| 摘要 |
PROBLEM TO BE SOLVED: To rapidly remove copper and tin from a molten steel by blowing the specified grain size range of powdered coal material against the surface of the molten steel from the upper side with a carrier gas while executing a vacuum treatment after regulating the quantity of oxygen in the molten steel. SOLUTION: The increase of an evaporative reaction boundary area is advantageous in order to increase the evaporating speed of copper and tin in the molten steel. For this purpose, the powdered coal material of 10-100μm in grain size is blown against the surface of the molten steel from the upper side with the gas to form a suboxide, the reaction between oxygen and carbon existing in supersaturation on the surface is made to progress in parallel together with the evaporating reaction. By this way, the surface of the molten steel becomes a disturbing state with the generation of a large quantity of CO gas and the evaporative reaction boundary area of the suboxide is increased. The blowing quantity of powdered coal material is specified to be 0.1-5.0 kg/min per wt. ton of the molten steel. Also, the blowing carrier gas is specified to be nitrogen or argon and the quantity of the gas is preferably 0.1-1.0 Nm<2> /min a wt. ton of the molten steel.
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