Welding
Processes
IPE 2111
Afia Ahsan
Lecturer
MPE, AUST
WELDING
Welding is a metal joining process in which two or more parts are joined or coalesced at their
contacting surfaces by suitable application of heat or/and pressure.
Sometimes, welding is done just by applying heat alone, with no pressure applied.
In some cases, both heat and pressure are applied; and in other cases, only pressure is
applied, without any external heat.
In some welding processes a filler material is added to facilitate coalescence.
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ADVANTAGES OF WELDING
❑ Welding provides a permanent joint.
❑ Welded joint can be stronger than the parent materials if a proper filler metal is used
that has strength properties better than that of parent base material and if defect less
welding is done.
❑ It is the economical way to join components in terms of material usage and fabrication
costs. Other methods of assembly require, for example, drilling of holes and usage of
rivets or bolts which will produce a heavier structure.
DISADVANTAGES OF WELDING
❑ Labor costs are more since manual welding is done mostly.
❑ Dangerous to use because of presence of high heat and pressure.
❑ Disassembly is not possible as welding produces strong joints.
❑ Some of the welding defects cannot be identified which will reduce the strength. 3
APPLICATION OF WELDING
❑Aircraft construction and Automobile construction
❑Bridges and Buildings, Household and Office furniture
❑Pressure vessels, Tanks and Storage tanks, Rail, Road equipment, Piping and Pipelines
❑Ships, Trucks and Trailers, Machine tool frames, Cutting tools and dies
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TYPES OF WELDING
Welding processes can be broadly classified into (i) Fusion Welding, and (ii) Solid State
Welding
Fusion Welding:
❑ In fusion-welding processes, heat is applied to melt the base metals. In many fusion
welding processes, a filler metal is added to the molten pool during welding to facilitate
the process and provide strength to the welded joint.
❑ When no filler metal is used, that fusion welding operation is referred to as autogenous
weld.
❑ Types: Arc welding, Submerged arc welding, TIG, MIG, Resistance welding, Thermit
welding, Oxyfuel gas welding, electron beam welding, laser welding
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TYPES OF WELDING
Solid State Welding:
❑ In this method, joining is done by coalescence resulting from application of pressure only
or a combination of heat and pressure.
❑ Even if heat is used, the temperature in the process is less than the melting point of the
metals being welded (unlike in fusion welding).
❑ No filler metal is utilized.
❑ Types: Diffusion welding, Friction welding/Stir welding, Ultrasonic welding, Cold welding,
Roll welding, Forge welding
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TYPES OF WELD JOINTS
Welding produces a solid connection between two pieces called a weld joint. A weld joint
is the junction of the edges or surfaces of parts that have been joined by welding. There
are five basic types of joints for bringing two parts together for joining.
(a) Butt joint (b) Corner joint (c) Lap joint
(d) Tee joint (e) Edge joint 7
TYPES OF WELD JOINTS
Butt joint: In this joint type, the parts lie in the same plane and are joined at their edges
Corner joint: The parts in a corner joint form a right angle and are joined at the corner of the
angle
Lap joint: This joint consists of two overlapping parts
Tee joint: One part is perpendicular to the other in the approximate of the letter ‘T’
Edge joint: The parts in an edge joint are parallel with at least one of their edges in common
and the joints is made at the common edge
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TYPES OF WELDS: FILLET WELD
❑ Fillet weld is used to fill in the edges of plates created by corner, lap and tee joints
❑ Fillet welds can be single or double ( i.e. welded on one side or both) and can be
continuous or intermittent
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TYPES OF WELDS: GROOVE WELD
Groove welds usually require that the edges of the parts be shaped into a groove to
facilitate weld penetration
Square groove weld Single bevel groove weld Single V-groove weld
single J-groove weld Single U-groove weld Double V-groove
weld for thicker
sections
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TYPES OF WELDS: PLUG WELD AND SLOT
WELD
Plug weld and slot weld: Plug welds and slot welds are used for attaching flat plates,
using one or more holes or slots in the top part and then filling with filler metal to fuse the
two parts together
Plug weld
Slot weld
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TYPES OF WELDS: SPOT WELD AND SEAM
WELD
Spot weld: It is a small fused section between the surfaces of two sheets or plates
Seam weld: Similar to a spot weld except it consists of a more or less continuously fused
section between two sheets and plates
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ARC WELDING
❑ It is a fusion welding process in which the melting and joining of metals is done by the
heat energy generated by the arc between the work and electrode.
❑ An electric arc is generated when the electrode contacts the work and then quickly
separated to maintain the gap. A temperature of 5500°C is generated by this arc.
❑ This temperature is sufficient to melt most of the metals. The molten metal, consisting of
base metal and filler, solidifies in the weld region. To have seam weld, the power source
moves along the weld line.
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ARC
Feature
WELDING: ELECTRODES
Consumable Electrode Non-Consumable Electrode
Electrodes that melt and become part of the Electrodes that do not melt and do not
Definition
weld. become part of the weld.
Made of materials like mild steel, nickel, or
Material Made of tungsten or carbon.
aluminum.
Used in Shielded Metal Arc Welding (SMAW), Gas
Used in Gas Tungsten Arc Welding (GTAW)
Usage Metal Arc Welding (GMAW), and Flux-Cored Arc
and Plasma Arc Welding (PAW).
Welding (FCAW).
Filler
Acts as both the electrode and the filler material. Requires a separate filler rod if needed.
Material
Not coated, but may require shielding gas
Coating Usually coated with flux (e.g., SMAW electrodes).
(e.g., GTAW).
Durability Shorter lifespan as it melts during welding. Longer lifespan as it does not melt.
Welding
Produces more slag and spatter. Produces cleaner and more precise welds.
Quality
Current
Can use AC or DC depending on the type. Generally, uses DC with a specific polarity.
Type
Cost Generally cheaper but consumed quickly. More expensive but lasts longer. 14
ARC WELDING: SHIELDING GAS
❑ This covers the arc, electrode tip and weld pool from external atmosphere. The metals
being joined are chemically reactive to oxygen, nitrogen, and hydrogen in the atmosphere.
❑ So, the shielding is done with a blanket of gas or flux, or both, which inhibit exposure of
the weld metal to air.
❑ Common shielding gas: Argon, Helium
ARC WELDING: FLUX
❑ Used mainly to protect the weld region from formation of oxides and other unwanted
contaminants, or to dissolve them and facilitate removal.
❑ During welding, the flux melts and covers the weld region giving protection and it should be
removed by brushing as it is hardened.
❑ Additional function, other than giving protection: stabilize the arc, and reduce spattering 15
ARC WELDING: POWER SUPPLY
Both AC and DC can be used; DC is advantageous as better arc control is possible.
ARC WELDING: POLARITY
❑ Straight polarity in which workpiece is positive, and electrode is negative is suitable for
shallow penetration (like in sheets) and joints with wide gaps.
❑ Reverse polarity in which workpiece is negative, and electrode is positive is suitable for
deeper welds.
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SHIELDED METAL ARC WELDING
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SHIELDED METAL ARC WELDING
❑ Shielded metal arc welding (SMAW) is an AW process that uses a consumable
electrode consisting of a filler metal rod coated with chemicals that provide flux and
shielding.
❑ The welding stick (SMAW is sometimes called stick welding) is typically 225 to
450mm (9–18 in) long and 2.5 to 9.5 mm (3/32–3/8 in) in diameter
❑ The filler metal used in the rod must be compatible with the metal to be welded, the
composition usually being very close to that of the base metal.
❑ The coating consists of powdered cellulose (i.e., cotton and wood powders) mixed
with oxides, carbonates, and other ingredients, held together by a silicate binder.
❑ Currents typically used in SMAW range between 30 and 300 A at voltages from 15 to
45 V
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SHIELDED METAL ARC WELDING
Figure: SMAW
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ADVANTAGES
❑ SMAW is the simplest of all the arc welding processes.
❑ The equipment can be portable, and the cost is low.
❑ This process finds innumerable applications, because of a wide variety of electrodes.
❑ A big range of metals and their alloys can be welded.
❑ Welding can be carried out in any position with highest weld quality
DISADVANTAGES
❑ Because of the limited length of each electrode and brittle flux coating on its mechanization is
difficult.
❑ The process uses stick electrodes and thus it is slower as compared to M1G welding.
❑ Because of flux-coated electrodes, the chances of slag entrapment and other related defects
are more as compared to MIG or TIG welding.
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APPLICATIONS
❑ Almost all the commonly employed metals and their alloys can be welded by this
process.
❑ SMAW is used both as a fabrication process and for maintenance and repair jobs.
❑ The process finds applications in (a) Tank, boiler and pressure vessel fabrications; (b)
Ship building; (c) Pipes and Penstock joining; (d) Building and Bridge construction; and
(e) Automotive and Aircraft industry, etc.
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GAS METAL ARC WELDING (GMAW)
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Gas metal arc welding (GMAW)
Gas Metal Arc Welding (GMAW) is frequently referred
to as Metal Inert Gas (MIG) welding is a commonly
used high deposition rate welding process. Wire is
continuously fed from a spool. MIG welding is
therefore referred to as a semiautomatic welding
process. Before igniting the arc, gas flow is checked.
Proper current and wire feed speed is set, and the
electrical connections are ensured.
Gases used for shielding include inert gas such as
argon, helium and carbon dioxide. The combination of
bare electrode and shielding gases eliminates the slag
covering on the weld.
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ADVANTAGES
❑ Because of continuously fed electrode, MIG welding process is much faster as compared to
TIG
❑ Thick and thin, both types of workpieces can be welded effectively
❑ No flux is used. MIG welding produces smooth, neat, clean, and spatter free welded
surfaces, which require no further cleaning and reducing welding cost.
DISADVANTAGES
❑ MIG welding cannot do deep penetration in the welded area.
❑ Since air drafts may disperse the shielding gas, MIG welding may not work well in
outdoor welding applications
❑ Weld metal cooling rates are higher than with the processes that deposit slag over the
weld metal
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APPLICATION
❑ The process can be used for welding of carbon and low alloy steels, stainless steels,
aluminum, magnesium, copper, nickel, and their alloys, titanium, etc.
❑ For welding tool steels and dies
❑ For the manufacture of refrigerator parts
❑ MIG welding has been used successfully in industries like aircraft, automobile and
shipbuilding
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GAS TUNGSTEN ARC WELDING (GTAW)
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GAS TUNGSTEN ARC WELDING (GTAW)
❑ It uses a non-consumable tungsten electrode and
shielding gas (inert gas) for shielding.
❑ Also called tungsten inert gas welding (TIG)
❑ usage of filler wire is optional and is heated by arc
and not transferred across the arc.
❑ The weld area is protected from atmospheric
contamination by a shielding gas (usually an inert
gas such as argon)
❑ Tungsten is a good electrode material due to its high
melting point of 3400°C.
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ADVANTAGES
❑ No flux is used; hence there is no danger of flux entrapment
❑ Because of clear visibility of the arc and the job, the operator can exercise a better
control on the welding process
❑ Weld in all positions and produces smooth and sound welds with fewer spatters
❑ It is very much suitable for high-quality welding of thin (0.125mm) materials
❑ It is a very good process for welding nonferrous metals and stainless steel.
DISADVANTAGES
❑Under similar applications, MIG welding is a much faster process as compared to TIG
welding, since TIG welding requires a separate filler rod
❑Filler rod end if it by chance comes out of the inert gas shield can cause weld metal
contamination
❑Equipment costs are higher than that for flux shielded metal arc welding. 28
APPLICATION
❑ Welding aluminum, magnesium, copper and their alloys, carbon steels, stainless
steels, high temperature and hard surfacing alloys like zirconium etc.
❑ Welding sheet metal and thinner sections
❑ Welding of expansion bellows, transistor cases, instrument diaphragms, and can-
sealing joints
❑ Precision welding in atomic energy, aircraft, chemical and instrument industries
❑ Rocket motor chamber fabrications in launch vehicles.
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SUBMERGED ARC WELDING
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SUBMERGED ARC WELDING
Submerged Arc Welding (SAW) is a common arc welding
process. It requires a continuously and consumable wire
electrode. The molten weld and the arc zone are
protected from atmospheric contamination by being
“submerged” under a blanket of granular fusible flux.
When molten, the flux becomes conductive and provides
a current path between the electrode and the work.
A thick layer of granular flux is deposited ahead of a
consumable electrode and arc is maintained beneath the
blanket of flux. A portion of flux melts and acts to remove
impurities from molten metal while the unmelted excess
provides additional shielding. This layer provides a
thermal insulation that slows the cooling of weld metal.
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ADVANTAGES
❑ Deep weld penetration and Sound welds are readily made
❑ High speed welding of thin sheet steels at over 100 in/min (2.5 m/min) is possible
❑ Welds produced are sound, uniform, ductile, corrosion resistant and have good impact
value.
❑ Single pass welds can be made in thick plates with normal equipment.
❑ The arc is always covered under a blanket of flux, thus there is no chance of spatter of
weld.
DISADVANTAGES
❑ Limited to ferrous (steel or stainless steels) and some nickel-based alloys;
❑ Normally limited to long straight seams or rotated pipes or vessels;
❑ Flux and slag residue can present a health & safety issue;
❑ Requires inter-pass and post weld slag removal. 32
APPLICATION
❑ Fabrication of pipes, pressure vessels, boilers, structural shapes, worn-out and earth
moving equipment, cranes and under structure of railway coaches and locomotives.
❑ Automotive, aviation, ship-building and nuclear power industry
❑ Rebuilding of worn-out parts and depositing wear resisting alloys. Hard facing of tractor
rollers and idlers and crane pulleys.
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THERMIT WELDING (TW)
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THERMIT WELDING (TW)
Thermit welding differs from other welding processes principally in that the heating is
obtained from the thermit chemical reaction rather than from fire or electric current. A
mixture of a metallic oxide and finely divided aluminum were ignited. The two materials
react exothermically thereby converting the mixture into a superheated mass of the metal
itself and a slag.
The superheated metal flows into a mold around the parts to be united and weld them into
one homogeneous mass while the slag overflows on top of the mold. Thermit welding now
finds only limited application, chiefly in the repair of large iron and steel castings, though it
was the traditional method for joining rails on site.
Chemical reaction:
Fe2O3 +2Al→2Fe+Al2O3 +Heat
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THERMIT WELDING (TW)
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ADVANTAGES
❑ The heat necessary for welding is obtained from a chemical reaction and thus no
costly power-supply is required. Therefore, broken parts (rails) can be welded on the
site itself.
DISADVANTAGES
❑ Thermit welding is applicable only to ferrous metal parts of heavy sections, i.e., mill housings
and heavy rail sections.
❑ The process is uneconomical if used to weld cheap metals or light parts.
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APPLICATION
❑ For repairing fractured rails (railway tracks).
❑ For butt-welding pipes end to end.
❑ For welding large fractured crankshafts.
❑ For welding broken frames of machines
❑ For replacing broken teeth on large gears.
❑ For welding new necks to rolling mill rolls and pinions.
❑ For welding cables for electrical conductors.
❑ For end welding of reinforcing bars to be used in concrete (building) construction.)
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OXYFUEL GAS WELDING
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OXYFUEL GAS WELDING
❑ In this process, various fuels are mixed with oxygen and
burnt to perform welding. Eg: Oxyacetylene welding
❑ Oxyacetylene welding (OAW):
❑ In this case, welding is performed by a flame formed by
the combustion of oxygen and acetylene. The flame
comes from a torch.
❑ A filler rod coated with flux is used sometimes which
prevents oxidation, creating a better joint.
❑ Acetylene is a famous fuel because it is capable of
generating a temperature of 3500°C.
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OXYFUEL GAS WELDING
The chemical reaction between oxygen and acetylene happens at two stages as given below.
C2H2 + O2 = 2CO + H2+ HEAT (First stage; inner core)
The products of first reaction are combustible and second reaction occurs as,
2CO + H2 + 1.5O2 = 2CO2 + H2O + Heat (second stage; outer envelope)
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OXYFUEL GAS WELDING
When both oxygen and acetylene are mixed in ratio of 1:1, then neutral flame is seen as
shown in figure. The outer envelope delivers a temperature of 1260°C and inner core has
approximately 3500°C.
The first stage reaction is seen in the inner cone of the flame (bright white colour),
while the second stage reaction is seen in the outer envelope (colorless but with tinges
ranging from blue to orange). The temperature is very high at the inner core which is
approximately 3500°C.
Total heat liberated during the two stages of combustion is 55×106 J/m3 of acetylene.
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ADVANTAGES & DISADVANTAGES
❑ The combination of acetylene and oxygen is highly flammable and hence hazardous
to environment.
❑ It is unstable at pressures much above 1 atm
❑ It is mandatory for the welder to wear gloves, goggles etc. as preventive measures.
❑ The equipment is relatively cheap and portable. So it is used as an economical,
versatile process that is well suited for low quantity production and repair jobs.
❑ It is rarely used to weld plates thicker than 6.5 mm.
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APPLICATION
❑ Automotive Repair – Used for bodywork and exhaust system repairs.
❑ Jewelry and Artwork – Precision welding for delicate and artistic designs.
❑ Metal Fabrication – Ideal for small-scale fabrication and repairs.
❑ Plumbing and HVAC Work – Used for joining copper pipes and other materials.
❑ Aerospace and Shipbuilding – Occasionally used for specialized repair tasks.
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RESISTANCE WELDING
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RESISTANCE WELDING
❑ Resistance Welding (RW) is a welding process where heat is generated at the joint by the
resistance of the metal to an electric current. Pressure is applied simultaneously or after
heating to create a strong weld. This process is widely used in high-production industries
because of its speed, efficiency, and automation potential.
❑ Different types of resistance welding are: 1. Spot welding, 2. Seam welding, 3. Projection
welding, 4. Flash welding, 5. Upset welding.
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ADVANTAGES
❑ High speed of welding.
❑ Low cost as less skilled workers can do it.
❑ No filler metal is needed.
❑ Highly suitable for automated production lines.
DISADVANTAGES
❑ The initial cost of equipment is high.
❑ Bigger job thicknesses cannot be welded. Typically used for metals up to 6mm thick.
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APPLICATION
❑ The attachment of braces, brackets, pads or clips to formed sheet-metal
parts such as cases, covers, bases or trays.
❑ Spot welding of car body panels, chassis, frames.
❑ Seam welding for fuel tanks, aircraft panels.
❑ Projection welding for nuts, bolts, connectors.
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FRICTION WELDING
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FRICTION WELDING
❑ Friction welding (FRW) is a solid-state welding process in which coalescence is
achieved by frictional heat combined with pressure. The friction is induced by
mechanical rubbing between the two surfaces, usually by rotation of one part
relative to the other, to raise the temperature at the joint interface to the hot working
range for the metals involved.
❑ No filler metal, flux, or shielding gases are normally used.
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ADVANTAGES
❑ Enables joining dissimilar metals
❑ There is no external application of heat or flux
❑ Minimal or no defects
❑ Fast Process
DISADVANTAGES
❑ Works best for cylindrical or flat parts.
❑ Some brittle materials may not respond well.
❑ Specialized machinery needed.
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APPLICATION
❑ Drive shafts, crankshafts, axles, engine valves.
❑ Nuclear components, wind turbine parts, oil drilling tools.
❑ Pipes, cutting tools, hydraulic cylinders.
❑ Turbine blades, jet engine components, missile parts.
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DIFFUSION WELDING
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DIFFUSION WELDING
❑ Diffusion welding (DFW) is a solid-state welding process where two surfaces are joined
by applying heat and pressure for an extended period, allowing atomic diffusion across
the interface without melting the base materials. It is primarily used for high-precision,
high-strength applications.
❑ Temperatures are well below the melting points of the metals (about 0.5 Tm is the
maximum), and plastic deformation at the surfaces is minimal.
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ADVANTAGES
❑ Creates extremely strong joints with high integrity.
❑ Minimal thermal stress
❑ Joints created by diffusion bonding are clean, of high quality, and free from discontinuity
and porosity.
❑ Works with dissimilar materials – Can bond titanium, aluminum, stainless steel.
DISADVANTAGES
❑ Slow process – Takes minutes to hours per weld.
❑ Although the running costs are low, the initial setup cost is high.
❑ Requires precise surface preparation – Poor contact leads to weak bonding.
❑ Limited to small or medium-sized parts – Not ideal for large structural welding.
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APPLICATION
❑ Jet engine parts, rocket components, turbine blades.
❑ Implants, prosthetics, surgical tools.
❑ Armor plating, missile components
❑ Sensors, semiconductors bonding.
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FORGE WELDING
Forge welding is a welding process in which the components to
be joined are heated to hot working temperatures and then
forged together by hammer or other means. Considerable skill
was required by the craftsmen who practiced it to achieve a
good weld by present-day standards. The process may be of
historic interest.
COLD WELDING
Cold welding (CW) is a solid-state welding process
accomplished by applying high pressure between clean
contacting surfaces at room temperature. The faying
surfaces must be exceptionally clean for CW to work, and
cleaning is usually done by degreasing and wire brushing
immediately before joining.
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ROLL WELDING
❑ Roll welding (ROW) is a solid-state welding process in which pressure sufficient to cause
coalescence is applied by means of rolls, either with or without external application of
heat.
❑ Roll welding is a variation of either forge welding or cold welding, depending on whether
external heating of the work parts is accomplished prior to the process.
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WELDING DEFECTS
Defects during welding may be caused by the presence of impurities and gases at the
liquification temperature, fast solidification of the weld metal, thermal shock and
microstructural changes. Common defects in welding and their remedies are discussed
below:
❑ Cracks: Cracks are fracture-type interruptions either in the weld itself or in the base
metal adjacent to the weld. This is perhaps the most serious welding defect because
it constitutes a discontinuity in the metal that significantly reduces weld strength.
❑ Cavities: These include various porosity and shrinkage voids. Porosity consists of
small voids in the weld metal formed by gases entrapped during solidification. The
shapes of the voids vary between spherical (blow holes) to elongated (worm holes).
Shrinkage voids are cavities formed by shrinkage during solidification.
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WELDING DEFECTS
❑ Solid inclusions: These are nonmetallic solid materials trapped inside the weld
metal. The most common form is slag inclusions generated during arc-welding
processes that use flux. Instead of floating to the top of the weld pool, globules of
slag become encased during solidification of the metal.
❑ Incomplete fusion: Also known as lack of fusion, it is simply a weld bead in which
fusion has not occurred through out the entire cross-section of the joint. A related
defect is lack of penetration which means that fusion has not penetrated deeply
enough into the root of the joint.
❑ Imperfect shape or unacceptable contour: The weld should have a certain desired
profile for maximum strength.
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WELDING DEFECTS
❑ Solid inclusions: These are nonmetallic solid materials trapped inside the weld
metal. The most common form is slag inclusions generated during arc-welding
processes that use flux. Instead of floating to the top of the weld pool, globules of
slag become encased during solidification of the metal.
❑ Incomplete fusion: Also known as lack of fusion, it is simply a weld bead in which
fusion has not occurred through out the entire cross-section of the joint. A related
defect is lack of penetration which means that fusion has not penetrated deeply
enough into the root of the joint.
❑ Imperfect shape or unacceptable contour: The weld should have a certain desired
profile for maximum strength.
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WELDING DEFECTS
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PHYSICS OF WELDING
❑ Power density
Power density can be computed as the power entering the surface divided by the
corresponding surface area: 𝑃
𝑃𝐷 =
𝐴
Here,
PD =power density, W/mm2 (Btu/sec-in2);
P =power entering the surface W(Btu/sec);
A=surface area over which the energy is entering,mm2(in2).
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PHYSICS OF WELDING
A heat source transfers 3000W to the surface of a metal part. The heat impinges the surface in a circular area, with intensities
varying inside the circle. The distribution is as follows 70% of the power is transferred within a circle of diameter 5mm and 90%
is transferred within a concentric circle of diameter 12 mm. What are the power densities in a) the 5 mm diameter inner circle and
b) the 12 mm diameter ring that lies around the inner circle?
Solution:
𝜋(5)2
a) The inner circle area A= = 19.63 𝑚𝑚2
4
The power inside this area, P= 0.70× 3000 = 2100 𝑊
2100
Power Density, PD= = 107 𝑊/𝑚𝑚2
19.63
𝜋(122 −52 )
b) The area of the ring outside the inner circle, A = = 93.4 𝑚𝑚2
4
Power, P= 0.9× 3000 − 2100 = 600 𝑊
6000
Power Density, PD= = 6.4 𝑊/𝑚𝑚2
93.4
The power density seems high enough for melting in the inner circle, but not sufficient in the ring that lies outside the inner circle
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PHYSICS OF WELDING
❑ Weld Travel Speed Calculation
𝐿
𝑆=
𝑇
Here,
S = Travel speed (mm/min)
L = Weld length (mm)
T = Weld time (min)
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PHYSICS OF WELDING
❑ Heat Input Calculation
Determines the amount of heat supplied during welding, affecting penetration and weld
quality. 𝑉×𝐼×60×𝞰
𝐻=
𝑆×1000
Here,
H = Heat input (kJ/mm)
V = Voltage (V)
I = Current (A)
S = Travel speed (mm/min)
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PHYSICS OF WELDING
❑ A welder is performing MIG welding (GMAW) to join two mild steel plates along a 600 mm
weld length. The welding machine is set to 24 volts and 180 amps, with a process
efficiency of 85%. The welder completes the weld in 2 minutes.
❑ A welder is performing TIG welding (GTAW) on a stainless-steel sheet to join two pieces
together. The weld joint requires a precise heat input to avoid distortion and ensure strong
fusion. The welding parameters are as follows: Weld Length = 750 mm, Voltage = 20 V,
Current = 150 A, Process Efficiency = 80%
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THANK YOU
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