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By Hana Livia Frota Coelho

Durante a laminação a quente a superfície de aço é exposta ao ar e água, sendo esta última utilizada para controlar a temperatura dos rolos e/ou a taxa de refrigeração do aço. Esta exposição leva à formação de uma camada de óxido na superfície das barras, que pode facilitar ou dificultar a corrosão, servindo como uma barreira ou como um caminho para íons presentes na atmosfera e, além disso, causar modificações nas propriedades mecânicas. O objetivo do presente estudo é avaliar o efeito do processo de resfriamento após laminação a quente sobre o desempenho de vergalhões de aço microligado frente a propriedades mecânicas e a formação da camada de óxidos. Os vegalhões produzidos com diferentes métodos de resfriamento tiveram análise de microestrutura, tração, microdureza, dobramento, espessura da carepa formada, análise de corrosão e foram expostos à atmosfera. O progresso da corrosão foi avaliado pela observação visual do produto de corrosão formado sobre a superfície das barras. A morfologia da camada de óxido após o processo de laminação foi estudada por microscopia eletrônica de varredura (MEV). As amostras que tiveram uma taxa de resfriamento maior, 63%P e 100%P, tiveram também um aumento nas propriedades mecânicas. A amostra 100%P foi a que obteve melhor comportamento frente ao ensaio de corrosão. Além disso, verificou-se que a camada de óxido inicial nas barras de aço, que são relacionados com o processo de fabricação, possuiam aderência diferente ao vergalhão, sendo a melhor condição observada nas amostras 63%P e 100%P.

Oct 30, 2017

By C. Cornejo, C. Schuffeneger, J. Rosas

"At the end of 2010 the AMSA Esperanza Concentrator started commissioning. Located in the Atacama Desert this project is the first of several large size concentrators developed recently to operate in Northern Chile. In addition to the new operations to be implemented in the short term, many existing installations are planning expansions. The use of large size equipment is one of the common characteristics of the new concentrators, but also new technologies are being considered and innovation is present in most cases. Sea water or desalinated water will be required to process large tonnages of sulphide copper ores as well as gold bearing ores, since process water supply from the Andes will no longer be available. The high cost of sea water or desalinated water supply and the high cost of energy are not a limitation as the current metal market scenario allows obtaining an attractive NPV even from installations designed to process relatively low grade ores. A review of the current concentrators being developed in Chile is presented, including a description of the main design issues related to technology and innovation. An analysis of the Chilean mining industry is also presented, detailing mine and plant capacities as well as expected final products.INTRODUCTION The mining sector in Chile has become a reference when analysing the large concentrator plants projected or currently in operation all over the world. At present and as a consequence of the high price of metal commodities, most South American countries have an active mining sector. Chile is known as a major producer of metals. First records of copper production exported to Spain are dated to the early XVII century. Since then Chile has produced over 13% of the total copper ever produced in the world. After 1990 Chilean mining and the associated cluster of activities has substantially grown to levels never reached before, especially in the production of copper, gold and other non-metallic minerals. This dramatic increase is the result of an economic policy based on delivering comparative advantages and incentives for the admission of foreign capital to offset the weak domestic investment in previous decades. Massive mining of its huge mineral resources has allowed Chile to be a world leader in the production of copper and other base metals and mineral products."

Jan 1, 2012

By W. F. M. GOSS

For the purpose of procuring data that could be used in estimating the value of the briquetting process as applied to American fuels, the United States Geological Survey, in cooperation with other interests, began in 1904, at the Louisiana Purchase Exposition, certain experiments involving the production and use of bituminous-coal briquets. It installed at St. Louis, and later at Norfolk, machines for the manufacture of such briquets, and the output of these machines has been tested in locomotive service on several different railroads in comparison with natural fuels. An elaborate and carefully executed series of tests involving the use of natural coals and of briquets made from the same coal, previously crushed, was carried out on a locomotive mounted at the testing plant of the Pennsylvania Railroad Company at Altoona, Pa.; and some preliminary experiments involving the use of briquets in marine service were made in connection with one of the Government's torpedo boats. A description of these tests is presented herewith. The results sustain the following general conelusions: 1. The briquets made on the Government's machines have well withstood exposure to the weather. and have suffered but little deterioration from handling. 2. In all classes of service involved by the experiments, the use of briquets in the place of natural coal appears to have increased the evaporative efficiency of the boilers tested. 3. The smoke produced has in no test been more dense with the briquets than with coal; on the contrary, in most tests the smoke density is said to have been less when briquets were used. 4. The use of briquets increases the facility with which an even fire over the whole area of the grate may be maintained.

Jan 1, 1911

Perception has the unfortunate habit of becoming reality. Urban inhabitants unfortunately do not regard mining as a legitimate or desirable business, despite its contribution to Australia's export income (+A $8,000 million, being nearly a third of all exports); share of GDP (it is 4.5%); and the fact that its presence fills up all the empty spaces northwest of the Adelaide-Melbourne-Sydney-Brisbane crescent of inhabitation. The huge economic contribution of Australia's minerals industry, resulting from providing more than half of merchandise exports (Figure 1), is achieved by employing only some 2% of the national work force (Gaulton, 1997). Unfortunately, the minerals industry's critics generally oppose exploration on the basis that what you don't know will not hurt you. It is the 'do-not-confuse-me-with-facts' philosophy or 'ostrich syndrome', which somehow crudely assumes that mining practices have stayed in the style popular circa late 1800s. Somehow ignorance really is bliss for these idealistic believers, who are reminiscent of the members of the Flat Earth Society!

Jan 1, 1997

By C. R. Copeland

Airborne dust emission standards are receiving growing attention. This trend is motivated by significant health studies that have shown adverse health effects due to exposure to dust. Currently, the air quality standards are not specific to particles in the nanoparticulate range (<1,000 nm). However, as our understanding of health related matters increases, it is very likely that nanoparticulate standards will be adopted. It was previously believed that typical comminution and material-handling practices could not result in airborne nanoparticulates. However, experimental studies using air monitoring and SEM have verified the presence of nanoparticulates in the air as a result of comminution and material handling. This means that emerging nanoparticulate air quality standards are a real possibility for industrial operations. With this emerging problem facing the minerals industry, effective suppression methods for nanoparticulates should be explored. Systematic studies have indicated that nanoparticulates from silica can be suppressed utilizing hygroscopic reagents such as calcium chloride. This reagent was as much as 93% more effective than water in suppressing silica nanoparticulates.

Jan 1, 2007

By P. Oyanader

"In 2001, the Catholic University of Chile undertook a maintenance benchmarking study of six open pit copper mines having mill capacities varying between 18,000 t/d and 156,000 t/d, and collectively responsible for 58% of Chilean copper production. This paper describes the methodology used to conduct the study, as well as the overall results. Key performance indices were selected to measure the effectiveness, efficiency, and development of the maintenance process. Using a balanced scorecard philosophy, these indicators were divided into client satisfaction, financial, internal process, and learning and growth indices.Maintenance was found, on average, to be responsible for 44% of mine production costs. Percentage planned maintenance of equipment fleets was found to be low by world standards, averaging 35%, 56%, and 44%, respectively, for blasthole drill, shovel, and haul truck fleets. Fleet availabilities were found to be significantly influenced by the percentage of planned maintenance achieved, while maintenance cost per equipment was found to decrease non-linearly with increases in percentage planned maintenance. Investment in technical training (including planned maintenance practice) was found to be low by global standards. The paper concludes that fleet availability and maintenance costs in Chilean open pit operations could be considerably improved by improving and/or developing maintenance planning standards, and investing in training personnel in planned maintenance techniques"

Jan 1, 2005

GARY STUBBLEFIELD RMCMI PRESIDENT 1993-1994 on behalf of the RMCMI Board of Directors and Officers of The Rocky Mountain Coal Mining Institute cordially invites you and your family to attend the 90th Regular Meeting and Convention June 26 thru 28, 1994 Snowmass Resort, Colorado

Jan 1, 1993

By Anna Paula Littig Berger

A remoção do fosfóro através do processo de desfosforação do ferro-gusa tem sido cada vez mais relevante, devido a influência que exerce de forma prejudicial as propriedades do aço e devido a extensão do cenário de escassez de minérios com menor teores de fosfóro. Este trabalho tem como objetivo a avaliação termodinâmica de misturas à base de dolomita e finos de minério utilizadas no processo de desfosforação realizado em panela para o refino do ferro-gusa. Verificou-se uma tendência de maiores valores de eficiência para o processo de desfosforação quando aumenta-se a razão de massa de desfosforante e massa de gusa.

Aug 17, 2017

By Francisco Alberto Marreiros da Rocha Filho

No processo de laminação a quente ocorre ocasionalmente a perda de ductilidade a quente que pode causar o fenômeno denominado como “abertura de cabeça” da barra durante a sequência de passes. Essa perda de ductilidade a quente pode ser severa e causar interrupções no processo produtivo. Esse fenômeno pode estar associado a diversos fatores entre eles: composição química do aço; defeitos presentes no tarugo; condições do processo de laminação; e temperatura do aço durante o processo, principalmente nos passes de desbaste e intermediários de laminação. No processo em estudo, a perda de ductilidade a quente ocorre associada à laminação de vergalhões a partir de tarugos oriundos diretamente do lingotamento contínuo. O presente trabalho tem como objetivo avaliar a influência da temperatura e da microestrutura formada ao longo do processo na perda de ductilidade a quente das barras através de um exame comparativo entre os vergalhões laminados com e sem o uso da etapa de reaquecimento.

Oct 30, 2017

By James P. Sloss

WHAT is the likelihood if any-that a real gold mining industry will be developed in the southern Appalachian region? Has the increase in the dollar value of gold from $20.67 to $35 per ounce potency to turn the trick? Suppose it be assumed that the price of gold will, at worst, not recede, and that the cost of digging ore and treating it of which the average level of commodity prices and wages is a fair index-will, at most, not exceed that prevailing in 1926. One may or may not accept these as reasonable assumptions; but one must arbitrarily remove some of the potential variables if one is to get anywhere on a problem like this. As a matter of fact, this article is not going to venture a conclusive answer to the question that has been posed; but it will endeavor to present some of the factors that have a bearing on the problem. The writer spent ten days visiting a dozen properties in Virginia and the Carolinas early in April, 1935, and in doing so got a first-hand slant on mining conditions in the domain of King Cotton.

Jan 1, 1935

The Wednesday Morning Session of the Rocky Mountain Coal Mining Institute was called to order by Albert Keenan of the Thompson Creek Coal and Coke Company, Denver, Colorado, in the absence of the President. He introduced Edward Prostel of the University of Wyoming Natural Resources Research Institute, Laramie, Wyoming, who spoke on "Coal Utilization Work at the University of Wyoming." (Please refer to the index for printed text of the paper.) Following Mr. Prostel&apos;s talk, R. Park Lamborn of the National Mine Service Company, Pittsburgh, Pennsylvania asked Mr. Prostel two questions: (1) What -has been done in tar research? and (2) Has there been large scale research on brickets? Mr. Prostel stated that he could not say too much about the first question as this research was done in the petroleum department and he would prefer to have a chemist talk about it. As to the second question, the system of carbonization is a big project. There are many possibilities. At the University they are trying to do that in the same unit that produces the char. This system was introduced in Canada. The brickets are bound with sulphite liquor. Mr. Schloss asked Mr. Prostel to report on a project that they have been working on at the University, and Mr. Prostel stated that some time ago they began to experiment to see if it would be economically possible to dry coal at the mine (coal containing 30% moisture) and then ship it a distance of 130 miles to be used. Results are that it would be possible, but will require a considerable quantity. He felt it might be possible to operate such a scheme in a few years.

Jan 1, 1957

By Ross W. Smith

Microflotation and surface chemical studies were conducted on a chromite from the Stillwater Complex in Montana and on some of the minerals usually found to be associated with such chromites. Considering the chromite it was found that aging the ground mineral in air or heating it markedly affected its flotation behavior. Much of the observed effects could be attributed to oxidation reactions involving surface chromium and iron species. Strongly acid pretreating the mineral appeared to reverse such effects. Thus, it can be concluded that the manner in which the mineral (or the ore) is pretreated is of utmost importance in its flotation. Work carried out on associated gangue minerals determined how they are likely to behave in a flotation environment and how certain foreign ions derived from a chromite ore itself can affect their surface characteristics and, thus, presumably also their behavior in a flotation circuit.

Jan 1, 1981

By Fred S. Karn

Inhibitors are used in coal mines as a precaution against accidental dust explosions. Although rock dust is the usual inhibitor many others have been tested. To facilitate testing a screening process using laser irradiation was proposed. The procedure includes irradiation of a coal-dust mixture followed by mass-spectrometric analysis of the evolved gases and an evaluation of the flammability characteristics of the gases. Carbonate-type inhibitors decreased the percentage of combustibles in the gases generated and inhibitors like NaCI (thermally stable salts) decreased the total gas generated. A suitable test procedure did not result from the investigation, demonstrating the inadequacy of fast heating, non-combustive techniques in rating inhibitors of coal dust explosions.

Jan 1, 1973

By Leonard Obert

This report describes a gage which, when used with my procedure for producing strain relief, will measure the resulting borehole deformation, From the borehole deformation the magnitude and direction of the principal stresses in a plane normal to the axis of the borehole can be calculated. The design considerations, mechanical construction, sensitivity, and stability of the gage are discussed. INTRODUCTION During the past two decades an increasing mount of consideration has been given to the problem of measuring and evaluating stress in rock around underground openings. Several investigators have made theoretical and model studies of the stress and (or) strain concentrations around simulated mine openings or in structural members, such as mine pillars or immediate roof. Other investigators have developed gages for directly or indirectly measuring stress or strain, and a number of reports present the results of measurements made with these gages. Because various methods and instruments have been developed, factors involved in this type of measurement will be briefly considered.

Jan 1, 1962

By J Parr, P Ashworth, S Johns, C Yeats, A Littleboy

The ocean floor is increasingly being discussed in terms of its resource potential. New discoveries, improved knowledge and access to unexplored areas of the deep sea and continental shelf are some factors contributing to a renewed interest in the seafloor exploration and mining industry. The industry has been referred to as the ænext minerals frontierÆ. To date, much of the research has focused on proving economic and technical viability of the industry, with environmental issues addressed locally. However, there is limited research internationally, and none known in Australia that considers the social viability of the industry, addressing issues such as regulatory contexts, international precedence and public acceptability. Does the nascent seafloor exploration and mining industry have a social license to operate? Does it have support amongst the wider community? If not, why not? The Wealth from Oceans National Research Flagship explored these questions by scoping the social issues that would surround an expansion. Two desktop studies provide insight into the current level of activity in seafloor exploration and mining, recent developments and the regulatory regimes on which the industry is based. One study focused on the situation in Australia, while the other was internationally focused. A series of workshops were held with key stakeholders from government agencies, industry and other interested parties, such as environmental groups and the fisheries industry. These workshops identified and explored the different stakeholdersÆ perceptions of the benefits, concerns, opportunities and key questions associated with an expansion of the seafloor mining industry. The desktop studies revealed that Australia is one of only a few countries with legislation specific to seafloor exploration and mining. Nevertheless, barriers to licence approval exist because of lack of precedent in applying this legislation. Consequently, the decision process can be vulnerable to political issues and subjective judgements. The outcomes from the stakeholder workshops suggest this inconsistency may be influenced by the high levels of concern and uncertainty over environmental impacts. Uncertainty over environmental impacts can influence the acceptability of an environmental impact assessment (EIA) and also mean the perception of risk is variable. Overall, this research suggests that the future of the seafloor exploration and mining industry will be highly dependent on AustraliaÆs ability to:improve the knowledge-base underpinning the regulatory regime,generate open and transparent communications between stakeholders, andimprove the understanding of policy and regulatory processes.

Jan 1, 2008

By Richard N. Zimmer

This paper discusses the installation of corrugated steel linings in bored raises at Inco&apos;s Thompson Mine. The procedure for the installation of these linings is outlined and the relative advantages are compared with conventional methods of ground support. Future trends in the use of corrugated steel products are then discussed.

Jan 1, 1978

By W. J. van Niekerk

Ballast Nedam is in Surinam constructing two bridges that will improve communications in the coastal region. The bridges will cross the Coppenam and Surinam rivers and will be founded on open-ended steel piles over 60 meters in length. The majority of piles are inclined and support prefabricated concrete girders forming the roadway. In most locations the stratum is consolidated cohesive layers extending to a depth in excess of 60 meters. For this reason, before pile driving operations commenced, it was decided that a number of test loads would be carried out determine the capacity of the piles. Loading tests were carried out on specially installed piles as well as on piles that would be used as working piles to support the structure. Working piles were dynamically tested using Pile Driving Analysis (PDA) equipment. This decision was based on the inclination of the piles, the cohesive nature of the soil and the increase of strength after the piles are driven. A good insight has been obtained into the real strength of the soil by comparing dynamic and static loading tests on vertical test piles. This made it possible to determine the required length of pile.

Jan 1, 2000

THE most important part of the routine survey work on a mine is the keeping up-to-date of plans and sections showing progress of stoping and development work, and the direction of the latter for the purpose of making necessary connections. Except in specialcircumstances, e.g., major horizoittal development, the exactitude required in this work is not extreme, and a method of survey in keeping with the demands of the work itself is all tbat is required.For example, no one would consider measuring the walls of a stope to a fraction of an inch; such extreme accuracy would be wasted.The stope walls being irregular, a mean is usually taken, and for ordinary purposes a survey with a limiting error of six inches is quite satisfactory for the purpose of plotting either stoping or development.It is the author&apos;s aim in this paper to describe the method in use at the North Broken Hill Oompany&apos;s British mine. This method, while being sufficiently accurate for the purpose in view, possesses the very great advantages of speed and simplicity of operation,with a minimum of necessary equipment. This latter is a very important item where several surveys on different levels have to be carried out on the one day.Let it be understood, however, that the use of this method does not dispense with the theodolite, but simply serves as a convenient adjunct to obtain details and to extend the accurate theodolite survey up rises and down winzes, and through ladderways orwinzes into stopes, where the use of a theodolite, if not actually impossible, is often exceedingly inconvenient. This is particularly so on the British mine, where a large proportion of the ore is won from narrow and complex-dipping lodes, and where vertical ore...

Jan 1, 1928

By J. Ran

Ground instability is among the major causes of serious incidents and production disruptions in the mining industry and has a significant impact on safety. Mining companies may have operations in a number of jurisdictions with varied regulatory requirements for ground control management. As these companies expand into countries where mining regulations are formative or lacking clear definition, ground control practices are usually developed by local mine personnel based on their experience. In many cases, inconsistent procedures and standards are generated, which can lead to an increase in occurrence of underground incidents due to difficulties and confusion in implementation. This situation has forced some mining companies to standardize their ground control practices by geographic regions or divisions. Though this approach is an improvement, it may not lead to effective management of ground control issues across all operations of a global mining company. Barrick Gold Corporation, with operations in North and South America, Australia and Africa, decided to adopt a global approach to ground control management. This global approach requires all Barrick operations to prepare and implement an effective ground control management plan (GCMP) based on site specific conditions and company guidelines. It is also required that the GCMP be developed through application of sound geotechnical engineering practices and be consistent with local regulatory requirements and Barrick safety policies. All Barrick underground operations have GCMPs in place, and its surface operations are now involved in the initiative. This paper presents Barrick?s global approach to underground mine ground control management and outlines the content and process for the development of a GCMP.

May 1, 2006

By J. L. Fuentes-Cantillana, Á. Rodríguez, P. Morillo

Evacuation operations from work places in the case of an emergency are the key to minimising the effects of catastrophic type accidents such as fires, explosions, cave-ins, floods, etc. The correct planning of these operations, having the necessary means for sounding alarms and communicating and suitable training of personnel are the key factors for guaranteeing successful evacuation. The article gives an analysis of the problem in the case of subterranean mining and various types of work developed by AITEMIN in this field, including the development of new alarm and communication means specially adapted to the characteristics of mining operations, development of tools for help in the preparation of emergency plans and experiences in the education and training of personnel.

Jan 1, 2003