| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel product having excellent fatigue crack propagation resistance, which has small crack propagation anisotropy and can be suitably used for welded structures requiring high structural safety, such as ships, offshore structures, bridges, buildings and tanks, and also to provide its manufacturing method. SOLUTION: The steel product has a composition composed of, by mass, 0.04 to 0.20% C, 0.05 to 0.50% Si, 0.5 to 1.8% Mn,≤0.05% P,≤0.02% S and the balance substantially Fe and containing, if necessary, one or more elements among Cu, Ni, Cr, Mo, Nb, V, Ti and B. Further, the microstructure of this steel product is composed mainly of a two-phase structure consisting of ferrite and pearlite with specified forms and has 65 to 85% ferrite. COPYRIGHT: (C)2008,JPO&INPIT
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