Patent ID: 7645964

Claim:
A high frequency heat treatment method for a fine bottom-closed hole, comprising the steps of: preparing a coil so as to be completely inserted into the fine bottom-closed hole; preparing a core for controlling a magnetic flux within the coil such that the core protrudes from upper and lower sides of the coil; heat-treating a target part of the fine bottom-closed hole under conditions of a heating time of 2˜3 seconds, an output power of 200˜300 kW, a quenching time of 3˜5 seconds, a positive electrode voltage of 4˜8 kV, and a positive electrode current of 2.0˜4.5 A; and quenching the heat-treated target part of the fine bottom-closed hole with cooling nozzles fixed around the heat-treated target part such that a sufficient amount of cooling water is injected uniformly over the whole heated part of the fine bottom-closed hole with a sufficient pressure via the cooling nozzles.