Advantages
It can destroy the casting structure of the steel ingot, refine the grains of the steel, and eliminate the defects of the microstructure, so that the steel structure is dense and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent; the bubbles, cracks and looseness formed during pouring can also be welded under high temperature and pressure.
Disadvantages
1. After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and stratification (interlayer) occurs. Stratification greatly deteriorates the tensile performance of the steel along the thickness direction, and interlayer tearing may occur when the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by the load.
2. Residual stress caused by uneven cooling. Residual stress is the internal self-balanced stress without external force. Hot-rolled steel sections of various cross sections have this type of residual stress. Generally, the larger the cross-sectional size of the steel section, the greater the residual stress. Although residual stress is self-balanced, it still has a certain impact on the performance of steel components under external forces. For example, it may have an adverse effect on deformation, stability, fatigue resistance, etc.
3. Hot-rolled steel products are difficult to control in terms of thickness and side width. Everyone is familiar with thermal expansion and contraction. Since the length and thickness of hot-rolled products meet the standards at the beginning, there will still be a certain negative difference after cooling. The wider the side width and the thicker the thickness, the more obvious this negative difference is. Therefore, for large-sized steel, the side width, thickness, length, angle, and side line of the steel cannot be too precise.
Hot rolled alloy tube
