| 摘要 |
PROBLEM TO BE SOLVED: To provide a galvanized steel sheet (inclusive of a galvannealed steel sheet) which has low strength of <500 MPa, and has excellent ductility and stretching formability even though the steel sheet has a composite structure containing martensite, and to provide a production method therefor. SOLUTION: A cold rolled steel sheet having substantial components containing, by weight, 0.010 to 0.06% C, <=0.5% Si, 0.5 to <2.0% Mn, <=0.20% P, <=0.01% S, 0.005 to 0.10% Al, <=0.005% N, <=1.0% Cr and 1.9 to 2.3%Mn+1.3Cr, and the balance Fe, and having a structure consisting of ferrite and a second phase inclusive of martensite, and in which the area ratio of the second phase is <=20%, also, the ratio of martensite occupying in the second phase is >=50%, and the closest intergranular spacing between the martensitic grains is <=5.4μm on the average is used as a base material, and a galvanized layer is formed on the surface.
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