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INSTITUTE OF WELDING & TESTING TECHNOLOGY
WELCOME
YOU
FOR THE TOPIC:
By: Narendra H. Singh

FUSION WELDING WITH PRESSURE:
“नातप्त लोहो न लोहे न संधीयते।”

POPULARLY USED FOR RESTRICTED JOINT APPLICATIONS WITH REDUCED
JOINT EFFICIENCY<85% FOR MASS PRODUCTION WITHOUT THE USE OF
SKILL, FILLER OR FLUXES. THEY ARE DESIGNED IN FACT TO OFFER A STEADY
& COST EFFECTIVE WELDING SOLUTION.
OVERLAPPED-SPOT, SEAM-WELD OF PRESSED SHEET PARTS, BARRELS, RAIL

COACH ROOF, TRANSFORMER-FINS, WIRE-INTERLOCKS, DISSIMILAR,
SIMILAR-STUDS, ERW-TUBES, KITCHEN-WARES, UTENSILS, ELECTRIC-
SWITCHES, MOTOR-VEHICLE PARTS, REFRIGERATOR CABINETS, WASHING
MACHINES, AND RAIL JOINT ETC.
SPOT WELD BY ERW VERSUS OTHER WELDING PROCESSES:
d
S S
Arc Spot Weld
Resistance Spot Welds
GTAW/TIG Spot MIG/MAG Spot Power Beam Spot

ERW Spot Weld
Resistance & Pressure Effect:
R1&R5 Resistance between tip and sheet; It is desirable to have:
R2 & R4 Sheet individual resistance; •R1,R2,R4,R5 low
R3 Surface contact resistance; •R3 high
R1 H = 0.24 x I2 x R x T.
R2 H = Heat input in Calories,

I2 = Current in amperes,
R3 R = Resistance of the work in ohms,
R4 T = Time the current flow in cycles

(50 CYCLES / SECOND)
R5
1 . SQUEEZE TIME - VITAL FOR ELECTRODE TO BE CLOSE ON TO THE METAL
AND APPLY THE RIGHT PRESSURE; WHICH VARIES WITH THE GAP BETWEEN
THE ELECTRODES.
2. UP SLOPE TIME – ESSENTIAL FOR THE CURRENT TO REACH FROM ZERO

THE PEAK.
3. WELD TIME - NECESSARY FOR PEAK CURRENT TO FLOW & HEAT.
4. DOWN SLOPE TIME – REQUIRES FOR THE CURRENT TO CUT OFF FROM PEAK
TO ZERO.
5. HOLD TIME - TAKEN BY THE ELECTRODES TO HOLD THE SHEETS

TOGETHER AFTER THE CURRENT FLOW STOPS. PRESSURE STILL APPLIED TO
ALLOW THE MOLTEN METAL TO SOLIDIFY.
6. OFF TIME - IS THE PERIOD BETWEEN THE END OF ONE SPOT CYCLE TO
START ANOTHER SPOT CYCLE.
Relation between Current and time:
A - WILL HAVE:
 LESS DISTORTION;
• LESS OXIDATION;
Current • GOOD WELDABILITY;
C
Time A: Strong current and short time
C: Small Current and long time
B: Medium current and medium time
EFFECT OF PRESSURE:
*Brings sheet into intimate contact thus effect contact resistance;
*Ensures completion of electric circuit;
*Ensures heat dissipation in weld zone and prevents surface fusion;
*If low: Surface burning and pitting of electrode;
*If High: More current is required;
*Measure the pressure between electrodes with calibrated pressure gauge

only.
PROPERTIES AND FUNCTION OF ELECTRODES:
REQUIREMENT OF ELECTRODES
1. ELECTRODES CENTERED AND FIXED SECURELY TO ELECTRODES HOLDER;
2. FREE MOVEMENT ALLOWING FOR CONSISTENT PRESSURE REPEATABIL-ITY;
3. QUICK RESPONSE OF THE ELECTRODE ARM ALLOWS FOR PRESSURE TO BE
MAINTAINED DURING WELDING;
4. ELECTRODES MUST HAVE LOW NATURAL RESISTANCE, HIGH HEAT CONDUCTIVITY
AND MAINTAINED HARDNESS EVEN AT HIGH TEMPERA-TURES;
5. HIGH CONDUCTIVITY ELECTRODES ARE USED FOR LOW CONDUCTIVE MATERIALS
AND LOW CONDUCTIVE ELECTRODES BEING USED FOR HIGH CONDUCTIVE
MATERIAL.
FUNCTIONS OF ELECTRODES:
1. SUPPLY SUFFICIENT WELDING CURRENT TO THE REQUIRED AREA;
2. HEATING DURING WELDING AND QUICK COOLING AFTER WELDING;
3. DEFINE THE WELDING ZONE AND MAINTAIN CORRECT PRESSURE;
SHAPE OF ELECTRODES:
1. AS TIP OF THE ELECRODE DETERMINE THE WELDING AREA ON THE WORK PIECE IT
IS NECESSARY TO MAINTAIN THE CONTANT SHAPE FREE FROM WEAR
2. MANY TYPES OF SHAPES ARE USED IN ELECTRODES
F - TYPES R - TYPES CF - TYPES CR - TYPES

P - TYPES
The most commonly used electrodes shapes are “p” and “CR” types.
ELECTRODE TIP: WATER
TEFLON TUBE
NEW
USED
2~3 mm
WEAR LINE 0.5 mm
6 mm
TIP DIA BE CHECKED AFTER DRESSING WITH GO / NOGO GAUGE
GO NOGO
6~8 mm > 8mm
GAUGE FOR TIP DIA

ALIGNMENT OF THE TIPS:
100 % Matching 90 % Matching < 90 % Matching
BEST SPOT ACCEPTABLE NOT OK

TIP ALIGNMENT
OK
ERW WELDING ELECTRODES:
ELECTRODE ELECTRODE TIPS
S
ERW SPOT WELDERS

RESISTANCE SPOT WELDING IS EXTENSIVELY USED FOR MAKING CAR BODY.

There are three basic types of resistance welding bonds:

I. Solid state,
II. Fusion, and
III. Reflow braze bond.
I. In a solid state bond, also called a thermo-compression bond, dissimilar

materials with dissimilar grain structure, e.g. molybdenum to tungsten, are
joined using a too short heating time, high weld energy, and high force.
There is little melting and minimum grain growth, but a definite bond and
grain interface. Thus the materials actually bond together while still in the
solid state. The bonded materials typically exhibit excellent shear and
tensile strength, but poor peel strength.
II. In a fusion bond, either similar or dissimilar materials with similar grain
structures are heated to the melting point (liquid state) of both. The
subsequent cooling and combination of the materials forms a “nugget” alloy
of the two materials with larger grain growth. Typically, high weld energies at
either short or long weld times, depending on physical characteristics, are
used to produce fusion bonds. The bonded materials usually exhibit
excellent tensile, peel and shear strengths.
III. In a reflow braze bond, a resistance heating of a low temperature brazing

material, such as gold or solder, is used to join either dissimilar materials or
widely varied thick/thin material combinations. The brazing material must
“wet” to each part and possess a lower melting point than the two work
pieces. The resultant bond has definite interfaces with minimum grain
growth. Typically the process requires a longer (2 to 100 ms) heating time at
low weld energy. The resultant bond exhibits excellent tensile strength, but
poor peel and shear strength.
SEQUENCE OF AN ERW SPOT WELDING PROCESS:
1- Lowering of the top electrode,
2-Application of the adjusted electrode force Set-up time, sequence,
3-Switching-on of the adjusted welding current for the period of the welding time.
Formation of the weld nugget in the joining zone of both work-pieces.
4- Maintaining the electrode force for the period of the set post-weld holding time.
5- Switching-off the force generating system and lifting the electrodes of the work piece.
P
r
Pressing Time
e
s
s
u
r
e On Time
Squeeze Time Weld Time Hold time Off Time
Initial Pressure Fused by the resistance heating at

high welding current WELD NUGGET is
formed
ERW SPOT WELDING - TIME SCALE

SQUEEZE TIME: is the time interval between the opening application of the electrode
force to the work piece and the initial application of ERW welding current. Squeeze time
is necessary to delay the welding current until the electrode force has attained its most
wanted level.
WELD TIME: in which the welding current is applied to the work part. The weld time is
measured and adjusted in cycles of the line voltages as are all timing functions. One
cycle is 1/50 of a second in a 50 Hz power system.
As the weld time is, more or less, related to what is required for the weld-spot, it is really
complicated to provide an exact value of weld time.
HOLD TIME: is the time, after the welding, when the electrodes are still applied to the
sheet to chill the weld. Considered from a welding technical point of view, the hold time
too is the most remarkable welding parameter.
Hold time is absolutely essential to permit the weld nugget to get solidified before the
part is released, but it must not be protracted too long, as this may cause the heat in the
weld spot to spread to the electrodes and cause over heating.
Then the ERW electrodes will be exposed to get further worn out. If the hold time is too
long and the carbon content in material is high (>0.1%), there is an additional risk to
obtain a brittle weld nugget; However, a longer hold time is normally recommended
while welding galvanized carbon steel.
If excessive heat is applied or applied too quickly, or if the force between the base
materials is too low, or the coating is too thick or too conductive, then the molten area
may extend to the exterior of the work pieces, escaping the containment force of the
electrodes (often up to 30,000 psi). This burst of molten metal is called expulsion, and
when this occurs the metal will be thinner and have less strength than a weld with no
expulsion. This burst of molten metal is called expulsion, and when this occurs the metal
will be thinner and have less strength than a weld with no expulsion.
Applying too little energy will not melt the metal or will make a poor weld. Applying too
much energy will melt too much metal, eject molten material, and make a hole rather
than a weld. Another feature of spot welding is that the energy delivered to the spot can
be controlled to produce reliable welds.
The common method of checking a weld's quality is a peel test. An alternative test is the
restrained tensile test, which is relatively difficult to perform, and requires calibrated
equipment. Because both tests are destructive in nature (resulting in the loss of sailable
material), non-destructive methods such as ultrasound evaluation are in various states
of early adoption by many OEMs.
No Splash
Nugget
Large
PRESSURE
Small
Explosion
CURRENT
Nugget diameter
3.5√t 5√t
The nugget diameter
WELDING TIME
should ideally be between
3.5t and 5t in order to
provide proper strength.
WELDING CURRENT
Typical minimum weld strength value (shear to failure) for ordinary carbon steel of 280 N/mm2
tensile strength minimum.
Nominal 3.5√t Nominal 4√t Nominal 5√t Nominal 6√t
Sheet Weld Weld Weld Weld Weld Weld Weld Weld
thickness diameter strength diameter strength diameter strength diameter strength
mm Ø mm k/N Ø mm k/N Ø mm k/N Ø mm k/N
0.6 2.7 1.3 3.1 1.6 3.9 2.0 4.6 2.3
0.8 3.1 2.3 3.6 3.0 4.5 3.6 5.4 4.2
1.0 3.5 3.2 4.0 3.7 5.0 4.3 6.0 5.1
1.2 3.8 4.1 4.4 4.6 5.5 5.4 6.6 6.2
1.6 4.4 5.5 5.1 6.0 6.3 7.4 7.6 8.3
2.0 5.0 7.2 5.7 8.4 7.1 10.8 8.5 13.0
2.5 5.5 10.6 6.3 11.8 7.9 14.5 9.5 17.3
3.0 6.1 12.0 6.9 14.0 8.66 17.8 10.4 22.0
4.4
Shear strength, N/mm2
4.2
4.0
3.8
3.6
Galvanized sheet steel

3.4
3.2
4.5 5.0 5.5 6.
Nugget size, in mm 0
Spacing Size
Minimum size & spacing - essentials for ERW spot-welding of ordinary steel.
Sheet Weld Size Spacing Sheet Weld Size Spacing
thickness mm Ø mm mm thickness mm Ø mm mm
0.38 - 0.62 3.0 9.7 2.15-2.52 6.6 39.6
0.63 - 0.87 3.8 15.7 2.53 - 2.91 7.1 42.7
0.88 - 1.13 4.3 19.1 2.92-3.29 7.4 46.0
1.14 - 1.38 5.1 23.9 3.30-3.67 7.6 49.3
1.39 - 1.64 5.3 26.9 3.68-4.05 8.1 52.3
1.65 - 1.89 5.6 30.0 4.06-4.22 8.4 55.4
1.90 - 2.14 6.1 35.1 Ref: D 8.7 Recommended Practices for Automotive
Weld Quality – Resistance Spot Welding.
ERW SPOT –WELDS:

RWMA CLASS OF ERW ELECTRODES:
I. RWMA Class- 1
II. RWMA Class-2
III. RWMA Class-3 and
IV. RWMA Class-4

RWMA RWMA RWMA RWMA Observations
Class-1 No. Applications Description
Zirconium C15000 Especially heat A small addition of Zr alloy to Cu
Copper treated Zr-Cu alloy improves resistance to softening &
that meets the deformation at high temperatures. It is
minimum electrical used for minimizing sticking tendency
conductivity & while doing spot welding of galvanized
Electrodes for hardness spec’s of materials. It is also used in many high
welding aluminum, Class-1 alloy temperature applications i.e. aerospace,
magnesium alloys, power generation, etc.
brass, bronze &
Cadmium C16200 A high conductivity Addition of Cd alloy to Cu adds
coated materials.
Copper work hardened Cd- hardness & resists softening. Well
These alloys can be
Cu alloy, but not utilized wherever high electrical
used for spot and
heat treatable. conductivity and fatigue strength are
seam welding.
needed. It is also specified for spot
welding of aluminum; the high thermal
conductivity enables it to prevent
electrode sticking over these soft and
conductive materials.
Note:- Cd-Cu has been replaced by Zr-
Cu (C15000) for all RWMA applications.
Zirconium - C18150 Typically heat treated Addition of Zr alloy to Cr-Cu adds
Chromium Cr-Zr-Cu alloy that creep resistance at high operating
Copper These are stronger than meets the minimum temperature and reportedly
Class-1 materials, have electrical and reduces the sticking tendency of
slightly lower electrical hardness specific’s electrodes to the work during spot
conductivity. Applied for of Class-2 alloys. welding of galvanized materials.
spot and seam welding Should be used in C18150 is chiefly specified for the
of hot & cold rolled heat treated use of electrodes.
steel, stainless steel and condition.
low conductivity brass &
Chromium C18200 A high conductivity Cr-Cu is the primary copper alloy
bronze. These are also
Copper Cr-Cu alloy that used for ERW spot & seam welding.
used as flash welding
obtains its best This alloy attains good hardness
dies, and as electrodes
mechanical traits by and conductivity by the combination
for welding galvanized
the heat-treatment of heat-treatment & cold -work.
steel & other coated
and cold-working C18200 is utilized for electrodes,
materials.
together. Should be holders, adopters, as well as
used in heat treated numerous electrical applications
status, only. where resistance to deformation at
high temperature is required or
whenever higher mechanical
aspects are needed than C11000 .
Their high hardness Heat treatable copper A very hard heat treatable copper
Nickel - C18000 makes them ideal for alloy with a alloy with moderate electrical
Silicon - spot & seam welding combination of high conductivity. C18000 is utilized
Chromium electrodes for metals of tensile strength and when a combination of very good
Copper high resistance such as good electrical & mechanical strength along with
Stainless-steel, Monel, thermal properties. moderate electrical/thermal
Inconel, Nichrome. As a Should be used in conductivity are required. It offers
casting, they are used heat-treated excellent value for the properties it
for flash-butt & condition. renders. It is a viable substitute for
projection welding C17500 and C17510 in several
electrodes and fixtures. applications.
Other uses are welding
Heat treatable copper A very hard heat treatable
gun apparatus, seam
Nickel - C17510 alloy with a beryllium-copper alloy with
welding bearing and
Beryllium combination of high moderate electrical conductivity.
other current carrying
Copper tensile strength and C17510 can be utilized when a
structural parts. It is
good electrical & combination of very good
suggested for flash,
thermal properties. mechanical strength along with
upset-butt & projection,
Should be used in moderate electrical & thermal
welding electrodes.
heat-treated conductivity are required.
condition.
Electrode material for Heat treatable Be-Cu The hardest and highest strength
Beryllium C17200 flash, upset-butt and alloy having unusual copper alloy, Be-Cu is specified
Copper projection welding combination of very high whenever the mechanical strength
applications where the hardness, high strength is the limiting design feature for a
pressures are very and lower electrical copper alloy. It is used frequently in
high & wear is severe conductivity than class-3 the form of inserts, tooling facings,
but the heat is not materials. Should be and seam welder bushings. It is
excessive. They are used in heat-treated available in annealed condition
used frequently in the state and considered which is more readily machined and
form of inserts and where there is concern thereafter heat-treated.
facings. They may also with high pressure
be used for seam density and severe wear,
welding bushings. but where heating, due
to its low conductivity, is
not excessive.
Electrodes for spot resistance welding have the property of transferring the electrode
force and the welding current. They are wearing parts and, therefore, simply replaceable.
Depending on the shape and type of electrode, solid electrodes or electrode caps, must
be either re-machined or recycled. The slide depicts ahead various types of electrodes,
electrode caps and holders.
Dependent upon the electrode application, different alloyed electrode materials are used,
as stated before. The added alloying elements influence the red hardness, the tempering
resistance, the conductivity, the fusion temperature, the electrode alloying tendency,
and, finally, the machine-ability of the electrode material. When beryllium is used as an
alloying element, the admissible M A C values must be strictly adhered to during re-
machining or dressing of the electrodes.
Already during the design phase of the components to be welded, importance

must be attached to a good accessibility of the welding point. Moreover, the
electrode force which is imperative to the process must be applied in a way
that no damage is done to the work piece. In the ideal case, the welding point
is accessible from the top and from below.
In order to avoid the displacement of the electrodes, the electrode working

surface shall be flat. Also during the design phase space must be provided for
an adequately large clearing zone around the working point, in order to
guarantee the unrestricted electrode approach to the working point.
PRINCIPLE STRUCTURE OF ERW SPOT WELDING EQUIPMENTS:
The main components are:
the machine frame,

the welding transformer with secondary lines, and
The electrode pressure system and the control system.
This principle design applies to spot, projection and roller seam welding
machines. Differences are to be found merely in the type of electrode fittings
and in the electrode shapes.
ERW welding typically employs power in the form of direct current, alternating current,
medium frequency half-wave direct current, or high-frequency half wave direct current.
However, AC current has the simplest arrangement and cost effective too, generally a
transformer supplies energy to the weld joint in the form of low voltage, high current AC
power; however, unavoidable are the disadvantages of current zeros and cooling of weld
nuggets. In relation to the average current values, peak loads occur and, with that,
increased electrode wear. Such extreme peak loads do not occur with DC . However, the
structural design of a DC supply unit is more complicated and thus more expensive than
the AC supply.
As conventional welding machines operate with a 50 Hz primary current supply, the

welding current can be controlled only in 20 ms units (1 period). When the inverter-
direct current or the medium-frequency technique is used, a finer setting of the current-
on time-cycle and more precise control of the welding current is possible.
Continued…
In order to realize the higher welding current in shorter times, the impulse
capacitor resistance welding technique is used. The rectified primary current
is stored in capacitors and, through a high-voltage transformer, converted to
high welding currents. The advantages of this technique are low heat input
and high reproducibility. Because of the high density energy, materials with
good conductivity too can be welded including multiple projection spot welds.
A disadvantage of this system is, apart from its high costs, the difficult
regulation of welding current.
PROJECTION SPOT WELD:
is a modification of ERW spot welding, indeed, in which the weld is localized by means of raised
sections or projections, on one or both of the work pieces to be joined. Heat is concentrated at the
projections, which permits the welding of heavier sections or the closer spacing of welds. The
projections can also serve as a means of positioning the work pieces. Projection welding is often used
to weld studs, nuts, and other screw machine parts to metal plate. It is also frequently used to join
crossed wires and bars. This is another high-production process, and multiple projection welds can be
arranged by suitable designing and jigging.
Depending on the demands on the joint strength or on the projection rigidity, different projection
shapes are applied. These are annular, circular or longitudinal projections. The welding projections are,
according to their size, adapted to the used plate thickness and may, therefore, appear as different
types in the work piece: embossed projections, solid projections and natural projections. The shape is
embossed onto the plate surface by appropriate die plates, dies and, if necessary, counter dies.
PROJECTION SPOT WELDER (RPW)
~
Step-2
~
Step-1
Ideal for the multiple spot welds, wherever the spacing is the chief constraint , by the design.
ERW PROJECTION SPOT-WELD:
Spacing
Pre-formed
Projections S
Wherever the space constraints, lower than the minimum requirements for ERW Spot Welds or uneven thickness
joint conditions exist, then the option of Projection Spot Welding is selected to obtain the acceptable weld nuggets.
FUSION WELDING BY PRESSURE

PRE-FORMED PROJECTIONS
PRE-FORMED PROJECTIONS
SEAM WELDING:
ERW seam welding is a process that produces a weld at the faying surfaces of two similar
metals. The seam may be a butt joint or an overlap joint and is usually an automated or
mechanized system. It differs from butt-welding in that butt welding typically welds the
entire joint at once where the seam weld forms progressively starting from one end. Like
spot welding, seam welding relies on two electrodes, usually made out of alloyed copper,
to apply pressure and current. The electrodes are disc shaped and rotate as the material
passes between them. This allows the electrodes to stay in constant touch with the
material to make a continuous long seam welds. The electrodes may also move or assist
the movement of the material.
Seam welding produces an extremely durable weld because the joint is forged due to the
heat and pressure applied. A properly welded joint formed by resistance welding is
typically stronger than the material from which it is formed.
In contrast to resistance spot welding the disc-shaped electrodes remain in contact and
turn continuously after the first weld spot has been produced. At the points where a
welding spot is to be produced again the current flow is initiated. Dependent on the
electrode twist rate and on the welding current frequency, spot welds or seal welds with
overlapping weld-nuggets are produced.
A transformer supplies energy to the weld joint in the form of low voltage, high current
AC power. The application of DC current also produces seal welds. The joint of the work
piece has high electrical resistance relative to the rest of the circuit and is heated to its
melting point by the current. The semi-molten surfaces are pressed together by the
welding pressure that creates a fusion bond, resulting in a uniformly welded structure.
Most seam welders use water cooling through the electrode, transformer and controller
assemblies due to the heat generated.
 Resistance seam welding (RSEW) is a resistance welding process
which produces coalescence at the faying surfaces the heat obtained
from resistance to electric current through the work parts held
together under pressure by electrodes OR A type of continuous weld
made between or upon overlapping metal parts.
 The resulting weld is a series of overlapping resistance spot welds

made progressively along a joint by rotating the electrodes.
WHEN TO USE:
 To make pressure & liquid tight joint;
 To make tubular section.
PART DESIGN CONSIDERATIONS:

• Avoid sharp radii or abrupt change in the contour of the seam;
• To locate parts, investigate if tooling holes are practical or tacking
operation necessary;
• Avoid obstructions along the seam path so sufficient electrode (wheel)
size can be utilized.
Refer: Automotive Welding Design AWS D 8.4 - XXXX

ARC STUD WELDER (SW):
Step-2 Step-1
~ ~
Stud
Weld metal Ceramic ferrule

A R C S T U D W E L D E R ’ S O P E R AT I O N A L S T E P S :
ARC STUD WELDER (SW) WITH CERAMIC FERULE

Designate Reference Numbers:
ISO 4603 : 2009
21 RESISTANCE SPOT WELDING;
211 Indirect Spot Welding;
212 Direct Spot Welding;
23 PROJECTION SPOT WELDING;

231 Indirect Projection Spot Welding;
232 Direct Projection Spot Welding;
22 RESISTANCE SEAM WELDING;

221 Lap Seam Welding;
225 Foil Butt Seam Welding;
26 RESISTSNCE STUD WELDING;

A R C S T U D W E L D - B E N D T E S T S 59
AUTHENTIC MEASUREMENT OF ERW SPOT-WELD BY THE PEEL TEST:
Spacing
Actual size is only the nugget or the button Ø s

S P O T W E L D T E S T: Ref. QW-462.8
Step -1 Step -2 Step -3
HOLD, BEND & PEEL THE PIECES APART

 P E E L T E S T: R e f . Q W - 4 6 2 . 8
Step -1 Step -2 Step -3
H O L D , B E N D & P E E L A PA R T
CROSS-TENSION TEST
S P O T W E L D S H E A R L O A D T E S T: Ref. QW-462.9
Ref: QW-462.10 & 11 Shear Strength Requirements of Spot or Projection Weld Test Specimens.
SINGLE OR MULTIPLE SPOT WELDS SHEAR TEST SPECIMENS
 S H E A R L O A D T E S T: Ref. QW-462.9
Ref: QW-462.10 & 11 योग् कर्मषु कौशलं।

Shear Strength Requirements of Spot or Projection Weld Test Specimens.
THANKS A LOT
SINGLE OR MULTIPLE SPOT WELD SHEAR TEST SPECIMEN

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INSTITUTE OF WELDING & TESTING TECHNOLOGY

By: Narendra H. Singh

“नातप्त लोहो न लोहे न संधीयते।”

OVERLAPPED-SPOT, SEAM-WELD OF PRESSED SHEET PARTS, BARRELS, RAIL

GTAW/TIG Spot MIG/MAG Spot Power Beam Spot

R2 H = Heat input in Calories,

R4 T = Time the current flow in cycles

2. UP SLOPE TIME – ESSENTIAL FOR THE CURRENT TO REACH FROM ZERO

5. HOLD TIME - TAKEN BY THE ELECTRODES TO HOLD THE SHEETS

Current • GOOD WELDABILITY;

*Brings sheet into intimate contact thus effect contact resistance;

*Ensures completion of electric circuit;

*Ensures heat dissipation in weld zone and prevents surface fusion;

*If low: Surface burning and pitting of electrode;

*If High: More current is required;

*Measure the pressure between electrodes with calibrated pressure gauge

F - TYPES R - TYPES CF - TYPES CR - TYPES

TIP DIA BE CHECKED AFTER DRESSING WITH GO / NOGO GAUGE

GAUGE FOR TIP DIA

100 % Matching 90 % Matching < 90 % Matching

BEST SPOT ACCEPTABLE NOT OK

ERW SPOT WELDERS

RESISTANCE SPOT WELDING IS EXTENSIVELY USED FOR MAKING CAR BODY.

There are three basic types of resistance welding bonds:

I. In a solid state bond, also called a thermo-compression bond, dissimilar

III. In a reflow braze bond, a resistance heating of a low temperature brazing

1- Lowering of the top electrode,

2-Application of the adjusted electrode force Set-up time, sequence,

Initial Pressure Fused by the resistance heating at

ERW SPOT WELDING - TIME SCALE

The nugget diameter

Galvanized sheet steel

ERW SPOT –WELDS:

RWMA CLASS OF ERW ELECTRODES:

II. RWMA Class-2

III. RWMA Class-3 and

IV. RWMA Class-4

Already during the design phase of the components to be welded, importance

In order to avoid the displacement of the electrodes, the electrode working

The main components are:

the machine frame,

As conventional welding machines operate with a 50 Hz primary current supply, the

ERW PROJECTION SPOT-WELD:

FUSION WELDING BY PRESSURE

 The resulting weld is a series of overlapping resistance spot welds

PART DESIGN CONSIDERATIONS:

Refer: Automotive Welding Design AWS D 8.4 - XXXX

Weld metal Ceramic ferrule

ARC STUD WELDER (SW) WITH CERAMIC FERULE

23 PROJECTION SPOT WELDING;

22 RESISTANCE SEAM WELDING;

26 RESISTSNCE STUD WELDING;

AUTHENTIC MEASUREMENT OF ERW SPOT-WELD BY THE PEEL TEST:

Actual size is only the nugget or the button Ø s

Step -1 Step -2 Step -3

HOLD, BEND & PEEL THE PIECES APART

Step -1 Step -2 Step -3

Ref: QW-462.10 & 11 योग् कर्मषु कौशलं।