| 摘要 |
PURPOSE: To provide an efficiently refining method of a stainless steel, by which chromium refining rate is large without increasing the erosion of a refractory under condition of high productivity and expensive reducing agent is not used at all. CONSTITUTION: A top blowing lance, in which a slitting type oxygen supplying tube 7 having concentrically 3-16 angular polygonal or concentrically circular cross section is arranged and 2-10 shield plates 8 are arranged at a part of the tip opening surface of the tube 7 and the ratio B/h of the long side length B (mm) and the short side length (h) (mm) on the individual tip opening surface separated with the plates 8 is 10-225 and in the case of using R (mm) for lance diameter, B×h/R ratio is 0.4-4, is used. Oxygen supplying rate is made to be 125-250Nm<3> /Hr.ton without shifting the tip part of the lance including the lance center point (a) in the vertical direction to the lance body 6. Under condition of remaining decarburizing slag produced in the previous heat in a furnace, molten iron in the following heat is charged and blown, temp.-raised and refined and then, after reducing the chromium content in the decarburizing slag, the decarburizing slag is removed and successively, a ferro-chromium alloy is melted and decarburization-refined in the same converter.
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