Multi-stage cold forging and experimental investigation for the outer race of constant velocity joints

As an important load-supporting automobile part that transmits torque between the transmission and the driven wheel, the outer race of CV (constant velocity) joints with six inner ball grooves has been conventionally produced by the multi-stage warm forging processes, which involves several operations including forward extrusion, upsetting, backward extrusions, sizing and necking, as well as additional machining. There is still no choice but to produce the complex shaped components other than by this warm forging process. As an alternative, multi-stage cold forging process is presented to replace these traditional warm forging. The multi-stage cold forging procedure is first considered through a process assessment regarding the traditional multi-stage warm forging one. Then, the process is simplified and redesigned as one operation to produce the forged outer race and the backward extrusions of the traditional process, and the sizing and necking are also combined into a single sizing-necking process. In addition, to ensure the appropriateness of the suggested process with respect to deformation behavior, a 3-dimensional finite element simulation on each sequence is performed, and experimental investigations are also carried out using SCr420H as the initial billet material. Finally, a comparative investigation of the process duration between the traditional multi-stage warm forging and the suggested multi-stage cold forging is presented. It is shown that the multi-stage cold forging process in this study could be successfully applied to the mass production of the outer race of the CV joints with the appreciably reduced processing duration for the machining process on the inner ball groove.