Rolling Processes: Hot Rolling and Cold Rolling Process Working Animation | Ifinfotech

 In todays session will learn about difference between hot rolling and cold rolling process. In hot rolling process, Metal is passing through two rolls, rotating in opposite directions, at a uniform peripheral speed. In hot rolling process the temperature is kept at above recrystallization temperature. In this process, to confirm desired thickness of rolled section, the space between rolls is adjusted and is always less than thickness of metal is being fed. When metal passes through rolls, there is change in its grain structure. here recrystallization temperature prevents metal from work hardening and due to this, Hot rolled metal does not show work hardening effect. Due to squeezing action, the grains are elongated in direction of rolling and velocity of material at exit is higher than that at the entry. In cold rolling process the Metal is fed into the rolls when its temperature is below the recrystallization temperature. here Cold rolling process employed for providing a smooth and bright surface finish to previously hot rolled metal. Before cold rolling, the hot rolled articles are cleaned through pickling and other operations. here same types of rolling mills are used as in hot rolling process. here part being rolled is generally annealed and pickled before final pass is made, so as to bring it to accurate size and obtain a perfectly clean surface. In hot rolling Process Coefficient of friction between rolls and metal is higher. Where in cold rolling process Coefficient of friction between rolls and metal is lower. In hot rolling process heavy reduction in size is possible. where in cold rolling process heavy reduction in size is not possible. In hot rolling process Close dimensional tolerances cannot obtained. where in cold rolling process Section dimensions can be finished to close tolerances. the surface finish in hot rolling process is poor but in cold rolling process smooth and oxide-free surface can be obtained. In hot rolling process. rolled metal does not show work hardening effect. but in cold rolling process, rolled metal show work hardening effect.