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By Ali S. Al-Watban

"In this paper, the room temperature friction and deformation properties of various polycrystalline diamonds; i.e. aggregates of diamond crystals with a ""binder"" phase of cobalt and a polycrystalline coating produced by a chemical vapour deposition processes (CVD) were studied when softer metallic and ceramic sliders were used. The experiments were conducted· at relatively low sliding speeds (10 mm/min), in a vacuum of 10-5 mbr after having cleaned the specimen surfaces by out-gassing them for about 30 min at 800 °C. As a result of increasing the number of traversals significant wear of the coated diamond by softer metallic sliders (aluminium and mild steel) was observed. With ceramic sliders, it is shown that the multiple traversals result in the formation of wear groove. With diamond silicon carbide, high friction and adhesion lead to significant metal transfer which then pre-empts cumulative deformation of the harder materials. With the diamond-cobalt composite, the friction is surprisingly low, there accumulation of wear debris on the tip of the slider but no permanent transfer of metal and the harder specimen is not damaged even after 5000 traversal.IntroductionPolycrystalline diamond is mainly produced as tool materials for the machining of hard metals and composites. Thus, the sliding friction and wear resistance are amongst the most important properties relevant to those applications.During cutting by PCD the wear mechanism is mostly influenced by the chemical affinity between the tool material and the workpiece. For example, diamond based materials are not recommended for machining ferrous materials because carbon is highly solubie in iron: This leads to the graphitisation of diamond particles and hence a high rate of diffusion wear is observed (Brookes and Lambert, 1982)."

Jan 1, 2000

Segregation roasting tests were carried out on Zaire cobalt oxide ores assaying about 2% Co and 3.5 to 6.5% Cu. The major parameters tested during the laboratory investigations were temperature, dosage and type of reducing agent, dosage and type of chloridizing agent, and particle size. Results showed that standard conditions suited to the segregation of copper ores, i.e. low temperature and low dosages of reducing and chloridizing agents, resulted in the segregation of copper only, while conditions suited to the segregation of lateritic nickel, i.e. higher temperature and increased dosages of reducing and chloridizing agents, led to a successful segregation of both copper and cobalt. Under the best conditions, 88% of the cobalt and 98% of the copper could be recovered in a concentrate assaying 32.5% Cu and 8.5% Co. Alternatives to process such a concentrate are briefly reviewed.

Jan 1, 1993

By Balasivanadha Prabhu, Prasad P. Shanmugasundaram, Narayani Narasimhan

"The grain refinement and mechanical properties of 6061 aluminium alloy produced by equal channel angular pressing (ECAP) have been analyzed in this present study. A innovative triple shear ECAP die was developed for the processing.It was observed that the grain refinement takes place for greater number of passes. It was also found that reducing the process temperature gives fine grain and high microhardness and hence improved propertiesIntroductionTechnological changes in manufacturing industries have depended heavily on development in materials processing and process technologies. Modem industries need high performance materials for severe service conditions. Hence, it is necessary to improve required material properties to achieve better performance and greater service life. As mechanical properties of the materials strong! y depend on grain size ( d) - Hall-Petch relationship [ 1-4], the ultrafine grained (UFG) materials offer superior mechanical properties based on the above relation.Synthesising massive nanocrystalline materials presents a challenge to basic research as well as to application-related processing efforts. Production of ultrafine gram microstructures in metals and alloys having different crystal structures but always an initially coarse microstructure using severe plastic deformation can significantly enhance the physical and mechanical properties of materials. Severe Plastic Deformation (SPD) is an efficient method to induce ultra fine grained structure in materials by deforming it to large strains. Traditional techniques for introducing deformation of higher strains, such as forging, extrusion, drawing or rolling do have the inevitable limitation on required equipments of exerting enough load or pressure to cause uniform nanometer level grain refinement."

Jan 1, 2011

By V. V. Satya Prasad, A. Sambasiva Rao

Electroslag melting technologies have recently been developed for recycling light scrap of valuable metals and alloys such as superalloys and oxygen free high conductivity (OFHC) copper at Defence Metallurgical Research Laboratory (DMRL), Hyderabad. Conventionally, electroslag melting processes use consumable electrodes. Because of the difficulty in compaction of scrap into a consumable electrode of satisfactory quality, non-consumable electrodes such as graphite and water-cooled copper have been designed. Electroslag remelting using a water-cooled non-consumable electrode was developed to melt scrap of a nickel base superalloy. Sound ingots with smooth surface finish and properties comparable to vacuum melted superalloys could. be obtained from scrap using this process. A modified electroslag crucible melting process using graphite crucible and graphite electrode was developed for recycling OFHC copper scrap. Copper ingots with less than 10 ppm oxygen and electrical conductivity"" 100% IACS could be produced. The same process was also utilized to produce copper-based alloys such as copper-chromium and copper-titanium starting from copper scrap.

Jan 1, 2000

By P. Blazy

A hydrometallurgical procedure for the recovery of metal from ore, particularly of copper from sulphide materials is described. In the course of this procedure, the raw material is first of all submitted to the action of an appropriate reducing system and then treated with a ferric salt solution which brings about the selective solubilisation of the elements to be recovered with respect to those constituting the pyritic phase. This procedure is investigated using two ore samples proceeding from massive sulphide deposits, presenting different chemical and mine- ralogical characteristics. The results of this investigation are compared with those obtained by a classical process employing a ferric salt solution. It appears that one solubilisation of copper takes place under particularly advantageous conditions when our procedure is used. The principal parameters affecting leaching of zinc, lead and copper are examined. The selectivity of this treatment is evaluated by following the change during the treatment in the pyritic phase.

Jan 1, 1976

By Aert Driessen

Australia has large resources of rare earths -- 4.35 Mt of contained rare-earth oxides (REO) in the demonstrated category and 1.69 Kt in the inferred category. Australia's demonstrated REO resources are contained in about equal proportions in placer deposits, which also host Australia's titanium and zircon resources, and in hard-rock deposits. The largest single deposit of rare earths, at Mount Weld in Western Australia, is contained in regolith overlying a carbonatite pipe. It has a demonstrated resource of 1.73 Mt of contained REO and yttrium oxide. The largest demonstrated resources of REOs in placer deposits are in the Murray Bash, southeastern Australia -- a total of 1.90 Mt of contained RE0 in six deposits. However, the REO-bearing minerals (monazite and xenotime) are of secondary importance and their recovery will be determined by the market for titanium dioxide and zircon. The Murray Basin and other pre-Pleistocene basins offer the greatest potential for discovering more REO resources. Australia produces about 7000 t/year of REO in monazite and xenotime nearly all from Western Australia, as by-product of mineral-sand mining; monazite production is about 12 000 t/year (6600 t REO) and intermittent xenotime production is about 50 t/year (25 t REO). About 8000 t/year of monazite containing about 4400 t REO is not recovered separately, or is lost in tailings, as is an unknown but smaller amount of xenotime.

Jan 1, 1992

By Nicholas E. Vanderborgh

Projections show that domestic coal will serve for the majority of energy supplies during the next decades. Thorough chemical cleaning of this coal can be accomplished in long-residence time, slurry-transport systems to produce high-quality fuel product. Concurrently, mineral recovery from coals will supplement existing ores. This paper describes this concept and gives preliminary engineering considerations for mineral recovery during transport operations.

Jan 1, 1982

By James A. Voigt

The efficient separation of metal species from aqueous streams by precipitation techniques requires 'a fundamental understanding of the various processes that occur during precipitation. These processes include particle nucleation, particle growth by solute deposition, agglomerate formation, and agglomerate break-up. The application of the population balance approach has been used to develop a kinetic model that accounts for these competing kinetic processes. The usefulness of the model is illustrated through its application to the precipitation of yttrium hydroxynitrate, YHN. The kinetic parameters calculated from the model equations and system-specific solution chemistry are used to describe several aspects of the effect of pH on the precipitation of the YHN. Implications with respect to the simultaneous precipitation of more than one cation type are also discussed through use of example systems: The effects of solution chemistry, precipitator design, and solvent choice are considered.

Jan 1, 1996

By Fan Xiao-Hui, Jiang Li-Juan, Chen Xu-Ling

"In order to solve air leakage of sintering testing cumbersome, inaccurate results, and other issues, the sinter machine air leakage characteristics were studied, and combining the mathematical modeling and the field detection. The temperature before air leakage was calculated by mathematical model, energy balance equation was established according to sintering process, using Adams prediction correction method which has stronge stability and high precision, to solve hyperbolic partial differential equation with astringency problem. The temperature after air leakage is detected by instruments, according to energy conservation calculation the sintering air leakage rate. According to the sintering continuity and periodicity, sintering air leakage location diagnosis expert system was established to judge specific air leakage locations.IntroductionStrengthening of modern blast furnace production depends on the quality of the raw material preparation to a large extent [1]. Technical and economic index of modern blast furnace production is advanced; the most important reason is the use of concentrated feed. Sintering plant is the ""kitchen"" of blast furnace’s concentrate. As we all know, sintering plant is major energy consumption of steel plant, in sinter process energy consumption, the solid fuel consumption of total energy consumption is 75%~80%, power is 13%~20%, ignition and combustion is 5%~10%. To reduce the air leakage of sintering plant is an effective measurement to save energy consumption. At present, our air leakage of sintering compared to the other developed countries is still a long way to go. Japan’s air leakage rate is about 30%, and 35%~60% air leakage of sintering machine at home, a big gap exists between the plants. At present the determination of air leakage is all for manual operation, long measuring period, considerable manpower and resources, and the results are significantly affected by operation. For air leakage of sintering control lag issues, research and development of diagnosis expert system for on-line monitoring model for air leakage and, through this research can reduce the use of detection equipment, detect sintering air leakage, improve the yield and quality of sintering production, reduce energy consumption, and extend equipment life span."

Jan 1, 2012

By J. Kevin Cotchen

The results of "submerged arc" electric furnace processing of a variety of materials is discussed with respect to the process and products, including the characteristics of the products (e.g. TCLP or Toxicity Characteristics Leaching Procedure). The materials melted include slags and wastes containing various metal oxides including copper, tin, lead, zinc, chrome, nickel and other associated elements. The findings of these tests are compared to those reported in the literature for other operations treating similar "wastes".

Jan 1, 1992

By Entov Vladimir M., Gilmer R. Burgos, Andreas N. Alexandrou

"Processing of metal alloys in their mushy state represents a new trend in metal processing. As part of this process, known also as thixocasting, a specially prepared slurry at a temperature in the mushy region is injected into a die. Parts produced using this technology offer better mechanical properties than those produced by casting, and comparable to those of forged alloys.In thixocasting, semisolid slurries are highly concentrated suspensions of rounded rosette-like crystals in eutectic liquid. The mechanical behavior of the slurry is determined by the structure and properties of the skeleton formed by the alpha phase particles. The skeleton structure is almost never at equilibrium, and its evolution is, governed by a number of kinetic phenomena of different c11'aracteristic time-scales. Therefore, the skeleton structure depends on the mechanical and thermal history of the material. As a result of these kinetic processes, the rheological properties of the material, such as effective viscosity and yield stress, decrease with structure breakdown, and increase with its development. In the present investigation, the behavior of semisolid slurries during processing is modeled using the conservation equations, and a Herschel-Bulkley fluid model. The rheological parameters are assumed to be functions of the solid volume fraction, and of a structural parameter that changes with processing history. The evolution of the structural parameter is described by a first order kinetic differential equation that relates the rate of build-up and break-down of the solid"

Jan 1, 2000

By James O'Brien, Lyman Frost, Grant Hawkes, S. Elangovan, Manohar Sohal, J. S. Herring, Joseph Hartvigsen, Carl Stoots

"Pressing environmental and energy security concerns have brought much needed attention to economic production of hydrogen as the secondary energy carrier for non-electrical markets as well as to meet increasing demand for crude upgrading and desulfurization. While steam reforming of natural gas is currently the dominant method of hydrogen production, it is depleting a valuable fossil fuel while emitting green house gases. Thus, in the long run, efficient, environmentally friendly, and economic means of hydrogen production using nuclear and renewable energy needs to be developed. High temperature electrolysis using solid oxide electrolyte cells is an exceptionally efficient means of generation of high purity hydrogen. It is also capable of directly converting steam and CO2 into synthesis gas. This co-electrolysis process enables conversion of CO2 recovered from concentrated industrial sources into a feedstock for synthetic fuels production. Use of CO2 provides a means of storing hydrogen in a concentrated and convenient form – a hydrocarbon. This is also an effective storage medium for intermittent renewable energy sources such as wind and solar.Ceramatec, Inc and the Idaho National Laboratory are applying solid oxide fuel cell technology to the production of synthesis gas by high temperature co-electrolysis of steam and carbon dioxide. This technology utilizes solid oxide fuel cell stacks to electrochemically remove oxygen from steam and CO2, leaving a clean stream of hydrogen and carbon monoxide suitable for fuel synthesis. By varying the relative concentrations of carbon dioxide and steam, the hydrogen to carbon monoxide product ratio can be controlled as required by the desired type of synthetic fuel being produced from the syngas. The resultant synthesis gas has been used as the feedstock to produce synthetic methane and Fischer Tropsch liquid fuels.Alkaline and proton exchange membrane electrolysis cells typically operate below 100°C, while solid oxide electrolysis cells operates in the 750-850°C range. This higher temperature improves the efficiency significantly. Practically, it translates into a lower cell operating voltage, 1.1-1.4V for high temperature electrolysis vs. ~1.8V for water electrolysis. Hydrogen production is stoichiometric with current in all types of electrolyzers.Carbon dioxide is a valuable resource as a feedstock for energy storage as a hydrocarbon. There is a vast amount of renewable energy that cannot be effectively utilized as grid electricity, but which could be used to convert CO2 to hydrocarbons, offering a solution to the even more difficult (than supplying grid power) challenge of production of sustainable, domestic transportation fuels. Conventional electrolysis and chemical processes could be deployed to accomplish this conversion. However, high temperature co-electrolysis of CO2 and steam to produce synthesis gas using solid oxide fuel cell technology has the potential of improving the efficiency by nearly 50%. A domestic synfuel industry will enable a much larger reliance on intermittent renewable energy than can be accommodated by conventional electric demand profiles while increasing our energy security."

Jan 1, 2010

By J. Schmidl

In non-ferrous metallurgy the service life of refractory materials typically ranges from several weeks up to three years or more and is strongly dependent on operating conditions. To support our customers with the most viable refractory solution for their needs RHI Magnesita follows a structured approach of thermo-chemical calculations, experimental evaluation from lab scale up to industrial field tests and post-mortem analysis of used refractory materials. This paper will give an overview of the RHI Magnesita refractory selection process and the most recent developments of the experimental setup for the so called HF-IF test. This is a dynamic corrosion test that allows to determine fundamental properties of different refractory material types under process conditions subjected with respective customers process materials. The HF-IF experimental procedure is an excellent tool to simulate refractory wear in industrial processes, diminishing risks associated with plant trials and support decision making to choose the optimal refractory solution for the customer.

By D. K. Panda

The behavior of single drops with gas evolution at the interface is of interest because this is one of the important reactions that occur in oxygen steelmaking vessels, where a large amount of iron-carbon drops are dispersed in an oxidizing slag. The carbon dissolved in these drops, reacts with the slag to form CO, which is evolved as a gaseous phase. A room- temperature model was used to study the nature of this type of reaction including the effect of various factors such as viscosity and the presence of surface active impurities. Experiments were done for reacting drops over a wide size range to observe various regimes of behavior. Large single drops were levitated in a counter current flow to produce a sufficiently long residence time to allow the study of the various stages in the reaction. The emphasis of this work was to obtain photographic evidence of a high quality to describe all possible modes of behavior, and so a lot of effort was given to developing and perfecting experimental techniques.

Jan 1, 1994

By G. Van Weert

Refractory gold ores and auriferous concentrates containing silver tend to form refractory silver jarosites during pressure oxidation. Earlier work with pure Ag2S has shown that the addition of iodine species to the autoclave feed yields cyanide soluble iodargyrite (Agl) instead. Near complete silver extractions from the autoclave product were obtained at a I-/Ag+ ratio of 5 or more. This paper reports on the pressure oxidation and cyanide leaching of two industrial refractory (arseno) pyritic silver-bearing concentrates: 1. from Peru (sulphosalts) and 2. from the USA (pyrite, with acanthite occlusions). While using a I-/Ag+ mol ratio of only 1 in the feed, it has been possible to obtain 98 and 97% Ag extraction from the two autoclave products by cyanide leaching, respectively. This compares to 11 and 54% Ag extraction from the as-received concentrates and 4 and 15% Ag extraction, respectively, after pressure oxidation without KI present. The results of the testwork are discussed in terms of concentrate mineralogy and pressure oxidation conditions.

Jan 1, 1994

By Evgueni Jak

Recent advances in analytical, experimental techniques, and computer-based theoretical modelling of fundamental properties and elemental processes, provide new opportunities to develop the next level of whole-of-reactor pyrometallurgical furnace models. These models have the potential to significantly improve the prediction of, and adding value to, industrial operations. In non-ferrous smelting, the starting point of these models is the development of multicomponent thermodynamic databases for gas-slag-matte-speiss-metal-solids phases supported by systematic experimental research. The whole-of-reactor-models additionally should take into account kinetic processes taking place at micro- and macro- scales, and other key factors. Examples of applications of the latest research tools and modelling approaches to analysis of industrial flash and top submerged lance (TSL) sulphide smelting processes are presented. Different levels of industrial modelling are discussed from elemental local reactions, through general and more detailed whole-of-reactor-models, to plant sections and further to whole plant operation models. Some principles for development of pyrometallurgical reactor models are discussed.

By Peter Stiaszny, Andrej Samoilov, Yuri Titovets, Gottfried Hribernig, Nikolai Zolotorevskii

"The model has been developed to simultaneously predict both transformation product portions and mean ferrite grain size from the same common · principles as a result of the austenite decomposition during any cooling path of dual phase steels. The transformation products considered are polygonal ferrite, pearlite, bainite and martensite. The model is based on the classical equations of nucleation-growth theory and also contains some empirical parameters. The chemical driving forces for nucleation and composition of elements at the phase interfaces are derived by computation thermodynamics. The empirical parameters related to the model were determined on the basis of a series of austenite transformation dilatometric curves and grain size measurements for continuous and interrupted cooling of several steel types. The model is aimed to predict phase transformation in the complex cooling conditions of the run-out table of the hot strip mill at YOEST-ALPINE STAHL LINZ GmbH as a part of the computer aided system for prediction and on-line controlling of the mechanical properties of hot-rolled strip.IntroductionThe term ""dual phase steels"" is used to refer to a steel consisting essentially of a dispersion of martensite in a fine-grained ferrite matrix. These steels are of increasing technological interest since they provide a better combination of strength and ductility than any other conventional steel sheet material. The strength is important because it offers an opportunity to produce lighter components, while good ductility is needed to permit easy forming of components. It is generally recognized that martensite plays an important role in determining the strength level of dual phase steels. A full understanding of the role played by the phases in determining such characteristics requires investigating in more detail how to optimize the martensite level of such steels, while maintaining good ductility remains the subject of continued research in the industry."

Jan 1, 2000

By G. A. Irona

Solids injection into non-ferrous converters and furnaces is becoming increasingly important for concentrate injection, removal of impurities, and recycling of dusts and other waste materials. The fundamental design aspects of these technologies will be reviewed, including gas and particle trajectories, lance clogging, heat transfer, and mass transfer including reaction rates and mixing. The use of soda ash for removal of impurities such as antimony and selenium will be used as an example of versatility of powder injection processes.

Jan 1, 1993

By Ryokichi Shimpo, Akio Fuwa

"In order to elucidate the present status of process-control technology, survey study has been made on the present process control schemes of representative copper smelting and converting processes in Japan. Conceptual control flow diagrams have been deduced and shown on respective functional reactors, i.e. drying, smelting, converting and fire-refining units, where the objective OUTPUT items are correlated to the INPUT variables through respective CAUSE-AND-EFFECT RELATIONSHIPSFuture view has been also discussed on several feasible and desirable improvement and refinement ~n measurements and control system for better copper smelting and converting operations.INTRODUCTIONIn other to seek for the better and efficient operation in copper smelting and converting process, survey study has been first conducted on the present process-control schemes of respective functional unit processes, i.e. drying, smelting, converting and refining unit processes, of representative copper production processes in Japan. Conceptual process flow chart of control scheme has been then deduced where output items are correlated to input items through the respective cause-and-effect relationships.After this survey study, future view has been discussed on the feasible and desirable improvement and refinement in the measurement and control system in these processes. Emphasis has been placed on the better and precise measurements of temperature, oxygen partial pressures in respective furnaces and end-point in converting and refining unit operations."

Jan 1, 1989

By Batric Pesic

Reactions of metallic iron were studied in several different aqueous solution systems: water, medium salt solution used for the growth of T ferrooxidans, ferric iron solution and solution containing T ferrooxidans. Each system was studied under abiotic and biotic conditions in the presence of T ferrooxidans and as a function of pH, particle size of iron powder, temperature, ferrous and ferric iron concentrations. It was found that metallic iron reacts with water differently than does with ferric iron in water. Surprisingly, T ferrooxidans were non-functional in the dissolution of metallic iron. Also, the reactions of metallic iron with pure water were indistinguishable from the reactions with water containing medium salts for bacterial growth. The reactions with ferric iron were also independent of medium culture compounds. The mechanisms of metallic iron reactions with ferric ions are different from the mechanisms of metallic iron reactions with water.

Jan 1, 2001