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By H. Tomlinson

"PURPOSE OF REPORTThe purpose of this report, which is the third of a. series on the coal mines of the Western States, is to give the findings of a study of the causes and methods of prevention of accidents from falls of root and coal in the mines of Lincoln County, Wyo. The three mines covered in this report, referred to as A. B. and C, account- for 9 per cent of the coal production in the county and nearly 9 per cent of the State's total production. For comparative purposes some statistical data are presented bearing upon the relation of injuries to their causes, to tonnage produced, to men employed, to days worked, and to days lost as the result of injuries.FATALITIES IN WYOMINGTo show the necessity for this study, Table 1 given the fatalities that occurred during 1928 in the bituminous—coal mines of the United States, of the State of Wyoming of Lincoln County, and in Mines A, B, and C, followed by a brief description of the Kemmerer coal dis-trict, its coal beds and immediate roof, thickness of cover, dip of coal beds, methods of mining timbering for roof support, roof testing, and supervision. All of these factors must be considered in any plan outlined to prevent accidents resulting from falls of roof and coal.ACKNOWLEDGMENTAcknowledgment is made to the officials of the operating companies for their cooperation and assistance during the study and collection of data to complete this report.GENERAL INFORMATIONLocation and Ownership The mines included in this report are within 18 miles north and south of Kemmerer, Lincoln County, Wyo. (fig. 1), and are owned and operated by various coal companies to supply the domestic, smelter and railroad markets. They are severed by branch lines of the Oregon Shorty Line Railroad Coal production and men employed underground in the three mines are indicated in essential detail in Table 2."

Sep 1, 1932

By R. V. Peche

Since 1952, Bond’s equation has been used as a standard to predict the specific energy of grinding for a given duty. The Bond’s equation considers that the exponent is constant for all conditions. Hukki, in 1961, pointed out that the exponent is a function of the particle size, and concluded that the Bond’s equation applies successfully for an intermediate range of sizes; out of this range the Bond’s equation leads to high error as demonstrated in this paper. More recently, in 2004, S. Morrell presented a new formula in which the exponents vary with the feed and product size. This paper is based on Hukki’s approach and presents a new general formula, in which the exponent varies only with the feed particle size. This new equation has been proven in 82 observable cases in Peru and other countries around the world, involving ball mills and vertimills in different configurations over a wide range of feed and product sizes, work indices and mill diameters; in most cases, the predicted value has an error less than 10% with regards to the observed value and no need for any correction factor. Keywords: Grinding, specific energy, particle size, work index, variable exponent

Jan 1, 2020

By P Marlow

Raiseboring is an attractive method of constructing shafts, being safe, fast and comparatively cheap. But this means back-reaming through weathered ground. However in the gravels and weathered near-surface rocks typical of the Western Australian goldfields, back reaming large diameter shafts through to the surface is risky and conventional sinking from surface has normally been required.An alternative construction approach has recently been used to stabilise the weak surficial materials and allow raiseboring through to the surface. The method is based on first installing rings of non-contiguous reinforced bored piles around the shaft perimeter, for temporary support, then back reaming shafts at full diameter through to the surface. Immediately after the reaming head is removed, the weak exposed materials are supported using remotely sprayed fibrecrete.The method has been successfully applied to four shafts since July 2007; 3 m and 4 m diameter shafts at Trident Mine, a 3 m diameter shaft at Wattle Dam and a 4.5 m diameter shaft at Athena Mine.Bored pile layout designs have varied from eight to 24 piles, of diameters 120 to 270 mm, in one or two rings. In one case, the top 10 m of the proposed shaft was pregrouted. Subsequent surveys have confirmed that fallout occurred in some shafts, out to the ring of piles, implying that the piles inhibited collapse.The practical implementation of the method was not always easy and many valuable lessons have been learnt. This paper documents key aspects of the method and the critical elements for its application.

Mar 21, 2011

Continuing with the effort of providing new and more effective exploration methods to the mining industry, where direct methods (drilling, cross-cutting, etc.) are not applicable, either for logistical or environmental reasons or because they are costly and sometimes ineffective, we present here a new seismic technique based on full wave recording of 3-D channel waves generated within the coal seam across a longwall. In the past two years we reported the application on In-Seam High Resolution Seismic Reflection (ISHRSR) and In-Seam Seismic Tomography (ISST) to map non-coal inclusions that disrupt the coal seam continuity. In the present paper we present a 3-D In-Seam Seismic Tomography (3-DTSST) method using 3-D channel waves recorded by three component high resolution geophones. The method allows to distinguish longitudinal and transversal components of the channel waves, similar to the spheroidal and toroidal modes for the free oscillations of the earth. The recording of these waves allows a more complete analysis of the free modal vibrations of channel waves, permitting a more complete inversion of the structure of the coal seam through which they travel. The full wave analysis provides additional insights of the detailed coal structure for larger, distances than for the ones previously reported using the one dimensional method. The refinement of the inversion software is also a contribution towards the better definition of the coal seam geometry and structures disturbing them such as sandstone channels, sandstone rolls, partings, mine voids, faults, fractures, etc. The method is illustrated with three case studies where subsequent mining revealed the virtues and limitations. The first example deals with the problem of mapping mine works in one side of a longwall panel which geometry is well known, to verify its applicability to map old mine works. The second example deals with a sandstone body that partially scoured the coal seam withing a longwall panel. The third shows an application of the method to map roof conditions in a longwall panel where this problem critically affected production scheduling and costs

Jan 1, 1996

By Heidy de Oliveira Simões

Visando entender os impactos causados pela formação de trincas e deformação das pelotas na qualidade física do material, foi desenvolvido um algoritmo que, através de análise automática de imagens, é capaz de medir o tamanho da trinca, sua largura e comprimento, bem como efetuar as medições de tamanho e morfologia da pelota queimada. Foram analisadas pelotas produzidas com minério hidratado (elevado teor de goethita) com 2 perfis térmicos distintos. Os dados obtidos na análise de imagem foram correlacionados com a resistência à compressão das pelotas e evidenciaram o tamanho das trincas denota notória correlação com a sua resistência física. A medição das trincas formadas pela deformação da pelota no leito (denominadas resiliência) permite evidenciar o quanto a pressão no leito de pelotas impacta na qualidade após a queima, bem como indica o ponto ótimo para que não acarretem em perda da resistência. A medição do tamanho das trincas térmicas mostra-se essencial, pois mesmo em perfis mais suaves de queima pode haver a formação de tais trincas, sendo que o tamanho e a abertura da trinca é que definem a melhor ou pior resistência. O conhecimento, e possível aplicação prática, da avaliação das trincas poderá auxiliar na otimização de perfis térmicos de fornos de pelotização.

Aug 16, 2017

By Donald I. Bleiwas

The U.S. Bureau of Mines has evaluated the potential availability of nickel from 36 deposits or districts in 16 market-economy countries (MECs), analyzing more than 95 percent of production in those countries. This study indicates the quantity of nickel available on the basis of net production costs and total costs with a 0-pct and a 10-pct discounted cash flow rate of return (DCFROR). Costs of production are expressed in dollars per pound of recovered nickel. The study also indicates sensitivities of the cost of production to energy, labor, and other factors. The studied deposits and properties contain approximately 33 Mmt of recoverable nickel. About 26 Mmt of nickel is potentially recoverable from laterite deposits, of which 4.5 Mmt can be produced at $2.50/lb or less with a 0-pct DCFROR. Approximately 7 Mmt of nickel is potentially recoverable from sulfide deposits, of which about 6.3 Mint could be produced at $2.50/lb or less at a 0-pct DCFROR. The price of nickel averaged above $6.00/lb in 1988. Sensitivity studies performed for both laterite and sulfide deposits indicate that the total cost of producing nickel from laterites is most sensitive to increases in energy costs and that the total cost of producing nickel from sulfide deposits is most sensitive to increases in labor costs; sulfides are also affected by changes in revenues from byproducts.

Jan 1, 1991

By Khaled M. Mohamed, Michael M. Murphy, Ted M. Klemetti, Heather E. Lawson

"The design of rib support systems in U.S. coal mines is based primarily on local practices and experience. A better understanding of current rib support practices in U.S. coal mines is crucial for developing a sound engineering rib support design tool.The objective of this paper is to analyze the current practices of rib control in US coal mines. Twenty (20) underground coal mines were studied representing various coal basins, coal seams, geology, loading conditions, and rib control strategies.The key findings are: (1) any rib design guideline or tool should take into account external rib support as well as internal bolting; (2) rib bolts on their own cannot contain rib spall, especially in soft ribs subjected to significant load—external rib control devices such as mesh are required in such cases to contain rib sloughing; (3) the majority of the studied mines follow the overburden depth and entry height thresholds recommended by the Program Information Bulletin (PIB) 11-29; (4) potential rib instability occurred when certain geological features prevailed—these include draw slate and/or bone coal near the rib/roof line, claystone partings, and soft coal bench overlain by rock strata; (5) 47% of the studied rib spall was classified as blocky—this could indicate a high potential of rib hazards; and (6) rib injury rates of the studied mines for the last three years emphasize the need for more rib control management for mines operating at overburden depths between 500 ft and 1,000 ft.IntroductionEfforts to improve the stability of underground mine ribs have continued for decades. These efforts by mining professionals around the world persisted throughout the 1990s and 2000s as well, though much of this work focused on rib support methodology and selection of proper support for a specific location. Despite these efforts, it is unfortunate that there has been a continual occurrence of rib-related fatalities in underground coal mines. While overall improvements in rib safety have been achieved, the average fatality rate is still about 1.3 fatalities per year over the last 18 years (Jones, 2014).To manage and control the rib hazard, rib support is used in U.S. coal mines. The current rib support methods for U.S. mines fall into two main categories: rib control based on intrinsic support systems and those based on external support systems. Intrinsic or rib-bolt support requires a roof bolting machine that can install a bolt fixture into the rib. Furthermore, the appropriate level of support needed to control the ribs with an intrinsic-based support system as well as the design parameters for those support systems for various mine conditions have not been established in U.S. coal mines. Furthermore, surface control systems are often an integral part of these support systems and must be considered in the system design."

Jan 1, 2015

By Frank J. Arland

Augered-Cast-in-Place piles have been used successfully for many deep foundation applications. The four case studies discussed herein describe ACIP pile projects where problems developed during ACIP pile installation requiring changes to the method or sequence of installation. The case studies illustrate the importance of understanding existing subsurface conditions and project constraints when considering the use of this pile type. Ground loosening and over-excavation of soil during the augering process, a significant concern for fine to medium sands and non-plastic silts below the water table, can significantly impact adjacent structures. This risk needs to be evaluated during the pile selection process and generally can be mitigated, but not eliminated, by requiring the use of piling equipment with high torque and slow auger rotation speed to advance the auger with minimum amount of rotation. In some applications where high lateral stresses in the soil are present such as at the base of retaining structures, the use of ACIP piles may not be appropriate if structure movement is unacceptable. On the other hand, ACIP piles have been successfully used to support deep foundations in preconsolidated varved deposits where the new structure was designed to accommodate recompression settlement.

Jan 1, 2004

By Gerson Evaristo de Paula Júnior, Bruno Santos Malaquias, Henriquison Magela Bottrel Reis

O desafio no processo de coqueificação está relacionado à elaboração de misturas de carvões que produzam coque com a qualidade para utilização nos altos-fornos. Foi avaliada, em escala piloto, a influência de materiais inertes (coque verde de petróleo [CVP], antracito e carvão com alto teor de inerte [CATI]) às misturas de coqueificação sobre a formação de microtexturas e a qualidade do coque. Os resultados indicaram que, para a mistura avaliada, a adição do CVP até 30% produziu coque com qualidade (DI15-150) adequada para os altos-fornos da Usiminas. As principais microtexturas foram do tipo mosaico, fragmentária, fusita, inerte anisotrópico e o próprio CVP. O antracito provocou redução significativa de DI15-150 e CSR. A análise de microscopia óptica revelou partículas livres na matriz de coque, contribuindo para a queda de qualidade. A adição de CATI às misturas de coqueificação resultou em forte queda na qualidade do coque e a microtextura do tipo mosaico foi predominante. De forma geral, o carvão com alto teor de inertes foi o que apresentou menos benefícios, diferentemente do CVP, que apresentou melhor resultado para ser utilizado nas misturas de coqueificação da Usiminas.

Oct 1, 2019

By R. J. Allan

"CANADA HAS A GREATER LAKE AREA than any other country. Discountin the Great Lakes, this fresh-water area, mainly in the Canadian Shield, is listed as approximately 300,000 sq. mi. Densities of lakes range up to 7,500 in a 5,294-sq. mi. area of the Shield, southwest of Reindeer Lake, Saskatchewan. Five areas chosen randomly from the Shield (Figure 1) contained sufficient lakes to provide samples at a density of at least one per 10 sq. mi. Regional geochemical surveys in the Appalachian area (Nova Scotia, Boyle et al., 1958; New Brunswick, Boyle et al., 1966) and in the Cordilleran area (Yukon, Gleeson, 1965) of Canada and in many other areas of the world have relied heavily on analyses of stream sediments. These surveys show that sampling of material related to the drainage system reflects the over-all trace element content of the rocks and surficial deposits in the drainage basin. In the Shield, the classic types of dendritic (and other) stream systems found elsewhere in the world are very rare. However, impeded and disorganized stream systems that abound with lakes can provide the exploration geochemist with an ideal composite drainage system sample in the form of lake sediment. This paper attempts to demonstrate the feasibility of, and review the theory and problems involved in, the use of lake sediment as a regional geochemical exploration medium. Most of the references to field examples are taken from a regional survey using lake bottom sediment as the sample medium over 1,500 sq. mi of the Coppermine basalt group and adjacent rocks (Figure 2). During this regional survey, detailed sampling of several lakes was carried out and the results are referred to at appropriate places in the text."

Jan 1, 1971

For the purposes of this discussion it is assumed that contributors should express the thoughts that arise from their personal experience. So wide is the range of mineral deposits, and so varied the methods employed in their discovery and development, that no two geologists are likely to have been impressed with the same applications of their science. The author's own personal experience has been, during recent years at least, very largely concerned with the broader aspects of the employment of scientific method and geological knowledge to the problems of exploration and exploitation, for the guidance of the general public and governmental authority rather than of mine executives and directors. The view-point thus reached is likely to differ in many respects from that of men who are much more intimately concerned with the mining problems of a single metal or a single mining field, and for this reason a statement may perhaps supplement those from others whose experience has been markedly different.It may well happen that, at some not distant date in the future, when systematic and comprehensive instruction in economic geology is embodied in the courses- prescribed for mining engineers during their years of training, the author's comments will be quitesuperfluous; but at the present time they appear to him to call for expression.The Need for Training of Mining Men in Economic Geology.Contact over a period of many years with mining men who have had different kinds of training and experience has been convincing that there is a general reluctance to acquire a full rational understanding of the geological factors involved in exploratory and developmental problems. The correction of this attitude is regarded as vital to the industry and it is necessary to insist that the outstanding requirement of the present day is the utilization of all branches of geological, investigation in the field and the laboratoryby men who have had systematic and specialized training in these matters. The science of geology is many-sided, but is, nevertheless, whole and essentially indivisible. No one can afford to disregard any fraction of its content 'or any of its methods of investigation.The greatest advances have been made in the understarnding of the occurrence of mineral deposits by those whose knowledge Qfbasal principles, has been soundest, whose endeavour has been to ascertain all their relationships in space and time, whose attention to detail of all kinds has been keenest, and at the same time, whose capability to distinguish between major and minor features has been most marked.With the passage of the years and the accumulation of data from many lands, it has been possible to build up a great body of information regarding the primary deposition and secondary alteration of mineral occurrences, which is of the utmost value in guiding thesearch for new deposits to take the place of those that become exhausted. This heritage is due not only to the efforts of gifted in...

Jan 1, 1950

By Lee T. J

The area, A, under a gamma-ray log that passes through a horizontal bed given by: A = gl/k. Here is the equivalent concentration of U3O8 in the body, l the thickness of the body, and k the calibration factor or sensitivityof the logger. The area is independent of the logging speed or logger time constant.This relationship, together with the first moment about the maximum of the log and its value there suflicient to determine the thickness, position of the centre of the bed from the log maximum and the concentration of U3O8.Numerical results obtained from artificial and field data show that the computed results arc as good as those obtained by methods such as the inverse filter technique and the iterative method. The present method yields results that arc easier to feed into an ore reserve data base.

Jan 1, 1981

By Rodolfo Lagos, Nicos Pfeiffer, Ben Harding, Clayton V. Deutsch

This paper documents a probabilistic resource modeling workflow for the Round Mountain epithermal gold deposit. The set of categorical and continuous variable simulated realizations provides a model of variability and uncertainty given the current orebody knowledge. These realizations can be used to quantify and understand expected deviations in reconciliation during mining and provide a more accurate measure of expected gold than an estimated model. Gold mineralization at Round Mountain is primarily contained within tertiary tuff units, which dip gently to the west and thicken towards the southern part of the orebody. Domain boundaries are modeled as combinations of lithology and alteration; alteration domains are constrained to be within the tuffs. Large-scale geologic uncertainty is strongly influenced by parameter uncertainty, particularly the input histogram. The spatial bootstrap characterizes prior global uncertainty in the input histogram for categorical and continuous variables. Categorical models are generated using hierarchical truncated pluri-Gaussian (HTPG) simulation. Continuous variable simulation is carried out within the simulated domain boundaries using trend models to account for non-stationarity.

Aug 19, 2023

By P. V. Brough, K. B. Gillaspie

DECISION to build a mill at the Bayard property was made in May 1942. Western-Knapp Engineering Co., of San Francisco, assisted by engineers of U. S. Smelting, handled the design and construction. Much of the milling equipment was moved from the Company's mill at Goldroad, Ariz. Wartime restrictions necessitated wood construction and paper sheathing except for structures adjacent to the Bullfrog shaft. Construction started in September 1942 and milling in March 1943. Bayard ores are processed in a single-ection mill. About half of the ore treated during the past year was hoisted through the Bullfrog shaft and the rest was trucked from other shafts. Coarse storage includes four bins, two of 120 tons each for Bullfrog ores and two of 85 to 120 tons each, served by a truck ramp. The low capacity figure refers to

Jan 1, 1948

By B. Matsetela, S. Amos, V. Nkuna

"The Kamoa-Kakula copper project—a joint venture between Ivanhoe Mines, Zijin Mining Group Co. Ltd, and the government of the Democratic Republic of Congo—has been independently ranked as the world's largest undeveloped high-grade copper discovery by international mining consultant Wood Mackenzie. It is a very large, near-surface stratiform copper deposit with adjacent prospective exploration areas within the Central African Copperbelt, approximately 25 km west of the town of Kolwezi and about 270 km west of the provincial capital of Lubumbashi. A phased development approach is currently envisaged. The first phase of the project involves the development of a 6 Mt/a underground mine and surface processing complex (dual stream concentrator) at the Kakula deposit, a discovery announced in early 2016. The second phase involves an integrated 12 Mt/a two-stage development, beginning with initial production from the Kakula mine, to be followed by a subsequent, separate underground mining operation at the nearby Kansoko mine, along with the construction of a smelter. Project description and locationThe Kamoa–Kakula project comprises a newly discovered, very large stratiform copper deposit with adjacent prospective exploration areas, located within the Central African Copperbelt in Lualaba Province, Democratic Republic of Congo (DRC). The Kamoa–Kakula project lies approximately 25 km west of the town of Kolwezi and about 270 km west of Lubumbashi. Ivanhoe owns a 49.5% share interest in Kamoa Holding, an Ivanhoe subsidiary that currently owns 80% of the project. Zijin Mining owns a 49.5% share interest in Kamoa Holding, which it acquired from Ivanhoe in December 2015 for an aggregate cash consideration of US$412 million. The remaining 1% interest in Kamoa Holding is held by privately-owned Crystal River.The Kamoa–Kakula project consists of the Kamoa exploitation licences (exploitation permits 12873, 13025, and 13026, which cover an area of 397.4 km2) and one exploration licence (exploration permit 703 covering an area of 12.74 km2). The Kamoa exploitation licences, approved 20 August 2012, grant Kamoa Copper the right to explore for, develop, and exploit copper and other minerals, for an initial 30-year term, expiring on 19 August 2042. The permits can then be extended for 15-year periods until the end of the mine’s life."

Nov 1, 2018

By Victor R. Spironello

Applications of three experimental design techniques to smelting operations are explained. The report describes a factorial design using three variables at two levels, a fractional factorial design which investigates seven variables, and response-surface methodology for optimization of electric- furnace smelting processes. These methods may be applied with a minimum of trials and at little expense. Further, the writer knows of no reasons why the same methods could not be applied to other operations as well, such as steelmaking.

Jan 1, 1970

By B. S. Gottfried

This paper is concerned with possible transport mechanisms which occur during segregated burning (i.e., burning in an oil reservoir in which the oil-bearing formation is overlain by a "clean" porous zone containing only gas). ,Two analytical models are presented. In the first, burning is assumed to occur at the gas-oil interface, and the dominant mechanism is taken to be the rate at which oxygen diffuses to the interface. The second model assumes that combustion occurs within the clean zone, with the dominant mechanism being the mechanism of fuel deposition from the oil-bearing formation to the clean zone. ,Comparison of the results of the analyses with limited experimental data indicates that the latter mechanism is much more plausible. Both models are idealized representations of the actual process and are somewhat conjectural, however, owing to the lack of more definitive laboratory or field data. INTRODUCTION In recent years there has been considerable theoretical and experimental research directed toward understanding the recovery of crude oil by underground combustion. Although two different recovery schemes have been proposed, known as forward and reverse combustion, it is only forward combustion that shows promise of becoming a practical recovery technique.17 Most of the analyses of the forward combustion process have considered it to be pistonlike; i.e., oil is displaced by a vertical combustion zone which, with its ensuing gases, pushes die oil forward as the flame front is propagated through the reservoir.l-8,ll,l2,14-16 However, information gained in field pilot studies indicates that, at least to a certain extent, forward combustion proceeds in a segregated manner in oil reservoirs.10 An ideal segregated system is one in which the oil-bearing formation is overlain by a "clean" porous zone containing only gas. The location of the combustion zone in such a system is not immediately evident, although combustion is believed to occur either at the gas-oil interface or within the clean zone. In either case, the combustion zone may be horizontal and it moves in parallel rather than in series with the produced oil. The purpose of this paper is to explore the likely mechanisms by which segregated burning can occur, and to determine the sensitivity of the resulting models to changes in various physical parameters. Two governing mechanisms are considered: the case of a horizontal combustion zone at the gas-oil interface with the rate of combustion governed by the rate at which oxygen diffuses to the interface, and the case of combustion within the clean zone with the combustion process controlled by the transport of fuel from the oil-bearing formation to the clean zone. Both models are somewhat hypothetical and involve considerable simplification of the actual process. However, the results allow some preliminary understanding of segregated burning which is useful in the absence of more definitive laboratory or field pilot data.

Jan 1, 1967

By Victor Caso Moreira

Neste trabalho é estudado o efeito do ferro no tamanho de grão e nas propriedades mecânicas do latão UNS C26000, também comercialmente conhecido como latão 70/30. Foram avaliados dois teores residuais: 0,0069% e 0,0592%. As amostras foram inicialmente laminadas até a espessura de 2,30 mm, submetidas a tratamento térmico de recozimento objetivando tamanho de grão de 0,030 mm. Posteriormente as amostras foram laminadas para outras três espessuras e submetidas a um novo recozimento. As amostras recozidas passaram por análise de tamanho de grão e foram submetidas a ensaios de tração, sendo obtidos resultados de limite de resistência à tração. Os comportamentos apresentados pelos materiais foram distintos entre si, sendo que o material com maior teor de ferro apresentou aumento das propriedades mecânicas em função do aumento da redução de espessura e o material com menor teor ferro apresentou redução do limite de resistência à tração. Quanto ao tamanho de grão, o material com menor teor de ferro apresentou pequena variação de tamanho de grão após o recozimento, enquanto o material com maior teor de ferro apresentou redução do tamanho de grão em função do aumento da redução de espessura, demonstrando inibição do crescimento de grão e estrutura heterogênea.

Aug 17, 2017

By Jovanir Francisqueto

O objetivo deste projeto foi elevar a produtividade do pátio de placas do Laminador de Tiras a Quente da ArcelorMittal Tubarão através da alteração do processo de sequenciamento do Laminador de Tiras a Quente com a criação do processo de realocação de placas após a formação da chance de laminação. O trabalho iniciouse com a definição de regras metalúrgicas de realocação de materiais e definição dos critérios operacionais e de atendimento a pedidos para posteriormente ser desenvolvido o software de otimização para a execução da realocação automática de placas na chance de laminação com foco na redução de movimentações no pátio do Laminador de Tiras a Quente. Com a implantação do processo/sistema espera-se conseguir uma redução de aproximadamente 60% nas movimentações de placas para formação da chance de laminação, conforme demonstrado nas simulações com dados reais e consequentemente reduzindo número de paradas de forno em função de problemas de produtividade do pátio de placas visando o aumento da produção do Laminador de Tiras a Quente em torno de 15 Kt/ano.

Aug 16, 2017

By Gustavo Estrela da Silva

O presente trabalho tem por objetivo avaliar a influência da taxa de resfriamento durante a solidificação na formação de diferentes microestruturas de ferros fundidos. Para tal, uma liga de ferro fundido com pequena adição de Si foi fundida em forno de indução e vazada em molde de areia, gerando um corpo de prova dotado de regiões com diferentes espessuras de parede, impondo ao metal líquido vazado diferentes taxas de resfriamento. Foi possível constatar que o aumento da taxa de resfriamento aumenta a tendência de formação de ferro fundido branco, respeitando-se o equilíbrio metaestável Fe-cementita, e que menores taxas de resfriamento priorizam a formação de ferro fundido cinzento (respeitando o equilíbrio estável Fe-grafita). Estudos macrográfico e micrográfico detalham as regiões de ferro fundido branco, mesclado e cinzento, e relacionam as diferentes morfologias obtidas com as taxas de resfriamento impostas.

Aug 8, 2018