REFINING METHOD AND REFINING APPARATUS OF MOLTEN STEEL

摘要

A refining method of molted steel including performing decarburization refining under reduced pressure by means of immersing a lower end opening portion of a cylindrical immersion pipe having a lance into a molten steel accommodated in a ladle, sucking the molten steel by adjusting a pressure in the cylindrical immersion pipe within a predetermined range, and blowing a stirring gas toward a surface of the sucked molten steel from a bottom portion of the ladle, characterized in that the pressure Pt (Torr) in the cylindrical immersion pipe is adjusted so as to meet equations (1): Pt > 760 - 1.297 x 10<7> /Dc<2> K = 1.71 x D1<0.211> x Dc<0.438> x Wm<-1.124> (2): x Qg<0.519> x Pt<0.410-0> > 0.046 and oxygen gas is blown onto a surface of the molten steel through the lance, thereby performing the decarburization refining under reduced pressure. in said formulas; K: capacity coefficient regarding decarburization reaction (l/min); D1: inner diameter of ladle (cm); Dc: diameter corresponding to the circle of cylindrical immersion pipe (cm); Wm: mass of molten steel per processing (t); Qg: blown quantity of stirring gas (Nm3/h).