Hot rolling is the forming process of steel plate, which refers to the rolling forming under the condition that the steel or alloy has not been completely cooled and softer. The main features are:
Advantages: the casting structure of ingot can be destroyed, the grain size of steel can be refined, and the defects of microstructure can be eliminated, so that the microstructure and mechanical properties of steel can be improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent, and the bubbles, cracks and looseness formed during pouring can also be welded under the action of high temperature and pressure.
1. After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, as well as silicate) in the steel are pressed into thin sheets, resulting in delamination (interlayer). Delamination greatly aggravates the tensile properties of steel along the thickness direction, and interlaminar tear may occur during weld shrinkage. The local strain induced by weld shrinkage is often several times of the yield point strain, which is much larger than that caused by load.
2.Residual stress caused by uneven cooling. The residual stress is the internal self-phase equilibrium stress without external force, and the hot rolled section steel with all kinds of sections has this kind of residual stress. The larger the section size of the general section steel is, the greater the residual stress is. Although the residual stress is self-phase equilibrium, it still has some influence on the performance of steel members under the action of external force. For example, it may have adverse effects on deformation, stability, fatigue resistance and so on.