The following is a comparison of the advantages and disadvantages of cold-rolled stainless steel strip and hot-rolled stainless steel strip:
Advantages: It can damage the casting structure of the 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, and then the steel is no longer an isotropic body to a certain extent; the bubbles, cracks and porosity formed during casting can also be welded under the effect of high temperature and pressure.
Defects: 1. After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, and silicates) inside the steel are pressed into thin sheets, showing a layered (interlayer) appearance. Delamination greatly deteriorates the ability of the steel to be pulled through the thickness, and can exhibit interlaminar tearing when the weld is shortened. The partial strain induced by weld shortening often reaches several times the yield point strain, which is much larger than the strain caused by the load; 2. Residual stress formed by uneven cooling. Residual stress is the stress of internal self-phase equilibrium without the effect of external force. Hot-rolled section steel of various sections has such residual stress. Generally, the larger the section size of the section steel, the greater the residual stress. Although the residual stress is self-balanced, it still has a certain influence on the function of the steel member under the effect of external force. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc.
Advantages: fast forming speed, high output value, and no damage to the coating, can be made into a variety of cross-section methods to meet the needs of application conditions; cold rolling can cause a large plastic deformation of the steel, thereby improving the yield of the steel point.
Defects: 1. Although there is no thermoplastic compression during the forming process, there is still residual stress in the section, which will definitely affect the properties of the whole and part of the steel; 2. The cold-rolled section is usually an open section, which makes the section free Change stiffness is lower. It is easy to change when it is bent, and it is easy to bend and twist when it is pressed, and the torsional resistance is poor; 3. The wall thickness of cold-rolled forming steel is small, and it is not thickened at the corners of the plate connection, so it can accept partial deformation. The ability to gather loads is weak. 3. The primary difference between hot rolling and cold rolling is:
1. The free changing stiffness of hot-rolled steel is higher than that of cold-rolled steel, so the torsion resistance of hot-rolled steel is better than that of cold-rolled steel.
2. Cold-rolled forming steel allows partial buckling of the section, and then can make full use of the bearing capacity of the member after buckling; while hot-rolled section steel does not allow local buckling of the section.
3. The reasons for the residual stress of hot-rolled steel and cold-rolled steel are different, so the distribution on the cross-section is also very different. The residual stress distribution on the section of cold-formed thin-walled steel is tortuous, while the residual stress distribution on the cross-section of hot rolled or welded steel is of thin film type.