| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a desulfurizing method which does not cause disturbance in the manufacturing process even when an S content in a plain steel or a low-sulfur steel has deviated from the upper limit of a target S concentration when the steel is tapped out from a converter, suppresses the increase of a manufacturing cost and can stably decrease the S content to a target upper limit or lower. <P>SOLUTION: In a process of producing a molten steel by decarbonization-smelting molten pig iron, tapping the molten steel out into a ladle from a converter, reducing slag existing on the bath surface of the molten steel in the ladle, and then, secondary-refining the molten steel in an RH vacuum degassing apparatus, the method for desulfurizing the molten steel comprises the steps of: deoxidizing the molten steel by adding Al into the molten steel in the RH vacuum degassing apparatus; and spraying a pre-melt flux for desulfurization, which contains, by mass%, 48 to 58% CaO and 42 to 52% Al<SB>2</SB>O<SB>3</SB>, but contains no CaF<SB>2</SB>, onto the bath surface of the molten steel in a vacuum degassing tank from a top-blowing lance installed in the RH vacuum degassing apparatus. At this time, it is preferable to charge MgO into the molten steel in the vacuum degassing tank before spraying the pre-melt flux for desulfurization. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
