Hot rolling and cold rolling are two key methods in steel processing, with significant differences in processing temperatures, processes and resulting product characteristics.
Hot rolling, which takes place mainly at high temperatures, is commonly used to produce thick plates and sections. This method enhances the plasticity of the metal, reduces deformation resistance, increases productivity, reduces costs, and improves the processing properties of the metal. However, the surface of hot rolled products is rougher and the dimensional accuracy may not be high enough due to shrinkage during the cooling process. In addition, hot rolling is difficult to accurately control the mechanical properties of the product, and may result in internal non-metallic inclusions being pressed into thin sheets, forming a delamination phenomenon, which affects the performance of the steel.
In contrast, cold rolling takes place at room temperature and is usually a further processing of the hot rolled product. Cold rolling can improve the mechanical properties and dimensional accuracy of the material, the product surface smooth. However, cold rolling may cause cold hardening of the material, resulting in a decline in stamping performance, and its strength and hardness is usually higher than the hot rolled products, the toughness is poor.
Specifically, the main difference between the two is reflected in:
Forming and performance: hot rolling can destroy the ingot casting organization, refine the steel grain, improve mechanical properties. Cold rolling is through the cold working of steel to produce large plastic deformation, improve the yield point. But the cold rolled steel section form is mostly open, free torsional stiffness is low, torsional performance is poor.
Residual stress: hot rolled steel section of residual stress caused mainly by uneven cooling, while the cold rolled steel section of residual stress is related to the cold working process. The two forms of residual stress distribution is also very different, the residual stress of hot rolled steel sections for the film type, while the residual stress of cold rolled steel sections for the bending type.
Cross-section buckling: cold rolled steel sections are allowed to cross-section local buckling, so as to take advantage of the bearing capacity after buckling; and hot rolled steel sections do not allow cross-section local buckling.
In summary, hot rolled and cold rolled each has its own characteristics, the choice of which processing method depends on the specific product requirements and application scenarios.
