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By O. Lashkari

Swirled Enthalpy Equilibration Device (SEED) is a new patented Slurry-on-Demand, SoD, processing route. The semi-solid slug preparation is carried out by off-center swirling of aluminum melt in a metallic mould. As part of the current research program on the semi¬solid processing of aluminum alloys, the morphological evolution of 356 aluminum foundry alloy microstructure is reported here. Semi-solid slugs were prepared using two different pouring temperatures of 645°C and 695°C respectively. Morphological evolution of the semi-solid microstructure was characterized using image analysis through measuring of primary a-Al particle size, number density, aspect ratio and sphericity. The possible relationships between microstructural features and process parameters were also investigated. The current report covers the effect of pouring temperature on the morphology of primary a-Al dendrites and attempts are made to explain the differences between the predicted percentage primary a-Al phase and those of the actual values in the as-cast slugs.

Jan 1, 2004

By Naizhong Xu

During the past 30 years, fully mechanized caving mining has played a positive role in the improvement of the efficiency of coal production, but which has also had a great influence on the mining environment, especially to environment damage of shallow mining areas in the central and western regions of China. The surface subsidence parameters are the basis of the surface environment evaluation and governance. During 1980~1990s of the last century in China, fully mechanized mining subsidence laws were researched more fully, however, since coal caving technology is affected by many factors, and researches on its mining subsidence laws (parameters) were found to be grossly inadequate. Through actually observed in recent years, it is considered that coal caving mining subsidence laws (parameters) can use fully mechanized mining law (parameters) for reference. Based on fully mechanized mining laws (parameters), this paper reveals the similarities and differences of the surface subsidence laws between fully mechanized caving mining and fully mechanized coal mining, which can guide the work of coal mining under buildings, water bodies and railways in new mine area and mine collapse governance.

Aug 1, 2013

By M. Sokoto, H. Hata, K. Nishina, K. Haiki

Fluoride ions in zinc electrolyte cause corrosion to aluminum cathode plates at zinc electrowinning process, so we have developed an iron compound as a fluoride ion adsorbent used in zinc sulfate solution. The iron compound is synthesized from FeC13 solution with a small amount of sulfate ion by neutralizing reaction with Na2CO3 solution. The fluoride ions adsorbed on the surface of the iron compound are desorbed in alkaline solution and the iron compound can be reuse as a fluoride ion adsorbent. Moreover, if adsorption capacity of the iron compound decreases, it can be dissolved in HCl solution and re-synthesized.

Jan 1, 2008

By D. Monder

Fuel cells are promising sources of electrical energy because of their exceptionally high efficiencies and low environmental emissions. Solid oxide fuel cells (SOFC) are high temperature, ceramic electrolyte cells, which unlike most other fuel cells, can work with a variety of fuels besides pure hydrogen, including hydrocarbons and hydrogen sulfide. In this presentation I present the models we have built for a single H2S fuelled SOFC. The goal is to model the electrochemical reaction coupled with mass transfer, fluid flow and current/voltage distribution in an yttria stabilized zirconia electrolyte fuel cell assembly operated between 750 and 850 °C. Two models of the above SOFC are discussed in this work, 1) an algebraic model derived by integrating a one-dimensional model along the thickness of the cell, and 2) a two-dimensional finite element axi-symmetric model. Important physical and kinetic parameters in the 1-D model are fitted using experimental data sets at three different temperatures and reasonable fits are obtained for the data sets at 800 °C and 850 °C. However, the third data set at 750 °C does not give a good fit using this model. We need to apply the curve-fitting to more data sets to investigate it further. The main conclusion that can be drawn from the present study is that the ohmic resistance of the cell is very high. Contact resistances are believed to be the reason behind this although there could be contributions from resistive interphases. The 2-D model also gives reasonable fits to data sets. One of the publications by the laboratory group doing the experimental work in our department presented very interesting data that shows the cell performance being a strong function of fuel flow-rate. We want to model this behaviour and will have to depend on the 2-D model as the 1-D model does not have flow-rates as parameters.

Jan 1, 2005

By K. Soucek, J. Ptácek, A. Hastíková, R. Kukutsch, P. Konícek, P. Waclawik

"Cable bolts are used frequently as a secondary support system (with steel arch support) in difficult stress-strain conditions of deep coal mines. The load transfer mechanism of cable bolts depends on several factors, such as the strength, deformation and geometric properties of the bolts, resin and the surrounding rock mass so-called cable-resin-rock system (CRR system). The bonding length and bolt/borehole diameter ratio strongly influence the final bearing capacity of the CRR system.The study presents the behaviour of CRR system during a pull-out test which is usually used in the carboniferous rock mass in the Czech part of the Upper Silesian Coal Basin. A series of 28 pull out tests were performed on 3-m-long cable bolts, with various combinations of borehole diameters and bonding lengths, to understand this behaviour. Boreholes were drilled into a solid rock mass consisting of fine-grained sandstone to guarantee similar conditions during the pull-out tests. Video inspection and measurement of borehole diameters were performed to determine their quality and real diameters. Three characteristics were observed from pull-out test results: ultimate pull-out load; displacement of the end of bolt and system stiffness. Numerical modelling by FEM (Finite Element Method) was used to determine the stiffness of the CRR system for variable bolt/borehole ratios and bonding lengths each under constant load. A linear elasto-plastic model and a mohr-coulomb model were used for cable and resin-rock respectively. The results of the experiment may contribute significantly to improving of the methodology of cable bolts installation as well as the design of used cable bolts."

Jan 1, 2015

By A. Singh

Deformation structures after tensile and compression tests on Mg926Zn64Y alloy extruded at 250°C and 400°C are studied, in as-extruded and heat treated conditions. The icosahedral phase particles stimulate recrystallization during extrusion, resulting in fine grain size. Tensile and compression tests at room temperature show comparable yield strength, with a yield asymmetry ratio up to 0.98. c-type dislocations are observed in the grains near the submicron size icosahedral phase particles. The source of these dislocations is believed to be dissociation of <c+a> type non-basal dislocations. No dislocation pile-ups on icosahedral phase particles are found. {10 1 2} type twinning occurs in compression.

Jan 1, 2006

By Y. Hanada

Electrorefining at higher current density is desirable due to the increase in productivity attained without expanding the plant size. However, increasing the current density in common commercial practice causes problems such as anode passivation, dendritic deposition, cathode impurities and energy consumption. In general, agitation of the electrolyte is effective in suppressing these problems. To apply the agitation to commercial practice effectively, the method of agitation is important. One possible method is agitation by gas injection. In this study, fluid motion characteristics with gas injection between electrodes were investigated using a water model. Flow patterns were observed and fluid velocity was measured using a particle tracking method. It was found that the time-averaged velocity near the electrode walls was of the order of 0.1 m/s in the conditions. The flow was highly turbulent. The turbulent component of velocity was the same order as the time-averaged velocity. The mass transfer coefficient between the wall and fluid doubled when the effect of turbulent intensity was taken into account. The effects of gas injection on the electrolysis behaviour at high current density were discussed in terms of the mass transfer. It is suggested that gas injection could suppress the problems at high current density.

Jan 1, 2007

By G. Diaz

Técnicas Reunidas (TR) has been involved for over 30 years in the development of process technologies for the recovery of zinc from different primary and secondary feed materials, such as the ZINCEXTM process. Because of the complexity of the feed mineral resources, solvent extraction (SX) is an invaluable technique to concentrate and purify zinc solutions. When applied to a pregnant leach solution, solvent extraction can produce an extremely high quality zinc electrolyte, suitable for obtaining SHG zinc ingots, after electrowinning and melting and casting processes. However, the high affinity of most organic extractants for Fe(III) poses a serious problem, which may adversely affect the zinc extraction process. Different methods may be applied to deal with the negative effect caused by Fe(III). An acid regeneration step and electro-reduction stripping have been considered as the most viable techniques to remove the iron from the organic phase. This paper describes some findings of Técnicas Reunidas in the area of zinc solvent extraction, especially on removing Fe(III) from the organic phase.

Jan 1, 2006

By P. C. Sui

Numerical investigation and parametric simulations of the coupled electrical conduction and mass diffusion in the GDL of a PEMFC are reported. The coupled transport is solved using a 2D, "under-the-rib" computational domain for the cathode GDL. The current density on the GDL/catalyst layer interface, which constitutes one of the boundary conditions for the GDL domain and reflects the activation overpotential in the catalyst layer and the ohmic loss in the membrane, is solved iteratively using a novel numerical algorithm. A parametric study is performed to investigate the effects on current density distribution of various operating conditions such as oxygen concentration and membrane resistance, and of design factors such as GDL geometry, anisotropic transport properties, and deformation under the land area. The results show that the current density distribution under the land area can be dominated by either electron transport or mass transport, depending on the operating regime.

Jan 1, 2005

By K. Regl, J. Berneder

"AMAG investigated different aspects to improve the resistance against grain coarsening in aerospace alloys during recrystallization and was successful in finding several opportunities to minimize this effect. The studies show that one aspect to counteract grain coarsening is the chemical composition and subsequently all phases that are formed during homogenization. Starting with a fine grain (~ 50 µm) can lead to a final grain size of few mm. On the other hand with a coarse initial grain size (approximately 150 µm) and the right chemical composition the grain size can stay almost constant despite different deformation steps. Additional we investigated different sequences for the component production to eliminate the problem of grain coarsening as a coarse grain has a detrimental effect on product performance.INTRODUCTION In the aircraft industry, aluminium sheets are most commonly deformed in their soft state, followed by solution heat treatment and natural or artificial aging. If the preceding deformation is in a critical amount, during the recrystallization at solution heat treatment grain coarsening can occur. A subsequent deformation to this condition leads to an orange peel surface, which requires additional polishing. Next to this extra effort the coarse grain size produces a drop in the mechanical properties, often below specification limits. If there is no subsequent deformation, this effect is not visible and without destructive testing there is no possibility to detect the error. As mentioned before, this effect occurs during recrystallization, which is a process that is driven by the stored energy in the microstructure. The two most important aspects for an increase of the stored energy are the increase of the grain boundaries fraction (smaller grain size) and the increase of the dislocation density caused by deformation. The increase in dislocation density during the deformation arise from trapping of existing dislocations and from the generation of new dislocations. During recrystallization all grains are built completely new, so all dislocations are removed (Humphreys & Hatherly, 2004). There are three requirements for recrystallization:"

Jan 1, 2018

By S. Eckert, M. Reuter, D. Obiso, S. Kriebitzsch, M. Akashi

The present paper focuses the application of CFD techniques to investigate the Top-Submerged- Lance (TSL) gas injection in liquid metal. Previous works of the authors have shown that up- and down- scaling procedures based on the modified Froude number have some shortcomings, as this approach does not take into account the interfacial and viscous forces. Indeed, surface tension and dynamic viscosity of the smelting slags (σ = 0.4-0.5 N/m, μ = 0.2 Pa·s) are higher than the operating fluids that have been used in literature (water, paraffin oil) to study TSL injection in down-scaled furnaces. In order to get closer to real systems, the authors study the TSL injection of Argon in a liquid metal. An experimental campaign was carried out in the X-ray lab at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), where the eutectic alloy GaInSn was used as liquid phase. The alloy is liquid at room temperature, and X-Ray imaging is used to picture the multiphase flow in a quasi-2D vessel. The aim of the present work is to demonstrate the applicability of CFD techniques to model multiphase flows involving liquid metals, and validate the model using the data produced at HZDR. The commercial software ANSYS Fluent® was used together with the Volume of Fluid model to directly resolve the gas-liquid interphase. Some features of the flow, such as the void fraction distribution and bubble detachment frequency are tracked with CFD and compared to the experimental data. INTRODUCTION In the last thirty years the TSL smelting technology has increasingly been used for industrial non- ferrous smelting processes and is now one of the significant pyrometallurgical processes. Developed in the early 1970’s at CSIRO, the furnace is nowadays commercialized in different market sectors, including copper and lead smelting, zinc fuming, waste treatment and slag recovery (Floyd, 2005). Despite the wide application of these reactors in the pyrometallurgical market, some aspects of the process are still not fully clarified, since in-situ measurements and optical accesses are prohibitive because of the high temperatures and aggressive conditions. Phenomena such as the bubbling regime, the slag solidification and the submerged combustion still need a deeper scientific investigation to obtain a better understanding of the process.

Jan 1, 2019

By D. L. Babbitt, Sniezek

"This paper deals with the varions methods for the rapid Joading of unit trains which are being: used by ore procossors to move their product to dock-s1de storage facilities or their ultimate customer. Some of the techniques that have been used include (1) volumetrie loading, both in motion and static, (2) batch weighing into moving cars and (3) batch weighing into cars that have been stopped. Particular emphasis shall be placed on the two systems now in use at the Adams Mine facility of Jones and Laughlin Steel Corporation and at Cliffs of Canada's Sherman Mine. Typical ""turnaround"" times, loading rates, types of cars, weighing accuracies, material handling concepts and maintenance considerations shall be discussed."

Jan 1, 1969

By M. Pötsch, W. Schubert

"The kinematic analysis of rock blocks is one part of a block stability assessment. It provides information about a block’s movability, i.e. if a block can detach from the adjacent rock mass and move towards the free space. This paper introduces an analytical method for the analysis of pure rotations of arbitrary finite polyhedral blocks. It enables the engineer to judge a block’s rotatability about a corner or an edge. The method is presented using a graphical and computational method. The application of the method is illustrated with an example. INTRODUCTIONThe kinematic analysis of rock blocks deals with the determination of the movability of blocks. Established methods typically cover: (a) translational motion (John 1968, Markland 1972, Londe et al. 1969, 1970, Goodman & Shi 1985, Warburton 1981) and (b) the specific rotational cases Toppling (Goodman & Bray 1977) and Slumping (Kieffer 1998). Mauldon & Goodman (1990, 1996) and Tonon (1998) introduced rotational kinematic analyses for three-joint pyramids and tetrahedral blocks extending Goodman & Shi’s block theory.All mentioned methods are subject to assumptions that limit the applicability to engineering problems. For example, the kinematic test of daylighting joints or intersections inherently assumes a finite block, which only can be proved by the finiteness theorem (Goodman & Shi 1985). Daylighting of an intersection or plane is not a sufficient condition for removability. Goodman & Shi’s and Warburton’s methods are limited to translational block motion. The methods for block rotations so far address tetrahedral blocks only. They also address only pure rotational modes and neglect the general motion of a rigid body. This paper introduces an analytical method for the analysis of the kinematic rotatability of finite rock blocks. It extends Mauldon's and Tonon's theory of rotatability of tetrahedra to arbitrary polyhedral blocks. A graphical method using the stereographic projection and a computational method are presented."

Jan 1, 2015

By Francis Breton, Lei Pan, Kun Liu

"Effects of Fe, Cu and Mg minor alloying elements on creep properties of 8xxx aluminum conductor alloys were investigated by conducting compressive creep tests at 100 ºC under a constant load of 69 MPa. The microstructural evolution was studied using an optical microscope and electron backscatter diffraction technique. The creep properties were characterized by the primary creep strain in the first stage and the minimum creep rate in the second stage of creep deformation. Results showed that additions of all three minor alloying elements (Fe, Cu and Mg) demonstrated a beneficial effect on the creep resistance but individual alloying elements exhibited different impacts on creep properties. The additions of Fe and Mg showed a strong impact on both the primary creep strain and minimum creep rate, while the Cu addition displayed a favorable effect on the primary creep strain but no impact on the minimum creep rate. Microstructure observation revealed that with increasing Fe contents, the volume fraction of fine intermetallic dispersoids gradually increased while the subgrain size and misorientation angle became smaller, providing strong barriers to the dislocation and grain boundary movements. The addition of Cu moderately reduced the subgrain size and misorientation angle and in combination of solid solution strengthening it promoted the retardation of the creep deformation during the primary stage.INTRODUCTIONThe 8xxx aluminum conductor alloys offer significant advantages such as low density, high conductivity to weight ratio and low price over copper conductors and become an attractive candidate in electrical engineering and building wiring (McQueen, Chia, & Starke, 1986; Birol, 2009; Engler, Laptyeva, & Wang, 2013). The mass resistivity of aluminum conductors is one-half of copper conductors. Thus, only one-half the weight of aluminum is required for equivalent capacities. Therefore, this unique property coupled with a relatively low price of aluminum offers significant economic advantage to develop aluminum conductor alloys for electrical applications in the electrical wire industry."

Jan 1, 2016

By Selvia Tourn, Liliana Castro

"Abstract - Argentina, a large country with an important agriculture industry, needs an ever-increasing amount of phosphorus and potassium, as essential elements for plant growth. Current requirements are met from imports, but potential resources exist in Argentina. For example, several phosphatic occurrences are known in paleo-marine basins, the most significant of which are in Tertiary units in Patagonia. In addition, two types of potassium deposits are also known in Argentina: evaporite deposits in the Neuquén Basin at depths of 750 m to 1500 m contain 22 to 25 wt% K2O equivalent; and glauconitic sandstone containing about 6 wt% K2O has been identified in Patagonia.Several experiments were undertaken to test unprocessed phosphate rocks as slow-release, direct-application fertilizers, with good results. In addition, it is proposed that direct application of glauconitic sands would provide an efficient and economic alternative source of potassium. Tests with glauconite samples are still in progress. The existence of both phosphate and glauconitic rocks in Patagonia suggests that development of an extractive industry for these materials would not only help Argentina approach self-sufficiency in fertilizer usage, but also assist in the socio-economic development of this region."

Jan 1, 2003

By F. Parada

During copper smelting and converting processes, slag generated is pyrometallurgically cleaned and then disposed, containing around 1 % of this metal. However, important amount of molybdenum initially contained in concentrates also goes to the slag phase. Research on molybdenum recovery from water granulated slags using acid leaching at low temperatures was conducted to find an efficient way for molybdenum extraction with lower magnetite in the slag. However because of the high fayalite content high acid consumption was found. Molybdenum can be recovered from solution using ionic exchange resins, but high silica content interferes with extraction. Some studies addressed to minimize silica extraction as well as alternatives of selective silica precipitation in order to develop a technically feasible process.

Jan 1, 2007

By R. Chen, K. Xia

In deep mining activities, blasting induced compressive stress wave would be reflected as tensile wave at a free surface around the openings, which would facilitate the tensile failure of the deep rock since it is much weaker in tension than in compression. It is thus critical to understand the dynamic tensile failure of rocks subjected to static tension for deep rock engineering applications. A modified split Hopkinson pressure bar (SHPB) system is adopted to load Brazilian disc (BD) samples statically, and then exert dynamic load to the sample through stress wave generated by impact. The pulse shaper technique is used to generate a slowly rising stress wave and thus to facilitate the stress equilibrium of samples during each test. Five groups of Laurentian granite (with tensile strength of 12.8 MPa) BD samples under the pretension stress of 0 MPa, 2 MPa, 4 MPa, 8 MPa, and 10 MPa are tested under different loading rates. The result shows that the dynamic tensile strength of the rock decreases with the increase of pre-tension stress, which is easy to understand because pre-tension stress weakens the rock sample. It is also observed that under the same pre-tension stress, the dynamic tensile strength increases with the loading rate, revealing the so-called rate dependency that is common for engineering materials. Furthermore, it is found that the loading rate sensitivity of the rock increases with the increase of pre-tension stress. A qualitative explanation for this phenomenon is that more microcracks are generated and activated under higher pretension stress, resulting in a more viscous material. Based on the results, an empirical equation is proposed to fit the data and explain the dynamic tensile behaviour of rock under pre-tension stress. A physical model is used to simulate the dependency of the dynamic tensile strength of rock on the pre-tension stress and the loading rate, which is shown to be in good agreement with the experimental results.

Jan 1, 2015

By M. F. Gallerneault, V. Fallah, A. Howells, W. M. T. Gallerneault

"The occurrence of recrystallization in cold-worked aluminum sheet during the brazing process leads to loss of strength, an inhomogeneous grain structure and reduced corrosion resistance. AlMgScZr alloys are known for their extraordinary recrystallization resistance due to the influence of Sc and Zr addition on their microstructure. Here, we investigate the effect of alloy composition (i.e. Mn, Mg, Sc, Zr content), cold-roll reduction and pre-aging treatment on the recrystallization behavior of cold-rolled sheets at brazing temperatures typically used during the manufacture of heat exchanger units. The analysis of recrystallization behavior is carried out through microstructural characterization and the results are compared with the behavior of a commercial, AA3xxx-based heat exchanger alloy.INTRODUCTION Control of recrystallization is of critical importance during brazing, which is a widely-used joining technique for aluminum alloys in aircraft structures (Heinz, 2000) and automotive heat exchangers (Miller, 2000; Marshall, 1993). Due to excessive local heat at brazing temperatures, the cold work texture of aluminum alloys in the cold-rolled sheets may undergo a local recrystallization process (Marshall, 1993). This leads to the formation of an inhomogeneous microstructure and thus anisotropic mechanical properties (Miller, 2000) and low corrosion resistance (Marshall, 1993) across the sheet. X800, a commonly-used Al-Mn alloy series for automotive heat exchangers applications, has been developed specifically for a higher strength as well as an enhanced corrosion resistance as opposed to the traditionally-used AA3003 alloy (Marshall, 1993). X800 alloys, however, exhibit a low recrystallization resistance at normal brazing temperatures, i.e. 590°C. In contrast, Al-Sc-Zr alloys have been shown to exhibit an extraordinary recrystallization resistance at such temperatures (Riddle, 2004) while also being corrosion resistant and possessing a high room-temperature strength (Fuller, 2002). This has been shown to be due to the formation of coherent, nanoscale Al3(ScZr) precipitates that effectively impede grain boundaries while also exhibiting very slow coarsening kinetics at high temperatures (Riddle, 2004; Jones, 2003; Ocenasek, 2001). In this study, we analyze the recrystallization behavior of X800 alloys under brazing conditions through introducing Sc and Zr into the system as well as varying the Mn and Mg content. The effect of processing route is also studied by introducing a pre-aging stabilization treatment as well as varying the cold-roll reduction prior to the final brazing anneal."

Jan 1, 2018

By Gino Palarchio

Dofasco is Canada?s 2nd largest steel manufacturer producing 4.5 million tons of flat rolled steel per year. They have revenues of over $3 billion and employ 7,000 people in their Hamilton, ON plant. Dofasco is North America?s most profitable steel producer and were recently ranked as the #1 steel maker in the world by Dow Jones. Motivation to Improve In the 1980?s the steel business was good. However, in the late 80?s and early 90?s things began to change. Globalization was beginning to influence the market, imports started arriving at lower prices and higher quality, hangover from the 1970?s inflation saw costs rising and prices dropping, there was a shift from a sellers to a buyers market, and shareholder returns were beginning to erode. Dofasco took a step back and evaluated their maintenance performance and found that they were operating in an environment where 70% of their work was reactive and only 30% was proactive. They also found that the rate of product quality improvement was flat and their average equipment availability was only 78%. At that point they realized that Equipment Reliability was key to improving product quality, production output, costs and shareholder return. They initiated a project to research, develop, and implement the most advanced maintenance practices and information technologies to achieve maximum equipment reliability.

May 1, 2001

By J. A. Hillier

The staff of the Hudson Bay Mining and Smelting concentrator have developed a new type of reagent feeder. Several factors encouraged the development of such a system: varying heads caused by the mixing of ores from several mines, the increasing number of flotation circuits operated and reagent feeding stations remote from the flotation operator's work area. The reagent feeders also had to be compatible with future plans for reagent control from an on-stream X-ray analyzer and computer system. The new feeder is a positive-displacement pump set to deliver a constant volume per stroke. At a remote panel, the feed rate is altered by changing the time between strokes. The feeders have been found to be reasonably trouble-free and accurate to less than 2 per cent error.

Jan 1, 1973