| 摘要 |
PURPOSE:To reduce the strain in a material to be heated and also to obtain the necessary quenching hardness by continuously detecting changing of temp. for the heated material during cooling and arranging a control circuit, which slowly cools the heated material, when the temp. becomes starting temp. of martensite transformation. CONSTITUTION:The material to be heated 7 in a treating room 3 is heated to the temp., until an austenite condition is attained. Next, by flowing water through a cooler 11 and driving the circulating fan 12, a coolant nitrogen gas is circulated in a closed vessel 1 and the heated material 7 is rapidly cooled by blowing on to the heated material 7 from the small holes 10. The changing of temp. in the heated material 7 during cooling is continuously detected by a thermocouple 15. The starting temp. of martensite transformation (Ms point) is set to a signal control circuit 17 as a threshold. When the detected temp. reaches the threshold, the command to the control box 16, stopping the circulating fan 12 or the command temporarily conducting to a heater 8 or the command reducing the pressure of nitrogen gas is outputted. By these commands, the heated material 7 thereafter is slowly cooled.
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