| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a hot working die capable of suppressing generation of large cracks from a water-cooling hole and early cracks in a corner part, and prolonging the lifetime of a die. SOLUTION: Firstly, a die material is heated in a gaseous nitrogen atmosphere with the pressure of≥1×10<SP>2</SP>kPa and at the temperature of 450-650°C, and then, vacuum-heated at the temperature of 700-800°C. The die material is further heated at the temperature of 850-1050°C by adding gaseous nitrogen of≥1 ppm in a furnace in which the pressure is set to be≤0.8 Pa. Next, the die material is cooled to 800-900°C, and maintained at least for three minutes at this temperature (a heat-insulating step S1). Thereafter, the die material is quenched to 400-700°C, and maintained at this temperature at least for three minutes (a heat-insulating step S2). In addition, the die material is oil-cooled to 150-200°C, maintained at this temperature at least for 20 minutes (a heat-insulating step S3), and slow-cooled at the cooling rate slower than that of natural cooling. COPYRIGHT: (C)2006,JPO&NCIPI
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