| 摘要 |
PROBLEM TO BE SOLVED: To suppress specific consumption of CaO-based flux in dephosphorization treatment of a subsequent step by reducing phosphorus concentration of molten iron subsequent to desiliconization treatment in a pre-treatment method of the molten iron where the molten iron is continuously subjected to desiliconization treatment and dephosphorization treatment with a slug-off step interposed therebetween by using one converter type refining furnace.SOLUTION: A pre-treatment method of molten iron includes: a desiliconization treatment step of supplying a gaseous oxygen source from a top-blowing lance 2 to molten iron 5 in a converter type refining furnace 1 and performing desiliconization treatment of the molten iron 5; a slug-off step of discharging a part of slag produced in the desiliconization treatment step; and, subsequent to the slug-off step, a dephosphorization treatment step of adding CaO-based flux thereto, supplying the gaseous oxygen source from the top-blowing lance 2 and performing dephosphorization treatment of the molten iron 5 remaining behind. A basicity of the slag at the time of completion of the desiliconization treatment is controlled so as to fall within a range from 1.1 to 1.5, and, when an oxygen amount other than one used for a desiliconization reaction out of an oxygen amount supplied into the converter type refining furnace 1 is defined as an exo-desiliconization oxygen amount in the desiliconization treatment step, specific consumption of the exo-desiliconization oxygen amount in the desiliconization treatment is controlled so as to fall within a range from 5.0 to 9.0 Nm/molten iron -t.SELECTED DRAWING: Figure 2 |
