Analysis of the complex deoxidation of carbon steel melts

The joint complex deoxidation of carbon steel melts is analyzed. A procedure is proposed to calculate the equilibrium oxygen concentration in a melt. Rail steel is used as an example to study the joint complex deoxidation of a melt by aluminum and silicon. Mullite (2Al₂O₃ · 3SiO₂) and kyanite (Al₂O₃ · SiO₂) are considered as the reaction products. Thermodynamic calculations demonstrate that the deoxidizing capacity of aluminum is increased in the presence of silicon in a melt. In this case, a substantial increase in the deoxidizing capacity in the concentration range 0.001–0.1 wt % Al is achieved when kyanite (Al₂O₃ · SiO₂) forms in the reaction products. The results of laboratory and industrial experiments on complex deoxidation are shown to agree well with the calculated data. These results demonstrate that the proposed calculation procedure can be recommended to determine the equilibrium oxygen concentration in a melt in the presence of several deoxidizing elements.     

Thermodynamics of manganese distribution between liquid iron and the CaO–Al2O3–SiO2–FeO–MnO system

The thermodynamics of distribution of constituents between liquid iron and the CaO–Al₂O₃–SiO₂–FeO–MnO system at 1600°C was studied using electrochemical indication of the equilibrium partial pressure of oxygen in both phases. The results show that oxidation potential of the Fe(l)–CaO–Al₂O₃–SiO₂–FeO–MnO system, expressed in terms of log p(O₂), is directly proportional to log (x(MnO) · x(FeO)/w| Mn |). Manganese distribution coefficient, L'_mn, in intersection CaO/Al₂O₃ = 1 decreases with increasing slag basicity expressed in terms of activity a(CaO) or 1/γ(MnO). Experimentally determined equilibrium constant K_Mn/Fe is equal to 2.7 for 1600°C. The number of exchanged electrons between Fe-O-Mn-Si electrode and the slag approaches the theoretical value.     

Phase equilibrium studies in the “MnO”-Al2O3-SiO2 system

Phase relations and the liquidus surface in the system “MnO”-Al₂O₃-SiO₂ at manganese-rich alloy saturation have been investigated in the temperature range from 1373 to 1773 K. This system contains the primary-phase fields of tridymite and cristobalite (SiO₂); mullite (3Al₂O₃·2SiO₂); corundum (Al₂O₃); galaxite (MnO·Al₂O₃); manganosite (MnO); tephroite (2MnO·SiO₂); rhodonite (MnO·SiO₂); spessartine (3MnO·Al₂O₃·SiO₂); and the compound MnO·Al₂O₃·2SiO₂.     

Formation and Evolution Mechanism of the Inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in Seamless Steel Tube Steel

Herein, the formation and evolution mechanism of inclusions of Al₂O₃·SiO₂·CaO and Al₂O₃·SiO₂·CaO·MgO in seamless steel tube steel are investigated. In the long strip defects on the longitudinal cross section of the steel tube after the rolling bar piercing, the defect is mainly formed by Al₂O₃·SiO₂·CaO·MgO inclusions and Al₂O₃·SiO₂·CaO·inclusions dotted with·CaS inclusions after the rolling. The typical inclusions in the different steelmaking stages are mainly composed of CaS, Al₂O₃·(SiO₂), CaO·(SiO₂), MnS·(TiN), Al₂O₃·SiO₂·CaO·(CaS)·(MnS), Al₂O₃·SiO₂·CaO·MgO·(MnO), Al₂O₃·SiO₂·CaO·MgO·(CaS)·(MnS), etc. In the billet, the average sizes of Al₂O₃·SiO₂·CaO-based and Al₂O₃·SiO₂·CaO·MgO-based inclusions are much larger than those of the other types of inclusions. Part of SiO₂ in the deoxidized products SiO₂ can be reduced by [Al], resulting in the formation of the Al₂O₃·SiO₂ composite inclusions. The SiO₂ in Al₂O₃·SiO₂ inclusions can continuously be reduced by the dissolved [Ca] to form the Al₂O₃·SiO₂·CaO composite inclusions. The SiO₂ in the Al₂O₃·SiO₂·CaO inclusions can be reduced by the dissolved [Mg] to form the Al₂O₃·SiO₂·CaO·MgO composite inclusions. Another formation process of Al₂O₃·SiO₂·CaO·MgO inclusions is the entrapment of ladle slag in the vacuum degassing (VD) stage, due to the strong agitation of the rising Ar bubbles in the vacuum condition of the VD stage.     

Thermodynamics of iron-manganese aluminate spinel inclusions in steel

The effect of manganese on the residual oxygen concentrations of liquid iron in equilibrium with alumina saturated iron-manganese aluminate spinel solid solutions was investigated at temperatures of 1550, 1600, and 1650°C. The relationship between the equilibrium concentrations of manganese and oxygen in iron melts containing up to 6 wt pct manganese has been established. The compositions of the spinel deoxidation products, (Fe _x Mn _j-x ) O · Al₂O₃, which were formed during equilibration with the iron melts were determined with electron microprobe and neutron activation analysis. From these results, new thermodynamic data pertaining to galaxite formation reactions have been derived and their implications with respect to the deoxidation of aluminum semikilled, silicon free, steels have been discussed.     

Thermodynamics of iron alumino-chromite spinel inclusions in steel

The effect of chromium on the oxygen concentration of iron melts in equilibrium with various spinel reaction products has been determined. Alumina crucibles were used and experiments were performed at 1550, 1600, and 1650°C. Thermodynamic relationships between the equilibrium concentrations of chromium and oxygen in the iron melts have been established for chromium concentrations ranging up to 20 wt pct. Results from X-ray and electron microprobe analyses for the composition of the deoxidation products, together with solute activity relationships, indicate that the composition of the equilibrium spinel phase changes progressively from iron aluminate in the absence of chromium, through a series of aluminate-chromite solid solutions, FeO (Al _x Cr_1−x )₂O₃, (<0.5 pct chromium), to a complex chromite spinel, Fe₂Cr₇O₁₂, (0.5 to 3 pct chromium), and finally chromium oxide, Cr₃O₄ (>3 pct chromium). Deoxidation diagrams have been constructed and the effects of small amounts of alloying elements on the deoxidation behavior of aluminum interpreted in terms of buffered reactions which maintain oxygen concentrations in the melt at levels in excess of those normally associated with aluminum killed steel in equilibrium with alumina alone.     

Selective Oxidation of TWIP Steel During Continuous Annealing

The selective oxidation of Al‐free and Al‐added TWIP steel after full austenitic annealing at 800°C in a N₂ + 10%H₂ gas atmosphere with a dew point of ?17°C was investigated by means of transmission electron microscopy. A thick MnO layer was formed at the surface of Al‐free TWIP steel after the recrystallization annealing. Small crystalline c‐xMnO · SiO₂ (x > 2) particles and amorphous a‐xMnO · SiO₂ (x < 0.9) particles were found at the MnO/steel interface. In the subsurface, the Mn depletion resulted in the formation of a narrow ferrite layer. The annealing of the Al‐added TWIP steel also resulted in the formation of a thick MnO surface layer. At the MnO/steel interface, Kirkendall voids were formed between the amorphous a‐xMnO · SiO₂ (x < 0.9) oxide and crystalline c‐xMnO · Al₂O₃ oxide in the case of Al‐added TWIP steel. In the subsurface, a thin layer was depleted of Mn and the original austenite had transformed into ferrite. Internal oxidation of Al to Al₂O₃ and the formation of crystalline c‐xMnO · Al₂O₃ (x > 1) compound oxide particles were found to occur at the grain boundaries of the Mn‐depleted ferritic zone. The present contribution highlights the implications of the selective oxidation of TWIP steels for their processing in continuous annealing and continuous hot dip galvanizing lines.     

Optimization of Intensified Silicon Deoxidation

For demanding wire applications steel cleanliness should be very high and the inclusions inevitably found in steel should be harmless. This means strict control of inclusions' size, quantity, and composition, pursuing deformable inclusions in rolling conditions. Primary inclusions are formed during steel treatment in the ladle. Most of these are removed to the ladle slag or on the lining. However, the rest of the inclusions still remain through the successive process stages, and some new inclusions are formed during casting and solidification. Conventionally, deformable inclusions are produced by Si–Mn deoxidation resulting in MnO–SiO₂–Al₂O₃ inclusions. This leaves, however, the oxygen content too high for demanding applications. In order to get really clean steel, the Si deoxidation needs to be strengthened by lowering the activity of SiO₂ forming in steel. This can be done by bringing the steel in intimate contact with a slag containing SiO₂–MnO–Al₂O₃ and additionally CaO and some MgO. With this kind of intensified Si deoxidation it is possible to produce steels with low oxygen content having inclusions that will elongate at rolling. In this paper thermodynamic examination of potential slag systems and compositions to equilibrate with steels having medium carbon and high silicon were scrutinized. The optimal slag composition for producing low‐O steels with deformable inclusions was evaluated by using FactSage thermodynamic calculation program. The lowest SiO₂ activities at the region in which slag is still liquid at 1400°C, can be found when slag composition is approximately 36–40 wt% SiO_2, 6–18 wt% Al₂O_3, 30–40 wt% CaO, 6–8 wt% MgO, and 2–4 wt% MnO. Industrial heats using intensified Si deoxidation and slag based inclusion engineering were produced in a steel mill with 60 tons heat size. Inclusions and slag compositions were in satisfactory accordance with the theoretical examinations, though some scattering was discovered.     

Calcium Modification of Spinel Inclusions in Aluminum-Killed Steel: Reaction Steps

Calcium treatment is a well-established way to modify solid alumina inclusions to liquid or partially liquid calcium aluminates. Spinels (Al₂O₃·xMgO) can also form in liquid steel after aluminum deoxidation. Like alumina, the spinels can be modified readily to liquid inclusions by a calcium treatment. The modification of spinels was studied by observing the transient evolution of inclusions, in laboratory and industrial heats. Spinel modification involves the preferential reduction of MgO from the spinel, with Mg dissolving in the steel, and it proceeds through transient calcium sulfide formation, just like in the case of alumina inclusions. Because magnesium dissolves in steel after the calcium treatment of spinels, the reoxidation of the melt will produce new spinels.     

Reduction of MnO from molten slags with liquid steel of high carbon content

This work estimated the reduction of MnO in slags of the CaO‐SiO₂‐FeO‐CaF₂‐MnO system and liquid steel with the initial composition (mass contents) 0.75 %Mn, 0.16 % Si and 0.5 to 2.0 % C, as an alternative to introducing Mn to the steel melt. The slag basicities (CaO/SiO₂) In the experiments were 2 and 3. MnO was obtained from manganese ore. The experiments were carried out in an open 10 kg induction furnace using Al₂O₃‐based refractory at 1873 K. The oxygen potential was measured throughout the experiments with a galvanic cell (ZrO₂‐solid electrolyte with a Cr/Cr₂O₃ reference electrode). The MnO reaction mechanism was analysed in terms of the slag basicity, the silicon and the initial carbon contents in the melt. The rate and the degree of MnO reduction were found to increase with the increasing of initial carbon content; however, the effect of slag basicity was less important. A kinetic analysis of the process was performed using a coupled reaction model.     

Properties investigation of CaO–Al2O3–SiO2–Li2O–B2O3–Ce2O3 mould flux with different w(CaO)/w(Al2O3) for heat-resistant steel continuous casting

The new CaO–Al₂O₃–SiO₂–Li₂O–B₂O₃–Ce₂O₃ mould flux was devised to realise smooth continuous casting of Ce-bearing heat-resistant steel. The new devised mould flux was based on calcium-aluminate system, so the w(CaO)/w(Al₂O₃) has great influence on the properties of the slag, which is similar to the basicity in the silicate system. The melting temperature, viscous properties, slag structure and crystalline phases with different w(CaO)/w(Al₂O₃) were investigated. The melting temperature of the mould flux could remain relatively steady with w(CaO)/w(Al₂O₃) in the range of 1.0–1.82. The main network former in the new slag was [AlO₄]-tetrahedron. The network formed by [AlO₄]-tetrahedron was destroyed by increasing w(CaO)/w(Al₂O₃), the viscosity decreased consequently. The mould flux show weaker crystallisation tendency with increasing w(CaO)/w(Al₂O₃). When the temperature decreased to 1100°C, the change of the fully crystallised phases with increasing w(CaO)/w(Al₂O₃) was as follows: Li₂O·Al₂O_3?+?2CaO·Al₂O₃·SiO_2?→?Li₂O·Al₂O_3?→?Li₂O·Al₂O_3?+?3CaO·Al₂O_3?+?CaCeAlO₄.     

Preparation of metallic iron powder from red mud by sodium salt roasting and magnetic separation

Red mud has become one kind of the most hazardous solid waste. In order to recover iron from red mud, the technology of sodium salt roasting and magnetic separation was developed. During the reduction roasting, additives (Na₂SO₄ and CaO) reacted with SiO₂ and Al₂O₃ of red mud, forming NaO?Al₂O₃?2SiO₂, 2CaO?Al₂O₃?SiO₂, 12CaO?7Al₂O₃, CaO?Al₂O₃ and 2CaO?SiO₂, which ameliorates the separation between iron and alumina during magnetic separation. Meanwhile, sodium sulphate also improved the growth of iron grains, increasing the iron grade and iron recovery. The metallic iron powder obtained contained 90·28 wt-%TFe (representing a metallisation degree of 94·87 wt-%) at 92·14 wt-% iron recovery under the optimum conditions, which can be briquetted as a burden material for steel making by electric arc furnace to replace scrap.

La boue rouge est considérée comme l’un des déchets solides les plus nocifs. Afin de récupérer le fer de la boue rouge, on a développé la technologie du grillage au sel de sodium et de la séparation magnétique. Lors du grillage réducteur, les produits d’addition (Na₂SO₄ et CaO) réagissent avec le SiO₂ et l’Al₂O₃ de la boue rouge, formant le NaO?Al₂O₃?2SiO₂, le 2CaO?Al₂O₃?SiO₂, le 12CaO?7Al₂O₃, le CaO?Al₂O₃ et le 2CaO?SiO₂, ce qui améliore la séparation entre le fer et l’oxyde d’aluminium lors de la séparation magnétique. Pendant ce temps, le sulfate de sodium a également amélioré la croissance des grains de fer, augmentant ainsi la qualité du fer et sa récupération. La poudre de fer métallique obtenue contenait 90·28% en poids de FeT (représentant un degré de métallisation de 94·87% en poids), avec une récupération de fer de 92·14% en poids en conditions optimales, qui pouvait être mis en briquettes comme matériau de lit de fusion pour la production de l’acier au four électrique à arc pour remplacer la ferraille.     

Thermodynamic estimation on the reduction behavior of iron-chromium ore with carbon

The thermodynamics for reduction of iron-chromium ore by carbon is discussed. The thermodynamic properties of iron-chromium ore were evaluated from our previous work on the activities of constituents in the FeO·Cr₂O₃-MgO·Cr₂O₃-MgO·Al₂O₃ iron-chromite spinel-structure solid solution saturated with (Cr, Al)₂O₃, and those of the Fe-Cr-C alloy were estimated by a sublattice model. The stability diagrams were drawn for carbon reduction of pure FeO · Cr₂O₃, (Fe_0.5Mg_0.5)O·(Cr_0.8Al_0.2)₂O₃ iron-chromite solid solution, and South African iron-chromium ore. The evaluated stability diagrams agreed well with the literature data. It was concluded that the lowest temperature for reduction of FeO · Cr₂O₃ in the iron-chromium ore was 1390 K and a temperature higher than 1470 K would be necessary to reduce Cr₂O₃ in MgO·(Cr,Al)₂O₃ in the prereduction process of iron-chromium ore. The composition of liquid Fe-Cr-C alloy in equilibrium with iron-chromium ore was also estimated under 1 atm of CO at steelmaking temperature. The predicted metal composition showed reasonable agreement with the literature values.     

Solubility of oxygen in Fe–Co melts containing titanium

Solutions of oxygen in Fe–Co melts containing titanium are subjected to thermodynamic analysis. The first step is to determine the equilibrium reaction constants of titanium and oxygen, the activity coefficients at infinite dilution, and the interaction parameters in melts of different composition at 1873 K. With increase in cobalt content, the equilibrium reaction constants of titanium and oxygen decline from iron (logK(FeO · TiO₂) =–7.194; logK(TiO₂) =–6.125; logK(Ti₃O₅) =–16.793; logK(Ti₂O₃) =–10.224) to cobalt (logK(CoO · TiO₂) =–8.580; logK(TiO₅) =–7.625; logK(Ti₃O₅) =–20.073; logK(Ti₂O₃) =–12.005). The titanium concentrations at the equilibrium points between the oxide phases (Fe, Co)O · TiO₂, TiO₂, Ti₃O₅, and Ti₂O₃ are determined. The titanium content at the equilibrium point (Fe, Co)O · TiO₂ ? TiO₂ decreases from 1.0 × 10^–4% Ti in iron to 1.9 × 10^–6% Ti in cobalt. The titanium content at the equilibrium point TiO₂?Ti₃O₅ increases from 0.0011% Ti in iron to 0.0095% Ti in cobalt. The titanium content at the equilibrium point Ti₃O₅ ? Ti₂O₃ decreases from 0.181%Ti in iron to 1.570% Ti in cobalt. The solubility of oxygen in the given melts is calculated as a function of the cobalt and titanium content. The deoxidizing ability of titanium decline with increase in Co content to 20% and then rise at higher Co content. In iron and its alloys with 20% and 40% Co, the deoxidizing ability of titanium are practically the same. The solubility curves of oxygen in iron-cobalt melts containing titanium pass through a minimum, whose position shifts to lower Ti content with increase in the Co content. Further addition of titanium increases the oxygen content in the melt. With higher Co content in the melt, the oxygen content in the melt increases more sharply beyond the minimum, as further titanium is added.     

Silico-ferrite of Calcium and Aluminum (SFCA) Iron Ore Sinter Bonding Phases: New Insights into Their Formation During Heating and Cooling

The formation of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter phases during heating and cooling of synthetic iron ore sinter mixtures in the range 298?K to 1623?K (25?°C to 1350?°C) and at oxygen partial pressure of 5?×?10^?3 atm has been characterized using in situ synchrotron X-ray diffraction. SFCA and SFCA-I are the key bonding phases in iron ore sinter, and an improved understanding of their formation mechanisms may lead to improved efficiency of industrial sintering processes.?During heating, SFCA-I formation at 1327?K to 1392?K (1054?°C to 1119?°C) (depending on composition) was associated with the reaction of Fe₂O₃, 2CaO·Fe₂O₃, and SiO₂. SFCA formation (1380?K to 1437?K [1107?°C to 1164?°C]) was associated with?the reaction of CaO·Fe₂O₃, SiO₂, and a phase with average composition 49.60, 9.09, 0.14, 7.93, and 32.15?wt pct Fe, Ca, Si, Al, and O, respectively. Increasing Al₂O₃ concentration in the starting sinter mixture increased the temperature range over which SFCA-I was stable before the formation of SFCA, and it stabilized SFCA to a higher temperature before it melted to form a Fe₃O₄?+?melt phase assemblage (1486?K to 1581?K [1213?°C to 1308?°C]). During cooling, the first phase to crystallize from the melt (1452?K to 1561?K [1179?°C to 1288?°C]) was an Fe-rich phase, similar in composition to SFCA-I, and it had an average composition 58.88, 6.89, 0.82, 3.00, and 31.68?wt pct Fe, Ca, Si, Al, and O, respectively. At lower temperatures (1418?K to 1543?K [1145?°C to 1270?°C]), this phase reacted with melt to form SFCA. Increasing Al₂O₃ increased the temperature at which crystallization of the Fe-rich phase occurred, increased the temperature at which crystallization of SFCA occurred, and suppressed the formation of Fe₂O₃ (1358?K to 1418?K [1085?°C to 1145?°C]) to lower temperatures.     

Thermodynamics on the formation of spinel (MgO·Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) inclusion in liquid iron containing chromium

The stability diagram of MgO, spinel solid solution (MgO·(Al _X Cr_1−X )₂O₃), and sesquioxide solid solution ((Al _Y Cr_1−Y )₂O₃) as a function of Mg, Al, and O contents at a constant chromium content (18 mass pct) in liquid iron is drawn at 1873 K. The interaction parameters between Mg and other solutes (Al, Cr, Ni, Ti, Si, and C) are determined by the experimental method, which assures equilibrium between Mg vapor and liquid iron, were applied to calculate the diagram. Titanium deoxidation is not recommended for the prevention of spinel formation, because Ti accelerates Mg dissolution from refractory or slag due to its high affinity for Mg (e _Mg ^Ti = − 0.64). The standard Gibbs free energies of formation for the three inclusions (periclase, spinel, and sesquioxide solid solutions) and the tielines between two solid solutions were calculated with the aid of the regular solution model and the thermochemical F*A*C*T database computing system, respectively. The phase stability regions and oxygen content in steel for the current Fe-Mg-Al-Cr (18 mass pct)-O system are compared with those of the previous non-Cr system. Detailed information on the spinel composition according to Mg and Al contents is also available from the present stability diagram.     

Thermodynamics of oxygen solutions in the complex reduction of Fe-Co melts

Thermodynamic analysis of the complex reduction of metal melts is considered. The proposed analytical method identifies the influence of the weaker reducing agent in amplifying the effect of the stronger reagent. The curves of oxygen solubility pass through a minimum. Analysis of the extremal curves of oxygen concentration in the melt as a function of the content of reducing agents yields a formula for the content of the stronger reducing agent such that the oxygen concentration is minimal. Thermodynamic analysis of the combined influence of aluminum and silicon on the oxygen solubility in Fe-Co melts indicates that the reaction products may contain both mullite (3Al₂O₃ · 2SiO₂) and kyanite (Al₂O₃ · SiO₂). The presence of silicon in the melt intensifies the reducing action of aluminum: slightly when mullite is formed and significantly when kyanite is formed. When kyanite is formed, the curves of oxygen solubility pass through a minimum, whose position depends on the aluminum content in the melt but not on the silicon content. The aluminum content at the minimum declines slightly from iron to cobalt, as for Fe-Co-Al systems. Further addition of aluminum elevates the oxygen concentration. The formation of the compounds Al₂O₃, 3Al₂O₃ · 2SiO₂, Al₂O₃ · SiO₂, and SiO₂ is investigated as a function of the Al and Si content in the melt.     

Activities of SiO2 and Al2O3 and activity coefficients of FetO and MnO in CaO-SiO2-Al2O3-MgO slags

The activities of SiO₂ and Al₂O₃ in CaO-SiO₂-Al₂O₃-MgO slags were determined at 1873 K along the liquidus lines saturated with 2CaO · SiO₂, 2(Mg,Ca)O · SiO₂, MgO, and MgO · Al₂O₃ phases using a slag-metal equilibration technique. Based on these and previous results obtained in ternary and quaternary slags, the isoactivity lines of SiO₂ and Al₂O₃ over the liquid region on the 0, 10, 20, 30, and 40 mass pct Al₂O₃ planes and those on the 10 and 20 mass pct MgO planes were determined. The activity coefficients of Fe _t O and MnO, the phase boundary, and the solubility of MgO were also determined.     

Thermodynamic conditions for inclusions modification in calcium treated steel

The presented paper discussed the fundamental or common thermodynamical relations between calcium-treated aluminium-killed molten steel and non-metallic inclusions. The phase and chemical analyses of inclusions have proven that the correctness of calcium addition can be confirmed and that the analysis of those phenomena can show the effects of previous calcium treatment of aluminium-killed steel. To make the process of manufacturing quality steel successful the factor affecting the necessary calcium addition should be taken into consideration already during the process. Steel, containing too much calcium could have CaS inclusions with a high melting point, while too low contents of calcium cause unsatisfactory modification of solid alumina inclusions to complex liquid calcium-aluminate inclusions. This research included the examination of thermodynamic relations in calcium addition and its reactions with solid Al₂O₃ inclusions. A detailed analysis of the CaO–Al₂O₃ binary system established the modification of solid alumina inclusions via the following intermediate phases: CaO · 6Al₂O₃, CaO · 2Al₂O₃, CaO · Al₂O₃ and liquid phase 12CaO · 7Al₂O₃ and finally again solid CaO, at 1873 K (1600°C). The investigation discusses the further research engaged in consideration of CaO- and Al₂O₃-activities change in each of the quoted intermediate phases. The system as a whole includes details of oxygen activities.     

Determination of Gibbs Free Energy of Formation of MnV2O4 Solid Solution at 1823 K (1550 °C)

The Gibbs free energy of formation of MnV₂O₄ solid solution saturated with either MnO or V₂O₃ was experimentally determined at 1823 K (1550 °C) by employing a chemical equilibrium technique. The MnV₂O₄ solid solution mixed with MnO or V₂O₃ was brought to equilibrium with either liquid Fe or liquid Cu to measure equilibrium compositions of the liquid metal. Using the available thermodynamic parameters such as Wagner’s interaction parameter for liquid Fe or Gibbs free energy of liquid solution composed of Cu-Mn-V-O, the Gibbs free energy of formation of the MnV₂O₄ solid solution from constituent oxides (MnO and V₂O₃) was then determined to be: MnO(s) + V₂O₃(s) = MnV₂O₄(MnO-satd.): $\Updelta g^\circ_{{\rm f,MnV}_{2}{\rm O}_{4}}$ = ?31.4 ± 2 (kJ/mol); MnO(s) + V₂O₃(s) = MnV₂O₄(V₂O₃-satd.): $\Updelta g^\circ_{{\rm f,MnV}_{2}{\rm O}_{4}}$ = ?37.8 ± 2 (kJ/mol). The $\Updelta g^\circ_{{\rm f,MnV}_{2}{\rm O}_{4}}$ values were independent of the oxygen partial pressure within the range from 2.0 × 10^?12 to 6.3 × 10^?11, employed in the current study.