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By G. H. Bishop

The kinetics of the inter granular penetration and embrittlement of [100] tilt boundaries in 99.998 pct pure nickel upon exposure to bismuth-rich Ni-Bi liquids have been determined in the temperature range from 700° to 900°C. The kinetics of penetration are parabolic in time at constant temperature over most of the temperature range. In a series of 43-deg bicrystals the rate of penetration is anisotropic with respect to the direction of penetration into the grain boundaries. In lower-angle bicrystals the penetration rate is isotropic. The rate of penetration decreases with tilt angle at 700°C. The activation energy for penetration in the 43-deg bicrystals is 42 kcal per g-atom independent of direction. It is concluded that the intergranular penetration and embrittlement in the presence of the liquid proceeds by a grain boundary diffusion process and not by the intrusion of a liquid film. This was confirmed by a determination that the kinetics of penetration and embrittlement were the same in the 43-deg bicrystals upon exposure to bismuth vapor under conditions such that no bulk liquid phase would be thermodynamically stable. WhEN solid metals are exposed to a corrosive liquid-metal environment, the grain boundaries are sites of preferential attack. Depending on the temperature, the composition of the liquid, and the composition, structure, and state of stress of the solid, a number of modes of attack are possible. This paper reports a study of the kinetics of intergranular penetration and embrittlement of high-purity nickel bicrystals upon exposure to bismuth which, together with an earlier study by Cheney, Hochgraf, and Spencer,&apos; demonstrates that there are at least two modes of intergranular attack possible in the Ni-Bi system. In the study by Cheney et al., columnar-grain specimens of 99.5 pct pure nickel were exposed to liquid bismuth presaturated with nickel in the temperature range 670" to 1050°C. They found that the majority of the boundaries, which were predominantely high-angle boundaries, were penetrated by capillary liquid films, the attack proceeding by a process which will be termed grain boundary wetting. This process occurs in a stress-free solid when twice the liquid-solid surface tension is less than the surface tension of the grain boundary,* i.e., when 2yLs < YGB In this case the penetration of the grain boundary by the liquid occurs at a relatively rapid rate, resulting in the severe embrittlement of a polycrystalline solid. Grain boundary wetting is a common mode of intergranular attack in systems in which the lower melting component is relatively insoluble in the solid, but the solid has an appreciable solubility in the liquid, for example, the Ni-Bi system, Fig. 1. In systems of this type at temperatures above the range of stability of any intermetallic phases, once the liquid is saturated with respect to the solid so that no gross solution occurs, chemical gradients are small, and surface tensions become major driving forces for attack, provided the solid is stress-free. The results of Cheney et al. appear to be typical of those encountered when grain boundary wetting occurs.&apos; Capillary films were observed in the boundaries after quenching from the exposure temperature. The mean depth of penetration increased linearly with time, and the activation energy for the process was found to be 22 kcal per g-atom. In a study of the Cu-Bi system Yukawa and sinott4 found that the depth of penetration of bismuth into high-purity copper bicrystals of orientations from 22 to 63 deg of tilt about (100) at 649°C ranged from 0.05 to 0.25 in. after a 12-hr anneal. This corresponds to a linear rate of 6 to 15 X 10~6 cm per sec. At the same reduced temperature of 0.68 the rate for the Ni-Bi system&apos; was 7 x lo-&apos; cm per sec. In another study of the Cu-Bi system, Scheil and schess15 determined the kinetics of grain boundary wetting in hot-worked commercial rod. While there were several complicating factors present in this study, there is general agreement with the above results. The kinetics of penetration were linear, the activation energy was 20 kcal per g-atom, and at 650°C the rate of wetting was 2 to 5 x 10-6 cm per sec. The rate of wetting in the A1-Ga system6 is somewhat

Jan 1, 1969

By N. K. Chen, R. Maddin

Single crystals of molybdenum were extended at temperatures from 1300° to 2500°C. It was found that with increasing temperatures, the yield becomes more pronounced and the number of slip bands for equal amounts of elongation decreases. Slip at high temperatures fragments the structure. OTHER than the investigations on sodium and potassium by Andrade and Tsien,&apos; the researches of Steijn and Brick&apos; on a iron single crystals at low temperatures are about the only studies of the influence of temperature on glide of body-centered cubic single crystals. The effect of test temperature on glide has been rather widely investigated with hexagonal crystals" and less widely with face-centered cubic crystals. ~~ a result of these studies it can be said that, in general, the onset of plastic flow as measured by the initial rate of strain hardening becomes more abrupt with increasing temperature, and the value of the yield decreases with increasing temperature. Strain hardening, however, is markedly affected by changes in temperature except at very low and very high temperatures where the strain hardening rate becames constant. In the present investigation it is shown that temperature affects the glide of molybdenum single crystals in much the same manner as crystals of other classes, it., for comparable strains the number of slip bands decreases with increasing temperature; shear along the slip bands increases with increasing temperature; the yield becomes more pronounced with increasing temperature of test; and the strain hardening approaches a constant at very high temperatures. In addition, it is shown that, in agreement with the work of Tsien and Chow, Qlip occurs on (110) planes in <Ill> directions. It is further shown that slip at high temperatures fragments the structure into either irregular sized cells or bent atomic planes which are roughly aligned in crystallographic directions. Experimental Procedure Single crystals 3 mm in diameter by about 25 mm long were prepared using the technique previously described.&apos; The furnace in which the crystals were grown served as the extension apparatus for the tension tests. It consisted of a 4 in. water-cooled brass tube 20 in. long which was continuously evacuated at the bottom. Two water-cooled copper electrodes held the specimen by means of spherical collets secured in place in the electrodes by set screws. These electrodes served also to transmit power and stress to the specimen. The lower electrode was clamped to a stand, while the upper electrode was fastened to one side of a lever arm flexibly supported at the top through a slightly offset pinion. A metal bellows operating elastically was attached to the upper electrode to affect a vacuum seal and allow freedom of motion. The level of the arm was adjusted by rotating a graduated nut. Rotation of the electrode was prevented by a key fitted into a groove. After the specimen was mounted and the vacuum secured, the lever arm was adjusted so that the bellows was at its relaxed position. This insured that the total weight of the specimen, the upper electrode, and the downpull of the vacuum were balanced by the horizontal beam. Since the specimen was heated by its own resistance, expansion of the specimen proceeded freely by this arrangement. During the time of heating the specimen, the beam was maintained in a horizontal position by turning the nut at the top. By graduating the lever arm and using a known dead weight on the lever arm to supply a tensile stress, the graduated nut could be read to 0.0001 in. extension. Since

Jan 1, 1955

By Michael B. Bever, Barton Roessler

The effects of deformation by wire drawing at 78OK on initially ordered and initially disordered specimens of the alloy Cu3Au were investigated. The resistivity, stored energy, drawing force, and microhardness were measured as functions of strain; microstructural changes were observed. The results are interpreted in terms of the structural imperfections and the changes in atomic configuration resulting from deformation. A few experiments on the effects of room-temperature annealing after deformation at 78°K were made; they suggest vacancy-promoted ordering in disordered alloys. BARTON ROESSLER, Junior Member AIME, formerly Graduate Student and Alcoa Fellow, Department of Metallurgy, Massachusetts Institute of Technology, Cambridge, Mass., is with Westinghouse Research Laboratories, Pittsburgh, Penn. MICHAEL B. BEVER, Member AIME, is Professor of Metallurgy, Massachusetts Institute of Technology. Based in part on o thesis by B. ROESSLER submitted in October, 1959 to the Massachusetts Institute of Technology in partial fulfillment of the requirements for the degree of Doctor of Science. Manuscript submitted April 6, 1961. IMD AN investigation of the effects of deformation at room temperature on the alloy Cu3 Au was reported in a recent paper,&apos; which included a review of the literature on the deformation of order-disorder alloys. In general, plastic deformation of ordered alloys reduces the degree of long-range order and causes corresponding changes in their properties. Deformation of disordered alloys changes their properties in a manner characteristic of solid solution alloys; these changes can in part be attributed to the destruction of short-range order. The effects of deformation on solid solution alloys are of two kinds: 1) generation of structural imperfections, which occurs as a result of deformation in any metallic system including pure metals, and 2) changes of atomic configuration, which are characteristic of solid solutions and particularly of order -disorder systems. These two types of effect are not independent of each other and the state of a deformed solid solution alloy is determined in a complex manner by the way in which the structural imperfections cause changes in atomic configuration both during and after deformation.

Jan 1, 1962

By J. L. Fitch, B. G. Hurd

The presence of gypsum in samples subjected to standard core analysis introduces serious errors in the measurement of water saturation and porosity. The magnitude of these errors, depending upon the type of analysis procedure used, has been evaluated experimentally and theoretically. Water-saturated pore volumes determined by vacuum distillation or retort procedures may be too high by as much as 48 per cent of the volume of gypsum present. The maximum error in this value determined by Dean-Stark extraction with toluene is 36 per cent of the gypsum volume. If pore space is measured by a Boyle&apos;s law type porosimeter the maximum erorr due to gypsum is 38 per cent of the original gypsum volume present. The conscientious core analyst may eliminate the errors caused by gypsum by either of two methods. He may apply suitable corrections for the water of crystallization removed from gypsum, or take special precautions to prevent dehydration of gypsum during core cleaning and alzalysis procedures. These alternatives are discussed and methods for obtaining reliable core analysis data are proposed. Gypsum (CaSO4 . 2H2O) occurs as a common mineral in many of the world&apos;s sedimentary basins. In addition to its presence as primary bedded evaporitic deposits, it is often found as secondary replacement zones and pore-fillings in host rocks. That it may cause false indications in porosity, both on neutron logs and in standard core analysis, has been generally recognized. False porosity interpretations from neutron logs result because the chemically bound water in gypsum attenuates neutrons as effectively as free water. Errors in core analysis result when gypsum is dehydrated prior to or during the analysis. Vacuum retort procedures used by many laboratories to determine fluid saturation and porosity effect a complete removal of water of crystallization from gypsum. The crystal water, distilled and collected with free water from the sample, is counted as water-sat11rated pore space. Dehydration of gypsum results in a decrease in volume occupied by calcium sulfate and a corresponding increase in pore volume. Thus, if gypsum is dehydrated by sample cleaning and drying procedures, subsequent porosity measurements with gas expansion or compression instruments will be high. The qualitative effect of gypsum on porosity determinations by retort procedures was discussed in a recent article by Bynum and Koepl3. They concluded that since false porosity was interpreted as being water saturated, determinations of oil content were not affected. Others in the industry, however, have pointed out that porosity values are often used with values of water saturation determined independently, e.g., from electric resistivity logs in making reserve estimates. Values of water saturation calculated from the formation resistivity using the Archie equation, S4= are actually low if values of are high due to gypsum. In this case, false porosity values due to gypsum could cause serious errors in calculations of oil-in-place. This investigation was made to determine quantitatively the effect of gypsum on porosity values determined by different core analysis procedures. EXPERIMENTAL PROCEDURES Dehydration of Gypsum The extent and rate of removal of water of crystallization from gypsum under conditions encountered in core analysis procedures were studied. Taken for the experiments were three types of relatively pure, naturally occurring gypsum, viz. selenite, satin spar and massive gypsum. Although all samples probably contained trace chemical impurities, each type lost the theoretical amount of water upon complete dehydration. An automatic recording thermobalance, similar to one described by Mauer2, was used to obtain dehydration rate data for samples heated in dry air. Water

By E. Klar, A. B. Michael

Differences in the electrical conductivities of copper powder sintered under reducing, selectively oxidizing, and neutral atmospheres are related to impurities in solution or as precipitated oxides. The precipitation of impurities as oxides during sintering in nitrogen is proposed for maximizing the conductivity of sintered copper. Conductivity equations for two-phase systems are summarized. Selected equations are applied to porous sintered copper and composite structures. A recent review of the influence of impurities on the electrical conductivity of copper by Gregory et al.1 emphasized that an impurity in solid solution has a much more pronounced effect on reducing the electrical conductivity than when present partly or wholly as a second phase. When impurities in solid solution can be precipitated as oxides, the copper is purified with respect to these elements and the conductivity is increased. Cast and wrought copper, therefore, frequently contain an intentional residual oxygen concentration to oxidize and precipitate impurities less noble than copper. Copper powders generally also contain impurities which can contribute to a reduction in the electrical conductivity of the sintered material. The most deleterious impurities commonly found in commercial copper powders which markedly decrease the electrical conductivity when in solid solution but which can be precipitated as oxides include iron, tin, antimony, arsenic, cobalt, and nickel. In addition to impurities, porosity in sintered copper also contributes to a reduction in the electrical conductivity. The work reported herein discusses the influence of impurities, sintering atmospheres, and porosity on the electrical conductivity of sintered copper. These are important factors for controlling the electrical conductivity of materials such as sintered copper electrical contacts. Several publications on the electrical conductivity of sintered copper and composite materials with random pores or obstacles have incorrectly considered the conductivity to be proportional to the volume fraction of conducting material. However, analyses and equations have been proposed, the earliest of which is perhaps Lord Raleigh&apos;s of 1892,&apos; which more accurately describe the conductivity of two-phase systems. These equations which in many cases allow one to closely estimate the electrical conductivity of porous sintered materials and two-phase composites will be reviewed and related to the measured electrical conductivity of sintered copper, copper-graphite. and Ag-W composites. INFLUENCE OF IMPURITIES AND OXIDIZING, REDUCING, AND NEUTRAL ATMOSPHERES Zone-Melted and Leveled Copper. The electrical conductivities of an electrolytic copper and a lower-purity compacting grade of copper powder after consecutive treatments in reducing or selectively oxidizing atmospheres are compared in Fig. 1. The powder and drillings from the electrolytic copper ingot were melted and solidified in a graphite crucible under hydrogen. The vertical zone leveling technique of multiple passes in opposite directions was used to obtain a uniform distribution of impurities. The electrical conductivity was measured on machined specimens 3 by 0.10 in. diam of the zone-leveled material and after the same specimens were consecutively treated as follows: 1) heating in hydrogen at 1600°F for 3 hr; 2) heating in air in a sealed tube so that 0.04 pct 0 was introduced; heating was started at 1000°F for 1 hr and continued at 1800°F for 8 hr; the stepwise diffusion treatment was used to avoid loss of copper due to evaporation of copper oxide at higher temperatures; and 3) final heating in hydrogen at 1600°F for 3 hr. A L&N Kelvin Bridge, type 4306, and a test fixture with knife edges 2 in. apart were used to measure the room-temperature conductivity with an estimated accuracy of ±0.5 pct. In all cases the conductivity of the electrolytic copper was approximately 100 pct of IACS. The conductivity of the impure copper was 80 pct of IACS both in the cast state and after heating in hydrogen. However, after the heating in air, the conductivity of the impure material was 100 pct IACS. After again heating in hydrogen, the electrical conductivity decreased to 60 pct of IACS. This decrease is attributed both to the dissolution of impurities and observed intergranular cracks due to the phenomenon of hydrogen embrittle-ment in copper. These data show that the electrical conductivity of commercial copper as represented by a compacting type powder can be increased significantly by the precipitation of impurities as oxides through heat treatment in an oxidizing atmosphere. Sintered Copper Powder. A commercial compacting type of copper powder pressed to various densities was sintered either in nitrogen, dissociated ammonia, or dissociated ammonia followed by a selectively oxidizing atmosphere of air in sealed Vycor tubes so that 0.06 pct O was added to the material. The electrical conductivity was measured perpendicular to the pressing direction on as-sintered specimens of approximately 3 by 0.25 by 0.15 in. The fully dense material was obtained by zone melting and leveling

Jan 1, 1969

By E. Kendall Cork

The traditional financial objective for a single mine company has been to operate as frugally as possible and to pay out most of the earnings as dividends. If the business is cyclical (as it is for most metals) the dividends might fluctuate quite widely. When the mine is exhausted the company disappears. This is still quite a viable strategy for a single mine company. It is not however a viable strategy for the world as a whole. The mining industry is built by mine development companies who can mobilize the people and capital to bring new mines into production. Their skills must include marketing, engineering, finance and other politics. It is very rare for a property to be brought in without the support of a major company that can provide all these services. The exceptions will usually have some other form of big brother support, for example the U.S. government uranium contracts at guaranteed generous prices. The mine development company will seek as a minimum to perpetuate itself by developing new mines in order to replace those which are running out. The more common and more ambitious objective is to grow -- that is to add to its ore reserves and current production by developing more new mines. The financial objectives for that company are very different. Obviously if all the earnings were paid out in dividends there would be nothing left to work with. The first financial policy then is to spend an appropriate amount on exploration for new properties. The next is to retain enough of the earnings to provide the capital for new projects at least sufficient for the equity. There is no magic formula as to what proportion of earnings should properly be distributed as dividends by a growth-oriented mine development company. As a rough rule of thumb distributing half or more will probably leave too little to work on and 30% or so is probably a good balance. However the circumstances differ widely from company to company. It may be useful to set an objective for the rate of growth of a company&apos;s earnings. Some have picked rates such as 15% per annum compounded. Others have set a target in real terms which might appear as 10 or 11% plus inflation. Obviously the arithmetic of compound interest is very attractive; however in practice there is much variation. Indeed current returns from existing operations swing widely with the business cycle and there is no assurance that economic new properties will be found according to someone&apos;s arbitrary time schedule. For example, Western Mining Corporation Limited in Australia explored for 30 years with little to show for it, but then found the great Australian nickel deposits and more recently the huge Roxby Downs copper. That long dry spell could not have fitted anyone&apos;s arbitrary calendar of growth and yet they would not have found such orebodies without that long period of effort. Should they have abandoned the search? Once a new property has been found or acquired there has to be a threshold rate of return on the new capital to be invested against which to evaluate the property&apos;s economics. Conventionally this seems to be 15% after tax, a number common in other heavy industries as well. In some cases it is expressed as a lower number plus allowance for inflation. Discounted cash flow analysis is a very useful tool but it does not make the decision. In the end a "go" decision depends on judgment of many factors some of which are numbers used in the DCF calculation whose credibility must be examined. It is curious how frequently investment proposals come in with the rates of return very close to 15%. The project advocates know that a number much less than 15% will not fly and that a number much more is not necessary. With much higher nominal and real interest rates of recent years, even though before tax, logic suggests that the hurdle rate should also rise. The power of compound interest is so great that 20% is very hard to achieve in any cash flow projection but 18% may be a sensible yard - stick. Once again it is remarkable how many project proposals come in with an 18% return. On the record the mining industry as a whole has not been overly restrictive in choosing its hurdle rates of return. This is shown by the abundance of metals in recent years and the failure of metal prices to keep up with inflation. All of the foregoing is standard text book stuff.

Jan 1, 1985

By J. S. Browning

The U.S. Bureau of Mines has been experimenting with flotation processes to separate the spodumene-beryl ores mined at Kings Mountain, N.C. The success to date as well as the present status of the process is discussed. Further experimentation is underway and studies will be made on the milling costs involved in the flotation process. The pegmatites of the Kings Mountain-Lincoln ton, N.C., area constitute the largest known domestic reserve of beryl and spodumene. The reserve is estimated to contain 90 million tons of pegmatic material with 1,280,000 tons of recoverable Li,O(lithia) as spodurnene.&apos; The pegmatites also contain 0.4 to 0.5 pct beryl disseminated throughout the orebodies. The pegmatites may contain a potential reserve of 240,-000 tons beryl, equivalent to approximately 34,000 tons of BeO. Different flotation methods for separating beryl from feldspar or quartz, or both, have been developed by various investigators.2-7 On the other hand, published information is limited on concentration of spodumene-beryl ores. As the response of beryl and spodumene to flotation is essentially the same, a successful separation of the two minerals depends upon use of a selective depressant or a selective collector for one of the minerals. Several years ago, the U.S. Bureau of Mines, recognizing the need for developing a large domestic supply of strategic beryl, undertook studies to develop improved methods of recovering this mineral. Because of the low beryl content of the pegmatites, economic production of the beryl entails its recovery as a byproduct of spodumene flotation. Thus, the development of procedures that would provide for maximum recoveries of the spodumene, as well as the beryl, was a primary objective of the studies. Tests were made on run-of-mine ore and spodumene flotation tailing from the Foote Mineral Co.&apos;s spodumene concentrator at Kings Mountain (Fig. 1). Pet-rographic analyses of the ore and flotation tailing are given in Table I. Detailed analyses and examinations of the ore and tailings revealed that the beryllium was present in the form of a low-alkali beryl. The crystals were small, rarely larger than 14-mesh diam, and were clear and colorless. About 10 pct of the Li20 content of the ore was present in the mica and feldspar components of the pegmatite. In some weathered ores the associated clays also contained small amounts of lithia. This is typical of pegmatites in the Kings Mountain area. LABORATORY TESTS In the past, a vigorous chemical treatment of the spodumene surfaces with acid or caustic soda has been considered essential for satisfactory selective flotation of the spodumene from the other minerals in pegmatites. Many tests were made during this investigation to determine if chemical treatment of the spodumene could be eliminated in favor of a reagent combination that would depress the other minerals while selectively floating the spodumene. A simple reagent combination and process was developed that gave better spodumene recovery and grade of concentrate than the more elaborate acid or caustic treatment methods previously used. The finely ground ore pulps were conditioned with either an ammonium, alkali, or alkaline earth lignin sulfonate and sodium fluoride, and the spodumene was floated and cleaned using oleic acid as the collector. The spodumene tailing was deslimed, conditioned with sulfuric acid and coco amine acetate, and floated to reject mica. The mica tailing was thickened and conditioned with hydrofluoric acid, then washed to remove the acid. The washed pulp was conditioned with sodium hydroxide for pH control, and the beryl was floated and cleaned with oleic acid as the collector. Table II summarizes the results of the laboratory test work. About 77 pct of the spodumene and 75 pct of the beryl were recovered from the pegmatitic material. The spodumene concentrate assayed 6.1 pct Li20 and 0.01 pct BeO, and the beryl product assayed 3.0 pct Li20 and 1.57 pct BeO. Similar results were ob-

Jan 1, 1961

By D. R. Wieland, H. T. Kennedy

The object of the work reported here was to determine the content of elemental sulfur in gaseous methane, carbon dioxide, hydrogen sulfide, and in mixtures of these gases, at pressures and temperatwes encountered in natural gas reservoirs. Sulfur content at equilibrium is reported for pure methane, carbon dioxide, hydrogen sulfide, and on three binary mixtures of each of the three pairs of gases at pressures of 1,000, 2,000, 3,000, 4,000, 5,000 and 6,000 psia and at temperatures of 150°, 200° and 250°F. In addition, the sulfur content of three ternary mixtures at the same temperatures and pressures are reported. The results indicate that the sulfur content is higher in the gases at higher temperatures and pressures. The content is highest in hydrogen sulfide, intermediate in carbon dioxide and lowest in methane. INTRODUCTION At ordinary pressures and temperatures, the concentration of a nonvolatile material, such as sulfur in a gas at equilibrium, is a function of the vapor pressure of the material and is independent of the nature of the gas. As the pressure and temperature increase, the gas assumes some of the properties of liquids, including the power to dissolve other liquids and solids, to an extent dependent on the nature of both the gas and the material dissolved. At equilibrium, the content of sulfur in the several gases considered here may thus be considered as solubilities which are fixed for a given composition of gas, temperature and pressure. The study of the solubility of elemental sulfur in gases is of interest because sulfur is sometimes present in reservoirs producing natural gas and must be present in the vapor phase. Upon reduction of pressure and temperature, the sulfur precipitates from solution in the reservoir and in the tubing and fittings. Due to the fact that the greatest pressure drop in the reservoir is around the wellbore, the volume of sulfur precipitated will be greatest in this locality and can cause a substantial reduction in the permeability of the formation in this area. As the natural gas flows up the tubing string, the pressure and temperature are further decreased, causing further sulfur precipitation. If the volume of free sulfur is large and remedial measures are not taken, complete plugging of the tubing can occur. Knowledge of the content of sulfur as a function of composition, temperature and pressure will enable the operator to determine what changes in pressure and/or temperature are necessary to keep the sulfur in solution. If the sulfur solubility is large and can be controlled, the operator may desire to produce the well at a high wellhead pressure and temperature and reclaim the sulfur at the surface. The high solubility of sulfur in hydrogen sulfide (5.6 per cent by weight at 5,000 psi and 200°F) suggests the feasibility of recovering sulfur by injecting this gas into sulfur-bearing reservoirs and expanding the produced gas to precipitate out the sulfur. The present project was designed to measure the solubility of sulfur in carbon dioxide, methane, hydrogen sulfide and mixtures of these three gases at various temperatures and pressures. These gases were the major constituents of the gas well where plugging by sulfur was encountered. A study of the published literature shows no data on the solubility of sulfur in any gas, although Hannay and Hogarth,&apos; in 1880 reported that it was soluble in carbon disdlide above the critical temperature of carbon disulfide. EQUIPMENT AND PROCEDURE Fig. 1 shows the layout of equipment employed to bring gases to equilibrium with sulfur and to isolate the quantity of sulfur contained in a known volume of gas. Pure gases were measured in the charging bomb at known temperatures and pressures and displaced into the reservoir bomb to make up the desired mixtures. When equilibrium was achieved

By E. W. Felegy

THE need for improved mine communication to increase efficiency and to insure greater safety has long been recognized. General and unrestricted communication between all points underground, and between the surface and all points underground, is probably the least advanced phase of the mining industry. An ideal system of mine communication must require no fixed wire installations. The equipment must be small, lightweight, and readily portable, and the power requirements low. A system that can be used not only under normal circumstances but also in an emergency, when the continuity of wires, tracks, and pipelines may be disrupted, must function independently of any aid furnished by standard installations. Radio communication offers possibilities of meeting all the requirements necessary for an ideal communication system in underground mines. Transmission of signals must be achieved through one or both of two mediums, through the air in mine openings or through the strata. The results or lack of results obtained by early investigators showed conclusively that radio communication by space transmission cannot be accomplished effectively beyond line-of-sight distances in underground passageways. A radio system underground therefore must depend solely upon transmission through soil and strata. The application of radio to underground mine communication was investigated by many individuals and agencies at different times in the last several decades, but little success was achieved before World war 11.2-0, The results of experiments during the war, and further knowledge gained in experiments with vastly improved communication methods and equipment after the war provided the background for additional research in radio communication in underground mines. During 1950 to 1.952 the University of Minnesota sponsored an investigation to determine the possibility of developing: a system of radio communication universally applicable in underground metal mines in the Lake Superior district. The possibility of using radio equipment to determine the imminence of rock bursts in deep copper mines in that district also was investigated. The investigation supplemented previous and concurrent emergency mine communication studies of the U. S. Bureau of Mines. Testing equipment and laboratory facilities maintained by the Bureau of Mines at Duluth, Minnesota, were used in the research program, which was conducted as a mining engineering graduate research problem by the present writer under the direction of T. L. Joseph and E. P. Pfleider. The radio units used in the research program were designed and built to specification solely to conduct tests of radio communication in mines. Two identical units were used in all tests. Each unit contained a transmitter section, a receiver section, and a power-supply section, mounted on a single chassis. The entire unit was enclosed in a single 10x12x18-in. metal case provided with a leather-strap handle for carrying purposes. The front of the case was hinged to open upward and provide easy access to the single control panel on which all controls were mounted. Storage batteries supplied the operating power for all tests. Standard 6-v automobile batteries were utilized to provide adequate capacity to conduct tests for a full day without exhausting the battery. A frequency range from 30 to 200 kc was covered in eight pre-fixed steps on each unit. The carrier frequencies were crystal-controlled and amplitude-modulated. The receiver employed an essentially standard superheterodyne circuit and was sufficiently sensitive to detect signal strengths of 5 micro v. A heterodyne circuit was employed in the transmitter to obtain the low-carrier frequencies used in the units. Power output of the transmitter, usually less than 2 w, rarely exceeded 3 w in any test. Tests were conducted in mines on the Vermillion iron range in Minnesota, the Gogebic iron range in Wisconsin, the Menominee and Marquette iron ranges in Michigan, and a copper mine in the upper Michigan peninsula. All tests were conducted when the mines were operating normally, and usual mining, maintenance, and transportation activities were in progress, so that any interference caused by normal production activities could be evaluated during the tests. Tests were made between different points underground in each mine, and between underground and surface points at some mines. Test readings obtained at any one mine were calibrated in the laboratory before another series of tests were begun at the next mine. The transmitter and receiver were separated by one or more levels in each test, and generally there was no other means of communication between test points. Two 100-ft lengths of rubber-covered wire were used for antenna wires on each unit in both transmission and reception. The ends of the wires were connected to ground points in one of several methods, depending upon physical conditions at each test site. The wires were clipped to metal rods about 200 ft apart in the back, side, or bottom of the mine opening where the character of the rock permitted driving rods. Both wires were clipped to points about

Jan 1, 1954

By L. Kaufman

An equation is derived relating AF a", the difference in free energy between austenite and martensite, to temperature and composition in the iron-chrmnium and iron-chromium -nickel systems. This equation is used to calculate at M,for low-carbon stainless steels. A method for utilizing the energetic equations to calculate M, in stainless steels is suggested. In addition, an explanation is given for the anomalous effect of chromium in forming a y loop concurrent with the lowering of M, in iron-base alloys. It has been demonstrated that the effect of alloying elements on the Ms temperature is strongly dependent upon the influence of the alloying element on the thermodynamic properties of the y and a phases. Notwithstanding the fact that alloying elements affect the Ms temperature by changing the lattice parameters, elastic constants, and inter-facial energies of the a and y phases, their primary role is a thermodynamic one. Thermodynamic analyses have been presented for the iron-carbon&apos;-4 and iron-nickele systems in which equations are derived for Fa and FY, the free energies of the b.c.c. (or b.c.t.) and f.c.c. phases. These equations, which can be obtained with the aid of the equilibrium diagrams, can be used to help predict the Ms vs composition curves. This paper deals with a calculation of the thermodynamic properties necessary to compute AFffLY for iron-chromium alloys. In view of the lack of direct information concerning the activity of chromium in the a and y phases of iron, the regular solution approximationa,g was utilized to bridge the gap. After the necessary equations were derived for the iron-chromium system they were used to calculate AFff— Y for stainless steels by combining them with the previous results obtained for iron-nickel alloys. The results of these calculations offer a means of rationalizing the anomalous behavior of chromium in iron-base alloys. The latter depends on the regular solution approximation in contrast to the explanation offered by zener , which is based upon the "magnetic specific heat effect." THERMODYNAMICS OF THE IRON-CHROMIUM SYSTEM If y represents the atomic fraction of chromium in an iron-chromium alloy, then the free energy of the b.c.c. phase Fa, the f.c.c. phase FY, and the difference in free energy between the f.c.c. and b.c.c. phases of the same composition are given through [3] and Fmy represent the free energies of mixing of the a and y phases; while @era -&apos; and uFea 4Y represent the difference in free energy between f.c.c. and b.c.c. chromium and iron respectively. The values of AEFe0ff4Y in the temperature range between 0" and 900K ( .

Jan 1, 1960

By J. P. Denny

The constitution of the Ga-In system was determined by thermal methods. An experimentally determined metastable equilibrium line (an extension of the indium-rich liquidus) was obtained. The various alloys were studied metallographically using polished samples obtained by a casting method. These low melting alloys required a special dry-ice assembly to maintain a suitable temperature. RECENT interest in alloys that are liquid at room temperature has led to rather extensive investigation of gallium-base alloys. Widely distributed over the earth, gallium could be produced in substantially larger quantities than at present, if a significant demand existed.&apos; One study&apos; has established its presence in 12 out of 14 zinc blends, in all of 15 aluminum ores, in 4 out of 12 manganese ores, in 35 out of 91 iron ores, and in all of 7 magnetite ores. It occurs as a rule in minute amounts, however, leading to high extraction costs. Recent quotations run from $2.50 to $7.50 per g. During the course of the present investigation, portions of the system Ga-In have been redeter-mined, and the results of this study are presented herein. Thermal and metallographic methods have been employed. Lecoq de Boisbaudran, the discoverer of gallium, conducted the first investigation" on Ga-In alloys in 1885. The temperatures of incipient melting, and of completion of melting, were determined at four alloy compositions. In 1936, Hansen&apos; constructed a eutec-tic-type phase diagram for the system Ga-In, based on . work. The existence of a Ga-In compound was regarded as improbable by Hansen, and subsequent investigations are in agreement. French, Saunders, and Ingle3 conducted a more complete study of the system in 1938, using thermal methods. Their phase diagram is a eutectic type, containing a unique concave-upward liquidus. The solid-solution range of gallium in indium was reported as 9.5 pct by weight, and that of indium as less than 1 pct, at the eutectic temperature. The eutectic composition, determined as being bracketed by the compositions showing a true horizontal at the eutectic temperature (16°C), was reported as 76 5-0.5 pct Ga and 24 i 0.5 pct In. Experimental Procedure The preparation of Ga-In alloys is simplified by the low melting points involved. Various compositions were prepared by melting in pyrex tubes, using a cover of distilled water or parafin to prevent the alloys from wetting the glass wall. In all cases, the melts were homogenized. by stirring. Where possible, both cooling and melting curves were determined. The extensive undercooling of gallium was found to prohibit a satisfactory cooling-curve analysis of gallium-rich alloys, however, and transition points on the gallium side of the eutectic could be determined only by melting curves. The inverse rate method of thermal analysis proved to be most satisfactory and was used to a great extent. Various heating and cooling rates were used, ranging from 0.2" to 5.0°C per min. Low temperature melting analyses were conducted within a constant temperature bath, maintained at about 70 °C. The alloys were solidified (under water or paraffin) within a pyrex tube, using dry ice; the tube was then sealed within a cold Dewar flask, the unit transferred into the constant temperature bath, and periodic temperature readings taken. The high temperature melting-curve determinations and all cooling-curve determinations were made in a vertical tube furnace. At near-eutectic compositions, the furnace was placed within a refrigerated room held at —20°C. Accordingly, the furnace on cooling approached —20°C asymptotically and permitted the determination of those phase transitions occurring below room temperatures. Temperatures were measured with a 30-gage iron-constantan thermocouple, immersed directly in the alloy. To prevent contamination of the melt, the leads and junction were coated with Lucite, applied by painting with a solution of Lucite in ethylene dichloride. Electromotive force measurements were made with a Leeds and Northrup precision potentiometer, type 8662. The couples were calibrated against the boiling point. of water and, at lower temperatures, against a calorimeter thermometer having a Bureau of Standards certificate. The melting points of gallium and indium used in the present investigation were determined as 29.-77° and 156.1°C, in good agreement with previously reported values of 29.78°C° and 156.4"C.&apos; The spec-

Jan 1, 1953

By L. B. Harris

Continuous cyclic unloading during tensile work hardening of polycrystalline zinc at room temperature enables specimens to sustain greatly increased extension. Such enhanced ductility is associated with creep-type extension, during which the cyclic component appears to promote relaxation of internal strains. It is possible to trace the transitions from tension, through enhanced cyclic extension, to fatigue and relate the observed behavior to simpler types of deformation. DISTINCTIVE deformation behavior has been shown to occur when loading includes both cyclic and unidirectional components. For aluminum and copper extended by a sequence of progressively biased strain reversals, coffin1 observed greater fracture ductility and lower flow stresses than during monotonic tension. This may be compared with the reduction in hardness obtained from conventional fatigue softening. But fatigue softening is accompanied by enhanced fatigue life,&apos; whereas Benham3 found that fatigue life was reduced when copper continuously extended during axial load cycling. The corresponding specimen elongation, for large cyclic load amplitudes, was greater than during normal tension. Under different conditions, Bendler and wood4 found that torsional fatigue initiated extension in copper under low tensile loads previously in equilibrium with the specimen; fatigue life was again reduced. Thus there is a type of cyclic softening which is associated with reduced fatigue life and which occurs when the cyclic loading is accompanied by a unidirectional strain component. Further, the fracture ductility or extension obtained from the unidirectional component can exceed that obtained in the absence of cyclic load. Specimen extension was not initiated by axial fatigue at small load amplitudes;3 hence Benham&apos;s work distinguishes between fatigue at large and small amplitudes, the former often being linked with unidirectional deformation because of similarities in strain Structure. The initiation of tensile extension during torsional fatigue,4 however, occurred with small amplitudes. Comparable changes in behavior have been ob- served during creep. kennedy&apos; found that combined cyclic and creep stresses on lead at 32°C increased the rate of elongation over that for simple creep, the consequence being a reduction in creep life. It was also demonstrated that small cyclic stresses applied after creep deformation initially increased recovery, but that prolonged application produced only normal fatigue hardening. It is clear that physical properties can be changed by interaction between the cyclic and unidirectional deformations, but owing to the number of different ways in which the deformations can be combined and the large number of possible variables for each combination, trends of behavior become easily obscured. One definite conclusion is that enhanced ductility or increased extension can be obtained by cyclic action, and it is this process that has been investigated for the tensile test by measurements of the extra tensile strain produced by the addition of a cyclic tensile component. EXPERIMENTAL PROCEDURE Material. Specimens were 99.99 pct Zn wire of 1.6 and 2.0 mm diam. Mean grain diameter was 0.02 mm, sufficiently small to give a ductile necked-down fracture under all loading conditions. All experiments were conducted at an average temperature of 20°C. Normal Tension. Unidirectional tensile curves at different strain rates were obtained from an In-stron testing machine, on which load-time curves were recorded autographically, using gage lengths of 5 and 10 cm. Straining was at constant cross-head velocity, and quoted strain rates are with reference to initial specimen length. Measurements of total elongation under simple tension were also made on the tensile machine that had been modified to incorporate an added fluctuating load. Combined Tension and Rapid Cyclic Load. An electromagnetic vibrator was coupled to the elastic beam of a Hounsfield ensometer- and driven sinus-oidally from a power amplifier at frequencies from 20 to 360 cps, the flexible connecting links on the tensometer being replaced by rigid fixtures to eliminate lateral vibration in the specimen. One end of the specimen was pulled by the normal extension drive of the tensometer while the other end, fixed to the elastic beam and vibrator, was subjected to rapid oscillations of load. It was thus possible to apply cyclic load to a tensile test without altering the rate of extension of the specimen

Jan 1, 1964

By Orville R. Lyons

This paper presents a method whereby the amount of misplaced material and the difficulty of the separation can be used to compare coal cleaning equipment of all types, from effectiveness and capacity standpoints. The correlations presented do not include all types of equipment currently available, but the method can be used to evaluate any make or type of coal cleaning equipment, both old and new. THE relative performance of coal washing equipment, or the effectiveness with which any type or make of equipment removes impurities from coal, has been most difficult to evaluate in the past. The most widely used yardstick is the Frazer and Yancey efficiency formula developed in 1922,&apos; but Yancey in a later article states that "washers treating coals of different density composition or operating at different densities of separation cannot be compared directly on the basis of this criterion."&apos; Prior to and since 1922, a variety of other methods has been used for comparison purposes, including the distribution curve, the error area, and the "ecart probable" or probable error. Yancey and Geer in discussing these methods conclude, "Performance can be evaluated in a number of different ways, with the choice of the proper method to use being dictated by the objectives of the investigation and the data available."&apos; It is true that performance can be evaluated in a variety of ways, but if the equipment is to be evaluated on an effectiveness basis, there should be only one universal comparison method. Varying methods have been used because one universal comparison method has not been found or developed. In the article previously quoted, Yancey and Geer state in clear terms the primary concept for a universal comparison method: "One of the simplest, and certainly one of the most obvious evaluations of washery performance is the quantity of sink material in the washed coal and the float material in the refuse. If the washery products are tested at the density at which the washing unit is operated, the sink in the washed coal and the float in the refuse represent material that has been misplaced." The quantity of misplaced material was used as a criterion of washery performance by Lincoln in 1913," by the United States Bureau of Mines in 1938,&apos; by Hancock in 1947," and by the national French research agency Cerchar in recent years.&apos; In 1950 Andersone proposed the use of this criterion as an efficiency value to replace the Frazer and Yancey formula. However, none of the above-mentioned investigators used the misplaced material concept in a manner that would provide universal coal-cleaning equipment comparisons. The Correlation Theory The ideal coal cleaning process would treat all sizes and would make a perfect separation at any given specific gravity. All material lower in density than the desired value would report in the coal product and all material higher in density would report in the refuse product. Unfortunately, no known cleaning process achieves this goal and there seems little likelihood that any process yet to be invented will do more than approach it. When coal is treated in volume under operating conditions, it is impossible to avoid mechanical entrapment, fluctuations in throughput and effective gravity of separation, and the creation of turbulent currents, even when a true heavy-liquid bath is used and the feed is closely sized and contains little intermediate gravity material. This being so, it is possible to appreciate the difficulties inherent in trying to obtain a perfect separation when treating a wide range of sizes and a feed containing high percentages of intermediate material, using turbulent currents to help create the effective separation gravity, under operating conditions which normally tend to be on the overload side. When coal is separated from refuse in any coal cleaning equipment, some refuse always reports to the coal and some coal to the refuse; the writer therefore assumed that there should be a relationship between the total amount of misplaced material produced by any given piece of equipment and the difficulty of separation as represented by the percentage of near gravity material in the feed. With small amounts of near gravity or k0.1 material in the feed there should be less misplacement of material than would occur with large amounts of near

Jan 1, 1953

By A. J. Griest, A. P. Young, P. D. Frost

A study was made of the effect of ß grain size on the tensile ductility of a-ß titanium alloys haet treated to strengths in the range 165,000 to 180,000 psi. It was concluded that the primary cause of $ embrittlement is the large grain size which is obtained so rapidly in many a-ß titanium alloys when heated into the ß field. It was also found that grain-boundary a and acicular intragranular a in the microstructure are not necessarily detrimental to the tensile ductility if the prior ß grain size is sufficientlv fine. BETA embrittlement occurs in a-ß alloys when the finish hot-working or stages of the subsequent heat treatment have been done at temperatures in the ß field. In order to avoid this embrittlement, for-gings must be finished at temperatures under the ß transus. For better workability, it would be desirable to forge at temperatures in the ß field. For this reason, research has been conducted to determine the cause of ß embrittlement. Although ß grain size has been considered as a possible contributing factor to ß embrittlement, only limited research has been done to evaluate its effect. The effect of addition elements on ß grain growth in unalloyed titanium has been studied by Liu.&apos; Complete mechanical property data, however, were not obtained for correlation with grain size. Ogden and coworkers2 have investigated the effect of both a and ß grain size and grain shape in Ti-Cr-Mo alloys. Their data indicated that tensile ductility was relatively insensitive to ß grain size at annealed strength levels (140,000 psi ultimate). No study has apparently been made to determine the relationship between ß grain size and ß embrittlement in a-ß alloys heat treated to high strength (180,000 psi ultimate). The high-strength condition is that in which ß embrittlement is particularly severe. Beta grain size is not easily varied through the use of a range of annealing times and temperatures in the ß field, because of the rapidity with which ß grain growth occurs. Short-time heating techniques are needed to obtain the smallest ß grains. EXPERIMENTAL PROCEDURE In this research, the experimental procedure was as follows: 1) Tensile and microimpact specimen blanks were resistance heated to produce a range of ß grain sizes. 2) The tensile and microimpact blanks were then solution-treated in the a-ß field and aged to produce predetermined ultimate tensile strengths in the range 165,000 to 180,000 psi. Tensile and impact ductility were then correlated with a grain size for constant strength levels. Materials—The alloys Ti-6A1-4V, Ti-4A1-4Mn, and Ti-16V-2.5Al are representative of the heat-treatable a-ß types in which ß embrittlement can be severe. The compositions and ß transi of the heats studied are given in Table I. The Ti-16V-2.5Al heat was melted and fabricated to 1/4 in. round at Battelle; the other alloys were obtained as 1/4 in. round rolled from commercial heats. The micro-structures of the as-rolled alloys were fine a-ß mixtures. This structure is typical of titanium alloys hot-worked extensively in the a-ß field. Resistance-Heating Treatments to Establish ß Grain Size—For direit resistance heating, a 1/4-in.-diam s~ecimen was heated with a 3000-watt transformer rated for 1000 amp with adjustable secondary voltage. The apparatus included a spray quench fixture. Both heating and quenching periods could be automatically controlled. For temperature measurements, 28-gage Chromel-Alumel wires were tack-welded to the specimen at its midpoint. A high-speed recorder-controller was used to control the heating cycle.

Jan 1, 1960

By Victor deWolfe

INTRODUCTION The Henderson Mine, located near Empire, Colorado, utilizes a continuous panel caving system to extract ore as one of the world&apos;s major producers of molybdenum. Any mine using a caving-by-gravity technique of mining must rely on closely controlled draw of the caved ore. This control is essential to insure proper caving action, to avoid damaging load concentrations of weight and to minimize the dilution of ore with waste material. Henderson is no exception. Draw control is a major factor in all production planning, from long- range plans to short-range and day-to-day ore scheduling. Draw control is reviewed constantly and administered daily in an effort to optimize production efficiency, ore recovery, and cave management. MINING METHOD The cave at Henderson is massive, moving slowly through large panels that are 244 m (800 ft.) wide by 610 m (2,000 ft.) long. Generally two cave areas are drawn at one time. The areas under active draw vary in size but can be as large as 244 m (800 ft.) by 244 m (800 ft. ) containing 400 draw points. Each draw point contains 45,360 mt (50,000 st) on the average and takes about two and one half years to exhaust. A complete panel is worked for seven to ten years. No pillar exists between panels, but rather a buffer zone of broken ore, or "static face," is left in each panel to be drawn with the adjacent, yet-to-be-caved panel in efforts of minimizing dilution of a working area from an exhausted one. (Figure 1) Production drifts are driven on 24.4 m (80 ft.) centers through the ore body. Between the production drifts are funnel-shaped draw bells on 12.2 m (40 ft.) x 24.4 m (80 ft.) centers to receive ore from the cave. Each bell is accessed by two draw points, one from the production drift on either side, thus forming a 12.2 m (40 ft.) x 12.2 m (40 ft.) draw pattern. Extraction of the ore is by rubber-tired, 3.8 m3 (5 yd3) load-haul-dump equipment. The LHDs then tram the ore a maximum of 49 m (160 ft.) to ore passes. Cave initiation and bell development are done from the undercut drifts which are parallel to and 17 m (55 ft.) directly above the production drifts. Longhole rings are drilled and blasted from the undercut drifts to define the bells and establish the undercut for caving. (Figure 2) DRAW CONTROL Since the cave line at Henderson is constantly advancing, it is necessary to be continually initiating new cave at one end while exhausting it at the opposite end. There must exist, therefore, an angle on the ore-waste contact in the broken rock from initiation to exhaustion. The basic concept of draw control is to keep this angle as smooth and even as possible, particularly at the time of exhaustion. If this is achieved, draw points are exhausted more or less in a line, avoiding pockets of remaining ore surrounded by exhausted areas. These pockets would cause spotty ore extraction at the time of exhaustion, increasing the amount of dilution occurring while introducing the potential for significant weight problems in the production area. To arrive at the desired angle on the ore- waste contact, maximum tonnage percentages are assigned to each row of draw points increasing at 10% or 15% increments (depending on cave size and velocity of draw) working away from the cave line. The available tonnage indicated by these percentages is the maximum allowable tonnage to be extracted from each draw point until the available tonnage percent- age is increased. As the cave moves, these percentages increase for each draw point regularly. However, in general the tonnage drawn from each draw point is kept at about 50% of this allowable maximum in order to maintain adequate available tonnage in the cave to sustain production for seven months if cave initiation were to cease. This available tonnage cushion is a safeguard built into the draw control program at Henderson to accommodate fluctuations in the rate of cave advance. When draw points move past the row of 100% tonnage availability, they are drawn past the desired 50% at the same increments per row until exhausted. (Figure 3) To achieve proper draw control, the number of LHD buckets to be taken from each draw point is assigned daily. The actual buckets taken, which may at times deviate from the

Jan 1, 1981

By J. C. Wilhoit, E. M. Galle

A three-dimensional photoelastic study was made to determine the stress state around the wall and bottom of a wellbore due to fluid pressure within the wellbore and unequal principal geostatic stresses. Models simulating the wellbore were made from a phthalic anhydride-cured epoxy resin. The frozen stress technique of three-dimensional photoelastic-ity was used to determine the stresses within the model. Two separate problems were solved: (1) hydrostatic pressure on all sides of the model with the exception of the inside of the hole, and (2) uniaxial compression perpendicular to the center line of the hole. The results are presented in the form of contour curves for each stress component. The curves cover a region which extends several hole radii from the bottom and wall of the hole. By proper use of these results, the state of stress may be calculated for any point on the wall or bottom of the hole, as well as for any point within the material that surrounds the hole. A systematic method is given for calculating these stress components for any combination of fluid pressure within the wellbore and system of unequal principal geostatic stresses, provided one of the principal geostatic stresses is parallel with the wellbore. The results show that stresses around the wall and bottom of a wellbore, induced by an uneyual system of principal geostatic stresses, are appreciably different from those induced by geostatic stresses that are hydrostatic. For uneyual principal geostatic stresses, the experimentally determined stresses on the wall of the hole several radii from the bottom are in good agreement with the stresses calculated by elastic theory. INTRODUCTION Interest in the problem of determining the stresses around and near the bottom of a wellbore, due to geostatic loading and fluid pressure within the wellbore, originated in the petroleum industry. The stresses on the wall of the wellbore are of interest due to their relation to lost circulation during drilling, the fracturing of formations during squeeze cementing and hydraulic fracturing of producing formations. The stresses on the bottom of the hole are of interest to the drilling segment of the industry because to produce a hole in the earth it is necessary to remove material from the bottom of the hole. This removal of material is produced by structural failure of the rock, whatever the criterion for failure may be. Cunningham and Eeninkl have shown that for certain conditions the effect on drilling rate of the bottom-hole stresses caused by a hydrostatic overburden pressure is small compared to other effects. This question, however, needs further experimental and analytical investigation. Much information concerning the stresses on the walls of wellbores has been published considering both equal and unequal principal geostatic stresses. The problem of determining the stresses around the bottom of the wellbore is considerably more complicated. However, previous investigators have obtained numerical and experimental solutions to the problem for equal principal geostatic stresses. whitworth2 and woods3 have obtained numerical solutions. word415 obtained a three-dimensional photoelastic solution, Durelli and Deily 6 obtained surface stresses only by photoelastic means, and Cheatham and Wilhoit7 determined the stresses around the bottom of a short cylindrical cavity. While Miles and McGuire, Harrison and Kieschnick and Hubbert and Willis 10 obtained the stresses on the wall of a wellbore for unequal principal geostatic stresses, they did not concern themselves with the stresses near the bottom of the hole. The estimates made by Hubbert and Willis of the differences between the principal geostatic stresses indicate that, to obtain a satisfactory solution for the stresses around the bottom of a wellbore, unequal principal geostatic stresses should be considered. This work is directed toward obtaining such a solution. The materials in the earth&apos;s crust are nonhomo-geneous, permeable and anisotropic. Previous

By E. S. Machlin

An extension of the thermodynamic theory has been made for the case of irreversible growth processes occurring by the motion of an interface. The theory is applicable to such diverse phenomena as diffusion, growth in recrystallization, continuous grain growth, growth of carbides, etc., growth of eutectoid products, growth in solidification, recovery, "slipless" flow, etc. THE publication of a recent book1 has served to focus attention on a very powerful means of treating certain irreversible processes. This method which has been formally described as the thermodynamic theory of irreversible processes is applicable to processes which involve an approach to equilibrium and for which the deviations from equilibrium are small. The irreversible processes can be classified into three groups: chemical reactions, transport processes (diffusion, heat and electrical flows), and relaxation phenomena involving a degradation of internal energy to more stable states. The limits of applicability of the theory can be precisely defined1,2 for each type of irreversible process. For example, in a chemical reaction at constant temperature and pressure, the Gibbs free energy released per mol in the process should be less than the thermal energy, RT. Another type of irreversible process, which sometimes involves a combination of the first two of the above-mentioned groups, is treated in this paper. This process is one characterized by the motion of an interface separating two regions having different values of free energy and may be briefly described as a growth process. Prigogine2 and Herring3 have treated special cases of this type of process. Previous conscious applications of the theory in metallurgy have been limited to the field of diffusion, one of the transport processes. Darken,4 Bardeen,5 Prigogine2 and others have made significant contributions in this respect. Some other applications of the theory are described in this paper. The Theory The thermodynamic theory of irreversible processes is based on the work of Onsager,6 DeDonder,7 Prigogine2 and others. A resume of the theory has been given by Prigogine2 and DeGroot.1 A brief description of the theory follows, although for a complete understanding the reader is urged to read the references. It is first assumed that the change in entropy, even for a system removed from equilibrium, is given by dS = [dU + pdV - Si µi, dn, - Sk Pk dxk]T-1 Using this expression, the irreversible entropy production in the system is calculated by subtracting the contribution to the change in entropy of the system by transfer of heat, work, or matter from the surroundings. Thus, for example, the irreversible entropy production of a system at constant temperature and pressure is given by dtS = — — dG (DeDonder7) Now it has been shown by Prigogine,2 DeDonder,7 and DeGroot1 that the rate of irreversible entropy production diS/dt, when calculated in the manner suggested, can be written as a sum of products of conjugate forces XK and fluxes Jk, i.e., d,s/ = Sk Jk Xk [I-1] dt The assumption is next made that a linear relation exists between a given flux and the forces, obtained from Eq. I-1, i.e., Ji = Sk Lik Xk (i = 1, 2, . . . n) [I-2] Generally, there is a degree of freedom in choice of the fluxes and forces. However, for all the choices consistent with Eq. I-1 the Onsager8 relations, based on the principle of microscopic reversibility, namely, Lik = Lki, are valid. The coefficients Lik, depending upon the choice of the conjugate fluxes and forces, may be more or less dependent upon the parameters defining the state of the system. In general, the proper choice of fluxes and forces utilizing Eq. I-1, makes the coefficients Lik independent of time. Also, because many of the three classes of irreversible phenomena have already been treated,1,2 a proper choice can be made by analogy. In any case, the validity of Eq. 1-2, from whatever choice made using Eq. I-1, must be tested by experimentation. The theory, thus, comprises the following steps: 1—The irreversible entropy production is calculated to yield Eq. I-1. 2—The terms in Eq. I-1 are grouped

Jan 1, 1954

By T. V. Philip, R. E. Lenhart

When commercial silicon iron sheets of varying magnetic quality are isothermally annealed at high temperatures, extremely large grains develop in the material having good magnetic properties. These grains are of the (110) [001] orientation and are formed by secondary recrystallization. The primary driving force for this secondary recrystallization is grain boundary free energy. For the secondary grains, activation energies of 103 kcal per mole for nucleation, and of 75.5 kcal per mole for growth, were obtained. The activation energy for nucleation of the secondary grains is consistent with a model involving redistribution of a precipitate acting as the primary grain growth inhibitor. SINGLY oriented silicon iron sheet was first produced in 1935.1 The material as commercially produced today has a very highly developed preferred orientation or texture; up to 95 pct of the grains are crystallographically oriented with their (110) planes in the plane of the sheet and their [loo] directions parallel to the rolling direction. This texture, usually written as (110) [00l], is referred to as the "GOSS" or the "cube-on-edge" texture. Because the magnetic properties of this material are superior to those of the nonoriented sheets in the direction of rolling, the oriented silicon iron has acquired tremendous industrial importance especially in the manufacture of transformer cores and other electrical equipment. The commercially produced material is essentially an iron-silicon alloy containing about 3 1/4 pct Si with minor impurities totaling less than 0.15 pct. The silicon steel heat is melted in the open hearth or electric furnace. The ingots are hot rolled, with or without being slabbed, to strips of 0.100 to 0.080 in. thickness. They are then cold reduced to an intermediate thickness, recrystallized, cold reduced to final thickness, decarburized, and finally annealed at a high temperature. During this high-temperature anneal, extremely large grains with the cube-on-edge texture are produced in the sheet. Several papers have appeared in the literature2-10 relating to the production of the Goss-textured material. Most of these describe the textures produced on cold rolling and on subsequent annealing of single crystal or polycrystalline silicon iron. May and Turnbull11,12 have recently shown the necessity of a second-phase dispersed impurity in the material for the production of the Goss texture. However, none of these papers describes in detail the nucleation and growth kinetics of the (110) [001] grains during the final high-temperature anneal.* The present work, therefore, is an attempt to understand the nucleation and growth kinetics of the cube-on-edge grains in the silicon iron sheet during the final high-temperature anneal.

Jan 1, 1962

By AIME

WELL known as an outstanding practical metallurgist, the Chairman of the Institute of Metals Division also possesses a rare combination of research and administrative abilities. Louis W. Kempf was born in Muskegon, Mich., on March 22, 1898. Following his graduation from high school, he obtained considerable experience in the automobile industry while employed by Continental Motors, the Studebaker Corp., and Dodge Brothers. He enlisted in the U. S. Army Signal Corps in 1917, and served overseas with an aviation unit. In 1919, Mr. Kempf entered the University of Michigan and earned both B.S. and M.S. degrees. While there he was elected to Tau Beta Pi, Phi Lambda Upsilon, Alpha Chi Sigma, and Gamma Alpha. In 1924, the Aluminum Co. of America secured his services as a research metallurgist. With a steady job he married Elizabeth Skelley in Cleveland in 1926. They have one son now seventeen. After six years Mr. Kempf was made manager of the Cleveland research division of the Aluminum Research Laboratories which position he held until last year. In 1945 he was promoted to assistant director of the Laboratories. He will direct research involving process metallurgy in Cleveland and New Kensington.

Jan 1, 1946

By AIME AIME

COMMITTEE No. 2 of the Iron and Steel Institute b f Great. Britain has presented its first report, of 27 printed pages, on blast-furnace plant and practice. This report outlines the various features of modern blast-furnace practice with brief comments thereon, and with references to some of the more recent methods devised for applying the principles and attaining the purposes aimed at&apos; under these headings.. In general, the trend in the United States is in the direction of larger and larger furnaces with ever increasing capacity from which, with improved details in methods and equipment, and attention to details of management, considerable progress in. economy of production has been attained, in fuel consumption and in other items of production cost.

Jan 1, 1929