| 摘要 |
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 mean grain size of ferrite is 10 mum or less, Vickers hardness of ferrite is 140 or more, mean grain size of carbide particles existing at grain boundaries of ferrite is 0.5 mum or less, and aspect ratio of carbide particles existing at the grain boundaries of ferrite is 2.0 or less.
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