Cold rolled steel is steel produced by cold rolling. Cold rolling is a steel sheet obtained by further thinning the No. 1 steel sheet to a target thickness under room temperature conditions. Compared with hot-rolled steel sheet, cold-rolled steel sheet has more accurate thickness, smooth and beautiful surface, and also has various superior mechanical properties, especially in terms of processability. Because cold-rolled raw coils are relatively brittle and hard, and are not suitable for processing, cold-rolled steel sheets are usually required to be annealed, pickled and surface smoothed before being delivered to customers. The maximum thickness of cold rolling is below 0.1--8.0MM, for example, the thickness of cold rolled steel plate in most factories is below 4.5MM; the minimum thickness and width are determined according to the equipment capacity and market demand of each factory.
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 rolling. Cold-rolled steel is when the final rolling temperature is lower than the recrystallization temperature of the steel. Hot-rolled steel is easy to roll and has high rolling efficiency, but under hot-rolled conditions, the steel is oxidized, and the surface of the product is dark gray. Cold-rolled steel requires high rolling mill power and low rolling efficiency, and intermediate annealing is required to eliminate work hardening during the rolling process, so the cost is also high, but cold-rolled steel has a bright surface and good quality, and can be directly used for processing. The finished product, so cold-rolled steel sheet is widely used.
Using hot-rolled steel coil as raw material, after pickling to remove oxide scale, cold continuous rolling is carried out, and the finished product is rolled hard coil. The cold work hardening caused by continuous cold deformation increases the strength, hardness and toughness and plastic index of rolled hard coil. , so the stamping performance will deteriorate and can only be used for parts with simple deformation. Hard-rolled coils can be used as raw material for hot-dip galvanizing plants, because hot-dip galvanizing lines are equipped with annealing lines. The weight of the rolled hard coil is generally 6~13.5 tons, and the hot-rolled pickled coil is continuously rolled at room temperature.
