VACUUM REFINING METHOD FOR MOLTEN STEEL

摘要

The present invention relates to a molten steel refining method for refining molten steel, the carbon content of which is not more than 0.1 weight %, by blowing oxygen gas for decarburization at a blowing speed so that a cavity, the depth of which is 150 to 400 mm, can be formed on the surface of molten steel in a straight barrel type vacuum refining apparatus in which a straight barrel type vacuum vessel having no vessel bottom and a ladle are arranged. When necessary, the above decarburizing processing conducted by blowing oxygen gas is combined with: an A1 heating process in which A1 added into the vacuum vessel is burned by oxygen gas blown into the vacuum vessel at a blowing speed such that the cavity depth can be 50 to 400 mm; a degassing treatment conducted in a high vacuum condition; a desulfurizing treatment in which a desulfurizing agent is blown into the vacuum vessel; or a burner heating treatment in which a combustion improving agent is blown together with oxygen gas, wherein each treatment except for the high vacuum degassing treatment is conducted in a degree of vacuum of 100 to 400 Torr.