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By P. O. Metz, E. L. Wiehe, J. S. Foster

BASED on their analyses of growth kinetics, ibbs' and Harris et al.' have recently proposed that the rate of subcritical graphitization of steel is controlled by the rate of diffusion of carbon in ferrite. illert has concluded that this is the rate controlling growth mechanism when the growing graphite particles are relatively large. Harris et al.' also propose that the matrix surrounding a growing graphite particle is plastically deformed to make room for the growing particle. If this plastic deformation does occur, then preferred recrystallization may be observed around the larger particles. If diffusion of carbon in ferrite is rate controlling, then a graphite particle growing in a matrix of, say, tempered martensite or pearlite, should be surrounded by a carbide depleted zone. Thus, the simple metallographic experiments reported here are sufficient to determine whether or not diffusion of carbon in ferrite is the dominant mechanism for the growth of graphite in steel. The present investigation considers graphitization in five alloys. The compositions are given in Table I. Graphitization was carried out at three temperatures: 900°K (627"C), 950°K (677"C), and 990°K ('717°C). Samples were reacted in both the martensitic and the pearlitic initial conditions. In the hypoeutectoid steels, Sets 7 and 8, .and in the hypereutectoid Fe-C binary, Set 6, graphitization was very limited after 1000 hr at temperature. In these samples graphite particles observed were less than 10 p in diam. In the hypereutectoid commercial steels, Sets 1 and 3, large graphite particles (100 p) did not appear until after 250 hr at temperature. The limited number of graphite particles observed and the range of sizes obtained prohibited measurement of growth rates in this investigation. However, in all samples showing graphitization, neithe a carbide depleted zone nor recrystallization was observed. illert's model predicts that diffusion of carbon in ferrite should become dominant for graphite particles larger than about 300 p in diam. The largest graphite particle observed in this investigation was approximately 450 p in diam. No evidence of carbide depletion was noted. Fig. 1 shows a typical graphite particle. This nodule is from an initially pearlitic sample from Set 3 after

Jan 1, 1970

By N. Kumar Kittusamy

The purpose of this study was to assess the adequacy of the cab design and to determine the percentage of musculoskeletal symptoms among workers. A questionnaire was designed to assess demographics, work information, job history, and musculoskeletal symptoms in operators of heavy construction equipment. Information concerning equipment included design of the seat/chair, levers, pedals, bothersome vibration, quality of egress from the equipment, proper preventative maintenance and repairs, and age of the equipment. The body regions that were evaluated included the neck, middle/upper back, low-back, shoulder/upper-arm, elbow/forearm, wrist/hand, hip, knee, and ankle/foot. One hundred and eighty nine operators completed the questionnaire. The results indicate that these workers are at risk for developing musculoskeletal disorders, the need to perform a larger survey to further substantiate the outcome, and the need to quantify risk factors (i.e., whole-body vibration and static sitting postures).

Jan 1, 2003

By G. Aggistalis, N. Kazilis, C. Rawlings, N. Rachaniotis, S. Raptopoulos, M. Knights, R. Game

The Egnatia Odos (Odos meaning road) is one of Greece’s largest ever highway construction projects and one of Europe’s most important. The Highway will assist in the connection of the Greek Ionian/Adriatic Coast with Turkey and the Black Sea reviving an historic Roman alignment “Via Egnatia” connecting Rome to Constantinople (now Istanbul). There are 74 twin tunnels (60 bored and 14 cut-and-cover) with lengths ranging from 160 m (175 yd) to 4,600 m (5,031 yd) and 100 m (109 yd) to 270 m (295 yd),respectively. The complex geology and resulting physical geography have had a major influence on both the design and construction of these tunnels. This paper describes the management, design and construction challenges of these numerous tunnels.

Jan 1, 2005

By G. Taylor

A 21st Century worker is one who works less with his physical power and more with mental ability. Such a worker is more skilled than a labourer and is consequently rewarded accordingly. A21st Century supervisor is one who ensures that workers are constantly supported so that they can maximize safety and productivity. A 21st Century manager is one who constantly searches for ways to maximize returns for the various stakeholders. Given the well-known constraints in narrow reef mining, all of the above is meaningless unless a mining method is found which provides conditions which support the 21st Century initiatives. [ ] The identified mining method is a continuous non-explosive stope breaking system using rocksplitter technology. Rocksplitting is defined as: The fragmentation of rock through high energy pulse wave transmission in a fluid-filled hole or hydro fracturing. Shotholes are effectively filled with a water-based geland 30 grams of explosive after which the hole is closed off with a ?rocksplitting gun?.

Jan 1, 2000

Research on the Differential Flotation of Iso-Floatable Lead-Zinc Sulfide Ore

Sep 13, 2010

Quartz, adularia and clay minerals from low-sulfidation epithermal veins at Hishikari were analyzed for their oxygen and hydrogen stable isotope compositions to establish the source of paleohydrothermal waters. Positive correlation between Au-Ag and adularia: quartz ratio, the presence of quartz pseudomorphs of bladed calcite, and Au-bearing smectite and vermiculite is indicative, but not definitive, evidence for the control of boiling on ore mineralization. Oxygen isotope equilibrium temperatures between quartz and adularia are about 220¦C and average homogenization temperatures of fluid inclusions vary between 190 to 210¦C. The calculated d18OH2O and dDH2O values (from quartz, adularia and early smectite) are consistent with paleohydrothermal fluids that were a mixture of magmatic and meteoric waters, or alternatively, the values could derive from heated meteoric water which had undergone isotope exchange during circulation through basement rock. Overall, d18Oqtz values in veins increase toward the north, most likely reflecting palaeo-fluid flow (source).

Jan 1, 2001

By V. F. Parry

The object of this report is to present certain pertinent data on the physical and chemical properties of South Arcot lignite and to present the results of several special tests to show how the raw lignite can be upgraded to superior fuels for certain special uses. The Bureau of Mines Branch of Coal Technology laboratories at Denver have advocated the drying and carbonization of all low-rank fuels for special uses and have introduced and developed new techniques for upgrading and refining noncoking coals. Application of these techniques to the South Arcot lignites was the object of the investigation, and this report presents significant data necessary for planning a fuel program based on utilization of dried and carbonized dusts. In general, the South Arcot lignite is similar in chemical properties to the high-moisture lignites found in the United States and has some physical properties similar to Australian brown coals. The samples submitted for test had lost moisture before delivery to the laboratory, and it has been necessary to estimate the analysis of the lignite in place in the mine. Various observations made in India by qualified technicians indicate that the bed moisture content of the entire seam is in the range of 54 to 56 percent. For estimating purposes in this report, the bed moisture content has been taken as 56 percent and the ash content of the fresh coal as 2.5 percent. The average analysis estimated for the as-mined lignite is: [Moisture percent 56.0 Volatile matter do.22.0 Fixed carbon do.19.5 Ash do.2.5 Heating value B.t.u. per lb. 4,890]

Jan 1, 1957

Control of flotation processes is mostly managed by plant operators, who assess the performance of the plant based on their own experience and other heuristic rules. These rules tend to be subjective or ill-defined, since most of them are concerned with the structure of the flotation froth, such as colour, bubble size and shape distributions, froth mobility and froth stability. These phenomena are very difficult to quantify objectively, and inexperience on the part of the operators, human error, etc., can lead to significant inefficiencies in plant operation. In this paper the development of a fuzzy system to support the control decisions of plant operators is described, which leads to significantly smoother control action and more stable plant operation than could be obtained with crisp sets of rules or manual control strategies. Keywords: flotation, fuzzy logic, image analysis, genetic algorithms, rule induction

Jan 1, 2000

By Terry R. Neumann

During 1983, U.S. Bureau of Mines personnel examined mines, prospects, and mineralized zones to evaluate the mineral resources and potential of the Funeral Mountains Wilderness Study Area (WSA), Inyo County, California. Eleven mineral properties and two mineralized zones were examined during this study. Of these, six are within the study area and seven adjacent. There are no active mines, in the WSA, nor is there evidence of past production from any claim within the study area. The WSA contains no identified mineral resources. However, occurrences of bentonite, zeolites, and strontium were found in the area. There is little likelihood for resource development of any occurrence in the WSA. The area, in the Basin and Range Physiographic Province, is dominated by a Paleozoic marine sequence. Segments of Tertiary continental fluviolacustrine sediments, including volcaniclastic rocks, abut and overlie the Paleozoic rocks in fault controlled basin areas. Significant concentrations of bentonitic clay and zeolites occur as alteration products in Tertiary tuffaceous sedimentary rocks. However, they are generally low-grade, thin, and discontinuous, precluding commercial development. Limestone, quartzite, and sand and gravel in the area are suitable for many types of construction uses, but similar deposits outside the WSA are closer to markets. No energy resources have been identified in the WSA.

Jan 1, 1984

By G. W. Birge

Carbonizing properties of the principal coal beds of Perry County, Ky., are described in this Bureau of Mines report. Seven samples, representing the Hindman, Flag, Haddix, and Fire Clay beds, were carbonized by the Bureau of Mines-American Gas Association (BM-AGA) method, and yields of products and physical properties of cokes were determined. Carbonizing properties of blends of Flag and Fire Clay coals, with 20 and 30 percent Pocahontas No. 3 low-volatile coal from McDowell County, W. Va., also were determined. Expanding properties of the Flag and Fire Clay coals and their blends were determined in the Bureau of Mines sole-heated oven. The Perry County coals tested are high-volatile A bituminous in rank and, with the exception of the Hindman-bed sample, which contained excessive sulfur, were chemically suitable for metallurgical use. The three coals tested in the sole-heated oven contracted less than normal for Appalachian coals of similar rank, Blending the Fire Clay and Flag coals with 20 or 30 percent low-volatile coal increased coke strength appreciably but increased the expansion beyond normal limits for industrial blends.

Jan 1, 1962

By J. H. Potgieter

This paper describes two cases of corrosion that occurred in dry-process, rotary, cement-clinker kilns. In the case of the kiln with five pre-heater stages, the attack occurred primarily from sulphates that probably originated in the raw feed and fuel being used in the plant and that penetrated the refractory lining. The corrosion was similar to ash-deposit corrosion often observed in steam boilers. In the second case the plant consisted of a long dry kiln with a single pre-heater fitted to the feed-end. In this case the corrosion could be ascribed to alkali chloride penetration through the refractory-brick lining and subsequent hot corrosion of the kiln shell.

Jan 1, 2004

By P. D. Lohn

The objective of this program was to develop nozzle designs to maximize the effective cutting length of a water jet. The results of the theoretical program directly support the Bureau of Mines Borehole Mining Program and their experimental program to improve the rock cutting capability of water jets. The borehole geometry requires turning the flow by 90 degrees and accelerating through the nozzle within a restricted length. Several suggestions for turning the flow are offered. The borehole space limitations constrain nozzle length, to the extent that a standard 13-degree tapered nozzle (6-1/2 degrees half angle) is too long to fit in the borehole, at production flow conditions. The design technique developed is computationally economical and enables examination of a large number of shapes and flow conditions. The nozzle design is based on design criteria of minimization of boundary layer thickness at the nozzle exit and minimization of the possibility of separation and cavitation. Six flow conditions, including pressures to 4500 psi and flow rates to 400 gpm, were examined, Best shapes were determined for all flow conditions. The best shape for a borehole reining application consists of an initial 4th degree polynominal (quartic) at the entrance followed by a straight section with a twenty degree (half-angle) taper at the exit.

Jan 1, 1976

By Paul C. Hyndman

The U.S. Bureau of Mines investigations of the three subunits (fig. 1) of the Homestead RARE II area (No. 6291) revealed no evidence of mining activity or mineral deposits in the area. The Iron Dyke Mine, 3 mi (5 km) outside the study area produced ore between 1916 and early 1982 from a volcanogenic massive sulfide deposit in the Permian volcaniclastic Hunsaker Creek Formation of the Seven Devils Group. The Hunsaker Creek Formation does not crop out in the RARE II area, but extends into the area beneath Miocene flows of Columbia River Basalt. The abundant basalt in the area could be used as aggregate or dimension stone, but equivalent deposits exist closer to markets. INTRODUCTION Location and Access The Homestead RARE II area (fig. 1) encompasses 6260 net acres (253U ha), in three units, of the Wallowa-Whitman National Forest in Baker and Wallowa Counties, Oregon. Two small units of 160 and 300 acres (65 and 120 ha) are 5 mi (8 km) north and east of the main study area. Homestead, Oregon, on the Snake River, is about 3 mi (4 km) south of the two small areas, and about 3 mi (4 km) northeast of the main study area. Peripheral access is provided by State Highway 86, U.S. Forest Service Road 39, and ancillary roads and trails.

Jan 1, 1983

By Roberto J. Guardia, Ted Lewtas, Peter Rasmussen, Klaus Winkler

As part of the Lake Fort Smith Water Supply Dam Enlargement project, located in northwest Arkansas, microtunneling methods were used to install two side-by-side,1.53m (60-in) inside-diameter steel pipes between the intake structure shaft and the lake. The 46.6 m- (153 ft-) and 41.7 m- (137 ft-) long tunnels were excavated in Pennsylvanian sedimentary bedrock ranging from coarse sandstone to siltstone and shale-like claystone. The intake tunnels were constructed 18.3 m (60 ft) below lake level from the dry shaft. Special installation methods and procedures described herein were used to complete the lake taps. Installation difficulties that caused minor delays are also reviewed. After the excavation of the Intake shaft was completed, the two lake taps were installed in approximately ten weeks with the same microtunneling machine.

Jan 1, 2005

By R Lethlean

The mining industry in its drive to optimise equipment use and minimise cost simply to remain profitable in an uncertain commodity market needs to develop a greater understanding of equipment capabilities and cost. The factors influencing mobile equipment fleet cost and performance commence at the time of mine planning and continue to exert an influence over the life of the mine. These factors must be understood at the early stages of any operationÆs planning process as they continue to impact both positively and negatively on fleet performance and operating cost throughout the life of the mine. The key factors examined in this paper include: grades; rolling resistance; fragmentation and truck loading.

Jan 1, 1998

By Steven W. Schmauch

A mineral survey by the U.S. Bureau of Mines and U.S. Geological Survey indicate the Blanco Mountain RARE II area has low potential. Lode deposits consist of small, mineralized quartz or quartz-gossan veins. The veins are sparse and widely separated and lead, silver and gold content is restricted in amount and concentration. No gold or other potentially economic minerals were found in a placer deposit. There is no evidence of industrial mineral, geothermal, or energy resource potential in the study area. INTRODUCTION A mineral resource survey of the Blanco Mountain RARE II area (No. 5059), Inyo and Mono Counties, California was conducted in July 1981. This report summarizes the results and interpretations of the Bureau of Mines investigation.

Jan 1, 1982

By J Zhou, D M. Hunter, S M. Iveson, K P. Galvin

The REFLUX Classifier is used to perform particle separations on the basis of density utilising a set of parallel inclined channels positioned above a vertical fluidised section. In continuous mode, feed enters part way up the vertical section, while fluidisation water is introduced from below. Lower density particles are conveyed upwards and collected in an overflow stream, while high density particles segregate onto the inclined surfaces, settle to the base of the system and empty via an underflow stream. Pressure transducers are used to measure the suspension density in the vertical section. This suspension density is maintained by a pneumatically controlled underflow valve to maintain a target suspension density or ‘set point’.Previously, Galvin et al (2010) demonstrated the significant improvement achieved via a new laminar-shear separation mechanism, achieved by utilising closely spaced inclined channels in the REFLUX Classifier. For the separation of low-density coal particles from mineral matter, a channel spacing of 6 mm proved effective; however, for the separation of gangue minerals from much higher density minerals such as iron ore, the shear-induced lift needs to be even higher. In this paper, we examine the influence of two different channel widths on the continuous processing of an industrial iron ore feed in the REFLUX Classifier. It was found that when moving from 6.0 mm to 3.0 mm channels, the ability of the system to reject coarser gangue material and retain finer high density material across a particle size range from 0.125 to 1.0 mm was increased, resulting in a higher grade product.CITATION:Hunter, D M, Zhou, J, Iveson, S M and Galvin, K P, 2017. Influence of shear rate on separation of iron ore fines using the REFLUXTM Classifier, in Proceedings Iron Ore 2017, pp 205–210 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Richard Addison

Introduction A staccato beat rings out across the Australian bush. The stamps are at work, slowly pulverizing gold-bearing ore for a patient, grizzled prospector. This is the State Battery near Marvel Loch, a tiny 22.6-t/d (25-stpd) capacity gold plant operated by the Western Australia government. It is one of many such plants located in remote corners of Western Australia and the Northern Territory. They are miniature custom mills operated for the benefit of prospectors and small mine operators. These state batteries are so called because they are operated by state governments and because the principal item of machinery in the plants are stamp batteries. They are fascinating anachronisms - throwbacks to times past, a century ago, to the hard and heady existence of gold rush days. Marvel Loch plant Typical of these operations, and perhaps a trifle more sophisticated than most, is the plant near Marvel Loch, a small center for mining and farming about 400 km (250 miles) due east of Perth. Marvel Loch. The name evokes visions of a pristine lake set in a cool, green, misty glen of the Scottish highlands. Actually, it is probably a hot, dry salt pan somewhere nearby. Just where the "loch" is difficult to discern. There is no sign of it on the map.

Jan 7, 1986

By C. Maree

Paper written on project work carried out in partial fulfilment of B. Eng (Chem. Eng.) This paper describes the development and use of a process simulator to optimize gypsum recovery at Afmine, a small plant near Yzerfontein on the South African West Coast. The simulator consisted of models of the major plant equipment, viz. hydrocyclones, surge bins, settling tanks, a primary sieve and a dewatering screen. Experimental data suggested that the equipment could be modelled satisfactorily from data published in the open literature. Simulation studies have indicated that gypsum losses on the plant could be reduced substantially by means of some relatively minor modifications to the plant layout. Moreover, sensitivity analyses of the plant have indicated that optimization of the settling tanks should receive priority over the other process units.

Jan 1, 2005

By S. Ndlovu

To investigate the influence of orientation of crystal lattice on the bacterial leaching of pyrite crystals, single crystals of 100, 111 and110 plane orientations were used for the study. Experiments were carried out in the presence of a Thiobacillus ferrooxidans culture. The different corrosion patterns observed on the surfaces of the bioleached samples suggests a variation in cell-surface interaction from one crystal plane to the other. The surface corrosion patterns generally reflected the influence of the symmetrical arrangement of the atomic planes in the lattice on which they formed. The results indicate that the surface properties of mineral sulphides may control the evolution of corrosion patterns and consequently the initial oxidation process in acid bacterial leaching.

Jan 1, 2004