| 摘要 |
PURPOSE: To provide a degassing decarburization method for molten steel by an RH device. CONSTITUTION: A liftable top blowing lance 5 is inserted into a vacuum chamber 1 and the molten steel is subjected to vacuum degassing decarburization by blowing gaseous oxygen under the conditions to satisfy the following equation to the surface of the molten steel in this chamber and burning the gaseous CO in waste gases in the chamber, thereby suppressing the temp. fall of the molten steel and melting the base metal B sticking to the walls in the chamber. L=(α.D<0.5.> Q)/[(dt )<0.5.> P<0.1.> W], where L: the distance (m) between the molten metal surfaces of the lance, D: the expanding rate of a nozzle throat (the outlet diameter of the nozzle/the diameter of the nozzle throat), Q: the flow rate of the gaseous oxygen (Nm<3> /min), dt : the diameter (m) of the nozzle throat, P: the vacuum degree in the vacuum chamber (Torr)(1<=P<=100), W: the reflux rate of the molten steel (Ton/min), a:αproportional constant (1.5<=α<=3). As a result, the temp. fall of the molten steel is suppressed and simultaneously, the degassing decarburization of the molten steel is made possible while the base metal sticking to the inside of the vacuum chamber is uniformly melted and decreased from the upper part to the lower part of the chamber walls.
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