Finding an efficient profile for the working (roughing) section in plane periodic rolling

Production units which employ both continuous casting and periodic step rolling (Pilger step rolling) are especially effective because they combine compactness, efficiency and energy conservation with the additional capability of easy adjustment to obtain finish rolled products of different thicknesses. Since the main deforming element is a periodic (step) rolling mill, unit productivity and quality depend greatly upon the profile of the roughing section (the pass system). Efficiency of a pass system is evaluated based on the maximized use of available ductility (for metals with limited ductility) and maximal operation of the rolling mill (for highly ductile metals). This condition is satisfied when the roll-separation forces are redistributed along the working section to attain highest possible equipment productivity. The known RPRs (relative partial reductions) are based on experimental or mathematically arbitrary functions. The discussed procedure was first developed for a graphical-analytical model, but is now computed using the program module Restore (IBM PC) to synthesize the profile of the roughing section on the basis of an assigned partial reduction function (since the computing speed and data storage of Intel 586 PC can perform serial calculations and iterations in less than a minute). In each specific case it was possible to determine the profile of the working section with the most uniform distribution distribution of the roll-separating forces along that section where the minimization condition is satisfied. This described computer algorithm has been used to design a series of mills for plane periodic cold rolling of sheet and strip. Optimized profiles of the roughing section have enabled rolling of hard-to-deform alloys (lead-bearing bronzes such as grade LS63-3) with a single pass reduction of 60%.