Question

Describe the differences between cold work and hot work? List some advantages and disadvantages of each.

Answer 1

Cold working Hot working . It is done at a temperature below the recrystallization Hot working is done at a temperature above recrystallization . It is done below recrystallization temperature so it is .Hardening due to plastic deformation is completely accomplished by strain hardening. eliminated Crystallization takes place . .Cold working increases ultimate tensile strength, yield point . In hot working, ultimate tensile strength, yield point, corrosion hardness and fatigue strength but decreases resistance to corrosion resistance are unaffected. . Material is not uniform after this working Material is uniform thought. There is more risk of cracks. More stress is required There is less risk of cracks . Less stress required " It does not require pickling because no oxidation of metal Heavy oxidation occurs during hot working so pickling is takes place. required to remove oxide.

Advantages of Cold working Advantages of Hot working 1. 2. 3. 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 1. 2. 3. 4. It reduces strain hardening Its components have better toughness Its components have better ductility Its components have better resistance to shocks and vibrations 4. Its components have high dimensional accuracy 5. Tooling required is comparatively inexpensive 5. Its components have better strength particularly the forged parts Disadvantages of Cold working Disadvantages of Hot working It reduces toughness of components It reduces ductility of components Rapid oxidation of surface due to high temperature Its components have poor surface finish compared with cold rolled parts 1. 1. 2. 2.