Wednesday, 30 October 2013

What are the difference between Hot Working and cold working?

Please find bellow the defferane between Hot Working and cold working of Manufacturing

1Working temperature is above the re crystallization temperature.
Therefore, it can be regarded as a simultaneous process of deformation and

Cold working temperature is below the crystallization temperature.So no appreciable recovery can take place during

2Coefficient of friction in hot forming is as high as 0.6.The coefficient of friction in cold forming i generally of the order of 0.1.
3hardening due to plastic deformation is completely eliminated by recovery and
re crystallization, only if the rate of re crystallization  is higher than deformation.
Harding is not eliminated in this case. This is always accompanied by work hardening.

4Refinement of crystal occurs.Grains are only elongated and distorted.
5Internal and residual stresses are not develop in the metal.Internal and residual stresses are developed.

6Surface finishing is not good.Better surface finishing is obtained.
7It promotes uniformity of materials.Uniformity of material is lost.
8Cracks and blow holes are welded up.Possibility of crack formation and its propagation is great.
9Mechanical properties such as elongation, reduction of area, and impact value are improvedCold working decreases elongation, reduction of area, and impact value.

            Answered by Vivek 
student, OCC (Online coaching Class)