Hot and Cold Working Process | Advantages, Disadvantages, Comparison

By | November 14, 2021

In this article we will discuss hot and cold working process of metals. First, we will learn hot working and then we will learn cold working of metals.

Before moving further let us understand concept of recrystallisation, it would be very helpful to us later.

What is recrystallisation temperature?

The temperature at which new stress-free grains are formed in a metal is known as recrystallisation temperature.

Hot Working

What is Hot working process?

Metal deformation process which is carried out above recrystallisation temperature is known as hot working process.

Examples of hot working processes of metals are hot rolling, hot forging, hot spinning, hot extrusion, hot drawing etc.

Advantages of hot working process

  • It reduces strain hardening
  • Its components have better toughness
  • Its components have better ductility
  • Its components have better resistance to shocks and vibrations
  • Its components have better strength particularly the forged parts
  • It reduces residual stress in the component

Disadvantages of hot working process

  • Rapid oxidation of surface due to high temperature
  • Its components have poor surface finish compared with cold rolled parts
  • It requires expensive tools

What is cold working process?

Metal deformation process which is carried out below recrystallisation temperature is known as cold working process.

Examples of cold working processes of metals are cold rolling, cold forging, cold spinning, cold extrusion, cold drawing etc.

Advantages of cold working

  • Its components have high hardness
  • Its components have high strength
  • Its components have better surface finish compared with the components made by hot working process
  • Its components have high dimensional accuracy
  • Tooling required is comparatively inexpensive

Disadvantages of cold working process

  • It reduces toughness of components
  • It reduces ductility of components
  • Its components have poor resistance to shocks and vibrations
  • It induces residual stress in the parts and proper heat treatment is required to relieve this stress

Comparison between hot working and cold working

Sr. no. Cold Working Hot Working
01 It is carried out below recrystallisation temperature  It is carried out above recrystallisation temperature
02 Residual stresses remain after cold working Residual stresses do not remain after cold working
03 Stress required for deformation is relatively higher Stress required for deformation is relatively lower
04 Tooling required is relatively cheaper Tooling required is relatively costly
05 It gives better surface finish It gives poor surface finish
06 It gives us close tolerances It does not gives us close tolerances
07 It may develop new cracks and propagate existing cracks It does not develop new cracks or propagate existing cracks

Featured image attribution: By Metoc – selftaken, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1105603

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