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By A. Jain

During sheet forming, metal experiences not only multi-axial load, it also undergoes strain path changes. For example, metal in the flange region may be drawn, may bend and unbend through a bead, before bending around a die radius, etc. Compression data were obtained from AZ31 sheet after pre-straining in compression along an orthogonal direction. The compression directions correspond to the sheet product (rolling-RD, transverse-TD, and normal-ND) directions. Three cases are examined: slip dominated deformation (ND) followed by twin dominated (RD or TD) deformation, twin dominated (RD or TD) followed by de-twinning (ND), and twin dominated (e.g. RD) followed by cross-twinning or secondary twinning (e.g. TD). Slip induced pre-straining simply hardens the material, while twin dominated pre-straining alters the texture allowing the material to either de-twin or re-twin upon changing the strain path. Polycrystal plasticity modeling has been used to predict qualitative features of the flow curves during strain path changes.

Jan 1, 2006

By T. Watanabe, M. Nakagawa, K. Kimapong

Ultrasonic wave was irradiated on metal surface in water to introduce compressive residual stress. The ultrasonic wave that was oscillated with 19.5 kHz ultrasonic transducer and amplified with a step type horn was irradiated. Slight plastic deformation occurred at the surface region of pure metal such as Cu and compressive residual stress was introduced. It seemed that the plastically deformed depth from the metal surface corresponded approximately to the depth of introduced residual stress. The higher compressive residual stress could be introduced into the surface of Cu-Zn brass and SUS304 stainless steel because work-hardening was simultaneously induced to those alloys. Furthermore, since martensitic transformation was induced by the plastic deformation in the case of SUS304, the compressive residual stress could be introduced more deeply into the surface region. The residual stress of SUS304 reached to the maximum value of 574 MPa by irradiating for 5min.

Jan 1, 2004

By G. T. Fisher

A continuous process is used at Phelps Dodge Sierrita Inc. to produce copper sulfate pentahydrate via a solution extraction ? crystallization approach to supply the animal feed market. A review of the fundamental concepts of the process and unit operations is presented. Improvements in the process are aimed at achieving a controlled size distribution of product crystals (-40+80 mesh) with minimization of fines by primary nucleation and crystal breakage. An independent temperature control design was implemented for the heat transfer medium (water) in each crystallizer, albeit using common headers in and out of the chiller. This design was developed to maintain a controlled degree of supersaturation in each vessel while preventing localized spontaneous nucleation of fines and reducing encrustation of the heat transfer surfaces in each crystallizer. A model was developed to calculate the heat load and heat transfer coefficient of each crystallizer along with the saturation copper tenor as a function of temperature and free acid.

Jan 1, 2007

By G. Kordosky

Leaching aids that result in an increase in leaching rates and overall copper recovery have the potential to be beneficial to copper leach/solvent extraction/electrowinning operations. It is generally accepted that effective leaching aids facilitate the penetration of leach solution into ore by lowering the surface tension of the leach solution. Surfactants are designed to do this, and a leaching aid containing the widely used surfactant class, alkyl phenol ethoxylates, has been suggested. Alkyl phenol ethoxylates were tested to determine how they may affect phase separation, entrainment and degradation in a copper solvent extraction plant. The test results suggest the use of leaching aids at a regular rate, or even for a short time period, may have a long term impact on copper solvent extraction. Several scenarios are evaluated regarding existing operations and future solvent extraction projects and cautionary suggestions related to the use of surfactants as leaching aids are given.

Jan 1, 2007

By A. Yousefpour, M. Hojjati, M. Simard, M. Laramée, M-A. Octeau

The need for effective and reliable joining methods grows as the use of advanced thermoplastic composites becomes widespread in aerospace industry. An experimental investigation of resistance welding of APC-2/AS4 thermoplastic composite laminates is presented. In this method, a heating element is placed between the bond-surfaces then the interface is heated by passing electrical current through the heating element. The polymer at the weld interface is melted due to resistance heating, then diffuses and consolidates under applied pressure, resulting in a weld. APC-2/AS4 prepreg, APC-2/AS4 commingled, and different grades of metal mesh heating elements were considered. A custom made resistance welding rig was designed and developed to perform lap-shear welds. The mechanical performance of the welds was quantified using single lap shear tests. The effects of different heating elements on the mechanical performance of the resistance-welded parts were investigated. Also, quality of the welds was examined under optical microscopy.

Jan 1, 2004

By G. C. Weatherly, D. S. Wilkinson, A. M. Limarga

In addition to the harsh environment, materials for high-temperature applications are often subjected to a significant mechanical loading. Several researchers have noted that the rate of oxidation can be affected by stress in a range of materials. We have recently studied this effect in y-TiAl, based on the preliminary work of Magnan and Weatherly which showed that nitridation rates on the tensile side of a flexural creep specimen could be 10 times higher than on the compressive side. We have since developed a four-point bending creep setup capable of controlled atmosphere testing. We present quantitative data on the effect of creep on scale growth under a range of atmospheric conditions. Finite element analysis will also be used to show how modest applied stresses can have a large effect on scale growth rates through the generation of large stresses due to the mismatch of creep rate between the metallic substrate and the scale.

Jan 1, 2004

By Q. Dong, S. A. Nightingale

An investigation has been carried out to assess the effects of an applied voltage on the dissolution rate of MgO refractory in a steelmaking like slag. In this study corrosion results obtained from dip tests using a dense direct bonded MgO refractory in a CaO-SiO2-Fe2O3-FeO-MgO slag are presented. These results demonstrate that the application of a voltage across a dense MgO refractory-slag interface can change the rate of refractory dissolution. For the slag composition used and the voltage range tested, it was found that a maximum corrosion rate was obtained at a voltage setting of -0.45V. The results of this investigation have been explained in terms of voltage affects on Marangoni (interfacial tension induced) stirring and its effect on the MgO dissolution reaction that is at least partly controlled by mass transfer in the slag.

Jan 1, 2004

By M. Kawahara, H. Sunayama

Oxidation rates of the cubic specimens, which were prepared by cutting the shaped magnesia-carbon bricks, were measured continuously with a thermo balance in the temperature range from 1273 to 1 823 K in N2-02 and Ar-02 mixed gas with 2.1 x 104 and 3.7x 102 Pa of oxygen partial pressure respectively. The effect of the graphite content, the maximum grain size of magnesia clinker and the oxygen concentration in the atmospheric gas on the oxidation rate for the MgO-C refractory has been investigated. The value of effective diffusion coefficient of O2, which diffuses through the porous decarburized layer, decreased with the decreasing of the porosity and the oxygen concentration in the external gas phase. It was speculated that the dense layer formed easily due to the high tortuosity of pores and the low recession speed of the carbon interface in the MgO-C bricks.

Jan 1, 2004

By S. Afshar, C. Allaire

Several studied have recently shown that the use of non-wetting additives is not always a sufficient solution to improve the corrosion resistance of refractories against molten aluminum. Once in contact with liquid aluminum, the coarse aluminosilicate aggregates, which do not benefit from the protective effect of non-wetting additives in the matrix, may be corroded. In some cases, the corrosion of aggregates, especially those containing a significant amount of free silica and/or alkalis, promotes corrosion in the surrounding matrix. The present work explores the possibility to protect the poor corrosion resistant aggregates via a lining procedure. A slip casting method, using either alumina or celsian-like composition based slurries, has been applied for lining of a series of aggregates. The results from this study show that such linings may prevent efficiently the corrosion of aluminosilicate aggregates. This work also analyzes the effects of firing temperature and lining quality on the corrosion behavior of aggregates

Jan 1, 2004

By P. Stantke

Glue, thiourea and chloride are the common reagents which are used in copper electrorefining to achieve fine-grained and smooth copper deposition. While thiourea and chloride are clearly defined chemical substances, glue is a natural product consisting of a mixture of amino acids in different constituent parts. The amino acids are continually degraded in the electrolyte by hydrolysis until they finally become completely inactive. This effect is well-known, largely constant and balanced by the continuous dosing of glue. In contrast, the behaviour of glue in the batch container is not always foreseeable. The glue can become partly or completely inactive by contamination with acid or bacteria, for instance. Usually this is not noticed, and partly or fully inactive glue is added to the electrolyte over a longish period, with the result that the copper growth is significantly impaired. Examples from operational practice show that, with the help of the CollaMat system, partly or fully inactive glue batches can be quickly detected.

Jan 1, 2007

By M. Kalin

Tailings deposits are frequently the source of ground water contamination due to the transport of contaminated tailings pore-water. If amendments to tailings covers could be made to facilitate a precipitation reaction and halt or reduce the generation of acid in pyritic tailings, the quality of pore-water quality would be improved which would in turn reduce the production of contaminants. The effects of phosphate wastes, added to base-metal mine tailings in Newfoundland, Canada, were tested. Laboratory and field experiments determined the effects of different mixing ratios of phosphate wastes to tailings volume (1:4, 1:8, 1:12 and 1:20, dry weight) for a total period of 3.2 years. The addition of phosphate at ratios of 1:4 to 1:12 substantially increased the pore water pH, and reduced both acidity and Zn concentrations. These results suggest that addition of phosphate wastes to tailings covers can reduce acidity generation and improve tailings pore-water quality.

Jan 1, 2004

By Inga Tuzovskaya1i

Three types of gold species were observed for gold-zeolites, prepared by reduction of ionexchanged Au species in a series of zeolites: (i) Au3+cations, (ii) neutral Au0 n or charged Aus+ n clusters suggested to be inside the zeolite channels, (iii) Au nanoparticles with diameter varied from 2 through 20 nm located on the external surface of zeolite microcrystals. Contribution of the gold species formed in zeolite after the ion exchange was found to depend on zeolite type, acidity of zeolite, temperature of reduction and time of storage of the exchanged and reduced Au-containing zeolites. Au3+ ionic species and clusters Aun were formed after the ion-exchange procedure (in contrast with the familiar production of Agn in same zeolites). Gold nanoparticles were observed only as the result of reduction of the Au-exchanged forms at elevated temperatures due to reduction of Au3+ species and aggregation of clusters.

Oct 1, 2003

By Chelto. D. Smith

With the pressure on mine and metallurgical managers to take accountability for responsible corporate governance in their operational area, it is no longer acceptable to rely on central departments in the organization to manage safety, health and environmental impacts of the company?s processes. Environmental impacts exist because of the production or mining process. Some of the inputs to the process are natural resources and some of the outputs of the process are the inputs to the environmental control equipment, plant and the environment itself. Environmental management therefore needs to be incorporated in production management to effectively control and reduce the impacts. Many aspects of environmental management are identical to production management and the systems to manage them will likewise be very similar. By examining key components of these two management systems a decision can be made whether environmental management and production management are structurally similar and can be integrated into a combined IT solution.

May 1, 2009

By D. Harris, S. Murugesan, G. Ye, G. Oprea, J. Rigby, T. Troczynski

The spinel-added and in-situ spinel bonded castables have been developed and widely used in steel industry. It is challenging to develop magnesia-based castables for the non-ferrous industry because the temperatures in industrial furnaces are significantly lower than those in the steel industry and therefore the binding systems of these castables must have the capability to develop a ceramic matrix below 1300°C. It is also challenging to develop a good binding system without addition of fume silica, because the hydration of magnesia may take place during installation, curing and firing of the castables. This work presents the experimental results on developing magnesia-based cement-free, silica fume-free refractory castables using hydratable alumina as the hydraulic binder and a spinel phase as the final ceramic binder. In order to activate the sintering and have a ceramic matrix well developed at the relatively low required temperatures, ultrafine aluminas, chromia, magnesium-aluminate spinel and aluminum titanate powders were used as components of the binding system.

Jan 1, 2004

By Michael Jerome Wallace

"This paper refers to the wet open circuit ball mil ls in operation at Sidbec-Normines'5 pelletizing plant at Port-Cartier, Quebec, which commenced operations in late November· 1977. Prior to detailing our experiences in the grinding area at Port-Cartier, a general description of the total Sidbec-Normines project is outlined.HI STORYSidbec-Normines was incorporated in 1976 to develop the Fire-Lake - Port-Cartier iron ore mining, concentrating and pelletizing project. The primary objective of Sidbec-Normines is to produce 6mi11 ion tons per year of oxide pellets, of which 3 mi 11 ion tons per year are of a low silica grade suitable for direct reduction purposes. The participants in the project are Sidbec, the Quebec Government steel producer, British Steel Corporation (lnt'l) and the Quebec Cartier Mining Company. Equity interest is held in the company by the participants in the proportions of 50.1%, 41.6:7% and 8.23%, respectively."

Jan 1, 1979

By Larry Urbanoski

"This paper describes the application of a radioisotopic energy dispersive X-ray aY1alyser to complete on-stream analysis in a base metal concentrator.The major components of the system are outlined and some description of the application, operating experiences and benefits are provided.IntroductionThe ma1n intent of this paper is to describe the on-stream analysis system in operation at the Geco concentrator. X-ray analysis systems installed in Canadian concentrators to-date may be broadly classified as wavelength dispersive analysers whereas the installation described herein is an energy dispersive x-ray analysis system. Energy dispersive x-ray analysis techniques may utilize radioactive sources to provide primary x-rays for excitation of elements and separate the secondary x-rays on the basis of energy levels. In contrast wavelength dispersive analysers apply high voltage x-ray tubes to provide primary x-rays and utilize crystals to disperse and thereby separate x-rays generated by bombardment of the sample."

Jan 1, 1978

By J. W. Stickney

"On July 1, 1977 Hudson Bay Mining and Smelting Company Limited announced the commencement of construction of a 3800 ton per day concentrator at Snow Lake, Manitoba. Snow Lake, a community of 2200 people, is located 130 road miles from the main metallurgical plants at Flin Flon.The design, detailed engineering and equipment selection for the project was awarded to Wright Engineers Limited of Vancouver, B.C., who would be working in close liason with Hudson Bay Mining personnel throughout the project.The feasibility of constructing a metallurgical plant in the Snow Lake area, in addition to the concentrator at Flin Flon, had been under study since 1964 with plants of varying capacities and designs being considered. Each successive study recommended a plant of increased capacity and sophistication and finally upon an in-depth study in 1976 of ore reserves, freight rates and operational benefits, the construction of a 3800 ton per day copper-lead-zinc concentrator appeared highly benificial."

Jan 1, 1981

By David F. Machuca-Mory

Modelling the geometry of a vein is a crucial step in resources estimation. The resulting models are used as mineralization domain boundaries and have a direct impact on the tonnage of estimated resources. Deterministic models are often built using time consuming wireframing techniques usually based on hand interpretation of the drillhole intercepts. Another approach consists in coding the drillhole samples by a function of their distance to the veins contacts. The coding is subsequently used for modelling the vein contacts away from drillholes. This is a more efficient approach and is able to provide a measure of tonnage uncertainty. The use of location-dependent variograms improves the modelling by incorporating local changes in the anisotropy of the vein structure. This combined approach results in more realistic vein models, particularly when the geometry of the vein has been are altered by folding, shearing and other structural processes. The approach is illustrated on a realistic case study.

Oct 1, 2009

By Christopher McElman

Real-time mine management solutions have evolved over time from closed, proprietary solutions, to a "system of systems" that may include a wide variety of off-the-shelf components and technologies. Modular Mining Systems has embraced open standards for their NextGen products to bridge the technology gaps between these systems. However, the remaining logical gaps must be overcome, in order to achieve truly seamless integration between discrete systems. When dealing with volatile real-time management problems, the effectiveness of business process modeling and middle-ware can break down. Scientific principles of military command and control applied to mining domain help to achieve better alignment and reach the highest level of integration. The combination of open standards and off-the-shelf hardware and software with a deliberately structured command-and-control approach provides a clear evolutionary path from ad-hoc connected systems towards real-time management of a seamlessly integrated digital mine.

Oct 1, 2009

By Cheryl L. Allen

Increasing energy costs associated with mining have become an issue that must be addressed by industry to ensure sustainable production. As underground mine ventilation systems account for 40% to 50% of a mine?s total energy requirement, initiatives to maximize their efficiency have been introduced worldwide. A control method known as Ventilation-On-Demand (VOD), which adjusts the ventilation system by responding to the activities of mine personnel and air quality, has been commissioned at Vale?s Coleman Mine. This initiative is an effort to reduce energy consumption, maximize efficiency of the ventilation system while ensuring air quality. There are five control strategies that can be executed with the VOD control system in place at Coleman Mine: Manual real time control Time-of-Day Scheduling Event-based control Environmental control Activity Based Control/Tagging This paper describes the system, control strategies and impact on energy consumption and flexibility of airflow distribution as applied at Vale?s Coleman Mine.

May 1, 2011