| 摘要 |
PROBLEM TO BE SOLVED: To provide a method with which oxygen activity on an interface of slag and metal is enhanced and highly efficient dephosphorize-refining can be obtained and slag is less produced. SOLUTION: When the dephosphorize-refining is applied to molten iron by performing addition of flux and top-blowing of oxygen, at least one among top-blown oxygen flowing amount, top-blown lance height, nozzle diameter and number of the lance and the adding quantity of the flux is adjusted so that the top-blown oxygen is not brought into direct contact with the molten iron by blocking the top-blown oxygen with the slag. Further, when desiliconize and dephosphorize-refining is performed to the molten iron, in the period of being >=0.1 mass% Si concentration in the molten iron, at least one among the top-blown oxygen flowing amount, the top-blown lance height, the nozzle diameter and number of the lance and the adding quantity of the flux is adjusted so that the top-blown oxygen is allowed to directly contact the molten iron. On and after the desiliconization progresses to <0.1 mass% Si concentration in the molten iron, at least one among the top-blown oxygen flowing amount, the top-blown lance height, the nozzle diameter and number of the lance and the adding quantity of the flux is adjusted so that the top-blown oxygen is not brought into directly contact with the molten iron.
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