Analysis of flow and stresses in flat bar hot rolling

Abstract

This chapter develops a three-dimensional flowline field to analyze the flow and stresses in flat bar hot rolling. The flow and stress field parameters are determined from kinematical and statical boundary conditions substituting experimentally obtained values of width spread, rolling load, and torque. A complete analysis of flow and stresses is obtained for a single-pass hot rolling of a square billet of AISI 1018 steel at 1000 °C. The distribution of axial velocity, effective strain rate, and normal and shear stresses are obtained in the two planes of symmetry of the billet. The results show that the rigid zones extend beyond the entry plane and ahead of the exit plane. The velocity distribution shows that there exists a plane of uniform axial velocity ahead of the neutral point. The effective strain rate is maximum at entry tending to zero at exit. The axial normal stress component at the billet sides is tensile, which explains the tendency for side cracks during bar rolling. The distribution of the frictional shear stress along the roll interface shows that neither the constant coefficient of friction model nor the constant shear factor model exists and the distribution follows the relative velocity model.