Study on the formation and prevention mechanism of internal voids in cross wedge rolling

A three-dimensional numerical simulation model of cross wedge rolling (CWR) was developed to analyze the influence law of die parameters on internal voids during CWR using a rigid-plastic finite element method (FEM), where particular attention has been given to the internal void generation mechanism during CWR of shaft parts from the analyses of morphology, stress, and strain. The main reason for the internal voids during CWR is the extremely uneven deformation of the core and surface of the rolled product. By adjusting the key die parameters in CWR, the influence of die process parameters on internal voids in CWR was studied. As a result, the larger the forming and widening angles, the smaller the diameter of the rolled workpiece after rolling, and when the distribution coefficient of area reduction is about 1, the more difficult it is for loose defects to occur. According to the simulation results, a new CWR die structure was proposed and rolling experiments were performed. No looseness was found in the center, which proved that optimizing the die was feasible.