Oxygen and carbon sensing in Fe—O—C and Fe—O—C—Xn melts at elevated carbon contents

In the present study on solid electrolyte probes, the attempt was made to measure accurate and reproducible EMF values representing the extremely low oxygen activities in Fe—O—C melts at varying C contents. Various types of sensors were designed and successfully tested in laboratory experiments. Reliable oxygen activities were measured in Fe—O—C melts up to 4 wt. % C under pure CO gas, and f_o and f_c values were derived as a function of C content at 1 400 to 1 600°C. Further measurements were made in Fe—O—4 wt. % C—X_n melts at various contents of X_n (S_n = Si, Mn, Cr). Moreover, a solid oxide electrolyte probe with a CO gas channel to measure oxygen and carbon activities was developed and successfully tested in high-carbon iron melts.     

Influence of aluminum and chromium on the activity of oxygen in nickel based melts at 1600?C

The activity of oxygen in technically important nickel melts containing 15 wt pct cobalt and 5 wt pct molybdenum has been determined at 1600‡C for various concentrations of chromium ranging from 0 to 30 wt pct and aluminum varying from 0 to 15 wt pct. The activity of oxygen was measured by an electrochemical technique using yttria-doped thoria electrolyte cells. The results obtained are analyzed in terms of activity coefficients of oxygen as a function of aluminum and chromium contents in the melts. Clear positive deviations of the experimentally determined from the calculated activity coefficients of oxygen were found when aluminum was added to Ni-Co-Mo melts with or without chromium. From the results obtained in the range between 1 and 10 wt pct aluminum, the following equilibrium constants for the reaction 2 [Al] + 3 [O] ⇋ Al₂O₃ in the nickel based melts at 1600‡C were calculated: loga ₀ =-2/3 log [pct Al] - 3.94 for 0 pct Cr loga ₀ = -2/3 log [pct Al] - 4.21 for 10 pct Cr loga ₀ = -2/3 log [pct Al] - 4.81 for 20 pct Cr loga ₀ = -2/3 log [pct Al] - 5.06 for 30 pct Cr.     

Thermodynamics of Oxygen Solution in Fe–Ni Melts Containing Boron

Fe–Ni alloys are widely used in engineering today. They are sometimes alloyed with boron. Oxygen is a harmful impurity in Fe–Ni alloys. It may be present in dissolved form or as nonmetallic inclusions. The presence of oxygen in Fe–Ni alloys impairs their performance. Research on the thermodynamics of oxygen solutions in Fe–Ni melts containing boron is of considerable interest in order to improve alloy production. The present work offers a thermodynamic analysis of solutions of oxygen in Fe–Ni melts containing boron. The equilibrium constant of the reaction between boron and oxygen dissolved in the melt in such systems is determined. The activity coefficients at infinite dilution and the interaction parameters in melts of different composition are also calculated. When boron reacts with oxygen in Fe–Ni melts, the oxide phase contains not only B₂O₃ but also FeO and NiO. The mole fractions of B₂O₃, FeO, and NiO in the oxide phase are calculated for different boron concentrations in Fe–Ni melts at 1873 K. For iron melts with low boron content, the mole fraction of boron oxide is ~0.1. With increase in the nickel and boron content in the melts, the boron-oxide content in the oxide phase increases. Its mole fraction is close to one for pure nickel. The solubility of oxygen in Fe–Ni melts is calculated as a function of the nickel and boron content. The deoxidizing ability of the boron improve significantly with increase in nickel content in the melt. The curves of oxygen solubility in Fe?Ni melts containing boron pass through a minimum, which is shifted to higher boron content with increase in nickel content in the melt. The boron content at the minima on the curves of oxygen solubility are determined, as well as the corresponding minimum oxygen concentrations.     

The rate of reaction of solid iron with oxidized “FeO”-CaO-SiO2-Al2O3 slags at 1360 °C—the chemical diffusivity of iron oxide

Measurements have been made of the rate of reduction of oxidized iron oxide-containing 41CaO-38SiO₂-21Al₂O₃ (wt pct) slags at 1360 °C by a rotating disc of solid iron. For initial total iron concentrations of between 1.8 and 13.4 wt pct and rotation speeds up to 1000 rpm, the rate is shown to be determined by mass transfer in the liquid phase. The chemical diffusivity of iron oxide (in cm² s⁻¹) is found to be given by the empirical expression log D = −6.11 + 0.08 (wt pct Fe). It is concluded that the values of the diffusivity are for melts at close to iron saturation. It is shown that the available measurements of the diffusivity of iron oxide in liquid slags are consistent with increasing diffusivity with increasing state of oxidation, with about a tenfold increase between melts in equilibrium with iron and those in equilibrium with oxygen at 1 atm.     

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.     

Formation of metallic phase on reducing-gas injection in multicomponent oxide melt. Part 2. Density and surface properties

The density and surface tension of melts of ferronickel (0–100% Ni) and oxidized nickel ore are measured by the sessile-drop method, as well as the interface tension at their boundary in the temperature range 1550–1750°C. The composition of the nickel ore is as follows: 14.8 wt % Fetot, 7.1 wt % FeO, 13.2 wt % Fe₂O₃, 1.4 wt % CaO, 16.2 wt % MgO, 54.5 wt % SiO₂, 4.8 wt % Al₂O₃, 1.5 wt % NiO, and 1.2 wt % Cr₂O₃. In the given temperature range, the density of the alloys varies from 7700 to 6900 kg/m³; the surface tension from 1770 to 1570 mJ/m²; the interface tension from 1650 to 1450 mJ/m², the density of the oxide melt from 2250 to 1750 kg/m³; and its surface tension from 310 to 290 mJ/m². The results are in good agreement with literature data. Functional relationships of the density, surface tension, and interphase tension with the melt temperature and composition are derived. The dependence of the alloy density on the temperature and nickel content corresponds to a first-order equation. The temperature dependence of the surface tension and interphase tension is similar, whereas the dependence on the nickel content corresponds to a second-order equation. The density and surface tension of the oxide melt depend linearly on the temperature. The results may be used to describe the formation of metallic phase when carbon monoxide is bubbled into oxide melt.     

The activities of sulfide and oxide components and the solubility of oxygen in copper-iron-sulfur-oxygen mattes at 1300 °C

The activities of iron and copper and the solubilities of oxygen in copper-iron-sulfur-oxygen mattes have been determined by equilibrating mattes with CO−CO₂−SO₂ gas mixtures of fixed partial pressures of oxygen and sulfur and equilibrating a small mass of platinum with the melt. Iron and copper transferred from the matte to form a platinum-iron-copper alloy in which the activities of iron and copper are the same as in the matte. The activities of iron and copper in the matte were then determined from knowledge of the activities of iron and copper in the system platinum-iron-copper. Sulfides ofW _Fe=0.1, 0.3, and 0.5 were studied, whereW _Fe=wt pct Fe/(wt pct Fe+wt pct Cu), and sulfur pressures of 0.005, 0.0158, and 0.025 atm and oxygen pressures of 3.16×10⁻¹⁰, 7.94×10⁻¹⁰, 2.00×10⁻⁹, and 3.16×10⁻⁹ were used. The activity of copper, which varied in the range 0.06 to 0.165, decreases with increasingp _{O 2} at constantW _Fe andp _{S 2} and decreases with increasingp _{S 2} at constantW _Fe and constantp _{O 2}. The activity of iron, which varied in the range 0.002 to 0.06, increases with increasingp _{O 2} at constantW _Fe andp _{S 2} and decreases with increasingp _{S 2} at constantW _Fe andp _{O 2}. The activities of the components Cu₂S, FeS, Cu₂O, FeO, and Fe₃O₄ were calculated from the activities of iron and copper, the partial pressures of oxygen and sulfur, and the approapriate equilibrium constants. The variations of the activities of these components with matte grade, oxygen pressure, and sulfur pressure are presented and discussed. Within the range of experimental conditions studied, the solubility of oxygen in the melts is given by wt pct O=2.59pO₂/0.225pS₂/−0.18 (1+9.0W _Fe)^1.86     

Thermodynamics of the oxygen solutions in boron-containing Fe–Co melts

A thermodynamic analysis of the oxygen solutions in boron-containing Fe–Co melts has been performed. The equilibrium constant of reaction between boron and oxygen, which are dissolved in iron–cobalt melts; the activity coefficients at infinite dilution; and the interaction parameters for melts differing in composition have been determined. The oxide phase formed in the Fe–Co melts containing boron and oxygen comprises FeO and CoO along with the B₂O₃ phase. The oxide phase compositions over Fe–Co–B–O melts are calculated. As the cobalt and boron contents in the melts increase, the mole fraction of boron oxide increases; in the case of pure cobalt, it is close to unity. The dependences of the oxygen solubility on the cobalt and boron contents in the melts are calculated. The deoxidizing capacity of boron substantially increases as the cobalt content in a melt increases. The composition dependences of the oxygen solubility in boron-containing Fe–Co melts have a minimum, which shifts to a low boron content as the cobalt content in the melts increases. The boron contents corresponding to the minimum in the oxygen solubility curves and the minimum oxygen concentrations corresponding to the boron contents are determined.     

Activities of chromium in molten copper at dilute concentrations by solid-state electrochemical cell

In order to obtain the activities of chromium in molten copper at dilute concentrations (<0.008 chromium mole fractions), liquid copper was brought to equilibrium with molten CaCl₂ + Cr₂O₃ slag saturated with Cr₂O₃ (s), at temperatures between 1423 and 1573 K, and the equilibrium oxygen partial pressures were measured by means of solid-oxide galvanic cells of the type Mo/Mo + MoO₂/ZrO₂(MgO)/(Cu + Cr))alloy + Cr₂O₃ + (CaCl₂ + Cr₂O₃)_slag/Mo. The free energy changes for the dissolution of solid chromium in molten copper at infinite dilution referred to 1 wt pct were determined as Cr (s) = Cr(1 wt pct, in Cu) and ΔG° = + 97,000 + 73.3(T/K) ± 2,000 J mol⁻¹.     

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.     

Phase Equilibria in Liquid Metal of the Cu–Al–Cr–O System

A thermodynamic analysis of phase equilibria in the Cu–Al–Cr–O system is carried out. Thermodynamic modeling of the liquidus surface of the Cu₂O–Al₂O₃–Cr₂O₃ oxide phase diagram is performed. To describe activities of an oxide melt, the approximation of the theory of subregular ionic solutions, the energy parameters of which were determined during modeling, is used. Melting characteristics of the CuCrO₂ compound are also evaluated in the course of the calculation. Coordinates of invariant equilibria points implemented in the Cu₂O–Al₂O₃–Cr₂O₃ ternary oxide system are established by the results of the calculation. Thermodynamic modeling of interaction processes in the Cu–Al–Cr–O system in occurrence conditions of a copper-based metal melt is also performed. The temperature dependence of the equilibrium constant of the reaction that characterizes the formation of the CuCrO₂ solid compound from components of the metal melt of the Cu–Al–Cr–O system is determined. The temperature dependence for the first-order interaction parameter (by Wagner) of chromium and oxygen dissolved in liquid copper is found. The results of thermodynamic modeling for the Cu–Al–Cr–O system are presented in the form of the solubility surface of components in metal, which makes it possible to attribute the quantitative variations in the metal melt concentration with qualitative variations in the composition of forming interaction products. It is determined by the results of modeling that particles of the |Al₂O₃, Cr₂O₃|_sol.sln solid solution are formed at valuable aluminum and chromium concentrations in the copper melt of the Cu–Al–Cr–O system as the main interaction product. The results of the investigation can be interesting for improving the technology process of smelting of chromium bronzes.     

Thermodynamic modeling of the reaction of lanthanum with components of iron-based melts

Thermodynamic analysis of binary and ternary oxide systems containing the oxide La₂O₃ permits the formulation of a database of energy parameters in the theory of subregular solutions for oxide melts adjacent to the region of existence of metallic melts in the phase diagram of the system. The temperature dependence of the equilibrium constants for the heterogeneous reduction of steel is established. The solubility surfaces of components in oxygen-bearing steel are plotted for the Fe–Al–La–O–C, Fe–Ca–La–O–C, Fe–Mg–La–O–C, Fe–Si–La–O–C, and Fe–Cr–La–O–C systems. Diagrams are plotted for the complex reduction of steel by alloys and mixtures containing active and alloying elements: Ca, Mg, Si, Al, Cr, and La. Analysis is undertaken for thoroughly reduced and sulfur-free steel. With the usual reduction system, in which rare-earth metals are added to the steel after the introduction of calcium, silicon, and aluminum, the inclusions that form—consisting of a conglomerate of calcium and magnesium aluminates—provide the substrate for the deposition of small fractions, actively interact with the liquid component of the inclusions, and dissolve in the liquid component. Therefore, La₂O₃ is not present as an independent phase in the metallic inclusions.     

Chromium vaporisation from Fe,Cr base alloys used as interconnect in fuel cells

Fe,Cr base alloys protected by Cr₂O₃ base oxidation scales are candidate materials for the metallic interconnect of solid oxide fuel cells (SOFC). The operating temperatures of such cells range between 800 and 950 °C. Cr₂O₃ base oxide scales are necessary since they show sufficient electrical conductivity unlike Al₂O₃ or SiO₂ scales. It is, however, disadvantageous that Cr₂O₃ base oxide scales form the volatile chromium(VI) species CrO₃(g) and CrO₂(OH)₂(g) under operating conditions at the cathode side of SOFC. The electrochemical reduction of these species forming solid Cr(III) oxides at the three‐phase boundary electrolyte/cathode/oxidant leads to a rapid degradation of the electrical properties of SOFC. The study of the chromium vaporisation of different Fe,Cr base alloys under SOFC operating conditions and its reduction by the coating of the alloy surface are, therefore, of topical interest in SOFC development. The commercial alloys Fe18Cr1Al (DIN 1.4742), Fe25Cr0.7Mn0.5Si (AISI 446), Fe20.4Cr5.7A10.3Si (DIN 1.4767) and the oxide dispersion strengthened (ODS) alloy Cr5Fe1Y₂O₃ as well as the model alloy FeCrMn (HNA) were investigated. These alloys form the following oxide scales under operating conditions on the cathode side: iron rich chromium oxides (DIN 1.4742), Cr,Mn spinel (AISI 446 and HNA), Al₂O₃ (DIN 1.4767), and Cr₂O₃ (Cr5Fe1Y₂O₃). The alloys DIN 1.4742 and Cr5Fe1Y₂O₃ were coated with a perovskite layer (25 to 30 μm thickness) made of La_0.90Sr_0.10CrO₃ (LSC) and La_0.8Sr_0.2MnO₃ (LSM) by the use of vacuum plasma spraying (VPS). The vaporisation studies were carried out under non‐equilibrium conditions using the vapour transportation method. The carrier gas consisted of synthetic air with a relative humidity of rH = 60%. Alloy plates of the dimensions 80 · 30 · 5 mm³ with rounded edges and a surface area of 48.5 cm² were used as samples in the vaporisation experiments carried out at 850 and 950 °C. Typical time periods of the vaporisation measurements were between 20 and 350 h. Alloy Cr5Fe1Y₂O₃ with Cr₂O₃ scale showed the highest chromium vaporisation rate among the uncoated samples. The latter showed the following factors for the reduction of the chromium vaporisation rate as compared to Cr5Fe1Y₂O₃ at 850 °C: 23 for AISI 446, 10 for HNA, 5 for DIN 1.4767, and 2 for DIN 1.4742. The different factors are explained by the different oxide scales mentioned above. The alloys with VPS coatings showed a reduction of chromium release by up to a factor of > 100. Investigations of the microstrucure of the perovskite coating revealed its densification during the transpiration experiments which in turn reduces the chromium vaporisation. Moreover, the Cr₂O₃ vaporisation was re‐determined under equilibrium conditions by the vapour transportation method leading to new results.     

Tracer diffusion of59Fe and51Cr in Fe-17 Wt Pet Cr-12 Wt Pet Ni austenitic alloy

The volume and grain-boundary diffusion of⁵⁹Fe and⁵¹Cr have been studied in an austenitic iron alloy containing 17 wt pct Cr and 12 wt pct Ni. The diffusivities in this alloy of these two tracers and⁶³Ni are compared with their diffusivities in pure iron and in other austenitic stainless steels. For volume diffusion at any particular temperature in the present alloy, Cr is the most rapid while Ni is the slowest, and all three tracers diffuse slower than that reported for pure iron or for other austenitic stainless steels. For grain-boundary transport, Fe diffuses most rapidly above 850°C and Ni diffuses most rapidly below that temperature. The activation energies for both volume and grain-bounary diffusion obey the relationshipQ _Ni <Q _Cr <Q _Fe. Formerly Presidential Intern in the Metals and Ceramics Division, Oak Ridge National Laboratory     

Interaction of exogenous refractory nanophases with antimony dissolved in liquid iron

The heterophase interaction of Al₂O₃ refractory nanoparticles with a surfactant impurity (antimony) in the Fe–Sb (0.095 wt %)–O (0.008 wt %) system is studied. It is shown that the introduction of 0.06–0.18 wt % Al₂O₃ nanoparticles (25–83 nm) into a melt during isothermal holding for up to 1200 s leads to a decrease in the antimony content: the maximum degree of antimony removal is 26 rel %. The sessile drop method is used to investigate the surface tension and the density of Fe, Fe–Sb, and Fe–Sb–Al₂O₃ melts. The polytherms of the surface tension of these melts have a linear character, the removal of antimony from the Fe–Sb–Al₂O₃ melts depends on the time of melting in a vacuum induction furnace, and the experimental results obtained reveal the kinetic laws of the structure formation in the surface layers of the melts. The determined melt densities demonstrate that the introduction of antimony into the Fe–O melt causes an increase in its compression by 47 rel %. The structure of the Fe–Sb–O melt after the introduction of Al₂O₃ nanoparticles depends on the time of melting in a vacuum induction furnace.     

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.     

Combined first principle and experimental study of oxide/alloy interface evolution during hot rolling 430 stainless steels

Abstract

A combined first principle and experimental study of the microstructural characteristics of oxide scales developed on type 430 stainless steel during hot rolling is presented. The oxide layer structures have been investigated by means of SEM, XPS and GDS. The oxide scales were found to have a multilayer structure with Si enrichment at the oxide/matrix interface and were identified as (Fe,Cr)₂O₃/(Fe,Cr)₃O₄/Cr₂O₃, FeO and Si rich region/Fe–Cr stainless steel from the outer to the inner layer. An atomistic model of the Fe–Cr/FeO interface has been generated through first principle methods based on density functional theory. Structural and electronic properties are compared to available experimental data and studied as they evolve across the Fe–Cr/FeO and Fe–Cr (Si)/FeO interface.     

Activities in liquid Fe−Al−O and Fe−Ti−O alloys

The solubility and activity of oxygen in Fe?Al and Fe?Ti melts at 1600°C were measured. The activity was measured electrochemically using the following galvanic cells: Cr-Cr₂O₃(s) ? ThO₂(Y₂O₃) ? Fe-Al-O(l), Al₂O₃(s) Cr-Cr₂O₃(s) ? ThO₂(Y₂O₃) ? Fe-Ti-O(l, saturated with oxide) Cr-Cr₂O₃(s) ? ZrO₂(CaO) ? Fe-Ti-O(l, saturated with oxide) Aluminum and titanium decrease the solubility of oxygen in liquid iron to a minimum of 6 ppm at 0.09 wt pct Al and 40 ppm at 0.9 wt pct Ti, respectively. The value of the interaction coefficients ε ₀ ^(Al) and ε ₀ ^(Ti) are ?433 and ?222, respectively. the activity coefficient of aluminum at infinite dilution in liquid iron is 0.021, while that of titanium is 0.038. The value of the aluminum equilibrium constant, the solubility product at infinite dilution, is 5.6×10^?14 at 1600°C. The ThO₂(Y₂O₃) electrolyte exhibited insignificant electronic conductivity at 1600°C down to oxygen partial pressures of 10^?15 atm, which corresponds to about 0.3 ppm O in unalloyed iron.     

A thermodynamic study of BaO + BaCl2 + Cr2O3 fluxes used for the removal of phosphorus from chromium-containing iron melts

Electrochemical measurements with solid-oxide galvanic cell of the type Mo/Mo + MoO₂//ZrO₂(MgO)//{Cu + Cr}_alloy + (Cr₂O₃)_slag/Mo were conducted at 1473 K in order to obtain the activities of Cr₂O₃ in BaO + BaCl₂ + Cr₂O₃ slags used for dephosphorization of chromium-containing iron melts. Based on the activity measurements, it is concluded that in the system BaO + BaCl₂ + Cr_{2 O3} at 1473 K, there are 1 two-phase region in saturation with pure Cr₂O₃(s) and 3 three-phase regions. The activities of Cr₂O₃ within such three-phase regions decrease with an increase in BaO/BaCl₂ mole ratios. The Cr₂O₃ activities in BaO + BaCl₂ + Cr2O3 fluxes are, in general, greater than those in CaO + CaCl₂ + Cr₂O₃, corresponding to much more effective dephosphorization by BaO + BaCl₂ + Cr₂O₃ fluxes rather than CaO + CaCl₂ + Cr₂O₃ slag.     

A thermodynamic study of silica-saturated iron silicate slags in equilibrium with liquid copper

The thermodynamic properties of silica-saturated iron silicate slags in equilibrium with liquid copper have been studied from oxygen partial pressure measurements in the temperature range from 1490 to 1580 K by means of a solid electrolyte galvanic cell. The following cells were used: Pt, Ni-NiO/O⁼/slag-Cu(l), Cr₂O₃, Pt; Pt, Fe-FeO/O⁼/slag-Cu(Fe sat.), Fe. A strong correlation was found between oxygen pressure and the copper content of the slag; the copper content increased from less than 1 pct near iron saturation to about 4 pct at an oxygen partial pressure of 7.2 x 10^?3 Pa. A similar correlation was found between the ferric iron/total iron ratio and the oxygen pressure. The oxygen content in liquid copper decreased with increasing iron content in liquid copper and increased slightly near iron saturation. This behavior could be explained qualitatively by using the standard free energy of formation of FeO and the activities of components.