The evolution of oxide inclusion size distribution and the shape of the distribution during steelmaking and casting and the process variables that influence the inclusion characteristics at different stages were investigated and documented. A statistical method for transforming the 2D size distribution to their actual 3D distributions and the application of a kinetic model to determine nucleation and growth mechanisms were tested. Finally, laboratory experiments were performed to study the effects of preexisting inclusions, steel active oxygen content, and supersaturation on the size and morphology of Al2O3 inclusions.
The inclusion size, composition, and morphology following steel deoxidation were found to depend on the steel conditions during deoxidation, and the method/sequence of deoxidant addition. The oxide size distribution evolved from lognormal to fractal and the distribution shape was quadratic or linear on a log-log plot. The distribution shape was preserved on both 2D and 3D analysis and used to identify new and aged inclusion populations. The Schwartz-Saltykov method for converting 2D data to 3D was found to be inadequate and the applied kinetic model could not explain certain observed trends. Finally, results from the laboratory study showed the oxide inclusion transformations from preexisting FeO and MnO\u27SiO2 inclusions to Al2O3 following Al-deoxidation. The reaction of Al with FeO was relatively fast compared to the sluggish reaction with MnO\u27SiO2. Al2O3 dendrites and clusters were observed after Al-deoxidation. The clusters consisted of spheres and dendrites and three possible sources of cluster formation were identified. The size of the spherical Al2O3 were larger with increased FeO size and results showed that increasing supersaturation had the strongest influence on the length of the dendrite --Abstract, page iv
