Advantages of hot rolling mill

1. Hot rolling can significantly reduce energy consumption and reduce costs. When hot rolling, the metal has high plasticity and low deformation resistance, which greatly reduces the energy consumption of metal deformation.

2. Hot rolling can improve the processing performance of metals and alloys, that is, the coarse grain of the cast state is broken, the crack healing is remarkable, the casting defects are reduced or eliminated, the as-cast microstructure is transformed into the deformed structure, and the processing property of the alloy is improved.

3. Hot rolling usually adopts large ingots and large reduction rolling, which not only improves production efficiency, but also creates conditions for increasing rolling speed and achieving the continuous and automatic rolling process.

Disadvantages of hot rolling mill

1. After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (sandwich) occurs. The delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible to cause interlayer tearing when the weld is shrunk. The local strain induced by weld shrinkage often reaches several times the yield point strain and is much larger than the strain caused by the load.

2. Residual stress caused by uneven cooling. The residual stress is the internal self-phase equilibrium stress without external force. The hot-rolled steel of various sections has such residual stress. The larger the section size of the general steel, the larger the residual stress. Although the residual stress is self-phase-balanced, it still has some influence on the performance of steel members under external force, such as deformation, stability, fatigue and other aspects that may have adverse effects.

3. Hot rolling can not control the mechanical properties required of the product very well, and the microstructure and properties of the hot-rolled product cannot be uniform. The strength index is lower than that of the cold hardened product, and higher than the fully annealed product; the plasticity index is higher than the cold hardened product, and lower than the fully annealed product.
4. The thickness of the hot-rolled product is difficult to control, and the control precision is relatively poor; the rough Ra value of the surface of the hot-rolled product is generally 0.5-1.5 μm. Therefore, hot rolled products are generally used as blanks for cold rolling.