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By I. Nikolic

Twin-roll casting is an integrated casting and rolling process that involves the continuous solidification of a melt and the plastic deformation of the solidified metal between two rotating rolls. Computer modeling is a valuable tool to help engineers understand the metallurgical process during twin-roll casting. However, commercially available software can only model either the fluid flow/heat transfer of the melt or the plastic deformation of the solid, but not both. In this study, an object-oriented finite element program was developed to simulate the steady-state fluid flow, solidification and plastic deformation of an A7,31 magnesium alloy in a horizontal twin-roll caster. The melt, the mush zone and the solid were treated as a generalized Newtonian flow in an Eulerian reference frame and different constitutive equations were employed to describe the material behaviours. The effect of operational parameters on the solidification process was discussed based on the simulation results.

Jan 1, 2010

By Hector Carreon

Due to elevated temperatures, excessive stresses and severed corrosion conditions, turbine engine components are subject to creep processes that limit the components life such as a turbine bucket. The failure mechanism of a turbine bucket is related primarily to creep and corrosion and secondarily to thermal fatigue. As a result, it is desirable to assess the current condition of such turbine component. By using eddy current images, it was shown that the eddy current technique could be used to monitor creep damage in a nickel base super-alloy. The eddy current results also show a significative variation in the electrical conductivity on the creep damage zone with respect to the background zone in nickel-base super-alloy samples. In addition, the absolute thermoelectric power coefficient show also a strong dependence associated with creep damage in nickel base super-alloy samples using a copper hot tip reference. The eddy current and thermoelectric power techniques seems to show promise as nondestructive evaluation tools for monitoring the level of creep damage in metallic alloys.

Jan 1, 2010

By Fumito Tanaka

The Mitsubishi Process is the sole pyrometallurgical process for the continuous production of blister copper from copper concentrates. Continuous converting originates from the application of the proven technology of a lime-ferrite slag (CaO-FeOX-Cu2O) on the Converting Furnace (C-furnace). Recent improvements on the C-furnace operation have included increasing the processing of recycled materials and the investigation of alternative fluxing agents. However, some minor oxides adversely affect C-furnace operation, with respect to magnetite behavior of the slag, with the most significant impact having been observed with the silica content of the slag. This paper will quantify the impact of silica on the lime-based slag, and discusses the controls that have been identified to sustain continuous converting operation.

Jan 1, 2005

By Kim Fagerlund

Boliden Harjavalta Oy operates a copper smelter in Finland, which is based on flash smelting together with Peirce-Smith converting of copper matte. This paper reviews a case study when a high arsenic feed mixture was successfully eliminated in order to guarantee the anode quality. Based on theoretical and practical knowledge in slag chemistry at Outokumpu Research, the CaO-fluxing practice was introduced. Description of a thermodynamic simulation using MTDATA and implementation of the results into converting practice is given. Results showed that the impurity fluctuations in raw materials could be effectively controlled by efficient utilization of different slag chemistry.

Jan 1, 2005

By Thomas P. Battle

Modern-day direct reduction of iron first developed as a small-scale, low capital and operating cost alternative to the blast furnace. Since commercialization of continuous DR technology in the late 1960s, the market for the products of direct reduction has grown to more than 74 million tonnes in 2012. The initial advantages of DR plants over BF facilities have grown over the years, for several reasons, including the increased size of DR modules, lower energy and emissions (particularly CO2), along with the flexibility to use a number of different reductants. The development of DR technology over the past forty years will be emphasized in this presentation, including recent developments that allow for even more direct sustainability comparisons with the iron blast furnace – and even combine the two technologies for improved synergies. Also briefly discussed will be the possibilities of using direct reduction for non-ferrous ores.

Jan 1, 2014

By Bowen Li

Silicon Carbide is an excellent refractory material. Its physical properties make it extremely useful, particularly in applications where corrosion resistance and wear are important considerations. Commercial silicon carbide refractory is frequently manufactured by bonding silicon carbide particles with clay; however, clay may cause problems in the sintered products. This study investigates the potential of replacing a portion of the clay with andalusite powder. The results show that micron size andalusite powder can improve not only the strength of the refractory but also the sinterability. The mechanisms for these improvements are discussed.

Jan 1, 2006

By Viviane Tavares

The technology advance of mobile devices makes consumers of these equipment do more constant exchanges, with this the obsolete devices discarding becomes an environmental problem, due its landfill accumulation. In order to minimize the environmental impacts caused by these equipment there?s the recycling necessity of polymers, ceramic and metallic materials. The main goal of this recycling is to study the printed circuit board of device mobile processing through ore treatment in order to recoup copper. Initially printed circuit boards were processed in a knives mill, in order to liberate the ferrous material, after that it was done the magnetic separation of the reduced residue. With the not magnetic fraction it was done the grain sized analysis and sulfuric acid and hydrogen peroxide leaching analysis. With the chemical analysis results proceeding from the leaching aliquot it was possible to observe that the leaching method with sulfuric acid and hydrogen peroxide presented greater copper recovery.

Jan 1, 2009

By Alaina B. Hanlon

Keywords: Undercooling, Convection, Dendrites, Stainless Steel, Levitation Certain Fe-Cr-Ni stainless steel alloys solidify from an undercooled melt by a two-step process in which the metastable ferrite phase forms first followed by the stable austenite phase. Recent experiments have shown that the lifetime of the metastable phase is strongly influenced by flow within the molten sample. The current research will provide insight to why flow affects the metastable phase. This new understanding will lead to the use of convection to control microstructural evolution in spray-forming of stainless steels. Simulations using a commercial computational fluid dynamics package, FIDAP, yield a range of convective flow velocities that cause mechanical damage to the dendrites which is compared to experimental results. If the convective velocities are great enough that the dendrites bend, then low angle boundaries form at the points of collision. These result in high energy sites that could serve as nuclei for the stable phase.

Jan 1, 2005

By K. Morsi

Carbon nanotube (CNT) reinforced metallic composites have been recently generating significant scientific interest, due to their expected superior properties compared with other composites. Out of the metallic matrices investigated for reinforcement with CNTs, aluminum has received considerable attention. A major problem has been the dispersion of CNTs in metallic matrices. This paper discusses preliminary results on the mechanical dispersion of CNTs in aluminum powder, powder processing, stability and characterization of aluminum dispersed with CNTs at reinforcement levels equal to and below 5 wt.%.

Jan 1, 2009

By Qingwei Wang

Heavy metal-containing wastewater from hydrometallurgical processes of lead-zinc was treated by biologics in a 200 m3/h industrial scale experiment. The result shows that Zn concentration declined from 50.28 mg/L~240.81 mg/L to 0.21 mg/L~1.98 mg/L, Pb from 1.00 mg/L~13.47 mg/L to 0.083 mg/L~0.71 mg/L, Cu from 0.24 mg/L~2.38 mg/L to 0.059 mg/L~0.40 mg/L, Cd from 2.12 mg/L~23.47 mg/L to 0.011 mg/L~0.071 mg/L and As from 0.50 mg/L~6.00 mg/L to 0.005 mg/L~0.10 mg/L. The concentrations of the above heavy metals in the treated water were lower than that in Integrated Wastewater Discharge Standard (GB8978~1996) in China. Furthermore, the treated wastewater was recycled and reused in smelter plant. Zinc content in hydrolytic sludge reached up to 34.04%, which indicates that this sludge can be used to recover valuable metals.

Jan 1, 2010

By A. Gibson

Most methods for the treatment of scrap printed circuit boards do not reclaim the components in working order as the boards are either fed to a copper smelter, to recover the valuable elements, or, simply landfilled. This work reports the dissolution of the solder in fluoroboric acid containing Ti4+ ions which was particularly selective for solder, allowing the components to be recovered. The solder was subsequently electrowon from the leachant. The boards were then shredded and the copper dissolved in ammonium sulfate and, then treated via solvent extraction to give an electrolyte suitable for electrowinning. The remainder of the metals were dissolved aqua regia, silver remained unattacked by the aqua regia, palladium precipitated as Pd(NH4)Cl6 in the presence of zinc and nickel, the gold was removed by solvent extraction and precipitated as nanoparticles. The aqua regia was then diluted and the zinc and nickel separated by solvent extraction.

Jan 1, 2009

By Liu Wei

In order to make clear the dissolving characteristic of the chrysocolla (CuSiO3?H2O) in the ammonia-ammonium chloride solution, a thermodynamic model of the chrysocolla (CuSiO3?H2O)-ammonia- ammonium chloride-water system is established using the exponential computation method based on both mass balance and charge balance equations. The equation group of the thermodynamic model is solved by the MATLAB Soft on PC. The condition which is favorable for dissolving high concentration of copper in solution is making out. The stable area of chrysocolla (CuSiO3?H2O) and the condition of chrysocolla (CuSiO3?H2O) converting to atacamite (Cu(OH)1.5Cl0.5) is also studied. A group of experiments are designed to validate the veracity of the results of the thermodynamic calculation.

Jan 1, 2010

By Huang Kai

By adding the solid oxalate acid powder into the solution of nickel chloride or its ammonia coordinated solution, the uniform compound particles were prepared and the precipitated particles were transferred to the mono-dispersed NiO particles by calcination. In this study, the various experimental conditions were investigated, the characteristics of the corresponding obtained particles were analyzed, and the formation mechanism of the particles was elucidated. It was found that the solid oxalate acid provided the solid-solution interface for the precipitation and induced the nucleation and growth of the product particles.

Jan 1, 2005

By Akihide Hosokawa

The void growth and coalescence in model materials involving a pre-existing three dimensional void array (i.e. multiple layers of a void array) was studied by X-ray computed tomography (XCT) coupled with in situ tensile deformation. To reduce the recording time, a new technique called fast tomography was employed. The model materials used in this paper were fabricated by the combination of an ultra-short pulsed laser machining system and a diffusion bonding technique, and two different types of arrays were prepared namely, FCC 1 and FCC 2 type array. This methodology allowed the authors to capture the entire process of growth and coalescence events of a void array embedded in the metal matrix. The failures in the both materials involved internal necking and shear localization. One of the highlights of this paper is that the plastic strain at the onset of void coalescence was measured for each model material. These values are in fact the adequate values to be compared with the coalescence strain predicted by existing void coalescence models such as the Brown and Embury model, the Thomason model and the Pardoen and Hutchinson model. The comparison suggested that the Brown and Embury model underestimated the coalescence in neither of the current model materials, while the Thomason model and the Pardoen and Hutchinson model showed a quite good agreement with the result for FCC 1 material. On the other hand the result from FCC 2 material agreed with none of the models probably due to the geometry of the void array that is not compatible with the existing models.

Jan 1, 2010

By K. Morsi

The interest in spark plasma sintering has been growing considerable over the past few years. This has been brought about by the unique advantages of the process, which include reduced sintering temperatures and times and the production of materials with unique microstructures and properties. Despite its current reputation as an outstanding process that has solved major problems such as nano-powder consolidation, it has so far been largely limited to the manufacture of simple shapes, due to its inherent geometric configuration. In this paper we present preliminary results on spark plasma "extrusion" that can allow the production of extended geometries via electric-current processing. Preliminary results on the processing and microstructure of spark plasma extruded aluminum are discussed.

Jan 1, 2009

By Linli Wu

During the measurement of contact angle, a misty band was observed near the substrate. Hsien-Nan Ho and Shinn-Tyan Wu thought this was because the oxygen atoms on the interface migrate to the droplet surface to form an oxide band near the substrate. But from our experiments misty band appeared before the drop reach to the substrate. Theoretically speaking, the oxygen partial was the same everywhere in the vacuum furnace. So there was no condition to provide enough oxygen forming oxide. This appearance would be explained more reasonably with the optics principle. Most reflected light would be absorbed by the substrate and the light cannot reach the observation area, so the misty band formed.

Jan 1, 2006

By C. E. M. Meskers

End-of-life Electronic and Electrical Equipment, o_cially called WEEE, is unjustly regarded as mainly a waste management problem. What is structurally overlooked is the enormous resource impact of these devices. EEE rep- resents a tremendous metal resource, which should be uti- lized through e_ective recycling, which has a much lower environmental footprint than primary production. The actual amount of end-of-life EEE recycled today is embar- rassingly low since insu_cient EEE is collected and part of the collected EEE is exported to developing countries, where it is largely not entering o_cial recycling systems. To achieve a global recycling society issues like technol- ogy, economics, life cycle structure, stakeholder aware- ness and legislation have to be addressed in a global, co-operative manner so that sustainable closed product cycles can be obtained. Requirements for a "global re- cycling society" are de_ned to address today's reality of global ows of used consumer products, taking into ac- count the likely needs of the future.

Jan 1, 2009

By Jewel A. G. Gomes

Green rust (GR) are layered Fe(II)-Fe(III) double hydroxides, having a pyroaurite-type structure consisting of positively charged hydroxide layers and hydrated ions in interlayers. This special feature of GR is very efficient for wastewater treatment as the pollutants are easily taken in or exchanged with the anions in the interlayers. It can be simply and cost-effectively produced by electrocoagulation (EC). Chicken processing plant (CPP) produces large amount of wastewater containing variety of readily biodegradable organic compounds, fats, and proteins. The possible re-use of properly treated CPP wastewater would be economic and environment friendly. In this study, we present our work on treatment of CPP wastewater using EC, specifically for the removal of COD. Analysis of the EC-treated water for reuse in the same plant is discussed considering the U.S.EPA regulations. Two types of EC-reactors were used for this purpose. To better understand the treatment mechanism, EC-floc was also characterized using XRD and SEM-EDS.

Jan 1, 2010

By Ramona Prillhofer

Salt slag is a waste product produced by the recycling of aluminum. In most European countries (e.g. Austria, Germany) the landfill disposal of this waste is forbidden because the slag contains soluble salts and these represent a potential source of pollution to the surface and groundwater. Additionally, consisting metal and some compounds in the salt slag can react with water and resulting from this, noxious gases are generated. The recovery of useful materials from these wastes is accordingly both environmentally necessary and economically feasible. This study describes a complete recycling-process for the salt slag, which includes a leaching-cristallization-process to obtain the oxidic residue, a pyrometallurgical-step to clear the oxidic residue and finally an extensive characterization of the achieved products. Due to the increasing price of raw materials, the utilization of the oxidic residue into commercial products has been investigated and application possibilities will be discussed.

Jan 1, 2009

By Carlos Maurício Fontes Vieira

In the present work a ceramic body, fabricated using a mixture of clays and sand, for roofing tiles, produced in Campos dos Goytacazes, north of the State of Rio de Janeiro in Brazil, was characterized. Characterization was performed by X-ray diffraction, thermo analysis, chemical analysis, particle size distribution determination and plasticity. In addition, technological properties related to water absorption, linear shrinkage and flexural rupture strength were determined in samples fired at 700, 900 and 1100oC. The results showed that the investigated ceramic body has satisfactory plasticity and presents a refractory behavior during firing due to the predominantly kaolinitic nature of the clays.

Jan 1, 2006