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By L. L. Ludwig, S. E. James, B. L. Motycka

Significant modifications to the electrolytic zinc plant operated by Big River Zinc Corporation were made at the end of the 1990's resulting in increased capacity and improved efficiencies. A new cell room, with the innovative use of acid-resistant concrete cells and a modern ventilation system, was installed to raise the capacity from 80,000 tonne/y to 106,000 tonne/y of finished zinc. Improvements to the leaching section include the conversion from a single to a two-step process, with associated equipment changes, to improve the quality of the residues produced. Another key change is the construction of a facility to allow the use of zinc oxides from secondary sources as a feed to the plant. This paper describes these improvements and the current operations.

Jan 1, 2000

By Versiane A. Leão

The hydrochloric leaching of chrysotile tailings and soapstone powders) is discussed. This two materials are magnesium compounds associated with carbonates and iron oxides. In this work the chemical and physical characterization of formers is presented and the thermodynamic analyses of leaching is carried out. Magnesium extraction is almost complete for chrysotile tailings while, for soapstone powders, one can be reached 60%. The behavior of iron and calcium impurities is discussed.

Jan 1, 1997

By Kazuyuki Kakegawa

"Sintered body of lead zirconate titanate (PZT) was prepared through the spark plasma sintering (SPS) technique. When the mixture of raw materials was calcined at 800°C and sintered at 900°C for 10 min. with SPS technique, the sintered body had almost theoretical density but was a mixture of lead titanate (PT) and PZT. When a calcining temperature of 1100°C was employed, sintered body had a single PZT phase but a lower density. High dielectric constant was obtained for a sample calcined at 800°C, sintered with SPS tecbriique and fired again in the air at 1100°C.IntroductionSpark plasma sintering (SPS) is a recently developed technique for sintering metals and ceramics1. The scheme of SPS is shown in Fig. 1. Sample is put in a graphite die in a vacuum chamber. It is pressed and pulse voltage is applied. The electric current heats the die. It is said that the pulse causes a spark-plasma between particles in the sample. Because of the spark- plasma, sample can be sintered at temperatures lower than that in the ordinary sintering by several hundred degrees of Celsius. The sintering period is also very short2Low sintering temperature and short sintering period in SPS technique cause low reaction rate. It is both disadvantage and advantage. In some cases, the reaction cannot be completed under the SPS conditions. If a mixture of several compositions having different properties can be sintered without a compositional change by the diffusion during the sintering, combination of properties, and therefore a design of property will be possible3. The low reaction rate of SPS may enable such combination."

Jan 1, 2000

By Hiroaki Nakano, Kenji Hara, Shunsuke Kawano, Takeshi Ohgai, Michiaki Ikeda, Hisaaki Fukushima, Shinji Yamashita, Tetsuya Akiyama, Hisayuki Kaku

"Ni-Fe alloys have an inverse magnetostrictive effect (Villari effect) in which its permeability varies according to the ·applied strain. This alloy film has a potential for application as force sensors such as torque sensors, tension sensors and so on. Electrodeposition is promising as a technique for preparing Ni-Fe alloy film because of its convenience and economy. In this paper, the effects of electrolysis conditions on the magnetic properties of electrodeposited Ni-Fe alloy films were investigated. Hysteresis loops of Ni-Fe alloy films on copper substrates from sulfate bath were measured by a vibrating sample magnetometer (VSM). The films of low coercivity, which were preferred when used as a force sensor were obtained by introducing certain additives to the sulfate type bath.INTRODUCTIONNi-Fe alloys show an inverse magnetostrictive effect (Villari effect) that their permeability varies depending on the applied strain. The films of this alloy have a potential for application as force sensors such as torque sensors, tension sensors and so on. The authors et al. tried to prepare Ni-Fe alloy films using the sputtering technique, and produced a prototype of Ni-Fe alloy torque sensor [I]. The sensitivity was higher in the torque sensor thus produced than the strain gauge type one, and this torque sensor enables non-contacted detection. It showed excellent durability and reliability. However, the formation of Ni-Fe alloys by sputtering requires higher costs and brought an another problem that the shape of the substrate on which the film was formed was considerably limited. This causes a hindrance to the wide-range application of the force sensors. Electrodeposition is promising as the technique for preparing Ni-Fe alloy films because of its convenience and economy. In this paper, the effects of the conditions of electrodeposition on the magnetic properties of Ni-Fe alloy films were studied."

Jan 1, 2000

By Suk J. Im, I. S. Min, Daesoo Kim

UFP are defined by atoms or their clusters having diameter in the range of l0Å-0.l.um. Due to a ratio of very large surface area to volume, they have peculiar properties such as extra high surface energy. Recently UFP deposition technique may find its new applications to various areas such as conductive/resistive film formation. In this method, gas flow with UFP jet through the nozzle which is considered to be a free molecular flow is maintained at a very high speed (~100m/s). Using this technique, mixture film of Fe and Ni, and Ag/ Ag-Alloy etc. were obtained, and their mechanical and electro-magnetic properties were determined. The experimental results are pending. The test results and discussion will be presented in the main paper.

Jan 1, 1988

By Shin-ya Kitamura

Kinetic modeling is very important to understand steelmaking reactions. The coupled reaction model proposed by Prof. D.G.C Robertson is the best suited program, and therefore, the author has applied it to the various steelmaking reactions, a few examples of which are discussed. Hot metal dephosphorization occurs under non-equilibrium conditions as it takes place between the slag, which has a high oxygen potential, and the hot metal, which has a low oxygen potential. A process simulation model based on the coupled reaction model was constructed. This model considers the solid and liquid slag, liquid metal phases, and the reaction between the solid and liquid slag, besides the reaction between the liquid slag and liquid metal. Using this model, the ruling factor to increase the reaction efficiency of dephosphorization has been verified. In the secondary refining process, the values of inclusion composition calculated by the thermodynamic model, under the assumption of equilibrium with the metal composition, were found to be different from those observed in practice. A kinetic model, incorporating the reactions between slag, metal, inclusion, and refractory has been postulated, and the composition change of inclusion during treatment has been analyzed.

Jan 1, 2014

By Brian G. Thomas

Quality problems in continuous casting of steel can be identified as they occur by monitoring mold signals (level sensor, thermocouples in the mold walls, friction etc.) and taking appropriate action (such as slowing casting speed, changing taper, changing a clogged nozzle, or later visual inspection of the surface for possible downgrading. Surface depressions and groups of deep oscillation marks form at meniscus and reduce local heat transfer as they move down the mold at the casting speed. This slows shell growth, increases shell surface temperature, and causes characteristic dips in mold thermocouple signals. More importantly, they are also associated with longitudinal cracks. Characteristic thermocouple signatures have been identified for many defects, including sticker breakouts, transverse depressions and deep oscillation marks, narrow-face bleeds, transverse comer cracks, longitudinal cracks, mold level fluctuation defects, and other problems. With the help of computational models, these mold signals should be used to troubleshoot defects, and to take appropriate corrective action. Keywords: Continuous casting, defect detection, thermocouple signals, on-line control

Jan 1, 2003

By F. Michael Hosking

Modeling of a furnace brazing process is described. The computational tools predict the thermal response of loaded hardware in a hydrogen brazing furnace to programmed furnace profiles. Experiments were conducted to validate the model and resolve computational uncertainties. The results from selected furnace simulations and measured thermal events were compared. Critical boundary conditions that affect materials and processing response to the furnace environment were determined. "Global" and local issues (i.e., at the furnace/hardware and joint levels, respectively) are discussed. The ability to accurately simulate and control furnace conditions is examined.

Jan 1, 1998

By Erwin Flender, Preben N. Hansen, Peter R. Sahm

"Until now FDM-Techniques have been widely used for Modeling Solidification Processes in Castings. Often a rigid, regular type of enmeshment (cubes, , --) have been used. This has the advantage of low CPU-costs, but the disadvantage of a zig-zag presentation of the interface between the casting and the mold. The last point is the reason why FEM-Techniques, giving the possibility of a true presentation of the shape in the enmeshment, are increasingly used. The disadvantage is the high CPU-costs. In this paper, a technique is presented, which uses the FDM-Mesh with the zig-zag presentation of shape and ADI-Algorithms to calculate temperatures and gradients. The new idea is that the calculated parameters are not presented related to the mesh in which they are calculated, but displayed using the true shape of the casting. Such an advantage of both low CPU-costs and shape correct presentation of the calculated results are achieved. IntroductionThe main reason for using a regular type of enmeshment is that it gives the possibility, via ADI-Algorithms, of obtaining a very fast FDM-Technique. The technique presented by P.R. Sahm and P. N. Hansen (1984), and also used by E. Flender (1985), is numerically so stable that average time steps, at least 200 times larger than the limit given by the explicit FDM-Technique, can be applied. To obtain reasonably good results, average time steps in the range of 20 to 50 times the explicit limit seems to be applicable. It should be pointed out,however, that FDM-Techniques can be used on arbitrary nets, the disadvantages being the same as for the FEM-Techniques. This has, among others, been discussed by P.R. Sahm and P.N. Hansen (1984)."

Jan 1, 1986

By John P. Hager

One possible approach for the recovery of mercury from acid plant blow-down sludge in smelters is the use of a vacuum retort reactor for the vaporization of the mercury with subsequent collection of metallic mercury in an attached condenser. An experimental study was undertaken to investigate the vaporization of mercury when present as a compound in the Hg-S-O and Hg-Se systems. A transpiration reactor was modified to operate under reduced pressure and with a continuous flow of inert sweep gas. A water-cooled cold finger was inserted into the exit end of the reactor to provide for the rapid quenching of the exit gases and the collection of the mercury. Rates of vaporization were measured at several temperatures for each compound and were generally found to be constant at a given temperature and reactor pressure. The results were used to determine the minimum operating temperature for 100% vaporization of the compound in 60 minutes. For Hg2SO4, HgSO4, and HgSO/2HgO the required temperatures. for a reactor pressure of 50 Torr. were determined to be 634°, 622°. and 603°C. respectively. For HgO, HgSe, and HgS the required temperatures were 557°. 451°. And 382°C. respectively. For HgS the rate of vaporization was also measured at a reactor pressure of 1 00 Torr. The rate of vaporization was found to be slower resulting in an increased vaporization temperature of 423°C. It was also determined that the mercury vapor present in the exit gas stream can back-react with the other gas species to a significant extent and can result in very little condensed metallic mercury. For the vaporization of both HgS and HgSe. the mercury vapor was found to have back-reacted to the extent that virtually none of the vaporized mercury was collected in metallic form. For the vaporization of Hg2S04? HgS04, and HgSO4*2HgO the amount of metallic mercury recovered varied from approximately 50% for HgS04*2HgO to approximately 10% for Hg2S04 and HgS04. Only for HgO was the recovered mercury in primarily elemental form. The application of the results to the operation of a vacuum retort and condenser system is discussed.

Jan 1, 2001

By Y. Ide, K. Kishitake

It is expected that an Al-Cr-N composite nitride film may have a higher resistance to oxidation at elevated temperatures than the well-known Ti-Al-N films. The formation conditions of Al-Cr-N films by a de reactive sputtering method and their properties were studied in this study. The films characterized with respect to their high temperature properties such as chemical composition, crystal structure, microhardness, wear and· friction. The crystal structure of the Al-Cr-N films changed from hexagonal phase to cubic phase with an increase in Cr content in the films. The resistivity to thermal oxidation of the Al-Cr-N films is superior to that of usual TI-Al-N films. A half of the friction coefficient in the Al-Cr-N film was obtained comparing with that in the ordinary TI-Al-N film at room temperature and the wear rate of Al-Cr-N film was 2 order smaller than that of TI-Al-N film. The Al-Cr-N films show a small friction coefficient at 500°C and then they are recognized to have good tribological characteristics.

Jan 1, 2000

By P. Mazumder

Numerical analysis is carried out to examine the effects of thermosolutal convection on the formation of complex patterns in directionally solidified binary alloys. A finite-difference analysis is used for dynamic modeling of a two-dimensional prototype of Vertical Bridgman system that takes into account heat transfer in the melt, crystal, and the ampoule; melt flow and solute transport. Actual temperature data from experimental measurements are used for accurately describing the thermal boundary conditions. A range of complex dynamical behavior is predicted in the melt flow due to flow transitions and this is found to be directly related to the spatial patterns observed experimentally in the solidified alloys. The model is applied to single phase solidification in the Al-Cu and Pb-Sn systems to characterize the effect of convection on the macroscopic shape of the interface. The application of the model to hyper-peritectic alloys in the Sn-Cd system shows that the presence of oscillating flow can give rise to a novel convection induced microstructure in which a tree-like primary phase in the center of the sample is embedded in the surrounding peritectic matrix.

Jan 1, 1999

By T. T. Chen

The manganese oxide scales, consisting mainly of MnO2, characteristically occur in banded colloform structures which adhere to porous layers of PbSO4 and PbO2 that oxidized from the rolled Pb-0.7% Ag anodes. Hydrous Mn oxides, Mn3O4 and amorphous Mn oxides are believed to be also present. Tiny particles of gypsum, PbSO4, SrSO4 and AgCl are entrapped in the colloform masses. The gypsum originated from the Zn electrolyte; strontium carbonate was added to the ZnSO4 solution to control Pb, and silver originated from the anodes. Some of the colloform bands contain minor amounts of Pb, implying a limited degree of dissolution of the Pb during electrolysis. Other colloform bands incorporate trace amounts of Zn. Colloform structures permeated with silica gel are presumably caused by the high silica content of the electrolyte.

Jan 1, 2009

By Zhiqiang Han, Anil K. Sachdev, Baicheng Liu, Guomin Han, Alan A. Luo

The growth of precipitate phase ,B-Mg11Al12 in Mg-Al alloy is closely related to interface anisotropy and elastic interaction. The aim of this work is to investigate the effects of the interface anisotropy and elastic interaction on the morphology evolution and growth kinetics of the precipitate. In the work, the precipitation of ,B was studied using phase field modeling. In the model, the chemical free energy of the precipitate and the matrix were obtained via thermodynamic calculation. It is demonstrated that the interface anisotropy results in lath-shaped precipitate and the elastic interaction affects the shape of the end of the precipitate. The interface anisotropy causes uneven growth in different directions and the elastic interaction influences its preferential growth orientation. By combining the interface anisotropy and elastic interaction in the phase field modeling, the results showed that the precipitate phase has a lath-shape with lozenge ends, which is in agreement with experimental observations.

Jan 1, 2013

By Jiangtao Li, Zhongwei Zhao, Xingyu Chen, Xuheng Liu

The method of ultrasonic-assisted leaching was used to extract vanadium from the stone coal, with alkali as leaching reagent. The effects of ultrasonic power, concentration of alkali, reaction temperature, liquid-solid ratio and reaction time were investigated, respectively. The optimal ultrasonic leaching condition for vanadium extraction is as follows: ultrasonic power 230W, concentration of alkali 5%, liquid-solid ratio 3:1, reaction temperature 90℃ and reaction time 1h. The leaching rate of vanadium reaches 76.4% under the optimal condition, which is 12.2% higher than that of non-ultrasonic leaching. The reason on enhancing the leaching rate of vanadium by ultrasonic leaching was discussed. It is indicated that the ultrasonic cavitation can increase the surface area of mineral, which is beneficial to facilitate the reaction rate. Keywords: stone coal; vanadium; alkaline leaching; ultrasonic

Jan 1, 2014

By G. Taylor, S. Bounds, G. Moran, M. Cross, K. Pericleous

"A variety of interacting complex phenomena takes place during the casting of metallic components. Here molten metal is poured into a mould cavity where it flows, cools, solidifies and then deforms in its solid state. As the metal cools, thermal gradients will promote thermal convection which will redistribute the heat around the component (usually from feeders or risers) towards the solidification front and mushy zone. Also, as the evolving solid regions of the cast component deform they will form gap at the cast-mould interface. This gap may change the rate of solidification in certain parts the casting, hence affecting the manner in which the cast component solidifies. Interaction between a cast component and its surrounding mould will also govern stress magnitudes in both the cast and mould - these may lead to defects such as cracks.This paper presents a multiphysics modelling approach to this complex process. Emphasis will be placed on the interacting phenomena taking place during the process and the modelling strategy used. Comparisons with plant data are also be given."

Jan 1, 1999

By Yong Zhao, Yan-hui Sun

Behaviors and evolutions of MgO·Al2O3 in non-oriented silicon steel during calcium treatment were investigated by thermodynamic calculations and high-temperature experiments. MgO·Al2O3 inclusions were the main type of inclusions before calcium treatment, which is also confirmed by the stability diagram of MgO/MgO·Al2O3/Al2O3 from thermodynamic calculations. After calcium treatment, the majority of original MgO·Al2O3 inclusions were mainly modified to CaO-MgO-Al2O3 system inclusions, this would be beneficial to improve castability and product quality of silicon steel. But there was no modification happening to some MgO·Al2O3 spinels which were directly surrounded by CaS inclusions. The content of Al2O3 occasionally existed a sudden increase besides a common decrease in the product layer of CaO·MgO·Al2O3. Then the evolution mechanisms of MgO·Al2O3 inclusions were proposed in present work. Thus, Al/Mg atom ratio had a significant influence on the modification of MgO·Al2O3 spinel.

Jan 1, 2016

By Min Chen, Lei Xu, Liang-yu Jin, Xue-liang Yin

For the purpose to reduce the high cost and heat storage loss of Al2O3-MgO bricks used as ladle linings, Al2O3-MgO-CaO bricks with lower theoretical density were fabricated and the densification behavior as well as mechanical property of this refractory was investigated. With addition of CaO, the initial sintering temperature of Al2O3-MgO refractory was decreased from 1300 to 1100°C associated with the expansive formation of CA2, and the compressive strength was also enhanced owing to the formation of bond linkage between CA6 and spinel. At high temperature, brick with 4% CaO content showed poor sinterability with high porosity because of the formation of platelet structure of CA6 grains, whereas brick with 8% CaO content was well sintered with higher relative density but lower bulk density than Al2O3-MgO brick, indicating that the densification as well as lightweight of Al2O3-MgO refractory was effectively promoted.

Jan 1, 2015

By C. E. Dodson

Conventionally hydrometallurgical recovery processes from sulphide concentrates include roasting, leaching, precipitation, impurity removal and zinc electrowinning. The use of the novel (yet commercially proven in other mineral and metallurgical industries) TORBED process reactor for the flash roasting of sulphides will be proposed. The potential advantages in its application will be discussed including very fine particle processing capability, lower cost smaller roasters, waste minimization, improved leaching efficiency and overall process simplification.

Jan 1, 1999

By R. Gampala

The consolidation of mom matrix composite monotapes occurs by the plastic (time independant) and creep deformation of monotape asperities. Past models of the process used seperate micromechanical analyses of the contact deformation by (rate independent) plasticity and power law creep (i.e steady state creep). These models are now used to simulate consolidation and to optimize/control consolidation process cycles so that the composite's microstructure is "steered" to, a user defined goal state. However, the models do not incorporate the sometimes dominant transient creep process and the instantaneous response of the plasticity mechanism causes finite discontinuities in the microstructure state vector field and therefore eliminates the possibility of using the powerful array of trajectory optimization schemes that all require continuous vector field for optimization and control. To overcome this problem, a inified creep/plasticity constitutive model that results in a continuous state vector field is used to rederive the contact deformation response during monotape consolidation. The contact blunting of a laterally constrained hemispherical asperity is first analyzed and its response represented by two coefficients; one relating the contact area to the blunting strain (C), the second, the mean contact pressure to the blunting rate (F).The C and F coefficients for this unified blunting problem are then obtained by finite element analysis, and detailed results presented for two composite matri-ces of topical interest (Ti-24A1-11Nb and Ti-6Al-4V).

Jan 1, 1996