Abstract
A previous report shows that induction hardened steels have greater amount of residual stress than usual quenched steels. Residual stress induced by martensite transformation may be the cause of cracking. It was occasionally found that the induction hardened steels cracked more frequently than usual quenched steels. In order to reject this failure surface hardened steels must be tempered at low temperature (150°, 200°), but hardness of induction surface hardened steels decreases even at this low temperature.
These two phenomena have been unavoidable failures for induction surface hardening. However, the author tried to employ mar-tempering, and found that strain and stress were very small and hardness decreased little. Successful results were obtained in the experiment.
