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What's the difference between hot rolling and cold rolling?

Steel plate is a kind of building materials commonly used in construction, and steel in the process of production will generally be divided into cold rolling and hot rolling two different ways of production, I believe that many friends like Xiaobian because they have not been exposed to this industry so the cold rolling and hot rolling this very professional term is not special understanding of its significance. Hot rolling and cold rolling is an essential process in steel plate or profile forming. Next, we will learn about the difference between hot rolling and cold rolling.

What's the difference between hot rolling and cold rolling?

1. Different modes of production

Cold rolling is relative to hot rolling, hot rolling is a kind of rolling above the crystallization temperature, and cold rolling is a kind of rolling below the crystallization temperature. When the steel plate comes out, it is the first hot rolling process, if the factory is directly, this is the hot rolled steel plate, the hot rolled steel plate after cold rolling process is made of cold rolled steel plate.

2. the surface quality is different

The surface structure of cold rolled steel is superior to that of hot rolled steel.

3. Different mechanical properties

The work hardening effect, or cold work hardening, results in the hardness of the surface of the cold rolled sheet and the hot rolled sheet being coiled between 1.2 and 25.4mm. However, the mechanical properties of hot-rolled steel plate are far less than that of cold-rolled steel plate, but it has very good toughness and ductility. Cold-rolled steel plate has a certain degree of work hardening and low toughness, but it can achieve a better flexion ratio. It is more suitable for cold-formed spring pieces and other parts. At the same time, because the yield point is close to the tensile strength, there is no predictability of danger in the process of use, and it is easy to occur accidents when the load exceeds the allowable load.

The definition of hot rolling and cold rolling?

1. Hot rolling

Using continuous casting slab or preliminary rolling slab as raw material, it is heated by stepping heating furnace, and then enters roughing mill after high pressure water dephosphorization. Roughing mill material enters finishing mill after cutting head and tail, and then carries out computer-controlled rolling. After the final rolling, it is cooled by laminar flow and picked up by winder to become straight coil. The head and tail of straight hair curls are often tongue and fishtail, and the thickness and width accuracy are relatively poor. There are often wavy, folded and tower-shaped defects on the side. Its coil weight will be heavier, the inner diameter of the steel coil is 760mm. The straight hair coil through the cutting head, cutting tail, cutting edge and multiple times of straightening, leveling and other finishing line processing, then cutting plate or rewinding, that is, to become hot rolled steel plate, flat hot rolled steel coil, longitudinal cutting strip and many other products.

2. Cold rolling

Cold rolling is to use hot-rolled steel coil as raw material, after pickling to remove the oxide skin and then cold continuous rolling, the finished product is rolled hard roll, due to the cold hardening caused by continuous cold deformation of the rolled hard roll strength, hardness, toughness and plastic indicators decline, stamping performance deterioration, can only be used for simple deformation parts. Rolled hard roll can be used as raw material in hot-dip galvanizing plant, because hot-dip galvanizing units are equipped with annealing lines. Rolled hard coil weight is generally 6~13.5 tons, the inner diameter of the steel coil is 610mm. In general, the sheet and coil of tandem cold rolling should be subjected to continuous annealing or cover furnace for annealing treatment, eliminate the cold hardening and rolling stress, to achieve the mechanical properties specified in the standard index.