Rolling force and length of strip head and tail sections under unsteady deformation conditions

Abstract

This paper describes the results of an experimental study that looked at the distribution of strains and rolling forces along the length of brass (L63), bronze (BrOF6,5-0,23) and copper (M3, M0) strips in a 150×235 twin rolling mill equipped with a microcontroller-based high-precision roll load measurement system. 2 and 3 mm thick workpieces with the widths of 10, 20 and 30 mm and the length of about 200 mm taken from the commercial batches of rolled copper, brass and bronze were used for the study. The workpieces were rolled at the Kolchugino and Kirov Non-Ferrous Metals Processing Plants. The reduction rate was varied within the range of 4 to 45%. The paper contains graphs showing the distribution of rolling forces along the strip length. The graphs indicate that the length of the strip head and tail sections, which experience unsteady rolling conditions, is dictated by the reduction degree, mechanical properties and dimensions of the strip. It was found that the length of the strip head and tail sections undergoing unsteady deformation tends to increase as the reduction rate increases. It was established that the initial mechanical properties of the strips had a significant effect on the unstable rolling duration and the length of the strip head and tail sections deviating from the given dimensions of the proper strip. Regression equations were obtained that can help predict the duration of unsteady rolling conditions with regard to copper strips as a function of their initial rigidity and reduction. The results of the study can be useful when finetuning rolling mills, as well as automatic gauge control systems, to ensure strips are rolled to precision along their entire length.