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By Milena Kellen Oliveira Mendes

O entendimento mais aprofundado dos parâmetros que afetam a temperabilidade dos aços carbono permitiu atingir propriedades antes alcançadas apenas por aços microligados. Assim, este trabalho teve como objetivo avaliar o efeito dos teores de C e Mn, assim como da temperatura de austenitização sobre a temperabilidade de aços baixo carbono, possíveis candidatos para aplicação na fabricação de vergalhões de grau 50. Três aços com composições químicas diferentes foram submetidos a ensaios de temperabilidade Jominy, considerando temperaturas de austenitização de 850ºC, 920ºC e 1050ºC. Curvas de dureza em função da distância Jominy foram construídas e análises microestruturais por microscopia óptica foram realizadas em toda a extensão dos corpos de prova. Os resultados obtidos mostraram que tanto o C quanto o Mn aumentam a temperabilidade dos aços. O Mn, por ser um elemento de liga estabilizador da austenita, dificulta a nucleação e crescimento de constituintes difusionais. O C mostrou ter maior influência sobre a temperabilidade, pois além de também ser um elemento gamagêneo, é responsável pelo cisalhamento da rede da austenita que resulta na formação da martensita. A temperatura de austenitização influenciou a temperabilidade dos aços estudados, porém seus efeitos devem ser estudados com maior profundidade.

Aug 16, 2017

By Luís Marcelo Marques Tavares

Pelotas de minério de ferro representam uma parcela significativa do mercado transoceânico de minério de ferro, contando com uma participação importante de empresas brasileiras. Pelotas concorrem favoravelmente com granulados e sínteres de minério de ferro na carga metálica de fornos, em particular devido à sua elevada resistência à degradação durante o manuseio e transporte. Entretanto, pelotas ainda sofrem desse problema, que resulta na geração de finos, removidos previamente à alimentação do forno, ou de cacos, que podem resultar no aparecimento de clusters em fornos de redução direta. Esses efeitos danosos da degradação podem ser minimizados caso uma metodologia adequada de caracterização de pelotas e de simulação do processo de manuseio se encontrasse disponível. O presente trabalho trata do desenvolvimento de metodologia inédita e inovadora para previsão de resultados de degradação de pelotas, desde a usina pelotizadora até o pátio ou forno do cliente, desenvolvido como parte da parceria entre o Laboratório de Tecnologia Mineral da COPPE/UFRJ e a Samarco Mineração. O trabalho mostra ainda uma validação preliminar a partir de um ensaio de quedas múltiplas em laboratório, mostrando ótima aderência. Um simulador do processo foi desenvolvido, o qual permite inserir as características das pelotas produzidas, bem como o fluxograma de manuseio, permitindo prever a intensidade da degradação.

Aug 16, 2017

By Eustaquio Vieira Junior

O Alto-Forno 2 da thyssenkrupp CSA, no Rio de Janeiro, iniciou sua primeira campanha em 16 de dezembro de 2010. No decorrer de sua campanha, verificou-se problemas de deslocamento de staves de ferro fundido, deformação dos staves de cobre e desgaste acentuado do refratário do top cone. Na análise dos eventos adotou-se a inspeção por vídeo endoscopia e em seguida foram tomadas algumas ações para recuperação e preservação do Alto-Forno 2, sendo estendidas também do Alto-Forno 1. Dentre as ações de preservação dos Altos-Fornos destaca-se a projeção robotizada de material refratário, shotcrete, visando reduzir o desgaste acentuado dos staves e deterioração de suas tubulações de refrigeração. O trabalho apresenta o detalhamento das técnicas utilizadas e seleção de materiais assim como os preparativos operacionais que garantiram o bom desempenho do Alto-Forno 2 nos momentos que antecederam a parada e após seu retorno à operação, mostrando que a atividade é viável do ponto de vista técnico e financeiro.

Oct 30, 2017

By Robert H. Richards

(Pittsburg Meeting, March, 1910.) THIS is in part a review paper, indicating the various steps that have been taken in developing hindered-settling apparatus, some of the standard data that have been obtained, and some of the conclusions one is led to as to the effect of it in improving concentrating-methods and machinery, and in part it brings in some unpublished work. CAUSES OF LOSS IN ORE-CONCENTRATION. In making a study of the separation of valuable minerals from the waste gangue, particularly by water concentrators, it is necessary to define, first of all, what are the causes of-loss that are likely to interfere with the concentration. Having made this definition; we can then study to see in what way the machines make their losses, and plan remedies for them in an intelligent way. Losses may be stated to occur as included grains, as flat or long grains, as fine free mineral, and as absolute slime. We will take, these up one by one, as follows: Included Grains.-Fig. 1 shows by a set of diagrams how included grains may occur: first, where the heavy mineral grains attached to the quartz are of large size; secondly, where they are of small size ; and thirdly, where very fine particles of heavy mineral are included in the quartz. We have to decide in regard to included grains whether they are rich enough to go direct to, the furnace, or poor enough to throw away, or whether they lie between these two points and require recrushing as the only means of severing the values from the waste. This last case is the only one requiring special treatment at our hands. We will therefore consider that next. * By mutual consent, this paper has been presented also before the Colorado Scientific Society, and the Canadian Mining Institute, Montreal.

Feb 1, 1911

By Jonathan K. Hrica, Brianna M. Eiter

The ability to identify hazards during a workplace examination is a critical skill for mineworkers to have in order to maintain a safe workplace. While research suggests that being able to successfully recognize hazards requires a complex set of competencies, it is unclear which competencies are most critical to adequately perform a workplace examination. This paper presents a hazard recognition competencies framework as an explanation of the competencies that affect mineworker hazard recognition. To better understand how the industry is selecting and preparing workplace examiners, researchers fromthe National Institute for Occupational Safety and Health (NIOSH) interviewed nine health and safety (H&S) professionals at surface stone, sand, and gravel mine sites throughout the USA. A primary purpose of these interviews was to verify the competencies included in the hazard recognition competencies framework and to understand why these competencies are critical. Finally, the results of this study are presented within the context of current NIOSH research findings related to hazard recognition.

Jul 27, 2020

By M. M. Fine

The flotation work on samples from nine fluorspar properties in Crittenden and Livingston Counties, Ky., reported herewith was part of a wartime project that resulted in increasing the supply of metallurgical-grade fluorspar. The samples were tailings, dumps, and waste rock that had been rejected in previous milling operations. All were treated successfully by flotation to yield metallurgical-grade concentrates with recoveries ranging from 77.5 to 98.3 percent of the fluorite. After the laboratory testing, the results of which were available to the owners and operators of the properties, many of the tailing ponds and rock dumps were milled. The real value of this report, therefore, is to show the operators of gravity concentration plants the possibilities of re-treating waste products by flotation either at some future time or currently with the gravity

Jan 1, 1948

By C. M. Kleemann

The paper describes the present milling practice at Western Mining Corporation Limited's new nickel mine at Kambalda in Western Australia. It details the crushing, autogenous grinding, flotation and spray drying circuits for the production of a nickel concentrate. It also indicates some of the metallurgical problems which have been encountered in concentrating this ore.

Jan 1, 1973

By Juan Anes, Omar Godínez, Adrián Tolentino, Mario Franco

Como aplicación práctica de las herramientas hidrodinámicas de flotación desarrolladas por Flottec, McGill y otros investigadores, el objetivo del estudio fue crear, para Minera Fresnillo, una herramienta preliminar de control de procesos, a nivel de la primera celda de la flotación primaria del circuito de plomo, con el fin de expandirla luego a toda la planta. El trabajo determinó ecuaciones matemáticas que describen las relaciones entre las variables de proceso e hidrodinámicas para aumentar la recuperación de plata mientras que disminuye la cantidad de insoluble al concentrado. Se desarrolló usando diseño de experimentos con tres variables (nivel de espuma, adición de espumante en ppm, y flujo de aire en cm/s) para observar los cambios en la recuperación de plata y plomo.

Sep 20, 2019

By Albert L. Toenges, Frank A. Jones

"INTRODUCTION The introduction of mechanized pining in coal mines, which has speeded loading, has emphasized the importance of efficient underground transportation systems. The purpose of this investigation is to study and analyze various systems now in use, and to derive conclusions therefrom. This report may be helpful to operators who are planning new systems of transportation or who are revising present systems to increase their efficiency. This paper is the first of a series on this subject and describes some systems of transportation utilizing rail haulage.ACKNOWLEDGMENTThe information used in preparing this report was obtained through the courtesy and cooperation of the officials of the companies whose mines wore studied. The descriptions of the transportation systems at the mines included herein have been checked for accuracy, and publication of the data has been approved by the executives of the several operating companies."

Jun 1, 1940

By B. H. Caudle, A. D. PUCKETT

This paper summarizes precent knowledge of the ignition qualities of pure hydrocarbons likely to be present in modern Diesel engine fuels, as shown by an extensive search of the technical literature. The report also discusses the possible significance of cetane number and hydrocarbon struc- ture. Cetane or cetene numbers, and other physical properties, are tabu- lated for about 100 hydrocarbons, and a bibliography is appended. In recent years the Diesel engine has enjoyed increasing popularity due to its dependability, inherent characteristics of fuel economy, and the fact that it operates on a fuel that hitherto has been available in comparatively large quantities at a low price. These qualities have en- abled the compression-ignition engine to compete very favorably with other types of prime movers in many fields and have led to predictions of fur- ther rapid expansion in the application of Diesel power. In a survey of the field of all petroleum fuels for combustion engines, Holaday et al (9) have predicted that by 1948 railroads will be using 10 times as much Diesel fuel as was used in 1939 and that over-all consumption will have doubled that of 1939. Other estimates of the yearly demand for Diesel fuels five years hence vary from 2,6 to 5 times the amount used in 1944. Into this picture has come the question of whether the greatly in- creased production to meet this estimated demand is compatible with the maintenance and possible improvement in quality of fuels necessary to satisfy future engines. Unfortunately perhaps for the Diesel engine, factors other than those of simple arithmetical multiplication must be considered. For example, the consumption of oil in central heating plants doubled from 1935 to 1943, and a further increase of 57 percent of the 1943 demand is expected by 1950. Jet propulsion has been developed to the stage where it is entirely practical for military aircraft. Catalytic cracking plants, many of which were constructed to meet the war- time accelerated demand for high-octane gasoline, are taking their place in the refining industry. All these developments, as well as the Diesel engine, require material of approximately the same boiling range. Virgin gas oils make excellent burner fuels, perform most satisfactorily in the gas-turbine units for aircraft according to present information, and are at a premium as catalytic cracking stock.

Jul 1, 1948

By R. E. Gray

[The purpose of the study is to investigate cases of subsidence over abandoned mined-out areas of the Pittsburgh Coal identified from published and unpublished sources and to determine through a consideration of the geology, topography, climate, mining activity, and evidence at ground surface, what mechanisms control subsidence .and under what circumstances it takes place. The study wan performed it two phases, the first to identify all documented incidents of subsidence in mined-out areas of the Pittsburgh coal Region; and the second, to study a particular portion of the region in detail, collecting pertinent data relative to the sites within, characterizing roil the nature of the subsidence and its economic consequences, and determining the applicability of the findings to other areas whore similar problems with the collapse of abandoned miner have been encountered.]

Jan 1, 1977

By M. E. Ryan, C. L. Hoebbel, E. J. Haas

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of any company or product does not imply endorsement does not constitute endorsement by NIOSH. ABSTRACT It has been suggested that effective disaster prevention and response in mining requires that elements of emergency management be incorporated into everyday operations, planning, and decision-making, much in the same way that the industry approaches routine risk management. Since Congress passed the MINER Act in 2006, the newly mandated structural and technological advancements in mine emergency response preparation have been made and are apparent, but measureable improvement in mineworker emergency preparedness is difficult to ascertain. To begin exploring whether measurable indicators of mine workforce preparedness can or should be addressed within a risk management framework, NIOSH researchers examined the datasets from two separate research efforts—one which measured the organizational safety climate and self-reported safety performance, and the other which measured individuals’ perceptions of their own self-escape competency. INTRODUCTION In response to the mine disasters in 2006, the United States Congress passed the Mine Improvement and New Emergency Response Act (MINER Act), which strengthened existing regulations [30 CFR, Part 48] and introduced new provisions to improve mine emergency response. Since that time, new technological and structural features, such as mandated redundant communication systems, personnel tracking systems, and lifelines in primary and secondary escapeways, have been installed in underground coal mines across the country. Additionally, mine operators are required to develop emergency response plans, provide adequate supplies of breathable air throughout the mine, provide more frequent and realistic expectations training, and are required to immediately notify the Mine Safety and Health Administration (MSHA) in the event of an accident. While the structural and technological advancements in emergency preparedness are readily observable and easily measured, levels of individual mineworker preparedness remain difficult to assess. There is a general consensus that deficiencies in competence in the non-routine tasks required for individual miners to effectively respond to a mine emergency likely remain (e.g., National Research Council [NRC], 2013), and NIOSH research continues address this concern (Haas, et al., 2015; Hoebbel et al., 2018). To maximize an operation’s capacity to effectively prevent disasters and/or respond to emergency events, it has been suggested that individual and emergency management efforts be incorporated into everyday operations, planning, and decision-making in much the same way organizations manage routine risks to health and safety (Haddow et al., 2017). To the authors’ knowledge, the mindful intersection of routine risk management policies and practices and emergency prevention and response readiness have yet to be empirically studied within the mining industry.

Jan 1, 2019

By K. C. Lahiri, H. P. Das, G. G. Sarkar

"The petrographic components of any particular rank of coal often show some distinct physical and chemical characteristics. Therefore, their pro-portionate distribution in a coal greatly influences the technological behaviour of the coal.In any size or gravity separation of a coal, the petrographic constituents become segregated to different degrees in some preferred size or specific gravity range. Therefore, a knowledge of the petrographic nature of the washed and/or screened fractions is often considered essential in selecting the most efficient method for coal preparation and in exploring the proper evenues for its utilization.A graphical method is described in this paper to indicate the mineral-matter content and the petrographic components of the washed fractions of a coal at different ash levels of separation in the form of a new washability diagram. This diagram can be conveniently used to assess or predict the petrographic composition of clean coal or sinks corresponding to any desired ash level in the cleans. With the help of this diagram, it is also possible to locate the yield level of cleans at which maximum enrichment of vitrinites and exinites occurs with the least amount of mineral-matter content."

Jan 1, 1971

By N. L. Wimmler

The chromite deposits along the Stillwater complex in Stillwater and Sweetgrass Counties, Mont., have at various times been studied and reported on by the Federal Geological Survey, the Montana Bureau of Mines and Geology, other Government agencies, and private interests, Several of the deposits were explored to a mall extent by the owners during the World War of 1914-17, but no production resulted. The importance of these deposits and the urgent necessity of developing large domestic sources of chromite were realized shortly before the beginning of the recent World War. These deposits were therefore investigated and developed by Government agencies and., as a result, now afford the largest known reserves of chromium in the United States. In 1939, under the authority of the Strategic Minerals Act, the Bureau of Mines and the Geological Survey made preliminary investigations of these deposits. As a result, the Bureau of Mines conducted an extensive program of trenching, diamond core drilling, and sampling. This work was begun in August 1939 and continued to April 1943. The Bureau of Mines also performed numerous metallurgical tests on the beneficiation of the chromite ores and concentrates and for the production of chromium metal there from. Research continues as a means toward utilizing these ores.

Jan 1, 1948

By Jian Wang, Kun Li, Hao Wu, Juan Nan

In this paper, in order to solve the problems of low accuracy and slow speed of fire flame recognition, an extreme learning machine (ELM) method based on improved Harris hawks optimization (IHHO) is proposed for fire flame recognition. A novel Harris hawks optimization (HHO) is used to solve the problem of parameter selection of ELM. In order to solve the problem that the original HHO is prone to fall into local optimum, firstly circle mapping is used to initialize the population to solve the problem of uneven distribution and small range of the initial population. Then the formula of escaping energy of HHO is modified to make the population have a large range in the middle and late iterations while gradually decreasing in the whole iteration process. Thus, the exploitation stage in HHO is improved to make the search range smaller near the optimal solution to accelerate the convergence process. Finally, at the end of each iteration, a certain number of individuals are selected to perform Gaussian and Cauchy hybrid mutation to prevent the IHHO from falling into local optimization. Through three groups of experiments, the effectiveness of the proposed IHHO and IHHO-ELM is verified. In experiment 1, the convergence performance of IHHO is significantly better than that of the other remaining algorithms in the test results of six benchmark functions. In experiments 2 and 3 of real fire flame recognition case, IHHO-ELM outperforms other remaining algorithms on the whole and has significant advantages in some indexes.

Jan 17, 2023

By Robert C. Hickman, Xavier B. Starnes

"The general location of the Kentucky, Fluorspar District and the Moore Hill fault area are shown in figure 1. An engineer3/ the Bureau of Mines visited the district in July 1942 and reported on the Moore Hill fault system. Subsequently the Bureau explored the Summers, Pepperbox, McCune, Eagle-Watson, Henry Watson, Davenport, Felix Tyner, and Eagle-Wring prop¬erties by core drilling. These properties and the principal faults are shown on figures 2 and 3.Collaboration of the Federal Geological Survey4/ was of great benefit, particularly in mapping the properties, determining the stratigraphy, and furnishing information on that and other geologic factors.Fluorite was noted as early as 1818 near Shawneetown in southern Illinois.5/ In 1835 an attempt was made to work deposit in Crittenden County, Kentucky, but interest centered chiefly upon the galena found with the fluorite. The first shipments of fluorspar from Kentucky wore made in 1373 from the Yandell mine of Crittendon County.6/ It is not known when the first work on the Moore Hill fault was done, but it seems probable that the Cullen-Eagle and Nancy Hanks were being ,worked in 1900. Gravel spar was found on the surface at the Two Brothers mine in 1904,7/ and the main shaft was started in 1914; work also began at .the Davenport in 1914, and in 1917 the Eagle-Watson was in production. A shaft was gunk on the Pepperbox in 1918, and in 1922 fluorspar was found and work was started on the Summers property. In 1924 work began at the McCune, Felix Tyner, Eagle-Wring, and probably the Hicks properties.No Good approximate record of production from each property on the Moore Hill fault system is obtainable, but an estimate based upon all data available is as follows:"

Sep 1, 1946

By Almon F. Robertson

This is one of a series of reports describing investigations made within the Missouri River Basin in Montana by mining engineers of the Bureau of Mines, Minerals Division, Region II. The primary purpose of these investigations is to provide basic information to agencies of the Department of the Interior and other agencies concerned with the planning of power and other water developments in the Missouri River Basin. This report contains only such factual data as have been authorized for public distribution. Special precautions have been taken not to reveal any information or data considered to be confidential. The field investigations for this report were made during the fall of 1948 and the summer of 1949. Virtually all of the known metallic mineral deposits and some nonmetallic (industrial) mineral deposits within Judith Basin County were investigated. Most of the mines and prospects have been inactive for many years; most of the old underground mine workings now are inaccessible or only partly accessible. Consequently, much of the information on many of the mines and prospects necessarily has been obtained from available U. S. Government and State publications and from owners and local residents.

Jan 1, 1951

By A. Deneys

This paper reviews industrial gases used in primary copper production. Copper smelting industrial gas demand has steadily increased since the first commercial oxygenconcentrate smelting in 1952 [1]. In copper production oxygen for smelting is the dominant industrial gas use followed by oxygen for converting. Nitrogen is finding increased use in copper smelters. Nitrogen is used for porous plugs for copper converting and anode refining [2-5]. Nitrogen can be used for concentrate drying [6,7] and is also used in some Ni-Cu smelters as a coolant in Peirce-Smith converting [8,9]. Industrial gas supply options of cryogenic or adsorbent based on-site plant or cryogenic liquid delivery are detailed.

Jan 1, 2007

By D. A. Temple, G. O. John

Until recently, the approach to the problem of treating complex ores bas been to produce, insofar as is possible, mono-metal concentrates which are treated in traditional zinc, lead and copper smelting circuits, with the residues and by-products from some of these circuits being retreated for the recovery of contained values either by a separate residue treatment process or along with the primary feed to the appropriate circuit. The continued development of the Imperial Smelting Process, with its ability to treat poly-metal concentrates, calls for a re-examination of the traditional approach to this problem, and this the paper attempts to do. A survey of recent progress in the technical development of the process is made and a summary of current operational performance is included.

Jan 1, 1971

By Daniel de Carvalho Silva

O presente trabalho estuda a evolução microestrutural e mecânica ao longo do processo de produção de um aço baixo carbono com micro adição de molibdênio, destinado a produção de chapas de aço dual phase galvanizadas. Para realização do estudo foi feita a caracterização microestrutural e mecânica ao longo do processo produtivo de amostras (placa, chapa laminada a quente, chapa laminada a frio “full hard”, e galvanizada) deste aço via microscopia ótica e eletrônica de varredura das amostras, avaliação da dureza via microdurômetro, do comportamento mecânico via ensaio de tração, este último somente nas amostras de chapa laminada a quente e galvanizada. Os resultados obtidos revelaram um aumento significativo na resistência mecânica do material conjugada uma alta ductilidade, devido principalmente ao refino de grão e a formação de dispersão de martensita.

Aug 17, 2017