METHOD AND APPARATUS FOR VACUUM-REFINING MOLTEN STEEL

PROBLEM TO BE SOLVED: To apply a vacuum-refining to molten steel with the industrial scale while improving the service life of a refractory by preventing the damage to the refractory at the bottom of a vacuum vessel with the blowing of oxidizing gas from a top-blown lance without sacrificing the refining performance of vacuum-degassing etc., and restraining the sucking-up of slag and further, thermal-spalling crack caused by a large opening hole part in an immersion cylinder. SOLUTION: One pair of immersion cylinders 13 arranged so as to communicate with the lower part of the vacuum vessel 12, is dipped into the molten steel 16 held in a ladle 15 set at the lower part of the immersion cylinder 13 and the vacuum-refining of the molten steel 16 is applied by blowing-stirring gas G into the molten steel 16 in the inner part of the immersion cylinder 13 to generate the circulation flow ascending/descending the inner part of the immersion cylinder 13. The immersion cylinder 13, in which at least the inner surface of the lower end opening hole part in the immersion cylinder 13 is formed as non-circular horizontal sectional shape almost along the outer-edge shape in an area where the circulation flow 20 exists is used to apply the vacuum-refining of the molten steel 16. COPYRIGHT: (C)2005,JPO&NCIPI