METHOD FOR IMPROVING REMOVABILITY OF SLAG AFTER DEPHOSPHORIZATION, AND METHOD FOR DEPHOSPHORIZING MOLTEN IRON USING THE SAME

摘要

PROBLEM TO BE SOLVED: To apply a dephosphorization to molten iron with which even in the case of applying the dephosphorization to the molten iron by using a dephosphorizing agent having substantially no containing of fluorine, the stable operation can be applied by effectively progressing the dephosphorization.;SOLUTION: When the dephosphorization in the molten iron is applied by using a converter-type furnace and using the dephosphorizing agent having substantially no-containing of the fluorine, a slag-basicity defined with mass-concentrating ratio of CaO and SiO₂ after dephosphorizing is made to be 2.5-3.5, and the molten iron temperature in a molten iron ladle after applying the dephosphorization, is made to be 1320-1380°C, and also, T-Fe concentration in the slag after applying the dephosphorization is controlled to be ≥5 mass% by keeping the bottom-blowing gas flowing rate to ≤0.18 Nm³/min/t, during the timing from before passing through 60% of the whole blowing time to the finish of the blowing. In this way, the removability of the slag after dephosphorizing, is improved and also, the growth of the stuck metal in the furnace is restrained and the low-phosphorus molten iron can stably be obtained.;COPYRIGHT: (C)2008,JPO&INPIT