UNIT-2 Welding Processes.pptx

 Welding is metal joining process for two pieces.
 It is very important permanent metal joining process.
 By this process we can join two pieces of same metal or
different metal.
 Metal pieces which are to be joined are heated at the ends are
keep these ends to gather and then either by applying pressure
or without pressure, also with adding filler metal or without
adding filler metal it can be joined.
Jigar Kalotra Mechanical Department
Metal Joining Processes
Welding

 Welding process are classified mainly in to two part
(1) Fusion or non pressure welding
(2) Plastic or pressure welding
Classification of Welding Process

 Fusion or non pressure welding
(1) Energy ray
- Electron beam welding
- Laser welding
(2) Electric arc
- Metal arc - Electroslag welding
- Carbon arc - Atomic hydrogen arc welding
- Tungsten arc
- Submerged arc
- Inert gas arc

(3) Chemical energy
- Oxy-acetylene welding
- Air-acetylene welding
- Oxy-hydrogen welding
- Thermit welding (Without pressure)

 Plastic or pressure welding
(1) Blacksmith furnace
- Lap weld
- Butt weld
- Tee weld
(2) Electric current
- Spot weld - Percussion welding
- Seam weld
- Projection weld
- Butt weld

(3) Mechanical energy
- Ultrasonic welding
- Friction welding
- Diffusion bonding
(4) Chemical reaction
- Thermit welding (Pressure type)
- Explosive welding
Classification of welding process

 Joint prepared by welding have nearly same strength of base
metal.
 Equipment's used for welding process are not more expensive
 Easy to change design of product.
 Easy to join similar and dissimilar metal.
 Machining can be reduced by welding process.
 By welding, product can be prepared with less time as
compared to other process.
 By welding process, product can be prepared light in weight as
compared to casting process.
Advantages of welding

 Automobile industries.
 Aircraft and ship building industries.
 To prepare tank, boiler, pressure vessels.
 In thermal power plant and refinery.
 To prepare agriculture equipment.
 To prepare pipeline and structural work.
 In bridge and building structure preparation.
 Railway locomotive, truck, trailer, crane, etc. preparation.
Application Of Welding

 This is fusion or non pressure type welding process. Gas
welding is done by burning a combustible gas with air or
oxygen in a concentrated flame of high temperature.
 As compared with other welding methods, the purpose of the
flame is to heat and melt the parent and filler metal of a joint.
 This is old and famous method.
 In this method different gases are used to prepare flame. At the
end molten metal is allowed to cool so we get good joint of
metal.
Gas Welding

 In this process proper mixture of oxygen and acetylene is
allowed to come at the tip of torch or blowpipe and than by
lightening it a flame is prepared at tip of blow pipe.
Oxy-acetylene Welding

 As shown in figure metal and filler metal are heated by flame.
Flame temperature is high.
 By this flame metal surface and filler metal which is shown as
welding rod gets melted and proper mixture is prepared than
by allowing to cool it we get good joint of two metal.
 In this process, oxygen and acetylene gases which we are
using are easily available in cylinders, or acetylene can be
prepared separately in plant by chemical reactions of calcium
carbide and water.
CaC2 + 2H2O C2H2 + Ca (OH)2
Oxy-acetylene Welding

 Tube or hoses conduct the gases to the torch or a blowpipe
held by the operator. The torch mixes the two gases properly
and emits them in to the flame.
 Based on mixture of gas proportion we get three different type
of flame at the tip of the torch.
 These flames are
(1) Neutral flame
(2) Carburizing flame
(3) Oxidizing flame
Oxy-acetylene Gas Flame

(1) Neutral flame : The neutral flame has no tendency to react
with materials being welded. The highest temperature is at
the tip of the inner cone and is capable of melting all
commercial metals. This flame is widely used to join steel,
stainless steel, cast iron, copper, aluminum etc.
(2) Carburizing flame : This flame is also known as reducing
flame. In this flame acetylene proportion is more and oxygen
less in gas mixture. As shown in figure this flame has three
part : one is innercone near to the tip of torch and second
part is white conical shape attached with inner cone.

Third part is feather which cover the previous two part. This
flame is used for welding nickel and alloy steel.
(3) Oxidizing flame : In this flame oxygen proportion is
more and acetylene is less in gas mixture. As shown in figure
this flame has two part. Innercone near to the tip of torch
is smaller in size as compare to the previous flames. Outer
cover part is white. This flame give specific voice like
whistle and gives highest temperature.

 Welding torch or blow pipe
 Pressure regulator
 Hose and hose fittings
 Gas cylinders
 Goggles
 Hand glows and apron
 Welding rod and wire brush
 Spark lighter
 flux
Equipment Used For Oxy-acetylene Welding

 Welding torch or blow pipe

 Pressure regulator

 Hose and hose fittings

 Gas cylinders

 Goggles, Hand glows and apron

 Welding rod and wire brush

 Spark lighter

 Flux

 Cleaning
 Preparation of edges
 setting up of edges
 Tack welding
Preparation Of Gas Welding

 Cleaning : Metal surfaces where it is to be joined must be free
from dust, oil, rust or any other elements. By wire brush or by
any other processes surface of metal must be clean. Clean
surface will give good joint.
 Preparation of edges : After cleaning metal ends a proper shape
are required to give its edge. Shape of edge depends on
different aspect such as design of weld, type of metal,
thickness of metal, weld strength requirement etc. edge can be
prepared by different process like milling, grinding, shaping,
filing etc.

 Setting up of edges : After preparation of edge, it very must
essential to put metal in a correct position. Fixture can be used
to put correct metal ends relative to each other.
 Tack welding : Setting up of edges must remain till welding
process finish. For this purpose before welding starts, at some
distance interval welding is done on edges. This is known as
tack welding.

 There are mainly two welding technique based on position and
direction of movement of welding torch and welding rod.
(1) Left-ward or forehand welding
(2) Right-ward or backhand welding
Gas Welding Techniques

(1) Left-ward or forehand welding : In this technique welding
torch and filler rod movement is toward left direction. Welding
torch is in right hand and filler rod is in left hand. As shown in
figure welding torch makes 60° to 70° angle and filler rod makes
30° to 40° angle with welding surface.

(2) Right-ward or backhand welding : In this technique welding
torch and filler rod movement is towards right direction.
Welding torch is in right hand and filler rod is in left hand but
both makes 40° to 50° angle with metal surface as shown in
figure.

 Cleaning of work piece edge.
 Preparation of edges.
 Setting up or alignment of edges.
 Setting up cylinder outlet gas pressure connected with
blowpipe as per requirements.
 Preparation of flame.
 Tack welding
 To perform welding operation
 Removal of slag
 Post welding operations (inspection and testing)
Procedure For Gas Welding

 This process is used easily for production and repairing work.
 Oxygen and acetylene gas flow is controlled by torch so
required flame can be prepared, hence it will help to get
required temperature of metal.
 Heating and cooling rate is low.
 Easy to control addition of filler metal.
 Initial and running cost is low.
 Equipment's are easily available and also easy to move.
Advantages Of Gas Welding

 Heavy sections parts are not economical to join by gas
welding.
 Gas flame temperature is limited as compared to other welding
process.
 Gas flame takes more time to heat the metal.
 More care is to be taken to store and movement of gas.
 Oxygen and acetylene gas cost is more.
Disadvantages Of Gas Welding

 To join thin metal.
 When high rate of heating or cooling gives bed effect on metal
than gas welding is very much useful.
 Gas welding is used in automotive and aircraft industry and for
sheet metal fabrication plant.
 Carbon steel, alloy steel, cast iron and aluminum, copper,
nickel, magnesium and its alloy can be joined by this process.
Application Of Gas Welding

 Arc welding is a fusion welding process. Heat source is
developed by electric arc.
 Electric arc is used to heat and melt the materials which are
required to join. To get electric arc electricity is passed through
metal which to be joint and electrode and metal are kept at
certain distance.
 This distance is known as air gap.
 This heat is used to melt the material. Temperature of arc is
6000° to 7000° 𝐶.
 This temperature depends on type of electrode, air gap distance
and electric pressure.
Arc Welding

 Figure shows electric circuit for arc welding. Electric supply
used in arc welding is having range of 15 to 60 volt and 25 to
800 ampere current. Any one supply either A.C or D.C supply
is used in arc welding.
Arc Welding

 A.C or D.C. machine
 Electrode
 Electrode holder
 Cable, cable connector
 Cable lug
 Chipping hammer
 Earth clamp
 Wire brush
 Safety goggle or hand screen
 Hand gloves and apron
Equipment's Used in Arc Welding

 A.C or D.C. machine

 Electrode

 Electrode holder

 Cable, cable connector

 Cable lug

 Chipping hammer

 Earth clamp

 Wire brush

 Safety goggle or hand screen

 Hand gloves and apron

Comparision of A.C and D.C. supply of arc welding
A.C. Supply D.C. Supply
A.C. transformer cost is low Rectifier or generator set cost is high
No movement of parts in transformer so
maintenance cost is low
Generator have rotating parts so
maintenance cost is high
Polarity is continuously changing so there
is equal heat on work piece and electrode.
Straight and reverse polarity is available so
any one can be used.
Very less possibility of arc blow. There is possibility of arc blow.
It can be used only when A.C. mains
supply is available.
An engine driven D.C. generator set can be
used even in absence of A.C. mains supply.
It is not suitable for non-ferrous metal. It is used for ferrous and non-ferrous
metal.

Types of Electrodes
Welding
Electrodes
Non
consumable
electrode
Carbon or
graphite
electrode
Tungsten
electrode
Consumable
electrode
Bare
electrode
Coated
electrode
Pure tungsten
electrode
Alloy
Tungsten
electrode

 Slag forming ingredients
 Gas forming ingredients
 Deoxidizing elements
 Alloying elements
 Arc stabilizing elements
 Binding elements
Electrode coating ingredients

 It forms slag which is light in weight so it flows on top of
molten pool and it prevent contact of air with molten metal and
hence oxidation also it reduce cooling rate so joint becomes
good.
 By deoxidizing elements molten metal becomes pure.
 Alloying element increases strength of weld.
 Keep steady arc.
 Minimize spattering effect.
 It will minimize defect like hot and cold cracking.
 It will increase penetration and surface finish.
Functions of electrode coating

 Carbon arc welding
 Metal arc welding
 Metal Inert Gas (MIG) arc welding
 Tungsten Inert Gas (TIG) arc welding
 Atomic hydrogen arc welding
 Plasma arc welding
 Submerged arc welding
 Electro slag welding
Different arc Welding Methods

 In this process carbon electrode is used. Arc is produced
between work piece and electrode. Generally D.C. supply is
used. Work piece is connected with anode and electrode is
connected with cathode. So straight polarity is used and
electrode gets less heat. By this arc 3200˚C to 3900˚C
temperature can be produced.
 When filler metal is not required then this process is used. If
filler metal is required then additional metal is added with
some flux.
 This process is used for steel sheet, copper alloy, brass, bronze
metal welding.
Carbon arc welding

 Metal electrode is used in metal arc welding. An arc is
produced between electrode and work piece. Temperature of
arc is 2400˚C to 2600˚C. at this temperature electrode and
metal will melt with flux. Flux will form slag on molten metal
and protect it from oxidation. By allowing to cool molten
metal a good joint is achieved.
 As shown in figure for this process A.C. or D.C. supply can be
used. Use of either supply depends on type of metal and
thickness of metal to joint. Generally coated electrodes are
used in this process and we get satisfactory joint.
Metal Arc Welding

Metal Arc Welding

 metal inert gas welding is vary much famous by short name
MIG welding. Also this process is known as Gas Metal Arc
welding process.
 As shown in figure with help of feed roll bare electrode is
supplied through welding head. An arc is developed between
work piece and electrode.
 During this process inert gas is passed through welding lead.
This gas passes surround to electrode and comes out at
welding head end and forms a protecting layer on molten
metal. D.C. supply is used in this process. 0.9 to 1.6mm
diameter electrode wire is used with 100 to 400 amp. current
Metal Inert Gas (MIG) arc welding

Advantages :
 In this welding flux is not required, process is speedy.
 By this process all thick and thin work piece can be weld
easily.
 Automatic arrangement can be done for this process.
 This process gives deep penetration more deposition rate.

Disadvantages :
 This process cannot move from one place to other place.
 Equipment are costly.
 Arc is not stable in outdoor arrangement.
 Cooling rate is more as compared to the process with slag.

Application :
 This welding process is used for silicon, low alloy steel,
stainless steel, aluminum, magnesium, copper, nickel and its
alloy, titanium etc. metals.
 This process is useful for tool steel and die welding,
refrigerator part production.
 Also it is used in aircraft, automobile, pressure vessel and
ship building industries.

 Tungsten Inert gas arc welding is known as TIG welding by
short name. this process is same as metal inert gas arc welding.
 Basic difference in this process is non-consumable tungsten
electrode is used. Tungsten has melting point temperature
6150℉ so it is not melting by arc.
 In this process if required filler metal is added.
 As shown in figure tungsten electrode is connected with
electric supply. A.C. or D.C. supply can be used for this
process. Electrode is passed through welding head and inert
gas is passed surrounded to electrode which prepare protection
layer on molten metal.
Tungsten Inert Gas (TIG) arc welding

Advantages :
 A.C. or D.C. supply can be used for this process.
 Flux is not used in this process so there is no possibility of
impurity in metal weld due to flux.
 Less spatter effect.
 It is used for all weld position and gives better quality joint.

Disadvantages :
 TIG welding process have less speed as compared to MIG
welding process.
 in TIG welding process filler metal is added from outside.
 If we do not take proper care than impurity can enter with
filler metal.

Application :
 TIG welding process is used to join aluminum and its alloy,
copper and its alloy, magnesium and its alloy, nickel alloy,
zirconium alloy, titanium alloy, refractory metal, carbon
steel, alloy steel, stainless steel etc.
 It is also used for thin section sheet metal work, transistor
case instrument, cane sealing, in aircraft and chemical
industry and in fabrication work.

 In this process two non consumable electrode are used. An arc
is produced between electrodes and hydrogen gas is supplied
at approximate 0.5 kg/cm2 pressure nearby to electrodes. As
shown in figure when hydrogen gas is passed through arc then
hydrogen molecule is converted in to atom and it reach to
work piece surface, where it combine and atoms getting
transfer back to molecule.’
 Due to this transformation liberation of heat takes place. This
heat gives temperature 4000˚C to 4200˚C which is used for
welding the metal.
 In this process filler metal can be added as per requirement.
Atomic Hydrogen Welding

 Single phase A.C. supply is used in this process. Hydrogen gas
protect the electrode and molten metal from oxidation.
Atomic Hydrogen Welding

 The scientific concept of the term plasma is “ A stream of
ionized partials”. Figure shoes tungsten electrode is cathode
and water-cooled copper nozzle as anode. Now gas like argon,
hydrogen or helium is passed through nozzle. This gas pass
through arc and gets ionized and becomes plasma.
 This plasma comes to metal surface and getting transfer back
atom to molecule. Due to this phenomenon liberation of heat
takes place. This heat utilize to melt the metal and we get
welding of metals.
Plasma Arc Welding

 High temperature up to 14000˚C is achieved by plasma. To
control temperature of nozzle material water is circulated near
to nozzle tip.
 This process is used for metal cutting also.
Plasma Arc Welding

 This process is arc welding process. In this process arc is
developed between bare electrode and workpiece. End of
electrode is covered by granular flux. Flux gets melt by heat of
arc and works as blanket for molten metal. The arc is
submerged so it cannot seen by eye.
 This process is also known as hidden arc welding or flux
covered arc welding. No pressure is applied to this process and
this process can be automatic or semi-automatic.
 Figure shows the submerged arc welding process. A.C. or D.C.
supply can be used in this process.
Submerged Arc Welding

 Wire electrode can be feed by feed roller and flux is supplied
through hopper. Flux will form a slag which protect weld
surface. Electrode works as filler metal and better quality joint
can be achieved by this process.
Submerged Arc Welding

 In this process arc is submerged by flux, so no spatter takes
place.
 Higher melting speed can be employed.
 Deposition rate is very high.
 Both A.C and D.C. supply can be used in this process.
 It can be used with equal success for both indoor and outdoor
welding work.
Advantages

 Operator cannot see the process under flux, so it is difficult to
decide correct welding speed.
 This process is convenient for simple flat position but difficult
for complicated shape.
 This process is not useful for cast iron, aluminum alloy,
magnesium alloy, lead and zink metal welding.
Disadvantages

 This process is useful for welding pressure vessel, boiler,
rotary furnace, rail rod, crane, locomotive coach and
fabrication.
 This process is suitable for welding low carbon steel, medium
carbon steel, copper and copper alloy, nickel and nickel alloy.
Application

 Without preparating edge a thick plate can be weld by this
process. In this process plates to be joined are put in vertical
position with a little gap between ends of work pieces. Figure
shows a schematic diagram of this process. The weld is
completed in single pass. No arc is visible. Flux is poured
around the electrode is converted to slag that floats on a layer
of molten metal-confined in the joint by water-cooled copper
shoes that slide on the sides.
Electro Slag Welding

UNIT-2 Welding Processes.pptx

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