METHOD FOR MAKING MANGANESE-CONTAINING LOW-CARBON STEEL

PROBLEM TO BE SOLVED: To keep a manganese yield ratio of a ferroalloy such as ferro-manganese high and to increase the amount of an inexpensive manganese source used, in making a manganese-containing low-carbon steel by performing vacuum decarburization smelting in a vacuum degassing unit.SOLUTION: In making a manganese-containing low-carbon steel by smelting non-deoxidized molten steel held in a ladle in a vacuum degassing unit, first in the vacuum degassing unit 1, the non-deoxidized molten steel 3 is subjected to vacuum decarburization smelting by feeding an oxygen gas thereinto through a top lance 13; thereafter after stopping the feed of the oxygen gas from the top lance, both ferromanganese and a manganese ore are added to the molten steel in the vacuum tank in such a ratio that the quotient resulting from the division of the amount of the carbon contained in the ferromanganese by the amount of the oxygen contained in the manganese ore is 0.5-1.0; the vacuum decarburization smelting is performed by using the oxygen contained in the manganese ore until the concentration of the carbon in the molten steel falls within the range of the concentration of the carbon of the manganese-containing low-carbon steel; and thereafter the molten steel is subjected to aluminum deoxidation.