| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for executing desulfurization of molten steel with only transitory reaction of an agent consisting essentially of CaO. SOLUTION: During tapping the steel, the molten steel is sufficiently deoxidized with Al and [sol.Al] in the molten steel is made to high and successively, lime is further added into a molten steel stream to execute the desulfurization and also, T.Fe+MnO is restrained to <2.0wt% and further, sol.Al is lowered to a prescribed content with oxygen-containing gas in a vacuum degassing apparatus of an RH, etc. At this time, T.Fe+MnO is made to <3.0wt% by controlling a ratio of sol.Al (WAl ) flowed into the vacuum vessel and valuable oxygen content (F02.val ) for oxidizing the molten steel in the vacuum vessel according to [Mn] before treatment. Further desirably, [sol.Al] after tapping the molten steel is made to >=0.050wt%, and the desulfurizing agent of only the lime is added and the lowering of sol.Al is executed under condition of satisfying the following equation with the RH. At the time of being (h) (height of a top-blown lance)<=1.5m, WAl /F02 >0.625[Mn]+0.625, and at the time of being (h)>1.5m, WAl /F02 >(0.625[Mn]+0.625)×(-0.12h+1.18).
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