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By Hidenori Hatta, Takero Watanabe, Hideo Yoshida

"The effect of the quenching rate on age hardening in an Al-6.0mass%Zn-0.75mass%Mg alloy sheet was investigated. The quenching rates and aging conditions were as follows: water quenching (WQ) or furnace cooling (FC) followed by pre-aging at 20°C,then artificial aging at 120, 160 or 200°Cwere performed. The peak strength of the FC and the WQ are very similarat120°C aging. It is important high strength was obtained even at the extremely slow quenching rate. On the other hand, the strength of the WQ significantly decreased compared to the FCat200°C aging. GP(I) zones were formed during the pre-aging at 20°C even if the cooling rate was very slow like the FC, and were transformed into the GP(II) ones at 70°C or higher and then into the ?’ phase. However, these zones were dissolved by reversion during heating to 200°C. Thus the strength of the WQ decreased. On the other hand, it is considered that an unknown cluster or GP zone with a thermal stability formed during the FC was not dissolved up to 200°C and was transformed into the ?’ phase. Therefore, a higher strength was obtained in the FC for the200°Caging.INTRODUCTIONAl-Zn-Mg alloys are widely available in commercial production because these alloy have lower quench sensitivity and can be produced by air cooling (AC). Heat treatable aluminum alloys are usually produced by water quenching (WQ) to increase their strength because a high cooling rate inhibits the precipitation of the stable phase during cooling and increases supersaturated solute atoms. However, Baba(1967)reported the strength of an Al-6%Zn-1.8%Mg(mass%) alloy without additional elements quenched by very slow cooling (15°C/min) was 96% of that quenched by WQ. Furthermore,the age hardening at room temperature (RT) occurs after annealing at 410°C followed by furnace cooling (FC, 0.5ºC/min or less)in these alloys. Therefore, the process of annealing at 410 to 430°C for 120 min followed by AC, and reheating at 230°C for 240 min, then cooling is recommended in the specifications (Japan Aluminum Association, 2011). Matsuda and Yoshida(1996)also recommended annealing at 300°C for Al-Zn-Mg alloy extruded products to inhibit age hardening at RT by precipitating the solute atoms and decreasing them in the matrix. It has been considered that the higher the content of excess quenched-in vacancy becomes by WQ, the higher aging rate at RT is obtained. Therefore,it is theoretically and commercially important to clarify the reason why the age hardening occurs relatively quickly in almost no excess quenched-in vacancies such as the FC, and why the same strength as the WQ can be obtained in the FC"

Jan 1, 2018

By Jr. Boyle

This report analyzes the availability of chromium in the form of ferroalloy products (high-carbon and low-carbon ferrochromium and ferrochromium-silicon) and chromite products (metallurgical, chemical, refractory, and foundry sands) in market economy countries (MEC's). A total of 873.5 Mmt of in situ material, containing 202.5 Mmt of chromium, in 10 MEC countries was analyzed for availability as of the January 1989 study date. Extraction and beneficiation of this in situ material would result in 475.4 Mmt of marketable chromite products. As analyzed, 288.5 Mmt of these chromite products would be available for export or for internal chemical and refractory use and 186.9 Mmt would be smelted in-country to produce 74.3 Mmt of high-carbon ferrochromium, 3.9 Mmt of low-carbon ferrochromium, and 2.0 Mmt of ferrochromium-silicon, all available for export. A network flow model, which includes centrally planned economy countries (CPEC's), was also constructed to analyze world chromium supply and demand interactions for the period 1986 through 1994 and to address a hypothetical North American embargo on direct imports of all South African chromium products beginning in mid-1990. The model shows capacity constraints developing in the MEC high-carbon ferro chromium industry in 1987 and a possible subsequent overreaction by the industry in terms of new capacity additions. The results suggest that sufficient chromium is available to North America should an embargo on direct imports from South Africa be imposed by its governments. However, the effect on export revenues in South Africa is relatively small, and timely increases to world ferrochromium, chemical chromite, and foundry sand chromite capacities would be required.

Jan 1, 1993

By A T. Spathis

The 11th International Symposium on Rock Fragmentation by Blasting (FRAGBLAST 11) was held in Sydney, Australia, between 24-26 August, 2015. The 93 papers, including six keynote presentations, covered exciting and practical topics in 20 sessions within 12 themes. Just fewer than 300 delegates from 27 countries attended. Four workshops were conducted on the weekend prior to the symposium, with three field visits after the symposium to Sydney region quarries, the Hunter Valley coal mining region, and the Kalgoorlie gold mining region. Delegates had the opportunity to visit the exhibition areas that showcased the latest products, software, hardware and systems in blasting technology. The keynote addresses were held in plenary sessions and set the tone for the parallel sessions that followed. They spanned the dynamics of the mining industry, the detonics of explosives, the interaction of stress waves and fracture mechanics in fragmentation, wall control blasting, and the importance of education and engineering for full process optimisation.

Jan 1, 2015

The Bureau of Mines, through its Minerals Availability Program (MAP), investigates the mineral supply potential of the United States and market economy countries (MEC's) for a number of minerals considered essential to the U.S. industrial base. Major activities include identification of important mines and mineral deposits, estimation of their mineral resources and production costs, and availability and sensitivity analyses. Products include data print-outs of geological and engineering information, discounted- cash-flow rate of return (DCFROR) analyses of individual mining operations, commodity availability appraisals, and analytic services to Government agencies. These products are used in assessing the mineral supply position of the United States: in setting priorities for research aimed at reducing production costs and minimizing adverse environ- mental impacts and regulatory compliance costs of mining and mineral processing operations; and in formulating and evaluating Government policies that affect minerals. Bureau MAP data and analyses have been provided to the executive and legislative branches to aid in consideration of trade, tax, and stockpile policy issues. A study of the economic potential of selected seabed mineral resources supports the regulatory responsibilities of the Department of the Interior in the U.S. Exclusive Economic Zone. Analytic studies of mineral project viability, industry competitiveness, and import dependencies were also undertaken for, or in cooperation with, U.S. and foreign government agencies, industry and trade organizations, and international lending institutions.

Jan 1, 1987

By Others, C. M. Weld

During the past two years the Bureau of Mines has issued a series of mimeographed reports giving the results of research work and experiments conducted as part of its war minerals investigations. In this bulletin the reports on manganese are presented, which range in scope from the beneficiation of the ore to the utilization of the metal. The bulletin is in eleven chapters, each comprising a separate report, arranged in the order given below. 1. General information regarding manganese, by C. M. Weld. 2. Uses of manganese other than in steel making, by W. C. Phalen. 3. Problems involved in the concentration and utilization of domestic low-grade manganese ores, by Edmund Newton. 4. Preparation of manganese ore, by W. R. Crane. 5. Leaching of manganese ores with sulphur dioxide, by C. E. Van Barneveld. 6. The Jones process for concentrating manganese ores; results of laboratory investigations, by Peter Christianson and W. H. Hunter. 7. Cost of producing ferromanganese ores, by C. M. Weld and W. R. Crane. 8. Production of manganese alloys in the blast furnace, by P. H. Royster. 9. National importance of allocating low-ash coke to the man- ganese-alloy furnaces, by P. H. Royster. 10. Electric smelting of domestic manganese ores, by H. W. Gillett and C. E. Williams. 11. Use of manganese alloys in open-hearth steel practice, by Samuel L. Hoyt. As each chapter was originally prepared as a unit, there is neces- sarily some duplication and overlapping. With certain exceptions, however, each paper is reproduced in practically its original form. In chapter 1, covering certain general phases of the industry, such as uses, specifications, prices, and statistics, the subject matter has been somewhat modified in view of changes in conditions.About 95 per cent of the manganese consumed in the United States goes into the manufacture of steel. The remaining 5 per cent is used in a number of minor industries, the chief of which is the manufacture of dry cells. These minor uses are described in chapter 2. No discussion of the geology of manganese eres is presented, but a short bibliography on the subject is appended. With few excep- tions the manganese deposits of the United States are irregular, pockety, and uncertain. Largely for this reason, mining methods are crude and hardly warrant descriptions. The concentration of manganese ores, however, is an important problem and involves some details not common to other ores. Chapter 3 discusses the concentration and utilization of low-grade ones, notes the relationship of concentration to metallurgical prao- tices, outlines concentrating processes, and treats of commercial problems. In general, as regards concentration methods, manganese ores may be divided into two groups, as follows: (1) Ores permitting mechanical separation of the manganese minerals and the gangue, and (2) ores in which the manganese minerals and the gangues are so intimately associated that separation requires some hydrometal- lurgical or pyrometallurgical process. Heretofore, attention has been confined almost wholly to mechanical separation, chiefly by gravity. In fact, so far as known, all production of concentrates has been by wet gravity methods, although during the war some companies investigated the commercial pessibilities of magnetic separation and reported favorable results, the construction of one magnetic con- centration mill being started. The usual wet gravity methods are described in chapter 4. During the war, the Bureau of Mines undertook investigations of methods applicable to ores of group 2. A hydrometallurgical process involving leaching with sulphur dioxide was studied at the mining experiment station of the bureau at Tucson, Ariz. The results of this work, presented in chapter 5, indicate that the process is metallurgically feasible but the cost makes it unattractive. The results of an investigation of a pyrometallurgical process known as the Jones process are presented in chapter 6. The process, which is still in the experimental stage, was found to be metal- lurgically sound. The manganese product is not a concentrate but an alloy, made directly from a lean unconcentrated ore. The custom- ary method is to manufacture alloys from high-grade ores or from concentrates of leaner ores. A discussion of the costs of ferro-grade manganese ores is pre- sented in chapter 7. This discussion is in general terms only, but should be of use in so far as it relates to competitive conditions.

Jan 1, 1920

The use of coal as a fuel causes air, pollution in; a number of different forms, and in nearly all stages of its, handling, preparation, storage, use and-disposal of its residue. First let us consider the handling of coal. As shipped, particularly to large utilities, it is run-of-mine bituminous made up of large chunks as well as pulverized particles. Because it 'is in an open car or barge, it is subject to the action o winds and the small particles may be blown around adding to the-particulate load in the atmosphere. Mien un¬loaded from the barge or car, there is again an opportunity for the wind to blow the fine particles around. All of us I am sure have seen a barge at the dock of a utility plant being unloaded by a clamshell bucket. This, after grabbing its load from the barge, lifts it some 60 or 70 feet and, then drops it on a conveyor, which carries the coal to a storage area.

Jan 1, 1964

A symposium on pneumatic transportation of solids was held at Morgantown, W. Va., October 19-20, 196'), under the cosponsorship of the Institute ref Gas Technology. Chicago, Ill., and the Bureau of Mines. Objective of the symposium was to present information on developments and projected programs in the technology of feeding, transporting, recompressing, and utilizing gas-solids mixtures Dr. Henry R. Linden, Director, Institute of Gas Technology and Harry Perry, Director of Coal Research, Bureau of Mines, in the initial addresses at the symposium welcomed more than 140 representatives of industry, educational institutions, and government from 16 states, Canada, Great Britain, etc.

Jan 1, 1966

A symposium on pneumatic transportation of solids was held at Morgantown, W. Va., October 19-20, 1965, under the cosponsorship of the Institute ref Gas Technology. Chicago, Ill., and the Bureau of Mines. Objective of the symposium was to present information on developments and projected programs in the technology of feeding, transporting, recompressing, and utilizing gas-solids mixtures. Dr. Henry R. Linden, Director, Institute of Gas Technology, and Harry Perry, Director of Coal Research, Bureau of Mines, in the initial addresses at the symposium welcomed more than 140 representatives of industry, educational institutions, and government from 16 states, Canada, Great Britain, etc.

Jan 1, 1966

Helium has probably aroused more varied scientific curiosity than any other single element. Discovered by spectroscopic examination of the sun during an eclipse in 1868, helium is now known to exist not only in the sun and other stars but on earth occluded in minerals, accumulated with natural gases in pockets in the earth's crust, and in the atmosphere surrounding the earth. Astronomers study its presence in the various stars of the universe for clues to their origin and history. Geochemists and geologists study its occurrences in rocks, minerals, and meteorites to determine the age of the earth and the manner of its formation. Pathologists study its effect on living tissues in search for the ideal combination with oxygen for artificial breathing mixtures in medicine, diving operations, and space vehicles. Chemists study its physical properties and use it to trace the sequence of events in reactions in which it does not participate. Geneticists and bacteriologists use it for special studies. Physicists study its behavior when liquefied and the behavior of materials cooled to nearly absolute zero by its use. Nuclear physicists learn more about the universe through study of the nuclear reactions that produce it. Through study of helium and greater knowledge of its origin and properties, science continues to unlock some of nature's more closely guarded secrets. Unknown on earth before 1895, and not discovered as a minor constituent of natural gas until 1905, helium with its simple atomic structure--a nucleus with two electrons orbiting in a closed shell--is a unique element. It is next to the lightest gas, only hydrogen is lighter. It occupies position number 2 in the Periodic Table of the Elements and heads the list of so-called "rare" or ?noble? gases. Most of the naturally occurring helium has an atomic mass of 4.003874 (oxygen = 16). A trace (1.7 x 10-5 mol percent) is the light isotope helium-3 whose atomic mass is 3.0169800 Unstable isotopes of mass numbers 5 and 6 have been authenticated. Isotopes of mass numbers 7 and 8 have been reported, but their existence is less well established. All the heavier isotopes are radioactive and are the product of nuclear reactions.

Jan 1, 1968

By HOWARD RICHARDS

THE dollar was, selected as the unit of currency by the Congress of the United States of America on Apr. 2, 1792. This "Dollar" currency is so much more convenient than the older British currency that the Canadian Government, among others, has adopted it with corresponding success. Just as the dollar is the unit of United States currency, so the meter is the international unit for measuring length. The various weights and measures used in - the United States have since Apr. 5,. 1893, been based on the metric standards. These fundamental standards are kept by the International Bureau of Weights and Measures, which is supported by the United States, Great Britain and the, other leading countries. of the world. Copies are held-in Washington and other capitals. (2) As the dollar is divided into 100 cents, so the meter, which is 10 per cent. longer than the yard, is divided into 100 centimeters or cm. And as the cent is divided into 10 mills, so the centimeter is divided into 10 millimeters or mm. In measuring clothing and other articles which do not require great accuracy, the centimeter is most con¬venient, so that such work is done in terms of centi¬meters.. Instead of speaking of a 15;2-in. collar, a 40-centimeter or 40-cm. collar is referred to. Where accuracy is needed, as in mechanical drawing, machineshop work, etc., millimeters are employed. Thus 8 mm., is the convenient equivalent for 5/16 inch.

Jan 1, 1921

By Jr. Abel

Subsidence is controlled by a complex combination of mining and geologic factors. For example, a world-wide compilation of data shows that, as the percentage of shale in the overying rock mass decreases and the amount of sandstone increases, the angle of draw (and the area affected by subsidence) decreases. Limestone in the overburden appears to cause as much as a three-fold decrease in the angle of draw compared to a like amount of sandstone. Increased amounts of sandstone were accompanied by a greater surface subsidence relative to the mining height. The total thickness of overburden did not appear to influence the subsidence magnitude above super-critical panels. The greater the thickness extracted the smaller percentage of that thickness that shows up at the surface as subsidence. The greater the percent of the seam extracted, the greater the subsidence reaching the surface. The maximum subsidence above room and pillar panels is dependent on the pillar height and minimum width as well as the other factors listed.

Jan 1, 1980

By W. G. Diamond

Lightweight aggregates have become increasingly important to the construction industry. From 1953 to 1960, the quantity of the aggregates used in concrete block, precast and prestressed concrete, and monolithic structures increased about 92 percent. The present study was conducted in Bureau of Mines Area IV which encompasses the South-Central States of Arkansas, Kansas, Louisiana, Mississippi, Missouri, Oklahoma, and Texas. This is an administrative area and does not delimit a market area or imply an economic unit. Because of the increasing importance of metropolitan areas in evaluating economic growth, significant data showing relationships between growth of the metropolitan areas and the lightweight aggregate industry are included.

Jan 1, 1964

By Bill Mariucci, Gary Almeraris

All Rights Reserved. Printed in the United States of America. Information contained in this work has been obtained by SME, Inc. from sources believed to be reliable. However, neither SME nor its authors guarantee the accuracy or completeness of any information published herein, and neither SME nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that SME and its authors are supplying information but are not attempting to render engineering or other professional services. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Any statement or views presented here are those of individual authors and are not necessarily those of the SME. The mention of trade names for commercial products does not imply the approval or endorsement of SME.

Dec 1, 2009

This volume constitutes the Survival Subsystem portion of the final report for the Coal Mine Rescue and Survival System (CMR&SS) program, which was conducted by the Westinghouse Electric Corporation under contract to the United States Bureau of Mines (Contract Number H0101262 dated June 17, 1970). The program was directed by the Special Systems Department of the Westinghouse Baltimore, Maryland, facility. The basic objectives of the CMR&SS program were to develop and test hardware to determine the efficacy of a variety of coal mine rescue and survival concepts and techniques. These concepts were drawn from two major sources: the Request for Proposal from the Bureau of Mines1 and the final report on the Mine Rescue and Survival Study conducted by the National Academy of Engineering2 (NAE).

Jan 1, 1971

The Bureau of Mines human factors research program is directed toward reducing accidents and improving the overall efficiency of the person-machine environment interface found in surface and underground mines. The focus of the hum factors program therefore, is to insure that sound knowledge is available concerning human capabilities and limitations, and that this knowledge is applied to the design, of mining equipment, work tasks, and management procedures. The papers presented in these proceedings summarize some of the recent Bureau research in hum factors. The papers focus on two broad areas, human resource issues and human engineering of equipment, tools, and work procedures found in mines.

Jan 1, 1987

By H. H. Schrenk

The purpose of respiratory protective equipment is to prevent the inhalation of harmful or objectionable atmospheres. Although constituents or contaminants that may render an atmosphere irrespirable or objectionable are numerous, they may be classified broadly as follows: I. Gaseous substance: n. A. Toxic. B. Inert (oxygen deficiency). II. Particulate matter (dispersoids). A. Solid. a. Dust (formed by disintegration). b. Pure (formed by condensation). B. Liquid. a. Mist (formed by disintegration). b. Fog (former by condensation).

Jan 1, 1940

This report is in partial fulfillment of Contract S0241051 awarded to COMINEC on June 27, 1974. 'Me purpose of the work under this contract is to develop a conceptual design for an automated longwall mining system. The conceptual design will serve as the basis for future design and development of an automated longwall mining system capable of sustained production in excess of 2,500 tons per shift with reduced manpower which will ultimately be demonstrated in an area where conventional longwall mining has been successful. 1.2 DEFINITION OF THE PROBLEM 1.2.1 Why An Automated System The most obvious benefit of automation and remote control in a longwall mining system is the reduction of accidents consequent upon a reduced working force in the hazardous face areas. However, another important aspect of the problem is the skilled labor shortage which is being compounded by the need for vastly increased coal production. The United States coal mining industry had a working force of almost 600,000 miners in 1928 but was able to muster only 145,000 miners in 1970. The miners required to staff the additional working sections and the new mines necessary to meet our energy needs are simply not available. Only automation and remote control will permit a reduced work force with increased production by keeping the face equipment operating continuously.

Jan 1, 1975

By Donald Bruce

The three types of specifications which are used for micropile work are: ? Performance Specifications: The contractor is permitted control over certain design and/or construction procedures but must demonstrate to the owner through testing and/or certification that the final product meets the specified performance criteria. This method allows and encourages the contractor to provide a competitive and/or innovative micropile design within the framework of the overall design requirements. The responsibilities for the work are shared between the owner and the contractor. ? Open Specifications: These leave the scope and design of the installation up to the micropile contractor. This method is the most common for securing bids on temporary micropile work. The responsibility for design and performance is clearly placed on the contractor. Open specifications are not recommended for permanent applications. This method allows the contractor to select the most economical micropile system. ? Prescriptive Specification: The Owner describes specific procedures that must be followed, but which may not necessarily describe the objective of the work. When prescriptive specifications are used, the owner is responsible for the proper performance of the system. The contractor is responsible for satisfying the details of the specifications. Performance specifications are the most common and best reflect the challenges and interests of micropile technology and applications.

Jan 1, 2004

The inherently explosion-proof mine (EPM) concept is based upon the non-flammability of certain combustible-oxidant-inert gas mixtures, and the effect of partial pressure of gases on physiological reactions. In a properly controlled underground environment, gas explosions are impossible, men can do work, and relatively high concentrations of methane would be permitted. A systems analysis has been performed to examine the physiological, engineering, and economic feasibility of such a concept, and methods and equipment are recommended for maintaining an EPM atmosphere in a bituminous coal mine producing a nominal two million tons of clean coal per year. It is concluded that: engineering feasibility can be demonstrated using subsystems and components that can be designed and built within the present state-of-the-art, that economic feasibility is possible within approximately five years, and that physiological feasibility is sufficiently promising to warrant continued investigation.

Jan 1, 2012

By R. W. Smith

Living and killed organisms, particularly microorganisms, and extracellular products derived from the organisms are increasingly finding use in minerals engineering. Goals include both enhancement of mineral processing/11.ydrometallurgica,l operations and remediation of mineral industry wastes. Some of the applications, such as biologically assisted leaching of ?sulfide ores and bioxidation of refractory gold ores, are well established commercial ?processes used around the world. Others, such as the use. of organisms for the removal of heavy metal ions from dilute aqueous streams, are nearing commercial application. Many other uses of microorganisms and. their derivatives are potentially possible. These include use of microorganisms in flocculation or flotation of minerals., remediation of organics potentially discharged from mineral engineering operations, degradation of cyanide, the recovery of bitumen from heavy oil reservoirs and tar sands and the solubilisation of lignites and low rank coals. In order to fully exploit these many possible uses of organisms and their derivatives, extensive fundamental .and .applied research work exploring the fundamentals, potential and practicality of the various possible uses of microorganisms in mineral engineering should be vigorously pursued. ?

Jan 1, 1991