METHOD AND APPARATUS FOR HIGH FREQUENCY-INDUCTION HEATING

摘要

PROBLEM TO BE SOLVED: To provide a method and an apparatus for high frequency-induction heating which apply a good heat-treatment to a workpiece having a portion the temperature of which easily rises and a portion the temperature of which hardly rises depending on the position in the axial direction.

SOLUTION: The method for high frequency-induction heating comprises: a hardening step of heating a workpiece 10 to a prescribed hardening temperature and then rapidly cooling the workpiece 10; and a reheating step of heating the workpiece 10 to the temperature lower than the hardening temperature and then slowly cooling the workpiece 10. In the method, an induction heating coil 2 which has a length according to the length of a portion of the workpiece 10 to be hardened and reheated and which has portions generating magnetic field lines of different densities depending on the portions in the axial direction is used. In the hardening step, the portion of the induction heating coil 2 which generate magnetic field lines of high density is brought close to the portion 10a of the workpiece 10 the temperature of which hardly rises to perform hardening. In the reheating step, the induction heating coil 2 used for the hardening step is used to perform heat-treatment and the relative positions of the induction heating coil 2 and the workpiece 10 in the axial direction are changed when the workpiece 10 is heated.

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