The cold-rolled sheet has higher hardness, finer grain size, and tighter internal structure. Its hardness is generally around HB180. The hot-rolled steel coil is used as raw material, and after pickling to remove the oxide scale, it is cold-rolled. The finished hardened coil is hardened by cold work caused by continuous cold deformation, resulting in an increase in its strength and hardness. This hardening not only increases the hardness of the cold-rolled sheet but may also reduce the toughness and plasticity index and deteriorate the stamping performance. Therefore, it can only be used for parts with simple deformation.

The hot-rolled sheet has lower hardness and better ductility. Its hardness is between HB120-150. The hot-rolled sheet uses a continuous casting slab or initial rolling slab as raw material. After being heated in a step-type heating furnace, it is made through rough rolling and finishing rolling processes. Its surface quality, appearance, and dimensional accuracy are worse than those of cold-rolled sheets, but it has good plasticity and is generally a medium and thick plate.

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