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By M. J. Bagshaw, J. D. Hunt, R. M. Jordan

"Continuous casting processes, and the roll casting process in particular, offer considerable potential to the Aluminium industry, both meatallurgically and economically.The three major limiting process problems that occur during roll casting are Centre Line Segregation', 'Sticking' where metal adheres to the rolls during casting, and 'Heat Line' formation. 'Heat Lines' are localised semi-continuous longitudinal defects, usually a few cms in width, where the cast metal leaves the roll bite partially molten. These defects occur at relatively low casting speeds when the mean slab exit temperature remains several hundred degrees below the solidus temperature. The objective of the work described here is to develop a better understanding of the roll casting process in general, and in particular, to understand the phenomenon of 'Heat Line' formation.A steady state two dimensional finite difference model has been developed to describe the roll casting process, incorporating a variable heat transfer coefficient through the roll bite. In the model the difference equations are formulated using a control volume method and latent heat is incorporated according to the Scheil equation. A Gauss-Seidel type technique is used to obtain the solution. Because the rate of heat evolution is non-linear the temperature in each box is determined by using a Newton-Raphson method. The solution for a box can be multi valued and therefore lead to instability particularly near the vicinity of the front. A stability 'criterion is presented which shows that to obtain a stable solution it is better to have long narrow boxes rather than boxes with small dimensions in both directions.The model explains why heat lines form in terms of the variable slab/roll heat transfer coefficient.Experimental measurements of slab exit temperatures are also presented. These were obtained on a Hunter twin roll caster for the binary AI-Cu system, at two compositions over as wide a range· of casting speeds as possible. The experimental results are compared with the predicted ones."

Jan 1, 1986

By D. R. Spink

A partial desulfurization roasting (PDR) technique has been developed for use on zinc concentrates whereby the sulfide sulfur associated with the iron content is selectively removed over a very short residence ?time in the roaster. The resulting PDR product is then leached for the selective removal of the iron. The resulting leach restdite is an upgraded zinc sulfide concentrate which has a very low iron content. The up-graded zinc concentrate can be subjected to a conventional dead roast without formation of deleterious zinc ferrite so that hot acid leaching and jarosite (or other) iron precipitation steps are obviated. Examples are presented for the treatment of three very different types of zinc concentrates.

Jan 1, 1990

By Masayasu Kawahara

"The extraction and separation of nickel, cobalt and copper were investigated with a solvent impregnated resin which was produced from UX84-I and XAD-4. The extraction behavior of metals with the solvent impregnated resin is similar to that with solvent extraction. The extraction ability of solvent impregnated resin improves when using finer particle resin and with a higher concentration of extraction solvent.IntroductionSolvent extraction is well known-as a method for separation of metallic elements in solution. However there are problems with intermediate phase and solvent loss. Ion exchange resin is also used in hydrometallurgy, but it is not fit for separating a large quantity of metals. Amberlite XAD-4 resin is known as a absorption agent of organic matter in water. It is expected that the resin which has the ability of extracting metals can be made by absorbing organic extractant on XAD-4 resin In this study, solvent impregnated resin (SIR) was produced from LIX84-I and XAD-4, and extraction and separation of nickel, cobalt and copper were conducted using SIR. The extraction properties of SIR were investigated, and a comparison between ordinary solvent extraction and SIR was made.Experimental ProcedureAmberlite XAD-4 was used as absorption resin for the organic extractant in this study. The physical properties of XAD-4 are shown in Table I. Amber lite XAD-4 has a large surface area and shows good ability to absorb organic matter in water, but the: resin does not have the ability of exchanging metallic ion."

Jan 1, 2000

By D. Georgiou

Direct sulphuric acid leaching of nickeliferous limonites is the process of choice to recover nickel and cobalt from equatorially located lateritic ores. These ores are rich-in-iron (-45 wt%) existing in the form of goethite enriched with nickel. The merit of this process is due to its high nickel selectivity because of simultaneous iron separation and acid regeneration. Under acid leaching conditions (-250 to 270°C) iron follows an acid dissolution-hydrolytic precipitation path yielding a very low concentration level depending on temperature and acidity of the final leach liquor. The primary precipitation product of iron is hematite which also forms as a scale on reactor internals along with co-existing aluminum. In this paper, an overview of the behaviour of iron solid products under process conditions is made. The evolution of goethite to hematite transformation, as well as the role of iron in reactor scale production, are studied using SEM/EDX characterization techniques.

Jan 1, 1995

By John Snowberger III, J. Brent Hiskey

The electrochemical dissolution of super alloys containing different amounts of rhenium was investigated. The initial part of the investigation focused on the anodic dissolution of rhenium from second-generation (3% Re) and third-generation (6% Re) nickel based alloys. Exploratory electrochemical tests were conducted to evaluate solution chemistries and to establish fundamental dissolution behavior of the alloys. These included rotating disc electrode (RDE) cyclic voltammetry, linear sweep voltammetry, and chronoamperometry tests. Electrolytes comprising sulfuric acid, hydrochloric acid, and ammonium sulfate were examined. Of these, a 0.1 M HCl solution proved to be extremely effective for electrochemical dissolution of samples of CMSX-4, CMSX-10, and SC-180 alloys. This paper discusses in detail the electrochemical behavior of these alloys.

Jan 1, 2014

By K. Kalgraf

The motion and stability of the metal/electrolyte interface is determined by Navier-Stokes equation. The equation may be decomposed into two independent equations by taking the divergence and curl of Navier-Stokes equation. The divergence determines the motion and stability of magneto-gravitational waves. The curl of Navier-Stokes equation gives an equation containing only velocity and magnetic field, and states that the magnetic field is driving a circulation pattern in the cell, and this magneto-flow has its own stability conditions. The waves are called Alfven waves, and their stability properties are related only to magnetic field and geometry.

Jan 1, 2001

By Douglas J. Harvey, Chi-Mou Ni

"This paper presents an analysis technique for the solidification of metal castings. This method, based on a modified finite difference scheme with an irregular mesh, is capable of dealing with the complex geometries of castings. The nonlinearities in material properties of specific heat and thermal conductivity, arising from the phase change during solidification, are accounted for in the step-by-step calculations. Two solidification problems are solved with this analysis technique and the calculated results compare satisfactorily with experimental data. IntroductionCasting process design engineers are often faced with the difficult problem of designing castings to be produced porosity-free. Since the solidification of metal is affected by many interacting variables such as the thermal conductivity, density, and specific heat of both the molten metal and the mold, it is easily seen why this is a difficult task.Typically, casting tooling design is an intuitive process which builds on past successful methods. After processing equipment is constructed, trial castings are made and examined for dimensions and integrity. Changes in the tooling are generally required to improve casting soundness or to reduce cycle time. In the permanent mold process, tooling is complex and difficult to alter after initial construction. The water-cooled steel molds are part of the complete automated system. Associated holding furnaces, pouring ladles, casting conveyers, and utility connections all make other than minor adjustments a costly and time consuming task. An analytical method for using the principles of heat transfer for predicting solidification patterns would be of great value in the permanent mold process by minimizing costly changes."

Jan 1, 1986

By Y. Y. Sheng

Plume flows created by gas injection into liquid metals have been studied extensively, however the dynamics of bubbles within the plume have not received adequate attention, particularly for large, irregular bubbles, characteristic of the processing of liquid metals. The present model uses a combined Eulerian-Lagrangian approach in which an estimated void fraction distribution is used to calculate the liquid flow field with a conventional Eulerian scheme. The trajectories of bubbles are then computed in a Lagrangian manner using the estimated flow field, and experimentally measured information on bubble drag coefficients', lateral migration due to lateral lift forces and interaction with turbulent eddies, and variation in bubble size due to break-up. Turbulence in the two-phase zone is modeled with a modified k-e model with extra source terms to account for the second phase which have been recently determined by the present authors. The computed void fraction and turbulent liquid flow field distributions are in good agreement with experimental measurements.

Jan 1, 1993

By J. Boltano

This paper discusses the study, design and implementation of the new gas handling system for the Caletones Smelter of Codelco-Chile. A discussion on design conditions for a future Sulphuric Acid Plant using Teniente Converter gases is also included. The old system which started to be modified in 1985 and relied on natural draft and used balloon flues, resulted in a limited gas handling capacity for operation under future process conditions. This system also caused excessive fugitive gases in the smelter working areas. The new system permits handling of process gases from the higher capacity Teniente Converters Installed in 1987-1989 improving the gas handling of the reverberatory furnaces and Peirce-Smith converters as well as the environmental conditions of the smelter. This system utilises improved converter gas hoods, evaporative cooling and electrostatic precipitators gas cleaning, and is based on natural draft.

Jan 1, 1992

The oxidation of ferrous ions by oxygen in sulphate solutions is a very slow process, but it tills long been known that the addition of sulphur dioxide increases the rate of reaction very significantly. The kinetics and mechanism of the process were investigated in the laboratory and the results confirmed the advantage of adding small amounts of sulphur dioxide to the oxygen stream for the removal of iron from solutions. The effect of various parameters on the overall rate of iron oxidation and precipitation was studied. In particular, temperature, acidity and composition of the gas mixture were considered and the optimum conditions for the precipitation of goethite were determined.

Jan 1, 1991

By Dan Wang, Qian Xu, Guangshi Li, Xionggang Lu, Xingli Zou, Zhongfu Zhou, Hongwei Cheng, Changyuan Lu

The preoxidation of the ore has a profound significance to the concentration, separation and purification of nickel and copper from the lean complex ore. In this paper, the natural Ni-Cu sulfide mineral samples under the elevated temperature condition in air were investigated, as well as under isothermal condition at 600 oC in air. The mineralogical characterization was studied using XRF, ICP and the Rietveld method. The oxidation behavior and the element migration of the Ni-Cu sulfide ore were studied by XRD, SEM-EDS and TG. The XRD Rietveld method was successfully developed in the phase identification and quantification of this complex ore powder sample. The oxidative intermediates (Cu/Ni-ferrite) were detected by XRD, and the process of the element migration was obviously revealed by the line scans using SEM-EDS. It is the preoxidation of this mineral that provides guidance for the extraction of valuable metals from low-grade Ni-Cu sulfide ores in the future.

Jan 1, 2015

By S. Sundarraj

The morphological transition between columnar and equiaxed structures is an important solidification phenomenon frequently observed in castings, especially complex parts with varying cross-section, The mechanical properties and the occurrence of defects such as hot tears are strongly dependent on the structure formed in the casting. Hence, it is important to understand the conditions leading to columnar or equiaxed structures. Although extensive work has been done in modeling solidification systems, almost all of the existing models are based on the assumption that the structure formed in the casting is either purely columnar or purely equiaxed. Prediction of the columnar-equiaxed transition (CET) requires a solidification model which accounts for the formation of both columnar and equiaxed structures, along with related microscopic and macroscopic solidification phenomena. In this paper a CET model is presented which: (i) takes account of both columnar and equiaxed structures, (ii) accounts for macroscopic heat transfer coupled with microscopic phenomena such as nucleation, growth and microsegregation, (iii) satisfies solute conservation, and (iv) is easy to implement in commercial finite element and finite difference software. The proposed model predictions of CET have been validated with available experimental results for a uni-directional solidification of an aluminum-copper alloy. A sensitivity analysis has also been carried out to determine the effects of various parameters on the CET model predictions. The model is being extended to other alloy systems and more complex geometries. This work will be published in due course.

Jan 1, 1996

By Takahiro Miki

Soldering material widely used is Sn-Pb alloy, which have low melting point and excellent electrical, strength properties and wettability. However, Pb is one of the toxic elements, which is undesirable due to environmental and safety reasons, thus Pb-free alternative alloy is preferred for new soldering materiaL Sn-Ag and Sn-Zn based alloys have been viewed as very promising candidates, among many potential substitutes. Addition of third element to these alloys will decrease melting point of the alloys. Hence, Sn-Ag-In and Sn-Zn-Mg alloys are expected to be suitable for replacing Sn-Pb solder alloy. In order to dcsign new Pb-free soldering materials, it is crucial to understand precise thermodynamic properties and phase diagrams of alloy systems. In the present work, ion current ratios of Ag to In and Mg to Zn were measured for Sn-Ag-In and Sn-Zn-Mg alloys by mass spectrometry, respectively. Also, the authors reviewed the thermodynamic properties of terminal binary alloys determined by other researchers and evaluated a thermodynamic functions to express the excess Gibbs free energy of each binary alloy. Thermodynamic functions to express the excess Gibbs free energy of liquid Sn-Ag-In and Sn-Zn-Mg ternary alloys were determined, utilizing the assessed Gibbs free energy of terminal binary alloys with the measured ion current ratios using mass speetrometer.

Jan 1, 2003

By Liwen Hu, Jianxun Song, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

The subchloride titanium was prepared by sponge titanium and titanium tetrachloride in the CaCl2 at 1173 K. The species were detected are mainly titanium dichloride, and the average valent in the melt are 2.05. The accurate equilibrium constants were obtained for the reaction 3Ti2+ = 2Ti3++Ti after the accurate activities of titanium chloride were evaluated with emf method, and the observed deviations from ideal behavior are discussed.

Jan 1, 2015

By Claudia Gasparrini

Uranium occurs in a variety of minerals, the more common primary ones of which are uraninite-pitchblende, coffinite and a group known as the complex multiple oxides. Identification and description of the uranium-bearing and associated minerals in ore samples may give a preliminary indication of the potential economic importance of the deposit and may also suggest initial approaches to metal extraction. The present paper reviews the common uranium minerals, describes their manner of occurrence and compares the types of deposits with which they are associated. Methods and techniques for their identification are described and their leaching characteristics discussed.

Jan 1, 1981

By Shoji Taniguchi, Lifeng Zhang

"In this paper, firstly the 3D single-phase turbulent steady fluid flow in a vessel with four baffles stirred by a single impeller is mathematically simulated. Turbulence is modeled by using the standard k - e model. Sliding-grid method is used to model the impeller. The flow domain is divided into two cylindrical, the inner one rotates at the same speed as the impeller, and the outer one is fixed with the baffles. Results indicate that the high-speed zone is near the paddles, and larger stirring speed generates larger fluid flow velocity. The calculated stirring intensity data are used to analyze the experimental results. Secondly the effects, such as filter pore size, gas flow rate and NaCl concentration, on bubble size are studied by experiment. For the particle removal rate by bubble flotation in this vessel, first order kinetics is adopted. The effects of initial number of the particles, gas flow rate, particle and bubble size, stirring speed and surface condition, on the removal rate constant are discussed, and an empirical equation is derived by experimental data. At last, a simple model is developed to study the particle attachment probability on bubble surface under turbulent flow conditions. IntroductionIt is well known that inclusions have a bad effect on steel quality. Trying to remove inclusions from liquid steel as many as possible is one of the main objects for the metallurgical workers. Lots of ways are developed to remove inclusions from liquid steel. Gas injection is an effective one. This technique is used to achieve homogeneity in the temperature and metal composition and to assist in the removal of second phase and dissolved impurities from molten steel. Gas injection is commonly applied to the secondary metallurgy processes and continuous casting, for example the ladle argon gas treatment, RH vacuum degassing, and the gas injection in the Submerged Entry Nozzles (SEN) of continuous casting mold, etc. The development of these processes focuses on achieving two conditions: fine bubbles and good mixing. Fine bubbles provide a large gas/liquid interfacial area and a high attachment probability to inclusions, and good mixing enhances the efficiency of impurity transfer."

Jan 1, 2000

By Roderick 1. L. Guthrie, Mei Li

"A mathematical model was developed to study the role of orifice shape in the detection of inclusions in LiMCA (Liquid Metal .cleanliness Analyzer) system. The fluid flow field within the ESZ was obtained by solving the Navier-Stokes equations. The trajectories of entrained particles were calculated using the equations for motion of particles. A numerical study of the effect of orifice shape on signal shape generated by inclusions passing through orifice showed that the signals in a parabolic orifice are gaussian in shape, while those in a cylindrical orifice are trapezoidal in shape. This signal shape difference needs to be taken into account when performing particle discrimination. Orifice shape influences also pass-through fraction of inclusions. Finally, a study of the orifice shape on critical conditioning currents suggested that as the polynominal coefficient of the parabolic orifice increases, the critical conditioning current, which is also the maximum operating current, decreases dramatically. These critical conditioning currents also increase as the fluid flow velocity within the ESZ increases. IntroductionThe presence of non-metallic inclusions in metals often leads to impaired mechanical properties such as a reduction in fatigue strength, and to processing problems such as tear-offs in deep drawing and increased breakage rates in wire drawing operations. Similarly, inclusions cause a variety of surface defects in rolled or extruded products.Prior to the development of the LiMCA system (1) at McGill University in the early 1980's, it was not possible to measure inclusions, in situ, in liquid metals. Compared with other techniques, such as sedimentation, filtration and metallography, which require considerable amounts of labor and time, the LiMCA method has the advantage of providing not only information on the volume concentration of inclusions, but also on the size distribution of inclusions immediately and quantitatively."

Jan 1, 2001

By Jae-Ho. Lee

Mercury is a toxic contaminant encountered in the extraction of gold from mercury-containing ores. It is found in the leach solution of CIP circuits and in the cathodes of the electrolyte cells used to electrodeposit the gold. The research conducted has examined the potential for selective removal of mercury from synthetic Au-Hg-CN electrolytes containing only gold, only mercury, and both gold and mercury. Cyclic voltammograms were obtained for mercury- coated copper electrodes with these cyanide electrolytes. Exchange current densities were determined from the voltammograms in the low overpotential region. Laboratory scale batch- electrolysis at constant current was also conducted for the electrolytes containing only mercury and both mercury and gold, at 20 and 50°C and from which the kinetic behavior associated with the process was analyzed. The surface of cathode before and after electrolysis was also characterized and a copper mercury intermetallic (CyHg,) was identified. Gold codeposited with mercury during the later stages of electrolysis. The results of this work corroborate that the mercury-amalgam copper electrode offers a viable electrochemical technique for the selective removal of mercury, however a high-surface-area cathode-cell would have to be utilized to provide for the desired selectivity.

Jan 1, 1994

By Kimura. E.

Continuous estimation of phosphorus content of molten copper is required to produce phosphorus deoxidized copper in a continuous casting operation. The phosphorus content of molten copper was related to its electric resistivity, which was measured by the four-probed technique with a specially-shaped cell. In a laboratory scale, the linear relationship between the above factors was confirmed in the temperature range of 1083OC through 1200°C. The phosphorus concentration range measured was from 40 to 500 ppm. The phosphorus content was monitored successfully by measuring the electric resistivity of the molten copper in the distributor of a continuous caster in an industrial scale.

Jan 1, 1992

By Guo Gongyi

An extraction chromatography by which 99.99 % pure scandium oxide can be prepared from the starting materiel containing about 70% scandium oxide has been developed by taking advantage of some peculiar properties of the complex chemistry and extraction chemistry of scandium. The purification of scandium was performed at room temperature with relatively fast rates in two chromatographic columns. The preliminary separation of scandium from impurities was done by extraction chromatography using tri-butyl phosphate as the stationery phase in the presence of citric acid, and the nearly complete separation in the presence of perchloric acid. The scandium recovery was greater than 90 %.

Jan 1, 1989