The rolls of rolling mill may break in practical application. According to the analysis of fracture phenomena, the main part of fracture is mainly concentrated in the roll ring, and the fracture section is irregularly inclined or a vertical section. So why does this happen?
To analyze this problem, we can explain it from many aspects. Professional mill manufacturers believe that, first of all, it may be due to the quality problems of the rolls themselves. Because the working rolls are directly in contact with the high-temperature slabs and bear various loads, they need to have good heat resistance. If the hardness of the roll body decreases greatly with the increase of the temperature of the roll, it means that the heat resistance of the roll is poor, which will seriously affect the overall performance of the roll.
At the same time, if the rolling conditions are analyzed, the rolling mill rolls must also have good wear resistance and appropriate hardness and strength. In fact, the mechanical fatigue of the surface layer caused by the cyclic load of the roll, and the thermal fatigue of the roll surface caused by the cyclic heating of the roll and the cyclic cooling of the cooling water will cause the wear of the roll and the appearance of hot cracks.
At the same time, the hardness standard of the roll is also very important. Generally, the hardness of the roll is inversely proportional to the thermal cracking resistance of the roll body. That is to say, the harder the roll body is, the better the wear resistance is, but the more fragile the heat crack resistance is. Generally speaking, the wear resistance and surface hardness of the roll is related to the hardness difference along the diameter direction of the roll body, so it is hoped that the smaller the hardness difference along the diameter direction of the roll is, the better, and the hardness is moderate.
Finally, in the actual rolling work, the roll will also bear a lot of loads. For example, in the rolling process, the rolls will be affected by the rolling pressure from the hydraulic device on both ends, the reaction force produced when the rolled piece is deformed, and also will bear the alternating load under the action of cold and hot.
