Thermodynamic assessment of Mg deoxidation reaction of liquid iron and equilibria of [Mg]-[Al]-[O] and [Mg]-[S]-[O]

Abstract

The deoxidation reaction of magnesium was investigated thermodynamically employing the equilibrium system between magnesium vapour and liquid iron in the molybdenum chamber sealed with an iron cover at 1873 K as a fundamental study to address the clean steel production technology in the steelmaking process. The previously reported thermodynamic data for magnesium deoxidation reaction are limitedly in good agreement with only their respective specific Mg concentration range, but fail to explain the thermodynamic equilibria generally over the wider range of magnesium concentration beyond the limited range. Therefore, the equilibrium constant, K-Mg for the magnesium deoxidation reaction as well as the first and second-order interaction parameters between magnesium and oxygen were determined over the extensive magnesium mass content range covering up to 0.04 %. Furthermore, the phase stability diagram based on the equilibria of [Mg]-[Al]-[O] in liquid iron for the purpose of controlling the oxide inclusions in the steelmaking process was accomplished using the determined thermodynamic parameters. The equilibria of [Mg]-[S]-[O] were also discussed in order to evaluate the utilisation of Mg as a desulphurizing agent as well as deoxidizer in the production process of low carbon steels.