Effect of Pre-existing Inclusions on the Size and Morphology of Al2O3: Single Stage Deoxidation with Varying Levels of Supersaturation

The effects of supersaturation and steel composition on the morphology of Al₂O₃ inclusions were investigated. Thermodynamic calculations with Factsage 7.0® were used to predict the degree of supersaturation and select the starting aluminum and oxygen amounts for the experiment. Deoxidation experiments were performed by melting the charge material and using specially designed samplers to study the local deoxidation reactions. The inclusions in the collected steel samples were analyzed on filter paper in 3D after extraction from the steel. The observed Al₂O₃ morphologies consisted of dendrites and clusters and results showed that increasing supersaturation had the strongest influence on the length of the dendrite. The observed clusters resulted from collision, heterogeneous nucleation and growth on existing Al₂O₃ inclusions, and possibly oxygen gradients and liquid steel convection during nucleation and growth of Al₂O₃.