Prediction of argon gas attachment to sliding gate in immersion nozzle (Note)

摘要

Argon gas is often introduced into the immersion nozzle of the continuous casting process to prevent adhesion of nonmetallic inclusions such as alumina on the inner wall of the immersion nozzle. Previous water model experi-ments suggest that the argon gas thus introduced attaches preferably to the sliding gate under a specific condition. The velocity of molten steel flow passing through the sliding gate is strongly affected by the attached gas.As a result, a biased flow is induced in the continuous casting mold. When the biased flow is pronounced, the velocity of meniscus flow sometimes exceeds a certain critical value and then mold powder is entrapped into the molten steel in the mold to cause defects of steel products. In this study a prediction method is proposed for the critical molten steel flow rate causing argon gas attachment to the sliding gate. A semi-empirical equation was proposed for predicting the critical condition for argon gas attachment to the sliding gate in the immersion nozzle of the continuous casting process. The adequacy of this method was partly verified from water model experiments. The predicted result for molten steel flow suggests a possibility of argon gas attachment to the sliding gate in the real immersion nozzle.