| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for dephosphorizing molten iron, with which molten iron is dephosphorized at the minimum unit requirement of CaO, while reducing the unit requirement of calcium ferrite as far as possible, to make [P] concentration in the molten iron after the treatment ≤0.020 mass%, and basicity of slag after the treatment ≤1.8. <P>SOLUTION: In the method for dephosphorizing the molten iron, quicklime, iron oxide and a refining agent containing ≥90 mass% calcium ferrite are charged into a furnace by using a top-bottom blown converter. Addition of the quicklime is carried out by adjusting the addition amount so that charging basicity at the point of time when 35% of the total blowing time of the top-blown oxygen elapses becomes 0.3-1.0, by using one or both of a method of charging the quicklime having grain size of 5-30 mm into the furnace from the upper part of the converter and a method of blowing the quicklime having grain size of ≤3 mm against the molten iron together with oxygen from a top-blowing lance. Further, addition of the refining agent containing ≥90 mass% calcium ferrite is carried out by adjusting the addition amount so that actual basicity becomes 1.5-1.8 during a period after the point of time when 35% of the total blowing time of the top-blown oxygen elapses till the time when 80% of the total blowing time of the top-blown oxygen elapses, by using a method for charging the refining agent having grain size of 5-50 mm into the furnace from the upper part of the converter. <P>COPYRIGHT: (C)2013,JPO&INPIT |
