2. Round Bar: Except the precise size of the bright material is generally hot rolled, there are also forging.
3. Strip Steel: Hot-rolled & Cold-drawn, cold rolled materials are generally thinner.
4. Steel Plate: Compare with hot rolling plate, the cold rolled plate is thinner.
5. Angle Joint Coin: Hot rolled
6. Steel Pipe: there’re two available in welded pipe like hot-rolled and cold drawn
7. Channel Steel & Universal Beam: Hot rolled
8. Rebar: Hot rolled steel
Overview
Hot rolling and cold drawn are the processes of steel plate and section steel, which have a great impact on the structure and properties of steel. Hot rolled steel is widely used and cold drawn steel specially for precision steel.
Hot Rolling Process
Hot rolled state is equivalent to normalizing treatment. By definition, steel ingots or billets are hard to deform and process at normal temperature, usually heated to 1100-1250°C for rolling. The termination temperature is generally 800-900°C, then cooling.
Most of steel are rolled by hot rolling method, it will generates oxide layer in high temperature, so it has a certain corrosion resistance and can be stored outdoors. But the oxide layer makes the surface rough and size fluctuations. It requires good mechnical properties steel that produced using hot-rolled semi-finished or finished products as raw material then cold-drawn.
Fast molding speed, high yield and no damage to the coating. It can cause significant deformation of steel, thereby increasing its yield point.
Cold Drawn Process
Hot rolled steel coils are used as raw materials for cold rolling, and after acid washing to remove oxide scale, which are subjected to pressure processing. The finished product is rolled hard coils.
It can destroy the casting structure of the ingot, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel structure is dense and the mechanical properties are improved.
The difference between cold rolling and hot rolling is mainly the temperature of the rolling process. "Cold" is room temperature, "hot" is high temperature. The recrystallization temperature of steel is 450 ~ 600°C. Due to pickling treatment, the surface of cold-drawn steel plate is smooth with oxidation layer and will be hardened during processing with better forming effect.
