Search Documents

By G. T. Homce

Most electric motor predictive maintenance methods have drawbacks that limit their effectiveness in the mining environment. The U.S. Bureau of Mines is developing an alternative approach to detect winding insulation breakdown in advance of complete motor failure. In order to evaluate the analysis algorithms necessary for this approach, the USBM has designed and installed a system to monitor 120 electric motors in a coal preparation plant. The computer-based experimental system continuously gathers, stores, and analyzes electrical parameters for each motor. The results are then correlated to data from conventional motor-maintenance methods and in-service failures to determine if the analysis algorithms can detect signs of insulation deterioration and impending failure. This paper describes system design and implementation. At this writing, however, installation is still underway, and field data analysis results are not yet available.

Jan 1, 1994

By J. B. Gayle

Both immediate and long-range economic factors are associated with blending anthrafines to produce metallurgical cokes, and they warrant careful consideration of the technology of carbonization of blends containing significant proportions of inert substances in general and anthrafines in particular. This situation has resulted in numerous publications dealing with various phases of the overall problem, particular emphasis being placed on the effects of inert substances on the yields and quality of cokes produced. Because relatively little attention has been given to the expansion behavior of coal blends containing inert substances, an investigation of this problem was undertaken using the Bureau of Mines sole-heated oven. Since experiments in the sole-heated oven do not measure wall pressures directly, a new method of interpretation of sole-heated oven data, which permits estimates of wall pressures, has been proposed.

Jan 1, 1955

By Grégory Miette

The paper deals with a process that allows the recycling in a cupola of EAF dusts with 18 % Zn. It produces dusts with zinc grade higher than 50 - 55 % and commercial cast iron with less than 200 ppm Zn, 50 ppm Pb, 0.15 % S. The paper focuses mainly on lab tests made with the aim to develop an effective formulation of self reducing - melting pellets. With such a formulation, agglomerates develop a breaking load higher than 125 - 150 kg without any thermal treatment. Zinc and lead are volatilized in the cupola with yields higher than 95 % at 1200 OC, before any melting. Sulphur is transfemed into gas and slag. All these conditions allow to lower zinc, lead and sulphur grades below the cast iron specifications. Results of first bench scale tests performed at Fonderie Piret to validate the process will be presented.

Jan 1, 2002

By Takahiro Miki

In order to use metallurgical grade silicon (MG-Si) as a starting material for solar cell, phosphorus has to be removed from silicon because phosphorus is a n-type dopant. On the other hand, silicon, ferrosilicon, and silicomanganese are widely used as deoxidizers in steel refining processes. Since most of the phosphorus introduced during the deoxidation process is brought into final products, it is important -to lower the phosphorus content of these alloys. Hence, thermodynamics of phosphorus in such metals is important for the evaluation of dephosphorization processes. In the present study, thermodynamic properties of phosphorus in molten Si-P alloys at 1723- 1848K and those of Si-Fe-P and Si-Mn-P alloys at 1723K have been determined by equilibrating respective metals in a controlled phosphorus partial pressure. The results are expressed as follows.

Jan 1, 1998

By Mario Sanchez, Jose Palacios, Fernando Parada

Carbon steels have less than 0.02% copper and have low atmospheric corrosion resistance. The addition of at least 0.20 wt% Cu improves this property. Also, 0.8 wt% Cu in steel shows a hardening potential for developing high strength corrosion resistant steels. Copper slags containing 42–45% of iron, silica and minor amounts of copper were used for producing Fe–Cu alloys by reducing the oxides contained in the slag to obtain a Fe-0.84 wt% Cu alloy, which could be suitable as feeding material to manufacture a corrosion resistance steel, and also would be an alternative for minimizing the copper industry ’s environmental impact, and to introduce the application of the Circular Economy concept to the natural resources exploitation, especially in countries where their economy is strongly based in mining and metallurgical extraction.

Mar 1, 2018

By Xiaolong Lin, Jianhui Peng, Zhongping Zhu, Guanghui Li, Zhizhong Li, Zhiwei Peng, Tao Jiang

As the absorbing material composed of sole carbon is difficult to meet the comprehensive requirements of microwave applications, preparation of carbonaceous nanocomposite materials becomes an effective method to increase microwave absorption properties. In this study, a novel nanocomposite composed of Co–Ni ferrite and graphene was synthesized via a simple and rapid microwave hydrotherma method in just a few minutes It was demonstrated that the minimum microwave reflection loss of the composite of 3 mm thickness with a low filling ratio (20 wt%) reached −13.1 dB at 17.2 GHz with an effective absorption bandwidth of 3.1 GHz. The good performance of the composite was believed to be a result of high dielectric loss of graphene associated with a multi-dielectric relaxation process and magnetic loss of the ferrite mainly originated from natural ferromagnetic resonance.

Mar 1, 2018

By A. M. Gaudin

In the first place, let me thank you for inviting me to appear before you today to speak to you on "Mineral Industry Problems - Present and Future". It is a distinguished honor for me to have this opportunity, and I am highly appreciative of this distinction. The beautiful surroundings of Gatlinburg and the pleasantness of a summer occasion are a wonderful tonic for all of us, yet they should not blind us to the seriousness of our Industry's problems No doubt, because of my past appearances before members of the Society of Mining Engineers, at which I discussed wholly scientific topics, or research in the Applied Sciences, you may be expecting me to revert to these subjects. But I intend to venture in a field that is new to me, yet old to all of us, the field of Economics.

Jan 1, 1962

By J. M. Stuve

In this Bureau of Mines investigation, the low-temperature heat capacities of polycrystalline phases corresponding to the sulfide compounds CoSO?89' CoS1?33, and CoS2 were measured by adiabatic calorimetry within the nominal temperature range 5 to 300 K. The derived absolute entropies S298 were 10.36±O.02, 12.96±O.03, and 16.31±O.03 cal?mol-1?K-l, respectively, assuming third-law behavior. In addition, the standard enthalpy of formation 8Hf298 of CoSO?89 was determined by bromine solution calorimetry. The derived value of 8Hf298 was -50.63±2.1 kcal?mol-1, based on the 8Hf298 of Co0. This result is considerably more negative than previously published formation values based on high-temperature gas equilibrium studies.

Jan 1, 1985

By I. E. A. Aghachi

During static strain-aging of low carbon steel, when the material is pre-strained, the dislocation density increases. If totally or partially unloaded and aged for a prescribed time, interstitial solute atoms diffuse under the influence of the dislocation stress fields, thus tending to lock dislocations causing an increase in yield stress. If held for long periods at certain aging temperature, a decrease in yield stress (over-aging) is observed following the initial increase. This behaviour has been variously attributed to either recovery of cold worked dislocation structure and/or formation and coarsening of carbide precipitates. The present work demonstrates that, using a "process control" model for the competing processes of hardening and softening, dislocation recovery is responsible for over-aging of mild steel specimens under conditions tested during this investigation. Keywords: Strain-aging, Precipitation, Recovery

Jan 1, 2003

By X. Cao, M. Xiao, M. Jahazi

Magnesium alloys have low hardness, wear, erosion and corrosion resistance. The repair of service-damaged aerospace components made of magnesium alloys is an attractive solution in terms of time and cost saving. The feasibility of applying laser beam technology to repair ZE41A-T5 magnesium alloy sand castings in the machined surface conditions was studied using a continuous wave 4 kW Nd:YAG laser system. The influence of process parameters such as laser power, cladding speed, wire feed rate and defocusing distance on the shape, size and area of single cladding beads is discussed using a process optimization software. Sound single clad beads with good geometric characteristics were obtained using strictly controlled laser process parameters. The overall results indicate that laser surface cladding using filler wire has the potential for repairing aerospace components made of cast magnesium alloys.

Jan 1, 2006

By Perry G. Cotter

The borides of the transition metals in Groups IV and VI exhibit, in addition to a certain degree of hardness, considerable resistance to heat and oxidation. They have high melting points (1,850°-3,060° C.) and low coefftcients of thermal expansion and can be bonded with other materials and hot-pressed to desired shape (cermets). Suggested uses for the borides include use in rockets and jet engines, as thermocouple protection tubes, as containers for molten metals in die casting, as flame-plated coatings on less refractory compositions to prevent erosion by hot gases, and as control rods and neutron shielding material in nuclear engineering, The Federal Bureau of Mines investigation of zirconium diboride started in 1950 at the Boulder City Nev,, Metallurgy Research Laboratory, Its purpose was to reduce the cost of raw materials for the production of zirconium diboride.

Jan 1, 1961

By AIME AIME

BECAUSE of its unequalled skill, your country in- creased its production until, in 1913, it produced 40 per cent. of the world's consumption of coal, iron ore, and cast iron; 45 per cent. of the steel; and 60 per cent. of the copper. Your industrial effort, in a general manner and your mining effort in particular, has been tremendous. In the general economy of the world, you occupy an incomparable position of power and action. All your curves of production, mineralogical, metallurgical, financial, commercial, have taken terrific trigonometrical tangents and you will easily under- stand the sorry position of your competitors. I must, therefore, pay a tribute of homage arid admiration to you all who, each in his sphere, have been the artisans of such prosperity and my earnest wish is that you continue in this way.

Jan 1, 1920

By Suresh K. Bhatt

Although overall worker productivity for U.S. underground coal mines is available, productivity by mining method and seam thickness is not. Mining technology has gone through dramatic changes in the past decade, and the industry has experienced a lack of accurate productivity Figures addressing these changes. This information is of great interest in planning for future mining systems as thick and shallow coal seams currently being mined are depleted and exploitation of thinner, deeper, and better quality seams is considered to partially meet the requirements of the 1990 Clean Air Act Amendments. In a cooperative program, the U.S. Bureau of Mines obtained raw mine level production and related data from U.S. Energy Information Administration for 1989 and 1990 and performed the needed statistical analysis. Base criteria, parameters, and salient results of the mine productivity analysis are presented in this report.

Jan 1, 1994

By J. Y. Kim

Silver contained in zinc calcines undergoes several phase changes as it proceeds through the leaching circuit of a roast-leach-electrowin zinc plant. In the present study, the flotation response of silver from leach residues prepared under a variety of carefully controlled operating conditions in the pilot plant has been examined. Flotation of neutral leach residue is shown to be technically viable and to merit consideration for those plants without a high acid leach circuit, but having significant silver values in the feed. Residue leach conditions must be kept slightly acidic to promote the formation of Ag2S, (Ag, CU)2S and Ag2S rims on residual unroasted sphalerite, while simultaneously avoiding the hydrolysis of soluble iron which depresses silver recovery and grade. Factors to be considered during integration of a flotation process into an electrolytic zinc plant are discussed.

Jan 1, 1990

By G. R. Hopkins

The petroleum-refining industry established a. new record in fuel effieciency at refineries in 1936, when 597,000 B. t. u. of heat mere required to refine a barrel of crude oil, compared with an average of 615,000 B. t. u. in 1935 (see fig. 1). The principal factor in the 'indicated gain in fuel efficiency at refineries in 1936 was an increase in crude runs of 11 percent over 1935. A large part of the heat utilized at refineries is consumed elsewhere than under stills, or in ways quite independent of crude-oil distillation. In other words, as the operating ratio ( crude runs divided by capacity) for re- fineries increases toward tine maximum of 100 percent, the fuel requirements show progressively smaller increases and the average B. t. u. consumption per barrel of crude refined declines.

Jan 1, 1938

By N. Bakhshizadeh

In this investigation, the aging effect on creep behavior of A12024-10%SiC composite fabricated by powder metallurgy was studied. P/M bars were manufactured by hot powder extrusion method at 450°C with a ratio of 16 to 1. Creep specimens were over-aged at 187 ºC for 43 h. It was found that almost full density composite with relatively homogenous distribution of reinforcing particles throughout the aluminum alloy matrix could be attained by direct powder extrusion process. Creep tests were conducted at temperatures from 275 to 325°C under stresses from 25 to 60 MPa. The analysis of the creep mechanism determined that dislocation glide was the predominant mechanism of plastic deformation. The activation energy of the creep process was found to be higher than that of lattice self-diffusion in pure aluminum.

Jan 1, 2007

By Heinrich Oscar Hofman

IN THE death of Professor Hofman who was born on Aug. 13, 1852 and died on April 28, 1924, the world has lost a great metallurgist and a great author of metallurgical literature. Measured in time his life was not quite seventy-two years, but measured in work accomplished it was much longer than this. It is not surprising that Dr. Hofman became a great scholar for his father, Karl Hofman, was on the faculty of Heidelberg University, and his early days were spent in these surroundings. He studied in the University under such men as Kirchoff and Bunsen and often spoke of the intimate relations he had with them. Following his course at Heidelberg, he studied at the Clausthal Mining Academy where he graduated with honors, receiving the degrees of Mining Engineer and Metallurgical Engineer in 1877.

Jan 1, 1924

By M. D. Carter

The availability of environmentally acceptable and reliable energy sources is an important issue for Federal, State, and local planners. A cooperative program by the U.S. Geological Survey, State geological surveys, and the U.S. Bureau of Mines has developed a national GIS-based systematic effort to collect, analyze, and depict data characterizing the relationship between restrictions to mining and the potential development of the Nation's coal resources. Land use/environmental and technologic/geologic restrictions are identified within selected 1:24,000-scale, 130-to 150-sq-km 7.5-min quadrangles and applied as overlays to maps of coal-bed thickness, depth, and mined-out areas. Tonnages of original, mined and lost-in-mining, remaining, restricted, and available resources are calculated. Resultant data files are transferred to the Bureau of Mines for recoverability and cost analysis.

Jan 1, 1995

By Martin Herrenknecht

Tunnel boring machine (TBM) development continues to take on not only larger diameters, but also more difficult ground conditions. Ground conditions consisting of unstable faces with water pressures up to 15 bar have required innovative design approaches. A systems approach has been required to produce tunneling machines that can safely excavate the tunnel in an efficient, cost-effective manner that stresses production and labor saving approaches. This article reviews the current design developments and present recent projects where these most recent principles have been applied. The world?s growing population and rapidly proceeding urbanization are boosting an enormous demand for new and high-capacity infrastructures to secure the mobility of goods and people. Densely populated areas face the challenge of providing efficient traffic infrastructure such as a modern public transport system. At the same time, the maintenance and modernization of supply and disposal structures for water, sewage, energy and communication are essential. Last but not least, are supra-regional transportation routes such as long distance water diversion schemes. All of these projects are as demanding and are characterized by a tight time schedule. In this context, the demand for efficient tunnels for traffic and utility lines is increasing, as new infrastructures often leads underground because of limited space above ground. Also, tunnels are the obvious choice to cross natural barriers like mountain ranges. To handle the complex and variable geological conditions and other constraints, such as low overburden, high water pressure or long tunnel drives while facing increasing demand of a quick completion of a project, mechanized tunneling sets standards regarding safety, profitability and environmental protection in traffic tunneling projects as well as in the trenchless construction of utility tunnels. Different machine types and working principles have been developed to master various geological and hydrogeological requirements. Continuous activity in research and development leads to constant improvement of the mechanized tunneling process.

Jan 1, 2008

By H. L. Lovell

The growing production of fly ash with the many attendant problems of economics, disposal and potential uses suggests an urgent need to consider those properties which are basic in its beneficiation. Fly ash is extremely variable and heterogeneous in all respects except its fine size. Because of its production in huge quantities, it becomes significant as a potential raw material. Detailed data are presented describing particle size and shape, density distribution and magnetic characteristics. The major components include combustible residuals, magnetite and silicates. These data are discussed in terms of beneficiation processes and uses, The results of air classification to produce a uniformly fine-sized low combustible product are encouraging. It is proposed that major increases in the future use of fly ash, must involve some form of beneficiation. Both the coal producing industries and the consuming utilities would benefit from increased utilization.

Jan 1, 1964