Thermodynamic analysis of deoxidizing ability of strontium in liquid iron: phase stability diagram IN Fe-Sr-O and Fe-Mg-Sr-O systems

Abstract

Strontium is considered to be a promising element-deoxidizer and a modifier of steels and alloys, especially in barium and calcium-containing alloys. However, the thermodynamics of its interaction with oxygen in liquid iron is not studied enough. The aim of the study is a thermodynamic analysis of the deoxidizing ability of strontium in liquid iron of the Fe-Sr-O and Fe-Mg-Sr-O systems using a method for constructing the surface of the solubility of components in a metal (SSCM). SSCM is a diagram linking the compositions of a liquid metal with the compositions of the products of interaction formed during deoxidizing. At the calculation, the chemical reactions occurring in the melt of the Fe-Sr-O and Fe-Mg-Sr-O systems and the equilibrium constants of these reactions, including the formation of liquid and solid strontium oxides from the components of the metal melt, were established. The first-order interaction parameters (according to Wagner) of strontium with oxygen and magnesium in liquid iron were determined. The oxygen solubility isotherms were constructed in the Fe-Sr-O systems (within the temperature range 1550-1650 °С) and FeMg-Sr-O (for the temperature 1600 °С). The maximum deoxidizing ability of strontium in liquid iron was determined. It was established that in comparison with magnesium, strontium is a weaker deoxidizer.