| 摘要 |
PROBLEM TO BE SOLVED: To efficiently perform dephosphorization in molten iron at a low cost while reducing the addition amount of CaF<SB>2</SB>to a minimum. SOLUTION: When molten low phosphorus iron is produced, the dephosphorizing treatment is performed by blowing gaseous oxygen and at least a part of refining agent onto the molten iron surface, and controlling the depth L of tdent occurring on the molten iron surface by blowing the gaseous oxygen or blowing the refining agent using the gaseous oxygen as carrier gas defined with the expression äL = L<SB>O</SB>×exp(-0.78L<SB>H</SB>/L<SB>O</SB>)}. Wherein, L<SB>O</SB>: L<SB>0</SB>= 63×(F<SB>O2</SB>/nd<SB>t</SB>)<SP>2/3</SP>, L<SB>H</SB>: height (mm) of the top-blown lance. F<SB>O2</SB>: supplying speed (Nm<SP>3</SP>/hr) of the gaseous oxygen from the top-blown lance, n: number of nozzle holes in the top-blown lance and d<SB>t</SB>: diameter (mm) of the nozzle hole in the top-blown lance (wherein, in the case of being different nozzle diameters in the plurality of nozzle holes, average hole diameter in the total nozzle holes is used). COPYRIGHT: (C)2004,JPO
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