| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold-rolled steel sheet with a high tensile strength of 340 MPa or higher, which has superior stamping performance, brittle resistance to secondary working and surface properties, and to provide a manufacturing method therefor. SOLUTION: This steel sheet has a chemical composition comprising 0.0005% or more but less than 0.010% C, less than 0.4% Si, more than 0.3% but 2.5% or less Mn, more than 0.02% but 0.10% or less P, less than 0.01% S, 0.15% or less sol. Al, less than 0.005% N, 0.20% or less Nb, less than 0.020% Ti as needed, while making Ti and Nb satisfy the following equations (1): (93/12)×C+0.037≤Nb and (2): Ti≤(48/14)×N+0.012%, and the balance Fe with impurities; and contains FeNbP-based compounds of 5.0×10<SP>5</SP>pieces/mm<SP>2</SP>by average number density. COPYRIGHT: (C)2007,JPO&INPIT
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