Numerical Simulation of Cross Wedge Rolling: Influence of Die Geometry, Process Conditions and Inclusion Content of Two Steels on the Formation of Internal Defects

Abstract

Cross wedge rolling (CWR) is a metal forming process used in the manufacturing of stepped rotational parts. In this process, a cylindrical billet is heated and plastically deformed into an axisymmetric product by the action of wedge-shaped dies moving tangentially relative to one another. Since internal defects in CWR can weaken the integrity of the final product and can ultimately lead to catastrophic failures, it is necessary to investigate the mechanisms of their generation and growth. This defect has its origin in the center of the rolled pieces and its causes are not fully identified yet. Based on the finite element method, numerical simulations of CWR in three dimensions were studied with a commercial software. Numerical simulations can provide useful information helping decision making about die geometry and process conditions and, therefore, is a valuable tool to define ideal process parameters. Aided by this tool, researchers try to understand the role of process variables and die geometric features on the internal defects formation. The purpose of this study was aimed at the variables: rolling speed, relative reduction and forming and stretching angles. Stress, effective plastic strain and damage values at the rolled parts cross section were chosen as analysis criteria in several situations according to a given set of process variables. Earlier practical tests performed by the author showed the significant influence of these variables, and also proved the random behavior of that influence. Due this randomness, further studies were done with two different steels (AISI 1045 and 38MnSiVS5) taking into account their chemical composition and the possibility of the inclusion content has any influence on the crack generation which causes the internal defects.