Evaluation of the Contamination in Tundishes During Filling Stage and Plasma Heating Practice Using a Novel Dynamic Model

Tundish contamination in the transient periods of operation can lead to the disqualification of steels with strict cleanliness requirements. In partially inertized tundishes, the major source of contamination is atmospheric air absorption in the filling procedure at the beginning of casting sequences. Furthermore, the use of steel heating practices such as plasma heating can also increase the absorption of gases in the steady casting periods. To improve the knowledge about the extension of contamination during the tundish operation, a new dynamic model was developed using computational thermodynamics and heat transfer routines taking into consideration the steel flow pattern of an industrial tundish. The model was constructed to interpret the equipment as a continuous stirred tank reactor with multiple sources of contamination. For the first heat of a casting sequence, the model was capable to predict the contamination behavior with good agreement over three different process set-ups. Also, a simplified approach developed to predict the contamination was able to reproduce a steady pattern of steel reoxidation. Overall, the tundish contamination was shown to have an accumulative behavior on the filling stage and a dissolution behavior on the casting stage. Moreover, the use of plasma heating practice increases the contamination towards the end of the heat due to the entrainment of atmospheric air components on the steel surface. Parametrized analyses of operational parameters and different degrees of tundish inertization show different trends in the gas pick-ups and may help tundish operation to mitigate the steel contamination in both the filling stage and plasma heat practice.