What is the difference between hot rolling and cold rolling?

What is the difference between hot rolling and cold rolling?

Cold rolling and hot rolling are two different steel rolling technology, as the name suggests, cold rolling is in the steel at room temperature for tying, the hardness of this steel. Hot rolling is the making of steel at high temperatures.

1. Hot rolling

Using continuous casting slab or blooming slab as raw material, the slab is heated by a stepping furnace, then the roughing mill is descaled by high pressure water, and the roughing mill is cut through the head, tail and then into the finishing mill

Controlled rolling, after the final rolling, it is cooled by laminar flow (computer controlled cooling rate) and coiler to become a straight coil. The head and tail of straight curly hair are often tongue and fishtail, and the thickness,

The width accuracy is poor, and the edge often has defects such as wave shape, fold edge and tower shape. The coil weight is heavy, and the inner diameter of the steel coil is 760mm. (The general pipe industry likes to use.) Curl straight hair by cutting the head,

Tail cutting, edge cutting and multi-pass straightening, leveling and other finishing line treatment, and then cutting plate or rewinding, that is: hot rolled steel plate, flat hot rolled steel coil, longitudinal cutting strip and other products. Hot rolled finishing coil is formed after pickling and oil coating. The product has the trend of partial replacement of cold rolled plate, the price is moderate, and it is loved by the majority of users.

2.

Cold rolling

Hot-rolled steel coil is used as raw material, and cold continuous rolling is carried out after pickling to remove the oxide skin, and the finished product is rolled hard coil. Because of the cold hardening caused by continuous cold deformation, the strength and hardness of rolled hard coil increase, and the toughness and plastic index decrease, so the stamping performance will deteriorate, and can only be used for simple deformed parts. Rolled hard coil can be used as raw material for hot dip galvanizing plant, because the hot dip galvanizing unit is set back

The fire line. The roll weight is generally 6~13.5 tons, and the inner diameter of the steel coil is 610mm.

Generally, the cold continuous rolling plate and coil should be subjected to continuous annealing (CAPL unit) or cover furnace annealing to eliminate the cold hardening and rolling stress, and achieve the mechanical properties specified in the corresponding standard.

The surface quality, appearance and dimensional accuracy of cold-rolled steel plate are superior to that of hot-rolled plate, and its product thickness is right-rolled to about 0.18mm, so it is favored by the majority of users. Cold-rolled steel coil as the substrate for deep processing products, become high value-added products. Such as electric galvanizing, hot dip galvanizing, fingerprint resistance galvanizing, color coated steel coil and vibration reduction composite steel plate, PVC

Coated steel plate, etc., so that these products have beautiful, high corrosion resistance and other excellent quality, has been widely used. Cold rolled steel coils must be finished after annealing, including cutting head, tail, trimming, leveling, leveling, rewinding, or longitudinal shear plate. Cold-rolled products are widely used in automobile manufacturing, home appliances, instrument switches, construction, office furniture and other industries.