| 摘要 |
PROBLEM TO BE SOLVED: To establish a technique which can spheroidize even a target high-C-low-Cr steel stably in spheroidizing to secure cold workability and grindability of a steel material.SOLUTION: Spheroidization consists of a frist-stage heat treatment and a subsequent second-stage heat treatment, and the conditions for the first- and second-stage heat treatments are as follows, respectively. (1) A programming rate of the first-stage heat treatment of lower than 400°C/h, a heating temperature of Apoint+10°C to Apoint+30°C and lower than 780°C, a heating retention time of 3-8 h, a cooling rate of 3°C/h or lower in the temperature range from Apoint to Apoint-20°C and a cooling finishing temperature of Apoint-35°C or lower. (2) A programming rate of the second-stage heat treatment of lower than 400°C/h, a heating temperature of Apoint+5°C to Apoint+25°C and lower than 780°C, a heating retention time of 0.5-2 h and a cooling rate of 5°C/h or lower in the temperature range from Apoint-15°C to Apoint-35°C. |
