Hot Rolled vs Cold Rolled Stainless Steel
Both hot rolling and cold rolling are processes of forming steel or steel sheets, which have a great influence on the microstructure and properties of steel. The rolling of steel is mainly hot rolling, and the cold rolling is only used for producing small steel and thin steel.
1. Advantages of hot rolling: It can destroy the casting structure of steel ingot, refine the grain of steel, and eliminate the defects of microstructure, so that the steel structure is compact and the mechanical properties are improved.
This improvement is mainly reflected in the rolling direction, so that the steel is no longer an isotropic body to some extent; bubbles, cracks and looseness formed during casting can also be welded under high temperature and pressure.
Disadvantages:
1. After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (sandwich) occurs.
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, which is much larger than the strain caused by the load;
2. The 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.
3. Cold rolling refers to the processing of steel sheets or steel strips into various types of steel at room temperature by cold drawing, cold bending, cold drawing and other cold working.
Advantages: fast forming speed, high output, without damaging the coating, can be made into a variety of cross-section forms to meet the needs of the use conditions; cold rolling can make the steel produce a large plastic deformation, thereby improving the yield of the steel point.
Disadvantages:
1. Although there is no hot plastic compression in the forming process, there are still residual stresses in the section, which will inevitably affect the overall and local buckling characteristics of the steel;
2. The cold-rolled steel is generally open-section, making the section free. The torsional stiffness is low. It is easy to twist when being bent, and it is prone to bending and torsion buckling when pressed, and the torsion resistance is poor.
3. The wall thickness of cold-rolled steel is small, and there is no thickening at the corner of the plate joint, which is subject to locality. The ability to concentrate loads is weak.
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