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By Saskia Duyvesteyn

For many applications in hydrometallurgy and water treatment it would be advantageous to use ion-exchange resins in stirred reactors. However, attrition of the resin may lead to significant losses of both resin and metal values and prevent water quality goals from being reached. We have studied the recovery of fine resin particles by froth flotation, using the model copper - Dow XFS4195 chelating resin system. As the functional group on the resin is a bis-picolylamine, the resin should be amenable to flotation by anionic collectors, such as sodium dodecylsulfate and sodium dodecylsulfonate. The kinetics of copper loading from dilute aqueous solutions in an agitated vessel were studied as a function of copper concentration, pH and resin bead size. The flotation of unloaded resin was investigated for different types of collector, collector concentration, conditioning time, and resin bead size. Potential applications are discussed.

Jan 1, 1995

Electrocrystallization studies were conducted in a concentrated acid-copper electrolyte to determine the influence of chloride ions and glue on copper nucleation and on the structure of thin copper layers. Electrochemical experiments allied to SEM and XRD examination were performed to characterize the mechanism of nucleation in the presence of additives at 65°C. Results indicated that most of the copper nucleation from a 83 g dm-3 Cu2+ solution, with 140 g dm-3 of H2SO4 is achieved in a matter of milliseconds, Although the presence of chloride and glue, at the concentration levels tested, does not seem to substantially modify the nucleation mechanism, the morphology, nuclei density and the copper film structure and orientation are changed by the presence of additives and by electrolyte stirring.

Jan 1, 1999

By T. Maruyama

The Tamano Smelter of Hibi Kyodo Smelting CO. ,Ltd. went into operation in 1972. The Flash Smelting Furnace that was originally adapted was equipped with electrodes that were attached to the settler substitute of the slag cleaning furnace. Later the development of our own original coke combustion technology was promoted and a new Tamano Type Flash Smelting Furnace (T-FSF), without electrodes, was put into operation in 1988. The technology of coke combustion and combustion the burner have continued to improve. As a result the copper losses in the slag have been reduced as well as a stable operation has been achieved. Furthermore, this has been accomplished while increasing the concentration feed and the matte grade The current objective is to continue to strive for high matte grade operation and to raise production efficiency while paying attention to the important subject of copper losses in the slag. In this report, the data related to the copper loss in the slag reduction are presented along with the influence of the thickness, settling time and coke. The recent operation conditions of the T- FSF are also presented.

Jan 1, 2003

By B. Balamurugan, D. J. Sellmyer, J. E. Shield, G. C. Hadjipanayis, Damien Le Ror, R. Skomski

"Rare-earth transition-metal (R-TM) alloys show superior permanent magnetic properties in the bulk, but the synthesis and application ofR-TM nanoparticles remains a challenge due to the requirement of high-temperature annealing above about 800 °C for alloy formation and subsequent crystalline ordering. Here we report a single-step method to produce highly ordered R-TM nanoparticles such as YCO5 and SmCO5, without high-temperature thermal annealing by employing a cluster-deposition system, and we investigate their structural and magnetic properties. Nanoparticles of size = 10 nm are monodispersed (s /d ~ 0.15) and have Hc values at T = 300 K of 8.0 and 4.5 kOe for YC05 and SmC05, respectively. Alignment of the easy axes is performed via a field applied to the clusters before deposition. These processing steps are highly desirable to create and assemble R-TM nanoparticle composites for future permanentmagnet applications.IntroductionMagnetic nanoparticles with high magnetocrystalline anisotropies (Ki > 1 MJ/m3) are required for permanent-magnet, recording-media, and other significant applications [1-3]. In this regard, bulk rare-earth transition metal alloys (R-TM) especially RC05 (R = Y and Sm) crystallized in the hexagonal CaCu5-type structure have shown a large Ki = 5 MJ/m3 (YC05) and 22 MJ/m3 (SmCo5) along with an appreciable saturation-magnetic polarization (Js, > 10 kG) and high curie temperatures (Tc > 1000 K) [2]. The challenges in controlling the size, sizedistribution, phase purity and crystalline ordering, however, limit the research on RCo5 nanoparticles [4,5]. The conventional arc-melting technique requires high-temperature annealing for alloy formation and subsequent crystalline ordering, which causes excess growth and thus results in nanocrystalline powders of particles sizes larger than 30 nm [6, 7]. Low-temperature wet-chemical techniques yield SmC05 nanoparticles of sizes smaller than 20 nm [5], but the control of phase purity is challenging due to the presence of surfactants and formation of other secondary phases [8]."

Jan 1, 2012

By J. M. Rapkoch

In late October 1996, an acid plant at a major U.S. copper smelter was faced with unexpected and rapidly increasing pressure drop across the gas cooling tower in the acid plant, indicating a build-up on the packing. This threatened to halt operations if not resolved. Earlier that month, a smaller vessel in the acid plant was found to be completely plugged with lead sulfate. It was feared that a similar fate awaited the gas cooling tower unless the scale build-up was stopped. Although lead sulfate is present in most copper smelter acid plants, this accumulation was unusually severe. An investigation was launched to find the source of the lead, determine how lead is transported to the gas cooling tower, recommend operating practices to prevent such severe scaling, and seek ways to recycle the lead value in the scale covered polypropylene packing. Late in the investigation it was learned that the lead originated from an improperly executed recycling program.

Jan 1, 2000

By Robert Vidal

A model of the homogeneous chemistry and transport processes within the separator of a chrome-alum electrowinning cell is introduced, discussed, and compared to experiment. The influence of diffusion, electromigration, and convection are included; it is found that convection was the dominant mode of transport for the experimental conditions. Simulation results explain experimental observations concerning an apparent disappearance of dichromate ions produced at the cell anode. The relation between potential drop across the diaphragm and the current and fluid flow is also illustrated. The model is used to recommend future experimental and theoretical work.

Jan 1, 1994

By G. Upadhya

Considerable success has been achieved recently in modeling microstructural evolution during solidification of castings bthrough the coupling of macroscopic heat transfer with microscopic solidification kinetics models. However, a complete model for simulation of solidification in complex shaped castings involves: (i) the description of fluid flow, during and after mold filling, coupled with (ii) heat transfer to the mold and surroundings by use of a macro model, followed by (iii) a description of subsequent solidification of liquid metal by use of a micro model for solidification of the alloy under consideration. This paper describes the coupling of solidification kinetics model to a 3D, transient, fully coupled fluid flow and heat transfer model. Coupling between the macremicro models is achieved by using the latent heat method. Micro models for the eutectics of gray, white and ductile iron are discussed. This coupled code has been used for predicting the thermal history and microstructural data for shaped castings. Various applications of the model, including prediction of shrinkage defects, grain density contours, and graylwhite transition region in the casting, are presented for a relatively complex casting geometry.

Jan 1, 1992

By Paykan Safe

Computational Fluid Dynamic (CFD) modeling provides a powerful tool to assist with the design of ventilation and fume control systems in smelters and other high temperature metallurgical facilities. For this paper, this tool has been used to analyze the off-gas flow patterns exiting the mouth of a Peirce-Smith converter into a water-cooled hood and drop out box. The effects of various process and physical plant design parameters on process gas and fume capture and potential build up on the converter hoods was examined, and the optimum design and operating parameters were determined.

Jan 1, 2000

By R. C. Chaturvedi, S. B. Padwal

"Padwal and Chaturvedi have developed the model based on M-K theory, considering Hosford's yield criterion and critical thickness strain criterion"" to predict the sheet metal forming limits under simple (constant) strain ratio paths. This analysis has been extended in this paper to predict the sheet metal forming limits under complex strain paths. The effects of exponent ""a"" in Hosford's yield criterion and strain paths on the forming limits under complex strain paths are studied using this analysis. The predictions of the present analysis are compared, both for simple and complex strain paths, with experimental results of Ishigaki for A.K. steel and also with the predictions of Rao and Chaturvedi's model. The quantitative analysis of the error in predicting the forming limits has also been carried out using a method suggested by the authors earlier.1. INTRODUCTIONThe constant strain ratio condition has been assumed in the theories developed for prediction of forming limit diagrams (FLO). In actual forming operation, this condition is seldom satisfied. Even in the case of simple single stage press formed components, the strain path becomes curved and non-linear. In the case of pressings with complex shapes, or multiple stages of forming, the changes in strain path are more pronounced and even abrupt.Experimental study of the forming limits, under two stage strain paths, by Ishigaki [1], has shown that the forming limits are path dependent. It has been observed that the forming limits lower than that under simple strain paths, may be obtained under certain strain paths (when the first stage strain path is either equibiaxial tension or uniaxial tension, followed by the second stage strain path as plane strain). Rasmussen's work [2J, on the theoretical study of forming limits under curvilinear strains paths, has shown that a large drop in formability can result from very small changes in strain path. Thus if a deformation process gives rise to failures due to plastic instability, the failure is not necessarily due to insufficient formability of the material. In such cases, FLOs based on constant strain ratio path should not be used directly in predicting the success or failure of the forming operation. Thus the knowledge of forming limits under complex strain paths is of great importance to the interpretation of press-shop problems."

Jan 1, 1994

By Y. H. Wang, S. Kou

"Three-dimensional weld pool convection was computer simulated using dimensionless variables. The electromagnetic force, the buoyancy force and the surface tension gradient on the pool surface were treated through the use of the dimensionless electromagnetic force, the Grashof number and the Marangoni number. Other typical dimensionless numbers such as the Prandtl number and the Peclet number were also used. The calculated and experimentally observed fusion boundaries were compared. The convection patterns were shown and the effect of the Marangoni number was demonstrated. IntroductionSeveral weld pool convection models have been developed by Oreper et al. (1,2), Chan et al. (3) and Kou et al. (4). These models describe two dimensional convection in stationary weld pools in a semi-infinite workpiece. Since the vast majority of arc welding practices involve a moving heat source and weld pool, and the workpieces are finite in thickness rather than semi -infinite, a 3-D convection model for a moving heat source and a workpiece of finite thickness is expected to be much more useful.Weld pool convection can strongly affect the structure and properties of the resultant welds. Variations in weld characteristics which are likely to occur from changes in weld pool convection are: weld penetration, macrosegregation, gas porosity, solidification structure, undercutting and surface smoothness. Apparently, the quantitative understanding of convection and heat flow in weld pools is of considerable practical interest. Mathematical models describing convection and heat flow in weld pools are essential, not only because of the quantitative understanding they provide, but also because of the difficulties associated with the experimental measurements of weld pool convection. These difficulties are mainly due to the fact that only surface flow, rather than the overall convection pattern in the weld pool, can be observed. In fact, due to arc glow even the observation of surface flow can be rather inconvenient."

Jan 1, 1986

By K. E. Gonsalves, G. M. Chow

"Nanostructured powders (particle diameter of 1 - 100 nm) have uses in electronic, magnetic, structural, thermal applications as well as advanced processing of materials. Among many methods of making nanostructured powders, chemical routes offer many attractive features such as feasibility of cost-effective bulk quantity production, design of chemistry at the molecular scale, and chemical homogeneity of the powders. In this talk, two systems of chemically synthesized nanocomposite powders are presented, namely, granular magnetic materials of Fe-Cu and Co-Cu, and thermal-structural materials of AIN-BN. Synthesis and processing, characterization and properties of these materials are discussed.IntroductionNanostructured powders (particle diameter of 1 - 100 nm) are attractive materials because of many useful properties (e.g. catalytic, optical, magnetic etc.) and processing advantages (e.g. lower sintering temperature) [1]. There are many methods of making nanostructured powders, for example, physical and chemical vapor deposition, mechanical attrition, and solution chemistry [1, 2]. A common method of making composite powders involves the grinding, mixing and blending of constituents powders, but it has the limitation of inhomogeneous mixing. Chemical routes have many useful features. Using solution chemistry, precursors can be molecularly tailored and homogeneously mixed at the molecular level. The chemical approach may result in better properties of the final product. Compared to vapor-phase fabrication techniques, chemical routes are more cost-effective in producing large quantity of material. In addition, control of particle size, size distribution and stabilization of the nanoscale particles against agglomeration can be more effectively manipulated via solution chemistry.In this paper, we present an overview of some of our work in nanocomposite powders prepared by solution chemistry. Metallic systems of FeCu and Co-Cu, and ceramic system of AIN-BN are discussed. The powders were characterized using x-ray diffraction (XRD) , scanning electron microscopy (SEM), conventional and high resolution transmission electron microscopy (TEM, HRTEM), vibrating sample magnetometry (VSM), inductively coupled plasmaatomic emission spectroscopy (ICP-AES)."

Jan 1, 1994

By Donald I. Bleiwas

World primary nickel production in 1987 is projected to be 770,000 mt, slightly higher than that in 1986. Market economy country (MEC) production in 1987 is projected to be about 524,000 mt, an increase of almost 5 pct over 1986 production. Production cutbacks and closures at Japanese ferronickel plants in 1987 resulted primarily from the strong yen and higher energy prices. Cutbacks also caused reductions in ore production from Indonesia, New Caledonia, and the Philippines. Technical problems affected production, to varying degrees, in Botswana, Indonesia, and Yugoslavia. World primary nickel production for 1988 is projected to be 787,000 mt, of which 536,000 mt will be produced in MECs. Increased production is projected from Botswana, Canada, Cuba, and possibly Greece and Yugoslavia, while slight production decreases are projected for Indonesia, New Caledonia, the Philippines, and Zimbabwe. .. South African nickel production in 1988 could be severly curtailed by social strife. In the early 1990's Brazil and China could be major economic competitors to Western nickel producers.

Jan 1, 1988

By S. S. Babu, T. Hong, T. DebRoy, S. A. David

"Oxide inclusions form in welds because of deoxidation reactions in the weld pool. These inclusions control the weld microstructure development. Thermodynamic and kinetic calculation of oxidation reaction can describe inclusion characteristics such as number density, size, and composition. Experimental work has shown that fluid-flow velocity gradients in the weld pool can accelerate inclusion growth by collision and coalescence. Moreover, fluid flow in welds can transport inclusions to different temperature regions that may lead to repeated dissolution and growth of inclusions. These phenomena are being studied with the help of computational coupled heat transfer, fluid-flow, thermodynamic, and kinetic models. The results show that the inclusion formation in steel welds can be described as a function of the welding processes, process parameters, and steel composition.IntroductionThe relationship between inclusions and formation of a high-toughness phase, namely acicular ferrite in low-alloy steel welds, is well known (1-4). Past research has focused on maximizing acicular ferrite amount in welds by controlling welding processes, process variables, and welding consumable parameters. Research has shown that there is a complex interaction between inclusion characteristics, prior austenite grain size, and weld metal hardenability. In a low-alloy steel weld, the small addition of titanium lead to a change in the inclusion composition and resulted in a transition in the microstructure from bainitic to acicular ferrite [see Fig. I]. This in turn lead to the best combination of strength and toughness. This paper describes the inclusion formation in low-alloy steel welds."

Jan 1, 1999

By Florian Kongoli

The so-called "fayalite" slag, despite problems associated with it, is the most widely used slag in copper smelting processes. Thirty years ago, in order to overcomes some drawbacks of this slag a new "calcium ferrite" slag was proposed especially for continuous copper converting. Since both slags have strong and weak points depending on the field of their application about 8 years ago another new "ferrous calcium silicate" slag was proposed that is expected to solve the drawbacks of each slag. This new slag is defined as mainly consisting of FeOx, CaO and SiO2 as its main components but it can practically have several combinations of these constituents. In order to determine the best area of this slag for possible industrial application the quantification of phase relations is an important subject. In this paper the work carried out by the authors in quantifying through an original physical model the phase relations, liquidus surface, liquidus regions, behavior of solid phases and the effect of minor components is reviewed. Several special compositions of this slag have been identified and discussed for possible applications in the industrial practice.

Jan 1, 2006

By S. M. Copley, M. Yankova, E. Y. Yankov, J. A. Todd

"Nanophased coupled growth structures, with spacings of -10 nm, have been observed in banded microstructures produced by laser melting hypoeutectic Ag-Cu alloys. These coupled growth structures comprised a Cu-rich phase of width - 1 nm and a Ag-rich phase of width - 9 nm. In this paper, microstructural observations of nanophased coupled growth structures in hypo eutectic AgCu alloys are presented. Laser beam velocities for the transition from banded to microsegregation free microstructures are modelled and compared with experimental values. Models are presented to show that, at a critical undercooling, initial growth of a Ag-rich, metastable, extended solid solution is rapid but slows to a halt as copper is partitioned into the liquid at the solid/liquid interface. Following nucleation, the coupled growth structure then grows until the partitioned copper is consumed, at which point growth of the Ag-rich solid solution is again accelerated. This cycle then repeats resulting in banded microstructures comprised of 750 nm of the Ag-rich extended, metastable solid solution, followed by 250 nm of the coupled growth structure.1. Structural Studies of Laser Melted and Resolidified TrailsPresented here are observations of laser melted and resolidified trails in Ag-Cu alloys obtained at beam velocities ranging from 0.7 to 34 cm S·I. When the laser beam is scanned along the surface (positive x-direction) with a velocity Vb a melt pool with the shape given in Fig. 1a moves with the beam. The isotherms move with the velocity, Vi,. = Vb cos.p. Calculations employing the thermal analysis of Kou, Hsu and Mehrabian [1] for the beam velocities of this investigation and for the thermal properties of AgCu alloys, indicated that, .p, the angle between the isotherm velocity and beam velocity should be small at the surface where microstructural studies were made. This prediction was supported by observations of trail cross-sections. Based on these observations, and the calculations which include latent heat effects, the isotherm velocity for observations near the surface in our investigation was taken to be 27 cm S-I."

Jan 1, 1994

By Munetaka Iwasaki

Nitrogen strongly affects mechanical properties of steel and therefore we may sometimes modify the various processes for its content. Numerous studies based on the results of chemical analysis of quenched samples were reported with a few exceptions of Hot Sievert method. The technique always poses a risk of uncertainty whether the true content of nitrogen in liquid metal is measured or not. In this study vacuum remelting under relatively low pressure was done to enhance gas phase mass transfer. Total pressure of the melt chamber was about 10-3 pa and electron beam heating was used. Mass spectroscopy was used for the direct observation of the rate of denitrization. Nitrogen molecules or atoms were detected by a mass spectrometer set above the melt. Continuous monitoring of the intensity of the fixed mass number may reflect the transfer of nitrogen from the melt to the vacuum. The results of the new and conventional techniques agree, both technique can be verified.

Jan 1, 1999

By Kouji Mimura, Manabu Kishida, Minoru Isshiki

"Purification of metallurgical grade silicon (MG-Si) by the plasma-arc zone melting method (PZM) has been examined. The process consisted in the horizontal displacement of a molten zone heated by Ar- and 10%H2+Ar- plasma-arc under atmospheric pressure. This technique, especially using hydrogen plasma-arc, promoted the segregation of impurities from the head to the tail of the bar and the vaporization of impurities of higher vapor pressures. Metallic impurities such as Fe, Ti, Cr, Mn,. Cu, Al and Ca were reduced to less than 1 mass ppm at the head side of the Si bar. Non-metallic impurities such as boron, phosphorous, carbon and oxygen were also reduced by the zoning effect and, furthermore, by activated hydrogen atoms dissociated in the high temperature plasma-arc according to the following reaction: Q (in liq.Si) + 2H = H20. Plasma-arc zone melting with hydrogen plasma has been recognized to become an effective purification technique of MG-Si for the production of a low cost solar grade Si (SOG-Si).IntroductionDemand of high-purity Si for solar grade silicon (SOG-Si) is supposed to be further growing in the near future. The purity of SOG-Si required for the photovoltaic cell is more than six nines. An expensive semiconductor grade silicon (SEG-Si) with the purity of around eleven nines has been used to satisfy the demand. Development of techniques and processes for the production of a low cost SOG-Si is therefore necessary [l]. Although many purification techniques, such as directional solidification, plasmaarc melting and electron beam melting [1-6], and processes, such as carbothermic reduction of high purity silica [7], have been examined and proposed for this purpose, a more efficient and practical purification technique is still required.In the present work, the purification of MG-Si has been investigated using a plasma-arc zone melting (PZM) technique developed by the authors. Plasma-arc melting, which is well· known as a useful melting method for various metals and alloys, has been recognized to be efficient for refining and degassing several metals if hydrogen is added to the plasma generating gas, resulting in the so-called hydrogen plasma-arc. For example, deoxidation of Fe, Co and Ta [8,9], decarburization of Fe [9] and removal of metallic impurities from Zr, Ta and Fe [10-12] have been reported. This excellent refining effect is considered to be caused by dissociated and activated hydrogen atoms formed in the high temperature plasma-arc."

Jan 1, 2000

By J. N. Hryn

This paper describes some of the work done in Phase 1 of a multi-year, five-phase program aimed at demonstrating the economic feasibility of producing commercial-scale quantities of commodity materials derived from salt cake residue-oxide. The amount of salt cake generated annually in the U. S. is estimated to be 510,000 tons, including 340,000 tons of residue-oxide. Used beverage can (UBC) processing accounts for the majority of residue-oxiae that could be made available for further processing into commercial products. To characterize the composition of residue-oxide. eight residue-oxide samples from various secondary processors were obtained and analyzed. Surprisingly, the composition of residue-oxide was found to be independent of source or alloy family being processed, with? the exception of slightly elevated silicon levels in 3XXand UBC residue-oxide samples. Major phases detected in the residue- oxide were? alumina, spinel, and aluminum hydroxides. Preliminary economic analyses indicated that the refractory market appears to be the best choice for high value-added products produced from residue-oxide with minimum processing. Bench-scale tests indicated that low silicon containing residue-oxide is ready to enter this market, but the elevated silicon content of UBC and 3XX residue-oxide preclude this possibility. A separation technology should 'be developed to remove silicon-containing . species from the alumina and spinel values Present in residue-oxide. This technology would then allow UBC and 3XX residue-oxides to be converted to significantly higher value-added products.

Jan 1, 1995

By J. C. Agarwal

Most metals are produced from minerals containing one or more of the desired metals, some contaminating metals, silicate, oxides, carbonates, and sulfides. Therefore, in the production of metals, there is generally a gaseous effluent in pyrometallurgical processes and a liquid effluent in hydrometallurgical processes. There are also solid residues such as waste ore, tailings, dust, and slag, created by the metal recovery processes. There are two important distinctions between the effluents and the residues: I. Effluents ? gases and liquids ? affect the neighboring environment for miles from the point of emission, while residues affect only the soil on which they are stored or dumped. 2. The environmental and economic effects of effluents are known and felt essentially immediately. By contrast, the environmental effects of the residues may not be known for a long time. For these reasons, the economic impact and the potential corrective actions required are very different for effluents and residues.

Jan 1, 1992

By M. A. Barakat

Large amounts of zinc ash and flue dust containing more than 80 % zinc are accumulated during galvanization processes at the surface of molten zinc bath and in the chimney respectively. Pyrometallurgical recovery of zinc from both of the ash and dust samples has been carried out. The ash was sieved with the help of an industrial sieve shaker provided with mesh sieve having a pore size 0.9 mm. The oversize fraction cut (+ 0.9 mm) was melted at 550 °C under ambient conditions. The produced ingot (1) was analyzed whereas the coarse fraction of the produced slag (+ 0.9 mm) was treated as the coarse ash or added to it. The dust was enriched with suitable fluxing salt prior to heat treatment at 600 °C for 1 h. The produced ingot (2) was analyzed whereas the resulting slag was mixed with the fines of the ash and treated by hydrometallurgical processing to prepare valuable salts of zinc. Parameters affecting recovery processes such as time, temperature and flux percentage were studied. Results obtained revealed that the two prepared ingots (1&2) were successfully recovered with recovery efficiency amounts to =85 %. The obtained samples meet the standard specifications with relatively low price. Also in the light of the strict environmental regulations of pollution control, reuse of these wastes materials will help in keeping the environment clean.

Jan 1, 2000