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A major domestic aluminum producer raised its price for primary aluminum metal from 44 cents per pound to 48 cents per pound, effective August 5, 1976. Other major producers have increased their list prices by equivalent amounts COAL: The strike which began July 19 in southern West Virginia enlarged by early August to involve approximately 80,000 miners in nine States. As of August 4, the aggregated loss of production is estimated to be 5.8 million tons. Reportedly, at this time, the railroads which serve the struck areas are feeling the largest impact with coke plants and electric utilities relying on stocks which are generally high.

Jan 1, 1976

By Robert R. Stein

Using an automated drill test fooure, the U.S. Bureau of Mines measured the sound power levels produced by a small, pneumatic, rotary roof drill. A series of tests was conducted to determine (1) the relative effectiveness of several drill muffling schemes and (2) the relationship between drill sound power and pneumatic power supplied to the drill. The influence of rotation rate (i.e., airflow) and feed thrust on the penetration rate of the drill was also noted.

Jan 1, 1989

A wide range of drill holes and process streams are sampled for resource estimation, grade control and contractual purposes in the minerals industry. However, despite the availability of training courses, conferences and both national and international standards on correct sampling practices, it is still surprising how often little attention is given to ensuring that representative samples are collected for analysis. The reason for this is that the responsibility for sampling is often entrusted to personnel who do not appreciate the significance and importance of sampling, with cost being the main driving force rather than whether the sample is representative of the material from which it was extracted. This seriously undermines the precision and accuracy of the analyses subsequently generated and can render the analysis process a total waste of time and money and expose mining companies to serious, potential, financial losses. Company management needs to reverse this situation and ensure that sampling is given the attention it deserves to generate representative samples for analysis.

Jan 1, 2009

By Shozo Saito, P. A. Beck

Mettrllographic and X-ray diffraction study of Cb-Co alloys in the Composition range of 7 to 33 nt. pct Cb, after annealing at 1175 °', showed that near 25 al. pct Cb on MgNi,-lype hexagonal Laves Phaseexists in a narrow composition range, and that an MgCl- type cubic Laves Phase occurs between approximately 27 and 32.6 ut. pd Cb. Lattice parameter and density measures indicated that, in both phases. the deviations from proper Loves sloichimetry result from the substitution of cobalt atoms for some 0f the columbium atoms. Tlle same phases occurant 1000'C, together with an additional phase of unknown structure, which appears between the hexagonal Laves phase and the cobalt-bose terminal solid solutions KOSTER and Schmid' identified a phase corresponding to the composition VCo,, and more recently the crystal structure of this phase has been determined.' In the Ta-Co system Korchynsky and Fountain recently found two intermediate phases at the composition Taco,, one of them metastable. In contrast to the V-Co and the Ta-Co systems, in the Cb-Co system no intermediate phase has been found4 at the composition CbCo,. The present investigation was undertaken in order to reexamine the question of the existence of such a phase. EXPERIMENTAL PROCEDURE Twelve alloys were prepared by arc-melting in a water-cooled copper crucible under helium atmosphere. Electrolytic cobalt and 99.9 pct pure colum-bium powder have been used as starting materials. It was found that melting losses can be reduced by compressing the colunlbium powder in the form of thin pellets before melting. For the alloys used the melting losses were not higher than 1 pct. The intended compositions of all alloys and the chemical analyses of three of them are given in Table I. Specimens from all alloys were annealed in evac- uated fused silica tubes at 1175°C for 3 days and quenched in cold water. A second set of specimens of most alloys was annealed at 1000°C for 7 days and then quenched in cold water. The annealed and quenched specimens were examined metallographically, using the following etchant: 60 pct glycerine +20 pct H,NO, + 10 pct HF + 10 pct water. Powder specimens for X-ray diffraction were prepared by crushing annealed solid specimens in a mortar. Alloys containing 27.3, 28, 29.7, and 32.6 at. pct Cb annealed at either 1175" or 1000°C were very brittle and it was found unnecessary to reanneal the powders. However, alloys containing 24.8 at. pct Cb, or less, especially those annealed at 1000°C, were much less brittle and re-annealing was required to remove the strains present in the crushed powders. In each case reannealing was done at the same temperature at which the corresponding solid specimens were annealed and it, too, was followed by quenching in cold water. In many instances X-ray diffraction patterns were also taken of the polished and etched solid specimens and compared with the corresponding X-ray diffraction patterns obtained with powders. The X-ray diffraction patterns were taken with an asymmetrical focusing camera, using CrK radiation. For precision lattice parameter measurements some X-ray diffraction patterns were taken with a symmetrical focusing camera, again using CrK radiation. EXPERIMENTAL RESULTS A microscopic examination of the alloys annealed at 1175°C revealed that the alloy containing 25.5 at. pct Cb was composed of a single phase, but that the 24.8 at. pct Cb alloy did contain a small amount of a second phase, identified by means of X-ray diffraction as having a fcc structure, undoubtedly the terminal solid solution based on cobalt. Apart from the few very weak lines corresponding to this minor phase, the X-ray diffraction patterns of these alloys could be well interpreted in terms of a MgNi,-type hexagonal Laves phase structure. The indexing of the X-ray diffraction pattern, Table 11, yas based on the lattice parameter values a, = 4.740A and c,

Jan 1, 1961

In west-central England, 183 m (600 ft) below the Cheshire Plain, lie the evaporate remains of an ancient sea. Stratified into nine beds of salt separated by marl bands, the deposit stretches roughly 21 x 12 km (13 x 7.5 miles) and contains reserves of rock salt estimated as high as 400 Gt (440 billion st). The Winsford Salt Works, one of England's largest underground mines, extracts the Cheshire salt and sells it for use as animal feed, for application in de-icing programs, and as a key ingredient in sodium fertilizer production and a variety of other industrial processes. Because road de-icing is an important market, demand for Winsford's salt varies with the severity of British winters. Design capacity is 2.25 Mt/a (2.5 million/year). However, production peaked at 2 Mt (2.2 million st) in 1987. Over the past five years, annual production has averaged 1.6 Mt (1.7 million st). Run-of-mine salt averages 92.5% NaCl, mixed with about 5% marl. The marl was formed by deposition of a reddish dust blown into the Cheshire basin from deserts in what is now central Europe. Association with the marl adds color to the salt, producing tea-colored crystals that resemble unrefined sugar. Adaptation of coal mining systems Rock salt mining in the Winsford district began at least as early as 1682. Mining at the current site dates from 1844 but was shut down from 1892 to 1928. In the early 1900s, a series of catastrophic collapses and floods plagued and ultimately shut down then-active Cheshire brine-salt producers. Subsequently, Winsford reopened and began adapting mechanized underground coal mining systems to rock salt extraction.

Jan 1, 1992

By P. J. Miranda, C. G. Anderson, L. G. Twidwell

Titanium is a metal of increasing worldwide strategic importance. The Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech of the University of Montana is currently directing two titanium research initiatives. The first program, Titanium Extraction Mining and Process Engineering Initiative (TEMPER), is focused on producing low cost titanium through the identification and development of new mining, beneficiation and extraction technologies which will significantly reduce the cost of titanium production. This will directly benefit worldwide commercial applications. Secondly, CAMP is evaluating new technologies for fabrication of titanium utilizing the Free Form Titanium Fabrication (FFTF) initiative. These technologies may drastically reduce the cost and time to manufacture titanium components. Because of the high strength to weight ratio of titanium coupled with its superior corrosion characteristics, these programs will be of vital importance to expanding the commercial and strategic applications of titanium. An overview of these two new titanium initiatives will be presented in this paper.

Jan 1, 2005

By Frank Clemens Smith

The occurrence of the tellurides of gold and silver, even in small quantities, is so rare that their metallurgical treatment has engaged little attention. A residence of several months at one of the few mines in North America the product of which consists entirely of such ore, has led me to arrange a method for its economical treatment. The mine referred to is the Huronian, situated a few miles distant from Jackfish Lake, in Ontario, Canada. The plan proposed is for this peculiar case, and is put on record as possibly suggestive and helpful .in any similar instance, should it occur. Since freight-rates from the mine to the nearest railroad-point were extremely high, and for other economical reasons, the method proposed is modified by the use, as far as possible, of the machinery already at the mine, and is so arranged that bullion instead of concentrates would be obtained as a final product. The ore-vein at the Huronian mine varied in width from about 4 feet at the surface to 2 feet and less at the lowest level—125 feet —and dipped southeast about 88. The rock consisted, on both foot- and hanging-walls, of soft, green Huronian slates carrying much highly crystalline but barren pyrite. The ore carried an inconsiderable amount of galena with iron and copper pyrites, argentite, hessite, sylvanite (or petzite), and probably altaite, the telluride of lead. Near the surface the ore showed considerable native gold, but this disappeared with greater depth. Two complete analyses of minerals containing tellurium are here attached, as they establish the presence of two important compounds: I. Analysis of a mineral supposed at the mine to be sylvanite, but agreeing more closely in composition with petzite (Ag, Au)2 Te: Ag = 41.062 Au =23.691 Te =32.007 Pb = 0.071 SiO2= 0.097 Fe = trace 96.928

Jan 1, 1890

By Gjergj Dodbiba, Toyohisa Fujita, Takahiro Kikuchi, I-Chen Wu

"In order to separate molybdenum (Mo) from the high-level radioactive liquid waste (HLLW), Pb-Fe based adsorbents were synthesized. The adsorbents were precipitated by adding sodium hydroxide in mixture of 1 mol/L lead nitrate and 1 mol/L ferric nitrate aqueous solutions. Each precipitate was then filtered, dried and ground to obtain a fine powder, which has been used as an adsorbent. Two main parameters were considered when synthesizing the adsorbents, i.e. the pH value at precipitation of adsorbent precursor and the calcination temperature of Pb-Fe based adsorbent. Moreover, the structures of the synthesized adsorbents were investigated by means of an X-ray diffractometer.The experimental results indicated that the calcination temperature of the Pb-Fe based adsorbent has a great influence on adsorption capacity of the adsorbent for Mo. It was found that when the Pb-Fe based adsorbent was calcinated at 500 oC, the sorbed concentration of Mo was the highest.1. IntroductionThe high-level radioactive liquid waste (HLLW), arising from the reprocessing of nuclear fuel are generally immobilized in an alkali borosilicate glass matrix. Broadly speaking, alkali borosilicate glasses are the matrix of choice for the immobilization of the HLLW, since they permit vitrification of waste stream of variable composition, [1]. Within this frame, the incorporation of molybdenum (Mo) is of particular interest in the vitrification of HLLW. Molybdenum is know to have a low solubility in borosilicate glass compositions and its presence in excess results in the phase separation of a complex yellow molten salt during vitrification, [1]. The formation of so-called “yellow phase” material during the vitrification process is undesirable since it leads to the accelerated corrosion of the inconel crucible liners. Furthermore, the “yellow phase”, which is reported to contain also other fission products, is soluble in aqueous solution providing a potential route for the leaching of radionuclides from the vitrified waste, should it come into contact with water, [1]."

Jan 1, 2008

Duval Corporation, the copper -producing subsidiary of Pennzoil United, Incorporated, operates two plants south of Tucson, Arizona: Esperanza and Sierrita. The newest, the Sierrita mine and mill, came into full production in 1971 at a rate of 72,000 tpd (now 87,000 tpd) which at that time made it the largest designed copper plant in the world. In 1968, the largest milling units then available were selected; these included fourteen 16$ ft by 19 ft long ball mills (5 m by 5. 9 m), each equipped with a 3,000 hp motor. The primary crushing plant contains two 60 in. by 89 in. Allis- Chalmers gyratories; each is constructed for two-side dumping by 120- and 150-ton trucks. Access to the maintenance areas to service the drive motors, eccentrics, apron feeders, and speedup conveyor is through hatches between the crushers. This area also contains a good- sized elevator and a stairway. The rather shallow dump pocket, the 300 -ton crushed ore pocket, and the overall design make for a fine, compact arrangement for two 60 in. crushers installed in a total height of 89 ft (27. 13 m) from dump level to top-of-concrete at the lowest level beneath the collecting or speedup belt. This efficient layout is reflected in the short changeout time for mantle and concaves (8 and 30 hours respectively) and the low crushing cost of $0.0416 per ton (first half of 1975). The crushers are installed on 64 ft (19.5 m) centers (Bougainville and Palabora, both with 54 in. crushers, are 55 and 43 ft or 16.76 and 13. 1 m respectively). The switchgear room is located between the truck dumping positions on one side of the installation and the hydroset units on the other side, with dust collecting equipment mounted over the latter. Protection of these units from rocks falling from the trucks is provided by concrete walls. Truck dumping is controlled from a central 25 ft high (7.6 m) control room, which permits fine observation of operations. Removal of oversize boulders from the dump pockets is done with a hydraulic grapple or a rock hook or sling attached to the auxiliary crane hook. Spare mantle stands and a maintenance room with a zinc melting furnace are located at one end of the surface facilities. The maintenance room is equipped with an access door for the crane, which is equipped with 80- and 20-ton hoists. The two 84 in. (2. 135 m) apron feeders receiving the 6 in. (152 mm) crushed rock discharge onto a 72 in. (1. 83 m) collecting and wear belt operated at a speed compatible with the 60 in. (1.524 m) takeaway belt running at a speed of 630 fpm (192 mpm). This belt feeds a 54 in.

Jan 1, 1978

By R. V. Ramani, C. B. Manula, A. Owili-Eger

That a close analogy exists between the flow of air in mines and the flow of current in electrical networks- has been known for a long time. The laws that have been used to solve series and parallel electrical circuits have been used to solve for the equivalent resistance in mine ventilation problems. Kirchhoff's current and voltage laws have also been adopted in solving mine ventilation network problems. It will be best to define a few terms here regarding networks, and with reference to Figure 1, these definitions can be elucidated. Figure 1 can be represented by the network in Figure 2 without losing any essential details. 1. A junction is a point where two or more airways meet. 2. The segment of a roadway connecting any two junctions is known as a branch. 3. A mesh is a closed path through the network. In the above network, B, C, D and F are the junctions, CF and CD are two of the branches and CFDC is a mesh. Kirchhoff's current law states that the sum of currents entering a junction. Applying this law to the junctions in the ventilation network, one obtains for junctions C and F, the following relationships: JUNCTION C: Q1 = Q4 + Q3 (1) JUNCTION F: Q2 + Q3 = Q5 (2) Similar relationships can be drawn for other junctions. Kirchhoff's voltage law states that in any complete electric circuit, the algebraic sum of the emf's must equal the algebraic sum of the voltage drops. In mine ventilation, the square law (Atkinson's

Jan 1, 1975

By R. E. Ogilvie, N. L. Peterson

Diffi-lsion measurements were conducted at all compositims in the bcc solid solution of the U-Nb system employing incremental couples at composition intemals of 10 at. pct. Diffusion coefficients were determined by the Matano method from concentration gradients obtained with the electron-probe microanalyzer. The activation energy for inter-diffi-lsion as a function of compositim shows three distinct regions: 1) 80 to 100 pct U.6= 30 kcal per mole; 2) 20 to 80 pct U, $ - 70 kcal per mole; 3) Oto 20 pet U, Q = i40 kcal per mole. The frequency factor, fi0 and the activation energy $ were found to be roughly related by the following equation: log Do ^9.7 X IO-5Q -6,6. The Kirkendall marker movement indicates that DU is larger than DNb between 16 and 100 pct U and DNb is larger than DU from 0 to 4 pct U. FOR practical as well as fundamental reasons, the rates of diffusion in alloys are of considerable consequence. Most solid-state reactions are largely dependent upon the diffusion of atoms through the lattice structure and along grain boundaries. The high-temperature strength and reasonable nuclear properties of niobium have prompted its use as a reactor material in contact with uranium fuel. Hence, diffusion data for the U-Nb system are of considerable importance. In the previous diffusion study1 on the U-Nb system using pure element couples, reliable data were obtained only in the range of 0 to 10 at. pct Nb due to the large variance of the diffusion coefficient with composition. Also, a large Kirkendall effect and considerable porosity in the uranium-rich areas of the specimen were reported, which suggests that the true diffusion coefficients are somewhat larger. The purpose of the present study was to obtain reliable diffusion coefficients at all compositions using incremental diffusion couples with intervals of 10 at. pct. In view of the abnormal self-diffusion be- havior of y uranium2-4 and some other bcc transition elements,&apos;-&apos; it was felt that a comparison of the interdiffusion coefficients in the bcc U-Nb system with those of Reynolds et al.9 for the fcc gold-nickel system might shed some light on the diffusion mechanism involved. Both systems have similar phase diagrams, in that complete solid solubility exists above a miscibility gap. EXPERIMENTAL PROCEDURE The uranium used in this investigation was obtained through the courtesy of Argonne National Laboratory. An analysis of this material detected only Si-30, A1-7, C-6, N < 10 and 0-18 ppm. The niobium was electron-beam melted material obtained from Stauffer-Temescal. The gaseous impurities were less than 50 ppm, and the spec troc hemical analysis showed Ta-500 and W-200 ppm. U-Nb alloys were prepared at composition intervals of 10 at. pct by melting the appropriate amounts of the pure elements in an arc furnace. The buttons were inverted and remelted 6 times to assure complete mixing. The buttons were then wrapped in molybdenum foil, canned in Zircaloy-2 or stainless steel, and hot rolled 30 pct reduction in thickness at temperatures between 850" and 1100°C. Alloys with 10, 20, 30, 40, and 90 at. pct Nb rolled quite easily under these conditions, but the 50, 60, 70, and 80 pct alloys remained brittle. After melting and rolling (when possible), the alloys were annealed for 24 hr at a temperature within 100°C of their melting point in a dynamic vacuum of better than 4 x 10-8 mm Hg. These treatments produced alloys which were homogeneous on a 1 p scale within the detectability limits of the electron probe. During fabrication, the alloys picked up as much as 100 ppm Mo and 100 ppm Zr. Other elements checked for but not found were Co, Cr, Fe, Mn, Ni, and Ti. The grain size of the annealed samples ranged from 3 mm for the uranium-rich alloys to 0.3 mm for the niobium-rich alloys. This permitted measurements of the concentration gradients in the diffusion samples without crossing more than one or two grains, thereby eliminating any grain boundary effects. The specimens were bonded by theU&apos;picture frame" technique as reported by Kittel.10 Specimens of composition b)U + (100 - x)Nb were sandwiched between two specimens of composition (x + 10)U + (90 - x)Nb after they were ground flat and parallel

Jan 1, 1963

By G B. Douglas

Lime-based neutralisation has long been the remediation treatment of choice for acidic mine pit waters. While suited to the attenuation of acidity, lime-based neutralisation may be difficult to implement efficiently due to variation in quality and the partial loss of neutralisation efficiency due to armouring. Large volumes of gypsum-bearing sludge may also require mechanical dewatering and transfer to final voids prior to resumption of in-pit mining or closure. Thus, operational costs may be substantially higher than primary neutralisation alone. Lime production also results in large greenhouse gas (CO2) emissions.Hydrotalcites (HT) are a class of Mg-Al layered double hydroxide minerals with the composition Mg6Al2(CO3 )(OH)16.4H2O. A range of other divalent and trivalent cations may also readily substitute for Mg (eg Cu, Ni, Pb, Zn), Al (eg Fe, La, Ce) and metalloids/oxyanions (SeO42-, AsO43 -/CrO42 -, MnO4-) for CO3 into the hydrotalcite structure. A common feature of acid mine pit waters, often overlooked in assessment of potential remediation options, is the frequent predominance of divalent and trivalent cations as a consequence of partial decomposition of both ore and gangue minerals during in-pit wall rock leaching. Thus, given the presence of substantial divalent and trivalent cations in acidic mine pit waters, an opportunity exists to exploit and in effect work harmoniously with the prevailing pit water composition to form a polymetallic hydrotalcite.The utility of hydrotalcites in the remediation of acidic mine pit waters lies in their ability to incorporate a wide range of contaminants; instantaneous formation, often in a single step; simple post-treatment solute composition; rapid settling; low sludge volume; and the potential to form ore-grade precipitates potentially amendable to reprocessing to (partially) recover remediation costs. Examples of hydrotalcite formation as a method to remediate contaminated acidic mine pit waters at laboratory-scale to full-scale will be presented.CITATION:Douglas, G B, 2015. Whither lime? In situ hydrotalcite precipitation as a method of remediation for acidic mine lakes, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 97–104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By C. H. Green

Recently two papers on the structure of eutectics were read before thc British Institute of Metals, one by F. L. Bradyl and the other by A. Portevin. 2 In the preparation of photomicrographs of laboratory specimens as illustrations for student work, and in connection with various researches, the writer has been working along the same line for some time and, therefore, was much interested in the results given, especially those of Portevin. He has correlated the information on the subject and has outlined a broad scientific basis for future work along this line. It is largely with the idea of adding something by way of illustration to the work already done that this paper is written. The eutectic is generally understood to mean the alloy having the lowest melting point of any alloy of the system, and in which the melt becomes supersaturated with reference to the two or more phases which separate out simultaneously or alternately. From the surface pattern, the eutectic means a structure with no primary crystals. It is not always easy to get the exact eutectic composition in making any alloy; in fact, a slight range in composition may be expected and some of the coarser particles may be richer in either of the composing metals. Even when chemical analysis shows the right composition, differences in density of the pure metals may cause segregation, or supercooling resulting from different crystallizing properties may give a surface pattern the appearance of being on one side of the eutectic point. However, the alloys on either side of the eutectic composition, showing primary crystals of one of the phases and the effect of the proeutectic form on the surface pattern of the eutectic make a very interesting study, which is slightly touched upon in this paper. The phases, or microconstituents, of a eutectic may be pure metals (Pb-Sb, Tl-Au), solid solutions (Cd-Zn), a pure metal and a solid solution (Ag-Sn), or a pure metal or solid solution with an intermetallic compound (Sb-Mg, Sb-Cu, As-Cu, Bi-Te, etc.).

Jan 1, 1925

By L. Sturkey

Quantitative X-ray diffraction studies of the precipitation of thorium in a Mg + 3.3 Th + 0.51 Zr alloy (HK31A) in both the as-cast and cold-worked states show that the precipitation may be described by f = 1 - e(t/T)1/2 over most of the aging period. The effects of cold work and temperature changes are determined. The precipitation of tile equilibrium Mg-Th compotund is Preceded by the formation of a transition phase of higher thorium content, with the cowposition Mg2Th and with a Laves-phase structure. Thorium-containing alloys of magnesium have assumed considerable commercial importance, especially for applications requiring exposures to temperatures greater than 500°F for appreciable lengths of time. The principal commercial wrought alloys in this system are HK31A, containing nominally 3 pet by weight thorium and about 0.7 pet by weight zirconium: and HM21A. containing 2 pet by weight thorium and 1 pet by weight manganese. These two alloys retain a high level of properties even after exposures of 100 hr at 600°F, while the more common alloys containing aluminum and zinc are badly overaged by these conditions. Therefore, in order to obtain some insight into the mechanism by which thorium produces high temperature stability in these wrought alloys, it seems desirable to investi- gate the effect of temperature and mechanical working on the precipitation processes involving thorium. Since the scattering power of a thorium atom for CuKa X-ray radiation is about ten times that for a magnesium atom, the magnesium alloys containing about 3 pet by weight thorium are ideal for quantitative measurements by X-ray diffraction of the amount of Mg-Th compound present at any time. Such quantitative measurements should be of theoretical importance in the study of the effects of time, temperature, and deformation on precipitation and precipitation hardening. Of the two commercial alloys, HM21A and HK31A, the latter is certainly the most suitable for study: In the Mg-Th-Zr2 system, only Mg-Th compounds need be considered, since no ternary compounds or binary Th-Zr3 and Mg-Zr4 compounds exist. The Zr is added to this alloy as a grain refining agent and probably plays a secondary role in precipitation. On the other hand. thorium and manganese form many

Jan 1, 1961

By R. L. Skaggs, D. T. Peterson

The effect of carbon in solid solution on the plastic behavior of thorium was studied by measuring the flow stress of Th-C alloys from 4.2" to 573°K and at several strain rates. Carbon was found to strengthen thorium primarily by increasing the thermally activated component of the flow stress. The strengthening due to carbon was directly proportional to the carbon content and decreased rapidly with increasing temperature up to 423" K. The flow stress also increased with increasing strain rate. The strengthening appears to be due to a strong short-range interaction between carbon atoms and dislocations. A yield point was observed in the Th-C alloys which increased with increasing carbon content. JTREVIOUS study of the mechanical properties of thorium has been confined largely to the measurement of the engineering properties. Work prior to 1956 has been summarized by Milko et al.1 who reported that additions of carbon to thorium sharply increased the room-temperature strength. In addition, the yield strength was observed to decrease rapidly over the temperature range from 25" to 500°C. In 1960, Klieven-eit2 measured the flow stress of thorium containing 400 ppm C. He found that over the temperature range from 78" to 470°K the flow stress was strongly dependent on temperature and rate of deformation. A drop in the load-elongation curve, or a yield point, was observed over most of the above temperature range. Above 470°K, the flow stress was nearly independent of temperature and strain rate. This strong temperature and strain rate dependence of flow stress is not generally observed in fcc metals. It is, in fact, more typical of the behavior reported for bcc metals. Bechtold,3 Wessel,4 and conrad5 have pointed out the striking difference between the commonly studied bcc metals and fcc metals in regard to the effect of temperature and strain rate on the flow stress. Zerwekh and scott6 studied the plastic deformation of thorium reported to contain 12 ppm C. They found that this material did not obey the Cottrell-Stokes law as expected for fcc metals. In addition, they found values of the activation volume smaller by an order of magnitude than expected for an fcc metal. They concluded that thorium was strengthened by a randomly dispersed solute. Thorium differs from many other fcc metals that have been studied extensively in that it shows a relatively high carbon solubility at room temperature. Mickleson and peterson7 report the solubility limit at room temperature to be 3500 ppm C. The lowest value reported is that of Smith and Honeycombe8 who report the limit to be 2000 ppm C at 350°C. The pres- ent investigation was a systematic study of the flow stress and yield point phenomenon of thorium over a broad range of carbon content, temperature, and strain rate. EXPERIMENTAL PROCEDURE The thorium used in this investigation was produced by the reduction of thorium tetrachloride with magnesium as described by Peterson et a1.&apos; Chemical analysis of the original ingot after arc melting and electron beam melting is shown in Table I. Alloys were prepared by arc melting this thorium with high-purity spectrographic graphite. Threaded specimens with a gage length 0.252 in. diam by 1.6 in. long were used for the constant stress or creep measurements. These specimens were machined from rod which had been cold-rolled and swaged to % in. diam. Tensile specimens were prepared by swaging annealed 3/8 -in.-diam rod to 0.102 *0.001 in. The as-swaged wire was cut to lengths of 2 in., annealed, and the center 1-in. gage length elec-tropolished to 0.100 ±0.001 in. The specimens were gripped for a length of 3 in. at each end by a serrated four-jaw collet which was tightened by a tapered compression nut. No slipping occurred in the grips and negligible deformation was observed outside the 1-in. gage length. Both the creep and tensile specimens were annealed at 730°C under a vacuum of 1 x X Torr. The resulting structures consisted of equiaxed recrystallized grains with a grain size of 3200 grains per sq mm for the tensile specimens and 2200 grains per sq mm for the creep specimens. After the specimens were prepared, samples were analyzed for nitrogen, oxygen, and hydrogen. The results of these analyses are given in Table 11.

Jan 1, 1969

By Edward W. Ames

"The Jewell tunnel property, situated 3/miles north of Garfield, Chaffee County, Colo., was examined by an engineer3 of the Bureau of Mines in June 1943. Field work began September 16, 1944, but was recessed from December 26, 1944, to gay 15, 1945, because of heavy snows, and was suspended July 12, 1945, when rehabilitation of the New York tunnel workings was completed to the point desired.In its program of exploration of Mineral deposits, the Bureau of Lines has as its promary objective the more effective utilization of our mineral resources, to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as seen .as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final report. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples of ore and performs beneficiation tests. Both these branches are under the supervision of Dr. R. S. Dean, assistant director.For their supervision of the project and their help in revising the report, particular acknowledgment is due Wm. P. Huleatt, district engineer, Denver, Colo., and Paul T. Allsman, chief, Salt Lake City Division, Mining Branch.The property is situated in secs. 15 and 22, T. 40 N., R. 6 E., N.R.F.M. Salida, the county seat, is on the main line of the Denver & Rio Grande Western Railroad. The property is reached from Salida by following U. S. Highway 50 westward for 18 miles to the village of Garfield, near Monarch Pass, then northward for 3 miles by a very steep mine-access road up Taylor Gulch (fig. 1).The highway to Garfield is accessible throughout the year, but the access road from Garfield is generally impassable from December until June because of snow."

Sep 1, 1946

By S. L. Windes

This report presents physical and petrographic properties of approximately 60 types of rock from operating mines or mineral-investigation projects and supplements Repot of Investigations 4459, Physical Properties of Mine Rock (hereinafter referred to as Part I). The physical properties evaluated include the following: Apparent specific gravity Apparent porosity Compressive strength Flexural strength (modulus of rupture) Impact touchiness Abrasion hardness Scleroscope hardness Modulus of elasticity (Yourg?s modulus) Modulus of rigidity Specific damping capacity Longitudinal bar velocity

Jan 1, 1950

By Jinsheng Wang, Wei Lv, Xuewei Lv, Pingsheng Lai, Jie Dang

The isothermal reduction kinetics of vanadium titanium magnetite sintering ore was investigated by thermo-gravimetric analysis at a temperature range of 1123–1223 K under 30% CO + 70% N2 gas mixtures. The apparent activation energy of reduction was calculated by iso-conversional method and its value is 36.7 kJ/mol. The model function describing the reduction mechanism was discussed by Sharp analysis and the results revealed that the reduction process is controlled first by random nucleation and nucleus growth mechanism (RNNGM) as reduction degree is lower than 0.5, followed by the mixed influence of RNNGM and phase boundary reaction when reduction degree is higher than 0.5.

Mar 1, 2017

By J. Campbell

Various models are discussed for the evaluation of the negative pressures which may occur in solidifying materials which exhibit various deformation modes: elastic-plastic, Bingham, viscous, or creep flow. The inadequacy of the previously proposed elastic-plastic solution for solidifying metals is revealed by comparison with the more reliable creep results which are given graphically for aluminum, copper, nickel, and iron. The maximum tensions experienced in the liquid phase of solidifying spheres ranging in size from large castings to submicron powders are in the range from —10&apos; to —105 atm for these metals. THERE has been much recent interest in the negative pressures associated with the volume change on solidification and in the possibility of the occurrence of cavitation. Considering the freezing of a highly supercooled liquid, an attempt to evaluate the stresses in the liquid ahead of the rapidly moving solidification front has been made by Horvay1 on a microscale and by Glicksman2 on a macroscale. In a casting of a wide freezing range alloy, the pressure differential due to viscous flow of residual liquid through the pasty zone has been discussed by Piwonka and Flemings,3 In a previous publication4 the author has attempted to estimate the negative pressure occurring in the residual liquid of a spherical casting, employing an elastic-plastic model to describe the collapse of the solidified shell under the internal tension. An earlier model assuming a rigid shell was shown to be inaccurate by many orders of magnitude. The elastic-plastic model is critically reviewed here, and other models are developed which are thought to be more closely related to metals and other materials near their melting points. The spherical geometry (Fig. 1) is chosen because the highest shrinkage pressures would be developed, although the analyses are readily adaptable to cylindrical geometry. A parallel sided casting experiences little internal tension because of the relatively easy dishing inward of the sides. (This commonly observed phenomenon has previously been attributed solely to atmospheric pressure.) Furthermore, small regions of confined liquid in a large solidified volume of a casting approximate reasonably well to spherical geometry. ELASTIC-PLASTIC MODEL The author has shown4 that as solidification proceeds the internal hydrostatic tension builds up until the elastic limit of the shell is exceeded. At this point the internal pressure is closely -2Y/3. Subsequently a plastic zone spreads from the inner surface toward the outer surface of the shell. When the whole casting is deforming plastically a rather more generalized analysis taking account of the externally applied pressure PA + 2y/b gives the internal pressure as: P = Pa + 2y/a + 2ys/b - 2 Y In(b/a) [1] The 2y/a and 2ys/b terms result from the tendency of the liquid-solid and solid-vapor interfaces to shrink, reducing their energy, and thereby helping to collapse the solid phase and compress the liquid phase. The 2y/b term would be important only for powders. The last term arises because of the plastic restraint of the solid, resisting collapse and so effectively expanding the residual liquid. From Eq. [I] it is easily shown that there is a minimum in the pressure at the radius amia= y/Y [2] which is of the order of 103K for the metals aluminum, copper, and iron, and corresponds to the minimum pressure Pmin = 2 Y[l-ln(bY/y [3] The results of a fully worked out elastic-plastic solution are given in a previous reporL4 The main criticism which may be leveled at this analysis when applied to metals at their melting points is the strong dependence of the yield stress on the strain rate. The strain rate varies with both solidification conditions (e.g., whether chill-cast or slowly cooled) and during solidification, as is indicated in the following section. Thus an appropriate choice of Y is very arbitrary. Before proceeding to a discussion of models which are strain-rate-dependent, it is necessary to evaluate the strain rate as a function of the rate of solidification. SOLIDIFICATION RATE Various empirical relations have been deduced5 for the rate of thickening of the solid shell by pour- out tests on partially solidified spheres. These, however, are unsatisfactory for our purposes since they become very inaccurate when the liquid core is very small. A theoretical approach is therefore necessary, and some solutions are set out below. Making the assumptions of constant surface temperature of the casting during freezing, no superheat, and a material freezing at a single temperature, Adams8 deduces the approximate solution: which becomes when b » a: Employing a semiempirical approach vallet6 finds:

Jan 1, 1969

By H. McIntire, R. Preston, D. Roberts

"Repeated 3D terrestrial digital photogrammetric surveys were conducted on hard rock mine pillars to characterize damage during secondary mining. Damage was quantified by measuring Depth of Failure, DOF, from spalling material and crack intensity, D21. These damage values were then correlated to visually assessed Pillar Damage Ratings and numerically estimated pillar loads. Measured damage, particularly Depth of Failure, correlated well with Pillar Damage Ratings. Numerical predicted pillar stress vs. damage exhibited the expected trend with shorter pillars being stronger. High resolution photographs and 3D models were also used to characterize damage mechanisms, which were found to be structurally constrained. INTRODUCTIONThe Doe Run companies Southeast Missouri Operations consists of six room and pillar lead mines (Brushy Creek, No. 29, Casteel, Buick, Fletcher and, Sweetwater) (The Doe Run Company, 2014). The mines are hosted in the Carbonates and Shales of the Viburnum trend with mining depths varying from 180 to 300 m. Pillars are commonly cut square with widths varying from 7 to 9 m and heights generally between 5 and 18 m, resulting in extraction ratios between 80 and 85% (Roberts et al., 1999). Figure 1 presents an idealized stratigraphic section through the Viburnum trend and Figure 2 shows a plan view of the five areas spanning the three mines included in this study."

Jan 1, 2015