Review of experimental data and modeling of the viscosities of fully liquid slags in the Al2O3-CaO-‘FeO’-SiO2 system

A general model based on the Urbain formalism has been developed, which enables the viscosities of liquid slags to be predicted for all compositions in the Al₂O₃-CaO-‘FeO’-SiO₂ system in equilibrium with metallic iron. Available experimental viscosity data have been analyzed and critically reviewed. The Urbain formalism has been modified to include compositional dependent model parameters. Experimental data in unaries, binaries, ternaries, and the quaternary system have been described by the model over the whole compositional and temperature ranges using one set of model parameters. This viscosity model can now be applied to various industrial slag systems.     

Modeling of viscosities of the partly crystallized slags in the Al2O3-CaO-“FeO”-SiO2 system

A viscosity model of the partly crystallized slag in the Al₂O₃-CaO-‘FeO’-SiO₂ system has been developed in conjunction with the thermodynamic computer package F*A*C*T. Proportions of solids crystallized out of the liquid phase and compositions of the remaining liquid phase predicted by F*A*C*T are used in the viscosity model. Various heterogeneous viscosity models have been tested using large experimental dataset in the Al₂O₃-CaO-‘FeO’-SiO₂ system in reducing conditions close to the equilibrium with metallic iron. The Roscoe equation with new empirical parameters was found to provide reasonable agreement with experimental data. Examples of model application to industrial nonferrous smelting slag systems are presented. This model can also be applied to coal ash slags.     

Viscosities of indium-lead liquid alloys

The viscosities of indium-lead alloys have been determined by using the Ostwald type viscometer. The values have been obtained by a relative technique since the viscometer has been calibrated with indium and lead. Isothermal viscosities show that the negative deviations from ideal mixing decrease with increase in temperature. The results are studied from the stand-point of thermodynamics. The temperature dependence can be described by Arrhenius relation. The activation energy depends on concentration and is close to 1.6 kcal/mole. In the studied temperature range, it has been established that the data can be fitted with Arrhenius relation and Andrade’s equation.     

A quasi-chemical viscosity model for fully liquid slags in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-‘FeO’-SiO<Subscript>2</Subscript> system

A structurally based viscosity model for fully liquid silicate slags has been proposed and applied to the Al₂O₃-CaO-‘FeO’-SiO₂ system at metallic iron saturation. The model links the slag viscosity to the internal structure of melts through the concentrations of various anion/cation structural units (SUs). The concentrations of structural units are equivalent to the second nearest neighbor bond concentrations calculated by the quasi-chemical thermodynamic model. This viscosity model describes experimental data over the entire temperature and composition range within the Al₂O₃-CaO-‘FeO’-SiO₂ system at metallic iron saturation and can be extended to other industrial slag systems.     

Rheology of model aerosol suspensions

The rheological properties of model aerosol suspensions at phase fractions of less than 5% w/v (phase ratio of 0.05) were investigated. The rheological profiles of lactose in chloroform, lactose in trichlorofluoromethane (Propellent 11, P11), and salbutamol sulphate in P11 have been investigated in the presence and absence of lecithin, a phospholipid surface-active agent. The relative viscosities of these disperse systems correlated with the increasing disperse phase fractions and the addition of surfactant was found to reduce these viscosities to a relative viscosity of approximately 1.0. The results suggest that the relative viscosity is a useful indicator of flocculation in these systems, and may be valuable in formulation development.     

Viscosity measurement of mould fluxes using inclined plane test and development of mathematical model

Abstract

During the current research and development activities at Tata Steel Teesside Technology Centre, UK, the inclined plane test (IPT) is adopted as a quick method to measure the viscosity/fluidity of mould powders being used currently for continuous casting of different steel qualities and section sizes. The usefulness of the IPT method was also validated by comparing the viscosities that were measured by a high temperature viscometer. It has been established that the IPT measured viscosity values are comparable with the mould powder supplier’s data. The IPT ribbon lengths of different powders have been correlated with the viscosities using an Arrhenius type relationship. The ribbon lengths of the solidified fluxes were found to have a good correlation with the molar ratios of the corresponding powders. Hence, the relationship was further tuned to develop a viscosity prediction model using the chemical compositions of the mould fluxes (i.e. the model can be used for a quick assessment of mould flux viscosity based on its chemical composition).     

Modeling the Viscosity of Silicate Melts Containing Lead Oxide

Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing lead oxide. The model requires three pairs of adjustable parameters that are fitted to the experimental viscosities in the following systems: pure PbO, PbO-SiO₂, and PbO-Al₂O₃-SiO₂. The viscosity of other ternary and multicomponent silicate melts containing PbO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by PbO with SiO₂, Al₂O₃, CaO, MgO, Na₂O, and K₂O. The deviation of the available experimental data from the viscosities predicted by the model is within experimental error limits.     

Densities and viscosities of some liquid alloys of zinc and cadmium

The densities and viscosities of the alloy systems Zn-Sn, Cd-Sn, and Cd-Pb and of zinc-and cadmium-rich Zn-Pb and Cd-Tl alloys have been determined accurately by absolute techniques of proven reliability. Isothermal molar volumes for all five systems show positive deviations from ideal mixing in agreement with other published data. Isothermal viscosities demonstrate large negative deviations from ideal mixing. In each system, solute additions give rise to sharp decreases in viscosity at the zinc-and cadmium-rich ends of the system, a phenomenon not reflected in the density data. To explain the viscosity results, it is proposed that alloying additions to zinc and cadmium alter the interatomic bonding associated with the surface structure of these metals causing disproportionate viscosity changes. Recent surface tension studies have aptly demonstrated that the surfaces of zinc and cadmium are atomically more ordered than the bulk metal.     

Estimation of the viscosities of binary metallic melts using Gibbs energies of mixing

In the present work, information on the integral molar Gibbs energies of mixing is employed to calculate the viscosities of binary substitutional metallic melts. A correlation has been established between the second derivative of the integral molar Gibbs energy of mixing with respect to composition and the corresponding function for the Gibbs energy of activation for viscosity. The viscosities predicted from available thermodynamic data in the case of a number of binary metallic systems using this correlation show satisfactory agreement with the values reported from experimental measurements. The value of this correlation in predicting the viscosities of complex metallic melts is also examined.     

Viscosity of Industrial Blast Furnace Slag in Indian Scenario

Twenty-five numbers of blast furnace slag samples are collected from different operational Indian blast furnaces. The viscosities of these slag samples are estimated using various models developed by several researchers for the purpose. Subsequently, viscosities of some selected slag samples are measured using a high temperature viscometer to choose the best possible model that can be used in the present investigation. On the basis of the results, a comparison is made between the various models bringing about the shortcomings of these mathematical models. It is observed that the estimated viscosities by Iida model are best fitted with the viscosities of slags measured by high temperature viscometer and hence, the viscosity data obtained by Iida model are analyzed at length to ascertain the compositional dependence of slag viscosity. It is observed that the industrial blast furnace slag viscosity is greatly influenced by its CaO/SiO₂ ratio, MgO and Al₂O₃ contents.     

The viscosities of lead,tin, and Pb-Sn alloys

The viscosities of lead, tin, and Pb-Sn alloys have been determined by an absolute technique using an oscillational viscosimeter. By careful experimentation, it has been possible to obtain results which are accurate to within ±0.5 pct. For the pure metals, the data are in good agreement with some recent work. The results obey Andrade’s equation ηv^1/3 = A expC/vT, the constants having values ofA = 2.54 × 10⁻³ and C = 86.30 for lead, andA = 2.75 × 10⁻³ and C = 88.49 for tin. No evidence has been found to support the reports of some investigators that Pb-Sn alloys experience structural changes or abnormal interatomic reactions in any specific composition ranges such as around the eutectic. The results confirm recent work that isothermal viscosities vary with composition in a linear manner. Formerly Research Scientist, Department of Energy, Mines and Resources, Ottawa, Canada     

Thermodynamic study and the phase diagram of the Mg-Sn system

By means of concentration cells of the following type, Mg (l)MgCl2 in (LiCl-KCl)_eut (l)Mg-Sn (1), the partial thermodynamic data of Mg in Mg-Sn liquid solutions have been obtained in the composition range of 0.1 ≤X _Mg ≤ 0.75 and at temperatures from 950 to 1100 K. These values are compared with thermodynamic data reported in the literature and used for the evaluation to obtain a complete set of thermodynamic functions for phase diagram calculations and for further interpretation by the associate model. This model, which accepts the existence of ‘Mg₂Sn as-sociates’ in the liquid alloys, enables calculations of viscosity by Kucharski’s method corre-lating properly with experimental data. Mutual correlations between thermodynamic properties, physical properties, structure, and the phase diagram of the Mg-Sn system were shown to in-dicate a maximum chemical short-range order close to the composition Mg2Sn.     

Heat flow parameters affecting dendrite spacings during unsteady-state solidification of Sn-Pb and Al-Cu alloys

Solidification thermal parameters and dendrite arm spacings have been measured in hypoeutectic Sn-Pb and Al-Cu alloys solidified under unsteady-state heat flow conditions. It was observed that both primary and secondary spacings decreased with increased solute content for Sn-Pb alloys. For Al-Cu alloys, the primary spacing was found to be independent of composition, and secondary spacings decrease as the solute content is increased. The predictive theoretical models for primary spacings existing in the literature did not generate the experimental observations concerning the Sn-Pb and Al-Cu alloys examined in the present study. The theoretical Bouchard-Kirkaldy’s (BK’s) equation relating secondary spacings with tip growth rate has generated adequately the experimental results for both metallic systems. The insertion of analytical expressions for tip growth rate and cooling rate into the predictive model, or into the resulting experimental equations in order to establish empirical formulas permitting primary and secondary dendritic spacings to be determined as functions of unsteady-state solidification parameters such as melt superheat, type of mold, and transient metal/mold heattransfer coefficient is proposed.     

Thermochemistry of binary alloys of transition metals: The Me-Ti,Me-Zr,and Me-Hf(Me = Ag,Au) systems

The standard enthalpies of formation of congruently melting intermetallic compounds in the (Ag, Au)-(Ti, Zr, Hf) binary systems were determined by high-temperature direct synthesis calorimetry at 1473 ± 2 K. The enthalpies of mixing for the liquid alloys in the same systems have been measured by the same technique in the range of compositions available for experiments at 1473 ± 2 K. The results obtained are compared with estimated values from Miedema’s semiempirical model.     

Thermochemistry of binary alloys of transition metals: The systems Me-Gd, Me-Ho, and Me-Lu (Me = Cu, Ag, and Au)

The standard enthalpies of formation of 18 congruently melting, intermetallic compounds in the (Gd, Ho, Lu)-(Cu, Ag, Au) binary systems have been determined by high-temperature direct synthesis calorimetry at 1473±2 K. The liquid-liquid enthalpies of mixing for many of the same alloys have also been obtained in the course of these measurements. The results obtained for the solid alloys are compared with values calculated from Miedema’s semiempirical model.     

Measurements of magnetic fields and electromagnetically driven melt flow in a physical model of a hall-héroult cell

A physical model (approximately one-tenth scale and operated at 1000 A) was constructed to simulate the electromagnetically driven flow occurring in Hall cells. The model contained Wood’s metal, in which magnetic fields and velocities were measured, as the single liquid. Data have been generated for (future) comparison with mathematical models of Hall cells. The model has also proved useful in examining the effects of cell changes and upsets long thought by operators to have an influence on cell performance. Effects of current maldistribution in the “collector bars,” “cold” anodes, “muck,” and alternative bus-bar arrangements have been observed. In many cases, these effects can be predicted qualitatively from an examination of the model’s magnetic field. S.K. Banerjee, having received his Ph.D. from the Department of Materials Science and Mineral Engineering at the University of California.     

Viscosities of Slags ‐ an Overview

Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well‐known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network. The measurements of slag viscosities often pose experimental challenges, especially with respect to the choice of materials. This paper takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions is brought out. A number of semi‐empirical models have been developed to estimate the slag viscosities in the case of multicomponent slags. A critical survey of these models is presented in this paper. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are, (1) Model by lida et al., (2) CSIRO model, (3) Pyroresearch Model, (4) Model by Tanaka et al., (5) Model approach by Reddy et al., and (6) KTH‐model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two‐phase mixtures are also taken up in the presentation.     

Viscosity measurement and prediction model of molten iron

In order to explore effects of element content and temperature on the viscosity, viscosities of molten iron were precisely measured by the oscillating crucible method. The results obtained are summarised as follows: The viscosity of molten iron rises first and then decreases with the decreasing temperature; the viscosities before and after the turning point are the viscosity property and the solidification property, respectively. The temperature of the turning point decreases with the increasing carbon content. The viscosity increases with the increasing silicon and titanium content; on the contrary, the viscosity shows a downward trend with the increasing manganese, phosphorus, and sulphur content. The mechanism of various elements on the viscosity was analysed; the quantitative relationship between the viscosity and element content was obtained. The prediction model of the viscosity was established based on the co-existence principle; the calculation results of the model were in accordance with the measurement.