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By Dielle Cristine Toledo Costa

Os aços austeníticos 304L quando processados tem suas propriedades mecânicas afetadas pelas transformações martensíticas induzidas pela deformação plástica (efeito TRIP). O objetivo deste trabalho foi avaliar esse comportamento em corpos de prova que sofreram deformações gradativas por meio de ensaios de tração uniaxial a partir de diferentes técnicas de análises microestruturais e mecânicas, a saber: ferritoscopia, difração de raios-x e ultramicrodureza. Os resultados obtidos foram satisfatórios e permitiram estimar o efeito da deformação na transformação martensítica e comparar as técnicas utilizadas.

Aug 8, 2018

STANDING COMMITTEES Executive-A. R. LEDOUX, chairman. Membership-GEORGE C. STONE, chairman. Finance-J. V. N. DORR, chairman. Library-E. GYBBON SPILSBURY, chairman. Papers and Publications--BRADLEY STOUGHTON, chairman. Nominations-POPE YEATMAN, chairman.

Jan 9, 1919

By R. P. Kofluk

The nickel-cobalt sulphides produced from limonitic laterite ores by Moa Nickel S.A. in Cuba are refined at the Corefco nickel-cobalt refinery in Canada. Significant economic implications are associated with the refining of precipitated sulphides containing elevated iron contents. The Moa Nickel S.A. operations encompass laterite mining, high pressure acid leaching (H PAL), and ultimately, precipitation of a mixed sulphide product. These processes are reviewed as they pertain to the control of iron and the formation of a mixed sulphide containing nominally 55% Ni, 5% Co and 1% Fe. The contributors to the iron content of the mixed sulphide product are reviewed; the major contributors are the HPAL operation and sulphide precipitation. The precipitation of iron during sulphide precipitation is influenced by the solution acidity, the iron and copper concentrations in the feed solution, and the presence of laterite leach solids. The significance of the copper concentration of the sulphide precipitation solutions is manifested by both physical and chemical modifications of the sulphide precipitates, presumably through the formation of fine copper sulfide seed particles.

Jan 1, 2006

By Charles F. Jackson

Waste filling has been employed for many years for supporting the walls of stopes and preventing failure and subsidence of the surrounding and overlying rock formations, and its effectiveness for this purpose has long been recognized. It is used for permanent support in ground where timbering (including square-setting) is inadequate for more than temporarily supporting the walls of the excavations. It should be rioted, however, that effective as a good, solid fill may be in resisting heavy side pressure and direct weight, its usefulness for supporting large areas of back and preventing breaking and movement of the overlying rocks is limited. Even the strongest and most uniform rocks will break if the unsupported span becomes too great; and since filling cannot be packed tightly against a horizontal back there is always a possibility of the back breaking and consequent subsidence if the maximum self-supporting span is exceeded. Planes of separation, such as bedding and fault planes, slips, and joints, are common in all rock masses; these may occur above the stoping area where their presence cannot be ascertained by observation. If too much reliance is placed upon filling for the support of a large horizontal area of back (as contrasted to support of vertical or steeply inclined walls) large masses of rock may break along a. plane of weakness, compress the fill, and leave an open space into which caving of the overlying rocks may continue until the space is filled. In this paper the term "waste filling" includes any filling material other than ore - waste mine rock, rock from surface quarries or opencuts, sand and gravel, mill sands, or slags from smelting operations.

Jan 1, 1935

By W. T. Walter

High-G centrifuges from five preparation plants were sampled to determine and quantify the various operating factors affecting performance. The operating factors that were considered include feed rate and percent solids, size of feed material, screen-basket type, hardness of coal and age of the flights. The performance parameters that were measured include product surface moisture, recovery and degradation of the coal. Regression equations with good significance levels were developed.

Jan 1, 1982

By Edward W. Parsons

To determine in what part and to what extent creep or movement exists in an installed rock-bolt anchor and the effect of the creep or bleedoff on the tension load on a rock bolt, as well as the effect of normal mining activity on the rock-bolt load and anchor, the Bureau of Mines conducted tests in the laboratory and in two mines using four types of expansion-shell anchors, the wedge bolt, and in one mine, explosive-anchored rock bolts. Specially mounted heavy-duty springs, calibrated to obtain load readings from spring movement, were installed on the test bolts to prevent a drastic reduction in tension load caused by slipping or seating of the anchor. A dial gage, reading to 0.0001 inch, measured movement of the anchor shell against the rock and seating of the anchor wedge plug in the shell. While all bolts had electrical resistance strain gages for load reading, only readings from the laboratory tests were used because those from the field tests were erratic. The tests revealed that most load loss resulting from static loading is due to the slippage and seating of the serrations on the anchor shell into the drill-hole wall. Dynamic loading, primarily from sudden shocks from nearby blasting, and possibly from ground movement or mining activity, will cause the anchor wedge plug to seat in the anchor shell.

Jan 1, 1969

By Xun An

Slag from an electric slag cleaning furnace was injected with methane and air mixtures to facilitate the recovery of copper and cobalt. The effects of methane-to-air ratio, gas flow rate and temperature on the reduction and metal separation were investigated. The results showed that over 90 percent copper and up to 60 percent cobalt could be recovered from the slag with a gas utilisation of around 70 percent, as calculated by thermodynamic simulation. Methane-to- air ratio was a major factor affecting the rate of reduction under the present experimental conditions. Further, injection of gaseous reductants greatly enhanced the coalescence and settling of entrained metal droplets. A reduction mechanism is proposed and the factors influencing the coalescence of copper droplets are discussed.

Jan 1, 1998

By L. M. Cenegy

Introduction The formation of scale is common in gold ore processing plants. A working definition of such scale is: "A hard, tightly adhering deposit formed in place by the precipitation of calcium-bearing mineral compounds from water." The most common scale found in gold processing plants is calcium carbonate (CaCO3) although calcium sulfate (CaSO4) is occasionally a problem. The problem of scale in carbon strip circuits Carbon strip circuits present a particularly challenging scale inhibition problem. Many of the factors that tend to promote scaling are present in these systems. For example, carbon strip circuits are run at high temperatures and high pH levels and require long batch cycle times. Tortuous paths are encountered by the strip solution circulating through heat exchangers, pipes and elbows, causing transient pressure drops throughout the system. Severe conditions such as these cause the water to possess a high scaling potential and may lead to the breakdown of some of common types of scale inhibitors. Formation of scale Natural waters contain dissolved minerals and gases that promote scaling. One of the contained gases, carbon dioxide (CO2), is an important factor in scale deposition. Carbon dioxide dissolves in water to yield carbonic acid according to the following reaction: [CO2 + H2O - H2CO3 (carbonic acid)] Carbonic acid rapidly dissociates to yield bicarbonate and carbonate ions depending on the pH of the system: [H2CO3 -s H+ + HCO-3 (pH range 6-10) HCO3 -a H+ + COO (pH range > 9)] In gold cyanidation processes, lime is added to raise the pH of the mill solution to 10 or above to promote cyanidation of the gold and to eliminate the possibility of hydrogen cyanide (HCN) formation. Lime contributes both hydroxyl ions (OH--) and calcium ions (Ca++) to the solution. The normal scale forming reactions in mill water systems were described by Beasley (1973) as: [HCO-3 + OH -s C03 + H2O Ca++ + C03 -a CaCO3] Factor affecting scale deposition According to Linke's (1958) solubility tables, the solubility of calcium carbonate in carbon-dioxide free water is only 13 mg/dm3 (13 mg/L) at 25° C (77° F). Scale deposition occurs when the concentration of calcium and carbonate ions in the solution exceeds the solubility of calcium carbonate. This occurs, in most cases, when the water has undergone some chemical or physical change. Some typical changes that might occur that lead to scale deposition are discussed below. Temperature An increase in temperature can greatly increase the tendency to form calcium carbonate scale. Studies by Miller (1952) have indicated that calcium carbonate is less soluble at higher temperatures. Hence, high temperatures promote scaling. For this reason, scale is often noticed on heat exchangers, autoclaves and other high temperature surfaces. Pressure A decrease in pressure may lead to an increase in the tendency to form calcium carbonate scale. Fulford's (1967) work has shown that scale is more soluble at high pressures. Hence, scale is likely to be prevalent in pump suction lines, elbows, baffles and other areas that produce turbulence and subsequent pressure drops. Change in pH Calcium carbonate scale is pH dependent and tends to form more readily at high pH. Any event that causes an increase in pH, such as the introduction of lime or caustic, would tend to initiate scale formation. Since most gold recovery operations are run at a pH above 10, the tendency to form calcium carbonate scale is always great. The use of scale inhibitors to prevent calcium carbonate scale Many products are commercially available to inhibit the formation of calcium carbonate scale. Some of the more effective types include phosphonates, as well as acrylate and maleate-based polymers and copolymers. Many of these products function by means of threshold

Jan 1, 1992

By H. S. Cannon, F. N. Rhines

The application of a static load to a copper powder compact during sintering at an elevated temperature accelerates the rate of sintering in such a way that a given load induces the same proportional increase in rate for all times of sintering. It is shown that sintering under a load is like creep under a fixed load in that the stress required to accomplish a given degree of densification is proportional to the logarithm of the sintering time. VIRTUALLY all of the theories of sintering that have been put forward within recent years have contained the assumption that the chief driving force of the process is the surface tension resident in the exposed surfaces and internal pores of the compact, or powder mass. An externally applied load might be expected to provide a somewhat equivalent driving force for sintering. It is known that the application of a compressive load, during sintering, hastens densification, but it is by no means clear whether sintering under the influence of surface tension alone and sintering under an applied load are fundamentally similar processes. The present study was undertaken in an effort to obtain an answer to this question and with the hope that the answer may contribute to an understanding of the mechanism of sintering. It has been found that there is a close relationship between sintering and creep processes. Copper powder compacts were sintered in hydrogen at 1000 °C under dead loads of 0 to 165 psi and the progress of sintering was observed by means of density measurements. Using a commercial reduced oxide copper powder, see Table I, cylindrical compacts Yz in. x x in. high were made at a pressure of 12,500 psi. For sintering, these were placed in a cylindrical graphite container into which they fitted snugly. A compressive axial load was applied to the compact through a graphite rod of similar diameter, which rested upon the upper end face of the compact; iron weights, in suitable amount, were placed upon the graphite rod to provide the load. This assembly was encased in a vertical silica tube within a resistance-type furnace capable of maintaining a substantially constant temperature within the working zone. After various predetermined times at temperature, the samples were removed from the furnace and their density was measured by conventional means. The heating-up and cooling-down times have been included in the computed sintering time, using the assumption that the sintering rate doubles for each increase of 10 °C in temperature. The experimental results are presented in Table 11. Upon metallographic examination of the specimens, it was found that there was no apparent change in the shape of the pores as a result of loading, i.e, no flattening, Fig. 1. Substantial contraction away from the container walls was observed in all samples sintered with loads of 10.5 psi and less.

Jan 1, 1952

By W. A. Selvig

"The tests described in this paper were conducted under the sponsorship of Subcommittee VII on Pulverizing Characteristics of Coal, a subcommittee of Committee D-5 on Coal and Coke, American Society for Testing Materials, with a view to evaluating various laboratory procedures for testing grindability of coal in connection with commercial pulverization of coal for use as powdered fuel. The subcommittee, at a meeting in New York City on February 21, 1934, selected for test four methods that had been developed during the past few years for testing grindabilitay of coal and were being used by coal-testing laboratories in the United States and Canada. These methods are:Bureau of Mines method, Cross method, Fuel Research Laboratory method, and Hardgrove method. Subcommittee VII agreed that the grindability tests should be made on five coals selected to cover a wide range of hardness. The Pittsburgh Experiment Station, Bureau of Mines, was asked to direct the investigation and to prepare representative samples of the coals. Laboratories of the fol. lowing institutions and companies agreed to cooperate by making grindability tests: Babcock & Wilcox Co., Foster Wheeler Corporation, Fuel Engineering Co., of New York, Fuel Research Laboratory of the Canada Department of Mines, and Northwest Experiment Station of the Bureau of Mines.ACKNOWLEDGMENTSHelpful suggestions in planning the investigation were made by A. C. Fieldner, chairman, Committee D-5 on Coal and Coke, A.S.T.M., and chief engineer, Experiment Stations Division, U. S. Bureau of Mines, Washington, D. C., and E. B. Ricketts, research engineer, New York Edison Co., New. York City.The coal samples were supplied through the courtesy of floats, Wheeler Corporation, New York City; Philadelphia & Reading Coal & Iron Co., Pottsville, Pa.; Pittsburgh Coal Co., Pittsburgh, Pa.; and Pocahontas Fuel Co., Inc., New York City."

Feb 1, 1936

By R. Hans

Removal of toxic anions from aqueous solution was studied using a Magnetic Ion Exchange (MIEX) resin which is a polyacrylic, strong base resin. Gravity based settling is made more efficient due to the magnetic nature of the resin which is advantageous over conventional ion exchange resins. In addition, the magnetic microspheres of MIEX have larger surface area in comparison to conventional ion exchange resins. Over the years MIEX has been successfully used and has gained significant popularity for efficiently removing dissolved organic matter from wastewater and groundwater. In the present study the efficiency of the MIEX resin was tested for the removal of chromium(VI), molybdenium(VI), vanadium(V) and arsenic(V) anions. Effects of pH (2-10) and temperature (25oC-55oC) were examined. In general, low solution pH values were favorable for anion uptake by MIEX. Except for chromium(VI), the metal ion uptake was significantly increased by the increase in solution temperature. The adsorption data were analysed on the basis of chemical speciation and heterogeneous kinetic models.

Jan 1, 2014

By F. T. Principe

In order for solvent extraction technology to be acceptable as an alternative to existing jarosite precipitation circuits, iron must be cleanly separated and concentrated into a feed stream suitable for downstream iron by-product recovery which meets market specifications and economics. Ten years ago, significant progress was made in a joint McCill University/CANMET project that involved iron extraction with mono(2-ethylhexyl) phosphoric acid and stripping with HCI. Our iron solvent extraction research was reactivated recently by looking into this and other members of the organophosphorus extractant family. Our research focuses on the mechanisms and control of anion (SO42/CI) transport across the various phases (Rafinate/Organic/Strip), iron build-up in the strip liquor, and extractant stability/selectivity. In this paper, these issues along with some other performance parameters are discussed using data derived from an extensive search of the two commercially available and best known members of the organophosphorus family, di-2-ethylhexyl (D2EHPA) and mono-2-ethylhexyl (M2EHPA) phosphoric acid. Further in this discussion, the challenges lying ahead in the development of sx systems that overcome the deficiencies of D2EHPA and M2EHPA are outlined. In particular, the necessity of considering secondary separation technologies that can further concentrate iron values in the chloride strip liquor to levels economically attractive for the production of saleable iron oxide by pyrohydrolysis is addressed.

Jan 1, 1998

By D. J. MacDonald

The Bureau of Mines has conducted bench-scale investigations leading to the design of an integrated process for producing reactor-grade zir-conium oxide (Zr02) from zircon sand, which avoids the air pollution, water pollution, fire hazard, and odor problems associated with the hexone-thiocyanate process. The integrated process consists of three steps: production of crude zirconyl sulfate solution, solvent extraction, and production of Zr02 from strip liquor. This report describes the solvent extraction step. Multistage, countercurrent liquid-liquid extraction with a tertiary amine in kerosine was used to separate zirconium from a dilute H2S04 solution containing hafnium and other impurities. Process steps de-scribed include extraction from an aqueous feed solution to form a hafnium-contaminated, zirconium-bearing organic-phase solution, scrubbing to separate zirconium from coextracted hafnium, stripping to transfer hafnium-free zirconium into an aqueous strip liquor, chloride-loading to produce a chloride-bearing organic solution, scrubbing with the chloride-loaded organic solution to remove traces of uranium impur-ity from the zirconium-bearing strip liquor, and regeneration to pre-pare the organic solution for reuse. These steps were performed simul-taneously in steady-state, bench-scale experiments. Zirconium recovery of up to 93 pct was achieved. Results of an economic evaluation are included.

Jan 1, 1984

By B. Mishra, W. A. Averill

"The application of various hydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, ego metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been investigated and suggested for dealing with some of these wastes and scrap material.The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EM] and decontamination and decommissioning [D&D].IntroductionThe high temperature carbothermic or metallothermic smelting reduction methods for metal production are associated with the generation of significant quantity of waste as slags, flue dusts, sludges, residues, effluent salts etc. Certain hydrometallurgical processes also generate lots of aqueous waste due to the inherent nature of the technique. Also, the gas-based reduction processes are not applicable to many stable metal compounds, such as alumina, titania, beryllia, lanthanide and actinide oxides, etc. due to thermodynamic considerations. All these methods cause substantial environmental hazard. There is a need to develop alternative processes which have low waste or ideally a ""zero-waste"" generation.Pyrochemical processes using molten salts provide a unique opportunity for the extraction and refining of many reactive and valuable metals either directly from the beneficiated ore (aluminum, beryllium, neodymium, plutonium, uranium, etc.) or from other process effluent that contain reactive metal compounds. The processes reduce metal compounds electrolytically (A12O 3 and BeCI2) on a carbon anode or by calciothermic reduction (Po, Nd). The by-product, in the latter case, is a calcium oxide saturated halide salt. The waste-treatment to recycle the halide has to be done as a separate step or stored as a contaminated waste. A successful separation technology can provide a new insight to the waste minimization strategy for the nuclear industry."

Jan 1, 1996

By X. Zhu, L. Chen, R. Guru, M. Peiravi, M. Mohanty, L. Ackah, B. Xu

"The overall goal of this study was to develop a suitable flowsheet to extract rare earth elements (REEs) from coal ash. Only the findings from the first part of this study is being reported at this time. A total of fourteen coal samples of different ranks were examined for REEs concentration. An anthracite coal sample, originating from Pennsylvania having more than 700 ppm (in the coal ash) was selected for the REE extraction tests. The experimental program completed so far included high temperature leaching using nitric acid, followed by the solvent extraction tests. A 4x2x2 experimental design was used to conduct a total of thirty two high temperature leaching tests by varying acid molarity (at 4 levels), solid content (at 2 level) and leaching time (at 2 level). The highest LREE (light REE) recovery of 90% and HREE (heavy REE) recovery of 94% were obtained from the most optimum leaching test condition while maintaining the impurity recovery to the leachate at less than 40%. Solvent extraction experiments were conducted to recover the REE’s from the above leachate solution using a variety of organic extractants including, TBP, Cyanex, D2EHPA and their combinations. D2EHPA was found to be the best extractant during this SX text series providing nearly 99% recovery of REEs. INTRODUCTION The demand for rare earth element and other strategic metals (REM) in the world is rapidly increasing due to their use in a variety of high technology applications. More than 100,000 tons of rare earth oxides (REO) are being used worldwide on an annual basis. However, we have less than 10% of the world reserve of rare earth element (REE) mineral deposits in the US. More than 60% of rare earth oxide (REO) was imported to the US from outside (mostly from China) in the year of 2013. However, China’s institution of export quota has significantly reduced the supply of REMs to the U.S. Hence, new ways of producing REM and/or finding substitutes for those metals for the high-tech applications need to be invented/discovered in a timely manner. Coal Combustion Byproducts (CCBs), which are discarded as waste materials in most cases, are known to contain REEs (in low concentration) that could be extracted using a suitable process flowsheet. This may be a worthwhile route to pursue considering the short supply of REMs and the abundance of coal ash in thousands of ash ponds in the US. On an annual basis, more than 110 million tons of Coal Combustion Byproducts (CCBs) are being produced while satisfying our nation’s need for electricity (ACAA, 2014). However, less than 50% of these CCBs are being successfully used in various applications and the remainder is being dumped as waste materials in the landfills and ash ponds."

Jan 1, 2017

By Ke Yang, Robert Liang

"Drilled shaft foundations are widely used for many types of structures, especially for highway bridges, high rise buildings, and costal structures. The lateral design considerations are crucial for those structures that are subjected to lateral thrust forces, winds, waves, and earthquakes. The p-y analysis is the most widely used method for the analysis and design of drilled shafts for lateral load applications in soils. However, existing p-y criteria were developed based on the lateral load tests on small diameter drilled shafts in soils. Although, a lot of lateral load tests have been conducted, there are a limited number of lateral load tests on large diameter drilled shafts embedded in clay. In this paper, a lateral load test on 2.44 m diameter fully instrumented drilled shafts in clay is presented. The site specific p-y curves are derived based on strain gage readings. The existing p-y curves are found to be much softer than the site specific p-y curves. Correspondingly, the deflection at the top of the test shaft under the maximum applied load is predicted to be eight times larger than the measured value using existing p-y criteria. A new p-y criterion is proposed in this paper. The proposed p-y criterion is proven to be able to capture the site specific p-y curves of the load test and to predict closely the deflections at the top of the test shaft. INTRODUCTIONDrilled shaft foundations are widely used for many types of structures, especially for highway bridges and costal structures. The lateral design considerations are crucial for those structures that are subjected to lateral thrust forces, winds, waves, and earthquakes. Although efforts have been made on studying lateral response of drilled shafts; nevertheless, only limited studies have been published on the behavior of large diameter drilled shafts under lateral loads and the corresponding design methods."

Jan 1, 2005

By James P. Bennett

The Bureau of Mines is investigating the acid resistance of ceramic materials to identify construction materials for emerging technology in chemical and metallurgical processes. Eight commercial ceramic materials, were evaluated: two red shale, two fireclay, one silicon carbide, one silica, one carbon, and one high-alumina. Samples were exposed to 10 wt pct H2S04 at 50° C and 10, 30, 50, 70, and 90 wt pct H2S04 at 90° C for time periods of 110 days. Statistically significant changes in cold crushing strength were observed in the silicon carbide and car-bon materials. Weight changes and the leach rate of Al, Ca. Fe. K, Mg, Na. Si, and Ti were also monitored. The most severe corrosion conditions were at 90° C and 30 to 50 wt pct H2S04 for the acidproof and at 10 wt pct H2S04 for the acid-resistant materials. The silica and the high-alumina materials were the most acid-resistant, followed by the higher density red shale and fireclay.

Jan 1, 1986

By W. E. Webb

This report describes a method the Bureau of Mines devised for measuring the dielectric constant and loss tangent of low-loss minerals at microwave frequencies. Determina-tion of these properties makes it possible to predict the effects of using microwave heating in potential mineral processing applications. The method uses a test cell and radio-frequency (RF) impedance analyzer with automated data acquisition and analysis. In this initial phase of microwave heating research, the Bureau measured dielectric constants and loss tangents at frequencies between 100 MHz and 1 GHz. The objective was to establish a reliable data base for use in predicting the effects of microwave heating on minerals. Comparison with previously measured data showed the Bureau's measurement method to be accurate to within ± 3 pct. This report describes the method and discusses the preliminary results of the Bureau's investigations. Typical comparative data are included.

Jan 1, 1986

By D. M. Thayer

Laboratory and pilot plant investigations have indicated that copper recoveries of 50% can be achieved with fine grinding and flotation of a copper reverberatory furnace slag, Microscopic and microprobe studies indicate that the recoverable copper is in the form of matte, chalcocite, and metallic copper; the percentage of copper in particles appearing to be copper-free was from 0.23 - 0.54%.

Jan 1, 1969

By Frederick W. Lee

List of contributing editors of Geophysical Abstracts:

Sep 1, 1932