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Hot-rolled seamless steel tubes are rolled at temperatures above the recrystallization temperature
Hot-rolled seamless steel pipe: hot rolling is relative to cold rolling, cold rolling is carried out below the recrystallization temperature of the rolling, and hot rolling is recrystallization temperature above the rolling. Advantages It can destroy the ingot casting organization, refine the steel grain, and eliminate the defects of the microstructure, so that the dense steel structure, mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that steel to some extent is no longer isotropic body; pouring bubble formation, cracks and loose, but also under high temperature and pressure welded. Disadvantages 1. After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, as well as silicates) in the steel are pressed into flakes and delamination (sandwiching) occurs. Stratification greatly deteriorates the properties of the steel in tension in the thickness direction and may cause interlayer tearing when the weld shrinks. Weld shrinkage induced local strain often reaches several times the yield point strain, much larger than the strain caused by the load; 2. Residual stress caused by uneven cooling. Residual stress is the internal self-equilibrium stress in the absence of external force. Hot-rolled steel of all kinds of cross-section has such residual stress. The larger the general section size of steel, the greater the residual stress. Although the residual stress is self-balanced, but the performance of steel components in the external force or have a certain impact. Such as deformation, stability, fatigue and other aspects may have adverse effects. 3. Hot-rolled steel products, the thickness and width of the poor control in this area. We are familiar with thermal expansion and contraction, since the beginning of the hot rolled out even the length and thickness of the standard, the final cooling or there will be some negative difference, the negative side of the wide and wide, thicker the performance of the more obvious. So for large steel, the width, thickness, length, angle, and edge of the steel can not be too precise. Learn more about this: