| 摘要 |
PURPOSE:To shorten cooling time of a core by stepwisely increasing the flow rate of atmospheric gas when the gas is fed into a heating furnace to cool the core. CONSTITUTION:After a heating coil 3 is energized to heat a core 1 by a heating method of induction current at 800-850 deg.C, atmospheric gas is fed from a gas inlet 9 into a heating furnace 2 to cool the core 1. In this case, the flow rate of the gas is set to the same amount at that at the heating time from the heat treating temperature to 600 deg.C, and increased by twice from 600 deg.C to 400 deg.C and by four times from 400 deg.C to 200 deg.C. According to the cooling method, the cooling period can be largely shortened, thereby improving the productivity. |
