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By L. C. Brown, J. S. Kirkaldy

Measurements have been made of carbon diffuswn in the five ternary austenites Fe-C-Si, Fe-C-Ni, Fe-C-Co, Fe-C-Mn, and Fe-C-Cr in which the carbon (component 1) diffuses through interstitial sites and the ternary addition (component 2) diffuses substitutionally. Values of the diffusion-coefficient ratio, D12/D11 were determined for each system with finite couples using the transient equilibrium method. The effect of temperature and of concentrations of both the carbon and substitutional component upon D12/D was examined and was found to agree with the theoretical predictions. It is concluded that within an experimental uncertainty of 10 to 15 pct, it is possible to calculate the ratio D12/D11 from purely thermody-namic data. Difficulties of measuring the other off-diagonal coefficient, 4,, are discussed. Any quantitative attack on the fundamentals of the hardenability problem in steel must begin with the multicomponent diffusion formalism and with the accumulation of data pertaining thereto. In a recent paper Kirkaldy and purdy 1 employed the formalism derived from irreversible thermodynamics to treat the problem of diffusion in ternary austenites. In the latter solutions, carbon diffuses through interstitial sites and the substitutional component diffuses through the lattice. Examples were given of diffusion in the systems Fe-Mn-C and Fe-Si-C. In the present paper, we present new results on and discuss their agreement with the thermody-namic theory. Since the theory has been slightly modified from the original presentation of Kirkaldy and Purdy, their results on Fe-Si-C and Fe-Mn-C have been recalculated and are presented here for completeness. The flux of the interstitial component with respect to a fixed lattice framework can be written as a linear expansion in the independent concentration gradients, where X1 and X2 are the independent thermody-namic forces in the lattice fixed frame of reference. These forces can be obtained from the general statement for forces in a volume fixed frame2 if the partial molar volume of carbon atoms is set equal to zero and that of the substitutional component 2 is set equal to unity, viz where the are the chemical potentials and the N's are mole fractions. Introducing into [3] and [4] the function If, as suggested by statistical arguments, the off-diagonal interaction L12 is sufficiently small, [6] reduces to i.e., the coefficient ratio becomes purely thermo-dynamic. The activity of components 1 and 2 in a dilute ternary system (standard state at infinite dilution) may be represented by the expansion3

Jan 1, 1964

By Sumantra Mandal

The hot deformed microstructure of the 15Cr-15Ni-2.2Mo-Ti modified austenitic stainless steel (commonly known as alloy D9) was investigated employing electron backscatter diffraction (EBSD). Hot compression tests were conducted in a Gleeble thermo-mechanical simulator at temperatures of 1173K-1373K (in steps of 100K) with a strain rate of 10 and 100 s-1 to different strains. Various kinds of deformation patterns were observed inside the deformed grains. These were inferred as the development of geometrically necessary boundaries or formation of parallel set of micro-bands. Recrystallized grains were partitioned from the deformed grains employing grain orientation spread approach. Extent of dynamic recrystallization (DRX) was found to be minimal at 1173K. DRX was predominantly found to happen at and above 1273K which increases with increase in strain. DRX nucleation and development mechanisms were discussed with respect to bulging of the parent grains and sub-grain rotation. Special emphasize is given on the role of annealing twins on DRX nucleation and subsequent expansion.

Jan 1, 2009

By M. Sengupta

International trade in minerals plays a very important role in the economic growth of many nations. Several less developed countries a1•e heavily dependent on their mineral exports for earning foreign exchange, which is needed for industrialization. Mineral exporting nations experience many problems in international mineral markets; the most important are tariff barriers, deteriorating terms of trade, instability in metal prices, etc. The formation of international mineral cartels to raise prices can be successful only to a limited extent and only for a short period of time.

Jan 1, 1976

By Jim A. King

The total pressure oxidation of copper concentrates is a potentially viable option for treating copper concentrates that are either low grade or contain significant impurities. Both concentrate types are heavily penalized in smelter contracts. The total pressure oxidation process involves autoclaving the copper concentrate at temperatures of 200-220 C under oxygen pressure. The autoclave discharge can be separated into a solid (oxidation residue) and a liquid (oxidation solution) product. The oxidation solution can be treated for copper recovery by solvent extraction - electrowinning or by direct electrowinning. The direct electrowinning recovery of copper requires prior removal of selenium and tellurium by cementation on finely divided scrap copper. The oxidation residue is washed thoroughly to remove acid and dissolved copper prior to precious metals recovery by conventional cyanidation in the presence of lime. The results of a benchscale investigation involving a number of copper concentrates are reported. Copper recoveries in autoclave oxidation and gold recoveries by cyanidation of the oxidation residue exceeded 99%. The results of benchscale experiments to demonstrate copper recovery are described. Various flowsheet options are presented.

Jan 1, 1993

The 63rd Regular Meeting of the Rocky Mountain Coal Mining Institute convened at the Stanley Hotel, Estes Park, Colorado, and was in session at 10:00 a.m. The first session was called to order by Past President George A. Nugent, Vice President and General Manager, Big Horn Coal Company, Sheridan, Wyoming. He thanked and offered his congratulations to the Program Committee for a very wonderful job, namely, John Reeves, Chairman, E. G. Fox, Lee Jensen, O. F. Lewis, J. Peperakis, R. M. von Storch, J. E. Ward and R. R. Williams, Jr. He thanked the suppliers for a fine cocktail party the evening before. Mr. Nugent's Opening Address and introduction of President James Westfield, Assistant Director, U.S. Bureau of Mines, Washington, D.C., follows: It is a real privilege to call this 63rd Regular Meeting of The Rocky Mountain Coal Mining Institute to order and to say welcome.

Jan 1, 1967

By P. Abachi

Cemented carbides or hard metals that generally consist of hard tungsten carbide and a tough metal binder such as cobalt are important in many segments of the world economy, ranging from automobile related components to machining, cutting, and drilling tools. For metal cutting operations such as turning and milling, replaceable cemented carbide inserts are frequently used. The exposure of inserts to very severe conditions (e.g. temperatures as high as 1000°C) in combination with very high loads, limits their lifetime. When the tools and components are scrapped, they are collected with a view to recovering the tungsten carbide and cobalt due to both their environmental aspects and their strategic importance. In this work, a selective electrolysis process was used for recovery of WC powder particles from cemented carbide scraps. The WC-10Co and WC-10Co-VC up to 3 wt.% VC was produced using powder metallurgy route. The mean particle size of WC, Co and VC were selected as 2.5, l.5 and 2.2 µm respectively. Referring to electrochemical curves of WC-10Co cemented carbides in hydrochloric acid solutions with different concentrations, the recovery rate was enhanced in IN acid. Therefore, this solution was selected for recycling of all samples. The surfaces of as-produced and corroded specimens were investigated using a scanning electron microscopy (SEM). Detection of corrosion products was provided by energy dispersive spectrometry (EDS). According to results, the selective electrolysis process could be useful in the recycling of scrap carbide materials, although more studies should be undertaken on economical aspects of the process and the quality of samples produced using recovered powders.

Jan 1, 2005

By G. W. Clark

"The mining of the ore bodies at Rabbit Lake has in the past been by the open pit method. This method is presently being used to develop the B-zone and will continue into the future with the development of two smaller ore bodies, the A-zone and D-zone. The Eagle Point orebody will be developed by an underground method which will provide production and employment into the next century.The ore bodies at B-zone, A-zone and D-zone are unique in that they are located under Wollaston Lake. To permit mining by the open pit method a steel-celled dyke has been constructed around the north end of the B-zone. This same dyking method will be used for the A -zone and D-zone. INTRODUCTIONMine development at Rabbit Lake commenced in 1970when a detailed engineering feasibility study established the viability of the Rabbit Lake deposit. In 1972 construction of the mill and camp site began. Construction materials were seasonally hauled to the site over a winter road until November 1973when the government of Saskatchewan completed an all-weather road to within six miles of the operation.In October 1974, stripping of the Rabbit Lake open pit began with the removal of overburden and lake bottom sediments from the previously drained Rabbit Lake. The first ore was processed by the mill in June 1975and by October the mill was producing three million pounds per year. The design capacity of five million pounds annually was first achieved in 1977 and maintained until 1981, when lower ore grades resulted in lower production rates .It was clear when mining at Rabbit Lake began that, without additional reserves, the Rabbit Lake operation had a life of less than 10 years. Exploration, therefore, continued in the immediate area in an attempt to discover additional uranium mineralization."

Jan 1, 1989

A major Brazilian iron ore producer, SA Minerayao da Trindade (Samitri), has recently completed modifications at two operations which involve the use of Derrick high frequency vibrating screens. Details of these modifications are presented, together with a review of product quality improvements.

Jan 1, 1997

By Elard Rodríguez Véliz

El objetivo del presente texto es mejorar el rendimiento de las brocas a través de una serie de análisis realizados durante el programa de perforación comprendidos entre los años 1974-1977. Para ello, se utilizó una metodología que implemente un código que elimine ciertas brocas utilizadas desde 1974 al 31 de diciembre de 1977, dado que el anterior no se adecuaba a las características. Posteriormente se realiza un cuadro comparativo del motivo del deshuso del anterior código, se señalan sugerencias y resultados del análisis de brocas, así como los factores de las fallas de las mismas.

Nov 20, 1978

By Rodney P. Smith

THE solubility of columbium nitride in ? iron has been determined for the temperature range 1191o to 1336°C from the nitrogen content and metallogra-phic examination of a series of Fe-Nb alloys.* (0.0 to 0.92 pct Nb) equilibrated with a purified gas mixture of 1 pct hydrogen in nitrogen. The method is the same as that used by Darken, Smith, and Filer' to determine the solubility of aluminum nitride in y iron. The variation in the furnace temperature during an equilibration period was about ± 2.0°C. Each sample was approximately 1/2 in. wide, 2 in. long, and 1/16 in. thick. A time series at 1200°C using samples of highest columbium content indicated that one day was sufficient for equilibrium; however, to be on the safe side all samples were left in the furnace for either two or three days. Afterequilibration, the samples were brought to room temperature by quenching in water. The experimental results are shown in Fig. 1. To be in accord with the values reported by Wriedt and Gonzalez2 and the temperature coefficient of our results at higher temperatures, the nitrogen content of iron at 1191oC is assumed to be slightly lower than our experimental value. Our data for the single-phase regions are not sufficiently accurate to establish an interaction coefficient for nitrogen in these alloys. However, the change in nitrogen content with change in alloy content for a number of systems (Fe-N-A1;3,1 Fe-N-Ni;372 Fe-N-Si.3949 Fe-N-V;3,5 Fe-N-Cr;3,6 Fe-N-Mo3,7) has practically the same value for the liquid alloy at a temperature near 1600°C as for the solid alloy at temperatures near 1200oC when the alloy content is below a few percent. On this basis the lines through the single-phase regions have been drawn with a slope corresponding to an increase in nitrogen of 0.0013 pct per 0.1 pct Nb.3 The straight lines through the two-phase regions were drawn with a slope corresponding to a one-to-one atom ratio of nitrogen to columbium in the nitride. The X-ray

Jan 1, 1962

By P. McGrath

From the mid-1980s through 1997, Echo Bay Alaska evaluated reopening the historic Alaska-Juneau (AJ) gold mine. Their original proposed project underwent numerous modifications in order to minimize the potential for significant environmental impacts. One of the major modifications involved changing .the tailings disposal method from a conventional tailings impoundment to submarine tailings disposal (STD). In 1995, the U.S. EPA began work on a Supplemental Environmental Impact Statement (SEIS) to assess the impacts of the STD proposal. Key features of the STD impact assessment included fate and transport modeling to determine the extent of tailings deposition and the use of ecological risk assessment to predict marine impacts during deposition and ecosystem recovery following STD. A key feature of the SEIS regulatory process included a rulemaking proposed by EPA to exempt the AJ tailings from effluent regulations. Critical to success in moving the project forward was early development of an interactive working relationship with other regulatory agencies and the public.

Jan 1, 1998

By Foster Fraas

This report describes the application of pulsed magnetic fields derived from alternating and intermittent magnetizing currents. Application of such pulsed magnetic fields to the matrix-type separator permits (1) the complete discharge of the magnetic fraction with wet feeds and (2) the dry separation at particle sizes down to 325 mesh. At smaller particle s indications are that frequencies above 60 hertz will be required. Applications of intermittent magnetizing current to the cross-belt separator give the cross-belt-separator an advantage over the conventional constant-field cross-belt and induced roll separators; the intermittent current enables the cross-belt separator to separate matted fibrous and magnetically coagulating feeds, a type of feed that occasionally occurs with mineral, industrial, and secondary materials.

Jan 1, 1973

Minerals are vital to any industrialized civilization. Annually, the United States uses more than 4 billion tons of new mineral materials, or about 40,000 pounds per person-about half being mineral fuels and the other half being metals and nonmetallics. Stable and economic domestic mining, mineral, metal, and mineral reclamation industries are essential to the economy. The value of United States energy and processed materials of mineral origin exceds $200 billion annually. Although a number of minerals are imported, especially some designated as "strategic and critical," most U.S. mineral supplies are derived from the domestic mines and processing facilities that you will be seeing, reading about, and visiting as you use this visitor guide. We hope you enjoy your experiences. This pamphlet, a guide to mining and mineral operations that may be observed or visited and some other points of interest relating to minerals, is intended to aid tourists and students who are interested in mining. Some may wish to study our Nation's romantic past; others may plan to enter the minerals industry as a career; still others may have a primary interest in conservation practices. The pamphlet is also intended to aid State and local officials, Chambers of Commerce, and mining firms in answering some of the many questions of tourists and students.

Jan 1, 1976

By Verônica Scarpini Candido

O alto consumo de energia e a elevada emissão de dióxido de carbono são os maiores problemas da indústria de cimento Portland relacionados à poluição do meio ambiente. Com o objetivo de reduzir estes problemas, os cimentos geopoliméricos despontam como uma nova classe de materiais de alto desempenho e não agressivos ao meio ambiente utilizados como aglomerante mineral capaz de substituir total ou parcialmente o cimento Portland. Estes cimentos são considerados quasi-frágeis devido ao seu comportamento elástico não-linear, provocado pela relaxação e redistribuição de tensões antes da ruptura. Todos os resultados obtidos no programa experimental para o concreto de cimento geopolimérico (CCG) foram comparados com aqueles obtidos para o concreto de cimento Portland (CCP), sob as mesmas condições de ensaio. Neste trabalho, são apresentados resultados de difração de raios-X (DRX), microscopia eletrônica de varredura (MEV) e análise térmica (DSC/TGA), a fim de reunir informações para um melhor entendimento da microestrutura do concreto geopolimérico.

Oct 30, 2017

Metso Minerals Process Technology Asia-Pacific (MMPT-AP) has been working with many mining companies worldwide performing `Mine to Mill' or Process Integration and Optimisation (PIO) studies. MMPT-AP has developed a proven methodology to improve the efficiency of the mine-mill interface and gain maximum benefit. The PIO methodology involves rock characterisation, mathematical modelling and simulation to generate a list of operational and control changes for both the mine and concentrator. Following the methodology, the list of recommendations is developed relatively easily; the more challenging part depends on the company. Success of a PIO project relies on the ability of an organisation to implement change - both operationally and culturally: the human element. When a PIO project is started, there is initial interest and commitment from the company. But how can this be maintained? How does an operation know if the benefit continues? MMPT AP is now developing long-term relationships with clients to ensure that the increased production and improved efficiency continues. Direct and indirect measurements are used to determine the key factors involved and to understand the cause/effect relationships. Simulation tools also can be used to compare current with recommended practices - so when material properties vary over time, the benefits can still be quantified. PIO is about empowerment: by measuring and understanding what parameters affect concentrator performance, the site personnel now have the knowledge to make a difference. Rather than simply reporting variable or poor concentrator performance, operations can predict when production will be affected and put controls in place to prevent it from happening. This requires support and commitment from the company or `buy in'. Ensuring this buy in continues is the challenge facing every company involved in PIO work - but the benefits are well worth it. This paper will review MMPT-AP's experiences in implementing PIO projects in the long term: from both the consulting and operational viewpoints. MMPT-AP's involvement with a number of companies will be discussed as examples of what works and what does not.

Jan 1, 2007

By R. Hagiwara, S. Kobayashi, K. Yasuda, T. Nohira, K. Kondo

To establish a process for the electrochemical recovery of rare earth elements from used magnet scraps, the electrochemical formation of RE-Ni alloys in molten NaCl-KCl-RECl3 salt at 973 K was investigated. Cyclic voltammetry and open-circuit potentiometry indicated the formation of several phases of RE-Ni alloys. The formation potential for each RE-Ni alloy phase was determined from the results of scanning electron microscopy and X-ray diffraction of alloy samples prepared by potentiostatic electrolysis of a Ni plate electrode at various potentials. The optimum electrolysis conditions for the separation of Nd, Dy, and Pr are discussed.

Jan 1, 2014

By Charles Prasky

This report describes fluidized bed techniques employed by the Bureau of Mines at Minneapolis to differentially sulfatize the manganese in two samples of low-grade manganiferous ferruginous carbonate slates from the Cuyuna Range district, Minn. Suitable mechanics of operation were established. A space rate of 1.25 to 1.5 fps, a retention time of 3 to 3.5 hours, a temperature of 700° C, and a 10 percent sulfur dioxide gas in air were adequate for sulfatizing the slates by fluidization. Under these conditions the overflow product removal rate from the 4-inch-diameter reactor was 4 to 5 pounds per hour. The sulfur dioxide was used more efficiently in the two-stage treatment than in the single-stage treatment. However, approximately 80 percent of the manganese was converted to sulfate by either treatment.

Jan 1, 1963

By R Lastra, Y Choi, C Hamilton, P Kondos

Hydroseparation (http://www.cnt-mc.com) was used to concentrate sized fractions (from <38 ¦m to 150 ¦m) of various ore products ahead of carbon-in-pulp (CIP)-treatment. The resulting size-by-size concentrates were mounted as monolayer polished sections and subjected to automated unattended precious metal searches by image analysis (see Lastra, Wilson and Cabri, 1999). Systematic variations in Au-deportment permit quantification of Au reporting as discrete grains from fresh-feed through to pressure oxidation (POX)- and CIP-feed. Application of hydroseparation, image analysis and assays to characterising tailings (from <10 ¦m to 106 ¦m) from four mine sites is also described. Results are encouraging enough to predict that the combination of hydroseparation (HS) and automated image analysis could become a standard methodology for study of precious metal ores and metallurgical products.

Jan 1, 2008

By Robert B. Parsons

"This article addresses the relationship between mine evaluation, the tax system, and economic risk. It is based on a paper presented by the author at recent seminars in Moscow and Tashkent on the subject of mine evaluation.IntroductionTaxation can have a strong influence on the feasibility of a mining project. For the most part, because metal prices are determined on a global basis, the mining concern is not able to pass on to its customers any portion of taxes which the concern has to pay. Taxes are a direct charge against the project. The purpose of the article is to highlight the various ways whereby different taxes can affect the financial viability of a mining operation.The first part of the paper identifies different forms of taxation, and the second part of the paper addresses the different forms of taxation in terms of risk analysis and impacts on the mining project. Finally, the third part of the paper makes brief mention of using the taxation system to provide incentives with respect to investment in mining activities."

Jan 1, 1993

By Jr. Watts, B. K. Cantrell, D. H. Carlson, K. L. Rubow, S. T. Bagley

"Permissible exposure limits (PELs) have been established for gaseous pollutants, carbon monoxide (CO), carbon dioxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), and some gas-phase hydrocarbons emitted in diesel exhaust. There is, as yet, no PEL recommended for diesel exhaust aerosol (DEA), nor is there a standard method for sampling this aerosol.The University of Minnesota and the U.S. Bureau of Mines have collaborated to develop a personal diesel exhaust aerosol sampler (PDEAS) which utilizes size-selective inertial impaction and gravimetric analysis. During the field tests of this sampler, numerous air quality measurements were made in underground coal mines that use diesel equipment.The mine mean DEA concentrations for the five mines surveyed, determined with the PDEAS in the haulageway, was 0.89 mg/m3, with a standard deviation of 0.44 mg/m3. DEA contributed 52 % of the respirable aerosol at this location.In three of the mines filter samples were collected for DEA-associated polynuclear aromatic hydrocarbons (PAHs) and biological activity determinations. Two of the mines were also monitored for the major gaseous constituents found in diesel exhaust. In general, the PAH and biological activity levels were similar for all three mines, and indicate that up to 25 % of the haulageway concentrations may be contributed by outby diesel vehicles. Measured concentrations of CO, CO2. NO, NO2, and SO2, were well below regulated levels.INTRODUCTIONDiesel exhaust contains pollutant gases, such as carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, and gas-phase hydrocarbons, as well as DEA. Much of the health-related concern focuses on DEA and associated organic compounds (Watts, 1992a). A wide variety of these PAHs have been identified and some are known carcinogens and/or mutagens. The U.S. Mine Safety and Health Administration (MSHA) has proposed new PELs for these and other contaminants (MSHA, 1989). MSHA has also published an advance notice of proposed rulemaking to establish a separate PEL for diesel particulate (MSHA, 1992)."

Nov 1, 1995