| 摘要 |
PROBLEM TO BE SOLVED: To obtain a steel product which has improved fatigue strength, on a surface layer, by arranging steel having a martensite transformation starting temperature lower than that of components in an internal layer by carburization, and causing compressive residual stress on the surface layer. SOLUTION: In the double layer steel product for a welded structure having excellent fatigue strength, the surface layer consists of a carburized layer. The martensite transformation starting temperature Mss(°C) of the surface layer and the martensite transformation finishing temperature Mfi(°C) of the internal layer other than the surface layer satisfy 50°C≤Mss≤350°C, and Mss≤Mfi-100°C. COPYRIGHT: (C)2004,JPO
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