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By C. G. Dunn

IT is well known that plastic deformation alters many of the properties of a metal and subsequent heat-treatment partially or completely restores these properties.1 In the deformed or strained state, the metal is unstable and tends to change toward a condition called a "strain-free state." The transformation occurs through recovery, recrystallization, and grain growth-processes that may take place singly or in combination. The distortion of the lattice of an individual grain of a metal in a state of strain may be rather complex in nature, because plastic deformation produces: (I) dislocations within mosaic blocks; (2) elastic variations of the lattice spacings; and (3) gross alterations throughout the lattice, especially along slip planes, along composition planes between a grain and its mechanical twins, and along boundaries of deformation bands. These gross alterations are of the nature of bent planes or rotated regions of the crystal lattice and are revealed by a spread in the orientation of the grain. Although we cannot describe these strains and their formation accurately because of insufficient knowledge, we can, nevertheless, use the information as well as possible to obtain a better understanding of recovery processes. In recovery, the lattice of a grain is not made anew as it is in recrystallization, but is improved or mended in such a way that the basic structure remains unaltered. Until recently observations were that recovery produced no marked changes in the shapes of spots in Laue diffraction patterns, whereas recrystallization did, but now it is known for silicon ferrite2 that Laue spots may become quite sharp entirely through recovery. Consequently, the shape of Laue spots alone would not be a suitable test to distinguish between recovery and recrystallization. There is considerable evidence that the micro- structure usually does not change visibly during recovery. Absence of a visible change in the microstructure, therefore, provides a sufficient test of recovery in many cases. However, including this observation in a definition of recovery as a necessary condition (this is usually done) is unfortunate, because recovery may, as will become evident later, produce new grain boundaries that are visible not only in the microstructure but also in the macrostructure. For the present, therefore, let us say that a necessary condition for a process to be one of recovery is that the principal orientation or orientations of a deformed grain be essentially unchanged throughout the transformation toward the strain-free state. Several transformations may occur that fulfill this condition, and the nature of the distortion in a grain indicates what these must be if the lattice is to be mended in part or fully. Consequently, it will be convenient as well as

Jan 1, 1946

By Oliver Bowles

Accidental explosions in coal mines are due to various causes, but many of them can be directly attributed to coal dust; others that probably in no way depend on dust as a primary cause are propagated, greatly intensified, and made more disastrous by the presence of coal dust. The fact that coal dust in a bituminous mine will explode as a result of a fire-damp explosion has been generally accepted for many years, but the belief has also been held by many that coal dust is not in itself dangerous when unmixed with an explosive gas. Therefore, in past years little attention was given to dust in mines free from fire damp, and many disastrous explosions have resulted from lack of knowledge of the danger from coal dust. In the explosives gallery and experimental mine of the Bureau of Mines experiment station, Pittsburgh, Pa., it has been proved repeatedly and conclusively that coal dust will explode violently when no inflammable gas is present. PROPAGATION OF DUST EXPLOSIONS A coal-dust explosion is an extremely rapid burning or combustion of the coal particles. Their burning consists essentially of the combination of the hydrocarbons in the coal with the oxygen of the air, a process that generates heat and flame and produces hot gases and water vapor. These gases and vapors have a volume many times that of the original coal particles; thus they exert an outward motion and pressure which constitute the explosive wave. When fine particles of coal are suspended in the air, each particle is surrounded by the oxygen of the air, and thus is well placed to oxidize or burn rapidly whenever the temperature is high enough. If some particles are ignited from any cause they will fire others, and the combustion will extend from particle to particle with extreme rapidity wherever enough coal dust of sufficient purity is present.

Jan 1, 1925

By Edward P. Barrett

DURING the past few years numerous references have been made in the technical press and Bureau of Mines Bulletin 270 to sponge iron' and so-called "direct metal" processes. The idea has been prevalent that sponge iron and "direct metals" are cheap commodities. In many instances it has been proposed that these processes be used to treat low-grade ores, utilizing low-grade coals as reducing agents. It is questionable whether or not high-grade sponge iron can be made from low-grade materials. Particles contain¬ing iron oxide and gangue become, upon almost complete deoxidation, particles containing metallic' iron and gangue. The possibility of mechanically separating the metallic iron from the gangue in these particles depends . on the physical characteristics of the particular ore under treatment. Some ores, in which the minerals constituting the gangue break free from the iron oxide upon crushing, may be concentrated magnetically after the iron oxides have been reduced to metal. The finely disseminated ores are least amenable to concentration. In general, high-grade sponge iron can only be made from high-grade raw materials. Sponge iron containing small amounts of sulfur can only be made from raw materials containing small amounts of sulfur or by

Jan 1, 1930

By A. CHESTER BEATTY

MAGNESIUM oxide is by far the most refractory of the common oxides, since it has a melting point of 5072 deg. F. as compared with 3110 deg. F., the melting point of silica (crystobalite) ; 3722 deg. F., the melting point of alumina (corundum) ; and 4127 deg. F., the melting point of chromite (Cr2O33FeO). Its large-scale use in the lining of metallurgical furnaces dates back to the latter part of the nineteenth century, when extensive deposits of magnesium carbonate were discovered in southern Austria in the province of Styria. Before the development of Austrian magnesite, calcined dolomite, a mixture of lime and magnesia, was used in basic steel-making furnaces. The lime in the dolomite was quite objectionable, since it slaked on exposure to the atmosphere, and dolomite therefore could not be made' .into permanent furnace bottoms or into brick. The Austrian magnesite, with its very low lime content, was free from these objections and soon displaced much of the dolomite. With the extensive development of basic steel-melting, the rise of the copper industry, and other metallurgical and chemical processes which dealt with chemically basic substances, the use of magnesite grain and magnesite brick increased rapidly.

Jan 1, 1931

By Q. Feng

Study has been carried out to apply fly ash as a high strength, water-resistant precast construction material through geopolymerization. Experiment results show that the working conditions such as water content, the concentration of NaOH, curing temperature and curing time, significantly affect the mechanical property of geopolymer matrix. Through optimization, an above 100 MPa compressive strength has been achieved with the geopolymerization products. Water soaking tests show that the geopolymerization product has a very high water resistance without losing noticeable compressive strength even after a one month soaking time. To elucidate the geopolymerization mechanism, microscopic techniques such as SEM/EDS and XRD are also applied to investigate the microstructure, the elemental and phase composition of geopolymerization products. The findings of the present work provide a novel method to apply fly ash as a high strength water-resistant precast construction material. INTRODUCTION Geopolymerization is a process of obtaining a polymeric structure from aluminosilicate by dissolving aluminosilicate sources in a strong alkali (NaOH) solution and condensation of free [SiO4] and [AlO4] tetrahedral units (Davidovits, 1985 and 1988; Duxson et al, 2005; Xu et al, 2000, 2002). After being cured at an elevated temperature for a specific time, the geopolymerization product shows a greatly increased compressive strength. Therefore, the product can be used as construction material such as bricks and road pavement. It provides a very promising method to apply aluminosilicate sources such as fly ash as a construction material for a sustainable development. Fly ash is a main industrial waste which needs to be carefully impounded because of its potential impact on environment. Many efforts have been tried to utilize fly ash as construction materials substituting Portland cement because of the following reasons. First, fly ash is a silica/alumina rich aluminosilicate source, which makes the specific material an ideal source for the geopolymerization process. Secondly, the particle size of fly ash is usually very small (< 50 microns) and it saves a lot of energy consumed during the production process of cement for grinding. Thirdly, fly ash is an ideal source for geopolymerization because it is reactive to alkali even at a mild temperature. In the past twenty years, many studies have been carried out on the geopolymerization of fly ash to a make construction material. However, there are some disadvantages associated with the conventional methods of treating fly ash (Palomo et al, 1999; Perera et al, 2007; Temuujin, et al, 2009; Hanjitsuwan et al, 2014). First, in most of the proposed geopolymerization methods, a salient amount of sodium silicate has to be added. It therefore makes it complex whether the achieved mechanical strength of geopolymerization products is due to a real geopolymerization process between fly ash and alkali or just largely the solidification of metal silicate in air at an elevated temperature. Secondly, the authors have noticed that when the geopolymerization product is soaked in water, the solution pH increases sharply and the products will lose its compressive strength gradually in water. Thirdly, the compressive strength of the geopolymerization product as reported is usually less than 50 MPa.

Jan 1, 2019

By Noel N. Moebs

The Bureau of Mines studied the feasibility of water diversion and overburden dewatering for underground coal mines in the Appalachian region. All relevant published literature pertaining to the occurrence and control of surface and ground water in underground coal mines was reviewed, and the impacts of mine water with respect to health and safety, production, environment, and costs were assessed and are described in this report. The report also identifies the sources of water inflow into underground coal mines, and gives a summary description and evaluation of techniques that can be used to reduce the amount of water entering these mines. Engineering practices currently used by operating coal mines in the Appalachian region to prevent the movement of ground and surface water into active coal workings were reviewed and are summarized. Major emphasis has been placed on the identification of geologic and hydrologic conditions of the site, the water control methods used, and an evaluation of their technical and cost effectiveness.

Jan 1, 1985

By Walter W. Kaufman

This Bureau of Mines manual for design of surface mine haulage roads covers such aspects of haulage road design as road alinement (both vertical and horizontal), construction materials, cross slope, and drainage provisions. Traffic control and design of proper lane widths to promote safe vehicle movement are included, as are suggested criteria for road and vehicle maintenance and for runaway-vehicle safety provisions. The aim of this publication is to provide those involved with surface mine haulage road design with a complete manual of recommended practices that, if implemented, will promote safer, more efficient haulage routes.

Jan 1, 1977

By A. G. Sharkey

THE PURPOSE of this investigation was to develop methods for analyzing coal derivatives and products from the Fischer-Tropsch synthesis. As part of this investigation it was necessary to study the mass spectral characteristics of many classes of compounds. The mass spectra of alcohols, the trimethylsilyl ether derivatives of alcohols, acetal-type compounds, ketones, esters, and naphthenes were correlated with structure, and analytical methods were formulated. A method was devised to determine the ratio of branched to normal hydrocarbons up to CIS in the Fischer-Tropsch product. Low-ionizing-voltage mass spectrometry was combined with type-analyses to analyze tar acids and neutral oils from coal. The necessary sensitivity correlations at low-ionizing voltage were developed, particularly for phenolic compounds. Special analytical techniques were developed for the mass spectral analyses of specific compounds and compound types including (1) oxides of nitrogen, (2) hydrogen sulfide, (3) isomers of butenes and pentenes, and (4) hydrogen deuteride. An investigation was made of the effects of various hydrocarbons and oxygenated compounds on tungsten filaments in the mass spectrometer. The operating characteristics of rhenium filaments under similar conditions were studied. Several improved sample handling techniques were developed, including an automatic manometer and a self-filling micropipet. Studies were made of anomalous and negative peaks in the mass spectra of certain gases.

Jan 1, 1967

By A. D. McMahon

Changes in world mine and smelter supply sources of zinc have led to changes in zinc supply patterns in the United States during the past 3 years, 1970-72. The result has been a growing reliance on foreign sources of zinc metal to furnish an ever-increasing portion of expending domestic requirements. This review of fundamentals and historical developments is intended to provide background in order to place the future of the U.S. zinc industry fn perspective. The properties and uses of zinc are described. A new study on U.S. reserves is presented with description by geographical region and comparisons with older reserve data. The technology of the zinc industry from prospecting through refining is described with emphasis on the metallurgy involved in the various methods of smelting. Production, consumption, and imports are discussed and illustrated with graphs and tables to review the past and present patterns. Government actions affecting the industry are shown.

Jan 1, 1974

By H. Reginald Hardy

This report describes the results of a research project carried out to investigate the feasibility of using transducer arrays, located on surface or in shallow boreholes, above an active coal mine to detect and locate the source of underground microseismic activity which normally occurs during mining. The initial stage of the project involves the design and development of a self-contained mobile microseismic monitoring facility capable of use in remote field locations. Following this a variety of transducers, and transducer field installation techniques were investigated to obtain optimum sensitivity and high signal-to-noise characteristics. Preliminary efforts were also undertaken to develop semi-automated techniques for analysis of microseismic field data. Using the facilities and techniques developed field studies were carried out at a number of surface locations over a central Pennsylvania coal mine operating at depths of the order of 500 feet. In particular studies were con-ducted over a previously mined development area, troubled by extensive problems of roof instability, and over two longwall panels during mining. Although many of the field studies were carried out during the development stage of the project, results in general have been most encouraging. Limited results were obtained over the development area, however excellent microseismic signals, correlating with underground strata instability, were detected over both long-wall areas, proving the general feasibility of surface monitoring techniques. More recent studies, carried out as part of a subsequent project, and utilizing modified geophone installation techniques at a third longwall site, have verified explicitly the feasibility of measuring underground microseismic activity from surface locations. Sections of typical field data are included in this report along with a brief review of the studies carried out at each of the field sites. Detailed analysis of data obtained at the second and third longwall test sites will be presented in a later report.

Jan 1, 1974

By G. E. Cole

"Amongst the mineral products of Canada gold holds the second place in value of yearly output. . . . . .The production of gold has increased steadily during the past six years and has somewhat more than doubled in that time. For the past four years Canada has been third among the gold producing countries of the world, surpassed only by the Union of South Africa, and the United States of America," and now yields somewhat more than 9 per cent of the annual output of the world."-"The Gold Situation in Canada". Bulletin of Development Branch, Canadian Pacific Railway. The history of gold mining in Canada is comparatively modern and does not take one further back than the late &apos;fifties of the 19th century. If the efforts of the early explorers in Canada were expended in "seeking with equal ardour, proselytes and gold", history fails of any record of their success in the search for the precious metal. As early as 1849 not a few Canadians travelled from the east by land and water to the Californian goldfields. In the then settled part of Canadathe east-people were alive to the value of any mineral discovery; but the west, owing to its remoteness and to there being no ready means of communication, was virtually isolated from the east.

Jan 1, 1927

By Shiro Ishii

When construction sites are in a densely- populated area or near roads, railroad or river, restrictions upon the ways of handling and using explosives such as dynamite and large demolition equipment are being increasingly stringent, in consideration of environmental pollution such as noise, vibration, dust, flyrocks etc., and safety precaution. In view of this, the development of safe and pollution-free technology for demolishing rocks at mines and reinforced concrete structure at building sites is strongly required. To meet such requirements, the demolition by means of expantion of mineral substances has been considered long before. Recently with the demolition technique using non-explosive demolition agent developed by ONODA CEMENT CO., LTD., holes are drilled into substances to be demolished, such as rocks and concrete before-hand. Then, slurry of such agent mixed with an appropriate quantity of water is poured into the holes. It hardens and expands with the passage of time, and the expansive stress reaches more than 3m/m2 in 10 to 24 hours. This expansive stress causes the material to crack. In this article, descriptions of the non- explosive demolition agent, BRISTAR manufactured by ONODA CEMENT CO., LTD., TOKYO, JAPAN, are given briefly with regard to its physical and chemical properties and its method of use; and the way it is used at an actual construction site is reported.

Jan 1, 1982

By I. Yu. Melekestseva

The Semenov hydrothermal sulfide cluster (13º31´N), consisted of five fields (Semenov-1, -2, -3, -4, and -5), was discovered in 2007 in the 30th cruise of R/V Professor Logatchev [Beltenev et al., 2007; 2009]. The hydrothermal fields are located on a seamount composed of ultramafic and mafic rocks, gabbro, plagiogranite, and their altered rocks. The Semenov cluster is considered to be the largest sulfide accumulation in the Ocean with massive sulfide (MS) resources of about 40 million tons [Beltenev et al., 2009]. MS of the Semenov-1, -3, -4, and -5 hydrothermal fields are mostly characterized by marcasite-pyrite composition whereas rich copper-zinc MS with high Cu and Zn contents (11.37?19.33 and 5.89?18.32%, respectively) and anomalous Au and Ag grades (22?188 ?127?1787 ppm, respectively) were dredged only at the Semenov-2 hydrothermal field associated with basalts (13°31.13´N, 44°59.03´W; 2360?2580 m of depths) [Ivanov et al., 2008].

Jan 1, 2010

By P. Cowx

The carbothermic reduction of zinc oxide rich Electric Arc Furnace baghouse dust in the Tetronics transferred arc plasma furnace to produce a non-toxic slag and a metallic zinc product is described. In particular, the operation of the zinc splash condenser coupled to the plasma furnace is examined and the effect of process variables on zinc recovery is discussed.

Jan 1, 1990

By Jean-Pierre Birat, François Hanrot, Gérard Danloy

Global warming presents an enormous challenge to the steel industry, which is both carbon-intensive and energy efficient. Lean production can provide some short-term emission mitigation, at the level of the Kyoto requirements. In the middle term, more use of scrap will also help alleviate emissions. But to reach much larger reductions in GHG emissions, on a par with the likely targets that will be set after the Kyoto period, the steel industry will have to imagine new production paradigms, which constitutes its most formidable challenge for the years to come. Carbon capture and sequestration, processes leaner in carbon use, electricity and hydrogen from green sources will have to be added together in a patchwork of process routes, which will have to be developed at great risk in the next decade, hopefully through broad international cooperation.

Jan 1, 2004

By M. Nichols

Where am I? Where are they? Where is it? These are the fundamental questions that need to be answered in managing people and resources. This paper explains how GPS positioning technologies answer those fundamental questions and provide better information management from initial exploration work through daily mine operations to reclamation work and environmental monitoring.

Jan 1, 1998

By G. A. Irons, D. Guo, D. Angheiina

To produce low-carbon (<30 ppm) steel in the tank degassing process, a ladle of steel with an oxidizing slag is placed in a vacuum tank equipped with bottom bubbling. The kinetics of this process are slow compared to the more prevalent RH degassing process, providing the impetus for the present work. There are several aspects to this work: water models of the fluid flow in the ladle; simulation of the decarburization (CO evolution) with C02 desorption in water; pilot-plant (60 kg) studies of the decarburization kinetics; mathematical modelling of the fluid flow in the ladle; mathematical models for each of the kinetic sites (plume, top slag and auto-nucleation); and full-scale trials. The results show that during the refining cycle the contribution from each reaction site changes, suggesting avenues for reducing cycling time and final carbon contents.

Jan 1, 2000

By Olli Hyvärinen

The capacity of Outokumpu Pori Copper Refinery has been increased by 50 % to 70 000 t/a in the last five years by adopting periodic current reversal, reducing spacing and installing some new cells in the old tank house building. Five years operation of PCR has proved that it is possible to achieve additional capacity with PCR and yet produce high quality cathodes. The impurity level in anodes has considerably increased, and recently, arsenic, antimony and sometimes bismuth have displaced nickel as the most critical impurity.

Jan 1, 1987

By S. Gopalan, J. D. Milshtein, S. N. Basu

Production of syngas is proposed utilizing the W/W03 redox system and employing a solarpowered two-step thermochemical cycle. Three chemical reactions occur in two chambers. Assisted by a solar concentrator, a high temperature reaction reduces W03 powder to metallic tungsten in both chambers. Subsequently, the temperature in one of the chambers is lowered and H2(g) is produced via re-oxidation of the tungsten powder using steam. The temperature in the other chamber is simultaneously lowered to an intermediate temperature and CO(g) is produced via oxidation of the tungsten powder using C02(g)· The gas streams coming out of the two chambers result in the syngas production. A complete thermodynamic analysis of the system is described. The W/W03 redox cycle offers greater gravimetric fuel productivity compared to previously proposed systems, and the entire cycle can be operated below 1273K.

Jan 1, 2013

By T G. Callcott

Australian coking coals are either class 434<tlj534<2l, at Port Kembla, or 634<3> at Newcastle. The former yield good blast-furnace cokes; the latter yield poor ones. However, increases in conventional strength indices, by methods applicable with normal coking ovens, seem unlikely to be economically attractive. Characterization of the coals has enabled an "economic" blend to be developed in the Newcastle area, and this has affected mining, preparation and handling operations. Coking studies have led to a specification for the making of strong coke, especially from the high-volatile Newcastle coals. Continuous coking studies, developed from the efforts to make very strong coke, have taken two directions. Firstly, coking thin layers of coal on strands; secondly, coking, in various types of vessels, compacts of coals with or with-out the inclusion of non-coking coals, iron ores or other inert materials. Gas, "sand" and hot metal coking have been tested for use in compact coking. Particular attention has been paid to pellets of coal and ore. The probable industrial problems in adopting any of the ideas are presently being examined.

Jan 1, 1963