3 April 2019

Difference between hot rolling and cold rolling

One of the important processes in metal manufacturing is rolling, but there are two methods available for rolling one is hot rolling and another is cold rolling. It is a common misconception that these processes relate to a specification of metal or grade of metal instead, they refer to how metal is processed at the mill. Now in this article, you can check it out the hot rolling vs cold rolling and some key difference between them. 

What is hot rolling?

Hot rolling is the process in which rolling the steel at a high temperature which is higher than the recrystallization temperature of steel.

What is cold rolling?

Cold rolling is a similar process to hot rolling, the steel is subjected to further cooling process at room temperature in cold reduction mills after being rolled. 

Main difference :

The main difference between these two processes is the temperature in which they are performed. Hot rolling is under high temperature also called as above recrystallization and the cold rolling is under room temperature also called as below recrystallization. 

Some more difference between hot and cold rolling process is explaining below. 
  • Hot rolling is the father of cold rolling which follows hot rolling. 
  • Hot-rolled metal does not show work hardening effect whereas it shows in cold roller metal. 
  • Co-efficient of friction between two rolls is higher in hot rolling it may even cause shearing of metal in contact with rolls and co-efficient of friction us lower in cold rolling. 
  • Experiment measurement is difficult in hot rolling while it can be carried out easily in cold rolling.
  • Heavy reduction area of a workpiece can be obtained in hot rolling whereas heavy reduction is not possible in cold rolling. 
  • The radius of rolls is generally higher for hot rolling and it relatively smaller in cold rolling. 
  • The very thin section is not obtained by a hot rolling process vice versa in the cold rolling process. 
  • Hot rolling does not allow partial buckling of cross-section while cold rolling is allowed to have local buckling. 
  • Mechanical properties are improved by beaking cast structure thus toughness increases in hot rolling and cold rolling increases the tensile strength and yield strength. 
  • The hot-rolled surface is not good it has metal oxide on it while the cold-rolled surface is smooth and oxide-free.