| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel sheet having excellent formability which has both characteristics of excellent strength flanging properties and total elongation in a high strength and superhigh strength region of an about 500 to 1,400 MPa class. SOLUTION: The high strength steel sheet has a composition containing, by mass, 0.06 to 0.6% C, 0.5 to 3% Si+Al, 0.5 to 3 Mn, <=0.15% (not inclusive of 0%) P and <=0.02% (not inclusive of 0%) S. Also, a base phase structure contains tempered bainite in >=50% by area of the whole structure. A second phase structure contains retained austenite in 3 to 30% by area of the whole structure and optionally contains further bainite/martensite.
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