The Application of Hardenability Assured Cold Forging Medium Carbon Steels to CVJ Outer Race

New steels were developed to make cold forgeability and induction hardenability compatible with each other. These new grades contain. 0.05%Si, 0.25%Mn, 0.15%Cr and 15ppmB. The carbon contents are the same as conventional carbon steels, 0.48% and 0.53%. Ferrite strengthening elements, Si and Mn; were decreased to reduce the hardness of the spheroidize annealed materials and, as a result, the flow stress during cold forging. Boron was added to maintain induction hardenability. It was confirmed that new grades show cold forgeability superior to that of conventional carbon steels such as SAE 1049 and 1053, while maintaining the same case depth during induction hardening.

These new grades have been applied to the production of cuter races for constant velocity joints, in which spheroidize annealed bars are cold forged in five stages followed by induction hardening. In this process, carburizing steels can be replaced by these grades, and an in-line process can be established.