The theoretical and experimental analysis of the effect of asymmetrical rolling on the value of unit pressure

Abstract

An analysis of asymmetrical band rolling in the last two stands of a finishing sheet hot rolling mill has been performed in the study. Investigations were carried out to determine the range of values of roll peripheral speed asymmetry ratios which would assure the permissible bending of band upon its exit from the roll gap and to reduce the value of the overall metal pressure on the rolls without causing overloading of the drives of the finishing group of the continuous sheet rolling mill. The application of asymmetrical rolling on the last two stands has made it possible to reduce deviations in band thickness, decrease the minimum thickness of finished sheet from 2.00 to 1.80 mm and increase the width of sheets produced in the thickness range from 1.80–2.00 to above 925 mm. The use of asymmetrical rolling can be compared with the use of tension and back tension with resulting reduction of the force of the overall metal pressure on the rolls. A lower value of the pressure force means a smaller elastic deflection of working stand elements and a possibility of using smaller values of working roll bending forces. There are no concrete guidelines in the literature concerning the choice of the values of roll peripheral speed asymmetry ratio for real sheet rolling mills, at which a reduction of the forces of the overall metal pressure on the rolls and either a straight band or the one with a small curvature enabling the accomplishment of the rolling process in successive rolling stands and band coiling will be obtained.