Non-Metallic Inclusion Generation and Evolution in Specialty Steelmaking Processes

In this study, inclusion evolution and slag/metal reactions were examined in various specialty steelmaking processes. Particular focus was paid to the differential processing conditions and compositions that are present in specialty steels, as these were expected to impact inclusion generation and evolution significantly compared to the more oft studied ladle and continuous casting processes. A number of separate studies were undertaken in the following areas: AOD and ladle treatment, IF experiments, vacuum metallurgy, electro-slag remelting, and boron nitride formation in the solid state. 

For AOD and ladle work, it was hypothesized that a one parameter EERZ model could simulate inclusion evolution in both vessels, which was partially supported. Additionally, the Mg*O associate was hypothesized to inaccurately model thermodynamic behavior at high temperatures, which was validated by analysis of AOD data and later by induction furnace experiments. For vacuum metallurgy, calcium was revealed to be a potential source of issues as a result of slowing down the kinetics of carbothermic reduction, which was the primary inclusion removal mechanism. In ESR, the loss of deoxidants and formation of manganese silicate inclusions was revealed to almost certainly be the result of oxidation at high temperatures of the process electrode in atmosphere. Finally, boron nitride formation was found to occur in the solid state under specific composition and temperature conditions.