Phase Equilibria and Thermodynamic Properties of the CaO-MnO-Al2O3-SiO2 System by Critical Evaluation, Modeling and Experiment

Abstract

A complete literature review, critical evaluation and thermodynamic modeling of phase diagrams and thermodynamic properties of the CaO-MnO-Al 2 O 3 -SiO 2 system at 1 bar pressure are presented. A few new quaternary liquidus measurements are also reported. The modeling is based solely upon model parameters obtained by critical evaluation and optimization of the four ternary subsystems. The predicted quaternary properties and phase diagrams are in very good agreement with measurements. Complex phase relationships are elucidated and discrepancies among the data are resolved. The database of model parameters can be used along with software for Gibbs energy minimization in order to calculate any phase diagram section or thermodynamic property from 25°C to above the liquidus at all compositions.KEY WORDS: solution thermodynamics; CaO-MnO-Al 2 O 3 -SiO 2 system; manganese alloy production; phase equilibria.es, but also equilibria between liquid slags and manganese alloys, were considered.In a few cases, there was disagreement between reported and calculated liquidus compositions. A few key experiments were thus carried out as part of the present study in order to resolve this conflict. It was found that the results verified the model calculations.The thermodynamically consistent phase diagram sections, calculated from the model parameters, elucidate the complex phase relationships in this system, and phase equilibria are predicted in regions of temperature and composition where no measurements have been reported.All thermodynamic calculations were performed with the FactSage thermodynamic computing system. 1) Phase equilibria are calculated by global Gibbs energy minimization. By coupling the presently developed database with other evaluated F*A*C*T databases for metallic solutions, gases, etc., FactSage can be used to compute complex slag/ metal/solid/gas equilibria. For example, equilibrium between CaO-MnO-SiO 2 -Al 2 O 3 inclusions and alloy phases can be simulated and studied. Examples of applications to inclusion engineering of Mn/Si deoxidized steel will be presented elsewhere. 7) Thermodynamic ModelsThe thermodynamic properties and phase equilibria of all binary and ternary sub-systems of the CaO-MnOAl 2 O 3 -SiO 2 quaternary system have been critically evaluated by the authors, [2][3][4]8,9) and optimized model parameters have been obtained which reproduce all available binary and ternary data within error limits.The following solution phases (phases of variable composition) are found in the CaO-MnO-Al 2 O 3 -SiO 2 quaternary system [2][3][4]8,9) : (i) slag (molten oxide phase), CaO- Liquidus projections of the four ternary sub-systems, calculated from the previously optimized model parameters, are shown in Fig. 1.For the molten oxide (slag) phase, the Modified Quasichemical Model 10,11) was used. This model has been recently further developed and summarized.12,13) This model takes into account short-range-ordering by consider- ing second-nearest-neighbor pair exchange reactions. Although manganese can exist i...

Thermodynamics of the MnO–FeO–MnS–FeS–SiO2 System at SiO2 Saturation under Reducing Condition: Immiscibility in the Liquid Phase

“…Such experimental technique has been successfully applied to the investigation of phase equilibria of both oxide systems [16][17][18][19][20][21] and sulfur-containing systems. 6,15,22,23) The MnO (99.9 mass pct., Kosundo), MnS (99.9 mass pct., Kosundo), FeO (99.9 mass pct., Kosundo), FeS (99.9 mass pct., Kosundo), and SiO 2 (99.9 mass pct., Kosundo) were dried at 110°C, and weighed in the desired proportions.…”

Inclusions Chemistry for Mn/Si Deoxidized Steels: Thermodynamic Predictions and Experimental Confirmations

“…This disagreement is not immediately explainable, but tentatively attributed to uncertainty of chemical analysis of low concentration of Si. It should be noted that the thermodynamic database used in the present computa- Table 2. tions was optimized by separate studies by the present authors 21) and Jung et al 30) Therefore, the calculation results presented in this paper are not a fitting, but solely prediction. Taking into account genetic uncertainties which are difficult to avoid in this type of experimental work, some data scatter shown in Fig.…”

“…The details of this model are described in detail elsewhere. 31,32) All model parameters for CaOMnO-SiO 2 -Al 2 O 3 systems were already optimized by the present authors 21) and the details of thermodynamic optimization of this system and model parameters are described elsewhere. 21) …”

“…Mn/Si deoxidized steel is chosen as the target steel, since it usually contains both liquid and solid inclusions during processing. For thermody-namic computations, a thermodynamic database for slag and inclusion, which was optimized by the present authors, [19][20][21] was used, and all calculations were performed using the FactSage thermochemical software. 22) …”

Subsolidus Phase Relations in the CaO–SiO₂–Nb₂O₅–La₂O₃ Quarternary System at 1273 K

“…[4][5][6][7][8][9][10][11][12] In the present work, the equilibrium phase relations in the CaO-SiO 2 -Nb 2 O 5 -La 2 O 3 system within the specified region were experimentally determined using the high-temperature equilibrium experiment followed The lack of phase diagrams and other related thermodynamic information for the silicate slag system with additions Nb and REE seriously restrict the comprehensive utilization of REE-Nb-Fe ore deposit resources in China. In this study, the equilibrium phase relations in the CaO-SiO 2 -Nb 2 O 5 -La 2 O 3 quarternary system at 1 273 K and 1 473 K were investigated experimentally using the high-temperature equilibrium experiment followed by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS …”