Thermodynamics of the oxygen solutions in manganese-containing Fe-Co melts

Thermodynamic analysis of the oxygen solutions in manganese-containing Fe-Co melts has been performed. The equilibrium constants of deoxidation reaction of iron-cobalt melts with manganese, the activity coefficients during infinity dilution, and the interaction parameters in various melts are found. During the deoxidation of manganese-containing Fe-Co melts, the oxide phase contains FeO and CoO along with MnO. The compositions of the oxide phase above Fe-Co-Mn-O melts are calculated. When the cobalt and manganese contents in the melts increase, the mole fraction of manganese oxide increases, and it approaches 1 in the case of pure cobalt. The dependences of the oxygen solubility in the melts on the cobalt and manganese contents are calculated. The deoxidizing capacity of manganese increases substantially with increasing cobalt content in the melt. The curves of oxygen solubility in Fe-Co melts have minima, whose values shift toward low manganese content in a melt. The manganese contents are determined at the minimum points in the oxygen solubility curves, and the corresponding minimum oxygen contents are found.     

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.     

Thermodynamics of the oxygen solutions in Fe-Ni-Ti melts

The oxygen solutions in Fe-Ni melts containing up to 3% titanium are analyzed thermodynamically. The results of the works that determined the fields of the oxide phases in iron and nickel deoxidized by titanium are generalized. The proposed calculation model is shown to adequately describe the titanium deoxidation of iron-nickel alloys. The deoxidizing capacity of titanium decreases as the nickel content in the melt increases to 40% and, then, increases sharply as the nickel content increases further. The oxygen solubility curves pass through a minimum, whose position changes from 0.5644% Ti for pure iron to 0.6332% Ti for pure nickel. The points of equilibrium between the TiO₂, Ti₃O₅, and Ti₂O₃ oxide phases are determined for six alloy compositions at 1873 K. The titanium deoxidation of Fe-40% Ni melts is experimentally studied, and the calculated and experimental results are in good agreement.     

Thermodynamics of oxygen solutions in Fe-Ni-V melts

The oxygen solutions in Fe-Ni melts with up to 5% V are analyzed thermodynamically. The results of the works in which the fields of the vanadium-deoxidized oxide phases in iron and nickel were determined are generalized. The thermodynamic model developed for the calculation of the deoxidation of iron-nickel alloys with vanadium is shown to be adequate. The deoxidizing capacity of vanadium decreases insignificantly as the nickel content in the melt increases to 20% and increases substantially as the nickel content increases further. The oxygen solubility curves pass through a minimum, whose position changes from 2.3192% V for pure iron to 0.7669% V for pure nickel. We determined the equilibrium point [V]* between the (Fe, Ni)V₂O₄ and V₂O₃ oxide phases for alloys of six compositions at 1873 K. In nickel, [V]* is almost 200 times lower than in iron. The deoxidation of the Fe-40% Ni melt with vanadium is studied experimentally, and the experimental results agree satisfactorily with the calculated data.     

Thermodynamics of oxygen solutions in Fe-Mn melts

Oxygen solutions in Fe-Mn melts are analyzed thermodynamically. The composition of the oxide phase is determined, and the equilibrium oxygen concentrations in Fe-Mn melts are calculated over a wide composition range. The oxide phase mainly contains MnO: even at a molar fraction of manganese of 0.02 in the melt, the molar fraction of manganese oxide in the slag is more than 0.9. This is due to a much higher oxygen affinity of manganese as compared to iron; that is, manganese additives to iron considerably decrease the oxygen solubility. When the manganse content in the melt is 19.32%, the oxygen solubility curve has a minimum corresponding to an oxygen concentration of 5.136 × 10^?3%. However, a further increase in the managanese content results in an increase in the oxygen concentration in the melt. In liquid manganese, the oxygen saturation concentration at 1873 K is 0.0472%. The interaction parameter e _o(Mn) ^o (?0.207) and the activity coefficient γ _o(Mn) ^o (1.131 × 10^?4) have been calculated for the first time.     

Thermodynamics of the oxygen solutions in iron-nickel melts

The oxygen solutions in Fe-Ni melts containing chromium, manganese, vanadium, carbon, silicon, titanium, or aluminum are studied thermodynamically. The equilibrium constants of the deoxidation of the melts by these elements are determined, and the activity coefficients for infinite dilution and the interaction parameters in alloys of various compositions are found. The oxygen solubilities in the alloys are calculated as a function of the nickel and deoxidizer contents. The deoxidizer contents at the minima in the oxygen solubility curves for the melts are determined, and the corresponding minimum oxygen concentrations are calculated. As the nickel content in the system increases, the deoxidizing capacities of chromium, manganese, and silicon are shown to increase substantially, and the deoxidizing capacity of carbon increases most strongly. As the nickel content in the melt increases, the deoxidizing capacities of vanadium and titanium first decrease insignificantly and then increase substantially. As the nickel content in the melt increases to 50%, the deoxidizing capacity of aluminum first decreases and then increases; in pure nickel, it is identical to that in pure iron.     

Thermodynamics of the oxygen solutions in niobium-containing Fe-Ni melts

A thermodynamic analysis is performed for the oxygen solutions in niobium-containing Fe-Ni melts. The deoxidizing capacity of niobium in iron??nickel melts is shown to be low. It decreases slightly as the nickel content in a melt increases to 40% and then increases insignificantly as the nickel content increases to 60%; a further increase in the nickel content leads to a marked increase in the deoxidizing capacity. The solubility curves of oxygen in iron??nickel melts passes through a minimum, whose position shifts toward higher niobium concentrations with increasing nickel content. Subsequent niobium additions increase the oxygen concentration in the melt. The equilibrium constants of the reactions of niobium deoxidizing of iron??nickel melts, the activity coefficients, and the interaction parameters characterizing Fe-Ni-Nb-O melts are determined.     

Thermodynamics of the oxygen solutions in zirconium-containing iron-nickel melts

Thermodynamic analysis of the oxygen solutions in zirconium-containing iron-nickel melts is carried out. The equilibrium deoxidation constants of the melts by zirconium, the activity coefficients at infinite dilution, and the interaction parameters in melts of various compositions are determined. The dependences of the oxygen solubility in the melts on the nickel or zirconium content are calculated. Zirconium is shown to possess a very high deoxidizing capacity in iron-nickel alloys. The zirconium contents at the minima in oxygen solubility curves and the corresponding minimum oxygen concentrations are determined. As the nickel content in a melt increases to ∼45%, the deoxidizing capacity of zirconium decreases and, then, increases. The deoxidizing capacity of zirconium in pure nickel is noticeably higher than that in pure iron.     

Thermodynamics of carbon and oxygen solutions in manganese melts

The thermodynamics of carbon and oxygen solutions in manganese melts is studied. An equation for the temperature dependence of the activity coefficient of carbon in liquid manganese is obtained (γ _C(Mn) ⁰ = ?1.5966 + (1.0735 × 10^?3)T). The temperature dependence of the Gibbs energy of the reaction of carbon dissolved in liquid manganese with the oxygen of manganese oxide is shown to be described by the equation ΔG _T ⁰ = 375264 ? 184.66T(J/mol). This reaction can noticeably be developed depending on the carbon content at temperatures of 1700–1800°C. The deoxidation ability of carbon in manganese melts is shown to be much lower than that in iron and nickel melts due to the higher affinity of manganese to both oxygen and carbon. Although the deoxidation ability of carbon in manganese melts increases with temperature, the process develops at rather high carbon contents in all cases.     

Thermodynamics of oxygen solutions in nickel melts containing aluminum and titanium

Thermodynamic analysis of oxygen solutions in nickel melt shows that, as aluminum and titanium are added to the melt, the solubility of oxygen decreases. However, after reaching 0.205% Al and 0.565% Ti, the oxygen concentration in the melt begins to rise with increase in the Al and Ti content. The minimum oxygen concentrations in the reduction of nickel melt by aluminum (1.44 × 10^–4% O) and titanium (2.98 × 10^–4% O) are determined. On that basis, we may propose the optimal approach to alloying nickel melts with aluminum and titanium. First, the melt is reduced by adding sufficient aluminum to minimize the oxygen concentration in the melt (~0.2% Al). Then the oxide formed is removed, so as to prevent repeated oxidation of the melt. Finally, the melt is alloyed with aluminum and titanium to obtain the required alloy composition.     

Oxygen solubility in silicon-containing Fe-Co melts

Thermodynamic analysis of the oxygen solutions in silicon-containing Fe-Co melts is performed. The equilibrium constant of silicon deoxidation of iron-cobalt melts, the activity coefficients for infinite dilution, and the interaction parameters for melts differing in composition are determined. The dependences of the oxygen solubility in the melts under study are calculated for different cobalt and silicon contents. The deoxidizing capacity of silicon increases substantially as the cobalt content in a melt increases. The curves of oxygen solubility in Fe-Co melts have a minimum; the minimum oxygen solubility shifts to a low silicon content as the cobalt content in the melts increases. The silicon contents for the minima in the curves of oxygen solubility and the minimum oxygen concentrations corresponding to the silicon contents are determined.     

Thermodynamics of lead silica-fluoride melts

Abstract

Activities of PbO in PbO-PbF₂ and PbO-PbF₂-SiO₂ melts were determined in the temperature range 1050–1250K using a galvanic cell incorporating a calcia-stabilized zirconia solid electrolyte. Compositions investigated included slag mixtures containing up to 30 mole % PbF₂ for the PbO-PbF₂ binary, and up to 20 mole % PbF₂ for the PbO-PbF₂-SiO₂ ternary. Results for the binary were in agreement with previously published values. An electron microprobe was used to examine for slag-electrolyte interactions, and necessary restrictions on run times and temperatures were noted. For melts in which the mole fraction of silica exceeded about 0.2, the activity of PbO was raised by the addition of PbF₂; the reverse was true at lower silica contents. The results are discussed with reference to the anionic constitution of the melts described in terms of O^2? and F^? ions and an array of silicate and silico-fluoride ions the chain members of which have the general formula Si_nO_3n+1?m F_m^(2n+2?m)?, where 1 ≤ n ≤ ∞ and 0 ≤ m ≤ 2n+2.

Résumé

Les activités de PbO dans les mélanges fondus PbO-PbF₂ et PbO-PbF₂-SiO₂ ont été déterminées entre 1050 et 1250 K par une cellule galvanique comprenant un électrolyte solide de zircone stabilisée avec CaO. Les compositions investiguées des mélanges de scories contiennent au moins 300% molaire de PbF₂ pour le binaire PbO-PbF₂ et au moins 200% molaire pour le ternaire PbO-PbF₂-SiO₂. Les résultats pour le système binaire sont en accord avec les valeurs déjà publiées. Dne microsonde a été utilisée pour examiner les interactions scories-électrolyte et d'évidentes restrictions de temps et de températures ont été notées. Pour les mélanges contenant plus de 20% molaire de silice, l'activite de PbO a augmenté avec l'addition de PbF₂ alors que l'effet inverse a été noté lorsque les quantités de silice étaient inferieures à 0.2. Les résultats ont été interprétés en se reférant à la constitution anionique des mélanges fondus décrite de la façon suivante: des ions O^2? et F^? et un arrangement de silicates et de silicates fluorés dont la chaîne a comme formule Si_nO_3n+1?m F_m^{(2n+ 2?m)?}, où 1≤ n ≤ ∞ et O≤ m ≤ 2n+2.     

Thermodynamics of metallurgical processes in manganese-based melts

The theory of quasi-regular solutions may be used to convert the molar interaction parameters from one type of alloy to another. Hence, the thermodynamic characteristics of manganese alloys may be estimated from data for iron alloys. On that basis, the molar and mass interaction parameters of elements in manganese melts may be calculated, as well as the heats of solution and activity coefficients of the elements and the change in Gibbs energy on reduction, desulfurization, denitrogenation, and reductive dephosphorization of manganese and also in the refining of manganese by chlorides and fluorides. The possibility of removing impurities from manganese is assessed.     

Thermodynamics of titanium-based melts: I. Thermodynamics of the dissolution of elements in liquid titanium

A method is described that involves the molar interaction parameters in liquid iron at a temperature of 1873 K, provides calculation of these parameters in liquid titanium at any temperature, and makes it possible to calculate the heats of dissolution of elements in liquid titanium and the activity coefficients of these elements. The changes in the Gibbs energy caused by the dissolution of some alloying and impurity elements in liquid titanium are calculated, and the activity coefficients of these elements are presented.     

Thermodynamics of phosphate and phosphide in CaO-CaF2 melts

The thermodynamics of phosphate and phosphide in CaO-CaF₂ melts was studied by equilibrating the melts in a graphite boat with CO-Ar mixtures and Ag-P alloys between 1400 and 1550 ‡C. The dependence of phosphate and phosphide concentrations on the partial pressure of phosphorus, the partial pressure of oxygen, and slag composition confirmed the behavior of P³ and PO ₄ ³ in the melts as thermodynamically expected, giving 0.52 and 8.5 x 10⁻⁴ as the values for the activity coefficients of Ca_3/2PO₄ and Ca_3/2P, respectively.     

Thermodynamics of oxygen solutions in liquid Ni,Co, Fe,and Mn metals

Pure gaseous oxygen at a pressure $p_{O_2 }^{1/2} = 1$ is taken as the standard state of oxygen dissolved in a liquid metal. In the case of such a standard state of oxygen, its activity is equal to the equilibrium oxygen partial pressure in the vapor, which is risen to a power of 1/2. This allowed us, using two thermodynamic functions, i.e., the standard Gibbs energy for the oxidation reaction of liquid metal with oxygen to form a lower oxide and the experimentally determined oxygen solubility in a liquid metal, to obtain equations for the energies of mixing of each metal with oxygen and to calculate them, to find linear temperature dependences of the energies of mixing, and to describe oxygen solutions in liquid metals by pseudoregular-solution model equations. Linear dependences of the solubility functions on the standard Gibbs energies for oxidation reactions of liquid metals are found. The aim of the study is to suggest the energies of mixing of four metals (Ni, Co, Fe, and Mn) with oxygen and their temperature dependences for the calculations of the activity coefficients and the activity of oxygen in the solutions of these liquid metals by the pseudoregular-solution model equations.     

Activity coefficient of oxygen in copper-sulfur melts

Activity coefficients of oxygen in sulfide-rich and metal-rich melts in the copper-sulfur system were determined at 1423 and 1523 K by means of a modified coulometric titration technique using the following cell: O (in Cu-S melts) |ZrO₂(+CaO)| air, Pt. The activity coefficient values increase rapidly with sulfur composition in the vicinity ofx _s = 0.3333. The data obtained for the matte saturated with the metal-rich melts are in good agreement with those obtained by Kuxmann and Benecke and Schmiedl. Those obtained for the metal-rich melts are in good agreement with the results of Sano and Sakao. Formerly Research Associate at The University of Wisconsin