Various type of heat treatments its definition and objective

It is defined as an operation or combination of different operations involving heating and cooling of metal or an alloy in solid state for the purpose of obtaining certain required structures and desirable properties of a combination of properties suitable for the particular application.

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 machine ability.
• 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.

Following heat treatment processes are mainly in use for achieving most of the objects of heat treatment:

• Annealing
• Spheroidising
• Normalising
• Hardening
• Tempering
• Case hardening or surface hardening
  • Carburising
  • Nitriding
  • Cyaniding
  • Induction hardening
  • Flame hardening