The Difference Between Cold Rolling And Hot Rolling

Hot rolling is to use slab (mainly continuous casting slab) as raw material, and after heating, it is made into strip steel by rough rolling unit and finishing rolling unit. The hot steel strip coming out of the last rolling mill of finishing rolling is cooled to the set temperature by laminar flow, and rolled into steel strip coils by the coiler. The cooled steel strip coils undergo different finishing operations according to different needs of users. Wire (leveling, straightening, cross-cutting or slitting, inspection, weighing, packaging and marking, etc.) processed into steel plate, flat coil and slitting steel strip products. To put it simply, after a steel billet is heated (that is, the red hot steel block in the TV), it is rolled several times, then trimmed, and corrected into a steel plate. This is called hot rolling.
Cold-rolled, using hot-rolled steel coils as raw materials, after pickling to remove scale, then cold rolling, the finished product is hard-rolled coils, and the strength and hardness of hard-rolled coils increase due to cold hardening caused by continuous cold deformation. The plastic index decreases, so the stamping performance will deteriorate, and it can only be used for parts with simple deformation. Hard-rolled coils can be used as raw materials for hot-dip galvanizing plants, because all hot-dip galvanizing units are equipped with annealing lines. The weight of hard-rolled coils is generally 6-13.5 tons, and the steel coils are continuously rolled at room temperature for hot-rolled pickled coils. The inner diameter is 610mm.
Product features: Because it has not been annealed, its hardness is very high (HRB greater than 90), and its machinability is extremely poor. It can only perform simple directional bending less than 90 degrees (perpendicular to the coiling direction).
To put it simply, cold rolling is processed and rolled on the basis of hot rolled coils. Generally speaking, it is a process of hot rolling---pickling---cold rolling.
Cold rolling is processed from hot-rolled plates at normal temperature. Although the steel plate will heat up due to rolling during the processing process, it is still called cold rolling. Due to the continuous cold deformation of hot rolling, the mechanical properties are relatively poor and the hardness is too high. It must be annealed to restore its mechanical properties, and it is called hard rolled coil without annealing. Hard rolled coils are generally used to make products that do not require bending or stretching.