PRELIMINARY TREATMENT METHOD OF MOLTEN IRON BY CONVERTER

摘要

PROBLEM TO BE SOLVED: To propose a preliminary treatment method of molten iron capable of securing stable flowing slag quantity at all times even when Si concentration in a molten iron is varied and suppressing the amount of flux to be used.SOLUTION: There is provided a preliminary treatment method of molten iron conducting a desiliconization treatment and a dephosphorization treatment using one converter. The method includes: controlling an oxygen gas flow rate from a top-blown lance according to the Si concentration in the molten iron while controlling a bottom-blown gas amount within a range of 0.06 to 0.30 Nm/t min during the desiliconization treatment; then conducting intermediate slag discharge for discharging at least a part of produced slag from the converter by interrupting supply of oxygen gas from the top-blown lance; and then, restarting the supply of oxygen gas for refining from the top-blown lance to conduct the dephosphorization treatment.