Difference Between Heat Treatment, Annealing and Tempering 

Posted By on April 28, 2016

Archiving a bit of information from a company I’ve purchased metal from in the past — good info.

Heat Treatment

Heat treatment is used to alter the physical and mechanical properties of metal without changing its shape. It is an essential process in metal manufacturing as it increases the desirable characteristic of the metal, while allowing for further processing to take place.

Heat treatment is a process during which the heating and cooling is carefully controlled. Steel, for example, responds well to heat treatment and is commonly heat treated for use in a variety of commercial applications.

Common objectives of heat treatment are to:

  • Increase strength
  • Increase hardness
  • Improve toughness
  • Improve machining
  • Improve formability
  • Increase ductility
  • Improve elasticity


Annealing involves heating the metal to a specified temperature and then cooling at a controlled rate; usually slowly. This fully or partially separates the constituent atoms, resulting in a refined microstructure.

Annealing is commonly used to:

  • Soften a metal for cold working
  • Improve machinability
  • Enhance electrical conductivity


Tempering is used to increase the toughness of iron alloys, particularly steel. Untempered steel is very hard but is too brittle for most applications. Tempering is commonly done after hardening to reduce excess hardness.

Tempering is used to alter:

  • Hardness
  • Ductility
  • Toughness
  • Strength
  • Structural stability

The full article with more information at:
Difference Between Heat Treatment, Annealing and Tempering – Metal Supermarkets


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