Successive cold working process

摘要

A billet is successively cold worked into a product such as a countershaft, an outer race for a constant-velocity joint, or the like by forming a chemically converted lubricating coating on a surface of the billet, forging the billet into an intermediate product at a temperature below a transformation temperature of the billet, covering a surface of said intermediate product with lubricating oil in a die cavity in a die assembly, and forging the intermdiate product at a temperature below the transformation temperature and before the intermediate product gains a predetermined hardness due to age hardening resulting from the first forging step.