| The study of gas-metal interactions has industrial significance in metallurgical processes. Despite the vast production volume, the high temperature kinetics of these processes are far from fully understood. The difficulty in accounting for the effects brought by the large temperature gradients that commonly exist between gas and liquid metal phases remains a major challenge. It is therefore essential to understand and quantify the influence of these conditions on mass transfer during metallurgical reactions.;In the production of stainless steel, one of the main objectives is to minimize oxidative loss of valuable alloying elements such as chromium during the decarburization process. Carbon dioxide has a lower oxidizing potential compared to oxygen gas, and could provide a potential solution to the problem of alloy loss during the oxidation refining of stainless steel. From an economic standpoint, in order to fully utilize the advantages associated with using CO2 as an alternative oxidant, decarburization should be carried out with alloy melts having high initial carbon contents. As a consequence of these considerations, an understanding of the oxidation kinetics of high carbon melts containing chromium is of fundamental importance in facilitating the implementation of a carbon dioxide based refining process.;In the present thesis, several specific experimental investigations were carried out, using electromagnetic levitation, to study the decarburization of Fe-Cr-Csat alloys by carbon dioxide. However, a significant discrepancy was found between the measured decarburization rates and those predicted from models based on conventional formulations for evaluating mass transport behaviour. Although the well-established models offer accurate predictions for systems with small temperature gradients, evidence suggests that they are not suitable for the system in question. As a result of this work, new dimensionless equations for mass transport have been developed, to account for the large thermal gradients that exist between the gas and liquid metal phases. The effects of thermal diffusion on the mass transfer of gases across the boundary layer have also been explored. In this context, for the first time, thermal diffusion factors for two binary gas mixtures (CO2-Ar and O2-Ar) at 1873K (1600°C) have been determined.;Based on the experience generated with the levitation of iron alloy droplets, an experimental methodology was developed for non-conductive silicon heating and conductive silicon levitation. Results are presented for the effects of specimen weight and applied power on the heating behaviour and temperature control of levitated silicon and silicon-iron alloy droplets. While extensive fundamental research is required to optimize the metallurgical processing of silicon and its alloys, this preliminary work provides a foundation for future studies involving the refining of metallurgical grade silicon in order to provide material which could then be used for solar grade applications. |
