| 摘要 |
PROBLEM TO BE SOLVED: To conduct prescribed annealing of the tip part of a hole by inserting the coil, which is formed of a square tube having electrical conductivity and has a specified number of coilings, at near the tip part of the cooling hole arranged to a die, energizing the high frequency electric current of a specified frequency to the coil and applying induction heating to a cooling hole. SOLUTION: A copper square tube coil 2 is coiled to a cylindrical magnetic body core 3 with a number of 1-2 coilings and is inserted into a cooling water hole. The outside diameter of the coil 2 is desirably about 2 mm smaller than the inner diameter of the cooling water hole. An power source frequency is selected in a range of 50-200 kHz depending on a die material. An energizing time is desirably 20-30 min. The coil 2, due to a copper square tube, has high magnetic force line intensity of a coil 2 tip, the part adjacent to the coil 2 tip is sufficiently heated. A number of coilings is 1-2, a cooling hole side face is not overheated but is raised to a prescribed temp. (about 650 deg.C). The tip part of the cooling hole is annealed to get prescribed toughness.
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