| 摘要 |
PROBLEM TO BE SOLVED: To easily improve the relaxation characteristic of a non-heat treated high-strength bolt. SOLUTION: After a non-heat treated bolt is formed (S10), the axial load equivalent to≥80% and <100% of the tensile strength of the bolt is applied to the bolt to provide the plastic strain by using a tensile tool (S12), and the bolt is unloaded and detached from the tool (S14). The detached bolt is subjected to the bluing treatment in the treatment condition range surrounded by each treatment condition of 5 minutes at 200°C, 60 minutes at 200°C, 1 minute at 250°C, 10 minutes at 250°C, 0.5 minute at 300°C, 5 minutes at 300°C, 0.5 minute at 400°C, and 1 minute at 400°C in the relationship between the temperature and the time for heat treatment (S16). According to the load application condition, the bluing treatment can be performed before applying the load, and the bluing treatment can be eliminated. The load can be applied by using a rotating and fastening tool in place of the tensile tool. COPYRIGHT: (C)2007,JPO&INPIT
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