| 摘要 |
An object is to provide a galvanized steel sheet with high yield ratio having not only a tensile strength TS of 590 MPa or more but also excellent ductility and stretch flange formability and a method for manufacturing the steel sheet. A high-strength galvanized steel sheet with high yield ratio having excellent ductility and stretch flange formability, the steel sheet having a chemical composition containing, by mass%, C: 0.04% or more and 0.13% or less, Si: 0.9% or more and 2.3% or less, Mn: 0.8% or more and 2.4% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01 % or more and 0.1% or less, N:0.008% or less, and the balance being Fe and inevitable impurities and a microstructure including, in terms of area ratio, 94% or more of a ferrite phase and 2% or less of a martensite ferrite phase, wherein the mean grain size of ferrite is 10 µm or less, the Vickers hardness of ferrite is 140 or more, the mean grain size of carbide particles existing at the grain boundaries of ferrite is 0.5 µm or less, and the aspect ratio of carbide particles existing at the grain boundaries of ferrite is 2.0 or less. |
