JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY
DBT,DEP,ME
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Welding And Fabrication
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DBT,DEP,ME
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JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY
Assembly is an important step for manufacturing solid products, especially when the shape of the product is complicated having multifarious geometrical features. It is neither feasible nor economical all the time to directly produce a product having intricate shapes. In such a scenario, making smal...
JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY
DBT,DEP,ME
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Joining of materials
• Joining includes welding, brazing, soldering, adhesive bonding of
materials.
• They produce permanent joint between the parts to be assembled.
• They cannot be separated easily by application of forces.
• They are mainly used to assemble many parts to make a system.
• 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.
• Some times, 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.
,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:
• Labour 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.
R. Ganesh Narayanan, IITG
,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, Resistance welding, Oxyfuel gas welding,
electron beam welding, laser welding
R. Ganesh Narayanan, IITG
, Arc welding: In this operation, electric arc is used to produce heat energy
and the base metal is heated. Sometimes, both pressure and heat are
applied.
Arc welding steps
Resistance welding: In this operation, electric resistance is
generated to the flow of current that generates heat energy
between two contacting surfaces that are held in pressure.
Gas welding: Oxyfuel gas welding is a welding operation in which heat is
generated by a hot flame generated mixture gas of oxygen and acetylene.
This heat is used to melt base material and filler material, if used.
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