The difference between cold-rolled steel and hot-rolled steel is not in the smelting process, but in the rolling temperature, or the end temperature of the rolling. The final rolling temperature is lower than the recrystallization temperature of the steel to become cold rolled steel. Hot-rolled steel is easy to roll and has high rolling efficiency. However, under hot-rolling conditions, the steel is oxidized and the surface of the product is dark and gray. Cold-rolled steel requires large mill power and low rolling efficiency. In order to eliminate work hardening during the rolling process, intermediate annealing is required, so the cost is also high. However, cold-rolled steel has a bright surface and good quality, which can be directly used for processing. Finished products, so cold rolled steel sheets are widely used.
