Search Documents

By D. S. Salonine

Aluminum alloys offer a wide range of capability with a unique combination of advantages that makes them the materials of choice for numerous products and markets. One of the most important applications is their use as the primary structure and outer envelope in aerospace vehicles. Wide and thorough studies on hot working and microstructure evolution of aluminum alloys have been made in Russia. The most important appear to be: - introducing the structure diagrams in strain rate - temperature coordinates which show areas of different microstructures (non-recrystallized, recrystallized, and mixed) after the hot deformation and the following heat-treatment for common aluminum alloys (Yu.M. Vainblat); - studying the press-effect ("structural effect" by V.I. Dobatkin); - learning the influence of hot worked substructure on aging mechanisms; conducting researches on press heat-treatment. These works allowed a deeper understanding and a better control of the mechanical behavior of aluminum products. Comparisons are made to equivalent developments in Europe and America.

Jan 1, 2004

By F. T. Cawood

The distinction between real estate ownership and that of interests in the property is fundamental to the appraisal of mineral properties. This distinction affects the nature and understanding of security of tenure and, consequently, the perception of what constitutes fair value. Legal matters are a particular concern because of their influence on security of tenure, ownership definition and use restrictions. The dynamics of the market and the complex interrelationships between the factors of production define value at a specific point in time for the bundle of rights, interests and assets that constitute a mineral property. Because each mineral property is unique, physically immobile and of a wasting nature, its usefulness to its owner and society must be optimized. The US Appraisal Institute (2001) classified the forces that affect land use as the cultural, political and economic attitudes of society. These forces culminate in laws that often dictate the purposes for doing appraisals. Once the legal definition of the asset is understood, valuers can decide on the valuation process that will support the final valuation approach.

Jan 1, 2004

By T. A. Jones

The Kelsey Centrifugal Jig is an enhanced gravity concentrator capable of separating fine minerals and/or minerals with relatively small differences in specific gravity. Since the first commercial installation at the Renison Bell tin mine in Australia, development and improvement in hardware has continued, including the introduction of the high-capacity J1800model Kelsey Jig. The Kelsey Centrifugal Jig is widely applicable to fine mineral recovery duties, with key application areas including mineral sands, tin, gold and nickel. Other areas of application include: iron ore, base metals, chromite, PGMs, soil remediation and scheelite. The latest developments on the Kelsey Jig are discussed together with a review of recent installations involving: • Fine gold / sulphide recovery from leach tailings • Magnesium mineral removal from nickel sulphide concentrates • High-grade zircon recovery from plant tailings

Jan 1, 2004

The 22nd Annual American Mining Hall of Fame Awards Banquet sponsored by the Mining Foundation of the Southwest will be held at the Westin La Paloma in Tucson, AZ on Saturday, Dec. 4, 2004. This year’s inductee, guest of honor and featured speaker at the banquet will be J. Steven Whisler, chairman and chief executive officer of Phelps Dodge. Whisler is also a director of Phelps Dodge, Burlington Northern Santa Fe, America West Holdings, the National Mining Association, the International Copper Association and the Copper Development Association.

Jan 1, 2004

By P. Gonzalez, C. Ariyo, L. Holappa

Oxidation state of titanium was determined in CaO-SiO2-TiOxslags in the composition range25–53 per cent CaO, 27–46 per cent SiO2, 10–55 per cent TiOxat 1873K using gas equilibration method. In the experiments, slags with different titanium oxide contents were equilibrated with a known carbon monoxide and carbon dioxide ratio. The results were used to determine the Ti3+and Ti4+contents as well as the activity coefficient ratio of corresponding oxides in the slag. The dependency of the activity coefficient ratio as a function of oxygen partial pressure was determined. Keywords: titanium, titanium oxide, activity, activity coefficient, slag iron, carbon monoxide,carbon doixide, gas, equilibrium.

Jan 1, 2004

By Gordon A. Irons, H. Y. Hwang

An impinging gas jet on a water surface was studied to understand momentum transfer in oxygen steelmaking. Depth, width and oscillation frequency of the jet cavity were measured and the splashes interpreted with Kelvin-Helmholtz instability and combined Rayleigh-Taylor and Kelvin-Helmholtz instability theory. A model to calculate separate gas and liquid velocities, applying the exact momentum boundary condition, is proposed.

Jan 1, 2004

By C. Nexhip, S. Sun

Critical to understanding and controlling phase mixing and separation in metallurgical processes, is the development of reliable experimental techniques to measure interfacial properties of melt systems. A series of experiments has been carried out to determine the effect of oxygen potential on the surface tension of liquid copper. Using an electromagnetic levitation method, a surface tension-oxygen chemical potential adsorption isotherm was produced for the Cu-O system at T 1400 K. The surface tension results show good agreement with the literature values e.g. within 3 per cent for pure copper. The Belton `ideal' adsorption isotherm was applied, and the following equation derived to best fit the experimental data ? =1251-77.5 1n41+ (2.79x105 . pO1/2)](mN.m Using this equation, the surface tension of copper was calculated/predicted as a function of oxygen potential at 1400 K, and showed excellent agreement with the experimental values. This confirmed that the adsorption behaviour of oxygen in liquid copper is ideal. The saturation coverage of oxygen on the surface of liquid copper was determined to be T0 = 6.65 µmoles.m,-2 corresponding to an area per adsorbed oxygen atom of ao ? 25 Å2. These values agree well with those cited in the literature, and our experimental data cover a very wide range of oxygen potential (10-5 to 10-17 atm). Keywords: levitation melting, surface tension, Cu-O alloys, oxygen potential, adsorption isotherm, surface coverage.

Jan 1, 2004

By D. K. Matlock, D. J. Hamre, J. G. Speer

Ultrafine ferrite (UFF) grains may be produced in surface layers of plate steels using controlled intermediate cooling followed by deformation. Experiments were conducted using a 0.12 C - 1.26 Mn steel on a Gleeble 1500 hot deformation simulator. Taguchi designed experiments were used to evaluate prior austenite grain size, intermediate cooling rate, intermediate cooling temperature, intermediate hold time and amount of reduction in order to observe the effects of variables and their interactions on the final microstructure while minimizing the number of required test runs. Evaluation of resulting microstructures and mechanical properties revealed a preferred thermal and mechanical history for developing ultrafine microstructures in surface layers of plate steels. Application of the fundamental concepts of phase transformations to industrial plate rolling is considered.

Jan 1, 2004

By R. G. Zaripova, N. D. Ryan, H. J. McQueen

The austenitic and ferritic stainless steels do not undergo any phase transformation that induces very fine grains in the product through thermomechanical processing as practiced in most other steels. Considerable grain refinement can be achieved by intense multistage deformation descending through warm to cold working; notably multi-axial forging of bulk material can attain high strains with diminished risk of cracking. Hot working to improve ductility yields finer grain sizes as the T is reduced and strain rate E raised; increased strain has limited effect due to the steady state regime. Ferritic steels develop subgrains with size diminishing as E rises and T falls with the advantage of retained strain hardening; recrystallization delivers grains several times the cell size. In austenitic steels, dynamic recrystallization (DRX) provides finer grains at higher E and lower T with a lower limit due to intergranular cracking. The DRX grains contain a strengthening substructure that can easily be retained by quenching; if static recrystallization is allowed to occur the grain size rises markedly. Multistage rolling with diminishing T is able to provide grain refinement to the same degree as straining at the finishing T yet provides better ductility. grains on recrystallization. As a result of the strain induced transformation to martensite, small subzero deformations of austenitic or duplex steels produce very high dislocation densities that yield marked grain refinement when they revert upon reheating.

Jan 1, 2004

By Satish Kate

Mining of Iron Ore in India is done by Surface Mining methods and most of the deposits are massive and are occurring in Hills, surrounded by green forest cover. While majority of iron ore produced are from mechanized mining systems, some quantities are also produced from semimechanised mines. In mechanized mines, apart from state-of-the-art level of mechanization, the Run-off-Mine ore is subjected to multi-stage crushing, screening and washing/beneficiation, for improving the grade and ensure segregating of different size range. The steel plants within the country have been operating their own captive mines, where both lumps and fines are used in their furnaces. In case of mines, which exclusively supply ores to export market, the lumps produced yield very high price and thus efforts are being made to maximize lumps recovery. The mine, where the author had been associated, is an export-oriented mine which supplies iron-ore to Japanese steel plants.

Jan 1, 2004

By S. Kashani-Nejad

The kinetics of the thermal decomposition of samples of Mg2(OH)3Cl.2H2O that were obtained by a novel leaching technique applied to a commercial magnesium electrolysis feed were investigated under ambient atmosphere. Thermogravimetric (TG) Analysis showed that decomposition of Mg2(OH)3Cl.2H2O exhibited a single intermediate stage wherein crystalline water was lost at roughly 108 °C. Conversion of the resulting Mg2(OH)3Cl to MgO, HCl and 1120 occurred at temperatures above 398 °C. Thermal decomposition of anhydrous Mg2(OH)3Cl was seen to be consist of two stages. Both stages exhibit first order kinetics with respect to the weight percent of Mg2(OH)3Cl remaining in the sample. However, the rates of decomposition in the two stages were significantly different. Detailed analysis of the kinetic data suggested that the rate of decomposition of Mg2(OH)3C1 was controlled by the rate of removal of the gases released. The change in decomposition rate during the course of the experiments was explained by HCI being released in stage 1 and followed by release of H2O in stage 2.

Jan 1, 2004

By A. Koning, P. Lauzon

Pressure hydrometallurgy operations require vessels to be lined with an impermeable membrane for corrosion protection and one or more courses of refractory or ceramic brick. Examples of unit operations that utilize composite lining systems include pressure oxidation autoclaves, sulphide precipitation autoclaves, chloride leach reactors, flash vessels, cyclone separators, and direct contact condensers (heater vessels and quench vessels). The refractory lining must satisfy multiple requirements: it must thermally insulate the membrane from process fluid, be structurally stable, provide erosion resistance, be chemically compatible with process fluid, and provide an economic service life. New hydrometallurgical processes are pushing the pressure, and temperature, with each new generation of plants. A fundamental understanding of all factors affecting the mechanical stability of the lining system is essential as lining designs move further away from the industry's experience base. The impact of irreversible chemical swell, operating factors, design factors, and installation factors are presented based on modifications to the traditional one-dimensional mechanical stress model. A new stability criterion - that the brick lining remain in contact with the steel shell membrane - is presented. This new stability criterion imposes new restrictions on the lining design.The effect of geometry and adding additional degrees of freedom to the analysis is explored using two-dimensional and three-dimensional Finite Element Analysis (FEA). The effect of these additional degrees of freedom on the results of the one-dimensional model are discussed.

Jan 1, 2004

By D. Norval, J. J. Dunkley

The process of atomisation is introduced and related to granulation. Some processes applicable to ferroalloys are discussed, along with their limitations and advantages. Examples of applications of atomisation to the processing of ferroalloys, including ferrosilicon and ferromanganese for use in the welding industry and as injectable additions to steel or cast iron are also presented. The economics of the process and the impact of process scale are discussed, along with criteria for process selection and system design.

Jan 1, 2004

By J. C. Carrasco, M. Sánchez, R. Jara, F. Marquez, F. Parada, R. Parra, J. Palacios

In past years, Chile has been the largest copper producer in the world and for 2002 mining represented country average of 10 % of the GDP, accounting for 47 % of the total exportation. As copper sulphides are the main mining resources in the country, the metal is produced using the classical processes of flotation and pyrometallurgical extraction. Seven copper smelter plants, which extends from the northern Atacama desert to the central part of the country produced1,522,000 metric tons of fine copper in 2002, approximately one half of total copper concentrate production, with a notorious environmental impact due to the great amount of slag produced during these extraction steps. In this work, a global characterization of copper pyrometallurgical slags produced and disposed of in Chile and worldwide is done, and the concept of total project development is considered to explain the scopes of the study, recovering different compounds and generating new activities around mining. The presentation is completed with the proposal of various methods and techniques being developed today in a joint project between smelter plants and the University of Concepción, with the support of the Chilean government and mining companies, addressed to generate new materials from copper slag. Recovery of copper, molybdenum, precious metals, silica and iron, that is the most abundant component of the slag, are the goals for this research. Metals, commercial compounds, alloys and different forms of iron oxides for steel industry are proposed products.

Jan 1, 2004

By K. P. Davey

In 1998 an initial objective was given to the author, to process valuable off grade High Carbon Ferro Manganese (FeMn) metal fines profitably. The previous attempts that had been made to re-melt these metal fines through the furnaces had resulted in poor furnace operation, mainly to do with lack of electrode penetration and furnace bed permeability. It was decided that the method to resolve these problems was to agglomerate the metal fines. During the study on the agglomeration of the metal fines, a decision was made to use furnace baghouse dust and stockpiled furnace baghouse dust and sludge (DSF) as a ?filler? in the metal fines. The primary reason for using baghouse dust was to eliminate an environmental hazard, whereas the secondary reason for using the DSF was to utilize manganese units contained in the dust. The off-grade metal fines and dust were compacted using a brick press, with cement and aluminum rich plastic clay as a binder, to obtain agglomerate that was cost effective. Through the re-melting of the agglomerated off-grade metal fines, it was realized that this agglomerate concept could have other uses, that of replacing ores on the furnace, at a lower cost. The agglomerate recipe was changed to create an agglomerate that had a high manganese to iron ratio, this replaced Comilog ore on the furnaces, thereby reducing overall furnace unit costs. Future work concerning agglomeration, is to reduce furnace costs further through agglomerating .0.5mm ultra ore fines and .0.3mm Gloria and Nchwaning sludge. Using this agglomerate replaces a portion of the Gloria and Nchwaning lumpy ore on the furnaces at a lower cost. This would eliminate problematic material that exists at the ASSMANG Manganese mines.

Jan 1, 2004

By P. R. Mohanty, Kaushik Dey

Blast-induced tunnel overbreak prediction in the past has been based on peak particle velocity measured far from the blast site with necessary extrapolation. This has often resulted in suggesting higher damage threshold levels of Acceleration/PPV for overbreak prediction (Bogdanhoff, 1995, Holmberg and Persson, 1997, Murthy and Dey, 2002). These, site-specific far-field blast vibration studies, have also revealed that predicted PPV levels for overbreak could lie in the range of 700-5000 mm/s, an extremely wide range to generalize. Experimental blasts were conducted, in an underground metal mine located in eastern India, with an objective to study the level of acceleration /peak particle velocity generated in tunnel blasting. Accelerometers and tri-axial geophones with measuring ranges upto 500 g, 254 mm/s respectively, were mounted on the tunnel floor close to the blast face, with sensor distances varying from 15.25m to 36.10m. Due to straight faces the measuring distance could not be reduced further anticipating, in particular, cable damage. The equipment used was of M/s Instantel Inc., Canada. The blast pattern used was burn cut with large dia relief holes providing the required free face. The blast hole depth was 1.8m. Tunnel overbreak was measured using a telescopic offset rod fabricated at Indian School of Mines, Dhanbad, India.

Jan 1, 2004

By J. H. Van Reenen, H. Thiele, C. Bergman

For some time spirals have been the process equipment chosen to recover metal in the size range 0.15 to 3mm from ferrochrome and silico/ferro manganese slags. Recoveries of metal obtained using spirals are usually about 70%. Spirals are also difficult to control. By combining a novel gate on the Apic pneumatic fines jig with the recently developed Apic classifier, metal recoveries of 76% and grades of over 90% have been obtained for FeCr and SiMn slags in the size range 0.15 to 3 mm. The paper compares classifier operating performance and costs with those spirals for FeCr and SiMn metal recovery from slags. The classifier technology can also be applied to chromite and iron ores and coal fines.

Jan 1, 2004

By L. B. Kirk, A. R. Kirk

At New World, Au-Cu-Ag mineralization occurs in stratiform car-bonate-hosted, massive sulfide-iron oxide, and skarn-replacement deposits. Regional pyritic-alteration, local massive sulfide mineralization and mine wastes generate acid drainage within the district. Water quality improves down gradient through dilution and mixing of acid and metal-rich mine water with bicarbonate-rich, low-metal surface and groundwater, and precipitation of metal-rich ferrihydroxide phases. Natural deposits of ferricrete indicate that pre-mining ARD has occurred, providing important clues to pre-mining water quality. The geoenvironmental model identifies the Cu-skarn mineralization as the primary target for ARD management. Closure success will be limited by the geoenvironmental nature of the natural mineralization.

Jan 1, 2004

By K Nilsson, G Cheong

Troy Resources NL acquired a 70 per cent interest in the Mina Sertpo gold project in Goißs State, Brazil, in 2001 following a successful bid for the highly competitive international tender of a tenement package put out by Western Mining Corporation (WMC). The Sertpo deposit is located on cleared grazing land 380 km west of Brasilia and is 30 per cent owned by Amazonia Mineracao Ltda, a private Brazilian company. It is a small high grade open-pittable orebody with a measured and indicated resource of 108 000 tonnes at a grade of 49.7 g/t for 172 500 ounces using a 2.0 g/t cut-off. Troy undertook the project management and development of the project while Amazonia managed the exploration activities and provided other services as required. The project development involved drilling metallurgical test holes, scouring the world to locate an available and suitable second-hand plant, and arranging shipping to andreconstruction in Brazil.

Jan 1, 2004

By P. D. Hodgson, G. L. Kelly, H. Beladi

"The formation of ultrafine ferrite by strain induced transformation is assessed using rolling and hot torsion experiments. These experiments are used to examine the impact of thermomechanical processing conditions and steel chemistry on strain induced austenite to ferrite transformation and the formation of ultrafine ferrite. The critical strain for dynamic strain induced transformation increased with increasing carbon equivalence, deformation temperature and austenite grain size. The deformation structure in the austenite grains changes with the thermomechanical processing conditions.Drawing on these results and the current literature, the important factors for the production of ultrafine ferrite are described and a mechanism proposed."

Jan 1, 2004