Search Documents

By James W. Echerd

Anthracite preparation developments, particularly in the early days of the anthracite industry, formed the basis for the modern coal preparation plants that have become so essential to the coal industry today. The anthracite industry, from early in the 19th century until relatively recently, was a leader in mining, preparation and marketing of coal, and played a leading role in the development of the industrial America we know today. Anthracite was discovered in America in about 1760--the story of Necho Allen is well known--but the rediscoveries leading to mining operations took place about 50 years later. The Wurtz brothers in 1815 at Scranton, the Smith brothers at Wilkes-Barre in 1807, Beach in Hazleton in about 1814, and Boyd in 1816 at Shamokin were all instrumental in promoting early mining and marketing of anthracite (J3. The early canals and railroads were built for the specific purpose of moving anthracite to the market areas. Eventually, the industry grew until, in 1917, it reached a production zenith of a little over 100,000,000 tons, representing about 20 percent of the total coal output in the United States. Almost half of the anthracite produced that year was consumed for domestic heating, a utilization that had dominated the industry for almost 100 years. Initially, anthracite had to be used by gunsmiths and blacksmiths, after which had followed the consumption of extensive quantities for railroads, blast furnaces and foundries, and electric power generation. Most of the markets have been lost to coke, oil, and natural gas. Near the anthracite regions, however, significant quantities are still used for domestic heating, power generation, carbon black manufacture, blending with bituminous coal to make metallurgical coke and fuel, and for other industrial purposes. Thus, anthracite production has not been entirely committed to history, but remains an active industry that follows modern practices in the mining, preparation, shipping, and utilization of a fuel that is still a valuable adjunct to the national economy. In fact, its inherent low sulfur content may make it an important fuel of the future. Estimates indicate there are reserves of anthracite to last for 300 years at a consumption rate of 50,000,000 tons/year. Anthracite Preparation Yesterday A 170-year history of the anthracite industry obviously is not the purpose of this discussion. A complete history of anthracite preparation, the rather unglamorous step in the processing of "mine run" hard coal to make it suitable for the user, is also not practical. Hence, the purpose of this report is to trace the development of some of the most important processes used through the years to meet a part of the demand for energy developed by our modern society. Anthracite preparation in the early days of the industry consisted solely of separating slate from the coal, by hand, underground (Z). This method prevailed for almost 20 years until wrought iron hand rakes were introduced to separate the large and small sizes. Shortly thereafter, the first attempts were made to size and clean the coal aboveground. The coal was dumped on a perforated cast iron plate, and men used sledge hammers to break the larger pieces into smaller sizes suitable for the market. The smallest sizes--that is, the material that went through the plate--were thrown away because they had no value at that time--a concept that existed for many years and actually was the basis for the subsequent "river" coal production and the many silt banks which are landmarks in the anthracite region. The larger sizes, at that time, sold for 50 cents per ton. The Batten breaker, or roll crusher, was invented in 1844, followed soon thereafter by the Snell-Diehm breaker (A). The latter had disadvantages, including excessive waste and fixed product size, but it later was improved in these respects. A breaker was also developed at Minersville, Pa., at about the same time that processed 200 tons of coal per day, using roll crushers and circular screens (1). Handpicking, from the beginning of anthracite preparation, was an important part of the cleaning process and was still being practiced as late as 1950. It was this process that involved the "breaker" boys of coal region lore. How much good handpicking accomplished depended on how much impurity was present in the coal--the more the impurities, the greater the reduction in ash. Thus, high-impurity streams were significantly improved, whereas picking of relatively clean coal was mainly to show an effort to make a quality product. As indicated, picking is largely a visual operation. It was and is wasteful of coal in the larger sizes since some good coal is always associated with the bad. However, it was probably much more effective' in the larger than the smaller sizes.

Jan 1, 1971

By J. W. Rutter, K. T. Aust

The temperature dependence of the rate of grain boundary migration was measured in bicrystals of zone-refined lead containing from 20 to less than 1 ppm by wezght of tin. The apparent activation energy in the temperature range from 320" to 200oC is markedly dependent upon the solute tin concentration and upon the orientation relationship of the grains adjacent to the grain boundavy. The quantitative experimental observat~ons are compared with the predictions of various theories of grain boundary migration. In previous work.&apos;?&apos; the mobility of individual grain boundaries was studied as a function of impurity concentration and type of boundary. Grain boundary migration occurred at the expense of dislocation arrays which were introduced into the specimen during solidification. Boundary mobility in zone-refined lead at 300°C was markedly decreased by small additions of tin. 0.004 wt pct being sufficient to decrease the rate of grain boundary migration by a factor of 1000. The mobility of grain boundaries having polar orientation relationships near 38 and 22 deg about <Ill>, and 28 deg about <100>, was much less sensitive to tin concentration in the range studied. As a result, these boundaries have relatively high mobilities. The present paper is a continuation of the above study. Data are now presented on the temperature dependence of the motion of individual grain boundaries in zone-refined lead as a function of solute tin concentration and orientation relationship of adjacent grains at the grain boundary. The experimental observations are compared with the predictions of a number of theories of grain boundary migration3-8 which, prior to the present experimental investigation, could not be critically evaluated. EXPERIMENTAL PROCEDURE The striation or lineage structure of melt-grown single crystals of zone-refined lead, containing various additions of tin, was utilized to provide a driving force for grain boundary migration, as previously described.1,2 Each grain boundary under study separated the striated single crystal from another grain which was introduced by localized plastic deformation and recrystallization of a small region of the sample. The speed of migration of grain boundaries in dilute alloys of tin in zone-refined lead was investigated as a function of 1) tin concentration from < 0.0001 to 0.002 wt pct, 2) temperature in the range of 200" to 320°C, and 3) orientation relationship of the adjacent grains at the grain boundary. The substructure driving energy available for grain boundary migration was estimated to be about 4000 ergs per cu cm, within a factor of two, from specimen to specimen.&apos; The specimen dimensions, and growth and alloying procedures for the preparation of striated single crystals of lead of known tin composition, were as described previously.&apos; Each bicrystal was carefully wrapped in aluminum foil, and annealed in a well-stirred salt bath consisting of 50 pct NaNO2 and 50 pct KNO3, for known periods of time at a series of constant temperatures (*2°C). The grain boundary positions, before and after each anneal, were determined by etching lightly in a solution of 5 pct nitric acid in methyl alcohol, in order to follow the motion of the boundary and determine its rate of migration. Thus, the rate of motion of the grain boundary in a single specimen was measured at various temperatures. The above procedure was carried out for each grain boundary in seventeen different bicrystal specimens.

Jan 1, 1960

By F. L. Wolf

THE catenary system of line construction possesses so many desirable characteristics from the operating standpoint that it has wide application for all types of electric traction. Many steam roads are electrifying sections of their lines, and in most cases are operating both steam and electric locomotives over the same track. This&apos; means that the overhead catenary system is subjected to the severe corrosive action of locomotive smoke, and data concerning the resistance of various alloys to this form of corrosion are very desirable from every point of view. Reliable and specific information and data on the subject of corrosion due to steam and smoke from locomotives are extremely meager and, on this account, extensive service tests, together with accelerated tests, have been made on a number of commercial metals and alloys. The observations and data recorded in this paper are the result of a, preliminary test which was started in 1923 and which has been carried on to the present time. The recognition of the need for even more detailed and accurate data has resulted in the undertaking of another test which has been in progress for about a year. The result of this test will be published in due course. Some years ago The Ohio Brass Co. was asked by one of the large steam railroad companies to furnish data on construction details for a catenary system which it was considering for one of its divisions. The selection of, materials which would give the necessary physical characteristics as well as withstand the severe corrosive action of locomotive gases caused electrical railroad engineers considerable concern. At that time, there were available no specific or authentic data on these important questions: no systematic investigation of the problem appeared to have been made, even though its importance was generally recognized. Such observations as had been made were crude in that they had been limited largely to visual inspection which too frequently is most misleading. However, the scattered information which was collected gave important clues as to how best to start an investigation.

Jan 1, 1930

By E. B. Spice

Although much may be learned about the economics of cold weather operations by studying successful mining ventures in southern and central Canada, it is the purpose of this article to extend the study by considering only permafrost areas. Geographically this means most of the country north of the 60th parallel. In this area, at the present time, only five Canadian companies are carrying on routine and successful mining operations on a year-round basis. However, there have been some score of unsuccessful ventures, and a number of properties in the development stage show promise of being producers. Problems of cold weather are worthy of study. It may be pointed out that successful mines in this area face problems of isolation and costly transportation as well as cold weather. To reach valid conclusions, consider the development of a mythical mineral deposit located on the 65th parallel in the heart of the barren lands; problems of isolation and transportation will be ignored.

Jul 1, 1956

By Heath E, van Calsteren P, Turner S, McDermott F

U-Th isotope studies of recent volcanic rocks may be used to evaluate the depths and rates of melt generation beneath mid- ocean ridges and ocean islands. Island arc rocks exhibit a similar range in Th isotopes to that seen in both MORB and OIB, but while those with high (230Th/232Th) tend to have excess 238U, many of those with low (230Th/232Th) are in isotope equilibrium. The excess 238U is attributed to the preferential mobilisation of U in hydrous fluids from the subducted slab within the last 100,000 years, whereas the low Th isotope ratios in the higher-K arcs are primarily due to the introduction of subducted sediment. Preliminary results from mineral separates from lavas on Soufriere on the island of St. Vincent indicate that some of the minerals crystallised up to 50,000 years prior to eruption.

Jan 1, 1995

By Chenming Liu, Xiao Lin, Bo Wang, Hongbin Cao, Xingang Li

Over 2 million tons of NH3-N were discharged in China per year recently, rare earth industry contributed 7.03% of NH3-N pollutant from industrial wastewater in 2007. Wastewater containing NH3-N and heavy metals mainly produced in RE extraction saponificated with ammonia and precipitated by ammonia bicarbonate. Generally, 1 ton REO cost 0.6-1.2 ton ammonia for extraction and 1.6 ton ammonia bicarbonate for precipitation, and produce 35-100 ton wastewater. Processes, like Na-saponificated, Ca-saponificated and Non-saponificated technique, are widely studied to reduce the adverse environmental effect of RE industry, while traditional processes still have advantage in production cost, process stability and product quality. In this study, a novel process that combines distillation and air-stripping is developed. NH3-N is removed and recovered based on relative volatility difference of NH3 and H2O. Phase equilibrium, heat equilibrium are calculated to determine process parameters. Hydrodynamic performance like flow field distribution is also simulated. Then, design parameters for distillation trays or structured packing are determined based on calculations and simulations. Besides, the phase diagram of (NH4)2SO4-NH4Cl-H2O in 30°C - 100°C, the typical salts composition of nonferrous wastewater, is studied to ensure commercial plants’ continuous operation. Ammonia removal tower (ART) with different high efficient column internals is designed to fit RE wastewater treatment requirement. The novel process has been commercialized in RE industry in Jiangxi, China. The commercial project operation results show the novel process reached a nearly zero-emission with >99.5% NH3-N was removed and then recovered as ammonia. Combined the novel process, the traditional REO separation process using ammonia and ammonia bicarbonate could achieve NH3-N reuse and the effluent quality meets the discharge standards.

Jan 1, 2016

By R Goddard

An alternative stoping method has been adopted for narrow vein stoping at the Tasmania Mine in Northern Tasmania. Colloquially described as ‘Radial-in-Reef’ (RiR) stoping, the method employs the drilling of radial rings in the plane of the Reef from a drill stub located at the geographic centre of the proposed stope panel.Production from the Western Zone of the Tasmania Reef has been undertaken remotely from the Reef since 2007, after a detailed geotechnical engineering analysis indicated that the integrity of the sill drives could not guarantee an acceptable level of confidence should an anticipated seismic event occur within a radius of 10 m. The key tenet of the remote mining approach was the exclusion of personnel from sill drives once stoping had commenced. The remote mining method had to be ‘retrofitted’ to four existing stoping blocks totalling 11 sill drives which totalled 160 m vertically. The remote mining method proved to be complex, cumbersome and very expensive. However, the ore was extracted successfully.By early 2010, previously developed ore had largely been exhausted and the future development with an orebody open at depth presented the opportunity to review the current extraction method. However, the new extraction method needed to maintain the tenet of excluding personnel from sill drives of active stoping blocks, but seek opportunities to reduce the difficult and costly aspects of the previous method. The new ‘Radial-in-Reef’ stoping reduced the development requirement from six to two drives per ore block. Cost implications aside, the significant reduction in prestoping extraction ratio was expected to also reduce the likelihood of seismicity. Transverse production rings were designed to be drilled radially from a drill stub mined from a mid-stope footwall drive. Stopes totalling up to 7000 tonnes were planned be fired in a single electronic blast. Extraction was designed to take place from a basal sill drive under teleremote operation. At the time of writing, the method was under trial.

Mar 21, 2011

By Joe Keane

DOUG HALBE: The kickoff speaker, and my unanimous choice, is Joe Keane. Joe was born in Butte, Montana, and began his association with the mining industry as an under- ground miner at age 16. Currently he is president of KD Engineering and Metcon Research. He had it lucky when he went to school because there were only 44 elements in the periodic table, I understand. [laughter] Here&apos;s Joe. JOE KEANE: I&apos;m doing this under protest. Maybe we can start the slides. Mr. Halbe gave me this topic, but I don&apos;t like it. I don&apos;t like Mr. Halbe either [laughter] because of the way he shanghaied me into this. He called me up on the phone and said this is what you&apos;re going to speak about: "Five Things I Never Want to See Again in Plant Design," and I said, "Huh!" Then I started getting stuff from SME about how to make a presentation. I have decided to change the title to "More Than Five Things I Never Want to See in Plant Design," since you can&apos;t have a completely negative speech; you have to have other topics. So we will have some other, not completely nonrelated, topics to sort of break the tension. I tried to find a joke to open with. I talked to Omar Mutati. All of his jokes were either about Bill Clinton, our beloved President, or they were too filthy to say in a mixed group. [laughter] So I decided to start this out with a profound statement. The pro- found statement is, "The meek shall inherit the earth, but not the mineral rights," [laughter] by J. Paul Getty. J. Paul Getty was one of my favorite guys because when a real obnoxious reporter asked him one day, "How can I become wealthy?" he said, "Drill for oil and find it."

Jan 1, 1998

By Carl Swartz

METALLURGISTS differ considerably in their opinions regarding the effect, if any, of small amounts of iron pyrites, or other iron compounds on zinc sulfide ores during the roasting operation. As a result, the literature on this subject expresses many conflicting ideas. The ore, previously crushed to pass through a one-millimeter screen, dries in the roasting kiln, losing water up to 200° to 300° C. At 150° C. iron pyrites begin to lose sulfur. As the temperature increases, while the ore is passing to the hotter part of the furnace, the sulfur burns to sulfur dioxide, leaving the metals as zinc oxide and ferric oxide. These two substances then interact to form zinc ferrite, a compound, yellow brown in, color, having the general characteristics of a spinet Like magnetite, another spinel, zinc ferrite is insoluble in alkalis and dilute acids. As a result, when leached with 10 per cent. sulfuric acid solution zinc values tied up in this compound remain behind. HISTORY In the electrolytic recovery of zinc from its ores, the roasted ores are usually leached with a 10 per cent. sulfuric acid solution. When the zinc ore contains iron pyrites as an impurity in an appreciable amount, the actual yield of metallic zinc is much lower than a theoretical calculation would indicate. Further, losses of zinc are, in a rough way, directly proportional to the amount of iron pyrites or other iron compounds present. When the iron is present in the ore in an isomorphous relation to the zinc, as in the case of a marmatite, a greater amount of zinc remains insoluble than when present as a true pyrite or marcasite. Work on the insoluble residues obtained from leaching of the calcines shows that the zinc lost is intimately tied up in this residue. Some investigators have suggested a definite compound, such as zinc ferrite, others merely a mixture of zinc and iron compounds.

Jan 1, 1927

By J. H. Hollomon, L. D. Jaffe

The hardenability concept has become widely used during the last few years for the choice and substitution of steels. Before the work of Grossmann,1 the systems for predicting hardenability from chemical composition could be used only over a narrow range of composition. Grossmann introduced a comprehensive system, which has been effective in calculating the hardenability of most types of moderate or low-alloy steels. However, occasions often arise that require the calculation of the hardenability of high-alloy steels from their chemical compositions. Experimental determinations of the hardenabilities of such steels indicate that the Grossmann system predicts much greater hardenabilities than are realized. The fact that cases do arise in which the Grossmann method does not apply indicates that the fundamental hypothesis of the system may not be generally applicable. It seems advisable to re-examine not only Grossmann&apos;s system but also the concept of hardenability itself. Hardenability If steel parts are to possess a martensitic structure after quenching, they must first be austenitized and then cooled through the pearlite and bainite transformation ranges sufficiently rapidly to avoid the formation of pearlite, bainite, and pro-eutectoid products.* If, on cooling, these transformations are avoided, the resulting structure can consist only of martensite (and retained austenite). The hardenability of a steel is measured in terms of the severity of the cooling conditions necessary to avoid the pearlite and bainite transformations. The less rapid is the cooling necessary to prevent the formation of bainite and pearlite, the higher is the hardenability. The pearlite and bainite reactions appear to be differently affected by the alloying elements. Not only is this indicated by the published isothermal transformation data, but recent work by Zener2 affords a rational interpretation of the differing effects of the alloying elements. Manganese,3 for example, appears to decrease the rates of the pearlite and bainite transformations by equal percentages, while molybdenum45 is approximately 10,000 times more effective in retarding the pearlite than in retarding the bainite transformation, on the basis of isothermal measurements. In some steels, the formation of bainite restricts the formation of martensite while

Jan 1, 1947

By L. D. Jaffe, J. H. Hollomon

The hardenability concept has become widely used during the last few years for the choice and substitution of steels. Before the work of Grossmann,1 the systems for predicting hardenability from chemical composition could be used only over a narrow range of composition. Grossmann introduced a comprehensive system, which has been effective in calculating the hardenability of most types of moderate or low-alloy steels. However, occasions often arise that require the calculation of the hardenability of high-alloy steels from their chemical compositions. Experimental determinations of the hardenabilities of such steels indicate that the Grossmann system predicts much greater hardenabilities than are realized. The fact that cases do arise in which the Grossmann method does not apply indicates that the fundamental hypothesis of the system may not be generally applicable. It seems advisable to re-examine not only Grossmann&apos;s system but also the concept of hardenability itself. Hardenability If steel parts are to possess a martensitic structure after quenching, they must first be austenitized and then cooled through the pearlite and bainite transformation ranges sufficiently rapidly to avoid the formation of pearlite, bainite, and pro-eutectoid products.* If, on cooling, these transformations are avoided, the resulting structure can consist only of martensite (and retained austenite). The hardenability of a steel is measured in terms of the severity of the cooling conditions necessary to avoid the pearlite and bainite transformations. The less rapid is the cooling necessary to prevent the formation of bainite and pearlite, the higher is the hardenability. The pearlite and bainite reactions appear to be differently affected by the alloying elements. Not only is this indicated by the published isothermal transformation data, but recent work by Zener2 affords a rational interpretation of the differing effects of the alloying elements. Manganese,3 for example, appears to decrease the rates of the pearlite and bainite transformations by equal percentages, while molybdenum45 is approximately 10,000 times more effective in retarding the pearlite than in retarding the bainite transformation, on the basis of isothermal measurements. In some steels, the formation of bainite restricts the formation of martensite while

Jan 1, 1947

By K. L. Myers, R. Espell, C. Deringer

Construction of the AA Pad reclamation was completed in the fall of 2000. Seeding of the ET cover began in the late fall of 2000 and continued through May of 2001. On Saturday afternoon, June 1, 2002, a large, very localized thunderstorm struck the reclaimed AA Pad site. Eyewitnesses present at the time described a dark storm cloud parked above the site for less than half an hour. Average rainfall intensity was measured to be 122 mm (4.8 inches) per hour and peak rainfall intensity was estimated to be 213 mm (8.4 inches) to 259 mm(10.2 inches) per hour. At the time of the storm, the construction was less than two (2) years old and the vegetation had only a single season of growth. The entire period from the end of construction until the date of the storm was a drought period with below normal precipitation. Other than a few small snowmelt events, there was no precipitation event large enough to produce any significant flow in the channel network. Therefore, the very first significant runoff event was the extreme event of June 1, 2002. The storm essentially represents a large-scale field test of the design concepts used at the AA Pad site. Shortly after the storm, data was collected and analyzed with the intent of learning as much as possible about the performance of the cover system design with the expectation that the newly acquired knowledge might be utilized in future designs to further improve the performance of similar cover systems during extreme events.

Jan 1, 2003

By S. B. Christy

The fact that many millions of gold have been extracted by the cyanide process, during the last five or six years, from South African tailings which could not be profitably worked by any other method previously tried upon them, lends a peculiar practical interest to this branch&apos; of metallurgy. Numerous writers have recently made valuable contributions on the process without exhausting the many complexities of the subject. Among the first American writers on the subject in its modern aspect were two former students of the University of California, Mr. Louis Janin, Jr., and Mr. Charles Butters. Young Janin was one of the first to enter this field, and performed much useful experimental work in the early stages of the history of the process. At about the same time, Mr. Charles Butters, who had left California to erect chlorination works for the Robinson mine at Johannesburg, became interested in the cyanide process, and, after getting the chlorination plant in working order, put up, for working the tailings from the Robinson mine, a cyanide plant which achieved the first large-scale success ever made with this process. The papers which Charles Butters, together with John E. Clennell and Edgar Smart, have contributed on the chemistry of the process, were among the first to give any adequate idea of its nature.* Another important contribution to the literature of the subject is the paper of Dr. A. Scheidell, published in 1894 as a " Bulletin of the California State Mining Bureau." This contains an admirable summary of the state of the art at the time of its publication.

Jan 1, 1897

By M. Goto, T., Matsutani, T. Igarashi

"PT. Smelting was established in February 1996 as a company to· construct the first copper Smelter and Refinery in Indonesia with US$500 million direct construction cost and operate it. The plant is located in Gresik, East Java, Indonesia and 20km northwest from Surabaya, 2nd largest city in Indonesia. The site was selected due to following .advantages.1. Adjacent PT: Petrokimia Gresik, - a fertilizer company, purchases all sulfuric acid produced through pipeline.2. Facing on the seashore of the Madura Strait, it is possible to unload copper concentrate from West Papua (3,000km from Gresik) and load granulated slag to the market.3. Close to the good harbor facilities at Surabaya for export the products.4. Gresik Industrial Area has adequate infrastructure.5. Surabaya is a quite nice city to live for people from abroad.The shareholder of PT. Smelting are Mitsubishi Materials Corporation (60.5%), PT. Freeport Indonesia (25:0%), Mitsubishi Corporation (9.5%) and Nippon Mining and Metals Co. Ltd. (4.5%).The Gresik Copper Smelter and Refinery is designed to produce 200,000 tpy of copper cathode from 660,000 tpy of copper concentrates supplied 100% by 'Grasberg Mine of PT. Freeport, Indonesia in West Papua (former Irian Jaya). Other by products are 600,000 tpy of sulfuric acid, 30,000 tpy of gypsum, 509 tpy of precious metal slime and 400,000 tpy of granulated slag. These are sold to domestic and international markets.This project adopted the Mitsubishi Continuous Copper Smelting and Converting Process in the Smelter for anode casting, Contilanod process comprising Hazelett twin belt caster and a Mannesmann's travelling shear were selected. ISA stainless steel cathode process is applied in refinery. The combination of contilanod anode and stainless steel cathode ensured good cathode quality from the very beginning of start-up SO2 gas generated from Smelter is treated by Lurgi-Mitsubishi double contact/absorption acid plant. All contact. wastewater from the plant is treated in multistage wastewater treatment plant.Electricity and oxygen are ·supplied ""over the fence"" by a company which is located in the site of the Gresik Smelter and Refinery."

Jan 1, 2000

By Thomas G. A

THE irregularity of the Mount Morgan (Queensland) ore body presents problems other than those only of mining. For irregularity of outline is coupled with irregularity of grade, and the ore varies so rapidly from profitable to non-profitable, and fromhighly siliceous to highly pyritic, that the task of estimating quantities and values of ore reserves is manifestly rendered a difficult one, while the actual disposal of the broken ore demands constant supervision.Four classes of ore are handled. The oxidized ore, cheaply mined and cheaply treated, is obtained by quarrying from the top of the mountain. Below the 315-ft. mine level (measured from the original summit) sulphide ore comes in, and this is divided into siliceous sulphide ore (too siliceous for economic smelting), sulphide ore suitable for smelting, and ore too poor either to be smelted or to be treated by wet process with the siliceous ore. It is with these three latter descriptions of ore that this paper principally deals.Although the output from many stopes in the mine may usually be presumed beforehand to be either smelting or wet-treatment ore, yet it is never safe to take this for granted, and constant assaying is necessary. At the same time the ore merges from one class into...

Jan 1, 1911

By J. B. Morgan

The mechanical behavior of MgCu2 from 20 o to 725°C has been determined by "brittle-ring" tensite-test techniques, axial compression, and bending experiments. Compressive ductility begins at 450°C (0.65 T/Tm) and slowly increases with increasing temperature white the tensile ductility is characterized by an abrupt brittle-ductile transition at 600°C (0.8T/Tm). The compressive strength increases eightfold from room temperature to 400°C with a "normal" decrease as the temperature is further increased. The tensile strength goes through a rather abrupt threefold increase above 600°C with a subsequent decrease at higher temperatures. The slip system is (111)[110] and the twinning system is (111)[112]. At high temperatures MgCu2 is quite rate-sensitive, and dynamic yield points are observed that are extremely orientation-dependent. The high-temperature creep behavior under constant load is characterized by an increasing strain-rate with time. The general characteristics of the mechanical behavior make it possible to classify MgCu2 with those materials in which initial mobile dislocation density and the dislocation velocity-stress dependence are significant in determining mechanical response. Mgcu2 is the C15 prototype of the cubic Laves phase. Its range of homogeneity extends from 32.8 to 35.5 at. pct Mg at 500°C and narrows at lower temperatures. The lattice parameter is reported to vary from 7.02 to 7.05A,1 and the compound is completely ordered to the melting point of 819°C. MgCu2 has a brassy metallic appearance, is extremely brittle, and many of its physical properties are intermediate between those of the constituent elements: the electrical resistivity is 3.5 x 10-6 ohm-cm, Young&apos;s modulus is 10x 106 psi, the shear modulus is 6 x l06 psi, and the thermal coefficient of expansion is 18.7 x 10-6 cm per cm per "C from 20" to 250°C. Usually, properties of intermetallic compounds as functions of temperature have been determined by hardness, compression, or impact behavior, and almost all of these experiments have been performed on polycrystalline materials. Tammann and Dahl,2 for instance, determined the onset of ductility in a series of binary intermetallics by ball-hardness measurements and found the onset to range between 0.71 and 0.96 T/T,. Lowrie&apos;s3 investigations included some tensile properties, and he found ductility beginning around 0.65 T/Tm for most materials examined. His work did include some data on polycrystalline, nonstoichiometric MgCu2, however. The present work is an attempt to extend the examination of the particular compound MgCu2 in single-crystal form in order to aid the formation of general concepts about mechanical be-

Jan 1, 1965

By Thomas J. Peters

In 1988, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied the 34,310-acre Diablo Mountain (Additional) study area (OR-001-058), in order to evaluate its identified mineral resources and occurrences. The study area lies along the east shore of saline Summer Lake in Lake County, OR, about 145 miles southeast of Bend and 45 miles northwest of Lakeview. The climate is semiarid and temperate, and the study area is almost treeless. Geologically, the (Additional) study area is in a region of fault block-formed mountains and basins, characterized by interior drainage. The area is mainly underlain by unconsolidated Quaternary and Pleistocene lake and playa sediments, which may include subsurface evaporite mineral deposits and resources. Near the center of the eastern margin of the study area are an occurrence of dolomitic limestone of unknown extent, and an area of basalt outcrop totaling 1.5 square miles. A veneer of windblown sand covers about one-half the study area.

Jan 1, 1989

By Bruce K. Hebblewhite

Tower Colliery is a longwall mine operated by BHP Coal Illawarra Collieries, Southwest of Sydney, Australia It mines the Bulli Seam at a depth of approximately 450m. The surface topography overlying the mine consists of several steep-sided river gorges, up to 68m in depth, which run at oblique angles across a sloping terrain Apart from some light rural development, the surface land is essentially natural bushland, but is traversed by a major freeway. This crosses one of the gorges on twin, six-span, box-girder bridges, with bridge piers up to 55m in height. Consequently, a major surface subsidence monitoring program has been in place for several years now, including intensive conventional, GPS and E DM surveying, plus real-time monitoring of critical components of the bridge structure. Although the bridge and freeway are outside the conventional angle of draw&apos; subsidence influence criteria, and have seen only negligible vertical deformation as a result of mining, there has been widespread evidence of regional horizontal deformation of the land surface, large distances away from the mining area The effect at the bridge has been well within acceptable tolerances, primarily because of the regional nature of the movements, with very little differential movement observed at the bridge piers Gorge closure and evidence of large headlands of land moving `en masse&apos; have been observed. Horizontal movements of hundreds of millimetres have been recorded in some locations where gorge closure has been monitored. Possible explanations of these movements include one or a combination of mechanisms such as pre-mining stress relaxation. valley notch effects, valley bulging, regional joint patterns, movement toward active goaf areas, vertical gorge shearing&apos; and shear failure of horizontal bedding planes below the surface This paper presents a case study of the regional horizontal ?subsidence displacements? measured during mining. and a discussion of the possible explanations for these phenomena

Jan 1, 2000

By Jim F. Lemons

The Bureau of Mines Minerals Availability System collected and analyzed data for 34 nonlaterite and 9 nickeliferous laterite domestic chromite deposits in order to assess their viability as sources of chromium under present technologic and economic conditions. These 43 deposits, none currently in production, contain approximately 6.3 and 22.3 million metric tons of Cr203 at the demonstrated and identified resource levels, respectively. Approximately 4.6 and 15.6 million metric tons of Cr203 are recoverable at the demonstrated and identified levels, respectively, for the 34 nonlaterite deposits. None of these resources are economically recoverable at January 1981 market prices. Production of metallurgical-grade chromite (market price $128 to $144) would require a minimum chromite market price of $237 per metric ton. Chemical-grade chromite production (market price $74 to $85) would require a chromite market price in excess of $188 per metric ton. From the 34 nonlaterite deposits, roughly 5.4 and 17.6 million metric tons of ferrochrome could be produced at the demonstrated and identified resource levels, respectively; however, a minimum market price of $770 per metric ton of ferrochrome would be required to stimulate production. The nine nickeliferous laterite deposits were not evaluated through production stages because of uncertainties in process technology and cost.

Jan 1, 1982

By D. E. Salman, R. R. Maclachlan, R. J. Barclay

"There is a considerable resource of data for spherical charge cratering, both as single charges and in row-of-charge geometr(1). The data are. however, based on cratering performance to a single free planar surface.In practice. the more common circumstance involves an angular surf ace geometry. such as occurs at the toe of a bench or the wall of a stope. It is for the purpose of investigating this circumstance that the described test work was conducted.The test objectives were: (1) to observe the change in single-charge cratering performance between planesurface and angle geometry; (2) to identify the optimum performance of single charges cratering to a plane surface. cratering from a bench sub-grade position and cratering from a condition of zero sub-grade or stope wall geometry; and (3) to observe the performance of row-of-charges cratering to an angular surface at various row burials and spacing. The row charge burial and spacing dimensions were to be expressed in simple numerical multiples of single-charge depth-of-burial data."

Jan 1, 1981