METHOD FOR REFINING MOLTEN STEEL AND APPARATUS THEREFOR

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 porti on of the ladle, characterized in that the pressure Pt (Torr) in the cylindrica l immersion pipe is adjusted so as to meet equations (1): Pt > 760 - 1.297 ~ 107 /Dc2 K = 1.71 ~ D10.211 ~ Dc0.438 ~ Wm-1.124 (2): ~ Qg0.519 ~ Pt0.410-0 > 0.046 and oxygen gas is blown onto a surface of the molten steel through the lance, thereby performing the decarburization refining under reduced pressur e. 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).