| 摘要 |
PROBLEM TO BE SOLVED: To provide an efficient dephoshorization smelting method increasing oxygen activity in a boundary between slag and a metal. SOLUTION: The method for dephosphorizing a molten pig iron with which top-blown oxygen does not contact directly by shielding with slag when dephosphorization smelting the molten pig iron by adding a flux and top-blowing oxygen, regulates at least one or more items among a flow rate of the top-blown oxygen, a height of a top-blowing lance, and a diameter of a lance nozzle outlet, so that the flow rate of top-blown oxygen F(Nm<3> /min/t) per 1t of the molten pig iron, and the ratio (H/d) of the distance (H) between a lance nose and the top surface of the molten pig iron, to the diameter (d) of the nozzle outlet, can satisfy the expression (1): F×134.1×(H/d)<-1.63> >0.3 (1). Alternatively, when the Si concentration of the molten pig iron is 0.1 mass% or more, the method regulates at least one or more items among the flow rate of top-blown oxygen, the height of the top-blowing lance, and the diameter of the lance nozzle outlet, so that the top-blown oxygen can directly come in contact with the molten pig iron.
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