Strip Warpage Behavior and Mechanism in Single Roll Driven Rolling

Abstract

Model rolling experiment was conducted to investigate strip warpage behavior during single roll driven rolling. It became clear that direction of strip warpage changes with change in so-called rolling shape factor which is defined as ratio of contact arc length to strip thickness. In case of the shape factor being small, rolled strip tends to warp toward the idle roll side, which is the consequence of larger exit velocity of the rolled strip for the driven roll side due to higher peripheral velocity of the driven roll. On the other hand, in case of larger shape factor, rolled strip tends to warp toward the driven roll side owing to larger forward slip ratio caused by larger thickness reduction for the idle roll side. In addition, two dimensional steady-state rolling analyses by a rigid plastic finite element method were conducted to investigate mechanism of the strip warpage behavior. Utilizing fine FE mesh and precise boundary conditions, the results of analyses show good agreement both qualitatively and quantitatively in strip warpage behavior with the experimental results mentioned-above. Moreover elaborate mechanical investigation based on the FE analyses reveal the fact that rolling deformation is realized by a set of macroscopic shear bands which penetrate strip thickness and are inclined with respect to the strip thickness direction, and it is concluded that intensity and configuration of the shear bands determine strip warpage behavior.