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By J. Gurland

A method of measuring the degree of contact between grains of 1 phase in multiphase alloys is derived. It is shown that the number and the areas of contacts between grains can be determined by metallographic analysis. Relations between the area of contact, the dihedral angle, and the mean free path of spherical grains are developed. It is often desirable to interpret the mechanical behavior of alloys in terms of structural features observed under the microscope. A quantitative description of microstructures of multi-phase alloys requires consideration of geometrical and topological factors such as the amount, size, and shape of grains and the continuity of the constituent phases. The number and dimensions of grains may be metallographically determined by applying the methods described by Smith and Guttman1 and by Fullman2 in their papers on the measurement of particle size and internal boundaries in opaque bodies. The present work intends to show that the same methods can be used to evaluate some of the parameters of phase continuity; namely, contiguity, number of contacts, and areas of contact of grains of 1 phase. Application of these concepts may be found in such problems as the calculation of electrical conductivity of 2-phase alloys, or the evaluation of the length of fracture path through grains of a brittle phase more or less dispersed in a matrix. I. DEFINITION The following definitions and derivations are based on 2-phase alloys, of which the units of the microstructure are grains. Contiguity is defined as the average fraction of surface area shared by 1 grain of a phase with all neighboring grains of the same phase. In a 2-phase alloy of constituents A and B, the contiguity of phase B is given by: where Cb is the contiguity of phase B aBß is the average area of contact between a grain of phase B and adjacent grains of phase B, aAB is the average area of contact between a grain of phase B and adjacent grains of phase A. The contiguity is a measure of the average degree of contact between grains of phase B in the 2-phase mixture. The ratio varies from 0 to 1 as the distribution of phase B changes from a completely dispersed to a fully agglomerated structure. Smith and Guttman1 have shown that the relative areas of 2 kinds of interfaces in a volume are directly proportional to the number of interfaces of each type intersected by a random line. The lines can be drawn on metallographically prepared surfaces as long as these are random sections through the sample. The contiguity ratio of phase B then becomes: Cb = 2NBB/NAB + 2N BB [2] where: NBB is the number of interfaces between grains of phase B intersected per unit length of random line. Nab is the number of interfaces between grains of phase B and grains of phase A intersected per unit length of random line. The factor 2 arises in Eq. [2] because each interface B-B is associated with 2 grains of B-phase, whereas the interface A-B involves only 1 grain of B-phase. The calculations of contiguity do not require any assumption as to volume fraction, particle size, or particle shape. Fullman2 gives an expression for the determination of the mean free path between particles. The mean free path PB between grains of phase A, i.e., through grains or agglomerates of phase B, may be found from the relationship: PB =2fB/NAB [3] where fB is the volume fraction of phase B. The calculation of the mean free path is independent of grain shape and grain size distribution. The calculation of the number of contacts and of contact area requires assumptions of grain shape, grain size, and contact shape. In the case of uni-

Jan 1, 1959

Pyrometallurgy has played a very important role in southern Africa for at least four centuries. It continues to do so, and recent years have seen many exciting developments in pyrometallurgical technology. The wonderfully diverse rich mineral deposits in this area of the world have provided some unique opportunities for industrial processes to be established. The ?Southern African Pyrometallurgy 2006? conference was set up to showcase southern African pyrometallurgical operations, and to provide a forum for the exchange of ideas between people working at various types of smelters. Papers have been obtained from a wide variety of pyrometallurgical plants in southern Africa. These descriptions of plant operations (as well as some history, and highlights of current work) will provide useful reference information for some time to come. Contributions are also included from universities, research organizations, and engineering companies, so that the full spectrum of pyrometallurgical activities can be covered. The plant descriptions will be published on a website, where they can be updated as and when required, with the eventual goal of having a description of every smelter in the region. The conference venue was selected to be the 'Cradle of Humankind' world heritage area, about 40 km from Johannesburg. Not only does this keep the conference within easy reach of the city and yet far enough out into the countryside to allow people to focus on the conference, it is also within easy reach of many pyrometallurgical plants. There is a particular significance to the choice of location, in that the Swartkrans area close to the Sterkfontein Caves is the site of the earliest evidence of the deliberate controlled use of fire by human beings (about 1.3 million years ago), and this is obviously a necessary precursor to pyrometallurgy. The area also lends itself to a very wide range of outdoor, social, and cultural activities to supplement the technical content of the programme. It is hoped that activities such as a hot air balloon safari and visits to the world-renowned Sterkfontein Caves and Wonder Cave will help to make the conference a memorable one for those able to attend. I trust that the ongoing value of the papers and presentations will make all the hard work of the many contributors most worthwhile.

Jan 1, 2006

By J-P Franzidis

A study was undertaken to determine the effect of five industrial frothers on the relationship between entrainment recovery and water recovery. The experiments were conducted using a Batequip rectangular 60 liter steel cell which was run in parallel with the first cell in a copper/silver prefloat rougher circuit. The concentration of the frothers ranged from 2.5 g/ton to 8.4 g/ton. The experiments were repeated at three different froth depths. A power function was found to fit this relationship with no discontinuity in the relationship caused by the changes in frother type and concentration and froth depth.

Jan 1, 2000

By W. A. Wright

The use and abuse of social media restate common employee relations issues. Business solutions to these issues require advanced preparation. Employers should establish and enforce social media policies to guide their reactions to employees? social media posts that reflect on the employer and its business.

Jan 1, 2011

By Irwan S. Halim

For tunnels in horizontally bedded rock, geologic factors affect the selection and design of the initial supports, including the rock propensity toward parting along bedding and the resulting high potential for rock slabbing during excavation. To evaluate this ground behavior, numerical analyses and results with Mohr-Coulomb, Hoek-Brown, and Ubiquitous Joint constitutive models were used, using the Upper Rouge CSO tunnel in Detroit, Michigan as an example. The different rock models and other geologic considerations are shown to impact the selection of the tunnel initial support and design. This paper emphasizes the appropriate selection of an analytical model based on the site specific geology to achieve an optimum initial support design.

Jan 1, 2008

By Allan J. Clark

This paper, describing the milling practice of the Homestake Mining Co., is one of a series being prepared by the Bureau of Mines. The author acknowledges the assistance of T. G. Chapman, one of the consulting engineers of the Bureau of Mines, in arranging this paper for publication.

Jan 1, 1931

By W. C. Holliman

Commercial production of synthetic rubber in the United States became a reality in 1931 when E. I. duPont de Nemours, Inc., announced the manufacture of Duprene, a synthetic rubber made by polymerizing r chloroprene. Duprene was later improved and reintroduced as neoprene. Since 1931 other synthetic rubbers and rubberlike materials have been announced and are now produced commercially or are in the pilot-plant stage in the United States. These include Thiokol, Buna S, Perbunan, Koroseal, Vistanex, Flamenol, Ameripol or Hycar, Chemigum, Butyl rubber, and Flexon. None of these is synthetic rubber in the strict chemical meaning of the word synthetic, as none is identical in chemical structure with natural rubber. However, all possess some of the physical properties of natural rubber, and in addition usually have some outstanding property not found in natural rubber that makes them superior for certain uses. Because of these superior qualitites, a considerable demand had arisen for synthetic rubbers before the present emer¬gency, although the price was several times that of natural rubber.

Jan 1, 1943

By Keith L. Harris

Economic activity in the United States picked up in the third quarter, according to the latest estimate released by the Department of Commerce. Real gross national product (GNP)--the Nation's output of goods and services--grew at a seasonally adjusted annual rate of 4.3%, or $17.6 billion, compared with a rate of 1.9% for the second quarter of 1985 and 1.6% for the third quarter of 1984 (table 1). The 4.3% rate is one percentage point above the preliminary estimate reported in the August/September issue of Minerals and Materials. Most of the upward revision was due to the change in business inventories and Government purchases, while the figure for net exports was revised downward substantially. The 4.3% growth bettered by 1.5% the average rate of growth in GNP from 1974 through 1984 and was 1.1 % above that of the period from 1975 through 1984 and 0.7% above that of 1980 through 1984. Of importance to the minerals industry was the $14.4-billion growth in personal consumption expenditures, $10.2 billion of which was for durable goods (especially domestically produced automobiles) and the growing residential investment. The net export deficit continued to grow, however, and investment in nonresidential structures, producers' durable equipment, and business inventories declined. Prices, as measured by the GNP fixed-weighted price index, increased at an annual rate of 3.1% in the third quarter, compared with 3.9% in the second quarter. The slower rate of inflation resulted mainly from a decline in energy prices, following second-quarter increases. Fourth-Quarter Prognosis Many of the economic data available for October and November indicate that the economy is growing modestly and will continue to grow over the next 3 to 6 months. The composite index of leading indicators, designed to predict economic activity within 3 to 6 months, rose 0.3% in October, the sixth consecutive monthly advance, according to the Department of Commerce. Six of the 11 available leading indicators were positive: Stock market prices rose, as did sensitive material prices, credit outstanding, and manufacturers' new orders for consumer goods and materials; initial claims for unemployment insurance decreased, and firms were getting slower delivery of goods. Four of the indicators were negative: Business formations, homebuilding permits, contracts and orders for plant and equipment, and money supply all declined. The average hours worked per week, already at a high level, remained unchanged.

Jan 1, 1985

By C. E. Hales

In an effort to improve efficiencies and reduce costs, AngloGold has embarked on a process to develop and deliver consistent, high quality, tailings based support or construction products to stopes and tunnels on request. A three-phase approach of product conceptualisation, design and delivery has been adopted. To date a substantial amount of laboratory development has taken place with promising results, indicating that the project aims are achievable. Dans un effort pour améliorer le rendement et réduire les coûts, AngloGold s’est embarqué dans une opération qui vise à développer et fournir aux chantiers d’extraction et tunnels, sur demande, des produits de construction ou de support basés sur rejets qui sont réguliers et de haute qualité. Une méthode à trois volets a été adoptée : conception, création et livraison. A ce jour, un développement important en laboratoire s’est produit, avec des résultats pleins de promesses, qui semblent indiquer que les buts du projet peuvent être atteints. In der Bemühung, die Effizienz zu steigern und Kosten zu verringern, hat AngloGold begonnen ein Verfahren zu entwickeln welches auf Anfrage konsistent hochqualitative auf Haufwerk basierender Unterstützung oder Bauprodukte für Abbaustellen und Tunnels entwickelt und liefert Eine Dreiphasenplan zur Produktkonzeptualisierung, Design und Lieferung wurde adoptiert. Bis jetzt hat eine substantielle Anzahl an Laborentwicklung mit vielversprechenden Resultaten stattgefunden und aufgezeigt, daß die Projektziele erreichbar sind.

Jan 1, 2003

The Rosebery and Hercules mines, situated in the Rosebery-Williamsford district in western Tasmania, have a history of production dating back to 1896-7, although full scale production did not commence until 1936, following the development of a satisfactory process of selective flotation (Hall, Cottle, Rosenhain and McGhie, 1953). The mineral composition of the Rosebery zinc-lead ores was first described in detail by Stillwell (1934). The Hercules ore is generally similar, but as yet no descriptions of it have beenpublished.Since Dr. Stillwell's paper appeared, the management of the Rosebery and Hercules mines has from time to time submitted a number of interesting mineral specimens to C.S.I.R.O. Mineragraphie Investigations. Examination of these specimens brought to light eight minerals, some relatively uncommon, not previously recognized in these ores.They are cassiterite, molybdenite, stannite, electrum, meneghinite, boulangerite, pyrargyrite and pyrrhotite. Some of the specimens are also rich in tetrahedrite and gold. In addition each of the other ore minerals described by Stillwell, viz. pyrite, sphalerite, galena, bournonite, chaleopyrite and arsenopyrite, was detected in one or more of the specimens examined during the present study. The principal gangue minerals were found to be quartz, manganiferous carbonate, sericite and barite, agreeing closely with the observations of Stillwell.The present study was based on the examination of the following eight specimens.

Jan 1, 1960

By Kevin Beirne

Most people involved in the mining industry are familiar with student-industry co-op work-study programs. Many colleges and universities have used them for years. Northern College’s Haileybury School of Mines student co-op program adds a new dimension of productivity to the college and the mining industry. The college is located in Hailey-bury, Ontario, Canada. An example of the program’s success is the school’s relationship with Sabin Metal’s SMC (Canada) Ltd.’s McAlpine Mill in Cobalt, Ontario. Students gain practical knowledge and experience while industry gains an eager-to-learn worker. And many of the college’s advanced research services are made available to industry to supplement their own capabilities. The McAlpine Mill was established to provide custom milling of slags and ores. It also recovers metal values from other products of the primary and secondary precious metal industries.

Jan 1, 1999

A compilation of papers presented at The Second WVU Conference on Coal Mine E1ectrotechnology in Morgantown, West Virginia on June 12 -14, 1974. Papers cover areas of electric power, electronic communications, detection and location of trapped miners, and electronic sensors and monitoring systems.

Jan 1, 1974

A consideration of mining ventures and the changes of an environmental nature that occur. The paper is introduced with a general statement claiming recognition that mining ventures are important to human well-being but that these need to be justified against the environmental changes that they bring about. The various factors that need to be considered are cited followed by an historical review of mining activities. The various environmental issues are discussed under three headings; socio-economic, physical and biological, prior to reviewing the world's demand for minerals including fossil fuels. In conclusion guidelines for appraising mining ventures relative to environmental changes that may occur, are given.

Jan 1, 1981

New GSP Trade Status Approved.--President Carter, by Executive Order effective March 30, has approved Generalized System of Preference treatment for imports of nonferrous metal products and other imports from Ecuador, Indonesia, Zimbabwe, Uganda, and Venezuela. As of May 2, Afghanistan and Ethiopia will be taken off GSP status. Under the Generalized System of Preferences, certain imports from developing countries are provided duty-free treatment. A country can lose its GSP status if its shipments of the product exceed $41.9 million or more than 50% of total U.S. imports during the preceding year. However, the President can waive the 50% rule in cases where total U.S. imports of an item in 1979 were less than $1 million. Certain nonferrous imports from Mexico, Peru, Chile, and Zambia are already covered by GSP. Hearings April 10 on International Tin Agreement.--The Fifth International Tin Agreement of which the United States is a signatory, which entered into force on July 1, 1976, will expire on June 30, 1981. A negotiating conference for a Sixth International Tin Agreement will be held under auspices of the United Nations at Geneva from April 14 to May 16, 1980.

Jan 1, 1980

By R. W. Lawrence

"Biological leaching can be used to enhance the recovery of gold and silver from refractory ores, concentrates and tailings. The method liberates precious metals associated with sulphide minerals such as pyrite and arsenopyrite making them amenable to cyanidation. The chemistry and features of biological preoxidation leaching is discussed. A summary of the results obtained on various ores, concentrates and tailings is presented.INTRODUCTIONRefractory precious metal ores in which gold and silver are finely disseminated in sulphide minerals such as pyrite and arsenopyrite are becoming more important to the mining industry. This is due both to a depletion of simpler, free-milling ores and to a significant increase in the price of gold in recent years. Whereas many ores can be directly cyanided with gold solubilizations over 90% obtained, the refractory ores respond poorly to direct cyanidation and require decomposition of the precious metal-bearing sulphide minerals to increase recoveries.Decomposition of sulphides by oxidation prior to cyanidation can be carried out by several means. The oldest method is roasting which removes unwanted ore constituents by high temperature oxidation and volatilization. In Canada, for example, roasting is used at Giant Yellowknife (Connell and Cross, 1981). Another method gaining increasing acceptance is pressure hydrometallurgy which uses aqueous oxidation conducted at high temperature and pressure. Homestake Mining Company have recently completed construction of a plant incorporating pressure oxidation at their Mclaughlin property in California (Guinivire, 1984)."

Jan 1, 1985

By R. W. Bartlett

DISILICIDE coatings, MeSi2, on refractory metals are usually grown by a solid-state diffusion reaction similar to the parabolic oxidation of metals. Two or more silicide compounds occur in each of the binary silicon-refractory metal systems. When an adequate source of silicon is available during the coating process, the lower silicide compounds are usually not formed.1 However, during service application of the coated refractory metal, continued heating causes further diffusion and growth of the lower silicides. A study of the growth kinetics of the lower silicides in the molybdenum and tungsten binary systems with silicon was previously reported.2 The present study is concerned with the growth kinetics of Ta5Si3 and Cb5Si3, formed as conjugate layers between TaSi2/Ta and CbSi2/Cb diffusion couples, respectively. Diffusion couples consisting of disilicide-coated tantalum and columbium sheet coupons were subjected to diffusion heat treatments, cross-sectioned, and scanned by an electron-microprobe analyzer to determine the relative X-ray intensity profiles. These profiles correspond closely to concentration profiles for the constituents, and were used to identify phases and locate phase boundaries. The analysis of a single specimen after a diffusion-anneal provides only one value for the Me5Si3 phase thickness, corresponding to the time and temperature of the diffusion treatment. Consequently, each isothermal curve showing the rate of accumulation or depletion of silicide phases required several samples with identical diffusion temperatures but different diffusion times. The disilicide coatings were prepared by pyrolizing commercially pure silane in a hydrogen carrier gas. The hydrogen was purified by passage through a palladium membrane. Commercially pure tantalum and columbium sheet metal coupons, 0.005 by $ by 2 in., were used. All of the coated specimens for each system were prepared together in a single group in order to minimize coating variations among individual specimens. During pyrolysis, the brightness temperature was maintained at 1200°C. With suitable flow rates at this temperature, only the disilicides of tantalum and columbium were formed in detectable amounts. Coated specimens were subjected to diffusion an-neals in a tube furnace with automatic proportional control within ±10°C. A H2-Ar mixture, deoxidized and dried over anhydrous magnesium perchlorate, was used to prevent oxidation during the diffusion anneal. Diffusion couples were cross-sectioned, polished and examined with an A.R.L. electron-microprobe X-ray analyzer. Both metal constituents in each specimen were simultaneously scanned using a 1-p beam spot size and either 1- or 2-µ steps. Analyses were performed using the Ka radiation of columbium and silicon, and the La, radiation of tantalum. For all specimens, an acceleration voltage of 30 kv was used, and integration was made against the specimen current. LiF and A DP monochrometers were used to isolate characteristic radiations. Three or more traverses were made on each specimen. The intensity scales were adjusted using the constituent metals and standard samples of the silicide compounds which had been verified by X-ray diffraction. The relative intensity profiles were used directly, in conjunction with the standard samples, to identify compounds and phase boundaries. The stoichiometries differ considerably between the silicide compounds in both systems, and the homogeneity range for these silicide compounds is narrow. These characteristics result in marked differences in relative intensities of the fluorescing elements—differences which permit ready identification of phases and phase boundaries. Projections of both electron back-scattered images and characteristic

Jan 1, 1967

By H. Tveit, E. H. Myrhaug, J. K. Tuset

Silicon metal as a commodity material is produced by carbothermic reduction of quartz in electric submerged arc furnaces, where CO2 forms as a by-product. Since 1997 the Norwegian Ferroalloy Producers Association have been engaged in research programmes aiming for reduced CO2-emissions associated with fossil carbon in their processes. One important issue has been to study how charcoal and wood chips perform compared to coal and coke in the silicon process. The ability of the carbon-rich reduction materials to react with SiO-gas is commonly assumed to be of large importance to the performance of the process. Based on laboratory experiments with different carbon materials, combined with estimation of parameters in a mathematical model of the reaction between carbon and SiO-gas, a foundation for a theoretical study of the performance of the carbon materials in a silicon furnace is established.

Jan 1, 2004

By Daniel H. McClain

A unique partnership between the Colorado Mine Safety and Training Program (CMSTP), the Colorado Rock Products Association (CRPA) and the Higher Education and Advanced Technology (HEAT)Center resulted in a video CD-ROM training program for new miners entering the aggregate industry. Cooperation from everyone involved, including the U.S. Mine Safety and Health Administration (MSHA),made this the product against which other training materials in the mining industry will be measured in the 21stcentury. This product’s versatility and wide application make it a tool that is as critical to a mine’s success as any earthmoving machine. The state and federal grant money involved allows this product to be affordable to small operators and independent contractors. The quality of this two CD-ROM set rivals any commercially made CD-ROM training.

Jan 1, 2003

The work described herein is the opening phase of an extensive system of underground excavation undertaken under contract with a Malayan authority.The specifications called for the lining of all tunnels in earth or broken rock with circular segmented cast iron lining, similar to that of the London tubes, and it is the installation of these linings which it is proposed to discuss.Owing to the long deferred delivery quoted and the obvious need for speed of access to the internal installation, it was decided to defer driving the completed circular section and substitute two small timbered headings.These could later be opened out in turn to full section and lined without prejudice to traffic, since both of them had access to the internal workings.NATURE OF ROCKThe rock series through which the circular sections were driven consisted of:(a) A wide zone of intrusive porphyritic granite, consisting generally of orthoclase phenocrysts in a ground mass of micro pegmatite. This area showed advanced weathering, varying from a stage showing slightly tinted kaolin containing approximately 20% of small boulders to one of ultimate decomposition to pure kaolin;(b) A narrow zone of weathered augite diorite, consisting of rock masses of a maximum weight of some 100-150 tons, isolated by clay seams up to 1 ft. 6 in. in width.The whole area was in a state of quasi-hydrostatic equilibrium, which resulted in heavy pressure immediately after excavation. Freshly broken faces would appear to be quite solid but, within a few minutes, would commence to sweat and "slab off" under pressure and, unless support was placed promptly, the whole face would burst out and run from above. Mucking was slow, owing to the plastic nature of the clay and the ease with which it puddled into slurry.In zone (b) a good deal of trouble was experienced because of the fact that the somewhat heavy blasting necessary tended to cause movement of the large rock masses. Subsequent scouring out of the supporting clay bands by the waterflow permitted settlement of the ground on to the timbers and many reinforcing sets were therefore required.The timbering of the pilot headings and its relation to the cross-section of the circular tunnels is shown in Fig. 1. Top and side spiling was driven in the ordinary way, but in bad ground intermediate sets and breast boards had to be placed. These sets were usually withdrawn after the...

Jan 1, 1941

By Ricardo Oliveira Gallart de Menezes, Claudio Gerheim Porto, Reiner Neumann

This study presents the results of the mineralogical characterization of Ti-Zr ore from the Jiboia deposit, located in the municipality of Brejo Grande, Sergipe State, Brazil. The goal is to identify the main Ti, Zr, and REE carrier phases in the different particle size fractions in order to subsidize the development of a cost-effective processing route for the production of heavy minerals concentrate. The mineral resources are estimated at 31.5Mt @ 3.5% of total heavy minerals (THM) for the Jiboia Ti-Zr deposit, of which 5 Mt @ 3.39% THM were classified as measured and indicated. The mineralogy of the heavy mineral concentrate recalculated to 100% is represented by 22% pseudorutile, 20% ilmenite, 15% zircon, 5% rutile, 2% monazite, and 36% gangue. The ore minerals are preferably concentrated in the 150 × 53-μm granulometric fractions, which represents 80% of the THM and only 27% of the ROM (Run-of-Mine) ore. Therefore, by cutting the ore to 150 μm, it is possible to discard 73% of the ROM mass and recover 80% of the THM, including 100% of the zircon and monazite which are the most valuable minerals present in the heavy mineral concentrate. The global recovery of THM starts to decline rapidly in the fractions finer than 106 μm and the mass disposal (tailing) does not follow in the same proportion. Higher zircon contents in the concentrates of the fractions finer than 150 μm imply a significantly lower recovery of heavy minerals like ilmenite, pseudorutile, and rutile that make the fractions coarser than 150 μm.

Jan 9, 2024