Work roll non-uniform wear and shape control performance of the 2250 hot temper mill in WISCO

A 2250 hot temper mill was first adopted in WISCO (Wuhan Iron & Steel (Group) Corp.) of China for wide strip production and it has both HCW and WRS mill type characteristics. During operation, some problems were found, for example, work rolls were worn badly and non-uniformly, there were especial adjusting phenomena of work roll bending force, and shape control was not satisfied. Continuous tracking measurements were carried out and the typical characteristic of W-shape work roll wear was found in a roll serving period. The influence coefficient of roll wear was proposed for analyzing the W-shape wear. The synthetical influences of work roll wear, bending force and axial shifting on the shape control were studied. The especial adjusting phenomena of work roll bending force were analyzed and explained on the base of trials. It is pointed that, with the roll wear increasing, the occurrence of Wshape work roll wear leads to the decrease in gap crown because of the positive crown of the work roll within the strip width range, and the method of gradually changing the bending force from positive to negative is to increase the gap crown for compensating the decrease in gap crown caused by work roll wear and axial shifting, which makes the loaded gap invariant.