METHOD FOR REFINING MOLTEN STEEL AND APPARATUS THEREFOR

摘要

A method for refining molten steel by immersing the lower opening end of a cylindrical immersion tube equipped with a lance into the molten steel contained in a ladle, controlling the pressure in the cylindrical immersion tube to a prescribed pressure range to suck up the molten steel, injecting an agitation gas from the bottom of the ladle towards the surface of the sucked-up molten steel, and decarburizing and refining the molten steel under a reduced pressure, characterized in that the method comprising the steps of; controlling the pressure Pt (Torr) in the cylindrical immersion tube so as to satisfy the following formulae (1) and (2), blowing oxygen gas to the surface of the molten steel through the lance, and decarburizing and refining the molten steel under a reduced pressure; Pt > 760 - 1.297 .times. 10 7/Dc2 ... (1) K = 1.71 .times. Dl0.211 .times. DC0.438 .times. Wm-1.124 .times. Qg0.519 .times. Pt-0.410 > 0.046 ... (2) wherein, K: capacity coefficient concerning the decarburizing reaction (1/min.) Dl: inner diameter of the ladle (cm) Dc: circle-reduced diameter of the cylindrical immersion tube (cm) Wm: mass of molten steel per processing (t) Qg: quantity of agitation gas injection (Nm3/h.).