Research of the asymmetric rolling of workpieces

Abstract

The asymmetric rolling process has proven itself well as a way to reduce the pressure on the rolls, reduce the rolling force, and improve the mechanical characteristics of the rolled metal. As the factors providing the asymmetry of the process, the mismatch of the circumferential speeds of the work rolls, the different diameters of the rolls, the coefficients of friction, and others are usually used. Methods that provide a change in the nature of the metal flow due to the action of working elements with a special configuration of the working surface are especially promising. This article presents the results of the study of the stress state, speed and power parameters when rolling a strip in biconical rolls with concave and convex surfaces. Analysis of the results obtained by analytical methods show that the intensity of shear deformation rates along the strip width is 0.36-0.65 s-1, which is impossible to implement when rolling in smooth cylindrical rolls, since there is an intense elongation of grains in the direction of rolling. The occurrence of the intensity of shear deformations creates favorable conditions in the deformation zone to prevent stretching of the structure and to reduce dangerous tensile stresses. The results of the study showed the prevalence of compressive stresses in the deformation zone, which prevent the intensive elongation of grains in the longitudinal direction, reduce tensile stresses and contribute to the leveling of mechanical properties, closing and welding of internal defects. Theoretical dependencies are proposed to calculate the force parameters for asymmetric rolling in biconical rolls. The obtained models of the stress state, velocity hodograph, force characteristics predict the efficiency of using the biconical rolls in cold and hot rolling mills.