DENITRIDING METHOD AND DENITRIDING AND DECARBURIZING METHOD FOR MOLTEN METAL

摘要

PURPOSE: To provide high-quality products by blowing an oxidizing gas to a coating slag surface to an extent of not coming into direct contact with molten metal. CONSTITUTION: The molten metal (molten steel) is charged into a refining vessel having a gas top blowing function. The surface of this molten steel is coated with the slag consisting essentially of CO and Al2 O3 at >=15kg per 1t thereof. The oxidizing gas contg. O2 and/or H2 O is thereafter blown to the slag surface to the extent of not coming into direct contact with the molten steel. The molten steel is thus subjected to a denitriding treatment. The concn. of Al in the molten metal is maintained at >=0.5% in at least one period during the denitriding treatment. Stirring by the bottom blowing gas is used in combination. The molten steel is subjected to a decarburizing treatment by blowing the oxidizing gas into the molten steel after the denitriding treatment. A flux contg. iron oxide is added to the molten steel for the denitriding treatment. As a result, the denitriding down to an extremely low nitrogen concn. level can be executed.