| 摘要 |
PROBLEM TO BE SOLVED: To provide a low carbon BH steel sheet which has a low yield ratio, does not generate yield elongation, and is suitable for press forming of an automobile outer plate etc.SOLUTION: A high-tension cold-rolled steel sheet has: chemical composition including, in mass%, 0.01-0.04% of C, 0.5% or less of Si, 1.5-2.0% of Mn, 0.05% or less of P, 0.01% or less of S, and 0.10% or less of sol.Al, and 0.005% or less of N, 0.36-0.70% of Cr, and 0.0003-0.0030% of B which satisfy the following formula (1); steel structure comprising ferrite as the main phase and a low-temperature transformation-forming phase including at least 0.5 area% of martensite as a second phase; and mechanical characteristics, such as a yield ratio of 0.65 or less and elongation at yield point of 0%. A high-tension plated steel sheet is obtained by performing electroplating on the cold-rolled steel sheet. (1) sol.Al≥2.04×N-2.63×B+0.024, wherein sol.Al, N, and B are mass% of respective elements. |
