This document provides an overview of different metal joining processes including riveting, bolting, and welding. It classifies welding processes based on heat source and interaction type, and discusses various welding techniques such as gas welding, arc welding, resistance welding, and solid state welding. The document also covers the history of welding development and parameters involved in successful welding like heat, pressure, and surface preparation.

1. Index
• Introduction
• Classification of Metal Joining Process
• Welding Process
• History Of Welding
• Classification of Welding Process
• Metal Joining Process In Body Shop
• Methods Of Testing

2. What is Metal Joining Process?
 Metal Joining is defined as joining of two
metal parts either temporarily with or with
out the application of heat or pressure.
Classification
 Rivetting
 Bolting
 Welding

3. Rivetting
Its is metal joining Process in which the
two metallic parts are joined by the rivets.
In this process, the mettalic parts to be
joined do not undergo any change in their
physical structure or atomic structure.
Rivetting is used widely in automobile
industry and in many other applications
where we do not require permanent
bonding

4. Bolting
In this metal joining process, the metallic parts
are joined together by means of Bolt and nut.
This Process is widely used in assembling of
parts are to be joined temporarily or
permanently.
Welding
In this metal joining process the two parts are to
be welded are fused together by application of
heat and pressure.
The welding processes depends on many factors
depending on the type of welding process.

5. Welding Process
DEFINITION:
Welding is a process of joining materials. Welding joins
different metals/alloys with a number of processes, in which heat is
supplied either electrically or by means of a torch. Welding is done
by application of heat or both heat and pressure. The most essential
requirements is Heat. Pressure may be employed, but this is not in
many processes essential.
CONCEPT OF WELDING:
The welding process evolves applying heat to the work
piece. The heat applied should be such that the work piece should
melt, i.e. the temperature at which welding is done, should be more
than the melting point of the work piece to be welded.

6. … cont. welding process
Basic Requirements of Welding Processes
1. The Two Metal (work pieces) should be in contact with each
other.
2. The weld Surface should be free from oxides, paint,
oil,dirt,grease etc.
3. Energy Source.
4. Shielding:
During Welding if the metal is exposed to air directly
the Oxygen in air reacts with the metal to form oxide which
results in poor welding. In order to avoid the shielding gas is
used.

7. … cont. welding process
Parameters of Welding
1. Heat:
The source of heat is very important. It may be provided
by different methods depending on the composition of the parts
to be joined, the application of the joints etc.
2. Pressure:
The pressure may or may not be required, depending on
the source of heat used for the welding and the quality or the
strength of the joint required.
3. Surface Preparation:
It is the basic necessity of the welding process. The parts to
be joined by the welding process should be free of oil, grease,
paint, dust etc. so as to get a very good quality weld.

9. History of Welding:
S.No Welding Country Discoverer
1 Gas Welding France Henry Louis Le- Chatelier
England Davy
England Auguste de meritens
2 Arc Welding
Sweden Oscar Kjellberg
USA Strohmenger
3 Stud Welding England Martin
4 Resistance Welding Philadelphia Elihu Thomson

10. Classification of Welding Processes
There are 35 different welding and brazing processes and
several methods are being used by the industry today. The
welding processes may be classified on the basis of
a. Source of heat.i.e. flame, arc etc.
b. Type of interaction.i.e. liquid/liquid (fusion welding )
or solid/solid (solid state welding).
The classification is shown in the chart.

11. Classification of Welding Processes
Welding Processes
Gas Arc Resistance Solid State Thermo-chemical Radiant- Energy
Welding Welding Welding Welding Welding Welding
Air – Carbon Arc Spot Cold Electron Beam
Acetylene Thermit Welding
Welding
SMAW Seam Explosive
Oxy- Atomic Hydrogen Laser Beam
Acetylene SAW Projection Friction Welding Welding
Oxy- GTAW Flash Butt Roll
hydrogen MIG R Diffusion
Pressure Electroslag Forge
gas
Plasma Arc Hot
Pressure
Ultrasonic
Welding

12. Gas Welding
Gas Welding is a fusion welding process. It joins metals,
using the heat of combustion of oxygen/air and fuel gas mixture.
The intense heat thus produced melts and fuses together the edges
of the parts to be welded, generally with the addition of a filler
metal.
Application of Gas Welding
i. For joining thin metals.
ii. For joining materials in whose case excessively hjgh temp.
or rapid heating and cooling of the job would produce
unwanted or harmful changes in the metal
iii. For joining most ferrous and non-ferrous metals, i.e. Al,
Cu, Ni, Mg, and its alloys etc.

13. Arc Welding
Arc Welding is a group of welding processes, wherein
fusion is produced by heating with an electric arc or arcs, mostly
without the application of pressure and with or without the use
of filler metal depending upon the base plate thickness.
Resistance Welding
Resistance welding is a group of welding processes
where in fusion is produced by the heat obtained from flow of
electric current in a circuit of which the work is a part and by
application of pressure. No filler metal is used.

14. Solid State Welding
A solid state welding process produces fusion at
temperatures essentially below the melting pointy of the base
materials being joined, without the addition of a filler metal.
Pressure is always applied.
Thermo chemical Welding
Thermo chemical welding process comprises of producing
fusion by heating with superheated liquid metal and slag resulting
from chemical reaction between a metal oxide and aluminum,
with or without the application of pressure. The liquid metal acts
a filler metal too.
Thermo chemical welding is used chiefly in repair of
assembly of large parts such as fractured rails, large fractured
crankshafts, replacing broken teeth on large gears, etc.

15. Radiant Energy Welding
Radiant Energy consists of fusion by focusing an energy
beam on the work piece. The heat is generated when the energy
beam strikes the work piece.
It is used for joining highly reactive materials like
titanium, zirconium etc. In this process, welds can be made even
at those points that are virtually inaccessible for other welding
processes. It is used for welding airplane, aerospace and other
types of equipments where especially low distortion is desired.