| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel sheet having excellent hydrogen embrittlement resistance, and a method for producing the same. SOLUTION: The high strength steel sheet excellent in hydrogen embrittlement resistance and having the maximum tensile strength of≥900 MPa is composed of a steel having a composition comprising, by mass, 0.07 to 0.25% C, 0.3 to 2.50% Si, 1.5 to 3.0% Mn, 0.005 to 0.09% Ti, 0.0001 to 0.01% B, 0.001 to 0.03% P, 0.0001 to 0.01% S,≤2.50% Al, 0.0005 to 0.0100% N and 0.0005 to 0.007% O, and the balance iron with inevitable impurities. The inside of the steel sheet includes a hard structure including ferrite as the main phase and martensite with a block size of≤1μm, and the surface layer of the steel sheet is composed of a decarburized layer with a thickness of≥0.5μm in which the volume ratio of the above hard structure is≤80% the volume ratio of a hard structure included at the position of the 1/4 thickness in the steel sheet. The method for producing the same is also disclosed. COPYRIGHT: (C)2011,JPO&INPIT |
