High-strength hot-dip galvanized steel sheet and a manufacturing method thereof

Disclosed is the high strength galvanized steel sheet, even a facility of reducing the annealing furnace only, Si of not plated are liable, Mn, relatively more content to the steel sheet and Al was foundation even if, non-coating does not occur, moreover stably provide high-strength galvanized steel sheet and excellent in workability and surface properties at high tension. A in the steel sheet Si, Mn, Si in the portion not forming the oxide by an oxide to a portion of the steel sheet surface layer by adding Ni even when containing Al is formed, Mn, Al surface segregation is to ensure favorable plating properties that is suppressed, determined strictly Si, the range of the Al further Mo, Cu, and allowed oxide generation promoting increase the effect of Ni in Sn addition, in yet TRIP , while avoiding the plating deterioration in Ni addition, Mo also added, by balanced to ensure austenite. Further, the present invention improves the press formability by defining a fraction of retained austenite in TRIP, the hydrogen concentration of the annealing conditions before the plating, and defines the dew point to promote the formation of oxides.