JPS6428320A - Method for melting dead low carbon and low nitrogen steel - Google Patents

Abstract

PURPOSE:To promote decarbonizing and denitrogenizing reactions in molten steel and to stably produce dead low carbon and low nitrogen steel by degassed-refining the molten steel with RH type vacuum degassing apparatus, etc., and also blowing Magnesio-wustite powdery body together with the circulating flow gas. CONSTITUTION:Non-deoxidizing molten steel 1 produced by oxygen blowing from the molten iron in a converter, etc., is charged into a ladle 2 and two submerged tubes 3 for the vacuum degassing apparatus are submerged and the pressure in the vacuum vessel 5 is reduced through an exhausting tube 4, and by injecting the circulating flow gas 6 of Ar, etc., from the uptake submerged tube 3 at one side, the molten steel 1 is circulated between a ladle 2 and the vacuum vessel 5 through both submerged tubes. The molten steel 1 is beforehand deoxidzed by addition of the deoxidizing agent of Al, etc., to come to about 0.005-0.20% of dissolved oxygen concn. By blowing the circulating flow gas 6 and also the Magnesio-wustite powdery body 8 from the powdery body blowing nozzle 7 arranged below the molten steel surface of the downtake submerged tube side in the vacuum vessel 5 at the position of 30-70mm, the decarbonizing and denitrogenizing reactions are promoted at the same time while holding the O2 concn. to 0.005-0.02%, to stably produce the dead low carbon and low nitrogen steel.