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By Nils Lippmann, Ulrich Weber, Siegfried Schmauder, Jr. Mishnaevsky

"A computational approach to the optimization of fracture resistance of multiphase materials (here - high speed steels) by varying their microstructure is presented. The main points of the optimization of steels are as follows: (1) development and verification of the model: numerical simulation of crack initiation and growth in real microstructures of steels, (2) computational experiment: simulation of crack growth in different idealized quasi-real microstructures and (3) the comparison of fracture resistances of different microstructures and the development of recommendations to the improvement of the fracture toughness of steels. Numerical simulations of crack growth in real microstructures of steels and different idealized carbide distributions are carried out. On the basis of the simulations, recommendations for the improvement of high speed steel microstructures are given. It is shown that the fracture resistance of the steels is much higher for the fine than for the coarse version of the same type of microstructures.IntroductionThe purpose of this work is to develop an approach to the optimal design of multiphase materials on the basis of numerical simulation of their behaviour under mechanical loading. We suggest here the following strategy:1. Collecting input data for the simulations: taking a micrograph of a microstructure, and determining mechanical properties and failure conditions of the material constituents [1, 2],2. Simulation techniques and assumptions are tested for a real microstructure of the material: crack growth in a real microstructure is simulated and then compared with the experimental data,3. Computational experiments: different microstructures of materials are tested in the numerical model under the same loading conditions. The calculated service properties of the different microstructures are compared, and recommendations are developed. As differentiated from the ""real"" experimental techniques, the computational experiment is much cheaper and not labor- and time-consuming."

Jan 1, 2001

By G. S. Hanumanth

Sedimentation of particles during the liquid metal processing of particulate metal-matrix composites can affect the homogeneity, and thereby the properties, of the cast product. A novel electrical probe has been developed to measure the in-situ volume fraction of ceramic particles in molten metal baths. Using this probe, sedimentation rates for 90 pm silicon carbide particles dispersed in molten aluminum A356 alloy were measured over a wide range of particle volume fraction, 0.05 to 0.3. The sedimentation rate was found to depend strongly on particle volume fraction; the time to clarify a 0.15 m depth increased from approximately 60 to 500 seconds as the volume fraction increased from 0.05 to 0.3. Measured sedimentation rates agree well with the predictions of a sedimentation model based on one-dimensional, two-phase flow theory in which the inter-phase drag function is derived from the momentum equation, utilizing the Richardson-Zaki Equation for sedimentation in aqueous systems. The implications for solidification are discussed.

Jan 1, 1993

By Junji Shibata

Zeolite synthesized from coal fly ash has many intelligent properties such as cation exchange, adsorption, catalyst and so on. The suitable use of the zeolite, however, is not established in an actual commercial scale yet. From the viewpoints of an effective usage of coal fly ash and the zeolite obtained from coal fly ash, we propose the new concept for environmentally friendly usage of zeolite, in which coal fly ash safely returns to the soil with growing plants and purifying wastewater. This method can make great contribution to recycle of coal fly ash, to purification of high nutritious water and to tree planting.

Jan 1, 2002

By B. G. Thomas

"Mathematical process models can be applied in several different ways to serve industry by inducing beneficial changes to process operation. This paper attempts to summarize the different uses, types, and attributes of these models, and to offer some ideas to consider when developing, using, and reporting on them. Process models range from empirical to mechanistic in nature and vary in complexity from simple analytical solutions to coupled, 3-D transient numerical simulations. They are classified here according to the way in which they are implemented in practice, viz. fully-online models, semi-online models, off-line models, and literature models. The purpose of the model should dictate how choices are made during its development. Ways to validate and compare the model with experiments are suggested. Examples are taken in the context of the author's experience in modeling the continuous casting of steel.IntroductionThe objective of this paper is to provide a partial introduction for this symposium by discussing some basic aspects of the application of mathematical process models in industry. Essentially, the aim is to explore how process models are used to benefit industry, and to offer some general comments and suggestions, based on the experience of the author, on how models can best meet this goal.This work is concerned with process models, which consist of systems of mathematical equations and constants that are solved on a computer to make quantitative predictions about some aspect(s) of the process. The specific variables required as input data and generated as output data are important features of the model. The equations often derive from a numerical solution to one or more differential equations and their boundary conditions. The model also includes the constants, which represent material properties, empirical relationships, and other knowledge about the process, and usually require considerable effort to obtain. Thus, general purpose commercial software packages, (ie. finite-element or finite-difference based codes), are not models in this context. They are useful tools, however, serving as frameworks for the development of process models."

Jan 1, 1994

By R. H. Rubisov

Sulphuric acid pressure leaching of nickeliferous laterites has attracted considerable attention from the nickel industry during the past five years. The process is especially advantageous for limonitic laterites that mostly contain goethite, because iron precipitates releasing acid and thus rendering low acid consumption. It is also applicable to mixtures of limonites and saprolites, although at higher acid consumption due to magnesium. Effective process design requires the solubility of metals that precipitate during the process to be known. In the present work, determination of metal solubilities is based on a simple speciation program that assumes the presence of only one dominant complex for each metal. The thermodynamic data for the precipitation reactions are extracted from high-temperature experiments with monometallic systems published previously. The validity of the approach is then tested against mixed bimetallic systems, and finally applied to calculate the solubility of aluminium, iron and magnesium in laterite leaching effluents "at temperature". In both cases of limonitic feed and limoniticfsaprolitic blends, the prediction closely follows metal solubilities measured experimentally at temperatures from 230 to 270°C and at terminal he acidities ranging from 10 to 75 g/L.

Jan 1, 1999

By Batric Pesic

Silver dissolution with thiourea was studied by using the rotating disk technique. The major parameters studied were: thiourea concentration (0-0.5M), ferric sulfate concentration (0-0.5M), sulfuric acid concentration (0-0.5M), and the effect of many foreign ions (Mn, o.i, Co, Ca, Na, etc.). Temperature effect was studied in the range 5-35 .C. The activation energy was 5.4 Kcal/mole. The dissolution of silver was first order with respect to ferric sulfate, and the secord order with respect to thiourea. Among the additives, copper had a dramatically negative effect. The strong oxidants such as hydrogen peroxide and manganese dioxide were also detrimental for silver dissolution. Silver does not dissolve with thiourea in the absence of ferric ions. Sulfuric acid does not participate in the dissolution reaction either. Chemically, the most important parameter for silver dissolution is the ferric sulfate/thiourea ratio. Thus, in the solutions with excess of ferric sulfate, a solid silver-thiourea complex is formed, which precludes transfer of silver into solution. In the solutions with the excess of thiourea, the free thiourea reacts with formed solid silver-thiourea complex and silver goes into the solution. The solid silver-thiourea complex was characterized according to its chemical composition. The complex contains 6.54%C, 2.49\H, 14.77%N, 16.09%0, 21.62%8, and 37.13% Ag. This composition corresponds to a Ag2so4.3'1U.2ff:i0 compound The soluble silver species are present in the solution as the dimers of AgTU+3 complexes.

Jan 1, 1989

By Bingliang Gao, Junli Xu, Michal Korenko, Jinzhao Guan, Liangxing Li, Zhongning Shi, Zhaowen Wang, Aimin Liu

Al-Si alloy, a precursor of solar grade silicon, was prepared by direct electrolysis in cryolite molten salt at 950 oC using high purity silica as material, liquid aluminum as the cathode and high purity graphite as the anode. The electrochemical behavior of Si(IV) ion was investigated using cyclic voltammetry method. The electrolysis products were characterized by XRD, SEM/EDS and ICP. The results indicate that the reduction process of Si(IV) on tungsten electrode is a two-step process and there is about 0.6 V gap between the two steps. The contents of boron and phosphorus in the aluminum-silicon alloy are 3 ppmw and 8 ppmw, which will make the directional solidification purification effectively and reduce the cost of preparation solar grade silicon from metallurgical grade silicon.

Jan 1, 2015

By M. C. Ruiz

The leaching behavior of chalcopyrite concentrate in acidic CuC12-NaCI-O2 solutions was investigated. Experiments were conducted under continuos flow of oxygen at atmospheric pressures. The results indicated that among the variables temperature has the largest influence on the dissolution of chalcopyrite in this medium, and high copper extraction can only be obtained at temperatures near the boiling point of the solution. It was also found that the stirring speed did not influence appreciably the dissolution of chalcopyrite. An increase in the oxygen flow rate up to 0.1 1/min increased the copper extraction. The total chloride concentration affects the dissolution of chalcopyrite up to about 4 M. Copper extraction of 93 % was obtained in leaching chalcopyrite of size fraction -400 # Tyler at 105 OC in 2 hours.

Jan 1, 1997

By A. Pagliero

The coulombimetric reduction method has been used as an evaluation technique for Pb-Ca-Sn anode corrosion in the LIX-SX-EW process. The proposed methodology involves three consecutive steps, i.e., cleaning, oxidation and reduction. They are carried out in the same experimental unit, in solutions containing 180 g/L H2S04 with and without the addition of cobalt. The authors have worked in a wide range of oxidation current densities, from 150 to 500 A/m2 for in a period from 0.5 to 120 hours. It can be concluded from the results that there would be a linear relationship between the applied electrical charge I*T (Coulomb) and the anode corrosion expressed as transformed Pb mass (mg), for solutions with or without the addition of cobalt. The exception is that for the last one the corrosion rate is 5 times faster, which was observed for every layer. From the evaluation of different corrosion layers, one can point out that its composition is mainly in the form of sulphate. In the presence of cobalt, about 67% of Pb would be as sulphate (PbSO4), about 27% as a basic oxide (PbO) and only 6% as oxide PbO2 on the surface. From this result, it appears that great transformations occurred in the metal/sulphate interface. Without the addition of cobalt, the proportion of oxide Pb02 on the surface increased up to 11.5%. According to the previous statement and considering that Pb was found mainly as sulphate, the authors recommend its determination be used as quality selection criterion. Its evaluation should be performed in the acid solutions with 200 ppm cobalt addition at an oxidation current density of 300 A/m2 for a period of 24 hours.

Jan 1, 1999

By B. Balamurugan, D. J. Sellmyer, J. E. Shield, G. C. Hadjipanayis, Damien Le Ror, R. Skomski

"Rare-earth transition-metal (R-TM) alloys show superior permanent magnetic properties in the bulk, but the synthesis and application ofR-TM nanoparticles remains a challenge due to the requirement of high-temperature annealing above about 800 °C for alloy formation and subsequent crystalline ordering. Here we report a single-step method to produce highly ordered R-TM nanoparticles such as YCO5 and SmCO5, without high-temperature thermal annealing by employing a cluster-deposition system, and we investigate their structural and magnetic properties. Nanoparticles of size = 10 nm are monodispersed (s /d ~ 0.15) and have Hc values at T = 300 K of 8.0 and 4.5 kOe for YC05 and SmC05, respectively. Alignment of the easy axes is performed via a field applied to the clusters before deposition. These processing steps are highly desirable to create and assemble R-TM nanoparticle composites for future permanentmagnet applications.IntroductionMagnetic nanoparticles with high magnetocrystalline anisotropies (Ki > 1 MJ/m3) are required for permanent-magnet, recording-media, and other significant applications [1-3]. In this regard, bulk rare-earth transition metal alloys (R-TM) especially RC05 (R = Y and Sm) crystallized in the hexagonal CaCu5-type structure have shown a large Ki = 5 MJ/m3 (YC05) and 22 MJ/m3 (SmCo5) along with an appreciable saturation-magnetic polarization (Js, > 10 kG) and high curie temperatures (Tc > 1000 K) [2]. The challenges in controlling the size, sizedistribution, phase purity and crystalline ordering, however, limit the research on RCo5 nanoparticles [4,5]. The conventional arc-melting technique requires high-temperature annealing for alloy formation and subsequent crystalline ordering, which causes excess growth and thus results in nanocrystalline powders of particles sizes larger than 30 nm [6, 7]. Low-temperature wet-chemical techniques yield SmC05 nanoparticles of sizes smaller than 20 nm [5], but the control of phase purity is challenging due to the presence of surfactants and formation of other secondary phases [8]."

Jan 1, 2012

By Gordon A. Irons, Diancai Guo

"Uneven movement of scrap during melting in an Electric Arc Furnace causes operation problems: cave-ins interrupt electric power input. The movement also influences the radiation heat loss to water-cooled side panels and roof. An apparatus has been built to simulate the flow of scrap that may be interlocked. It has been observed that flow starts at the point where the suspended length of the pile bottom reaches the average scrap size, and proceeds in the form of cave-ins, but scrap pieces slide with each other as ordinary granules. After a cave-in, the pile angle usually remains much larger than the normally observed angle of repose. The force balance of a partially suspended scrap pile has been analyzed, and the equivalent cohesion due to interlocking estimated. A numerical model has been developed to simulate the scrap flow. Simulated results agree reasonably with observed phenomena.IntroductionWhen one considers the melting of steel scrap in an electric arc furnace (EAF), it is helpful to understand the movement of the material during meltdown. As industrial experience demonstrates, scrap movement greatly affects EAF operation. In a typical operation, scrap is dropped into the furnace from scrap buckets. The roof and electrodes are swung into position, and power is applied to the electrodes situated over the scrap. The electrodes ""bore"" into the scrap by melting into the steel in the immediate vicinity of the electrodes as they are lowered. If solid scrap pieces gradually slide towards the arc area, the electric power supply can be maintained at a high level, with few interruptions or drastic electrode adjustments. This results in a high production rate and low power consumption per tonne of steel produced. On the other hand, if the charge moves down unevenly, i.e. in large surges, usually called cave-ins, the electrodes must be drastically raised, and power supply frequently interrupted. This is also accompanied by a high level of harmonics induced in the power network, deteriorating the quality of electricity supplied to other users.In addition, the movement of scrap in an EAF also influences the furnace heat efficiency, as the scrap pile is much closer to the electric arcs compared to the furnace wall and roof, and absorbs more radiated heat. Early exposure of the wall and roof to the arcs will increase the heat loss due to radiation, and reduce the service life of the furnace."

Jan 1, 2004

By Dong Liu, Zejian Yang, Yong Li, Tao Jiang, Xiangxin Xue, He Yang

"The structure, composition, morphology, and adsorption property of UV-vis light of as-prepared samples were characterized using XRD, SEM, FTIR-EDS, and UV-vis DRS. UV-visible light induced photocatalytic degradation of methylene blue ~) over Ti02-doped diopside was investigated. Experimental results show that doping Fe + induced the formation of Ti-0 or Ti-0-Si in diopside, and promoted the light adsorption property of diopside. Photocatalytic reactivity of Ti02-doped diopside obviously depended on content of doping Ti02. The diopside with 3% Ti02 exhibited the superior photocatalytic activity with 76% degradation of methylene blue under light irradiation for 3 h.IntroductionPhotocatalytic technology has been extensively studied in the process of dealing with inorganic and organic pollutants. Ti02, with its own non-toxic, stable, low-cost and other advantages, has become the most widely studied photocatalytic materials[l-SJ_ The low utilization quantum made it restricted in the practical application. SrTi03 as the representative of the perovskite[9·121, Bi2W06 for the composite oxide[13,141, also attracted wide interest in the photocatalytic studies. However, these photocatalytic material has been mostly prepared in relatively strict experimental conditions with chemical reagents, they had small production, high cost, which made them difficult for practical applications.In our country, there has 400 million tonnes of ti-bearing blast furnace slag (TBBFS) each year in the process of smelting pig iron, which has lead to waste of titanium resources and pollution of the surrounding environment. In recent years, studies have shown that TBBFS instead of pure Ti02 to be photocatalytic materials is feasible[ 151. TBBFS has not only been higher photocatalytic degradation activity for the o-nitrophenol, methyl orange, nitrobenzene and other organic matter[16-191,but also exhibited excellent in the process of dealing with inorganic heavy metals in waste water (containing Cr6+i201. If TBBFS can be successfully applied to photocatalytic technology, the will make large accumulation of titanium-bearing slag reasonable used, so as promote the re-use of energy. At present, our understanding of the photocatalytic activity of TBBFS is steadily deepening. Photocatalytic activity ofCaTi03 has been reported as one of the main minerals ofTBBFS [21'21J, However, there were few studies for Another major mineral of TBBFS - diopside which had the content of9-15%. diopside would doped with Ti02 In the process of smelting pig iron, therefore, Ti02-doped diopside's photocatalytic activity in the UV-Vis was mainly studied in this paper."

Jan 1, 2013

By P. Felix

A discussion on the need of visualization and animation tools in modelling solidification processes is made. An outline of an approach for the production of a video computer animation is provided. A number of examples including, 2 and 3 dimensional melting, filling, and macrosegregation are presented.

Jan 1, 1993

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

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

Jan 1, 1998

By C. M. F. Vieira

Crushed fired brick waste, known as grog, screened at two different particle size, 840 (20 mesh) and 180 µm (80 mesh), was used in mixtures with clayey body to make typical red ceramics for bricks. The effect of the grog addition up to 20 wt.% on the properties of bricks fired at 700oC was evaluated. The results indicated that both the particle size and the amount of grog addition changed the fired properties of the clayey body. Additions above 5 wt.% of grog, with a coarser particle size, decreased the mechanical strength of both the dry body and the fired ceramic pieces. By contrast, grog with a finer particle size may be used up to 10% wt. without deteriorate the properties and corresponding microstructure of the clayey body.

Jan 1, 2009

By Sang-Su Lee

This paper shows the application of the porous plug system in the Mitsubishi continuous copper smelting and converting process. This system has already been adopted and utilized in the steel industry to enhance productivity. Recently, some copper smelters have adopted this system but the results have not been satisfactory. The porous plug system was installed at the anode furnace in December 2001 to reduce the oxidation time and decrease the oil consumption. A good effect was that the nitrogen stirring of the melt through porous plugs improved the melt heat transfer. As the result of the enhancing heat transfer the oil consumption and the build up inside the furnace were actually decreased. But until now the oxidation time has not been sufficiently reduced. In the future, further research and tests are needed in order to increase the productivity and save costs.

Jan 1, 2003

By J. R. Goode

There are at least a dozen methods of selectively removing cerium from a mixture of the rare earth elements (REE) including separation techniques based on the oxidation of cerium to the quadrivalent state. Several of the oxidation processes have been operated on a commercial scale, others have been tested and in some cases are part of proposed flowsheets. In this paper, we describe and compare the various methods. We also present preliminary estimates of the costs of early Ce removal and discuss recovery and purity aspects of the options.

By Sebastiaan Peelman

NdFeB permanent magnets are the best available magnets used in many technology applications. However, at their end-of-life (EoL) most of magnets and the contained REEs are lost during the recycling of the bulk metals. The REEs are classified as the most critical raw materials in the European Union, and recycling of REEs from EoL products will reduce their criticality and contribute to the sustainability of REE. Various technological routes have been reported, but most of the methods are effective for highly concentrated magnets or magnet scrap, which is greatly dependent on expensive pre-dismantling processes. This paper presents various innovative metallurgical solutions to the effective REE recovery from current industrial practice for WEEE recycling, including the ferrous scrap from WEEE shredder products and shredder residues from computer hard disk drives. Both hydrometallurgical and combined hydro- and pyrometallurgical REE recovery routes are developed after demagnetization and physical upgrading.

By L. Deininger

The QSL plant in the existing "Betzelius" Stolberg GmbH lead smelter in StolberglGermany was commissioned in August, 1990. Following some modifications to the process and equipment which had become necessary in line with the implementation of this new techno- logy, conclusive operating results are now available. These will be reported together with a short description of the plant design. In May 1992, raw material feeding to the QSL reactor in the new lead smelter of Korea Zinc Co. in OnsanlKorea was started. As all the experience gained up to that point in time in the Stolberg plant had already been incorporated in this plant prior to start-up, it reached stable, satisfactory operating conditions in a short period of time. After an introductory description of the plant important operating results will be reported. The operating experience gained in the two plants fully confirms the correctness of the in- ventors' creative ideas in the 70s. The QSL process meets all demands made on modern, ecologically compatible and energy-saving lead production technology. The paper ends with suggestions on how the QSL process will be optimized further in the future.

Jan 1, 1994

By ZhiLong ZHAO, Lin Lin, Zhancheng Guo, Jingtao GAO, Huiqing Tang

Grain sticking often occurs in the fluidized bed reduction of f ine iron ore, which is closely related to the precipitation morphology of metallic iron on the surface of ore particles. In this work, simulating the gas-solid reduction process of iron ore, in situ observations were carried out to investigate effects of doping mineral oxides on the precipitation morphology evolution of metallic iron during reduction of iron oxides with CO. Results indicate that the precipitation morphology of metallic iron is related to the quantity of doped mineral oxides. The minimum mole fraction of doped oxide ( xyOA N ) that can inhibit the growth of iron whiskers is related to its cation radius ( Ax r ), extranuclear electronic layers ( Ax n ) and valence electrons ( Ax q ). Their relation can be expressed as:

Jan 1, 2016