| 摘要 |
PROBLEM TO BE SOLVED: To provide a controlling method for an Al concentration in a molten steel having a high Si, capable of controlling the Al concentration to be in the very narrow range even at the high Si contents in the molten steel. SOLUTION: When a highly Si-containing molten steel held in a ladle, is treated by adding an Al source in a RH vacuum-degassing tank to control the concentration of Al, the concentration of FeO and Al2O3 is, in advance, analyzed before degassing treatment, and the yield of addition of Al source is estimated from this analyzed value based on the formula: the yield of Al (%)=a×((FeO)/2.1)-(Al2O3))+b, wherein (FeO) is the concentration FeO (mass%) of a slag in the ladle, (Al2O3) is the concentration of Al2O3 (mass%) in the slag in the ladle, and a and b are constants depending on the kinds of steel, facilities and the like. And at the same time, the Al source is added in the above molten steel, after progressing of a floatation treatment wherein SiO2 in the molten steel is made to float by degassing treatment.
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