Method of quenching workpiece with hole, assistive tool for use in quenching, and crankshaft

摘要

A ferrite core partly covered with ceramics members is loaded into an oil hole defined in a pin, and high-frequency induction hardening is effected on the pin while the ferrite core is being held in position by copper wires. At the same time, a magnetic field is generated from the ferrite core to produce a high-frequency induction hardened layer having progressively spreading skirt regions extending from a position in the vicinity of a center in an axial direction of the oil hole toward openings in ends of the oil hole.