JPS5629611A - Simultaneous dephosphorizing desulfurization of blast furnace molten pig iron - Google Patents

Abstract

PURPOSE:To perform the dephosphorization and desulfurization of molten pig iron effectively and simultaneously by adding cryolite, fluorite, and iron oxide in specific proportions based on the amounts of quick lime and molten pig iron to the pig iron of blast furnace, whose Si content is requlated to a given value or less. CONSTITUTION:Molten pig iron in a ladle is preferably mixed with iron sand of a grain size of 0.5mm. or less as an oxidizing agent for regulating its Si content to 0.20% or less, preferably 0.15% or less. Then, the molten pig iron freed of silica is mixed with a dephosphorizing-desulfurizing agent, or a refining agent, composed of 15-40wt% (based on quick lime) cryolite having excellent slag generating property capability, 8wt% or less fluorite, and 80-200wt% iron oxide as an oxidizing agent. In this case, the ratio of the refining agent to the amount of molten pig iron is designated to 3.0-8.5wt%. Thus, a slag having excellent fluidity and excellent reactivity involving dephosphorization and desulfurization can be formed and therefore the dephosphorization and desulfurization of low-Si molten pig iron can be effectively performed.