INDUCTION HEATING METHOD AND HARDENING METHOD

摘要

PROBLEM TO BE SOLVED: To provide an induction heating method for induction-heating two heated parts with a great difference between AC power frequencies oscillated to two resonance circuits respectively from one oscillator.

SOLUTION: An annular induction heating coil 14 which is close to and along an outer circumference wall 110a is used as an induction heating coil 14, and an annular one which is close to and along an inner circumference wall 110b is used as an induction heating coil 16 in order to simultaneously hardening the outer circumference wall 110a and inner circumference wall 110b of a bush 110. A deep hardening layer d1 is formed on the outer circumference wall 110a, and a shallow hardening layer d2 is formed on the inner circumference wall 110b. Therefore, a first AC power with a frequency in a range of 1-50 kHz is fed to the induction heating coil 14 and a second AC power with a frequency in a range of 50 kHz-1 MHz is fed to the induction heating coil 16. The frequency of the AC power is appropriately determined depending on material of the bush 110 and a depth of the hardening layer or the like.

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