| 摘要 |
PROBLEM TO BE SOLVED: To prevent the obstruction in operation caused by CO gas, to reduce the wear of a refractory, to restrain the generation of oxide of valuable metal, etc., and to obtain molten steel having high cleanliness by adding an exothermic agent in an immersion tube dipped into the molten steel under reducing the pressure after receiving the molten steel having high carbon concn. melted at a temp. lower than a target temp. in a refining furnace, executing oxygen blowing and raising the molten steel temp. to the target temp. SOLUTION: The carbon concn. in molten steel decarburize-refined in a refining furnace is made to 0.20-1.2 wt.% and the molten steel 12 is tapped off into a ladle 11 at a lower temp. by 10-90 deg.C than a target temp. (ordinary molten steel tapping temp.). The pressure in an immersion tube 13 and a vacuum vessel 15 is reduced to 500-750 Torr and continuous stirring is executed in the direction shown with an arrow mark while blowing gaseous argon from a porous plug 21. The prescribed quantity of Al or an Al alloy in a storing hopper 18 is continuously added into the immersion tube 13 as an exothermic agent and also, the Al is burned by blowing the stoichiometrically necessary oxygen from a lance 20 on the molten steel surface 19 and the temp. of the molten steel 12 is easily and efficiently raised with this exothermic heat to become the target temp.
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