| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing an extra-low sulfur steel, which can desulfurize molten steel better than a conventional method, by top-blowing a CaO-based desulfurization agent into the molten steel in a reduced pressure while using no fluorite and adding little Al to the molten steel. SOLUTION: The molten steel includes 0.5% or less C, 0.01-2.0% Si, 0.2-2.0% Mn, 0.005% or less S and 0.01-0.5% Al. The method for manufacturing the extra-low sulfur steel by desulfurizing the molten steel through blowing a CaO-based flux containing no CaF<SB>2</SB>onto the surface under the reduced pressure includes controlling a feeding rate of the CaO-based flux V (kg/min/t) in terms of a pure CaO content can satisfy a relationship expressed by the following expression (1); 0.35×ln[Al]+1.9≥V≥0.32×ln[Al]+1.55, wherein [Al](%) is an Al content in the molten steel. COPYRIGHT: (C)2008,JPO&INPIT
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