PURPOSE: To improve the efficiency of decarburization of molten steel in the last stage of decarburization and to enhance the yields of iron and manganese by refining the molten steel by blowing in a converter and adding a substance contg. manganese oxide to the molten steel in the converter after decarburization proceeds.
CONSTITUTION: Molten steel having a reduced phosphorus content by pretreatment is refined by blowing in a converter. At the time when the concn. of carbon in the molten steel is reduced to a prescribed value by the progress of refining, a solid substance contg. manganese oxide is added to the molten steel in the converter. Since the solid substance is moved in the molten steel over a wide range, the molten steel is efficiently decarburized.