Control of flow lines during the forging process of bearing outer rings with a deviated groove

In this paper, the evolution of flow lines during the forging of bearing rings was investigated. The formation mechanisms of flow-line defects were revealed by a finite element method (FEM) simulation of the entire forging process. To avoid the flow-line disorder caused by the bearing ring manufacturing method, two hot forging processes were employed to optimize the flow-line distribution of an M50 steel bearing ring with a deviated groove. The simulation and experimental results show that the punching die and the location of the punching recess had a significant effect on the flow-line formation. The V-shaped punching pin and punching recess setting at the bottom of the billet resolved the flow-line disorder caused by the punching process. Finally, a bearing outer ring with a reasonable flow-line distribution was obtained. Furthermore, the improved hot forging process reduced the average grain size and improved the M₂C carbide-aggregation phenomenon. Given the direction of the flow lines, the bearing ring exhibited mechanical anisotropy in the tensile direction.