Theoretical study of the effect of work roll barrel profiling in a cold rolling mill’s continuous stands on the flatness of finished steel strips

Work roll barrel profiling compensates for the elastic deformation of the roll system and uneven thermal convexity along the barrel’s length, and also ensures a “hereditary” cross-sectional shape, thereby achieving flat strip production. Using a well-known model of flatness indices, the effect of the longitudinal cross-sectional shape of roll barrels in the stands of a continuous cold rolling mill on the quality of finished rolled products is examined. It is known that the rolling forces and roll barrel profiling, taking into account roll wear, have the most significant impact on the shape quality of rolled steel strip. Using the example of producing strip with thicknesses ranging from 0.3 to 1.2 mm and a width of 1250 mm in a five-stand 1700 mill, it is demonstrated that changing the roll profiles in the first and intermediate stands of the mill can significantly affect the flatness of the finished strip without changing or degrading its transverse profile. This is due to the low strip rigidity in these stands and the high rolling forces, which, combined with the roll barrel profile, significantly impacts the strip shape. Using calculations using a known model, changes in the roll barrel profiles in a continuous cold rolling mill are ranked according to their impact on the flatness of the finished flat steel product. An algorithm for adjusting the roll barrel profiles due to excessive flatness in the rolled strip is formulated. The effectiveness of the proposed roll barrel correction method is theoretically confirmed through calculations using a known model. The use of a correction algorithm reduced the flatness amplitude of rolled steel strip from 12 to 2 mm. The results of this study can be used to select roll barrel bulges for cold rolling mills.