Difference between hot working and cold working process
Answers
When plastic deformation of metal is carried out at temperature above the recrystallization temperature the process, the process is known as hot working. If this deformation is done below the recrystallization temperature the process is known as cold working.Answer:
Explanation:
The distinction between hot working and cold working does not depends solely on the temperature, but rather on the processing temperature with respect to the material recrystallization temperature. When the processing temperature of the mechanical deformation of steel is above the recrystallization temperature, the process is termed as hot working; otherwise, it is cold working.
For hot working processes, large deformation can be successively repeated, as the metal remains soft and ductile. The hardness of the material cannot be controlled after hot rolling and it is a function of chemical composition and the rate of cooling after rolling. The hardness is generally lower than that of cold rolling and the required deformation energy is lesser as well. However most metal will experience some surface oxidation resulting in material loss and poor final surface finish.
Cold working processes allow desirable metal qualities that cannot be obtained by hot working, such as eliminating errors attending shrinkage. As such, a much more compact and higher dimensional accuracy metal can be obtained with cold working. Furthermore, the final products have a smoother surface (better surface finish) than those of hot working and the strength, hardness as well as the elastic limit are increased. However, the ductility of the metal decreases due to strain hardening thus making the metal more brittle. As such, the metal must be heated from time to time (annealed) during the rolling operation to remove the undesirable effects of cold working and to increase the workability of the metal.