Inclusion modification by calcium treatment in liquid steel processing

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There is an ever increasing demand for cleaner steels with a low oxide micro-particle (inclusion) content. This increasing demand has highlighted the limitations of our current knowledge in controlling and predicting micro-particle development during liquid steel where the formation of micro-particles is an unavoidable consequence of the current industrial steelmaking process resulting from 400-1000 ppm of oxygen in solution. Ca treatment by powder injection or wire feeding is a common technique used in steel refining to modify oxide inclusions, desulphurize steel and control the shape of sulphide inclusions. Too little or too much addition of calcium leads to incomplete or excessive modification of alumina inclusions or the formation of solid calcium aluminates or CaS, which are detrimental to the castability of steels.The proposed project will focus on the modification of alumina micro-particles' phase, size and morphology as a function of calcium additions and composition of liquid steel, and develop information leading to improved process design at the industrial scale. This will involve thermodynamic calculations and laboratory experiments, with industrial trials by the partner organisation ArcelorMittal Dofasco. This understanding of how the micro-particles form and develop during steel processing will determine the optimum rate of calcium addition as a function of steel oxygen and sulphur content so as to predict the lowest cost production strategies.