Modelling and analysis of bubble entrapment by solidification shell in steel continuous casting considering bubble interaction with a coupled CFD-DBM approach

Abstract

In steel continuous casting processes, argon gas is usually injected to prevent nozzle clogging. However, some argon bubbles may be captured by solidifying shell and result in defects in the final slab. A mathematic model with a coupled CFD-DBM approach is developed to study the bubbles entrapment behavior in the continuous casting process and bubbles distribution inside the slab. The coalescence and breakup of bubbles are considered in the discrete bubble model (DBM). An advanced bubble capture model based on force balance of bubble in front of the solidifying is used for the determination of bubble entrapment. Close agreements are achieved for the size and number density of captured bubble in the measurement layers of an industrial slab. The results show that most bubbles are captured near the meniscus, but bubbles have a greater tendency to be captured away from the meniscus as their size decreases. The fractions of captured bubbles at different regions of wide and narrow faces in the continuous casting mold are analyzed, as well as the effect of casting speed and gas flow rate. The distributions of number density and average size of bubbles inside the steel slab are obtained under different operation conditions. The results show successfully some known phenomena and other new predictions.