| 摘要 |
PROBLEM TO BE SOLVED: To provide a treatment method which reduces the concentration of dissolved P by efficiently forming P inclusions in molten iron by the addition of La and/or Ce, and also does not need to remove the formed inclusions. SOLUTION: When adding La and/or Ce into the molten iron containing 3.5% or less of C, 2.5% or less of Si, 3.0% or less of Mn, 0.0001 to 0.5% of P, and 3.0% or less of Al, the method for treating the molten iron includes: setting (CaO/Al<SB>2</SB>O<SB>3</SB>) in slag at 0.5 to 11 and (CaO/SiO<SB>2</SB>) at 0.45 or more; and controlling [R] (mass%) which is the concentration of La and/or Ce in the molten iron, according to [P] which is the concentration of P in the molten iron, [O] which is the concentration of O and [S] which is the concentration of S (mass%, respectively), so as to satisfy the following expression (1), preferably the expression (2), and more preferably the expression (3) in addition to the expressions of (1) or (2), wherein the expression (1) is 5.5×10<SP>-5</SP>/[P]≤[R]; the expression (2) is 5.5×10<SP>-5</SP>/[P]≤[R]≤8.6×10<SP>-3</SP>/[P]; and the expression (3) is 0.1<ä[R]-0.8([S]+[O])}/(0.8[P])<28. COPYRIGHT: (C)2009,JPO&INPIT
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