Numerical analysis and experimental validation on multi-stage warm forging process of deep groove ball bearing—a modified punch geometry with microstructure and defect analysis

In this study, a multi-stage warm forging process for making bearing rings is numerically and experimentally investigated. The aim of the study is to determine the crucial station of the finishing forging process such that the tool wear is prolonged and tool fracture should be minimized. In addition, in order to ensure the appropriateness of the suggested modification, a 3-dimensional finite element simulation on each sequence is performed and carefully compared with experimental investigations. Numerical simulation results indicate that the redesigned upper punch geometry, radius (R2) of the finishing forging process, demonstrate drastically different deformation rates (the effective strain/effective stress distribution) and material flow patterns, as compared with chamfer (C2) counterpart. Accuracy of the numerical models has been verified by comparing with experimental measurements. In addition, the numerically and experimentally validated process includes the detailed tooling design and dimension variation, which are of great importance in maintaining the overall structural integrity of the forging die/punch and thus, the stability of the whole process. Concerning on the waste ratio comparison, the method-used steel rods are as raw materials, and the IR/OR ring form is given by hot/warm forging and sequential cold rolling processes, and the waste ratio decreases to ~9 %. Finally, it is shown that the multi-stage warm forging process in this study could be successfully applied to the high-quantity production (10,000 pieces/h) of the IR/OR of the deep groove ball bearing with the stability and structural integrity of the whole process.