Improvement of Productivity in a Cold Forged and Induction Hardened Part by Using a New Steel

Rear spindles of passenger cars have usually been made by hot forging medium carbon steels. But in recent years, they have gradually been replaced with cold forgings. In spite of the efficiency improvement over the hot forging process, the cold forging process still utilizes spheroidizing heat treatment as well as quenching and tempering to obtain stable induction hardenability. To find a way to eliminate the heat treating steps in the cold forging process, the authors investigated the effects of several alloying elements on cold forgeability and the hardenability of the cold forged steel in rapid heating.

A new steel composition was thus developed which produces satisfactory mechanical properties and fatigue resistance in the induction hardened part without the spheroidizing and quenching and tempering heat treatments. The reduction in the manufacturing cost for a rear spindle of a passenger car was estimated to be about 15%.