| 摘要 |
PROBLEM TO BE SOLVED: To provide a reduced pressure refining apparatus inexpensive in equipment cost and a melting method of clean and inexpensive low carbon steel using this apparatus. SOLUTION: This refining apparatus is the one in which a cylindrical immersion tube 3 dipped at the lower end thereof into molten steel in a ladle 2 is set at the upper part of the ladle 2 and its inner part is reduced in pressure to suck up molten steel and to execute the refining. A lance 6 for blowing gas toward the molten steel surface is arranged at the upper part of the cylindrical immersion tube 3, and also, a blowing means for stirring gas is arranged at a position passing through the free surface of the molten steel sucked up in the cylindrical immersion tube 3. Further, a pressure adjusting means is arranged so that the pressure Pt (Torr) in the cylindrical immersion tube 3 satisfies the following formula I, and at the same time, a volume coefficient K (l/min) satisfies formula II. Formula I: Pt>760-1.297×107/Pc2 Formula II: K=1.71×Dl0.211×Dc0.438×Wm-1.124×Qg0.519×-Pt-0.410>0.046.
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