| 摘要 |
A galvanized steel sheet excellent in strength-ductility balance and bake-hardenability as well as a method for producing the same are provided. The chemical components thereof include C, Si, Mn, P, S, Al, N and Cr at content ratios of 0.005 to 0.04%, 1.5% or lower, 1.0 to 2.0%, 0.10% or lower, 0.03% or lower, 0.01 to 0.1%, less than 0.008% and 0.2 to 1.0%, respectively, with Mn (mass%) + 1.29Cr (mass%) being in the range of 2.1 to 2.8, and further include iron and unavoidable impurities as the balance. The structure thereof consists of a ferrite phase and a martensite phase with a volume fraction being at least 3.0% and less than 10%, the average particle diameter of the ferrite is larger than 6 µm and not more than 15 µm, and 90% or more of the martensite phase exists in a ferrite grain boundary. In addition, in the production process of such a galvanized steel sheet, a steel sheet obtained in a cold rolling step is annealed at a temperature being at least the Ac1 point and not more than the Ac3 point. |
