Search Documents

By Alessandra Souza Martins

O aço inoxidável super duplex vem apresentando um desempenho satisfatório em ambientes de maior agressividade. Esse tipo de aço possui boas propriedades de resistência mecânica, resistência à corrosão e tenacidade ao impacto. Entretanto, mesmo apresentando desempenho satisfatório, esses aços podem apresentar problemas de corrosão quando sofrem algum tratamento térmico, devido à precipitação de uma fase deletéria chamada de alfa linha (?’), a qual precipita em temperaturas entre 300°C e 550°C e pode ocasionar uma diminuição da resistência à corrosão e tenacidade do material. Portanto, o objetivo deste trabalho é avaliar a resistência à corrosão dos aços inoxidáveis super duplex de grau 5A e 6A após sofrerem tratamento térmico a 475oC. A diferença entre os aços de grau 5A e 6A ocorre na presença de cobre e tungstênio na composição química do aço com grau 6A. A resistência à corrosão dos corpos de prova foi avaliada por meio das seguintes técnicas eletroquímicas: polarização anódica, espectroscopia de impedância eletroquímica e temperatura crítica de pite. A resistência mecânica dos corpos de prova foi avaliada por meio da técnica de dureza Brinell. Foi realizada também a caraterização microestrutural e a quantificação das fases do material. Os resultados mostraram um aumento da dureza do material, indicando um aumento da presença da fase ?’ com 10 horas de tratamento térmico apresentaram maior resistência à corrosão.

Aug 8, 2018

By L. Douglas Smoot

This research program was a theoretical and experimental study to improve understanding of the mechanisms of flame extinguishment in methane-coal dust-air-suppressant mixtures. This final report is a summary of work conducted during this grant, sponsored by the Bureau of Mines. Work under this new grant closely followed a recently completed contract for the Bureau of Mines that was conducted at this laboratory, and results of the earlier contract are also summarized in this report, as required in the grant work statement. The experimental effort was concentrated on supplementing the limited data available to describe laminar flames in methane-coal-air-suppressant mixtures. The theoretical effort was devoted to developing a comprehensive model that could be used to explain and extrapolate the experimental data. Selected for study were the following flames: Methane-air; methane-air plus KHCO , KNO3, K C204, KBr, Al203 or Monnex; methane-coal dust-air; coal dust-air with size, volatiles content, and concentration as variables, and coal dust-air plus KHCO3, KN03, KBr, NaCl or CaC03.

Jan 1, 1978

FOR many years past it has been the practice at the Bairnsdale School of Mines to treat any parcels of auriferous concentrates sent in from the surrounding district by roasting them in a handworked reverberatory, and then chlorinating or cyaniding the product. According to Donald CIark, who has done a large amount of work on these ores, the results obtained were fairly satisfactory extractions of over 90 per cent being claimed. With some modifications, the method has been very generally adopted, not only in Gippsland but throughout Victoria. It is, however, difficult to get exact information as to the extractions actually obtained, and unfortunately no records of working results have been kept at the Bairnsdale School of Mines.Having treated several lots of ore by this method during 1907 and 1908 with unsatisfactory results, the writers thought it desirable to make a detailed investigation on some particular ore, both in the laboratory and on a working scale. The ore selectedwas a parcel of low-grade concentrates from Stirling, a small mining field situated about forty miles to the east of Bairnsdale. This ore was chosen chiefly on account of the heavy and inexplicable volatilization loss which took place even on roasting with the greatest care; the loss amounting to between 10 and 15 per cent. In the experiments here related, three main objects were kept in view:-1. To determine with what mineral 01' minerals the gold and silver were associated...

Jan 1, 1909

By Romano J. Micciche

One of the largest scale uses of a multiple, high-strength steel bar tiedown system is described. Tiedowns were installed to resist hydrostatic uplift forces acting on a section of the Interstate Highway Route I-90 southern approach roadway to the Third Harbor Tunnel, in Boston, Massachusetts. Site specific information is discussed regarding design, testing, and installation of Tiedowns. Conclusions are presented regarding the overall performance of this system and the application of this type of tiedown system on future projects.

Jan 1, 1994

By José Porras

El presente trabajo señala el proceso de optimización en la mina a través del área de Tecnología de la Información, superintendencias y las áreas directas de las operaciones. En ese sentido, durante el diagnóstico de todos lo procesos levantados como geología, planeamiento mina, operaciones mina, mantenimiento, logística, control de gastos, se determinó mejorar las oportunidades que generen valor, como las oportunidades de control y reducción de costos, gastos, y su relación con los resultados obtenidos en su ejercicio.

Sep 9, 2007

By R. R. Tatiya

Data obtained from a copper mine were used in a comparative study of the reserve estimates generated by applying geostatistical methods to surface borehole data, underground core drilling results and assay values from chip sampling. Global estimation of the deposit performed by kriging of the low-density sampling data from the surface boreholes did not provide reliable results, but could identify the potentially mineralised zones. The reserve generated from core drilling results correlated well with that estimated from chip sample data and with that estimated by the conventional methods used at the mine. A satisfactory reserve evaluation could, therefore, be obtained by kriging of the data from the underground core drilling alone, provided that a systematic sampling procedure was adopted. Estimates based on chip sampling information could be used as a check, which could avoid the current practice of chip sampling of most of the mine workings. The aim should be to develop a semi-variogram for the deposit, which could be used to estimate the reserves by kriging

Jun 19, 1905

By David C. Lager

While not a new construction technique "top/down" construction is seeing increased use in high rise building construction. Using diaphragm wall, drilled shaft and mining construction techniques, top/down construction enables construction of both the below grade basements and high rise structure simultaneously. To date the top/down method has been used on at least four major building projects in the United States. This paper will review the economic, engineering, construction and schedule issues associated with top/down technology on two projects -Olympia Centre, Chicago, and One Westwood, Los Angeles. Top/Down construction is currently under consideration on several additional projects in the United States.

Jan 1, 1987

By A. G. Starliper

The Bureau of Mines made laboratory investigations to determine the feasibility of utilizing fine tungsten wires to reinforce a number of nonferrous metals and alloys and a superalloy, S-8l6. The composites of tungsten filament and metals were chosen to attain elevated temperature strength and corrosion resistance. Oriented clean or precoated tungsten wires were incorporated with the other metals by extrusion, swaging, and infiltration casting. Although widely varying characteristics were found in the composites, none were considered satisfactory for high-temperature use, chiefly because of reactions between the matrix metal-tungsten surface. Diffusion, solution, and chemical reactions between matrix and tungsten wires were sufficiently slow for some combinations, such as 15 v/o 8-816, to exhibit increased high-temperature strength for a limited time. A few metals failed to wet or bond to the tungsten surfaces, while a few responded after precoating with a third metal.

Jan 1, 1968

By S. E. Chetlin

In the mid-1970?s, the market value of tangible assets of S&P 500 companies far outstripped the value of intangible assets, including intellectual property (e.g., 83% tangible assets v. 17% intangible assets).1 By 2005, the picture was quite different. By that time and continuing to 2010, S&P 500 companies? market value of intangibles was about 80%, with tangible assets accounting for only 16% of market value.2 This swing highlights the importance in today?s world of understanding intellectual property rights and varying strategies and options for protecting them. This paper discusses intellectual property rights particularly patents and trade secrets, specifically: 1) types of intellectual property; 2) choosing the mode of intellectual property protection; 3) obtaining patent protection; and 4) using patents as a sword versus a shield.

Jan 1, 2012

This paper describes certain analytical methods used at the Rosepery Mine and Treatment Plant of the Electrolytic Zinc Co. of Australasia Ltd., which are not generally in use and may therefore be of more interest than a description of the normal routine methods which are used in most of the mining assay laboratories of the Commonwealth, and which have been published previously.The ore mined and treated at Rosebery is of a complex nature and demands closer control in the concentrating plant than is necessary on some other similar mining fields.It is necessary for the mill shift supervisors to keep constant control on the grade of lead and zinc concentrates produced on their respective shifts, and further, it is essential to maintain an economic compromise between grade of concentrates and the recovery of the particular concent:t:ate. This necessitates a more frequent check on concentrate grade tp.an is provided by the daily assays carried, out by the assay office. Rather than employ trained ,assayers on shift work, "quick methods" of analysis, which could be carried out by the operators, 'were adopted.'In such methods, it is desirable that the necessary manipulation should be reduced to the following:-a. Taking the sample, drying and mixing.b. Weighing the necessary amount of sample-for assay.c. Adding the reagents for use in the assay without change of beakers.d. Titration and calculation.Such a contraction of, the normal technique would be impracticable for many determinations, but in the case of lead...

Jan 1, 1949

By J. Konnerup-Madsen, T. Unlu, H. Stendal

Paper presented at the conference Economic geology in Europe and beyond II, models for mineral deposits in sedimentary basins, held in Keyworth, UK, 13-14 April 1994. The region includes the Deveci siderite/goethite deposit and the Hasancelebi, Karakuz and Kuluncak magnetite/goethite deposits; Deveci is the only mine in operation. The area consists of a serpentine-gabbro complex overlain by a volcano-sedimentary sequence hosting the iron ores. At least three generations of hydrothermal alteration have affected all rock types except the latest trachytic dykes. The Deveci deposits occur in a pyroclastic volcano-sedimentary sequence with shales and carbonates equivalent to the main mafic sequence, whereas the other three deposits formed contemporaneously with the intrusion of trachytic dykes. The deposits are of the volcanic-exhalative type, with syngenetic siderite in pillow lavas or stratiform layers the primary and main Fe-bearing mineral. In the west hydrothermal alteration has replaced siderite in pillow lavas with magnetite or has remobilised sideritic iron into magnetite veins

Apr 1, 1995

By M. A. T. Cocquerel, M. G. Burcher, J. G. Eacott

"This paper is based on work carried out to examine the feasibility of increasing the smelting rate of two oil-fired calcine-charged reverberatory furnaces . Various constraints prevented physical enlargement of the furnaces and so allention turned to the use of preheated combustion air or oxygen enrichment to bring about the required increase in production. As a basis for further calculation, a furnace heat balance is determined using the smelting metallurgy and combustion data for the current operation. Various other operational data are tabulated and compared with similar data from other operating copper smelters.New heat balances are derived for various levels of combustion air preheat at the current smelting rate, and the effects of air preheat on oil consumption, combustion air and waste gas volumes are tabulated. These data are used to demonstrate the level of increased throughput which would be obtained before constraints in existing gas handling equipment are encountered.A similar exercise for oxygen enrichment is set out, with oil consumption, combustion air and waste gas volumes at various enrichment levels tabulated for the current smelting rate. These data are in turn used to demon strate the smelting rate which would be achieved at a practical level of enrichment before waste heat boiler and gas handling constraints are encountered.The energy implications for both cases are summarized."

Jan 1, 1980

By James E. Aplin

Previous studies have shown that fracturing of roof strata precedes ultimate failure, and that the fracture development causes an accompanying increase in the apparent resistivity of the strata. Using this principal, a microprocessor controlled resistivity roof fall warning system (RRFWS) was developed that automatically sequences through and records up to 32 electrodes that may serve as either voltage or current electrodes. This capability permits increased coverage with a minimal number of required electrodes. The data is stored in a nonvolatile memory and on an optional printout, making the system nonsusceptible to loss of mine-power. To further save battery power, the system's electronics shut down between readings, except for a carbon molybdenum steel real-time clock. At a preprogramed interval, the RRFWS reactivates and repeats the sequence. If the absolute change or the rate of change of resistivity exceeds a predetermined limit the system is capable of sounding an alarm. In addition to the monitor, a stainless steel mod led split-set electrode was also developed that permits long-term corrosion-free contact.

Jan 1, 1983

By P. R. A. Andrews

Areas of bubble contact were delineated for topaz and tourmaline in the presence of chloride, fluoride, sulfate, phosphate, oxalate, and citrate ions using dodecylamine hydrochloride collector. The limits of pH and the minimum collector concentration were established using the bubble pick-up technique. Bubble contact did not occur below the p.z.c. (point of zero charge), estimated to be 5.6 for topaz and 6.6 for tourmaline, in the presence of chloride ion. Flotation below the p.z.c. was, however, extended by citrate, oxalate, phosphate, sulfate, and fluoride ions. Oxalate, citrate, and fluoride ions displayed the greatest pH range of activation, followed by phosphate and sulfate ions. Chloride ion acted as an indifferent electrolyte. Topaz was selectively activated with respect to tourmaline by fluoride and phosphate ions. Topaz was activated by fluoride ion between pH 2.4 and 5.6. Tourmaline flotation in this pH range was virtually insignificant. Topaz was activated by phosphate ion between pH 4.9 and 7.4. Tourmaline flotation in this pH range was only partial. Activation appeared to be strongest when anionic protonated species were in maximum concentration. Strong activation also corresponded to very stable metal ion species thought to be formed on the surface of each mineral.

Jan 1, 1991

By Linda Gaines

Use of vehicles with electric drive, which could reduce our oil dependence, will depend on lithium-ion batteries. But is there enough lithium? Will we need to import it from a new cartel? Are there other materials with supply constraints? We project the maximum demand for lithium and other materials if electric-drive vehicles expanded their market share rapidly, estimating material demand per vehicle for four battery chemistries. Total demand for the United States is based on market shares from an Argonne scenario that reflects high demand for electric-drive vehicles, and total demand for the rest of the world is based on a similar International Energy Agency scenario. Total material demand is then compared to estimates of production and reserves, and the quantity that could be recovered by recycling, to evaluate the adequacy of supply. We also identify producing countries to examine potential dependencies on unstable regions or future cartels.

Jan 1, 2010

By Kot F. v. Unrug

The present combination of coal market prices and reserves, situated in the Central Appalachian Coal Field, is such that mining of smaller coal reserve blocks has become economically attractive. In above drainage deposits, and particularly under mountain ridges, overburden depth can be changing within a wide range. Mines operating in these deposits are usually developing mains along the center of the ridge, with panels projecting from the mains towards the outcrop. Due to changing topography, proximity of the outcrop, and related cover depth, the panels have various lengths. In this reported case study, a mine in Pike County, Kentucky, along the Kentucky ?West Virginia border, difficult ground conditions were encountered, during the development of the mains, under shallow cover, along a narrow mountain ridge. An area having unusual density of vertical joints was encountered. Mining operations were suspended because of roof stability concerns. The ground conditions were studied, analyzed, and control measures proposed to ensure safe passage through the difficult roof area of the mine. The advancement of the mains, through this area of challenging ground conditions, was successfully completed. In this paper, ground conditions are described, with an explanation of the geologic process contributing to their formation. It is interesting to note that similar locations were predicted by the authors, to be encountered in the same mine, based upon the experience gathered from studying conditions of the case described within this paper. When approaching the predicted locations, stability problems appeared to be even more challenging than those encountered previously. Due to changes in the coal market, mine management chose to move the affected mining section to another area of the mine having better coal quality. The advancement of the mains, through the difficult ground conditions, was temporarily postponed. Based upon the analysis of a probable kinematical mechanism of blocks in the mine roof, ground control measures were proposed. The actual application of these principles proved to be appropriate, ensuring safe passage through the difficult ground conditions encountered in the mine.

Jan 1, 2006

By V. Prostakova, M. Shevchenko

The copper smelting gas / slag / matte / metal / solids system with the Cu-Fe-Ca-Si-O-S major elements has been a long-term focus of the present overall research program using integrated experimental and modelling approach for the phase equilibria characterisation and development of a thermodynamic database. A systematic investigation of phase equilibria of slag systems in equilibrium with Cu metal is providing information for systems where copper coexists in slag with lead, zinc, and aluminium oxides as major components. Experimental studies involve high-temperature equilibration of synthetic samples; rapid quenching; and measurement of the compositions of equilibrium phases using electron probe X-ray microanalysis (EPMA). Particularly important feature of the present study a wide range of temperatures (660-1670°C) being characterised that reveals major inconsistencies in the existing thermodynamic description of the multicomponent system, and allows to establish the thermodynamic properties from phase equilibria in a reliable way. FactSage-based thermodynamic modelling is integrated with experimental research. Initial thermodynamic assessments are used to identify priorities for experiments, planned to provide specific data for thermodynamic optimisation. Significant improvement in the accuracy of the phase equilibria description is achieved, in particular in the PbO-Cu2O-SiO2, ZnO-Cu2O-SiO2, and Cu2O-CaO- Al2O3 systems in equilibrium with metallic Cu. INTRODUCTION Slags high in lead and copper are generated in primary metal production in the smelting of lead sulfide concentrates and in pyrometallurgical metal recycling systems. The compositions of these slags are varied due to increased fraction of recycled materials in the feed as well as introduction of previously unused chemical elements to modern technology. Therefore, their processing becomes chemically more complex; in that way they contain a large number of different metals. These slags form complex non-ideal solutions (with possible formation of several immiscible slags) that can coexist with stoichiometric solids, solid solutions, mattes and molten metal depending on the bulk composition and process conditions. Predicting the outcomes of smelting and refining processes is becoming increasingly difficult. To assist in the optimisation of these metallurgical processing operations, a comprehensive research program is underway to develop accurate thermodynamic databases for these non-ferrous process systems.

Jan 1, 2019

By J. K. Whyatt, W. P. Blake, T. J. Williams

A study at the Idaho mine revealed that, despite the apparent randomness of seismic events, common characteristics defined five recurring types. These characteristics included the geological structure that slipped, the first-motion pattern and the location and intensity of damage. Many large events caused little or no damage, and where it did occur it was concentrated at intersections between slipping structures and mine openings. Of 39 events between 1989 and 1994 with local magnitudes of 2.5 or more, 10 were caused by slip on bedding planes in the southern limb of the mine, 6 occurred near the vein along a set of near-vertical faults that form the central shear zone, 8 were strike-slip events on the Southern Control Fault, 4 were by slip on the vein itself and 10 involved strike-slip and/or dip-slip movement along the North Control Fault. Strategies for control of mining-induced seismicity need to consider all five types of event, lest a strategy to reduce one type increases others

Jun 19, 1905

By William E. Souder

The behavioral accident simulator (BAS) is a computer program that can be used to simulate accident situations. It demonstrates how the potential to have an accident grows or diminishes as a result of changes in various environmental, organizational, and behavioral factors. It calculates the number of fatalities that may result from various conditions and graphically displays these data. The BAS is useful for studying systems of accident causes, for demonstrating the various ways to diminish fatalities, and for training employees. This Bureau of Mines report provides the detailed instructions needed to use the BAS.

Jan 1, 1988

By M. van Biljon

The possible closure and subsequent flooding of South Deep Gold Mine?s neighbouring Randfontein Estates Limited No. 4 Shaft (REL 4) necessitated the construction of five concrete plugs in the connecting tunnels to prevent the ingress of groundwater into REL4 from flooding South Deep mine. Several technical investigations had been carried out before and during construction of the plugs in order to reduce the probability of groundwater flow through the boundary pillar between the two mines or through the rock mass immediately around the plugs. This paper describes the geological, hydrogeological and stability investigations carried out to evaluate the structural competence of the boundary pillar.

Jan 1, 2006