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By K. G. Davis

Dilute alloys of silver and of thallium in tin have been solidijzed unidirectionally under controlled conditions, to study the segregation associated with a cellular interface under conditions where both thermal and solute convection are present. Autoradiography and radioactive tracer counting techniques were combined with electron-probe microanalysis to study both macro- and microsegregation. It was found that, for concentrations giving only small amounts of constitutional supercooling, cell formation had little effect on the macroscopic distribution of solute along the specimen. At higher concentrations the effective distribution coefficient was higher than that expected for a smooth interface. Node spacing was independent of initial solute content at lower concentrations, becoming greater as keff increased. Silver content at the segregation nodes of silver in tin alloys was independent of initial concentration and considerably in excess of the eutectic composition. SINCE the investigation of cell formation at advancing solid-liquid interfaces by Rutter and Chalmers,' a large volume of work has been dedicated to the determination of solidification conditions under which a planar interface will break down into cellular form. Early experiments were explained satisfactorily by the concept of constitutional supercooling,2 but, due to poor measurement of temperature gradients in the liquid, lack of accurate data on liquid diffusion and equilibrium distribution coefficients, and uncertainty about the effects of thermal and solute convection, these experiments cannot be used as proof for the theory. More recent work, however, has shown that under conditions where convection is eliminated or can be ignored good correlation is observed.3,4 Investigations into segregation at cell caps5 and at cell nodes6-'' have been made, but no measurements appear to have been done on the overall, macroscopic segregation down a unidirectionally solidified rod of material which has solidified with a cellular substructure. This has practical importance in casting, where regions of material with cellular substructure are often encountered, and also in zone refining where the thermal conditions necessary for a planar interface are unattainable. Further, as will be shown, the macroscopic segregation can give information on the following question. Granted that a cellular solid-liquid interface develops from a planar one when the conditions for constitutional supercooling are exceeded, how much supercooling is present after the cells have formed? EXPERIMENTAL PROCEDURE AND RESULTS Specimen Preparation. Specimens 25 cm long with a square cross section 0.6 by 0.6 cm were grown in graphite boats by solidification from one end. Alloy compositions are given in Table I. Two specimens of each composition were grown. The tin was 5-9 grade and the silver and thallium both 4-9 grade. Ag110 and Tl204 were used as tracers. Each composition had the same quantity of tracer so that auto radiographs of specimens containing different concentrations of the same element could be easily compared. Thermocouples inserted through the lid of the boat into a dummy specimen showed that, over the first 10 cm of growth, thermal conditions were quite steady, with a rate of interface advance of 5.8 cm per hr and a temperature gradient in the melt ahead of the interface of 3.0°C per cm. The specimens were seeded from tin crystals of a common orientation to eliminate orientation effects. Dilution of the specimen by seed material was minimized by the provision of a narrow neck between specimen and seed crystal. Macrosegregation. After growth, the specimens were sectioned with a spark cutter. The rods of silver alloy were cut into 1-cm lengths and analyzed for Ag110 using a y -ray counter with fixed geometry. The specimens containing thallium were cut into 2-cm lengths and analyzed for T1 204 by taking 13 counts from each end of the cut lengths through an aperture in lead sheet approximately 0.4 cm square. The results are summarized in Figs. 1 and 2. To find the effective distribution coefficient for the silver in tin alloys under smooth interface conditions, the region of substructure at the bottom surface of one of the 10 ppm specimens, see Fig. 3, was removed by spark machining before counting. Autoradiography. For both alloy systems the samples were polished on sections taken alternately parallel and perpendicular to the growth direction, and autoradiographed by placing the polished surfaces in contact with Kodak "Process Ortho" film. Figs. 3 and 4 show the structures revealed. The alloy containing 10 ppm Ag showed substructure only after a few centimeters of growth, and then substructure was limited to a narrow layer at the base. The "speckled" substructure reported previously in this system4 is here clearly seen to be an intermediate stage between planar and cellular interface conditions. The other samples show a remarkable similarity considering

Jan 1, 1969

By H. I. Aaronson, W. L. Winterbottom, G. M. Pound

On the basis of a statistical thermodynamic treatment of the data of smithz2 on the activity of carbon in austenite, a Darken and smith23 deduced that the interaction energy, wy, between carbon atoms occupying nearest-neighboring interstitial sites is repulsive. Aaronson, Domian, and pound 24 (ADP) have applied two different statistical thermodynamic analyses to the same data. One analysis, a composite of the treatments of Darken and Smith,23 Speiser and Spret-nak," and Kaufman, Radcliffe, and Cohen,26 primarily takes account of the positional entropic effects of wy in dilute solutions. The other, due to Lacher 27 and Fowler and Guggenheim," is also applicable to more concentrated solid solutions. The equations which both analyses produce for a,, can be rearranged so that, when In a,, is plotted against the appropriate function of the carbon content of the austenite, the plot will have a slope of unity when the correct value of wy is employed. Since no other constant need be simultaneously evaluated in order to make this determination, ascertaining the most probable value of wy from Smith's data on the bases of these analyses was an elementary problem in least-squares statistics. ADP demonstrated that the wy's obtained from both analyses vary with temperature in a statistically significant manner. McLellan, Gerrard, Horowitz, and sprague 29 (MGHS), on the other hand, have recently made a new statistical thermodynamic study of a,, and have concluded from this study that wy is independent of temperature. The equation which they derived for a,, is: where 0 = ratio of the mole fraction of carbon atoms to that of iron atoms, z = number of sites from which occupancy is excluded by the presence of a carbon atom and the repulsive character of its interaction with nearest-neighboring carbon atoms (z = zb in Ref. 24), and x = a geometric parameter taking account of overlapping of the exclusion shells of nearby carbon atoms. z is 1 when wy = 0 and 13 when wy = Q. For a given value of z there is a definite value of X . In the absence of an equation connecting z and X, MGHS computed geometrically the value of x at several integral values of z; x increases from 0.47 to 8.67 as z is increased from 2 to 5. MGHS fitted Eq. [I] to the a,, data of Ellis, Davidson, and Bodsworth30 at 925° and 1050°C and to the data of smithz2 at 1000°C. Confining z to integral values in the range 4 to 6, and also somewhat restricting AG, the values of z, X, and AG were sought which would minimize the average root mean square percent deviation, D, of the calculated a,, values from those obtained experimentally. Finding that D was almost always smallest when z = 5, they concluded that z is independent of temperature. Since:23, 26 where R = gas constant and T = absolute temperature, and w,, was considered to be similarly invariant, this statement cannot be strictly true. The temperature range employed, however, was small and the interval between the values of z tested was sufficiently large so that the results could still be consistent with a constant The statistical treatment of the a,, data applied by MGHS is clearly quite approximate. Since more than three values of a,, are available at each temperature, z, and X, and AG have actually been over deter mined, rather than underdetermined as their treatment implies. In order to make more complete and exact use of the a,, data, we shall employ the Legendre Method of Least Squares, as described by Whittaker and Robinson. This technique permits conversion of the overdetermined system of equations produced by the substitution into Eq. [I] of the available pairs of a,, and 0 data at a given temperature into an even determined system. Solution of the latter system yields the most probable value of each of the three constants. This procedure will allow a statistically rigorous test to be made of the conclusion drawn by MGHS in respect of the temperature dependence of In order to obtain linear iiequations of conditions" from Eq. [I], the exact values of the three unknown constants are replaced by G/RT = =/RT + y, where z, i, and aG are estimated values of the constants. This allows the conditional equations to be written in the form:'l where fi -f6, i, =/RT) = the right-hand side of Eq. [I] for a given pair of ayi and values. When applied to Eq. [I], these relationships become: The i equations of condition are reduced to three "normal equations" in the manner discussed by Whittaker and Robinson. The normal equations are then solved for a, ß, and y. Both of these operations are most conveniently performed by means of the computer technique of Winterbottom and Gjostein.32 This technique was used iteratively until the value of 0 (the most sensitive of the three correction factors) became 10.01. (Until they became small, a, 8, and y

Jan 1, 1969

By Foster J. Witthauer

First mining operations in the Tyrone District, located just north of the Burro Mountains in Grant County, New Mexico, commenced in the 1870's. A major operation was undertaken by Phelps Dodge Corporation in the early 1900's when a 2,000 ton per day underground mine was developed and a gravity concentrator was built east of the mine and across the Continental Divide. It was during this time that the picturesque Tyrone townsite was built and occupied. In 1921, however, the underground operation was closed because of high operating costs and low demand for copper. The area was drilled extensively during the 1950's and in October 1966 Phelps Dodge announced the pending development of the new Tyrone with a large open-pit mine, a modern concentrator, suitable support facilities, and a new townsite to be located between the mine and Silver City. Stripping for the pit and construction of shop and milling facilities began in 1967. By the spring of 1969, ore was being stockpiled near the primary crusher. Operation of the concentrator on a 3-shift per day basis commenced on July 17, 1969. The concentrator as initially built had one primary, two secondary, and five tertiary cone crushers, two grinding sections of six ball mills each, two flotation sections, four filters, and four tailing thickeners. The capacity was about 30,000 tons per day. In 1971 and 1972, the capacity was increased to 48,000 tons per day by the addition of one secondary and two tertiary crushers, one section of eight ball mills, one flotation section, two filters, and four more tailing thickeners. Centralized automatic control was built into the original and expanded facilities to the greatest extent possible, considering the state of the art at that time. Installation of additional control

Jan 1, 1976

By Carl A. Allen

Page Introduction................... 367 FactoRs Affecting the Choice of Method......... 367 Review of Stoping Methods.............. 368 Underhand Stoping................ 368 Overhand Stoping................ 370 Longitudinal or Flat-Back Stoping........... 371 Rill-Cut Stoping................. 372 Saw-Tooth Back Stoping.............. 372 Shrinkage Stoping................ 372 Combination Stoping................373 Side Stoping.................. 374* Breast Stoping................. 374 Sublevel Stoping.........,....... 374 Square-Set Stoping................ 376 Filling Methods................. 376 Caving Methods of Mining......... 376 Top Slicing.................. 377 Sublevel Caving................. 379 Block Caving ................. 380 Back Caving into Chutes.............. 381. Costs of Mining Methods.............. 382 Costs of Willing and Blasting. Comparison of Stoping Methods ... 383 Lighting................... 386 Timbering and Handling Ore in Stopes.. A Comparison of Square-Set and Top-Slicing Methods..............386 Tramming.................... 380 Mining oF the Massive Porphyry CoppeR Deposits ....390 Utah Copper and Boston Consolidated Mines.....391 Ray Consolidated Mine.............. 392 Miami Mine.................. 392 Inspiration Mine................ 395 Ohio Copper Mine...........395 Development.................... 398 Appendix..................... 399 Costs of Mining................. 399 Costs of Development............... 406

Jan 1, 1915

By C. Richard Tinsley, Norman Miskelly, S. James Hodge

Construction of the Ranger uranium project, located 230 kms east of Darwin in the Northern Territory, Australia, commenced in January 1979. Energy Resources of Australia Ltd (ERA) was incorporated in February 1980 to acquire all the rights in the project. The total cost to ERA of these rights was A$407 million, made up of A$125 million in cash to the Federal Government and the issue of 125 million A$1.00 shares at par, plus a payment of A$16 million in cash to each of Peko-Wallsend Ltd. (Peko) and EZ Industries Ltd. (EZ). ERA's cash requirements to complete the project were estimated in October 1980 to be A$553 million. Project loans, secured by first ranking debenture stock, were arranged for a total of US$390 million, while second-ranking debenture loans totalling A$60 million were [ ] obtained from the vendors, Peko and EZ. Overseas participants (power utilities who had agreed to purchase uranium yellowcake under contract) arranged to take up 25% of the equity capital for A$102.5 million; Peko and EZ were allotted 30.5% each as satisfaction of vendors' consideration; and 14% representing A$57.5 million was issued to Australian residents in an underwritten public flotation in November, 1980. The loan and equity financing arrangements required the successful resolution of many complex and interlocking factors, including technical and economic feasibility, agreement with Aboriginal interests, compliance with Government policies, and securing of sales contracts.

Jan 1, 1985

By J. C. Shyne, T. D. Gulden

The steady-state creep behavior, in compression, of indium containing a dispersion of atomized glass particles was studzed over a range of temperature, stress, and composition. The observed behavior was not consistent with a simple model of dislocation climb over dispersed particles. From room temperature to about 100°C the temperature dependence could be described by an activation energy about one and a half times that of self-dijfusion in indium while at higher temperatures a much higher ternperature dependence was observed. THE value of dispersion-hardened and precipitation-hardened alloys has long been recognized. The mechanism of hardening, however, is not completely understood, especially at elevated temperatures where dispersed particles increase creep resistance. Following the suggestion of Schoeck1 that the rate of creep in dispersion-hardened materials is controlled by dislocation climb over second-phase particles, Ansel and weertman2 derived steady-state creep equations for dispersion-hardened materials. Their derivation was based on dislocation climb over non-deformable spherical particles in a metallic matrix. For low stresses they predicted a linear relation between applied stress and steady-state creep rate. For stresses large enough to cause dislocations to pinch off around the precipitate particles, the theoretical creep rate was shown to be proportional to the fourth power of stress. For very high stresses an exponential stress dependence was predicted. In all cases the theoretical creep rate is linearly proportional to the diffusion coefficient. This provided the primary temperature-dependent factor. Subsequently, Ansel and Lenel3 reported some experimental data on SAP, a composite of aluminum and aluminum oxide, that was in good qualitative agreement with the above theories. Their experimental creep rates, however, were four orders of magnitude less than the theory predicts. This was attributed to a low density of active dislocation sources in the material; somehow the dispersed particles inactivated the dislocation sources instead of merely interferring with dislocation motion. Meyers and sherby4 have recently reported on the creep behavior of SAP. Their results were inconsistent with a simple dispersion-strengthening model and led them to conclude that a continuous network of oxide controls the high-temperature mechanical characteristics of SAP. Because of the rather complex mechanical behavior of SAP and the lack of agreement about the morphology of its oxide phase, it appeared desirable to study the creep of a dispersion-strengthened material of controlled morphology. For the present work a dispersion of spherical glass particles imbedded in a matrix of indium was chosen. The microstructure of this material was similar to the idealized uniform dispersion of hard spheres in a deforming matrix assumed by Ansel and Weertman in their theoretical treatment. SPECIMEN PREPARATION For experimental convenience, it was decided to use a low melting-point metal in this investigation. It was necessary that the metal not be oxidized readily up to its melting temperature and that it wet the second-phase particles. It was desired that the material chosen for the dispersed phase be available as a fine powder with closely controlled size and shape. The material chosen to satisfy these requirements consisted of a matrix of indium metal containing a dispersion of atomized particles of a soft soda-lime-silica glass ranging from 5 to 30 µ in diam. The glass particles had a highly regular spherical shape. The composite was made by stirring the glass powder into liquid indium maintained at a temperature just above the melting point of indium, 156°C. The creep specimens were prepared by a hot pressing operation. Five to ten g of the mixture were placed in a steel die and pressed at 125°C for 5 min under a pressure of 30,000 psi. The resulting specimens were cylinders about 3/8 in. in diam and ranged from 0.4 to 0.7 in. high. By following this procedure a uniform dispersion was obtained in the creep specimens. Typical microstructures of specimens containing twenty and forty volume percent glass powder are shown in Figs. 1 and 2. Unfortunately, grain size could not be determined by the metallo-graphic techniques used. CREEP TESTING PROCEDURE Creep tests were performed in compression under constant stress. The specimens were placed in

Jan 1, 1963

By B. C. Wonsiewicz, G. Y. Chin

THE presence of deformation bands in cold-worked metals is known to influence the development of deformation textures1 but has not been considered in any theoretical treatments. At the present time the most rigorous theory of deformation textures appears to be based on Taylor's concept of homogeneous deformation of a crystal within a polycrystalline aggregate.' For each crystal the Taylor theory allows the operation of several equivalent combinations of five or more slip systems. Hence deformation bands can arise from the operation of a separate combination of slips in each of several portions within a crystal. On the other hand, a second type of band may occur as a consequence of slip on systems other than those selected on the basis on homogeneous deformation. This type appears to be associated with crystals of symmetrical orientations, such as the [loo] and [lll.] axial orientations in drawn wires of fcc single crystals studied by Ahlborn.3 In this note we propose a simple mechanism of deformation banding of the second type, and compare the theoretical results for wire drawing of [loo] and [Ill] with Ahlborn's observations. In outlini the model requires that the work to accomplish a given overall shape change by banding be less than or equal to the work to accomplish the same change by homogeneous deformation. While the work by homogeneous deformation, WH = ?T ;dri, can be calculated exactly by the equivalent methods of Taylor2 or of Bishop and Hill,4 the work by banding, WB, is less certain. The latter consists of 1) Wi, work by slip within a band, 2) Wb, work associated with formation of a boundary between bands, and 3) Wc, work to correct the difference in shape change arising from banding and homogeneous deformation. The Wi term can be evaluated explicitly for a band with an assumed set of slip systems, but a satisfactory analysis of Wb and Wc has not been obtained. Since WB = Wi + Wb + Wc WH, for banding to occur, however, a necessary condition is Wi = WH . Hence it seems reasonable to choose a band with the lowest value of Wi among competing bands consistent with Wi = WH, and then minimize Wb and Wc by arranging the physical configuration of the selected band. Wc is minimized by combining neighboring bands such that their net strain matches the macroscopic strain as closely as possible, and Wb is minimized by enforcing strain compatibility across the boundary between two neighboring bands, similar to the case of a grain boundary.5 It is realized that this procedure is not completely satisfactory, but it does seem to explain Ahlborn's observations reasonably well. The procedure is now outlined for the two corner orientations. a) [l00]. Fig. 1 shows a (100) stereographic projection. The results of the Taylor analysis for axi-symmetric flow by homogeneous deformation6 show that, while [loo] itself is unstable, the rotation of the tensile axis will nevertheless be confined to within about 15 deg from [loo]. Alternatively, less work may be expended by banding with slip on a pair of systems with primary-conjugate relationship, e.g., (ll1)[10l.I + (li1.)[110]. The latter represents minimum Wi for all possible bands.* Since there are four symmetrically

Jan 1, 1970

By W. W. Norton

THE gradually increasing proportion of sulphide ores which lead smelters of to-day are called upon to handle has caused the roasting problem to become one of ever greater importance. We may look back a score of years or so and recall the old hand roasters, some of which turned out a finely divided roasted product, and others fashioned with a "fuse-box" wherein the roasted ore was slagged. Then came mechanical furnaces of several types, the Brückner cylinder, the Brown-O'Harra, the Ropp, and others, all designed to cut out the cumbersome hand labor of the old reverberatories. Roasting costs were thereupon reduced and tonnages stimulated to a gratifying extent. However, it seems to have been early recognized that this very feature of a greater amount of roasted sulphide ore as compared with oxide ore brought with it a train of difficulties at the blast furnaces. The mechanically roasted ore was fine physically, the blast furnaces were choked and the troubles of the smelterman were not at an end. Then the Huntington-Heberlein pot system of roasting appeared upon the scene, and later on the Dwight-Lloyd machines were invented, and inasmuch as both of these processes were designed not only to roast the ore but to agglomerate it as well, it was apparent that distinct steps in advance has been achieved. At the Murray plant, modern up-to-date roasting practice is fully exemplified and there are now in successful operation roasting furnaces or devices of several sorts: namely, Godfrey revolving-hearth furnaces, Wedge multiple-hearth mechanical roasters, Dwight-Lloyd. sintering machines, and Huntington-Heberlein pots. Godfrey and Wedge furnaces will properly handle material high in sulphur, say ores with 25, 30, and 35 per cent. of that element; D. &.L. machines and H. & H. pots will positively not treat efficiently ores or mixtures containing anywhere near the sulphur content mentioned, but are confined to charges containing in the neighborhood of 15 or 18 per cent. In passing, it may also be explained that, so far as the knowledge of the writer goes, Godfrey and Wedge furnaces do not economically eliminate sulphur to an extent

Jan 8, 1914

Discussion of the paper of ALBERT D. BROKAW, to be presented at the Colorado meeting, September, 1915, and printed in Bulletin No. 1:16, April, 1918, pp. 947 to 950. LEE HAGER,* Houston, Tex. (written (discussion t).-In no other oil region of the world, perhaps, have the geological principles, of such high value in many fields, found so little practical application as in the

Jan 8, 1918

By Norman E. Lehman

Pyrometasomalic mineralization occurs within meta-morphosed Paleozoic carbonates intruded by Laramide granodiorites. Two types of alteration developed shams in the district. The dominant type is post-magmatic which developed an early hydrous endoskarn phase, and intermediate anhydrous exoskarn phase, and a late hydrous phase affecting both sham types. A rare, second type is magmatic in age, lacks the hydrous phases, and developed a mineralogically-zoned endoskarn. Garnet exoskarns lacking associated plutonic rocks are stratigraphically controlled and contain an early anhydrous phase, an intermediate hydroxyl-bearing phase, and a late hydrous phase associated with base metal deposition.

Jan 1, 1981

By E. A. Nichols

The purpose of this paper is to present a contour map that shows the geographical variation in geothermal gradients in the Mid-Continent and Gulf Coast oil fields. Introduction Frequently there arises the need for an estimation of the temperature to be expected at a predetermined depth in working with a wildcat or in deepening old production into 'Ones that are relatively unknown. The study of geothermal gradients in oil fields has been made previously by many investigators. One of the pioneers in this work was C. E. Van Orstrand,' who, as well as most of the other investigators, was primarily interested in the relation between temperature and depth in a given locality. Between 192r and 1929, American Petroleum Institute Research Project NO. 25 fostered a thorough study of earth temperatures.2 K. IV. French did some work in California, the results of which were published in 1939.3 In most of these studies, an attempt was made to correlate temperatures in a rather localized area. This paper will show the results of an attempt to correlate temperature gradients over rather large Portions of the Mid-Continent and Gulf Coast area. Method of Obtaining Data It has been found that for complete thermal equilibrium to be established in a well, the well must stand undisturbed for a period of several hours to several weeks, depending upon the way the well was produced prior to the shut-in period. The data in this paper were obtained in conjunction with running pressures in wells or in taking samples of reservoir fluid. Glass maximum recording thermometers were used in all but a few instances. The wells had been shut in from one hour up to I. or 12 days. Since the wells were normal producing wells, some of the shut-in times undoubtedly were insufficient for complete thermal equilibrium to have been established and the temperatures measured do not necessarily represent the true earth temperatures. They do represent the temperature conditions that will be encountered in a well that is producing oil. The data, therefore, can be useful in working with or in estimating the temperatures to be expected in producing reservoirs. In obtaining a thermal gradient by dividing the difference in temperature of the formation and the mean annual surface temperature by the depth of the formation, one is assuming the depth-temperature line to be straight. Depth-temperature curves are almost straight lines (Fig. I). However, on close examination of accurate data, a slight curvature usually is observed. Most wells yield curves with slopes increasing with increasing depth. These curves are believed to be from wells that are in and are underlain by sedimentary material. Some few curves have slopes that decrease with increasing depth. These curves are believed to be from wells that are underlain rather closely by granite or some other igneous rock. Most investigators

Jan 1, 1947

By E. A. Nichols

The purpose of this paper is to present a contour map that shows the geographical variation in geothermal gradients in the Mid-Continent and Gulf Coast oil fields. Introduction Frequently there arises the need for an estimation of the temperature to be expected at a predetermined depth in working with a wildcat or in deepening old production into 'Ones that are relatively unknown. The study of geothermal gradients in oil fields has been made previously by many investigators. One of the pioneers in this work was C. E. Van Orstrand,' who, as well as most of the other investigators, was primarily interested in the relation between temperature and depth in a given locality. Between 192r and 1929, American Petroleum Institute Research Project NO. 25 fostered a thorough study of earth temperatures.2 K. IV. French did some work in California, the results of which were published in 1939.3 In most of these studies, an attempt was made to correlate temperatures in a rather localized area. This paper will show the results of an attempt to correlate temperature gradients over rather large Portions of the Mid-Continent and Gulf Coast area. Method of Obtaining Data It has been found that for complete thermal equilibrium to be established in a well, the well must stand undisturbed for a period of several hours to several weeks, depending upon the way the well was produced prior to the shut-in period. The data in this paper were obtained in conjunction with running pressures in wells or in taking samples of reservoir fluid. Glass maximum recording thermometers were used in all but a few instances. The wells had been shut in from one hour up to I. or 12 days. Since the wells were normal producing wells, some of the shut-in times undoubtedly were insufficient for complete thermal equilibrium to have been established and the temperatures measured do not necessarily represent the true earth temperatures. They do represent the temperature conditions that will be encountered in a well that is producing oil. The data, therefore, can be useful in working with or in estimating the temperatures to be expected in producing reservoirs. In obtaining a thermal gradient by dividing the difference in temperature of the formation and the mean annual surface temperature by the depth of the formation, one is assuming the depth-temperature line to be straight. Depth-temperature curves are almost straight lines (Fig. I). However, on close examination of accurate data, a slight curvature usually is observed. Most wells yield curves with slopes increasing with increasing depth. These curves are believed to be from wells that are in and are underlain by sedimentary material. Some few curves have slopes that decrease with increasing depth. These curves are believed to be from wells that are underlain rather closely by granite or some other igneous rock. Most investigators

Jan 1, 1947

By E. E. Barker

Although flotation was known to be a successful process prior to 1312, Utah Copper Co.'s ores were not entirely treated by this process until 1923. Experiments had been conducted, of course, prior to that time, and in February, 1917, the first unit of the Arthur plant was changed over from gravity concentration to flotation. On May 16, 1918, the entire Arthur plant was on flotation, excepting the coarse concentrate which was tabled prior to fine grinding. The reasons for the delay in adopting flotation at these plants were, first, that it was decided to await the outcome of the litigation with the Butte & Superior Mining Co., which began with an injunction served on Oct. 3, 1911. This litigation continued for years. Then the demands on the plants in the war years 1916, 1917 and 1918, really precluded any further drastic changes during that period, as all efforts were bent on maximum tonnage, and the cry of tonnage, rather than of recovery, was the major issue. The postwar depression followed these years of intensive production, so that it was not until 1922 that the Magna plant was equipped to use this process. Excepting, then, the amount of coarse concentrate that was tabled, 1923 was the first year when the Utah Copper Co.'s ores were on a full flotation basis. Effect of Flotation on Ore Reserves The object of this paper is to point out the effect that flotation has had on the operations of the Utah Copper Co. In 1905, when D. C. Jackling began making history in copper, the ore reserves were 34,000,000 tons, with a grade of 2 per cent. copper and a mill capacity of 700 tons daily. The point of cut-off between nonprofitable and profitable grades was 1.2 per cent. A few years later the capacity was increased to 6000 tons, when 1.1 per cent. became the point of cut-off. Ore reserves had climbed to 80,000,000 tons, having a grade of 1.9 per cent. In 1911 there was an ore reserve of 300,000,000 tons, with a grade of 1.5 per cent. and a cut-off of 1 per cent.; in 1918 the ore reserve was approximately 400,000,000 tons, and a grade of 1.38 per cent., and point of cut-off 0.95 per cent., based on normal costs and prices. Up to this

Jan 1, 1928

By C. Wegert, L. E. Paulson, S. A. Cooley, R. C. Ellman

The Grand Forks Energy Research Center (GFERC) and Commonwealth Edison of Chicago jointly conducted tests in which 400 tons of subbituminous and lignite coals were dried in a commercial scale dryer, oil sprayed and cooled, then shipped from Pekin, Ill., to Grand Forks, N.D., and stockpiled. Cars containing raw coal and dried coal which had not been sprayed, were also transported for comparative purposes. During transit, observations were made of changes in the coals' moisture content, dust losses, and temperature.

Jan 1, 1977

By G. Derge, R. E. Grace

A S detailed studies of mass transport in hetero- geneous systems are made, a knowledge of the chemical diffusion coefficients in various liquid and solid phases is necessary to understand the kinetics of any total reaction. For example, in zone refining some information must be available about the diffusion coefficients of various species in the liquid and solid regions near the moving interface. In liquid-liquid reactions, of which slag-metal reactions are of particular interest to metallurgists, the diffusion coefficient of a transferring species must be known accurately in both phases in order to predict a transfer coefficient for the over-all process. Diffusion data for various elements in liquid iron and iron-carbon alloys have been roughly deter-

Jan 1, 1959

By Hugh M. Roberts

In the spring of 1915, then a 30-year old geologist in the employ of the E. J. Longyear Co., of Minneapolis, Minn., I accompanied prospectors to ex- amine outcrops of supposed nickel ore situated a mile or two in from the shore of a lake in the Kenora district of northwestern Ontario. The deposit proved to be bog iron ore containing traces of nickel. We were stormbound there for three days, a circumstance which gave rise to a tale that was told at our fire one night. It seems that Sandy and Jock, two prospectors, were crossing the bay of a large lake in a canoe. They were bucking headwinds; the waves grew higher. Jock called out from the stern, "Sandy, can ye na pray a little." Sandy pressed his knees a little closer into the bow and, between strokes of his paddle, sought for words, which came haltingly, "Save us this time . . . Oh Lord . . . and we promise . . ." when Jock, peering through the spray sang out, "I would na commit yourself, Sandy, I think I see lond ahead."

Jan 1, 1965

By Pol Duwez, Ellis P. Frink, Paul Pietrokowsky

Ti-Au alloys in the composition interval 0 to 66 213 atomic pct Au have been studied over a temperature range from 400° to 1500°C. A partial phase diagram has been established from micrographic and macroscopic observations. All intermediate phases, Ti3Au, TiAu, and TiAu., exhibit open melting maxima. It has been observed that small additions of gold lower the allotropic transformation temperature of titanium. The P solid solution decomposes eutectoidally to a solid solution plus Ti3Au. The solubility of gold in a solid solution decreases with temperature. THERE have been several papers in the literature pertaining to the alloy system Ti-Au. However, a comprehensive study of this interesting constitu- tion diagram has not been conducted. Previous investigations have been concerned with the crystal structure of intermediate phases or partial phase diagrams. This paper represents a partial constitution diagram, Ti-TiAu,, the first portion of an investigation of the entire binary system. Laves and Wallbaum' reported the intermediate phase Ti,Au to be isomorphous with CuAu, L12 type. In a more recent paper, Duwez and Jordan' have concluded that TiAu has an atomic arrangement which is related to Cr,Si. The intermediate phase

Jan 1, 1957

By J. H. Brophy, A. L. Prill, H. W. Hayden

An error lzas been found in the conventional way of determining the time exponent of linear shrinkage for the solution-precipitation stage of liquid-phase sintering. Large amounts of shrinkage due to initial rearrangenzent result in erroneously low exponents and tni si dentification of the rate-controlling process. Two alternative, mathematically correct, methods of calculation are applied to existing data on Fe-Cu, WC-Co, and Tic-Ni-Mo. This results in reidentifi-cation of the rate-controlling process and somewhat better agreement with related data. In each case the solution-precipitation process is solution-controlled and not diffusion-controlled. THE liquid-phase sintering process has been the object of a considerable amount of research for many years. Linear shrinkage vs time data at various sintering temperatures have been used recently in an attempt to identify the prevailing mass-transport processes in a number of metallic and nonmetallic systems. There is an analytical error inherent in the methods previously used for handling data during the "solution-precipitation" stage of shrinkage which must be recognized before the correct rate-controlling processes can be determined. It is the purpose of this paper to show how the error has affected previous conclusions and to suggest corrections. A number of mechanisms have been proposed to explain experimental observations during sintering in the presence of a liquid phase. The earliest of these is due to Price, Smithells, and williamsl who attributed the observed growth of the solid phase to the simultaneous solution of smaller particles and growth of larger particles. From the work of Lenel et al.2,3 and Gurland and Norton4 has come the suggestion that the liquid-phase sintering process may be divided for analysis into three steps: 1) rearrangement upon formation of the liquid phase; 2) solution and reprecipitation of the solid phase in the liquid; and 3) "coalescence" or a final stage of sintering, characteristically slower than the solution-precipitation process. The sequence of steps is shown schematically in Fig. 1. Kingery5 presented a thermodynamic and kinetic analysis of the first two "stages" of the liquid-phase sintering process in which the functional dependence of lineal shrink- age on time at temperature was used to identify the rate-controlling mass-transport process. Table I summarizes the time dependences and processes considered by Kingery.5 This method of data presentation has been employed by Kingery and coworkers for Fe-CU,6 WC-Co, and a number of nonmetallic systems," and bv Whalen and Humenik for Tic-Ni-Mo and Fe-cu.8 In each of these studies, the rate-controlling step during the "solution-precipitation" stage was identified from the slope of the curve in that stage on a logarithmic plot such as Fig. 1. However, in all of the previous studies, at a certain composition, relatively large amounts of shrinkage due to rearrangement preceded the solution-precipitation stage. Under these conditions, the larger the amount of rearrangement shrinkage the

Jan 1, 1965

By E. C. Harder

In view of the gradually decreasing known reserves of high-grade manganese ore and the rapidly increasing consumption of iron-manganese alloys in the steel industry, it is well to turn our attention to the development of low-grade manganiferous ore deposits and to the utilization of these ores in steel manufacture. The dependence of this country on imported manganese ore and ferromanganese has been forcibly brought to the attention of steel makers during the last few years by the cessation of manganese-ore imports from Russia, the restriction of manganese-ore imports from India and of ferromanganese imports from Europe. Should the importation of manganese ore from Biazil cease, the steel industry of this country would face a serious situation. The present practice of steel making requires ferromanganese in large quantities and ferromanganese of the grade used at present can be produced only from high-grade manganese ores such as the United States appears to possess only in insignificant amounts. There are in the United States, however, large reserves of manganiferous iron ore which could probably be used extensively in the steel industry if certain changes in the practice of steel manufacture were made. Thus high-grade manganese ore could be conserved. Among the most important deposits of manganiferous iron ore in this couniry are those of the Cuyuna iron-ore district of Minnesota. It is probable that in case of restriction of foreign supplies, the users of manganese in the United States would have to rely to a large extent on the Cuyuna district to make up the shortage. Manganiferous iron ore was found in association with iron ore in the Cuyuna district in many of the early drilling operations and the possibility of its utilization was in the minds of various explorers in the dis-

Jan 1, 1918

By E. H. Edwards, J. Washburn, E. R. Parker

The mechanism of strain hardening was discussed in connection with some recent observations on the stress-induced motion of dislocation boundaries and on the simple shear deformation of zinc, cadmium, and copper crystals. THE nature of work hardening accompanying plastic deformation of metals has long been the subject of speculation. As early as 1925, Becker' suggested a thermodynamic process to explain slip based on the statistical probability for the occurrence of local glide steps. The theory that plastic glide was due to the presence of lattice defects known as dislocations was first introduced in 1934 by Taylor: and Orowan, and Polanyi.4 Taylor presented a rather complete analysis of the behavior and interaction of dislocations. He assumed a certain type of stress field to be associated with a single dislocation, and postulated that work hardening would result from plastic flow in two ways. First, dislocations following one another across a slip plane might encounter a barrier which would impede their movement, thereby gradually diminishing and eventually stopping plastic flow on that plane. The second mechanism involved the concept of dislocations traveling in opposite directions on nearby planes attracting one another to form a meta-stable lattice. The interaction of dislocations in such an array was shown to be large enough to require an increase in stress before plastic flow would continue. Kochendorfer5,6 extended the concept of work hardening involving a back stress due to an accumulation of like dislocations on a slip plane. He suggested that the formation of a new dislocation is hindered by those dislocations already present. The hardening resulting from the interaction of newly forming dislocations with bound dislocations was designated as "formative hardening," and indicated to be the only type of hardening necessarily connected with the slip process. In another detailed picture of work hardening, Mott and Nabarro7 assumed that sufficient dislocations are primarily present in the crystal as a consequence of growth irregularities (mosaic structure) to initiate slip. Work hardening resulted from the interaction of migrating dislocations with localized internal stresses produced during deformation. More recently, however, Mott8 as modified his treatment to include the generation of dislocations at Frank-Read sources and he accounts for the hardening by the formation of sessile dislocations. It has been widely accepted that metals of hexagonal structure, usually possessing only one set of glide planes, exhibit mechanical behavior markedly different from those having cubic structures. However, the differences in behavior of the two classes may be less fundamental than suggested. Rohm and Kochendorfer9 have shown that a single crystal of aluminum subjected to approximately simple shear gives the type of stress-strain curve associated with the hexagonal metals. Similar behavior has been demonstrated for gold and silver crystals by Andrade and Henderson.'" Thus when glide in cubic metals is restricted to one plane, the strain hardening characteristics closely resemble those of the hexagonal metals. It would appear, therefore, that an investigation of some of the strain hardening properties of single crystals sheared in simple glide might provide a more complete understanding of the phenomenon of work hardening. This report relates a number of recent observations made on single crystals of copper, zinc, and cadmium tested in simple shear. In addition, pertinent observations of effects accompanying stress-induced movement of dislocation boundaries are reported. Experimental Procedure and Results Details of the production and advantages of the type of single-crystal shear specimen employed for the following tests have been presented in a previous publication.n The method of testing makes

Jan 1, 1954