Thermodynamic Modeling of Isotherms of Oxygen Solubility in Liquid Metal of the Fe–Mg–Al–O System

The thermodynamic modeling of phase equilibria in the liquid metal of the Cu–Na–O, Cu–K–O and Cu–Na–K–O systems in the temperature range of 1100–1300 °С was done. The calculations were performed using the methodology of constructing a surface of component solubility in the metal melt, which does not only allow us to calculate the isotherms of oxygen solubility in the molten metal, but also to link the changes in the composition of such molten metal with quality changes in the composition of the interaction products. The isotherms of the oxygen solubility in the liquid metal of the Cu–Na–O, Cu–K–O and Cu–Na–K–O systems were constructed.

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Thermodynamic modeling of isotherms of oxygen solubility in liquid metal of Fe – Mg – Al – O system

Izvestiya Ferrous Metallurgy ◽

10.17073/0368-0797-2019-8-639-645 ◽

2019 ◽

Vol 62 (8) ◽

pp. 639-645 ◽

Cited By ~ 1

Author(s):

G. G. Mikhailov ◽

O. V. Samoilova ◽

L. A. Makrovets ◽

L. A. Smirnov

Keyword(s):

Solid Solution ◽

Liquid Metal ◽

Liquid Iron ◽

Thermodynamic Modeling ◽

Equilibrium Constants ◽

Oxygen Solubility ◽

Ionic Solutions ◽

Temperature Range ◽

Oxide Melt ◽

Oxide Phases

Studying the interaction between oxygen and magnesium and aluminum dissolved in liquid iron is an important task in order to choose optimal parameters for refining and casting of steels. Relevance of this research is caused by determining the possibility and conditions for formation of unfavorable refractory particles of magnesium oxideand magnesian spinel in a metal melt. In the course of this research, thermodynamic modeling of phase equilibria implemented in liquid metal of such systems as Fe – Mg – O, Fe – Al – O and Fe – Mg – Al – O within the temperature range of 1550 – 1650 °С was carried out. Calculation was made using the technique of constructing the solubility surfaces for the metal components which connects quantitative changes in composition of a liquid metal with qualitative changes in composition of products obtained as a result of interaction of a metallic melt’s components. The modeling method was based not only on using equilibrium constants of reactions occurring between components of the systems under research in the selected temperature range, but also on taking into account the values of interaction parameters of the first order (according to Wagner) of elements in liquid iron. In order to simulate activities of the oxide melt conjugated with the metallic one, approximation of the theory of subregular ionic solutions was used. To model activities of oxides solid solution, approximation of the theory of regular ionic solutions was used. And the theory of ideal ionic solutions was used for the solid solution of spinels. In the course of the work, isotherms of oxygen’s solubility in liquid metal of systems Fe – Mg – O, Fe – Al – O and Fe – Mg – Al – O have been constructed, and regions of thermodynamic stability of oxide phases conjugated with the metallic melt have been determined. In particular, compositions area of a liquid metal which is going to be in equilibrium with the solid solution of spinels | FeAl 2 O 4 , MgAl 2 O 4 | solid solution has been determined for Fe – Mg – Al – O system. Results obtained in the course of thermodynamic modeling have been compared to experimental data.

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THERMODYNAMICS OF THE PROCESSES OF INTERACTION OF LIQUID METAL COMPONENTS IN Fe – Mg – Al – La – O SYSTEM

Izvestiya Ferrous Metallurgy ◽

10.17073/0368-0797-2018-6-460-465 ◽

2018 ◽

Vol 61 (6) ◽

pp. 460-465

Author(s):

G. G. Mikhailov ◽

L. A. Makrovets ◽

L. A. Smirnov

Keyword(s):

Rare Earth ◽

Liquid Metal ◽

Rare Earth Elements ◽

Phase Equilibria ◽

Thermodynamic Modeling ◽

Equilibrium Constants ◽

Rare Earth Metals ◽

Oxide Systems ◽

Metal Melts ◽

Steel Deoxidation

At the present time, rare-earth elements in metallurgy are used in the form of mischmetal – a rare-earth elements natural mixture (with atomic numbers from 57 to 71). It contains about 50 wt. % of cerium. The remaining elements are mainly lanthanum and niobium. The specific composition is determined by the ore deposit. Inconstant composition of the modifier containing rare-earth metals (REM) can significantly reduce its efficiency. Experimentally, for every branded steels composition the ratio of various REMs can’t be selected because of the high costs of obtaining technically pure rare-earth metals. The task of determining the each rare earth element optimum concentrations and complex ligature composition can be solved by thermodynamic modeling. In the framework of thermodynamic modeling, the interaction between magnesium, aluminum and lanthanum with oxygen in liquid iron is presented. And the thermodynamic model of steel deoxidation by these active metals composition is considered. On the basis of available literature data on the phase diagrams of the systems MgO – Al2O3 , MgO – La2O3 and La2O3 – Al2O3 , the coordinates of the invariant equilibria points in the system MgO – La2O3 – Al2O3 were determined. The phase diagram of the system MgO – La2O3 – Al2O3 was constructed. It made possible to establish all phase equilibria realized in the process of deoxidation of steel with magnesium, lanthanum and aluminum and to describe these phase equilibria by chemical reactions equations. The activity of the components in liquid oxide melts was determined using the theory of subregular ionic solutions, which takes into account the dependence of the coordination number of cations on the composition of the oxide melt. The activity of components in metal melts conjugated with oxide systems were determined by Wagner’s theory using the parameters of the first order interaction. Equilibrium constants values for the steel deoxidation reactions are installed indirectly by thermodynamic calculations. On the basis of the obtained data the components solubility surface in the metal melts of Fe – Mg – Al – La – O system was constructed, which allowed to determine the liquid metal composition regions associated with the corresponding oxide phase.

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