| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat treatment method with which in the case of performing a sub-aging treatment under vacuum state, the aging hardness in the desired range can be obtained. SOLUTION: A maraging steel-made metallic ring is rolled into a prescribed length and a re-solution treatment is applied, and after correcting the peripheral length, the aging treatment and nitriding treatment are applied. The sub-aging treatment is applied by heating the metallic ring after correcting the peripheral length, so that the temperature sets to 400-460°C under vacuum state of≤10<SP>-2</SP>Pa and the time and the temperature in a Larson Miller parameter expressed by the following equation P=äT(20+logt)×10<SP>-3</SP>} set in the range of 13.5-15.5. Wherein, T: absolute temperature (K) and t: time (h). Gas-cooling of the metallic ring applied to the sub-aging treatment is performed till the temperature when the aging precipitating reaction stops. The metallic ring subjected to the gas cooling is subjected to nitriding treatment in the atmosphere containing at least ammonia gas at a temperature of 460°-500°C. COPYRIGHT: (C)2005,JPO&NCIPI
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