parent metal, but neither using
capillary action as in brazing nor intentionally melting the parent metal.
Joint
A connection where the individual components, suitably prepared and
assembled, are joined by welding or brazing.
Weld
A union of pieces of metal made by welding.
Welding
An operation in which two or more parts are united by means of heat,
pressure or both, in such a way that there is continuity in the nature of the
metal between these parts.
2-1
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Type of
joint Sketch Definition
Butt Connection between the ends or edges
of two parts making an angle to one
another of 135-180 inclusive in the
region of the joint.
2-2
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
In a butt joint
In a corner joint
Autogenous weld
A fusion weld made without filler metal by TIG, plasma, electron beam, laser
or oxy-fuel gas welding.
Slot weld
A joint between two overlapping components made by depositing a fillet
weld round the periphery of a hole in one component so as to join it to the
surface of the other component exposed through the hole.
2-3
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Plug weld
A weld made by filling a hole in one component of a workpiece with filler
metal so as to join it to the surface of an overlapping component exposed
through the hole (the hole can be circular or oval).
Heterogeneous
Welded joint in which the weld metal and parent material have significant
differences in mechanical properties and/or chemical composition. Example:
A repair weld of a cast iron item performed with a nickel-based electrode.
Dissimilar/Transition
Welded joint in which the parent materials have significant differences in
mechanical properties and/or chemical composition. Example: A carbon
steel lifting lug welded onto an austenitic stainless steel pressure vessel.
2-4
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Filler metal
Metal added during welding, braze welding, brazing or surfacing.
Weld metal
All metal melted during the making of a weld and retained in the weld.
Fusion line
Boundary between the weld metal and the HAZ in a fusion weld.
Weld zone
Zone containing the weld metal and the HAZ.
Weld face
The surface of a fusion weld exposed on the side from which the weld
has been made.
Root
Zone on the side of the first run furthest from the welder.
Toe
Boundary between a weld face and the parent metal or between runs.
This is a very important feature of a weld since toes are points of high
stress concentration and often are initiation points for different types of
cracks (eg fatigue and cold cracks). To reduce the stress concentration,
toes must blend smoothly into the parent metal surface.
2-5
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Weld
Parent zone
Weld
face metal
Parent
metal
Toe
HAZ
Weld
metal Root Fusion
line Excess weld
metal
Penetration
Parent metal
Excess weld
metal
Weld zone
Toe
Fusion line
Weld face
2-6
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Included angle
The angle between the planes of the fusion faces of parts to be welded. For
single and double V or U this angle is twice the bevel angle. In the case of
single or double bevel, single or double J bevel, the included angle is equal
to the bevel angle.
Root face
The portion of a fusion face at the root that is not bevelled or grooved. Its
value depends on the welding process used, parent material to be welded
and application; for a full penetration weld on carbon steel plates, it has a
value of 1-2mm (for the common welding processes).
Gap
The minimum distance at any cross-section between edges, ends or
surfaces to be joined. Its value depends on the welding process used and
application; for a full penetration weld on carbon steel plates, it has a value
of 1-4mm.
Root radius
The radius of the curved portion of the fusion face in a component prepared
for a single or double J or U, weld.
Land
Straight portion of a fusion face between the root face and the radius part of
a J or U preparation can be 0. Usually present in weld preparations for MIG
welding of aluminium alloys.
2-7
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Used for welding thin components from one or both sides. If the root gap is
zero (ie if components are in contact), this preparation becomes a closed
square butt preparation (not recommended due to problems caused by lack
of penetration)!
Single V preparation
Included angle
Angle of
bevel
Root face
Gap
Double V preparation
The depth of preparation can be the same on both sides (symmetric double
V preparation) or deeper on one side (asymmetric double V preparation).
Usually, in this situation the depth of preparation is distributed as 2/3 of the
thickness of the plate on the first side with the remaining 1/3 on the
backside. This asymmetric preparation allows for a balanced welding
2-8
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
sequence with root back gouging, giving lower angular distortions. Whilst a
single V preparation allows welding from one side, double V preparation
requires access to both sides (the same applies for all double sided
preparations).
Single U preparation
Included angle
Angle of
bevel
Root
radius
Land
Double U preparation
Usually this type of preparation does not require a land, (except for
aluminium alloys).
2-9
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
2-10
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Single J preparation.
Double J preparation.
2-11
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
As a general rule:
Actual throat
thickness = design
throat thickness
Run (pass)
The metal melted or deposited during one pass of an electrode, torch or
blowpipe.
Layer
A stratum of weld metal consisting of one or more runs.
2-12
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Leg length
Distance from the actual or projected intersection of the fusion faces and the
toe of a fillet weld, measured across the fusion face (z on drawings).
Actual throat
thickness
Design
throat
thickness Leg
length
Leg
length
2-13
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
a = 0.707 z or z = 1.41 a
2-14
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Vertical leg
size
Throat size
2-15
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Bevel
weld Fillet
weld
Weld slope
Angle between root line and the positive X axis of the horizontal reference
plane, measured in mathematically positive direction (ie counter-clockwise).
Weld rotation
Angle between the centreline of the weld and the positive Z axis or a line
parallel to the Y axis, measured in the mathematically positive direction (ie
counter-clockwise) in the plane of the transverse cross-section of the weld in
question.
2-16
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
Vertical-down
PF Welding position in which the
welding is downwards. PG.
2-17
www.twitraining.com
Rev 2 April 2013
Terms and Definitions
Copyright TWI Ltd 2013
2.8 Weaving
Transverse oscillation of an electrode or blowpipe nozzle during the
deposition of weld metal, generally used in vertical-up welds.
Stringer bead
A run of weld metal made with little or no weaving motion.
2-18
www.twitraining.com
Section 3
Welding Imperfections
and Materials Inspection
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
1 Cracks.
2 Cavities.
3 Solid inclusions.
4 Lack of fusion and penetration.
5 Imperfect shape and dimensions.
6 Miscellaneous imperfections.
3.2 Cracks
Definition
Imperfection produced by a local rupture in the solid state, which may arise
from the effect of cooling or stresses. Cracks are more significant than other
types of imperfection as their geometry produces a very large stress
concentration at the crack tip making them more likely to cause fracture.
Types of crack:
Longitudinal.
Transverse.
Radiating (cracks radiating from a common point).
Crater.
Branching (group of connected cracks originating from a common crack).
3-1
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
The cracks can be wide and open to the surface like shrinkage voids or sub-
surface and possibly narrow.
3-2
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
thermal shrinkage of the cooling weld bead can cause these to rupture and
form a crack.
It is important that the welding fabricator does not weld on or near metal
surfaces covered with scale or contaminated with oil or grease. Scale can
have a high sulphur content and oil and grease can supply both carbon and
sulphur. Contamination with low melting point metals such as copper, tin,
lead and zinc should also be avoided.
3-3
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Apply preheat slow down the cooling rate and thus avoid the formation of
susceptible microstructures.
Maintain a specific interpass temperature (same effect as preheat).
Postheat on completion of welding to reduce the hydrogen content by
allowing hydrogen to diffuse from the weld area.
Apply PWHT to reduce residual stress and eliminate susceptible
microstructures.
Reduce weld metal hydrogen by proper selection of welding
process/consumable (eg use TIG welding instead of MMA, basic
covered electrodes instead of cellulose).
Use a multi-run instead of a single run technique and eliminate
susceptible microstructures by the self-tempering effect, reduce
hydrogen content by allowing hydrogen to diffuse from the weld area.
Use a temper bead or hot pass technique (same effect as above).
Use austenitic or nickel filler to avoid susceptible microstructure
formation and allow hydrogen to diffuse out of critical areas).
Use dry shielding gases to reduce hydrogen content.
Clean rust from joint to avoid hydrogen contamination from moisture
present in the rust.
Reduce residual stress.
Blend the weld profile to reduce stress concentration at the toes of the
weld.
3-4
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Lamellar tearing
Lamellar tearing occurs only in rolled steel products (primarily plates) and its
main distinguishing feature is that the cracking has a terraced appearance.
3-5
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Two main options are available to control the problem in welded joints liable
to lamellar tearing:
Cavity
Interdendritic
Gas pore shrinkage
Linear porosity
Interdendritic Transgranular
Elongated cavity
microshrinkage microshrinkage
Worm hole
Surface pore
3-6
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
3.3 Cavities
3.3.1 Gas pore
A gas cavity of essentially spherical shape trapped within the weld metal.
Isolated.
Uniformly distributed porosity.
Clustered (localised) porosity.
Linear porosity.
Elongated cavity.
Surface pore.
Causes Prevention
Damp fluxes/corroded electrode Use dry electrodes in good condition
(MMA)
Grease/hydrocarbon/water Clean prepared surface
contamination of prepared surface
Air entrapment in gas shield Check hose connections
(MIG/MAG, TIG)
Incorrect/insufficient deoxidant in Use electrode with sufficient deoxidation activity
electrode, filler or parent metal
Too great an arc voltage or length Reduce voltage and arc length
Gas evolution from priming Identify risk of reaction before surface treatment
paints/surface treatment is applied
Too high a shielding gas flow rate Optimise gas flow rate
results in turbulence (MIG/MAG, TIG)
Comment
Porosity can be localised or finely dispersed voids throughout the weld
metal.
3-7
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Gross contamination of preparation Introduce preweld cleaning procedures
surface
Laminated work surface Replace parent material with an unlaminated
piece
Crevices in work surface due to joint Eliminate joint shapes which produce crevices
geometry
Comments
Worm holes are caused by the progressive entrapment of gas between the
solidifying metal crystals (dendrites) producing characteristic elongated
pores of circular cross-section. These can appear as a herringbone array on
a radiograph and some may break the surface of the weld.
3-8
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Damp or contaminated surface or Clean surface and dry electrodes
electrode
Low fluxing activity (MIG/MAG) Use a high activity flux
Excess sulphur (particularly free-cutting Use high manganese electrodes to produce
steels) producing sulphur dioxide MnS. Note free-cutting steels (high sulphur)
should not normally be welded
Loss of shielding gas due to long arc or Improve screening against draughts and
high breezes (MIG/MAG) reduce arc length
A shielding gas flow rate that is too high Optimise gas flow rate
results in turbulence (MIG/MAG,TIG)
The origins of surface porosity are similar to those for uniform porosity.
Crater pipe
Causes Prevention
Lack of welder skill due to using processes Retrain welder
with too high a current
Inoperative crater filler (slope out) (TIG) Use correct crater filling techniques
Crater filling is a particular problem in TIG welding due to its low heat input.
To fill the crater for this process it is necessary to reduce the weld current
(slope out) in a series of descending steps until the arc is extinguished.
3-9
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Solid
inclusions
Tungsten
Copper
Causes Prevention
Incomplete slag removal from underlying Improve inter-run slag removal
surface of multi-pass weld
Slag flooding ahead of arc Position work to gain control of slag.
Welder needs to correct electrode angle
Entrapment of slag in work surface Dress/make work surface smooth
3-10
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Unfused flux due to damaged coating Use electrodes in good condition
Flux fails to melt and becomes trapped in Change the flux/wire. Adjust welding
the weld (SAW or FCAW) parameters ie current, voltage etc to produce
satisfactory welding conditions
Cause Prevention
Heavy millscale/rust on work surface Grind surface prior to welding
3-11
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Contact of electrode tip with weld pool Keep tungsten out of weld pool; use HF start
Contact of filler metal with hot tip of Avoid contact between electrode and filler
electrode metal
Contamination of the electrode tip by Reduce welding current; adjust shielding gas
spatter from the weld pool flow rate
Exceeding the current limit for a given Reduce welding current; replace electrode
electrode size or type with a larger diameter one
Extension of electrode beyond the normal Reduce electrode extension and/or welding
distance from the collet, resulting in current
overheating of the electrode
Inadequate tightening of the collet Tighten the collet
Inadequate shielding gas flow rate or Adjust the shielding gas flow rate; protect the
excessive draughts resulting in oxidation weld area; ensure that the post gas flow after
of the electrode tip stopping the arc continues for at least five
seconds
Splits or cracks in the electrode Change the electrode, ensure the correct
size tungsten is selected for the given
welding current used
Inadequate shielding gas (eg use of Change to correct gas composition
argon-oxygen or argon-carbon dioxide
mixtures that are used for MAG welding)
Lack of
fusion
3-12
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Lack of union between the weld and parent metal at one or both sides of the
weld.
Causes Prevention
Low heat input to weld Increase arc voltage and/or welding current;
decrease travel speed
Molten metal flooding ahead of arc Improve electrode angle and work position;
increase travel speed
Oxide or scale on weld preparation Improve edge preparation procedure
Excessive inductance in MAG dip Reduce inductance, even if this increases
transfer welding spatter
During welding sufficient heat must be available at the edge of the weld pool
to produce fusion with the parent metal.
3-13
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Lack of union along the fusion line between the weld beads.
Causes Prevention
Low arc current resulting in low fluidity of Increase current
weld pool
Too high a travel speed Reduce travel speed
Inaccurate bead placement Retrain welder
Lack of inter-run fusion produces crevices between the weld beads and
causes local entrapment of slag.
Lack of fusion between the weld and parent metal at the root of a weld.
Causes Prevention
Low heat input Increase welding current and/or arc voltage;
decrease travel speed
Excessive inductance in MAG dip Use correct induction setting for the parent
transfer welding, metal thickness
MMA electrode too large Reduce electrode size
(low current density)
Use of vertical-down welding Switch to vertical-up procedure
Large root face Reduce root face
Small root gap Ensure correct root opening
Incorrect angle or electrode Use correct electrode angle.
manipulation Ensure welder is fully qualified and competent
Excessive misalignment at root Ensure correct alignment
3-14
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Lack of
penetration
Incomplete penetration
Causes Prevention
Excessively thick root face, insufficient Improve back gouging technique and ensure the
root gap or failure to cut back to sound edge preparation is as per approved WPS
metal when back gouging
Low heat input Increase welding current and/or arc voltage;
decrease travel speed
Excessive inductance in MAG dip Improve electrical settings and possibly switch to
transfer welding, pool flooding ahead spray arc transfer
of arc
MMA electrode too large Reduce electrode size
(low current density)
Use of vertical-down welding Switch to vertical-up procedure
3-15
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
If the weld joint is not of a critical nature, ie the required strength is low and
the area is not prone to fatigue cracking, it is possible to produce a partial
penetration weld. In this case incomplete root penetration is considered part
of this structure and not an imperfection This would normally be determined
by the design or code requirement.
Both fusion faces of the root are not melted. When examined from the root
side, you can clearly see both of the root edges unmelted.
3-16
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Undercut
Causes Prevention
Melting of top edge due to high welding Reduce power input, especially
current (especially at the free edge) or high approaching a free edge where overheating
travel speed can occur
Attempting a fillet weld in horizontal-vertical Weld in the flat position or use multi-run
(PB) position with leg length >9mm techniques
Excessive/incorrect weaving Reduce weaving width or switch to multi-
runs
Incorrect electrode angle Direct arc towards thicker member
Incorrect shielding gas selection (MAG) Ensure correct gas mixture for material type
and thickness (MAG)
Care must be taken during weld repairs of undercut to control the heat input.
If the bead of a repair weld is too small, the cooling rate following welding
will be excessive and the parent metal may have an increased hardness
and the weld susceptible to hydrogen cracking.
3-17
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Excess weld metal is the extra metal that produces excessive convexity in
fillet welds and a weld thickness greater than the parent metal plate in butt
welds. It is regarded as an imperfection only when the height of the excess
weld metal is greater than a specified limit.
Causes Prevention
Excess arc energy (MAG, SAW) Reduction of heat input
Shallow edge preparation Deepen edge preparation
Faulty electrode manipulation or build-up Improve welder skill
sequence
Incorrect electrode size Reduce electrode size
Travel speed too slow Ensure correct travel speed is used
Incorrect electrode angle Ensure correct electrode angle is used
Wrong polarity used (electrode polarity Ensure correct polarity ie DC+ve
DC-ve (MMA, SAW ) Note DC-ve must be used for TIG
3-18
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Weld heat input too high Reduce arc voltage and/or welding current;
increase welding speed
Incorrect weld preparation ie excessive Improve workpiece preparation
root gap, thin edge preparation, lack of
backing
Use of electrode unsuited to welding Use correct electrode for position
position
Lack of welder skill Retrain welder
3-19
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
3.6.4 Overlap
Causes Prevention
Poor electrode manipulation (MMA) Retrain welder
High heat input/low travel speed Reduce heat input or limit leg size to 9mm
causing surface flow of fillet welds maximum for single pass fillets
Incorrect positioning of weld Change to flat position
Wrong electrode coating type resulting Change electrode coating type to a more
in too high a fluidity suitable fast freezing type which is less fluid
For a fillet weld overlap is often associated with undercut, as if the weld pool
is too fluid the top of the weld will flow away to produce undercut at the top
and overlap at the base. If the volume of the weld pool is too large in a fillet
weld in horizontal-vertical (PB) position, weld metal will collapse due to
gravity, producing both defects (undercut at the top and overlap at the
base), this defect is called sagging.
3-20
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Misalignment between two welded pieces such that while their surface
planes are parallel, they are not in the required same plane.
Causes Prevention
Inaccuracies in assembly procedures or Adequate checking of alignment prior to
distortion from other welds welding coupled with the use of clamps and
wedges
Excessive out of flatness in hot rolled Check accuracy of rolled section prior to
plates or sections welding
Misalignment between two welded pieces such that their surface planes are
not parallel or at the intended angle.
3-21
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Insufficient weld metal Increase the number of weld runs
Irregular weld bead surface Retrain welder
Causes Prevention
Severe arc blow Switch from DC to AC, keep arc length as short as
possible
Irregular weld bead surface Retrain welder
Although this imperfection may not affect the integrity of the completed weld,
it can affect the width of HAZ and reduce the load-carrying capacity of the
joint (in fine-grained structural steels) or impair corrosion resistance (in
duplex stainless steels).
3-22
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
A shallow groove that occurs due to shrinkage at the root of a butt weld.
Causes Prevention
Insufficient arc power to produce positive bead Raise arc energy
Incorrect preparation/fit-up Work to WPS
Excessive backing gas pressure (TIG) Reduce gas pressure
Lack of welder skill Retrain welder
Slag flooding in backing bar groove Tilt work to prevent slag flooding
A backing strip can be used to control the extent of the root bead.
3.6.10 Burn-through
3-23
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Causes Prevention
Insufficient travel speed Increase the travel speed
Excessive welding current Reduce welding current
Lack of welder skill Retrain welder
Excessive grinding of root face More care taken, retrain welder
Excessive root gap Ensure correct fit-up
This is a gross imperfection which occurs due to lack of welder skill but can
be repaired by bridging the gap formed into the joint, but requires a great
deal of attention.
Local damage to the surface of the parent metal adjacent to the weld,
resulting from arcing or striking the arc outside the weld groove. This results
in random areas of fused metal where the electrode, holder or current return
clamp have accidentally touched the work.
Causes Prevention
Poor access to the work Improve access (modify assembly sequence)
Missing insulation on electrode Institute a regular inspection scheme for
holder or torch electrode holders and torches
Failure to provide an insulated Provide an insulated resting place
resting place for the electrode holder
or torch when not in use
Loose current return clamp Regularly maintain current return clamps
Adjusting wire feed (MAG welding) Retrain welder
without isolating welding current
An arc strike can produce a hard HAZ which may contain cracks, possibly
leading to serious cracking in service. It is better to remove an arc strike by
grinding than weld repair.
3-24
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
3.7.2 Spatter
Causes Prevention
High arc current Reduce arc current
Long arc length Reduce arc length
Magnetic arc blow Reduce arc length or switch to AC power
Incorrect settings for GMAW process Modify electrical settings (but be careful to
maintain full fusion!)
Damp electrodes Use dry electrodes
Wrong selection of shielding gas Increase argon content if possible, however if
(100%CO2) too high may lead to lack of penetration
Spatter is a cosmetic imperfection and does not affect the integrity of the
weld. However as it is usually caused by an excessive welding current, it is
a sign that the welding conditions are not ideal so there are usually other
associated problems within the structure, ie high heat input. Some spatter is
always produced by open arc consumable electrode welding processes.
Anti-spatter compounds can be used on the parent metal to reduce sticking
and the spatter can then be scraped off.
3-25
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
Chipping mark
Local damage due to the use of a chisel or other tools.
Underflushing
Lack of thickness of the workpiece due to excessive grinding.
The acceptance of a certain size and type of defect for a given structure is
normally expressed as the defect acceptance standard, usually incorporated
in application standards or specifications.
3-26
www.twitraining.com
Rev 2 April 2013
Welding Imperfections and Materials Inspection
Copyright TWI Ltd 2013
If the defect is too deep it must be removed and new weld metal added to
ensure a minimum design throat thickness.
3-27
www.twitraining.com
Section 4
Destructive Testing
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
4 Destructive Testing
Introduction
European Welding Standards require test coupons made for welding
procedure qualification testing to be subjected to non-destructive and then
destructive testing.
The tests are called destructive tests because the welded joint is destroyed
when various types of test piece are taken from it.
Destructive tests can be divided into two groups, those used to:
Qualitative tests are used to verify that the joint is free from defects, of
sound quality and examples of these are bend tests, macroscopic
examination and fracture tests (fillet fracture and nick-break).
Design engineers use the minimum property values listed for particular
grades of material as the basis for design and the most cost-effective
designs are based on an assumption that welded joints have properties that
are no worse than those of the base metal.
4-1
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Test specimens
A transverse tensile test piece typical of the type specified by European
Welding Standards is shown below.
Test pieces may be machined to represent the full thickness of the joint but
for very thick joints it may be necessary to take several transverse tensile
test specimens to be able to test the full thickness.
Method
Test specimens are accurately measured before testing, then fitted into the
jaws of a tensile testing machine and subjected to a continually increasing
tensile force until the specimen fractures.
The tensile strength (Rm) is calculated by dividing the maximum load by the
cross-sectional area of the test specimen, measured before testing.
The test is intended to measure the tensile strength of the joint and thereby
show that the basis for design, the base metal properties, remain the valid
criterion.
Acceptance criteria
If the test piece breaks in the weld metal, it is acceptable provided the
calculated strength is not less than the minimum tensile strength specified,
which is usually the minimum specified for the base metal material grade.
In the ASME IX code, if the test specimen breaks outside the weld or fusion
zone at a stress above 95% of the minimum base metal strength the test
result is acceptable.
4-2
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
The test is to measure tensile strength and also yield (or proof strength) and
tensile ductility.
Specimens
Machined from welds parallel with their longitudinal axis and the specimen
gauge length must be 100% weld metal.
Round cross-section
Method
Specimens are subjected to a continually increasing force in the same way
that transverse tensile specimens are tested.
4-3
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Typical load extension curves and their principal characteristics are shown
below.
Load extension curve for a steel that Load-extension curve for a steel (or other
shows a distinct yield point at the metal) that does not show a distinct yield
elastic limit. point; proof stress is a measure of the
elastic limit.
To calculate elongation:
To calculate UTS:
4-4
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Design engineers need to ensure that the toughness of the steel used for a
particular item will be sufficient to avoid brittle fracture in service and so
impact specimens are tested at a temperature related to the design
temperature for the fabricated component.
C-Mn and low alloy steels undergo a sharp change in their resistance to
brittle fracture as their temperature is lowered so that a steel that may have
very good toughness at ambient temperature may show extreme brittleness
at sub-zero temperatures, as illustrated below.
47 Joules
28 Joules
Energy absorbed
Brittle fracture
- 50 - 40 - 30 - 20 - 10 0
Testing temperature - Degrees Centigrade
Three specimens are normally tested at each temperature
Specimens
Test specimen dimensions have been standardised internationally and are
shown below for full size specimens. There are also standard dimensions
for smaller sized specimens, for example 10 x 7.5mm and 10 x 5mm.
4-5
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Specimens are machined from welded test plates with the notch position
located in different positions according to the testing requirements but
typically in the centre of the weld metal and at positions across the HAZ, as
shown below.
Typical notch positions for Charpy V notch test specimens from double V butt
welds.
Method
Test specimens are cooled to the specified test temperature by immersion in
an insulated bath containing a liquid held at the test temperature.
Impact specimen on
the anvil showing the
hammer position at
point of impact.
Impact testing machine.
4-6
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
The energy absorbed by the hammer when it strikes each test specimen is
shown by the position of the hammer pointer on the scale of the machine.
Energy values are given in Joules (or ft-lbs in US specifications).
Three Impact test specimens are taken for each notch position as there is
always some degree of scatter in the results, particularly for weldments.
Acceptance criteria
Each test result is recorded and an average value calculated for each set of
three tests. These values are compared with those specified by the
application standard or client to establish whether specified requirements
have been met.
4-7
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
A specimen that exhibits extreme brittleness will show a clean break, both
halves of the specimen having a completely flat fracture face with little or no
lateral expansion.
A specimen that exhibits very good toughness will show only a small degree
of crack extension, without fracture and a high value of lateral expansion.
Methods
There are three widely used methods:
The hardness value is given by the size of the indentation produced under a
standard load, the smaller the indentation, the harder the metal.
4-8
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
d1 d2
d
2
Both the Vickers and Brinell methods are suitable for carrying out hardness
surveys on specimens prepared for macroscopic examination of weldments.
The Brinell method gives an indentation too large to accurately measure the
hardness in specific regions of the HAZ and is mainly used to measure the
hardness of base metals.
4-9
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Calculating the size of a crack that would initiate a brittle fracture under
certain stress conditions at a particular temperature.
The stress that would cause a certain sized crack to give a brittle fracture
at a particular temperature.
Specimens
A CTOD specimen is prepared as a rectangular or square shaped bar cut
transverse to the axis of the butt weld. A V notch is machined at the centre
of the bar, which will be coincident with the test position, weld metal or HAZ.
A shallow saw cut is made at the bottom of the notch and the specimen put
into a machine that induces a cyclic bending load until a shallow fatigue
crack initiates from the saw cut.
4-10
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Method
CTOD specimens are usually tested at a temperature below ambient and
the specimen temperature is controlled by immersion in a bath of liquid
cooled to the required test temperature.
For each test condition (position of notch and test temperature) it is usual to
carry out three tests.
4-11
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
The figures below illustrate the main features of the CTOD test.
Fracture toughness is expressed as the distance the crack tip opens without
initiation of a brittle crack.
Acceptance criteria
An application standard or client may specify a minimum CTOD value that
indicates ductile tearing. Alternatively, the test may be for information so that
a value can be used for an engineering critical assessment (ECA).
A very tough steel weldment will allow the mouth of the crack to open widely
by ductile tearing at the tip of the crack whereas a very brittle weldment will
tend to fracture when the applied load is quite low and without any extension
at the tip of the crack.
4-12
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Specimens
There are four types of bend specimen:
Face
Taken with axis transverse to butt welds up to ~12mm thickness and
bent so that the face of the weld is on the outside of the bend (face in
tension).
Root
Taken with axis transverse to butt welds up to ~12mm thickness and
bent so that the root of the weld is on the outside of the bend (root in
tension).
Side
Taken as a transverse slice (~10mm) from the full thickness of butt welds
>~12mm and bent so that the full joint thickness is tested (side in
tension).
Longitudinal bend
Taken with axis parallel to the longitudinal axis of a butt weld; specimen
thickness is ~12mm and the face or root of weld may be tested in
tension.
4-13
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Method
Guided bend tests are usually used for welding procedure and welder
qualification.
The diameter of the former used for a particular test is specified in the code,
having been determined by the type of material being tested and the ductility
that can be expected from it after welding and any PWHT.
The standard that specifies the test method will specify the minimum bend
angle the specimen must experience and is typically 120-180.
4-14
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Acceptance criteria
Bend tests pieces should exhibit satisfactory soundness by not showing
cracks or any signs of significant fissures or cavities on the outside of the
bend.
Small indications less than about 3mm in length may be allowed by some
standards.
This method for assessing the quality of fillet welds may be specified by
application standards as an alternative to macroscopic examination.
It is a test method that can be used for welder qualification testing according
to European Standards but is not used for welding procedure qualification.
Specimens
A test weld is cut into short (typically 50mm) lengths and a longitudinal
notch machined into the specimen as shown below. The notch profile may
be square, V or U shape.
Method
Specimens are made to fracture through their throat by dynamic strokes
(hammering) or by pressing, as shown below. The welding standard or
application standard will specify the number of tests (typically four).
4-15
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Acceptance criteria
The standard for welder qualification, or application standard, will specify the
acceptance criteria for imperfections such as lack of penetration into the root
of the joint and solid inclusions and porosity that are visible on the fracture
surfaces.
Test reports should also give a description of the appearance of the fracture
and location of any imperfection.
Objective
The same as for fillet fracture tests.
Specimens
Taken from a butt weld and notched so that the fracture path will be in the
central region of the weld. Typical test piece types are shown below.
4-16
www.twitraining.com
Rev 2 April 2013
Destructive Testing
Copyright TWI Ltd 2013
Method
Test pieces are made to fracture by hammering or three-point bending.
Acceptance criteria
The standard for welder qualification or application standard will specify the
acceptance criteria for imperfections such as lack of fusion, solid inclusions
and porosity that are visible on the fracture surfaces.
Test reports should also give a description of the appearance of the fracture
and location of any imperfection.
4-17
www.twitraining.com
Section 5
Non-destructive Testing
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
5 Non-destructive Testing
5.1 Introduction
Radiographic, ultrasonic, dye penetrant and magnetic particle methods are
briefly described below. Their relative advantages and limitations are
discussed in terms of their applicability to the examination of welds.
5.2.2 X-rays
X-rays used in the industrial radiography of welds generally have photon
energies in the range 30keV up to 20MeV. Up to 400keV they are generated
by conventional X-ray tubes which, dependent upon output may be suitable
for portable or fixed installations. Portability falls off rapidly with increasing
kilovoltage and radiation output. Above 400keV X-rays are produced using
devices such as betatrons and linear accelerators, not generally suitable for
use outside of fixed installations.
5-1
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
Increased portability.
No need for a power source.
Lower initial equipment costs.
5-2
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
5-3
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
5-4
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
weld defects. Since velocity is a constant for any given material and sound
travels in a straight line (with the right equipment) ultrasound can also be
used to give accurate positional information about a given reflector. Careful
observation of the echo pattern of a given reflector and its behaviour as the
ultrasonic probe is moved together with the positional information obtained
above and knowledge of the component history enables the experienced
ultrasonic operator to classify the reflector as slag, lack of fusion or a crack.
A flaw detector:
- Pulse generator.
- Adjustable time base generator with an adjustable delay control.
- Cathode ray tube with fully rectified display.
- Calibrated amplifier with a graduated gain control or attenuator.
An ultrasonic probe:
- Piezo-electric crystal element capable of converting electrical vibrations
into mechanical vibrations and vice versa.
- Probe shoe, normally a Perspex block to which the crystal is firmly
attached using suitable adhesive.
- Electrical and/or mechanical crystal damping facilities to prevent
excessive ringing.
5-5
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
Ultrasonic equipment.
5-6
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
5-7
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
Advantages Limitations
Inexpensive equipment Only magnetic materials
Direct location of defect May need to demagnetise components
Surface conditions not critical Access may be a problem for the yoke
Can be applied without power Need power if using a yoke
Low skill level No permanent record
Sub-surface defects found 1-2mm Calibration of equipment
Quick, instant results Testing in two directions required
Hot testing (using dry powder) Need good lighting - 500 lux minimum
Can be used in the dark (UV light)
5-8
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
5-9
www.twitraining.com
Rev 2 April 2013
Non-destructive Testing
Copyright TWI Ltd 2013
5-10
www.twitraining.com
Section 6
WPS/Welder Qualifications
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
6 WPS/Welder Qualifications
6.1 General
When structures and pressurised items are fabricated by welding, it is
essential that all the welded joints are sound and have suitable properties
for their application.
Table 6.1 is a typical WPS written in accordance with the European Welding
Standard format giving details of all the welding conditions that need to be
specified.
6-1
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Table 6.1 Typical sequence for welding procedure qualification by means of a test
weld.
The test coupon is subjected to NDT in accordance with the methods specified
by the Standard visual inspection, MT or PT and RT or UT.
6-2
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
EN ISO 15614
Specification and qualification of welding procedures for metallic materials,
welding procedure test.
Part 1
Arc and gas welding of steels and arc welding of nickel and nickel alloys.
Part 2
Arc welding of aluminium and its alloys.
ASME Section IX
Pressurised systems (vessels and pipework).
AWS D1.1
Structural welding of steels.
AWS D1.2
Structural welding of aluminium.
Some alternative ways that can be used for writing qualified WPSs for some
applications are:
6-3
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
6-4
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
6-5
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
The welding conditions that are allowed to be written on a qualified WPS are
referred to as the qualification range and depend on the welding conditions
used for the test piece (as-run details) and form part of the WPQR.
Essential variable
Variable that has an effect on the mechanical properties of the weldment
and if changed beyond the limits specified by the standard will require
the WPS to be re-qualified.
Non-essential variable
Variable that must be specified on a WPS but does not have a significant
effect on the mechanical properties of the weldment and can be changed
without the need for re-qualification but will require a new WPS to be
written.
1 Make another test weld using similar welding conditions to those used
for the affected weld and subject this to the same tests used for the
relevant WPQR to demonstrate that the properties still satisfy specified
requirements.
2 Remove the affected weld and re-weld the joint strictly in accordance
with the designated WPS.
Most of the welding variables classed as essential are the same in both the
European and American Welding Standards but their qualification ranges
may differ.
6-6
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Welders also need to have the skill to consistently produce sound (defect-
free) welds.
EN 287-1
Qualification test of welders Fusion welding.
Part 1: Steels.
6-7
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
EN ISO 9606-2
Qualification test of welders Fusion welding.
Part 2: Aluminium and aluminium alloys.
EN 1418
Welding personnel Approval testing of welding operators for fusion
welding and resistance weld setters for fully mechanised and automatic
welding of metallic materials.
ASME Section IX
Pressurised systems (vessels & pipework).
AWS D1.1
Structural welding of steels.
AWS D1.2
Structural welding of aluminium.
Table 6.3 shows the steps required for qualifying welders in accordance with
EU Standards.
6-8
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
The welding engineer writes a WPS for a welder qualification test piece.
The welder makes the test weld in accordance with the WPS.
A welding inspector monitors the welding to ensure that the welder is
working in accordance with the WPS.
6-9
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Figure 6.3 Example of a WPQR document (test weld details) to EN15614 format
6-10
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Some welding variables classed as essential for welder qualification are the
same types as those classified as essential for welding procedure
qualification, but the range of qualification may be significantly wider.
6-11
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Records/evidence are available that can be traced to the welder and the
WPSs used for production welding.
Supporting evidence must relate to volumetric examination of the
welders production welds (RT or UT) on two welds made during the six
months prior to the extension date.
Supporting evidence welds must satisfy the acceptance levels for
imperfections specified by the EU welding standard and have been
made under the same conditions as the original test weld.
6-12
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Figure 6.4 Example of WPQR document (details of weld test) to EN15614 format.
6-13
www.twitraining.com
Rev 2 April 2013
WPS/Welder Qualifications
Copyright TWI Ltd 2013
Figure 6.5 Example of a welder qualification test certificate (WPQ) to EN287 format.
6-14
www.twitraining.com
Section 7
Materials Inspection
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
7 Materials Inspection
7.1 General
One of the duties of the visual/welding inspector is materials inspection and
there are a number of situations where this will be required:
Steels.
Stainless steels.
Aluminium and its alloys.
Nickel and its alloys.
Copper and its alloys.
Titanium and its alloys.
Cast iron.
These materials are all widely used in fabrication, welding and construction
to meet the requirements of a diverse range of applications and industry
sectors.
There are three essential aspects to material inspection that the Inspector
should consider:
7-1
www.twitraining.com
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
S Structural steel.
355 Minimum yield strength: N/mm at t 16mm.
J2 Longitudinal Charpy, 27Joules 20C.
G3 Normalised or normalised rolled.
Commonly used materials and most of the alloys can be fusion welded
using various welding processes, in a wide range of thickness and where
applicable, diameters.
7-2
www.twitraining.com
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
Non-specific inspection
Carried out by the manufacturer in accordance with his own procedures
to assess whether products defined by the same product specification
and made by the same manufacturing process, comply with the
requirements of the order.
- Type 2.1 are documents in which the manufacturer declares that the
products supplied comply with the requirements of the order without
inclusion of test results.
-Type 2.2 are documents in which the manufacturer declares that the
products supplied comply with the requirements of the order and
includes test results based on non-specific inspection.
Specific inspection
Inspection carried out before delivery according to the product
specification on the products to be supplied or test units of which the
products supplied are part, to verify that these products comply with the
requirements of the order.
- Type 3.1 are certificates in which the manufacturer declares that the
products supplied comply with the requirements of the order and in
which test results are supplied.
7-3
www.twitraining.com
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
Non-specific inspection*
May be replaced by specific
inspection if specified in the material
standard or the order.
Specific inspection
Quality management system of the material
manufacturer certified by a competent body
established within the community and having
undergone a specific assessment for materials.
7-4
www.twitraining.com
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
General inspection.
Visible imperfections.
Dimensions.
Surface condition.
General inspection
This takes account of storage conditions, methods of handling, number of
plates or pipes and distortion tolerances.
Visible imperfections
Typical visible imperfections are usually attributable to the manufacturing
process and include cold laps which break the surface or laminations if they
appear at the edge of the plate. Ultrasonic testing using a compression
probe may be required for laminations which may be present in the body of
the material.
Dimensions
For plates this includes length, width and thickness.
For pipes this includes length and wall thickness and also inspection of
diameter and ovality. At this stage of inspection the material cast or heat
number may be recorded for validation against the material certificate.
Surface condition
The surface condition is important and must not show excessive millscale or
rust, be badly pitted or have unacceptable mechanical damage.
7-5
www.twitraining.com
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
There are four grades of rusting which the inspector may have to consider:
Rust Grade A: Steel surface largely covered with adherent millscale with
little or no rust.
Rust Grade B: Steel surface which has begun to rust and from which mill
scale has begun to flake.
Rust Grade C: Steel surface on which the mill scale has rusted away or
from which it can be scraped. Slight pitting visible under normal vision.
Rust Grade D: Steel surface on which mill scale has rusted away. General
pitting visible under normal vision.
7-6
www.twitraining.com
Rev 2 April 2013
Materials Inspection
Copyright TWI Ltd 2013
7.6 Summary
Material inspection is an important part of the inspectors duties and an
understanding of the documentation involved is key to success.
These methods may include but are not limited to: Spark test, spectroscopic
analysis, chemical analysis, scleroscope hardness test, etc. These types of
test are normally conducted by an approved test house but sometimes on-
site and the inspector may be required to witness them to verify compliance
with the purchase order or appropriate standard(s).
7-7
www.twitraining.com
Section 8
8.2 Definitions
Normative document
Document that provides rules, guidelines or characteristics for activities or
their results. The term normative document is generic, covering documents
such as standards, technical specifications, codes of practice and
regulations.*
Standard
Document established by consensus and approved by a recognised body. A
standard provides, for common and repeated use, guidelines, rules,
characteristics for activities or their results, aimed at achieving the optimum
degree of order in a given context.*
Harmonised standards
Standards on the same subject approved by different standardising bodies,
that establish inter-changeability of products, processes and services, or
mutual understanding of test results or information provided according to
these standards.*
Code of practice
Document that recommends practices or procedures for the design,
manufacture, installation, maintenance and utilisation of equipment,
structures or products. A code of practice may be a standard, part of a
standard or independent of a standard.*
Regulation
Document providing binding legislative rules adopted by an authority.*
Authority
A body (responsible for standards and regulations legal or administrative
entity that has specific tasks and composition) that has legal powers and
rights.*
8-1
www.twitraining.com
Rev 2 April 2013
Codes and Standards
Copyright TWI Ltd 2013
Regulatory authority
Authority responsible for preparing or adopting regulations.*
Enforcement authority
Authority responsible for enforcing regulations.*
Specification
Document stating requirements, meaningful data and its supporting medium
stating needs or expectations that are stated, generally implied or
obligatory.**
Procedure
Specified way to carry out an activity or process*. Usually a written
description of all essential parameters and precautions to be observed when
applying a technique to a specific application following an established
standard, code or specification.
Instruction
Written description of the precise steps to be followed based on an
established procedure, standard, code or specification.
Quality plan
Document specifying which procedures and associated resources shall be
applied by whom and when to a specific project, product, process or
contract.*
8.3 Summary
Application standards and codes of practice ensure that a structure or
component will have an acceptable level of quality and be fit-for-purpose.
8-2
www.twitraining.com
Rev 2 April 2013
Codes and Standards
Copyright TWI Ltd 2013
Comments
Standard Number Year Status AMD = amended
COR = corrected
BS 499-1 2009 Current
8-3
www.twitraining.com
Rev 2 April 2013
Codes and Standards
Copyright TWI Ltd 2013
Comments
Standard Number Year Status AMD = amended
COR = corrected
BS 4515-1 (2009) 2009 Current
BS 4570 (1985) 1985 Partly Partly superseded by:
Superseded BS EN 1011-8:2004 AMD
BS EN 383
8-4
www.twitraining.com
Rev 2 April 2013
Codes and Standards
Copyright TWI Ltd 2013
Comments
Standard Number Year Status AMD = amended
COR = corrected
BS EN 910:1996 1996 Superseded Superseded By: BS EN ISO
5173:2010 + A1 2011
8-5
www.twitraining.com
Rev 2 April 2013
Codes and Standards
Copyright TWI Ltd 2013
BSENISO156143:2008 2008
BSENISO156144:2005 2008
COR2008
BSENISO156145:2004 2004
BSENISO156146:2006 2006
BSENISO156147:2007 2007
BSENISO156148:2002 2002
BSENISO1561410:2005 2005
BSENISO1561411:2002 2002
BSENISO1561412:2004 2004
BSENISO1561413:2005 2005
8-6
www.twitraining.com
Section 9
Welding Symbols
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
9 Welding Symbols
A weld joint can be represented on an engineering drawing by a detailed
sketch showing every detail and dimension of the joint preparation, as
shown below.
8-12
R6
1-3mm
1-4mm
Single U preparation.
9-1
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
European Standard
EN 22553 Welded, brazed & soldered joints, Symbolic representation on
drawings.
American Standard
AWS A2.4, standard symbols for welding, brazing and non-destructive
examination.
These standards are very similar in many respects, but there are also some
major differences that need to be understood to avoid misinterpretation.
9-2
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
Fillet weld
Surfacing (cladding)
Backing run
(back or backing weld)
Backing bar
9-3
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
9-4
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
Examples of supplementary symbols and how they are applied are given
below.
Convex double V
butt weld
Note: If the weld symbol does not have a supplementary symbol then the shape of
the weld surface does not need to be indicated precisely.
9-5
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
An arrow line.
A dual reference line consisting of a continuous and a dashed line.
1 = Arrow line
2a = Reference (continuous line)
2b
2b = Identification line (dashed line)
= Welding symbol (single V joint)
Joint line
The arrow side is always the end of the joint line that the arrow line points to
(and touches).
It can be at either end of the joint line and it is the draughtsman who decides
which end to make the arrow side.
9-6
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
Arrow line
arrow line
Arrow side
arrow side
Other side
other side
other side
Other side arrow side
Arrow side arrow line
Arrow line
For a non-symmetrical weld it is essential that the arrow side and other side
of the weld are distinguished. The convention for doing this is:
Symbols for the weld details required on the arrow side must be placed
on the continuous line.
Symbols for the weld details on the other side must be placed on the
dashed line.
9-7
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
or
9-8
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
Dimensions for the cross-section of the weld are written on the lefthand
side of the symbol.
Length dimensions for the weld are written on the righthand side of the
symbol.
In the absence of any indication to the contrary, all butt welds are full
penetration welds.
Some examples of how these symbols are used are shown below.
Partial
Partialpenetration
penetration s10
10mm single
singleVVbutt
buttweld
weld
8mm
a6
Filletweld
Fillet weldwith
with6mm
6mmthroat
6mm
9-9
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
l Length of weld.
(e) Distance between adjacent weld elements.
n Number of weld elements.
The use of these letters is shown for the intermittent double-sided fillet weld
shown below.
100mm
z n x l (e)
Z8 3 150 (100)
z n x l (e) Z8 3 150 (100)
9-10
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
z n L (e)
z n L (e)
9-11
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
111 = MMA
121 = SAW 111
131 = MIG
135 = MAG
A closed tail can also be used into which reference to a specific instruction
can be added.
WPS 014
9-12
www.twitraining.com
Rev 2 April 2013
Welding Symbols
Copyright TWI Ltd 2013
Arrow side
Other side
9-13
www.twitraining.com
Section 10
10.2 Productivity
With most welding processes, welding in the PA (flat or 1G) position results
in the highest weld metal deposition rate and therefore productivity.
For TIG welding, the higher the current, the more energy there is for fusion
so the higher the rate at which filler wire can be added to the weld pool.
Volts x Amps
Arc energy ( kJ / mm)
Travel speed ( mm / sec) x 1000
Heat input is the energy supplied by the welding arc to the workpiece and is
expressed in terms of arc energy x thermal efficiency factor.
The thermal efficiency factor is the ratio of heat energy into the welding arc
to the electrical energy consumed by the arc.
10-1
www.twitraining.com
Rev 2 April 2013
Introduction to Welding Processes
Copyright TWI Ltd 2013
Heat input values into the weld for various processes can be calculated from
the arc energy by multiplying by the following thermal efficiency factors:
Example
A weld is made using the MAG welding process and the following welding
conditions were recorded:
Volts: 24
Amps: 240
Travel speed: 300mm per minute
Volts x Amps
Arc energy ( kJ / mm)
Travel speed ( mm / sec) x 1000
24 240
= 300 / 60 1000
5760
= 5000
Welding position and the process have a major influence on the travel
speed that can be used.
For manual and semi-automatic welding the following are general principles:
10-2
www.twitraining.com
Rev 2 April 2013
Introduction to Welding Processes
Copyright TWI Ltd 2013
Overhead welding tends to give low heat input because of the need to
use low current and relatively fast travel speed.
Welding in the flat position (downhand) can be a low or high heat input
position because the welder has more flexibility about the travel speed
that can be used.
Of the arc welding processes, SAW has the potential to give the highest
heat input and deposition rates and TIG and MIG/MAG can produce very
low heat input.
Typical heat input values for controlled heat input welding will tend to be
~1.0-~3.5kJ/mm.
For MIG/MAG, arc voltage has a major influence on droplet transfer across
the arc.
Welding current
Welding current has a major influence on the depth of fusion/penetration
into the base metal and adjacent weld runs.
As a rule, the higher the current the greater the penetration depth.
Penetration depth affects dilution of the weld deposit by the parent metal
and it is particularly important to control this when dissimilar metals are
joined.
Polarity
Polarity determines whether most of the arc energy (heat) is concentrated at
the electrode surface or at the surface of the parent material.
10-3
www.twitraining.com
Rev 2 April 2013
Introduction to Welding Processes
Copyright TWI Ltd 2013
The location of the heat with respect to polarity is not the same for all
processes and the effects/options/benefits for each of the main arc welding
processes are summarised below.
Polarity
Process
DC+ve DC-ve AC
Best penetration Less penetration but higher Not suitable for
deposition rate (used for some electrodes.
MMA
root passes and weld Minimises arc blow
overlaying)
Rarely used due Used for all metals except Required for Al/Al
to tungsten Al/Al alloys and Mg/Mg alloys to break-up
TIG
overheating alloys the refractory
oxide film
GMAW solid Used for all metals Rarely used Not used
wires and virtually all
(MIG/MAG) situations
Once an arc has been struck and stabilised there is a relationship between
the arc voltage and current flowing through the welding circuit that depends
on the electrical characteristics of the power source.
10-4
www.twitraining.com
Rev 2 April 2013
Introduction to Welding Processes
Copyright TWI Ltd 2013
100
OCV
Voltage, V
50
Arc voltage variation
A
B
C
Current, A XYZ
For manual welding (MMA and manual TIG) the welder sets the required
current on the power source but arc voltage is controlled by the arc length
the welder uses.
A welder has to work within a fairly narrow range of arc length for a
particular current setting, if it is too long the arc will extinguish, too short and
the electrode may stub into the weld pool and the arc extinguish.
For the operating principle of this type of power source see Figure 10.1.
The welder tries to hold a fairly constant arc length (B in Figure 10.1) for the
current (Y) that has been set. However, he cannot keep the arc length
constant and it will vary over a small working range (A-C) due to normal
hand movement during welding.
10-5
www.twitraining.com
Rev 2 April 2013
Introduction to Welding Processes
Copyright TWI Ltd 2013
The power source is designed to ensure that these small changes in arc
voltage during normal welding will give only small changes in current (X to
Z). Thus the current can be considered to be essentially constant and this
ensures that the welder is able to maintain control of fusion.
The drooping shape of the volt-amp curves has led to constant current
power sources sometimes being said to have a drooping characteristic.
Wire feed speed and current are directly related so that as the current
increases, so does the feed speed and there is a corresponding increase in
the burn-off rate to maintain the arc length/voltage.
The operating principle of this type of power source is shown in Figure 10.2.
A welder sets voltage B and current Y on the power source. If the arc length
is decreased to C (due to a variation in weld profile or as the welders hand
moves up and down during semi-automatic welding) there will be a
momentary increase in welding current to Z. The higher current Z gives a
higher burn-off rate which brings the arc length (and arc voltage) back to the
pre-set value.
Similarly, if the arc length increases the current quickly falls to X and the
burn-off rate is reduced so that the arc length is brought back to the pre-set
level B.
Thus, although the arc voltage does vary a little during welding the changes
in current that restore the voltage to the pre-set value happen extremely
quickly so that the voltage can be considered constant.
The straight-line relationship between voltage and current and the relatively
small gradient is why this type of power source is often referred to as having
a flat characteristic.
10-6
www.twitraining.com
Rev 2 April 2013
Introduction to Welding Processes
Copyright TWI Ltd 2013
100
OCV
Voltage, V
50
Arc voltage variation
A
B
C
Current, A X Y Z
Figure 10.2 Typical volt-amp curves for a constant voltage power source.
10-7
www.twitraining.com
Section 11
MMA Welding
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
The most versatile welding process, MMA is suitable for most ferrous and
non-ferrous metals, over a wide range of thicknesses. It can be used in all
positions, with reasonable ease of use and relatively economically. The final
weld quality is primarily dependent on the skill of the welder.
When an arc is struck between the coated electrode and workpiece, both
surfaces melt to form a weld pool. The average temperature of the arc is
approximately 6000C, sufficient to simultaneously melt the parent metal,
consumable core wire and flux coating. The flux forms gas and slag which
protect the weld pool from oxygen and nitrogen in the surrounding
atmosphere. The molten slag solidifies, cools and must be chipped off the
weld bead once the weld run is complete (or before the next weld pass is
deposited). The process allows only short lengths of weld to be produced
before a new electrode needs to be inserted in the holder.
Electrode angle
75-80o to the horizontal
Consumable electrode
Filler metal core
Flux coating
Direction of electrode travel
Parent
metal
Weld metal
MMA welding.
11-1
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
1
10
9 2
8 3
4
7
6 5
Power sources for MMA welding are transformers (which transform mains
AC-AC suitable for welding), transformer-rectifiers (which rectify AC-DC),
diesel or petrol driven generators (preferred for site work) or inverters (a
11-2
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
An OCV.
Initiate the arc.
Welding voltage between 20 and 40V to maintain the arc during welding.
Suitable current range, typically 30-350 amps.
Stable arc-rapid arc recovery or arc re-ignition without current surge.
Constant welding current. The arc length may change during welding,
but consistent electrode burn-off rate and weld penetration
characteristics must be maintained.
Current (amperage)
Voltage
Travel speed Affects heat input
Polarity
Type of electrode
11-3
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
11.3.2 Voltage
The welding potential or pressure required for current to flow through the
circuit is the voltage (U). For MMA welding the voltage required to initiate
the arc is OCV, the voltage measured between the output terminals of the
power source when no current is flowing through the welding circuit.
For safety reasons the OCV should not exceed 90V and is usually 50-90V.
Arc voltage that is required to maintain the arc during welding and is usually
20-40V and is a function of arc length. With MMA the welder controls the arc
length and therefore the arc voltage which in turn controls weld pool fluidity.
11-4
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
OCV 90V
Welding amperage
11-5
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
When using DC the welding arc can be affected by arc blow, the deflection
of the arc from its normal path due to magnetic forces.
Rutile electrodes
Contain a high proportion of titanium oxide (rutile) in the coating which
promotes easy arc ignition, smooth arc operation and low spatter. These
electrodes are general purpose with good welding properties and can be
used with AC and DC power sources and in all positions. The electrodes are
especially suitable for welding fillet joints in the horizontal/vertical (HV)
position.
11-6
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
Features:
Moderate weld metal mechanical properties.
Good bead profile produced through the viscous slag.
Positional welding possible with a fluid slag (containing fluoride).
Easily removable slag.
Basic electrodes
Contain a high proportion of calcium carbonate (limestone) and calcium
fluoride (fluorspar) in the coating, making the slag coating more fluid than
rutile coatings. This is also fast freezing which assists welding in the vertical
and overhead positions. These electrodes are used for welding medium and
heavy section fabrications where higher weld quality, good mechanical
properties and resistance to cracking due to high restraint are required.
Features
Low hydrogen weld metal.
Requires high welding currents/speeds.
Poor bead profile (convex and coarse surface profile).
Slag removal difficult.
Cellulosic electrodes
Contain a high proportion of cellulose in the coating and are characterised
by a deeply penetrating arc and rapid burn-off rate giving high welding
speeds. Weld deposit can be coarse and with fluid slag, deslagging can be
difficult. These electrodes are easy to use in any position and are noted for
their use in the stovepipe welding technique.
Features
Deep penetration in all positions.
Suitable for vertical-down welding.
Reasonably good mechanical properties.
High level of hydrogen generated, risk of cracking in the HAZ.
11-7
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
Operating factor should not be confused with the term duty cycle which is a
safety value given as the % of time a conductor can carry a current and is
given as a specific current at 60 and 100% of 10 minutes, ie 350A 60% and
300A 100%
11-8
www.twitraining.com
Rev 2 April 2013
Manual Metal Arc/Shielded Metal Arc Welding (MMA/SMAW)
Copyright TWI Ltd 2013
Advantages:
Field or shop use.
Range of consumables.
All positional.
Very portable.
Simple equipment.
Disadvantages:
High skill factor required.
Arc strikes/slag inclusions.
Low operating factor.
High level of generated fumes.
Hydrogen control.
11-9
www.twitraining.com
Section 12
TIG Welding
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
12 TIG Welding
12.1 Process characteristics
In the US the TIG process is also called gas tungsten arc welding (GTAW).
Melting is produced by heating with an arc struck between a non-
consumable tungsten electrode and the workpiece. An inert gas shields the
electrode and weld zone to prevent oxidation of the tungsten electrode and
atmospheric contamination of the weld and hot filler wire (as shown below).
Tungsten is used because it has a melting point of 3370C, well above any
other common metal.
Welding current.
Current type and polarity.
Travel speed.
Shape of tungsten electrode tip and vertex angle.
Shielding gas flow rate.
Electrode extension.
12-1
www.twitraining.com
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
(A.C.)
Current
DC-ve AC DC+ve
type/polarity
Heat 70% at work 50% at work 30% at work
balance 30% at electrode 50% at electrode 70% at electrode
Weld profile Deep, narrow Medium Shallow, wide
Cleaning No Yes every half cycle Yes
action
Electrode Excellent Good Poor
capacity (3.2mm/400A) (3.2mm/225A) (6.4mm/120A)
12-2
www.twitraining.com
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
Pure tungsten electrodes are used when welding light metals with AC
because they maintain a clean balled end, but possess poor arc initiation
and stability in AC mode compared with other types.
Thoriated electrodes are alloyed with thorium oxide (thoria) to improve
arc initiation and have higher current carrying capacity than pure
tungsten electrodes and maintain a sharp tip for longer. Unfortunately,
thoria is slightly radioactive (emitting radiation) and the dust generated
during tip grinding should not be inhaled. Electrode grinding machines
used for thoriated tungsten grinding should be fitted with a dust
extraction system.
Ceriated and lanthaniated electrodes are alloyed with cerium and
lanthanum oxides, for the same reason as thoriated electrodes and
operate successfully with DC or AC and as cerium and lanthanum are
not radioactive, they have been used as replacements for thoriated
electrodes.
Zirconiated electrodes are alloyed with zirconium oxide with operating
characteristics between the thoriated types and pure tungsten. They are
able to retain a balled end during welding, so are recommended for AC
welding. They have a high resistance to contamination so are used for
high integrity welds where tungsten inclusions must be avoided.
12-3
www.twitraining.com
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
Argon.
Helium.
Mixtures of argon and helium.
Note: For austenitic stainless steels and some cupro-nickel alloys, argon
with up to ~5% hydrogen improves penetration and reduces porosity.
12-4
www.twitraining.com
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
Back purging
It is necessary to protect the back of the weld from excessive oxidation
during TIG welding, achieved by using a purge gas, usually pure argon.
For pipe welding spools it is relatively easy to purge the pipe bore, but for
plate/sheet welding it is necessary to use a purge channel or sometimes
another operator positions and moves a back purge nozzle as the weld
progresses. For purging large systems soluble dams or bungs are required
and can it can be a complex operation.
The initial stage of back purging is to exclude all the air at the back of the
weld and having allowed sufficient time for this the flow rate should be
reduced prior to starting to weld so there is positive flow (typically
~4 l/min).
Back purging should continue until two or more layers of weld have been
deposited.
12-5
www.twitraining.com
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
Electrode
Stickout extension
If the electrode extension is too short, the electrode tip will not be
adequately heated leading to an unstable arc.
If the electrode extension is too long, the electrode tip might overheat,
causing melting and lead to tungsten inclusions.
As a general rule stickout length should be 2-3 times the electrode
diameter.
Thermal shock to the tungsten causing small fragments to enter the weld
pool is a common cause of tungsten inclusions and is why modern power
sources have a current slope-up device to minimise this risk.
This device allows the current to rise to the set value over a short period so
the tungsten is heated more slowly and gently.
12-6
www.twitraining.com
Rev 2 April 2013
TIG Welding
Copyright TWI Ltd 2013
Using filler wires, TIG is used for making high quality joints in heavier gauge
pipe and tubing for the chemical, petroleum and power generating
industries.
It is also used in the aerospace industry for items such as airframes and
rocket motor cases.
12.7 Advantages
Produces superior quality welds with very low levels of diffusible
hydrogen so there is less danger of cold cracking.
No weld spatter or slag inclusions which makes it particularly suitable for
applications that require a high degree of cleanliness, eg pipework for
the food and drinks industry, manufacturing semiconductors, etc.
Can be used with filler metal and on thin sections without filler and can
produces welds at relatively high speed.
Enables welding variables to be accurately controlled and is particularly
good for controlling weld root penetration in all welding.
Can weld almost all weldable metals including dissimilar joints but
welding in position is not generally used for those with low melting points
such as lead and tin. Especially useful in welding reactive metals with
very stable oxides such as aluminium, magnesium, titanium and
zirconium.
The heat source and filler metal additions are controlled independently
so it is very good for joining thin base metals.
12.8 Disadvantages
Gives low deposition rates compared with other arc welding processes.
Need higher dexterity and welder co-ordination than with MIG/MAG or
MMA welding.
Less economical than MMA or MIG/MAG for sections thicker than
~10mm.
Difficult to fully shield the weld zone in draughty conditions so may not
be suitable for site/field welding.
Tungsten inclusions can occur if the electrode contacts the weld pool.
No cleaning action so low tolerance for contaminants on filler or base
metals.
12-7
www.twitraining.com
Section 13
MIG/MAG Welding
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
13 MIG/MAG Welding
13.1 Process
Known in the US as gas metal arc welding (GMAW), the MIG/MAG welding
process (Figure 13.1) is a versatile technique suitable for both thin sheet
and thick section components in most metallic materials. An arc is struck
between the end of a wire electrode and the workpiece, melting both to form
a weld pool. The wire serves as the source of heat (via the arc at the wire
tip) and filler metal for the joint and is fed through a copper contact tube
(also called a contact tip) which conducts welding current into the wire. The
weld pool is protected from the surrounding atmosphere by a shielding gas
fed through a nozzle surrounding the wire. Shielding gas selection depends
on the material being welded and the application. The wire is fed from a reel
by a motor drive and the welder or machine moves the welding gun or torch
along the joint line. The process offers high productivity and is economical
because the consumable wire is continuously fed.
13-1
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Advantages:
Continuous wire feed.
Automatic self-regulation of the arc length.
High deposition rate and minimal number of stop/start locations.
High consumable efficiency.
Heat inputs in the range 0.1-2kJ/mm.
Low hydrogen potential process.
Welder has good visibility of weld pool and joint line.
Little or no post-weld cleaning.
Can be used in all positions (dip transfer).
Good process control possibilities.
Wide range of applications.
Disadvantages:
No independent control of filler addition.
Difficult to set up optimum parameters to minimise spatter levels.
Risk of lack of fusion when using dip transfer on thicker weldments.
High level of equipment maintenance.
Lower heat input can lead to high hardness values.
Higher equipment cost than MMA welding.
Site welding requires special precautions to exclude draughts which may
disturb the gas shield.
Joint and part access is not as good as MMA or TIG welding.
Cleanliness of base metal, slag processes tolerate greater contamination.
13-2
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
13.2.2 Voltage
The most important setting in spray transfer as it controls the arc length. In
dip transfer it also affects the rise of current and the overall heat input into
the weld. Increase both wire feed speed/current and voltage will increase
heat input. Welding connections need to be checked for soundness as any
loose ones will result in resistance and cause a voltage drop in the circuit
and will affect the characteristic of the welding arc. The voltage will affect
the type of transfer achievable but this is also highly dependent on the type
of gas being used.
13-3
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
13.2.3 Gases
Ar Ar-He He CO2
For non-ferrous metals and their alloys (such as Al, Ni and Cu) an inert
shielding gas must be used, usually pure argon or an argon rich gas with a
helium addition. The use of a fully inert gas is why the process is also called
metal inert gas (MIG) welding and for precise use of terminology this should
only be used when referring to the welding of non-ferrous metals.
100%CO2
CO2 gas cannot sustain spray transfer as the ionisation potential of the gas
is too high it gives very good penetration but promotes globular droplet
transfer also a very unstable arc and lots of spatter.
Argon +15-20%CO2
The percentage of CO2 or oxygen depends on the type of steel being
welded and the mode of metal transfer used. Argon has a much lower
ionisation potential and can sustain spray transfer above 24 welding volts.
Argon gives a very stable arc, little spatter but lower penetration than CO2.
Argon and 5-20%CO2 gas mixtures give the benefit of both gases ie good
penetration with a stable arc and very little spatter. CO2 gas is much
cheaper than argon or its mixtures and is widely used for carbon and some
low alloy steels.
13-4
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Argon +1-5%CO2
Widely used for stainless steels and some low alloy steels.
Figure 13.5 Active shielding gas mixtures for MAG welding of carbon, C-Mn and
low alloy steels. Blue is a cooler and red a hotter mixture gas.
Gas mixtures with helium instead of argon give a hotter arc, more fluid weld
pool and better weld profile. These quaternary mixtures permit higher
welding speeds but may not be suitable for thin sections.
Stainless steels
Austenitic stainless steels are typically welded with argon-CO2/O2 mixtures
for spray transfer or argon-helium-CO2 mixtures for all modes of transfer.
The oxidising potential of the mixtures is kept to a minimum (2-2.5%
maximum CO2 content) to stabilise the arc but with minimum effect on
corrosion performance. Because austenitic steels have a low thermal
conductivity, the addition of helium helps to avoid lack of fusion defects and
overcome the high heat dissipation into the material. Helium additions are
up to 85%, compared with ~25% for mixtures used for carbon and low alloy
steels. CO2-containing mixtures are sometimes avoided to eliminate
potential carbon pick-up.
13-5
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Figure 13.6 Active shielding gas mixtures for MAG welding of stainless steels. Blue
is a cooler and; red a hotter gas mixture.
Argon
Can be used for aluminium because there is sufficient surface oxide
available to stabilise the arc. For materials sensitive to oxygen, such as
titanium and nickel alloys, arc stability may be difficult to achieve with inert
gases in some applications. The density of argon is approximately 1.4 times
that of air so in the downhand position, the relatively heavy argon is very
effective at displacing air. A disadvantage is when working in confined
spaces there is a risk of argon building up to dangerous levels and
asphyxiating the welder.
Argon-helium mixtures
Argon is most commonly used for MIG welding of light alloys but an
advantage can be gained by use of helium and argon/helium mixtures.
Helium possesses a higher thermal conductivity than argon and the hotter
weld pool produces improved penetration and/or an increase in welding
speed. High helium contents give a deep broad penetration profile but
produce high spatter levels. With less than 80% argon a true spray transfer
is not possible. With globular-type transfer the welder should use a buried
arc to minimise spatter. Arc stability can be problematic in helium and
argon-helium mixtures, since helium raises the arc voltage so there is a
larger change in arc voltage with respect to arc length. Helium mixtures
require higher flow rates than argon shielding to provide the same gas
protection.
13-6
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Figure 13.7 Inert shielding gas mixtures for MIG welding of aluminium,
magnesium, titanium, nickel and copper alloys. Blue is a cooler and red a hotter
gas mixture.
13-7
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Summary of shielding gases and mixtures used for different base materials
for MIG/MAG welding
Shielding Reaction
Metal Characteristics
gas behaviour
Carbon Argon-CO2 Slightly Increasing CO2 content gives hotter arc,
steel oxidising improved arc stability, deeper penetration,
transition from finger-type to bowl-shaped
penetration profile, more fluid weld pool giving
flatter weld bead with good wetting, increased
spatter levels, better toughness than CO2.
Minimum 80% argon for axial spray transfer.
General purpose mixture: Argon-10-15%CO2.
Argon-O2 Slightly Stiffer arc than Ar-CO2 mixtures minimises
oxidising undercutting, suited to spray transfer mode,
lower penetration than Ar-CO2 mixtures, finger-
type weld bead penetration at high current
levels. General purpose mixture: Argon-3%
CO2.
Ar-He-CO2 Slightly Substituting of helium for argon gives hotter arc,
oxidising higher arc voltage, more fluid weld pool, flatter
bead profile, more bowl-shaped and deeper
penetration profile and higher welding speeds,
compared with Ar-CO2 mixtures. High cost.
CO2 Oxidising Arc voltages 2-3V higher than Ar-CO2 mixtures,
best penetration, higher welding speeds, dip
transfer or buried arc technique only, narrow
working range, high spatter levels, low cost.
Stainless He-Ar-CO2 Slightly Good arc stability with minimum effect on
steels oxidising corrosion resistance (carbon pick-up), higher
helium contents designed for dip transfer, lower
helium contents designed for pulse and spray
transfer. General purpose gas: He-Ar-2%CO2.
Argon-O2 Slightly Spray transfer only, minimises undercutting on
oxidising heavier sections, good bead profile.
Aluminium, Argon Inert Good arc stability, low spatter and general-
copper, purpose gas. Titanium alloys require inert gas
nickel, backing and trailing shields to prevent air
titanium contamination.
alloys Ar-He Inert Higher heat input offsets high heat dissipation
on thick sections, lower risk of lack of fusion
defects, higher spatter and higher cost than
argon.
13-8
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Figure 13.8 The effect of travel speed. As travel speed increases, reducing
penetration and width, undercut.
13-9
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Contact tip
Gas nozzle
Contact tip
setback
Electrode Contact
Nozzle-to- extension tip to work
work (stand-
Arc length distance
off) distance
Workpiece
Figure 13.10 Contact tip to workpiece distance; electrode extension and nozzle to
workpiece distance.
Figure 13.11 Effect of increasing the contact tip to workpiece distance. Arc length
remains same length.
13-10
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Increased extension
At short CTWDs, radiated heat from the weld pool can cause overheating of
the contact tube and welding torch which can lead to spatter adherence and
increased wear of the contact tube.
13-11
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Joint access and type should also be considered when selecting the
required gas nozzle and flow rate. Too small a nozzle may cause it to
become obstructed by spatter more quickly and if the wire bends on leaving
the contact tube, the shielding envelope and arc location may not coincide.
Arc Voltage, V
Welding Current, A
Figure 13.14 Arc characteristic curve.
13-12
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
In dip transfer the wire short-circuits the arc 50-200 times/second and this
type of transfer is normally achieved with CO2 or mixtures of CO2 and argon
gas + low amps and welding volts <24V.
Spray transfer occurs at high currents and voltages. Above the transition
current, metal transfer is a fine spray of small droplets projected across the
13-13
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
arc with low spatter levels. The high welding current produces strong
electromagnetic forces (pinch effect) that cause the molten filament
supporting the droplet to neck down. Droplets detach from the tip of the wire
and accelerate across the arc gap. The frequency with which the droplets
detach increases with the current. The droplet size equates to the wire
diameter at the threshold level but decreases significantly as the welding
current increases. At very high currents (wire feed speeds), the molten
droplets can start to rotate (rotating transfer). The arc current is flowing
during the drop detachment resulting in maximum penetration and a high
heat input. When the correct arc voltage to give spray transfer is used, the
arc is short with the wire tip 1-3mm from the surface of the plate.
With steels it can be used only in downhand butts and H/V fillet welds but
gives higher deposition rate, penetration and fusion than dip transfer
because of the continuous arc heating. It is mainly used for steel plate
thicknesses >3mm but has limited use for positional welding due to the
potential large weld pool involved.
Pulsing the welding current extends the range of spray transfer operation
well below the natural transition from dip to spray transfer. This allows
smooth, spatter-free spray transfer at mean currents below the transition
level, eg 50-150A and at lower heat inputs. Pulsing was introduced originally
to control metal transfer by imposing artificial cyclic operation on the arc
system by applying alternately high and low currents.
A typical pulsed waveform and the main pulse welding variables are shown
in Figure 13.17. A low background current (typically 20-80A) is supplied to
maintain the arc, keep the wire tip molten, give stable anode and cathode
roots and maintain average current during the cycle. Droplet detachment
occurs during a high current pulse at current levels above the transition
current level. The pulse of current generates very high electromagnetic
forces which cause a strong pinch effect on the metal filament supporting
the droplet the droplet is detached and projected across the arc gap. Pulse
current and current density must be sufficiently high to ensure that spray
transfer (not globular) always occurs so that positional welding can be used.
Pulse transfer uses pulses of current to fire a single globule of metal across
the arc gap at a frequency of 50-300 pulses/second. It is a development of
13-14
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
spray transfer that gives positional welding capability for steels, combined
with controlled heat input, good fusion and high productivity and may be
used for all sheet steel thickness >1mm, but is mainly used for positional
welding of steels >6mm.
The globular transfer range occupies the transitional range of arc voltage
between free-flight and fully short-circuiting transfer. Irregular droplet
transfer and arc instability are inherent, particularly when operating near the
transition threshold. In globular transfer a molten droplet several times the
electrode diameter forms on the wire tip, gravity eventually detaches it when
its weight overcomes surface tension forces and transfer takes place often
with excessive spatter. Before transfer the arc wanders and its cone covers
a large area, dissipating energy.
There is a short duration short-circuit when the droplet contacts with the
molten pool but rather than causing droplet transfer it occurs as a result of it.
Although the short-circuit is of very short duration, some inductance is
necessary to reduce spatter, although to the operator the short-circuits are
not discernible and the arc has the appearance of a free-flight type.
13-15
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
13.2.9 Inductance
When MIG/MAG welding in the dip transfer mode, the welding electrode
touches the weld pool causing a short-circuit during which the arc voltage is
nearly zero. If the constant voltage power supply responded instantly, very
high current would immediately begin to flow through the welding circuit and
the rapid rise in current to a high value would melt the short-circuited
electrode free with explosive force, dispelling the weld metal and causing
considerable spatter.
Inductance is the property in an electrical circuit that slows down the rate of
current rise (Figure 13.18). The current travelling through an inductance coil
creates a magnetic field which creates a current in the welding circuit in
opposition to the welding current. Increasing inductance will also increase
the arc time and decrease the frequency of short-circuiting.
Current
13-16
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
1
10
9 2
3
7
6
5
13-17
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
2 3
13-18
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
4
5
1 Torch body.
2 On/off or latching switch.
3 Spot welding spacer attachment.
4 Contact tips.
5 Gas diffuser.
6 Gas shrouds.
7 Torch head assembly (minus the shroud).
13-19
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
The higher the level of de-oxidants in the wire, the lower the chance of
porosity in the weld. The quality of the wire winding, copper coating and
temper are also important factors in minimising wire feed problems.
Quality of wire windings and increasing costs
a) Random wound. b) Layer wound. c) Precision layer wound.
Check that the liner is the correct type and size for the wire. One size of liner
generally fits two sizes of wire, ie 0.6 and 0.8, 1 and 1.2, 1.4 and 1.6mm
diameter. Steel liners are used for steel wires and Teflon for aluminium
wires.
13.4.5 Connections
The electric arc length in MIG/MAG welding is controlled by the voltage
settings, achieved by using a constant voltage volt/amp characteristic inside
the equipment. Any poor connection in the welding circuit will affect the
nature and stability of the electric arc so is a major inspection point.
13-20
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
The cored wire consists of a metal sheath containing a granular flux which
can contain elements normally used in MMA electrodes so the process has
a very wide range of applications.
Most wires are sealed mechanically and hermetically with various forms of
joint. The effectiveness of the were joint is an inspection point of cored wire
welding as moisture can easily be absorbed into a damaged or poor seam.
Baking of cored wires is ineffective and will not restore the condition of a
contaminated flux within a wire.
13-21
www.twitraining.com
Rev 2 April 2013
MIG/MAG Welding
Copyright TWI Ltd 2013
Note: Unlike MMA electrodes the potential hydrogen levels and mechanical
properties of welds with rutile wires can equal those of the basic types.
Advantages Disadvantages
High productivity Lack of fusion (dip transfer)
Easily automated Small range of consumables
All positional (dip, pulse and FCAW) Protection for site working
Material thickness range Complex equipment
Continuous electrode High ozone levels
13-22
www.twitraining.com
Section 14
Weld Pool
Consumable
electrode Flux Feed
Weld Metal
Arc Parent Material
Slag
Submerged arc welding is able to use where high weld currents (owing to
the properties and functions of the flux) which give deep penetration and
high deposition rates. Generally DC+ve is used up to about 1000A because
it produces deep penetration. On some applications (ie cladding operations)
DC-ve is needed to reduce penetration and dilution. At higher currents or
with multiple electrode systems, AC is often preferred to avoid arc blow
(when used with multiple electrode systems, DC+ve is used for the lead arc
and AC for the trail arc).
14-1
www.twitraining.com
Rev 2 April 2013
Submerged Arc Welding
Copyright TWI Ltd 2013
(A.C.)
Materials joined
Welding of carbon steels.
Welding low alloy steels (eg fine grained and creep resisting).
Welding stainless steels.
Welding nickel alloys.
Cladding to base metals to improve wear and corrosion resistance.
14.2 Fluxes
Flux is granular mineral compounds mixed to various formulations.
Type of fluxes
Fused Agglomerated
14-2
www.twitraining.com
Rev 2 April 2013
Submerged Arc Welding
Copyright TWI Ltd 2013
Fused fluxes are produced by the constituents being dry mixed, melted in an
electric furnace then granulated by pouring the molten mixture into water or
on to an ice block. Subsequently these particles are crushed and screened
to yield a uniform glass-like product.
Welding current.
Type of flux and particle distribution.
Arc voltage.
Travel speed.
Electrode size.
Electrode extension.
Type of electrode.
Width and depth of the layer of flux.
14-3
www.twitraining.com
Rev 2 April 2013
Submerged Arc Welding
Copyright TWI Ltd 2013
Welding current effect on weld profile (2.4mm electrode diameter, 35V arc voltage
and 61cm/min travel speed).
Arc voltage effect on weld profile 2.4mm electrode diameter, 500A welding
current and 61cm/min travel speed.
Increasing the arc voltage with constant current and travel speed will:
14-4
www.twitraining.com
Rev 2 April 2013
Submerged Arc Welding
Copyright TWI Ltd 2013
Reducing the arc voltage with constant current and travel speed will produce
a stiffer arc which improves penetration in a deep weld groove and resists
arc blow.
Deposition rate
At any given amperage setting, a small diameter electrode will have a
higher current density and deposition rate of molten metal than a larger
diameter electrode. However, a larger diameter electrode can carry more
current than a smaller one, so can ultimately produce a higher deposition
rate at higher amperage.
14-5
www.twitraining.com
Rev 2 April 2013
Submerged Arc Welding
Copyright TWI Ltd 2013
14-6
www.twitraining.com
Rev 2 April 2013
Submerged Arc Welding
Copyright TWI Ltd 2013
14-7
www.twitraining.com
Section 15
Heating flame
Slag jet
Oxy-fuel cutting.
These conditions are fulfilled by carbon steels and some low alloy steels.
However, the oxides of many of the alloying elements in steels, such as
aluminium and chromium have melting points higher than those of iron
oxides. These high melting point oxides (which are refractory in nature!)
may shield the material in the kerf so that fresh iron is not continuously
exposed to the cutting oxygen stream, leading to a decrease of the cutting
speed and ultimately an unstable process. In practice the process is
15-1
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
Advantages
Steels can generally be cut faster than by most machining methods.
Section shapes and thicknesses difficult to produce by mechanical
means can be cut economically.
Basic equipment costs are low compared with machine tools.
Manual equipment is very portable so can be used on site.
Cutting direction can be changed rapidly on a small radius.
Large plates can be cut rapidly in place by moving the torch rather than
the plate.
Economical method of plate edge preparation.
Disadvantages
Dimensional tolerances significantly poorer than machine tool
capabilities.
Process essentially limited to cutting carbon and low alloy steels.
Preheat flame and expelled red hot slag present fire and burn hazards to
plant and personnel.
Fuel combustion and oxidation of the metal require proper fume control
and adequate ventilation.
Hardenable steels may require pre and/or post-heat adjacent to the cut
edges to control their metallurgical structures and mechanical properties.
Special process modifications are needed for cutting high alloy steels
and cast irons (ie iron powder or flux addition).
Being a thermal process, expansion and shrinkage of the components
during and after cutting must be taken into account.
The preheating flame has the following functions in the cutting operation:
15-2
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
Preheating time.
Effect on cutting speed and productivity.
Cost and availability.
Volume of oxygen required per volume of fuel gas to obtain a neutral
flame.
Safety in transporting and handling.
Some of the more common fuel gases used are acetylene, natural gas
(methane), propane, propylene and methylacetylene propadiene (MAPP)
gas.
15-3
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
The face of a satisfactory cut has a sharp top edge, drag lines, which are
fine and even, little oxide and a sharp bottom edge. Underside is free of
slag.
A satisfactory cut is shown in the centre. If the cut is too slow (left) the top
edge is melted, there are deep grooves in the lower portion of the face,
scaling is heavy and the bottom edge may be rough, with adherent dross. If
the cut is too fast (right) the appearance is similar, with an irregular cut
edge. Plate thickness 12mm.
With a very fast travel speed the drag lines are coarse and at an angle to
the surface with an excessive amount of slag sticking to the bottom edge of
the plate, due to the oxygen jet trailing with insufficient oxygen reaching the
bottom of the cut.
15-4
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
A satisfactory cut is shown in the centre. If the preheating flame is too low
(left) the most noticeable effect on the cut edge is deep gouges in the lower
part of the cut face. If the preheating flame is too high (right) the top edge is
melted, the cut irregular and there is an excess of adherent dross. Plate
thickness 12mm.
A satisfactory cut is shown in the centre. If the blowpipe nozzle is too high
above the work (left) excessive melting of the top edge occurs with much
oxide. If the torch travel speed is irregular (right) uneven spacing of the drag
lines can be observed together with an irregular bottom surface and
adherent oxide. Plate thickness 12mm.
15-5
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
Advantages
Not limited to materials which are electrical conductors so is widely used
for cutting all types of stainless steels, non-ferrous materials and non-
electrical conductive materials.
Operates at a much higher energy level compared with oxy-fuel cutting
resulting in faster cutting speeds.
Instant start-up is particularly advantageous for interrupted cutting as it
allows cutting without preheat.
Disadvantages
Dimensional tolerances significantly poorer than machine tool
capabilities.
Introduces hazards such as fire, electric shock (due to the high OCV),
intense light, fumes, gases and noise levels that may not be present with
other processes. However, in underwater cutting the level of fumes, UV
radiation and noise are reduced to a low level.
Compared with oxy-fuel cutting, plasma arc cutting equipment tends to
be more expensive and requires a fairly large amount of electric power.
Being a thermal process, expansion and shrinkage of the components
during and after cutting must be taken into consideration.
Cut edges slightly tapered.
15-6
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
a) b)
15-7
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
Advantages
Approximately five times faster than chipping.
Easily controllable, removes defects with precision as they are clearly
visible and may be followed with ease. The depth of cut is easily
regulated and slag does not deflect or hamper the cutting action.
Low equipment cost no gas cylinders or regulators necessary except on-
site.
Economical to operate as no oxygen or fuel gas required. The welder
may also do the gouging (no qualification requirements for this
operation).
Easy to operate as the equipment is similar to MMA except the torch and
air supply hose.
Compact with the torch not much larger than an MMA electrode holder,
allowing work in confined areas.
Versatile.
Can be automated.
Disadvantages
Other cutting processes usually produce a better and quicker cut.
Requires a large volume of compressed air.
Increases the carbon content leading to an increase in hardness in of
cast iron and hardenable metals. In stainless steels it can lead to carbide
precipitation and sensitisation so grinding the carbide layer usually
follows arc air gouging.
Introduces hazards such as fire (due to discharge of sparks and molten
metal), fumes, noise and intense light.
15-8
www.twitraining.com
Rev 2 April 2013
Thermal Cutting Processes
Copyright TWI Ltd 2013
When correctly applied, MMA gouging can produce relatively clean gouged
surfaces. For general applications, welding can be carried out without the
need to dress by grinding, however when gouging stainless steel, a thin
layer of higher carbon content material will be produced which should be
removed by grinding.
15-9
www.twitraining.com
Section 16
Welding Consumables
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
16 Welding Consumables
Welding consumables are defined as all that is used up during the
production of a weld.
This list could include all things used up in the production of a weld;
however, we normally refer to welding consumables as those items used up
by a particular welding process.
These are:
SAW
FUSED
Flux
Size.
Type or specification.
Condition.
Storage.
16-1
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Electrodes for MMA/SMAW are grouped by the main constituent in their flux
coating, which in turn has a major effect on the weld properties and ease of
use. The common groups are:
Some basic electrodes may be tipped with a carbon compound which eases
arc ignition.
16-2
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
16-3
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Mandatory
designation:
Covered electrode
Minimum
yield strength
Charpy V notch
minimum test
temperature C
Chemical composition
Electrode covering
Optional designation:
Positional designation
Diffusible hydrogen
ml/100g weld metal
16-4
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Mandatory
designation:
Covered electrode
Minimum
tensile strength
Electrode covering
Chemical composition
Heat treatment
condition
Optional designation:
Optional supplemental
impact test at 47Jat
same test temperature
given for 27J test
Diffusible hydrogen
ml/100g weld metal
16-5
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Method A
Minimum yield Tensile strength, Minimum E% b,
Symbol N/mm2 N/mm2 N/mm2
35 355 440-570 22
38 380 470-600 20
42 420 500-640 20
46 460 530-680 20
50 500 560-720 18
Lower yield Rel shall be used. b Gauge length = 5 x
Method B
Symbol Minimum tensile strength, N/mm2
43 430
49 490
55 550
57 570
Method A
Symbol Temperature for the minimum
average impact energy of 47J
Z No requirement
A +20
0 0
2 -20
3 -30
4 -40
5 -50
6 -60
Method B
Impact or Charpy V notch testing temperature at 27J temperature in
method B is determined through the classification of tensile strength,
electrode covering and alloying elements (Table 8B) ie E 55 16-N7 which
must reach 27J at 75C.
16-6
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Method A
Uses an alpha/numerical designation from the tables as listed below:
Method B
This method uses a numerical designation from the table as listed
below
16-7
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Hydrogen scales
Diffusible hydrogen is indicated in the same way in both methods, where
after baking the amount of hydrogen is given as ml/100g weld metal ie H 5
= 5ml/100g weld metal.
16-8
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
C Electrode coating and electrical characteristic D AWS A5.5 low alloy steels
Code Coating Current type Symbol Approximate alloy deposit
A1 0.5%Mo
Exx10 Cellulosic/organic DC + only
B1 0.5%Cr + 0.5%Mo
Exx11 Cellulosic/organic AC or DC+ B2 1.25%Cr + 0.5%Mo
Exx12 Rutile AC or DC- B3 2.25%Cr + 1.0%Mo
Exx13 Rutile + 30% Fe powder AC or DC+/- B4 2.0%Cr+ 0.5%Mo
Exx14 Rutile AC or DC+/- B5 0.5%Cr + 1.0%Mo
Exx15 Basic DC + only C1 2.5%Ni
Exx16 Basic AC or DC+ C2 3.25%Ni
Exx18 Basic + 25% Fe powder AC or DC+ 1%Ni + 0.35%Mo +
Exx20 High Fe oxide content AC or DC+/- C3
0.15%Cr
Exx24 Rutile + 50% Fe powder AC or DC+/- D1/2 0.25-0.45%Mo + 0.15%Cr
Exx27 Mineral + 50% Fe powder AC or DC+/- 0.5%Ni or/and 0.3%Cr
Exx28 Basic + 50% Fe powder AC or DC+ G or/and 0.2%Mo or/and
0.1%V
For G only 1 element is required
16-9
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Type (specification)
Correct specification/code
E 46 3 INi
Checks should also be made to ensure that basic electrodes have been
through the correct pre-use procedure. Having been baked to the correct
temperature (typically 300-350C) for 1 hour then held in a holding oven
(150C max) basic electrodes are issued to welders in heated quivers.
Most electrode flux coatings deteriorate rapidly when damp so care must be
taken to inspect storage facilities to ensure they are adequately dry and that
all electrodes are stored in controlled humidity.
Vacuum packed electrodes may be used directly from the carton only if the
vacuum has been maintained. Directions for hydrogen control are always
given on the carton and should be strictly adhered to. The cost of each
electrode is insignificant compared with the cost of any repair, so basic
electrodes left in the heated quiver after the days shift may be rebaked but
would normally be discarded to avoid the risk of H2 induced problems.
16-10
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
16-11
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
The main purpose of the copper coating of steel MIG/MAG welding wire is to
maximise current pick-up at the contact tip and reduce the level of
coefficient of friction in the liner with protection against the effects of
corrosion being secondary.
Wires are available that have not been copper coated as copper flaking in
the liner can cause many wire feed problems. These wires may be coated in
a graphite compound, which again increases current pick-up and reduces
friction in the liner. Some wires, including many cored wires, are nickel
coated.
Wires are available from 0.6-1.6mm diameter with finer wires available on a
1kg reel, though most are supplied on a 15kg drum.
Argon + MAG Spray or pulse welding Active additive gives good fluidity
1-2% O2 or of austenitic or ferritic to the molten stainless and
CO2 stainless steels only improves toe blend.
Electrode wires for welding other alloy steels are generally graded by
chemical composition in a table in a similar way to MIG and TIG electrode
wires. Fluxes for SAW are graded by their manufacture and composition of
which there are two normal methods, fused and agglomerated.
16-12
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
Fused fluxes
Mixed together and baked at a very high temperature (>1,000C) so all the
components fuse. When cooled the resultant mass resembles a sheet of
coloured glass, which is then pulverised into small particles.
Agglomerated fluxes
A mixture of compounds baked at a much lower temperature and bonded
together by bonding agents into small particles. They are dull, generally
round granules that are friable (easily crushed) and can also be coloured.
Many agents and compounds may be added during manufacture unlike the
fused fluxes. Agglomerated fluxes tend to be of the basic type and produce
weld metal of an improved quality in terms of strength and toughness, at the
expense of usability they are much less tolerant of poor surface conditions
and generally produce a slag much more difficult to detach and remove.
16-13
www.twitraining.com
Rev 2 April 2013
Welding Consumables
Copyright TWI Ltd 2013
The weld metal properties result from using a particular wire with a particular
flux in a particular weld sequence so the grading of SAW consumables is
given as a function of a wire/flux combination and welding sequence.
Tensile strength.
Elongation, %.
Toughness, Joules.
Toughness testing temperature.
All consumables for SAW (wires and fluxes) should be stored in a dry,
humid-free atmosphere. The flux manufacturers handling/storage
instruction and conditions must be very strictly followed to minimise any
moisture pick-up. Any re-use of fluxes is totally dependent on applicable
clauses within the application standard.
16-14
www.twitraining.com
Section 17
Weldability of Steels
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
17 Weldability of Steels
17.1 Introduction
Weldability simply means the ability to be welded and many types of
weldable steel have been developed for a wide range of applications.
The ease or difficulty of making a weld with suitable properties and free from
defects determines whether steels are considered as having good or poor
weldability. A steel is usually said to have poor weldability if it is necessary
to take special precautions to avoid a particular type of imperfection.
Another reason for poor weldability may be the need to weld within a very
narrow range of parameters to achieve properties required for the joint.
WPSs give welding conditions that do not cause cracking but achieve
the specified properties.
Welders work strictly in accordance with the specified welding
conditions.
Welding inspectors regularly monitor welders to ensure they are working
strictly in accordance with the WPSs.
17-1
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Cold cracking Cracks occur when the weld has cooled down.
HAZ cracking Cracks occur mainly in the HAZ.
Delayed cracking Cracks may occur some time after welding has
finished (possibly up to ~72h).
Underbead cracking Cracks occur in the HAZ beneath a weld bead.
Although most hydrogen cracks occur in the HAZ, there are circumstances
when they may form in weld metal.
Figure 17.2 Hydrogen induced cold crack that initiated at the HAZ at the toe of a
fillet weld.
17-2
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Because H atoms are very small they can move about (diffuse) in solid steel
and while weld metal is hot can diffuse to the weld surface and escape into
the atmosphere.
17-3
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Methods to minimise the influence of each of the four factors are considered
in the following sub-sections.
Hydrogen
The main source of hydrogen is moisture (H2O) and the principal source is
being welding flux. Some fluxes contain cellulose and this can be a very
active source of hydrogen.
Welding processes that do not require flux can be regarded as low hydrogen
processes.
Other sources of hydrogen are moisture present in rust or scale and oils and
greases (hydrocarbons).
Tensile stress
There are always tensile stresses acting on a weld because there are
always residual stresses from welding.
17-4
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
The only practical ways of reducing the influence of residual stresses may
be by:
These measures are particularly important when welding some low alloy
steels that are particularly sensitive to hydrogen cracking.
For C and C-Mn steels a formula has been developed to assess how the
chemical composition will influence the tendency for significant HAZ
hardening the carbon equivalent value (CEV) formula.
The CEV formula most widely used (and adopted by IIW) is:
% Mn %Cr % Mo %V % Ni %Cu
CEVIIW %C
6 5 15
17-5
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
The element with most influence on HAZ hardness is carbon. The faster the
rate of HAZ cooling after each weld run, the greater the tendency for
hardening.
Procuring steel with a CEV at the low end of the range for the steel
grade (limited scope of effectiveness).
Using moderate welding heat input so that the weld does not cool quickly
and give HAZ hardening.
Applying preheat so that the HAZ cools more slowly and does not show
significant HAZ hardening; in multi-run welds maintain a specific
interpass temperature.
The CEV formula is not applicable to low alloy steels, with additions of
elements such as Cr, Mo and V. The HAZ of these steels will always tend to
be relatively hard regardless of heat input and preheat and so this is a factor
that cannot be effectively controlled to reduce the risk of H cracking. This is
why some of the low alloy steels have a greater tendency to show hydrogen
cracking than in weldable C and C-Mn steels which enable HAZ hardness to
be controlled.
17-6
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Transverse
cracks
Y
a)
b)
Figure 17. 3:
a) Plan view of a plate butt weld showing subsurface transverse cracks;
b) Longitudinal section X-Y of the above weld showing how the transverse cracks
lie at 45o to the surface. They tend to remain within an individual weld run and may
be in weld several layers.
17-7
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Their appearance in this orientation gives the name chevron cracks (arrow-
shaped cracks). There are no well defined rules for avoiding weld metal
hydrogen cracks apart from:
17-8
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
a)
b)
Figure 17.4:
a) Solidification crack at the weld centre where columnar dendrites have trapped
some lower melting point liquid;
b) The weld bead does not have an ideal shape but has solidified without the
dendrites meeting end-on and trapping lower melting point liquid thereby resisting
solidification cracking.
17-9
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Sulphur and copper can make steel weld metal sensitive to solidification
cracking if present in the weld at relatively high levels. Sulphur
contamination may lead to the formation of iron sulphides that remain liquid
when the bead has cooled down as low as ~980C, whereas bead
solidification started above 1400C.
Figure 17.5 shows a weld bead that has solidified under unfavourable
welding conditions associated with centreline solidification cracking.
17-10
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
D W/D1:2
Direc tion o
direction off
ttravel
ravel
The weld bead has a cross-section that is quite deep and narrow a width-
to-depth ratio greater than 1:2 and the solidifying dendrites have pushed the
lower melting point liquid to the centre of the bead where it has become
trapped. Since the surrounding material is shrinking as a result of cooling,
this film would be subjected to tensile stress, which leads to cracking.
In contrast, Figure 17.6 shows a bead with a width-to-depth ratio less than
1:2. This bead shape shows lower melting point liquid pushed ahead of the
solidifying dendrites but it does not become trapped at the bead centre,
thus, even under tensile stresses resulting from cooling, this film is self-
healing and cracking avoided.
Direction
of travel
Figure 17.6 Weld bead with favourable width-to-depth ratio. The dendrites push
the lowest melting point metal towards the surface at the centre of the bead centre
so it does not form a weak central zone.
SAW and spray-transfer GMA are the arc welding processes most likely to
give weld beads with an unfavourable width-to-depth ratio. Also, electron
17-11
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
beam and laser welding processes are extremely sensitive to this kind of
cracking as a result of the deep, narrow beads produced.
TIG welding when using a current slope-out device so that the current
and weld pool depth gradually reduce before the arc is extinguished
(gives more favourable weld bead width-to-depth ratio). It is also a
common practice to backtrack the bead slightly before breaking the arc
or lengthen the arc gradually to avoid the crater cracks.
Modify weld pool solidification mode by feeding the filler wire into the
pool until solidification is almost complete and avoiding a concave crater.
17-12
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Fusion
boundary
HAZ
Crack propagation by
tearing of ligaments between
Through-thickness De-cohesion of de-cohesion inclusion stringers
- inclusion stringers
residual stresses
from welding
Inclusion
stringer
Figure 17.7
a)Typical lamellar tear located just outside the visible HAZ;
b) Step-like crack a characteristic of a lamellar tear.
17-13
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
17-14
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Plate surface
Through-
thickness
tensile test
piece
Reduction of
diameter at
point of
fracture
Plate surface
Figure 17.8 Round tensile test piece taken with its axis in the short-transverse
direction (through-thickness of plate) to measure the %R of A and assess
resistance to lamellar tearing.
Using clean steel that has low sulphur content (<~0.015%) and
consequently relatively few inclusions.
Procuring steel plate that has been subjected to through-thickness
tensile testing to demonstrate good through-thickness ductility (as
EN 10164).
Through-thickness stress
Through-thickness stress in T, K and Y joints is principally the residual
stress from welding, although the additional service stress may have some
influence.
17-15
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Figure 17.9 Reducing the effective size of a weld will reduce the through-thickness
stress on the susceptible plate and may be sufficient to reduce the risk of lamellar
tearing.
susceptible plate
Susceptible plate extruded section
Extruded section
Figure 17.10 Lamellar tearing can be avoided by changing the joint design.
17-16
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Weld metal
buttering
Susceptible plate
Figure 17.11 Two layers of weld metal applied usually by MMA to susceptible plate
before the T butt is made.
Appearance
Called weld decay because a narrow zone in the HAZ can be severely
corroded but surrounding areas (weld and parent metal) may not be
affected.
Sensitive HAZ.
Corrosive liquid in contact with the sensitive HAZ, in service.
17-17
www.twitraining.com
Rev 2 April 2013
Weldability of Steels
Copyright TWI Ltd 2013
Service environment
Corrosion of HAZ determined by service conditions, type of chemicals
and temperature.
Problem not solved by trying to address service conditions but by
selection of material, taking account of effects of welding/welding
parameters.
Chromium migrates to
the site of growing
17-18
www.twitraining.com
Section 18
Weld Repairs
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
18 Weld Repairs
18.1 Two specific areas
Production.
In-service.
The reasons for making a repair are many and varied, from the removal of
weld defects induced during manufacture to a quick and temporary running-
repair to an item of production plant. The subject of welding repairs is also
wide and varied and often confused with maintenance and refurbishment
where the work can be scheduled.
A number of key factors need to be considered before any repair, the most
important being it is financially worthwhile. Before this judgement can be
made, the fabricator needs to answer the following questions:
18-1
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
Detailed assessment to find out the extremity of the defect possibly using
a surface or sub-surface NDT method.
Cleaning the repair area (removal of paint grease, etc).
Once established the excavation site must be clearly identified and
marked out.
An excavation procedure may be required (method used ie grinding,
arc/air gouging, preheat requirements, etc).
NDT to locate the defect and confirm its removal.
A welding repair procedure/method statement with the appropriate
(suitable for the alloys being repaired and may not apply in specific
situations.) welding process, consumable, technique, controlled heat
input and interpass temperatures, etc will need to be approved.
Use of approved welders.
Dressing the weld and final visual.
NDT procedure/technique prepared and carried out to ensure that the
defect has been successfully removed and repaired.
Any post repair heat treatment requirements.
Final NDT procedure/technique prepared and carried out after heat
treatment requirements.
Applying protective treatments (painting, etc as required).
Production repairs
Repairs are usually identified during production inspection. Evaluation of the
reports is by the Welding Inspector or NDT operator. Discontinuities in the
welds are only classed as defects when they are outside the range
permitted by the applied code or standard.
Analysis
As this defect is surface-breaking and at the fusion face the problem could
be cracking or lack of sidewall fusion. The former may be to do with the
material or welding procedure, if it is done the latter can be apportioned to
the welders lack of skill.
18-2
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
Assessment
As the defect is open to the surface, magnetic particle inspection (MPI) or
dye penetrant inspection (DPI) may be used to gauge the length of the
defect and ultrasonic testing (UT) to gauge the depth.
Excavation
If a thermal method of excavation is to be used, ie arc/air gouging it may be
a requirement to qualify a procedure as the heat generated may affect the
metallurgical structure, resulting in the risk of cracking in the weld or parent
material.
18-3
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
18-4
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
Confirmation of excavation
NDT must confirm that the defect has been completely excavated from the
area.
18-5
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
In-service repairs
Most in-service repairs are very complex as the component is likely to be in
a different welding position and condition than during production. It may
have been in contact with toxic or combustible fluids so a permit to work will
be needed prior to any work. The repair welding procedure may look very
different to the original production procedure due to changes.
Other factors may be taken into consideration such as the effect of heat on
surrounding areas of the component, ie electrical components, or materials
that may be damaged by the repair procedure. This may also include
difficulty in carrying out any required pre- or post-welding heat treatments
and a possible restriction of access to the area to be repaired. For large
fabrications it is likely that the repair must also take place on-site without a
shutdown of operations which may bring other considerations.
Joining technologies often play a vital role in the repair and maintenance of
structures. Parts can be replaced, worn or corroded parts can be built up
and cracks repaired.
In many instances, the Standard or Code used to design the structure will
define the type of repair that can be carried out and give guidance on the
methods to be followed. Standards imply that when designing or
manufacturing a new product it is important to consider a maintenance
regime and repair procedures. Repairs may be required during manufacture
and this situation should also be considered.
Normally there is more than one way of making a repair, for example, cracks
in cast iron might be held together or repaired by pinning, bolting, riveting,
welding or brazing. The choice will depend on factors such as the reason for
failure, material composition and cleanliness, environment and the size and
shape of the component.
18-6
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
It is very important that repair and maintenance welding are not regarded
as activities which are simple or straightforward. A repair may seem
undemanding but getting it wrong can result catastrophic failure with
disastrous consequences.
The small cost of analysis could prevent a valuable component being ruined
by ill-prepared repairs or save money by reducing or avoiding the need for
preheat if the composition is leaner than expected. Once the composition is
known, a welding procedure can be devised.
18-7
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
Is PWHT practicable?
Although desirable, PWHT may not be possible for the same reasons
preheating is not. For large structures local PWHT may be possible but care
should be taken to abide by the relevant codes because it is easy to
introduce new residual stresses by improperly executed PWHT.
Is PWHT necessary?
PWHT may be needed for several reasons and the reason must be known
before considering whether it can be avoided.
18-8
www.twitraining.com
Rev 2 April 2013
Weld Repairs
Copyright TWI Ltd 2013
For all repair welds it is vital to ensure that welders are properly motivated
and carefully supervised.
As-welded repairs
Repair without PWHT is, normal where the original weld was not heat
treated but some alloy steels and many thick-sectioned components require
PWHT to maintain a reasonable level of toughness, corrosion resistance,
etc. However, PWHT of components in-service is not always easy or even
possible and local PWHT may cause more problems than it solves except in
simple structures.
18-9
www.twitraining.com
Section 19
As long as these stresses are above the yield point of the metal at the
prevailing temperature, they continue to produce permanent deformation,
but in so doing are relieved and fall to yield-stress level so cease to cause
further distortion. But, if at this point we could release the weld from the
plate by cutting along the joint line, it would shrink further because, even
when distortion has stopped, the weld contains an elastic strain equivalent
to the yield stress. Visualise the completed joint as weld metal being
stretched elastically between two plates.
a)
b) c)
The stresses left in the joint after welding are referred to as residual
stresses. From the above it can be seen there will be both longitudinal and
transverse stresses (in the case of a very thick plate there is a through-
thickness component of residual stress as well).
19-1
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Tension
Compression
In longitudinal stresses the weld and some of the plate which has been
heated are at or near yield-stress level. Moving out into the plate from the
HAZ, the stresses first fall to zero (the tensile stress region extends beyond
the weld and HAZ into the parent plate) and beyond this there is a region of
compressive stress. The width of the band where tensile residual stresses
are present depends on the heat input during welding, the higher the heat
input the wider the band where these tensile residual stresses occur.
19-2
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Tension Compression
All fusion welds which have not been subjected to postweld treatments, the
vast majority of welded joints, contain residual stresses. Procedures
developed to minimise distortion may alter the distribution of the residual
stresses but do not eliminate them or even reduce their peak level.
19-3
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
19-4
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
8 Material properties.
9 Amount of restraint.
10 Joint design.
11 Fit-up.
12 Welding sequence.
The magnitude of thermal stresses induced into the material can be seen by
the volume change in the weld area on solidification and subsequent cooling
to room temperature. For example, when welding C-Mn steel, the molten
weld metal volume will be reduced by approximately 3% on solidification
and the volume of the solidified weld metal/HAZ will be reduced by a further
7% as its temperature falls from the melting point of steel to room
temperature.
19-5
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
For example, in a single V butt weld, the first weld run produces longitudinal
and transverse shrinkage and rotation. The second run causes the plates to
rotate using the first weld deposit as a fulcrum so balanced welding in a
double-sided V butt joint can produce uniform contraction and prevent
angular distortion.
Longitudinal bowing in welded plates happens when the weld centre is not
coincident with the neutral axis of the section so that longitudinal shrinkage
in the welds bends the section into a curved shape. Clad plate tends to bow
in two directions due to longitudinal and transverse shrinkage of the
cladding, producing a dished shape.
19-6
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
19.4.2 Restraint
If a component is welded without any external restraint, it distorts to relieve
the welding stresses. Methods of restraint such as strongbacks in butt
welds, can prevent movement and reduce distortion. Restraint produces
higher levels of residual stress in the material, so there is a greater risk of
cracking in weld metal and HAZ especially in crack-sensitive materials.
19-7
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Pre-setting of parts.
Pre-bending of parts.
Use of restraint.
The technique chosen will be influenced by the size and complexity of the
component or assembly, the cost of any restraining equipment and the need
to limit residual stresses.
19.5.1 Pre-setting
The parts are pre-set and left free to move during welding, see Figure 19.2.
The parts are pre-set by a pre-determined amount so that distortion
occurring during welding is used to achieve overall alignment and
dimensional control.
19-8
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
19.5.2 Pre-bending
Pre-bending or pre-springing parts before welding pre-stresses the
assembly to counteract shrinkage during welding. As shown in Figure 19.3,
pre-bending using strongbacks and wedges can pre-set a seam before
welding to compensate for angular distortion. Releasing the wedges after
welding will allows the parts to move back into alignment.
The figure below shows the diagonal bracings and centre jack used to pre-
bend the fixture, not the component, counteracting the distortion introduced
through out-of-balance welding.
When welding assemblies all the component parts should be held in the
correct position until completion of welding and a suitably balanced
fabrication sequence used to minimise distortion.
19-9
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Welding with restraint will generate additional residual stresses in the weld
which may cause cracking. When welding susceptible materials a suitable
welding sequence and the use of preheating will reduce this risk. Restraint
is relatively simple to apply using clamps, jigs and fixtures.
Flexible clamps
Can be effective in applying restraint but also in setting up and maintaining
the joint gap (can also be used to close a gap that is too wide), Figure
19.4b.
a) b)
c) d)
19-10
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Fully welded (welded on both sides of the joint) strongbacks (Figure 19.4d)
will minimise both angular distortion and transverse shrinkage. As significant
stresses can be generated across the weld which will increase any tendency
for cracking, care should be taken in their use.
Pre-set parts so that welding distortion will achieve overall alignment and
dimensional control with the minimum of residual stress.
Pre-bend joint edges to counteract distortion and achieve alignment and
dimensional control with minimal residual stress.
Apply restraint during welding using jigs and fixtures, flexible clamps,
strongbacks and tack welding but consider the cracking risk which can
be quite significant, especially for fully welded strongbacks.
Use an approved procedure for welding and removal of welds for
restraint techniques which may need preheat to avoid inperfections
forming in the component surface.
Elimination of welding.
Weld placement.
Reducing the volume of weld metal.
Reducing the number of runs.
Use of balanced welding.
19-11
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
If possible the design should use intermittent welds rather than a continuous
run to reduce the amount of welding. For example in attaching stiffening
plates, a substantial reduction in the amount of welding can often be
achieved whilst maintaining adequate strength.
Figure 19.6 Distortion may be reduced by placing the welds around the neutral
axis.
As most welds are deposited away from the neutral axis, distortion can be
minimised by designing the fabrication so the shrinkage forces of an
individual weld are balanced by placing another weld on the opposite side
of the neutral axis. Where possible welding should be carried out alternately
on opposite sides instead of completing one side first. In large structures if
distortion is occurring preferentially on one side it may be possible to take
corrective action, for example, by increasing welding on the other side to
control the overall distortion.
19-12
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Figure 19.7 Reducing the amount of angular distortion and lateral shrinkage.
Joint preparation angle and root gap should be minimised providing the weld
can be made satisfactorily. To facilitate access it may be possible to specify
a larger root gap and smaller preparation angle. By reducing the difference
in the amount of weld metal at the root and face of the weld the degree of
angular distortion will be correspondingly reduced. Butt joints made in a
single pass using deep penetration have little angular distortion, especially if
a closed butt joint can be welded (Figure 19.7). For example thin section
material can be welded using plasma and laser welding processes and thick
section can be welded in the vertical position using electrogas and
electroslag processes. Although angular distortion can be eliminated there
will still be longitudinal and transverse shrinkage.
19-13
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Completing the joint with a small number of large weld deposits results in
more longitudinal and transverse shrinkage than using in a larger number of
small passes. In a multi-pass weld, previously deposited weld metal
provides restraint, so the angular distortion per pass decreases as the weld
is built up. Large deposits also increase the risk of elastic buckling
particularly in thin section plate.
If welding alternately on either side of the joint is not possible or if one side
has to be completed first, an asymmetrical joint preparation may be used
with more weld metal being deposited on the second side. The greater
contraction resulting from depositing the weld metal on the second side will
help counteract the distortion on the first side.
19-14
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Adopting best practice principles can have cost benefits. For example, for a
design fillet leg length of 6mm, depositing an 8mm leg length will result in
the deposition of 57% additional weld metal. Besides the extra cost of
depositing weld metal and the increased risk of distortion, it is costly to
remove this extra weld metal later. Designing for distortion control may incur
additional fabrication costs, for example, the use of a double V joint
preparation is an excellent way to reduce weld volume and control distortion
but extra costs may be incurred in production through manipulation of the
workpiece for the welder to access the reverse side.
Tack welding.
Back-to-back assembly.
Stiffening.
Tack welding
Ideal for setting and maintaining the joint gap but can also be used to resist
transverse shrinkage. To be effective, thought should be given to the
number of tack welds, their length and the distance between them. Too few
risks the joint progressively closing up as welding proceeds. In a long seam
using MMA or MIG/MAG the joint edges may even overlap. When using the
submerged arc process the joint might open up if not adequately tacked.
19-15
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Figure 19.9 Alternative procedures used for tack welding to prevent transverse
shrinkage.
Directional tacking is useful for controlling the joint gap, for example closing
a joint gap which is or has become too wide.
When tack welding it is important that tacks to be fused into the main weld
are produced to an approved procedure using appropriately qualified
welders. The procedure may require preheat and an approved consumable
as specified for the main weld. Removal of the tacks also needs careful
control to avoid causing defects in the component surface.
Back-to-back assembly
By tack welding or clamping two identical components back-to-back,
welding of both components can be balanced around the neutral axis of the
combined assembly (see Figure 19.10a). It is recommended that the
assembly is stress-relieved before separating the components or it may be
necessary to insert wedges between the components (Figure 19.10b) so
when the wedges are removed the parts will move back to the correct shape
or alignment.
19-16
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Stiffening
Figure 19.11 Longitudinal stiffeners prevent bowing in butt welded thin plate joints.
Welding process
General rules for selecting a welding process to prevent angular distortion:
19-17
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Welding technique
General rules for preventing distortion are:
Figure 19.12 Angular distortion of the joint as determined by the number of runs in
the fillet weld.
Without restraint angular distortion in both fillet and butt joints is due to joint
geometry, weld size and the number of runs for a given cross-section.
Angular distortion, measured in degrees as a function of the number of runs
for a 10mm leg length fillet weld is shown.
If possible, balanced welding around the neutral axis should be done, for
example on double-sided fillet joints, by two people welding simultaneously.
In butt joints, the run order may be crucial as balanced welding can be used
to correct angular distortion as it develops.
19-18
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Welding sequence
The welding sequence or direction is important and should be towards the
free end of the joint. For long welds the whole of the weld is not completed
in one direction. Short runs, for example using the back-step or skip welding
technique, are very effective in distortion control (Figure 19.13).
19-19
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
19-20
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Use packing pieces which will over-correct the distortion so that the
spring-back will return the component to the correct shape.
Check that the component is adequately supported during pressing to
prevent buckling.
Use a former or rolling to achieve a straight component or produce a
curvature.
As unsecured packing pieces may fly out from the press, the following
safe practices must be adopted:
- Bolt the packing pieces to the platen.
19-21
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
Spot heating
Spot heating is used to remove buckling, for example when a relatively thin
sheet has been welded to a stiff frame. Distortion is corrected by spot
heating on the convex side. If the buckling is regular, the spots can be
arranged symmetrically, starting at the centre of the buckle and working
outwards.
Line heating
Wedge-shaped heating
To correct distortion in larger complex fabrications it may be necessary to
heat whole areas in addition to using line heating. The pattern aims at
shrinking one part of the fabrication to pull the material back into shape.
Apart from spot heating of thin panels, a wedge-shaped heating zone should
be used; Figure 19.18 from base to apex and the temperature profile should
be uniform through the plate thickness. For thicker section material it may
be necessary to use two torches, one on each side of the plate.
19-22
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
a. b.
c.
19-23
www.twitraining.com
Rev 2 April 2013
Residual Stresses and Distortions
Copyright TWI Ltd 2013
General precautions
The dangers of using thermal straightening techniques are over-shrinking
too large an area or causing metallurgical changes by heating to too high a
temperature. When correcting distortion in steels the temperature of the
area should be restricted to approximately 600-650C, dull red heat. If the
heating is interrupted or the heat lost, the operator must allow the metal to
cool then begin again.
19-24
www.twitraining.com
Section 20
Heat Treatment
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
20 Heat Treatment
20.1 Introduction
The heat treatment given to a particular grade of steel by the steelmaker/
supplier should be shown on the material test certificate and may be
referred to as the supply condition.
Applied to
Relatively thin, lower strength C-steel.
Applied to
Relatively thin, high strength low alloy (HSLA) steels and some steels with
good toughness at low temperatures, eg cryogenic steels.
Normalised
After working (rolling or forging) the steel to size, it is heated to ~900C then
allowed to cool in air to ambient temperature; which optimises strength and
toughness and gives uniform properties from item to item for a particular
grade of steel (Figure 20.1).
Applied to
C-Mn steels and some low alloy steels.
20-1 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
Normalising:
Rapid heating to soak temperature (100% austenite)
Short soak time at temperature
Temperature, C Cool in air to ambient temperature
~ 900C
Time
Figure 20.1 Typical normalising heat treatment applied to C-Mn and some low
alloy steels.
Applied to
Some low alloy steels to give higher strength toughness or wear resistance.
~ 900C
Quenching Tempering
cycle cycle
Time
Figure 20.2 A typical quenching and tempering heat treatment applied to some low
alloy steels.
20-2 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
Solution annealed
Hot or cold working to size, steel heated to ~1100C after.
~ 900C
Temperature, C.
Austenite + ferrite
(
As-rolled or Control-rolled
Ferrite + pearlite hot rolled Or TMCP
() iron carbide
Time
Figure 20.3 Comparison of the control-rolled (TMCP) and as-rolled (hot rolling)
conditions.
Quenching
Time
Figure 20.4 Typical solution heat treatment (solution annealing) applied to
austenitic stainless steels.
20-3 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
Applied to
Austenitic stainless steels such as 304 and 316 grades.
Annealed
After working the steel (pressing or forging, etc) to size, it is heated to
~900C then allowed to cool in the furnace to ambient temperature; this
reduces strength and toughness but improves ductility (Figure 20.5).
Annealing:
Rapid heating to soak temperature (100% austenite).
Short soak time at temperature.
Slow cool in furnace to ambient temperature.
Temperature, C
~ 900C
Time
Figure 20.5 Typical annealing heat treatment applied to C-Mn and some low alloy
steels.
Applied to
C-Mn steels and some low alloy steels.
Figures 20.1-20.5 show thermal cycles for the main supply conditions and
subsequent heat treatment that can be applied to steels.
The temperature at which PWHT is usually carried out well below the
temperature where phase changes can occur (see Note), but high enough
to allow residual stresses to be relieved quickly and to soften (temper) any
hard regions in the HAZ.
20-4 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
The major benefits of reducing residual stress and ensuring that the HAZ
hardness is not too high for steels for particular service applications are:
Because the main reason for and benefit of PWHT is to reduce residual
stresses, PWHT is often called stress-relief.
Maximum heating rates specified for C-Mn steel depend on the thickness of
the item but tend to be in the range ~60 to ~200C/h.
20-5 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
20-6 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
~ 600C
Controlled heating
and cooling rates
~300C
Soak
time Air cool
Time
Figure 20.6 Typical PWHT applied to C-Mn steels.
It is also important to ensure that the fuel particularly for oil-fired furnaces
does not contain high levels of potentially harmful impurities, such as
sulphur.
Width of the heated band (must be within the soak temperature range).
Width of the temperature decay band (soak temperature to ~300C).
20-7 www.twitraining.com
Rev 2 April 2013
Heat Treatment
Copyright TWI Ltd 2013
Figure 20.7 shows typical control zones for localised PWHT of a pipe butt
weld.
Weld seam
temp. temp.
decay heated band decay
band band
20-8 www.twitraining.com
Section 21
There are four aspects of arc welding safety that the visual/welding
inspector must consider:
Electric shock.
Heat and light.
Fumes and gases.
Noise.
The electric shock hazard associated with arc welding may be divided into
two categories:
21-1
www.twitraining.com
Rev 2 April 2013
Arc Welding Safety
Copyright TWI Ltd 2013
Welding lead from one terminal of the power source to the electrode
holder or welding torch.
Welding return lead to complete the circuit from the work to the other
terminal of the power source.
Earth lead from the work to an earth point. The power source should also
be earthed.
All three leads should be capable of carrying the highest welding current
required.
Duty cycle
All current carrying conductors heat up when welding current is passed
through them. Duty cycle is a measure of the capability of the welding
equipment in terms of the ratio of welding time to total time which can be
expressed as:
W
e
l
d
i
n a
g t
t
i m
m e
e
D
u
t
y
c
y
c
l
e
x
1
0
0
T
o
t
l
i
21-2
www.twitraining.com
Rev 2 April 2013
Arc Welding Safety
Copyright TWI Ltd 2013
By observing this ratio the current carrying conductors will not be heated
above their rated temperature. Duty cycles are based on a total time of 10
minutes. For example: a power source has a rated output of 350A at 60%
duty cycle. This particular power source will deliver 350A (its rated output)
for six minutes out of every ten minutes without overheating.
Failure to carefully observe the duty cycle of equipment can over-stress the
part and with welding equipment cause overheating leading to instability and
the potential for electric shock.
The welding arc creates sparks with the potential to cause flammable
materials near the welding area to ignite and cause fires. The welding area
should be clear of all combustible materials and the inspector should know
where the nearest fire extinguishers are and the correct type to use if a fire
does break out.
21.3.2 Light
Light radiation is emitted by the welding arc in three principal ranges:
Wavelength,
Type
nanometres
Infrared (heat) >700
Visible light 400-700
Ultraviolet radiation <400
21-3
www.twitraining.com
Rev 2 April 2013
Arc Welding Safety
Copyright TWI Ltd 2013
Arc eye develops some hours after exposure, which may not even have
been noticed. The sand in the eye symptom and pain usually lasts for 12-24
hours but can be longer in more severe cases. Fortunately it is almost
always a temporary condition. In the unlikely event of prolonged and
frequently repeated exposures permanent damage can occur.
Visible light
Intense visible light particularly approaching UV or blue light wavelengths
passes through the cornea and lens and can dazzle and, in extreme cases,
damage the network of optically sensitive nerves on the retina. Wavelengths
of visible light approaching infrared have slightly different effects but can
produce similar symptoms. Effects depend on the duration and intensity of
exposure and to some extent the individual's natural reflex action to close
the eye and exclude the incident light. Normally this dazzling does not
produce a long-term effect.
Infrared radiation
Infrared radiation is of longer wavelength than the visible light frequencies
and is perceptible as heat. The main hazard to the eyes is that prolonged
exposure (over years) causes a gradual but irreversible opacity of the lens.
Fortunately, the infrared radiation emitted by normal welding arcs causes
damage only within a comparatively short distance from the arc. There is an
immediate burning sensation in the skin surrounding the eyes should they
be exposed to arc heat and the natural reaction is to move or cover up to
prevent the skin heating, which also reduces eye exposure.
21-4
www.twitraining.com
Rev 2 April 2013
Arc Welding Safety
Copyright TWI Ltd 2013
The fume plume contains solid particles from the consumables, base metal
and base metal coating. Depending on the length of exposure to these
fumes, most acute effects are temporary and include symptoms of burning
eyes and skin, dizziness, nausea and fever. Zinc fumes can cause metal
fume fever, a temporary illness similar to flu. Chronic, long-term exposure to
welding fumes can lead to siderosis (iron deposits in the lungs) and may
affect pulmonary function. Cadmium, is a toxic metal found on steel as a
coating or in silver solder. Cadmium fumes can be fatal even under brief
exposure, with symptoms much like those of metal fume fever. These two
should not be confused. Twenty minutes of welding in the presence of
cadmium can be enough to cause fatalities, with symptoms appearing within
an hour and death five days later.
21.4.2 Gases
The gases resulting from arc welding present a potential hazard. Most of the
shielding gases (argon, helium and carbon dioxide) are non-toxic when
released, but displace oxygen in the breathing air, causing dizziness,
unconsciousness and death the longer the brain is denied oxygen.
To reduce the risk of hazardous fumes and gases, keep the head out of the
fume plume. As obvious as this sounds it is a common cause of fume and
gas over-exposure because the concentration of fumes and gases is
greatest in the plume. In addition, use mechanical ventilation or local
exhaust at the arc to direct the fume plume away from the face. If this is not
sufficient, use fixed or moveable exhaust hoods to draw the fume from the
general area. Finally, it may be necessary to wear an approved respiratory
device if sufficient ventilation cannot be provided. As a rule of thumb, if the
air is visibly clear and the welder is comfortable, the ventilation is probably
adequate.
21-5
www.twitraining.com
Rev 2 April 2013
Arc Welding Safety
Copyright TWI Ltd 2013
To identify hazardous substances, first read the material safety data sheet
for the consumable to see what fumes can be reasonably expected from
use of the product. Refer to the Occupational Exposure Limit (OEL) as
defined in the COSHH regulations which gives maximum concentrations to
which a healthy adult can be exposed to any one substance. Second, know
the base metal and determine if a paint or coating would cause toxic fumes
or gases. Particular attention should also be made to the dangers of
asphyxiation when welding in confined spaces. Risk assessment, permits to
work and gas testing are some of the necessary actions required to ensure
the safety of all personnel.
Noise
Exposure to loud noise can permanently damage hearing, cause stress and
increase blood pressure. Working in a noisy environment for long periods
can contribute to tiredness, nervousness and irritability. If the noise
exposure is greater than 85 decibels averaged over an 8 hour period then
hearing protection must be worn and annual hearing tests carried out.
Normal welding operations are not associated with noise level problems with
two exceptions: Plasma arc welding and air carbon arc cutting. If either of
these is to be performed then hearing protectors must be worn. The noise
associated with welding is usually due to ancillary operations such as
chipping, grinding and hammering. Hearing protection must be worn when
carrying out or when working in the vicinity of these operations.
21.5 Summary
The best way to manage the risks associated with welding is by
implementing risk management programmes. Risk management requires
the identification of hazards, assessment of the risks and implementation of
suitable controls to reduce the risk to an acceptable level.
21-6
www.twitraining.com
Section 22
Calibration
Rev 2 April 2013
Calibration
Copyright TWI Ltd 2013
22 Calibration
22.1 Introduction
BS 7570 - Code of practice for validation of arc welding equipment, is a
standard that gives guidance to:
22.2 Terminology
BS 7570 defines the terms it uses, such as:
When considering welding equipment, those with output meters for welding
parameters (current, voltage, travel speed, etc) can be calibrated by
checking the meter reading with a more accurate measuring device and
adjusting the readings appropriately.
Equipment that does not have output meters (some power sources for
MMA, MIG/MAG) cannot be calibrated but can be validated to see the
controls are functioning properly.
22-1
www.twitraining.com
Rev 2 April 2013
Calibration
Copyright TWI Ltd 2013
For the main welding parameters, recommendations from the Standard are
as follows.
Current
Details are given about the instrumentation requirements and how to
measure pulsed current but there are requirements given, specified, or
recommendations made, about where in the circuit current measurements
should be made.
The implication is that current can be measured at any position in the circuit
the value should be the same.
Voltage
The standard emphasises that for processes where voltage is pre-set (on
constant voltage the power sources) the connection points used for the
22-2
www.twitraining.com
Rev 2 April 2013
Calibration
Copyright TWI Ltd 2013
voltage meter incorporated into the power source may differ from the arc
voltage, which is the important parameter.
This is illustrated by the figure which shows the power source voltage meter
connected across points 1 and 7.
Power
source
2 3
77 1 Wire feeder
4
Arc voltage
{
55
6
6
However because there will be some voltage drops in sections 1-2, 3-4 and
6-7 due to connection points introducing extra resistance into the circuit, the
voltage meter reading on the power source will tend to give a higher reading
than the true arc voltage.
Even if the power source voltage meter is connected across points 3 and 7
(which it may be) the meter reading would not take account of any
significant voltage drops in the return cable, section 6-7.
22-3
www.twitraining.com
Rev 2 April 2013
Calibration
Copyright TWI Ltd 2013
The magnitude of any voltage drops in the welding circuit will depend on
cable diameter, length and temperature and the Standard emphasises the
following:
It is desirable to measure the true arc voltage between points 4-5 but for
some welding processes it is not practical to measure arc voltage so
close to the arc.
For MMA it is possible to take a voltage reading relatively close to the
arc by connecting one terminal of the voltmeter through the cable sheath
as close as ~2m from the arc and connect the other terminal to the
workpiece (or to earth).
For MIG/MAG the nearest practical connection points have to be 3-5 but
a change from an air to a water-cooled torch or vice versa may have a
significant effect on the measured voltage.
Voltage drops between points 5-6 will be insignificant if there is a good
connection of the return cable at point 6.
The Standard gives guidance about minimising any drop in line voltage by
ensuring that the:
The Standard gives data for line voltage drops (DC voltage) according to
current, cable cross-section and length (for both copper and aluminium
cables).
Travel speed
Welding manipulators, such as rotators and robotic manipulators, as well as
the more conventional linear travel carriages, influence heat input and other
properties of a weld and should be checked at intervals. Most of the
standard devices can be checked using a stopwatch and measuring rule but
more sophisticated equipment, such as a tacho-generator, may be
appropriate.
22-4
www.twitraining.com
Section 23
Preheat is used when welding steels for a number of reasons and it helps to
understand why. One of the main reasons is to assist in removing hydrogen
from the weld. Preheat temperatures for steel structures and pipework are
calculated by taking into account the carbon equivalent (CEV) and thickness
of the material and the arc energy or heat input (kJ/mm) of the welding
process.
The welding inspector would normally find the preheat temperature for a
particular application from the relevant WPS. In general, thicker materials
require higher preheat temperatures, but for a given CEV and arc
energy/heat input, they are likely to remain similar for wall thickness up to
approximately 20mm.
23.2 Definitions
Preheat temperature
Temperature of the workpiece in the weld zone immediately before any
welding operation (including tack welding).
Normally expressed as a minimum but can also be specified as a range.
Interpass temperature
Temperature of the weld during welding and between passes in a multi-
run weld and adjacent parent metal immediately prior to the application
of the next run.
Normally expressed as a maximum but should not drop below the
minimum preheat temperature.
23-1
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
Local Global
Flame applied
preheat
23-2
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
Gas/electric ovens
Generally used for PWHT but can be used for large sections of material to
give a controlled and uniform preheat.
With flame applied preheating sufficient time must be allowed for the
temperature to equalise throughout the thickness of the components to be
welded, otherwise only the surface temperature will be measured. The time
lapse depends on the specification requirements.
Where?
23-3
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
Why?
Applying preheat has the following advantages:
Slows down the cooling rate of the weld and HAZ, reducing the risk of
hardened microstructures forming; allowing absorbed hydrogen more
opportunity of diffusing out, thus reducing the potential for cracking.
Removes moisture from the region of the weld preparation.
Improves overall fusion characteristics during welding.
Ensures more uniform expansion and contraction, lowering stresses
between weld and parent material.
23-4
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
23-5
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
23-6
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
23.4.3 Thermocouple
Based on measuring the thermoelectric potential difference between a
hot junction (placed on the weld) and a cold junction (reference junction).
Measures a wide range of temperatures.
Accurate, gives the actual temperature.
Can be used for continuous monitoring.
Need calibration.
Thermister
Examples of thermocouples.
23-7
www.twitraining.com
Rev 2 April 2013
Application and Control of Preheat
Copyright TWI Ltd 2013
23.5 Summary
The visual/welding inspector should refer to the WPS for both preheat and
interpass temperature requirements. If in any doubt as to where the
temperature measurements should be taken, the senior welding inspector or
welding engineer should be consulted for guidance.
Both preheat and interpass temperatures are applied to slow down the
cooling rate during welding, avoiding the formation of brittle microstructures
(ie martensite) and thus preventing cold cracking.
23-8
www.twitraining.com
Section 24
Gauges
Rev 2 April 2013
Gauges
Copyright TWI Ltd 2013
24 Gauges
Specialist gauges
Measure the various elements that need to be measured in a welded
fabrication including:
1
2
3
4
5
6
24-2 www.twitraining.com
Rev 2 April 2013
Gauges
Copyright TWI Ltd 2013
24-3 www.twitraining.com
Rev 2 April 2013
Gauges
Copyright TWI Ltd 2013
Angle of preparation
Scale reads 0-60 degree in 5
degree steps.The angle is read
against the chamfered edge of
the plate or pipe.
Linear misalignment
Can be used to measure
misalignment of members by
placing the edge of the gauge on
the lower member and rotating
the segment until the pointed
finger contacts the higher
member.
Pitting/mechanical damage,
etc
The gauge can measure defects
by placing the edge of the gauge
on the plate and rotating the
segment until the pointed finger
contacts the lowest depth.
24-4 www.twitraining.com
Rev 2 April 2013
Gauges
Copyright TWI Ltd 2013
Excess weld metal can be easily calculated by measuring the leg length,
and multiplying it by 0.7. This value is then subtracted from the measured
throat thickness = excess weld metal.
24-5 www.twitraining.com
Appendix 1
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
Appendix 1
Multiple Choice Questions Paper 1
1 Which mechanical test can be used to measure the toughness of weld metal,
HAZ and parent material?
a Macro.
b Nick break.
c Hardness.
d Charpy impact.
2 Which is the best destructive test for showing lack of sidewall fusion in a 25mm
thickness butt weld?
a Nick break.
b Side bend.
c Charpy impact.
d Face bend test.
4 A fabrication procedure calls for the toes of all welds to be blended in by grinding.
The reason for doing this is to:
5 For full penetration single-sided butt joints, root bead penetration and profile are
mainly influenced by:
a Root face.
b Bevel angle.
c Root gap.
d Included angle.
A1-1
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
6 Which of the following would be cause for rejection by most fabrication standards
when inspecting fillet welds with undercut, a small amount of?
a Depth.
b Length.
c Width.
d Sharpness.
7 When visually inspecting the root bead of a single V-butt weld it should be
checked for:
a Leg length.
b Weld profile.
c Weld width.
d Throat thickness.
9 The European Standard for NDE of fusion welds by visual examination is:
a EN 15614.
b EN 2560.
c EN 287.
d EN 17637.
10 Visual inspection of a fabricated item for a high integrity application should cover
inspection activities:
A1-2
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Linear misalignment.
b Root gap being too large.
c Root faces being too small.
d Welding current too high.
13 When visually inspecting the face of a finished weld which of the following flaws
would be considered the most serious:
15 A Code of Practice is a:
a Entrapped slag.
b Entrapped gas.
c Lack of inter-run fusion.
d None of the above.
a Throat thickness.
b Leg lengths.
c Penetration depths.
d Both a and c.
A1-3
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
19 In a bend test, when the face of the specimen is in tension and root is in
compression, the test is called a
:
a Root bend.
b Side bend.
c Face bend.
d Longitudinal bend.
20 Heavy porosity on the surface of some MMA welds made on a construction site is
most likely to be caused by:
a Excessive amps.
b Excessive OCV.
c Excessive travel speed.
d Current too low.
24 Which of the following fillet welds is the strongest assuming they are all made
using the same material and welded using the same WPS?
A1-4
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
25 A typical included angle for MMA welding a full penetration pipe butt joint is:
a 35
b 70
c 90
d Dependent on the pipe diameter.
26 A fillet weld has an actual throat thickness of 8mm and a leg length of 7mm, what
is the excess weld metal?
a 2.1mm
b 1.8mm
c 3.1mm
d 1.4mm
29 BS EN 17637 allows the use of a magnifying glass for visual inspection, but
recommends that the magnification is:
a x2.
b x2 to x5.
c x5 to x10.
d Not greater than x20.
30 The majority of welder qualification tests are carried out using unbacked joints,
because:
A1-5
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
1 Deflection of the arc by magnetic forces that can make welding difficult to control
is commonly known as:
a Arc initiation.
b Arc misalignment.
c Arc blow.
d Arc constriction.
a E 38 3 R.
b E 6013.
c E 7018 - G.
d E 51 33 B.
3 Which type of electrode is used for stovepipe welding for overland pipeline
construction?
a Rutile.
b Cellulosic.
c High recovery rutile.
d Acid-rutile.
4 The three main types of MMA electrodes used for welding C and C-Mn steels
are:
5 A WPS may specify a maximum width for individual weld beads (weave width)
when welding C-Mn steels. If the width is exceeded it may cause:
6 You notice that MMA electrodes with the flux covering removed are being used
as filler rods for TIG welding. This should not be allowed because:
a It is wasteful.
b The rod diameter may be too large.
c The weld metal composition may be wrong.
d The rod is too short.
A1-7
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Tungsten spatter.
b Risk of crater cracking.
c Risk of arc strikes.
d Interpass temperature.
8 Which type of power source characteristic is normally used for manual welding?
a Constant voltage.
b Flat characteristic.
c Constant current.
d A motor generator.
a Arc voltage.
b Welding speed.
c Ferro-silicon in the electrode coating.
d Current.
10 Pipe bores of some materials must be purged with argon before and during TIG
welding to:
11 The chemical composition of the weld metal deposited by a C-Mn steel MMA
electrode is usually controlled by:
a Provide deoxidation.
b Improve strength.
c Improve toughness.
d Provide more resistance to hydrogen cracking.
A1-8
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Reduce porosity.
b Give controlled root penetration.
c Avoid the need for a back purge.
d By acting as a backing for the root run.
e
14 According to AWS 2.4 a weld symbol for the other side is placed:
15 The term low hydrogen electrode is often used for certain electrodes. What type
of covering will they have?
a Cellulosic.
b Rutile.
c Acid.
d Basic.
A1-9
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Joules.
b N/mm2.
c J/mm2.
d kJ/mm.
a Nickel.
b Manganese.
c Molybdenum.
d Aluminium.
20 Nick break and fillet fracture tests are used for assessing:
a Weld quality.
b Weld metal ductility.
c Weld metal toughness.
d Resistance to fracture.
a 18%Cr, 8%Ni.
b 2.25Cr 1Mo.
c 9%Cr,1Mo.
d 9%Ni.
a Excessive current.
b Incorrect baking and storage of electrodes.
c Bad batch of electrodes.
d Too low an OCV.
A1-10
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a WPS number.
b Welding process. 141
c Filler material.
d Acceptance standard.
28 The current/polarity used for TIG welding all materials except aluminium and
magnesium is:
a DC negative.
b DC positive.
c AC.
d Square wave AC.
a 150-200C.
b 200-250C.
c 300-350C.
d 400-450C.
A1-11
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
30 If welding travel speed is doubled but the current and voltage remain the same
the heat input will be:
a Reduced by 50%.
b Increased by a factor of two.
c About the same.
d Reduced by approximately 25%.
A1-12
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Neutral.
b Agglomerated.
c Fused.
d All about the same.
2 A large grain size in the HAZ of a C-Mn steel weld joint may have:
a Low ductility.
b Low toughness.
c High toughness.
d High tensile strength.
a C-Mn steels.
b Austenitic stainless steel.
c Low alloy steels for elevated temperature service.
d Low carbon steels for cryogenical service.
5 The property of a material which has the greatest influence on welding distortion
is its:
a Yield strength.
b Coefficient of thermal expansion.
c Elastic modulus.
d Coefficient of thermal conductivity.
6 Which of the following is a suitable shielding gas for FCAW of stainless steels?
a 100% argon.
b 70% argon + 30%He.
c Argon + 5% hydrogen.
d Argon + 20% CO2.
A1-13
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Solidification cracking.
b Hydrogen cracking.
c Lamellar tearing.
d Weld decay.
a 100%CO2.
b 100% Argon.
c 80% argon + 20% CO2.
d 98% argon + 2% O2.
11 Which of the following is associated with SAW more often than it is with MMA
welds?
12 EN ISO 5817 (Level C) specifies that the limit for the diameter (D) of a single
pore in a weld is:
A1-14
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
14 Lamellar tearing has occurred in a steel fabrication. What technique could have
been used to find it before the weld was made?
a X-ray examination.
b Liquid penetrant examination.
c Ultrasonic examination.
d It could not have been found by any inspection method.
15 Preheating a low alloy steel prior to welding will minimise the risk of:
a Porosity.
b Excessive distortion.
c HAZ cracking.
d Lack of fusion.
a 600-650C.
b 1000-1100C.
c 700-800C.
d 880-920C.
17 For GMAW the burn-off rate of the wire is directly related to:
18 When MMA welding a 60mm wall nozzle to a 100mm wall vessel shell, preheat
temperature should be checked:
A1-15
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
19 A crack running along the centreline of a weld bead could be caused by:
21 The use of low carbon austenitic stainless steels and stabiliser stainless steels
will minimise the risk of:
a HAZ cracking.
b Weld decay.
c Weld metal cracking.
d Distortion.
22 Which type of SAW flux is susceptible to breaking down into fine particles during
circulation?
a Fused.
b Neutral.
c Alloyed.
d Agglomerated.
24 BS EN ISO 5817 (Level B) specifies the limit for excess weld metal (h) on a butt
weld as:
A1-16
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
25 A C-Mn steel is being welded by MMA and the electrode run-out lengths that
have been used are much shorter than specified by the WPS. This deviation may
give:
26 The first procedure prepared for a Weld Procedure Qualification test weld is a:
a pWPS.
b WPS.
c WPQR.
d WPAR.
a Is too slow.
b Can be a safety hazard.
c May damage the material.
d Causes problems with coating operations.
a 550J/mm.
b 55J/mm.
c 5.5J/mm.
d 5kJ/mm.
30 Initiation of a TIG arc using a high frequency spark may not be allowed because
it:
A1-17
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
10s
a
10
s
s10
b
10
c
s10
d
a Time.
b Type of isotope.
c Source-to-film distance.
d Source strength.
4 Which element has the greatest effect on the HAZ hardness of C-Mn steel?
a Molybdenum.
b Chromium.
c Titanium.
d Carbon.
5 Preheating a steel plate with a carbon equivalent value (CEV) of 0.48 may be
required to:
A1-19
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
7 In friction welding, the metal at the interface when the joining occurs is described
as being in the:
a Liquid state.
b Intercritical state.
c Plastic state.
d Elastic state.
9 Which of the following cutting methods is suitable for cutting stainless steel?
a Plasma.
b Oxy-acetylene.
c Oxy-propane.
d It depends upon the thickness.
10 Which of the following would be classed as the most serious type of defect?
11 Ultrasonic testing has an advantage over other NDT methods for the detection of:
A1-20
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
12 Exceeding the maximum interpass temperature specified for a C-Mn steel weld
joint may give:
a Excessive porosity.
b Burn through.
c Lower toughness.
d Higher strength.
13 MIG/MAG welding has a tendency to give lack of sidewall fusion when using:
14 The temperature range over which a steel goes from having high to low
toughness is called the:
15 For SAW what is the effect of raising arc voltage but keeping all other parameters
the same?
16 Changing an essential variable beyond the allowed limits for a qualified wielding
procedure:
17 With reference to the various grades of stainless steels which of the following
statements is true?
A1-21
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a E 6010.
b E 7016.
c E 7018.
d E 6013.
19 Welds made with very high heat input will show a reduction in:
a Tensile ductility.
b Notch toughness.
c Fatigue strength.
d Creep resistance.
a Using inductance.
b Using 100%CO2.
c Using Ar + 30%He.
d Increasing the stick-out length.
22 Repair welding of in-service plant and equipment may be more difficult than
making repairs during initial fabrication because:
a Thulium 170.
b Ytterbium 169.
c Iridium 192.
d Cobalt 60.
A1-22
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
a Using a densitometer.
b Using an image quality indicator (IQI).
c From the kVA used.
d From the source/tube to work standoff distance used.
25 A transverse tensile test from a Weld Procedure Approval Record (WPAR) test
plate is used to measure the:
26 The highest and lowest heat input positions are considered to be:
a PB highest; PA lowest.
b PE highest; PC lowest.
c PD highest; PB lowest.
d PF highest; PG lowest.
27 What type of covering will an electrode have that is suitable for welding 60mm C-
Mn steel and can give good weld metal toughness at -50C?
a Rutile.
b Basic.
c Cellulosic.
d Choice will depend on the welding position.
28 The dip transfer or short-circuiting mode of metal transfer used for MIG/MAG
welding is characterised by:
29 Carbon equivalent values (CEV) are used to determine how to avoid the risk of:
a Hydrogen cracking.
b Lamellar tearing.
c Solidification cracking.
d Weld decay.
A1-23
www.twitraining.com
Rev 2 April 2013
Appendix 1
Copyright TWI Ltd 2013
30 When two different material types are welded together the joint is referred to as:
a A composite joint.
b A transition joint.
c An autogenous weld.
d Heterogeneous joint.
A1-24
www.twitraining.com
Appendix 2
Appendix 2
CSWIP 3.1 Training Questions for Plate Butt Weld 1
Weld Face
1 Maximum excess weld metal height (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 50-75mm.
c 10-30mm.
d 80-110mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 50-65mm.
b 22-35mm.
c None observed.
d 8-18mm.
e Accept.
f Reject.
A2-1
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a Smooth intermittent.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
5 Crater pipes in the weld: Which answer best matches your assessment of the
total accumulative area and would you accept or reject your findings to the given
acceptance levels?
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 70-90mm.
b 30-60mm.
c None observed.
d 5-10mm.
e Accept.
f Reject.
A2-2
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3 areas.
b 4 areas.
c None observed.
d 1area.
e Accept.
f Reject.
a 4 areas.
b 1 area.
c None observed.
d 3.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
A2-3
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total and would you accept or reject your findings to the given
acceptance levels?
a 35-40mm.
b 20-25mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-10mm.
c None observed.
d 15-23mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total length and would you accept or reject your findings to
the given acceptance levels?
a 31-39mm.
b 18-22mm.
c None observed.
d 40-60mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 15-30mm.
b 5-8mm.
c None observed.
d 0-2mm.
e Accept.
f Reject.
A2-4
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
17 Sharp indications of mechanical damage in the root area weld and parent
material (excluding hard stamping): Which answer best matches your
assessment of the accumulative total and would you accept or reject you findings
to the given acceptance levels?
18 Crater pipes in the weld root area: Which answer best matches your assessment
of the total number of areas and would you accept or reject your findings to the
given acceptance levels?
19 Burn-through in the root area: Which answer best matches your assessment of
the total number of areas and would you accept or reject your findings to the
given acceptance levels?
a 1area.
b 2 areas.
c None observed.
d 3 areas.
e Accept.
f Reject.
A2-5
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
20 Angular distortion: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels (measure from the
weld centreline to the plate edge).
a 3-5mm.
b 6-8mm.
c None observed.
d 1-2mm.
e Accept.
f Reject.
A2-6
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-7
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-8
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
Weld Face
1 Maximum excess weld metal height (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 45-80mm.
c 0-40mm.
d 100-120mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-30mm.
c None observed.
d 5-18mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 60mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A2-9
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 35-45mm.
b 15-25mm.
c None observed.
d 5-10mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3.
b 4.
c None observed.
d 1.
e Accept.
f Reject.
A2-10
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
a 4 areas.
b 1 area.
c None observed.
d 3 areas.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c 0-1mm.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 4-5mm.
b 2-3mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 35-40mm.
b 15-25mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
A2-11
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-10mm.
c None observed.
d 13-20mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total length and would you accept or reject your findings to
the given acceptance levels.
a 31-39mm.
b 18-22mm.
c None observed.
d 40-60mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 15-30mm.
b 5-8mm.
c None observed.
d 0-2mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A2-12
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
17 Sharp indications of mechanical damage in the root area weld and parent
material (excluding hard stamping): Which answer best matches your
assessment of the accumulative total number and would you accept or reject
your findings to the given acceptance levels?
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn-through in the root area: Which answer best matches your assessment of
the accumulative total and would you accept or reject your findings to the given
acceptance levels?
a 1 area.
b 2 areas.
c None observed.
d 3 areas.
e Accept.
f Reject.
20 Angular distortion: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels, measure from the
weld centreline to the plate edge.
a 3-5mm.
b 6-8mm.
c None observed.
d 1-2mm.
e Accept.
f Reject.
A2-13
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-14
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-15
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
Weld Face
1 Maximum excess weld metal height (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 40-60mm.
c 0-30mm.
d 75-100mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-30mm.
c None observed.
d 5-18mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 50mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A2-16
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 70-90mm.
b 30-60mm.
c None observed.
d 91-100mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3 total.
b 4 total.
c None observed.
d 1 total.
e Accept.
f Reject.
A2-17
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
9 Sharp areas of mechanical damage (excluding hard stamping and pop marks):
Which answer best matches your assessment of the total number of areas and
would you accept or reject your findings to the given acceptance levels.
Weld Root
a 2-3mm.
b 4-5mm.
c 0-1.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 2-3mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 40-55mm.
b 25-35mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
A2-18
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 30-45mm.
b 0-15mm.
c None observed.
d 16-29mm.
e Accept.
f Reject.
14 Root concavity or shrinkage: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels.
a 31-39mm.
b 18-22mm.
c None observed.
d 40-60mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 40-60mm.
b 5-8mm.
c None observed.
d 2-4mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A2-19
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
17 Sharp indications of mechanical damage in the root area weld and parent
material (excluding hard stamping): Which answer best matches your
assessment of the total number of items and would you accept or reject your
findings to the given acceptance levels?
a 2 observed.
b 1 item observed.
c None observed.
d 3 or more items observed.
e Accept.
f Reject.
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn-through in the root area: Which answer best matches your assessment of
the total number of areas and would you accept or reject your findings to the
given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 Angular distortion: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels (measure from the
weld centreline to the plate edge).
a 3-4mm.
b 5-6mm.
c None observed.
d 1-2mm.
e Accept.
f Reject.
A2-20
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-21
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-22
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
Weld Face
1 Maximum excess weld metal height (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 30-50mm.
c 0-25mm.
d 100-120mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 12-18mm.
b 8-10mm.
c None observed.
d 2-6mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 10-20mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A2-23
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 30-39mm.
b 40-55mm.
c None observed.
d 5-10mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 2.
b 3.
c None observed.
d 1.
e Accept.
f Reject.
A2-24
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
9 Sharp areas of mechanical damage (excluding hard stamping and pop marks):
Which answer best matches your assessment of the total number of areas and
would you accept or reject your findings to the given acceptance levels.
a 4 areas.
b 1-2 areas.
c None observed.
d 3 areas.
e Accept.
f Reject.
Weld Root
a 0.5-1mm.
b 1.5-2mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 35-40mm.
b 20-25mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
A2-25
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-10mm.
c None observed.
d 15-23mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total length and would you accept or reject your findings to
the given acceptance levels.
a 31-39mm.
b 18-22mm.
c None observed.
d 40-75mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 15-30mm.
b 5-8mm.
c None observed.
d 40-50mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A2-26
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
17 Sharp indications of mechanical damage in the root area weld and parent
material (excluding hard stamping): Which answer best matches your
assessment of the accumulative total and would you accept or reject your
findings to the given acceptance levels?
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn-through in the root area: Which answer best matches your assessment of
the accumulative total number of areas and would you accept or reject your
findings to the given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 With refrence to cluster porosity which answer best matches your assessment
and would you accept or reject your findings to the given acceptance levels.
a 20-30mm2.
b 31-40mm2.
c None observed.
d 12-18mm2.
e Accept.
f Reject.
A2-27
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-28
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-29
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
Weld Face
1 Excess weld metal height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 16-29mm.
c 0-15mm.
d 40-50mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-30mm.
c None observed.
d 5-12mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 60-70mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A2-30
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
a 0-15mm2.
b Greater than 100mm2.
c None observed.
d The area is between 70-90mm2.
e Accept.
f Reject.
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 40-60mm.
b 20-39mm.
c None observed.
d 5-10mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3.
b 4.
c None observed.
d 1.
e Accept.
f Reject.
A2-31
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
9 Sharp areas of mechanical damage (excluding hard stamping and pop marks):
Which answer best matches your assessment of the total number of areas and
would you accept or reject your findings to the given acceptance levels.
a 4.
b 1-2.
c None observed.
d 3.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 2-3mm.
b 0-1mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 30-40mm.
b 20-25mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
A2-32
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-40mm.
b 0-10mm.
c None observed.
d 15-23mm.
e Accept.
f Reject.
14 Root concavity or shrinkage: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels.
a 31-39mm.
b 18-25mm.
c None observed.
d 40-75mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 15-30mm.
b 5-8mm.
c None observed.
d 0-2mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept
f Reject.
A2-33
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
17 Sharp indications of mechanical damage in the root area weld and parent
material (excluding hard stamping): Which answer best matches your
assessment of the total number of items and would you accept or reject your
findings to the given acceptance levels?
a 2 items observed.
b 1 item observed.
c None observed.
d 3 or more items observed.
e Accept.
f Reject.
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn-through in the root area: Which answer best matches your assessment of
the total number of areas and would you accept or reject your findings to the
given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 Angular distortion: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels (measure from the
weld centreline to the plate edge).
a 2-4mm.
b 6-8mm.
c None observed.
d 0-1mm.
e Accept.
f Reject.
A2-34
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-35
www.twitraining.com
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
A2-36
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 2
Copyright TWI Ltd 2013
Acceptance
Table number
A2-37
www.twitraining.com
Appendix 3
Pipe Reports and Questions
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Appendix 3
Weld Face
1 Maximum excess weld metal height. (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 30-50mm.
c 0-28mm.
d 55-70mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 13-19mm.
b 20-30mm.
c None observed.
d 8-12mm.
e Accept.
f Reject.
A3-2
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a Smooth intermittent.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
a Area is 10-15mm2.
b Area 190-210mm2.
c None observed.
d Area 130-160mm2.
e Accept.
f Reject.
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 70-90mm.
b 30-60mm
c None observed.
d 5-25mm.
e Accept.
f Reject.
A3-3
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3.
b 4.
c None observed.
d 1.
e Accept.
f Reject.
a 4.
b 1.
c None observed.
d 2.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
A3-4
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 35-40mm.
b 20-25mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-10mm.
c None observed.
d 15-23mm.
e Accept.
f Reject.
14 Root concavity or shrinkage: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 31-39mm.
b 5-12mm.
c None observed.
d 40-60mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 60-70mm.
b 71-80mm.
c None observed.
d 1-15mm.
e Accept.
f Reject.
A3-5
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
17 Sharp areas of mechanical damage in the root area weld and parent material
(excluding hard stamping): Which answer best matches your assessment of the
accumulative total number of items and would you accept or reject your findings
to the given acceptance levels?
a 2-3.
b 1.
c None observed.
d 4-5.
e Accept.
f Reject.
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn through in the root area: Which answer best matches your assessment of
the accumulative total number of areas and would you accept or reject your
findings to the given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
A3-6
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
20 Cluster porosity: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels (measure from the
weld centreline to the plate edge).
a 3-5mm2.
b 26-88mm2.
c None observed.
d 12-20mm2.
e Accept.
f Reject.
A3-7
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Weld Face.
1 Maximum excess weld metal height: (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 30-60mm.
c 0-25mm.
d 100-120mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-30mm.
c None observed.
d 8-12mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 25mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A3-8
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
a 10-15mm2.
b Greater than 100mm2.
c None observed.
d 40-65mm2.
e Accept.
f Reject.
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 40-90mm.
b 30-60mm.
c None observed.
d 5-10mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3.
b 4.
c None observed.
d 1.
e Accept.
f Reject.
A3-9
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
9 Sharp areas of mechanical damage: (excluding hard stamping and pop marks):
Which answer best matches your assessment of the total number of areas and
would you accept or reject your findings to the given acceptance levels?
a 4.
b 1.
c None observed.
d 3.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject
11 Root penetration height: (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 65-75mm.
b 45-60mm.
c None observed.
d 110-135mm.
e Accept.
f Reject.
A3-10
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 35-55mm.
b 10-30mm.
c None observed.
d 65-90mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total length and would you accept or reject your findings to
the given acceptance levels.
a 45-55mm.
b 73-90mm.
c None observed.
d 60-70mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 30-40mm.
b 5-8mm.
c None observed.
d 0-2mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A3-11
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
17 Sharp areas of mechanical damage in the root area weld and parent material
(excluding hard stamping): Which answer best matches your assessment of the
accumulative total number of areas and would you accept or reject your findings
to the given acceptance levels?
a 2-3.
b 1.
c None observed.
d 4-5.
e Accept.
f Reject.
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn through in the root area: Which answer best matches your assessment of
the accumulative total number of areas and would you accept or reject your
findings to the given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 Porosity: Which answer best matches your assessment and would you accept or
reject your findings to the given acceptance levels (measure from the weld
centreline to the plate edge)?
a 35-45mm2.
b 60-80mm2.
c None observed.
d 12-22mm2.
e Accept.
f Reject.
A3-12
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Weld Face
1 Maximum excess weld metal height (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 65-80mm.
c 10-25mm.
d 100-120mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-30mm.
c None observed.
d 5-12mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 50mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A3-13
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
a 0-5mm2.
b Greater than 100mm2.
c None observed.
d 70-90mm2.
e Accept.
f Reject.
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 68-80mm.
b 45-60mm.
c None observed.
d 30-40mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 3.
b 4.
c None observed.
d 1.
e Accept.
f Reject.
A3-14
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
a More than 2.
b 1.
c None observed.
d 2.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (Highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 40-60mm.
b 20-35mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
A3-15
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-15mm.
c None observed.
d 15-23mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total length and would you accept or reject your findings to
the given acceptance levels.
a 31-39mm.
b 8-16mm.
c None observed.
d 40-60mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total length and would you accept or reject your findings to the given acceptance
levels?
a 15-30mm.
b 5-8mm.
c None observed.
d 0-2mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A3-16
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
17 Sharp areas of mechanical damage in the root area weld and parent material
(excluding hard stamping): Which answer best matches your assessment of the
accumulative total and would you accept or reject your findings to the given
acceptance levels?
18 Porosity in the weld root area: Which of the following answers best matches your
assessment of the accumulative total area and would you accept or reject your
findings to the given acceptance levels?
19 Burn through in the root area: Which answer best matches your assessment of
the accumulative total number of areas and would you accept or reject your
findings to the given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 Porosity: Which answer best matches your assessment and would you accept or
reject your findings to the given acceptance levels (measure from the weld
centreline to the plate edge)?
a 30-50mm2.
b 60-80mm2.
c None observed.
d 10-20mm2.
e Accept.
f Reject.
A3-17
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Weld Face
1 Maximum excess weld metal height (highest individual point measured): Which
answer best matches your assessment and would you accept or reject your
findings to the given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 80-100mm.
c 135-150mm.
d 110-130mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-50mm.
c None observed.
d 2-6mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a 20-30mm in length.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A3-18
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
a 35-45mm2.
b Greater than 55-80mm2.
c None observed.
d 20-30mm2.
e Accept.
f Reject.
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 110-130mm.
b 95-105mm.
c None observed.
d 65-85mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 2.
b 3.
c None observed.
d 1.
e Accept.
f Reject.
A3-19
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
9 Sharp areas of mechanical damage (excluding hard stamping and pop marks):
Which answer best matches your assessment of the total number of areas and
would you accept or reject your findings to the given acceptance levels.
a 4.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None.
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 35-40mm.
b 20-25mm.
c None observed.
d 0-10mm.
e Accept.
f Reject.
A3-20
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-10mm.
c None observed.
d 15-23mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total and would you accept or reject your findings to the given
acceptance levels?
a 8-12mm.
b 18-22mm.
c None observed.
d 20-40mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total l and would you accept or reject your findings to the given acceptance
levels?
a 15-25mm.
b 35-45mm.
c None observed.
d 50-60mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A3-21
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
17 Sharp areas of mechanical damage in the root area weld and parent material
(excluding hard stamping): Which answer best matches your assessment of the
accumulative total number of items and would you accept or reject your findings
to the given acceptance levels?
a 2-3.
b 1 item.
c None observed.
d More than 4 items.
e Accept.
f Reject.
18 Porosity in the weld root area: Which answer best matches your assessment of
the accumulative total area and would you accept or reject your findings to the
given acceptance levels?
19 Burn through in the root area: Which answer best matches your assessment of
the accumulative total number of areas and would you accept or reject your
findings to the given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 Cluster porosity: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels. (measure from the
weld centreline to the plate edge)?
a 3-5mm2.
b 6-8mm2.
c None observed.
d 1-2mm2.
e Accept.
f Reject.
A3-22
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Weld Face
1 Excess weld metal height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
2 Incomplete fill: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a None observed.
b 40-55mm.
c 30-40mm.
d 60-70mm.
e Accept.
f Reject.
3 Slag inclusions: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 60-70mm.
b 20-50mm.
c None observed.
d 5-12mm.
e Accept.
f Reject.
4 Undercut: Which answer best matches your assessment of the imperfection and
would you accept or reject your findings to the given acceptance levels?
a Smooth intermittent.
b Sharp but less than 1mm deep.
c None observed.
d Sharp but more than 1mm deep.
e Accept.
f Reject.
A3-23
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
5 Porosity in the weld: Which answer best matches your assessment of the total
accumulative area and would you accept or reject your findings to the given
acceptance levels?
a 0-20mm2.
b Greater than 30-50mm2.
c None observed.
d 60-70mm2.
e Accept.
f Reject.
6 Cracks: Which answer best matches your assessment of the total accumulative
length and would you accept or reject your findings to the given acceptance
levels?
7 Lack of fusion: Which answer best matches your assessment of the total
accumulative length and would you accept or reject your findings to the given
acceptance levels?
a 30-40mm.
b 45-55mm.
c None observed.
d 60-70mm.
e Accept.
f Reject.
8 Arc strikes: Which answer best matches your assessment of the total number
and would you accept or reject your findings to the given acceptance levels?
a 2.
b 4.
c None observed.
d 1.
e Accept.
f Reject.
A3-24
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
a 4.
b 1-2.
c None observed.
d 3.
e Accept.
f Reject.
Weld Root
a 1-2mm.
b 3-4mm.
c None observed.
d Greater than 5mm.
e Accept.
f Reject.
11 Root penetration height (highest individual point measured): Which answer best
matches your assessment and would you accept or reject your findings to the
given acceptance levels?
a 3-5mm.
b 1-2mm.
c None .
d Greater than 5mm.
e Accept.
f Reject.
12 Lack of root penetration: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 30-40mm.
b 21-29mm.
c None observed.
d 41-50mm.
e Accept.
f Reject.
A3-25
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
13 Lack of root fusion: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 28-35mm.
b 0-10mm.
c None observed.
d 15-26mm.
e Accept.
f Reject.
14 Root concavity or root shrinkage: Which answer best matches your assessment
of the accumulative total and would you accept or reject your findings to the given
acceptance levels?
a 31-39mm.
b 18-22mm.
c None observed.
d 40-60mm.
e Accept.
f Reject.
15 Root undercut: Which answer best matches your assessment of the accumulative
total and would you accept or reject your findings to the given acceptance levels?
a 35-45mm.
b 20-30mm.
c None observed.
d 50-60mm.
e Accept.
f Reject.
16 Cracks in the root: Which answer best matches your assessment of the
accumulative total length and would you accept or reject your findings to the
given acceptance levels?
a 10-17mm.
b 0-4mm.
c None observed.
d 5-8mm.
e Accept.
f Reject.
A3-26
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
17 Sharp indications of mechanical damage in the root area weld and parent
material (excluding hard stamping): Which answer best matches your
assessment of the accumulative total number of items and would you accept or
reject your findings to the given acceptance levels?
a 2-3.
b 1.
c None observed.
d 4-5.
e Accept.
f Reject.
18 Porosity in the weld root area: Which of the following answers best matches your
assessment of the accumulative total area and would you accept or reject your
findings to the given acceptance levels?
19 Burn through in the root area: Which answer best matches your assessment of
the accumulative total number of areas and would you accept or reject your
findings to the given acceptance levels?
a 1.
b 2.
c None observed.
d 3.
e Accept.
f Reject.
20 Cluster porosity: Which answer best matches your assessment and would you
accept or reject your findings to the given acceptance levels (measure from the
weld centreline to the plate edge)?
a 30-50mm2.
b 60-80mm2.
c None observed.
d 12-22mm2.
e Accept.
f Reject.
A3-27
www.twitraining.com
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
RETEST RETEST 10YR 10YR CANDIDATETOFILLALLBOXESINDICATEDINBLUE
1 2 3 4 5 6 7 INITIAL
1 2 INITIAL RETEST
WI 3.1 EXAM _
O O O O O O O O O O O O
INVIGILATORNAME: INVIGILATORSIGNATURE:
VERSION _
O O O O O O O
EXAMDATE: EVENTCODE
GENERALTHEORY TECHNOLOGYTHEORY
A B C D A B C D A B C D CANDIDATENAME: CANDIDATESIGNATURE:
1 1 31
Iagreewiththetermsandconditionsof Tick DateofBirth
2 2 32 thisexamination Box D D M M Y Y
3 3 33 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
MACROA
_ _
O O O O O O O O O O O O O O O O O O O O A B C D E F
4 4 34 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 1
5 5 35 _
O O O O O O O O O O _
O O O O O O O O O O
_
O O O O O O O O O O _
O O O O O O O O O O 2
6 6 36 _
O O O O O O O O O O _
O O O O O O O O O O
3
7 7 37 BOOKINGREFERENCEOFFICEUSEONLY CANDIDATENUMBERFOROFFICEUSEONLY
4
8 8 38
5
9 9 39
PLATE PIPE 6
10 10 40 A B C D E F A B C D E F
7
11 11 41 1 1
8
12 12 42 2 2
9
13 13 43 3 3
10
14 14 44 4 4
11
15 15 45 5 5
12
16 16 46 6 6
17 17 47 7 7
MACROB
18 18 48 8 8 A B C D E F
19 19 49 9 9 1
20 20 50 10 10 2
21 21 51 11 11 3
22 22 52 12 12 4
23 23 53 13 13 5
24 24 54 14 14 6
25 25 55 15 15 7
26 26 56 16 16 8
27 27 57 17 17 9
28 28 58 18 18 10
29 29 59 19 19 11
30 30 60 20 20 12
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Acceptance
Table number
macro only
Remarks Maximum allowance Remarks
A3-28
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Weld face
A B C
Notes: Excess weld metal height = Misalignment = Weld width = Toe blend =
C D
A
Notes: Excess weld metal height = Misalignment = Toe blend = Weld width =
A3-37
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
A B C
C D A
A3-38
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
Weld face
A B C
Notes: Excess weld metal height = Misalignment = Weld width = Toe blend =
C D
A
Notes: Excess weld metal height = Misalignment = Toe blend = Weld width =
A3-39
www.twitraining.com
Rev 2 April 2013
Appendix 3
Copyright TWI Ltd 2013
A B C
C D A
A3-40
www.twitraining.com
Appendix 4
Rev 2 April 2013
Appendix 4
Copyright TWI Ltd 2013
Across
7 For stovers (10)
9 The forces of magnetism on the weld pool (3,4)
10 An electrode with good toughness (5)
13 For creep resistance (10)
14 L in 316L (3)
18 Without filler wire (10)
24 I am often clustered (8)
26 CEV (6,10,5)
28 A solid inclusion (4)
30 Carelessness in welding causes me (3,6)
32 Used to examine grain structure (5)
33 I add strength and hardness (6)
34 A very hard and brittle microstructure (10)
36 Slope out to prevent me (6,5)
38 I can cut anything (6)
42 UTS (8,7,8)
44 A mode of transfer used in all positions (3)
45 Constant in GTAW (8)
46 Common gas used for GTAW (5)
47 Used for radiography over 50mm (6)
48 I may be essential or not (8)
49 When welding I must never go below this (7,7)
Down
1 IQI (5,7,9)
2 Used for weld detail (6)
3 I have a half life of 74.4.days (7)
4 Technique used to minimise distortion (4,4)
5 Can be caused by excess purge pressure (9)
6 Polarity for carbon GTAW (1,1,9,8)
8 10 x 10 x 55 long (6)
11 I suffer from this when depleted of chromium (4,5)
12 I am caused by unbalanced expansion and contraction (10)
15 This word is generally associated with rejection by most codes (9)
16 Only applicable in dip transfer (10)
17 Keeps rods at 70 degrees on site (6)
19 Used in mechanical testing over 12mm (4,4)
20 A step-like crack (8,7)
21 Preheating can minimise my chances (6)
22 SAW flux (5)
23 You can get me by 0.7 of your leg (6,6)
25 Used to apply a magnetic field (4)
27 A SAW flux easily crushed (12)
29 If my root is in compression this is me (4,4)
31 My purging powers prevent this (9)
35 Can be caused by an increased vertex angle (8,10)
37 All equipment should have this (11)
39 Polarity for welding aluminium with GTAW (11,7)
40 An electronic hazard (4,9)
41 If you slow down I go up (4,5)
43 Below this I turn molecular (5,7)
A4-1
www.twitraining.com
Appendix 5
Rev 2 April 2013
Appendix 5
Copyright TWI Ltd 2013
Appendix 5
Macro and Micro Visual Inspection
Macro-examination
Macro-etching a specimen is etched and evaluated macrostructurally at low
magnifications, is frequently used for evaluating carbon and low alloy steel
products such as billets, bars, blooms and forgings as well as welds. There
are several procedures for rating a steel specimen by a graded series of
photographs showing the incidence of certain conditions and is applicable to
carbon and low alloy steels. A number of different etching reagents may be
used depending upon the type of examination. Steels react differently to
etching reagents because of variations in chemical composition, method of
manufacture, heat treatment and many other variables.
Micro-examination
Performed on samples either cut to size or mounted in a resin mould. The
samples are polished to a fine finish, normally one micron diamond paste
and usually etched in an appropriate chemical solution prior to examination
on a metallurgical microscope. Micro-examination is performed for a number
of purposes, assess the structure of the material and examine for
metallurgical and anomalies such as third phase precipitates, excessive
grain growth, etc. Many routine tests such as phase counting or grain size
determinations are performed in conjunction with micro-examinations.
Metallographic weld evaluations can take many forms. In its most simplest,
a weld deposit can be visually examined for large scale defects such as
porosity or lack of fusion defects. On a microscale, it can be phase balance
assessments from weld cap to weld root or a check for non-metallic or third
phase precipitates. Examination of weld growth patterns is also used to
determine reasons for poor mechanical test results. For example, an
extensive central columnar grain pattern can cause a plane of weakness
giving poor Charpy results.
A5-1
www.twitraining.com
Rev 2 April 2013
Appendix 5
Copyright TWI Ltd 2013
Photomacrographs
A5-2
www.twitraining.com
Rev 2 April 2013
Appendix 5
Copyright TWI Ltd 2013
Training
Macroscopic
A5-3
www.twitraining.com
Rev 2 April 2013
Appendix 5
Copyright TWI Ltd 2013
Training Macro 1
1
10 2
8 4
5
7
6
A5-4
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
1 What is the indication at position 1 and would you accept or reject the indication
to the given acceptance levels?
a Slag inclusions.
b Porosity.
c Excessive grain size.
d Tungsten inclusions.
e Accept.
f Reject.
a Fusion zone.
b Fusion boundary.
c Toe of the weld.
d Undercut.
a Fusion boundary.
b Acid marks.
c Polished area.
d Heat affected zone.
4 What is the indication at position 4 and would you accept or reject the indication
to the given acceptance levels?
5 What is the indication at position 5 and would you accept or reject the indication
to the given acceptance levels?
a Gas cavity.
b Lack of sidewall fusion.
c Slag trapped at the toes of the weld.
d Lack of inter-run fusion and slag.
e Accept.
f Reject.
A5-5
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
6 What is the indication at position 6 and would you accept or reject the indication
to the given acceptance levels?
a Slag inclusion.
b Lack of root fusion.
c Lack of root penetration.
d Burn-through.
e Accept.
f Reject.
7 What is the indication at position 7 and would you accept or reject the indication
to the given acceptance levels?
8 What is the indication at position 8 and would you accept or reject the indication
to the given acceptance levels?
a Lamellar tearing.
b Hydrogen cracks.
c Laminations.
d Stress cracks.
e Accept.
f Reject.
9 What is the indication at position 9 and would you accept or reject the indication
to the given acceptance levels?
a Overlap.
b Toe of the weld with good transition.
c Toe of the weld with poor transition.
d Undercut at the toe of the weld.
e Accept.
f Reject.
A5-6
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
Training Macro 2
2
10
8 4
6
7
A5-7
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
1 What is the indication at position 1 and would you accept or reject the indication
to the given acceptance levels?
2 What is the indication at position 2 and would you accept or reject the indication
to the given acceptance levels?
a Undercut.
b Poor toe blend.
c Underfill.
d Lack of sidewall fusion.
e Accept.
f Reject.
3 What is the indication at position 3 and would you accept or reject the indication
to the given acceptance levels?
a Lamellar tearing.
b Corrosion crack.
c Hydrogen crack.
d Lamination.
e Accept.
f Reject.
4 What is the indication at position 4 and would you accept or reject the indication
to the given acceptance levels?
A5-8
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
5 What is the indication at position 5 and would you accept or reject the indication
to the given acceptance levels?
a Toe crack.
b Hydrogen crack.
c Overlap.
d Lamellar tear.
e Accept.
f Reject.
6 What is the indication at position 6 and would you accept or reject the indication
to the given acceptance levels?
a Spatter.
b Lap.
c Overlap.
d Hydrogen crack.
e Accept.
f Reject.
7 What is the indication at position 7 and would you accept or reject the indication
to the given acceptance levels?
a Gas cavity.
b Silicon inclusion.
c Slag inclusion.
d Copper inclusion.
e Accept.
f Reject.
A5-9
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
10 What is the indication at position 10 and would you accept or reject the indication
to the given acceptance levels?
a Slag line.
b Overlap.
c Lamination.
d Lamellar tear.
e Accept.
f Reject.
A5-10
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
Training Macro 3
10
9
2
8
7 4
6 5
A5-11
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
1 What is the indication at position 1 and would you accept or reject the indication
to the given acceptance levels?
a Linear crack.
b Overspill.
c Overlap.
d Lamination.
e Accept.
f Reject .
2 What is the indication at position 2 and would you accept or reject the indication
to the given acceptance levels?
a Saw marks.
b Lamellar tear.
c Segregation bands.
d Laminations.
e Accept.
f Reject.
3 What is the indication at position 3 and would you accept or reject the indication
to the given acceptance levels?
a Mechanical damage.
b Lap.
c Arc strike.
d Lamellar tear.
e Accept.
f Reject.
4 What is the indication at position 4 and would you accept or reject the indication
to the given acceptance levels?
A5-12
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
5 What is the indication at position 5 and would you accept or reject the indication
to the given acceptance levels?
a Slag.
b Silicon.
c Spatter.
d Copper.
e Accept.
f Reject.
6 What is the indication at position 6 and would you accept or reject the indication
to the given acceptance levels?
a Overlap.
b Crack.
c Incomplete root penetration.
d Incomplete root fusion.
e Accept.
f Reject.
7 What is the indication at position 7 and would you accept or reject the indication
to the given acceptance levels?
a Transverse crack.
b Transverse hydrogen crack.
c Lack of inter-run fusion.
d Shrinkage crack.
e Accept.
f Reject.
8 What is the indication at position 8 and would you accept or reject the indication
to the given acceptance levels?
9 What is the indication at position 9 and would you accept or reject the indication
to the given acceptance levels?
a Slag inclusion.
b Silicon inclusion.
c Gas cavity.
d Shrinkage defect.
e Accept.
f Reject.
A5-13
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
10 What is the indication at position 10 and would you accept or reject the indication
to the given acceptance levels?
a Porosity.
b Slag inclusion in weld metal.
c Silicon inclusions in weld metal.
d Tungsten inclusions in weld metal.
e Accept.
f Reject.
A5-14
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
Training Macro 4
1
2
10
9 7 6
8
A5-15
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
2 What is the indication at position 2 and would you accept or reject the indication
to the given acceptance levels?
a Overlap.
b Toe of the weld with good transition.
c Toe of the weld with poor transition.
d Undercut at the toe of the weld.
e Accept.
f Reject.
3 What is the indication at position 3 and would you accept or reject the indication
to the given acceptance levels?
a Undercut.
b Poor toe blend.
c Underfill.
d Lack of sidewall fusion.
e Accept.
f Reject.
4 What is the indication at position 4 and would you accept or reject the indication
to the given acceptance levels?
5 What is the indication at position 5 and would you accept or reject the indication
to the given acceptance levels?
a Silicon inclusion.
b Slag inclusion, lack of sidewall fusion and lack of inter-run fusion.
c Gas cavity.
d Gas cavity and lack of sidewall penetration.
e Accept.
f Reject.
A5-16
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
a Shrinkage.
b Linear distortion.
c Short transverse distortion.
d Angular distortion.
e Accept.
f Reject.
7 What is the indication at position 7 and would you accept or reject the indication
to the given acceptance levels?
a Silicon inclusion.
b Slag inclusion.
c Slag inclusion, lack of inter-run fusion and lack of sidewall fusion.
d Elongated gas pore.
e Accept.
f Reject.
8 What is the indication at position 8 and would you accept or reject the indication
to the given acceptance levels?
a Crack.
b Lack of inter-run fusion.
c Lack of sidewall fusion.
d Fusion boundary line.
e Accept.
f Reject.
10 What is the indication at position 10 and would you accept or reject the indication
to the given acceptance levels?
a Lamellar tearing.
b Hydrogen cracks.
c Laminations.
d Stress cracks.
e Accept.
f Reject.
A5-17
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
Training Macro 5
2
3
1
4
10
6
9
7
8
A5-18
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
1 What is the indication at position 1 and would you accept or reject the indication
to the given acceptance levels?
a Mechanical damage.
b Lap.
c Arc strike.
d Lamellar tear.
e Accept.
f Reject.
2 What is the indication at position 2 and would you accept or reject the indication
to the given acceptance levels?
a Lamellar tearing.
b Hydrogen cracks.
c Laminations.
d Stress cracks.
e Accept.
f Reject.
3 What is the indication at position 3 and would you accept or reject the indication
to the given acceptance levels?
a Undercut.
b Poor toe blend.
c Underfill.
d Lack of sidewall fusion.
e Accept.
f Reject.
4 What is the indication at position 4 and would you accept or reject the indication
to the given acceptance levels?
a Undercut.
b Poor toe blend.
c Underfill.
d Lack of sidewall fusion.
e Accept.
f Reject.
A5-19
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
5 What is the indication at position 5 and would you accept or reject the indication
to the given acceptance levels?
6 What is the indication at position 6 and would you accept or reject the indication
to the given acceptance levels?
a Shrinkage.
b Linear misalignment.
c Short transverse distortion.
d Transition weld set-up.
e Accept.
f Reject.
a Fusion boundary.
b Acid marks.
c Polished area.
d Heat affected zone.
A5-20
www.twitraining.com
Rev 2 April 2013
Appendix 5 Macro and Micro Visual Inspection
Copyright TWI Ltd 2012
Macro 1 Macro 2
1 1a 1b 1c 1d 1e 1f 1 1a 1b 1c 1d 1e 1f
2 2a 2b 2c 2d 2e 2f 2 2a 2b 2c 2d 2e 2f
3 3a 3b 3c 3d 3e 3f 3 3a 3b 3c 3d 3e 3f
4 4a 4b 4c 4d 4e 4f 4 4a 4b 4c 4d 4e 4f
5 5a 5b 5c 5d 5e 5f 5 5a 5b 5c 5d 5e 5f
6 6a 6b 6c 6d 6e 6f 6 6a 6b 6c 6d 6e 6f
7 7a 7b 7c 7d 7e 7f 7 7a 7b 7c 7d 7e 7f
8 8a 8b 8c 8d 8e 8f 8 8a 8b 8c 8d 8e 8f
9 9a 9b 9c 9d 9e 9f 9 9a 9b 9c 9d 9e 9f
10 10a 10b 10c 10d 10e 10f 10 10a 10b 10c 10d 10e 10f
Macro 3 Macro 4
1a 1b 1c 1d 1e 1f 1 1a 1b 1c 1d 1e 1f
1
2a 2b 2c 2d 2e 2f 2 2a 2b 2c 2d 2e 2f
2
3a 3b 3c 3d 3e 3f 3 3a 3b 3c 3d 3e 3f
3
4a 4b 4c 4d 4e 4f 4 4a 4b 4c 4d 4e 4f
4
5a 5b 5c 5d 5e 5f 5 5a 5b 5c 5d 5e 5f
5
6a 6b 6c 6d 6e 6f 6 6a 6b 6c 6d 6e 6f
6
7a 7b 7c 7d 7e 7f 7 7a 7b 7c 7d 7e 7f
7
8a 8b 8c 8d 8e 8f 8 8a 8b 8c 8d 8e 8f
8
9a 9b 9c 9d 9e 9f 9 9a 9b 9c 9d 9e 9f
9
10a 10b 10c 10d 10e 10f 10 10a 10b 10c 10d 10e 10f
10
Macro 5
1 1a 1b 1c 1d 1e 1f
2 2a 2b 2c 2d 2e 2f
3 3a 3b 3c 3d 3e 3f
4 4a 4b 4c 4d 4e 4f
5 5a 5b 5c 5d 5e 5f
6 6a 6b 6c 6d 6e 6f
7 7a 7b 7c 7d 7e 7f
8 8a 8b 8c 8d 8e 8f
9 9a 9b 9c 9d 9e 9f
A5-21
www.twitraining.com
CSWIP 3.1 Welding Inspection The Course
Introduction
Course Reference WIS 5
It is the sole responsibility of the candidate to provide the 20 x Pipe Butt Questions 105 Min
above. Failure to do so will delay results and certification
being issued.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
0-1
CSWIP 3.1 Examination Notification of Examination Results
70% pass
mark
Any standard/code required for
the examinations will be provided
on the examination day
0-2
TWI Certification Ltd
CSWIP Secretariat
TWI Certification Ltd
Granta Park
Great Abington
Cambridge CB21 6AL
United Kingdom
0-3
CSWIP 3.1 Welding Inspection Main Responsibilities
Code compliance.
Typical Duties Of Welding Inspectors
Workmanship control.
1-1
Welding Inspectors Equipment Welding Inspectors Gauges
1
Measuring devices: 3
Ammeter.
Magnifying glass
Torch/flash light.
Gas flowmeter.
Before welding.
During welding.
After welding.
1-2
Typical Duties of a Welding Inspector Typical Duties of a Welding Inspector
Before Welding
Before Welding
Equipment:
Welding Procedures:
All inspection equipment is in good condition and
Are applicable to joints to be welded and approved. calibrated as necessary.
Are available to welders and inspectors. All safety requirements are understood and necessary
equipment available.
Welder Qualifications:
List of available qualified welders related to WPSs. Materials:
Certificates are valid and in-date. Can be identified and related to test certificates.
Are of correct dimensions.
Are in suitable condition (no damage/contamination).
Before Welding
Before Welding
Consumables:
In accordance with WPSs. Fit-up
Are being controlled in accordance with procedure. Complies with WPS.
Number/size of tack welds to code/good workmanship.
Weld Preparations:
Comply with WPS/drawing.
Free from defects and contamination. Pre-heat
If specified.
Welding Equipment: Minimum temperature complies with WPS.
During Welding
During Welding
Weather conditions Welding consumables
Suitable if site/field welding. In accordance with WPS.
In suitable condition.
Controlled issue and handling.
Welding Process(es)
In accordance with WPS.
Welding Parameters
Welder Current, voltage and travel speed as WPS.
Is approved to weld the joint.
Pre-heat (if required) Root runs
Minimum temperature as specified by WPS. If possible, visually inspect root before single-sided welds
maximum interpass temperature as WPS are filled up.
1-3
Typical Duties of a Welding Inspector Typical Duties of a Welding Inspector
After Welding
During Welding
Weld Identification
Inter-run dressing Identified/numbered as required.
Is marked with welders identity.
In accordance with an approved method (and back
gouging) to good workmanship standard.
Visual Inspection
Distortion control Ensure weld is suitable for all NDT.
Visually inspect and sentence to code requirements.
Welding is balanced and over-welding is avoided.
Dimensional Survey
Ensure dimensions comply with code/drawing.
Other NDT
Ensure all NDT is completed and reports available.
Pressure/Load Test
Ensure test equipment is suitably calibrated.
Monitor to ensure compliance with procedure.
Ensure all records are available.
Resume: Resume:
Check all documentation.
Check amperage, voltage, polarity.
Check all consumables.
Check materials, dimensions and condition. Ensure the correct technique, run sequence.
Preheating, method and temperature. Check run out lengths, time lapses.
Check fit and set-up. Cleaning between passes.
Ensure no undue stress is applied to the joint. Interpass temperatures.
Check welding equipment. Consumable control.
Maintenance of records and reports.
1-4
WI Duties After Welding Summary of Duties
Resume: It is the duty of a Welding Inspector to ensure all the welding and
associated actions are carried out in accordance with the
Post cleaning.
specification and any applicable procedures.
Visual inspection of completed welded joint.
Check weld contour and width.
PWHT. A Welding Inspector must:
Dimensional accuracy. Observe
Weld reports. To observe all relevant actions related to weld quality throughout
Tie up with NDT. production.
Monitor any repairs. Record
To record, or log all production inspection points relevant to quality,
including a final report showing all identified imperfections.
Compare
To compare all recorded information with the acceptance criteria and any
other relevant clauses in the applied application standard.
Any Questions
?
Copyright TWI Ltd 2013
1-5
CSWIP 3.1 Welding Inspection Welding Terminology and Definitions
What is a Weld?
2-1
Double Sided Butt Preparations Joint Preparation Terminology
Double sided preparations are normally made on thicker materials,
Included angle Included angle
or when access form both sides is unrestricted.
Angle
Double - J Double - U Angle of
of
bevel
bevel
Land
Angle of bevel Angle of bevel Fillet weld Edge weld Compound weld
Root
Radius
Root Gap Root Gap Root Face
Root Face
Land
Butt weld Plug weld Spot weld
Single - J Butt Single Bevel Butt
2-2
Welded Lap Joints Welded Closed Corner Joints
Weld
metal
Heat
Affected Weld
Zone Boundary
Excess Root
C D A, B, C & D = Weld Toes Penetration
Root
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Weld Width
Maximum Solid Solid-liquid Boundary
Temperature weld
Grain growth zone
metal
Recrystallised zone
Partially transformed zone
Tempered zone
Unaffected base material
2-3
Toe Blend Features to Consider
Mitre fillet
Concave fillet a
A concave profile is preferred for
joints subjected to fatigue loading
b
a = Vertical leg length
Convex fillet b = Horizontal leg length
Note: The leg length should be approximately equal to the material thickness.
2-4
Deep Penetration Fillet Weld Features Deep Penetration Fillet Weld Features
a
b b
a = Design Throat Thickness
b = Actual Throat Thickness b = Actual Throat Thickness
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Calculating throat thickness from a known leg length: Calculating leg length from a known design throat
thickness:
2-5
Features to Consider Fillet Weld Sizes
Importance of fillet weld leg length size Importance of fillet weld leg length Size
(a) (b)
4mm 6mm
4mm 8mm (b)
(a)
4mm 2mm 4mm 6mm
Approximately the same weld volume in both Fillet Welds, but the Cross Sectional Area
effective throat thickness has been altered, reducing considerably
the strength of weld B. Question: How much larger is the csa (b) comparable to (a)?
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
4mm 6mm
Joint Design and Weld Preparation Joint Design and Weld Preparation
2-6
Joint Design and Weld Preparation Weld Preparation
root face
root gap
Typical Dimensions
Bevel angle 30 to 35
Root face ~1.5 to ~2.5mm
Too large = burn-through Too small = lack of root penetration
Root gap ~2 to ~4mm
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Joint design/weld preparation to reduce weld volumes Welding process impacts upon weld preparation
12 to 15
35
MMA MAG
High heat input process allow a larger root face, less weld metal
required, less distortions, higher productivity. Requires machining slow Can be flame/plasma cut fast
and expensive. and cheap.
If the gap is too big risk of possible burn-through, if gap is too Large tolerance set-up can be
small risk of lack of penetration. Tight tolerance easier set-up.
difficult.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
2-7
Weld Preparations Weld Preparations
Access impacts upon weld preparation Access impacts upon weld preparation
Access impacts upon weld preparation Type of joint impacts upon weld preparation
Pipe weld preparation - one side access only! Corner joints require offset
offset
for wall thickness up to 3 mm
for wall thickness 3 to 20 mm
for wall thickness over 20 mm Danger of burn-through Easy set-up no risk of
difficult to set-up burn-through
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Type of joint impacts upon weld preparation. Type of parent material impacts upon weld preparation
Lap and square edge butt joints do not require To reduce distortions on stainless steels welds, reduce
preparation. included angle and increase root face.
To avoid lack of side wall fusion problems aluminium
require larger included angles than steel.
60 70-90
30 35-45
2-8
Weld preparations Weld Preparations
Thickness of parent material impacts upon weld Thickness of parent material impacts upon weld
preparation preparation.
A single bevel groove requires a volume of weld metal Reduce weld volume by:
proportional to the square of plate thickness
Reduced included angle
Its lack of symmetry lead to distortions
Thickness of parent material impacts upon weld Thickness of parent material impacts upon weld
preparation. preparation
Reduce weld volume by:
Reduce weld volume by:
Use U prep instead V prep
Increase root face
PF symmetric PC asymmetric
Weld first into the deeper side after welding to half of preparation preparation
the depth, back gouge the root. complete welding on If symmetric preparation is used in the PC position the
the shallow side first. weld may spill out of the groove
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
2-9
Weld Preparation Weld Preparation
Type of loading impacts upon weld preparation. Type of loading impacts upon weld preparation.
60
Welding Terminology
Any Questions
?
Copyright TWI Ltd 2013
2-10
CSWIP 3.1 Welding Inspection Features to Consider
Root
TWI Training & Examination
penetration
Services
Root bead width
x Causes
Too small a root gap.
x x
Arc too long.
Wrong polarity.
Electrode too large for joint preparation.
Incorrect electrode angle.
Too fast a speed of travel for current.
3-1
Welding Defects Welding Defects
Incomplete root Fusion
Too large diameter
electrode.
Causes
Causes Excessive amperage during
Root gap too large. welding of root.
Insufficient arc energy. Excessive root gap.
Excessive back purge TIG. Poor fit up.
Excessive root grinding.
Improper welding technique.
Causes Causes
Root gap too large. Excessive welding current.
Excessive arc energy. Welding speed too high.
Small or no root face. Incorrect electrode angle.
Excessive weave.
Electrode too large.
3-2
Welding Defects Welding Defects
Lack of fusion
Overlap
Causes
Contaminated weld
preparation.
Amperage too low.
Amperage too high
Excess weld (welder increases speed of
metal travel).
Causes
Insufficient weld metal Causes
deposited. Insufficient weld metal deposited.
Improper welding technique. Improper welding technique.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Causes
Excessive moisture in flux or preparation.
Contaminated preparation.
Low welding current.
Arc length too long.
Damaged electrode flux.
Removal of gas shield.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
3-3
Welding Defects Welding Defects
Gas pores/porosity Inclusions - Slag
Causes
Insufficient cleaning between passes.
Contaminated weld preparation.
Welding over irregular profile.
Incorrect welding speed.
Arc length too long.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Causes
Insufficient cleaning between passes. Causes
Contaminated weld preparation.
Welding over irregular profile. Contamination of weld caused by excessive current
Incorrect welding speed. through electrode, tungsten touching weld metal or parent
Arc length too long. metal during welding using the TIG welding process.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Causes
Excessive arc energy.
Causes
Excessive arc length.
Excessive amperage during welding of root.
Damp electrodes.
Excessive root grinding.
Arc blow.
Improper welding technique.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
3-4
Welding Defects Welding Defects
Chisel
Chisel Marks
Marks Grinding Marks
Causes
50mm
3mm
2mm
Angular distortion
Measure the distance to the edge of the plate (50mm).
Use a straight edge (rule) to find the amount of distortion
Also Known as: Hi Low, mismatch or misalignment. then measure the space (3mm).
This reported as Angular distortion 3mm in 50mm.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Welding Defects
?
3 mm
3mm
3-5
CSWIP 3.1 Welding Inspection Destructive Testing Definitions
3 x Toughness The following mechanical tests have units and are termed
Destructive tests include: (Charpy V quantitative tests to measure mechanical properties of the
notch)
Bend test. joint.
Tensile tests (transverse welded joint, all weld metal).
Impact test. 2 x Ductile (Bend Toughness testing (Charpy, Izod, CTOD).
test)
Tensile test. Hardness tests (Brinell, Rockwell, Vickers).
Hardness test.
Macro/micro examination. 2 x Strength The following mechanical tests have no units and are
(transverse termed qualitative tests for assessing weld quality.
tensile)
Macro testing.
Bend testing.
Fillet weld fracture testing.
Butt weld nick-break testing.
Malleability.
Ductility. Ability of a material to
withstand deformation
Toughness.
under static Bend Test
Hardness. compressive loading Specimen
Tensile Strength. without rupture.
Charpy Specimen
Fracture Fillet
Specimen
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
4-1
Destructive Testing Mechanical Testing
Welding Procedure Qualification Testing
Top of fixed pipe
2 Typical positions for test pieces
Specimen type position
Hardness Testing
Macro + hardness. 5
3
Transverse tensile. 2, 4
Bend tests. 2, 4
Charpy impact tests. 3
Additional tests. 3
4
5
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Definition
Measurement of resistance of a material against Objectives:
penetration of an indenter under a constant load. Measuring hardness in different areas of a welded joint.
There is a direct correlation between UTS and hardness. Assessing resistance toward brittle fracture, cold
cracking and corrosion sensitivity.
4-2
Vickers Hardness Test Vickers Hardness Test Machine
Vickers hardness tests:
Indentation body is a square based diamond pyramid (136
included angle).
The average diagonal (d) of the impression is converted to a
hardness number from a table.
It is measured in HV5, HV10 or HV025.
Adjustable
Diamond Indentation shutters
indentor
=1.6mm 120Diamond
=10mm steel ball Cone
steel ball
Impact Testing
4-3
Charpy V-Notch Impact Test Charpy V-Notch Impact Test
Pendulum
Specimen (striker)
Weld metal Fusion Line (FL) FL+2mm FL+5mm Parent material
Objectives:
Measuring impact strength in different weld joint areas.
Assessing resistance toward brittle fracture.
Information to be supplied on the test report:
Material type.
Notch type.
Specimen size.
Test temperature.
Notch location. Anvil (support)
Impact Strength Value.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Machined notch.
Fracture surface
8 mm
100% bright
crystalline brittle
fracture.
100% Ductile
Machined notch.
Large reduction in
area, shear lips.
Randomly torn,
dull gray fracture
ASTM: American Society of Testing Materials. surface.
4-4
Charpy Impact Test Mechanical Testing
Reporting results
Location and orientation of notch.
Testing temperature.
Energy absorbed in joules. Tensile Testing
Description of fracture (brittle or ductile).
Location of any defects present.
Dimensions of specimen.
Rm
ReH
ReL
4-5
Tensile Tests Tensile Test
Transverse Tensile
Specimen
4-6
All Weld Metal Tensile Test All-Weld Metal Tensile Test
BS 709 / BS EN 10002
Original gauge length = 50mm
All Weld Metal Tensile Testing Increased gauge length = 64
Direction of the test *
Elongation % = Increase of gauge length X 100
Original gauge length
Elongation % = 14 X 100
50
Elongation = 28%
Tensile test piece cut along weld specimen.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
4-7
STRA (Short Transverse Reduction Area) STRA Test
Original CSA
Reduced CSA
Purpose
To examine the weld cross-section to give assurance that:
The weld has been made in accordance with the WPS.
The weld is free from defects.
Specimen Preparation
Macro/Micro Examination Full thickness slice taken from the weld (typically ~10mm thick).
Width of slice sufficient to show all the weld and HAZ on both
sides plus some unaffected base material.
One face ground to a progressively fine finish (grit sizes 120 to ~
400).
Prepared face heavily etched to show all weld runs & all HAZ.
Prepared face examined at up to x10 (& usually photographed for
records).
Prepared face may also be used for a hardness survey.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
4-8
Macro Preparation Macro/Micro Examination
Purpose
To examine a particular region of the weld or HAZ in order to: Object:
To examine the microstructure.
Macro/microscopic examinations are used to give a
Identify the nature of a crack or other imperfection.
visual evaluation of a cross-section of a welded joint.
Specimen Preparation Carried out on full thickness specimens.
A small piece is cut from the region of interest (typically up to ~
20mm x 20mm). The width of the specimen should include HAZ, weld
The piece is mounted in plastic mould and the surface of interest and parent plate.
prepared by progressive grinding (to grit size 600 or 800).
Surface polished on diamond impregnated cloths to a mirror finish They maybe cut from a stop/start area on a welders
Prepared face may be examined in as-polished condition and then approval test.
lightly etched.
Prepared face examined under the microscope at up to ~ 100
1000X.
Objectives:
Detecting weld defects (macro).
Measuring grain size (micro).
Detecting brittle structures, precipitates, etc.
Assessing resistance toward brittle fracture, cold cracking and
corrosion sensitivity.
Information to be supplied on the test report:
Material type.
Etching solution.
Magnification.
Grain size.
Location of examined area.
Weld imperfections (macro).
Macro examination Micro examination Phase, constituents, precipitates (micro).
4-9
Mechanical Testing Bend Tests
Object of test:
To determine the soundness of the weld zone. Bend testing can
also be used to give an assessment of weld zone ductility.
There are three ways to perform a bend test:
Bend Testing
Side bend tests are normally carried out on welds over 12mm in thickness.
Root/face
t up to 12 mm
bend
Thickness of material - t
4-10
Bend Testing Mechanical Testing
Hammer
Object of test:
To break open the joint through the weld to permit
examination of the fracture surfaces.
Specimens are cut to the required length.
A saw cut approximately 2mm in depth is applied along
the fillet welds length. 2mm
Fracture is usually made by striking the specimen with a Notch
single hammer blow.
Visual inspection for defects.
Hammer
2mm
Notch
This fracture indicates This fracture has
lack of fusion occurred saw cut to root
4-11
Fillet Weld Fracture Tests
Hammer
Reporting results:
Thickness of parent material.
Throat thickness and leg lengths.
Location of fracture.
Appearance of joint after fracture.
Depth of penetration.
Defects present on fracture surfaces.
Object of test:
To permit evaluation of any weld defects across the
fracture surface of a butt weld.
Specimens are cut transverse to the weld.
Nick-Break Testing A saw cut approximately 2mm in depth is applied along
the welds root and cap.
Fracture is usually made by striking the specimen with
a single hammer blow.
Visual inspection for defects.
Weld reinforcement
may or may not be
removed Lack of root Inclusions on fracture
penetration or fusion line
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
4-12
Nick-Break Test Summary of Mechanical Testing
Test procedure:
Under pressure leakage proof test
Blank off all openings with solid flanges.
Vessel configuration: Use correct nuts and bolts, NOT G clamps.
The test should be done after any stress relief. Two pressure gauges on independent tapping points
should be used.
Components that will not stand the pressure test (eg
For safety purposes bleed all the air out.
flexible pipes, diaphragms) must be removed.
pumping should be done slowly (no dynamic pressure
The ambient temperature MUST be above 0C stresses).
(preferably 15-20C). Test pressure - see relevant standards (PD 5500, ASME
VIII). Usually 150% design pressure.
Hold the pressure for minimum 30 minutes.
?
welds)!
Dry off any condensation.
Watch the gauges for pressure drop.
Check for distortion of flange faces, etc.
4-13
CSWIP 3.1 Welding Inspection Non-Destructive Testing
Non-Destructive Testing
Surface crack detection
Liquid penetrant (PT or dye-Penetrant).
Magnetic particle inspection (MT or MPI).
Volumetric inspection
Ultrasonics (UT).
Radiography (RT). Penetrant Testing (PT)
Each technique has advantages and disadvantages with
respect to:
Technical capability and cost.
Note: The choice of NDT techniques is based on consideration of
these advantages and disadvantages
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Step 1 Pre-Cleaning
Main features:
Ensure surface is very Clean normally with the use of a solvent.
Detection of surface breaking defects only.
This test method uses the forces of capillary action.
Applicable on any material type, as long they are non porous.
Penetrants are available in many different types:
Water washable contrast.
Solvent removable contrast.
Water washable fluorescent.
Solvent removable fluorescent.
Post-emulsifiable fluorescent.
5-1
Penetrant Testing Penetrant Testing
Step 2 Apply penetrant Step 3 Clean off penetrant
After the application, the penetrant is normally left on the The penetrant is removed after sufficient penetration time (dwell
components surface for approximately 15-20 minutes (dwell time). time).
The penetrant enters any defects that may be present by capillary Care must be taken not to wash any penetrant out off any defects
action. present.
5-2
Penetrant Testing Penetrant Testing
?
Relatively little training required.
Can use on all materials.
Disadvantages
Good surface finish needed.
Relatively slow.
Chemicals - health and safety issue.
Main features:
Surface and slight sub-surface detection.
Relies on magnetization of component being tested.
Only Ferro-magnetic materials can be tested.
Magnetic Particle testing (MT) A magnetic field is introduced into a specimen being tested.
Methods of applying a magnetic field, yoke, permanent magnet,
prods and flexible cables.
Fine particles of iron powder are applied to the test area.
Any defect which interrupts the magnetic field, will create a
leakage field, which attracts the particles.
Any defect will show up as either a dark indication or in the case
of fluorescent particles under UV-A light a green/yellow indication.
Collection of ink
particles due to
leakage field
A crack like
indication
Electro-magnet (yoke) DC or AC
Prods DC or AC
5-3
Magnetic Particle Testing Magnetic Particle Testing
Any Questions
Ultrasonic Testing (UT)
5-4
Ultrasonic Testing Ultrasonic Testing
UT set
Defect Back wall
A scan
Initial pulse echo echo display
Material Thk
defect
0 10 20 30 40 50
Advantages Disadvantages
Initial pulse Rapid results. Trained and skilled operator
Defect echo Both surface and sub-surface required.
defect 0 10 20 30 40 50
detection.
Requires high operator skill.
Skip CRT Display Safe.
Capable of measuring the Good surface finish required.
depth of defects. Defect identification.
May be battery powered.
Couplant may contaminate.
Portable.
initial pulse No permanent record.
defect echo Calibration required.
defect 0 10 20 30 40 50
5-5
Ultrasonic Testing Ultrasonic Testing
Ultrasonic Testing
Any Questions
?
Radiographic Testing (RT)
5-6
Radiographic Testing Radiographic Testing
Source
Source
Image quality indicator
Image quality indicator
Radiation beam Radiation beam
Test specimen
Radiographic film Test specimen
Densitometer
7FE12
Contrast - relates to the degree of difference.
Definition - relates to the degree of sharpness.
Sensitivity - relates to the overall quality of the radiograph.
Step/Hole type IQI Wire type IQI
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
5-7
Single Wall Single Image (SWSI) Single Wall Single Image Panoramic
Film
Film Film
Double Wall Single Image (DWSI) Double Wall Single Image (DWSI)
Identification.
Unique identification. EN W10
IQI placing.
Film
Pitch marks indicating A B
readable film length.
IQIs are placed on the film side. ID MR11
Source outside film outside (multiple exposure).
This technique is intended for pipe diameters over 100mm. Radiograph
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Double Wall Single Image (DWSI) Double Wall Double Image (DWDI)
Film
5-8
Double Wall Double Image (DWDI) Double Wall Double Image (DWDI)
Identification. 4 3 4 3
EN W10
Unique identification.
IQI placing.
Radiography Radiography
The type of isotope (the wavelength of the gamma rays). Caesium < 10 mm
5-9
Radiographic Testing Radiographic Testing
Any Questions
Comparison with ultrasonic examination
Disadvantages
Health and safety hazard.
?
Not good for thick sections.
High capital and relatively high running costs.
Not good for planar defects.
X-ray sets not very portable.
Requires access to both sides of weld.
Frequent replacement of gamma source needed (half life).
5-10
CSWIP 3.1 Welding Inspection Welding Procedure Qualification
Question:
What is the main reason for carrying out a Welding Procedure
Qualification Test?
(What is the test trying to show?)
Welding Procedures Answer:
To show that the welded joint has the properties* that satisfy the
design requirements (fit for purpose).
TWI Training and Examination
* properties
Services
Mechanical properties are the main interest - always strength but
toughness hardness may be important for some applications.
Test also demonstrates that the weld can be made without defects.
6-1
Welding Procedure Qualification Welding Procedure Qualification
Answer: Answer:
A variable, that if changed beyond certain limits (specified by A variable, that if changed beyond certain limits (specified by
the Welding Standard) may have a significant effect on the the welding standard) may have a significant effect on the
properties* of the joint. toughness and/or hardness of the joint.
* particularly joint strength and ductility Note: ASME calls variables that affect toughness as supplementary
essential variables (but does not refer to hardness).
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
6-2
Welding Procedures Welding Procedures
Components of a welding procedure
In most codes reference is made to how the procedure are to be
devised and whether approval of these procedures is required.
The approach used for procedure approval depends on the code: Parent material
Type (grouping).
Example codes: Thickness.
AWS D.1.1: Structural Steel Welding Code. Diameter (pipes).
BS 2633: Class 1 welding of Steel Pipe Work. Surface condition).
API 1104: Welding of Pipelines. Welding process
BS 4515: Welding of Pipelines over 7 Bar. Type of process (MMA, MAG, TIG, SAW etc).
Equipment parameters.
Other codes may not specifically deal with the requirement of
Amps, volts, travel speed.
a procedure but may contain information that may be used in
writing a weld procedure. Welding Consumables
Type of consumable/diameter of consumable.
Brand/classification.
EN 1011 Process of Arc Welding Steels. Heat treatments/ storage.
Purpose of a WPS
6-3
Welding Procedures Welding Positions
PA 1G / 1F Flat / Downhand
Monitoring Heat Input
PB 2F Horizontal-Vertical
As Required by BS EN ISO 15614-1:2004
PC 2G Horizontal
In accordance with EN 1011-1:1998
PD 4F Horizontal-Vertical (Overhead)
Welding Procedures
Monitoring Heat Input
PG As Required by BS EN ISO 15614-1:2012
PA In accordance with EN 1011-1:1998
PF When impact requirements apply, the upper limit of heat input
PB
qualified is 25% greater than that used in welding the test
piece.
PC
When hardness requirements apply, the lower limit of heat
PD input qualified is 25% lower than that used in welding the test
piece.
6-4
Welding Procedures Welding Procedures
TABLE 5 BS EN ISO 15614-1:2012
TABLE 6 BS EN ISO 15614-1:2004
t>30 >5 a No
t>100 Not applicable 50 to 2t Restriction
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Butt Parent metal thickness at the joint. a is the throat as used for the test piece
Fillet - Parent metal thickness. Note 2:
Set-on branch - Parent metal thickness. Where the fillet weld is qualified by means of a butt
Set-in / through branch - Parent metal thickness. test, the throat thickness range qualified shall be
based on the thickness of the deposited metal.
T-butt - Parent metal thickness.
For branch connections and fillet welds , the range of qualification
For special applications only. Each fillet weld shall
shall be applied to both parent materials independently. be proofed separately by a welding procedure test.
6-5
Welding Procedures Welding Procedures
TABLE 7 BS EN ISO 15614-1:2004
Heat input
Arc energy
The amount of heat generated in the welding arc per The energy supplied by the welding arc to the work
unit length of weld. Expressed in kilo Joules per piece.
millimetre length of weld (kJ/mm).
Expressed in terms of; arc energy x thermal efficiency
Arc energy (kJ/mm)= Volts x Amps factor.
welding speed(mm/s) x 1000
Thermal efficiency factor is the ratio of heat energy
introduced into the weld to the electrical energy
consumed by the arc.
6-6
Monitoring Heat Input Monitoring Heat Input
Thermal efficiency factor k of welding processes Abbreviations and symbols
Process No Process Factor k
121 Submerged arc welding with wire 1.0 I Arc welding current (Amps)
111 Metal-arc welding with covered electrodes 0.8 k Thermal efficiency Factor
131 MIG welding 0.8 v Welding Speed (mm/min)
135 MAG welding 0.8 Q Heat Input (kJ/mm)
114 Flux-cored wire metal-arc welding without gas shield 0.8 U Arc Voltage (Volts)
136 Flux-cored wire metal-arc welding with active gas shield 0.8
137 Flux-cored wire metal-arc welding with inert gas shield 0.8 Q= k U x I x 10-3 = kJ/mm or Amp x volts x time
138 Metal-cored wire metal-arc welding with active gas shield 0.8
v ROL x 1000
139 Metal-cored wire metal-arc welding with inert gas shield 0.8
Example
AE (kJ/mm) = Volts x amps
A MAG weld is made and the following conditions
were recorded; Travel speed(mm/ sec) x 1000
= 24 x 240
Arc volts = 24 (300/60) x 1000
Welding amperage = 240 = 5760
Travel speed = 300mm / minute. 5000
According to EN Standards
Welder Approval Question:
Example BS EN 287
What is the main reason for qualifying a welder?
6-7
Welder Qualification Welder Qualification
According to EN 287
According to EN 287
The finished test weld is subjected to NDT by the methods
specified by the EN Standard - Visual, MT or PT and RT or UT.
An approved WPS should be available covering the range of
qualification required for the welder approval.
The test weld may need to be destructively tested - for certain
materials and/or welding processes specified by the EN
The welder qualifies in accordance with an approved WPS.
Standard or the Client Specification.
A welding inspector monitors the welding to make sure that
A Welders Qualification Certificate is prepared showing the
the welder uses the conditions specified by the WPS.
conditions used for the test weld and the range of
qualification allowed by the EN Standard for production
EN Welding Standard states that an Independent Examiner,
welding.
Examining Body or Third Party Inspector may be required to
monitor the qualification process. The Qualification Certificate is usually endorsed by a Third
Party Inspector as a true record of the test.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
A Certificate may be withdrawn by the Employer if there is reason to A variable, that if changed beyond the limits specified by
doubt the ability of the welder, for example: the EN Standard, may require more skill than has been
A high repair rate. demonstrated by the test weld
not working in accordance with a qualified WPS.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Welding position. The test weld should be carried out on the same material and
same conditions as for the production welds.
Weld Backing (an unbacked weld requires more skill).
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
6-8
Welder Qualification Welder Qualification
Information that should be included on a welders test certificate are: The inspection of a welders qualification test.
Welders name and identification number. It is normal for a qualified inspectors usually from an independent
Date of test and expiry date of certificate. body to witness the welding.
Standard/code eg BS EN 287. Under normal circumstances only one test weld per welder is
Test piece details. permitted.
Welding process.
Welding parameters, amps, volts. If the welder fails the test weld and the failure is not the fault of the
Consumables, flux type and filler classification details. welder eg faulty welding equipment then a re-test would be
Sketch of run sequence. permitted.
Welding positions.
The testing of the test weld is done in accordance with the
Joint configuration details.
applicable code.
Material type qualified, pipe diameter etc.
Test results, remarks. It is not normal to carry out tests that test for the mechanical
Test location and witnessed by. properties of welds eg tensile, charpy and hardness tests.
Extent (range) of approval.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Welder Qualification
Any Questions
?
Example:
Welder Approval
Qualification
Certification
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
6-9
CSWIP 3.1 Welding Inspection Material Inspection
Specification
Welded seam
Specification
Other checks may need to be made such as: distortion tolerance, Other checks may need to be made such as: distortion
number of pipes and storage*. tolerance, number of plates and storage.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Direction of rolling
Lamination
Cold Laps*
Segregation line
Laminations are caused in the parent plate by the steel making
process, originating from ingot casting defects.
Segregation bands occur in the centre of the plate and are low
melting point impurities such as sulphur and phosphorous.
Lamination Segregation Laps are caused during rolling when overlapping metal does not fuse
to the base material.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
7-1
Lapping Lapping
Lapping Lamination
Any Questions
Plate Lamination
Copyright TWI Ltd 2013
? Copyright TWI Ltd 2013
7-2
CSWIP 3.1 Welding Inspection Quality in Welding
Standard/Codes/Specifications Standard/Codes/Specifications
Standard Specification
8-1
Standard/Codes/Specifications Standard/Codes/Specifications
BS EN 26848 BS EN 440
Specification for tungsten electrodes for inert gas shielded arc Wire electrodes and deposits for gas shielded metal arc of
welding and for plasma cutting and welding. non - alloy and fine grain steels.
Any Questions
?
Copyright TWI Ltd 2013
8-2
CSWIP 3.1 Welding Inspection Weld Symbols on Drawings
Welding Symbols
TWI Training & Examination
Services By symbolic representation.
A method of transferring information from the design office to Advantages of symbolic representation:
the workshop is: Simple and quick plotting on the drawing.
Does not over-burden the drawing.
Please weld
here No need for additional view.
Gives all necessary indications regarding the specific joint to
be obtained.
The above information does not tell us much about the wishes of
the designer. We obviously need some sort of code which would be Disadvantages of symbolic representation:
understood by everyone. Used only for usual joints.
Requires training for properly understanding of symbols.
Most countries have their own standards for symbols.
Some of them are AWS A2.4 & BS EN 22553 (ISO 2553)
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
9-1
Reference Line Reference Line
or
Fillet weld.
Double V Double U
9-2
Dimensions Supplementary Symbols
Concave or Convex
Reference
lines
Arrow line
Arrow side
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
9-3
ISO 2553/BS EN 22553 ISO 2553/BS EN 22553
Other side
Both sides
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
a b
Mitre Convex
Toes
Concave shall be
c d
blended
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
9-4
Fillet Welds ISO 2553/BS EN 22553
Welds to be
z
staggered
z nl (e) a nl (e)
2 x 40 (50)
111 z nl (e) a nl (e)
3 x 40 (50) or
Process
6 z
80 80 80
6
z nl(e) a nl(e)
8 90 90 z nl(e) a nl(e)
90
or
8
9-5
ISO 2553/BS EN 22553 ISO 2553/BS EN 22553
MR
All dimensions in mm M
z5 3 x 80 (90)
z6 3 x 80 (90)
5
80 80 80 Single-V Butt with Single-U Butt with
5 permanent backing strip removable backing strip
6 90 90 90
6
Single-V Butt flush cap Single-U Butt with sealing run
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
s10
9-6
ISO 2553/BS EN 22553 Butt Weld Ex ISO 2553/BS EN 22553 Compound Weld Ex
z 10 3 x 50 (50)
AWS A2.4 Welding Symbols
50
50
10
9-7
AWS Welding Symbols AWS Welding Symbols
Welding Process
Depth of Root Opening
Bevel
GSFCAW
1(1-1/8) 1(1-1/8)
1/8 1/8
60o 60o
GMAW
Effective Groove Angle
Throat GTAW
SAW
3 10
SMAW
3 10
GSFCAW Process
1(1-1/8)
3 3
Applicable to any
single groove Single Bevel
weld
10
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
3rd Operation RT
Sequence of Sequence of
Operations Operations MT
2nd Operation
MT
1st Operation FCAW
FCAW 1(1-1/8)
1(1-1/8) 1/8
1/8
60o
60o
9-8
AWS Welding Symbols Fillet Welds
6 leg on member A 8
8
6/8
6 5 leg on
Member A 5x8
vertical
member
8 5
8
Member B
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
z l-e
z l-e z l-e
z l-e
Symbol to AWS A2.4
Symbol to AWS A2.4
9-9
Any Questions
?
Copyright TWI Ltd 2013
9-10
CSWIP 3.1 Welding Inspection Welding Processes
Welding is regarded as a joining process in which the
work pieces are in atomic contact.
10-1
Welding Process Comparison Welding Processes
Process Electrical characteristic Electrode current type
?
MIG/MAG Flat / constant voltage DC+ve,
10-2
Welding Processes and Equipment
11-14-1
MMA Welding Parameters Constant /Drooping Current Characteristics
Current
Range set by electrode, diameter, material type OCV Amperage range
+/- 5 amps
and thickness. 50-90
- Voltage +
Too low poor start, lack of fusion, slag Operational
inclusions, humped bead shape. range 20-40V
Too high spatter, excess penetration, undercut,
burn-through.
Polarity - Amperage +
As arc length increases
Can be DCEP, DCEN, AC. voltage increases and
Determined by operation and electrode type. amperage decreases
11-14-2
Typical Welding Defects Advantages and Disadvantages
Plastic foil sealed cardboard box Use industrially extracted cellulose powder, or
Rutile electrodes.
General purpose basic electrodes.
wood flour in the formula.
Characteristic smell when welding.
Courtesy of Lincoln Electric Slag remains thin and friable.
Tin can Strong arc action and deep penetration.
Cellulosic electrodes. AWS E6010 types DC; E6011 run on AC.
Courtesy of Lincoln Electric
High amount of TiO2, (rutile sand or ilmenite). High amount Fe powder added.
Coatings often coloured. More weld metal laid at the same current.
AWS type E6012 are DC; E6013 run on AC. Coating much thicker, forms deep cup.
Many designed for flat position. End of coating can rest on workpiece.
Fluid slag, smooth bead, easy slag removal. Slag easy release, sometimes self-releasing.
Need some moisture to give gas shield. Only for flat position.
Not low hydrogen. These AWS E7024 have recovery between 150
Available for ferritic and austenitic steels. and 180%.
Fair mechanical properties. Recovery = Weld metal wt x100/core wire wt.
11-14-3
Basic Electrodes BS EN 2560 MMA Covered Electrodes
?
Cellulosic E XX X C EXX10
EXX11
Rutile E XX X R EXX12
EXX13
Rutile Heavy Coated E XX X RR EXX24
Basic E XX X B EXX15
EXX16
EXX18
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
11-14-4
TIG Basics
Gas noozle
Non-consumable
TIG Welding tungsten electrode
Gas shield
Arc
Filler Rod
Weld Pool
TWI Training & Examination
Weld Metal
Services Parent Metal
Power control
Scratch start
panel Transformer/ Tungsten touched on workpiece.
Rectifier
Short-circuit starts current.
Power return Arc established as torch lifted.
cable Inverter
power source
Can leave tungsten inclusions.
Lift Arc
Torch
assemblies Power control Electronic control very low short-circuit current.
panel Builds to operational current as torch lifted.
Tungsten
electrodes Power cable HF
Superimposition of HF high voltage spark.
Flow-meter
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
DCEN
Most used. OCV Amperage range
50-90 +/- 5 amps
Tungsten cooled by electron emission.
Workpiece receives more heat.
- Voltage +
DCEP Operational
range 20-40V
Will clean oxide from Al and Mg.
Heat tends to melt tungsten.
Can be done with water cooled torch.
- Amperage +
AC As arc length increases
voltage increases and
Usual way to weld Al and Mg to get cleaning. amperage decreases.
11-14-5
Cathodic Cleaning Square Wave Maximum Square Wave Maximum Penetration
AC AC
70 70 30 30
30 30 70 70
0
+
Negative cycle Positive cycle
-
0
11-14-6
Ideal for Root Runs Manual TIG
Tungsten
electrode
Torch cap / tungsten Electrode
housing collet Collet
holder
Torch
body Ceramic
Torch types: Gas cooled: cheap, simple, large size, short life for nozzle
component parts.
Water cooled: recommended over 150A, expensive, On/off
complex, longer life of parts. switch
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
11-14-7
TIG Welding Sequence Purpose of These Functions
3 4 5
1 2
2 4
1 5
11-14-8
Pipe Backing Gas Dams Purging Methods
Increase
High current carrying but slightly radioactive.
W + CeO2 grey (Europe), orange (USA) Vertex
Good for low current DC work. angle
W + La2O3 black Decrease
Increasing use to replace thoriated.
W + ZrO2 white (Europe), brown (USA) Bead width
Electrode tip for low increase Electrode tip for high
Used for AC. current welding current welding
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
11-14-9
Orbital TIG Orbital TIG
11-14-10
Disadvantages of TIG
?
Not good in draughty conditions.
Low tolerance of contaminants.
Tungsten inclusions can occur.
MIG/MAG Welding
11-14-11
MIG/MAG Equipment Wire Feeding
Internal wire
feed system Power cable &
hose
assembly
Power control
panel
Liner for wire
15kg wire spool
Welding gun Separate wire feeder Wire feeder in set
Power return assembly
cable
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
11-14-12
Torch Components The Relationship Between Amps and Volts
Welding gun assembly Welding gun body
(less nozzle) Voltage Dial on weld
On/Off switch machine
Spatter Hose
- Voltage +
protection port
Arc Length
Nozzles or Spot welding
- Amperage +
shrouds spacer
11-14-13
The Effect of Increasing Arc Voltage Shielding Gas
Argon:
OK for all metals weldable by MIG.
Supports spray transfer, not good for dip.
Low penetration.
Carbon dioxide:
Use on ferritic steel.
Arc Length @ Arc Length @ Supports dip and globular, not spray.
28 V 250A 34 V 230A
Ar based mixtures:
Add He, O2, CO2 to increase penetration.
>20Ar + He, >80Ar + O2, CO2 can spray and dip.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Metal Inert Gas (MIG) Depending on shielding gas and voltage, metal crosses
Usually Ar shielding. from wire to work in:
Can be Ar + He mixture gives hotter action. Spray mode wire tapers to a point and very fine
droplets stream across from the tip.
Used for non-ferrous alloys, eg Al, Ni.
Globular mode large droplets form and drop under
Metal Active Gas (MAG) action of gravity and arc force.
Has oxidising gas shield. Short-circuiting (dip) mode wire touches pool
Can be 100% CO2 for ferritic steels. surface before arc re-ignition.
Often Ar + 12 to 20% CO2 for both dip and spray. Pulsed mode current and voltage cycled between
Ar + O2 for stainless steel. no transfer and spray mode.
11-14-14
Dip Transfer Dip Transfer
Time (sec)
11-14-15
Gas Metal Arc Welding Spray Transfer
Spray Transfer
When current and voltage are raised together higher energy is
available for fusion (typically > ~ 25 volts & ~ 250 amps). Continuous transfer of
metal.
This causes a fine droplets of weld metal to be sprayed from the High voltage long arc.
tip of the wire into the weld pool. High heat input.
Transfer-mode advantages Fluid weld pool.
High energy gives good fusion.
High deposition.
High rates of weld metal deposition are given. No spatter.
These characteristics make it suitable for welding thicker joints.
Transfer-mode disadvantages.
It cannot be used for positional welding.
Advantages
Good fusion.
Small weld pool allows all-position welding. The self adjusting arc
quickly re adjusts to
establish equilibrium.
Disadvantages
More complex and expensive power source.
Difficult to set parameters. AMPS 190 AMPS 170
VOLTS 23 VOLTS 23
But synergic easy to set, manufacturer provides
programmes to suit wire type, dia. and type of
gas. Although the arc length remains the same, the current will decrease
due to the increased resistance of lengthening the CTWD.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
11-14-16
The effect of decreasing CTWD Contact Tip to Nozzle Distance
Although the arc length remains the same, the current will increase
due to the decreased resistance of shortening the CTWD. Set up for Dip transfer Set up for Spray transfer
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
MIG/MAG Attributes
Advantages
High productivity
Disadvantages
Lack of fusion (dip) Any Questions
Easily automated Small range of
?
All positional (dip and consumables
pulse) Protection on site
Material thickness range Complex equipment
Continuous electrode Not so portable
11-14-17
Gas Shielded Principle of Operation
11-14-18
Backhand (Drag) Technique Forehand (Push) Technique
FCAW Disadvantages
11-14-19
SAW Principle of Operation SAW FILMS
Arc between bare wire and parent plate. Flux fed from hopper in continuous mound
along line of intended weld.
Arc, electrode end and the molten pool
submerged in powdered flux. Mound is deep to submerge arc. No spatter,
weld shielded from atmosphere, no UV light.
Flux makes gas and slag in lower layers under
heat of arc giving protection. Un melted flux reclaimed for further use.
Wire fed by voltage-controlled motor driven Only for flat and horizontal-vertical positions in
rollers to ensure constant arc length. most cases.
Transformer/
Power return
Rectifier
cable
Granulated
flux
Column and boom Gantry
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
11-14-20
SAW Equipment Tractor Units
Wire reel
For straight or gently
curved joints.
Slides
Flux Ride tracks alongside joint
hopper or directly on workpiece.
Wire feed
Can have guide wheels to
motor
Feed roll track.
assembly
Good portability, used
Torch
assembly
where piece cannot be Courtesy of ESAB AB
moved.
Tracking
system Courtesy of ESAB AB
Contact tip
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Courtesy of ESAB AB
11-14-21
Constant Current Power Wire
Welding current.
Current type and polarity.
Welding voltage.
Travel speed.
Electrode size. Extension bars Run off plate Extension bars
Electrode extension WHY? simulating
identical joint
Width and depth of the layer of flux. preparation
11-14-22
Any Questions
11-14-23
CSWIP 3.1 Welding Inspection Oxyfuel Gas Cutting Process
A jet of pure oxygen reacts with iron, that has been preheated to its
ignition point, to produce the oxide Fe3O4 by exothermic reaction.
Cutting Processes This oxide is then blown through the material by the velocity of the
oxygen stream.
Different types of fuel gases may be used for the pre-heating flame in
oxy fuel gas cutting: ie acetylene, hydrogen, propane etc.
TWI Training & Examination Services
By adding iron powder to the flame we are able to cut most metals
- Iron Powder Injection.
The high intensity of heat and rapid cooling will cause hardening
in low alloy and medium/high C steels they are thus pre-heated
to avoid the hardening effect.
Cut too slow - top edge is melted, Cut too fast - pronounced break Preheat flame too low - deep groves Preheat flame too high - top edge is
deep groves in the lower portion, in the drag line, irregular cut in the lower part of the cut face. melted, irregular cut, excess of
heavy scaling, rough bottom edge. edge. adherent dross.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
15-1
Oxyfuel gas cutting quality Mechanised Oxyfuel Cutting
Good cut - sharp top edge, fine and even drag lines, little oxide and
a sharp bottom edge.
Can use portable carriages or gantry type machines high
productivity.
Accurate cutting for complicate shapes.
Nozzle is too high above the works - Irregular travel speed - uneven space
excessive melting of the top edge, between drag lines, irregular bottom with
much oxide. adherent oxide.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Advantages: Disadvantages:
No need for power supply High skill factor.
portable.
Wide HAZ.
Versatile: preheat, brazing,
surfacing, repair, straightening Safety issues.
Cutting and bevelling head. Low equipment cost. Slow process.
Plasma Cutting
15-2
Plasma Cutting
Any Questions
15-3
Welding Consumables
Welding Gases
Each consumable is critical in respect to:
GMAW, FCAW, TIG, Oxy- Fuel.
Supplied in cylinders or storage tanks for Size.
large quantities.
Classification/supplier.
Colour coded cylinders to minimise
wrong use. Condition.
Subject to regulations concerned
handling, quantities and positioning of Treatments eg baking/drying.
storage areas.
Handling and storage is critical for consumable control.
Moisture content is limited to avoid cold
cracking. Handling and storage of gases is critical for safety.
Dew point (the temperature at which the
vapour begins to condense) must be
checked.
16-1
Quality Assurance Welding Consumables
Welding Consumables:
Filler material must be stored in an area with controlled
temperature and humidity.
Poor handling and incorrect stacking may damage coatings,
rendering the electrodes unusable.
MMA Covered Electrodes
There should be an issue and return policy for welding
consumables (system procedure).
Control systems for electrode treatment must be checked
and calibrated; those operations must be recorded.
Filler material suppliers must be approved before purchasing
any material.
16-2
MMA Welding Consumables MMA Welding Consumables
Cellulosic electrodes: Cellulosic Electrodes
Covering contains cellulose (organic material).
Produce a gas shield high in hydrogen raising the arc Disadvantages:
voltage. Weld beads have high hydrogen.
Deep penetration / fusion characteristics enables welding at
Risk of cracking (need to keep joint hot during welding to allow
high speed without risk of lack of fusion.
H to escape).
Generates high level of fumes and H2 cold cracking.
Not suitable for higher strength steels - cracking risk too
Forms a thin slag layer with coarse weld profile.
high (may not be allowed for Grades stronger than X70).
Not require baking or drying (excessive heat will damage
electrode covering). Not suitable for very thick sections (may not be used on
thicknesses > ~ 35mm).
Mainly used for stove pipe welding.
Hydrogen content is 80-90 ml/100 g of weld metal. Not suitable when low temperature toughness is required
(impact toughness satisfactory down to ~ -20C).
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
16-3
MMA Welding Consumables MMA Welding Consumables
Basic Electrodes
Advantages Disadvantages
Compulsory
High toughness values. High cost.
Low hydrogen contents. High control.
Low crack tendency. High welder skill required.
Convex weld profiles.
Poor stop/start properties.
Optional
16-4
BS EN 499 MMA Covered Electrodes BS EN 499 MMA Covered Electrodes
16-5
AWS A5.1 and A5.5 Alloyed Electrodes Moisture pick-up
Vacuum
Use straight from the pack If not used within 4
packed basic within 4 hours - No rebaking! hours, return to
Use from quivers
Weld
at 75C
electrodes oven and rebake!
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
16-6
Covered Electrode Treatment MMA Welding Consumables
1: Electrode size (diameter and length).
Any Questions
?
2: Covering condition: adherence, cracks, chips and concentricity.
3: Electrode designation.
EN 499-E 51 3 B
Must be kept clean and free from oil and dust. EB inserts (Electric Boat Company).
16-7
Fusible Inserts Fusible Inserts
Consumable inserts: Application of consumable inserts
Used for root runs on pipes.
Used in conjunction with TIG welding.
Available for carbon steel, Cr-Mo steel, austenitic stainless
steel, nickel and copper-nickel alloys.
Different shapes to suit application.
Radius
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Shielding Gases for TIG Welding Shielding Gases for TIG Welding
Helium
Argon
Costly and lower availability than Argon.
Low cost and greater availability.
Lighter than air - requires a higher flow rate compared with
Heavier than air - lower flow rates than Helium.
argon (2-3 times).
Low thermal conductivity - wide top bead profile.
Higher ionisation potential - poor arc stability with AC, less
Low ionisation potential - easier arc starting, better arc forgiving for manual welding.
stability with AC, cleaning effect.
For the same arc current produce more heat than argon -
For the same arc current produce less heat than helium - increased penetration, welding of metals with high melting
reduced penetration, wider HAZ. point or thermal conductivity.
To obtain the same arc power, argon requires a higher
To obtain the same arc power, helium requires a lower
current - increased undercut.
current - no undercut.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Shielding Gases for TIG Welding Shielding Gases for TIG Welding
Hydrogen Nitrogen
Not an inert gas - not used as a primary shielding gas. Not an inert gas.
Increase the heat input - faster travel speed and increased High availability cheap.
penetration.
Added to argon (up to 5%) - only for back purge for
Better wetting action - improved bead profile. duplex stainless, austenitic stainless steels and copper
Produce a cleaner weld bead surface. alloys.
Added to argon (up to 5%) - only for austenitic stainless Not used for mild steels (age embrittlement).
steels and nickel alloys. Strictly prohibited in case of Ni and Ni alloys (porosity).
Flammable and explosive.
16-8
TIG Welding Consumables Welding Consumables
Any Questions
?
MIG/MAG Consumables
EN 440 - G 46 3 M G3Si1
Weld deposit produced by
gas shielded metal arc
welding
16-9
MIG/MAG Welding Consumables MIG/MAG Welding Consumables
Wire designation acc. AWS A-5.18: How to check the quality of welding wires:
Chemical composition of the solid wire or
Cast diameter
of the weld metal in case of composite
Helix size - limited to 25 mm to
electrodes
avoid problems with arc
Minimum UTS of weld metal (ksi) wandering!
Standard number
AWS A-5.18 ER 70 S-6 Cast diameter improves the contact force and defines the contact point;
usually 400-1200 mm.
Designate an electrode/rod (ER) or
only an electrode (E)
Solid (S) or composite (C) wire Contact point close to contact tip Contact point remote from contact tip
end - GOOD! end - POOR!
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Argon (Ar):
MIG process (131) MAG process (135) Higher density than air; low thermal conductivity the arc has
a high energy inner cone; good wetting at the toes; low
ionisation potential.
BS EN 439
Helium (He):
Lower density than air; high thermal conductivity uniformly
distributed arc energy; parabolic profile; high ionisation
Group I - Ar, He Group R - Ar Group M - Ar + Group C - CO2, potential.
and Ar-He + H2 (<35%) CO2/O2 CO2 + O2 Carbon Dioxide (CO2):
mixtures (<50/15%) (<30%) Cheap; deep penetration profile; cannot support spray
transfer; poor wetting; high spatter .
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
16-10
MIG/MAG Welding Consumables Welding Consumables
Any Questions
Flux Core Wire Consumables
16-11
FCAW Wire Designation FCAW Wire Designation
Wire designation acc. BS EN 758: Wire designation acc. AWS A-5.20:
Diffusible hydrogen content (optional) 27J at -40C requirement (optional)
Shielding gas Electrode usability (polarity, shielding
Light alloy additions and KV); can range from 1 to 14
Tensile properties Welding position (0 - F/H only; 1- all
positions)
Standard number
Designates an electrode
EN 758 - T 46 3 1Ni B M 4 H5 E 71 T-6 M J H8
Minimum UTS of weld metal (ksi x 10)
Tubular cored electrode
Flux cored electrode
Impact properties
Shielding gas for classification
Type of electrode core
Diffusible hydrogen content (optional);
Welding position (optional) can be 4, 8 or 16
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Any Questions
?
SAW Consumables
16-12
SAW filler material SAW filler material
Welding wires Welding wires can be used to weld:
Supplied on coils, reels or drums.
Random or line winding. Carbon steels.
Low alloy steels.
Creep resisting steels.
Stainless steels.
Nickel-base alloys.
Special alloys for surfacing applications.
Welding wires can be:
Courtesy of Lincoln Electric Courtesy of Lincoln Electric Courtesy of ESAB AB Solid wires.
Coil (approx. 25 kg) Reel (approx. 300 Drum (approx. 450 kg) Metal-cored wires.
kg)
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Wires must be kept clean and free from oil and dust.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
16-13
SAW Consumables SAW Consumables
Welding flux:
SA Welding flux:
Might be fused or agglomerated.
Must be kept warm and dry.
Supplied in bags. Handling and stacking requires care.
Must be kept warm and dry. Fused fluxes are normally not hygroscopic but particles can
hold surface moisture.
Handling and stacking requires care.
Courtesy of Lincoln Electric
Only drying.
Fused fluxes are normally not hygroscopic but particles can Agglomerated fluxes contain chemically bonded water.
hold surface moisture so only drying. Similar treatment as basic electrodes.
Agglomerated fluxes contain chemically bonded water. Similar For high quality, agglomerated fluxes can be recycled with
new flux added.
treatment as basic electrodes.
If flux is too fine it will pack and not feed properly.
If flux is too fine it will pack and not feed properly. It cannot be Cannot be recycled indefinitely.
recycled indefinitely.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
16-14
SAW Consumables SAW Consumables
QU 3 Why are cellulose electrodes commonly used for the TWI Training & Examination
welding of pressure pipe lines?
Services
QU 4 Give a brief description of fusible insert and state two alterative
names given for the insert?
16-15
Inspection of Consumables BS EN 10204-Type of documents
BS EN 10204-Type of documents
Specific
inspection
documents Any Questions
Type 3.1 Type 3.2
?
Name: Inspection certificate 3.1. Name: Inspection certificate 3.2
Content: statement of Content: statement of
compliance with the order compliance with the order
(include specific test results!) (include specific test results!)
Who validate it - the Who validate it - the
manufacturer inspection manufacturer inspection
(independent of manufacturing (independent of manufacturing
department!) department!) +
purchasers/official designated
authorised inspector.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
16-16
CSWIP 3.1 Welding Inspection Weldability of Steels
Definition
It relates to the ability of the metal (or alloy) to be welded
Weldability of Steels with mechanical soundness by most of the common
welding processes. The resulting welded joint retain the
properties for which it has been designed is a function of
many inter-related factors but these may be summarised
TWI Training & Examination as:
Services Composition of parent material.
Joint design and size.
Process and technique.
Access.
17-1
Steel Alloying Elements Materials
Iron Fe
Nickel (Ni): Carbon C is for Strength
Used in stainless steels, high resistance to corrosion from acids, Manganese Mn is for Toughness
increases strength and toughness.
Silicon Si < 0.3% Deoxidiser
Aluminium Al Grain refiner, <0.008% Deoxidiser + Toughness
Molybdenum (Mo):
Affects hardenability. Steels containing molybdenum are less susceptible Chromium Cr Corrosion resistance
to temper brittleness than other alloy steels. Increases the high Molybdenum Mo 1% is for Creep resistance
temperature tensile and creep strengths of steel. typically ~ 0.5 to 1.0%. Vanadium V Strength
Nickel Ni Low temperature applications
Niobium (Nb): Copper Cu Used for weathering steels (Corten)
Vanadium (V): a grain refiner, typically ~ 0.05% Sulphur S Residual element (can cause hot shortness)
Titanium (Ti) : Phosphorous P Residual element
Copper (Cu): Titanium Ti Grain refiner, Used a a micro alloying element
(S&T)
Niobium Nb Grain refiner, Used a a micro alloying element
Present as a residual, (typically < ~ 0.30%) added to weathering steels
(~ 0.6%) to give better resistance to atmospheric corrosion. (S&T)
(S&T) = Strength & Toughness
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
17-2
Classification of Steels Classification of Steels
Types of weldable C, C-Mn and low alloy steels. Types of weldable C, C-Mn and low alloy steels
low alloy steels.
Carbon Steels
Carbon contents up to about ~ 0.25%. Strength and toughness raised even higher by very
Manganese up to ~ 0.8%. small additions of grain refining elements like
Low strength and moderate toughness. aluminium, niobium, vanadium.
Higher strength grades may be referred to as HSLA
Carbon-Manganese Steels steels (high strength low alloy steels, eg API 5L X65
Manganese up to ~ 1.6%. and higher).
Carbon steels with improved toughness due to
additions of manganese.
17-3
Carbon Equivalent Formula Classification of Steels
Mild steel (CE < 0.4)
The weldability of the material will also be affected by
Readily weldable, preheat generally not required if low hydrogen
the amount of alloying elements present. processes or electrodes are used.
Preheat may be required when welding thick section material, high
restraint and with higher levels of hydrogen being generated.
The carbon equivalent of a given material also depends on
its alloying elements.
The higher the CE, higher the susceptibility to brittleness, C-Mn, medium carbon, low alloy steels (CE 0.4 to 0.5)
and lower the weldability. Thin sections can be welded without preheat but thicker sections
will require low preheat levels and low hydrogen processes or
The CE or CEV is calculated using the following formula:
electrodes should be used.
CEV = %C + Mn + Cr + Mo + V + Cu + Ni
Higher carbon and alloyed steels (CE > 0.5)
6 5 15 Preheat, low hydrogen processes or electrodes, post weld heating
and slow cooling may be required.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
17-4
Hydrogen Induced Cold Cracking Hydrogen Induced Cold Cracking
Crack type:
Hydrogen HAZ and weld metal cracking.
There is a risk of hydrogen cracking when all of the 4
factors occur together:
Location: Hydrogen:
HAZ (longitudinal) weld metal (transverse). More than 15ml/100g of weld metal
Stress:
Steel types:
All hardenable steels. More than the yield stress
Temperature:
Including: Below 300C.
HSLA (high strength low alloy) steels. Quench and tempered
steels TMCP (thermal mechanically controlled processed) steels. Susceptible Microstructure:
Hardness Greater than 400HV Vickers (Martensite).
Susceptible Microstructure: martensite.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
May occur:
17-5
Hydrogen Induced Cold Cracking Hydrogen Induced Cold Cracking
Steel in expanded condition
Cellulosic electrodes produce
Hydrogen Above 300oC hydrogen as a shielding gas
diffusion Hydrogen absorbed in a
long, or unstable arc
Hydrogen introduced in
weld from consumable, oils,
or paint on plate Hydrogen
crack
H22
H
17-6
Hydrogen Induced Cold Cracking Hydrogen Induced Cold Cracking
Precautions for controlling hydrogen cracking List of hydrogen scales from BS EN 1011:
Pre heat, removes moisture from the joint preparations, part 2.
and slows down the cooling rate. Hydrogen content per 100 grams of weld metal
Ensure joint preparations are clean and free from deposited.
contamination.
The use of a low hydrogen welding process and correct
arc length. Scale A High: >15 ml
Ensure all welding is carried out is carried out under Scale B Medium: 10 ml - 15 ml
controlled environmental conditions.
Scale C Low: 5 ml - 10 ml
Ensure good fit-up as to reduced stress.
The use of a PWHT.
Scale D Very low: 3 ml - 5 ml
Avoid poor weld profiles. Scale E Ultra-low: < 3 ml
List of welding processes in order of potential lowest To eliminate the risk of hydrogen cracking how do you
hydrogen content with regards to 100 grams of remove the following:
deposited weld metal.
Hydrogen: MMA (basic electrodes). MAG cleaning
weld prep etc.
TIG < 3ml
MIG < 5ml Stress: Design, balanced welding.
ESW < 5ml
Temperature: Heat to 300oC (wrap and cool slowly).
MMA (Basic Electrodes) < 5ml
SAW < 10ml Hardness: Preheat-reduces cooling rate which
FCAW < 15ml reduces the risk of susceptible
microstructure.
17-7
Hydrogen Cold Cracking Avoidance Hydrogen Cold Cracking Avoidance
Increasing plate thickness. Ensure good fit-up: minimum root gap and
misalignment.
Restraint - rigid fixtures Avoid restraints: preset the join.
weld volume.
Preheat may help: to slow down cooling rate.
insert in plate.
Large weld passes: higher deposition rate.
Multi-pass vs single pass. Minimise volume of weld metal: less residual stress.
PWHT from preheat temperature.
Small weld beads vs large weld beads. Dress weld toes at preheat temperature.
t = t1+t2 t = t1+t2+t3
17-8
Combined Thickness Combined Thickness
The chilling effect of the joint The chilling effect of the joint
Heat flow
Heat flow
17-9
Hydrogen Cold Cracking Avoidance Hydrogen Cold Cracking Avoidance
Maintain calculated preheats, and never allow the inter-
Slow Cooling Rate pass temperature to go below the pre-heat value.
Apply or increase preheat - BS EN 1011 Part 2
Gives recommendations on suitable preheat Use Low Hydrogen processes with short arcs and ensure
levels. consumables are correctly baked and stored as required.
17-10
Solidification Cracking Solidification Cracking
Sulphur in the parent material may dilute in the weld Factors for solidification cracking
metal to form iron sulphides (low strength, low
melting point compounds). Columnar grain growth with impurities in weld
metal (sulphur, phosphor and carbon).
The amount of stress/restraint.
During weld metal solidification, columnar crystals
Joint design high depth to width ratios.
push still liquid iron sulphides in front to the last
place of solidification, weld centerline . Liquid iron sulphides are formed around solidifying
grains.
High contractional strains are present.
The bonding between the grains which are High dilution processes are being used.
themselves under great stress. may now be very poor
There is a high carbon content in the weld metal.
to maintain cohesion and a crack will result, weld
Most commonly occurring in sub-arc welded joints.
centerline.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Solidification crack Shallow, wider weld bead Deep, narrower weld bead
17-11
Solidification Cracking Solidification Cracking
Add Manganese to weld metal Solidification cracking in austenitic stainless Steel
17-12
Lamellar Tearing Lamellar Tearing
Critical area Critical area
Factors for lamellar tearing to occur
Low quality parent materials, high levels of impurities
there is a high sulfur content in the base metal.
Joint design, direction of stress 90 degrees to the
rolling direction, the level of stress acting across the
joint during welding.
Note! very susceptible joints may form lamellar tearing
under very low levels of stress.
Critical High contractional strains are through the short
area transverse direction.
There is low through thickness ductility in the base
metal.
There is high restraint on the work.
17-13
Lamellar Tearing Lamellar Tearing
Modifying a Tee joint to avoid lamellar tearing
Modifying a corner joint to avoid lamellar tearing
Non-susceptible Susceptible Improved
Susceptible Non-Susceptible
Susceptible
During the welding of stainless steels, a small grain area 3 A sensitized stainless steel may be de-sensitized
in the HAZ, parallel to the weld will form chromium carbide by heating it to above 1100C where the chrome
at the grain boundaries. This depletes this grain of the carbide will be dissolved. The steel is normally
corrosion resisting chrome oxide quenched from this temperature to stop re-
We say that the steel has become sensitised or has association*.
become sensitive to corrosion*
17-14
Inter-Granular Corrosion Inter-Granular Corrosion
Steel Type: Austenitic stainless steels. At this temperature range chromium is absorbed by the
carbon at the grain boundaries, which causes a local
depletion of chromium content in the adjacent areas.
Susceptible Microstructure: Sensitised HAZ grain
boundaries. The depletion of chromium content in the affected areas
results in lowering the materials resistance to corrosion
attack, allowing rusting to occur.
Sensitisation range where peak temperatures in the When heated in the range 6000C
HAZ reaches about 6000C to 8500C. to 8500C Chromium Carbides
form at the grain boundaries
Areas depleted of
Chromium below
12.5%.
17-15
Weld Decay Weld Decay
A most important function in the metallurgy of steels, is the At temperatures below Ac/r 1, (LCT) iron exists like this*
ability of iron to dissolve carbon in solution*.
The carbon atom is very much smaller than the iron atom and Alpha iron
does not replace it in the atomic structure, but fits between it*.
This structure occurs below 723 C and is
body centred, or BCC in structure
It can only dissolve up to 0.02% Carbon
Iron Carbon
atoms atoms* Also known as Ferrite or BCC iron*
*
Iron is an element that can exist in 2 types of cubic structures,
depending on the temperature. This is an important feature*. Compressed representation could appear like this
17-16
Basic Atomic Structure of Steels The Important Points of Steel Microstructures
Some steels if cooled quickly their structure looks like this* Solubility of Carbon in BCC & FCC phases of steels*
Martensite can be defined as: Ferrite: a Low carbon solubility. Maximum 0.02%*
A supersaturated solution of carbon in
Austenite: g High carbon solubility. Maximum 2.06%*
BCT iron (Body Centred Tetragonal)
It is the hardest structure we can produce
Martensite: The hardest phase in steels, which is
in steels*
produced by rapid cooling from the
Austenite phase:
*
It mainly occurs below 300 C*
Compressed representation could appear like
this
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Any Questions
steels by thermal treatment, it can be said that the
formation of Martensite is caused by the entrapment of
carbon in solution, produced by rapid cooling from
temperatures above the Upper Critical*
?
In plain carbon steels there must be sufficient carbon to
trap. In low alloy steels however, the alloying elements play
a significant part in the thermal hardening of steels*
17-17
CSWIP 3.1 Welding Inspection Weld Repairs
Cleaning the repair area, (removal of paint, grease, etc). A weld repair may be used to improve weld profiles or
A detailed assessment to find out the extremity of the defect. extensive metal removal:
This may involve the use of a surface or sub surface NDE
method. Repairs to fabrication defects are generally easier than
repairs to service failures because the repair procedure
Once established the excavation site must be clearly identified
and marked out.
may be followed.
An excavation procedure may be required (method used i.e. The main problem with repairing a weld is the
grinding, arc-air gouging, preheat requirements etc). maintenance of mechanical properties.
NDE should be used to locate the defect and confirm its During the inspection of the removed area prior to
removal.
welding the inspector must ensure that the defects have
A welding repair procedure/method statement with the been totally removed and the original joint profile has
appropriate* welding process, consumable, technique, been maintained as close as possible.
controlled heat input and interpass temperatures etc will need
to be approved.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
18-1
Weld Repairs Weld Repairs
Production Repairs
Weld repairs can be divided into 2 specific areas: Are usually identified during production inspection.
Before the repair can commence, a number of elements need to Service Repairs
be fulfilled:
Can be of a very complex nature, as the component is very
If the defect is surface breaking and has occurred at the fusion likely to be in a different welding position and condition
face the problem could be cracking or lack of sidewall fusion. than it was during production.
If the defect is found to be cracking the cause may be associated
with the material or the welding procedure.
It may also have been in contact with toxic, or combustible
fluids hence a permit to work will need to be sought prior to
If the defect is lack of sidewall fusion this can be apportioned to any work being carried out.
the lack of skill of the welder.
The repair welding procedure may look very different to the
In this particular case as the defect is open to the surface, MPI or
DYE-PEN may be used to gauge the length of the defect and U/T original production procedure due to changes in these
inspection used to gauge the depth. elements.
18-2
In Service Weld Repairs Weld Repairs
This may also include difficulty in carrying out any required pre Are there any alternatives to welding?
or post welding heat treatments and a possible restriction of What caused the defect and is it likely to happen again?
access to the area to be repaired.
How is the defect to be removed and what welding process is to
For large fabrications it is likely that the repair must also take be used?
place on site and without a shut down of operations, which
may bring other elements that need to be considered. What NDE is required to ensure complete removal of the defect?
Will the welding procedures require approval/re-approval?
YES
Train the Qualify the
Is repair the Replace welder welder
right decision? NO the part
NO
18-3
Production Weld Repairs Cost of Weld Repairs
Original weld Cost Repair weld Extra cost
Side View of defect excavation
Cut, prep, tack weld Inspector Repair report (NCR etc)
W
Welder time Inspector Identify repair area
D Consumable & gas Inspector Mark out repair area
Visual inspection Welder Remove defect
NDT Inspector Visual inspection of excavation
Documentation Inspector NDT area of excavation
Inspector Monitor repair welding
Side View of repair welding Welder time
Consumable & gas
Inspector Visual inspection
NDT
Extra repair Documentation
Penalty % NDT
Any Questions
18-4
CSWIP 3.1 Welding Inspection Residual stress
Cool with
At room restraint present
temperature
On heating to
400C 200mm
Cool with
On cooling to restraint removed
200mm 1mm room
temperature
199mm 1
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Ambient temperature.
Heat to 400C.
Cool with restraint present. Cold weld unfused
19-1
Types of residual stress Types of residual stress
Transverse residual stress after welding Longitudinal residual stress after welding.
Maximum stress = YS at
room temperature. Compression Tension
Tension
YS at room
temperature
Compression
The longer the weld, the higher the tensile stress! The higher the heat input the wider the tensile zone!
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
YS at PWHT YS at room
temperature temperature
After PWHT, peak residual stress is less than a quarter of its initial level!
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
400mm
5mm
Separate cooling.
398mm
Combined cooling.
400mm
19-2
Distortion
19-3
Factors Affecting Distortion Factors affecting distortion
Fit-up:
Root gap - increase in root gap increases shrinkage.
Welding sequence:
Angular distortion
Number of passes - every pass adds to the total
contraction.
Transverse shrinkage
Travel speed - the faster the welding speed, the producing angular
less the stress. distortion.
Build-up sequence.
Transverse
shrinkage producing
distortion.
19-4
Distortion Prevention Distortion prevention
a
function of number of runs
for a 10 mm leg length
b Use of wedges for
weld).
components that distort 10mm
on separation after
welding. N
Distortion Prevention
Distortion - Best practice for fabrication corrective
techniques
Using tack welds to set up and maintain the joint gap.
Identical components welded back to back so welding can be
balanced about the neutral axis.
Attachment of longitudinal stiffeners to prevent longitudinal bowing in
butt welds of thin plate structures.
Where there is choice of welding procedure, process and technique
should aim to deposit the weld metal as quickly as possible; MIG in
preference to MMA or gas welding and mechanised rather than
manual welding.
In long runs, the whole weld should not be completed in one
direction; back-step or skip welding techniques should be used.
Copyright TWI Ltd 2013
19-5
CSWIP 3.1 Welding Inspection Heat Treatment
Why?
Improve mechanical properties.
Change microstructure.
Reduce residual stress level.
Heat treatment of welded structures Change chemical composition.
How?
Flame oven.
TWI Training & Examination Electric oven/electric heating blankets.
induction/HF heating elements.
Services
Advantages:
Easy to set up. Advantages:
Good portability. Ability to vary heat.
Repeatability and Ability to continuously
temperature maintain heat.
uniformity.
Disadvantages:
Elements may burn out or
Disadvantages: arcing during heating.
Gas furnace heat treatment Limited to size of Local heat treatment using
parts. electric heating blankets
20-1
Heat Treatment Cycle Heat Treatment
Variables for heat treatment process must be carefully controlled.
Recommendations
Temperature
SoakingTemperature and Provide adequate support (low YS at high temperature).
time at the attained
temperature Cooling rate Control heating rate to avoid uneven thermal expansions.
Control soak time to equalise temperatures.
Control temperature gradients - NO direct flame
impingement.
Temper.
Stress relief.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
To control the structure of the weld metal and HAZ on The heat input.
cooling.
The carbon equivalent (CE).
To improve the diffusion of gas molecules through an
atomic structure. The combined material thickness.
To control the effects of expansion and contraction. The hydrogen scale required (A, B, C, D).
Preheat controls the formation of un-desirable
microstructures that are produced from rapid cooling of
certain types of steels. Martensite is an undesirable grain
structure very hard and brittle it is produced by rapid
cooling form the austenite region.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
20-2
Heat Treatments Heat Treatments
180
Slows down the cooling rate, which reduces the risk
160
of hardening.
140
Allows absorbed hydrogen a better opportunity of 120
diffusing out, thereby reducing the risk of cracking. 100
20-3
Post Weld Heat Treatment Post Weld Heat Treatment
Removal of Residual Stress PWHT Procedures - Basic Requirements
At PWHT temp. the yield Maximum Heating Rate
Cr-Mo steel - typical
500 strength of steel is reduced Usually from 300 or 400C - need to avoid large temperature gradients
Yield Strength (N/mm2 )
Temperature: 920C hold for sufficient time (full austenitization). Temperature: 550-6500C no phase transformation.
Cooling: Hold, slow cooling in furnace. Cooling: Hold, furnace or controlled cooling.
Result: Produces a very soft, low hardness material suitable Result: Relieves residual stresses, improves
for cold working or machining operations. stability during machining, reduces
Decreases toughness and lowers yield stress hydrogen levels, prevents stress corrosion
Homogenising annealing. cracking.
Any Questions
Post Hydrogen Release (according to BS EN1011-2)
Temperature: Approximately 250C hold up to 3 hours
Cooling: Slow cool in air
?
Result: Relieves residual hydrogen
Procedure: Maintaining pre-heat / interpass
temperature after completion of
welding for 2 to 3 hours.
20-4
CSWIP 3.1 Welding Inspection Welding Related Risks
Fire and Explosion Hazard Onsite Checking Gas Cylinder for Leaks
Leak testing.
21-1
Welding Fume and Gases Welding Fume
Effect of welding fume and gasses on health:
Welding fume sources:
Fume - particulate and toxic: irritation of nose, throat, lungs,
asphyxiation. Parent material. (Cr6 thought to
Ozone - irritation of nose, throat lungs; excess mucous secretion, be carcinogeni c!)
coughing. Welding consumables.
(filler, flux, gas).
Nitrous oxide, hydrogen chloride, phosgene - delayed irritation
and toxic effect on upper respiratory tract; excess fluid in lungs. Action of heat/UV on air:
nitrous oxide and ozone
Carbon monoxide - oxygen deficiency, drowsiness, headache, Surface treatments.
nausea; fatal oxygen starvation. (paint, plating, coatings).
Carbon dioxide - oxygen deficiency, asphyxiation. Cleaning fluids.
Argon, helium, nitrogen asphyxiation.
Hydrogen, other fuel gases - explosion, fire, asphyxiation.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
b In breathing zone.
Keep head out of fume.
Work upwind of weld.
c Regular monitoring.
Use local fume extraction.
d Regular auditing.
21-2
Welding Fume Respiratory Protective Equipment (RPE)
Requirements
How to avoid welding fume exposure:
Must be suitable for purpose.
Use fresh air welding helmets.
Must be approved by relevant organisations.
Use respirators as second line of defense. Must be fully maintained.
Must be safely stored.
Must be correctly fitted.
Selection, maintenance and fitting require trained staff.
Users must be trained in its use.
Points to be considered:
Points to be considered: Check weld connections and cable insulation.
Bad! Good!
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
21-3
Eye injuries and skin burns Eye Injuries and Skin Burns
Electric arc produces ultra violet/infra red light Wear safety goggles and visor during grinding.
Gives arc eye and skin burns! Wear ear defenders.
Measures to be taken:
Wear PPE.
Choose shade of filter according to welding process.
Summary
?
Is there enough insulation between your body and the work piece?
Are all connections tight, including the earth ground?
Are electrode holder and welding cable in good conditions?
Do not operate with power source covers removed!
Disconnect input power before servicing!
Do not touch electrically live parts or electrode with skin or wet
clothing!
Insulate yourself from work and ground!
21-4
3.1 Weld Inspection Calibration/Validation
Demonstration of
Validation can be done on equipment with and without Welding process
conformance to
meters or gauges. control
specified requirements
Parameters to be measured:
Oil fill transformers etc.
Welding current. Preheat / inter-pass
All equipment can be Validated but not all equipment Arc voltage. temperature.
can be Calibrated. Travel speed. Force/pressure.
Shielding gas flow rate. Humidity.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
22-1
Arc Voltage Measurement Travel Speed Measurement
Definition: The potential difference across the welding arc. Definition: The rate of weld progression.
Measured in case of mechanised and automatic welding
Varies with the arc length.
processes.
Measured with a voltmeter.
In case of MMA can be determined using ROL and arc
Measured in V. time.
The voltmeter may be connected only across the circuit
(to the workpiece and as close as possible to the
electrode).
If the voltmeter is connected at the welding power
source, a higher voltage will be recorded (due to
potential drops across cables).
Usually not required for MMA and TIG.
22-2
Welding Temperatures - How? Temperature Test Equipment
Test equipment Temperature sensitive
materials:
Thermocouple Crayons, paints and pills.
(TE) Cheap.
Temperature Convenient, easy to use.
sensitive Thermistor
materials (TS) (CT)
Optical/electrical
devices for
Contact contactless Doesnt measure the
thermometer measurement (TB) actual temperature!
(CT)
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
Thermistors
Thermocouple Are temperature-sensitive resistors
whose resistance varies inversely
Based on measuring the thermoelectric potential with temperature.
difference between a hot junction (on weld) and a
cold junction. Used when high sensitivity is
Accurate method. required.
Measures over a wide range of temperatures. Gives the actual temperature.
Gives the actual temperature. Need calibration.
Need calibration.
Can be used up to 320C.
22-3
PAMS (Portable Arc Monitor System) Use of PAMS
What does a PAMS unit measure?
Wire feed speed monitoring
Welding Gas flow rate
current (Hall (heating
effect device) element
sensor) Incorporated pair of
rolls connected to a
tachogenerator
Wire feed speed
(tachometer)
Arc voltage
(connection
leads) Temperature
(thermocouple)
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
22-4
Calibration and Validation Welding Parameter Calibration/Validation
In theory any MMA operation could require monitoring In theory, this might require monitoring of all the
of: activities previously mentioned.
The equipment thus required would be:
Welding current. Ammeter.
Arc voltage. Voltmeter.
R.O.L. Stop watch. OR a PAMS
Preheat/interpass temperature.
Tape measure.
Electrode treatment and storage.
Thermometer.
In practice (depending on the application) only the Calculator.
welding current could require monitoring with a tongue All of the above equipment would require calibration; any meters
test ammeter. fitted to the power source or electrode ovens would also require
calibration.
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
In theory, the following would require monitoring: A welding power source can only be calibrated if it
Wire feed speed. has meters fitted.
Amperage. The inspector should check for calibration stickers,
Voltage. dates etc.
Travel speed. A welding power source without meters can only be
Gas flow rate. validated that the control knobs provide
Repeatability of the controls. repeatability.
The main role is to carryout in process monitoring
In practice, a data logger would be preferred to monitor to ensure that the welding requirements are met
all the parameters; also a PAMS would be required to during production.
check the repeatability of the control knobs.
22-5
Any Questions
?
Copyright TWI Ltd 2013
22-6
CSWIP 3.1 Welding Inspection Example of Weld Face
EXAMPLE PLATE REPORT
Candidates Name.. Specification..
Welding Position..
MEASURE
WELD FACE
FROM
fusion 1.5 max
87 22 230 236 30
THIS
Services 51 8 153 40 Arc
Strike
DATUM
Slag
Centreline 241
inclusion
crack
EDGE
NOTES: Excess Weld Metal = Linear Misalignment = Toe Blend = Weld Width =
10 247
20
THIS
128 50
Incomplete root
DATUM
penetration
3 Mark the answer in the OMR
grid in pencil and accept or reject
accordingly. When you are sure
EDGE
Any Questions
?
Copyright TWI Ltd 2013
A2-1
CSWIP 3.1 Welding Inspection Pipe Inspection
2
After you have observed an imperfection and determined its type, you
3
4
must be able to take measurements and complete the thumb print
5
report sketch
6
Root gap The first thumb print report sketch should be in the form of a repair
HI-LO Single Purpose Welding Gauge
dimension map of the weld. (ie all observations are Identified sized and located)
The thumb print report sketch used in CSWIP exam will look like the
Internal following example.
alignment
The thumb print is to used in conjunction with the multiple choice
questions during the examination
120
120
Smooth Undercut
<1.0mm
NOTES:
Excess Weld Metal Height = Misalignment = Weld Width = Toe Blend = NOTES: Excess Penetration Height = Toe Blend =
Copyright TWI Ltd 2013 Copyright TWI Ltd 2013
A3-1
Pipe Inspection Examination
A3-2
CSWIP 3.1 Welding Inspection Macro Inspection Examination
2
7
5 4 3
A5-1
Macro Inspection Macro Inspection
1 1
8
Welded With SMAW Welded With SMAW
7
6 7
2
2
3
3
6
4 5
4
6
2
6
3
5
5
4 4 3
10 Acceptance Levels
Table Number
Macro Only
6 2
Slag/Silica
Inclusions
metaltic inclusions trapped in the
weld metal or between the weld
metal and the parent material.
50mm. continuous or intermittent. Accumulative
totals shall not exceed 50mm 1mm diameter
2
Under cut is defined as a grove The length of any undercut shall not exceed 50mm
melted into the parent metal, at the continuous or intermittent. Accumulative totals shall
3 Undercut toes of the weld excess metal, root or not exceed 50mm. Max D = 2mm for the excess
0.5mm deep
adjacent weld metal. weld metal. Root undercut not permitted.
Trapped gas, in weld metal,
Individual pores 1.5 max.Cluster porosity 10mm in
elongated, individual pores, cluster
4 Porosity area.Elongated, piping or wormholes
porosity, piping or wormhole
15mm max. L continuous or intermittent. 1mm diameter
porosity.
3 10 Penetration
Excess weld metal, above the base
material in the root of the joint. At no
point shall the penetration fall below
Max H 2mm
As for plate and pipe
the thickness of the material.
Lack of root The absence of weld metal in the root
9 5
Not permitted
11 penetration area. Refer to Table 10
2
Lack of root Inadequate cross penetration of both Lack of root fusion, not to exceed 50mm total
12
fusion root faces. continuous or accumulative. No t permitted
4 13
Burn
through Excessive penetration , collapse of
Not permitted Not permitted
the weld root
A5-2
Any Questions
A5-3