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By Joner O. Alves

The disposal of scrap tires has been a serious environmental problem. The treatment of this waste by pyrolysis and combustion has advantages since the landfill space is dwindling and the production of fuel becomes of technological interest. However, that processes needs a rigid control of emissions. This work presents a study of the light hydrocarbon gases (HC) generated during the burn of waste tire chips in a two-stage laminar-flow horizontal furnace. Different temperatures in the primary and secondary stage of the furnace were tested, and the oxygen/nitrogen percentage was also varied during the combustion process. A gas chromatograph was used to identify and quantify the components of the gaseous products of combustion and pyrolysis. The results showed the behavior of the gases during the burn of tires, providing valuable information to the control of hydrocarbon emissions.

Jan 1, 2010

By Tianjiao Luo

The electroless copper plating process for continuous carbon fiber using CuSO4?5H2O as the main salt and formaldehyde as reducing agent was experimentally studied, including the effects of pH values and concentration of chelating agents, stabilizing agents and reducing agent on the electroless plating process. The surface morphology and the composition of coating were investigated by means of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), and deposited the coating thickness was measured by way of dissolution. The results indicated that the pretreatment of carbon fiber before plating was so important. This pretreatment could prevent the formation of the black cores, furthermore, it could form many active absorption cores with Ag as the center on the carbon fiber surface. Used the optimized parameters in this process, which led to a stable solution for plating, a homogeneous copper coating was conducted with the carbon fiber plated with favorable mechanical performance and high adhesion strength.

Jan 1, 2006

By Yuanbing Ling

Keywords: Calcium sulfate, Sulfuric acid, Phase transformations, Thermodynamic analysis As part of a boarder research project, seeking the development of a cost-effective process for direct production of the high value material, -calcium sulfate hemihydrate, from sulfuric acid at atmospheric as opposed to elevated pressure conditions, the fundamental work presented here has been undertaken. This includes experimental monitoring of phase transformation reactions and thermodynamic analysis of the relationships among the various phases, namely, calcium sulfate dihydrate, hemihydrate and anhydrite in aqueous sulfuric acid solution at temperatures ranging from 20oC to boiling point.

Jan 1, 2004

By Takashi Miyamoto, Hideo Nakae, Hideki Yamaura, Takeshi Yanagihara

"For the production of partially composed metal matrix composites, namely discontinuous MMCs, using a casting· process, the interpenetrated phase composites with SiC particles were fabricated by pressureless iDfiltration using molten Al-Si alloys. This process is based on a wetting phenomenon, therefore, we discussed the technique based on the reactive wetting. The SiC particles coated by diluted water glass were sintered in a mullite Tammann tube and simultaneously infiltrated with molten Al-Si alloys in air at 1173~1573K. As for the improvement of the wettability between the SiC and the liquid aluminum alloy, Fe3O 4 powder was mixed with the water glass due to the thermit reaction between Fe3O4 and molten aluminum alloy. In some experiments, pure aluminum powder was placed on the sintered SiC to increase the interfacial area and the chemical reaction between the sintered Sic. and the melt. By combining these conditions, we succeeded in the complete infiltration without pressure at 1173K.IntroductionAs is well known, the mechanical properties of metal matrix composites (abbreviated MMCs) are superior than that of ordinary metals. However, their use has not been widely accepted because the production cost is very high due to their poor machinability. Therefore, the production of partially composed, namely discontinuous MMCs, by as the Lanxide process [l,2] has been investigated for many years. The Lanxide process, it takes a long time, sometimes up to 10h, in a nitrogen atmosphere for the infiltration. Therefore, the cost will be higher for common use. On the other hand, a high 'pressure process has been adopted for the production of discontinuous MMCs by the Toyota Motor Corp.[3]."

Jan 1, 2000

By Xingjian Gao

The mechanical properties of a low carbon low alloy steel in the austenite and _-ferrite regions have been examined by thermal-tensile tests using a Gleeble-1500D system at temperatures in the range 600oC to 1300oC and at a strain rate of 10-3/s; these being the conditions that apply to the unbending operation during the continuous casting of steel. The yield strength and tensile strength of steel decreased with increasing test temperature and the embrittlement zone occurred in the temperature range 800oC to 970oC. In the embrittlement zone, the fracture surfaces and microstructures of the tensile specimens were examined by scanning electron microscope. The results showed that the cause of the embrittlement at 950oC in which the minimum %R of A was around 36% is the second phase particles precipitated along the _ grain boundary during deformation leading to inter-granular brittle fracture.

Jan 1, 2010

By H. Antrekowitsch

Nowadays, the pyrometallurgical treatment in copper smelters is the common process for the recycling of metals from the electronic scrap. Furthermore the European Directive on the Waste from Electrical and Electronic Equipment (WEEE) and the Directive on the Restriction of Hazardous Substances (RoHS), increase the importance of electronic scrap recycling. Besides these a high amount of plastic and inert components in these materials leads to problems at the processing. An optimisation concerning the internal recovery and the high amount of plastic is necessary to reach the recycling quota of the European directive. The majority of the scrap is treated mechanically in order to separate in a first step plastics from metals, iron from nonferrous metals and harmful substances from valuable materials. But the quality of the different fraction often rather low and further treatment leads to higher costs. Therefore an interaction between mechanical treatment and metallurgical processing should be realised. The Christian Doppler Laboratory for Secondary Metallurgy of Nonferrous Metals at the Institute of Nonferrous Metallurgy at the University of Leoben carried out investigations concerning the optimisation of the metallurgical recycling and the treatment of the input materials especially of printed circuit boards.

Jan 1, 2006

By Z. Sun, H. A. Davies

"Current understanding of the mechanisms by which glassy and crystalline thin ribbons are formed in high speed continuous casting processes is considered. A computer model of the combined heat and momentum transfer during melt spinning has been developed. The influence of roll velocity and of heat transfer coefficient (between the melt and the roll) on the temperature and velocity distributions within the melt puddle is analysed and the thickness of the extracted ribbon computed. The relative importance of heat and momentum transfer under different conditions is assessed and differences between the casting of crystalline and amorphous strip highlighted.IntroductionHigh speed continuous casting of thin metallic ribbon and strip is currently of considerable interest both to metal processers and to those studying process mechanisms. The practical interest arises both from the potential economic benefits to be gained from a shorter and more energy-efficient production route and from the ability to obtain extended and uniform thin strip having a metastable microcrystalline or amorphous structure with enhanced or unique properties. The latter arise from the rapid solidification associated with the cooling of very thin sections of melt brought into intimate thermal contact with one or two rapidly moving heat sinks.The principal processes for casting thin strip include free jet, chill-block melt-spinning (GBMS) (1), melt drag (MD) (2), planar flow casting (PFG) (3) and twin-roll casting (TRG) (4). For the first three of these, all essentially variants of melt-spinning, melt flows through a nozzle onto the circumferential surface of a rapidly rotating roll, whereas for TRG the melt passes into the nip between two contra-rotating rolls. We shall be concerned in this paper with the single-roll melt spinning processes only. For these, a puddle is established where the melt contacts the roll surface and the length of this puddle l is a function of the process conditions, notably the circumferential velocity of the roll Us and the volumetric flow rate of the melt Q. The contact time between any point on the roll surface and this puddle, or residence time eR(= l /Us) determines the thickness of ribbon t extracted from the puddle. This thickness, in turn, partly governs the cooling rate T and the amount of undercooling in the melt and thus the microstructure of the solidified ribbon."

Jan 1, 1986

By Gennady I. Gulyayev

A mathematical model of plastic deformation occurring in cold plug drawing of mother tubes with initial cross-sectional wall thickness variations (CSWTV) has been developed. The main provision of the model is that eccentricity em is of such value that projection of all forces acting upon the plug in the deformation zone along the axis perpendicular to the drawing axis equals to zero. Calculations have proven that with other conditions being equal increase in the die cone angle and the deformation cycle number reduces CSWTV. Theoretical findings were confirmed by practical results. Keywords: cold, drawing, plug, die cone, plastic deformation.

Jan 1, 2003

By D. Death

The Tapping Camera Prototype (TCP) is an instrument being developed to record and analyse video of the molten metal stream entering a tapping crucible as it is tapped from an aluminium reduction cell. The development aims to provide potroom floor operators with continuous real time vision of the tapping process and provide an alert in the event of excessive bath contamination in the extracted metal stream. Longer term the system may provide sufficient data to enable control of the tapping process. The TCP mounts a wireless camera and periscope to view the molten metal stream via a peephole in the tapping crucible. Real time video is recorded to either digital video tape or computer disk for subsequent video analysis to quantify the bath material drawn into the tapping crucible with the molten aluminium. The images transmitted by the camera are available on a handheld LCD video screen. This work is an initiative of the CSIRO?s Light Metals Flagship.

Jan 1, 2006

By V. E. Antonov

Hydrides of iron and iron-based alloys are thermodynamically stable only at hydrogen pressures in the gigapascal range and rapidly loose hydrogen under ambient conditions. At low temperatures, however, these hydrides can be retained in a metastable state at atmospheric pressure after being cooled under the high pressure to liquid nitrogen temperature. This review will discuss the current state of studies on phase transformations in the Fe-H and related systems and also on the composition, crystal structure and physical properties of the hydrides, both under high hydrogen pressures and in the "quenched" metastable state at ambient pressure. The studies at ambient pressure include magnetization measurements, X-ray and neutron diffraction, Mossbauer spectroscopy and inelastic neutron scattering. In the sections on Mossbauer and structural investigations of hydrides of Fe-Cr and Ni-Fe alloys new experimental results will be presented.

Jan 1, 2002

By Yue-yuan Li

China has abundant magnesite resource, but the low-grade and powder ores have always been rejected, which influences the comprehensive utilization of resource and often causes circumstance problems. The present work investigated the preparation of magnesia whisker using magnesite tailings as starting materials by preparation magnesium carbonate whisker as precursor firstly in the route of calcination, hydration, carbonation and pyrolysis, follows by second calcination of the precursor. The influence of pyrolysis conditions and additives on morphology of magnesium carbonate crystal as well as the influence of calcination conditions on morphology of magnesia whisker was investigated. The results showed that thermal decomposition products was MgCO3?3H2O. Magnesium carbonate whisker with length of 10~60 µm and the length-to-diameter ratio of 10~20 was prepared when soluble magnesium salt was added. While temperature was elevated at 1°C?min-1, magnesia whisker with length of 10~60µm was obtained.

Jan 1, 2010

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 Keith S. McIntosh

The fire assay process for the quantitative recovery of platinum group elements (PGE?s) prior to subsequent analysis traditionally is a time-consuming process. Samples derive from various ore types and contain PGE?s at the ppm or ppb levels, making concentration of the elements mandatory before assaying. Traditionally sample turn-around times are of the order of 24 hours. The whole sequence of sample preparation, fire assay and subsequent analysis of PGE?s have been automated by Anglo Platinum. Some of the major challenges on the road to automation will be discussed and the novel solutions that were implemented. The engineered solution included robotic automation of the whole sequence, from sample preparation, up to the final element by element assay. The final system allowed for rapid (less than one hour) and accurate analysis of PGE?s even in streams containing very low levels, such as flotation tailing streams and drill core samples.

Jan 1, 2006

By Preston C. Holloway

Transformational roasting involves the heating of a material along with specific additives to induce mineralogical changes in the starting material. By controlling the chemical composition, roasting atmosphere, temperature and time of reaction, the mineral transformations induced during roasting can be engineered to control the distribution of valuable, or harmful, metals and to produce new mineral assemblages that are more amenable to conventional methods of metals recovery or to environmentally safe disposal. To date, this type of process has only been applied to the recovery of a limited number of metals, but current research is looking to expand the application of these techniques to the recovery of metals from a wider range of materials. An introduction to these techniques is presented along with preliminary results from their application to metals recovery from zinc bearing wastes, such as zinc ferrite leach residues and carbon steel electric arc furnace dust.

Jan 1, 2006

By Albert Wraith, Thomas Price, Wayne Boyd, Skip (I. E. ) Hills, Cameron Harris

Most Peirce-Smith converters inject air through tuyeres, with nitrogen representing the majority of gas passing through the process. The nitrogen controls the temperature of the vessel by carrying away heat from the reactions, both globally and locally at the tuyere tip. However, nitrogen adds energy to the bath and contributes to splashing and limits the blowing rate. High oxygen smelting has made streams of gas containing high concentrations of sulphur dioxide commonplace, which can be used to substitute SO2 for nitrogen and drastically changes Peirce- Smith converting (and all other smelting/converting processes as well). Less SO2 is required to carry away the same quantity of heat, which allows higher concentrations of oxygen and leads to the possibility of increased production. The paper investigates this substitution, its impact on converter productivity, and on the remainder of the plant. 181

Jan 1, 2009

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transfonnation under the condition of continuous casting by heated mold was studied. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition are reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable techniques will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solid-liquid zone have an important influence on the formation of the above defects. When the solid-liquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the remaining liquid cannot counteract the solidification contraction, a rough surface will appear. If the solidification surface further into the mould, the ingot in the mould will have a great friction force when pulling and will form a hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which easily results in leaking. A vibration or unstable operation will cause an ingot winding during pulling.

Jan 1, 2003

By Art Cooper

Granulation systems are customarily viewed as problem areas in metallurgical operations. The inherent risk of explosion when combining a high temperature melt with water creates a safety hazard. Separation of the granulated material from the quenching medium generally involves equipment that can have significant maintenance and operating costs. Granulation systems' reliability and availability can negatively affect the plant production. Against this background, granulation systems have been treated by design firms and producers as an add-on and a necessary evil. The technology is becoming better understood and solutions to common problems are being found. This paper will discuss typical problems in common systems, and some of the improvements that have been made, with particular reference to non-ferrous applications.

Jan 1, 2006

By Ludovic Charpentier

Production of metallic wires directly from liquid jets would avoid drawbacks of extrusion (space needed, damaging, cost?) and enable recycling. But liquid jets tend to break, due to capillary instabilities, unless a solid layer (coating or start of solidification) surrounds it. We recently developed a process to produce tin wires, cooled by water flow parallel to the jet. Superficial oxidization of tin produces a glass coating around the jet. Studies showed the length of wires increased when increasing speed of tin jets, and that water average speed should be the closest possible to the jet one to have smooth fibers. Producing 1 mm diameter wires is possible. The length of wires is limited by the experimental setup, which does not provide possibilities to coil the wire. Most of other metals do not generate glass-like oxides. The lack of coatings makes it necessary to reduce the capillary instabilities to obtain fibers.

Jan 1, 2006

By Tian Sugui

By means of the measurement of the enduring property and microstructure observation, an investigation has been made into the influences of the element Re and TCP phase on the enduring property of the single crystal nickel base superalloys. Results show that the needle-like TCP phase is precipitated along the <110> orientation on {111} planes in Re-containing/free superalloys during the long term aging, the TCP phase is identified as µ phase, and the precipitated µ phase in 4.5%Re alloy is gradually spheroidized during aging. Thereinto, the needle-like µ phase may obviously decrease the enduring lifetimes of the alloys due to the consumption of the refractory elements and the effect of the stress concentration. But the stress concentration is not easily generated in the regions near the spherical-like µ phase, which is a main reason of reducing the enduring lifetime of 4.5%Re alloy to a small extent.

Jan 1, 2010

By S. Prasad

The effectiveness of ultrasonic velocity measurements and attenuation of the propagating pulse was evaluated as a means of Non-Destructive characterization of cold worked and annealed copper. Commercial copper is subjected to mechanical working such as forging, rolling and thermal treatment to induce re-crystallization. The microstructural changes that occur in copper and a variation in its mechanical properties are subjected to analysis using the ultrasonic technique. The signal processing is carried out using the wavelet analysis technique. The features of wavelet analysis namely, localization in space and the presence of an infinite set of basis functions allows removing noise from the time series and components of a non-stationary signal to be analyzed. This is seen to improve the accuracy of the results obtained from the ultrasonic technique in the case of copper, which has distinct coarse grains that are difficult to inspect due to backscattering from the grain boundaries.

Jan 1, 2010