The document provides an overview of metal joining processes, which can permanently or temporarily join two metal parts using techniques such as riveting, bolting, welding, brazing, and soldering. Each method has specific applications, advantages, and limitations, detailing how they achieve joints without altering the physical structure of the metals involved. The comprehensive classification and explanations of these processes highlight their significance in various industries, particularly in automotive and aerospace.

1. METAL JOINING
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2. Contents
• Introduction
• Classification of Metal Joining Process
• Riveting
• Bolting
• Welding
• Brazing
• Soldering

3. What is Metal Joining Process?
Ø Metal Joining is defined as joining of two metal parts either
temporarily or permanently with or with out the application
of heat or pressure.
Classification
Ø Riveting – Permanent Joining
Ø Bolting – Temporary Joining
Ø Welding/Brazing/Soldering – Permanent Joining
RIVET BOLTED WELDED

4. Classi&ication
of
Metal
Joining
Process
Brazing
Soldering
Screw
Welding Bolting

5. METAL JOINING PROCESS
1. WELDING PERMANENT JOINT
2. BRAZING PERMANENT JOINT
3. SOLDERING PERMANENT JOINT
4. ADHESIVE BONDING SEMI-PERMANENT
5. MECHANICAL ASSEMBLY
a) BOLT & SCREW NON-PERMANENT
b) RIVETING PERMANENT
c) CLAMPING NON-PERMANENT
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6. Riveting
Its is metal joining Process in which the two metallic parts
are joined by the use of rivets.
In this process, the metallic parts to be joined do not
undergo any change in their physical structure or atomic
structure. However Force is required for riveting
Riveting is used widely in automobile and aerospace
industry and in many other applications where we require
permanent/semi-permanent bonding and where bolting
and welding is not an option.
Mostly done for low thickness sheet metals and Aluminium

7. TYPES OF RIVET

8. PROCESS OF RIVETING
LAP RIVET
BUTT RIVET
RIVET JOINT

9. In this metal joining process, the metallic parts are
joined together by means of Bolt/Screw (and/or
nut).
This Process is widely used in assembling of parts
are to be joined temporarily or joints which require
periodic maintenance.
Two main types of loads on bolted joints:
Tension
Shear
Bolting

10. Bolted
Joints
-­‐
Details
Screw Joint Bolted Joint Stud Joint
Nut
Washer
Bolt Head
Thread
Shank
Washer
Nut
Bolt

11. Common types of Washers
Common types of Nuts
Common types of Bolt Heads
q Components of a Bolted Joints
1. Bolt
2. Washer
3. (and/or) Nut
q Different combinations of the above may
be used for a joint depending on the load
12.9 Class Bolt/Nut Means
12 . 9
12×100 = 1200 MPa is UTS
9×10= 90% of 1200 = 1080 MPa is YS
Similarly for 10.9/8.8/4.4 etc etc

12. In this metal joining process the two parts that are
to be welded are fused together by application of
heat and pressure (sometimes).
Permanent Fusion happens between joining metals
The welding processes depends on many factors
depending on the type of welding process:
Oxy-acetylene welding
SMAW
GMAW
GTAW
FCAW; SAW; ESW; ERW etc….
Welding

13. Welding is a process of permanently 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.
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.
Welding (contd…)

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

15. Classification of Welding Processes…

16. Basic Requirements of Welding Processes
1. The Two Metal (work pieces) should be either in contact with
each other or closely placed (concept of root gap).
2. The weld surfaces should be free from oxides, paint, oil, dirt,
grease etc.
3. Energy Source, Electrode and Filler Metal rod/ wire.
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.

17. 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 high 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.

18. 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. Pressure creates friction and the heat
thus produced leads to fusion. No filler metal is used.

19. 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.

20. 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 equipment where especially low distortion is
desired.

21. Gas Welding
SMAW
GTAW/TIG
GMAW/MIG
SAW
Friction
Welding

22. TYPES OF WELD JOINTS

23. STANDARDS USED FOR WELDING
u AWS A03.0: "Standard welding terms and
definitions"
u ISO 9692: "Welding and allied processes.
Recommendations for joint preparation."
u BS 499-2C: "Welding terms and symbols. European
arc welding symbols in chart form"
TYPES OF BUTT WELD TYPES OF WELDS
TYPES OF WELD JOINTS….

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WELDING SYMBOLS

25. WELDING DEFECTS
A welding defect is any flaw that compromises the usefulness
of a weldment.
Some common Weld Defects are:
q LACK OF FUSION
q LACK OF/ EXCESS PENETRATION
q INCLUSION (COPPER/ TUNGSTEN/ SLAG)
q POROSITY
q UNDERCUT
q WELD CRACK
q MISMATCH
q LAMELLAR TEARING
Weld Testing Methods:
q Visual Inspection
q Dye Penetration Test
q Ultrasonic Test
q Radiography
q Mechanical Properties
(UTS/YS)
q Acid Etch Test
Weld Defects

26. Brazing
Brazing is metal joining Process in which the filler metal or
alloy is heated to a temperature above 450OC and melted
Only filler metal melts and deposits fusing the workpiece.
Workpiece doesn’t melts. Base Metal is heated and filler
metal is distributed between two close fitting parts by
capillary action
Torch/ Dip/ Furnace/ Induction/ Salt-bath Brazing
Filler metals:
Aluminium- Silicon; Copper; Brass; Copper-Silver; Nickel alloy etc

27. BRAZING
MERIT AND DEMERIT
MERIT
Ø Dissimilar metals which can not be welded can be joined by brazing.
Ø Very thin metals can be joined.
Ø Metals with different thickness can be joined easily.
Ø In brazing thermal stresses are not produced in the work piece. Hence
there is no distortion.
Ø Using this process, carbides tips are brazed on the steel tool holders.
Ø Very Quick process
DEMERIT
Ø Brazed joints have lesser strength compared to welding.
Ø Joint preparation cost is more.
Ø Can be used for thin sheet metal sections.

28. Soldering
Solder is an alloy of Tin (63%) & Lead (37%)
60/40 Solder melts at 361 F
Soldering is metal joining Process in which the filler metal
or alloy is heated to a temperature below 450OC and melted
Only filler metal melts and deposits fusing the workpiece.
Extensively used in electronics and jewelry industry
Merits and Demerits same as Brazing

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30. This is purely an academic work and has no financial or other
interest.
The authors are acknowledge the various reference sources and
are grateful to all the people and firms who’s sources have been
used
The results achieved in this should be independently verified.