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By R. Ratnagiri, B. Minaie

"In order to expeditiously produce defect-free metallic components in materials processing applications, the relationship between the process parameters and the product properties needs to be well understood while minimizing the production engineering iterations. To achieve this goal, a realistic mathematical formulation of the process should be carried out and an appropriate numerical modeling of various phenomena occurring in such process should be implemented. The materials processing of transforming the molten material into a finished metallic component involves fluid flow and solidification/melting. In the present paper, a finite element based analysis of the fluid flow ·and solidification/melting phenomena in cavities is presented and the various issues in modeling these phenomena are discussed. These transport phenomena play an important role in determining the final characteristics and material properties of the part by affecting the formation of defects and microstructure. A realistic numerical modeling of these phenomena can significantly reduce the rejection rates during the process and can increase the quality of the final product.IntroductionDuring the intelligent materials processing of various metallic components, it is often required to have a thorough knowledge of the behavior of the transport phenomena involved in this process. This is due in large to the coupling that exists between the transport phenomena and the final material properties of the components produced during materials processing. This interrelationship demands that the pertinent transport phenomena in the form of fluid flow and solidification/melting be studied and predicted accurately. In many materials processing applications, the fluid flow is in the form of either a forced convection free surface flow intended to fill a cavity or a natural convection flow resulting from the gravity when the cavity is filled. In either case, the phase change in the form of solidification/melting is also involved in order to complete the process. However, the thermal history during this phase change has a direct impact on the material properties of the final part and the possible defect formation that may be involved. This thermal history itself is dependent on the nature of the fluid flow during the earlier stages of the process. As such, there is a coupling between the fluid flow, phase change, microstructure, and defect formation in the resulting component. It is therefore necessary to analyze these phenomena in order to find optimum methods to produce good quality parts by minimizing the defects that may be generated. Such an analysis can result in the development of appropriate numerical models for the process that can facilitate the economical and timely manufacturing of various components with high consistency. The present paper discusses the issues related to the transport phenomena encountered during materials processing of components engineered largely by using various combination of convective fluid flow and solidification/melting in cavities."

Jan 1, 1994

By Yan Beygelzimer, Alexander Spuskanyuk, Victor Varyukhin

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

Jan 1, 2001

By G. White

Traditional atmospheres used for Aluminum annealing have been air, exothermic gas, and cryogenic purity Nitrogen. Air and exothermic gas have several problems associated with them such as surface discoloration, toxic emissions, and explosion hazards. High Oxygen levels can cause Magnesium streaking and oil staining, and therefore pure Nitrogen has been the atmosphere of choice for high quality Aluminum coils. A comparative study was made on key Aluminum alloys annealed in Nitrogen with different Oxygen concentrations to determine the effect on surface quality. The atmosphere composition inside the furnace was analyzed during the purge and heat cycle to determine its effects on purge times and exhaust emissions. The Aluminum coils after annealing were visually inspected for surface staining before and after rolling. The lab study revealed that Nitrogen with up to 1.0% Oxygen is acceptable, and did not adversely effects the surface quality or any of the other processing variables. However it isbelieved that higher Oxygen concentrations are acceptable depending on the rolling oils and alloy systems.

Jan 1, 1996

By Behrouz Abedian, Livia M. Racz

"We address dynamic interactions between high-energy, reactive surfaces of polymer-matrix composites and solid surfaces. A common characteristic of these interfaces is that bonding occurs readily upon contact. In many industrial and biomedical applications, it is desirable to suppress this bonding phenomenon. This interfacial effect is discussed in light of the development of our new method of handling polymer-matrix composites in dental applications. This method involves vibration of the solid-polymer interface at different frequencies. For each material, there is a critical frequency at which the sum of the viscoelastic and inertial energies of the fluid at the surface exceeds the energy available for bonding. When the polymer is vibrated at or beyond this frequency, it does not adhere to solid surfaces. An important aspect of the developed process is that it can be used to characterize surface and interfacial properties of polymers under dynamic conditions, whereas existing techniques are restricted to the study of bulk dynamic properties.IntroductionThe purpose of this paper is to report on the development of a new method for manipulating polymer-matrix composite materials used in dental applications, and the potential of this process for use in materials characterization. The materials under discussion have polymer matrices of a combination of bisphenol A-glycidyl methacrylate (BIS-GMA) and triethylene glycol dimethacrylate (TEGDMA), and contain filler particles of silica and/or zirconia glasses. These materials are called direct aesthetic restorative materials, and are used for filling of cavities, repairing chipped teeth, and for other restorations in which appearance is of importance. They have the appearance of natural tooth material, and are therefore in great demand for use in the anterior portion of the mouth(l,2)."

Jan 1, 1998

By W. G. Davenport

Chapter 10 showed that any given smelting task, e.g. production of 65% Cu matte, 1500 K, from CuFeS2, can be done with many different combinations of: blast%02 hydrocarbon fuel blast temperature. This chapter repeats the Chapter 10 calculations but reports the results in terms of the mass industrial oxygen mass hydrocarbon fuel blast preheat energy combinations that will produce 65% Cu matte, 1500 K, from CuFeS2 concentrate. It also determines the energy inputs equivalent to these combinations.

Jan 1, 2001

By Robert W. Bartlett

"Bioheap pretreatment of sulfidic refractory gold ore prior to cyanide leaching is a promising new technology, especially for low-grade ores that cannot afford to be oxidized by pressure leaching or roasting. When an ore contains both refractory and non-refractory (oxidized) gold, an economic decision must be made whether, or not, to pretreat before cyanide leaching. This choice is more complex than the familiar ore/waste cut-off grade decision. Pretreatment usually increases recovery but delays receiving revenue. Based on choosing the processing route that maximizes the present value of the ore, an equation is developed that computes a ""critical cyanide leachable gold grade"" for determining whether pretreating will be profitable. If the ore's actual cyanide leachable grade, without pretreatment, is above this ""critical grade,"" it will not pay to pretreat. The waste/ore cut-off grade, pretreatment yield (leachable grade after pretreatment), total gold grade, pretreatment operating cost and the project's financial discount rate are parameters in the equation. Results of example calculations are provided. This equation can be used for mine development planning and, when bioheap pretreatment is an available option, for daily operating decisions on individual ore blocks.IntroductionOres that are refractory because of sulfide mineral encapsulation of microscopic gold are becoming important. These ores must be pretreated to oxidize the sulfides to liberate the gold prior to cyanide leaching. The conventional pretreatment process technologies are pressure leaching with oxygen and two-stage fluid bed roasting. However, low-grade refractory ores cannot afford the high operating costs of these processes. And, small mines with limited reserves cannot justify the high capital costs of these processes."

Jan 1, 1997

By D. S. Barr

The Freeport McMoRan chlorination circuit is comprised of four related processes: ore chlorination, gas scrubbing, chlorine supply and excess hypochlorite removal ("hypo kill"). Each of these processes are described, and related to the pertinent mineralogic components in the carbonaceous ore feed to the plant. The chlorination system in use at Jerritt Canyon to passivate forms of preg-robbing organic carbon has proven to be a cost effective and efficient means to recover gold from low sulfide carbonaceous refractory ores, where gold may not be specifically associated with either the sulfides or the carbon.

Jan 1, 1987

By Kunihiko Takeda, Kimio Imaizumi, Tsuyoshi Arai

"The study on the preparation of mono-dispersed liquid droplet was performed using ultrasonic as one of the steps of producing the perfectly mono-dispersed particle. The ultrasonic system was a 33.6kHz ultrasonic generator, an amplifier, an electric distortion element, and a bolted Langevin type horn installed in .a cell. For the first time, a liquid pillar under a nozzle of the cell ·was stably formed. Then, dense and coarse parts were alternatively constructed by oscillating the wavelength of the ultrasonic.· The diameter of those liquid droplets were found to be· perfectly uniform, therefore, it was measured by ""multiplex photography"" using a synchronized stroboscope with the ultrasonic.- From the results, more than 30,000 of perfectly uniform liquid droplets in 1 second were observed by this method.IntroductionRecently, research on the control of physical form is done in various fields of industry. Some examples are the processing technology of the minute compound material of micro-machines and integrated circuits, and the form control of molecule size like catalysts. There is a need for such material to take on various forms in correspondence to its use. ""Form control"" as used in this study will indicate ""research on physical chemistry factors which determine the size of the material"" and will refer to the contour uniformity of comparatively little particles. A well-known method of preparing particles is to spout a mist of liquid and slurry from a nozzle l) 2). Particles for metals, catalysts and food have been prepared by this method. In this case, although an approximate particle diameter can be decided by controlling the nozzle diameter and the violent outflow velocity, it is not easy to completely control ·the contour and to prepare a particle with uniform diameter. ·However, the preparation of perfectly uniform particles is necessary for solders for the adhesion of electronic wiring 3), ion exchange resins4), catalysts and so on. Large quantities of fine particles and super-fine particles are generated when manufactured in the usual way. Large quantities of these fine· particles and super-fine particles have polluted the internal and external' environments of factories. The products yield' ·decreases, also. From such a background, this study examines the preparation of perfectly uniform particles that could be· collected -100% as products. Recently, NASA has succeeded in the preparation of perfectly uniform particles in zero gravity 5). But the preparation of 'perfectly uniform particles by this method is difficult, and it can not be used in general industry"

Jan 1, 2000

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen temary system, which is of fundamental importance for discussing the recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, Sb015 and Sb203 in the PbO-SbOu and PbO-Sb203 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By Masayuki Kudoh, Kiyotaka Matsuura

"Molten aluminum and nickel cast onto a steel block exothermically react and produce molten nickel monoaluminide, NiAI, which is simultaneously joined to the steel. The heat of the exothermic reaction is transferred to the steel block, and steel near the surface of the block is melted. The depth of the melted steel increases with both the initial temperature of the steel block and the thickness of the produced NiAI. Iron from the melted steel dissolves in the molten NiAI, and an intermetallic compound of NiAI-Fe pseudo-binary system is produced. During solidification of the intermetallic compound, it is strongly joined to the steel. The Ni.Al-Fe intermetallic compound has an excellent resistance to oxidation and corrosion.IntroductionAn intermetallic compound of nickel monoaluminide, NiAl, offers many advantages over conventional superalloys, such as higher melting temperature, lower density, greater specific modulus and higher thermal conductivity [1]. NiAl also exhibits excellent high-temperature oxidation resistance when doped with zirconium or hafnium, and excellent high-temperature corrosion resistance when doped with chromium or yttrium, that are superior to existing high temperature alloys or coating materials [1-4]. On the other hand, NiAI is significantly brittle at temperatures below 600 K [5-7], which is the most sigriificant disadvantage of NiAI. A possible way to overcome the disadvantage and to utilize NiAl as an environmental-resisting high-temperature structural material may be joining of NiAl to a ductile material."

Jan 1, 2000

By B. Farouk, D. Apelian

"A numerical model has been developed to predict the temperature history of particles injected in a low pressure d.c. plasma jet. The temperature and velocity fields of the plasma jet are predicted as a free jet by solving the parabolized compressible Navier-Stokes equations using a spatial marching scheme. Particle trojectories and heat transfer characteristics are calculated using the predicted plasma jet temperature and velocity fields. Correction factors have been introduced to take into account non-continuum effects encountered in the low pressure environment. The plasma jet profiles as well as the particle/plasma interactions under different jet pressure ratios (from underexpanded to overexpanded) have been investigated.I. IntroductionIn the plasma spraying process a d.c. plasma jet is used as a heat source to melt and accelerate powder particles which subsequently impinge and solidify on a given substrate. During low pressure plasma deposition (LPPD) prooess, the plasma jet is expanded into a low pressure environment (40-80 Corr) which results in high plasma jet velocities with Mach numbers ranging from 2 to 3. Previous efforts to predict heat transfer and fluid flow in plasmas have made use of incompressible flow formulation employing turbulence models [1-3] for atmospheric plasma spraying. However, these theoretical calculations have been limited to the subsonic flow regime; hence, the compressibility effects and viscous heat dissipation were neglected. In the LPPD process, the plasma jet is operated at the supersonic flow regime, therefore, the compressibility effects and viscous heat dissipation are no longer negligible. This is the main motivation of this work.In addition, production of high quality dense deposits requires that a large fraction of the injected particles be in a molten state when they impact the substrate. An additional motivation for this work is that it is important to understand the plasma/particle heat and momentum transfer since these phenomena dictate both the particle thermal history and particle trajectory.Early computational works in supersonic nozzle field flow [4,5,6] consisted of patching methods that divided the flow field into an invisoid free stream and a viscous boundary and. mixing layers. Each was analyzed independently and coupled through appropriate boundary conditions. Later schemes [7,8] involved solving time-dependent, compressible Navier-Stokes equations over the entire computational domain. These schemes show a great promise in predicting flows with complex structure, and where the viscous effects became prevalent."

Jan 1, 1986

By Zhou Jiemin

A mathematical model is developed to determine the economic thicknesses of refractories and insulations in rectangular furnaces, Both the heat loss cost and the lining investment are taken into account to achieve a minimum operation cost. For the sake of calculating the heat flux, the paper is particularly concerned with the simulation of the three-dimensional transient heat conduction processes in the lining and a Douglas-Rachford method is used to solve the finite difference equations, The model has been used to design an industrial electric resistance furnace operated periodically. the values of temperatures and power consumption measured from the furnace correspond with the model results.

Jan 1, 1991

By Lu Lin, Yan-ping Bao, Min Wang

In order to forecast the cost of dephosphorization during BOF process, and achieve economical dephosphorization of BOF. The mathematical model of dephosphorization cost for BOF process was established. The model calculations show that, when the silicon content and phosphorus content are increased in hot metal, and the final phosphorus content of BOF is decreased, the dephosphorization cost will be increased. The silicon content of hot metal is increased of 0.1% in the plant, the dephosphorization cost is added by 9 RMB/ton steel. The De-P cost of mode A is much higher than the other two modes for three typical production modes of single slag melting process, when the phosphorus content of hot metal is higher than 0.14%, an increase in the phosphorus content by 0.01%, the De-P cost of mode A is added by about 7 RMB/ton steel. Meanwhile, when the phosphorus content of hot metal is lower than 0.165%, the De-P cost of mode C is higher than mode B’s. For BOF single slag melting process, the dephosphorization cost calculated by model is between ± 2%, proving that the model is reliable for the prediction of dephosphorization cost.

Jan 1, 2015

By Charles Zimmerman

The Genesis gold mine, owned and operated by Newmont Gold Co., is located in section 31, T36N, R50E within Eureka County, Nevada along the Carlin Trend of sediment-hosted disseminated gold deposits. Mining commenced in 1986 with present mineable and stockpiled reserves listed at 17,711,000 tons of ore averaging 0.073 opt Au, totalling 1.292 million ounces of gold. Ore is primarily hosted within Devonian calcareous siltstones that have been subjected to intensive argillization and silicification episodes. Additional mineralogic and geochemical features of the Genesis ores include enrichment in iron-oxides, kaolinite, arsenic and antimony; the ore zone is relatively depleted in carbonates and sulfides as a result of supergene and hypogene oxidation. Two major structural zones enhanced the permeability of the siltstones and served as the main hydrothermal conduits within the deposit. Prior to the main ore stage, the host rocks were subjected to metasomatic effects caused by emplacement of the Juro-Cretaceous Goldstrike granodiorite pluton and associated dikes and sills. Micron-size gold occurs in clays, micro-crystalline quartz, and in arsenical complexes. Non-oxidized carbonaceous and sulfidic ores and silica-locked ores result in variable preg-robbing and refractory responses during cyanide recovery. Selective mining and milling has resulted in the successful treatment of the Genesis orebody.

Jan 1, 1988

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 K. G. F. Janssens

In the process of annealing a deformed metal the microstructure changes due to concurrent recrystallization, grain growth and precipitation. It is common knowledge that all three of these microstructural transformations show a strong dependence on each other, and that an overall model must take the relevant interactions into account. Aiming at the development of an approach which is useful in the more general case, a computational model is being developed which allows the prediction of the three dimensional grain topology and orientation distribution function of any metal submitted to subsequent deformation and annealing, taking into account concurrent recrystallization, grain growth and precipitation and starting from a statistical representation of the deformed microstructure. In this contribution a case study is presented which illustrates the potential and limits of the state of the art in the field. Keywords: Microstructure Evolution Modeling, Irregular Cellular Automata, Deformation, Precipitation, Recrystallization, Grain Growth

Jan 1, 2003

By George H. Edwards

Most cullets consumed in large-volume glass manufacturing processes receive little processing beyond crushing. But lead-glass cullets for specialty glasses such as industrial lighting refractors or cathode-ray tubes are combined with metals and various coatings that prohibit their direct recycling into the glass-melting processes that created them. In many cases, the contained lead renders these cullets hazardous. At present, virtually all industrial processes to separate one cullet from another depend on hand sorting, and thus are necessarily costly per unit weight. Lead-glass cullets of differing lead content are of interest because they offer the possibility of separating one glass composition from another by high-speed, automated processes at low cost. A potential process for comminution, cleaning, and separation of lead-glass cullets would involve primary and secondary crushing, magnetic and other metals separation, attrition scrubbing in water, separation of glass types by gravity techniques, drying if necessary, sampling, and preparation for transport to the point of use. Process water would be filtered to remove finely divided coating materials and glass, and reused. If carried out on a scale similar to a specialty industrial mineral processing plant, the cost per unit weight of such processing should be substantially less than the raw material value of the cullet in specialty glass production. The added value of avoiding waste disposal costs makes this process economically attractive.

Jan 1, 1994

By P. Wieser, D. Feke

"Priming of filters with small pores is influenced by the surface tension of the liquid metal and may be complicated by freezing • Freezing followed by melting has been observed experimentally. This process has been modeled on the basis of one dimensional heat flow by radiation to the filter and by conduction in the metal. Also considered are super-heat of the metal and the initial filter temperature. The results of the model provide useful guidelines for the application of filters. IntroductionFiltration has been recognized as a valuable method of refining by removing suspended phases from liquid metals or alloys. Woven fiberglass type fabrics and wire screens were used initially in the aluminum industry. With the introduction of the ceramic filters that exhibit improved inertness and refractoryness, filtration has been introduced to higher melting alloys including cast irons, superalloys, stainless steels, as well as low and medium carbon low alloy steels. A considerable literature is delveloping rapidly on the progress in applications and the advances in understanding the mechanisms and effectiveness of filtration processes (1-8).With the use of filtration for different alloy systems for the production of cast to shape parts a bewildering variety of gating system modifications has been developed (Figure 1) to accommodate the installation of filters in the mold. The modifications have two principal purposes: 1) the runner expansion is intended to compensate for the resistance to flow due to the filter and that of the captured inclusions, and 2) the metal reservoir upstream of the filter, provides a temporary by-pass which permits metal to flow across the filter and heat it until priming can be accomplished. priming of.filters by low and medium carbon steel is readily accomplished but, compared to such alloys as cast iron or 19 Cr-9Ni stainless steel, requires greater precautions to avoid failure to prime by excessive freezing on or inside the filter pores. This problem is further examined below:"

Jan 1, 1986

By Seshadri Seetharaman, Nurni N. Viswanathan, Haijuan Wang

"In order to make the stainless steel making process efficient and environment friendly, it is essential to minimize the loss of chromium to the slag phase. With a view to investigate the advantages of using CO2 to attain moderate oxygen partial pressures in the oxidant gas during the decarburizations of stainless steel, the present experiments were carried out to understand the oxidation kinetics of Fe-Cr alloys and Fe-V alloy with gas mixtures containing CO2. In the present work, the oxidation behavior of Fe-Cr and Fe-V was examined by thermogravimetric analysis (TGA). Various mixtures of O2 and CO2 were used as the oxidant gas and the oxidation rate was followed by the weight changes as a function of time.The experiments demonstrated that the oxidation rate is independent of temperature at present experimental situation, but has strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture. The wetting of alumina by the iron drop and the change of the drop shape during the course of the oxidation were investigated by X-ray radiography."

Jan 1, 2010

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen ternary system, which is of fundamental importance for discussing the' recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, SbO1.5 and Sb2O3) in the PbO-SbO1.5 and PbO-Sb2O3 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003