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By Susanne Pignolet-Brandom

Reflected light microscopy scanning electron microscope energy dispersive spectroscopic analysis and backscatter electron image and electron microprobe chemical analysis have been used to study lead sinter and lead blast furnace slag. These studies provide invaluable information on the phases present their intergrowths, and their chemical composition. Such information increases the understanding of the nature of pyrometallurgical processes and the behavior of minor elements during these metallurgical processes.

Jan 1, 1987

By Eric J. Grimsey

Steady state Excel models for a copper flash smelter and an iron blast furnace are used to enhance the teaching of pyrometallurgical smelting principles within a fourth year level process engineering unit delivered at the Western Australian School of Mines. A lecture/workshop approach has been adopted in which student teams undertake process simulation assignments that illustrate the multifaceted responses of process outputs to variation of inputs, the objectives being to reinforce their understanding of smelting principles. The approach has proven to be popular with students, as evidenced by the consistently high ratings the unit has received through student feedback. This paper provides an overview of the teaching approach and process models used.

Jan 1, 2014

By W. Kasprzak

Press-fit systems are widely used to seal oil lines in the automotive engine components. In the case studied a ball plug made from the 7075 A1 alloy was inserted into a 319 Al alloy cast component. The oil lines were subjected to the required component service pressure. This paper addresses the analysis of the ball plug/casting hole press-fit performance. The tools used to investigate the plug system included: the SEMIEDS technique for the assessment of the plug and the casting hole wall surface integrity; image analysis methods for the characterization of the ball plug/casting hole interface; matrix microhardness measurements of the plug and casting components; laboratory ball plug insertion, speed and force correlation; as well as the ball shearing mechanism analysis. Laboratory tests indicated that optimization of the aluminum matrix hardness in the 319 A1 alloy cast components resulted in considerable improvement of the press-fit system sealing properties.

Jan 1, 2002

By Alexandre Bonan

The paper reports on the results of a kinetic study on the oxidation reaction of aqueous free cyanide ions with H202, in the presence of Cu(2+) catalyst. The variables and respective ranges studied were the following: (CN) ° = 10 -100 mg/l pH = 10 -11 (H202/CN) mol ratio = 1 -3 (Cu/CN) mol ratio = 0 -0.25 The results lead to the development of a semi-empirical model whish incorporates both the useful oxidation reaction and the parallel alkaline decomposition of H202.

Jan 1, 1992

By James O'Brien, Lyman Frost, S. Elangovan, J. Stephen Herring, Joseph Hartvigsen, Carl Stoots, Anthony Nickens

"Carbon dioxide recovered from concentrated sources, such as metallurgical reduction furnaces, cement kilns and fossil power plants can provide a valuable feedstock for a synthetic fuels industry based on energy from nuclear, solar, wind and hydropower sources. High temperature co-electrolysis of CO2 and steam to produce synthesis gas has been demonstrated using reversible solid oxide fuel cell technology. Where a source of high temperature process heat is available, such as from an advanced high temperature nuclear reactor or solar dish concentrator, the endothermic electrolysis reactions can utilize both thermal and electrical inputs in such a way that the conversion efficiency within the cell is 100%. Synthesis gas produced in a coelectrolysis cell has been further reacted over a catalyst to produce conventional hydrocarbon fuels. Widespread implementation of synfuel production from CO2 will enable a much larger reliance on intermittent renewable energy than can be accommodated by conventional electric demand profiles.IntroductionFor the past several years, Ceramatec, Inc and the Idaho National Laboratory (INL), have been studying the feasibility of high temperature solid oxide electrolysis for large-scale, nuclearpowered hydrogen production under the U.S. DOE’s nuclear hydrogen initiative (NHI) as an alternative to the thermochemical process. Parallel to this effort, the INL and Ceramatec have been researching high temperature co-electrolysis of mixtures of steam and CO2 to produce syngas:"

Jan 1, 2008

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen temary system, which is of fundamental importance for discussing the recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, Sb015 and Sb203 in the PbO-SbOu and PbO-Sb203 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By Daniel C. McLean

Extraction data for Cu, Zn and Fe were obtained from 4.5" and 10" columns using massive sulfide ore and natural acid mine water. The purpose was to determine if recycling of solution through the column would produce leach liquors of 4 g/l Cu and Zn at extraction rates of 1 g/l per pass at typical flow rates of 0.002 to 0.006 gpm/sq.ft. Test results exceeded expectations. Cu and Zn concentrations of 4 g/l were obtrained within 4 to 6 cycles. Concentrations greater than 6 g/l Cu and 8 g/l Zn were reached within 10 cycles. Concentrations of greater than 40 g/l of Fe and free sulfuric acid were obtained with no decrease in biological activity being observed. No reagents were used.

Jan 1, 1995

By Zhi-biao Yin

Copper smelter flue dusts often cannot be directly recycled to the smelting process and accumulate as hazardous wastes requiring environmentally acceptable disposal. Because of the limited amount of flue dust, a separate copper extraction process must be simple and require-a small plant investment. A flue dust process has been developed, consisting of the following steps: (1) roasting a pelletized mixture of hydrated lime and flue dust to fix arsenic and sulfur as insoluble calcium salts, (2) heap leaching the roasted pellets with a buffered ammonia/ammonium salt solution to extract copper as an ammine complex in a lined cell that is the final repository of the leached pellets, and (3) boiling ammonia from the lixiviant to precipitate copper. Condensed ammonia and the filtered solution are returned to leaching. Heap leaching in the final repository cell lowers the capital investment significantly compared with competing extraction processes. Chemistry with respect to arsenic, sulfur and copper is discussed.

Jan 1, 1992

By Pertti Koukkari

The novel Jarogain process combines treatment of the jarosite residue of zinc manufacturing and processing of arc furnace dust from steelmaking to a holistic recovery technology. The new hydrometallurgical approach is targeted to recover the major constituents (Fe, Zn, Pb) as well as valuable components such as Ag, Au, In and Ga from the jarosite-dust mixture as reusable concentrates. The fractionation process proposed by VTT and Aalto University takes advantage of jarosite being readily fine powder and directly available for wet chemical processing. Jarogain process provides an energy efficient opportunity for jarosite utilization as value added products. The experimental proof-of-concept of key stages of the process will be outlined with a comparison of available pyrometallurgical treatments of jarosite waste. The techno-economical assessment is based on estimated investment and variable production cost using the discounted cash flow (DCF) analysis.

By Jr. Napolitano, Jr. Sanders

"Morphological evolution of a dendritic growth front in a binary alloy is simulated using a cellular automaton approach to establish the feasibility of modeling such growth with a local rule-based scheme. The motivation for this work is derived from the need to predict the development of solidification structures within real components of complex geometry, where significant constraint of the thermal and solutal fields may exist. Such cases present complex boundaries and large domain sizes, which may preclude the effective use of more conventional methods. In this work, a model is presented which couples a two-dimensional alternate-direction-implicit finite-difference diffusion solution with a cellular automaton growth algorithm to simulate morphological evolution in alloys solidifying under directional growth conditions. Temperature, composition, and interface curvature are incorporated into a local growth potential which is used by the automaton, allowing the interface to evolve. Alloy solidification is simulated over a range of experimental conditions, producing various structures. Issues addressed include morphological instability, primary spacing selection, interface curvature, microsegregation, and tip conditions.IntroductionThe development of dendritic structure plays an essential role in alloy solidification. Virtually every microstructural feature, within a cast alloy component, is related to the interface morphology present during solidification. Conventional solidification theory, describing dendrite tip kinetics and mushy zone phenomena, provides a means for estimating overall microstructural parameters for an alloy solidified under steady-state conditions. Microstructural prediction for actual components, which are finite in size and complex in geometry, requires a description of the evolution of the interface morphology under transient conditions and geometrical constraint and an understanding of how the structure propagates through the mold. Any useful simulation tool must be equipped to handle these circumstances within the limits of computational feasibility."

Jan 1, 1998

By C. Peter Hayes

The world continues to change and with it the supply of minerals and metals, the location of centres of production of primary metal and the increasing levels of metals and materials recycling. New technologies are being developed to meet the ongoing search by industry for lower costs, cleaner production and new markets. To keep abreast with these changes, and to utilise fully, the potential benefits of these technical advances, the industry will need a professional workforce having different knowledge, skills and professional attributes than in the previous millennium. What are these skills and attributes? How to best attract and develop the metallurgists of the future, and provide for the ongoing educational and research needs of the industry?

By L. Yin, R. B. Haber, N. Sobh, D. A. Tortorelli, R. W. Hyland Jr.

"We optimize continuous quench process parameters to produce a desired precipitate distribution in aluminum alloy extrudates. To perform this task, an optimization problem is defined and solved using a standard nonlinear programming algorithm. Ingredients of this algorithm include a cost function, constraint functions and their sensitivities with respect to the process parameters. These functions are dependent on the temperature and precipitate size which are obtained by balancing energy to determine the temperature distribution and by using a reaction-rate theory to determine a discrete precipitate particle size distribution. Both the temperature and the precipitate models are solved via the finite element method. Since we use a discrete particle size model, there are as many as 105 degrees-of-freedom per finite element node. After we compute the temperature and precipitate size distributions, we must also compute their sensitivities. This seemingly intractable computational task is resolved by using an element-by-element discontinuous Galerkin finite element formulation and a direct differentiation sensitivity analysis which allows us to perform all of the computations on a PC.1 IntroductionThis work addresses the need for an integrated design capability that links microstructure evolution to the process parameters. It is motivated by the manufacture of lightweight aluminum-alloy extrusions for use in automotive structures. Aluminum alloys offer obvious benefits, however, care must be taken to manufacture favorable microstructures that ensure acceptable structural performance. For example, the manufacturing process for 6000-series components involves hot extrusion of cast aluminum billets followed by either an air or water quench process. The bill~t's initial grain structure is dramatically altered during extrusion by massive mechanical deformations and recrystallization processes. The microstructure continues to evolve during the quench, as complex chemical processes determine the formation of precipitates. The control of the precipit'ate size distribution is vital. Indeed, large precipitates located on grain boundaries serve as crack initiation sites which adversely effect structural crash· worthiness."

Jan 1, 2000

By S. Sundarraj

The morphological transition between columnar and equiaxed structures is an important solidification phenomenon frequently observed in castings, especially complex parts with varying cross-section, The mechanical properties and the occurrence of defects such as hot tears are strongly dependent on the structure formed in the casting. Hence, it is important to understand the conditions leading to columnar or equiaxed structures. Although extensive work has been done in modeling solidification systems, almost all of the existing models are based on the assumption that the structure formed in the casting is either purely columnar or purely equiaxed. Prediction of the columnar-equiaxed transition (CET) requires a solidification model which accounts for the formation of both columnar and equiaxed structures, along with related microscopic and macroscopic solidification phenomena. In this paper a CET model is presented which: (i) takes account of both columnar and equiaxed structures, (ii) accounts for macroscopic heat transfer coupled with microscopic phenomena such as nucleation, growth and microsegregation, (iii) satisfies solute conservation, and (iv) is easy to implement in commercial finite element and finite difference software. The proposed model predictions of CET have been validated with available experimental results for a uni-directional solidification of an aluminum-copper alloy. A sensitivity analysis has also been carried out to determine the effects of various parameters on the CET model predictions. The model is being extended to other alloy systems and more complex geometries. This work will be published in due course.

Jan 1, 1996

By Tan Pengfu

By using computer-aided techniques of equilibrium calculations for multicomponent and multiphase systems, a computer model has been developed to simulate QSL, KIVCET and Outokumpu flash lead smelting processes. A mathematical description is studied using two zones or three zones, namely smelting zone and slag reduction zone for QSL furnace, or offtake shaft zone, smelting shaft zone and electric furnace zone for KIVCET furnace. The amount of each component in lead, slag and gaseous phases under equilibrium is calculated by using the data of free energies of formation and activity coefficients. The predictions by the present computer model are compared with the known data from QSL-Plant at Korea Zinc Co. in Korea, KIVCET-Plant at Nuova Samim Co. in Italy and Outokumpu Co. in Finland. The agreements between the computer predictions and the known data are excellent, so that the present computer model can be used to monitor and optimize the actual industrial operations of direct lead smelting.

Jan 1, 1998

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 I. S. Escobar

Copper, particularly the oxygen-free grade Cu-OFP, is a candidate material for containers for the long-term isolation and disposal of high-level radioactive waste (HLW) in underground repositories. After having been buried for a few hundred years, all oxygen will have been consumed in the repository, and corrosion of the copper will be caused entirely by contact with dissolved sulfides. Chloride is another potential corrodant, but in deep repositories where groundwater is neutral or slightly alkaline, the effect of chlorides can be ignored on thermodynamic grounds. Thus, the corrosion of copper in the presence of sulfide ion and under reducing conditions has been studied using cyclic voltammetry and Tafel slope measurements. It is possible to determine the effect of sulphide ion on copper corrosion resistance which is minimized at low temperature and also at low sulphide concentration. The presence of anions such as HCO3 under environmental conditions produces a beneficial effect because these ions are inhibitors.

Jan 1, 1999

By Bien Ferrer

In most smelting operations, there is a strong incentive to improve safety, reduce downtime and extend the campaigns of furnaces and related equipment. An asset management strategy that is based on information, rather than simple throughput metrics and intuition, can be developed to improve uptime and unlock value currently unrealized at existing smelters. Advances in digital technology, including data analysis, modelling and monitoring for hot pyro-metallurgical vessels, make it possible to assess the current condition of an asset, as well as to make more informed projections about its future condition, using on-line and historical data. This would allow practices around asset management to be more proactive and less reactive, with the end-result of optimized uptime. ‘Digital Asset Management’ describes a concept in which digital technology is used to support an asset management strategy and accelerate decision-making by providing information on what, why and how an asset should be designed, operated or maintained. With the overall goals of effective resource utilization, optimized operations, capital efficiency and social acceptance, Smelter 4.0 is a program of holistic improvement and is underpinned by the effective use of data to drive decisions. This paper focuses on Asset Reliability, which is one of the improvement pillars of Smelter 4.0, and introduces a methodology that is aimed at closing the gap between recorded data and evidence-based decision-making through Digital Asset Management.

By Peter K. Liaw, Charlie R. Brooks, David C. Joy, Wei Zhao

In this paper, effects of oxidation, porosity and fiber-fabric stacking sequence on flexural strength of a continuous silicon carbide fiber (SiCr) fabric-reinforced SiC ceramic-matrix composite (CFCC) were studied. The failure mechanisms were correlated with flexural strengths of CFCC samples, both before and after oxidation. Microstructures and fractography were investigated using scanning electron microscopy (SEM). The chemical change after oxidation, such as Si, C, and 0, and their distributions, were detected by the SEM energy-dispersive X-ray spectroscopy (EDXS) line-scan chemical analysis technique. These effects on the strength of the CFCC can be attributed to following reasons: (i) The decrease in the flexural strength after oxidation is mainly due to degradation of the strength of Nicalon fibers and the damage of fiber/matrix interface both caused by high-temperature chemical reactions, (ii) Porosity is not too important in affecting the strength of the CFCC, when the bonding of the forced flow chemical vapor infiltration (FCVI)-SiC matrix is stronger than that of the fiber/matrix interface. However, a higher porosity content will be harmful, because higher porosity will both decrease the effective elastic modulus of the FCVI-SiC and make pore-linkage easier to occur, which is more likely to cause premature failure, (iii) The variation in the lamina stacking sequence of the CFCC changes the elastic stress distributions along the thickness direction of specimens, the magnitude of ceramic matrix-cracking stress, the effective elastic moduli of the laminate, and different crack initiation sites as well as different failure modes, and thus, leading to the scatter in the flexural strength of the CFCC.

Jan 1, 1998

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 J. L. Sanchez

Using a special double-zone transpiration reactor, the vapor transport chemistry of vanadium pentoxide in the presence of water vapor has been investigated. Three possible volatile hydroxides above V,O,(s) are reported in the literature: VO,(OH),, V,O,(OH),, and VO(OH),. In the present study, it was established that VO(OH), is the principal gaseous hydroxide species formed. The predominant reaction was found to be: { } The vapor pressure of VO(OH), was measured as a function of temperature, water pressure, oxygen pressure and flowrate. The results have been used to determine the Gibbs free energy of the above reaction as a function of temperature: { } The results of the present work were combined with thermodynamic data reported in the literature to obtain expressions for the AGO for the reaction above V,0,(1) and the AGO of formation (units in cal/g-mole).

Jan 1, 1993