Search Documents

By John Fallavollita

Conventional gas atomization produces powders that vary widely in size distributions and microstructures, thus making it very costly to produce powders tailor made in a narrow size distribution and microstructure. Furthermore, it is difficult to determine the relationships between atomizer operating conditions and resulting powder characteristics. The Impulse Atomization Process (IAP) was developed at the Advanced Materials and Processing Laboratory to produce powders with narrow size distributions. Powders produced by the IAP were reproducible and their sizes could be easily controlled by adjusting experimental conditions. Characteristics of Zn, Sn-Pb, AI-Cu, and Cu powders will be described to illustrate the flexibility of the process to tailor-make powders.

Jan 1, 1994

By Patrick M. Eduafo, Brajendra Mishra, Mark L. Strauss

Direct acid leaching of rare earth metals (REMs) from waste lamp phosphors is non-selective, leading to co-dissolution of impurities mainly calcium, phosphorus, silicon, iron and zinc. Calcining the phosphor powder at different temperatures followed by leaching with HCl isn’t efficient for the extraction of all the chief rare earths especially cerium (Ce), lanthanum (La) and terbium (Tb). Therefore, multi-stage leaching operations are required for the separation of the REMs in phosphor dust. This paper will outline a new process for extracting Ce, La, Tb, Eu and Y from waste fluorescent lamps using a three-stage leaching and separation process. A flowsheet has been developed which shows this process is selective and efficient.

Jan 1, 2015

By Shengqin Zhang, Yousef Mohassab, Feng Chen, Hong Yong Sohn, Mohamed Elzohiery, Amr Abdelghany

A novel ironmaking process is under development at the University of Utah aimed at producing iron directly from iron oxide concentrate in a flash reactor. This process will reduce hazardous emissions and save energy. The kinetics of magnetite reduction with hydrogen was previously investigated in our laboratory in the temperature range 1150 to 1400 oC at large temperature increments (~100 oC increments). Due to the significant melting that occurs above 1350 oC, the reduction kinetics was measured and analyzed in two distinct temperature ranges of 1150 to 1350 oC and 1350 to 1600 oC (~50 oC increments). Experiments were performed using magnetite concentrate particles of different sizes under various hydrogen partial pressures and residence times. Reduction degrees of more than 90 % were achieved in a few seconds at temperatures as low as 1250 ºC. Different rate expressions were needed to obtain reliable agreement with experimental data.

Jan 1, 2016

By Dariusz Kopyci ski, Józef Dorula

The study proves that by introducing the iron powder and disintegrated steel scrap to low-sulphur cast iron still before the inoculation carried out with a conventional graphitising inoculant, the mechanical properties similar to those obtained during the inoculation treatment carried out on cast iron with the recommended high sulphur content are achieved. The said operation increases the number of crystallisation nuclei for dendrites of the primary austenite. In this case, the iron particles act as substrates for the nucleation of primary austenite, due to a similar crystallographic behaviour of the regular face centred cubic lattice The more numerous are the dendrites of primary austenite, the less free space is available in the interdendritic spaces for the formation of graphite eutectic grains, which makes the structure more refined (more eutectic grains) and the mechanical properties higher.

Jan 1, 2016

By Cui Wang, Bing Dai, Haibin Zuo, Jianliang Zhang

The damage mechanism of ductile cast iron cooling stave applied to No.4 blast furnace of Guofeng steel was analyzed through damage investigation in details, the damage causes: hightemperature gas flow erosion, wear of burden, high-temperature ablation, carburizing damage, improper operation on blast furnace, etc. were given out both in macroscopic and microscopic views. It can be obtained from metallographic diagrams that the diameter of graphite nodules increases, the number per unit area reduces, and roundness declines, successively, from cold to hot surface, which are not conducive to stave longevity. In summary, the material for staves manufacture should be better in comprehensive mechanical properties to prolong the service life, thus making blast furnace long campaign.

Jan 1, 2015

By Noritaka Horii, Katsuyoshi Kakinuma, Hiroshi Yamamura

"ZrO2 and Y2O 3-doped ZrO2 gel film were obtained by spin coating of sol from Zr-n-propoxide, n-propanol, acetylacetone, nitric acid, and water on a silica glass as a substrate. ·Dried gel films crystallized to monoclinic, tetragonal, cubic and their mixed phases, depending on the chemical composition of sol, .firing temperature, and coating cycles. ZrO2 films with highly preferential orientation were successfully obtained from a solution containing a large amount of n-propanol. The highly oriented ZrO2 film was found to have high transparency compared with non-oriented 'films. Electrical conductivity of 8 mol% Y2O 3 doped ZrO2 film was also measured.Introduction3 mol% Y2O 3 doped ZrO2, which has a tetragonal symmetry is ·well known to have a strong mechanical property and a high toughness. (1) On the other hand, 8 mol % Y 2O 3-doped ZrO2 is high oxide-ion conducting material and is applied to oxygen sensor, oxygen pump, and solid oxide fuel cell (SOFC). (2) Sol-gel methods using metallic alkoxide are widely applied for synthesizing ceramics such as high-purity fine particles, thin film, and fiber. (3) For ceramics films, many reports have been made on SiO2, (4) TiO2, (5) and PZT. (6) Several case studies have been done on zirconia film based on the sol-gel method, (7) - (11) but very few on preferentially oriented film and on systematic Y zO3 doping. Almost zirconia ceramic· films reported were prepared by means of dip-coating. Kamiya et al. (12) and Ganguli et al (13) converted zirconia into fiber. Sol from Zr alkoxide is usually very unstable, and a stabilizing agent such as glycol or ß-keton is used beforehand (7) (14)."

Jan 1, 2000

By Timothy W. Skszek, Adrian S. Sabau, Hebi Yin, Xiaoping Niu

The microstructure evolution during solution treatment plays an important role in mechanical properties of heat-treated aluminum alloys. In this paper, models were reviewed that can predict the microstructure evolution during the solutionizing process of the aging heat treatment of aluminum alloys. The dissolution ofMg2Si particles has been modeled as a diffusion process of Mg in the a-Al matrix. The evolution of volumetric fraction of fragmented silicon as a function of time and temperature was also considered. The growth and coarsening of silicon particles during the heat treatment was considered. It was found that constitutive equations and required property data for most of the phenomena that need to be considered are available. Several model parameters that need to be obtained from material characterization were identified. Pending the availability of these model parameters, this comprehensive model can be used to describe the microstructure evolution of aluminum alloys in order to optimize the solutionizing heat treatment for energy savings.

Jan 1, 2013

By Richard L. Werner

The petrographic microscope as a tool in determining impurities and grain size of limestones, clays, sand and coal ash for possible use as raw materials is discussed. Its use in the determination of the mineral composition of various size fractions of the raw mix, after fine grinding in ball mills, and of the waste dust from the rotary kiln. A description is given of the typical clinker crystals; alite, belite, tricalcium aluminate and ferrite. The process problems indicated by various changes in the crystal characteristics are listed with possible solutions. Finally the microscope as used in relation to field problems with concrete such as air void volume, percent hydration of the cement, cement aggregate bonding and the determination of solid additives, is presented.

Jan 1, 1982

By Mariana H. Staia

Thermodynamic calculations based on the free energy minimization method were performed for the system Ti-Fe-Mn-0-C1-C in order to evaluate the chemistry associated with the chlorination of an ilmenitic concentrate using CCl4. In the calculations various weight ratios of FeTi03/ CC14, a , were considered, which varied between 0.32 to 0.98 at temperatures ranging from 673 K to 1273 K , at atmospheric pressure. The results obtained indicated that the operating conditions for a process in a packed bed reactor, which implies the chlorination of both Fe and Ti, are 0.39 < a < .49 at T 1173 K.

Jan 1, 1993

By Y. Shigeno

The reactivity of a porous solid is a strong function of its pore structure (porosity, pore surface area and pore size distribution). It follows that reactivity could be altered by altering pore structure; one way to achieve this is by chemical vapor infiltration whereby a gaseous species is reacted in the porous solid to produce a solid. Experiments were carried out in which the pore structures of various carbons were modified by cracking methane within the pores; oxidation rates of the carbons were then measured for both infiltrated and original samples. For coke it was found that two indices of coke performance used in the steel industry (CRI and CSR) can be greatly improved following a small amount of infiltration. Infiltration/oxidation results are interpreted in terms of measured pore structure changes.

Jan 1, 1993

By Zhiqian Zhang, Chao Wu, Chao Li, Hongxu Li, Yu Chen, Xiangxin Hao

"In this paper, the life cycle assessment models for automobile lightweight materials including high-strength steel, aluminum alloy and magnesium alloy are developed by Gabi software. The evaluation models and evaluation indicators such as acidification effects, rich eutrophication effect, ozone layer depletion effects, global warming, resource consumption and formation of ozone potential were taken into account. It is shown that the effects of acidification and ozone formation are mainly derived from the run phase of high-strength steel and they have strong environmental impact load. While considering the entire life cycle with materials production phase and resource consumption, the aluminum and magnesium alloy appe art o have large r environmental load than high-strength steel. Base d on the evaluation, some optimization tips are proposed.IntroductionAs the increasing of car ownership, automobile has its two sides. One which is the convenient, efficient and fast traffic vehicle; the other is aggravating energy consumption, emissions and environmental pollution. The car industry faces heavy pressure with energy saving, safety and environmental protection. Nowadays, the main study ways for automotive energy-saving and environmental protection are power system improvement, alternative energy sources and technologies. For limitation of technique, development cycle and market share, the development of car is little progress at this stage and the application has been restricted. And another important way is the lightweight of vehicle. Usually there are three ways to get the lightweight automobile body structure, automobile body structure optimized design, using advanced body manufacturing technology, development and application of lightweight high strength body material.The life cycle assessment (LCA)[1lis commonly used to evaluate environmental factors and potential environmental impacts of products and services. As an environmental management tool of product-oriented, it becomes increasingly popular in industry. In this study, the concept of LCA and GaBi software was used to develop models for the three automotive lightweight materials, evaluate the environmental impact and make horizontal and vertical contrast by choosing variety of evaluation systems and indexes."

Jan 1, 2013

By C. Cánepa

In the treatment of many problems related with the optimization of a given ore dressing process, microscopic studies can provide invaluable assistance. Such studies are generally carried out through mineralogical determinations both qualitatively and quantitatively. Frequently the solution of a specific problem requires the combination of these in adequate proportions. Often the nature? of the problem poses some conditions regarding the way the microscopic determinations are made in order to yield useful information. Most publications applied to mineral beneficiation show results of ore microscopy without mentioning the methodological details involved in the determinative work and therefore it is not possible to judge their reliability and/or their relevance. As methodology must necessarily change from case to case, it is very important for the microscopist to identify first the direct and indirect mineralogical information required to solve the problem. Without such guidelines selection of methods for the qualitative and/or quantitative determinations cannot be made.

Jan 1, 1981

By Christian Trassy, Pierre Proulx

"Inductive plasmas are now commonly used in material processing: spraying, powder synthesis, densification or spheroidization. An inductive discharge presents, in the coil region, recirculation eddies due to the Lorentz forces, resulting in an axial backflow. If the central jet is strong enough to ""pierce"" the recirculation this axial backflow disappears on the centerline, but the external layer of the injection flow is skimmed by the remaining eddy, and particulates are rejected to the discharge periphery. To avoid this disadvantage, it is common to introduce the injection pipe inside the discharge, so that its outlet is positioned after the recirculation eddy. The powders remain confined in the axial zone, to the expense of shortened residence time.In order to increase the efficiency of the particle trajectories, a double flow injector has been designed. It enables the particles to travel closer to the axis, while the outer schrouding gas is skimmed and passes through the electromagnetic eddies. This injector is made up of two concentric tubes. The powders are injected with the carrier gas in the inner tube. A schrouding gas is injected in the annular space between the inner and the outer tubes. The powder is confined to the vicinity of the axis, resulting in a more homogeneous thermal treatment.Tungsten powders have been spheroidized with and without this device. Using the double flow injection, the spheroidization yield has been increased from 70 % up to 95 %.The design of such an injection device has. been studied and improved using numerical modelling. Another useful tool, a visualisation technique described elsewhere, has been used for the experimental study, that drastically simplifies the comparison between experimental and theoretical results: injecting yttrium oxide into the discharge results in a colorful display of the 4000 K isothenn: the ""cold"" zone, below 4000, appearing as red, and the ""hot"" zone as blue. Furthermore, it is of great industrial interest since it is a very cheap and efficient way to obtain a picture of an important isotherm."

Jan 1, 1999

By J. Sofra

The quantity of copper produced by secondary material processing is increasing as metal producers look to cleaner and cheaper sources of copper. The need to smelt secondary copper more economically, to process a wide range of materials with large fluctuations in size and composition and to cope with the increasingly stringent environmental constraints have put considerable pressure on existing conventional secondary copper smelters. The Top Submerged Lance process, developed and commercialized by Ausmelt Ltd offers a low cost technology, which is particularly adapt at processing copper-bearing scrap and residues. The application of Ausmelt Technology to replace conventional secondary copper processing operations introduces potential for significant advantages in environmental performance, and improved process efficiencies through the use of cheaper hels and reductants, the high rate of metal recovery and the flexibility inherent in the technology to process various feed material types. The economical, process and environmental benefits of its application are highlighted for both the smelting and converting stages of copper production.

Jan 1, 1997

By Jefferson Caponero

The tire is an expressive component of Municipal Solid Waste, manly when its occupied volume is considered. Its treatment by pyrolysis stands for a list of advantages, such as: landfill releasing and a production of a high quality fuel. The exploitation of new natural resources is becoming more difficult each day, basically due to the environmental damages caused by this type of activity. This work presents a study on the thermal behaviour of Brazilian tires using thermogravimetric analysis and differential thermal analysis, in order to optimise the pyrolysis process of tires. Samples of I to 2 mm were investigated at atmospheres of nitrogen, argon, oxygen and mixtures of these gases at temperatures up to 1273K, under heating rates between 1 to 50 Klmin . The results showed that the behaviour of each sample is related to both the atmosphere composition and the heating rate.

Jan 1, 2001

By W. F. Ranson, R. C. Progelhof

"I. THE PROBLEM: MANUFACTURING PRODUCTIVITYThe 1985 President's Commission [I] on Industrial Competitiveness found compelling evidence of the declining economic position of the United States in world markets. The annual rate of increase in the United States productivity is approximately one-seventh that of our major trading partners over the last decade: profit levels in manufacturing investments are below those of the mid-1960's; an increasingly negative trade balance since 1971; and a sharp decline in the United States share of world trade in manufactured goods for more than two decades. A particularly dramatic example of the shifting economic balance is the fact that Japanese productivity growth has been five times greater than that of this country since 1960. In face, Japan's productivity now exceeds that of the United States in such critical industries as steel, transportation equipment, electronics and electrical machinery.American employees have experienced the competitive consequences of this nation's lagging industrial performance. Between 1980 and 1984 alone, the population of non-farm employees engaged in manufacturing dropped from 22.4% to 20.6%. This reduction in manufacturing must be arrested.Commissions RecommendationsThe comprehensive set of recommendations offered by the President's Commission recognized the nation's ""key competitive advantages"", technology and human resources, and calls for their strengthening. Particular emphasis is placed on manufacturing technology and the fact that this country does not translate research into new technologies rapidly and fully.""Perhaps the most glaring deficiency in America's technological capabilities has been our failure to devote enough attention to manufacturing or 'process' technology. It does us little good to design state-of-the-art products if within a short time our foreign competitors can manufacture them more cheaply. The United States has failed to apply its own technologies to manufacturing. Robotics automation and statistical quality control were all first developed in the United States but in recent years they have been more effectively applied elsewhere""."

Jan 1, 1988

By Tracey Brommer, Britt Elin Gihleengen, Elsa Olivetti, Randolph Kirchain

"Increased demand resulting from the economic and environmental advantages of recycling secondary materials has constrained secondary material supply. As a result of constrained supply, the conventional strategy to maximize recycled content in an individual aluminum alloy must be expanded to maximizing total recycled content in a given production period. This work compares the performance over a two week period of an actual remelter for two strategies; a sequential charge-by-charge optimization framework and an integrated approach that explicitly incorporates the production schedule. Optimizing across the entire two week production is found to increase recycled content and minimize primary and alloying material additions. It is expected that as the scrap material market continues to be constrained by high demand, longer term batch planning strategies that can optimize material allocation will deliver improved performance.IntroductionIntensifying economic and environmental pressure to incorporate secondary aluminum into products is pushing remelters to explore additional strategies and tools to increase recycled content. Aluminum remelters are exploring alternative sources of secondary materials because of constrained secondary material supply and relatively high primary and secondary material cost [1]. Computational models, such as blending models are a tool that could help industrial remelters mitigate supply and cost challenges and thereby increase recycled content. In particular, computational tools can help manage the incorporation of new raw materials of variable quality. Blending models find many industrial applications and have been explored for over sixty years originating with the classic nut-mix problem dating back to 1950’s [2]. Blending models optimize the raw material input to make a desired product subject to a series of constraints such as product specifications and material availability. Deterministic and linear blending model formulations are presently implemented in some industrial aluminum remelters [3]. The primary reluctance of aluminum remelters against computational model implementation is the incapability of their blending models to reflect the intricacy of industrial remelting conditions [4]. For example, to reduce calculation time, industrial aluminum blending models usually optimize a batch plan for a single alloy and are not formulated to optimize several products simultaneously. Since such a model does not include knowledge of subsequent charges in the optimized batch plan, the resulting batch plans tend to deplete the “cleanest” secondary materials leaving the more uncertain and compositionally challenging materials for later charges. As a result, a remelter may override the calculated batch plan or leave certain scrap materials out of the material input to conserve these materials for alternative products scheduled for later production. This work explores an alternative aluminum charge planning tool that can optimize across an extended production schedule and compares it to a heuristic sequential optimization strategy reflecting an industrial remelter."

Jan 1, 2012

By Julien Favre, Akihiko Chiba, Damien Fabregue, Yuichiro Koizumi, Eric Maire

"The mechanical behavior of Co-20Cr-15W-10Ni alloy is studied by compression tests at high temperature. Microstructures after deformation are evaluated using SEM-EBSD. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T>1100°C, <0.1s-1), and at high strain rate (~10s-1). Dynamic recrystallization is discontinuous and occurs by grain boundaries nucleation, leading to a necklace structure. The nucleation mechanism is most likely to be bulging of grain boundaries. However, recrystallization occurs also by rotation of annealing twins which can bulge as well. The modeling of mechanical behavior gives a fair quantification of flow softening due to dynamic recrystallization, indicating the progress of dynamic recrystallization with deformation.IntroductionCobalt-chromium alloys are used in biomedical applications for the elaboration of implants due to their outstanding mechanical properties and their high resistance to corrosion. For stent application a large ductile behavior is required in addition to the high mechanical strength. Indeed stents have to undergo a deformation until e˜40% during their expansion [1]. Conventional Co-Cr-Mo (CCM) alloys exhibit limited ductility (maximal deformation about e˜30%) [2]. Co-Cr-W-Ni (L-605) alloy is a better candidate for stent elaboration since its fracture strain can exceed 40% (comparable to nickel superalloys (Figure 1), while it keeps high mechanical strength. In spite of the presence of nickel element in this alloy, biocompatibility is sufficient for vascular implants, therefore L-605 alloy is extensively used for heart valves and stent elaboration [3]."

Jan 1, 2012

By N. J. Tannyan

Laboratory bath smelting tests were conducted to determine the feasibility of smelting nickel- copper concentrate directly to a low iron matte in one step. Concentrate, air/oxygen and a silica flux were fed to a matte-slag bath kept in MgO crucibles at I 300°C. Various oxygen enrichments and smelting rates were used to maintain 0.5 to 2 wt% iron in the product matte. The slag losses are comparable to those obtained under similar industrial conditions. Due to the highly oxidizing conditions required to produce mattes with low iron contents, it is not recommended to target iron contents below about 2% in the matte. The specific bath smelting rates were equal to or higher than those in various industrial bath smelting processes.

Jan 1, 2003

By A. D. Zunkel

The zinc in electric arc furnace dust (EAFD) arises from the fuming and oxidation of the zinc present, mainly as galvanizing, in automotive scrap. The dust is collected from the electric furnace offgases in bag filters and is classified by the EPA as a hazardous waste (K061). As more zinc is used in galvanized sheet on automobiles and more automobile scrap is recycled via the EAF, the more zinc will be available for recovery and recycling. EAFD will become a more prevalent and important source of zinc compared to the traditional zinc sulfide concentrates ifit can be cost effectively processed.

Jan 1, 1995