HIGH FREQUENCY INDUCTION HARDENING APPARATUS FOR SHAFT- LIKE WORK AND HIGH FREQUENCY INDUCTION HARDENING METHOD

摘要

PROBLEM TO BE SOLVED: To prevent the overheat of a recessed part, such as key groove, without needing hand-work with an operator, plug, etc. SOLUTION: In a high frequency induction hardening apparatus used for induction hardening of a shaft with steps forming the key groove as the recessed part on the peripheral surface to execute the induction hardening, a rotating mechanism for rotation-driving the shaft with steps, an induction coil 100 for executing the induction heating, a gap changable mechanism, with which the gap between a heat conductive part 110 and the shaft with steps in the case of facing the key groove to the heating conductive part 110 in the induction heating coil 100 becomes larger than the gap in the case of no facing the key groove to the heating conductive part 110 in this induction heating coil 100, and a cooling jacket for spouting the cooling liquid onto the peripheral surface to execute the induction hardening, are provided. The heating conductive body 110 in the induction heating coil 100 is provided with three of the first to third arc-like heating parts 110A, 110B, 110C having different radiuses.