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By Chi-Ming Chang

Alloy powders are commonly used in the purification of zinc sulfate solutions for use in standard electrowinning practice. The primary goal of this research was to study the use of zinc-lead alloys for similar reactions in the galvanic stripping of impurities from organic solutions. The effects of various parameters on the electrochemical behavior of commercially produced zinc-lead alloy powders were determined. A qualitative evaluation and summary of the influence of the more pertinent parameters on iron removal from di-(2-ethylhexyl) phosphoric acid (D2EHPA) by galvanic stripping is given. Water concentration, oxygen content and reaction temperature were the principal factors affecting the reaction rate and process efficiency. Activation energies were also calculated and indicated that the reaction changes from chemical to diffusion control .with increasing temperature in the range of 35" to 45°C. The results showed that zinc-lead alloy gave faster reaction rates with less sensitivity to process variables than SHG zinc as a reducing agent for galvanic stripping. The role of lead could be as cathodic sites for the reaction which enhances the zinc dissolution or anodic half reaction. The morphology of the zinc-lead alloy surfaces, before and after the reactions, supports this assumption.

Jan 1, 1998

By K. C. Mills, P. N. Quested, A. P. Day, R. F. Brooks

"Methods have been developed to measure the physical properties of molten materials relevant to the fluid flow in high temperature processes. Data for the densities, viscosities and surface tensions of Al-, Ni- and Fe-based alloys are compared with (i) values for the pure metals and (ii) estimated values obtained from models making use of chemical composition of the alloy. Experimental values for metallurgical slags are also given and compared with estimated values.1 IntroductionPhysical property data has proved very useful in improving process control and product quality. For instance, in the continuous casting of steel the viscosity (TJ) of the mould flux is important since it determines (i) the optimum casting conditions, nVc = 2.5±1 dPas (m min-1) where V c is the casting speed and (ii) the level of slag entrapment (which leads to inclusions) in the metal. Thus data for properties like viscosity are exceedingly useful in understanding the process and the problems encountered and the causes of defects and problems.Another interesting development which has helped to increase our knowledge of processes and improve process control and product quality is the development of mathematical models of the fluid and heat flow in the process. These models have been developed to the stage where one of the prime requirements is for good physical property data for the industrial materials involved. Recently, Oxley [1] has shown that the use of reliable, experimental, property values for the commercial alloy in a commercial software package produced a significant improvement in the prediction of casting defects. Thus reliable property data are required for liquid metals but also for (i) liquid slags since many processes involve the use of a slag to refine and protect the metal or to lubricate the mould and (ii) refractories, sand and investment moulds."

Jan 1, 1999

By J. L. Delplancke

During copper electrowinning in sulphate electrolyte, intense oxygen evolution takes place at the anode. Lead alloy anodes are progressively replaced by dimensionally stable anodes in order to avoid the cathode contamination by dissolved lead. The electroactive coating of these anodes has to be as cheap as possible, adherent to the substrate, electrochemically stable and has to be efficient at high current density and high temperature. This requirement is even demanding in case of copper electrodeposition for the production of thin copper foils for the electronic industry. The production of thin (20 µm thick) copper foils for the printed circuit boards requires high purity copper electrodeposited at a current density as high as 7,000 A/m2. The choice of a long term coating composition is driven by economics. The purpose of this paper is mainly to review the anode compositions suitable for copper electrowinning and for copper electrodeposition at high current density. A short description of preliminary results obtained with a new anode coating on a titanium substrate is also presented.

Jan 1, 1999

By David Bequette, Ray D. Peterson, Cynthia K. Belt

"With a need to cut production costs in the metals industry, cost savings from energy efficiency improvements are critical. Opportunities can be found by reviewing furnace systems and practices so that the melting and holding processes operate at the highest energy efficiency. Many of the changes can be implemented with a minimum of expense or capital investment. This paper will review several low cost methods to optimize energy efficiency on reverberatory melting or holding furnaces. These five methods (furnace utilization, idle procedures, fire rate, controls, furnace pressure) will be explained and information given to implement these changes. Included are several rules-of-thumb and benchmarks for aluminum reverb furnaces.IntroductionEnergy can be a significant portion of the total manufacturing costs for metals and materials manufacturing involving thermal processing such as heat treating, melting, and high temperature processing. Natural gas prices have dramatically varied over the last few years. While no one can foresee the future, prices are expected to increase from the current low prices. More recently, emphasis is being put on the reduction of greenhouse gases with the potential of additional costs to industry.One of the first steps in an energy management program is to measure the energy usage of the process [1]. The results are typically understood in relation to the mass melted in kWh / mT [BTU / lb]. For the purposes of this paper, furnace energy efficiency is calculated over a month or even a year and thus includes hold times. This efficiency is typically different from the values quoted by furnace manufacturers. Those values are for limited short term tests at highutilization.Once you know the performance for your furnaces, these should be compared to industry benchmarks. For aluminum melt furnaces with cold air burner systems, a benchmark value or goal is 1800-2000 BTU/lb [1160-1290 kWh/mt], though some of the best have reached 1600 BTU/lb [1030 kWh/mt]. Furnaces with regenerative burners can attain 1100-1200 BTU/lb [710- 775 kWh/mt]. There are some designs of multi-chamber furnaces or oxygen furnaces that have improved on these numbers, perhaps as low as 950 BTU/lb [615 kWh/mt]. Typically, as the degree of sophistication and energy efficiency of the furnace increases, so does the cost."

Jan 1, 2010

By Nobuhiro Kuriyama

Electrochemical activation behavior of an AB2-Laves-phase type hydrogen storage alloy, Zr0,9Ti0.lNi1.lCo0.1Mn0.6V0.2 was studied to make clear activation process of pellet-type metal hydride electrodes. An alkaline treatment of the electrodes with heated alkaline solution gave alloy surface enriched with nickel, and the treated electrode was more easily activated. The treated electrode desorbed more hydrogen during the first charge-discharge cycle, and was activated without induction period. A cross sectional view of the activated electrode showed finer pulverization of alloy particles than the annealed alloy, and impedance spectroscopy indicated larger surface area of the electrode using the as-cast alloy. Since the as-cast alloy contains inhomogeneities, multi-phase microstructure and stress in the particle, the finer pulverization of alloy particles with hydrogenation are considered to increase surface area in an earlier cycle in the case of the as-cast alloy, which leads larger reaction area and faster activation of the as-cast alloy electrode.

Jan 1, 2002

By Cailing Zhen, Jian Pan, Deqing Zhu, Xianlin Zhou, Yanhong Luo, Guixiang Huang

The grate-kiln process has been widely applied for oxide pellet production with the quick development of steel industry in China, but ring formation takes place which adversely affects the productivity and properties of fired pellets. Rotary kiln at high temperature seems a black box, and ring formation is difficult to measure directly by current technology. It’s of great importance to monitor ring formation during firing of pellets. Therefore, a method for estimating the thickness of ring formation in rotary kilns was studied, based on working out theoretically the relationship between ring thickness and the outside surface of the kiln, according to steady-state heat transfer across a cylinder, which provides a soft-sensing technique for ring formation at high temperature, and achieves stable pellet production .

Jan 1, 2015

By Carlos A. Ferreira, Betina Hansen, Marco A. S. Rodrigues, Marcela P. Proença

"Nowadays, the concern with the reduction of industrial pollution has motivated researchers to found out new technologies for treatment of industrial waste. The clean technologies, as electrodialysis, are capable of treating these residues, minimizing the impacts when they are discarded directly on the environment. Membranes of SPS/HIPS, PAniCSA/SPS/HIPS, SPAN/SPS/HIPS were developed using chemical mixture method. Membranes were characterized by Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA) and Scanning Electronic Microscopy (SEM). Membranes were submitted to electrical polarization and to electrodialysis at NaCl and KCl solutions, in order to determine ionic transport through the membranes. Results were compared with commercial membranes. The average percent extraction for Na+ ions obtained by membrane was beyond 20%.IntroductionThe high environmental impact caused by the galvanoplastic industries represents today a world concern(1). In the galvanoplasty, thin metallic layers are deposited on metallic surfaces(2) through chemical methods or electrochemical process. This industrial process presents some disadvantages that limit its utilization, as the generation of toxic effluents containing concentrations of heavy metals usually above the limits allowed for his release in receiving bodies(1), the production of galvanic sludge which is considered hazardous waste and that is very difficult to treat, beyond the high consumption of water (3).Stimulated by the development of new ion-exchanged membranes with high selectivity, lower electrical resistance, and improved thermal, chemical and mechanical properties, the use of electrodialysis in the wastewater treatment has recently gained a broader interest(5). The electrodialysis (ED) is a mass separation process in which electrically charged membranes and an electrical potential difference are used to separate ionic species from an aqueous solution(5). The technique permits the recovery and the reutilization of the waste products from the industrial process, avoiding the discharge of them on the environmental (acting as clean technology)."

Jan 1, 2008

By E. A. Thiers

The causes of structural changes in the markets for high technology alloying metals are discussed in terms of technological, economic, and financial trends. Recent market imbalances have affected producers in developed and developing countries differently. Possible response strategies for suppliers in the two types of countries are examined that may alleviate future market imbalances.

Jan 1, 1988

By Wei-ling Wang, Ryosuke O. Suzuki, Xiang-ning Meng, Miao-yong Zhu

"A finite-element thermal-stress model of continuous casting mold is conducted to predict deformation of copper plates and its change with different cooling structure. The results show that deformation behavior of copper plates is mainly governed by cooling structure and thermal- mechanical conditions, deformation amount is related to structure geometry, and a small deformation mutation occurs in cooper-nickel boundary due to different properties. The maximum deformation of hot surface centricities of wide face locate at 100 mm below meniscus and that of narrow face locate at meniscus and terminal of water slots and significant curvature fluctuations on both sides of copper-nickel boundary. The maximum deformation of centricities is increased up to 0.05 mm with thickness increment 5 mm of copper plates, and maximum deformations are only depressed 0.01 mm and 0.02 mm with increments of 1 mm nickel layer thickness and 2 mm water slot depth respectively.IntroductionIn conventional continuous casting of steel, a large amount of sensible and latent heat of molten steel dissipate in primary cooling zone and make continuous casting mold under enormous heating load giving rise to thermal stress, deformation, high-temperature fatigue and creep not only depress mold life-span, but reduce casting stability [1] Many studies focused more on heat transfer, solidification and shrinkage of solidifying shell to provide inverse proposals for optimizing cooling system and even designing new taper of mold [2,3], but it is generally useless to those of having been manufactured or being put into production. Therefore, mold-related forward problems show necessity to be discussed deeply, and stress and deformation distributions based on special thermal conditions in mold should be analyzed in order to explore suitable cooling structure of mold directly. Samarasekera et al. [4] examined heat flow and distortion of two-dimensional longitudinal sections and investigated effect of cooling water velocity, copper plates thickness and carbon content on formation of rhomboidity and longitudinal comer cracks. O'Connor et al. [5] developed a three-dimensional mathematical model to compute thermo-mechanical state in thin-slab mold and calculated temperature and deformation of mold wall to assess roles of various process parameters on impacting mold life. Thomas et al. [6] predicted temperature, distortion and residual stress in mold and indicated increased distortion requires increased remachining, which reduces mold life and increased residual stress increases the probability of a catastrophic crack failure. Park et al. [7l determined heat-flux profiles in funnel-shaped and parallel thin-slab molds based on an inverse heat conduction model and thermocouple temperature measured in-plant and put them into three- dimensional finite-element thermal-stress model to predict temperature, distortion and residual stress of mold wall. Korie et al. [SJ focused on prediction of temperature, distortion and residual stress in mold and in particular to clarify that mold life is significantly affected by temperature and its rigidity, but little effect by mechanical including clamping force, bolt prestress, friction and ferrostatic pressure. Meng et al. [9l predicted temperature and thermal stress in a slab mold and analyzed effect by cooling system geometry and casting speed quantitatively. In present study, a three-dimensional finite-element thermo-mechanical model with type-switched element is transformed from previous heat-transfer finite-element model [9l, and mold deformation is simulated in order to shed light on thermo-mechanical behavior with special thermal conditions and different mold geometry at high casting speed."

Jan 1, 2013

By Guo Chen, Jin Chen, Jinhui Peng

In this paper, solving common problem of electrostatic precipitator (ESP), which was frequently ruptured of the cathode insulation in the production process were studied. The microwave heating airflow technology was introduced, which takes full advantage of its unique properties, solves the output problem of the high temperature air, achieves purpose of energy conservation, important economic significance and environmental significance. The mathematical models and designing of microwave high-temperature hot air system was calculated. The common forms of heat exchangers and comparative analysis were also introduced. The conditions found to be at the temperature of 240 °C. Under optimum conditions, the microwave heating power was 1482 W. Based on the mention results, this microwave heating method can be applied effectively and efficiently way for the production process of electrostatic precipitator.

Jan 1, 2015

By Kenji Morinaga, Hiromichi Takebe

"Ge-S binary glasses in the range 57 to 90 at %S at 0.5 to 3 at %S intervals were prepared by a conventional melting technique using fused quartz ampoules as melting containers. Impurities contaminated during preparation process are evaluated by IR spectroscopy. The causes of impurity contaminations are discussed. Density data in a systematic series of Ge-S glasses is demonstrated. IntroductionSulfide glasses are of particular interest for new laser and nonlinear optical materials in the near-infrared and infrared regions [1]. Sulfide glasses have the features of low-phonon-energy and high refractive index with moderate rare-earth ion solubility. The low-phonon-energy is favorable for the reduction of nonradiative rate for the emission of rare-earth ions. The high refractive index results in a high radiative-rate and in a high third-order nonlinearity. However, impurities may degrade the superior optical properties of sulfide glasses.In this work Ge-S glasses were prepared by a conventional melting technique. Impurities contaminated during the preparation process are evaluated and their causes are discussed for future improvements. The measured densities of Ge-S glass samples were compared with the results of previous studies [2], [3]. Ge-S glasses have some favorable properties for practical .applications including non-toxicity, good thermal and chemical stabilities."

Jan 1, 2000

By Jewel A. G. Gomes

Lead has long been an USEPA priority pollutant and an important environmental and health concern because of its toxicity at ppb levels. In light of health and exposure data for lead, the EPA has set standards for Maximum Contaminant Level (MCL) and a MCL Goal (MCLG) as 15 ppb and 0 ppb, respectively. An accurate and rapid measurement of lead in the field remains a technical challenge. In this work, a relatively new method of deploying a nanoband electrode system using anodic stripping voltammetry has been optimized by changing deposition potential, electrolyte, and plating time used for the measurement of Pb(II) in water samples. Green rust has been proven to be an efficient intermediate matrix for removal of lead contaminants. We also report here the removal efficiency of lead using green rust produced by electrocoagulation, both directly and indirectly. Lead containing floc was also characterized through XRD, SEM, and EDAX techniques.

Jan 1, 2008

By Julie M. Melluish

The metallurgical response of the Point Leamington deposit has been studied. Two series of bench tests were conducted and various ore samples and flotation products were examined using image analysis techniques. The majority of sphalerite and chalcopyrite grains in this texturally complex ore were found to be smaller than 10 micrometres. Copper recoveries were low with losses mainly as fine inclusions in pyrite. Sphalerite recoveries were somewhat better due to a generally coarser habit. Gold and silver recoveries were also low and only solid solution silver was identified in the ore. The deposit shows poor economic prospects unless additional tonnage of high grade zinc ore can be delineated.

Jan 1, 1989

By Hideyuki Takahashi, Taro Aichi, Kazuyuki Tohji, Makoto Muramatsu, Rie Sato

"There are several ways to condition lead-based alloy anodes for zinc electrowinning: electrochemical treatment, chemical treatment and physical treatment. Two advantages of physical treatments are their productivity and variety. In this report, physical treatments, including blasting with silica, alumina, steel grit and cut zinc wire, were tested. The laboratory tests confirmed there were differences in the formation of anode scales during electrowinning and in the suppression of lead dissolution from the anodes. With an increase in the surface roughness, the misfit between the PbC""2 and the MnC>2 was mitigated and the anchor effect was promoted; these effects resulted in dense Mn oxide scales on the anode.IntroductionZinc is widely used for hot-dip zinc plating and for die casting alloys. As a supplier of materials, we have endeavored to produce zinc that is economical and contains as little impurity as possible. As a result of our efforts, a technology for consistently providing special high-grade (SHG) zinc has been established. However, as seen in the issuance of the Restriction of Hazardous Substances (RoHS) Directive, public awareness of the industrial impact of heavy metals on the environment has been heightened. Increasing efforts to control environmentally sensitive substances will be necessary for our production processes.Electrolytic SHG zinc is produced by electrodeposition in an acidic solution with a Pb-Ag or Pb-Ag-Ca alloy for the anode and an Al alloy for the cathode. Pb alloy anodes are widely used because of their excellent durability; however, they are a source of Pb, which is the main impurity of the product."

Jan 1, 2012

By Shun Fujieda, Shigeru Suzuki, Kozo Shinoda, Tetsuo Fujita

"Dowa's scorodite, synthesized by oxidation of Fe(II) ions in the presence of As(V) ions at atmospheric pressure, was characterized. The scorodite was well crystallized and had a very low solubility. To examine the conditions for stable storage of the scorodite for long periods, experiments with various synthesis and leaching conditions were done. The scorodite had a very low arsenic solubility in sea water. It was estimated in consecutive leaching tests that the arsenic concentration would eventually converge to zero. The prevention of arsenic leaching by adding goethite or ferrihydrite was limited in some cases. Very low toxicity was confirmed by toxicity tests. The investigation results suggest that disposal at a specifically designed well-controlled storage place is preferable for the scorodite whose toxicity had been made sufficiently low. Disposal to an isolated final disposal site with more stringent prevention for the outflow of toxic substances was thought another option.IntroductionArsenic is a considerable environmental concern. A system of technologies for the effective immobilization, storage and final disposal has been sought. Dowa Metals & Mining Co. Ltd. has developed a unique scorodite synthesis method (DMSP®) which works at ambient pressure [1]. The scorodite is precipitated by oxidizing Fe(II) ions in a high-concentration As(V) solution. The scorodite produced in this way does not readily release arsenic because of its high crystallinity. Final disposal is necessary because scorodite currently has no commercial value. A standard method for the final disposal of scorodite has not been established because its long-term stability under various conditions has not been fully examined."

Jan 1, 2012

By Entov Vladimir M., Gilmer R. Burgos, Andreas N. Alexandrou

"Processing of metal alloys in their mushy state represents a new trend in metal processing. As part of this process, known also as thixocasting, a specially prepared slurry at a temperature in the mushy region is injected into a die. Parts produced using this technology offer better mechanical properties than those produced by casting, and comparable to those of forged alloys.In thixocasting, semisolid slurries are highly concentrated suspensions of rounded rosette-like crystals in eutectic liquid. The mechanical behavior of the slurry is determined by the structure and properties of the skeleton formed by the alpha phase particles. The skeleton structure is almost never at equilibrium, and its evolution is, governed by a number of kinetic phenomena of different c11'aracteristic time-scales. Therefore, the skeleton structure depends on the mechanical and thermal history of the material. As a result of these kinetic processes, the rheological properties of the material, such as effective viscosity and yield stress, decrease with structure breakdown, and increase with its development. In the present investigation, the behavior of semisolid slurries during processing is modeled using the conservation equations, and a Herschel-Bulkley fluid model. The rheological parameters are assumed to be functions of the solid volume fraction, and of a structural parameter that changes with processing history. The evolution of the structural parameter is described by a first order kinetic differential equation that relates the rate of build-up and break-down of the solid"

Jan 1, 2000

By Tom McCullough

The purpose of this paper is to discuss the implementation and results derived from installing oxy-fuel burners in a l80 ton copper reverbatory melting furnace. Specific results will be discussed in the areas of melt chemistry, furnace modifications, productivity, process enhancements, and the combustion system capabilities.

Jan 1, 1996

By Xuyang Liu, Xuewei Lv, Chenguang Bai, Meilong Hu

"The electro-deoxidation process for ilmenite concentrate in molten salt was studied by cyclic voltammetry and AC impedance spectroscopy. The results from cyclic voltammetry are consistent with those of AC impedance spectroscopy. The results showed that the electro-deoxidation process for ilmenite concentrate consists of two steps. In the first step, Fe is reduced from the ilmenite concentrate. The second reaction is the decomposition of TiCh. CaTiCh is an intermediate product. At low voltage, the electrochemical reaction is the main step. With the increasing potential, the diffusion of ion is the main rate controlling step for the electro-deoxidation of FeTiO3.IntroductionTitania and titanium-rich products are mainly prepared from ilmenite concentrates (FeTi03), which contain about 40%-60% T1O2 after ore dressing and other physical or chemical processes [1]. At present, the main methods to prepare titania are the sulfuric acid process and the chloride process, but the sulfuric acid process consumes a large amount of sulfuric acid and the materials requirements for the chloride process are strict [2], Since the Electro-Deoxidization in Molten Salt (FFC) method was put forward in 2000, many researchers have successfully extracted the metal and alloys by this method, such as Ti, Cr, Tb, Si, Al-Si, TiV, FeTi, etc. [3-7], FeTi alloy is a typical hydrogen storage material, and because of its favorable properties, the preparation of FeTi alloy has become a hot research topic [7-9]. However, the mechanism of electro-deoxidization has not been studied thoroughly [10-11]. Therefore, in this study, the electro-deoxidation process for titanium concentrate was investigated by electrochemical methods, and the study makes a contribution to improving the current efficiency of the electrolysis."

Jan 1, 2012

By Yanping Xiao

In submerged-arc furnace (SAF) for smelting chromite ores into ferrochrome, there exist large temperature gradients and wide distributions of mineralogy and compositions in the furnace, due to the complexity of feed structure and electrical-thermal-chemical interactions. This leads to various zones in the furnace and thus different reaction mechanisms. In the present paper, the behaviour of chromium in the submerged arc furnace is discussed in various reaction zones, including solid state chromite reduction in the packed bed zone, chromite dissolution and reactions in the smelting and coke bed zone, and recovering chromium from slag to metal. In the gas-solid reaction zone, the reaction mechanism is discussed based on the experimental observations and analysis. In the smelting zone, the behaviour of partially reduced chromite and slag formation are analyzed based on the information in literature. The slag in FeCr process contains mainly Al2O3, MgO, SiO2, CaO and CrOx, featured by chromium with both divalent and trivalent oxidation state, which plays an important role for chromium recovery into metal. The factors influencing the slag and metal interfacial reactions and the chromium recovery are addressed.

Jan 1, 2006

By W. Gong

Their outstanding thermal stability and high energy product make Sm(Co,Fe,Cu,Zr),-type alloys attractive for advanced applications. The near net-shape production of Sm(Co,Fe,Cu,Zr), bonded magnets make them potentially superior to any magnets made by sintering. Although pioneering work done by Shimoda et al. and other investigators provide insights on the proper compositions and process control of this alloy system, additional work is still necessary to improve our understanding of alloy behavior at various processing stages and to increase the production yield during powder processing. In this paper we report on the development of anisotropic Sm(Co,Fe,Cu,Zr), alloy powders for the bonded magnet application. Our focus is on the development of a moderate coercivity powder requiring a relatively low magnetizing field to charge the magnets to their optimum Br, Hci and BHmax. The magnetic properties are related to the evolution of the microstructure at various processing stages and the average particle size and size distribution of powders.

Jan 1, 1997