热轧和冷轧的区分（The distinction between hot and cold rolled）.doc

热轧和冷轧的区分（The distinction between hot and cold rolled） What is the difference between hot rolling and cold rolling Hot rolling and cold rolling steel or steel plate forming process, which has a great influence on the microstructure and mechanical properties of steel, steel rolling are mainly composed of hot rolling, cold rolling is only used in the production of small section steel and sheet. The advantage of hot rolling is that it can destroy the casting tissue of the steel ingot, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel structure is solid and the mechanical properties are improved. This improvement is mainly reflected in the direction of rolling, so that the steel is no longer isotropic to some extent. The bubbles, cracks and loose bubbles formed during pouring can also be soldered under high temperature and pressure. The drawback is that after hot rolling, the non-metallic inclusions (mainly sulphides and oxides, as well as silicates) inside the steel are pressed into thin slices and stratified (laminated). Layering of steel in the direction of the thickness of the steel is greatly deteriorated, and there may be a laminar tear at the weld shrinkage. 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. Two is residual stress caused by uneven cooling. The residual stress is the stress of internal self - equilibrium under the action of no external force, and the hot rolled sections of various sections have such residual stresses, and the larger the section size of the normal section steel, the greater the residual stress. Although the residual stresses are self - balanced, the performance of steel components under external forces has some influence. Such as deformation, stability, fatigue and other aspects can have adverse effects. Cold rolling refers to the processing of steel plates or steel strips into various