I have previously talked about the advantages of hot rolling mills, and at the same time, in the actual operation, it also includes some shortcomings. Do you know what its main drawbacks are? For this question, we can answer from four aspects. First, after hot rolling, some non-metallic inclusions contained in the steel are pressed into thin sheets, and delamination occurs.

If the stratification problem is serious, it will have a great negative impact on the performance of the steel. It may even cause problems with interlayer tears when the weld shrinks. Secondly, after the hot rolling mill is processed, cooling treatment is also required. During the cooling process, the problem of uneven cooling is apt to occur. As a result, some residual stress is caused.

We know that this residual stress may have some effect on the steel itself. In general, hot-rolled sections of various cross-sections have such residual stresses, and it increases as the section size of the section increases. Therefore, the steel members treated by the hot rolling mill may have some adverse effects when subjected to external forces, such as deformation, stability, and fatigue resistance.

In the third aspect, during the processing of the hot rolling mill, the mechanical properties required for the product are not well controlled, and the microstructure and properties of the hot rolled product are often difficult to achieve a uniform state. In addition, its strength index is also lower than that of cold work hardened products.

The last problem is that the thickness of the product processed by the hot rolling mill is not easy to achieve good control, and the control accuracy achieved is poor. In comparison, the roughness of the surface is also greater than the roughness of the cold rolled product, so the hot rolled product is usually used as the blank for cold rolling.