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By G. B. Harris

Much has been written over the past decade concerning the disposal of arsenic from metallurgical processes. In Canada, there are proposed regulations which would classify arsenic in the Primary Group of twenty one persistent, toxic pollutants to be banned or phased out. Since many nickel and cobalt ores, not to mention those of copper, gold and uranium, contain significant amounts of arsenic, it is pertinent to assess the current state-of-the-art of its disposal. The literature is reviewed, and it is demonstrated that from a purely chemical point of view, the family of ferric arsenates largely immobilize arsenic. There is clear evidence from laboratory studies that both crystalline ferric arsenate (scorodite) and amorphous ferric arsenates in which the molar Fe/As ratio is at least three (Fe/As = 3) have very low arsenic solubility; plant data are given to support this. The debate over the long term stability of these compounds continues however; the evidence presented for long term stability and for compound breakdown is critically reviewed in the light? of the recent structural studies, and the role of base metals in these compounds evaluated. Finally, conclusions are drawn as to the viability of a purely chemical process for the long term disposal of arsenic from metallurgical processes.

Jan 1, 1993

By R. P. King

The essential features of an image analysis system for the measurement of mineral liberation are described. Good procedures for image acquisition and image processing prior to image analysis are defined. The basic stereological methods for the measurement of volume fraction, surface area per unit volume, particle size distribution and liberation spectra are given. The appropriate methods for fractal correction when measuring perimeters of irregular features and for frame correction when measuring linear intercepts are developed. Practically useful and accurate procedures for the stereological correction of particle size and liberation distribution methods are given.

Jan 1, 1995

By Anna Wasilkowska

The study concentrates on the effects exerted by microstructure, deformation history and uniaxial stress conditions (temperature, stress state, strain rate) on the mechanical properties offerritic TRIP-aided steels for automotive applications. In low-alloyed TRIP-steels it is quite difficult to separate the effect of the austenite to martensite phase transformation from the influence of the ferritic matrix contributing to the yield stress and uniform elongation. Investigation of transformation kinetics of retained austenite as a function of the deformation temperature show that using the parameter k to characterize the retained austenite stability allows to identify regious of different temperature sensitivity separated by a transition temperature of 10±5°C. The observed low strain-rate sensitivity of the flow stress is an intrinsic property of the ferritix matrix and points to defomtation governed by slip. The ultimate tensile strength is much stronger affected by temperature than the yield stress. The influence of the temperature on the elongation is complex, because of the heating of the specimens by 60-l20°C at moderate and high strain rates. The increase of the total strain can be understood in terms of thermal softening of the ferrite. On the other hand, the steep increase of the stress during dynamic testing is an effect of accommodated elastic and plastic strains in the matrix. The strain- hardening exponent is dependent on the conditions imposed during testing. The martensite transfomtation rate is lower and the critical stress for martensite nucleation is much higher under compression compared to tensile loading. In secondary tensile tests, the yield stress increases steeply, and the ultimate tensile strength and the total elongation depend linearly on the amount of pre-straining. The results confirm that in the range of 8=10-4 s-l the TRIP-effect governs room temperature plasticity. Keywords: TRIP-steels, mechanical properties, strain rate sensitivity, temperature sensitivity, austenite stability

Jan 1, 2003

By S. Neven

The smelting of copper anode slimes, a material which contains mostly lead, silver, copper and selenium, has been practiced for many years with a view to recovering the silver and associated small amounts of gold. However, a theoretical understanding of the process has been lacking and this handicaps efforts to improve and intensify smelting operations. In the past few years work has been done in this area and this work will be reviewed in the paper. The underlying thermodynamics of the oxidation of silver-copper selenide mattes has been developed and used as a basis for the construction of a computational thermodynamics model which attempts to predict the composition of all condensed phases during the course of smelting. The model will be outlined and its successes in matching experimental data, as well as its current deficiencies, will be considered. Supporting work on the thermodynamics of silver solubility in slags, on activity-composition relationships in the Ag-Se system and work in progress on the oxidation state of copper in the slags will be reviewed. These projects are designed to provide further detailed data which will improve the robustness of the thermodynamic model.

Jan 1, 1999

By M. Soltanieh

The liquidus surface? and tie-lines in the nickel-cobalt-sulphur ternary system have been determined between 1<273-1573 K. The experiments were conducted by equlibrating the liquid sulphide with the metallic alloy phase. The liquid sulphide phase was sampled and chemically analyzed. The alloy was analyzed by electrol} microprobe. Combining the present results with the.avai1abl~ literature data, the thermodynamic properties of this system were calculated.

Jan 1, 1998

By R. Cavanagh

Studies relating to the fixation of sulfur by reaction of 4 to 8 mm diameter cylinders of calcined limestone or dolomite with high strength sulfur dioxide in the temperature range 880°C to 1020°C were undertaken. Dolomites are far superior in sulfate capacity and reactivity than dense limestones even at high strength SO2. The sulfation reaction was first order with respect to SO2 concentration below 100 percent. Zero reaction rate at 100 percent SO2 concentration indicates that sulfate was the exclusive reaction product and that sulfite had no role in the reaction. At relatively low SO2 concentrations gaseous diffusion through the reaction product layer has a marked effect on the rate. As SO2 concentrations were increased up to 100 percent more complex rate controlling mechanisms unfold. By sectioning partially reacted dolomitic limestone pellets a moving interface was observed. Reaction ceased because of pore plugging for dense non-porous limestones at 30% conversion. With dolomitic material virtually complete sulfation of the calcium was observed. S.E.M. analysis showed that the average atom ratio Ca:S was 1.01, thus supporting the argument that little if any of the magnesium was sulfated.

Jan 1, 1996

By Cesar Garban

The samples of the washings are characterized of the ore for physical, chemical and metalurgical properties for representivity. the optimum values are determined for the recuperation of gold of the washings of the gold ore from the zone El Callao, Venezuela by acidic solutions of thiourea of the following parameters: Ph , contact time, composition of the liquid mixture, ratio of solid to liquid, grade of liberation, in an apparatus designed for contacting solid powder of the mineral with liquid solution of thiourea mantained in suspension by bubles of compressed air. The experimental results showed that the velocity of lixivation in primier time of (20) minutes is rapid and practically 2/3 part of the reaction is completed. For experimental design of parameters, the optimum conditions of recuperation of gold determind in this experimental investigation are:

Jan 1, 1999

By S. q. Honingh, G. Van Weert

Currently produced zinc-enriched blast furnace dust is stored on site at CORUS IJmuiden. To end this practise, a research program was started in 1996. Four technologies were studied: oxidative autoclave leaching in a chloride medium, fluid bed pyrohydrochloridisation (pyrohydrolysis) to yield lead-zinc-free (hematite) calcine, EAF (plasma) smelting/zinc fuming, and incorporation of the dust in 'iron foundry cupola charges. All aim to remove zinc and lead, recycle the iron residue internally, and produce a saleable zinc-lead product.

Jan 1, 2000

By Ravi Vancheeswaran

The consolidation of ceramic fiber reinforced metal matrix composites is a key process step in the synthesis of high performance composite systems. A simulation tool has recently been developed for predicting the evolution of the composites internal state microstructural variables (eg. relative density, fiber microbendinglfracture, and chemical reaction layer thickness at the fiber-matrix interface) during the consolidation processing of spray deposited composite mono-tapes. A Generalized Predictive Control (GPC) scheme is used in conjunction with the simula-tion tool to design near optimal process paths that minimize fiber damage and reaction product thickness while simultaneously maximizing the composites relative density. The microstruc-tural evolution depends nonlinearly on the process conditions and therefore the scheme uses a constantly updated linearization of the model to optimize the input process variable vector. A control simulation is presented to illustrate the performance of the design scheme and to assess the feasibility of its use for the achievement of goal state microstructures at the completion of consolidation cycles.

Jan 1, 1996

By Zengjie Wang

Investigation on hydrochloric acid leaching of the ilmenite from Panzhihua, China was carried out to prepare synthetic rutile. The leaching parameters were optimized to obtain high content of TiO2 in the products. The experimental data suggest that an optimum leaching can be realized with 30% acid, a solid/liquid ratio of 1/4 at 95°C for 4h, and ore ground for -400 mesh size. After the acid leaching, an additional alkaline leaching process using hot NaOH solution was performed, and then the products was in grain form followed by heat treated at 900°C for 2h in order to extract Si and increase the particle size of synthetic rutile. The final product has a high content of TiO2 (about 95%), a low content of chlorine consuming elements (total CaO+MgO =0.07%) and a suitable particle size distribution for chlorination process.

Jan 1, 2008

By M. Z. Quadir, M. A. Islam, P. J. Hazell, G. J. Appleby-Thomas, J. P. Escobedo

The mechanical response of closed-cell aluminium metallic foams subjected to low and high strain-rate loading has been investigated. A set of quasi-static and dynamic (shock) compressive tests have been conducted on closed-cell aluminium foams (CYMAT) with densities of 0.50 and 0.30 g/cc. Post-mortem characterization via optical microscopy and electron backscatter diffraction (EBSD) was performed on pristine and deformed specimens to elucidate the dominant deformation mechanisms in these materials. The combination of these techniques allowed for the assessment of critical deformation parameters such as changes in cell geometry and morphology, as well as microstructural evolution and deformation of the aluminium cellular network. These findings aim to aid in the design and development of optimized material structures for impact and blast protection.

Jan 1, 2015

By J. Murdoch Mackenzie

Two commercial nickel solvent extraction plants treating laterite leach solutions and using LIX®84-I have been operated in Australia. These circuits employ similar extraction chemistry but differ in their leaching and stripping operations. An alternative process involving elements of both can be conceived. The preparation of the feed solution to solvent extraction plays an important role in nickel extraction using LIX®84-I and the special features of manganese removal and cobalt oxidation in the preparation of the PLS are discussed. This paper compares these three circuit configurations with special reference to the extraction and reductive stripping of cobalt, the transfer of zinc and copper to the strip aqueous, ammonia transfer and sulfur transfer. The potential degradation of the organic and remediation using re-oximation is discussed. Keywords: Nickel, Solvent Extraction, Oxime

Jan 1, 2004

By Miroslav Raudensky, Kallol Bera, Jaroslav Horsky, Jee G. Chang, Ampere A. Tseng

"A combined experimental and finite element approach to study the local heat transfer coefficient is presented in this paper. The heat transfer coefficients at different cooling regimes in a roll are quantified by an inverse heat conduction technique; the heat transfer phenomena involved are then discussed. A discussion of the application of the heat transfer information found in the present study for better design of a roll cooling system is also included. Finally, an identification of areas where further work is needed is presented.IntroductionIn metal rolling processes, the roll is used as a tool to deform the workpiece at very high speeds. As shown in Fig. 1, the heat transfer phenomena involved in the process are complicated by the interaction between the roll and the strip, mainly including 1) the heat transferred from the workpiece to rolls in the contact regions, 2) the heat created in the interface due to the deformation of the workpiece and the friction between the workpiece and roll, and 3) the heat removed by watercooling as well as the ambient air. All of these transport phenomena occur at extremely high pressure, high speed, and high heat flux; these make the control of the roll temperatures an extremely challenging problem.In hot rolling, proper cooling of rolls can lead not only to improve the roll shape quality by controlling the thermal crown of the roll, but also to extend the roll life by minimizing the thermally induced stresses [1,2]. Also, knowledge of roll temperatures can contribute to insights about the roll/workpiece interfacellubricant behavior, and lead to the desired surface condition of the workpiece. Therefore, adequate roll cooling or control of roll temperatures is of critical concern to mill designers and process engineers. In order to have proper operation of the process, a good understanding of the influence of cooling practices on the roll is essential [3]."

Jan 1, 1994

By Janusz Majta

The aim of this work is to investigate the control of microstructure evolution through variation of particular deformation parameters in the two-phase (intercritical) region. Niobium-microalloyed and low-carbon steels were investigated. A detailed examination of the factors affecting the ferrite microstructures of tested steels indicated that there were distinct advantages of finishing at temperatures in the austenite-ferrite region. The various results of deformation in the two-phase region are presented. Consequently, the influence of the most important process parameters on the microstructure evolution and mechanical response of the material is determined. The prime objective of the realized research work is the determination of relationship between the history of deformation and final product quality i.e. texture and mechanical properties. To reach the objective, the constitutive equations are proposed for modeling the effects of the hot-deformation process occurring in the austenite and austenite-ferrite region of low carbon and microalloyed steels on the mechanical properties of the resulting product. These models link advanced, finite element approaches simulating metal flow and heat transfer during hot-plastic deformation with constitutive equations describing microstructural processes and mechanical properties.

Jan 1, 2003

By W. Hoffelner

Plasma technology has become increasingly important for the treatment of several types of waste (toxic, nuclear, metal-bearing scrap). Plasma furnaces combine the advantages of a closed hearth process with a very versatile (several plasma gases can be employed) and effective heat source. It can be successfully used for recovery of metals with subsequent purification and/or vitrification of residuals from drosses or filter dusts.

Jan 1, 1994

The direct removal of lead ions from D2EHPA-kerosene using metallic zinc as the reducing agent was evaluated. The electrochemical process, called galvanic stripping, is a potential alternative stripping technique when standard chemical methods are not adequate. Four parameters found to be important in the rate of lead removal were studied in a factorially designed experiment. The variable evaluated included D2EHPA concentration, temperature, zinc surface area and solution agitation. Temperature and surface area were found to be the most significant, while agitation and D2EHPA concentration had less influence on the reaction. An activation energy of 22.5 Kcal/mole was calculated indicating a chemically-controlled process. The reaction was also sensitive to the concentration of oxygen in the system. The zinc required was considerably in excess of stoichiometry, possibly due to the dissolution and redeposition of lead: In general, the results were encouraging and demonstrated that lead impurities could be removed from D2EHPA using cementation type reactions.

Jan 1, 1995

By Xiang-ning Meng, Miao-yong Zhu

"A three-dimensional finite-element heat-transfer model is conducted to predict temperature of hot copper plate in a slab continuous casting mold and the effect of casting speed on temperature difference between copper plate and solidifying shell is simulated in combination with process data. The results show that centre temperature of hot copper surface at casting speed 1.8 m·min-1 and 2.0 m·min-1 are higher than that of 1.6 m·min-1 casting speed 4.7-5.2 °C and 11.2-12.2 °C respectively and temperature is not increased linearly with casting speed. Temperature difference in meniscus between mold and shell is influenced obviously by casting speed and increased 4.0- 6.0 °C with increment of casting speed 0.2 m·min-1• Fluctuation of temperature difference in meniscus is a main reason to deteriorate casting quality as increasing casting speed.IntroductionIn conventional continuous casting of steel, a large amount of sensible and latent heat of molten steel dissipates in primary cooling zone and mold becomes a critical component of caster to govern steel quality, meanwhile, thermal load on mold is increased constantly and environment is also more abominable since high productivity and quality are required and high-effective technologies are applied. So, an in-depth understanding of thermal behavior of mold at high casting speed is essential to design cooling structure and maintain casting stability. Many studies have been carried out to shed light on thermal behavior in mold. Chow et al. [l] applied a mathematical model to heat transfer in billet mold at a high casting speed to give a new taper in order to minimize mold-strand interaction. Thomas et al. [2] researched relation between mold geometry and temperature distribution based on a finite-element heat-transfer model. Lu et al. [3] indicated that slab mold temperature are mainly affected by thickness of copper plate and nickel layer by a heat transfer model. Samarasekera et al. [4, 5] researched temperature of copper plates for both billet and slab molds and effect of a large number of factors ranging from water quality to casting speed. Park and Thomas et al. [6, 7] developed a finite-element thermal-stress model to determine temperature and thermal distortion and stress in both thin and slab molds and O'Connor et al. [8] applied an elastic-plastic-creep finite-element model in a funnel shaped mold to achieve same goals. Cicutti et al. [9] evaluated heat transfer and temperature fluctuation in a slab mold and proposed an expression to predict global heat flux as a function of process parameters and an index to quantify thermal instability. All mentioned above shown that thermal behavior is not only important to casting stability, it is also premise to further understand mechanical behavior in mold."

Jan 1, 2011

By Paul Dewison

For nine years, from mid-1987 to mid-1996, the copper market enjoyed what appeared to be an endless boom in which prices were much higher relative to production costs than for most other base metals. After the boom ended abruptly mid-1997 with the Sumitomo affair, copper was burdened by an overhang of new projects that promised to swamp demand in what, with the Asian financial and economic crisis of 1997, had become a considerably worse consumption environment. Now, demand prospects do not look so bad. If, as we suspect, we will be dealing with a more rational market in the future, it becomes all the more important to forecast accurately the prospects for consumption. In this paper, we present a new methodology for copper demand forecasting. The methodology forms the backbone of the demand-side analysis for the multi-client study entitled "Long Tenn Outlook for Copper", co-authored by Metalica Ltd. and Bloomsbury Minerals Economics (BME). Key components of the methodology are as follows. (1) Relate demand to economic structure. (2) Focus on products rather than refined consumption. (3) Apply a consistent products/applications analysis to all countries and time series. (4) Incorporate scrap market dynamics within the analytical framework.

Jan 1, 1999

By Alicia E. Ares

316 L Stainless Steel samples were solidified directionally under conditions which produced the columnar to equiaxed transition. The position of the transition was located in each sample and the distance from the bottom of the ingot was measured. During solidification the distribution of temperatures were measured by means of thermocouples located strategically. From the measured temperatures the following parameters were derived; the local temperature gradient, the cooling rate and the velocities of the liquid and solidus fronts. Comparing the location of the transition and the values of these parameters it was found that the temperature gradient reaches negative values of as low as -13.44 "C/cm, and velocities of the fronts of around 0.1 cm/s. Also, a supercooling of 5.81°C were measured which was associated with the supercooling for the nucleation and growth of the equiaxed grains ahead of the columnar front. In addition the primary and secondary dendritic spacing was measured in both regions. The spacing was compared with the predictions from available models. The results are presented and discussed in the frame of the results obtained for other alloys

Jan 1, 2002

By Liu Chunpeng

Under an inert atmosphere, the temperature enhancement of nickel bearing pyrrhotite irradiated by microwave was measured with a special metal-sheathed thermocouple and the non-isothermal rate equations were obtained. Under the controlled oxygen potential of the reacting gas in the microwave field, over 90% sulfur contained in the pyrrhotite is converted into elemental sulfur directly, the iron and the nickel are transformed into FeO,, NiO, NiFe,O, and FeSiO,. According to the experimental data the rate of the elemental sulfur produced is in diffusional control and the non-isothermal equation derived is

Jan 1, 1993