Edge drop of GO steel strips at the hot rolling mill 2000 PJSC «NLMK»

Abstract

One of the quality characteristics of hot-rolled strips is the transverse thickness variation. The transverse thickness difference is defined as the maximum difference between the measured values of the thickness of the strip in its middle, as well as at a distance of 10 to 40 mm from the edge, depending on the standard used. In many ways, the transverse thickness variation determines the manufacturability of subsequent processing, and also affects the breakage during subsequent cold rolling. Moreover, in recent years there has been a trend towards establishing additional requirements for the transverse thickness variation of electrical steel strips, which often leads to an increase in edge trim to meet these requirements; in particular, this refers to the value of the edge drop of the cross-sectional profile, which is defined as the difference in the thickness of the strip between the edge of the strip and 40 mm from the edge. It is known that the contour of the cross-sectional profile of a hot-rolled strip is inherited by a cold-rolled strip, while the value of the transverse thickness difference decreases in proportion to the elongation coefficient. Thus, hot rolling has a significant effect on the transverse thickness variation of the finished cold-rolled strip. The urgency of the issue of edge drop increases due to the tendency to reduce the size of the side trim of steel strips, which directly affects the consumption coefficient, especially for expensive steel grades, which include transformer steel. To minimize the edge drop value, it is necessary to know the causes of its occurrence and rely on an adequate calculation of the shaping of hot-rolled strips. To create a predictive model of edge drop, rolling parameters are taken into account that affect the shape of the active generatrix of the work rolls. In the presented work, an analysis was made of the influence of hot rolling parameters on the edge drop of rolled strips of GO (transformer) steel. The revealed patterns will form the basis of the developed mathematical model.