| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength cold-rolled steel sheet having excellent square tube drawability and shape fixability even in high strength satisfying TS of≥440 MPa. SOLUTION: The steel sheet has a composition where, in constitution components, particularly, regarding Mn, Mo, Cr and V, the range in formula M=[%Mn]+3[%Mo]+1.3[%Cr]+0.5[%V]≥2 is satisfied, and further has a steel structure composed of a mixed structure essentially composed of a ferritic phase, and comprising a martensitic phase of≤15% by volume fraction. Further, the r value (r<SB>D</SB>) in a direction forming 45°with the rolling direction is≥1.2, and also, regarding in-plane anisotropy (Δr value) shown by the following formula, the range of -1.0≤Δr value≤-0.3 is satisfied (wherein,Δr value=(r<SB>L</SB>-2×r<SB>D</SB>+r<SB>C</SB>)/2). COPYRIGHT: (C)2009,JPO&INPIT
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