Both hot rolling and cold rolling are processes for forming steel plates or profiles. They have a great influence on the structure and properties of steel. The rolling of steel is mainly hot rolling, and cold rolling is usually only used to produce small-sized sections and sheets. Equal dimensionally accurate steel.

By definition, steel ingots or billets are difficult to deform and process at room temperature. Generally, they are heated to 1100-1250 °C for rolling. This rolling process is called hot rolling. The termination temperature of hot rolling is generally 800-900 °C. After that, it is generally cooled in the air, so the hot rolling state is equivalent to normalizing treatment, and most steels are rolled by hot rolling. The steel delivered in the hot-rolled state has a layer of iron oxide scale on the surface due to the high temperature, so it has corrosion resistance and can be stored in the open air.

Cold rolling refers to the rolling method of changing the shape of the steel by extruding the steel under the pressure of the roll at room temperature. Although the processing also heats up the steel sheet, it is still called cold rolling. Specifically, the hot-rolled steel coil for cold rolling is used as the raw material, and the oxide scale is removed by pickling, and then pressure processing is performed, and the finished product is a hard-rolled coil.

Generally, cold-rolled steel such as galvanized steel and color steel plate must be annealed, so the plasticity and elongation are also good, and it is widely used in automobiles, home appliances, hardware and other industries. The surface of the cold-rolled sheet has some smoothness, and the hand feels smoother, mainly due to the pickling. The surface finish of the hot-rolled sheet generally cannot meet the requirements, so the hot-rolled steel strip needs to be cold-rolled, and the thickness of the hot-rolled steel strip is generally 1.0mm, and the cold-rolled steel strip can reach 0.1mm. Hot rolling is rolling above the crystallization temperature point, and cold rolling is rolling below the crystallization temperature point. The change of the shape of the steel by cold rolling belongs to continuous cold deformation. The cold work hardening caused by this process increases the strength and hardness of the rolled hard coil. , Toughness and plastic index decreased.