The Advantages and Disadvantages of Hot RollingAuthor : hani Time : 2018/10/16
Hot rolling can greatly reduce energy consumption and costs. The metal plastic deformation is high during hot rolling, and the deformation resistance is low, which reduces the energy consumption of metal deformation.
Hot rolling can improve the processing performance of metals and alloys. That is to say, the coarse grains during foundry are broken, the cracks are healed, the casting defects are reduced or eliminated, and the as-cast microstructure is transformed into a deformed structure to improve the processing properties of the alloy.
Hot rolling usually uses large ingots and large reduction rolling, which not only improves production efficiency, but also creates conditions for increasing rolling speed and achieving continuous and automated rolling process.
After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, causing delamination (sandwich). The delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible that interlaminar tearing occurs 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.
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 section 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 may have adverse effects.
Hot rolling does not control the mechanical properties required for the product accurately, and the microstructure and properties of the hot rolled product are not uniform. The strength index is lower than that of the cold work hardened product, and higher than the fully annealed product, the plasticity index is higher than that of the cold work hardened product, and lower than the fully annealed product.
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 to 1.5 μm. Therefore, hot rolled products are generally used as blanks for cold rolling.
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