Local Variations of Strain and Strain Rate in Roll Bite Region During Rolling of Steels

A combined experimental-numerical approach has been developed to quantify the strain rate variation of the workpiece in the roll bite region. In this approach, cold rolling experiments at a production mill were conducted first. Then tensile and microhardness tests were performed on workpieces before and after cold rolling to establish the relationship between the microhardness and plastic strain of the material. Microhardness measurements were also conducted in the roll bite region on a partially cold rolled workpiece. A finite element rolling simulation was performed to predict the spatial variations of the strain and strain rate. Through microhardness matching, it was found that the finite-element predicted strains agree very well with those actually existing in the rolled workpiece. Consequently, the finite-element predicted strain rates, whose time-accumulation directly gave strains which matched the actual strains, were verified. Finally, a finite-element simulation of both cold and hot rolling was conducted to assess the effect of several major rolling parameters on the strain rate variation in the bite region. Results show that the spatial variations of strain rate in the roll bite region are extremely nonuniform for both cold and hot rolling.