Showing papers in "Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science in 1989"

Electromagnetic refining of aluminum alloys by the CREM process: Part I. Working principle and metallurgical results

Abstract: In the first part of this paper, the working principle of a new electromagnetic continuous casting process is described. The main peculiarities of this process are (1) the presence in the sump of a strong electromagnetically driven forced convection, which promotes the production of a fine equiaxed structure, and (2) the fact that the thickness of the segregation zone tends toward zero. Local measurement methods are applied to the study of electromagnetic and hydrodynamic phe-nomena inside the sump of aluminum alloy billets. Further, the evolution of both the grain size and the thickness of the segregated surface layer with the electric power input is presented. In summary, this new technology presents the advantages of avoiding the addition of grain refiners and substantially reducing the scalping operation.

Estimation of the surface tensions of binary liquid alloys

Abstract: A simple method to estimate the surface tensions of binary alloys has been developed by assuming that the partial molar excess free energies are proportional to the number of nearest neighbors in both the bulk solution and in the surface itself. In order to estimate the surface tension of the alloys, excess free energies of the alloys and the surface tensions of the pure components are required. This method has been applied to ten alloys exhibiting positive, positive as well as negative, and negative deviations from ideal solution behavior. The method depends upon the reliability of the thermodynamic data for the bulk solutions, and, further, it is important to use an interpolation scheme that is consistent with the Gibbs-Duhem requirement, when the thermodynamic data are presented in tabular form as a function of composition. To accomplish this interpolation, a special calculation technique is presented.

Study on the foaming of CaO-SiO 2 -FeO slags: Part I. Foaming parameters and experimental results

Abstract: In order to understand the effect of slag composition on foaming in iron and steelmaking processes, slag foaming was quantitatively studied for CaO-SiO2-FeO slags in the temperature range of 1250 °C to 1400 °C. It was found that slag foaming could be characterized by a foaming index (Σ), which is equal to the retention or traveling time of the gas in the slag, and the average foam life ( τ). The effects of P2O5, S, MgO, and CaF2 on foaming were studied. As expected, slag foaming increased with increasing viscosity and decreasing surface tension. It was found that suspended second-phase solid particles such as CaO, 2CaO SiO2, and MgO stabilized the foam and had a larger effect on foaming than changes in viscosity and surface tension for the slags studied.

Prediction of weld pool and reinforcement dimensions of GMA welds using a finite-element model

Abstract: Mathematical models of the gas metal arc (GMA) welding process may be used to study the influence of various welding parameters on weld dimensions, to assist in the development of welding procedures, and to aid in the generation of process control algorithms for automated applications. In this work, a three-dimensional (3-D), steady-state thermal model of the GMA welding process has been formulated for a moving coordinate framework and solved using the finite-element method. The model includes temperature-dependent material properties, a new finite-element formulation for the inclusion of latent heat of fusion, a Gaussian distribution of heat flux from the arc, plus the effects of mass convection into the weld pool from the melted filler wire. The influence of weld pool convection on the pool shape was approximated using anisotropically enhanced thermal conductivity for the liquid phase. Weld bead width and reinforcement height were predicted using a unique iterative technique developed for this purpose. In this paper, the numerical model is shown to be capable of predicting GMA weld dimensions for individual welds, including those with finger penetration. Also, good agreement is demonstrated between predicted weld dimensions and experimentally derived relations that describe the effects of process variables and their influence on average weld dimensions for bead-onplate GMA welds on steel plate.

Study on the foaming of CaO-SiO2-FeO slags: Part II. Dimensional analysis and foaming in iron and steelmaking processes

Abstract: An empirical equation for the foaming index Σ of a CaO-SiO2-FeO slag was obtained by dimensional analysis. The effect of second-phase particles on slag foaming was well described by calculating the viscosity of the mixture using the modified Einstein equation. The anticipated foaming in basic oxygen furnace (BOF), electric arc furnace (EAF), and bath-smelting processes was estimated using the parameter Σ for various operating conditions and slag compositions. For BOF operations, it is predicted that foaming is most extreme in the middle of the blow, and a stable foam in EAF is achieved with less basic slags with low FeO contents. For bath smelting, foam heights of 5 m are possible, and a higher degree of prereduction prior to smelting will reduce foaming (because of smaller gas evolution) and possibly increase production rates. Running the process at a higher pressure will also reduce foam heights, because the volume of gas generated is less.

The mechanism of adsorption of aurocyanide onto activated carbon

Abstract: The mechanism of adsorption of aurocyanide onto activated carbon and its subsequent elution are examined in this study, with special reference to the effects of acid and alkali treatment on the system. The results, including a careful analysis of the distribution of all ions in the ad-sorption and elution processes, are discussed, and evidence for the adsorption and elution mech-anisms involved is presented. It is proposed that, under normal plant conditions, aurocyanide is extracted onto activated carbon in the form of an ion pair, Mn+[Au(CN)2]n], and eluted by hydroxide or cyanide. The hydroxide or cyanide ions react with the carbon surface, rendering it relatively hydrophilic with a decreased affinity for neutral species. Additional adsorption mechanisms are shown to operate under other conditions of ionic strength, pH, and temperature, and it is suggested that this may account in part for the lack of agreement among workers.

Electromagnetic refining of aluminum alloys by the CREM process: Part II. Specific practical problems and their solutions

Abstract: An experimental investigation, described in Part I and bearing on aluminum alloy billets produced by the CREM process, has shown that the main characteristics of this new technology are the elimination of the need for grain-refiner master alloys and a marked reduction of the scalping operation. Part II reports on the examination of the problems specific to the CREM process, which occur particularly during slab casting. The three-dimensional (3-D) aspect of the electromagnetic and fluid flow phenomena, the effect of the electrical conductivity of the ingot mold, and the improvement of the process design are examined.

A heat-transfer model for the rotary kiln: Part II. Development of the cross-section model

Abstract: A model of rotary kiln heat transfer, which accounts for the interaction of all the transport paths and processes, is presented in a three-part series. In this second paper, the development of a unified model for heat transfer at a kiln cross-section is described. Heat transfer within the kiln refractory wall was solved using a finite-difference approximation for one-dimensional transient conduction. A ray tracing technique was applied to derive coefficients for radiative heat transfer in the kiln freeboard, and the finite-difference model was extended into the contacting bed ma-terial in order to calculate the exchange between the covered wall and the bed. The cross-section model is shown to simulate the measured thermal performance of the pilot kiln for several feed materials: fine and coarse sand, limestone, and pctroleum coke. The interaction among the heat-transfer processes at cross-sections of the pilot kiln was examined, and explanations were made for both the observed close coupling of the bed and inside wall temperatures and the high rates of heat input to the bed occurring near the kiln entrance and in the presence of an endothermic bed reaction. Conclusions regarding the likely effects of kiln internal devices on heat transfer to the bed and the importance of preheaters are reached from the model predictions for a 4 m I.D. prototype kiln.

The columnar-to-equiaxed transition in Al 3 Pct Cu

Abstract: A columnar-to-equiaxed transition is observed in Al 3 pct Cu solidified directionally from a chill face. The transition occurs when the temperature gradient in the melt ahead of the columnar dendrites decreases to 0.6 ‡C/cm at dendrite growth rates of about 5 x 10-3 cm/s. Increasing the nuclei density by adding 171 ppm of TiB2 to the melt produces a fine-grained structure without columnar growth. Adding 100 ppm TiB2 has no effect on the cast structure or columnar-to-equiaxed transition. The results are considered in relation to the model for the columnar-to-equiaxed transition proposed by Hunt.[2]

A heat-transfer model for the rotary kiln: Part I. pilot kiln trials

Abstract: A model for rotary kiln heat transfer, which accounts for the interaction of all the transport paths and processes, is presented in a three-part series. In this first paper, the pilot kiln facility is described, and the significant results from the heat-transfer trials are identified. Limestone, Ottawa sand, and pctroleum coke were heated using a range of firing rates, while other operating variables were held nearly constant. Measurements were made to obtain the net rates of heat transfer for the bed material, freeboard gas, refractory wall, and, unique to the study, the radial heat flux at the inside refractory surface as a function of circumferential position. High rates of net heat input to the bed material, occurring very near the feed end, were found to decline quickly with distance, and for an inert bed, leveled out at a value well below the rate of loss through the kiln wall. The onset of an endothermic bed reaction resulted in sharp increases in both the temperature cycling at the inside refractory surface and the net heat input to the bed, but no corresponding jump in the kiln wall heat loss. The temperatures of the bed material and inside refractory surface always were coupled closely, even in the presence of bed reaction. Regenerative heat transfer from the covered wall to the contacting bed material was not a major component of the net input to the bed, and for the inert bed, negative regeneration was en-countered beyond the kiln midpoint.

The influence of weathering on the reduction of llmenite with carbon

Abstract: The reduction of synthetic ilmenite and three ilmenite concentrates (Westralian Sands Limited (WSL), Western Mineral Sands (WMS) and Florida) with coal at 1000 ‡C to 1100 ‡C was stud-ied using thermogravimetry and X-ray diffraction, optical microscopy, and electron probe microanalysis of the products. The rate of reduction and the size of the iron particles decrease with increasing degree of weathering of the concentrate. Stoichiometric ilmenite reduces faster than pseudorutile (Fe2O3-3TiO2), which is a product of weathering. The addition of FeCl3, which promoted the nucleation of iron, increased the rate of reduction, and significant coars-ening of the iron was obtained at 1000 ‡C. In general, the products of reaction are iron, rutile, reduced rutiles, unreduced ilmenite or a-oxide, and pseudobrookite solid solution. A small amount of manganese (1.2 to 1.6 pct MnO) present in the concentrates stabilizes a pseudobrookite phase which retains a significant amount of iron. The manganese also forms an a-oxide phase, (Fe,Mn)TiO3, which is mainly a manganese titanate and concentrates toward the center of the reducing particles.

A mineralogical study of the deportment and reaction of silver during copper electrorefining

Abstract: The majority (>95 pct) of the silver in copper anodes occurs in metastable solid solution in the copper matrix; only a small percentage is present in solid solution in Cu2(Se,Te) inclusions, as a constituent of complex Cu-Pb-As-Sb-Bi oxides or as tiny grains of Ag-Cu alloy. During elec-trorefining, the silver in the copper matrix dissolves, but it is rapidly removed from the elec-trolyte by a variety of reactions. Part of the silver is precipitated in elemental form by cuprous ion, but some of this metallic silver subsequently redissolves. Some of the dissolved silver precipitates as a complex Cu-Ag-Pb-As-Se oxidate phase which agglomerates the particles in the anode slimes, and some reacts with the Cu2(Se,Te) inclusions liberated from the anode to form, sequentially, silver-bearing copper selenide, AgCuSe, copper-bearing silver selenide, and Ag2Se. Several selenide species are present in the anode slimes, and individual selenide particles com-monly consist of more than one selenide species. Because of the diversity and complexity of the silver-bearing phases present, the Ag/Se ratio in the anode is only an approximate indicator of the selenide species present in the anode slimes.

Liquid break-up in gas atomization of fine aluminum powders

Abstract: Formation of powder particles has been studied in aconfined design atomizing nozzle. Liquid metal (AA 2014) is presented in the form of a thin film to the atomizing gas in this type of operation. Upon contacting, the film breaks up into large droplets of diameters up to 500 /im (primary break-up). These droplets undergo further disintegration in flight to produce the powder (secondary disintegration). Photographs taken using a high-speed flash indicate that this takes place by stripping. It is proposed that the fine range of the particles are the products of stripping break-up, while the coarse range are stable particles obtained when stripping stops and the remaining particle becomes too small to undergo further disintegration. Size distribution curves often contained two or more peaks providing support for different formation mechanisms for fine and coarse particles. All particles were dense and single droplets except for the very large ones (>55 μm)which had satellites of fine particles on the surface and showed porosity in some cases. Particles <30 μm in general were fully spherical, whereas larger ones also showed oblong features. No evidence was found for small particles agglomerating to produce large ones.

Emission spectroscopy of plasma during laser welding of AISI 201 stainless steel

Abstract: The rates of vaporization of alloying elements from the weld pool were related to the emission spectra of the plasma during pulsed laser welding of AISI 201 stainless steel under various welding conditions. The temperature distribution in the plasma was determined from the spectra obtained from various locations in the plasma plume. The extent of ionization of the plasma was calculated from the electron temperatures To understand the role of surface active elements, emission spectra and the vaporization rate of iron that resulted from the welding of ultrapure iron samples were compared with those from the welding of oxidized samples or samples that were doped with sulfur or oxygen.

Thermosolutal convection during dendritic solidification of alloys: Part i. Linear stability analysis

Abstract: This paper describes the simulation of thermosolutal convection in directionally solidified (DS) alloys. A linear stability analysis is used to predict marginal stability curves for a system that comprises a mushy zone underlying an all-liquid zone. In the unperturbed and nonconvecting state .e.}, the basic state), isotherms and isoconcentrates are planar and horizontal. The mushy zone is realistically treated as a medium with a variable volume fraction of liquid that is con-sistent with the energy and solute conservation equations. The perturbed variables include tem-perature, concentration of solute, and both components of velocity in a two-dimensional system. As a model system, an alloy of Pb-20 wt pct Sn, solidifying at a velocity of 2 X 10-3 cm s-1 was selected. Dimensional numerical calculations were done to define the marginal stability curves in terms of the thermal gradient at the dendrite tips,G L ,vs the horizontal wave number of the perturbed quantities. For a gravitational constant of 1g,0.5 g, 0.1g, and 0.01g, the marginal stability curves show no minima; thus, the system is never unconditionally stable. Nevertheless, such calculations quantify the effect of reducing the gravitational constant on reducing convection and suggest lateral dimensions of the mold for the purpose of suppressing convection. Finally, for a gravitational constant of 10-4 g, calculations show that the system is stable for the thermal gradients investigated (2.5 ≤G L ≤ 100 K-cm-1).

Tin-based reactive solders for ceramic/metal joints

Abstract: Contact angle measurements on silicon-nitride substrates were conducted on tin-based alloys, containing titanium and zirconium, to determine the suitability of these alloys as filler metals for low-temperature joining of ceramics. Titanium-containing alloys exhibited excellent wettability characterized by contact angles less than 20 deg, whereas the Zr-containing alloys exhibited contact angles around 50 deg. The superior wettability of the Sn−Ti alloys is attributed to the higher activity coefficient of Ti in Sn−Ti alloys. The liquidus temperature of the Sn−Ti alloys is in the 400°C to 600°C range. Hence, these alloys are expected to reduce the residual stress problem.

Fluid flow and bath temperature destratification in gas-stirred ladles

Abstract: The transient fluid flow and temperature distributions in argon-stirred ladles have been investigated. The governing equations of unsteady fluid flow and energy were solved numeri-cally with a control-volume technique, while the turbulence was modeled by the two-equationk- ∃ model. The two-phase zone was described by novel experimental equations, which char-acterize the gas-fraction distribution in the bath for a wide range of variables in both aqueous and liquid metal systems. Fully transient computational results are presented and compared against transient temperature computations based on a steady-state velocity field. The resulting mixing times compare closely with industrial experience.

Two-dimensional model for twin-roll continuous casting

Abstract: A numerical algorithm for the two-dimensional solidification problem in the twin-roll continuous casting system is presented in this paper Attention is focused on the elucidation of heat transfer and flow characteristics in both the liquid and the solid phases The present mathematical model can be applied to general full Navier-Stokes and energy equations, thereby covering the wide range of twin-roll casting conditions The boundary fixing method (BFM) is adopted to handle the moving boundary, and the resultant transformed governing equations for the solid and liquid regions are solved separately by using a usual explicit-type finite difference method In this paper, a general numerical methodology is presented, and the quantitative relationships between the important control parameters in continuous casting of twin-roll type (such as the roll speed, the roll gap, the initial temperature of molten materials, the material properties, the solidification profile, and the endpoint of solidification) are clarified in detail The present numerical results have been compared with experimental results obtained separately to check the validity of the proposed method

Thermosolutal Convection during Dendritic Solidification of Alloys: Part II. Nonlinear Convection

Abstract: A mathematical model of thermosolutal convection in directionally solidified dendritic alloys has been developed that includes a mushy zone underlying an all-liquid region. The model assumes a nonconvective initial state with planar and horizontal isotherms and isoconcentrates that move upward at a constant solidification velocity. The initial state is perturbed, nonlinear calculations are performed to model convection of the liquid when the system is unstable, and the results are compared with the predictions of a linear stability analysis. The mushy zone is modeled as a porous medium of variable porosity consistent with the volume fraction of, interdendritic liquid that satisfies the conservation equations for energy and solute concentrations. Results are presented for systems involving lead-tin alloys (Pb-10 wt pct Sn and Pb-20 wt pct Sn) and show significant differences with results of plane-front solidification. The calculations show that convection in the mushy zone is mainly driven by convection in the all-liquid region, and convection of the interdendritic liquid is only significant in the upper 20 pct of the mushy zone if it is significant at all. The calculated results also show that the systems are stable at reduced gravity levels of the order of 10−4 g 0 (g 0=980 cm·s−1) or when the lateral dimensions of the container are small enough, for stable temperature gradients between 2.5≤G l≤100 K·cm−1 at solidification velocities of 2 to 8 cm·h−1.

Equilibrium partition coefficients in iron-based alloys

Abstract: Accurate relationships between equilibrium partition coefficients and solute concentration are required for the prediction of solute redistribution during solidification. Thermodynamic analyses are presented to relate these coefficients to fundamental thermodynamic quantities. Using the most accurate data available, partition coefficients are calculated for ten Fe−X (X=Al, C, Cr, Mn, Ni, N, P, Si, S, Ti) binary systems and compared with literature values. Equations are presented to allow for prediction of these partition coefficients as a function of temperature, as well as liquidus temperature as a function of composition. In addition, partition coefficient values are examined for the ternary systems Fe−Cr−C, Fe−Mn−Ni, and Fe−Ni−S.

Decarburization kinetics of liquid Fe−Csat alloys by CO2

Abstract: The kinetics of the decarburization reaction of Fe−Csat liquid alloys by CO2 were investigated at 1600°C under conditions where the rate is not significantly affected by liquid- or gas-phase mass transfer. Rates of decarburization were measured by monitoring the change in gas composition with an in-line mass spectrometer. Small amounts of S, P, Sn, and Pb were alloyed with the Fe−Csat melt to determine their effect on the interfacial rate constant. The rate constant measured for the Fe−Csat−S alloys is in agreement with previous results for Fe−S alloys and was found to be inversely proportional to sulfur concentration at low sulfur levels. For high S-containing alloys where the surface is saturated with sulfur, a residual rate was observed. The effects of phosphorus and lead on the rate constant are negligible. Tin decreases the rate constant, but the effect is small, even when the tin content is as high as 2.6 wt pct.

Mathematical modeling of minor-element behavior in flash smelting of copper concentrates and flash converting of copper mattes

Abstract: A mathematical model has been developed to describe the behavior of minor elements during flash smelting and flash converting The model incorporates equations describing volatilization of minor elements from the molten particles and distribution of these elements between the molten phases in the settler The basic premise of the volatilization model is that at the surface of the molten particle, the partial pressures of the minor-element species are those at equilibrium Transport of the minor-element species to the gas then is described by external mass transfer Good agreement has been obtained between observed and predicted behaviors The effects of oxygen enrichment, matte grade, and wall temperature, as well as the bath temperature, on minor-element behavior have been elucidated

Steel dissolution in quiescent and gas stirred Fe/C melts

Abstract: The dissolution rates of commercial black iron rods in iron/carbon melts under isothermal conditions were measured. The effect of melt carbon content, temperature, natural convection, and gas stirred forced convection conditions were investigated. The experimental data under natural convection conditions (no external stirring) were fitted with a dimensionless correlation for vertical cylinders: Sh = 0.13(Gr . Sc)0.34, representing mass transport control dominated by turbulent natural convection. Under bottom injection gas stirring conditions, it was found that the kinetic power input had little effect on the rod dissolution rates which were controlled by the total gas flow rate. Derived mass transport coefficients under gas stirring conditions were found to have the following dependence on the gas injection rates:k m ∝Q 0.21, wherek m = mass transport coefficient andQ = gas flow rate. A comparison of the experimental results with previously measured mass transfer coefficients under forced convection conditions gave a plume velocity flow rate dependence ofU ∝Q 0.3. A general discussion of gas stirring fluid dynamics and resulting mass transport effects is presented.

Physical characteristics of gas jets injected vertically upward into liquid metal

Abstract: The time-averaged structure of plumes has been measured with a two-element electroresistivity probe during upward injection of nitrogen or helium into mercury in a ladle-shaped vessel. From these measurements and data obtained earlier for air jets in water, general correlations linking the spatial distribution of gas fraction with the Froude number and gas/liquid density ratio have been developed. Early evidence suggests that these correlations should be applicable to gas-stirred metallurgical baths. Measurements of the profiles of bubble velocity and bubble pierced length reveal that the kinetic energy of the gas is dissipated close to the nozzle, and buoyancy dominates flow over most of the plume.

Plasma spraying of ceramic particles in argon-hydrogen D.C. Plasma jets: Modeling and measurements of particles in flight correlation with thermophysical properties of sprayed layers

Abstract: The behavior of alumina or stabilized zirconia particles in flight in Ar−H2 d. c. plasma jets (up to 40 kW) has been studied. Measurement of the temperature distributions in the plasma jets (by emission spectroscopy) has shown the importance of the electrodes and are chamber designs on the length and diameter of the jets. The important cooling effect of the surrounding air has also been shown, and the parameters controlling it have been studied. Modeling of the momentum, mass, and heat transfers between plasma and particles as well as measurements of the trajectory, velocity, surface temperature distributions, and particle evaporation have enabled us to determine the influence of the different paramters, such as size and injection velocity distributions, particle morphology,etc., on the particle molten state upon impact. These calculations and measurements on the particles in flight have been correlated to some physical properties of deposits.

Physical chemistry of the carbothermic reduction of alumina in the presence of a metallic solvent: Part II. Measurements of kinetics of reaction

Abstract: The carbothermic reduction of alumina was studied in the temperature range of 1700°C to 1850°C in the presence of either tin or copper as the metallic solvent. The total pressure in the smelting system was controlled at pressures between 0.08 and 0.20 atm. The overall reaction is Al2O3(s)+3C(s)=2Al+3CO(g). The rate of reduction of alumina was found to depend strongly on temperature, increasing by three orders of magnitude between 1700°C and 1850°C. Total pressure and activity of aluminum in the solvent bath also affected the rate of reduction. Changes in the alumina particle type and size, in the carbon type, in the carbon-to-oxygen ratio, and in the pellet size had little effect on the rate of reduction of alumina. The kinetics of reduction are shown to follow a pseudo-first order kinetic model.

Flow separation and liquid rundown in a gas-atomization process

Abstract: “Rundown≓ filming mode was studied in a confined design gas-atomization nozzle of converging/ diverging construction In this mode, liquid metal runs down to a certain distance up to ≈3 mm on the outer surface of the metal delivery tube in the form of a thin film Atomization then takes place through the disintegration of this film by the oncoming gas The rundown effect was simulated by water, and the supersonic gas flow outside the nozzle was visualized by Schlieren photography It was found that rundown is caused by the liquid being drawn into a separated flow region on the wall of the delivery tube This separation comes about as a result of the action on the boundary layer of adverse pressure gradients associated with the shock waves in the gas flow Geometric conditions required for observing rundown are discussed, and a method is outlined for assessing whether a given nozzle design is likely to produce the effect Evidence is also presented for the filming of the liquid on the tip of the nozzle by radial spreading

Standard enthalpy of formation of Sc5Si3

Abstract: The standard enthalpy of formation of Sc5Si3 has been determined by solute-solvent drop calorimetry at (1473±2) K. The following value is reported: ΔH f o (mean)=−(719.1±34.0) kJ mol−1. This result is compared with corresponding published values for the enthalpies of formation of Me5Si3, with Me=Mn, Cr, V, Ti. This comparison shows regularly increasing negative enthalpies of formation from Mn5Si3 to Sc5Si3.

The kinetics of nitrogen absorption and desorption from a plasma arc by molten iron

Abstract: A plasma torch and refractory-lined furnace with a 10 kg capacity were used to study the kinetics of nitrogen absorption and desorption in molten iron. In this study, melts containing both oxygen and sulfur were used. In accord with earlier studies, a limiting rate constant of 0.020 cm/s-pct was observed at high oxygen and/or sulfur contents. At lower oxygen and/or sulfur contents, the measured desorption rates are smaller than most of the reported values and appear to be limited by mixed melt, mass transfer chemical control. Absorption of nitrogen from the plasma arc is limited by mass transfer in the melt. The dominant form of convection in the vicinity of jet impingement is surface tension driven flow. The reaction N(g)=N(pct) appears to be responsible for the enhanced nitrogen content of the melt. The nitrogen content of a melt in equilibrium with the atomic nitrogen content of an Ar-5 pct N2 plasma jet was determined to be 0.30 wt pct or thirty times the equilibrium value.

Activities of boron in the binary Fe-B, Co-B, and Cu-B melts

Abstract: Activities of boron in the binary Fe-B, Co-B, and Cu-B melts have been directly determined by the electromotive force (emf) measurement. Boron-saturated liquid Cu-B alloy was used as the reference electrode and a ternary 28 wt pct Al2O3-29 wt pct B2O3-43 wt pct CaO oxide melt was used as the electrolyte. Deviations of the boron activities from Raoult's law have been found largely negative for the Fe-B and Co-B systems but largely positive for the Cu-B system. Boron activities calculated from the literature data have not been in good agreement with the measured data. Activities of iron, cobalt, and copper have been calculated from the obtained boron activities by means of the Gibbs-Duhem equation. Some modifications to the liquidus curves on the Fe-B and Co-B phase diagrams have been presented.