Patent ID: 8216695

Claim:
A process for hot-dip galvanization in which a steel sheet is treated by oxidization/reduction for better quality of galvanization and then galvanized, wherein an annealing line of hot-dip galvanizing equipment is composed of a first non-oxidizing zone, a second oxidizing zone, and a third reducing zone arranged in an order of first to third zone in line; wherein a steel sheet containing silicon of 0.2-3.0 weight percent is oxidized during oxidization/reduction by flames blown to it in the oxidizing zone and then reduced and annealed in the reducing zone, characterized in that said steel sheet on which rolling oil sticks is heated under conditions where the excess air ratio r 1 is 0.9 or higher but below 1.00, the temperature t (° C.) of the steel sheet is 450° C. or higher, and said excess air ratio r 1 and temperature t (° C.) of the steel sheet satisfy the expression: t≦−1000×r 1 +1750 in said non-oxidizing zone; and said steel sheet is then heated by flames which are directly applied for direct heating by burners whose nozzles are directed toward the upper and lower surfaces of said steel sheet and extend in the lateral direction of said steel sheet, under a condition where an air-fuel ratio r 2 is 1.00 or higher in said oxidizing zone.