Takashi Horino, Technical Development Department, Research and Development Headquarters, NETUREN CO., LTD.
Double hardened layer induction hardening is a heat treatment method combining standard induction hardening and contour hardening using super rapid induction heating. A double hardened layer which is composed of a contour hardened layer on the surface and a regular hardened layer below can be achieved on the steel parts by applying this method. By this method, fine-grained microstructure and large compressive residual stress can be obtained on the surface of the hardened layer. In order to improve the quality of heat treatment to a higher level and expand the range of application, it is necessary to accurately predict heat treatment distortion, residual stress, and structural change by using a computer simulation. In this study, an induction hardening simulation system incorporating the phase transformation model from martensite to austenite through the tempering process is constructed for predicting the results of double hardened layer induction hardening. We introduce that dimensional change, residual stress and hardness distribution after double hardened layer induction hardening can be predicted using this system.