CONTINUOUS ANNEALING AND HOT DIP PLATING METHOD AND CONTINUOUS ANNEALING AND HOT DIP PLATING SYSTEM OF STEEL SHEET CONTAINING SI

摘要

The present invention provides, in a hot dip platingsystem having an annealing furnace for hot dip platingsteel sheet containing Si, a continuous annealing and hotdip plating method and system causing internal oxidationwithout causing surface oxidation of the Si in the steeland avoiding a drop in the plating ability of the steelsheet and retardation of alloying, that is, a continuousannealing and hot dip plating method using an annealingfurnace having, in order, a front heating zone, rearheating zone, soaking zone, and cooling zone and a hotdip plating bath, comprising heating or soaking the steelsheet at a steel sheet temperature of a temperature rangeof at least 300°C or more by indirect heating, making anatmosphere of the zones one comprised of hydrogen H: 1 tovol% and a balance of nitrogen and unavoidableimpurities, making a steel sheet peak temperature duringheating at the front heating zone 550 to 750°C and makingthe dew point less than -25°C, making dew points of thefollowing rear heating zone and soaking zone -30°C to 0°C,and making a dew point of the cooling zone less than -- 25°C.