Heat Treatment:
Heat treatment is carried out to achieve one or more of the following objects:
The development of certain micro-constituents in the metals due to heat treatment is mainly responsible for improvement in their properties.
Heat treatment can be defined as an operation or combination of different operations involving the heating and cooling of a metal or alloy in solid state for the purpose of obtaining certain required structures and desirable properties or a combination of properties suitable for the particular applications without changing the compositions.
Objectives of Heat Treatment:
Heat treatment is carried out to achieve one or more of the following objects:
- To relieve the stresses set up in the material after hot or cold working in order to improve machinability.
- To improve mechanical properties like tensile strength, hardness, ductility, shock resistance etc.
- To modify the structure of the material to improve its electrical and magnetic properties.
- To increase the qualities of a metal to provide better resistance to heat, corrosion and wear.
- To change grain size.
- To stabilize the structure against dimensional changes under moderate temperatures by successive heating cycle to a temperature just above the encountered ambient temperature.
Following heat treatment processes are mainly in use for achieving most of the objects of heat treatment:
- Annealing
- Spheroidising
- Normalising
- Hardening
- Tempering
- Case hardening
(a) Carburising
(b) Nitriding
(c) Cyaniding
(d) Induction hardening
(e) Flame hardening
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