Cold rolled vs Hot rolled steel
Steel is rolled using two types of processes – cold rolling and hot rolling. Well, when steel is rolled at more than the temperature of re-crystallisation, it is called hot rolled steel. When steel is rolled at a lower temperature, it is called cold rolled steel.
While hot rolled steel is obtained at a temperature of 1000 degrees, the cold rolled steel is obtained at 50 degrees. The hot rolled steel loses its hardness, and softens, once it is heated at a high temperature. The hot rolled steel has to then be treated to strengthen it. On the other hand, the cold rolled steel is obtained by beating it with heavy hammers, as it does not soften like the hot rolled steel.
When steel undergoes the cold rolling process, it becomes harder and stronger. When steel is hot rolled, the finished tolerances are loose. With cold rolled steel, the tolerances are much closer.
In terms of finishing as well, both the hot rolled steel and the cold rolled steel are different. The Hot rolled steel comes with a rough blue-grey finish, and rounded corners. On the other hand, the cold rolled steel comes with a shiny blue-grey surface, and square corners.
In size as well, the hot rolled and the cold rolled steel are different. The hot rolled steel comes in plus minus 0.01 inches, or even more than that. On the contrary, the cold rolled steel comes in less than 0.01 inches.
Another difference that can be seen between cold rolled and hot rolled steel, is that cold rolled steel has fewer carbon inclusions.
Summary
1. Hot rolled steel is obtained at a temperature of 1000 degrees; the cold rolled steel is obtained at 50 degrees.
2. When steel is hot rolled, the finished tolerances are loose, unlike cold rolled steel.
3. The hot rolled steel comes with a rough blue-grey finish, and rounded corners. On the other hand, the cold rolled steel comes with a shiny blue-grey surface, and square corners.
4. The hot rolled steel comes in plus minus 0.01 inches, or even more than that. The cold rolled steel comes in less than 0.01 inches.
5. The cold rolled steel is harder and stronger than the hot rolled steel.