9th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking - STEELSIM2021

AOD process consists of two main stages: decarburization and reduction of slag. In the decarburization stage, oxygen is injected through nozzles – and also through top lance in combined-blowing vessels – to remove dissolved carbon from the metal bath. The oxygen injection is diluted with nitrogen or argon to avoid excessive oxidation of alloying elements, such as chromium and manganese. After the decarburization stage, the slag contains large amounts of solid chromium-containing oxide phases, and it may also contain undissolved lime particles, so-called ‘free lime’. Consequently, the slag has a high solid fraction and is highly viscous. During the reduction stage, the chromium oxide content of the slag is reduced by the addition of reductants. This, in combination with the addition of slag formers and fluxes, makes the slag almost completely liquid. However, there is a lack of information regarding the dynamic evolution of the slag composition and its physical properties during the reduction stage. To this end, a sampling campaign was conducted to measure the dynamic changes in metal and slag composition. To determine the phase structure and viscosity of the slag, comparative computational thermodynamics calculations were carried out using Thermo-Calc and FactSage software. The results provide new information on the dynamics of the reduction stage in the AOD process.