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By Lifeng Zhang

The transport of fluid, heat and particles (bubbles and solid inclusions) in flowing molten steel is investigated in steel refining ladles, the continuous casting tundish, continuous casting mold and strand, and steel ingot casting processes. Inclusion removal from the molten steel by flow transport and bubble flotation, and inclusion growth by collision and diffusion are discussed. Removal of impurity elements such as [C] and [O] during steel refining are reported.

Jan 1, 2006

By K. Olsen

As aluminum alloy usage in automobiles grows, there are increasing demands on recycling processes and facilities to deal with mixed alloy automotive aluminum scrap. These processes and facilities strive to produce near virgin aluminum stock, which can be relatively costly and difficult. One alternative is to use physical processing methods to upgrade the scrap properties instead of chemically refining the scrap. The Impulse Atomization Process (LAP, patent pending) is a new process for making metallic and ceramic powders. It can produce fine homogeneous microstructures in scrap aluminum alloys due to high undercooling and rapid solidification. The particles have a very narrow size distribution and are in a convenient form for consolidation. This paper compares and contrasts the microstructural features of Impulse Atomized. and quenched Impulse Atomized powders,' for both AL6061 and a scrap aluminum alloy composition.

Jan 1, 1995

By Donald J. Hallbom

Limonitic nickel laterites slurries exhibit complex rheological properties including time dependency that varies from thixotropy to rheopexy. Chronic problems may occur if plant designers and operators fail to take time dependency into account. Stress decay tests indicate that laterite slurry takes roughly two minutes to approach steady state after a step change in the shear rate. As a result, most rheometer measurements are taken at a non-equilibrium state, making evaluation difficult. Two minutes is also long relative to the time that a unit of slurry in a processing plant is at any given shear state, so the slurry may never reach equilibrium. This paper presents a method to describe the rheology of laterite slurry using a Flow Array, which describes the rheology using an array of instantaneous flow curves crossed by an equilibrium flow curve. A rate equation for structural change in non-equilibrium conditions allows time dependence to be efficiently modeled. This flow array allows the flow behavior of time- dependent slurry to be predicted in non-equilibrium conditions using a simple time-step methodology. Keywords: Rheology. nickel laterite, hydraulic transport, pressure acid leach, flow array

Jan 1, 2004

By M. Rubinstein, N. C. Koon, B. N. Das, V. G. Harris

"Copper and gold - based alloys having giant magnetoresistance properties were produced by melt spinning from arc melted and cast rods. The ribbon width varied between 1 and 2 mm and the ribbon thicknesses were in the range of 30 to 50 11m. The uniform microstructure of the cast rods indicated the composition homogeneity in the starting material. The ribbons showed composition uniformity across the cross section from EDX analysis. However, the spun ribbon microstructure changed from a 'frozen in' region near the wheel side to a nanosize spherically precipitated phase towards the freely frozen surface. The evolution of the microstructure from the spun ribbon state to the annealed ones was studied by optical microscopy, SEM and TEM. The structural information of the spun and annealed specimens was obtained from X - ray, electron diffraction, electron microscopy and ferromagnetic resonance. Magnetoresistance was measured by the four point probe method.IntroductionRecently. Giant Magnetoresistance. GMR. has been observed in sputtered thin films alloys of Ag. Au and Cu with Co and Fe [1. 2. 3]. The sputtered films are produced by condensation of the alloys from the vapor phase. These Ag. Au and Cu alloys are miscible and homogeneous in the vapor and liquid phase (except Ag alloys which exhibit phase separation even in the liquid phase) but immiscible and heterogeneous in the solid phase. In our work we have produced thin ribbons of the Cu and Au alloys about 30 µm thick from the miscible state in liquid phase by rapid solidification melt spinning. The microstructural development of the ribbons was investigated in the as - spun condition and on annealing. The other properties such as magnetization. GMR and Mossbauer Spectroscopy were also investigated in the various microstructural conditions of the ribbons."

Jan 1, 1994

By Cyro Takano

An alternative use for recycling of waste from bag house of iron ore sinter plant was tested by producing and evaluating" at laboratory scale, the self reducing cold bonded pellets. This waste was characterized and the self-reducing pellets were produced using anthracite coal fines as reductant and Portland cement or hydrated lime/Blast Furnace slag as binder. It was used the molar ratio of Fe2O3/C (fix) equal to 3. Evolution of cold strength with curing time, for different contents of binder, was evaluated. Cold strength of 200N/pellet was obtained, for sinter dust, after 10 days of curing. Suitable hot strength was also presented and no decrepitation and swelling were observed. Good fractional reduction was obtained at 950°C and 1137°C. These results show that this material may be used by the Self-Reducing Processes for hot metal production, as an alternative route for this dust destination.

Jan 1, 1996

Novel techniques were developed to obtain samples from and make measurements in the shaft of the flash furnace at the Kalgoorlie Nickel Smelter. The data obtained was used to validate mathematical models of the burners and the reaction shaft. Particle, gas and wall temperatures were measured along with the oxygen potential of the molten particles. Collected particles were characterised by sizing, chemical analysis and optical microscopy. The region of the shaft immediately beneath the burner where the rate of change was most rapid received special attention.

Jan 1, 1993

By R. Escalera-Lozano, M. Herrera-Trejo, M. A. Pech-Canul, J. López-Cuevas, A. L. Leal-Cruz, M. I. Pech-Canul

"The use fly-ash (FA) and rice-hull-ash (RHA) offers the potential for the manufacture of hybrid Al/SiCp/spinel composites via reactive infiltration, both with recycled aluminum. The main reason behind this statement is the beneficial role that both waste materials play in preventing the degradation of SiCp reinforcements when the composites are processed with aluminum in molten state. Experimentally, MgAl2O4 is formed in situ during the infiltration of SiCp-preforms in the temperature range 1050-1150 oC for 50-70 min in argon atmosphere at a pressure slightly above to that of the atmospheric pressure. Results reveal that both FA and RHA help in preventing SiCp dissolution and the subsequent formation of the unwanted Al4C3; and although FA-composites still might be susceptible to corrosion via Al4C3 -by the interaction of native carbon in FA with liquid aluminum- a proper FA treatment significantly mitigates its deleterious effect. Primary corrosion mechanisms and strategies to overcome the potential degradation effects are outlined.IntroductionOwing to inherent materials characteristics and post-processing complications –such as corrosion damage- development of metal matrix composites (MMCs) from recycling/waste sources might be a challenging task. Fly-ash (FA) and rice-hull-ash (RHA) are two primary waste materials that offer excellent opportunities for the development of Al matrix composites. Due to its singular hollow-spherical shape and low density, FA has attracted the attention of many researchers. For this reason, most of the efforts to develop Al-based composites from waste materials have been centered on the use of fly ash. Extensive research efforts in the use of FA for Al-based composites have been undertaken by Rohatgi and coworkers [1-4]. In addition to lowering costs, incorporation of fly ash into aluminum has been proved to decrease the materials’ density, increase their hardness, abrasion resistance and stiffness [1]. One of the major outcomes from the mechanical evaluation of aluminum composites prepared with fly ash is that related to their compression characteristics. Typical compressive stress-strain curves form A356/hollow fly ash composites show a linear elastic region followed by a plateau (associated to the collapse of the hollow particles), and then an increase in stress, representing densification of the foam. The crushing of the cenospheres in the composites has been related to an enhancement in the energy absorption capabilities of the material and to a better damage tolerance [4]."

Jan 1, 2008

By V. Baltazar

The behaviour of arsenic and antimony during copper electrorefining was studied in order to identify the conditions under which good quality copper cathodes could be produced from anodes with high levels of these impurities. Examination of the effect of current density over the range 21 to 37 mA/cm2 indicated that the relative amounts of As and Sb entering the electrolyte affected the onset of passivation. When the ratio of As/Sb entering the electrolyte was greater than 2, the anodes showed no sign of passivation even at the highest current density; when the ratio was less than 2, the anodes passivated at 37 mA/cm2. Cathode analyses showed that anodes with an As/Sb dissolution ratio less than 2.0 tend to produce cathodes of inferior quality even at normal current densities (25.7 mA/cm2). The criterion of a minimum As/Sb dissolution ratio of 2.0, and mathematical correlations for the distribution of As and Sb between the electrolyte and slime developed in a previous study, allow the calculation of the maximum allowable Sb level in en anode for a given As concentration. Analyses of plant data at the CCR Division of Noranda Inc. for the last four years of operation have demonstrated that the use of this as a quality control tool has allowed the quality of copper cathodes to be maintained despite a significant increase in the average Sb levels in anode receipts.

Jan 1, 1987

By S. Kang, D. G. C. Robertson

Slag cleaning furnaces require extensive wall cooling because they involve the use of a superheated slag bath. This is in direct contrast to smelting furnaces, where the wall is usually (but not always) protected by "banks" of solid charge. In order to understand the heat transfer and flow in slag cleaning furnaces a number of model studies have been carried out using molten wax to simulate the slag. Wax is a good model fluid because, like slag, it has a high Prandtl number. Wax models cannot simulate the behavior close to the electrodes (DC arc or AC submerged), but they can and do give a good simulation of the flow and heat transfer at the wall. An understanding of these phenomena is of great importance for the design of cooling panels in the walls of the furnace. Since superheated molten slag will eventually wear away any refractory bricks over time, the wall cooling must be designed to form a frozen layer of slag, referred to as a "freeze lining". The heat flux density (Q/A) required to do this is given by Q/A = h* ?T, where h is the heat transfer coefficient in the slag phase at the wall, and Li T is the superheat (bulk slag temperature - liquidus temperature). Both Q/A and h vary greatly with position and both are usually a maximum at the slag line. In the experimental work, molten wax baths were heated by block heaters to provide similar energy densities to those encountered in commercial slag cleaning furnaces. This procedure was considered to be valid since most of the electrical energy into a furnace bath is dissipated as heat. Gas stirring was used to simulate the gas evolved at the electrode in real furnaces - the quantity of this gas could be estimated from a knowledge of electrode consumption. The similarity criterion was equal gas flow per unit area of surface, in model and prototype. Heat transfer coefficients were measured in the models as a function of power density, gas stirring, superheat, etc., and could be related to the full-scale operations by the use of dimensional analysis.

Jan 1, 1999

By Tatsuo Inoue, Marnoru Mizuno, Toru Matsuoka, Kenichiro Abe

"The distribution of particle reinforcements and the residual stresses in metal matrix composite are simulated by considering the motion of particles and the solidification of matrix associated with temperature variation in the course of centrifugal casting process. In the analysis, a heat conduction equation including heat generation due to latent heat and also mechanical work as well as heat input from successively accumulated element on the air/metal boundary is solved by the finite element technique. After the movement of particles subjected to the centrifugal force and drag are analyzed, the residual stresses are elucidated by using a unified constitutive equation which can describe the behavior both in liquid and solid states. Results of the simulation are compared with the experimental data, and the validity and utility of the procedure is confirmed.IntroductionProcess simulation of metal matrix composite (MMC) is required to determine the mechanical properties of the materials and the efficient process and conditions of the fabrication. Properties of bonding matrix with reinforcements in the course of the processing, for example, affects the strength of the composite, while the final costs of the productions depends on the efficiency of fabrication. Therefore, the simulation of processing of MMC is prerequisite in order to clarify the mechanism to fabricate the material which has been expected to maintain high mechanical properties and the cost performance.Some techniques of processing MMC[l] have been developed so far. Among them, the centrifugal casting technique [2-5] has many attractive characteristics as processing of the MMC: The centrifugal casting technique makes the reinforcements such as particles or short fibers to be distributed in the radial direction by the centrifugal force acting on reinforcements due to the difference in density between reinforcements and matrix. Since the distribution of reinforcements affect the mechanical properties of MMC, the composite with functionally gradient mechanical properties can be provided by the centrifugal casting technique."

Jan 1, 1994

By M. E. Karabin, R. J. O'Malley

"A mathematical model of the roll casting process has been developed which predicts macro-variables, such as roll separating force, roll torque, and strip exit speed for a range of roll speeds. Continuum variables, such as interface pressure, interface shear stress, freeze-front shape, and internal temperature distribution are also predicted.The model consists of two independent segments: solidification and rolling. The solidification model is two-dimensional (thickness and rolling direction) and is capable of handling alloy solidification. The solidification model is employed until solidification through the thickness is complete, then the rolling solution is activated.The rolling model is a one-dimensional (rolling direction) mechanical solution based on the von Karman approach, coupled with a two-dimensional thermal solution. The flow stress is expressed as a function of the average through-thickness temperature of the strip.Experiments were performed using a laboratory roll caster to test and refine the model. Experimental strip exit temperatures were used as input to the model. Experimental and predicted roll torque and strip exit speea were forced into agreement at a single reference roll speed to obtain values for the coefficient of friction and the interfacial heat transfer coefficient. Using these values, good agreement was obtained between predicted and experimental torque and strip exit speed over the entire range of roll speeds examined."

Jan 1, 1986

By Guozhu Ye, Eric’ Burstrom

"Despite of numerous solutions for recovery of zinc from EAF dust have been suggested and tested in laboratory scale over the last three decades, Waelz kiln process is still the most dominating process for treatment of EAF dust. Few of the proposed alternative methods have gone beyond the laboratory tests. This paper will give you insights to some of the concepts that have been pilot tested at MEFOS. The innovative aspects of these concepts will be shown and the major results will be highlighted. These include the following concepts: - Production of a crude zinc oxide product with low halide content for zinc electrowinning using a DC furnace with hollow electrode- Production of a bypass filter dust containing more than 50%ZnO by injection of EAF dust to the electric arc furnace during refining combined with a bypass filter system- Elimination of zinc ferrite by CaO treatment for electrowinning with EZINEX process - Selective reduction of iron oxide in zinc ferrite for simultaneous recovery of ZnO andmetallic ironIntroductionRecovery of zinc from EAF dust is dominated by the Waelz process since EAF dust has been classified as hazardous waste by EPA in the early 1980´s. A large number of alternative processes have been suggested and tested without commercial success due to two major reasons [1]:- High content of chlorine and fluorine for the pyrometallurgical alternatives- High content of ZnOFe2O3 for the hydrometallurgical processesMany innovative concepts for treatment of EAF dust for zinc recovery have been pilot tested at MEFOS in the past 20 years. This paper will review some of the concepts focusing on the two problems mentioned above."

Jan 1, 2008

By G. Kugler, M. Tercelj

"The use of the up-to date light alloys and their development are in the sharp ascent especially in transportation industry. In the last years the use of the magnesium alloys for the various purposes was strongly increased. The aim of present research was to study the influence of solidification rate on hot workability and on obtained mechanical properties of AM60 magnesium alloy. The study was also focused on possibility to omit prior homogenisation process which would result in cost reduction. The solidification of gravity cast alloy has been investigated with various methods of the thermal analysis: in situ simple thermal analysis and simultaneous thermal analysis. In order to reveal optimal hot working conditions the deformation behaviour was studied in the temperature range 200-450°C and strain rates between 0.001-lOs-1. Mechanical properties have been studied with tensile and impact toughness testing.IntroductionIn recent years, the increased demand for magnesium alloys has been mainly driven by the need of automotive and transportation industry to reduce the weight, as this is the most important parameter to reduce the energy consumption. Beside their very low weight in comparison to other metals, the magnesium alloys are characterized by good machinability, corrosion resistance and good mechanical properties, and can thus compete with aluminium alloys and for some applications even with steels. Due their decreased workabilty they are typically used as cast alloys, but in recent years also the research of their wrought state has become more extensive [1-7]. Decreased hot workability of magnesium alloys originates from their hexagonal close-packed structure. One of the most popular magnesium alloys with great potential for many applications is AM60 (MgA16Mn), which is predominately used for casting. But its application could be increased if the mechanical properties, could be improved. This can be done by hot working. Namely it is well known that wrought microstructure is characterized by better mechanical properties in comparison to as-cast state. On the other hand due to its low hot workability the homogenization process is required prior hot deformation, which results in increased production costs. Thus the aim of the present research was to study the influence of solidification rate on hot workability of AM60 alloy in order to improve its mechanical properties and to check the possibility of producing near-net-shape casting products omitting homogenisation process by employing small additional deformations after casting. Within the framework of this research the solidification of gravity cast AM60 alloy has been investigated with various methods of the thermal analysis."

Jan 1, 2011

By H. Sieber

Multilayer samples of tantalum and aluminum with the composition of Al-25Ta were prepared by cold rolling of elemental foils. The microstructure and phases were characterized by XRD, SEM and TEMISAED and the reactive phase formation was examined by DSC and DTA measurements in multilayer foils rolled for different deformation levels. The rolling procedure yields a decrease of the Ta particle size in the Al matrix and also results in the formation of a multilayer structure with a thickness of the elemental foils down to 200 nm in average. No phase formation is observed during the cold rolling procedure. While XRD and DSC measurements show no phase formation up to the melting of aluminum for samples rolled up to 40 F&R (fold and rolling) passes, in samples rolled for 50 or more F&R passes a first phase formation reaction yield an interfacial layer of TaAl3. Contrary to former studies in the investigated cold rolled Al- 25Ta multilayers the reaction starts at temperatures as low as about 340°C. The first stages of the reaction are associated with two exothermic maxima, that increase in amplitude and shift to lower temperatures with increasing number of F&R passes. At higher temperature the TaA13 reaction layer thickens very sluggishly and yields a third exothermic maxima at about 600°C. Isothermal DSC scans show the reaction is not finished for samples containing elemental particles larger than 1 pm after annealing at 550°C for 5h. In all the investigated samples no Al- Ta phase other than Tad3 was observed to grow for heat treatments up to 800°C. Multilayer samples heated up to 1400°C show a morphology consisting of small AITa2 particles embedded in a single phase TaA13 matrix. The multilayer microstructure and reaction product morphology are characterized by SEM and TEM investigations in cross-section and plan view geometry.

Jan 1, 1998

By J. J. Rush

Neutron scattering and analysis techniques are extremely powerful, often unique, probes for the characterization of the amount, location, bonding states, and dynamics of hydrogen in all classes of materials. Developments over the past decade at the NIST Center for Neutron Research and elsewhere have greatly increased the sensitivity and dynamic range of neutron methods. In this paper, we provide a flavor of the capabilities of modem neutron instrumentation for the study of hydrogen in a number of technologically interesting systems, including metal hydrides, fuel-cell materials, fullerenes, and disordered carbons.

Jan 1, 2002

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen temary system, which is of fundamental importance for discussing the recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, Sb015 and Sb203 in the PbO-SbOu and PbO-Sb203 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By Jackson Jenkins

The second survey of world copper SXEW plants has been completed. Solvent extraction and electrowinning data published in 1996 has been updated and leach data from seventeen plants is now included. The following pages list the results of the thirty- two plants that responded to the survey. Selected information is summarized in graphical form.

Jan 1, 1999

By Akira Yazawa

To realize highly efficient process in extractive metallurgy, continuous operation nearly in equilibrium is preferable, but most metallurgical processes consist of plural steps with different chemical potentials. Traditional two-step process of sintering followed by reduction is continuous in each step, but is heterogeneous reaction system far from equilibrium, and the chemical potentials are varied considerably along the distance the charge travels in a reactor. This route will become old-fasioned in next century due to the various inherent problems caused especially by sintering process. To establish reasonable new smelting processes, the important tasks of the metallurgists are how to introduce feed and reacting gas in the reactor, and also how to overcome the difference in chemical potential in the reactor system. Based on the ways to solve theses tasks, recent proposals of new smelting process for copper and lead are classified and discussed with the help of sulfur-oxygen potential diagram. On such potential diagram, each equilibrium step in continuous smelting is expressed at a fixed point, and two reactors with different chemical potentials must be connected by continuous molten flow through launder or partition wall. In the latter case, the reactor is apparently single, but some technical problems must be overcome. While, in a batch smelting like converter, potential variation is successively realized along a path on chemical potential diagram with the time elapsed. To establish immediate equilibrium, continuous steady flow of reactants into well mixed reactor is indispensable. In modern smelting process, the ore is mostly supplied in the form of powder which have huge surface area and fluid character, and consequently injection process must be very attractive. Several examples are discussed for both of copper and lead smelting, and promising future technologies are suggested.

Jan 1, 1988

By K. A. Lewandowski

Agglomeration of ore can be used to immobilize fine particles during heap leaching by agglomerating them into granules. Without agglomeration, the fine ore particles can migrate within the heap, clogging flow channels and producing large areas where access of solution to the ore is very poor. The benefits of agglomeration are well-known in gold heap leaching operations, which can be effectively agglomerated using binders such as Portland cement due to the alkaline leaching solutions used. However, agglomeration has not been very effective in the heap leaching of copper ores, because these ores require an acidic leaching solution. Acid destroys the effectiveness of most binders, causing the agglomerates to disintegrate as soon as the leaching solution is applied. In order to gain the benefits of agglomeration in copper heap leaching, an economical, acid-resistant binder is needed. The two issues that needed to be addressed were: 1) Lack of effective methods for evaluating binder acid resistance before performing expensive, time-consuming, full-scale heap leaching tests, and 2) The vast majority of known binders react poorly to acid conditions, and so a basis was needed for determining which binders are most likely to be acid-resistant. In this paper, the development of two new tests for evaluating binder acid resistance in the laboratory are described. The ?soak test? determines the degree to which agglomerates disintegrate and release fines on contact with acidic solution, measuring the relative quantities of fines released by agglomerates made with different binders under controlled conditions, and serves as a rapid means for comparing large numbers of binders. The ?percolation test? measures several different parameters to determine how a binder is likely to perform in heap leaching: 1) the degree of ?slump? and compaction of agglomerates as they are wetted by acidic solutions; 2) the hydraulic conductivity of the agglomerate bed; 3) the migration of fines through the bed as the solution flows through it; and 4) the quantity of liquid retained in the agglomerates after they are drained. Using these tests, a broad spectrum of binders were examined. Soak testing determined that the most acid-resistant binders were nonionic polymers. Five of these binders were further evaluated using percolation testing.

Jan 1, 2006

By Gabriel Plascencia

Copper was oxidized in the temperature range from 300 to 1000 °C under different pressures of oxygen, In the range from 300 to 500 °C, copper oxidizes following the logarithmic rate law; while in the range from 600 to 1000°C oxidation follows the parabolic rate law. Transition from logarithmic to parabolic growth occurs at about 525°C. X-ray diffraction was performed on oxide scales to account for the CuO/Cu2O ratio at different temperatures. Activation energies found in this work are in good agreement with reported values.

Jan 1, 2003