| 摘要 |
PURPOSE: To provide a method for improving forming property of products and mechanical properties after heat treatment by conducting normalizing before performing spheroidizing, thereby improving non-uniformity of microstructure and hardness. CONSTITUTION: The spheroidization heat treatment method of hot working tool steel comprises a normalizing step of heating a work for hot working tool steel to a temperature of 920 to 950 deg.C, holding the work at the temperature of 920 to 950 deg.C for 1 hour/50 mm, and air cooling the heated work to a temperature of 300 to 350 deg.C; and an annealing step of heating the normalized work to a temperature of 830 to 850 deg.C, holding the work at the temperature of 830 to 850 deg.C for U+30 min/25 mm, cooling the heated work to 400 deg.C in a maximum cooling rate of 25 deg.C/hr, and further furnace cooling the work to a temperature of 200 deg.C or less.
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