WELDING

DEFINATION OF WELDING : Welding is a process of joining two or more parts

by the application of heat and (or) pressure, Such joints are permanent in nature.
Usually coalescence is achieved by fusion. Very often filler metals are used during
welding.

More than 50 different welding processes available today. Some are very popular among
the industries such as SMAW, GMAW, GTAW, SAW, FCAW etc. whereas
some are very specific and limited to few industries such as USW, RSW, DW etc.
 GTAW (Gas Tungsten Arc Welding or TIG) : Gas Tungsten Arc Welding
(GTAW)also known as Tungsten Inert Gas welding (TIG) is an electric arc welding
process that produces an arc between a non- consumable electrode (tungsten which does
not melt due to its high melting point) and the work piece to be welded. The weld is
shielded from the atmosphere by a shielding gas that forms an envelope around the weld
area. However, a filler metal is usually used in the process.

• Initially developed in 1941 by Russel Meredith for welding magnesium, as its oxides
have high m.p. than parent metal .

• TIG designated nowadays as GTAW(Gas tungsten arc welding)

• Currently used for welding aluminium, stainless steel, titanium, nickel, copper, etc.

• Highly attractive replacement for gas welding as inert gas is used for shielding instead
of slag.

Why Use TIG Welding?

 Can be used to join almost all metals, with superior weld quality, generally free of
defects
 Free from spatter that occurs with other arc welding processes
 Can be used with or without filler metal as required for the specific application
 Provides excellent control of root pass weld penetration
 Can be used to produce inexpensive autogenous (fusion) welds with good penetration
 Provides for separate control over the heat input and filler metal additions
 Limitations

 Travel speeds and deposition rates are relatively low, increasing weld cost
 A high degree of operator skill is required to produce quality welds
 Process is not easily automated

 THE TIG PROCESS : • Arc is struck between the non-consumable tungsten

electrode and the work piece to fuse metals

• Arc is covered by a layer of shielding gas which acts as the flux and keeps the nitrogen
and oxygen in the air from coming in contact with the molten puddle.

• When the puddle is formed on the base metal, the torch is moved along the joint until
the workpiece is fused together

• A filler rod may or may not be used

• If a filler rod is used, it should be the same composition as the base metal.

• The filler rod is fed manually into the leading edge of the puddle.

• The torch may be moved in a semicircular motion to vary the width of the bead.

FEATURES OF TIG WELDING : • Temperature may be in the range of

10000k

• Automatic and manual techniques can be used

• TIG may be done in all positions.

• Metal thickness upto 5mm

• Weld speed from 8mm/s to 50mm/s

• With superior arc and weld puddle control, clean welds are produced

• No sparks or spatter because only the necessary amount of filler metal is added to the
welding pool.
 • No smoke and fumes unless

• No flux required as argon gas protects the weld pool from contamination

GMAW :GMAW was developed in the late 1940’s and is also called MIG/MAG
Welding. Since then it unfolded into becoming a major element in industry today. It is
suitable for welding a variety of ferrous and nonferrous metals. 4 The arc continuously
melts the wire as it is fed in the weld puddle. The weld area is shielded by a flow of gas
such as argon, helium, carbon dioxide, or gas mixtures. The consumable bare wire is fed
automatically through a nozzle into the weld area. Metal can be transferred into the
weld−bead in three ways: Spray, Globular and Short circuiting. Each way has its own
advantages and disadvantages. The process is rapid, versatile, economical and can easily
be automated (continuos welding without electrode changing).

Why Use MIG Welding?

 It is a high-productivity, low cost welding process

 It can be used to weld all types of commercially available metals and alloys
 Welding can be done in all positions with proper selection of equipment and parameters
MIG WELDING TIG WELDING

1. This welding is known as metal inert gas 1. This is known as tungsten inert gas
welding. welding.

2. Metal rod is used as electrode and work

piece used as another electrode. 2. Tungsten rod is used as electrode.

3. It is gas shielded metal arc welding. 3. It is gas shielded tungsten arc welding.

4. Continuous feed electrode wire is used 4. Welding rods are used which are slow
which are fast feeding. feeding.

5. The welding area is flooded with a gas 5. Gas is used to protect the welded area
which will not combine with the metal. form atmosphere.

6. MIG can weld materials such as mild

steel, stainless steel and aluminum. A range 6. TIG weld things like kitchen sinks and
of material thicknesses can be welded from tool boxes. Pipe welding and other heavier
thin gauge sheet metal right up to heavier tasks can also be performed, you just need
structural to have a unit that is capable of putting out
plates. the amount of power that you need.

7. MIG requires consumable metallic 7. It used non consumable tungsten

electrode. electrode

8. Electrode is feeded continuously from a 8. It does not require

wire reel. electrode feed.

9. DC with reverse polarity is used. 9. It can use both A.C and D.C.

10. Filler metal is compulsory used. 10. Filler metal may or may not be used.
 11. It can weld up to 40 mm thick metal
sheet. 11. Metal thickness is limited about 5 mm.

12. MIG is comparatively faster than TIG. 12. TIG is a slow welding process.

 Using a continuously-fed electrode maintains a high operator duty cycle and minimizes
the occurrence of defects on starts and stops
 Deep weld penetration can be obtained which permits the use of small weld sizes for
equivalent weld strengths in certain applications
 Minimal post-weld clean-up is required due to the absence of a covering slag on the weld
bead
 Welding speeds and weld metal deposition rates are higher than those obtained with
Stick Welding
 Ideal for multi-pass welding (with proper filler metal selection)
 Less operator skill is required compared to Stick Welding
 Fume rates are at very low levels compared to Stick Welding and Flux Cored Welding
 A wide selection of filler metal compositions and diameters are available to weld thick or
thin material
 This process is ideal for mechanized welding
 This process offers improved electrode deposition efficiency compared to Stick
Welding and FCAW
 X-ray quality welds can be produced

Limitations

 Welding equipment is more complex, more costly and less portable than that for Stick
Welding
 The required welding torch makes reaching into constricted areas difficult, and the need
for good gas shielding necessitates the torch being relatively close to the weld area
 The welding arc with its gas shield must be protected from drafts that might cause the
shielding to be blown away from the arc. This limits the use of the process outdoors
unless protective shields are placed around the work area
 Relatively high levels of radiated heat and light may cause operator discomfort and initial
resistance to the process
 Burn through is a common issue when welding extremely thin materials (<1/16”)
 With conventional transfer when welding out of position, weld metal deposition rates are
less than those achieved with Flux Cored Welding
 This process does not perform well where base metal contamination is a problem. The
base metal must be clean and rust free

WELDING DEFECTS :

The defects in the weld can be defined as irregularities in the weld metal produced due to
incorrect welding parameters or wrong welding procedures or wrong combination of filler
metal and parent metal.
Weld defect may be in the form of variations from the intended weld bead shape, size and
desired quality. Defects may be on the surface or inside the weld metal. Certain defects
such as cracks are never tolerated but other defects may be acceptable within permissible
limits. Welding defects may result into the failure of components under service condition,
leading to serious accidents and causing the loss of property and sometimes also life.

Various welding defects can be classified into groups such as cracks, porosity, solid
inclusions, lack of fusion and inadequate penetration, imperfect shape and miscellaneous
defects.

1. Cracks

Cracks may be of micro or macro size and may appear in the weld metal or base metal or
base metal and weld metal boundary. Different categories of cracks are longitudinal
cracks, transverse cracks or radiating/star cracks and cracks in the weld crater. Cracks
occur when localized stresses exceed the ultimate tensile strength of material. These
stresses are developed due to shrinkage during solidification of weld metal.

Fig 13.1: Various Types of Cracks in Welds

Cracks may be developed due to poor ductility of base metal, high sulpher and carbon
contents, high arc travel speeds i.e. fast cooling rates, too concave or convex weld bead
and high hydrogen contents in the weld metal.

2. Porosity

Porosity results when the gases are entrapped in the solidifying weld metal. These gases
are generated from the flux or coating constituents of the electrode or shielding gases
used during welding or from absorbed moisture in the coating. Rust, dust, oil and grease
present on the surface of work pieces or on electrodes are also source of gases during
welding. Porosity may be easily prevented if work pieces are properly cleaned from rust,
dust, oil and grease. Futher, porosity can also be controlled if excessively high welding
currents, faster welding speeds and long arc lengths are avoided flux and coated
electrodes are properly baked.

Fig 13.2: Different Forms of Porosities

3. Solid Inclusion

Solid inclusions may be in the form of slag or any other nonmetallic material entrapped in
the weld metal as these may not able to float on the surface of the solidifying weld metal.
During arc welding flux either in the form of granules or coating after melting, reacts with
the molten weld metal removing oxides and other impurities in the form of slag and it floats
on the surface of weld metal due to its low density. However, if the molten weld metal has
high viscosity or too low temperature or cools rapidly then the slag may not be released
from the weld pool and may cause inclusion.

Slag inclusion can be prevented if proper groove is selected, all the slag from the
previously deposited bead is removed, too high or too low welding currents and long arcs
are avoided.

Fig 13.3: Slag Inclusion in Weldments

4. Lack of Fusion and Inadequate or incomplete penetration:

Lack of fusion is the failure to fuse together either the base metal and weld metal or
subsequent beads in multipass welding because of failure to raise the temperature of base
metal or previously deposited weld layer to melting point during welding. Lack of fusion
can be avoided by properly cleaning of surfaces to be welded, selecting proper current,
proper welding technique and correct size of electrode.

Fig 13.4: Types of Lack of Fusion

Incomplete penetration means that the weld depth is not upto the desired level or root
faces have not reached to melting point in a groove joint. If either low currents or larger arc
lengths or large root face or small root gap or too narrow groove angles are used then it
results into poor penetration.

Fig 13.5: Examples of Inadequate Penetration

5. Imperfect Shape

Imperfect shape means the variation from the desired shape and size of the weld bead.

During undercutting a notch is formed either on one side of the weld bead or both sides in
which stresses tend to concentrate and it can result in the early failure of the joint. Main
reasons for undercutting are the excessive welding currents, long arc lengths and fast
travel speeds.

Underfilling may be due to low currents, fast travel speeds and small size of electrodes.
Overlap may occur due to low currents, longer arc lengths and slower welding speeds.
 Fig 13.6: Various Imperfect Shapes of Welds

Excessive reinforcement is formed if high currents, low voltages, slow travel speeds and
large size electrodes are used. Excessive root penetration and sag occur if excessive high
currents and slow travel speeds are used for relatively thinner members.

Distortion is caused because of shrinkage occurring due to large heat input during
welding.

6. Miscellaneous Defects Various miscellaneous defects may be multiple arc strikes i.e.
several arc strikes are one behind the other, spatter, grinding and chipping marks, tack
weld defects, oxidized surface in the region of weld, unremoved slag and misalignment of
weld beads if welded from both sides in butt welds.

Cold Cracking

Causes Remedies
 Preheat as per Welding Procedure
high thermal severity
Specification

Welding consumables must be hydrogen

Hydrogen in the weld metal
controlled

Presence of impurities Remove impurities

Weld of insufficient sectional area Proper weld of sufficient sectional area

As per requirement Use of welding speeds

High welding speeds and low current density
and current density

Crater Cracking

Causes Remedies

Unfilled Crater Filler crater with proper technique

Crater crack in sub-merged arc welding Utilize run out tab

Hot Cracking

Causes Remedies

high welding current Medium welding current

Arc Strike Cracking

Causes Remedies

Improper welding technique Use proper welding technique

Rapidly Cooling of welding area Proper Cooling of welding area

poor joint design that does not diffuse heat Proper weld joint design

impurities (such as sulphur and phosphorus) Remove impurities

Preheating Don’t Preheating

speed fast & long arcs Speed medium & medium arcs

Base metal contamination Avoid contamination of base metal

Hat Cracking

Causes Remedies

Not enough speed Increase welding speed

Much voltage Proper voltage

Under Bead Crack

Causes Remedies

More presence of Hydrogen Reduce presence of Hydrogen

Unequal contraction of base metal & weld Equal contraction of base metal & weld
metal metal

Longitudinal Crack

Causes Remedies
 Rapid cooling of weld Use Proper or matched electrode

Improper joint preparation Reduce Rigidity of weldment

High restraint of joint Use higher ductile welding filler metal

?????? Use Preheat or Reduce cooling rate

Reheat Crack

Causes Remedies

Less cooling rate Increase cooling rate

Improper Preheating Proper Preheating

Porosity

Causes Remedies

Improper coating on the electrode. Use low hydrogen welding process

Improper Preheating Use preheat

Longer arcs Increase heat input

Too low and too high arc currents Clean joint surfaces and

Faster arc travel speeds Reduce arc travel speeds

Incorrect welding technique Use proper welding technique

 Unclean job surface Adjacent surfaces

Improper base metal composition Reducing excessive moisture

Distortion

Causes Remedies

Excessive layers & faulty joint preparation Tack weld parts with allowance for distortion

Improper bead sequence Use proper bead sequence

Improper set-up and fixture Tack or clamp parts securely

Excessive weld size Make weld of specify size

Over-heating of base metal (thin plate)

Gas Inclusion

Causes Remedies

high sulphur content in the work piece or

Reduce sulphur content
electrode

excessive moisture from the electrode or work

Avoid moisture
piece

too short of an arc Use proper welding current or polarity

wrong welding current or polarity

 Slag Inclusion

Causes Remedies

Improper cleaning Proper cleaning

Presence of grease & dirt Avoid grease & dirt

Incomplete slag removal from previous bead Complete remove slag from previous bead

Gap & Improper preparation of groove Avoid more Gap

Lack of Fusion

Causes Remedies

Improper manipulation of welding electrode Minimum heat input to be maintained

Weld joint design. Avoid molten pool flooding the arc

Improper heat input Proper cleaning of oxides slag

Correct Electrode angle

Surface contamination which leads slag
formation prevents fusion

Lack of Penetration

Causes Remedies

Use proper joint geometry

Improper joint ( U joint give better than J
 butt joint )

Follow current WPS ( welding procedure

Less welding current
specification )

Root gap too small Use small electrode in root

Too large root face Increase root opening

Faster arc travel speed Reduce arc travel speed

Large electrode diameter Medium electrode diameter

Misalignment Proper alignment

Lamellar Tearing

Causes Remedies

Poor ductility of weld metal Use the base metal which has higher ductility

High Sulphur content of the base metal Low sulphur & Low inclusions in base metal

Hydrogen in the weld Use low hydrogen in welding

Tensile stresses in thickness direction Decrease the stress by Modification

 Under Cut

Causes Remedies

Excessive welding current Use the right adequate welding current

Wrong electrode angle Proper electrode angle

Excessive side manipulation

What makes a good weld?

A key skill in manufacturing is welding and ensuring a good weld is vital for the integrity of
a product. A brittle or porous weld presents a serious safety concern for industrial
applications and the vast majority of manufacturers have rigorous procedures in place to
ensure welds meet quality standards.
Here’s a guide to factors that will ensure a good weld.
Ensure a clean surface
Metal surfaces need to be thoroughly cleaned of impurities like water, oil, and flux before
they are welded while aluminium needs to have the outside layer of oxide removed before
welding commences. The presence of impurities will cause porosity in the weld – that is
tiny holes that weaken the join.
Mind the gap
A factor that often results in welds failing is an incorrect gap or poor edge preparation
between the two parts being joined. If the gap is too big there is a danger the weld bead
will simply burn away the edges of the two parts, insufficient gap when joining thicker
materials will result in lack of weld penetration. To ensure a good weld, you need to pay
particular attention to the edge preparation and correct required gap.

Know the best process

There are a number of weld processes, such as MIG, TIG, Stick (MMA) and Flux-
cored, and knowing when to use each technique is an important factor in getting a good
weld.
MIG, or metal inert gas, is a type of wire welding that is suited to production welding of
mild steel sheet and plate, it uses an inert gas to protect the molten weld pool, which
sometimes makes it difficult to use outdoors in windy conditions. Another type of wire
welding is flux-cored welding, which takes place without gas and is therefore more suitable
for outdoor work. Stick welding is typically the best choice for quick onsite repairs while
TIG, or tungsten inert gas, welding works well on stainless steel and aluminum where the
look and presentation of the weld is important.

Bad welds can be traced back to poor workmanship, poor design, or a little of both.

Weld defects happen for a host of reasons. Air may creep into the weldment to cause
porosity. The wrong amount of heat can cause cracking. Bad welding technique can
cause undercuts or incomplete penetrations of one kind or another.

Various factors contribute to weld problems, but many lead back to the same place. In
fact, most causes of weld defects can be traced back to two general areas: first, a
combination of poor instruction and workmanship; second, poor weld design and/or
material choice.

WELDING JOINT CONFIGURATION :

The 5 Different Types Of Welding Joints:

Different jobs need different types of welds. Different types of welding joints are
made to stand up to the needs and forces of each individual application. The experts
at Cliff’s Welding have been mastering the art of these welds for over 50 years.

Tee Welding Joint

Tee Joint
Tee welding joints are formed when two members intersect at a 90° angle which makes the
edges come together in the center of a plate or component. Tee Joints are considered a
 type of fillet weld, and can also be made when a pipe or tube is welded onto a base plate.
Extra care is required to ensure effective penetration into the roof of the weld.

Welding Styles Used To Create T-Joints

 Plug weld
 Fillet weld
 Bevel-groove weld
 Slot weld
 Flare-bevel-groove weld
 J-groove weld
 Melt-through weld

Lap Welding Joint

Lap Joint
Lap welding joints are used most often to joint two pieces with differing
 thicknesses together. Also considered a fillet type, the weld can be made on one or both
sides. A Lap Joint is formed when 2 pieces are placed in an over lapping pattern on top
of each other.

Welding Styles Used To Create Butt Joints:

 Slot weld
 Plug weld
 Bevel-groove weld
 Spot weld
 Flare-bevel-groove weld
 J-groove weld

Edge Welding Joint

Edge Joint
Edge welding Joints are often applied to sheet metal parts that have flanging edges or
are placed at a location where a weld must be made to attach to adjacent pieces. Being a
groove type weld, Edge Joints, the pieces are set side by side and welded on the same
 edge. For heavier applications filler metal is added to melt or fuse the edge completely
and to reinforce the plate.

Welding Styles Used To Create Edge Joints:

 Bevel-groove weld
 Square-groove weld or butt weld
 J-groove weld
 V-groove weld
 Edge-flange weld
 U-groove weld
 Corner-flange weld

Corner Welding Joint

 Corner Joint
Being one of the most popular welds in the sheet metal industry the Corner welding
joint is used on the outer edge of the piece. This weld is a type of joint that comes
together at right angles between two metal parts to form an L. These are common in the
construction of boxes, box frames and similar fabrications.

Welding Styles Used To Create Corner Joints:

 Spot weld
 Fillet weld
 V-groove weld
 Square-groove weld or butt weld
 U-groove weld
 Bevel-groove weld
 Flare-V-groove weld
 J-groove weld
 Corner-flange weld.
 Edge weld
 Butt Welding Joint

Butt Joint
Being the universally accepted method for attaching a pipe to itself it’s also used for
valves, flanges, fittings, and other equipment. A butt welding joint is also known as a
square grove weld. It’s the easiest and probably the most common weld there is. It
consists of two flat pieces that are side by side parallel. It’s a very affordable option.

Welding Styles Used To Create Butt Joints:

 Bevel-groove butt weld

 Square-groove butt weld
 V-groove butt weld
 U-groove butt weld
 J-groove butt weld
 Flare-bevel-groove butt weld
 Flare-V-groove butt weld

Fillet Welding Joint

Fillet Welded Joints

Fillet Welded Joints are just another terminology for corner, lap, and tee joints. Fillet
Welded Joints are the most common type of welding joint and accounts for nearly 75% of
joints made with arc welding. You do not need to prepare the edge and this type of joint
make it easy to weld piping systems. Butt welds are more expensive than fillet welds. Fillet
welds are mostly used in piping systems to join pipe to socket joints.

Joint Preparation

Welding joints can be prepared in numerous ways including:

 Casting
 Shearing
 Machining
 Forging
 Filing
 Stamping
 Oxyacetylene cutting (thermal cutting process)
 Routing
 Grinding
 Plasma arc cutting (thermal cutting process)

A Brief Word On Welding Safety

If you’re just learning or even if you’ve done welding for years it can’t be said enough that
it’s critical to be fully aware of your surroundings when you begin to weld. You must take
the time to know who’s around trying to watch and what dangers you are exposing
yourself to.

Welding vs Riveting

Welding and riveting are two ways to join metal to metal. They both have their particular
pros and cons. Different situations call for one or the other. Neither is best for every
possible situation. We’ll take a look at the different strengths and weaknesses of both
metal joining systems.
What is a Standard?

Simply stated, a standard is a document used repeatedly as a rule, guideline or definition.

It is developed by a committee of experts who work within different areas of a particular
industry – this ensures that the standard is well-rounded.

All AWS standards are approved by the American National Standards Institute
(ANSI). This means that during the standards development process, AWS follows a
strict set of rules and requirements that serve to govern not only the standards approval
process, but also all of the technical committees responsible for their maintenance.

American Welding Society (AWS) Standards

The American Welding Society (AWS) publishes over 240 AWS-developed codes,
recommended practices and guides which are written in accordance with American
National Standards Institute (ANSI) practices. The following is a partial list of the
more common publications:

Standard
Title
Number

Standard symbols for welding, brazing, and non-destructive

AWS A2.4
examination

AWS A3.0 Standard welding terms and definitions

Standard
Title
Number

Specification for carbon steel electrodes for shielded metal arc

AWS A5.1
welding

Specification for carbon steel electrodes and rods for gas shielded
AWS A5.18
arc welding

AWS B1.10 Guide for the nondestructive examination of welds

AWS B2.1 Specification for Welding Procedure and Performance Qualification

AWS D1.1 Structural welding (steel)

AWS D1.2 Structural welding (aluminium)

AWS D1.3 Structural welding (sheet steel)

AWS D1.4 Structural welding (reinforcing steel)

AWS D1.5 Bridge welding

AWS D1.6 Structural welding (stainless steel)

AWS D1.7 Structural welding (strengthening and repair)

AWS D1.8 Structural welding seismic supplement

AWS D1.9 Structural welding (titanium)

AWS D3.6R Underwater welding (Offshore 7 inland pipelines)

AWS D8.1 Automotive spot welding

Standard
Title
Number

AWS D8.6 Automotive spot welding electrodes supplement

AWS D8.7 Automotive spot welding recommendations supplement

AWS D8.8 Automotive arc welding (steel)

AWS D8.9 Automotive spot weld testing

AWS D8.14 Automotive arc welding (aluminium)

AWS D9.1 Sheet metal welding

AWS D10.10 Heating practices for pipe and tube

AWS D10.11 Root pass welding for pipe

AWS D10.12 Pipe welding (mild steel)

AWS D10.13 Tube brazing (copper)

AWS D10.18 Pipe welding (stainless steel)

AWS D11.2 Welding (cast iron)

AWS D14.1 Industrial mill crane welding

AWS D14.3 Earthmoving & agricultural equipment welding

AWS D14.4 Machinery joint welding

AWS D14.5 Press welding

AWS D14.6 Rotating Elements of Equipment

Standard
Title
Number

AWS D15.1 Railroad welding

AWS D15.2 Railroad welding practice supplement

AWS D16.1 Robotic arc welding safety

AWS D16.2 Robotic arc welding system installation

AWS D16.3 Robotic arc welding risk assessment

AWS D16.4 Robotic arc welder operator qualification

AWS D17.1 Aerospace fusion welding

AWS D17.2 Aerospace resistance welding

AWS D18.1 Hygienic tube welding (stainless steel)

AWS D18.2 Stainless steel tube discoloration guide

AWS D18.3 Hygienic equipment welding

International Organization for Standardization (ISO) Standards

International Organization for Standardization (ISO) has developed over 18500

standards and over 1100 new standards are published every year. The following is a
partial list of the standards specific to welding:

Standard
Description
Number
Standard
Description
Number

Welded, brazed and soldered joints - symbolic representation on drawings

ISO 2553
(1992)

Welding consumables. Covered electrodes for manual metal arc welding of

ISO 2560
non-alloy and fine grain steels. Classification

Covered electrodes for manual arc welding of creep-resisting steels -

ISO 3580
Code of symbols for identification

Covered electrodes for manual arc welding of stainless and other similar
ISO 3581
high alloy steels - Code of symbols for identification

ISO 3834 Quality requirements for fusion welding of metallic materials, five parts.

Welding and allied processes - Nomenclature of processes and reference

ISO 4063
numbers

Welding. Fusion-welded joints in steel, nickel, titanium and their alloys

ISO 5817
(beam welding excluded). Quality levels for imperfections

Welding and allied processes — Classification of geometric imperfections

ISO 6520-1
in metallic materials — Part 1: Fusion welding

Welding and allied processes — Classification of geometric imperfections

ISO 6520-2
in metallic materials — Part 2: Welding with pressure

ISO 6947 Welds. Working positions. Definitions of angles of slope and rotation

ISO 9606 Qualification test of welders — Fusion welding, parts 1 to 5

Welding and allied processes. Recommendations for joint preparation.

ISO 9692-1
Manual metal-arc welding, gas-shielded metal-arc welding, gas welding,
Standard
Description
Number

TIG welding and beam welding of steels

Welding and allied processes. Joint preparation. Submerged arc welding

ISO 9692-2
of steels

Welding and allied processes. Joint preparation. Part 3: TIG and MIG
ISO 9692-3
welding of aluminium and its alloys

Petroleum and natural gas industries - Pipeline transportation systems -

ISO 13847
Welding of pipelines

Welding - Guidance on the measurement of preheating temperature,

ISO 13916
underpass temperature and preheat maintenance temperature

ISO 13918 Welding - Studs and ceramic ferrules for arc stud welding

Welding - Electron and laser-beam welded joints - Guidance on quality

ISO 13919-1
level for imperfections - Part 1: Steel

Welding - Electron and laser-beam welded joints - Guidance on quality

ISO 13919-2
level for imperfections - Part 2: Aluminium and its weld able alloys

Welding - General tolerances for welded constructions - Dimensions for

ISO 13920
lengths and angles - Shape and position

ISO 14112 Gas welding equipment - Small kits for gas brazing and welding

Welding consumables — Gases and gas mixtures for fusion welding and
ISO 14175
allied processes. Replaced EN 439:1994 in Europe.

ISO 14341 Welding consumables. Wire electrodes and deposits for gas shielded
Standard
Description
Number

metal arc welding of non alloy and fine grain steels. Classification

ISO 14554 Resistance welding

ISO 14744 Electron beam welding, six parts

Specification and qualification of welding procedures for metallic

ISO 15607
materials - General rules

ISO/TR
Welding - Guidelines for a metallic material grouping system
15608

Specification and qualification of welding procedures for metallic

ISO 15609
materials - Welding procedure specification, five parts.

Specification and qualification of welding procedures for metallic

ISO 15610
materials — Qualification based on tested welding consumables

Specification and qualification of welding procedures for metallic

ISO 15611
materials — Qualification based on previous welding experience

Specification and qualification of welding procedures for metallic

ISO 15612
materials — Qualification by adoption of a standard welding procedure

Specification and qualification of welding procedures for metallic

ISO 15613
materials — Qualification based on pre-production welding test

Specification and qualification of welding procedures for metallic

ISO 15614
materials - Welding procedure test, 13 parts.

ISO 15615 Gas welding equipment. Acetylene manifold systems for welding, cutting
Standard
Description
Number

and allied processes. Safety requirements in high-pressure devices

Qualification testing of welders for under-water welding. Diver-welders

ISO 15618-1
for hyperbaric wet welding

Qualification testing of welders for under-water welding. Diver-welders

ISO 15618-2
and welding operators for hyperbaric dry welding

ISO 17635 Non-destructive testing of welds. General rules for metallic materials

Welding - Welding of reinforcing steel - Part 1: Load-bearing welded

ISO 17660-1
joints

Welding - Welding of reinforcing steel - Part 1: Non-load bearing welded

ISO 17660-2
joints

ISO/TR
Welding — Grouping systems for materials — European materials
20172

ISO/TR
Welding — Grouping systems for materials — American materials
20173

ISO/TR
Welding — Grouping systems for materials — Japanese materials
20174

Welding for aerospace applications. Qualification test for welders and

ISO 24394
welding operators. Fusion welding of metallic components
WELDING SYMBOLS

Most blueprints for a welding project heavily peppered with them. The skeleton of
a welding symbol has an arrow, a leader line (attached to the arrow), a horizontal reference
line, a tail, and a weld symbol (not to be confused with welding symbol, which refers to the
whole thing.

Basic Welding Symbols

Weld symbols are used to indicate the welding processes used in metal
joining operations, whether the weld is localized or "all around",
whether it is a shop or field weld, and the contour of welds

Arc and Gas Supplementary Symbols

Supplementary Symbols

These welds are indicated by using a process or

specification reference in the tail of the welding symbol as shown in
figure 3-4.

Figure 3-4

When the use of a definite process is required (fig. 3-5), the process
may be indicated by one or more of the letter designations shown in
tables 3-1 and 3-2.
Definite Process Reference - Figure 3-5

Letter designations have not been assigned to arc spot, resistance spot,
arc seam, resistance seam, and projection welding since the weld
symbols used are adequate.

Designation of Cutting Processes by Letters

When no specification, process, or other symbol, the tail may be omitted (fig. 3-6).

Other Common Weld Symbols

Figures 3-7 and 3-8 illustrate the

weld-all-around and field weld symbol, and resistance spot and
resistance seam welds.
Weld All Around and Field Weld Symbols

Resistance Spot and Resistance Seam Welds

Location Significance of Arrow

Fillet, Groove, Flange, Flash, and Upset welding symbols. For these
symbols, the arrow connects the welding symbol reference line to one
side of the joint and this side shall be considered the arrow side of
the joint (fig. 3-9).

Arrow Side Fillet Welding Symbol

The side opposite the arrow side is considered the

other side of the joint (fig. 3-10).

Other Side Fillet Welding Symbol

Projection Welding, Resistance Spot, Resistance Seam, Arc Seam, Arc Spot and
Plug Welding Symbols

For these symbols, the arrow connects the

welding symbol reference line to the outer surface of one member of the
joint at the centre line of the desired weld. The member to which the
arrow points is considered the arrow side member. The other member of
the joint shall be considered the other side member (fig. 3-11).

Plug and Slot Welding Symbols

Near Member

When a joint is depicted as an area parallel to the

plane of projection in a drawing and the arrow of a welding symbol is
directed to that area, the arrow side member of the joint is considered
as the near member of the joint, in accordance with the usual
conventions of drafting (fig. 3-11).

Near Side Welding Symbol

When a joint is depicted by a single line on the drawing

and the arrow of a welding symbol is directed to this line, the arrow
side of the joint is considered as the near side of the joint, in
accordance with the usual conventions of drafting (fig. 3-12 and 3-13).

Arrow Side V-groove Welding Symbol

Other Side V-groove Welding Symbol

Location of Weld With Respect to Joint

Arrow Side

Welds on the arrow side of the joint are shown by placing the weld symbol on the side of
the reference line toward the reader (fig. 3-14)

If you're new to MIG welding and you'd like a simple training so you can learn quickly,
without the headaches,

Welds on the Arrow Side of the Joint

Other Side

Welds on the other side of the joint are shown by placing the weld
symbol on the side of the reference line away from the reader (fig.
3-15).

Welds on the Other Side of the Joint

Both Sides

Welds on both sides of the joint are shown by placing weld symbols on
both sides of the reference line, toward and away from the reader (fig.
3-16).

No Side Significance

Resistance spot, resistance seam, flash, weld symbols have no arrow side
or other side significance in themselves, although supplementary
symbols used in conjunction with these symbols may have such
significance. For example, the flush contour symbol (fig. 3-3) is used
in conjunction with the spot and seam symbols (fig. 3-17) to show that
the exposed surface of one member of the joint is to be flush.
Resistance spot, resistance seam, flash, and upset weld symbols shall be
centered on the reference line (fig. 3-17).

Spot Seam and Flash or Upset Weld Symbols

References and General Notes

Symbols With References

When a specification, process, or other

reference is used with a welding symbol, the reference is placed in the
tail

Symbols Without References

Symbols may be used without specification, process, or other references when:

A note similar to the following appears on the

drawing: "Unless otherwise designated, all welds are to be made in
accordance with specification no...."

The welding procedure to be used is described elsewhere, such as in shop instructions

and process sheets.

General Notes

General notes similar to the

following may be placed on a drawing to provide detailed information
pertaining to the predominant welds. This information need not be
repeated on the symbols:

"Unless otherwise indicated, all fillet welds are 5/16 in. (0.80 cm) size."

"Unless otherwise indicated, root openings for all groove welds are 3/16 in. (0.48 cm)."

Symbol Without a Tail

When no specification,
process, or other reference is used with a welding symbol, the tail may
be omitted .

Weld All-Around and Field Weld Symbols

Welds extending completely around a joint are indicated by mans of

the weld-all-around symbol . Welds that are completely around a
joint which includes more than one type of weld, indicated by a
combination weld symbol, are also depicted by the weld-all-around
symbol. Welds completely around a joint in which the metal intersections
at the points of welding are in more than one plane are also indicated
by the weld-all-around symbol.

Field welds are welds not made in a shop or at the

place of initial construction and are indicated by means of the field
weld symbol

Extent of Welding Denoted by Symbols

Abrupt Changes

Symbols apply between abrupt changes in the

direction of the welding or to the extent of hatching of dimension
lines, except when the weld-all-around symbol is used.

Hidden Joints

Welding on hidden joints may be

covered when the welding is the same as that of the visible joint. The
drawing indicates the presence of hidden members. If the welding on the
hidden joint is different from that of the visible joint, specific
information for the welding of both must be given.

Location of Weld Symbols

Weld symbols, except resistance spot and resistance seam, must be
shown only on the welding symbol reference line and not on the lines of
the drawing.

b. Resistance spot and resistance seam weld symbols may be placed directly at the
locations of the desired welds

Use of Inch, Degree and Pound Marks

Inch marks are used for indicating the diameter of arc spot, resistance
spot, and circular projection welds, and the width of arc seam and
resistance seam welds when such welds are specified by decimal
dimensions.

In general, inch, degree, and pound marks may or may not be used on welding symbols, as
desired.

Construction of Symbols

Fillet, bevel and J-groove, flare bevel groove, and corner flange
symbols shall be shown with the perpendicular leg always to the left
(fig. 3-18).

In a bevel or J-groove weld symbol, the arrow shall point with a

definite break toward the member which is to be chamfered (fig. 3-19).
In cases where the member to be chamfered is obvious, the break in the
arrow may be omitted.
Information on welding symbols shall be placed to read from left to
right along the reference line in accordance with the usual conventions
of drafting (fig. 3-20).

For joints having more than one weld, a symbol shall be shown for each weld (fig 3-21).

The letters CP in the tail of the arrow indicate a complete

penetration weld regardless of the type of weld or joint preparation
(fig. 3-22).

When the basic weld symbols are inadequate to indicate the desired
weld, the weld shall be shown by a cross section, detail, or other data
with a reference on the welding symbol according to location
specifications given in para 3-7 (fig. 3-23).

Two or more reference lines may be used to indicate a sequence of

operations. The first operation must be shown on the reference line
nearest the arrow. Subsequent operations must be shown sequentially on
other reference lines (fig. 3-24).

Additional reference lines may also

be used to show data supplementary to welding symbol information
included on the reference line nearest the arrow. Test information may
be shown on a second or third line away from the arrow (fig. 3-25).
When
required, the weld-all-around welding symbol must be placed at the junction of
the arrow line and reference line for each operation to which it applies.
The field weld symbol may also be used in this manner.
WELDING PROCESSES:

MIG (Metal Inert Gas) Welding or GMAW (Gas Metal Arc Welding):

The concept of combining two pieces of metal together with a wire that is connected to
an electrode current, is referred to as Metal Inert Gas (MIG) welding. In this type of
welding process, a shielded gas is used along the wire electrode, which heats up the two
metals to be joined. A constant voltage and direct current power source is required for
this method, and this is the most common industrial welding process. The MIG or
GMAW process is suitable for fusing mild steel, stainless-steel as well as aluminium.
Arc Welding or SMAW (Shielded Metal Arc Welding):

Arc welding is also called as Shielded Metal Arc welding, or simply referred to as
‘Stick’. This is the most basic of all welding types. The welding stick uses electric
current to form an electric arc between the stick and the metals to be joined. To weld iron
and steel, this type of welding is often used in the construction of steel structures and in
industrial fabrication. Stick welding can be used for manufacturing, construction and
repair work.

TIG (Tungsten Inert Gas) or GTAW (Gas Tungsten Arc Welding):

A non-consumable tungsten electrode is used in this type of welding process. This
tungsten electrode is made use of to heat the base metal and create a molten weld
puddle. By melting two pieces of metal together, an autogenous weld can be created.
For this type of welding, the welder needs to have a lot of expertise as it’s a very complex
process. This welding process is employed to carry out high-quality work when a
superior standard finish is required, without making use of excessive clean up by sanding
or grinding.

FCAW (Flux-Cored Arc Welding):

As an alternative to shield welding, Flux-cored Arc Welding was developed. This

welding process is quite similar to MIG or GMAW process, except for the fact that in
FCAW a special tubular wire filled with flux is used and shielding gas is not always
needed, depending on the filler. This type of welding is well-known for being extremely
inexpensive and easy to learn. However, there are several limitations in its applications
and the results are not often aesthetically pleasing as some of the other welding methods.
The semi-automatic arc is often used in construction projects, thanks to its high welding
speed and portability.
WELDING TERMS:

Arc Blow — is the arc going everywhere that you DON'T want it to go. It only happens
in DC, happens a lot welding up into a corner, and is believed to be caused somehow by
magnetism. It sometimes helps to move the work clamp to a different position on the steel.

Arc Cutting — can be done with a 6010 or 6011 rod with the machine turned up to "warp
10". (very hot) Other rods can be used but these two are the best. It is where you cut
through the steel using the force of the arc. It doesn't make the prettiest cut, but will do in
a pinch when you don't have a torch.

Arc Gouging — is where the steel or metal is cut using an

arc from a carbon electrode. The electrode is solid carbon
wrapped in copper for conductivity. The stinger has
compressed air and when a button is pushed, it blasts air at
the molten metal being cut. The machine is turned to "warp
10" which means you are using a LOT of amps (heat).

An example of this is when we went to a job where 5 stainless steel tanks about 10 stories
high had almost every weld flunk an x-ray test. We gouged the weld on the outside, then
re-welded them. We then gouged the welds on the inside and re-welded into our previous
weld.

Thick stainless can't be torch cut, and even if it could, the heat would cause it to warp.
Arc gouging keeps the heat concentrated at the cut.

Alloy — is an element added to a metal. An example is mild steel with chromium (resist
rust), and nickel (makes it less susceptible to oxidation which is rust) which makes a form of
stainless steel.(the most common stainless is 304)

Alternating Current — reverses back and forth from positive to negative on a sine wave. It
makes for an erratic arc on most welding processes and that is why DC is preferred.

Amperage — measures electricity flowing and is the same as current, which is your heat.

Arc — is what is between the end of the electrode and the base metal. The resistance
causes heat.

Automatic Welding — is a weld made by equipment such as robots.

Backup Strip — is a strip or section of steel butted up to an open gap between two
pieces of steel. 6010 welding rods can be used for open butt welding, but 7018 cannot
and requires a backing strip to provide a surface for the electrode to weld to. Some
backup strips are cut off and some are left in place.

Bead - the deposited filler metal on and in the work surface when the wire or electrode is
melted and fused into the steel. A stringer bead is a narrow bead with only a dragging
motion or light oscillation, while a weave bead is wider with more oscillation.

Bevel - an angle cut or grinded at the edge of the work-piece to allow more penetration
for a stronger weld.

Blown-up - what you will be if you weld or cut on containers with fumes. NEVER weld or
cut on any container unless it is new or you know it has been cleaned and safety certified!
Containers can be toxic, flammable, or explosive.

Brush - steel wire bristled hand brush, disc brush for a hand grinder, cup brush for hand
grinder, or wheel brush for bench grinder. They're used to clean mill scale, oxidation, dirt,
oil etc. off of steel surfaces. Cleanliness is of utmost importance on the work piece to
assure there will be no weld defects. It is important to use a stainless steel brush and mild
steel brush correctly.

Build-Up Weld - building up the surface of a steel part such as the teeth of a sprocket,
surface of an idler wheel (keeps the track in place on tracked vehicles such as bull dozers
or cranes), or bucket on a front-end loader. In most cases it is far less expensive to have a
welder build up a component than it would be to replace the part. Build-up welds are
usually done with hard surface electrodes.
It is also a good way for a new welding student to learn proper re-starts and tie-ins.

Busted Out - failing a weld test because of defects in the welds. "He busted out on his
test plates and didn't get hired."

Butt Joint - Only the top and bottom surface can be welded. Without good penetration,
this weld does not have the strength of a multi-pass fillet weld, or beveled joint.

Cap - the last bead of a groove weld, it can be made with a weave motion back and forth,
or with stringer beads tied into each other.
Also what you need to wear on your head when welding Mig vertical, or any process
overhead, to keep hot sparks off of your head. (see Cussing.) Welder's hats have a small
bill and are so high they need a warning light to keep airplanes from crashing into them.
This is so they can be turned and pulled down over your ear when welding pipe and your
head is tilted. You don't EVEN want a glob of molten metal going into your ear! You
can literally hear it sizzle as you suffer through the burn. Welding hats could win any ugly
hat contest with all the crazy polka dots, paisley and other crazy designs.

Coalescence - this is when the metal or steel is fused (joined) grasshopper.

Coated Electrode - That is the flux on the filler metal of a welding rod. They used to
use bare rods only in the horizontal position. Someone noticed that a rusty rod worked
better than a brand new one so they started experimenting with different coatings on
different rods. They found that some coatings produced a shielding gas that protected
the weld pool from contaminants in the atmosphere. Contaminants cause Porosity and
Longitudinal Cracking. With the weld pool protected the weld was smooth and sound
and could be used in different positions rather than just flat.

Concavity - It is when a Fillet Weld bead sags inward from the root Face to the Root.
Consumable Insert - This is where a filler wire or rod is in a gap and you weld it into the
base metal along with your wire or rod. It becomes one with the weld grasshopper.
Convexity - This is when a Fillet Weld bead protrudes outwards from the Root to the
Face.

Corner Joint - One of the five basic weld Joints. It is when the edges of two plates butt
up to each other at a 90 degree angle. It usually provides a groove to fill providing good
Penetration.

Cover Glass or Cover Plate - Clear glass or plastic lens in a hood or cutting goggles
that protects the #5 (for cutting) or #10,11, 12 lens (for welding) from getting spatter on
them. Gripes the heck ought to' me when a student forgets to put it in when they change
out the lens. They then weld with it and the spatter ruins the glass which aren’t cheap!.

Crack - Where the weld fractures or breaks apart. A good example would be welding on
cast iron. If it is not pre-heated and post-heated right, or if the wrong electrode is used, it
will crack BIG TIME. Sometimes the crack will run right in front of the weld pools as
you weld.
Crater - At the end of the weld bead you burn into the steel without depositing any filler
metal which leaves a depression in the base metal. When doing a Restart, you want to
start at the end of the crack, weld back into where the weld stopped, and then proceed in
the direction you were welding. This pre-heats and gives a good Tie-in into the bead you
just laid.

Critical Temperature - This is when the base metal transitions from solidus to liquidus as
you heat it during the welding process. It's right at that point where it goes from being
solid mass, to melting and becoming liquid. This is a great term to discuss at a cocktail
party to make you sound smart, ESPECIALLY if your audience doesn't know much
about welding!

Current - In the electric circuit the current is the flow of electricity. What you're welding
on resists the flow and that forms heat. AMPS are the measurement of your current. To
get a bit more technical, current is negatively charged electrons passing through a
conductor, which is usually a wire.

Cylinder - What we store oxygen and acetylene in for cutting, and SHIELDING
GAS for the MIG and TIG welding processes. They come in different sizes and you
wanta' research before you buy. If you get too small of one, you'll get real tired of refilling
it all the time.

Defect - Something that ain't right with the weld. Main defects are Longitudinal Cracks,
Porosity, Slag Inclusion, and the "Cardinal Sin" of welding…Undercut.

Depth of Fusion - How deep your filler metal penetrates into the metal from the surface.

Direct Current - DC welding is the smoothest welding producing the least amount of
spatter. The current is flowing one way, from negative to positive. (Cathode to Anode)
It is similar to when you turn on a water hose and the water flows out. With DC the
current ALWAYS flows the same direction.

Direct Current Electrode Negative - Electricity flowing OUT OF the welding Rod
or Wire is dispersed into the work piece therefore giving less penetration. About 1/3 of
the heat is on the end of the rod and 2/3 on the work piece. This is what you want to use
for thin gauge metals.

Direct Current Electrode Positive - Electricity flowing INTO the welding Rod or Wire
and therefore putting more heat at the rod or wire end. This gives you 2/3 heat on the
rod and 1/3 on the work piece, which gives greater penetration for thick metals because
the arc force digs into the steel before depositing filler metal.

Ductility - Is the metal bending and staying bent without breaking.

Duty Cycle - This is how long a machine can run in a ten minute period of time before it
overheats.

10% = 1 minute out of every 10.

20% = 2 minutes out of every 10.
On up to 100% which would run the full time without stopping.

For a machine in a factory or construction site you'd want a 100% duty cycle.
For your hobby workshop you might get by with 20 or 30%.

Edge Joint - The outer edge of two plates butted up 90 degrees parallel to each other.

Edge Preparation - Before welding the edge of a plate or pipe, care is taken to ensure a
sound weld. It may be torch cut or bevelled, machined with a grinder, filed, or all three.

Electrode - Electrodes come either covered with flux, or just bare wire. In the field an
electrode is called a "rod" in stick welding, and "wire" for Mig and Flux Cored Arc
Welding.

There are MANY different types of electrodes.

In WWII bare rods were used that could only be used in the flat position. It was VERY
easy to stick these rods, and I can only imagine how frustrating it must have been to use
them. One day a guy noticed that a rusty rod he picked up welded better than the brand
new ones.

Electrode Holder - A hand clamp that holds a welding rod and conducts electricity out
of the rod in direct current electrode negative, or into the rod in direct current electrode
positive.

Face - On plate or pipe welding there is a root pass, hot pass, filler pass, and cap. The
root penetrates through the back of the plate, the cap is on the surface which you are
welding, which is the face.
Ferrous Metal - Iron comes from ore that is mined from the Earth.

Filler Metal - This is metal added to the weld pool. A weld can be made with or without
filler metal. Thin gauge metal is sometimes welded by melting the two base metals
together.

Flash Burn - This is a burn from the radiation produced from the ULTRA VIOLET
rays from the welding arc. It can burn the skin similar to sunburn, and even blister the
cornea. You don't realize it until hours later when it feels like someone is rubbing hot sand
in your eyes.

Fillet Weld - The king of welds because it is used in so many applications, it is mostly
used on Tee joints. .

Two pieces of metal butted together at a 90 degree angle, a bead is run half way into
each piece. Depending on the thickness, it could take one bead, or multiple beads
TIED-IN to each other.

Fillet Weld Face - The surface or top of the weld.

Fillet Weld Leg - From the intersection of the joint to the end of the weld. There will be a
leg for each plate.

Fillet Weld Toe - Is the end of the weld at the end of the leg. Again there will be one for
each plate.

Fillet Weld Root - Where the weld begins at the intersection of the joined plates.

Fillet Weld Throat - The distance from the root to the face.

Flow Meter - The pressure in a SHIELDING GAS bottle can be up to 2400 lbs.
per inch. The flow meter reduces this to a working pressure, usually around 20 to 25
cubic feet per hour.
Flux:
Cleans the surface and when burned makes a SHIELDING GAS that protects the
weld POOL, or PUDDLE from atmospheric contaminants that cause DEFECTS.

Flux-Cored Arc Welding (FCAW) - Long thin flat strip is run through a series of dies
until it begins to curl up on the sides. FLUX is then added and it continues through the
dies until it is rolled into a tubular wire.

Similar to SOLID STEEL WIRE, it is rolled and used similar to MIG usually set to
DIRECT CURRENT ELECTRODE NEGATIVE. When the wire is
melted to become FILLER METAL, the FLUX burns and forms a SHIELDING
GAS.

Therefore, no SHIELDING GAS is needed, so it can be used in drafty areas or

even in the wind, unlike it's cousin MIG.

Fumes - Whether you are a skilled JOURNEYMAN, or NEWBIE, you should

always be careful of fumes when cutting and welding.

From GALVANIZED zinc fumes which make you sick, to more dangerous phosgene
gas which can be emitted from the UV RAYS around some cleaning solutions,
FUMES can be dangerous!

Always make sure you have proper ventilation, especially in confined quarters!

Fuse - If you purchase a welder to use around the house, make sure you have the proper
fuse so you don't blow everything out. In older houses, make sure the wiring has been
updated or you could cause a fire when they overheat.

Galvanized - An electrochemical process where mild steel is hot-dipped into liquid zinc to
make it anti-corrosive. I was surprised to learn it has been done for 150 years!
When you weld on galvanized steel you have to burn through the zinc coating first and it
produces FUMES that can make you feel sick like you've been punched in the gut.

Groove Weld - When a very strong weld is needed, such as where two columns are
spliced together on a high-rise, it is important to get the maximum penetration and fusion.
This is done by cutting a BEVEL so that you can weld solid from the ROOT, to the
FACE of the PARENT METAL.
Heat Affected Zone - Something many welders do not consider, but they should.
Anytime you weld on metal or steel, you are heating the area next to the weld. After it is
heated, it cools at different rates depending on the temperature in the shop or field.
On construction projects in the winter, this can be very rapidly. Both the heating and
cooling can affect the properties depending on what base metal you are welding on.
The heat affected zone on mild steel is usually no big deal. However, if you weld on cast
iron, for example, without properly pre-heating and post-heating, it will crack right before
your eyes.

Inverter - Relatively new, I first heard of them about 13 years ago. A power source for
welding machines that is much more efficient than the normal transformers most machines
use, and therefore much smaller units.

When I first started welding thirty years ago in a black iron shop, I used a welder that
looked like a big atomic bomb with a box on top of it. It was at least four feet wide, two feet
deep and about three feet tall.

Today they have machines that can do everything that one could, plus some and they're
the size of a small suit case which is much more convenient for the shop and field.

Iron Workers - There are a couple of meanings here. The first is the union I belong too,
the International Association of Bridge, Structural, Ornamental and Reinforcing Iron
Workers. As the title suggest, we work on structures, everything from high rise office
towers, to dams, power houses etc. After a 3 year apprenticeship, I became a structural
welder. There are other gangs (crews) such as the Raising Gang, Plumb Gang, Bolt-up
Gang, and Miscellaneous Gang. Although I've worked on them all, I spent most of my
time on various Welding Gangs seeing as how welding is my true love!

Intermittent Weld: A very common mistake in welding is welding it too much! A lot of
welders, especially those new to the trade, figure "the more the weld the better it'll hold."
Well, it AIN'T true! Many times one or two inches of weld every couple of inches will
hold just as good as a continuous weld.

Jig - Jigs hold the metal or steel you are working on in place as you are fabricating. They
can be steel clamped with a vice or C-clamp, bolts tack-welded to a table, or very
elaborate frames. Positioners in large fab shops hold the work piece, spin, rotate, or
revolve so that you can weld in the flat or horizontal position.

Joint - Intersection where two different sections of parent metal meet. To be listed under
welding joints. On a power house, they'd ask how many joints we welded each day.

There were many different types such as beam to beam, beam to column, x braces etc.

Keyhole - When welding an open butt, or open groove weld JOINT with stick, MIG or
TIG, a "keyhole" will open up. When the sides of the plate burn away on each side of the
WELD POOL a hole is formed which allows for good tie in and penetration.

The keyhole must not be allowed to grow too large or the WELD POOL will waterfall
out the back of the joint.

If the keyhole grows too large, stop welding immediately, let the plate cool and make the
proper adjustment to correct the problem. (Too much heat, wrong rod angle, or staying
too long in the puddle may be the cause.)

Leads - These are the lines from the machine to what you are welding that carry the
current. They are lots of copper wires woven into one to conduct electricity, then covered
with a non-conductive rubber or plastic wrap.

It is important to make sure there are no rips or a tear in the leads exposing bare wire
which could arc on a grounded surface. Besides being a shock or fire hazard, it would
especially be bad if it came in contact with a pressurized gas bottle!

Machine Welding - Equipment performs the weld while a person watches to make sure it
is working right. They will also visually inspect the completed weld. Whether with robotics,
or machine welding, most companies prefer someone who has actually welded in the field
because they have a "feel" for it.

Manual Welding - A person is doing the actual welding. In SMAW (stick) they are
holding the STINGER and manipulating the WELDING ELECTRODE to
control the WELD POOL. In MIG they are using a Mig gun feeding wire to do the
same. In TIG they're using a torch and manually feeding a filler rod.

Melting Rate - How much of the rod (electrode), wire, or TIG rod is melted in a certain
amount of time.