Papers by Keyword: Thermodynamic Modeling

Abstract: Thermodynamic modeling of phase equilibria in a liquid metal of Fe–La–Ce–O system at 1600 °С, using the technique of constructing the solubility surfaces for the components of a metal, was carried out. The calculation technique allowed assessing the depth of liquid iron de-oxidation at a complex use of lanthanum and cerium as deoxidizing agents. Also, diagrams of de-oxidants’ consumption for one ton of liquid oxygen-containing iron were calculated in the course of the work. Carrying out a calculation of the solubility surfaces for the components of a metal required simulation of phase diagrams of the following oxide systems: FeO–La₂O₃–Ce₂O₃, FeO–CeO₂–La₂O₃, CeO₂–La₂O₃–Ce₂O₃. The obtained results might be of interest for optimization of the use of rare-earth metals in steelmaking technology.

Abstract: The results of thermodynamic modeling of the effect of aluminum (0.005–0.1%), contained in the metal at constant silicon concentrations (0.2%) and carbon (0.1%) on the boron reduction process from the slag of the system CaO-SiO₂-MgO-Al₂O₃-B₂O₃ basicity (CaO)/(SiO₂) equal to 5 in the temperature range 1400–1700 °C, in steps of 50 °C are presented. For modeling, the software complex HSC Chemistry 6.12 developed by Outokumpu Research Oy (Finland) was used. The calculations using the Equilibrium Compositions module at a gas-phase pressure of 1 atm, containing 2.24 m³ of N₂ (gas) as a neutral additive were performed. The obtained simulation results indicate the thermodynamic possibility of boron reduction from the slag of the CaO-SiO₂-MgO-Al₂O₃-B₂O₃ system by silicon and aluminum, whose concentration in the metal is insignificant – 0.2 and 0.005–0.1%, respectively. It was found that an increase in the initial aluminum content in the steel promotes an increase in the concentration of reduced boron in the metal with a content of 4% B₂O₃ and a given temperature. Thus, at a process temperature of 1650 °C, an increase in the initial aluminum content from 0.005 to 0.1% made it possible to increase the boron concentration in the metal by 28.5%. The results of thermodynamic modeling characterizing the effect of temperature on the degree of boron reduction at different aluminum contents are presented. Experiments on the inter-phase distribution of boron between the slag of the CaO-SiO₂-MgO-Al₂O₃-B₂O₃ system and the metal were carried out in a high-temperature Tamman resistance furnace. Low-carbon steel containing 0.005% Al was used. It was shown that aging of the metal under the slag containing 4.3% of B₂O₃ is accompanied by reduction of boron, the amount of which in the finished steel is 0.0089%. The coefficient of boron assimilation (K_B) is 5.8%, which is in principle correlated with the results of thermodynamic modeling. The obtained results of thermodynamic modeling and experimental data showed that it is possible in principle to directly microlite boron steel by reducing it with aluminum and silicon contained in the metal.

Abstract: A method for calculation of the diagrams of steel deoxidation and modification by calcium, magnesium, aluminum and boron was developed. The coordinates of the liquidus surfaces of the oxide systems B₂O₃–Al₂O₃–MgO, B₂O₃–Al₂O₃–CaO, B₂O₃–MgO–CaO were found at 1873 K. The energy parameters were determined for the theory of subregular ionic solutions of the studied oxide systems. The coordinates of the solubility surfaces for the systems Fe–Mg–Al–B–O, Fe–Ca–Al–B–O, Fe–Mg–Ca–Al–B–O were calculated. The effect of the total pressure on solubility of magnesium and calcium in liquid iron was studied. The activity of the components of the metallic melt was calculated using the first-order interaction parameters (Wagner's theory). The activities of the components of solid solutions (oxides and spinels) were equated with their molar fractions. It was shown that during extensive refining of metal from the oxygen, only a small fraction of boron oxidizes and these oxides form fraction of the oxide melts. The major non-metallic oxide inclusions were magnesia spinel, calcium bialuminate and liquid oxide formations. The "free" boron was dissolved in liquid metal in amounts which were in equilibrium with oxide phases.

Abstract: 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.

Abstract: The Na–Cu and Na–K systems present a big interest for the study due to the use of liquid sodium and melt of sodium and potassium in the nuclear industry as a coolant in nuclear reactors. In the present work, thermodynamic modeling of phase equilibria in the Na–Cu and Na–K systems is carried out, based on the available published experimental data. This modeling was done using the “FactSage” software package (version 7.0). The set of Redlich–Kister equation parameters was obtained, that allows to describe the dependence of Gibbs energy from composition and temperature for solutions that can be formed in the studied systems. Phase diagrams (T–x diagrams) of the investigated systems were calculated.

Abstract: Using rare earth metals as deoxidizers is an efficient way of getting highly deoxidized copper melt required for certain bronzes production. Thermodynamic modeling of phase equilibria in the Cu–La–O system in the temperature range of 1100–1300 °С was performed to assess a possible depth of copper melt deoxidation with lanthanum, and also to determine the resulting oxide phases. During the experimental part of the work, Cu–La–O system metal samples were melted and then studied with the JEOL JSM 6460-LV scanning electron microscope equipped with the energy-dispersive spectrometer providing electron microprobe analysis to specify formed nonmetallic inclusion type.

Abstract: The thermodynamic modeling of alloy systems consisting of stable and metastable phases e.g. high-alloyed mottled cast iron can be problematic. Thermodynamic databases are rather well-developed for low, medium and high alloyed steels (e.g. HSS) but the application of those databases is not yet very common for high-alloyed (mottled) cast irons. The Thermo-Calc software together with the TCFE7 database is used to calculate isopleth and property diagrams, using the CALPHAD method. Additionally Scheil-Gulliver calculations are performed to simulate the effects of microsegregation during solidification. The results from the thermodynamic calculations are compared with measurements on own samples and with literature values. Those measurements include quantitative light-optical analysis, SEM with BSE detector, EDX measurements for the distribution of the alloying elements as well as XRD and DSC measurements. The investigations show the possibilities which are offered by thermodynamic calculations for high-alloyed mottled cast iron as well as the limitations and the compromises which have to be taken into account when calculating stable and metastable phases existing next to each other.

Abstract: The effect of aluminum oxide additives on the phase relations in borosilicate glass based on the system Na₂O–B₂O₃–SiO₂ was investigated by means of the thermodynamic modeling. The phase equilibrium realized in this system was obtained using software package "FactSage" (version 6.4). The effect of aluminum oxide additives on the composition of the crystalline phases and residual melt formed during the cooling of borosilicate melts has been studied. The analysis of the diagrams has allowed establishing the regions of partial and complete melting of the substance depending on the chemical composition. The analysis allows determining the temperature of the melting process of a glassy matrix material. The combination of stable borate, silicate, mixed borosilicate, aluminosilicate and boroaluminate phases were determined for a wide range of compositions and temperatures. Boundaries of the regions formation of these phases depending on the composition and the temperature were determined. It allows assessing the prospects for absorption of elements in radioactive waste immobilization. The modeling of the crystallization melts formed in the studied systems was performed.

Abstract: The paper presents a method for increasing stainless steel 04Cr25Ni6NMo3 corrosion-resistant properties. An increased corrosion resistance develops due to the stabilization of the structure of titanium steel. The titanium additive changes the phase composition of the carbide phase and enhances the corrosion-resistant properties. Change of the phase composition of the carbide phase is analysed by means of the thermodynamic modelling.

Abstract: The aim of this work is conducting theoretical and experimental research of the processes and modes of high-temperature processing of steel slags for more complete extraction of the metal component. "FactSage" software complex (version 6.4) was used to execute the thermodynamic modeling of the processes occurring during the recovery of metals from steelmaking slags. The experimental research included experiments on solid-phase and liquid-phase recovery of slag samples at the temperatures of 1000 – 1500 °C. The results of thermodynamic modeling and experimental high-temperature slag processing allows speaking about the advisability of preliminary solid-phase recovery slag in the atmosphere of carbon monoxide with subsequent high-temperature (liquid phase) recovery to obtain separate metal fractions.