Plated steel plate and manufacturing method thereof

Abstract

A method for producing a coated steel sheet by reheating a steel slab containing 0.15-0.25 wt % of carbon (C), more than 0 wt % but not more than 1.5 wt % of silicon (Si), 1.5-2.5 wt % of manganese (Mn), more than 0 wt % but not more than 1.8 wt % of aluminum (Al), 0.3-1.0 wt % of chromium (Cr), more than 0 wt % but not more than 0.03 wt % of titanium (Ti), more than 0 wt % but not more than 0.03 wt % of niobium (Nb), and the balance of iron (Fe) and unavoidable impurities. Hot-rolling, cooling and coiling the steel slab, thereby producing a hot-rolled steel sheet. Pickling the hot-rolled steel sheet, then cold rolling. Annealing the cold-rolled steel sheet at a temperature between 820° C. and 870° C., followed by cooling at a finish-cooling temperature between 350° C. and 450° C.; tempering the cooled steel sheet at a temperature between 450° C. and 550° C.; and hot-dip galvanizing the tempered steel sheet.