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By W. B. Hickman, J. J. Pickell, B. F. Swanson

Many physical properties of the porous media-immiscible liquid system are dependent upon the distribution of fluids within the pores; this in turn, is primarily a function of pore structure, liquid-liquiri interfacial tcnsion and liquid-solid wetting conditions. The cnpillary pressure hysteresis process provides a means of investigating the influence of pore structure upon fluid distribution for consistent sur/acc conditions. Invcstigntiot2s indicate that residual non-wetting-phase saturations /ollozuir,g the imbibition process (i.e.,wetting phase displacing nor2-wctting phase) are dependent upon both pore structure and initial non-raetting phase saturation and suggest that residual fluid is distributed as Discontinuous ,globules, one to a few pore sizes in dimension, thrnugh the entire range 01 pore sizes originally occupied. It clppears that air-mercury capillary pressure dala adequntely rellect the distribution of fluiris in a water-oil system when strong wetting condition preliczil. An oil-air counter-current imbibition technique has also been found to provide a rapid rneans of obtaining residual-initial saturation data. In a majority of cnses, rcsidual saturations detf-rniinecl from the oil-air or air-mercury process reasonably approximate residual oil saturation following water drive of a strongly water-wet medium. INTRODUCTION A reliable estimate of recoverable reserves depends not only on the amount of original oil-in-place but also on pore geometry and distribution of fluids within the pores. A critical parameter determining the recovery from a reservoir under waterflood, for example, is the amount and distribution of residual oil within the various rock types present. The purpose of this paper is to investigate the mechanism of capillary trapping and assess its importance in laboratory measureqents of residual oil saturation. The degree of wettability of a reservoir rock is recognized as an important factor in waterflood or imbibition experiments. In this paper, however, only the water-wet case has been considered. Considerable experimental evidence1 suggests that for water-wet rocks, capillary forces predominate in tile distribution of fluids and that viscous forces in the range normallv of interest in the reservoir have a minimum influence on residual oil saturation. It follows that if the ultimate recovery is controlled by pore geometry, a unique residual non-wetting phase saturation should exist for a given set of initial conditions. Two laboratory procedures.found to be extremely useful in the study of pore structure and degree of fluid interconnection at various saturations are decribed. Although air-nercury capillary injection curves have been used2 previously to characterize the drainage case, the withdrawal or imbibition case can provide valuable supplementary data. The air-mercury process, however, has several disadvantages; it is difficult to run in a sufficiently accurate manner, mercury does not always act as a strongly non-wetting liquid and in the air-mercury process the sample is rendered unsuitable for future analyses. An alternative process is described in which air is the non-wetting phase and naptha, hentane, octane or toluene is the wetting phase. INTERFACIAL TENSION AND CAPILLARY PRESSURE Interfacial tension between immiscible fluids is due to the difference in attraction of like molecules as compared with their attraction to molecules of the neighbouring fluid. This net attraction results in a tension at the interface. To extend the interface; thus, interfacial tension s can also be thought of as free surface energy. Interfacial tension is normally expressed as dynes/cm, and interfacial energy is measured in ergs/cm2 hence, both have dimensions ml A 2 and are numerically equal.

Jan 1, 1967

NEW YORK MEETING PAGE Winchell, H. V.-Geology of Pachuca and El Oro, Mexico. Discussed by Frederick MacCoy, Robert Hawxhurst, Jr 2 WILKES-BARRE MEETING Kynor, Herbert D.-Mechanical Mining of Anthracite. Discussed by C. Evans, Jr., S. J. Jennings, W. J. Richards, Geo. S. Rice, and the author 3 Stein, C. H.-Ashley Planes for Handling Freight Traffic. Discussed by Graham Bright, Douglas Bunting, S. J. Jennings, R. V. Norris, C. H. Strange, Edwin Ludlow, W. J. Richards, and the author 3 Markle, Donald.-Anthracoal: A New Domestic and Metallurgical Fuel. Discussed by William Griffith, Edwin Ludlow, E. M. Chance, Charles Dorrance, E. W. Parker, G. H. Ashley, C. A. Burdick, Geo. S. Rice, and the author :.. 7 Griffen, John.-Slush Problem in Anthracite Preparation. Discussed by Henry Flood, Jr 11 Eavenson, H. N.-Lynch Plant of United States Coal and Coke Co. Discussed by E. V. d'Invilliers, C. Evans, Jr., Graham Bright, Geo. S. Rice, Geo. Otis Smith, A. M. Rodgers, C. T. Starr, C. A. Burdick, and the author 15 Bunting, Douglas.-Mine Fires Extinguished by Sealing. Discussed by Geo. S. Rice, J. B. Warriner, H. H. Otto, Edwin Ludlow, E. M. Chance, F. B. Nold, H. M. Chance, W. L. Jacobus, J. A. S. Ritson, R. D. Hall, Geo. S. Rice, and the author 18 Bright, Graham.-Determination of Electrical Equipment for a Mine Hoist. Discussed by F. L. Stone, Geo. S. Rice, L. F. Mitten, and the author 34

Jan 12, 1921

By P. M. Robinson, J. S. LI. Leach

The heats of solution oj' indiurrr, tin, lend, nrzd tellurium have been calculated from the measured heat effects when mechanical mixtres of indium and telLuium tin and tellurium, and lead and tellurium were added to liquid bismuth. The results are in good agreement xith publislzed values.s for the separate sollction of each eleltzent in bismuth. The heats oj solution of cadmium and tellurium calculated from the rneasuved heat effects on adding trechanical mixtures of these elements do not ugree zc,itl the published values jbv the separate solution of each element. It is shown that at 623°K Ile interaction between cadmium and tellurium dissolved in liquid bismuth is strong enough to led lo preciPitation of solid CdTc. The heats oj- jor-mation of CdTe at 273" nd 623°K (1)-c crilculated fi-or the measured heat ejlfecls. The calcnlaled az'erage deviation from the Kopp-l\'ez?,zunrz rule fov solid CdTe is less than 0.06 cat per g-atom- C over this lertzperalure range. Tlze importance 0.f these oDserl.ations to the determination of heals of formation hy metal solution calorimetry is considered. LIQUID metal solution calorimetry is a convenient method for determining the heats of formation of solid compounds. In this technique the heat of formation is the difference between the measured heat effects on dissolution of the compounds and of mechanical mixtures of the components in the liquid metal.' The heat of solution of the mechanical mixture may be calculated from the measured heat effect. At infinite dilution of the solutes, this heat of solution is equal to the sum of the heats of solution of the separate components. If the heat of solution of one of the components is known, the value for the other can be derived; if both are known, they may be used to check the accuracy of the calorimetric technique. The heats of formation of the tellurides of cadmium, indium, tin, and lead have recently been measured by metal solution alorimetr. The heats of solution of indium, tin, lead, and tellurium at infinite dilution in liquid bismuth at 623"K, calculated from the measured heat effects on solution of the mechanical mixtures, are in good agreement with the published values. The heats of solution of cadmium and of tellurium calculated from the measured heat effect on solution in bismuth at 623'K of mechanical mixtures of cadmium and tellurium, however, do not agree with values estimated from the literature. 1) EXPERIMENTAL PROCEDURE AND RESULTS The Heats of Solution of Indium, Tin, Lead, and Tellurium in Bismuth. The heat effects were measured when mechanical mixtures corresponding to the compounds In,Te, InTe, In2Te3, In2Te5, SnTe, and PbTe were dissolved in bismuth. The calorimetric procedure and the method of calculation have been described elsewhere.' The heats of solution of the mechanical mixtures were obtained by subtracting the change in heat content per gram-atom of the sample between the addition temperature (273°K) and the bath temperature (623"K), (H623°K - H273°K)S, from the measured heat effects. The calorimeter was calibrated with pure bismuth. The reported values of the measured heat effects are based on (HGoK - ^273oK)Bi = 4.96 kcal per g-atom.3 The measured heat effects are found to be linear functions of the solute concentrations of the bath in the dilute solution range. The values, extrapolated to infinite dilution, are listed in Table I, together with the heats of solution of the mechanical mixtures calculated using the published values of (H 623°K - H273°k)s for indium, tin, lead,3 and tellrium. All the error limits quoted in this work represent the spread of values obtained. The heats of solution in liquid bismuth at 623°K of mechanical mixtures of indium and tellurium in four different proportions were determined. Values of the heats of solution of the two components were then calculated from the resulting four simultaneous equations: The heats of solution at infinite dilution of tin and lead in liquid bismuth at 623°K were calculated from the heats of solution of the mechanical mixtures of tin and tellurium and of lead and tellurium using the heat of solution of tellurium calculated above. These values of the heats of solution are listed in Table I1 together with some published values for comparison.

Jan 1, 1967

By C. D. Woodward

THE Anaconda Copper Mining Co. purchases 25,000 kw. of electric power for its mining operations at Butte Mont. This power is delivered, over duplicate feeders, in the form of 60-cycle, 2400-volt, three-phase current, to five compressor plants, where most of the energy is used for driving air compressors. At the compressor plants are located the switching apparatus for controlling the 2400-volt power and distributing it to the various mines. At these points, also, there are a number of motor-generator sets for converting the alternating current to 275-volt. direct current for the haulage systems. Pole lines convey the power from the compressor plants to outdoor transformer substations at most of the mines. When it is not economical to distribute the power at the lower voltages in the mines, transformers and motor-generator sets are placed at strategic points .underground. All power is purchased on a maximum-demand basis, therefore there is installed at one of the compressor plants an eight-element totalizing graphic wattmeter. This instrument records simultaneously the value of all power taken at the numerous points of delivery, which not only eliminates the diversity factor but permits load dispatching between compressor and pumping plants, and thus materially reduces the maximum demand from the power system. As most of the mine hoisting is done, by 90-lb. compressed-air winding engines, the air-compressor equipment for the winding engines and mining operations is quite extensive. The standard air compressor has a rating of 7500 cu. ft. per min. of free air, and most of the compressors are directly connected to synchronous motors. The synchronous motors are designed for 80 per cent. leading power factor, thus facilitating power-factor correction of total mine load. Consequently by cooperation with the power company, the voltage of the power received at the compressor plants is constant.

Jan 2, 1922

By Eugene F. Poncelet

Glass squares compressed on edge by steel jaws in poor contact with them developed jagged "partial-contact" cracks caused by the formation of local tensile stresses. Compressed by steel jaws in perfect contact, they developed smooth "release cracks" during release of the pressure, caused by the formation of local tensile stresses during the release of the pressure. All these cracks were parallel to the pressure. A Microflash photograph of a disintegrating specimen under sufficient pressure reveals a network of fractures roughly normal to each other, also "release cracks" and a disintegration cloud. The Griffith theory is amended to account for the formation of a first crack. A new theory, based on the theory of thermal agitation and wave propagation, is proposed to account for the progress, velocity and forking of cracks. The network of fractures is shown to have been caused by reflection at a free boundary of pressure pulses emanating from a first crack. Postulating equal distribution of energy in the pulses emitted on either side by a crack in particles, the smaller fragments are shown to continue fracturing preferentially while some of the coarser fragments remain as residual pieces. As comminution of the smaller fragments proceeds, the solid is reduced to a collection of residual particles of smaller and smaller sizes, accounting for the disintegration cloud. Experimental Procedure Apparatus A crushing device was built, consisting of a steel frame and two polished, hardened steel jaws to crush plate-glass samples. This device was placed between the plates of a hydraulic press (Fig. I). For centering the pressure, the upper jaw was guided vertically and provided with a rounded top. Later it was replaced by a steel jaw ground out of a 2½-in. steel ball, the lower surface being ground to an optical flat (Fig. 2). Four rollers were used to eliminate side thrust. Screws and centering blocks served to center the specimen in the crushing device. Hard steel shims placed under the shoulder of the upper jaw limited the "follow through'' of the jaw after failure of the specimen. Stress distribution was first examined with a polariscope mounted on an optical bench, using monochromatic light. It was found convenient to mount polaroid, quarter wave and monochromatic plates directly on the device itself. A Microflash unit* was used as light source for the photographs. A gold-paint pattern was fused on the plate-glass specimens and connected into the spark-

Jan 1, 1947

By Kenneth K. Humphreys

INTRODUCTION What is automation? Why automate? Webster's New Collegiate Dictionary defines automation as "the automatically controlled operation of an apparatus, process or system by mechanical or electronic devices that take the place of human organs of observation, effort, and decision." This definition gives an implied answer to the second question, )"Why automate?" Automation, automatic control devices and process control equipment receive their justification in supplementing or replacing manpower, which results in decreased operating costs. In the past, processes were operated with a minimum of instruments for the purpose of merely guiding the operators. Processes were manually controlled by the operator on the basis of simple temperature, pressure, flow and level indications on a panel. Today the tendency is to design a new plant to operate in a fully automatic manner according to a preset pro- gram utilizing a minimum of manpower. In addition to this direct cost reduction savings in manual labor, increased equipment capacity results from uniformity of flow and uniform control of process variables. This control eliminates or minimizes surges and permits equipment to be operated at or near its ultimate capacity and, for a given material through- put, permits the use of smaller process equipment. Automatic control, therefore, be it in the field of coal processing or in any industrial field, is simply a problem of economics. Control equipment is justified in terms of its contribution toward increasing productivity, increasing profit margins or producing a new and saleable product at a profit. Instruments and control devices can be divided into two general groups: (1) units which measure, and (2) units which both measure and control a process variable. In coal processing, the first class of instruments, those which measure only, include analytical devices such as automatic ash, moisture and sulfur measuring units and the simple pressure, temperature, flow and level indicating devices mentioned previously. The second group of instruments, those which both measure and control, include a wide variety of units such as continuous weighing devices on conveyor belts and photoelectric cells which gauge the position of railroad cars on the track and insure that the cars are in the proper location for loading (see Chapter 15). The latter types of units as used in the coal industry differ from those used in other industries in one significant point. In coal processing these instruments need not be as highly sophisticated and accurate as in other industries; hence their cost is proportionately lower than in other industries. Because of the economic fact that coal sells for only a fraction of a cent per pound compared to dollars per pound for many chemical products, and

Jan 1, 1968

By R. G. Gifkins

Mean boundary migration depended linearly upon creep extension under various conditions. Prolonged annealing or air-casting increased the proportion of immobile boundaries at a given stage of tests. Grain growth during annealing followed a power law. The linking of migration and sliding in creep and models for migration are examined; activation energies are calculated from these models. Segregation of oxygen to boundaries appears to be a controlling factor. THE idea that boundary migration and boundary sliding during creep are linked has often been suggested,'-5 especially when evidence has been obtained for an alternation between the two processes. In simple bicrystals sliding can occur without any migration6 but in more complex bicrystals7 it is observed. McLean' and Couling and Roberts 5 made measurements of both sliding and migration; McLean concluded that there was no linking of the two processes whereas Couling and Roberts supported the idea. McLean' also developed a model for migration during creep and annealing. The present work was initiated as part of a study of the recrystallization of lead during creep9 but has been extended to examine some aspects of the mechanism of migration. MATERIALS AND METHODS Specially refined high-purity lead* was used; the total of impurities, excluding oxygen, was 0.0008 wt pct. Oxygen was removed as far as possible by melting in vacuo, treating at 550" to 600°C with hydrogen and then casting at 450°C under a vacuum of 10-2 mm Hg; the oxygen was then believed to be 0.00005 wt pct. Specimens were made from extruded strip and then annealed at the required temperature in an air oven, controlled to 5 lac. They were then polished in a mixture of acetic acid and hydrogen peroxide. At this stage some specimens were etched to give grain contrast and their grain sizes determined by the intercept method. Migration of boundaries during creep was measured on the surface of polished (not etched) specimens, directly loaded at room temperature (22°C) or 50°C (52"C) to initial stresses of 300 to 700 1b per sq in. Twenty six vacuum-cast hydrogen-reduced specimens were used and, in addition, two specimens were from material air cast after hydrogen reduction ("partial" air cast) and two from air-cast material not treated with hydrogen ("full" air cast). Duplicates were made in the majority of tests. At intervals through the creep tests, specimens were unloaded and the migration measured, normal to the direction of migration at the point of measurement, for each boundary along standard traverses. Usually between 110 to 180 boundaries were measured at each of some twelve stages of the tests. Migration was measured on the projected image (X100) using prism illumination. Fig. 1 illustrates the method of measurement and shows the kind of variation of migration found from boundary to boundary and along particular boundaries. Fig. 2 gives an example of more extensive migration. The mean value of distance migrated was generally reproducible to *10 pct but occasional points gave a scatter of *20 pct. The correctibn applied by McLean8 to allow for the contribution sliding makes to the apparent distance of migration could not be used, for the sliding at most boundaries was too small to measure with the equipment available. There were two reasons for supposing the correction unnecessary in the present work;

Jan 1, 1960

[The following discussion, comprising both remarks made at the Chicago meeting and contributions since forwarded to the Secretary, is based upon the following papers, presented at that meeting : "Segregation and its Consequences in Ingots of Steel and Iron," by Alexandre Pourcel, Paris, France. (See p. 105, mans. xxii.) " Microscopic Metallography," by F. Osmond, Paris, France. (See p. 243, Trans. xxii.) " Microstructure of Ingot-Iron in Cast Ingots," by Prof. A. Martens, Berlin, Germany. (See p. 37.) " Microstructure of Steel," by Albert Sauveur, South Chicago, Ill. (See p. -546, Trans. xxii.) "Farther Observations on the Relations Between the Chemical Constitution and Physical Character of Steel," by William R. Webster, Philadelphia, Pa. (See p. 113.) "The Heat-treatment of Steel," by H. M. Howe, Boston. Mass. (See p. 466.) Since all these papers were considered together, no attempt has been made to separate the discussion strictly under the several heads.] William R. Webster, Philadelphia, Pa.: I desire to say that in my first paper (Trans., xxi., 766) the actual ultimates were subtracted from the estimated ultimates, whereas in the paper submitted at this meeting the estimated ultimates are subtracted from the actual, thus giving contrary signs. The latter method corresponds with the direct effect. of low and high finishing-temperatures ; that is, a plus difference indicates low, and a minus difference high, finishing-temperature. I make this explanation to prevent confusion in comparing the two papers. Mr. Sauveur has shown that there is a close relation between the size of the grain and the ultimate strength, and also that the size of the grain depends on the temperature at which the material is finished in rolling, and on the chemical composition of the steel. I have shown that there is a close relation between the chemical

Jan 1, 1894

By R. E. Goodman, M. A. Mahtab

The, state of stress around a vertical wellbore in rock following nonlinear stress-strain laws is examined by means of finite element analysis. The wellbore, is considered an axisymmetrier body with axisymmetric loading. The initial vertcal and borizontal stresses are "locked" in the rock elements around the wellbore and a new state of stress is generated by the displacements which occur around the borehole. A point-uise variation of the elastic moduli is made on the basis of the new stress state and the triaxial data. The initial stresses tire now reintroduced along with tile changed moduli and original boundary constraints. This procedure is repeatrd until convergent stresses are reached. The effect of nonlinearity on streases is examined for a 6,000-ft wellbore in a scbistose gnezss and Berea sandstone using results of laborratory triaxial compression tests. The results sbou that the effect is restrited to one well radius from the bottom periphery of the bole. Beyond a distance of one-quarter radius, the elfect of nonlinearity on stresscs IS almost always less than percent for the cases conszdered, The consideration of a static pressure inside the well does not magnify the effect of monlinearity on borehole stresscs. INTRODUCTION The terms " wellbore" and "borehole" here designate cylindrical openings in the ground with vertical axis and a circular cross-section. A knowledge of the stress redistribution that occurs on excavating a wellbore is important in understanding (1) the behavior of the lined or unlined hole, (2) hydraulic fracture response, and (3) the effect of stress redistribution on drillability; also it is important in predicting initial stresses in the virgin ground, and in analyzing the response of measuring instruments placed in the borehole. Our knowledge of the state of stress around a wellbore has been restricted to homogeneous, isotropic, elastic material and derives chiefly from the analysis by Miles and Toppingl and the photoelastic work of Galle and Wilhoit2 and Word and Wilhoit.3 In this investigation the state of stress is examined for a nonlinear elastic material by means of finite element analysis. Many rocks possess stress-strain curves that depart notably from straight lines in their initial or final portions. While the literature contains abundant stress-strain data from triaxial tests (axisymmetric loading) on cylindrical rock specimens, there is little information on rock deformability under nonaxisymmetric loading conditions such as occur at each point around the bottom of a wellbore. Although there is some knowledge of the effect of intermediate principal stress on rock strength, there is virtually nothing known about its effect on rock deformability; therefore, we have assumed here that the effect of intermediate principal stress can be ignored. A schistose gneiss4 and Berea sandstone5 were selected as representative rocks for this analysis. The traditional graphs of deviator stress (ol -o3) vs axial strain were reworked to give the tangent modulus as a function of the deviator stress for varying values of the minor principal stress. The result is a nesting family of skewed, bell-shaped curves for tile gneiss (Fig. 1A) and the sandstone (Fig. 2A). A similar replotting of the lateral strain data defines the variation of Poisson's ratio (v) with the deviator stress and confining pressure. These curves, shown in Fig. 1B for the gneiss and in Fig. 2B for the sandstone, are not so well ordered as the tangent modulus curves. However, all of these display an increase of v with deviator stress application, but the rate of increase diminishes with confinement. The ET and v curves for the two rock types are tabulated in Tables 1A and 1A for use in a digital computer so that material properties corresponding to a given state of stress can be assigned by interpolation. STATEMENT OF THE PROBLEM Given a state of stress in the ground prior to drilling a hole (initial stresses), we assume that

Jan 1, 1969

By J. E. 214-000-000-010 Warren, M. R. J. Wyllie, T. Meidav, L. Scharon, R. Uhley, A. J. deWitte

By considering the stoichiometry of the underground combustion process, an equrztion was derived relating the point velocity of the combustion front as a function of the air flux, fuel content, efficiency' of oxygen uitilization, hydrogen:carbon ratio, and ratio of carbon dioxide In carbon monoxide produced. In addition, an equation for cnlcrllating the amount of injected air necessary 10 produce the oil from I Cu. ft of reservoir space was derived. This equation has a direct bearing on evaluating compression costs for the process. Values calculated from these equations are in good agreement with experimentnlly obscrvcd values obtained from laborator) tube runs reported in the literature. The equations are also u\eful for atlcrlyzinf: experinlental data for inconsistencie.r.. I NTRODUCTION The injection of energy in the form of heat into an oil-bearing formation as a means of increasing the recovery of oil has been the subject of much discussion and experimentation as far back as 1920. The ideas have ranged from the injection of steam to the direct use of electricity as a means of getting thermal energy into a formation. However, most laboratory and field studies have been confined to the process whereby a portion of the crude in the reservoir is burned to generate the necessary heat to increase the mobility of the oil by reducing its viscosity. A recent paper by W. L. Martin, et al.', described the results of a number of laboratory experiments in which the combustion process was studied in a sandpack. Studies such as this indicate that with the temperatures involved, the oil is partially coked in this process and it is this coke which provides the fuel for combustion. The combustion of this residual coke can be analyzed theoretically by applying simple stoich-iometric principles to the combustion process. It is the purpose of this paper to compare the results reported in these experiments with those obtained from theoretical considerations. The variables studied by Martin, et al, among others, include combustion front velocity, air flux, oxygen utilization, fuel concentration, ratio of carbon dioxide and carbon monoxide in combustion gases, and the hydrogen:carbon ratio of the residual fuel. All these variables come into consideration when the stoichiometry of the combustion process is studied. The experimental conditions and results are tabulated in Tables 3 and 4 of Ref. 1. For purposes of comparison with calculated results, it was necessary to change the units of a number of the variables. UNDERGROUND COMBUSTION STOICHIOMETRY The combustion or oxidation of the carbonaceous residue or "coke" on the sand can be described in terms of the equation: where n is atomic ratio of hydrogen to carbon, m is ratio of moles of CO2 to CO produced, and CH. is taken as the unit molecular weight, realizing that actually the coke has a large range of high molecular weights. Assuming that all the fuel laid down in the sand is burned, the ratio of moles of oxygen consumed to moles of coke can be written as follows. Moles 0MolesMolescoke In terms of moles O2 per pound of coke, where 12 + n is the molecular weight in pounds per mole. If the 0, consumed is measured in standard cubic feet (60°F and 1 atm) and the coke in pounds per cubic foot of formation, 2, then:

By R. O. Williams

It is shown that Ni3Al precipitates homogeneously from nickel-rich alwminum alloys as plates on the (100) planes. Prior to actual precipitation a process occurs which is believed to be one of increasing short-range order. After precipitating the Ni3Al plates enlarge through competitive growth. Discontinuous precipitation can occur simultaneously with the above processes. Recent ideas of the origin of precipitation strengthening appear adequate to explain the hardness changes. REMARKABLY little appears to be known about the precipitation process in Ni-Al alloys in spite of their technical importance. This investigation originated to supply additional information about precipitation in general, this system in particular. Information on the structures and kinetics have been obtained through the use of hardness, X-rays, microscopy, calorimetry, and resistivity on high-purity alloys. PROCEDURES Six alloys, Table I, were prepared by melting carbonyl nickel and high-purity aluminum in alumina crucibles in vacuum and casting into 1-in. graphite molds. All rods were homogenized at least once at 1300°C for 24 hr prior to swaging and this was repeated on the first three alloys after 75 pct reduction. Alloy 4 could be reduced only 10 pct at 1000°C (probably in two-phase field) prior to fracture but 1/4-in. samples quenched from 1100°C were readily reduced cold. Alloy 5 was reduced 15 pct cold but failed on the next pass while alloy 6 of essentially the same aluminum content failed inter-granularly without apparent flow up to 1000°C. The alloys were heated in hydrogen at the elevated temperatures and formed thin, coherent aluminum oxide coatings which provided excellent oxidation resistance at lower temperatures. However, freshly prepared surfaces showed considerably less resistance at 500"to 700°C in air and apparently resulted in internal oxidation. As a consequence, low-temperature agings were carried out in evacuated tubes. RESULTS The isothermal hardening behavior of these alloys at 500"and 565C is given in Figs. 1 and 2. These results were obtained from samples cold worked 75 pct, recrystallized at 1000°C (1100°C for the 7.8 pct Al) and quenched in water. This recrystallization was used to give smaller grain sizes so as to obtain more uniform hardness values and the points represent an average of five readings. The electrical resistivity was measured on 1/16-in. wires quenched from 1000°C during aging at 495°C to give Fig. 3. The energy release and its rate are given in Fig. 4 for the 6.9 pct Al alloy during aging around 500°C. Inasmuch as this was a single run, its accuracy is not known but certainly the general shape and magnitudes are correct. The method used to obtain these results is described elsewhere.' Data for the aging at 600°, 700°, and 800°C of these alloys cold worked 50 pct are given in Fig. 5. Supplementary information from microscopy and X-ray diffraction have been included to indicate recrystallization, discontinuous precipitation and the appearance of superlattice lines from the Ni3Al. The hardness of these alloys as annealed, aged, cold worked, and cold worked and aged is given vs composition in Fig. 6. Those samples which were isothermally aged, Figs. 1 and 2, were reaged at 532°C and at successively higher temperatures for the indicated times to give the data of Fig. 7. These results as well as certain others, support the idea that the level of hardness reached for temperatures above 600°C are equilibrium values more or less independent of path. This being the case, the breaks in the curves would be the complete solution of the Ni,Al. The electrical resistivity versus temperatures for some of these alloys, both aged and unaged, is given in Fig. 8 along with those data from heating slowly (10 deg per day) to high temperatures. Interesting points include the lowering of the Curie temperature (the change in slope), the lack of any indications of a solubility limit and the large temperature coefficient for the Ni3Al. A slight break for Ni3Al around 100C shows up but this is not a Curie temperature as Ni3Al is not ferromagnetic down to -190°C. Metallographically both the nickel-rich solid solution and the Ni3Al appear very much like pure nickel. Profuse twin boundaries are present both

Jan 1, 1960

By W. P. Sykes

Seven years ago, Dr. S. L. Hoytl presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned. Steps in Preparation While the past 25 years have contributed a valuable store of working knowledge in the field of powder metallurgy, many of the process controls are derived entirely from experience and are not as yet finally explained by a specific physical or chemical phenomenon. For most of the cemented carbides such difficulties are aggravated by our lack of knowledge not only of the complex alloy systems involved, but also by the possible changes in structure and even in composition which may accompany variations in temperature, heating time, and furnace atmospheres. The principal steps in the preparation of these cemented carbide alloys are fairly well known, but to supply a foundation for discussion these steps are briefly outlined as follows : 1. Formation of the metal carbide in the form of powder by heating a mixture of carbon and the metal powder or oxide for several

Jan 1, 1938

By J. C. Swartz

New measurements of graphite and cementite solubilities in ferrite have been obtained to resolve disagreements among previous data. To measure graphite solubility, specimens of iron were equilibrated with rarious carburizing atmospheres at temperatures be-twee~z 480" and 1435°C. The carbon activity of each atmosphere relative to graphite was taken from published data. After quenching from each equilibration treatment the concentration of carbon (typically 10 pprn by wt) was determined from the height of the Snoek peak in the internal friction spectrum. A few inclividual analyses by combustion support the reszdts of Smith on the solubility of graphite near the eutectoid temperature. Combination of these combustion and internal friction analyses determines In a, (at 0.01 wt pct) = 24,000/RT - 12.72, where a, is the activtity relative to graphite in ferrite at fixed cornposition. The same specimens were used to determine the solubility of self-stressed cementite precipitates. The results indicate solubilities of 6.3, 23.2, and 68 pprn carbon by wt at respectively 400°, 500". and 600°C. The once large discrepancy between the cementite solubility determined by internal frictiori and that calculated from flee energy data has been almost completely resolved. A recent study1 (hereafter designated I) on the solubility of cementite in a iron did not fully resolve the disagreement among previous data. The remaining disagreement is illustrated by the phase diagram in Fig. L The data of I are represented by the line labeled "stress-free" cementite. They determine a heat of solution of cementite of (14.8 * 0.2) kcal per mole which contrasts with the (20 * 1) kcal per mole derived from Smith's graphite solubility2 and the formation energy of cementite.3 Toward resolving this disagreement we have obtained new data on the solubilities of graphite and cementite. METHODS As in I the Snoek peak in the internal friction spectrum was used to measure the concentration of carbon dissolved in ferrite. This method relies on the relation C=kQ-1 [1] in which C is the concentration of dissolved carbon, Q-I is the Snoek peak height, and k is a proportionality factor which is a function of the peak temperature, polycrystalline texture, and other parameters characteristic of the ferrite lattice. To determine true heats of solution via Eq. [1], it is necessary to establish that k is independent of the temperature from which the specimen is quenched. Some evidence on this point is contained in a separate report.* Additional evidence is shown by the data points in Fig. 1. These represent the Snoek peaks of two specimens carburized to about 10 ppm C, copper plated, and quenched first from 888º then from 588°C. The copper plate was removed before each Snoek peak measurement. These data show that there is no detectable dependence of k on quenching temperature. The solubility of graphite was determined by repeatedly carburizing various specimens of iron wire with gas mixtures of known carbon activity relative to graphite. To cover a wide temperature range within the a phase boundaries it is desirable to use as low a carbon concentration as is compatible with reasonable precision. With the present internal friction apparatus the best compromise of these desires is a concentration near 10 wt ppm. The dashed line in Fig. 1 was used to approximate the activity of carbon* for

Jan 1, 1970

By Lawrence A. Shepard, Richard H. Krock

A series of ductile, two phase W-Ni-Fe composites, sintered in the presence of a liquid phase, were tested in tension. Identical room temperature stress-strain curves were obtained for specimens containing from 80 to 92 wt pct W (58 to 75 vol pct W particles). The composites exhibited a maximum elongation of 29pct at room temperature, and 10.7 pct at 77 °K. The tungsten particles in the composite elongated by the same amount at these temperatures. Single-phase alloy specimens matching the composition of the composite matrix showed about one half the flow stress of the composites. The test results demonstrated that the mechanical properties of W-Ni-Fe composites are determined by the tungsten particles alone and are independent of matrix volume fraction or mean free path over the composition range studied. A general prediction of the plastic behavior of two-phase alloys or composites from a knowledge of the properties, size, shape, and dispersion of the individual components is not, at present, possible. The excellent theoretical and experimental exposition of the dispersion-strengthening problem applies only to cases where the stronger phase is present as fine particles and in volume fractions of a few percent. Materials in which the stronger phase constitutes a significant fraction of the volume, although of broad engineering interest, have received comparatively little analytical attention. This important group of materials is the concern of the present study. The degree of deformation of each phase during the plastic working of a ductile two-phase alloy has been established by Boas and Honeycombe,1 Clare-brough,2 and Clarebrough and berger.3 These workers empirically correlated the recrystallization temperature of the individual phases with the degree of cold work sustained by each. It was shown that the deformations of both phases are equal and therefore the same as that sustained by the composite whole when the volume fraction of the stronger phase exceeds 35 pct. At yielding, however, deformation begins in the weaker phase. A direct correlation of composite strength, as a function of deformation, with the strength of the individual components cannot be made. In the presence of stronger phase particles, the flow stress of the weaker matrix phase is enhanced by an additional hydrostatic component. The development and potential magnitude of matrix strength promotion upon straining has not even been experimentally established. Quantitative work in this field has been confined to ceramic-metal composites. These materials fracture at strains considerably below 1 pct by cracking of the ceramic particles.4-6 An indication of the potential constrained matrix strength capacity is given by the observation by Nishimatsu and Gur-land4 that the maximum tensile strength of a WC-Co composite is almost double the bulk strength of the cobalt matrix. The relationship between composite strength and geometry is ordinarily expressed in terms of the mean-free matrix path (referred to subsequently as MFP) between the stronger particles.* This factor takes into account both the volume fraction of matrix phase and the average size of the particles. unke17 concluded that composite strength varied directly with the decreasing log MFP, following the Gen-samer8 relationship. However, Gurland and ~radzil~ reported a strength maximum at an MFP of the order of 1 p in WC-Co composites. A ductile two phase metallic composite was chosen for the present investigation of composite mechanical properties with the view of avoiding the difficulties and ambiguities noted above. The W-Ni-Fe heavy alloy of Green, Jones, and pitkin9 contains 80 to 94 wt pct W, and nickel and iron in a weight ratio

Jan 1, 1963

By Eugene F. Poncelet

Glass squares compressed on edge by steel jaws in poor contact with them developed jagged "partial-contact" cracks caused by the formation of local tensile stresses. Compressed by steel jaws in perfect contact, they developed smooth "release cracks" during release of the pressure, caused by the formation of local tensile stresses during the release of the pressure. All these cracks were parallel to the pressure. A Microflash photograph of a disintegrating specimen under sufficient pressure reveals a network of fractures roughly normal to each other, also "release cracks" and a disintegration cloud. The Griffith theory is amended to account for the formation of a first crack. A new theory, based on the theory of thermal agitation and wave propagation, is proposed to account for the progress, velocity and forking of cracks. The network of fractures is shown to have been caused by reflection at a free boundary of pressure pulses emanating from a first crack. Postulating equal distribution of energy in the pulses emitted on either side by a crack in particles, the smaller fragments are shown to continue fracturing preferentially while some of the coarser fragments remain as residual pieces. As comminution of the smaller fragments proceeds, the solid is reduced to a collection of residual particles of smaller and smaller sizes, accounting for the disintegration cloud. Experimental Procedure Apparatus A crushing device was built, consisting of a steel frame and two polished, hardened steel jaws to crush plate-glass samples. This device was placed between the plates of a hydraulic press (Fig. I). For centering the pressure, the upper jaw was guided vertically and provided with a rounded top. Later it was replaced by a steel jaw ground out of a 2½-in. steel ball, the lower surface being ground to an optical flat (Fig. 2). Four rollers were used to eliminate side thrust. Screws and centering blocks served to center the specimen in the crushing device. Hard steel shims placed under the shoulder of the upper jaw limited the "follow through'' of the jaw after failure of the specimen. Stress distribution was first examined with a polariscope mounted on an optical bench, using monochromatic light. It was found convenient to mount polaroid, quarter wave and monochromatic plates directly on the device itself. A Microflash unit* was used as light source for the photographs. A gold-paint pattern was fused on the plate-glass specimens and connected into the spark-

Jan 1, 1947

By E. A. von Hahn, T. R. lngraham

The rates of cementation of pd11 on electropolislzed copper cylinders were studied in aqueous perchloric acid solutions at pdII concentrations from 0.02 to 0.1 mM. The cylinders were rotated at various high speeds to reduce the diffusion layer to a minimum thickness. In 0.1 M HClO4 solutions, the cemented palladium is dense, adherent, and shiny. The rate data indicate that there are two stages in the deposition. In the initial stage, the rate of cementation is first order with respect to the pd11 concentration. The second stage is much slower. The first stage is consistent with rate control by the diffusion of pd11 ions to the copper surface, and/or chemical reaction at the surface, and the second stage is consistent with rate control by the diffusion of copper ions from the cop-per surface through the deposit of cemented palladium, out to the main body of solution. In 0.001 M HClO4 solution, only the first stage is evident and the rate is more rapid than at higher acidities. This rate enhancement is attributed to PdOH+ ions that predominate at low acidity and aye more reactive than unhydrolyzed pdII. The deposit is porous and loose. All of the cemented deposits are Pd-Cu alloys rather than pure palladium. Activation energies are 9.5 kcal per mole in 0.1 M HClO4 and 7.4 kcal per mole in 0.001 M HClO4. CEMENTATION or displacement reactions occur between aqueous solutions of metal salts and immersed metals according to the general equation: where M1 is electrochemically the more noble metal. Although these reactions find considerable application in metals recovery processes (e.g., the cementation of copper192 or gold3), in electrorefining processes (e.g., solution purification before electrolysis4,5), and in plating and metal finishing processes,6 few studies have been made of the kinetics of such reactions.7-9 The rates of cementation reactions will depend on one or more of the following factors: a) chemical reactions at the metal-solution interface; b) ionic transport to or away from the interface;'-' and c) the character and adherence of the cemented deposit on the substrate metal,6a,10 because the deposit will inhibit the rate of transport of dissolving ions (M2m+) into the solution. In this investigation, the kinetics of the early stages of cementation were studied to obtain an understanding of the reaction mechanism under conditions in which the deposit was sufficiently thin that its inhibiting effect could be disregarded. To achieve this, very dilute solutions in Mn+ were used. Cementation rates are often fast in the initial stages and transport-contr01led.9 To find conditions under which transport control would shift to chemical control, very high stirring velocities were used to minimize the diffusion-layer thickness. Of the many possible cementation reaction systems, the palladous perchlorate-copper system was chosen for this investigation because it was believed to involve simple ion-for-ion exchange. In addition, there are no interfering side reactions, such as the reduction of hydrogen ions, and anion effects are usually absent in perchlorate solutions. EXPERIMENTAL Materials. Reagent-grade chemicals and redistilled water were used in all experiments. Palladous perchlorate stock solutions (0.02 M) were prepared by dissolving 99.5 pct Pd sponge (Johnson Matthey and Mallory Ltd.) in concentrated nitric acid, adding concentrated perchloric acid, evaporating twice slowly (to prevent PdO precipitation) to a small volume, and diluting in a volumetric flask. To prevent gradual hydrolysis of PdII, the stock solutions were made 0.4 M in HC104. Tests for pdIV (Ref. 11) and C1- were negative. Copper strips were cut accurately from 0.025-in. electrolytic tough pitch sheet, Sample 1 (Mines Branch stock or Canadian Copper Refineries Ltd., Montreal), or from oxygen-free, high-conductivity sheet, Sample 2 (American Metal Climax O.F.H.C. brand, sold by Utility Brass and Copper Corp., Brooklyn). The strips were annealed for 1 hr at 335°C in a stream of purified nitrogen (Union Carbide, Linde Division) which had

Jan 1, 1967

By Louis Huber

THE Liberty tunnels extend through a very steep hill in Pittsburgh (locally called Mount Washington) for a distance of slightly over a mile. The two tunnels parallel each other and are 59 ft. apart, center to center (Fig. 1). They are for vehicular traffic, and in each there is ample space for two lines of vehicles. Northbound traffic, towards downtown Pitts- FIG. I.-NORTH PORTAL OF LIBERTY TUNNELS. NOTE THE WINDBREAK AT END OFEAST TUNNEL. burgh, is confined to the east tunnel and southbound traffic to the west tunnel. The South Hills residential district is separated from downtown Pittsburgh by Mount Washington, a steeply rising escarpment south of and adjacent to the Monongahela River. The Mount Washington district immediately south of the Monongahela River has been reached, for many

Jan 1, 1927

By A. B. Cox, L. W. Wark

In the paper on the development of the flotation process at Broken Hill (Australia) prepared by the Broken Hill Branch of the Australasian Institute of Mining and Metallurgy and published in its Proceedings for 1930 (N. S. 80), it is stated that the concentration of ores by flotation has been established on a commercial basis in Australia since 1904 and that differential flotation was practised at Broken Hill in 1912. Since then, progress in flotation practice throughout the world has been rapid, and during recent years the knowledge of the reactions between comparatively modern so-called chemical promoters or collecting agents and the mineral surfaces has been broadened by the published accounts of many investigators, particularly those working in American universities. Because of the benefits the Australian mining industry has derived from the flotation process, it was felt that the industry should take some part in the efforts that are being made to extend the knowledge of the principles on which the flotation process is based. Accordingly, early in 1930, three Broken Hill mining companies—the Broken Hill South, the North Broken Hill, and the Zinc Corporation—together with the Electrolytic Zinc Co. of Australasia, Ltd., and the Mount Lyell Mining & Railway Co., established a laboratory in the chemistry department of the University of Melbourne for the purpose of investigating the principles underlying flotation. Subsequently, the Burma Corporation, Ltd., expressed a desire to cooperate. The two authors are directly employed and controlled by these six organizations, and the cost of the investigation is divided equally among them. The research has been carried out under the general direction and in close cooperation with Harry Hey, chief metallurgist for the Electrolytic Zinc Co. of Australasia, Ltd., and the authors desire to place on record their indebtedness to him for his ever willing help and constructive criticism. After an extensive search of the literature, it was decided to determine in a preliminary investigation whether the effect of chemical collectors could be evaluated quantitatively by the "contact-angle" method. This preliminary investigation showed that with the bubble machine of

Jan 1, 1935

By O. K. Miniato, L. Massé, K. Nobe, J. S. Aronofsky, W. F. 213-000-000-016 Seyer

MUCH work has been done dealing with the effect of mechanical stress on electrode potential in an electrochemical system. The contradictory nature of the experimental results indicates the complexity of the problem although thermodynamic considerations show that a simple relationshir, should exist. In those systems where a gas was the electromotive active substance satisfactory agreement between theory and practice has been found. Des Coudres' found this to be so even when the active substance of the electrode, in this case mercury, was in the liquid state. In contrast, attempts to correlate theory and experiment for the solid state have met with a very limited success. The early workers in this field, Andrews,2 Walker and Dill3 used iron, certainly one of the most reactive of metals. Others have made use of less active metals such as copper and nickel. Recently Fryxell and Nachtrieb4 investigated the electrochemical behavior of gold and silver under both tensile and compressive stresses and concluded that it was doubtful whether true stress potentials could ever be measured. Much of the lack of success to measure the thermodynamic stress potential can be ascribed to the presence or formation of a complex film on the metal surface in contact with the electrolyte. Further, the theoretical stress potential is very small and therefore difficult to measure directly. Thus the calculated emf between a 24 B & S gage cold-drawn copper wire stressed with a weight of 1 kg and an unstressed portion of the same wire is only 2.60 X 10"7 volts. This is very small compared to that which can be produced by chemical reactions at the metal electrolyte interface which in turn can be so large as to mask completely the stress potential. Hence in this type of measurement all chemical side effects must be eliminated or reduced as much as possible. It was for this reason that the system copper-sodium chloride solution was selected for study. INSTRUMENTATION In the many preliminary experiments conducted, two major difficulties were encountered. The first was to measure the small electro-potentials to be expected and the second to obtain a suitable electrode surface. The conventional potentiometric method was found to be unsatisfactory for measuring the small emf expected. However, by using an L & N No. 2290 galvanometer having a resistance of 915 ohms consistent measurements were possible. The reference electrode was always the unstressed one made from the same sample of wire. The steady current flow was approximately 10-8 amp. Lewis and Randell5 have stated that for currents of the order of 10-8, if there is no sensible polarization, the measured emf may be taken as a reversible one. To check the galvanomenter readings an alternative method was devised to measure the potential difference between the wires. This involved a Liston-Falb d-c breaker amplifier model 10, an L & N k-2 potentiometer and a moving-coil galvanometer having a sensitivity greater than 0.1 µv (microvolt) per mm. To increase further the output voltage of the amplifier a d-c amplifier, model B. L.-932 was introduced into the circuit. This amplifier was in turn connected to a Brush recorder which had been calibrated previously by the test signals from the Liston-Falb instrument. These test voltages employed took into account the impedance of the input current. Unfortunately, this method had too low a sensitivity for measurement below 10 µv. Above this value the voltage agreed reasonably well with those obtained directly by the simple galvanometer method. The main advantage of the amplifier setup was that one did not have to wait until no deflection occurred on the galvanometer in the circuit when first exposing the wires to the solu-

Jan 1, 1959

By L. L. Swift

AT the present time there are four base metals being used for automotive bearing alloys. Of course there are numerous variations in the amounts of alloying elements added to each base metal and nearly all of these alloys have the conventional, if not classical, duplex structure; that is, they are composed of a hard constituent embedded in a soft matrix. The well-known theory is that the former will wear well, while the latter will be plastic enough to allow the bearing to be broken in and conform to the contours of the shaft. The requirements of the modern bearing have been most aptly described by W. M. Corse: In order to meet the engineering demands of today a good bearing metal must be able to carry the weight of the shaft and stand up under steady or suddenly applied loads, or even blows in some types of service. A certain amount of plasticity is desired to compensate for minute irregularities in the shaft or bearing surface, and to permit yielding, thereby avoiding dangerous stresses in bearing and shaft and preventing overheating and rapid wear of parts. Less plasticity is required in a bearing metal if the surfaces of bearings and journals are machined accurately, aligned, and kept in alignment. It is desirable, of course, that a bearing metal have a low coefficient of friction. Under most operating conditions the friction depends on the unit pressure of the bearing, the speed, the temperature, and the properties of the lubricant. A good bearing metal must have a low rate of wear to reduce the necessity for frequent replacements, and adjustment of the bearings. It must wear more rapidly, however, than the journal or shaft running on it, because replacement of the journal or shaft is more difficult and costly than replacement of the hearing., The hardness of, the bearing alloy is a property closely related to several of the foregoing. With a duplex microstructure, the measurement of hardness with any of the usual commercial devices means little. The Bierbaum method of measuring the hardness of the individual constituents was developed to, fill this need. MICROCHARACTER The Bierbaum microcharacter2.3 measures the scratch-hardness of a solid by pulling a weighted diamond point over the surface. The diamond point is ground. so that it is the corner of a cube, and mounted

Jan 1, 1938