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By Kenshi Kawabata, Mitsuji Ueda, Junko Umeda, Katsuyoshi Kondoh, Kantarou Kaneko

Solid-state recycling process of in-house scraps of machined magnesium (Mg) alloy wastes has been established to directly produce wrought materials via the repetitively plastic deformation by Roll-compaction (RCP) and the conventional hot extrusion. The coarse chips, wasted in machining AMX602 (Mg-6Al-0.2Mn-2Ca) cast billets used for the gate bar used in Electronic Toll Collection (ETC) of the high-way system, were employed as the input materials in this study. RCP process enabled to serve coarse Mg alloy powder consisting of refined grains and intermetallics with no re-melting. They were easily consolidated by hot extrusion, and their wrought alloys showed both homogeneously refined grains less than 1~2 µm by dynamic recrystallization and randomized texture by repetitive plastic deformation on the input wastes. These materials revealed extremely advanced mechanical properties of high tensile strength of 356MPa and high ductility of 14.8%, compared to the originally virgin materials with 270MPa TS and 5% elongation. When applying the same Mg alloy wastes via RCP process to the mass production in the company, the large-scale extruded materials also indicated the superior tensile properties. It means that this direct solid-state process is held as “Up-grade recycle of metal wastes”.

Jan 1, 2008

By Chuanhong Li, Zuohua Lin, Zhancheng Guo

"Catalytic mechanism of CeO2 in combustion of coals was investigated in this paper. Catalytic combustion of four kinds of coals with different metamorphic grades by CeO2 was examined, suggesting that catalytic function of CeO2 increases with increase of metamorphic grade of the coals. One important reason for CeO2 promoting combustion of the coals is that pyrolysis of anthracite is advanced by CeO2, which not only raises the pyrolysis rate and pyrolysis conversion ratio, but increases contents of light components in pyrolysis gas; and both pore space and specific surface area of the pyrolysis char are enlarged by CeO2, which is another reason. In order to realize in situ catalysis for reducing catalyst consumption, it is crucial to increase catalyst particle number and enhance the bonding force between catalyst and coal. In addition, remarkable energy saving effect was observed when a nanometer calcium-based rare earth catalyst obtained by hydro-thermal synthesis was applied to catalytic combustion of coal injection into blast furnace.Introduction Coal combustion is acknowledged as one of the most important coal applications. Since addition of catalysts could reduce the ignition temperature of pulverized coal and accelerate the coal combustion, catalytic combustion is generally accepted as an effective measure to realize fast combustion of coal. Furthermore, different catalysts added may produce different effects on ignition temperature of coal. It is reported activity of catalysts with the same cation follows this order: OH->CO3 2->Cl->SO4 2-; while that of the catalysts which have the same anion follows: Cs+>Rb+>K+>Na+>Ba2+>Li+>Sr2+>Ca2+>Mg2+>Be2+ [1-4] .Due to the special physical and chemical structure, CeO2 plays an important role in the catalysis field. Many literatures point out that CeO2 not only has great catalytic effect on energy conversion, succeeded in catalyzing combustion of gaseous fuels such as CH4, CO, etc. but also can catalyze combustion of some liquid and solid fuels such as JP-10, black carbon, carbon deposit in the automobile exhausts and so on [5-9].Pyrolysis, the first step of combustion, directly influences ignition temperature and combustion rate of coals. So a great variety of catalysts were applied to catalyze pyrolysis of coals. And plenty of studies suggest that the alkali and alkaline-earth metal compounds inherent in the coals show apparent catalytic effect on coal pyrolysis. Meanwhile, addition of alkali and alkaline-earth metals into coal combustion process also indicates obvious catalysis effect, accelerating coal pyrolysis, improving pyrolysis conversion ratio, increasing contents of pyrolysis gases and changing composition of the pyrolysis gases [10-15].Although alkali and alkaline-earth metal compounds have good catalysis effect on coal combustion, their application in the catalysis field was limited because of their erosive attack to the combustion equipments. In contrast, CeO2, as a substitution of the traditional coal catalysts, presents widely potential application due to its good catalysis ability, non-corrosive and nontoxic. However, investigation on CeO2 catalyzing coal combustion is rarely reported. In this work, catalytic mechanism of CeO2 in coal combustion was studied, in an attempt to provide theoretical foundation for developing new catalysis technologies."

Jan 1, 2009

By Honglei Zhang, Wuguo Xiang, Xinhao Huang, Guotao Xu, Xilai Chen

"The service behavior of refractories used in hot air pipeline for hot air stoves in a 3200 M3 blast furnace of WISCO was analyzed. The damage factors can be concluded as the poor quality of and alusite based bricks, the severe thermal shock damage, the more porosity in structures, loose bonding capability, and the unreasonable choice of materials and design of bricks. By analysis, the service life of hot air stoves can be enhanced by the measurements such as the reasonable choice of materials and their match, the use of light-weight refractories, the improvement of brick type, etc. Thereafter, the normal production operation of hot air stoves is guaranteed.IntroductionThe No.7 blast furnace of WISCO has been used for about 5 years and it was mid-repaired in March, 2012. The top phenomena of worn hot air pipelines are brick drop, breakage, severely local wear and deformation, existing hidden danger, so the worn hot air pipelines were renewed. Investigations have been done on the stove damage and design [1,2]. In order to clarify the wear mechanism, the used refractories for hot air pipelines were sampled and analyzed, the properties and structures of worn materials and reused materials are relatively studied."

Jan 1, 2013

By F. Guevara

The paper presents results of physical and turbulent three-dimensional numerical simulation of the gas flow in the wind box and reaction shaft of the concentrate burner of a flash furnace. Physical simulation work was carried out in a 1:5 linear scale model, where the velocity field was measured using a Pitot tube. The mathematical model consists of the three-dimensional averaged Navier-Stokes equations, turbulent kinetic energy and dissipation of turbulent kinetic energy using the Renormalization Group (RNG) theory for the k-e turbulence model. Computations were performed using FLUENT, based in a finite- volume code. The geometry of the concentrate burner was separated in two sections: wind box and reaction tower. Results obtained at the exit of the wind box were used as boundary conditions for the reaction shaft. The effect of boundary conditions on the numerical results was also studied. Results of physical and numerical simulations show an asymmetry of the velocity field at the exit of wind box. This asymmetry is possibly due to existence of a separated flow in the back of the exit ring. The agreement of physical and numerical results assess the capacity of the turbulence RNG k-e model to reproduce correctly the behaviour of the velocity field at the exit of the concentrate burner.

Jan 1, 1999

By David Ellis

The next generation of Reusable Launch Vehicle (RLV) will utilize regeneratively cooled combustion chamber liners in the engines. The current design calls for using a new Cu-8 at. % Cr-4 at. % Nb (Cu-8 Cr-4 Nb) alloy for the liners. Work is ongoing to characterize the thermophysical and mechanical properties of the alloy from - 253 to 800°C, the temperature range to which the alloy will be subjected during service. The alloy has been commercially produced in quantity for NASA. The powder size has been characterized and the microstructure examined. The powder was extruded into bar using a commercial extrusion press. In addition, samples have been hot isostatically pressed (HIPed) at NASA Glenn Research Center. Both processing methods produced fully consolidated material. Transmission electron microscopy (TEM) revealed highly faulted Cr2Nb and some elemental precipitates. Cryogenic tensile testing showed the extruded specimens had significantly higher strengths than NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr) even after being subjected to a simulated braze cycle. The Young's moduli (Cu-8 Cr-4 Nb) were lower than NARloy-Z. The lower moduli is highly beneficial for reducing thermally induced stresses in rocket engine combustion chamber liners and similar applications.

Jan 1, 1999

By E. J. Peuraniemi

Recently commissioned Kennecott-Outokumpu flash converting was developed to replace the approved but environmentally outdated Peirce-Smith -converting to satisfy the globally tightening emission regulations. In the present study, dust formation and reaction mechanisms of two copper mattes with different experimental parameters were studied in lean suspension conditions. Both mattes had very high copper content of approximately 75 wt% and low iron content of 4.5 wt% and 1.2 wt% Fe. A laboratory scale, vertical laminar-flow furnace with a low feeding rate was used to simulate the phenomena taking place in the reaction shaft of a flash converter. Experimental conditions included temperature of 1300 °C with reaction gas oxygen contents of 20 vol%, 50 vol%, and 75 vol%. In the experiments, sieved particle fractions were fed to the furnace and sampled after short reaction time intervals by quenching them into a water film. Collected particles were analysed chemically for their main elements to define their removal rates. Also, optical and scanning electron microscopy with EDS-analyser were applied to determine phenomena occurring during reactions. Kinetics of oxidation as well as ignition of particles are discussed. Changes in particle morphology, size, and composition are reviewed to describe dust formation and reaction mechanisms.

Jan 1, 1999

By C. G. Bastos Andrade, V. F. Justo, F. R. Valenzuela-Diaz, M. G. S. Valenzuela, C. M. Matos, C. Volzone

For industrial use, the smectite clays are usually treated with inorganic acid of high concentration at temperatures under boiling point, which provide the bentonite´s bleaching power. In the present paper, a sample of brown smectite from Paraiba, Brazil, was submitted to treatment under moderate conditions (90°C, reaction times of 1, 6, 12, 18 and 24hours in close reactor, concentration of the aqueous solution of hydrochloric acid 1.5M, clay/acid solution ratio of 1g/10mL), aiming to reduce impurities, responsible for the color of the clay, without causing significant changes in their structure. The samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDS), stereomicroscopy, Cation Exchange Capacity (CEC), Thermal Analysis (TG/DTA), and X-ray diffraction (XRD). It was observed a bleaching in samples with time of 12h to 18h. With the DRX was possible to monitor the peak intensity of the clay structure and the sample with 12 hours of treatment was not significantly altered its crystalline structure, maintaining the peak clay at d(001). The most pronounced changes in the bleaching occurred within the first 12 hours of acid treatment. Thus, clay can be used in products with high added value.

Jan 1, 2015

By K. Osseo-Asare

Rate laws for the hydrogen reduction of metal ions are typically of the form: [r = -d[M(II)]/dt = k[M(II)]xPy2H] where k is an apparent rate constant, [M(II)] and PH2 represent dissolved metal concentration and hydrogen pressure respectively, while x = 0 - 1 and y = 0.5 - 2. Half-order dependences have been reported for some M(II)/H2 systems; however, no satisfactory explanations have been offered. In an effort to bridge this gap in our understanding, the published precipitation rate data (for M(II) = Cu(II), Ni(II), and Co(II)) are reviewed (with emphasis on the reported reaction orders) and compared with the corresponding but limited electrochemical polarization data. Based on the available literature on the electrochemical kinetics of the M/M(II) and H2/H+ systems it is demonstrated theoretically that, under certain conditions (e.g., in the presence of electron-conducting solids), the rate of the M(II)/H2 reaction can be expressed as: [-d[M2+]/dt = k[M2+]2/1P2/12H] It is concluded that electrochemical processes probably play an important role in the hydrogen reduction of metal ions, especially for systems that involve heterogeneous catalysis.

Jan 1, 2003

By He De-wen

The increasing population and living standard in urban areas, have been accompanied with the growing quantity and composition complexity of rubbish, which are causing well-known social effects of pollution, while rubbish (solid waste) is a recyclable resource. To convert rubbish into useful materials, the essential measure is to carry out sorted collection of rubbish. The preconditions of implementing sorted collection are presented in the paper. 1 Characteristics of rubbish composition and amounts of recyclable contents are basic condition to implement sorted collection. 2 The existing available technologies of recycling, economic benefit from recycling, and disposal scheme of residual rubbish are restrained condition for sorted collection. 3 Public understanding and support to sorted collection are the key to success. 4 The government policies to be favorable for sorted collection is the pledge of success. 5 The establishment of a steady solid waste recycling market is also a guarantee to implement sorted collection continuously. 6 To establish management system of rubbish recycling as soon as possible. Further, the methods and procedure of sorted collection are discussed in detail and beneficial comments and theoretical basis to promote sorted collection of rubbish in urban area are presented; it will contribute reference value to municipal solid waste management.

Jan 1, 2006

By Rodney Clary

Building on work completed in earlier papers, the current paper presents a techno-economic evaluation of two recently demonstrated technologies for treatment of arsenic containing refractory gold concentrates. Using defined project parameters and inputs, the authors compare capital and operating cost estimates for pressure oxidation (POx), and the Albion Process™. The paper incorporates data now publicly available from the Albion Process™ plant, which has operated at the GeoProMining Gold (GPM Gold) project in Armenia since 2014, as well as recent POx circuits.

By V. A. Bryukvin

It has been found that by superimposing symmetric alternating current over the process, the rate of nickel and cobalt leaching from metallized products with copper sulfate solutions increases by a factor of 1.5 to 2.0 and the apparent activation energy of the process investigated is reduced from 12 down to 6.6 kcal/mole. It appears especially attractive to use alternating current for anodic dissolution (oxidation) of metallic scrap of refractory metals and their alloys in ammonia electrolytes permits production of high-grade commercial products in the form of respective ammonium salts using a short and virtually reagent-free process flowsheet. Similar approaches can be applied also for electrochemical processing of nickel and copper scrap in sulfuric acid media with subsequent recovery of pure sulfate salts or electrolytic processing. Electrochemical technology for recycling of tungsten-cobalt (WC 15) and tungsten-rhenium (WR 20) alloys has been also investigated. In the former case, anodic oxidation of carbide alloy was carried out in nitric acid electrolyte with production of pure tungstic acid. The research conducted has indicated that the physicochemical effect of alternating current results in a lower activation energy of electrode reactions due to changes in the mechanisms of the electrode reactions themselves.

Jan 1, 2006

By Jeaneth S. Benedetto

The physical and chemical processes developed for recovery of uranium and phosphor from phosphoro-uraniferous ore bodies consists of three basic steps: concentration of the phosphate bearing uranium by flotation, chemical dissolution of the concentrate by wet phosphoric acid and extraction of uranium by solvent. In this process two products are obtained: 1) uranium and 2) phosphoric acid. The purpose of this work was to develop technological know-how of phosphoric acid purification though an extraction of P2O5 by solvents. It was investigated by two lines of research. In the first one the uranium was extracted before the phosphoric acid purification. In the second, the phosphoric acid was extracted before uranium recovery. The comparison of the two processes is shown in this paper. Experimental work was developed on a laboratory scale to select and optimize the process variables. After the laboratory study, the research of extraction and stripping was continued on a pilot scale in pulsed perforated-plate columns in order to investigate the main operational and process conditions. The first phosphoric acid extraction experiments showed good results using a raffinate sample obtained from the uranium extraction process. It was possible to obtain a high purity phosphoric acid.

Jan 1, 2003

By Marco A. S. Aguiar, Luis G. S. Sobral, Vânia Mori, Paulo A. Medeiros da Silva

"Copper occurs in the crust of the earth, predominantly, as sulphides. Among the copper sulphide minerals, the chalcopyrite is the most abundant and the most refractory to the conventional oxidative processes. This work aims at developing an electrolytic process for treating a copper sulphides flotation concentrate, more precisely chalcopyrite (CuFeS2) and bornite (Cu5FeS4) in the percentages of 70 and 30%, respectively.This paper presents a low-cost operational electroleaching process for treating copper sulphides flotation concentrates, with a high chalcopyrite content. This research practical work aims at improving the copper extraction from that sulphide mineral, in a relatively short time with low-operating cost taking into consideration the influence of a cationic surfactant. The electrolyte of the electrolytic reaction system was a 2,0 mol.L-1 NaCl solution containing CTAB, a cationic surfactant. The electroleaching system contains one DSATM (dimensionally stable anode) anode and two nickel or copper foams (threedimension electrodes. During the electroleaching process the chloride ions are oxidized to chlorine at the anode surface, which in contact with the aqueous phase generate enough hypochlorite ions to oxidize chalcopyrite.The copper ions released from the chemical oxidation process are reduced at the cathode surface as metallic copper."

Jan 1, 2008

By D. Donald Downey

Pilot Testing Ion Exchange Resin (IEX) can go from very simple beaker testing to complicated column testing. Space velocities, regenerant quantities, loading capacities, ion leakage, are all terms that get accumulated together to prove or disprove a resin’s (or resins’) ability to load a single ion (or specific set of ions). Not getting all the resin’s operating parameters correct will disqualify (or at least skew) the results. Laboratory tests for capacity, moisture content, bead size, metals fouling, etc.—what does it all mean? At last count, there were over twenty-five separate ion exchange resin tests (analyses) that were available to end users. Standard testing procedures identify the resin properties but more specific procedures can be used to identify problems with equipment operation. Then, there are the costs to consider; simple cation resin testing (moisture content, total capacity and bead integrity) is in the $200/sample range. However, add to this Chatillon, Russian Ball Mill Test, HIAC particle size, metals and % regeneration test procedures and the lab work can increase to over $1000/sample. In this paper, the author will explain the “must-do” pilot and test procedures and why they are important and the key to understanding how resin performs ion exchange.

By E. Daniel Baker

"The term ""oxide disseminated gold deposits"" refers to near surface, gold-bearing veins, faults, and shear zones that typically contain appreciable amounts of oxidized ore or gossanous material, resulting from oxidation of sulphides.The concept of oxide gold deposits underwent a dramatic change after the discovery of the Carlin gold mine in north-central Nevada in the early 1960's. Now the term implies large tonnage, low-grade bulk minable deposits that are processed by milling and/or heap leach methods.Oxide gold deposits may now be classified into two types: (1) primacy ores derived directly from the effects of hydrothermal alteration on host rocks, and (2) secondary oxide ores derived from the supergene oxidizing effects of circulating post-mineral meteoric waters on gold-bearing sulphides. Each type of deposit has unique diagnostic mineralogic and metallurgical characteristics that must be addressed to achieve successful exploration strategies and viable metallurgical exploitation.The author would like to thank the management of Newmont Metallurgical Services and Newmont Mining Company for allowing presentation of this paper. Thanks are due Sevkett Acar, Donald M. Hausen, Jerry R. Odekirk, and D. Erik Spiller for their critical review of the manuscript. Also, thanks are extended to all those cited and uncited whose hard work and dedication have led to the discovery and exploitation of near-surface oxide gold deposits. Our knowledge would be greatly limited without the dedication and research of many others."

Jan 1, 1997

By Munyaradzi Kwatara, Ron Schonewille, Edgar Peek, Juzer Tayabally

"The potential recovery of nickel from a South-American saprolitic laterite ore using the segregation roasting technique was investigated. The ore was heated to temperatures that ranged between 900 and 1 000°C in a rotary kiln. In all the tests, the laterite ore was first mixed with a predetermined amount of calcium chloride and either coal or coke. By varying the temperature, calcium chloride and reductant in the different tests, a preliminary set of optimal conditions was established for the specific laterite ore that was tested. A combination of chemical analysis and electron-probe-micro-analysis (EPMA) were used to determine and evaluate the effectiveness of segregation roasting on the recovery of nickel. The present paper describes the test procedure and the results that were obtained.IntroductionIt is known that laterite ore resources account for an estimated 72% of the world's nickel resources, with sulfide sources accounting for the remaining 28%. Yet sulfide resources account for 58% of the world's primary nickel production while laterite resources account for the remaining 42% [I]. There are numerous reasons for this discrepancy, but the most important one is the mineralogical and compositional complexity that is associated with laterite ore deposits. For example, this complexity currently offers only limited opportunities for upgrading, thereby creating capital intensive whole ore processing facilities. It then follows logically that the identification and application of a low-cost processing option for the treatment of laterites could potentially open up an opportunity for exploiting these vast untapped laterite resources.To this end, a preliminary screening investigation was initiated by Xstrata Process Support to evaluate the potential application of the so-called (nickel) segregation process as a unit operation that could potentially be integrated into a laterite processing flow sheet. Laboratory bench tests were performed on this segregation process and this paper details some of the findings from this preliminary investigation."

Jan 1, 2011

By Edward P. Hagarty

The Hazardous and Solid Waste Amendments (HSWA) of 1984 added Subtitle I to the Resource Conservation and Recovery Act (RCRA), authorizing the Environmental Protection Agency (EPA) to develop and implement a new regulatory program for Underground Storage Tanks (USTs) containing petroleum and other regulated substances. Technical standards required for release detection, prevention, and correction as necessary to protect human health and the environment were promulgated as described in 53 Federal Register 37082 (September 23, 1988). Virginia State Regulations (VR 680- 13-02) and U.S. Army Regulations require that a Corrective Action Plan and a Site Clearance Report be prepared to explain the details of remediation of any contaminated media. Construction of new buildings is proposed in two different areas at Fort Myer in Arlington, Virginia, where USTs containing gasoline, diesel and heating oil were located. Tightness testing performed on these USTs in September 1991 indicated that some of the tanks were leaking. Many of the tanks were removed for permanent closure. Initial Abatement (excavation of contaminated soil) was &ed out immediately. A detailed Site Characterization Study which included Hydropunch", field screening using immunoassay, and pilot test - dual phase (water and soil gas) extraction was conducted. Environmental media were analyzed for volatiles, semi-volatiles and metals. A detailed risk analysis (RA) was performed to determine risk-based clean up levels for benzene, toluene, ethylbenzene, xylenes (BTEX); polycyclic aromatic hydrocarbons (PAHs); and methyl-tertiary butyl ether (MTBE). The RA also discussed the presence of lead in the soil. Before constructing any buildings in these contaminated areas, remediation must be conducted in accordance with the State, Federal and other applicable regulations. The remedial alternatives evaluated included Vapor Enhanced Groundwater Extraction, Soil Vacuum Extraction, Soil Washing, Soil Steaming, Active and Passive Ventilation SolidificationlStabilization, Vapor Barrier Construction, and Excavation with Off-site Disposal. This paper discusses: (a) delineation of soil contamination @) risk analysis (c) evaluation of remedial alternatives and selection of the most appropriate technology and (d) consideration of various regulatory issues.

Jan 1, 1994

By Oszkar Bíró, Peter Mittag, Bernhard Aigner, Stefan Pirkeri, Philipp Glttleri

"This paper considers CFD modeling of processing and melting of small metallic particles by means of electrical heating. The particles fall continuously onto a liquid metal bath which is heated by an electric arc. After melting of the particles liquid metal is tapped.The charging behavior of the particles in the supply unit as well as in the reactor freeboard is studied by means of Euler-Euler granular simulations. The flow situation in the metal bath due to gas injection and magnetic fields is calculated by combining Navier-Stokes and Maxwell solvers. The macroscopic melting process occurring during the continuous charging of the particles is studied by kinetic laws for melting reactions. The temperature field is evaluated by balancing heat sources due to Joule's heating and heat losses due to latent heat of melting as well as convection and radiation.As a result of these simulations the fully three-dimensional flow fields of particles and gas in the atmosphere is obtained. Furthermore the flow field as well as the magnetic field in the metal bath can be studied. As a main result the three-dimensional concentration field of the still unsolved particles in the liquid metal can be evaluated.IntroductionIn this paper a metallurgical process for melting small iron particles is investigated by means of CFD-simulations. In a first process step the preheated and already mostly reduced iron particles fall continuously into the reactor through a vertical tube mounted at the lid of the furnace. In a second step the particles are melted in the liquid metal bath. Meanwhile the melt is heated by electric arcs to provide the heat needed for melting the incoming particles.In Figure I a sketch of the geometry setup considered in this paper is provided. The particles fall from a height of approximately 12 meters onto the bath surface in the center of the furnace. The melt is heated by electric arcs that are placed symmetrically around the center axis."

Jan 1, 2001

By Yan Beygelzimer, Alexander Spuskanyuk, Victor Varyukhin

"The main idea of the report is that the yield surface can be presented as thick, ""foamed surface"" with dimensionality exceeding two. By other words, perhaps, the yield surface is fractal, i.e. it belongs to the class of geometric objects with fractional dimensionality. Apparently, fractal structure of the yield surface is determined by the fractal structure of natural materials. ""Cloud of internal stresses"" term is introduced to describe the stress distribution in representative volume element. Its plastic flow is determined by the interaction of this cloud with the thick yield surface. Thick yield surface and internal stress cloud concepts allow to determine an additional correlation between micro mechanical models of polycrystals and phenomenological theory of plasticity.1. IntroductionClassical plastic flow models are not satisfying the modem requirements. There are two main directions in their development. The first, mathematical, is connected with the development of the general theory of rheological relationships; the second, physical, is connected with the development of the representative volume element (RVE) models which are based on specific ideas about deformation mechanisms. Within the framework of the first direction, the macroscopic experimental data is formalized; the second approach deals with the generalization of physical research results for the different scale levels that are involved in plastic deformation.These approaches have advantages and disadvantages. In phenomenological theories, the advantages are the mathematical simplicity and laconic formulation of constitutive relations, which allows using them in practical calculations. However, the mathematical models of this class can not be considered as general, they are useful only for the description of limited range of deforming processes. On the other hand, physical theories that are based on the description of real plastic deformation mechanisms are very explanatory and predictive, but they lack mathematical simplicity. The above circumstances lead us to the necessity of compromise that can be found in determining the constitutive relations for RVE, which structure and parameters would bear the information about rnicrolevel and mesolevel phenomena. In this synthesis direction, the fundamental role belongs to [1,2], etc."

Jan 1, 2001

By Ashish D. Patel, Ramesh S. Minisandram

"Vacuum Arc Remelting (VAR) is the final and, hence, critical melting step for the production of a sound, segregation-free ingot for the manufacture of alloys used in rotating components in aircraft engines. A mathematical model for this process has been developed by the Specialty Metal Processing Consortium (SMPC). The model predicts temperature distribution in the solidifying ingot, flow in the molten metal pool, and the electromagnetic field in the ingot. These predictions may be used to estimate the effect of melting parameters on the pool profile in the ingot. In this paper, typical pool shapes and flow fields during VAR of Alloy 718 and Ti-6Al-4V are presented. The differences in the pool profile are primarily due to vastly different melting conditions. The model predictions are compared to the observed pool shapes from industrial-size VAR ingots.1. IntroductionVacuum Arc Remelting (VAR) is a process in which an electrode is melted in vacuum by the heat from a DC electric arc. Metal droplets from the electrode fall into the molten metal pool, which solidifies in a water-cooled copper crucible to form the ingot, as shown in Figure I. The ingot obtained from VAR is sound, and has superior cleanliness and chemical homogeneity. Hence, the process is the final melting process for most nickel-base superalloys and titanium alloys used in the manufacture of critical rotating components (discs & blades) of aircraft engines. Modeling of this process provides an insight into the effect of melting parameters on the molten metal pool in the solidifying ingot, which is a key first step in process optimization and defect prevention. In this paper, typical pool shapes, both measured and predicted, for VAR of Alloy 718 and Ti-6Al-4Vare presented. Alloy 718 is the most common VAR-processed nickel-base superalloy; whereas Ti-6Al-4V is the ''workhorse"" alloy for titanium-based alloys."

Jan 1, 2004