Thermodynamic Optimization of the CaO-MgO-Al2O3-SiO2-CrOx System containing Cr6+ oxides

Abstract

To understand complex chemical reactions in many ceramic and metallurgical processes, the development of an accurate thermodynamic database is important. The CALPHAD (CALculation of PHAse Diagram) approach is one of the most efficient way to make thermodynamic database, which can be early applied to the prediction of complex reactions and phase relations in multicomponent systems. The goal of this study is to make thermodynamic database of Cr6+ containing CaO-MgO-Al2O3-SiO2-CrOx system. That is, the goal of this study is the addition of Cr oxides (Cr2+, Cr3+, and Cr6+ oxidation state in liquid slag) to the current FACT oxide database covering CaO-MgO-Al2O3-SiO2 system. All the phase diagram data and thermodynamic property data of the CaO-MgO-Al2O3-SiO2-CrOx system were critically evaluated and optimized in this study. Cr2+ and Cr3+ containing oxide systems were assessed in the past, but many systems are reoptimized to improve the accuracy of the database. The Gibbs energy of liquid oxide is described using the Modified Quasichemical Model (MQM). Solid solutions are modeled in the consideration of their crystal structure data. The present database can be used to estimate many complex reactions in special steel and stainless steel production. Weathering and corrosion behavior of chromite based refractory could be calculated by using this database.