| 摘要 |
PROBLEM TO BE SOLVED: To provide a gas cooling method along a cooling curve by driving a motor for a cooling fan to get its maximum output while preventing burnout of the motor and driving the motor at the speed of revolution corresponding to the temperature of the metallic material. SOLUTION: In the gas cooling method of the metallic material in which the metallic material W heated to the hardening temperature is subjected to the forced convection cooling in the in-furnace atmosphere, the preset cooling curve is compared with the in-furnace atmospheric temperature or the in-furnace metallic material temperature, the speed of revolution of the motor M for driving the cooling fan is controlled based on the difference therebetween. When the output of the motor reaches the limit, the motor for driving the cooling fan is continuously rotated at the maximum output limit irrespective of the load fluctuation caused by the temperature change.
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