Patent ID: 9309586
Filing Date: 2016-04-12
CPC Classification: C21D,C22C,C23C

Claim Text:
1. A method for manufacturing a high-strength galvanized steel sheet including a zinc plating layer, having a mass per unit area of 20 g/m 2 to 120 g/m 2 , disposed on a steel sheet containing 0.01% to 0.18% C, 0.02% to 2.0% Si, 1.0% to 3.0% Mn, 0.001% to 1.0% Al, 0.005% to 0.060% P, and 0.01% or less S on a mass basis, the remainder being Fe and unavoidable impurities, the method comprising: annealing and galvanizing the steel sheet in a continuous galvanizing line equipped with an all-radiant tube-type furnace, wherein the steel sheet is not oxidized prior to annealing, and setting the temperature of the all-radiant tube-type furnace such that the furnace temperature reaches a temperature region of A° C. and a temperature region of B° C. during the annealing and galvanizing process, wherein the annealing and galvanizing is performed at an atmosphere dew-point temperature of −5° C. or higher when the furnace temperature is in the regions of A° C. and B° C., and wherein the atmosphere dew-point temperature is −50° C. to −10° C. when the furnace temperature is outside the regions of A° C. and B° C., where 600≦A≦780 and 800≦B≦900.