Comparison of Hot Working and Cold Working Processes

Comparison between hot working and cold working processes can be done in aspects like carried out temperature, stress set up, tolerances, hardening, deformation, surface finish, improved properties, cracks formation.
Hot Working
Cold Working
1 Hot-working is carried out above the recrystallization temperature and below the melting point. Hence the deformation of metal and recovery take place simultaneously. Cold working is carried out below the recrystallization temperature. As such, there is no appreciable recovery.
2 No internal or residual stresses are set up in the metal in the hot working process. In the cold working process, internal or residual stresses are set up in the metal.
3 If cracks and blow boles are present in the metal, they can be finished through hot working. In cold working, the existing cracks propagate and new cracks may develop.
4 Close tolerance can not be maintained. Better tolerance can be easily maintained.
5 The surface finish of the hot working process is comparatively not good. The surface finish of the cold working process is better.
6 It results in improvements of properties like impact strength and elongation. It also results in improvements of properties like impact strength and elongation.
7 If the hot working process is performed properly, it does not affect ultimate tensile strength, hardness, corrosion resistance yield strength and fatigue strength of the metal. It improves ultimate tensile strength, hardness, yield strength but reduces the corrosion resistance of strength of the metal.
8 Due to recrystallization very negligible hardening of metal takes place. Since cold working is done below recrystallization temperature the metal gets work hardened.
9 Hot-working refines metal grains resulting in improved mechanical properties. Most of the cold working processes lead to distortion of grains.
10 Due to higher deformation temperatures, the stress required for deformation is much less. The stress required to cause deformation is much higher.
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