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By Jonkion M. Font

As a comprehensive contribution to the understanding of oxygen-blowing of matte smelting, the copper and nickel solubilities between the FeOx SiO2-MgO slag with saturated SiO2 and the Cu2S-Ni3S2 FeS matte with the NCu/(NcU+NNi) of 1, 0.75, 0.5, 0.25 and 0, in a MgO crucible were investigated at 1573 K under controlled partial pressures of SO2 at 0.1, 0.5 and 1 atm. The partial pressures of SO2, S2 and O2 were controlled by using an Ar-SO2-S2 gas mixture after passing through a sulfur reservoir. It was clarified that, at a given matte grade, the solubility of copper in the slag was independent of pso2 while that of nickel increased with increasing pso2. This notable difference was considered to be ascribable to the chemical formulas of the mono-metallic sulfides in which one copper atom combines with ½ sulfur atom while one nickel atom combines with 2/3 sulfur atom. It was also clarified that, at a given iron content in the matte, the pot and ps2 were independent of the matte species. This was ascribable to aFeS in the matte, which was independent of the matte composition, Ncu/(Ncu+NNi), at a given iron content in the matte.

Jan 1, 1999

By J. D. Budai, D. H. Lowndes, D. P. Norton, D. K. Christen, B. C. Chakoumakos, J. R. Thompson, B. C. Sales

"Artificially-layered structures, consisting of (Sr,Ba,Ca)CuO2 layers in the tetragonal, ""infinite layer"" crystal structure, have been grown by pulsed-laser deposition. Superlattice chemical modulation is observed for structures with SrCuO2 and (Sr,Ca)CuO2 layers as thin as a single unit cell (~3.4 Å). In addition, novel thin film superconductors were formed by using the constraint of epitaxy to stabilize SrCuO2/BaCuO2 superlattices in the infinite layer structure. Using this approach, two new structural families, Ba2Srn-1CUn+l O2n+2+ d) and Ba4Srn-1CUn+3O2n+6+ d, have been synthesized which superconduct at temperatures as high as 70 K. These results represent not only the synthesis of new structural families of superconductors, but also demonstrate that pulsed-laser deposition and epitaxial stabilization can be effectively used to engineer artificially-layered thin-film materials.Advances in the understanding of epitaxial thin-film growth of the cuprates have heightened interest in creating artificially layered superconductors.(1-3) The layered structure of the copper oxide superconductors opens the possibility of forming novel materials by carefully controlling the epitaxial growth of sub-units of the crystal structures. Thin-film growth methods offer unique opportunities for the atomic engineering of new high-temperature superconducting (HTSc) materials through the ability to form artificially layered crystal structures.(4,S) Moreover, the surfaces of single-crystal substrates provide an ""atomic template"" that can be used to stabilize epitaxial films in metastable crystal structures.An important development in forming new HTSc compounds by artificially-layered epitaxy has been the epitaxial growth of (Sr,Ca)CuO2 films in the so-called infinite layer structure.(6-17) This material, which can be considered the parent compound of all of the copper oxide superconductors, has a relatively simple, layered structure consisting of CUO2 planes separated by planes of alkaline earth elements.(18) Bulk synthesis of (Sr,Ca)CuO2 with the tetragonal, infinite layer structure generally requires the use of high pressure and high temperature bulk processing techniques.(19-24) However, recent experiments show that this metastable compound can be epitaxially stabilized at less than atmospheric pressure, resulting in the growth of tetragonal (Sr,Ca)CuO2 single crystal thin films of the infinite layer defect perovskite structure by pulsed-laser deposition (PLD) over a wide range of growth conditions.(6-17)"

Jan 1, 1994

By Kim Verbeken, Evelien Van de Steene, Marc Verhaege, Jeriffa De Clercq

"AbstractThe industry is confronted with stricter discharge levels and an increasing awareness to avoid toxic waste (such as heavy metal containing sludge obtained in physicochemical water treatment) and recover valuable metals. This can be realized by ion exchange or by electrodeposition. Both techniques however show an optimum concentration range to efficiently remove and/or recover metals: electrolysis can recover the metal in its metallic form but suffers from low efficiency when applied to diluted solutions, whereas ion exchange can only be applied economically in the low ppm range.A combination of ion exchange followed by electrodeposition was applied to an industrial wastewater. The strong acidic ion exchange resin was stripped with H2SO4 giving a solution of 9g/L nickel. From this solution, nickel was electrodeposited in an ammonia buffer on a Ti-mesh cathode with high current efficiency. It is shown that organic compounds (surfactants, brighteners, …) present in the industrial wastewater do not influence the recovery process.IntroductionAlmost all rinse waters emerging from metal plating plants are generated during the washing operation of plated materials. These solutions with low metal content must either be recycled within the process or be discarded to the surface water after decreasing their metal content to acceptable levels determined by the local environmental regulations, which become more and more stringent. Today, the most commonly used practice is a physico-chemical treatment (precipitation) and a resin post treatment to meet the standards. A more sustainable approach should use a technology to recover efficiently the metal or metal salt without the production of sludge and the effluent should be consistent with environmental regulations."

Jan 1, 2008

By Fabiola Alvarez, Ana E. Bote, Daniel Pasquevich

"The oxidation of aluminum and its alloys was extensively studied for improving the corrosion resistance in structural materials having high specific strengths. But this reaction involves the formation of a very thin barrier layer on the metallic pieces. Furthermore, the ·recent development of the directed melt oxidation process for producing metal-ceramic; composites has renewed the interest in the study of interaction between gases and metals. Oxidation experiments in the presence of different chlorine partial pressures and at different temperatures were performed in ·a thermogravimetric balance, and microstructures were analyzed by electronic microscopy and X-ray diffraction. The oxy-chlorination kinetics was determined and the oxide formed W(IS amorphous at temperatures below 600 °C and crystalline .at higher temperatures. The appropriate experimental conditions for the fastest completed oxidation was further determined.IntroductionThe use of fine powders for the manufacture of ceramic components has significant advantages. They include excellent sinterability; low sintering temperature and better microstructure leading to improved mechanical properties. The conventional method of producing fine oxide powders involves controlled precipitation and pirolysis of suitable salts. The main limitation of the high temperature decomposition route is the evolution of environmentally unacceptable and corrosive gases. Controlled precipitation of hydroxides from solutions of salts, followed by thermal treatment involves large volumes of solutions and the calcination step that can induce grain growth (1).Direct oxidation of aluminum metal for producing alumina powder requires high temperatures for the direct oxidation of molten Al alloys by a vapor phase oxidant process (2, 3) or high technological process like thermal plasma reactor ( 4).Oxidation of high purity aluminum (5, 6) below the melting temperature· is initially characterized by a nearly linear reaction rate, followed by a rate which decreases rapidly with further weight gain. However, the oxidation rate of an aluminummagnesium alloy is much faster and it does not conform to any common oxidation law, but it is nearly parabolic at temperatures between 200 and 400 °C, an nearly linear· above 400 °C."

Jan 1, 2000

By Mikiya Tanaka, Mikio Kobayashi, Kazuya Koyama, Yoshihiro Nishisu

Preparation of multicomponent powders are very useful and important for producing the materials with complicated and homogeneous structure. Therefore multicomponent powders have a lot of attention in the field of advanced value-added materials. The aqueous processing in hydrometallurgy has a broad potential for producing multicomponent homogeneous precipitates. Furthermore the aqueous processing has a future potential for integrating the separation, precipitation and synthesis processes. In this presentation the precipitation from homogeneous solution including rare-earths and/or common metals is presented. These precipitates probably consist of almost monodispersed, multicomponent and spherical particles by precisely controlling several reaction factors, reaction temperature, concentrations of starting materials, pH and so on. The separation of the nucleation stage and the growth stage of the particles is very important and how to control the reaction factors to realize enough separation is discussed. In this presentation the systems of Y-Eu-0, Y-Fe-0 and Y-Al-0 are mainly presented. In addition the precipitation-stripping method from organic phase is presented focusing the synthesis of multicomponent powders of Ni-La-0 system. These precipitates have multicomponents homogeneously and so they are converted to multicomponent ceramic powders by calcination. They are important compounds as phosphor, opto-magnetic materials, optical materials, hydrogen storage alloy or as the related precursors. In this presentation some characterization of these particulate materials is included.

Jan 1, 1998

By Phillip B. Messersmith, Emmanuel P. Giannelis

"A versatile in-situ polymerization approach is described for the synthesis of polymerceramic nanocomposites consisting of two-dimensional layers of mica-type silicate (MTS) within polymer matrices. Functionalized, organically modified mica-type silicates (OMTS) were used to promote delamination/dispersion of the host layers and initiate polymerization of organic rrionomer. Epoxy nanocomposites prepared in this manner exhibit substantial modulus reinforcement at low silicate loadings. The water vapor permeability of the poly(?-caprolactone) nanocomposite containing 4.8% silicate by volume was reduced by nearly an order of magnitude compared to pure poly (?-caprolactone).IntroductionPolymer matrix nanocomposites are a relatively new class of materials with dimensions typically in the range of 1-100 nm.1 In general, because of the ultrafine phase dimensions involved, nanocomposites exhibit new and improved properties when compared to their micro- or macrocomposite counterparts. We as well as others are currently investigating the design, synthesis and characterization of polymer-ceramic nanocomposites. Our effort, in particular, has focused on the use of mica-type silicates (MTS) with various thermoplastic and thermosetting matrices.2-5MTS's belong to the general family of 2: 1 layered silicates. Their crystal structure consists of layers of two silica tetrahedral sheets fused to an edge-shared octahedral sheet of either aluminum or magnesium hydroxide. Stacking of the layers leads to a regular van der Waals gap or interlayer.6 Isomorphic substitution within the layers generates negative charges that are counterbalanced by cations residing in the interlayers. Although the natural forms of MTS's usually contain hydrated Na+ or K+ ions, ion exchange reactions with organic cations (e.g. alkylammonium ions) can render the normally hydrophilic MTS's organophilic."

Jan 1, 1994

By R. W. Charles

The Los Alamos National Laboratory, under the sponsorship of the U.S. Department of Energy; is involved with laboratory and field experiments to assist in development of the Hot Dry Rock concept of geothermal energy. The field program consists of experiments in which hot rock of low permeability is hydraulically fractured between two wellbores. Water is circulated from one well to the other through the fractured hot rock. Our field experiments are designed to test reservoir engineering parameters such as heat-extraction rates, water-loss rates, flow characteristics including impedance and buoyancy, seismic activity, and fluid chemistry. Laboratory experiments were designed to provide information on the mineral-water reactivity encountered during the field program. Two experimental circulation systems tested the rates of dissolution and alteration during dynamic flow. SOlubil ity of rock in agitated systems was studied. Moreover, pure minerals, samples of the granodiorite from the actual reservoir, and Tijeras Canyon granite have been reacted with distilled water and various solutions of NaCl, NaOH, and Na.CO.. The results of these experimental systems are compared to the observations made in field experiments done within the hot dry rock reservoir at a depth of approxi-mately 3 km where the initial rock temperature was 150 to 200°C.

Jan 1, 1981

By M. Nilmani, J. Sofra

The transverse distributions of the solids discharge velocity and mass flux at the discharge end of vertical and inclined lances were measured in order to detennine the transverse distributions of the axial momentum flux, which is a dominant factor influencing the penetration behaviour of particles into melts during submerged injection. The effects of gas velocity (10 - 30 m/s), solids loading (5 - 10), lance length (0.15 - 1.0 m), lance inclination (vertical downward - horizontal) and particle density (2500 - 8900 kg/m3 ) were investigated, while the lance diameter and particle size were fixed at 10 mm and 220 µm respectively. The particle velocities and mass fluxes were measured by image analysis of particles illuminated in a laser-generated light sheet aligned vertically through the axis of the lance at the discharge point. The particle discharge velocity profiles for vertical downward flows were synunetrical about the centre-line of the lance, with the maximum velocities occurring at the centre-line. The velocities increased with increasing gas velocity, increasing lance length and decreasing particle density in accordance with previous observations. The transverse mass flux profiles were also synunetrical for vertical downward flows, however at the lower gas velocities the peaks in the profiles were displaced from the centre-line of the lance by a fractional diameter of about 0.15. The particle discharge velocity profiles become increasingly asynunetric as the lance orientation was changed from vertical to horizontal, with higher particle velocities present near the top wall of the lance. The mass flux profile also became asyrrunetric as the horizontal orientation was approached, however in this case, the profile became biased towards the bottom of the lance. The effect was much more pronounced for a gas velocity of 10 m/s than for 30 m/s, showing the relatively stronger gravitational influence as the velocity was reduced.

Jan 1, 1996

By Chen Song

Cobalt basic carbonate particles were precipitated from 1.0mol cobalt nitrate or cobalt sulfate solution with ammonia carbonate. By controlling the zeta-potential of the particles and the ionic strength of the solution, the uniform particles with ellipsoid or rod shapes were obtained. During the precipitation process, the interface tension was diminished to the minimum and therefore the Ostwald ripening and secondary nucleation were both inhibited. The morphology and the size control by zeta-potential seem to be the result of thermodynamics rather than classical crystalline kinetics. The particle sizes were in the range of 0.4-0.6, 0.3-0.4 micrometer. After thermolysis, the spinel-type C0304 particles were produced. The morphologies of C0304 particles were similar to that of their precursors.

Jan 1, 2003

By Jilai Xue, Jun Zhu, Baisong Li

"TiB2-C/C Function Gradient Materials (FGM) is used in cathode materials to improve aluminum wettability and melt penetration in aluminum electrolysis. In this investigation, FGM was tested for use as part of the cathode materials, where a 10 mm thick TiB2-rich layer was on the top as an Al-wettable surface, the TiB2-C layers in the middle as a gradient layer and the carbon on the bottom as a base. Electrical resistances ofFGM were determined in the temperature range of25- 9600C in argon atmosphere. The results show that the present of TiB2-C gradient layer can reduce the open porosity and the electrical resistance of the cathodes materials at elevated temperatures. The cathode samples after aluminum electrolysis usually demonstrates an increase in electrical resistance, but the application of FGM layer can compensate such an increase for certain extend due to less variation in porosity and lower the level of melts penetration.IntroductionCarbon is still used for aluminum reduction cathodes dominantly, but it has a poor wetting properties by liquid aluminum and the anode-cathode distance has to be kept about 4-5cm with an additional 1.3-2.0 V voltage drop [l]. TiB2 has better wettability by liquid aluminum with higher electrical conductivity and stronger chemical resistance to the electrolyte attack. And the wettability ofTiB2-C composites cathode on liquid aluminum can be also improved, while liquid aluminum can completely wet the cathode surface ifTiB2 content exceeds 27% [2-4]. However, during the process of TiB2-C composites cathodes preparation and aluminum electrolysis, the deformation by temperature variation or sodium penetration are great disparity between TiB2 and carbon due to their physical properties difference. This will accelerate the cathodes cracking and deterioration."

Jan 1, 2013

By A. V. Tarasov, V. M. Paretsky

"A mathematical model of the low-temperature (soft) nickel oxide reduction (SNOR) in a tubular kiln has been developed including an equation describing changes in the nickel oxide content of the solid material along the length of the kiln; an equation describing the changes in the content of reagents ensuring nickel reduction (i.e., hydrogen and carbon monoxide) in the gas phase along the kiln length; as well as the temperature along the kiln length. The kinetic relationships used for the development of the model had been determined based on experiments conducted specially for this purpose. Model investigations were conducted to determine the distribution of such parameters along the length of the kiln as the contents of metals oxides in the solids, partial pressure of hydrogen and carbon monoxide, variations of the temperature depending on the SNOR process conditions, including the kiln rotation speed. Based on the data obtained, a simplified regression model of the reducing roasting process was developed.IntroductionAt the SeveroNickel complex (Russia) a technology has been developed and is being introduced on a commercial scale for low-temperature (soft) nickel oxide reduction (SNOR) in tubular kilns.The SNOR process has a number of advantages, the main of which are the higher degree of metallization and higher chemical activity of reduced nickel oxide attributable to the lower fusion of the surface of the grains of reduced material due to lower process temperature (800-1000°C) and improved reducing ability of the gaseous phase. However, the fact that the process is conducted in a gaseous phase sets higher requirements to the consistency of its composition necessitating careful continuous monitoring and control of the main process parameters."

Jan 1, 2001

By Qingwei Qin, Ping Xue, Guangqiang Li

Ausmelt furnace slag contains about 0.9% Cu (mass %). With increasing the amount of Ausmelt furnace slag, the recovery of copper from it will produce an enormous economic yield. The recovery of copper by floatation from slow cooled Ausmelt furnace slag was studied in this paper. The phases and composition of the slow cooled slag were analyzed. The factors which affected the copper recovery efficiency such as grinding fineness, pH value of flotation medium, different collectors and floating process were investigated. It was shown that the size distribution of the primary grinding and secondary grinding of middling were 75% for particles less than 0.074mm and 82% for particles less than 0.043mm respectively. The closedcircuit experimental results with butyl xanthate as collector in laboratory showed that the copper grade reached 16.11% and the recovery rate of copper reached 69.90% and the copper grade of tailings was only 0.2%.

Jan 1, 2015

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 Shuqiang Guo, Xionggang Lu, Yuyang Bian, Weizhong Ding, Lan Jiang, Kai Tang, Changyuan Lu

For recovery of rare earth elements from the NdFeB based permanent magnet scraps, a high temperature process was used. Permanent magnets scraps were firstly oxidized in air. The optimal oxidation conditions under air are at temperature of 700oC holding for 30min. After the oxidation process, the oxides were reduced by graphite crucible at 1500oC under Ar atmosphere. By this way, the rare earth elements were recovered in the form of oxides, and Fe was separated to the metal phase. Boron distributed in both the rare earth oxides (REO) containing slag and the metal phase. In order to reduce the boron contents in the rare earth oxides, the carbon saturated iron bath and NdFeB added carbon saturated iron bath were used to refine the slag. By this process, the rare earth oxides with a comparatively high purity of 98.2% were gotten.

Jan 1, 2015

By S. Shrivastava

A structure based model has been developed for the prediction of viscosities of K20-B20, melts. These melts exhibit an anomalous behavior of viscosity with continuous variation in B203 content. A maximum and a minimum are observed at low temperatures, which disappear on raising the temperature above the softening range. The addition of K20 to the borate melts causes two opposing phenomena: (1) depolymerization effects and the related breakdown of network structure resulting in the formation of singly bonded oxygens, which weakens the structure and hence causes a decreases in viscosity, and (2) the formation of four coordinated borons (BO4 tetrahedra) which strengthen the structure leading to an increase in the viscosity. The structural changes taking place in these melts on varying the temperature and the alkali content have been reviewed and are incorporated in developing this model. The predicted values are in excellent agreement with the experimental values over the whole temperature and composition range.

Jan 1, 1992

By Y. Takasaki

For zinc hydrometallurgical extraction, reducing the electric power consumption of the electrowinning process is an important issue for energy savings. At the Zinc & Lead 2000 symposium, the authors suggested that by using the Pb-0.5%Ag-0.6%Ca alloy, the electrolysis energy can be decreased compared to the conventional Pb-0.9%Ag alloy. In this study, the corrosion behaviors of the Pb-Ag-Ca electrode in a sulfuric-acid electrolyte were investigated. Based on the results Or me Pb-0.5%Ag-0.6%Ca anode after 20 days of electrolysis, the bath voltage and the quantity of anode slime decreased compared to the Pb-I%Ag anode. Subsequently, beta-PbO2 on the electrode surface was detected by XRD and its peaks were sharper than the Pb-1 %Ag anode. Moreover, a dense beta-PbO2 layer on the 0.6%Ca a anode surface was observed. Therefore, it was suggested that the dense beta-PbO2 layer on the anode surface is one of the factors that leads to a lower bath voltage and decreasing quantity of anode slime.

Jan 1, 2003

By Cheng Gong-jin, Chu Man-sheng, Liu Zheng-gen, Zhang Yong, Liu Jian-xing, Xue Xiang-xin

"High chromium vanadium-titanium magnetite is one kind of Fe-V-Ti-Cr composite ore resources, which owes high utilization value. Owing to lacking systematic study on the sintering of this ore home and abroad, effects of carbon addition and basicity on sintering process and sinter metallurgical properties, such as sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation were investigated systematically under laboratory conditions in the paper. The results shows that, when high chromium vanadium-titanium magnetite proportion is kept unchanged as 13% in sintering feeds, sintering process index and metallurgical properties are the optimum under carbon addition 5.0% and basicity 2.70, which meets the requirements of blast furnace burdens. This research provides technical parameters for practical sintering production of high chromium vanadium-titanium magnetite.IntroductionHigh chromium vanadium-titanium magnetite (hereinafter abbreviated as hi§h-Cr V-Ti magnetite), in which Fe is closely symbiotic with Ti and isomorphous with V and Cr1'- l, is one kind of typical vanadium-titanium magnetite resources with high comprehensive utilization value but the difficulties are extremely high due to complex chemical composition and mineral structure. At present, the feasible and mainstream utilization process of high-Cr V-Ti magnetite should be the route of agglomeration-blast furnace smelting. Thus, sintering production is the foundation for high-Cr V-Ti magnetite utilization. However, till now there are few research documentations on high-Cr V-Ti magnetite sintering home and abroad. Under the above background, this study focused on detailed researches of high-Cr V-Ti magnetite sintering. Sintering process uses the powders or fine iron ores to produce artificial rich ore with good metallurgical properties 4l Solid fuel provides 90% heat requirement during sintering15J. The appropriate amount of fuel and flux should be added during sintering in order to provide necessary heat and maintain the desired basicity16l. That is to say, carbon addition and basicity are two key factors affecting metallurgical properties of sintering products17J. Therefore, the effects of carbon addition and basicity on sintering process and metallurgical properties, including sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation, are systemically investigated under laboratory conditions in the study, on purpose to achieve the optimization of sintering process for high-Cr V-Ti magnetite."

Jan 1, 2013

By Dieter Wanner

Off-gas cleaning from metallurgical? plants, requires in many cases very low dust contents which are, difficult to achieve with conventional scrubbers, even with high energy input. Lurgi has developed a scrubber which improves the separation of the fine dust by electrical charge prior to the scrubbing zone,, An Electrostatic Scrubber has been successfully installed for the off-gas cleaning from slag granulation after a waelz kiln achieving less than l mg/m3 in the clean gas.

Jan 1, 1992

By Vojteh Leskov?ek

The tribological load is the load on forging tools resulting from the relative motions between the plastically deformed workpiece and the die. In comparison to many other forming processes hot die forging has an especially disadvantageous tribological system. The advantages of the application of hard coatings, which are well known for cutting tools, are to a much lesser extent explored for casting, extrusion, molding and forging tools. Increasing the lifetime of these tools is an important task in surface engineering because of the complex loading conditions and often complicated tool geometry. The plasma-assisted chemical-vapor-deposition (PACVD) technique is well suited to depositing hard coatings onto large dies and molds. The aim of this study is to present and discus results obtained on a duplex PACVD hard coating in an industrial application like the hot forging of automotive parts. A new generation of vacuum-melted and remelted (VMR) hot-work tool steels has been developed; these can reach a hardness of 58 HRc, and have a fracture toughness at this hardness equivalent to that of standard hot-work tool steels at 45 HRc. This offers one of two advantages: the steels can be used at the higher hardness to provide resistance to wear or deformation, or, when used at a hardness of 47?49 HRc for hot forging, to provide temper resistance, nitriding behavior and adhesive wear resistance. The results presented here are from a preliminary investigation. The experimental results indicate that the introduction of a proper duplex PACVD hard coating will lead to an improved wear resistance and a longer lifetime for the hot-forging dies. Furthermore, by using a hard, low-friction coating excellent anti-sticking properties can be obtained. At this stage of the investigation it is also necessary to carry out pilot trials to determine the wear resistance and the tool life in practice.

Jan 1, 2006

By Edgar Peek

Lixiviant regeneration is by definition a precondition for any hydrometallurgical process. In chloride hydrometallurgy either HCl or Cl2 has to be regenerated in order to establish an economically viable metallurgical process. One such regeneration process is widely used with steel pickling where HC1 is regenerated through the thermal decomposition of ferrous chloride in either spray roasters or fluid bed pyrohydrolyzers. This standard HC1 regeneration process deserves to be considered as a potential separation process, since thermodynamic calculations show that a fluid bed pyrohydrolyzer can function as a ferrous-nonferrous separator. Several nonferrous,metals such as zinc, lead and cadmium can be volatilized as a chloride under ferrous chloride pyrohydrolysis conditions. If such a nonferrous metal volatilization could be achieved in the case of slurry feeding of "contaminated" iron oxides, then this would increase the Fe/H2O ratio of the (process) feed and thus save on fuel per ton of iron, while yielding a marketable iron oxide product. Previous test work on synthetic materials revealed that the near-complete separation of zinc, lead and cadmium from iron oxide was possible in a pyrohydrolytic atmosphere, even if zinc was present as zinc ferrite (more than 99.5%). This investigation, which was carried out in a tube furnace at 1100 K has now been extended to treat synthetic zinc minerals and also franklinite ore. For the latter, it was found that 85% zinc volatilization could be achieved in 4 hours at 1300 K. It is postulated that complete zinc volatilization could not be attained due to the formation and/or presence of gahnite and hardystonite, which might be stable in HCl/H2O atmospheres at 1100 K. The effect of adding small amounts of calcium chloride to react with gahnite and hardystonite to give zinc chloride and both calcium aluminates and silicates is being discussed. Test work on slurry feeding of this complex ore in a recently constructed 4-inch diameter fluid bed pilot unit has been planned for the near future.

Jan 1, 1995