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By Goren Lindkvist

Elkem has a small industrial scale. Muti-Purpose furnace at the MEFOS Metallurgical Research Facility in Lulea, Sweden. The furnace is 2 meters in diameter with installed power of 4.8 MVA, equipped with oil coiled freeze lining, gas tight electrode seals and feed chutes and a slag flow control for continuous tapping. During tests in June, 1991, the furnace was continuously operated on a high silica slag at loads from 1.5 to 4,0 MW. The slag was then charges to a low silica, high iron and lime composition. Steel plant dust was added, smelted and reduced. The slag was made more ceramic by adding alumobrick and alumina. Data from the start-up and initial operating phase of the, Elkem EAF dust plant at Laclede Steel will also reviewed.

Jan 1, 1992

By Linda C. White

The use of red mud, a waste product of the ?Bayer? process for bauxite refining, was investigated for its arsenic removal effectiveness from aqueous solutions under various conditions. Red mud efficiently removed As(III) between a pH range of 7.6 and 9; and As(V) in the pH range between 5.5 and 6. Pre-washing of the red mud with salt water considerably improved its arsenic adsorption capabilities. With appropriate red mud dosage, the residual arsenic in solution was decreased below the regulated acceptable arsenic limit (0.1 mg/L) from aqueous industrial wastes. The arsenic adsorption followed first-order rate kinetics and fitted the Langmuir isotherm model. Results suggest that red mud is potentially a useful adsorbent for removal of arsenic from contaminated water or industrial waste solutions.

Jan 1, 2003

By Jennifer Mager, G. P. Martins, Dean Mussatti

"The role of lead, at low concentrations in high pH cyanide-electrolytes, on the dissolution behavior of gold, has been a topic of scientific and industrial concern for well over a century. The recent paper by Kondos et al [1] at CANMET (1995) this continuing interest and apparent importance. Nevertheless, the mechanism(s) by which this (and other heavy metal) component influences the electrodics of this electrochemical system has still not been unequivocally demonstrated. Instead, several plausible hypotheses, by pioneering researchers in this field, have been advanced and reiterated OVer the ensuing years. While it is generally accepted, based on equilibrium elctrode-potential calculations, that reduction (or co-reduction when oxygen is present in the electrolyte) of lead on the gold surface may occur due to cementation (contact reduction), the cemented lead has never been characterized. The work presented has reexamined the role of lead in this system, by delineating the species distribution of these system components and by interpreting the results of potentiodynamic studies in conjunction with SEM analyses of a gold electrode.1. INTRODUCTIONThe leaching of gold ores in cyanide electrolytes has been practiced for well over a 100 years. Research conducted on this topic has been primarily focused on the effects of operating parameters such as concentrations of oxygen and cyanide, and the pH of the electrolyte; or the leaching behavior of carbonaceous and sulfitic gold-bearing materials.Mechanisms by which pure gold is leached in alkaline cyanide media, with oxygen serving as the oxidant, have been subjected to continual examination and re-examination in the published technical literature during this century. Recently, it has been speculated that without the presence in the electrolyte of trace heavy metals, such as lead or mercury, that gold would not be leachable. Researchers who have tackled this topic, have either considered heavy metals to be a natural occurrence in these systems and ignored the role they may serve in the leaching process, or they have deliberately focussed on controlling their concentrations in the system to undetectable limits. As a result, conflicting findings have been reported for what would appear - depending on the details provided in these reports - to be identical systems."

Jan 1, 1997

By Honggang Zhong, Tan Yi, Qijie Zhai, Zhao Dan, Xinping Mao, Huigai Li

"The influence of superheat degree on the distribution and volume content of inclusions were studied in 65Mn thin slab produced by compact strip production(CSP) in Zhujiang Steel in China, The results showed that the diameters of inclusions are mainly less than 5µm. Most of the inclusions gathered at the 1/4 thickness direction for the thin slab of 27? superheat degree, compared with the center position for that of 37?. There are more inclusions larger than 50µm in the low superheat samples, which is caused by the short floating time. In addition, the inclusions were observed and analyzed by metallurgical microscope, SEM and EDS in order to ensure their composition, type and further find their source. It was find that the types of these inclusions mainly are Al2O3, SiO2,CaO and their composites, a few of them are TiN and MnS.IntroductionIt is well known that inclusions have a great impact on the strength, plasticity, fracture toughness, cutting performance, fatigue property and corrosion resistance of steels. Especially, with the demand for thinner slab, the cleanness is increasingly becoming more significant as a quality criterion[1]. High manganese and carbon steels not only demonstrate high strength but also proper plasticity. There are many problems unsolved for 65Mn steel as a result of the low solidification rate, bad thermal strength, crack sensitivity and low casting temperature[2,3].The superheat of the molten steel has a great impact on the erosion of refractory lining, molten steel fluidity and non-metallic inclusion behavior[4]. The serious erosion situation of ladle lining, nozzle and casting tundish will give rise to more inclusions at a high superheat. Meantime higher superheat will make second dendrite arm spacing coursing and element segregation which lead to inclusion, bubble formation and shrinkage cavity. On the contrary, it is hard for non-metallic inclusions to float up with a low superheat value. Inclusions of 65Mn steel, which produced in different superheat condition by CSP, were studied for the sake of higher slab properties including statistics and EDS analysis."

Jan 1, 2012

By S. P. Vanka, B. G. Thomas, S. Sivaramakrishnan

"During the continuous casting of steel, transient 'flow events can be very important to the generation of quality problems, such as shear entrainment, surface level fluctuations and bubble entrainment. These phenomena can be better predicted using Large Eddy Simulation (LES) models than the K-E models, which have been extensively studied. In this work the turbulent transient flow in a water model of a continuous caster has been both simulated using LES models and measured using Particle Image Velocimetry (PIV). The results of PIV and LES have been compared to validate the LES model and also to enhance the understanding of the prominent transient features of the flow field. The flow near the top surface in PIV was found to contain periods of 5-1 Os when the velocities were three to four times their mean values, which is of importance to the shear entrainment of the liquid flux. In both simulation and PIV the upper roll structure is found to change chaotically from a single large recirculation structure to a set of distinct vortices. The inlet swirl in PIV is seen to persist more than halfway across the mold, causing a characteristic staircase velocity vector pattern when viewed in a plane parallel to the wide faces. The lower rolls in PIV are significantly asymmetric for very long periods of time (- I-hour) and go through a repeating sequence of features. One of these features involving a short circuit between the upward and downward flow in the lower roll is also seen in the simulation and is of significance to bubble entrapment.IntroductionThe turbulent flow through the nozzle and in the mold of the continuous caster has been studied extensively using computational Reynolds Averaged Navier Stokes (RANS) models of turbulent flow [1,2]. Defects, such as internal inclusion of liquid fl4x through surface shear, pencil pipe defects due to bubble entrapment, surface defects due to level fluctuations are caused by transient flow phenomena oc'curring in the mold. These phenomena can be better predicted using transient Large Eddy Simulation [3] or ""LES"" models."

Jan 1, 2000

By L. Katgerman, E. N. Straatsma, Suyitno

"Single-roll strip casting process is studied using computational fluid dynamics which takes into account fluid flow, heat transfer and solidification. The computational model is based on the conservation Jaws of momentum, energy and continuity. Correlation of strip thickness, solidification zone length, and puddle shape on single-roll strip casting of Al-1 %Mn is explored. Feeding pressure and roll speed are investigated. The results show that the··strip thickness slightly increases with pressure, similarly the length of solidification zone. The variations of strip thickness and solidification zone length with roll speed show a sharp decline for strip thickness and slight decline for the length of solidification zone with increasing roll speed. The constraint and free-jet flow have different feature in term of flow field. Severe turbulence is observed on the free-jet flow.IntroductionThe near-net shape casting of strip metals is a demand nowadays. The demand is particularly stimulated by the challenge to become more competitive through enhanced performance. The improvement in the existing processes and new innovative technologies are introduced by the metal industry to gain better product quality, more efficiency in energy consumption, low throughput, yield and operating costs [1-3].There are many advantages that can be obtained by the direct casting of strip. The most prominence is the elimination of hot rolling. Beside that the high rate of heat extraction associated with strip casting offers the possibility of a finer, Jess segregated cast structure. The microstructure will result in the improvement of mechanical properties compared to conventional material, or alternatively the opportunity of using grades of metal outside the normal range for continuous casting.The concept of single-roll strip casting has been difficult to commercialize, because of the complex interactions between fluid flow, solidification, shrinkage, and stress, which lead to serious quality problems. Besides that, the quality and the thickness of the strip are affected by the thermal properties of the strip, roll cooling conditions, roll geometry, and other process parameters. To understand how these parameters affect the strip formation, some researchers have modeled the process [4]."

Jan 1, 2004

By Fei Ruan, Chang Jie, Jieyu Zhang, Jifang Xu, Kuochih Chou

"Viscosity is an important physical parameter of slag in metallurgical processes. Most studies of aluminosilicate and aluminate systems assume that aluminum occurs in tetrahedral coordination. In this case, the O/Al value was utilized to describe the slag structure in terms of the network character of aluminosilicate and aluminate systems. Composition and viscosity data from the literature and the trends were analyzed according to the O/Al value and temperature. It is shown that the O/Al value explains the trends in more than ten systems, containing more than 200 data points. In aluminosilicate system, the trend that viscosity value changed with the O/Al value which implies that alumina works as network modifier such as basic oxides or works as network former. In aluminate system, irrespective of the system and temperature, viscosity decreased steadily when O/Al value increased.IntroductionMetallurgical slags, which are made of oxides and many also contain fluorides, play an important role in metallurgical processes such as iron making, steel making and secondary refining processes. Aluminosilicate slags are applied in a wide range in metallurgical processes. A polymerizing effect of the addition of aluminum and an association of aluminum with low-field strength cations is further supported by the physical variations in aluminosilicate and aluminate systems. The behavior of alumina in silicate melts has been studied by various authors [1-6]. It is generally accepted that Al2O3 is amphoteric [7] because Al3+ ions can behave in profoundly different ways in a silicate melt. When added to a pure silica melt, Al2O3 acted as a network modifier, breaking the bridging oxygen of the pure silica network, thereby decreasing the viscosity in a similar manner to other network modifiers, such as CaO, MgO etc. to form [1/2Ca (AlO4)]4- complexes. However, when added with alkali or alkali-earth metal oxides, some of the Al3+ ions assumed tetrahedral coordination and replaced Si in the liquid network, the missing charge was compensated by Me+ or Me2+ ions. Therefore Al2O3 acted as network former [8, 9]."

Jan 1, 2011

By Binxu Zhaug, Mark Jolly, Xiaojun Dai

"In conventional investment casting process of aluminium alloys for the application of the aerospace industry, to assure the quality of the final casting, usually the foundry uses large runner system which results in low yield, high energy consumption and high GHGs emission. In one case of this investigation, the yield is between 5 ~ 10% which means that the current casting process wastes large amount of energy and generates lots of scraps. By applying a new casting method, the bulky runner system and the melting/holding time are significantly reduced, the quality of the casting is improved, and in the meantime the related energy consumption and GHGs emission are significantly decreased. In the investigation, the energy efficiencies and GHGs emission between the current and traditional processes are calculated and compared.1. IntroductionAs one of the conventional casting process, Investment Casting Process (ICP) and its applications can be traced to thousand years ago [l]. In current casting industry, ICP still plays an important role in the production of small and precious castings with high quality requirements in automobile and aerospace industries. Both casting quality and manufacturing costs which mainly consist of energy costs have crucial effects on the competitiveness of castings in the market. In the production of aluminium alloy castings using ICP, the energy cost and energy efficiency of a casting facility depend mainly on the efficiency of its melting and heat treating performance. In association with the two performances, more than 60 % of the total process energy costs are symbolised in a typical casting facility [2]. Additionally, in conventional ICP of aluminium alloys for the application of the aerospace, to assure the quality of the final casting, typically the foundry uses huge runner system including big risers/feeders which cause low yield, creates lots of scraps and generates high energy consumption. Consequently, there are huge opportunities for casting industry to choose the best practices for potential energy saving. Furthermore, the reasons such as the stringent limitation of environmental legislation in Europe and the pressure of the rising energy price force the casting industry to reduce the energy consumption and greenhouse gases (GHGs) em1ss10n."

Jan 1, 2012

By A. Buzaianu, P. Motoiu, G. Popescu, C. A. Popescu, I. Rusu, A. F. Olteanu

"In recent years, the recycling magnesium metallurgy has developed new types of alloys, some of which exhibiting special electrochemical characteristics. Their application has found a fertile field in the energy conversion technologies. The paper introduces some technologic data on the recycling of aeronautical parts and scrap materials generated from the disassembling of magnesium alloy components, attempting to also solve the recycling of magnesium painted parts. The approach is meant to establish a superior quality method for recycling discarded parts or the excess of re-melting material in order to reduce environmental impact and costs. Magnesium-base alloys used as anodic materials are characterized by a high uniformity of the structural properties as well as by superior electrochemical performances, as compared to the ""classically"" used materials: Zn, Pb, etc. In nonconventional applications of magnesium alloys used as sacrificial anodes working in seawater, special alloying elements contribute to improving anodic processes. The influence of these alloying elements on magnesium sacrificial anodes was studied. It was found that the use of recycled materials in anode manufacture could reduce the Mg alloy cost by as much as up to 75% of the cost for virgin material, including the costs for the entire sequence of collection and transportation from a molding factory to a refinery, re-melting and composition adjustment.1. IntroductionMagnesium alloys are valuable materials because they exhibit low density, good forming and machining qualities, particular electrochemical properties and have a high recycling potential. There exists a false idea about the high costs of the use of magnesium alloys, partly justified by the lack of secondary materials suppliers and the insufficient knowhow in the diverse user industries to provide for an efficient substitution of conventional magnesium alloys for multipurpose applications. These circumstances have lately spurred the magnesium industry to develop new alloys and coatings and to improve processing techniques [1]. As a result, magnesium supply has greatly expanded and so have the research and development efforts to achieve complete recycling of Mg alloys.In consumer markets, magnesium is frequently selected because it helps reduce enery consumption. For example, an equal volume part made of magnesium is 23% the weight of a steel part and 64% the weight of an aluminium part."

Jan 1, 2008

By Nagahiro Saito, Takahiro Ishizaki, Mituhito Hirota, Akio Fuwa

"Owing to their extremely high toxicity in the environment, the dioxins have been attracting social, technical and scientific attention in recent years. The authors theoretically had predicted the thermodynamic properties of all the dioxins via quantum chemistry and statistical thermodynamics and elucidated the generation-decomposition behavior of dioxins in the equilibrium calculation· of C-H-0-Cl system. In actual combustion processes, it is said that metallic compounds have much influences on the dioxins behavior. The aim of this study is to reveal the roles of metallic compounds the generation-decomposition behavior of dioxins is revealed from the viewpoints of quantum chemistry. Especially, the catalytic effect of copper has been investigated for the reaction, 2HCl(g)--H2(g}+Cl2(g) and for the etherification reaction from precursors, which is Phenol(g) here, to dioxins. The catalytic role of Cu is shown to have much influence on the generation -decomposition of dioxins.1. IntroductionIt is well known that dioxins are very harmful not only for our health but also for that of our children and grandchildren because they are very stable substance and their reaction rates of decomposition are considerably low. On the other hands, it is not well know how dioxins are generated and decomposed; the generation-decomposition conditions and paths as well as the catalysts to decompose them'1l. The authors believe that the thermodynamic and kinetic study of dioxins is useful to find a solution to these issuers. The authors have been investigating the following problems to reveal the generation-decomposition behavior of dioxins; (a) the prediction of the thermodynamic parameters of dioxins (2), (3), (b) the generation -decomposition behavior of non-chlorinated dioxins by the thermodynamic equilibrium calculations in C-H-O system(4) and (c) the generation-decomposition behavior of dioxins by the thermodynamic equilibrium calculations in C-H-O-CI system(5). Summaries of these thermodynamic researches are as follows.(I) The thermodynamic parameters for dioxins, which had been unknown and/or inaccurate'6 l, could be predicted and are available within the scientific accuracy."

Jan 1, 2000

By Masahiro Hirasawa

"As a fundamental study on pyrometallurgical process that involves recycling steel-making dusts, of which major components are oxides of Zn and Fe, and waste polyvinyl chloride simultaneously ·at. a temperature below 1273 K, the reactions between the mixture of ZnO + Fe20 3 and PVC or the compound ZnFez04 and PVC are investigated in a series of thermogravimetric and small scale reactor experiments under inert atmosphere at below 1273 K. The reaction mechanisms are discussed· on the .basis of the thermogravimetric data. From the results of reactor experiments, it is shown that the chlorination of Zn in the oxides by Cl in PVC, the vaporization of ZnC12, the reduction of iron oxide to metal Fe by C and H in PVC, and, thereby, the separation of Zn and Fe in the oxides take place simultaneously at the temperature ~= 1200 K.IntroductionSteelmaking dusts are metallurgical wastes consisting mainly of oxides of Zn and Fe with smaller amounts of other heavy metal elements, such as Pb. In the recent investigation, [1] the present authors have investigated the fundamental aspects of a potential pyrometallurgical process· of recycling steel-making dust with polyvinyl chloride (PVC) at temperature T < 1273 K under Ar atmosphere. The performance of a similar process, in which HCl in the combustion gas of PVC is used to chlorinate Zn in the EAF dust under oxidizing atmosphere, has been investigated by Tailoka and Fray [2] with fundamental experiments. Figure 1 shows an example of the potential ·diagram of Zrt-Cl-0 and Fe-Cl-0 systems. In the figure, we can find two regions where ZnCl2(g) can be separated from Fe containing compounds. One is ZnCiz-Fe20 3 coexistence region at higher oxygen and chlorine potentials and the other is ZnCl2-Fe coexistence region at lower oxygen and chlorine potentials. The process adopted by Fray and coworkers is aimed mainly at the performance of Zn/Fe separation in the higher oxygen potential region. In the present study, the lower oxygen potential region is focused on."

Jan 1, 2000

By Zhang Chuanfu, Tan Pengfu

"A thermodynamic model is developed to simulate nickel flash smelting process. In the nickel flash furnace, oxidation of concentrate occurs at one end, and reduction of slag occurs at the other. The model makes use two zones, namely the reaction shaft/settler zone and the appendage zone and accounts for 6 phases (matte, slag, silica, magnetite, Cu-Ni alloy and gaseous phase), 13 elements (Ni, Co, Cu, Fe, S, 0, N, C, H, Si, Al, Mg and Ca) and 33 chemical components in nickel flash smelting system. The compositions of matte, slag and gaseous phases in equilibrium are calculated by using the data of free energies of formation and activity coefficients of components. Two nickel sulfide species are used to allow for the modeling of sulfur-deficient mattes. The model predictions are compared with the known industrail data from Kalgoorlie Nickel Smelter, and excellent agreement is obtained. The model can be a very useful tool for monitoring and optimizing the actual industrial operations of nickel smelting process. The distribution behaviors of Ni, Co, Cu, Fe, S and 0 in the nickel smelting furnace depend on the process parameters such as smelting temperature, volumes of air, the content of the elements~ charge and oil.1. IntroductionThe nickel flash smelting furnace essentially consists of a reaction shaft where nickel sulfide concentrate is partially oxidized with air, a settle zone where matte and slag are allowed to separate, and a slag cleaning end where coke is added to provide for the reduction of the oxidized nickel from slag, and electrodes are used to provide heat.The theoretical model to consider a mass balance for copper flash furnace is developed by S. Goto and R. Shimpo[1][2J. However, this can not be true for nickel flash furnace as a whole since oxidation of concentrate occurs at one end (in the reaction shaft/settler), and reduction of slag occurs at the other (in the appendage). Despite these limitations, an acceptable pseudo-thermodynamic description of the furnace can be achieved using essentially two zones, namely the reaction shaft/settler zone and the appendage zone. Compositions of gas, slag and matte in two zones are calculated."

Jan 1, 1998

By Takeshi Ohgai, Hisaaki Fukushima, Tetsuya Akiyama, Joon-Seo Ki

"Recently, an intensive attention has been paid to the electrodeposition of Zn-Cr alloy in the field of the production of super-highly corrosion-resistant alloy plated steel sheets for the next generation. In this study the electrodeposition of Zn-Cr alloys from the sulfate baths was conducted to investigate the codeposition mechanism of Cr with Zn. As a result, Cr was codeposited with Zn at higher current densities in both polyethyleneglycol(PEG)-free and PEG- containing baths. However, PEG made it possible to reduce Cr+ to the metallic state and Cr existed in the form of Cr(III) hydroxide in the deposits obtained from PEG-free bath. The measurements of the partial polarization curve of Zn and the pH in the cathode layer revealed that PEG acted as a polarizer to shift the cathode potential to the reduction potential of the composited hydroxides of Zn and Cr formed due to the pH rise in the cathode layer.1. IntroductionRecently, much attention has been paid to the electrodeposition of Zn-Cr alloys because of its application to the production of super-highly corrosion-resistant alloy plated steel sheets for the next generation1Hl_ Some researches have already tried to commercialize this type of steel sheet. High corrosion-resistance of this steel sheet is brought about by codeposited Cr in the alloys. According to Piontelli's classification5l concerned with metal deposition from aqueous solution, Cr belong; to an inert metal and its deposition is associated with a large amount of hydrogen evolution. Therefore the current efficiency for Cr deposition is extremely poor. It has been also reported that Cr is unable to codeposit in the electrodeposited Zn film in the absence of a certain additive in the solution. 0-compounds group colloids7l, ether group organic compounds8), 9>, peptide based compounds10l, etc., have been found to be effective additives to induce the codeposition of Cr with Zn. However, few studies have been made on the codeposition mechanism of Cr with Zn. In this research, the fundamental electrodeposition behavior of Zn-Cr alloys from sulfate baths was investigated to clarify the codeposition mechanism."

Jan 1, 1998

By Lucas Barbosa de Souza Martins, Felipe Perissé Duarte Lopes, Nathalia Carneiro Garcia Rosa, Lucas Lopes da Costa, Sergio Neves Monteiro, Rubén Jesus Sanchez Rodriguez

"The fibers extracted from the stem of the banana plant are relatively stronger and have been used as reinforcement of polymer matrix composites. In addition to quasi-static mechanical properties, there is a need to characterize the dynamic behavior of banana fiber composites subjected to thermal and mechanical constraints. In this work, the temperature variation of the dynamicmechanical parameters of polyester composites incorporated with up 30% in volume of banana fibers were investigated by DMA tests. The storage and loss moduli as well as the tangent delta were measured from 20 to 200°C in a TA Instrument operated with the flexural mode at 1 Hz. The results showed that the incorporation of banana fibers tends to increase the viscoelastic stiffness of the polyester matrix. It was also observed changes in the T g and the structure dumping capacity of the composites with increasing fraction of banana fibers.IntroductionNatural fibers with high amount of cellulose, also known as lignocellulosic fibers, have been used from primeval times by our civilization. In the last century, synthetic fibers such as nylon, carbon, aramid and glass fibers gained interest owing to superior strength and precise dimensional control. Natural fibers were then replaced by synthetics in many fields such as textiles and appliances. In the past decades, however, environmental issues drawn, once again, the attention to lignocellulosic fibers as possible substitute for intensive energy-consuming and long term polluting synthetics, specially the glass fiber [1]. In particular, research works have disclosed the potential advantages associated with the use of lignocellulosic fibers as the reinforcing phase in polymer composites [2-7]. Among the advantages it is worth mentioning the renewability, recyclability, biodegradability and the fact that natural fibers are neutral with respect to C02 emissions responsible for global warming. Moreover, as compared to synthetics, lignocellulosic fibers present lower density and cost as well as reduced wear caused to the processing equipment. On the other hand, in terms of composite reinforcement, hydrophilic lignocellulosic fibers present drawbacks such as weak adhesion to hydrophobic polymeric matrices in addition to dimensional limitations and non-uniform properties."

Jan 1, 2011

By W. E. Wallace, J. A. Warren, D. Josell, D. Wheeler

"We present the results of experiments and modeling of flip-chip geometry solder joint shapes under shear loading. Modeling, using Surface Evolver, included development of techniques that use an applied vector force (normal and shear loading) as input to determine a vector displacement of the pads connected by the solder joint (standoff height and misalignment). Previous solutions solved the converse problem: fixed displacements used to determine required applied force. Such solutions were inconvenient for applications, where the applied force (chip weight) is known. Also, for geometric and materials studies of solder joint shapes involving multiple parameters, determining the equilibrium displacement from applied force by bracketing solutions could become computationally expensive. Measurements of solder joint standoff height and misalignment as functions of the applied force (normal and shear), solder volume and pad diameter are presented. Experiments were carried out for solder ball diameters from 0.38 mm (0.029 mm3 volume) to 0.15 mm (0.0019 mm3 volume) on pads of diameter 0.64 mm and 0.35 mm. Fitting of simulation to experimental results gave optimized values for the contact angle and surface tension of the solder which were consistent with measured and literature values. IntroductionIn packaging technology flip-chip has become an important method for attaching semiconductor devices to substrates. Generally, the chip and substrate are bumped with solder and then the chip is flipped onto the substrate and the solder reflowed to form conductive interconnects. An epoxy underfill is normally flowed between the substrate and chip to reduce the thermal fatigue on the solder joints. A flip-chip assembly is illustrated in Figure 1.In flip-chip applications, the use of an integrated underfill/solder bump system [1, 2) removes an extra process step, namely infiltration of the underfill. However, the presence of an underfill will retard the self-alignment of the flip-chip. A first step in understanding and predicting this retardation is to develop a model to describe normal and lateral force-displacements curves when underfill material is not present. At this stage it is unclear whether static surface tension theory is sufficient to describe a complete model for flip-chip realignment even without underfill."

Jan 1, 2001

By George E. Cook, Peter C. Levick, Francis M. Wells

"Relationships are established between the peak current of a pulsed, rectangular current waveform and the pulse current duty cycle under conditions of constant arc power. By appropriate choice of these interrelated parameters, it is shown that the arc pressure may be varied over a wide range even though the arc power is held constant. The methodology is suggested as a means of countering the effect of gravity in 5-G welding, while maintaining constant heat input to the weld. Combined with appropriate penetration sensors, the methodology is additionally suggested as a means of controlling penetration. IntroductionBoth low frequency pulsation (typically 0.1 - 20 Hz) and high frequency pulsation (> 100 Hz) are often used with GTA welding. Benefits derived from pulsing include improved weld quality and better process control.Advantages cited for low frequency pulsation include claims that the total heat input to the weld is reduced, the weld bead size is reduced, weld penetration is increased, grain size is reduced, porosity is reduced, weld distortion is reduced, thinner materials can be welded successfully, and the tolerance of the welding process to material and production variations is improved (1-16). With respect to the latter, pulsing aids control of weld bead penetration by increasing the tolerance to component dimensions and joint fit-up. It also reduces the sensitivity to disparities in heat sink, and it helps to reduce distortion in thin section material or distortion attributable to poor clamping. In certain materials it can reduce the sensitivity to surface oxides and to cast to cast compositional variations (16). Low frequency pulsation is also useful in welding thick materials mated by a prepared groove. In these applications the low frequency pulsation is used to obtain proper sidewall fusion as the tungsten electrode is weaved from one side of the groove to the other. In this case the weld current pulsation is synchronized with the cross seam weave pattern, such that the high current pulses occur at each sidewall. This type of low frequency pulsation has proven particularly useful in welding with narrow width groove designs (17-21). Finally, Ecer (22) has shown that the pulsed current arc is more stable against magnetic disturbances than an equivalent constant current arc."

Jan 1, 1986

By G. A. Irons, D. Guo

"The average spout height and width produced by bottom gas injection in a water model of a steel ladle were measured with an image processing technique. It was revealed that the spout height could be described by a Gaussian curve. A combined SIMPLE -VOF model was developed to simulate the liquid surface and flow. The results showed that, though the model produced reasonable velocity distributions and free surface positions, the spout height due to the dynamic head of the rising liquid was substantially lower than observed, indicating that the bubble dynamics at the bath surface play an important role in spout height.IntroductionDue to the enormous importance of gas injection and stirring in metallurgical processes, there have been numerous publications on water and numerical modeling of such vessels. The free surface of the bath has received considerably less attention, despite its importance. At the free surface there are often important chemical phenomena occurring that require a good understanding of the fluid flow; these would include reoxidation of steel, metal splash and fume formation. Furthermore, to understand the details of slag-metal interactions such as slag entrainment, metal losses to slag and the transport phenomena associated with refining reactions, it is necessary to understand the plume and spout interactions first.There have been few experimental studies of the free surface of liquid in gas-injected ladles [1- 3], and even fewer on numerical modeling. Brimacombe and co-workers [1] studied the gas void fraction in the spout region, using a double-tip electrical resistance probe. This sensor cannot distinguish between gas in bubbles about to break and gas in the freeboard. Thus, it is a matter of judgement as to the position of the free surface. Schwerdtfeger and co-workers [2] used a single probe configuration with a wire and a counter electrode in the liquid, so that the height of the continuous liquid phase was unambiguously determined. Irons and co-workers [3] measured the spout height by ultrasonic and electrical capacitance techniques. These techniques were as reliable as the resistance techniques, but were restricted to low flow rates."

Jan 1, 2001

By K. A. Lewandowski

Agglomeration of ore can be used to immobilize fine particles during heap leaching by agglomerating them into granules. Without agglomeration, the fine ore particles can migrate within the heap, clogging flow channels and producing large areas where access of solution to the ore is very poor. The benefits of agglomeration are well-known in gold heap leaching operations, which can be effectively agglomerated using binders such as Portland cement due to the alkaline leaching solutions used. However, agglomeration has not been very effective in the heap leaching of copper ores, because these ores require an acidic leaching solution. Acid destroys the effectiveness of most binders, causing the agglomerates to disintegrate as soon as the leaching solution is applied. In order to gain the benefits of agglomeration in copper heap leaching, an economical, acid-resistant binder is needed. The two issues that needed to be addressed were: 1) Lack of effective methods for evaluating binder acid resistance before performing expensive, time-consuming, full-scale heap leaching tests, and 2) The vast majority of known binders react poorly to acid conditions, and so a basis was needed for determining which binders are most likely to be acid-resistant. In this paper, the development of two new tests for evaluating binder acid resistance in the laboratory are described. The ?soak test? determines the degree to which agglomerates disintegrate and release fines on contact with acidic solution, measuring the relative quantities of fines released by agglomerates made with different binders under controlled conditions, and serves as a rapid means for comparing large numbers of binders. The ?percolation test? measures several different parameters to determine how a binder is likely to perform in heap leaching: 1) the degree of ?slump? and compaction of agglomerates as they are wetted by acidic solutions; 2) the hydraulic conductivity of the agglomerate bed; 3) the migration of fines through the bed as the solution flows through it; and 4) the quantity of liquid retained in the agglomerates after they are drained. Using these tests, a broad spectrum of binders were examined. Soak testing determined that the most acid-resistant binders were nonionic polymers. Five of these binders were further evaluated using percolation testing.

Jan 1, 2006

By Wayne Bell, Xiaodi Huang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng

"The equations for determining microwave field attenuation length and half-power depth in magnetic materials were derived from Maxwell’s equations. The microwave field attenuation length and the half-power depth for a magnetite concentrate were calculated and the temperature dependence of them was determined. It is demonstrated the microwave field attenuation length and the half-power depth highly depend on temperature and decrease with increasing temperature up to 900 °C. The variations of field attenuation length and the half-power depth with temperature indicate the microwave power attenuates much faster than the field strength in materials. The evaluations of field attenuation length and microwave half-power depth can be used to characterize the microwave dissipation behaviors in the sample and optimize the dimensions of the material in microwave heating.IntroductionMicrowave has been applied in materials processing for its distinguished advantages including rapid heat transfer, volumetric and selective heating [1,2]. However, most research work involving microwave heating are confined to non-magnetic materials (e.g. ceramics), with limited attention paid to the heating of mixed property materials (e.g. magnetite and other ferrites) under microwave irradiation [3-5]. Since many magnetic materials exhibit good and even better microwave absorption capability than non-magnetic counterparts, it is quite necessary and deserved to take advantage of this property and then improve the heating efficiency. To achieve this aim, further understanding on the microwave heating mechanism, especially the microwave propagation/dissipation behaviors in magnetic materials is required.The dissipation behavior of microwave in materials has been identified as one of the key factors that affect the efficiency of heating under microwave irradiation and this behavior can be characterized by several parameters. Apart from traditional penetration depth (TEM power penetration depth, Dp = 1/(2*a), where a is the TEM field attenuation factor), two other parameters, field attenuation length (Df) and half-power depth (Dh), are also applied to indicate the microwave dissipation in materials [6].The accurate determination of such parameters can help in optimizing the dimensions of the load in a microwave furnace, producing more uniform heating under microwave irradiation and avoiding thermal runaway."

Jan 1, 2011

By Huanyu Zhang, Zhancheng Guo, Liqiang Fan, Huiqing Tang

"In this study, a simple process has been developed for zinc oxide recovery from RHF (rotary hearth furnace) secondary dust. The results have shown that a high dissolution efficiency of soluble zinc was achieved with water leach at ambient temperature with a liquid/solid ratio of 10/1 in 30min while 20% of the dust was left as solid residue. The rate of dissolution increased slowly after the dissolution efficiency reached 90%. The leaching process was found to be controlled by external diffusion. After separation, zinc was precipitated in leached liquor by introducing a precipitation agent of potassium hydroxide. The resulting solid was purified and dried at 393K. Zinc powder in the form of ZnO with purity of 98.5 mass% was obtained with an average size of 12.4µm.IntroductionThe RHF (rotary hearth furnace) direct reduction process is widely used in many iron and steel enterprises to deal with various metallurgical dusts [l]. The basic principle of this process is that first various metallurgical dusts (BF dust, EAF dust and so on) are pelletized with a coal reductant, and they are then subjected to a fast reduction using RHF after being dried. Highly metallic pellets are produced and at the same time, nonferrous elements such as Zn, Pb, K and Na are evaporated into the RHF flu gas as secondary dust. Zinc is listed by the Enviromnental Protection Agency as one of the 129 priority pollutants. Therefore, recovering zinc from the industrial wastes is important in terms of enviromnental protection [2-3]. On the other hand, nowadays China is in shortage of zinc resource and the annual output from metal recycle only accounts for some 13% of the total zinc resource. There are many ways proposed to recover zinc from various wastes [ 4-7]. The aim of this paper is to recover zinc oxide from RHF secondary dust by a method with water leach followed by caustic precipitation. This work investigated the influence of the leaching temperature and leaching liquid/solid ratio on the zinc recovery efficiency. The process consisted of three stages: (1) leaching with water; (2) liquor/residue separation; and (3) zinc precipitation in caustic milieu."

Jan 1, 2014