Search Documents

The nature of metallurgical engineering?applying and optimising chemical and physical processing of ores into useful materials?is reviewed. Important trends that shape the context in which metallurgical engineers practise are identified ? increased global production of primary metals, declining prices, environmental constraints, and increased property requirements of materials. A successful department of metallurgical engineering is one which employs a team of academic leaders to develop graduate engineers who are productive across the full range of metallurgical processing. Keywords: metallurgical engineering, primary metals, commodity prices, processing

Jan 1, 2003

By André de Albuquerque Vicente

O valor do PREN da liga pode levar a uma previsão equivocada da resistência à corrosão por pite pois, caso haja um desbalanceamento das frações volumétricas da ferrita d e da austenita, as composições químicas das fases poderão ser muito diferentes daquela da liga. Neste caso o PREN de uma das fases pode ficar abaixo do PREN da liga. Caracterizou-se três chapas de aços inoxidáveis duplex laminados com diferentes PRENs: UNS S32304 (Lean Duplex), UNS S31803 (Duplex) e UNS S32750 (Super Duplex). Várias técnicas complementares de análise microestrutural foram utilizadas, tais como de espectrometria de emissão ótica, microscopia óptica e microscopia eletrônica de varredura com EDS acoplado. Realizaram-se análises metalográficas quantitativas para a determinação das frações volumétricas de ferrita d e da austenita e análises químicas semi-quantitativas das fases presentes utilizando-se um MEV com EDS acoplado.

Oct 30, 2017

By Davi Alves Marques

Este trabalho visa analisar a temperabilidade dos aços ABNT 1045 e ABNT 4140 através do ensaio Jominy e correlacionar suas propriedades com a variação microestrutural devido ao gradiente de transferência de calor através dos corpos de prova, também como analisar o efeito dos elementos de liga presentes. O ensaio Jominy foi realizado segundo a norma ABNT A255-10. Foi observado que o aço ABNT 4140 apresenta maior temperabilidade que o ABNT 1045 devido à maior profundidade de têmpera e, por conseguinte, apresentou produtos de transformação martensítica em profundidades maiores do corpo de prova. Visto que o teor de carbono em ambos os aços é aproximadamente igual, a maior temperabilidade do ABNT 4140 se dá devido aos elementos de liga presentes. Os elementos de liga do ABNT 4140 contribuem para uma maior percentagem de carbono equivalente, quando comparado ao ABNT 1045, deslocando assim o diagrama de transformação isotérmica para a direita, reduzindo então a taxa de resfriamento crítico.

Oct 30, 2017

By S. Michael, T. E. Moongo

Electrowinning consumes a substantial amount of electrical energy, and owing to the ever-increasing unit cost of electrical power there is a need to improve current efficiency in the process. This research was carried out to design a continuous quality improvement framework for improving electrowinning current efficiency by applying statistical process control (SPC) on an online industrial copper electrowinning operation. A sequential mixed research methodology was applied and a statistical software package utilized for analysing data. It was concluded that metallurgical short-circuits (hotspots) had the most significant effect on current efficiency. Bringing hotspots under statistical control resulted in a 5.40% improvement in current efficiency, which is equivalent to approximately 74 t of 99.999% pure grade A copper cathode production over a period of 1.5 months.

Jan 1, 2021

By Hugo Leandro Rosa

A CBMM aplicou aços micro ligados ao nióbio em dois tipos de caçambas de carregadeiras de rodas que operam na usina de Araxá, Brasil. O objetivo foi avaliar os benefícios destes aços relacionados com redução dos custos, aumento da produtividade e vida útil dos componentes. Uma das máquinas analisadas coleta peças quentes de ferro nióbio para carregamento dos silos do britador. O uso de um aço ferramenta de alta resistência e resistente ao desgaste solucionou os problemas de deformação, desgaste e rachaduras durante o serviço, aumentando a vida útil da caçamba em cerca de 190%. A outra máquina avaliada foi uma carregadeira de rodas que opera na mina de minério de nióbio. O novo desenho com aços de alta resistência mecânica e resistente ao desgaste reduziu o peso em 14%, correspondendo ao incremento na capacidade de carga. A carga extra possibilitou um aumento na produtividade dos caminhões de 42 toneladas. Com os novos materiais, as trincas anteriormente encontradas na caçamba da pá carregadeira foram eliminadas, enquanto foi mantida a resistência ao desgaste antes oferecida pelo aço revestido com carbeto de cromo reduzindo também os custos de investimento em 7%.

Aug 17, 2017

By Yeole Shivraj Narayan, Nunna Nagabhushana Ramesh, Banoth Balu Naik, Alluru Ramya

MicroEDM process is mainly used for producing miniaturized features like microholes on different types of materials that are hard to cut and difficult to machine. One typical application of microEDM process is microhole drilling operation. Choice and utilization of optimum pulse parameters is of utmost importance for achieving superior surface quality and higher machining rates. However, the process is characterized by low machining rates and considerable overcut as compared to conventional EDM drilling. An attempt is made to investigate the effect of pulse parameters on maraging steel 300 alloy during micro EDM drilling. Parameters like pulse on time, pulse off time, voltage and current are explored through 09 experiments replicated thrice using Taguchi method. Machining characteristics like material removal rate and overcut are studied while drilling micro holes of 500 µm diameter using brass electrode. Evaluation of microhardness after microdrilling is also performed. It is found that puls on time and current influenced the machining characteristics. Minimal change is observed int he microhardness of the alloy after microdrilling.

Mar 1, 2018

By Valois R. Shea-Albin

Ground control problems are an important factor affecting safety, production, and efficiency in underground coal mines. A major portion of ground control problems encountered in underground coal mines can be attributed to geologic features in the strata surrounding the extracted coal seam. The U.S. Bureau of Mines has compiled information from numerous sources on the geological features that contribute to ground control problems in underground coal mines. The compilation includes (1) sedimentary features such as paleochannels, crevasse splays, clastic dikes, mold-and-cast structures, concretions, and lithologic factors, and (2) structural features such as folds, fractures, joints, cleat, and faults. The compiled information will aid in identifying the features, predicting their occurrence in advance of mining, and controlling or minimizing roof failure when these features are encountered in an underground coal mine.

Jan 1, 1993

By H. B. Hill

The Salt Flat field, formerly called the Joe Bruner field, is located northeast of the town of Luling in Caldwell County, Tex. This field, which is a fault structure, approximately parallels and is about 5 miles east of the Old Luling field. The proved area is approximately 1,280 acres, on which 332 producing wells (September, 1930) have been drilled. The majority of the wells are producing from the Edwards limestone at an average total depth of 2,700 feet. A few wells are producing from the Austin chalk or from other formations above the Edwards limestone. The Wilcox formation is exposed, and the fault trace in places is scarcely evident. The strike of the structure is approximately N. 20 to 45° The displacement of the fault is probably 200 to 500 feet. The discovery well was completed in the Austin chalk by the Lutex Oil Co. during April, 1928. In October, 1926, the Sun Oil Co. completed the discovery well in the Edwards pay. This well was an important discovery, as it indicated the potential oil possibilities of the Edwards limestone in echelon fault structures. The discovery led to the development of the third fault field in the Edwards limestone and opened up a large area for future prospecting.

Jan 1, 1931

By Karl C. Dean

The current emphasis on environmental problems has focused attention on the massive nationwide accumulations of mine, mill, and smelter wastes that represent potential air and water pollution hazards. The pollution hazards can be reduced or eliminated by utilization or stabilization of these wastes. The U.S. Bureau of Mines, since the inception of the Solid Waste Disposal Act of 1965, has been conducting research to determine the practicality of various utilization and stabilization procedures. Investigations include partial extractions of desirable waste components and full utilization of the wastes as simulated soils or in ceramic or other structural products. Chemical, vegetative, and combined chemical-vegetative methods of stabilization have been actively studied. This report updates information previously developed by the Salt Lake City Metallurgy Research Center and presents the current status of antipollution solid waste work 1/,2/.

Jan 1, 1970

By H. E. Frimmel

Abstract - Most of the gold in the Late Archean Witwatersrand Basin is of detrital origin but, in its present form, it is metamorphosed. The only relict detrital features preserved are the morpho­logical characteristics of some placer gold particles. Regional burial metamorphism in the shallower and deeper levels of the Witwatersrand Supergroup reached temperatures around 300°C and 350°C at pressures between 2 kbar and 3 kbar, respectively , estimated from phase relations, chlorite-chloritoid exchange thermometry and chlorite thermometry . Metamorphism of the gold involved compositional homogenization of individual gold particles and partial recrystallization. Various infiltration events caused the partial mobilization of the gold at slightly lower temperatures, between 240°C and 300°C. These infiltrations can be related to crustal extension during the deposition of massive carbonate sequences of the Transvaal Supergroup (around 2.5 Ga), and later to the emplacement of the Bushveld Complex, and to the Vredefort event around 2.0 Ga ago. The mobility of the gold was dependent on the sulfur fugacity prevailing in a particular horizon which, in turn, was deter­ mined by the amount of pyrite (and other sulfides) present in that horizon. With the sulfur fugacity being controlled by stratigraphy, low fluid:rock ratios in a pyrite-rich horizon were most conducive for the mobilization of the gold. Thus, long-range gold mobilization in the Witwatersrand Basin can be expected to be the exception rather than the rule.

Jan 1, 1994

By Charles R. Boardman

Recent underground nuclear tests in tuff, alluvium, salt, and granite have yielded data essential to the evaluation of mining applications of contained nuclear detonations. The data indicate that for these media the cavity radius is predictable within ±20% without regard to the properties of the rock in the immediate shot environment. Properties of the chimney of broken rock resulting from collapse of the cavity, on the other hand, are found to be related to the properties of the rock and its preshot structural weaknesses. Seismic effects and radioactivity distribution are sufficiently documented to serve as a basis for predicting the safety conditions associated with detonations for a variety of yields.

Jan 1, 1964

By F. Hörtkorn, Y. Narainsamy

Rather quietly, a new generation of European norms dealing with earthworks has been developed over the past few years, in particular a part of EN 16907 pertaining to extractive waste. Whereas the majority of the parts deal with routine geotechnical aspects, one part deals specifically with tailings dams. The standard is currently in draft form but if this becomes a European Standard, members of the European Union are bound to comply with the regulations. As such, the standard has the capacity to influence mining in Europe and potentially in South Africa. In this paper we review the standard and compare it to the South African standard on mine residues and the recently published Global Industry Standard on Tailings Management (GISTM). We conclude found that although the European norm makes great strides towards increasing tailings dam safety, there is room for improvement. The current South African standard has served well since its inception, but can be improved by using concepts from the European and global tailings standards.

Jun 2, 2022

By T. F. Curry, L. B. Berger, H. A. Watson, S. J. Pearce

The conduct of work at elevated air pressures , such as in caissons and in tunnel - driving in subaqueous strata , poses safety problems not encountered in mining and tunneling operations at ordinary atmospheric pressure . This publication discusses some of the problems involved and presents information on the following subjects : ( 1 ) Physiological effects of gases at elevated pressure . ( 2 ) Use of respiratory protective equipment in rescue or recovery operations in event of fire or other emergency in pressurized tunnels . ( 3 ) Effect of elevated pressure on performance of some gasdetecting instruments ; interpretation of the results . Various types of respiratory protective devices are discussed in relation to their possible use at elevated pressures , especially the 2 - hour , selfcontained , recirculating - oxygen - breathing apparatus , which has had wide use in the United States during rescue and recovery work in the mining industry . A modified procedure that eliminates the hazard of oxygen poisoning enabling the safe use of this apparatus at elevated pressures , up to 45 pounds per square inch , gage , and tests to verify its practicability are described . procedure involves control of the partial pressure of oxygen in the breathing

Jan 1, 1964

By S. D. F. Rocha1, L. Katsarou, G. P. Demopoulos

"Crystalline scorodite (FeAsO4·2H2O) has been pointed out as the most stable compound to immobilize arsenic for disposal due to its good stability performance according to EPA’s TCLP test. However, in anaerobic conditions, arsenic releasing is increased to undesired levels due to scorodite reductive break down, in eh <100 mV at 5.5< pH <7 which causes contamination of groundwater. In this work, the concept of encapsulation by controlled deposition of mineral coatings immune to pH or redox potential variations is presented. Aluminum and calcium phosphates were evaluated as coatings and the release of arsenic from scorodite previously coated with phosphates was substantially decreased when compared to the VALUES (obtained from crude scorodite, both in oxic and anoxic conditions. INTRODUCTIONThe widely acknowledged hazardous properties of arsenic as a soil and natural water contaminant and its adverse health effects when present in drinking water have led to very strict environmental regulations (Mandal & Suzuki, 2002) aiming at the drastic reduction of the presence of arsenic in the effluents of the mining and metallurgical industries.In Canada, the Metal Mining Effluent Regulations (Government of Canada, 2002) dictate that the maximum monthly mean concentration in tailings for arsenic must be lower than 0.5 mg/L. At the same time the new Environmental Protection Agency’s (EPA) standard for drinking water foresees concentrations of arsenic less than 0.01 mg/L, which means that the leachability limit for the industrial waste is set at 1 mg/L arsenic (EPA, 1994; Le Berre et. al, 2007). One of the preoccupations of the mining and metallurgical industries is directed to the elimination of arsenic presence in all its effluents, especially since arsenic is commonly found in many ores mainly in the form of oxides and sulphides. After processing of arsenic-containing ores and concentrates, arsenic can be present either in solid residues and tailings, liquid effluents or in flue dusts. Several of these forms of arsenic waste materials are soluble and therefore may cause the contamination of ground water, if disposed of without further treatment."

Jan 1, 2012

By David Lynn Passmore

The reliability of mine operators reports to the Health and Safety Analysis Center of the U.S. Deparetment of Labor of days lost from work by injured miners is .267.

Jan 1, 1985

By O. Moselhi

The purpose of this research is to evaluate the impact of Building Information Modeling (BIM) on Just-In-Time (JIT) material delivery, with a focus on how the use of BIM can help improve efficient implementation of JIT and reduce the cost of material management. Previous research and a number of case studies have addressed the positive impact of BIM on construction at large but none focused on JIT in construction. This paper presents a methodology for selecting reliable material vendors. It also utilises the integration of BIM and scheduling software to generate quantities of material and its required delivery time to improve the flow process and improve its reliability to minimise related delays and productivity losses arising from idle and non-productive time of equipment and labour on jobsites. 4D visualization is utilized to support coordination and timing of JIT material deliveries in an effort to minimize congestion on job sites. Case studies on JIT material deliveries are presented and the impact of BIM implementation on reducing the cost of material management is evaluated. The joint effect of BIM and JIT on quality control, elimination of waste, reduction of inventory buffers, and on relationships with material vendors are evaluated by analysing and comparing data from case studies. The paper also presents a methodology based on multi-attribute decision criteria for modelling the selection criteria for material vendors. The model can assist in ranking vendors not only based on cost and quality but also on their reliability in delivering material on time.

Aug 1, 2013

The inauguration of a geological department for the mines of North Broken Hill Limited necessitated the provision of accurate plans and sections upon which geological facts and projections might be plotted.Unfortunately, the basic data were very inadequate. For the British Section, sill survey plans were available, but no regular stope plans. Filling surveys had been preserved for many stopes, but on innumerable pieces of tracing linen, without heights of any kind, and not altogether reliable (as indicated by the finding of very inconsistent duplicates). For the bulk of the old stopes no plans exist at all. The expenditure of much time and patience has resulted in the co-ordination of most of the existing stope data, but the British Section must for the rest of its life continue to have surprises in store, as has been the case for many years past. Manufacture and preservation of stope records has, of course, been on a sound footing during recent years. No reliable cross-sections of the British Section were available.The Marsh, Junction, and Junction North Sections have for the most part very poor data. In the North Section, level plans were fairly reliable, and cross sections of the lode made for ore reserve purposes have been preserved for quite a few years. No floor plans of stopes were kept, however, until a couple of years ago.Diamond Drill records vary in quality. Practically none exist for the Junction and Junction North Sections. Logs have been kept for the British Section drill holes, but are...

Jan 1, 1940

By D. L. Passmore, J. D. Bennett

The reliability of mine operators&apos; reports to the Health and Safety Analysis Center of the US Department of Labor of days lost from work by injured miners is 0.267.

Jan 1, 1987

By J. Gurland

THE microstructure of sintered carbides consists of particles of metal carbides, such as WC and TiC, embedded in a metallic binder which is usually a cobalt—or nickel-rich solid solution. One of the important factors influencing the strength of the alloys is the degree of dispersion of the carbide particles in the binder matrix. While it is generally accepted

Jan 1, 1960

By D. Men, R. Q. Honaker, J. C. Hower

"Maceral separation is one possible technique to expand coking coal resources, either by increasing the blending ratio of non- or slightly caking coal or rationally utilizing the coking coal according to the different behaviors of macerals in coking. The success of maceral enrichment for a given coal using flotation is dependent on the differences in flotation kinetic rate among macerals. This paper presents the flotation rates and zeta potentials of the vitrinite-rich and inertiniterich maceral concentrates obtained from six coal samples of different ranks – from high-volatile B bituminous coal with mean random vitrinite reflectance (Rrandom) of 0.64 percent to low-volatile bituminous coal with Rrandom of 1.73 percent – using a float-sink procedure. The flotation results show that vitrinite-rich concentrates can be produced in tap water using froth flotation only with frother for the high-volatile B and A bituminous coal samples, but there was no good performance for the high-volatile C bituminous and medium- to low-volatile bituminous coal samples. The zeta potential results show that froth flotation could probably separate the high-volatile C bituminous coal samples well by adjusting pH, but there was no good performance for the higher-rank coal samples. IntroductionMetallurgical coke is used in blast furnaces for steel production and is produced by the carbonization of coking coal. Because caking coals are rare and expensive, they are often blended with non- or slightly caking coals. Considering the tight supply-demand situation for coking coal in China, it is important and urgent to develop highly efficient technologies for rationally utilizing and expanding coking coal resources (Mochizuki et al., 2013)."

Jan 1, 2015