Material Science MECHANICAL THEORY

Heat Treatment Process : Types, Hardening

Heat Treatment Process: Modification of grain size in a steel component by either heating or cooling process so that the strength of the Steel can be changed is called a heat treatment process.

heat treatment process
heat treatment process

Every heat treatment process contains three steps

1.Heating

2.Holding and

3.Cooling

1.Heating:

Small grains will combine and form larger grains.

2.Holding:

All grains will turn into uniform shape and size.

3.Cooling:

Based on the rate of cooling, the final grain size is produced.

Note 1:

If a Steel component is heated to a high temperature followed by Rapid cooling process implies large grains will break down into small grains and thereby the hardness increases.

H1<H2

Note 2:

If a Steel component is heated to a high temperature followed by slow cooling process => small grains will combine and forms larger grains implies hardness decreases.

Types of Heat Treatment Process:

  1. Hardening
  2. Annealing
  3. Normalising
  4. Tempering
  5. Martempering
  6. Austempering
  7. Case hardening
  8. Surface Hardening

The Various Types of Heat Treatment Processes are discussed below.

1.Hardening:

  • Applicable to Steels with C%=(0-2.11)%
  • Obtained hardness in steel components by heating followed by Rapid cooling process.
  • Due to Rapid cooling process or quenching, the component will undergo very fast cooling process the smallest grains will be produced which possess the highest hardness also and it is called as Martensite Phase.
  • During the hardening process, the outer surface of the component will come in contact with the Quench medium ⇒ the outer envelope will be converted into martensite immediately ⇒ outer envelope produce martensite Phase.

The other seven types of Heat Treatment Process are presented soon.

Read:

Iron-Carbon Phase Diagram

 

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