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By Qin Hua, Xiangru Chen, Qijie Zhai, Yongsheng Yan, Liang Chang

"In this paper, pure bainite ductile iron and their alloying form of 0.2wt% niobium were prepared by a controlled cooling heat-treatment. The effect of niobium alloying on the microstructure, hardness and impact toughness of bainite ductile iron was studied. The results show that adding niobium effectively improves the hardness and toughness of bainite ductile iron. The hardness and the impact toughness of niobium-alloyed bainite ductile iron were investigated by varying the temperature at which samples were fed to the incubator.IntroductionThere are two essential methods to prepare the bainite ductile iron: isothermal quenching [I-31, and alloying [4• 51• Isothermal quenching process is very time and energy consumable, concerned as a high cost technique for mass production. Besides, there are certain limitations on the size and shape of castings in this process. In addition, it potentially harms the environment. As for the alloying, Ni, Mo, and Cu have to be utilized to obtain bainite. However, the large demand and high cost of Ni makes it not feasible in practice.It is well known that niobium can promote the formation of carbon compound, and improves the stability ofundercooled austenite, which is preferred to the increase of the hardenability. Previous studies showed that niobium could refine the grain and improve the mechanical properties of gray cast iron [6-81 • Therefore, in the present work, the effects of niobium and the temperature at which samples were fed to the incubator on the microstructures and properties of niobium alloyed bainite ductile iron were investigated."

Jan 1, 2014

By Keri Ledford, Stephanie Lin, Jason Nadler

Novel processes are being developed to fabricate thin copper thermal wick samples of a targeted porous microstructure. Structures of desired porosity, thisckness and pore size and distribution are achieved by tayloring the incorporation of sacrificial polymer beads in to slurry precursors. The thickness of the final structure is dictated by precisely controllable slurry application methods, such as spin coating. Ina subsequent heat treatment, th epolymer components thermally decompose and the remaining copper particles sinter to form a reticulated foam. The resulting microstructures are characterized in terms of porosity, permeability and specific surface area.

Jan 1, 2012

By Walter Curlook

An improved process of hydrometallurgical treatment of laterite ores of the limonitic type for the recovery of nickel and cobalt using sulphuric acid has been developed and patented [I]. The major improvement is brought about by recycling a significant portion of the "mother liquor" emanating from the pressure leaching reaction back to the feed preparation stage thereby substituting for all or at least a major proportion of the fresh water that must be added. The amount of process effluent waters is correspondingly reduced. Concomitantly with the major savings in fresh water requirements, a degree of reduction in new sulphuric acid requirements is effected, along with a savings in limestone and lime required for subsequent neutralizations. Keywords: Acid pressure leaching; Nickel laterites

Jan 1, 2004

By K. Pagalthivarthi, P. V. Desai

"During solidification of alloys, many inter-related physical processes, such as melt convection, mass diffusion, heat transport, macrosegregation and melt-undercooling occur. Several research workers have studied one or more of these effects separately. To answer important questions on solidification behavior, an overall approach interrelating the processes is necessaryAs a first step toward accomplishing the overall modeling, the freezing of a binary liquid metal is examined. The various stages during freezing of the alloy are critically described to build a continuum model for the entire process. Diffusive mixture theory is used to write the conservation equations for the liquid and the mushy zones. The concept of local thermodynamic equilibrium in the presence of curvature effects is used to restrict the number of degrees of freedom within the mushy zone. Constitutive equations relating flux quantities and affinities, the governing differential equations and boundary conditions are discussed briefly for the freezing process.IntroductionA solidification study encompasses such facets as solifidication time, microstructure, macrosegregation of the solute, shrinkage effects and soundness of the casting. Influence of one or more of the coupled heat and mass transfer phenomena such as local solute redistribution, thermosolutal convection, melt undercooling at dendrite tips and heat dissipation to the ambient have all been previously examined [1-3J. Several studies have examined the individual facets of alloy solidification as isolated processses. In fact, the transport processes occur simultaneously and a comprehensive model should include their inter-relationships. In particular, some of the existing studies of the mushy zone [4-6J do not emphasize thermodynamic completeness. This work represents an attempt to develop a thermodynamically consistent model of the entire solidification process on physical grounds."

Jan 1, 1986

By Jayagopal Ucbil, M. Krishna, V. T. Vijayalakshmi

"The pitting susceptibility of aluminium metal matrix composites reinforced with garnet particles has been examined using static weight loss method by exposing the metal matrix composites (MMC) specimens to the action of IN HCI acid at laboratory temperature for different time intervals. It was found that the corrosion rate decreased with increase in weight percentage of reinforcement while the corrosion rate was a function of the matrix alloy but not of the reinforcement material. Further, it was found that the rate of corrosion was dependent on the interface region formed between the reinforcement and the matrix. A comparison of the base matrix with the corresponding composite when subjected to heat treatment for varying periods of 4, 8, and 12 hours respectively was made. The comparison revealed that corrosion resistance of the composite increased with the duration of heat treatment and this has established a considerable improvement in corrosion resistance of the composite when compared with the base matrix.IntroductionMetal matrix composites (MMCs) offer designers many added benefits, as they are particularly suited for applications requiring good strength at high temperature, good structural rigidity, dimensional stability, and light weight [1-5]. The trend is towards safe usage of the MMC parts in the automobile engine, which work particularly at high temperature and pressure environments [6-7]. Particles reinforced MMCs have been most popular over the last two decades. Among the MMCs, the most popular families are represented by aluminium reinforced with ceramic particles. Although the incorporation of the second phase into a matrix material can enhance the physical and mechanical properties of the base metal, it could also significantly change the corrosion behavior."

Jan 1, 2000

By A. Rohkohl, R. Piillenberg

The QSL plant at "BERZELIUS" Stolberg GmbH in Stolberg, Germany was commissioned in 1990, introducing a new era of lead smelting in the more than 150-year-old history of the lead smelter. The lead smelter in Stolberg has changed its appearance several times during its existence. Therefore, at many locations on the site, old and obsolete buildings and equipment parts can still be seen. They are often located side by side with new modern constructions like the QSL-plant and the mercury removal plant, and reflect the specific contrast between tradition and modern technology. After a brief description of the development of the smelter and its decision to implement the current novel plant, the most recent operating results are reported. Following some modifications to the process and equipment, which had become necessary along with the implementation of the new technology, the plant is in operation today at approximately 30% above its design capacity. These achieved production levels are not restricted by the QSL-reactor but by precedent and subsequent available equipment. The QSL-plant entirely complies with the demands of modern, energy-saving, ecologically compatible lead production technology. Stringent environmental standards are maintained on a continuing basis. The demonstrated viability and flexibility of the overall process permits the operation to adapt quickly to the prevailing economical situation worldwide.

Jan 1, 2000

By D. D. Harbuck

The U.S. Bureau of Mines recently identified a significant new source of scandium in an Oklahoma tantalum waste residue (approximately 0.24 pct Sc). Because scandium is a strategic and critical metal which the Department of Defense has classified for special consideration, the Bureau is researching methods of recovering scandium and associated metals from this and other process residues. A variety of operating parameters were evaluated to determine the best technique for recovering scandium. Testing showed that by sulfating the residue at temperatures as low as 150' C for reaction times as short as 0.5 hr, over 94 pct of the scandium converted to a water soluble form. Solvent extraction using DEHPA selectively recovered 100 pct of the scandium from the water leach solution.

Jan 1, 1992

By Corby G. Anderson

Today, with a stringent economic and environmental climate prevailing in the copper business, there is increased interest in evaluating new processing alternatives for production. Hydrometallurgical pressure oxidation of copper concentrates is one of the more viable approaches and several technological candidates have emerged. Of these, an overlooked but industrially proven methodology utilizing nitrogen species catalyzation in the oxidizing pressure leach system may prove to be a feasible process alternative for the future. In this paper, the history of the system and its application to chalcopyrite concentrates will be outlined. In particular, a methodology for effective treatment of precious metals bearing chalcopyrite concentrates via partial oxidation at low temperatures and pressures will be discussed. Finally, the perceived economics of this unique industrially proven process will be delineated.

Jan 1, 1999

By A. V. Tarasov

In the course of research aimed at improving the performance of the Vanyukov smelting process (VP) for treating sulfur raw materials in a pilot-scale furnace it has been found that an increase in the calcium oxide content up to 12% to 14% in case of smelting to produce high-grade matte results in a decrease in the copper content of slag by 0.05% to 0.3%. The residual copper content of slag can be computed by a formula taking into account an increase in the calcium oxide content of the feed material and that in the slag. In the course of research for improving the performance of the zinc-containing slag fuming process with blowing of the slag bath with combustion products of natural gas it has been found that the silica and calcium oxide contents have an effect on the degree of zinc sublimation. In case of slag containing 24.4% SiO₂ and 6.95% CaO by weight (SiO₂:CaO = 3.51), the residual zinc content of slag was 3.25%. The minimum residual zinc content of 1.95% was obtained in case of slag containing 22.5% SiO₂ and 14.5% CaO by weight (SiO₂:CaO = 1.55). An increase in the CaO content of slag up to 16% by weight with a ratio of SiO₂:CaO = 1.25 to 1.35 permits minimization of zinc losses in slag by achieving a residual zinc content of final slag in the order of 1%.

Jan 1, 2006

By Henrlk Gripenberg

To solve the environmental and financial problems of the traditional Rotary Salt Furnace process, a new salt-free method for aluminum dross and scrap melting, ALUREC, has been developed by AGA and its partners, Hoogovens Aluminium and MAN GHH. AGA and Hoogovens Aluminium developed the main process concept and jointly carried out trials on pilot plant scale. Owing to excellent results" the partners decided to jointly erect a commercial scale test plant. The order for the design and erection of the furnace went to MAN GHH. The three companies designed the test plant and began operation in the spring of 1994. The results have been excellent and the process is expected to be a technical and commercial success.

Jan 1, 1995

By Nexhmedin Lohja

Macro management of metallurgical industries becomes an important issue in certain situations especially when some government owned metallurgical industries are on the verge or have stopped being feasible. In these cases a government lead macro management in collaboration with domestic institutions and foreign scientific and management expert companies is decisive in order to steer them to a profitable path. This process is not necessary an easy one and incorporates many unknowns and various alternatives. In this paper the macromanagement of the metallurgical industries in Albania will be described as a particular case along with a survey of its mineral deposits, metallurgical facilities and various perspectives for future development. As a country with many mineral resources, the exploration, research, exploitation and processing work of mineral ores before 1990 constituted an important activity of its economy, especially in the exportation of various products of this industry. Since 1990 this activity slowed downs considerably for various reasons and this prompted the necessity of a government lead macromanagement in collaboration with domestic institution and foreign expert companies. This process aims at improving and renewing the technologies in the metallurgical industry in order to transform it into a feasible branch of economy. This goal is being implemented among others through proper geological surveys, rehabilitating and renewing the existing facilities through domestic and foreign investments, the transformation of the ownership or the management from state-owned to local or foreign private companies, etc. Priority is given to the raising of the processing range of the traditional minerals such as chromium, copper, nickel-iron etc. as well as developing new perspective technologies to treat new mineral deposits.

Jan 1, 2006

By Toshiyuki Kozuka

CdTe semi-conducting materials have been expected as solar cell materials because its theoretical energy conversion ratio is very high. The actual efficiency still low, however, many research works have been done in order to improve the efficiency. And crystal orientation is one of possibilities for that. In this work, a new method using intense magnetic field for a control of texture of CdTe crystals will be proposed, where the CdTe film was electro-deposited under an intense magnetic field. CdTe is less affected by magnetic field, because of its cubic structure, but Cd or Te has hexagonal structure, which is sensitive for magnetic field. In this paper, crystal orientation of Cd or Te film, which can be utilized as basic layer for CdTe deposition, will be developed.

Jan 1, 2006

By Basak Anameric

Pig iron nugget process was developed by Kobe Steel as an environmentally friendlier, economical alternative to traditional blast furnace process. The process aimed to produce highly metallized, slag free pig iron nuggets throughout a single stage heat treatment, utilizing coal as a reducing ? carburizing agent. The objective of this work was to determine whether the pig iron nuggets produced at the laboratory conditions had comparable physical and chemical properties with the blast furnace pig iron. The physical and chemical properties of the pig iron nuggets were determined utilizing x-ray fluorescence spectroscopy, x-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and apparent density measurements. The pig iron nuggets had similar chemical composition and apparent density values (6.7 ? 7 g/cm3) with blast furnace pig iron and they had microstructures similar to low carbon white cast iron. These properties make them a competitive alternative to blast furnace pig iron.

Jan 1, 2006

By Harold R. Kokal

Lisakovsky is a 3-billion ton oolitic iron ore deposit in north-central Kazakhstan operated by Orken LLP, a subsidiary of Ispat Karmet and the LNM Group. The iron oxide minerals are goethite and limonite. The gangue occurs as discrete quartz grains and an unidentified form of colloidal silica-alumina. The concentrate produced contains about 49.5 percent iron (Fe) and 0.6-0.8 percent phosphorus (P) or 10-20 times the acceptable phosphorus level. The phosphorus is intimately associated with the iron oxide and colloidal gangue, no discrete phosphorus minerals are found, and beneficiation is not possible. Therefore, to reduce the phosphorus, a hydrometallurgical process that includes roasting followed by leaching in dilute sulfuric acid has been developed. Phosphorus extraction is 70-90 percent, with only a minor loss of iron. The process has been tested in the laboratory and in a pilot plant at 50-300 kg/h. Construction of a 900,000 t/y demonstration plant is underway.

Jan 1, 2003

By Jenifer S. Heath

Human health risk assessments can be used in mine permitting, and are frequently used to investigate areas of potential contamination and as a basis for remediation decision making. While some states and US Environmental Protection Agency (USEPA) Regions have their own guidance for the conduct of human health risk assessments, USEPA Headquarters guidance and the underlying science are changing and advancing rapidly. Even outside the US, USEPA guidance can affect risk assessment costs and conclusions, which in turn can affect cleanup costs or permitting options. This paper summarizes recent USEPA guidance and scientific evidence related to human health risk assessment for mining sites. This paper is designed for non-risk assessors, and so focuses on the potential applications and implications of the new guidance rather than the mathematical and theoretical details.

Jan 1, 1999

By Kensuke Sassa, Shigeo Asai, Norihisa Waki

"A new method for separating inclusions from a molten metal using a high magnetic field has been proposed. The principle of this method based on the magnetization force has been confirmed in experiments of separating intermetallic compounds imitating inclusions from molten Al-Si-Mn-Fe and Al-Si alloys. In order to measure a magnetic susceptibility, the Gouy's method has been so modified by using a super-conducting magnetic as to work in a high temperature up to 1473K. A theoretical expression for the magnetization force, which is indispensable to evaluate the magnetic susceptibility, has been derived. The magnetization forces acting on intermetallic compounds which were used in the magnetic separation were measured over the range of liquidous to solidous temperatures and the magnetic susceptibilities of the intermetallic compounds were obtained from measured magnetization forces by use of the theoretical expression.I. IntroductionRecent developments in the technology of super-conducting magnets have given rise to the circumstance that a high magnetic field over a relatively large space is readily available without liquid helium. Then, it has been found that a high magnetic field provides magnetic effects to nonmagnetic substances and various interesting phenomena have been reported in the broad science fields of physics, chemistry and biology1). ""A science related to a high magnetic field"" in which many fields are transversally viewed from the standpoint of a high magnetic field2 ) is going to be established. In particular, new phenomena and functions brought by the science related to a high magnetic field are also useful for Material Science and Engineering so that the creation of Materials Science and Engineering related to a high magnetic field"" has been conceived 3).Now, when a substance regardless of being magnetic or nonmagnetic is put in a magnetic field, it feels a magnetization force, which is familiar to such a force that a magnet attracts iron. The force is in proportion to the product of magnetic field strength, its gradient and susceptibility so that a precipitated substance can be separated from a molten metal based on the difference between susceptibilities of a substance and a melt. This is a basic principle of the magnetic separation. So far the application of the magnetic separation has been limited to the separation of ferromagnetic substances from a nonmagnetic medium. A high magnetic field, however, has enabled to separate nonmagnetic substances from a nonmagnetic medium.In this study, a new method to separate inclusions from a molten metal using a high magnetic field has been proposed. The principle of the method was verified by experimental works and the feasibility on the elimination of inclusions in steelmaking processes has been studied"

Jan 1, 2000

By Sridhar Seetharuman

Sulfur and oxygen dissolved in nickel and cupronickel melts can be removed as gaseous oxides of sulfur by a vacuum treatment. Presented in this paper is a new matched thermochemical diagram that permits direct evaluation of the equilibrium partial pressure of SO, as a function of temperature over an alloy of specified composition. The matched thermochemical diagram consists of a central plot which shows the integral Gibbs' energy of mixing for the binary system S-O2, at different temperatures. The central plot is flanked on either side by terminal plots of the chemical potentials of oxygen and sulfur, as functions of temperature, for different alloy compositions. By projecting the chemical potentials of oxygen and sulfur from the terminal plots on to the central diagram, the equilibrium pressure of SO2,can be directly read on the nomograms on the central plot at different temperatures. The matched thermochemical diaerams are - useful in assuring the efficiency of vacuum refining.

Jan 1, 1993

By Jennifer Murphy, Brad S. Schake, Karol Holmes, John R. FitzPatrick, Mike H. West

"The separation and purification of uranium from either nitric acid or hydrochloric acid media can be accomplished by using either solvent extraction or ion-exchange. Over the past two years at Los Alamos, emerging programs are focused on recapturing the expertise required to do limited, small-quantity processing of enriched uranium. During this period of time, we have been investigating ion-exchange as a method for extraction/purification of uranium from acidic media. In addition, waste stream polishing is associated with this effort in order to achieve more complete removal of the uranium prior to recycle of the acid. Extraction chromatography has been demonstrated to further polish the uranium from both nitric and hydrochloric acid media thus allowing for a more complete recovery of the actinide material and creation of less waste during the processing steps.We will discuss contact experiments for evaluation of eleven different resins for uranium removal from nitric acid, the evaluation (again by contact experiments) of uranium elution from the ion-exchange media by various chemicals, and small-scale experiments for the removal of 235U from nitric acid. Larger-scale (1 DO-gram) flow experiments, using depleted uranium, were done after the small-scale evaluation of the selected resin. A discussion is also included concerning the shortcomings of the contact experiments and how the flow experiments were modified in order to overcome these problems. We will also discuss the application of ion-exchange for some specific process needs at Los Alamos.Contact experiments were used to evaluate some commercially available solvent-impregnated resins in addition to evaluation of several resins of this type synthesized in our laboratory. These experiments involved both nitric and hydrochloric acid media. The data from these experiments will be used to determine the column size and amount of resin required to polish the waste stream produced by the ion-exchange process described above. Small-scale flow experiments will be described and data given on the mass balances achieved using this two step process.Future work for evaluation of new ion-exchange and solvent-impregnated resins as well as the search for new eluants will be discussed. Other future experiments for both processes, including large-scale experiments, will be discussed in detail."

Jan 1, 1996

By E. B. Freidina

We have investigated a new electrochemical process for preparing lead-calcium alloys. Calcium metal, reduced fiom a molten chloride mixture, forms an alloy with liquid lead cathode. The addition of calcium carbonate to conventional CaC12-NaCl electrolyte enables us to avoid chlorine production on the anode and replace it with oxygen and carbon dioxide. The ternary system CaClz-NaC1-CaCO3 has a range of melt compositions, where the electrolysis can be held below 650°C. In order to prevent the side reaction of carbon deposition on the cathode we have separated the anolyte from the catholyte with alumina diaphragm. The factors, which affect the level of impurities and the current efficiency of the process, are discussed.

Jan 1, 1999

By Laihua Wang, Peter Hayes, Hae-Geon Lee

"This paper introduces a new process for the efficient removal of dissolved gases and inclusions from liquid metals. This process involves the creation and dispersion of fine bubbles in molten metals by introducing inert or reactive gas into a region of turbulent flow. The highly turbulent metal flow splits the gas into fine bubbles and results in good mixing between the gas and molten metal phases. These conditions are ideal for contacting inclusions in the metal with the bubbles and subsequent flotation of the inclusions to the metal-slag interface where the inclusions are then absorbed by the covering slag layer. Dissolved gases, such as [H], [0], [N] in the metals are also transferred to the gas bubbles and removed from solution.The process concept has been previously demonstrated using a full-scale air/water model to simulate the ladle-to-tundish system of continuous casting of steel. The present cold modelling work has further demonstrated the ability of the process to remove gas solutes. The results indicate that the efficiency of new process is several hundred times greater than that of conventional high speed rotating injectors which are currently applied in the treatment of liquid light metals.IntroductionDuring metal smelting, refining and alloying processes, unwanted gas and second phase liquid or solid impurities are incorporated into liquid metals. In the case of steelmaking, the gas-forming impurities include [0], [H] and [N], and the solid impurities as a result of deoxidation include Ah03, Si02 inclusions. Common impurities in liquid aluminium are dissolved hydrogen and solid Ah03. To avoid subsequent problems during processing and to improve the physical properties of the metal products it is necessary to significantly reduce the level of impurities."

Jan 1, 1996