Working conditions of the rolls: The working conditions of the rolls in the mill parts are the most complicated. Residual stresses and thermal stresses are generated in the preparation process of the rolls prior to manufacture and use. It is further affected by various cyclic stresses, including bending, torsion, shear, contact stress and thermal stress. The distribution of these stresses along the roll body is uneven and constantly changing, not only because of design factors, but also by the wear, temperature and roll shape of the rolls during use. In addition, rolling conditions often have abnormalities. Rolls that are improperly cooled after use can also be damaged by thermal stress. Therefore, in addition to wear, the rolls often have various local damages and surface damage such as cracks, breaks, peeling, and indentation. A good roll should have a good match between strength, wear resistance and various other performance indicators. In this way, not only is it durable under normal rolling conditions, but it can also be less damaged in the event of some abnormal rolling. Therefore, in the manufacture of rolls, the metallurgical quality of the rolls should be strictly controlled or external measures should be taken to enhance the load carrying capacity of the rolls. Reasonable roll shape, hole shape, deformation system and rolling conditions can also reduce roll work load, avoid local peak stress and prolong roll life. The roll consumption is determined by three factors: 1 rolling mill, rolled material and rolling conditions, and reasonable selection of rolls; 2 roll material and its manufacturing quality; 3 roll use and maintenance system.