| 摘要 |
PROBLEM TO BE SOLVED: To execute a reforming treatment without bringing about the extension of the total time and developing such a problem as the entrapment of slag by making inert gas flow into molten steel at a specified flow rate from a position of a specified depth from the molten steel surface in a ladle during molten steel circulation treatment. SOLUTION: During the molten steel circulation treatment executed by using an RH vacuum degassing apparatus, the inert gas is made to flow at 10-300 Nl/min flow rate into the molten steel from the position of 5-50 cm depth from the molten steel surface in the ladle and the amount of the oxides such as FeO, Fe2O3 and MnO in the slag in the ladle is reduced to reform the slag in the ladle. The Al concn. in the molten steel as a deoxidizer may be between 0.007-0.2%. As the gas blowing device, a lance, a consumable pipe, etc., can be used. In the case of using the lance, a single hole straight shape, a T-type two hole shape or a T-type four hole shape, etc., can be used as the tip nozzle shape. As the inert gas, gaseous argon, helium, etc., can be used.
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