| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-workability high-strength cold rolled steel sheet having excellent chemical conversion treatability, and to provide a method for production thereof. SOLUTION: This steel sheet is characterized in that: it has a composition consisting of, by mass, 0.05 to 0.30% C, 0.8 to 3.0% Si, 1.0 to 3.0% Mn,≤0.10% P,≤0.01% S, 0.01 to 0.1% Al,≤0.008% N and the balance Fe with inevitable impurities; it has, at its surface, flat portions in which an estrangement from a filtered waviness curve, with respect to a roughness cross sectional curve 1, is≤±2μm and recessed portions in which a maximum depth from the filtered waviness curve is≥5μm; the average area of the recessed portions 2 is 0.001 to 0.1 mm<SP>2</SP>; and the area ratio of the recessed portions is 5 to 50%. COPYRIGHT: (C)2009,JPO&INPIT
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