Measurement of viscosity,density and surface tension of metal melts

A modified procedure for measuring viscosity, surface tension and density of metallic melts, using a gas bubble viscosimeter, is presented. The principle of measurement is based on the relation between rate of ascent of a gas bubble in the melt and the melt viscosity. The rate of bubble ascent is determined by registering the moment of detachment by pressure measurement in the lance and the moment of arrival of the bubble at the melt surface by video film and an image processing system. The procedure is tested and the limits of its application are determined by comparative measurements on reference metals. After tests on reference metals, measurements are taken of the viscosity, density and surface tension of Al-Cu alloys in the temperature range 960 – 1465 K with copper contents of 12.23 to 58.5%. The relationships between these values and temperature and composition of the melt are investigated, and corresponding approximation formulae derived.     

New method for simultaneous measurement of viscosity,density and surface tension of metallic melts at high temperatures

A new method for determination of the viscosity of metallic melts based on the measurement of the velocity of gas bubbles in the melt, is developed. Gas bubbles are produced at known depth through a capillary tube. The time needed by the bubble to reach the surface of the melt is measured with the help of a laser beam. The method is tested with reference metals (Sn, Pb, Cu). The results show that there is a large dependence of the bubble velocity on the viscosity although the diameter of the bubbles is large. The recorded pressure curve in the capillary tube during the bubble formation allows the measurement of the surface tension and the density of the metallic melt to be determined by using the method of the maximum bubble pressure.     

From viscosity and surface tension to marangoni flow in melts

This article covers some of our recent work on slag viscosity, the surface tension of liquid Cu-O alloys, and the relative role of Marangoni and bulk flow on refractory wear in iron-silicate slags. A viscosity model developed for slags containing SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, MnO, FeO, PbO, NiO, Cu₂O, ZnO, CoO, and TiO₂ is capable of representing the effects of temperature, silica, and network-modifier cations within a wide range of temperatures and compositions. It forms a useful part of a computational package for multiphase-equilibrium (MPE) calculations and for predicting slag viscosities. The models are well applicable to a range of industrial slags (blast furnace, new iron making, base-metal and Platinum Group Metals (PGM) smelting, and coal-ash slags). The package has also some capability of predicting the viscosity of slags containing suspended solids. The surface tension of liquid copper-oxygen alloys has also been analyzed. The adsorption behavior of oxygen in liquid copper is well represented by the combined Langmuir-Gibbs isotherm. According to the rate data for silica-rod dissolution in liquid iron-silicate slags at 1573 K, the preferential attack at the slag line diminishes as the linear velocity of flow at the surface of the rotating silica rod reaches 9 to 16 cm/s. A tentative analysis gives the critical condition, that relates the critical Reynolds (Re) and Marangoni (Ma) number by the equation Re*²=0.13 Ma*. This article is dedicated to Professor Ken Mills. The authors have been inspired by Ken and have benefited greatly from his encouragement in their research in a number of areas. This article is based on a presentation given in the Mills Symposium entitled “Metals, Slags, Glasses: High Temperature Properties & Phenomena,” which took place at The Institute of Materials in London, England, on August 22–23, 2002.     

The density and surface tension isotherms of manganese-silicon melts

Summary Density measurements carried out at 1350 and 1550°C confirmed that Mn-Si melts strongly deviate from Raoult's equation. In the range 20–80 at.% Si, the partial-molar volumes undergo a substantial change: ¯V_mn decreases from 9.97 to 6.5 cm³/g-mole, while V_Si increases from 6.60 to 11.06 cm³/g-mole.The surface tension isotherm has a maximum near Mn₂Si-Mn₅Si₃, which attains 1150 ergs/cm², and an inflection point near MnSi. The temperature coefficients of the alloys of this system are practically equal (0.2 ergs/cm²-deg C).     

A new experimental method for determining liquid density and surface tension

A summary concerning the measurement of liquid density relying on the Archimedes principle has been presented, based on which a new effective method with a specially designed bob for determining liquid density has been suggested. The application of this method to ethyl alcohol solution and liquid glycerol, as well as a theoretical error analysis, shows that this new method is significant, because not only can it simplify the procedure of measurement but it can also offer more precise results. Besides, this method can further provide surface tension or contact angle simultaneously. It is expected that this new method will find its application in hightemperature melts. leave from Thermodynamics and Phase Diagram Lab, University of Science and Technology Beijing     

Volume and surface properties of nickel melts containing bismuth impurity determined from the density and the surface tension

The physicochemical and the structural properties of the nickel-based melts with a low (impurity) bismuth content, which, like lead, is one the most harmful impurities in cast high-temperature nickel-based superalloys, are studied using the surface tension and the density. It is found that the surface tension increases as the bismuth impurity content varies from zero to 0.05 wt %, which corresponds to transition of excess substance from the surface into the volume.     

Calculation of the surface tension of salt melts with divalent ions

The surface tensions of alkaline-earth metal halides and alkali metal sulfates and carbonates are calculated. Molten salts are described in terms of a charged rigid sphere model using the generalized mean spherical approximation. The calculated surface tensions of these salts are compared to the experimental data, and fitting parameters are not used in these calculations.     

Study of the surface properties of nickel-based melts by the constrained drop method: I. Surface tension

The constrained drop method is used to study the surface tension σ of the following melts at 1773–1923 K and p _Ar = 0.1 MPa: nickel of various grades (with various oxygen contents), binary Ni-Al (Re) alloys, and a complex Ni-Re-(W, Mo, Co) alloy. The value of σ of liquid nickel is shown to decrease with increasing oxygen content in it. The additions of aluminum (6%) and rhenium (3–7%) to nickel in binary alloys weakly change its surface tension. Alloying elements (W, Mo, Co) in Ni-Re-(W, Mo, Co) alloys insignificantly affect σ of their melts.     

含铬转炉渣黏度和表面张力的计算模型

为预测含铬转炉渣的黏度和表面张力,基于炉渣离子与分子共存理论,并结合前人实测的系列含铬转炉渣黏度和表面张力数据,建立含铬转炉渣黏度和表面张力关于温度和结构单元之间的计算模型。模型的计算值与文献的实测值吻合较好,通过模型,有助于预测含铬转炉渣的黏度和表面张力。结果表明,随着Cr₂O₃含量的增加,炉渣黏度升高,表面张力增大,Cr₂O₃对表面张力的影响最大;随着FeO含量的增加,炉渣黏度降低,表面张力减小;随着碱度的增加,炉渣黏度升高,碱度对黏度的影响最大,而对表面张力的影响是先增加后减小,在碱度为1.8时存在极大值。     

Prediction of surface tension in metallic and ionic melts in thermophysical database system

A so-called excess surface tension model in a thermophysical database of IDMSKM system is described in this paper. The functional expression for excess Gibbs energy of mixing with mole fraction for binary solutions by Redlich & Kister has been applied to correlate excess surface tension defined in this paper with mole fraction for the same, therefore, the surface tension could be represented in a quaternary polynomial function of mole fraction. The predicted surface tension values by this model demonstrate a reasonable accuracy in binary metallic as well as ionic systems. The model exhibits a better generality than the previous ones for surface tension evaluations, hence its application could be expected to expand.     

Effect of the mechanical activation of Ln2O3 Oxides (with Ln = Gd, Dy, Ho, and Lu) on the surface tension and density of borate melts

Effect of the mechanical activation of Gd₂O₃, Dy₂O₃, Ho₂O₃, and Lu₂O₃ oxides on surface tension ?? and density ?? of borate melts is studied. Linear temperature dependences of ?? and ?? are found, and the temperature coefficients are calculated. The dependence of ?? on the lanthanide number in the periodic table is found and exhibits nonmonotonic behavior of the melts. The effect of mechanical activation on ?? and ?? is explained by the formation of complex lanthanide ions, which have uniform geometry in the borate melts.     

Kinematic viscosity of Mg-Al melts in the magnesium-rich portion

Kinematic viscosity ν of Mg-Al melts containing up to 14 at % second component is measured by the method of damped torsional vibrations of a crucible with a melt. The measurements are performed in the temperature t range between liquidus and 900°C upon heating of a sample after its melting and upon subsequent cooling. Kinematic viscosity isotherms and the concentration dependences of the activation energy of viscous flow are constructed.     

Comparison of surface tension measurements using the levitated droplet method

Measurements of the surface tension of some metals by the levitating drop technique have been carried out by two independent laboratories in order to establish the levels of agreement. Results obtained for pure iron, cobalt, and copper showed reasonable agreement, but in the case of stainless steel, significant differences were apparent, which were shown to be a consequence of the different hydrogen concentrations in the respective environmental gases. Surface tension values for pure gold obtained by this method showed good agreement with the data obtained by established methods and show that the levitating drop technique is capable of yielding reliable results. Formerly with the Department of Metallurgy and Materials Science at the University of Toronto     

Structure and properties of the slags of continuous converting of copper nickel-containing mattes and concentrates: III. Influence of the slag composition on the surface tension and density of slag melts

The surface tension and density of the slags that form during the continuous converting of copper mattes and concentrates into blister copper are determined. The slag melt compositions are varied over a wide range of (Fe + Ni) concentrations and SiO₂/CaO and (Fe)/(Cu + Ni) ratios. The surface tension and density are measured by the bubble pressure technique. The concentration of iron and nickel in a slag and the (Fe)/(Cu + Ni) and SiO₂/CaO ratios affect the density and surface tension.