Modeling of reoxidation inclusion formation in casting of steel

Reoxidation inclusions are the most common form of inclusions that are found in steel castings, and are a major cost factor in the production of steel castings. Therefore, it is crucial to control the formation of reoxidation inclusions in steel castings.;Reoxidation is mainly caused by the reactions of elements dissolved in the liquid steel with oxygen coming from the surrounding atmosphere during steel pouring. In the present study, the mechanisms of oxygen absorption by the liquid steel are elucidated. Both gas transport control and oxidizer transport control models are developed to predict the oxygen absorption rate during steel pouring. The results are verified by experimental data taken from the literatures.;In order to predict the composition of reoxidation inclusions during steel castings, mathematical models are developed and combined with oxygen absorption rate models. The models are then implemented in the Thermo-Calc software. Both lever rule and Scheil approaches are employed. The consumption of elements in the steel is predicted and compared with experimental data taken from the literatures. The gas boundary layer thickness in the models is adjusted to fit the experimental data and compared with those calculated by empirical correlations.;Finally, models are used to predict the composition of reoxidation inclusions for four different plate castings, including low Al and high Al carbon steels, and low alloy and high alloy steels as a function of steel composition and atmospheric conditions. The results are compared with experiments taken from the literatures. The mass fraction of absorbed oxygen in the liquid steel is determined by matching the predicted and measured reoxidation inclusion compositions. The effect of steel composition on the reoxidation inclusion composition is also investigated. The results demonstrate the capability of the models to predict the composition of reoxidation inclusions in steel castings.