| 摘要 |
PROBLEM TO BE SOLVED: To provide marine steel in which fatigue crack propagation rate under cyclic stress is suppressed to increase fatigue crack propagation resistance and which is excellent in corrosion resistance to such an extent that it can be put to practical use even without coating or electrical protection, and particularly marine steel in which durability against crevice corrosion is improved and also durability against corrosion owing to wet environments and salt adhesion caused by seawater. SOLUTION: The marine steel has a prescribed chemical composition and also has a composite structure consisting of a soft phase and a hard phase. Further, a ratio between a Vickers hardness of the hard phase (Hv<SB>1</SB>) and a Vickers hardness of the soft phase (Hv<SB>2</SB>), (Hv<SB>1</SB>/Hv<SB>2</SB>), ranges from 1.5 to 5.0, and the grain size of the soft phase is≤20μm by circle-equivalent diameter. COPYRIGHT: (C)2007,JPO&INPIT
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