| 摘要 |
PURPOSE: A cold-rolled steel sheet and a manufacturing method thereof are provided to obtain a cold-rolled steel sheet with superior workability at the normal temperature and excellent formability. CONSTITUTION: A cold-rolled steel sheet comprises C of 0.01-0.10%, Sn of 0.05-0.25%, B of 0.001-0.003%, Zr of 0.08-0.20%, N of 0.002-0.006%, Mn of 0.4-0.8%,Al of 0.02-0.08%, P of 0.03-0.08%, S of 0.015% or less, and Fe and inevitable impurities of the remaining amount. The atomic ratio of Zr and C, Zr/C, is 0.2-0.7 and the atomic ratio of B and N, B/N, is 0.5-1.5. Zr-based carbide precipitation is formed in the cold-rolled steel sheet. The cold-rolled steel sheet includes equiaxed ferrite and acicular ferrite.
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