Search Documents

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 C. A. Pickles

At the present time, pyrometallurgical processes are employed for the recovery of lead from battery scrap. These processes have serious pollution problems, primarily due to the emfssion of sulphur dioxide and airborne lead in the form of dust and fume. In addition it is necessary to dispose of solid wastes and liquid effluents which contain lead and in some cases sodium sulfide-containing compounds. In this work an improved process was investigated for the recovery of lead from battery residue. This involved pelletization of the residue with sodium carbonate and moisture. Then, the pellets were melted without carbon and the .sodium sulphate salt was removed. Subsequently, the molten lead oxide was reduced with carbon. This process minimizes the sulphur dioxide emissions and leads to very low sulfide contents of the sodium sulfate salt

Jan 1, 1992

By Graham J. C. Carpenter, Marc Charest, Jason Lo

"The method of producing magnesium-based composites with silicon carbide (SiC) particulates embedded in the matrix of magnesium AZ9I D alloy by the squeeze-casting technique are described. This method involves the fabrication of a SiC particulate preform and the subsequent squeezing of molten magnesium into the preform. In this study, alumina, aluminum phosphate and a proprietary binder were used for the fabrication of SiC particulate preforms. The procedures employed in the fabrication of SiC! AZ9ID composites are presented, together with the results of characterization of the composites using optical and transmission electron microscopy. Special attention is given to the reaction products in the bulk alloy and at the interfaces between SiC particles and the AZ9ID matrix alloy.1. IntroductionInterfacial, microstructural and metallurgical characteristics play an important role in determining the mechanical properties of a composite. In theory, reinforcing magnesium with SiC particulates should provide an improvement in strength and modulus of the composite over the unreinforced counterpart. However, many factors resulting from the fabrication process can cause degradation rather than improvements to the mechanical properties. In particular, the interfacial characteristics are known to critically influence the properties of composites [1]. Before evaluating the mechanical properties of a composite, it is always useful to examine the microstructure, which is closely related to the mechanical behavior. This helps to reduce the labor-intensive steps of sample preparation for mechanical property evaluation, which can be particularly difficult as a result of the high hardness of composite materials, as well as providing a wealth of information on the microstructural and interfacial characteristics, particularly the reaction products caused by processing. This information is also pertinent in understanding the factors governing the mechanical properties of the composites.There are many factors which determine the nature of the interfacial characteristics of a SiClMg composites. Qualitative estimations of the interfacial bonding have been performed based on thermodynamics, electronic and electrostatic concepts. In addition, the kinetic conditions during the fabrication play an important role. From an interfacial energy standpoint, the driving force for the formation of a metal/ceramic interface is the decrease in free energy that occurs when intimate contact is established between metal and ceramic surfaces. The simple representation of the energy change per unit area of interface formed (~G) is given by Dupre equation [2]:"

Jan 1, 1996

By Susumu Okabe

Mitsubishi Continuous Copper Converter employs the top blowing lance system for the continuous supply of reaction gases into the molten bath. In order to avoid the excessive refractory wear caused by the melt splash without loss of the reaction efficiency, the furnace design and the blowing condition should be optimized. Empirical equations which correlate the splashing rate on the' side wall with the dimensions of the furnace, lance position, lance size, gas velocity and bath properties were obtained by by the physical model study, and compiled into a computer program. The computer program is effectively utilized for the analysis of the actual operation and for the optimum design of new furnaces.

Jan 1, 1998

By I. Kim, J. C. Choi, W. D. Cho

"The effect of yttrium addition on the oxidation behavior of Fe3Al intermetallic compound was investigated in the range of temperature 800 to 1100 °C in 0.2 atm 02 in terms of oxidation rate and oxide adhesion. The oxidation rate of alloys, Fe-14.3 wt% Al and Fe-14.1 wt% Al-0.3 wt% Y, was nearly identical and the parabolic rate constant calculated as a function of temperature is Kp=5128 exp[-39506(cal/mol)/RT] mg2/cm4 hr.Rapid cooling and ultrasonic stress tests were carried out to test adhesion of scale formed on the alloys. While the oxide layer formed on the Fe-Al alloy without Y was found to be fragile and detached easily during the tests, the oxide layer formed on the Fe-Al alloy containing Y was protective, dense, and adhesive. The following two mechanisms were proposed to explain the adhesion improvement of Ah03 formed on the Fe3Al containing yttrium : (1) the addition of yttrium decrease generation of growth stress in alumina scale because the preferential diffusion of yttrium through grain boundary in alumina scale prevent internal oxidation of Al, one of main causes of growth stress, and (2) the second phase formed on the oxide scales prevents crack propagation through the scales, leading to better mechanical stability of the oxide scales.IntroductionIron aluminides have attracted the attention of many researchers as a candidate for use at high temperature because of their excellent oxidation resistance due to the formation of protective alumina scale. In order to resist aggressive environments at elevated temperatures, oxide scale formed on iron-uluminum alloy must satisfy the following three requirements : (1) thermodynamic stability (2) slow growth rate (3) adherence on substrate. According to Wallwork and Hed [l], the most suitable alloys for high temperature application are Fe, Ni, and Co alloys with the protection of Si02, Cr203, and Ah03 scales. While chromium oxide can vaporize as Cr03 above 1000 °C and silicon oxide may form low melting silicate [2,3], Alz03 has a high melting point and is the most stable among the three oxides thermodynamically [6]. In this respect, iron aluminides forming alumina seem to be most suitable for use at high temperature. However, alumina scale formed on the iron aluminum alloys tends to be easily spalled during oxidation due to the combination of growth stress and thermal stress."

Jan 1, 1998

By Zhenglong Li

A process has been developed to recover titanium from a blast-furnace slag which contains about 20-25% Ti02 and 12% Fe. In this process. "hot" slag from the blast furnace is directed to a separate furnace where it is reheated with additives to form two simple slag phases: one is titanium enriched anosovite (Ti3O5) and the other is a titanium lean non-crystal glass phase. The modified slag is then processed by conventional beneficiation techniques to produce a marketable titanium concentrate and a usable slag material. This paper focus on separating anosovite from glass by electrostatic separation and froth flotation.

Jan 1, 1996

By Ken-ichiro Uemura

"The DIOS process has been developed for eight years since 1988. The research project was started with the element studies carried out by each of the five integrated steel making companies in Japan, the final two and half years were spent for the pilot plant studies. Operation were conducted in the entirely closed and pressurized system successfully as planned. From the result, the DIOS process was proved to be viable as a future iron-making process substitutable for the conventional blast furnace. In addition, a lot of findings were obtained. Hot metal productivity was primarily determined by a oxygen flow rate, and a coal consumption varied depending on the productivity. The post combustion ratio was a little lower than expected from the result of the element study. It was supposed to relate the gas-reforming with coal or volatile matter in the free space of the furnace. Hot metal carbon content seemed to depend on the char content in slag.INTRODUCTIONThe JISF's DIOS pilot plant (DIOS=Direct Iron Ore Smelting Reduction Process) has finished its last campaign of the operations in January 1996. The project was started in 1988 as a joint research of the Center for Coal Utilization, Japan and the Japan Iron and Steel Federation (JISF) with a subsidy for promoting coal productions and utilization technologies from the Agency of National Resources and Energy, the Ministry of International Trade and Industry(MITI). Throughout the pilot plant test, a total of over 20,000 tons of hot metal was produced for more than 2,000 hours of the operation. Recorded production rate was 538 ton/day for 3 days at a specific coal consumption of approx. 1,000kg/hmt. Long-term operation was carried out in the fifth campaign for 18 days, which has proved that the entirely closed and pressurized DIOS process works well as planned. In Figure 1 is shown the representative operational performance obtained in the first five campaigns. The project is going to be finished by the end of March this year after investigating the technical viability and economic potential of the process, and completing the conceptual design of the DIOS commercial plant. In this paper, the system and facilities of the DIOS process are first introduced and some of the results of the pilot plant test are detailed later."

Jan 1, 1996

By Masanori Abe, Yoshitaka Kitamoto, Kazuhiro Nishimura

"Ferrite plating is a chemical processing which utilizes Fe2+ - Fe3+ oxidation to synthesizing polycrystalline films of ferromagnetic spinels (MFe20 4, M = Fe, Co, Ni, Zn, Al, Cr, TI, etc:) directly from an aqueous solution at 24 - 100°C. This low temperature process allows us to fabricate new ferrite film devices on · substrates of such non-heat-resistant materials as plastics, GaAs integrated circuits, and biomaterials. Synthesized from an aqueous solution the ferrite plated ·films are highly biocompatible. Thus various magnetic device and biomedical applications have been proposed and realized using ferrite-plated films. Ferrite-encapsulated polymer microspheres are applied to antibody carries for enzyme immunoassay, and also to toners/carriers for photocopying. Perpendicular magnetic recording media utilizing plated CoNi ferrite films are proposed. The low-temperature synthesized films of NiZn and Co ferrites are potentially used as soft-magnetic and/or insulating layers, respectively at high/microwave frequencies.IntroductionFerrite plating is a processing which facilitates the formation of crystalline spinel ferrite films with various compositions, (Fe, M)30 4 (M = Fe, Co, Ni, Zn, Al, Cr, TI, etc.), directly from an aqueous solution at 60 - 100°C [1]. This opened the door to fabricating novel ferrite-film devices using substrates of such non-heat-resistant materials as plastics and GaAs integrated circuits [2-4]; conventional ferrite film preparation techniques such as sputtering, vacuum evaporation, MBE, LPE, etc., require high temperatures(> -600°C) for crystallization of ferrites, which deteriorates the non-heat-resistant substrates. Recently we extended ferrite plating to be preformed at room temperature [5, 6]. This enables us to use as substrates such organic materials as biomaterials (e.g. enzymes) having very low heat-resistance."

Jan 1, 2000

By W. D. Keller

Scanning electron microscopy (SEM) accompanied by X-ray energy dispersive analysis (XES) is a useful tool in process clay mineralogy. The texture of kaolin, illustrated by SEM, gives a clue to its mode of genesis and probable industrial application. One type of kaolin, originating dominantly by weathering, has an open texture, slakes readily, and is used for filling and coating paper. Another type, in contrast, originates by diagenesis of Al-silicate sediments, and spectacularly resists slaking, thereby enabling it to maintain its bulk density and controlled size and shape of particles after crushing and moistening; this meets an important requirement for the manufacture of refractories. Ratios of elemental Al:Si that may be rapidly determined by SEM and XES yield information on the origin and purity of bauxite and bauxitic clays, and aid in quality control and processing of them. SEM of dissimilar textures of quartz, as in chert and novaculite, are evidence for geothermometry on a stratigraphic scale that is potentially useful in delimiting thermally favorable or unfavorable areas for hydrocarbon exploration, and possibly for unexposed metallic ore deposits.

Jan 1, 1982

By F. Michael Hosking

Modeling of a furnace brazing process is described. The computational tools predict the thermal response of loaded hardware in a hydrogen brazing furnace to programmed furnace profiles. Experiments were conducted to validate the model and resolve computational uncertainties. The results from selected furnace simulations and measured thermal events were compared. Critical boundary conditions that affect materials and processing response to the furnace environment were determined. "Global" and local issues (i.e., at the furnace/hardware and joint levels, respectively) are discussed. The ability to accurately simulate and control furnace conditions is examined.

Jan 1, 1998

By Wei Yin, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

Copper anode slime is an increasingly significant resource for precious metals such as Au, Ag and Pd. The extraction of Au, Ag and Pd from decopperized anode slime by different pretreatments and different lixiviants including cyanide, chloride, thiourea and thiosulfate have been investigated. When oxidizing roasting pretreatment was carried out under the conditions of roasting time 120min and temperature 625 ℃, the removal ratios of S and Sb could reach 82.18% and 98.52%, respectively. And the following alkaline leaching of calcine could result in the dissolution of 46.40% Cu and 98.48% Pb. The optima leaching ratios of Au, Ag and Pd reached 99.48%, 97.69%, 94.79% by cyanide leaching, and 95.01%, 79.84%, 96.59% by chloride leaching, and about 95.21%, 95.66%, 48.79% by thiourea/thiosulfate leaching.

Jan 1, 2015

By Cong Wang, Kexin Jiao, Yongan Zhao, Haibin Zuo, Jianliang Zhang

Traditional refractory materials for blast furnace hearth lining are mainly composed of carbon bricks and the ceramic cup. However, these materials can’t meet the demands for long service life design of blast furnaces. In this paper, a new refractory called carbon composite brick (CCB) was introduced, which combined the advantages of carbon bricks and the ceramic cup. In this case, the resistance of the CCB against corrosion was equal to the ceramic cup and the thermal conductivity of the CCB was equal to carbon bricks. From the results of more than 20 blast furnaces, the CCB could be well used in small blast furnaces and large blast furnaces. In the bad condition of low grade burden and high smelting intensity, the CCB gave full play to the role of cooling system, and effectively resisted the erosion of hot metal to improve the service life of blast furnaces.

Jan 1, 2015

By Cindy L. Williams

"The Blue Star subdistrict in the Carlin Trend, Nevada, includes multiple mines with 33.9 t Au in reserve and past production totaling 89 .1 t Au. The deposits are characterized by zoned alteration mineralogy and gold grades. From orebody centers outward the zones include: 1) a silicified core with erratic gold grade; 2) adjacent mill-grade (> 1.37 Au git) intense quartz-sericite-pyrite alteration; 3) enveloping leach-grade (0.21 Au g/t to 1.37 Au git) weaker sericite-kaolinite-quartzpyrite alteration; 4) surrounding decarbonatized and intensely argillized waste and leach grade ore; 5) pervasively decarbonatized waste rock; and 6) peripheral waste with weak decarbonatization and local propylitic alteration. Zoned alteration extends as much as 1500 m beyond orebodies.Understanding Blue Star subdistrict zoned alteration assemblages and gold grades has increased geologists' ability to provide practical and economically significant information to geotechnical engineers, mine planners and drill and blast personnel. Alteration influences geotechnical pitslope design because each assemblage has distinct rock strength. Geotechnical engineers use three-dimensional models of incompetent alteration types as a foundation for pit-slope design. In the drill and blast cycle, hard and soft alteration types require modified practices (powder column, blast hole spacing, delay design etc.) for optimum blast energy distribution. Further, geotechnically instable alteration types require careful blast procedures to prevent backbreak whic~ damages ultimate walls. In addition to mine planning and mining applications, zoned alteration assemblages extending beyond orebodies provide a useful exploration guide. Metallurgical character also varies with alteration type. Intensely quartz-sericite-pyrite altered or silicified ore has relatively high partical-size dependency and poor leach recoveries. Moderately sericite-kaolinite-quartz-pyrite altered rock, in contrast, shows little size dependency and good leach recoveries.The author sincerely thanks L. Schutz, P. Williams, C. Clode, W. Trudell, P. Herrera, M.DKunkel, M. Goings and numerous other Newmont geologists, metallurgist, engineers and support staff who made this paper possible."

Jan 1, 1997

By Steven R. Izatt

IBC Advanced Technologies, Inc. (IBC) has developed a mercury selective product, which can be used by sulfuric acid producers as either a polisher, or as the primary technology for mercury removal from sulfuric acid. The Molecular Recognition Technology (MRT) separations material selectively binds Hg2+, and to a lesser extent Hg+, out of concentrated sulfuric acid. Mercury output levels of less than 0.1 ppm can be attained by the MRT system. Pilot plant tests have been successfully conducted at base metal smelting operations. A large-scale commercial plant is due for commissioning in 2003. Results from these projects will be discussed.

Jan 1, 2003

By Yoichi Takeda

The CaO-FeO,-Cu20 slag has been practically applied to continuous converting of copper, and also has potential for refining of copper. Liquidus lines of the slag system and phase stability diagram for the liquid slag and the existing solid compounds under copper saturation are presented. Liquidus composition was determined by chemical analysis of slag sample saturated primary solid. The temperatures of invariant equilibria were investigated by thermal analyses. Oxygen potentials on the liquidus lines, the univariant and invariant equilibria were estimated from the relation slag composition and oxygen potential that relation was confirmed in separate experiments.

Jan 1, 2003

By C. J. Parradies

During injection into a die, semi-solid metal alloys exhibit a shear-rate, history-dependent flow response. Simulating the injection of a thixotropic material requires that empirically determined boundary conditions and viscosity are specified as a function of both temperature and shear rate history. Experiments were performed using an industrial die casting machine that was instrumented with sensors to measure the pressure and temperature during the injection of a semi-solid aluminum alloy through a tube. This benchmark experiment was used to develop a simulation of the die casting process that could then be applied to more complex die geometries. The results of the experiments were analyzed using the exact, steady state solution for a power law fluid and simulations accounting for slipping at the boundary between the semi-solid metal and the die. Results indicated that the no-slip condition cannot be used to simulate the velocity boundary condition, because the measured pressure is much lower than that predicted by the models. An estimated apparent slip coefficient was introduced to account for the reduced pressure. During some of the experiments, a sudden drop in the measured pressured, prior to decreasing the ram velocity, coincided with observations of segregation in the form of concentric rings visible on the polished surface of cross-sections cut from material remaining in the tube.

Jan 1, 1997

By P. Kerr

Iron segregation is pre-dated by copper and nickel segregation processes for which the experimental methodology and reaction chemistry were established. The accepted reaction sequence for segregation involves the generation of hydrogen chloride, the chloridization and volatilization of the metal chloride, and precipitation of the metal from the metal chloride in the vicinity of carbon. Iron segregation roasting offers a potential extraction solution for processing oxide deposits with complex mineralogy or waste streams such as Minette-type iron deposits, nickel laterites, ilmenite, red mud, electric arc furnace (EAF) dust, mill scale and slag. After subsequent magnetic separation, one is left with a high grade metallic iron powder which can be marketed for powder metallurgy or briquetted to serve as a direct reduced iron (DRI) product. The non-magnetic product is typically concentrated oxides including rutile, alumina, or oxides of V, P, and rare earths, etc. that may be economically recoverable with subsequent processing. While operating conditions vary for different metals, they share the requirements of an elevated operating temperature and a mixture of oxide ore, carbonaceous additive and a chloride additive in varying amounts all in a closed reactor to allow for reducing conditions and contain the volatile chlorides. This process is then followed by some form of physical separation. Testwork performed by the authors shows promising results that may aid in future development of the process. Segregation roasting of iron will likely never displace traditional beneficiation and ironmaking technologies; however, it has great potential in niche markets where traditional technologies have failed or current technologies generate substantial waste.

By W. G. Davenport

Chapters 19 and 20 examine direcHo-copper flash smelting and flash converting. This chapter compares the two processes and suggests which is likely to be 'the more economic for a given concentrate. It: (a) uses Chapter 19's direct-to-copper industrial oxygen and oil requirements (b) adds the energy required for electric furnace recovery of Cu from direct-to-copper slag (Czemecki et al 1999) (c) combines Chapter 20's, flash converting calculations with Chapter 18's flash smelting calculations to determine their combined industrial oxygen and hydrocarbon fuel requirements (d) adds the energy required to granulate, crush and dry flash smelting matte for the flash converter (e) adds the energy required to granulate and dry flash converter slag for recycle to flash smelting (f) compares direct-to-copper and flash smelting/flash converting in terms of their total equivalent hydrocarbon ener.gy requirements.

Jan 1, 2001

By Georgios Kolliopoulos

Water is a critical commodity of our generation and a key compound for the chemical and mining industries. Sustainable industrial development is directly associated with the ability to recover clean water from contaminated sources. Forward Osmosis (FO) is a low-energy footprint membrane process allowing the recovery of clean water from high salinity effluent streams. In FO, water is recovered spontaneously into a concentrated draw solution (CDS). Energy is required to separate the recovered water from the resulting dilute draw solution (DDS). In the current work, the fundamentals of the FO process and the most important aspects affecting its performance are discussed. An energy comparison of FO and conventional water recovery technologies is presented. Finally, the opportunities FO presents in the field of hydrometallurgy are analyzed.

By R. Schaller, Ch. Karcher, A. Thess

"Electron beam evaporation of liquid metals is an innovative technology increasingly used in industry to produce very thin coatings of high purity. In this process the surface of a metal ingot, placed in a water-cooled copper crucible, is heated by bombarding it with a high-energy electron beam gun. The material melts, forming a free surface and eventually starting to evaporate. The rising vapor cloud condensates as a thin film on a moving substrate. The strong energy input at the free surface gives rise to vigorous thermos capillary and buoyancy driven convective motion within the melt, leading to unwelcome heat losses. This paper aims to show how these losses can be reduced by optimizing the geometry of the crucible and by using external magnetic fields. We present both experimental and numerical results.IntroductionElectron beam evaporation of liquid metals [l] is an innovative PVD-technology which is excellently suited for the industrial production of high-quality coatings. In this vacuum process a high-energy electron beam heats up the surface of a metal ingot. The ingot melts and forms a free surface. A schematic view of the arrangement is shown in Figure 1. When the temperature of the free surface exceeds the actual (pressure-dependent) saturation temperature of the ambient gas, the liquid starts to vaporize. The rising vapor cloud finally condensates on a moving substrate located at some distance above. To guarantee a superior quality of the coating the melt is typically confined in a water-cooled copper crucible. The intensive cooling is necessary to avoid chemical reactions between the melt and the crucible walls, that is, crucible materials and their reaction products are practically excluded from evaporation."

Jan 1, 1999