| 摘要 |
PROBLEM TO BE SOLVED: To provide a dual phase type high tensile strength steel sheet having excellent elongation and stretch flanging properties, and exhibiting the value of TS (tensile strength)×äEl (elongation)×λ}<SP>1/2</SP>satisfying≥30,000, and to provide a production method therefor. SOLUTION: The steel sheet has a composition comprising, by mass, 0.03 to 0.20% C,≤2% Si, 0.5 to 3% Mn,≤0.10% P,≤0.01% S, 0.01 to 0.1% Sol.Al,≤0.005% N,≤1% Cr and≤1% Mo, and the balance iron with inevitable impurities, and a structure in which the average crystal grain size of martensite is≤2μm, the average crystal grain size of ferrite is≤2μm, and the volume ratio of martensite is 20 to <60%. COPYRIGHT: (C)2004,JPO&NCIPI
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