The document discusses various metal joining processes including welding, soldering, brazing and adhesive bonding. It covers gas welding and electric arc welding processes in detail. For gas welding, it describes oxy-acetylene welding equipment and process parameters. For electric arc welding, it explains different power sources for DC and AC, electrode types, and safety equipment used. It also discusses welding positions, joint designs, and factors affecting weld quality.

1. Presented by
Department of Mechanical Engineering
Unit - 03
Metal Joining Processes
MANUFACTURING PROCESSES - II
2141908

2. Unit No. 3 (Metal Joining Processes)
Principle of welding, soldering, Brazing and adhesive bonding.
Classification of welding and allied processes
Capabilities and applications
welding parameters
general concepts of weldability
welding metallurgy and weldament design
Gas welding and gas cutting
Arc welding
Power sources and consumables
Resistance welding
Spot, Projection and seam welding process
Atomic hydrogen
Ultrasonic
Plasma and laser beam welding
Electron beam welding
special welding processes
e.g. TIG, MIG, friction and explosive welding, welding of C.I. and Al.
Defects of welding and remedial actions
Numerical Calculation of Different process parameters of welding.
Teaching Hours – 12 and Percentage Weightage 25% (18 Marks)

3. Welding
Welding is a process in which localized coalescence
(Permanent Joint) is produced by heating the material upto
suitable temperature with or without application of filler
material.
If filler material is different from base material it is
heterogenous welding.
Advantages:-
 Different Material can also be welded.
 Welding can be done anywhere.
Disadvantages:-
 In the heat affected zone properties of base material is also
affected.
 To dismantle, we have to break the weld
 Initial investment is more
 Highly skilled operator is required

4. Soldering
 The melting point temperature of filler material is less than 450°C
and it is also less than melting point temperature of base material.
 Filler material is an alloy of lead and tin is known as solder.
 The flux used in soldering is zinc chloride (ZnCl2) and HCI.
 The strength of joint is less when compared to brazing.
 Used in electronic industry.
Brazing
The melting point temperature of filler material is more than 450°C
but less than the melting point temperature of base material.
Filler material is an alloy of copper and zinc, copper and silver,
copper and aluminium. This is known as spelter.
The flux used is borax and boric acids.
Strength is more.
Used in pipe fitting where leak proof joints are required for intricate
light weight components.

10. Types of Joints
(a) Butt joint,
(b) Corner joint,
(c) Lap joint
(d) Tee joint
(e) Edge joint
Groove Welds
(a) Square groove weld, one side;
(b) single bevel groove weld;
(c) single V-groove weld;
(d) single U-groove weld;
(e) single J-groove weld;
(f) double V-groove weld for thicker sections
(dashed lines show original part edges)

11. Fillet Welds
(a) Inside single fillet corner joint;
(b) outside single fillet corner joint;
(c) double fillet lap joint;
(d) double fillet tee joint
(dashed lines show the original part edges)
(a)Plug weld and
(b)Slot weld
Plug Weld and Slot Weld

12. Spot Weld and Seam Weld

13. Various positions that a weld

14. # Welding
Position
Description AWS
Designation
Axis
Direction
1 Flat
The bottom of material is on the
ground and groove is on upper side. 1G
Weld axis is
parallel to the
ground.
2 Horizontal
One of the longer edges of any one is
on ground.
2G
Axis is parallel to
the ground.
3 Vertical
One of the shorter edges of both the
piece is on the ground and work piece
is kept vertical
3G
Weld axis is
perpendicular to
the ground.
4 Overhead
The weld piece is above the head in
which the groove side is on bottom.
4G
Weld axis is
parallel to ground.
Welding Position

15. Welding Positions
FLAT
HORIZONTAL
VERTICAL
OVERHEAD
INCREASING DIFFICULTY

16. Welding Terms
Base Metal:- The metal to be joined or cut is termed the base metal.
Penetration:- It is the depth up to which the weld metal combines with the
base metal as measured from the top surface of the joint.
Backing:- It is the material support provided at the root side of weld to aid in
the control penetration.
Root:- It is the point at which the two pieces to be joined by welding are
nearest.
Toe of Weld:- It is the junction between the weld face and the base metal.
Weld Face:- It is the exposed surface of the weld.
Bead: - It is the metal added during a single pass of welding. The bead appears
as a separate material from the base metal.

17. Welding and Allied Processes

18. Selection of Welding Process
1) Types of metal and its metallurgical characteristics
2) Types of joint, its location and welding position
3) End use of the joint
4) Cost of production
5) Structural (Mass) size
6) Desire performance
7) Experience and abilities of manpower
8) Joint design
9) Accuracy of assembling required
10)Welding equipment available
11)Work sequence
12)Welder skill

19. Parameters affecting Quality of Welding
1) Skill of worker
2) Welding parameters (Temp. or Force or Resistance)
3) Shielding medium
4) Working environment
5) Work layout
6) Plate edge preparation
7) Fit-up and alignment
8) Protection from winds during on site welding
9) Dimensional accuracy
10)Suitable distortion control procedures in place

20. Condition for obtaining satisfactory welds
1] Source of Energy (Heat Generation)
Flame,
Arc,
Resistance,
Friction,
Ultrasonic,
Explosion
2]Surface Contaminants
Organic films,
Absorbed gases
Chemical compound,
Flux are used to clean oxide film and other contaminants
3]Protecting metal from atmospheric contamination
Protect Oxygen and Nitrogen present in air
Shielding Gases are used like Argon, Helium, CO2
Carbon also produce by burning of the Flux coating consumable electrode
4]Control of weld metallurgy
Heat Affected Zone (HAZ)
Heat treatment control Cooling rate and Alloying elements are added

21. Gas Welding (Oxy Fuel Gas)
Fuel Gases Max. Temp. Neutral Temp.
Acetylene 3300° C 3100° C
Propylene 2860° C 2500° C
Propane 2700° C 2450° C
Hydrogen 2870° C 2350° C
Methane 2740° C 2350° C
Natural Gas 2400° C 2350° C
Gas Welding Equipment
Gas Cylinders
Pressure Regulator with Gauges
Nozzles, Hose Pipe and Fittings
Welding Torch

22. Oxy-Acetylene welding use for almost material and Alloy
Compare to other higher temp. produce
Consist of CO2 and Water vapours, which present the molten metal from oxidation
Acetylene gas also called Fuel gas (C2H2)
Produced by reaction of calcium carbide(CaC2) with water (H2O)
Oxygen gas is compressed in cylinder at a pressure of 15 MPa.
Acetylene gas is compressed in cylinder at a pressure of 1.7 Mpa.
Oxy-Acetylene Welding

23. Combustion
 O2 and C2H2 in equal proportions by volume, burn in the inner white cone.
 In cone oxygen combines with the carbon of the acetylene to from CO.
 While Hydrogen is liberated.
C2H2 + O2 → 2CO + H2 + Heat 448 kg/mol
 On passing into outer envelope of flame. two separates reaction take place.
 CO combines with O2 from atmosphere and burn to from CO2
 Hydrogen also burn with O2 from the atmosphere to from water vapour H2O
4C0 + 2H2 + 3H2 → 4CO2 + 2H2 812 kg/mol

24. Oxy-Acetylene Welding
Advantages
 Versatile process
 Portable and can be moved almost everywhere
 Easy control flame
 Temperature control easy
 Cost and Maintenance of gas welding equipment is low
 Rate of heating and cooling is relatively low
 Good weld quality
Disadvantages
 As compared to arc welding take longer time for metal heat
 Due to thermal effects larger heat area and increased grain growth,
 Distortion and less corrosion resistance
 Expensive
 Handling and Storing of gas necessitate lot of safety precautions
 Heavy section cannot be joined economically
 Skilled operator required
 Difficult to prevent contamination
Application
 To joint most ferrous and non-ferrous metals
 To join thin materials
 Automobile and Aircraft industries
 Sheet metal fabricating planes.

25. Method of Welding
Leftward (or Forward or Forehand) welding
 Direction of weld is RHS to LHS
 Blow pipe angle 60° - 70° from surface of W/P
 Filler road angle 30° - 40° from surface of W/p
 Vertical joint are welded
 Restricted to welding 5mm thick Plates
Rightward (or Backward or Backhand) welding
 Direction of weld is LHS to RHS
 Blow pipe angle 40° - 50° from surface of W/P
 Filler road angle 40° - 50° from surface of W/p
 Horizontal and Overhead joint are welded
 Used for thicker material
 Faster by 20 to 25% compared to Leftward
 Less acetylene 15 to 20% is needed compared to Leftward
 Amount of distortion in work is minimum

26. Types of Flames
 Gases in the ratio of 1:1 by volume
 C2H2 = O2
 Used for CI, MS, LCS, Al
 Excess fuel gas (C2H2 ) is used
 C2H2 > O2
 Used for Medium carbon steel, Ni
 Excess oxygen (O2) is used
 C2H2 < O2
 Used for Copper alloys, Brass, Bronze, Zinc

27. Types of Flames

28. Welding rods (Filler materials) for Gas Welding
Filler metal rod, 90 mm long and Diameter range 1.6 mm to 9.5 mm
Coated welding rods which have coating of flux
Bare welding rods having no coating of flux

29. Gas welding Fluxes
Composing of Borates or Boric Acid, Soda ash and small amount of
other compounds E.g. Sodium Chloride, Ammonium Sulphate and iron oxide .
During welding if the metal is heated in air, the atmospheric oxygen
react and forms oxides, which result in poor quality, low strength of joint.
To avoid atmospheric contamination.
Flux is fusible and non-metallic.
Available in powder, paste or liquid form.
Gas welding process it directly apply on the surface, or dipping the
heated end of the filler rod.

30. Gas Cutting

32.  Also called as flame cutting.
 Welding torch and cutting torch is different.
 Cutting torch has an additional tube for high pressure oxygen, along with cutting tip or
nozzle.
 Tip is provided with center hole through which jet of pure oxygen passes.
 Oxygen has affinity for iron and steel. At ordinary temp. this action is slow, but
eventually an oxide in the form of rust materializes.
 Oxy-Fuel cutting uses acetylene and oxygen to preheat metal to red hot .
 Uses pure oxygen to burn away the preheated metal.
 When iron is heated to temp. 750 – 870° C , the steel is burnt into an iron oxide.
 Metal upto 760 mm can cut.
 Used in ship-building, structural fabrication, maintenance work
 Accuracy is not good.
 CI, Non-ferrous alloys and high manganese alloy are not cut.
Gas Cutting

33. Equipment
 Welding power source
 Electrode holder
 Ground clamp
 Welding cables and connectors
 Accessory equipment (chipping hammer, wire brush)
 Protective equipment (helmet, gloves, etc.)
Electric Arc Welding

34. Electric Arc Welding Power Source

35. DC Reverse Polarity and Straight Polarity

36. Electrical Arc Welding – Alternating Current (AC)

37. DC, Electrode positive
(DC Reverse Polarity)
DC, Electrode Negative
(DC Straight Polarity)
AC
Penetration
Shallow Deep Intermediate
Heat Generation
2/3rd at electrode
1/3rd at w/p
1/3rd at electrode
2/3rd at w/p
50% on both
Metal deposition rate High Low Intermediate
Thickness of work
to be welded
Thin sheets Thick sheets Intermediate
Stable smaller arc Easier Easier Difficult
Arc blow Severe Severe Insignificant
Electric Arc Welding Power Source

38. Electrical Arc Welding – Electrodes
1) Consumable electrode
(1)Bare electrode
These electrodes do not prevent oxidation (Hence joint is weak)
Used for minor repairs
(2)Flux coated electrode
To prevent oxidation (Weld bead by creating a gaseous around arc)
To make the formation of the slag easy
To facilitate the stability of arc
2) Non-consumable electrode
Electrode are 12 mm in diameter and 450 mm long.
Not consumed during welding process
E.g.. Carbon, Graphite, Tungsten

39. Welding - Accessory equipment

41. Arc Eye Certain types of UV radiation can produce an injury to the
surface and mucous membrane (conjunctiva) of the eye called "arc eye,"
"welders' eye" or "arc flash.“
Pain – Photophobia - Tearing and Reddening –Sensation of eye

42. Welding - Personal Protective Equipment

44. Electric Arc Welding
The metal is melted by the heat of an electric arc.
1) Metallic arc welding
2) Carbon arc welding
3) Atomic hydrogen welding
4) Shielded arc welding

45. The intense heat of the arc
forms a molten pool in the metal being
weld, at same time melts the tip of the
electrode.
Metallic arc welding
Application
To weld Low carbon steel
and high alloy austenitic stainless
steel

46. Carbon arc welding
Work is connected to
negative and carbon rod or electrode
connected to the positive.
Voltage required AC 30 volts
and DC 40 volts. Economically on DC
supply.
Approximately twice current
required to raise the work to weld
temp.
Application
Used for filling blow holes in
casting

47. Atomic hydrogen welding
• Heat is obtained from AC current.
• Arc drawn between two tungsten
electrodes in an atmosphere of
hydrogen.
• As hydrogen gas passes through the arc,
the hydrogen molecules are broken up
into atoms
• They recombine on contact with the
cooler base metal generating intense
heat sufficient to melt the surfaces to be
welded, together with the filler rod.
• Envelop of hydrogen gas also shields the
molten metal from oxygen and nitrogen
and thus prevents weld metal from
deterioration.
• Weld obtained are homogeneous and
smooth
Advantages
• No flux or separate shielding gas is used.
• Less distortion
• Welding of thin metal is possible
Limitations
• Higher operating cost
• Welding speed less
• Cannot used for depositing large quantities of metals
Application
High grade work on SS & most non-ferrous metals

48. Shielded arc welding (SMAW)
• Molten weld is protected from action of
atmosphere by an envelope of
chemically reducing or inert gas
• As molten steel has an affinity for oxygen
and nitrogen, it will, if exposed to the
atmosphere, enter into combination with
these gases forming oxides and nitrides.
• Due to this injurious chemical
combination metal becomes weak,
brittle and corrosion resistant.
• Flux coating on the electrode used for
shielding.
• Flux producing slag which floats on top of
molten metal and protects it from
atmosphere, produce envelope of inert
gas around the arc and the weld.
• Temperature range 6000 – 7000° C
• source performed both AC and DC

49. Purpose of Shielding Gas (Inert Gases)
• Shielding gas shields the solidifying molten weld from oxygen as well as
impurities and moisture in the air.
• Which may weaken welding due to the corrosion tolerance of the weld &
Generate porous.
• Cools down welding gun
• Gases components are argon, helium, carbon dioxide and oxygen
• Form a protective envelope around the weld area
• Used in
1. MIG
2. TIG
3. Shield Metal Arc

50. Classification of Electrodes as per Indian Standard
Structural steel electrodes were classified as per IS 815:1974
Revised code is IS 814:1991
IS 815:1974
As per IS 815 electrodes are designated with letters and digits.
P X X X X X X S
Prefix (P) is either E or R which indicates solid extruded (E) or reinforced extruded (R)
Electrode.
1st digit – Indicates type of coating.
2nd digit – Indicates weld positions in which electrode can be used.
3rd digit – Indicates welding current conditions.
4th and 5th digit – Indicate UTS and YS of all weld metal.
6th digit – Requirement of minimum % elongation and absorbed energy in charpy V-
notch impact test of weld metal.
Suffix (s)
P – Deep penetration electrode
H – Hydrogen controlled electrode
J, K and L – Amount of metal recovery in case of iron powder electrode
Suffix (s) are optional and may or may not be given if not applicable.

51. As per IS 814 electrodes are designated with letters and digits as
given below:
E L X X X X S
E indicates extruded solid electrode,
L is a letter to designate type of coating,
1st digit indicates UTS and YS of deposited weld metal,
2nd digit gives percentage elongation and impact values of weld metal deposited,
3rd digit gives welding positions in which electrode can be used and
4th digit gives the current conditions for the use of electrode.
Suffix(s) are optional and indicate special characteristics of electrode such as H1,
H2, and H3 indicate hydrogen controlled electrodes with different amount of
diffusible hydrogen J, K, L indicate different amount of metal recovery in weld
pool in case of iron powder electrodes and X means radiographic weld quality.
Revised code is IS 814:1991

52. Size and Welding Current for Stick Mild Steel Electrodes
 Electrode metallic core wire is the same but the coating constituents give the
different characteristics to the welds.
 Based on the coating constituents, structural steel electrodes can be classified in
the following classes
1) Cellulosic Electrodes : high cellulosic content more than 30% and TiO2 up to 20%
2) Rutile Electrodes : TiO 2 up to 45% and SiO2 around 20%
3) Acidic Electrodes : iron oxide more than 20% or 40% , TiO2 10% and CaCO3 10%
4) Basic Electrodes : CaCO3 around 40% and CaF2 15-20%
Electrodes Coating

53. TIG – GTAW (Tungsten Inert Gas – Gas Tungsten Arc Welding)

54. TIG – GTAW
• Heat provided by a very intense electric
arc which is struck between a virtually
non-consumable tungsten electrode and
metal workpiece.
• Electrode does not melt and become a
part of the weld.
• Filler metal is required, a welding rod is
fed into the weld zone and melted with
base metal in same manner as that used
with oxyacetylene welding.
• Weld zone is shielded from the
atmosphere by an inert-gas which is
ducted directly to the weld zone where it
surrounds the tungsten.
• Inert-gas which does not combine
chemically with the metal being welded.
• The major inert gases that are used are
argon and helium.

55. TIG – GTAW
Advantages
 TIG welds are stronger, more ductile and more corrosion resistant compare to
ordinary shield arc welding.
 No granular flux is required
 Little weld metal splatter or weld sparks that damage surface of the base metal
compare to traditional shield arc welding.
Limitations
 Slower travel speed than other welding processes
 Equipment cost higher and skilled person required
Application
 Fusion welding of aluminium and its alloy, Stainless steel, Magnesium alloys, Nickel
base alloys, Copper base alloys, Carbon steel and Low alloy steel.
 Used for the combining of dissimilar metals, hard facing and the surfacing of metals

56. MIG – GMAW (Metal Inert Gas – Gas Metal Arc Welding)

57. MIG – GMAW
• Inert-gas consumable electrode process
• MIG process is a refinement of TIG
process
• Tungsten electrode has been replaced
with a consumable electrode.
• Electrode is driven through the same
type of collet that holds a tungsten
electrode by a set drive wheels.
• Consumable electrode acts as a source
for the arc column as well as the supply
for the filler metal.
• Bare-wire, Magnetic flux, Fluxed-cored
electrode

58. MIG – GMAW
Advantages
 Higher deposition rate
 Faster then SMAW due to continuous feeding of filler metal.
 Welds produced arc of better quality
 No slag formation
 Deeper penetration is possible
 Weld metal carries low hydrogen content
 More suitable for welding of thin sheets
Limitations
 Less adaptable for welding in difficult to reach portions
 Equipment used is costlier and less portable
 Less suitable for outdoor work
Application
 Practically all commercially available metals can be welded
 Used for deep groove welding of plates and castings

59. TIG – GTAW vs. MIG – GMAW

60. Plasma Arc Welding
• Plasma arc consist of an electronic arc
plasma gas. And gases used to shield the
jet column.
• DC Power supply with drooping volt
ampere output and with 70 open line
volts.
• ‘ Transferred arc ’ plasma jet torch is
similar to TIG torch, expect that it has the
water-cooled nozzle between electrode
and work.
• Nozzle constricts the arc, increasing its
pressure.
• Plasma the collision of gas molecules
with high-energy electron, is then swept
out through nozzle
• Forming the main current path between
electrode and work piece.
• Plasma arc and transferred arc are
generated between tungsten electrode
or cathode and the work piece, or anode.
Types of torches for welding and cutting with
Plasma Arc
1. Transferred arc
2. Non-transferred arc
Temperature of plasma is around
50000°C but the welding process it is restricted
to 20000°C.
Argon and argon mixture used since
they do not attack tungsten or copper cathode.

61. • ‘ Non-transferred arc ’ torch extends the arc from electrode, or cathode to end of
nozzle.
• Nozzle acts as anode
• Plasma jet is completely independent of work piece, with power supply contained
within equipment.
Plasma Arc Welding
Advantages
 Almost all metal can be welded, with out filler metal possible.
 No change in microstructure due to temp.
 Less weld defects
Limitation
 Plasma arc will produce extensive ultraviolet and infrared radiation, which is
harmful for skin.
Application
 Welding of Stainless steel, Titanium, metal having high melting points and super
alloys.
 Used in Aeronautical industry, Precision instrument industry, Jet engine
manufacturing.

62. Laser Beam Welding
Light amplification by stimulated emission of radiation
• Focusing of a monochromatic light into
extremely concentrated beams.
• Carefully focused of light that
concentrates tremendous amount of
energy on a small area to produce fusion.
• When capacitor bank is triggered energy
is injected into wire that surrounds the
flash tube.
• Wire establishes an imbalance in the
material inside the flash tube.
• Thick xenon often is used in material for
flash tube, producing high power levels
for very short period of time.
• Flash tubes or lamps flashes thousands
of flashes per second.
• Lamps become converting electrical
energy into light energy.
• Laser goes through Focusing device
where it is pin-pointed on the w/p

63. Laser Beam Welding
Advantages
 Weld dissimilar metals
 High electrical resistant metal is also weld
 High degree of precision
 High production rate
 Weld can be made in air or with shielding gas
Limitation
 High reflective material can’t be welded.
 High energy loss.
 High skilled operation.
 High equipment cost
 Eye protection required.
 Limited to 0.3 mm thick or less material thickness weld.
Application
 Welding of Cu and Al alloys in electrical industries.
 High quality of weld in aviation, aerospace and defense.

64. Thermit Welding
Finely divided aluminium iron oxide
Reaction : 8Al + 3 Fe3O4 = 4 Al2O3 + 9Fe + heat
• Method of uniting iron or steel parts by
surrounding the joint with steel at a
sufficient high temp. to fuse the adjacent
surface of the parts together
• Wax pattern of desire size and shape is
prepared around the joint or region
• Wax pattern is then surrounded by sheet
iron box and the space between box and
pattern is filled and rammed with sand
• After cutting, pouring and heating gates
risers a flame is directed into the heating
oven due to which the wax pattern melts
and drains out heating is continued to
raise the temp. of the parts.
• Thermit mixture is packed in the crucible
of conical shape formed from a sheet-
iron casting lined with heat resisting
cement and is ignited with magnesium or
torch yielding a highly superheated
(3000° C) molten-iron and slag of
aluminium oxide
• Molten iron is then run into the mould
which fuses with parts to be welded and
forms a thermit collar at the joint

65. Thermit Welding
Advantages
 Can be used anywhere
 Low set-up cost
 Not a highly skilled operation
 Most suitable for thick sections welding
Limitations
 Only thick sections can be welded
 High set-up and cycle time.
Application
 Shipping, Steel and Railroad industries
 Used for welding non-ferrous

66. Electron-Beam Welding
• Fusion joins metal by bombarding a
specific confined area of the base metal
with high velocity electrons.
• When electron strike work surface , their
energy is converted into heat, instantly
vaporizing metal, creating keyhole.
• Operation is performed in vacuum to
prevent reduction of electron velocity.
• If vacuum not used, electron would strike
small particles in atmosphere, reducing
their velocity and decreasing their
heading ability.
• Process allows fusion weld of great depth
with minimum width because beam can
focused and magnified.
• Depth of weld bead to width of weld
bead ratio is of the order of 20/1.

67. Electron-Beam Welding
Advantages
 Eliminates contamination of both weld zone and weld surface
 Dissimilar metals and reactive metals can be welded.
 Welding speed may be fast as 2500 mm/min
 Weld or cut any metal or ceramic, diamond
 Material thickness 150 mm can weld
 Energy conversion efficiency is high, about 65%.
Limitation
 High initial investment
 High operating and maintenance cost
 Work size is limited due to vacuum chamber
 High cost of precision tooling
Application
 Welding of automobile, airplane, aerospace, etc
 Welding of Ball bearing over 100 mm
 Welding of titanium, nickel, SS and its alloys
 Fabrication of gas turbine parts

68. Explosive Welding
• Welding is achieved
through very high contact
of pressure developed by
detonating a thin layer of
explosive placed over one
of the pieces to be joined.
• Low intensity explosive are
used.
• Plastic deformation is used
for joining.
• Two plates which are to
weld are maintain at a
distance (stand off) then
movable plate hit the target
and plastic deformation
take place.
 High velocity (4572-7620 m/s)
• Trinitrotoluene (TNT)
• Cyclotrimethylenetrinitramine (RDX)
 Mid-low velocity (1524-4572 m/s)
• Ammonium nitrate
• Dynamites

69. Advantages
 High joint strength
 Dissimilar metals can be welded
 Inexpensive equipment
 Large size plate can be welded
 Good for plate cladding
Limitation
 High set-up time
 Trained operators are require
 Inherently dangerous process
 Accuracy less
Application
 Suitable for cladding plates and slab with dissimilar metals, such as for chemical
industry.
 Explosive cladding used in die-casting industries
 Tubes and pipes are often joined
 Sealing and Joining of boilers plates and tubular heat exchangers
Explosive Welding

70. Ultrasonic Welding
 Power source of frequency converter which converts 50 cycle line power into high
frequency electrical power . Frequency is 20 kHz to 60 kHz
 Transducer which changes high frequency electrical power into vibratory energy.
 Ultrasonic vibrations combined with static clamping force produces dynamic
shear stresses between contact of two w/p materials.
 Then local plastic deformation will take place and joint formation will take place
at the interface.
 Transducer changes high frequency electrical power into ultrasonic vibrating
energy.
 The bonding will take place in solid state without applying external heat, filler
metal, and max. pressure.

71. Advantages
 High productivity
 Thin pieces can be welded
 Welds are free from foreign inclusions
 Post cleaning of weld not required
Limitation
 Not suitable for welding of thick plates
 Life of equipment is less
 Not economical as compared to other processes
Application
 Joining electrical and electronics components.
 Thematic sealing of materials and device
 Welding of aluminium wire and sheet
 Fabricating nuclear fuel elements.
Ultrasonic Welding

72. Resistance Welding
Resistance welding is produced by means of electrical resistance (Heavy
Electrical Current) across the two components and Mechanical pressure is applied at
this moment to complete the weld.
 Heat generated in this process is given by
H = I2RT
H = Heat generation (Joules)
I = Current (Amperes)
R = Resistance (Ohms)
T = Time of current flow (Seconds)
With out addition of any filler material, and shielding gases.
Electrodes :- Higher electrical conductivity as well as higher hardness
Electrode Materials :- Pure Copper, Copper Cadmium and Copper Chromium

73. 1. Current: Enough current is needed to bring the metal to its plastic state of welding.
2. Pressure: Mechanical pressure is applied first to hold the metal pieces tightly
between the electrodes, while the current flows through them called weld pressure,
and secondly when the metal has been heated to its plastic state, to forge the metal
pieces together to form the weld, called forge pressure.
3. Time of Application: It is the cyclic time and the sum total of the following time
period allowed during different stages of welding
a. Weld Time: Time period during which the welding current flow through
the metal pieces to raise their temp.
b. Forge Time: Time period during which the forge pressure is applied to the
metal pieces.
c. Hold Time: Time period during which the weld to be solidify.
d. Off Time: The period of time from the release of the electrodes to the
start of the next weld cycle.
4. Electrode contact area: The weld size depends on the contact area of the face of the
electrodes
Parameter Affecting Resistance Welding

74. Classification of Resistance Welding Processes
1) Resistance Spot Welding
2) Resistance Seam Welding
3) Resistance Projection Welding
4) Resistance Butt Welding
1) Upset Welding
2) Flash butt Welding
For Lap Joints
For Butt Joints

75. Resistance Spot Welding
 Step down transformer are used
 High current is used (3,000 A to
40,000 A) depending on material &
their thickness
 Maximum resistance will be at the
interface between the two sheets
due to presence of air gap
 Because of heat, metal liquefied
and due to mechanical pressure
two metal joined
 Copper electrodes are used
 Indentation is produced by
applying pressure

76. Advantages:
 High production rate
 Very economical process
 High skill not required
 Most suitable for welding of sheet metals
 Dissimilar metal can be welded
 No edge preparation is needed
 Operation may be made automatic or semi-
automatic
Limitations:
 Suitable for thin sheets only
 High equipment cost
Application:
 Fabricating sheet-metal products (Lap welding of
thin sheets)
 Welding of Automobile bodies, Refrigerator
bodies and high quality work in automobile
engines
Spot welding Machines:
1) Press type spot or projection welders
2) Rocker arm type
3) Portable welders
Resistance Spot Welding

77. Resistance Seam Welding
 Continuous spot welding is seam welding
 Electrode are in the form of rollers and Pressure is applied by rollers
 Works moves in direction perpendicular to roller axis
 Current interrupted 300 to 1500 times a minute to give a series of overlapping spot
welding
 Cooling is achieved by a constant stream of water directed to electrode near weld.

78. Resistance Seam Welding
Advantages:
 High production rate
 Dissimilar metal can be welded
 No edge preparation is needed
 Operation may be made automatic or semi-automatic
 Leak proof joints are obtained
 Used for welding thin materials
Limitations:
 Suitable for thin sheets only
 High equipment cost
Application:
 Welding of pressure tanks (Light and leak proof), transformers, for oil switches,
evaporators condensers, aircraft tanks, paint and varnish containers etc

79. Resistance Projection Welding
 Welding of two sheets without any
indentation
 On one of the sheets some projection
will be provided by using embossing
operations.
 Form of multi-spot welding in which a
number of welds are made
simultaneously
 Pieces to be welded are arranged
between two flat electrodes which
exert pressure as the current flows
 Areas which of projection are raised to
welding heat and are joined by the
pressure exerted by electrodes
 Projection are provided in the thicker
sheet or the sheet which has higher
thermal conductivity
 Projection are flattened during the
welding

80. Advantages:
 Good bond between two pieces
 Complicated electrode shape is not required
Limitations:
 Suitable for thin sheets only
 High equipment cost
 Materials like brass and aluminium can not be projection welded satisfactory
Application:
 Steel plate, galvanized sheet steel, and stainless steels can be joined using projection
welding.
Resistance Projection Welding

81. Resistance Butt Welding
Upset Welding
 Welding of which is employed to join bars and
plates together end-to-end.
 One bar is held in a fix clamp in butt welding
machine and other bar in movable clamp.
 Clamp is electrically insulated, being connected
to source of current
 Two ends to be joined are brought into contact
and current is switched on, resistance at the
joint causes the ends to heat up to welding
temp.
 Switched off the current and pressure applied
from movable platen
Application:
 Welding of non-ferrous materials for
welding bars, rods, wire
 Steels rails whose c/s area is as
much as 6.25 cm2

82. Resistance Butt Welding
Flash Welding
 Two workpiece which are to be welded will be clamped in the electrode holders, high
pulsed current in the range of 1 x 105 amps is supplied to the workpiece material.
 Two electrodes holder are used of which one is fixed and other is movable
 Initially current is supplied and movable clamp is forced against the fixed clamp due to
contact of these two w/p at high current, flash will be produced
 Current is stopped and axial pressure is increased to make the joint.
 Weld is formed through plastic deformation

83. Resistance Butt Welding
Flash Welding
Application:
 Welding of Mild Steel, Alloy Steel and
Titanium
 Used for end to end or edge to edge joining
 Used in automobile construction on the body,
axles, wheels, frames etc
 Welding of motor frames, transformer tanks
etc

84. Friction Welding
 Often termed as “inertia welding”
 Two surfaces to be welded are rotated
relative to each other under light
normal pressure.
 When interface temperature increases
due to frictional rubbing and when it
reaches the required welding temp.
sufficient normal pressure is applied
and maintained until the two pieces
get welded.
 Shape of weld joint depends on the
rotational speed and axial forced
applied
 Filler metal, fluxes, shielding gases are
not required
 Suitable for circular parts that is butt
welding of round bars and tubes

85. Advantages
 High quality welds
 The process is clean
 Low initial capital cost
 Low-cost power requirement
 Very little loss of material through
exclusions
 Annealing of weld zone is not necessary
Limitation
 Limited to smaller components
 Part must be round and withstand high
torque
Application
 H.S.S twist drills
 Gas turbine shaft
 Aero-engine drive shaft and valves
 Refrigerator tubes of dissimilar metals
 Steering columns
 Welding of sintered products
Friction Welding

86. Weldability
Weldability is defined as the capacity of a metal to be welded under the fabrication
conditions imposed in a specific suitably designed structured and to perform
satisfactory in the intended service.
Affecting Factors of Weldability
1) Composition of metal
2) Brittleness of metal
3) Thermal properties
4) Welding technique
5) Filler materials
6) Flux materials
7) Strength of metal at high temp.
8) Affinity of oxygen and other gases before and at welding temp.
9) Shielding atmosphere
10) Proper treatment before and after deposition of metal

87. Welding Metallurgy and Weldament design

88. Given: V = 20 Volts; I = 200 Ampere; α = 20 mm2; v = 5 mm/s; Qms = 10 J/mm3; η = 0.85
R = 100 μ Ω
Net heat supplied;
Qn = VI x η
= 20 x 200 x 0.85
= 3400 W
Heat required for melting;
Qm = α x v x Qms
= 20 x 5 x 10
= 1000 W
Melting efficiency;
ηm = Qm / Qn
= 1000 / 3400
=0.2941
= 29.41 %
Welding Example = 1

89. Welding Example = 2
Given: t = 1.2 mm; I = 5000 Ampere; T = 0.20 second; d = 6 mm;
Assume Qms = 10 J/mm3; R = 100 μ Ω
Net heat supplied;
Qn = I2 x R x T = 50002 x 100 x 0.20 = 500 x 106 W
Volume of Weld;
Vw = π/4 x d2 x t = π/4 x 62 x 1.2 = 33.93
Heat required for melting;
Qm = Vw x Qms = 33.93 x 10 =339.3 W
Heat generated in the weld zone
Q = Qn - Qm = 500 x 106 – 339.3 = 4.99 x 109
Assume (Qm)Heat required to melt copper may be taken as 10 J/mm3
(R) Resistance 100 μ Ω

90. 1. Principle of welding, soldering, Brazing and adhesive bonding.
2. Classification of welding and allied processes
3. Capabilities and applications
4. Welding parameters
5. General concepts of weldability
6. Gas welding and gas cutting
7. Arc welding
8. Power sources and consumables
9. Atomic hydrogen
10. Ultrasonic
11. Plasma and Laser beam welding
12. Electron beam welding
13. Special welding processes E.g. TIG (GTAW) , MIG (GMAV)
MSE - 2015 Syllabus

91. Assignment – Unit No.3 (for MSE-2015 only)
1. Common welding terminology
2. Classification of welding processes
3. Types welded joint & Welding Positions
4. Welding Electrode, Welding Flux, Filler Metals, Shielding Gas
5. Arc welding, Gas welding and Gas cutting
6. TIG (GTAW), MIG (GMAV) and SAW
7. Electro Beam welding, Laser Beam Welding,
8. Thermit welding, Explosive Welding

92. Department of Mechanical Engineering
Shroff S.R. Rotary Institute of Chemical Technology