| 摘要 |
PROBLEM TO BE SOLVED: To provide a molten iron preliminary treatment method for continuously performing a desiliconizing treatment and a dephosphorizing treatment for molten iron using one converter type refining furnace while performing a slag-off process in between, which is capable of preventing a rephosphorization reaction during the desiliconization treatment, and performing a sufficient dephosphorizing treatment in terms of cost and quality.SOLUTION: A molten iron preliminary treatment method includes: a desiliconizing treatment process for performing a desiliconizing treatment of molten iron by supplying an oxygen source to the molten iron 5 in a converter type refining furnace 1 from a top-blown lance 2; a slag-off process for discharging at least part of the slag 6 generated in the desiliconizing treatment process from the converter type refining furnace; and a dephosphorizing treatment process for performing a dephosphorizing treatment of the molten iron caused to remain by adding a CaO-base flux inside the converter type refining furnace and supplying an oxygen source from the top-blown lance after the slag-off process. The basicity of the in-furnace slag ([mass% CaO]/[mass% SiO]) is adjusted according to the temperature of the molten iron and the concentration of the ion oxide in the slag so that the composition of the in-furnace slag in the desiliconizing treatment process is not in the saturation region of SiO. |
