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By Philip Nash, Jie Zhou, Joshua Blackketter

"Large ingots tend to have internal defects such as shrinkage cavities and porosities, which have to be closed during the cogging stage to ensure sound internal quality of forged parts. In this work, finite element methods were used to simulate open die forging passes, with varying parameters that affect the void closure behavior profoundly. Numerical models ware constructed in ABAQUS, DEFORM and FORGE using data taken from footage of the forging process and material mechanical data obtained from the Gleeble compression tests. Forging variables such as pass rotation, reduction per pass, and feed ratio were studied with intense attention paid on the special properties of H13 steel, so that this study can be applied to solve real world problem.IntroductionCenterline defect closure is a frequently studied but still challenging topic in open die forging industry. In practice, open die forging is employed as an effective hot forming process to make desired shape of metal products as well as to ensure center consolidation of internal defects which result from the casting process. Nowadays, remarkable large forgings have been more and more required to meet industries demand. However, the increase in ingot size has tended to result in considerable macrosegregations and shrinkage cavities or voids, which need to be worked thoroughly during the forging process; but the size of the products and limitations of manufacturing capacity, such as the press load, make it difficult to achieve adequate local deformation to close those defects. Therefore, choosing optimal forging parameters under given work condition to ensure good internal quality of forged products is critically important."

Jan 1, 2012

By Tsembel Darjaa, Toru H. Okabe, Yoshiaki Umetsu

"With the purpose of extracting molybdenum and rhenium from molybdenum sulfide concentrate; .electrolysis of slurry, solvent extraction and ·precipitation operations were carried out. The slurry of the concentrate in 10 mass% NaCl aqueous solution was continuously circulated into a vertical type 10 stack bipolar electrolytic cell consisted of carbon electrode disks, and, the concentrate was dissolved by electrochemically generated oxidizers at 313 K. The current efficiency for molybdenum dissolution was 73 % after 10 hours electrolysis, and the leach solution was found to contain 0.2 mol/l of molybdenum and 4x10-5 mol/l rhenium. This result shows the dissolution is more than 8 times faster than that obtained using a single cell. The leach solution from electro-oxidation was then subjected to a solvent extraction for rhenium which is then recovered as sulfides. After rhenium separation, molybdenum was precipitated by pH adjustment, and solid MoO3 (H2O)x crystals, free of sulfate, were obtained from the leach solution containing large amount of so42-.IntroductionIn the past, electro-oxidation using a bipolar cell was applied for leaching molybdenite concentrate and ores at U. S. Bureau of Mines [1-3] and also at Bhabha Atomic Research Center [4]. In· these previous studies, Moebious type bipolar cells, in which electrode plates were vertically inserted into the free surface of the electrolyte, were employed and its effectiveness was demonstrated.Recently, the present authors studied on leaching of Mongolian molybdenite concentrate, and the effectiveness of leaching of the concentrate by electro-oxidation in alkaline and acidic NaCl solutions was demonstrated [5]. The leaching reaction during the process can be explained by the 18 electron transfer reaction of molybdenite (MoS2) with the oxidizers produced in-situ by electrolysis of NaCl aqueous solution. Further investigation was made with respect to various process parameters for electrooxidation such as pH, pulp density and temperature of the slurry, and the dissolution behavior of minor elements such as iron, copper, and rhenium [6]. Solubilities of molybdenum in the leach solution at, various temperatures and pH .was · studied, and feasibility of molybdenum recovery by hydrolysis of molybdenum species was demonstrated. By adjusting the pH of the leach solution, molybdenum oxides or hydroxides free from sulfate were successfully obtained from the solution containing large amount of sulfate ion. Rhenium present in the concentrate at a level of several tens of mass ppm was found to dissolve into the leach solution, and co-precipitate with the molybdenum compounds. Rhenium in the leach solutions, therefore, has to be recovered before precipitation of molybdenum, otherwise it is lost in the precipitate."

Jan 1, 2000

By J. Smuts

The mixed-valence iron silicate ISCORITE (Fe7Si010) was identified recently in a number of ironmakingmater1als, some of which were first produced more than a century ago. Although the existence of iscorite was not reported before 1967 and published phase diagrams do not make provision for it, the morphology of the phase in all the materials that were examined suggests that it is stable under a variety of conditions. It is shown that is-corite can accommodate various foreign cations in its lattice where they can replace Fe and/or Si. The morphology of is-corite in a number of materials of different origin is shown in relation to iron oxides and silicates in optical and SEM/BSE images.

Jan 1, 1991

By Dengfu Chen, Huabiao Chen, Yunwei Huang, Mujun Long, Youguang Ma, Lintao Gui

In the current work, a three-dimensional model coupling turbulent flow, heat and solute transport was developed to investigate the solute transport and redistribution in the mold of slab continuous casting where the Reynolds number is very high and the molten steel flows strongly. The conservation equations of momentum, energy and species for a multicomponent system which includes solute element C, Si, Mn, P, S were solved with the commercial software ANSYS Fluent. The parameters used in the model are based on the actual continuous casting. The fluid flow, temperature distribution and solute elements distribution were analyzed. Results showed that negative segregation occurred near the strand surface, and the species concentration reached a peak value at the solidification front during solidification. The segregation degree of solute element S is higher than the other solute elements because of its lower equilibrium partition coefficient. The species concentration in the liquid pool is homogeneous because of the turbulent flow effect.

Jan 1, 2015

By Yuzo Hiroshige, Kiyotaka Tahara, Hiroki Hatayama, Masaharu Motoshita, Tomohiko Akahori

Large amount of rare earth metals is stored in the used electric products. Hitachi has started to develop the environment-friendly process for rare earth metals recovery from used magnets. We report here the environmental impact of our process, in comparison with the conventional recycle process utilizing solvent extraction. As an evaluation method, Life-cycle Impact assessment Method based on Endpoint modeling ver.2 (LIME2) developed by the National Institute of Advanced Industrial Science and Technology (AIST) in Japan is applied. It was found that the environmental impact of the new process was more than that of the conventional process. For further reduction of its environmental impact, minimization of energy consumption to operate the equipment was most effective. Decreasing the amount of magnesium, used as an extractant, and the improvement of the extraction rate of rare earth metals were also considered as specific options for reducing energy consumption in the plant development.

Jan 1, 2014

By R. Boom, C. F. Balentina, J. H. L. Voncken

During vitrification of bottom ash generated from the combustion of municipal solid waste (MSW), a Fe-Cu based alloy phase with great value was formed. In order to find proper commercial use in metallurgical industry, it is necessary to separate Cu and Fe. The present study focuses on the sulfide treatment at temperatures of 1400 – 1500oC, in particular with FeS containing minerals. Various sulfide compounds such as Na2S, Al2S3 and Ni3S2 were added to promote the copper removal. Pyrite and zinc sludge (containing ZnS) as waste streams were studied with specific interests. The results showed that both zinc sludge and pyrite are effective for copper removal with the highest removal efficiency of 95% by using pyrite. The copper content drops from 12 wt% to about 2 wt%. However, it is still difficult to remove copper completely from the alloy in one step, and a multi-step operation is needed.

Jan 1, 2008

By Alicia Esther Ares, Carlos Enrique Schvezov, Alejandra Silvina Roman, Claudia Marcela Méndez

In this paper the structure of aluminum based alloys and their corrosion behavior by using different electrochemical techniques as characterization methods are considered. Currently, it becomes imperative to know the role of the Al2Cu against the susceptibility to corrosion of these alloys. The present work aims to studying the electrochemical behavior of aluminum base alloys with the following compositions: Al-1wt.%Cu, Al-4.5wt.%Cu and Al-15wt.%Cu (with different grain structures), in 1M NaCl solutions, at room temperature. Cyclic potentiodynamic polarization tests were performed and were found that the alloys with more than 1wt.%Cu in the matrix have an unstable behavior and without tendency to reach passivity. The equivalent circuits derived from electrochemical impedance spectroscopy technique (EIS) generally showed two capacitive contributions. The susceptibility to corrosion becomes a complex function, not only of copper concentration and structure, but also with interdendritic spacings and distribution of phases in the alloys.

Jan 1, 2015

By M. H. Staia

A Venezuelan ilmenite concentrate has been chlorinated at a temperature of 700" C by carbon tetrachloride. In the experimental rig, built at laboratory level, the direct chlorination process yielded a TiCI, recovery of approximately 85% after 280 minutes processing. The partial pressure of carbon tetrachloride was nearly atmospheric (0.94 atm). Product vapors from the reactor were fractionally condensed in a condenser which was maintained at a temperature of 250°C meanwhile TiCl, vapors were condensed in refrigerated coils at a temperature of -20°C. The concentrate used in this investigation was obtained by applying gravitational and magnetic concentration methods to the black sands. The experimental results have shown the need to asses the influence of the weight ratio of ilmenite to carbon tetrachloride on the resultant products. The equilibrium of the heterogeneous system has been calculated taking into account the initial experimental conditions.

Jan 1, 1995

By Virgil Optasanu, Yvon Lacroute, Eric Lesniewska, Tony Montessin, Pauline Vitry, Eric Bourillot, Cédric Plassard

A general challenge in metallic components is the need for materials research to improve the service lifetime of the structural tanks or tubes subjected to harsh environments or the storage medium for the products. One major problem is the formation of lightest chemical elements bubbles or different chemical association, which can have a significant impact on the mechanical properties and structural stability of materials. The high migration mobility of these light chemical elements in solids presents a challenge for experimental characterization. Here, we present work relating to an original non-destructive, with high spatial resolution, tomographic technique based on Scanning Microwave Microscopy (SMM), which is used to visualize in-depth chemical composition of solid solution of a light chemical element in a metal. The experiments showed the capacity of SMM to detect volume. Measurements realized at different frequencies give access to a tomographic study of the sample.

Jan 1, 2015

By V. Ramachandran

In view of the increasing environmental regulations that have been promulgated in the last 30 years, non-ferrous smelters and refineries have learnt to handle effectively the process waste streams that need to be bled from the system for impurities' control. The cations of concern are copper, lead, zinc, cadmium, mercury, thallium, nickel, silver, sodium and potassium. Anionic species of arsenic and selenium also need to be addressed, Sulfates and chlorides-not a major concern at present-have come under scrutiny in the recent past. The current paper reviews several treatment options with reference to a) types of waste streams processed b)process chemistry c )discharge options and recovery of treated water and d) sludge disposal. The long term goal of any smelter and/or refinery should be to achieve zero liquid discharge from the plant. Methods to obtain zero discharge are discussed.

Jan 1, 2003

By James J. Komadina, Robert R. Beebe

"Heap leaching of gold ores has enjoyed wide acceptance in the arid and semi-arid regions of the western U.S., Australia and South America. There are areas, however, where cold weather or excessive precipitation can limit the usefulness of heap leaching. Even in Nevada difficulties can be encountered which call for special operating procedures.The paper discusses the general climatological limitations and some of the techniques used to extend heap leaching into colder conditions. A case history of the Cripple Creek and Victor Gold Mining Company operation in Colorado examines 'valley-fill"" technology as an ideal cold-climate solution, where topographical conditions permit.AcknowledgementsThe authors gratefully acknowledge the management of Independence Mining Company for their permission to present this paper. The contributions of Golder Associates; Pikes Peak Mining Company Environmental Affairs Department staff, and the Colorado Department of Mines and Geology were all invaluable in successfully concluding this project.BackgroundWhen heap leaching of oxidized gold ores was introduced in the rnid-1970s it was aimed at large tonnages of low-grade material which could not, in general, be developed via conventional milling. Normally, the reasons for this were economic rather than technical: capital and operating costs for milling were simply too high. At first, grade was almost the only criterion, but deposits too small to justify milling were also potential targets for heap leaching.Renewed interest in gold was centered in the western United States and Australia, where exploration for milling-grade deposits had never really died. When heap leaching came along, it was in these areas that the first developments took place. Coincidentally, these same areas were favorable for heap leaching: climates were temperate for most of the year and competing land uses were limited. Even so, in the western United States in particular, winter temperatures were low enough to complicate operations. Precipitation was less a problem, although heavy snowfalls could periodically interfere as well."

Jan 1, 1997

By Tracie Zoeller, G. Paul Neitzel, Jr. Sanders

"As-cast aluminum alloy microstructures are highly segregated. Coring occurs when solute is rejected during solidification resulting in a non-uniform solute distribution across the dendrite arms. Furthermore, coarse constituent phases are formed in the interdendritic channels as a result of coring. These constituents are either soluble or insoluble and can form from the major solute elements, or the impurity elements iron and silicon. The dissolution of these constituents, or precipitates, is an important consideration in determining the microstructural evolution of an alloy. The properties of an alloy are significantly affected by the morphology of the precipitates. Precipitates can be either beneficial or detrimental to the properties of the alloy. Regardless of the nature of the precipitates present, it is useful to understand the dissolution process. A diffusion-limited dissolution model for planar precipitates is presented and compared to an analytical solution and to models in the literature. Experimental data for the dissolution of AhCu precipitates in a dilute alloy are compared to the proposed model, and found to have good agreement.IntroductionDuring the processing of precipitation hardening alloys, beginning with the solidification step and ending with the final solution heat treatment step, there are a variety of particles that form. Some of these particles must be dissolved and solute redistributed and re-precipitated in a more homogeneous distribution than as it first appears in the as-cast microstructure. The particles can be classified by size as microstructure develops during processing. Coarse particles that form during solidification can either be soluble, partially soluble or insoluble. These particles can be the result of coring of the major solute elements as well as the limited solubility of elements such as iron and silicon. Iron and silicon can combine with the major solute elements such as copper in 2xxx alloys forming coarse phases often referred to as constituents. Figure l(a) shows the as cast microstructure with the constituent phases, Al2Cu and the insoluble phases containing Al-Fe-Mn-Cu-Si [7]. During preheating the soluble phases such as AhCu that were formed by eutectic decomposition must be taken back into solution, whereas the insoluble phases remain essentially unchanged by most thermal operations. Figure l(b) and (c) show some of these constituents after subsequent preheating steps. In Figure l(b), AhCu platelets are shown and in Figure l(c) the remnants of the AhCu phase are noticeable, along with Mn-bearing dispersoid phases. Reduction in the volume fraction and size of these phases improves the ductility and fracture toughness as well as reducing the inhomogeneities that occur during coring. Also adjacent to the dendrite arm boundaries are smaller AhCu phases that precipitate by a solid-state transformation on cooling to room temperature."

Jan 1, 2004

By Gavin Beer

The Chelopech Copper/Gold Mine, located in west-central Bulgaria, has been in operation since 1953 producing a low-grade copper/gold concentrate containing up to six percent arsenic by weight. The penalties and restrictions imposed on smelting this concentrate, have seen the past operators of the mine strive to find a balance between achieving acceptable metal returns from the smelters and installing novel or unproven technologies in the face of changing political and economic climates. This paper documents the colourful history of the concentrate processing alternatives that have been investigated and implemented over the 45 year life of the Chelopech Mine, culminating in the high pressure oxidation option that is now the focus of a Definitive Feasibility Study (DFS) presently being undertaken by GRD Minproc Limited. The fundamental chemistry of the preceding alternatives is outlined followed by a discussion as to why each was ultimately not employed. A detailed description of the technology proposed in the DFS is given including: pressure oxidation, arsenic fixation, SX/EW copper recovery, CIL gold recovery and AVR/SART cyanide/copper recovery processes. Keywords: Arsenic, Scorodite, HPOX, Chelopech, Dundee

Jan 1, 2005

By Mark Cross, Diane McBride, Nick Croft

Extractive metallurgical processes rate amongst the most complex from the perspective of computational modeling. They typically involve multi-phase and multi-component fluid flow in very complex geometries, heat transfer driven by a number of interacting phenomena, solidliquid- gaseous phase change and mass transfer together with complex thermodynamics and associated chemical reactions. Beyond the model building itself, key challenges have always involved being able to identify the phenomena present together with interactions to characterize processes and experimental laboratory and plant data to parameterize the arising models – it is in this milieu, which require considerable process understanding and subtlety of thought, that David Robertson has made his contributions. We will review the achievements, over the last couple of decades, in computational modeling of extractive metallurgical processes and address some of the remaining challenges to enable simulation based process design, as we move through the 21st century.

Jan 1, 2014

By T. Alboussiere, O. Paireau

"We have designed an experiment to simulate natural convection in a direct-chill aluminium ingot. In this experiment we induce natural convection within a hemisphere filled with liquid-metal (mercury). The device consists of a copper hemispherical bowl closed by a copper plate. The top is maintained at superheat temperature while the boundary is cooled. While the temperature measurements were found using thermocouples, the velocities were obtained using an original technical procedure that relies on MHD properties. By applying a steady local magnetic field, we measure the velocity. The distribution of temperature and velocity can be separated into a thermally stratified core bounded by thermal wall jets. These wall jets greatly influence the degree of macrosegregation in ingots.1. Natural Convection in Aluminium CastingIt is well known that the quality of the final product in aluminium casting depends on the movements within the liquid metal such as forced or thermogravitational convection. Strong buoyancy-driven flows are known to occur in the liquid metal pool of an aluminium ingot caster. These flows have a significant influence on the metallurgical structure of the ingot through the redistribution of heat, fragmented dendrites and segregated material within the pool. Macrosegregation mechanisms depend on favourable temperature and flow distributions in the sump, and these factors will determine the pattern and degree of macrosegregation. Moreover, for many years, the importance of thermally-driven natural convection in casting has been underlined (Cole & Bolling, 1965). In this way, a precise determination of the velocity and temperature fields is required in order to improve understanding of the macrosegregation mechanisms. That is precisely the aim of this paper, which provides experimental data of the flow and the temperature distributions in a natural convection experiment. We intend, with this laboratory experiment, to determine accurately the velocity field, particularly within the thermal boundary layer where the effects of the flows may have an important role in the transport of crystals."

Jan 1, 1999

By Charles W. Kenney

Mercury contamination of soil at an old chemical plant surrounded by a residential community and adjacent to a river has provided unique challenges for the current owner. Inorganic and organic mercury compounds had accumulated over the past 50 years to levels that require remediation. Hazen Research, Inc. conducted a multi-phased program to characterize contaminants and their occurrences, evaluate various treatment technologies, and demonstrate the selected technology at bench and pilot scales. A combined physical cleaning and chemical treatment was demonstrated to meet treatment goals for the site. This paper discusses the methods of process selection and results of the bench-and pilot-scale testing.

Jan 1, 2003

By Georgette Smits

The gun-sprayed refractory lining of electrothermal furnaces used for the manufacture of carbon disulphide from liquid sulphur and charcoal at between 800 and l000°C are severely attacked during the process. A mineralogical study of samples of eroded refractory material disclosed that carbon disulphide had penetrated the lining, causing the precipitation of sulphides and carbon, and the decomposition of mullite, a major constituent of the lining, to corundum and amorphous silica. Calcium, iron, titanium, and chromium are undesirable cations in a refractory that is used in furnaces for the production of carbon disulphide, since they react readily with this substance. A series of tests, in which samples were exposed to different amounts of carbon disulphide for various residence times and at different temperatures, was carried out with eight types of aluminosilicate-based castable and brick refractory materials, to compare their resistance to attack by carbon disulphide. Mineralogical investigation of the test cores showed that castable refractory materials are unsuitable for this type of process because of the presence of calcium aluminates and other impurities in the cement. Of all the refractories that were tested, a mullite brick of low porosity, containing a minimum amount of impurities, appeared to be the most suitable for use in this type of operation.

Jan 1, 1989

By Andreas H. Vassiliou

Organic materials are major constituents of the ore in several uranium deposits. Some of these deposits have been described as "urano-organic" because, the organic materials are believed to have provided the dominant control for the accumulation and deposition of uranium and are directly and intimately intermingled with the uranium. The nature of these urano-organic deposits has been problematic in terms of (a) the origin of the associated organic materials and (b) the specific form of' occurrence of uranium. The organic materials in urano-organic deposits have been genetically related to both coal and petroleum or their progenitors or deriva-tives. Analytical data presented here (infrared, chemical. D.T.A.) suggest that coaliferous materials or related plant derivatives represent the main source of the organic fractions in practically all major urano-organic ores analyzed from the Colorado Plateau and other areas. Recognition of the specific form of occurrence of uranium in urano-organic deposits has been problematic mainly because the uranium is usually in an extremely fine-grained and disseminated state in the organic matrix. Electron microprobe and X-ray diffraction analyses presented here show that fine-grained uranium minerals, specifically uraninite or coffinite. are disseminated in the organic matrix as the predominant form of uranium in most major deposits; however. the presence of true organo-uranium compounds is also suggested for some deposits.

Jan 1, 1981

By Karin Soldenhoff

Recovery of uranium in conventional ion exchange circuits, using strong base or weak base resins containing quaternary or tertiary amine functional groups, is based on an anion exchange mechanism. In saline liquors, chloride competes with uranium for the active resin sites and reduces resin loading. This results in significant negative impacts on the IX process in terms of plant throughput and operating costs. In this paper we present the results of a study on the recovery of uranium from an acidic in situ leach liquor containing approximately 9 g/L chloride. A range of resins was tested, and a high capacity strong base resin was identified with significantly enhanced loading compared to conventional resins. Other process-relevant criteria such as loading kinetics and elution efficacy are also discussed. The process developed was successfully tested during a recent ion exchange pilot plant operated in conjunction with a field-leach trial.

By Fuqiang Zheng, Shuai Wang, Ting Duan, Yufeng Guo, Tao Jiang, Andrew Yakovlevich Travyanov

Organic compound binder can effectively enhance the strength of green pellet and reduce the addition amount of binder during pelletizing. However, compared with traditional bentonite binder pellet, the compressive strength of the preheated and roasted pellets significantly declined. It is of significance to resolve this problem for the application of organic compound binder. In this paper, magnetite concentrate was used as raw material, carboxymethyl cellulose (CMC)- bentonite compound was used as binder, characteristics of preheated and roasted pellets and the effects of additives on that were systematically studied, The results show that sodium acetate can effectively improve the characteristics of the finished compound binder pellets. The compressive strength of the preheated and roasted pellets were increased by 52/N·p-1 and 342/N·p-1 respectively when the addition amount of sodium acetate is 2.2%wt of compound binder. Moreover, sodium acetate has no adverse effect on pelletizing process and drying characteristics of green balls.

Jan 1, 2015