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By J. H. Reynolds

The possibility of using a semiconductor, metal, semiconductor structure as a light detector is discussed. A brief theoretical argument is presented which predicts that this structure should have pho-toresponse characteristics similur to those of a metal-semiconductor diode, but with the magnitude of the current increased by a transistor gain factor. Measurements made at low frequencies on a particulur S-M-S device agree u~th this prediction aizd shoul that significant gain factors are attainable. The current gain is substantially higher than that predicted for the metal base transistor. It is proposed that the operation of these units is more closely approxinzated by the metal-gate model which predicts higher current gains. A qualitative discussion of its high-frequency performance indicates that detection of light modulated at microwave frequencies by a S-M-S deuice is possible. ADVANCES in the technology of chemical vapor deposition'-4 have made it possible to form a S-M-S structure consisting of a thin metallic layer sandwiched between layers of single-crystal semiconductor. It has been proposed5-7 that, if the metal layer is made sufficiently thin, this structure could be used in an amplifier having several advantages over presently available transistors including higher-frequency performance. Calculations8 predict that the maximum gain-bandwidth product is nearly an order of magnitude higher than that of a bipolar transistor having the same geometry. Maximum oscillating frequencies in the microwave range are predicted. Electrical measurements made on S-M-S devices have shown that, although the theoretical frequency characteristics are not presently attainable, current and power gain is obtained. Another possible application of the S-M-S structure is its use in a light detector. This structure is a three-layer relative of the metal-semiconductor diode. Light detection using M-S diodes is the subject of considerable present interest. They are known to have a short response time and the ability to detect light having a photon energy below the semiconductor bandgap. In this paper, the mechanism by which S-M-S photocurrent is generated is discussed. An expression is derived which shows that the response characteristics are similar to those of a M-S diode, but that the magnitude of the current is increased due to the transistorlike behavior of the device. The results of low-frequency response measurements on a particular S-M-S structure are presented. These agree with the theoretical predictions and show that significant gain factors are attainable. A qualitative discussion of the high-frequency characteristics is presented which predicts that detection of light at microwave frequencies by a S-M-S device is possible. THEORY In this discussion, the photocurrent, iT, measured across terminals attached to the semiconductor emitter and collector layers is related to the current pho-toemitted from the metal base layer. The latter will be referred to as the primary photocurrent. The behavior of the primary photocurrent is determined by the characteristics of the two metal-semiconductor diodes. The diode photoemission is illustrated in Fig. 1, which shows the emitter and collector potential barriers. The metal thickness has been greatly exaggerated. As will be discussed later, the actual barrier shape can be much more complex, but this diagram illustrates the essential features of the photoemission process. An absorbed photon having an energy greater than the barrier height can emit an electron into the emitter or collector. Since this process is discussed

Jan 1, 1968

By Robert F. Mehl

THE purpose of a symposium, I take it, is to gather together a group interested in a common intellectual field, in order to exchange views, and to appraise the state of knowledge. Symposia are the more successful, the greater the activity in the chosen field and the wider the range of applicability of the information gained. From time to time, as emphasis changes from one field of research to another, a given subject may enjoy popularity and later retire into a scientific somnolence, for fashions change even among engineers and scientists. The subject of this symposium, however, enjoys the advantages of wide applicability and of high current interest and productivity in results. It is a timely subject for a symposium; with much new information, surely metallurgical engineers should now devote an increasing attention to its application to practice. In beginning the symposium, I shall attempt briefly to appraise our basic knowledge in the field, to survey instances of practical usefulness, and to suggest where new work might be most productive of useful results. There are many examples of direct practical application of diffusion knowledge, and it is the purpose of the several papers in this symposium to review these. In this introduction I shall attempt to take a broad view, which, while it will but poorly serve the engineer in the solution of any given problem, may perhaps be of some use in assessing the state of knowledge in this field. RATE OF DIFFUSION Liquid Metals The process of diffusion among liquid metals, of gases in liquid or solid metals, or among solid metals, is ubiquitous, to say the least. The manufacture of alloys by the intermelting of metals, the addition of ferroalloys to molten steel, the deoxidation of molten alloys, all involve diffusion in the liquid state. The oxidation of molten copper for purposes of purification, the unsought oxidation of alloys generally during melting and casting, the reaction of liquid steel with oxidizing slags in the open-hearth furnace, the absorption of nitrogen by liquid steel, particularly in the bessemer furnace, all operate by the diffusion of gases in liquid metals. These processes have not been studied much from the viewpoint of rates of diffusion. Alloys are made by melting metals with stirring and with allowance of time for mixing (which is diffusion) but I know of no studies that seem to define the necessary times, and though in only very rare cases can faulty properties of the finished castings be ascribed to inadequate mixing, and though certainly in most cases, with stirring, the rate of diffusion is adequate to give sufficient mixing, a more quantitative treatment would be good to have. It is not wholly certain that thorough and sufficient mixing is at all times attained, for I suspect that ferroalloy additions to steel, and that additions of aluminum to steel as a deoxidizer, especially in the sampling of steels

Jan 1, 1944

By P. E. Schauer

During the initial nine-year deple-tion of the McKamie-Patton pool gas-condensate reservoir, the pressure behavior and fluid analyses indicated pressure maintenance by gas injection would be attractive relative to continued pressure depletion. As a result, a gas cycling program was inaugurated in Aug., 1949, which has since maintained reservoir pressure. In order to evaluate the benefits of this program, the recoveries for natural depletion and for cycling followed by blowdown were determined by calculating the fractional balance of the molar quantities of vapor and liquid remaining in the reservoir and produced at the surface for various stages of depletion. The results of the investigation show theoretical ultimate recovery due to the cycling program will be 42 per cent greater than would be realized under pressure depletion type operation. INTRODUCTION The benefits of gas injection pressure maintenance programs in condensate reservoirs have been recognized and qualitatively described in several papers1-8 during the past 15 years. Some of these papers also describe methods for calculating the increased recovery realized from cycling; however, as a rule, hypothetical reservoirs were used as examples".'.. This paper presents an evaluation of the pressure maintenance program for the McKamie-Patton condensate reservoir and includes a description of the fractional balance method employed to determine the benefits. Reservoir Development and Characteristics The McKamie-Patton pool, Lafayette County, Ark., was opened in June, 1940, with production obtained from the oolitic Smackover lime at a depth of approximately 9,300 ft. The structure is an anticline 8 miles long by 1 to 2 miles wide, and is one of many productive Smackover structures in Southern Arkansas. Of predominant importance is the condensate-bearing gas cap portion of the reservoir, which covers approximately 4,000 acres, attains a maximum thickness of some 200 ft, and has an average thickness of 90 ft. Development of the cap was accomplished with 21 wells drilled on 160 acre spacing. An isopach map of the cap is shown in Fig. 1. In addition, an oil rim is present along most of the periphery of the pool. Production practice includes field separation of black oil, and a high pressure gathering system which carries total well stream from gas cap wells to a plant where condensate is separated and the gas is processed for recovery of natural gasoline, butane, and propane. Since the gas contains appreciable hydrogen sulfide, it is removed by amine contact, after which free sulfur is produced by the Claus process. Core analyses from 1,767 gas cap formation samples averaged 14.2 per cent porosity and 379 md dry air permeability. Connate water was restored on seven samples of gas cap rock by air-brine capillary techniques, from which the interpreted water saturation averaged 28.17 per cent. During the early life of the field, it was believed the recovery mechanism, based on several of the other regional Smackover reservoirs, might be a natural water drive. However, subsequent production and pressure history revealed that the gas cap would not be produced by water drive, but would behave as a closed reservoir. In this respect, during the nine-year period of natural depletion from initial production to Aug., 1949, the cap production of 84.3 billion

Jan 1, 1958

By D. J. Brown

Froth flotation is now used to recover millions of tons of fine coal,(-1/2 mm), every year. For example, in Great Britain, 4-million tons of flotation concentrate was produced in 1960, about 3% of the mechanically cleaned out- put and 2% of the total salable output. Coal flotation is not so widely practiced in the U. S. as it is in Europe since much American coal occurs in thick seams of high grade and does not require cleaning. However, in the U. S., as elsewhere, the increasing mechanization of coal mining machinery has lead to a lowering in size and grade of product from the mine and to an increasing need for cleaning of coal to improve the grade before sale. With an increasing proportion of fines in the product, froth flotation has assumed a greater importance as a cleaning process for coal. In the last three years, over 40 flotation plants have been put into operation in the Appalachian area of the U. S.80 Fine coal recovered by means of froth flotation may be used as a powdered fuel alone or mixed with coarser grades. The removal of this fine coal from washery water makes possible the recirculation and re-use of the water and also leads to improved and more consistent operation of jigs and other separating machines which function less effectively when there is a build-up of fine solids in the washery water. Finally, froth flotation is of assistance in the production of a clarified effluent which may be discharged from the washery without polluting local rivers, streams, or wells. The 1961 cost of installing a new coal flotation plant in Great Britain would be about $19,000 per ton of dry solids input per hour, including the cost of new buildings and coal and shale filtration and water clarification equipment. The figure for the gravity concentration of the large coal, the main plant, would be about $4,800 per tph. The operating cost for the new coal flotation plant would be about $1.10 per ton. Even at this level of cost the cleaning operation is economic in Great Britain for coking coals. In the U. S., a froth flotation cost of 14$per ton of cleanfilter cake was quoted early in 1958 for one operation,l though admittedly this was a special case. Assuming a cake moisture con- tent of 30%, it is estimated that this cost is equivalent to a figure of 256 per ton of dry solids input, for the incorporation of coal flotation in an existing washery. A cost oh 416 per ton of concentrate was quoted76 in a recent analysis of flotation economics, this cost being brought up to $1.11 per ton after payment of royalty, welfare and association dues and taxes. Capital cost was $120,000 for a plant producing 133 tpd of concentrate. Before considering the treatment of coal by flotation it is appropriate to survey some of the properties of coal which are of importance in the process.

Jan 1, 1962

By B. C. Riblet

THE president of a large smelting and refining company once telegraphed me that they had acquired extensive mining interests in northern Peru and requested me to inspect their properties as it would be necessary to install a system of aerial tramways between their mines and treatment plant. The concentrator was about 50 mi. from the coast, reached by a fairly good motor road. From the concentrator an aerial tramway would he required, about 6 mi. long, to their first property, a gold and silver mine. The lower terminal of the tramway was at an elevation of 4000 ft. and the mine at an elevation of 9500 ft.

Jan 1, 1937

By M. Adnan Goksel

The paper describes the most common cold bond processes including the Carbonate-Bond, Grangcold, Cobo, MTU and others, and outlines these along with bonding mechanisms, physical and chemical characteristics of the products, and applications to various minerals and waste materia1s.

Jan 1, 1977

By G. P. Hulst

The Parkes process lead refinery of the International Lead Refining Co., at East Chicago, was built by the International Smelting & Refining CO. to treat the lead bullion produced by its Tooele plant, at Tooele, Utah. The plant was designed and constructed under the direction of the writer. Ground was broken Apr. 16, 1912, and exactly six months later the plant was in operation and lead was being cast. The capacity of the plant, running 25 days per month, is 5,000 tons. The four products of the plant are common lead, corroding lead, antimonial lead, and Dore bullion. The site is an area, 64 acres in extent, lying north of 151st Street, between McCook Avenue and the Canal. The Indiana Harbor Belt Railroad, Baltimore & Ohio Chicago Terminal, and Pennsylvania Railroad enter the yard at the plant. There are five storage tracks and space for storing 100 cars in the yard. the main lead to the storage tracks passes over a 100-ton track scale on entering the yard.

Jan 1, 1915

By R. L. Dalton, L. A. Rapoport, C. W. Carpenter

Procedures have been developed to study the performance characteristics of unconfined pilot water floods using scaled laboratory models. The effects of operating conditions on pilot performance for variozrs well patterns have been investigated. The limitations of the laboratory model studies are outlined. Relationships between the oil recoveries of pilots and large-scale floods have been established. The applications of model studies to the prediction of large-scale waterflood performance and pilot flood design are discussed. INTRODUCTION Pilot water floods are undertaken to evaluate operational procedures and to gain advance information about the performance of an extensive water flood. In general, however, the performance of a pilot flood is not directly indicative of what can be expected from a large-scale pattern water flood. This difference stems from the fact that the over-all flow configurations are not the same for the two systems. A water flood normally consists of an array of identical well patterns. In such an array, the perimeters of the well patterns are axes of symmetry and act as impermeable boundaries. Thus, an extensive, pattern water flood can be visualized as a repetition of "confined" floods. In contrast, a pilot water flood involving only one or a few well patterns is "unconfined". Here the well patterns are not balanced by other flood units; hence, the perimeter of the pilot area does not act as an effective boundary. Accordingly, only a portion of the fluids injected (and also of those originally contained within the pilot area) is captured by the producers of the pilot. The rest escapes into the surrounding reservoir. This usually causes the amounts of oil and water produced in the pilot to be different from those recovered by a producer in an extensive water flood. Moreover, the recovery observed in the pilot can be expected to be greatly influenced by operating conditions, i.e., by the bottom-hole pressures at the injection and producing wells. The above considerations show that full utilization of pilot test results and reliable prediction of large- scale water floods require a knowledge of the relationship between the recovery performance of confined and unconfined well patterns. To date, only limited basic information is available on the behavior of pilot water floods. Craig, et al,' have investigated the effects of initial gas saturation, oil-to-water mobility ratio, and well damage on the oil recovered from a single, "normal" five-spot pilot pattern (Fig. 1). Rosenbaum and Matthews2 studied the effect of initial gas saturation and mobility ratio on the ratio of production rate to injection rate for various groupings of five-spot patterns. Paulse113 investigated the effect of mobility ratio and distance from the pilot to the edge of the reservoir on the areal sweep in a single "inverted" five-spot (Fig. 1). However, none of these studies considered the effect of operating conditions on pilot flood behavior. Moreover, hardly any of the work to date dealt explicitly with the oil-recovery performance of the pilot floods. The purpose of this paper is to introduce the concept of interrelation between pilot flood behavior and operating conditions, to illustrate this interrelation by means of experimental data and to compare the recovery performances of dif-

By J. W. Matousek, C. S. Samis

me thermodynamic properties of the components in the Cu-Ni-S ternary system have been studied by measuring the H2S/H2 ratios in a gas phase equilibrated with the molten matte at 1200°C. The measured sulficr potentials have been extended by extrapolation and combtned with previously published data to permit the thermodynamic analysis of the ternary system by integration techniques. A simplifying assumption of ideality in the Ni3Sz-CuS pseudobinary has been made. SINCE copper and nickel metals were first extracted from their sulfide ores the interaction between the two metals and sulfur has been of industrial and theoretical interest. The processes developed to extract copper and nickel have been reported periodically in the literature. The theoretical studies on the Cu-Ni-S ternary have been restricted to problems directly associated with production. It is only within recent years that the binary systems related to this ternary have been analyzed thermodynamically and mathematical devices developed to permit a corresponding treatment of the ternary system. In 1910 an investigation of the role of nickel in Cu-Ni-Fe-S mattes was reported,' It was concluded from this work that nickel is not an element replacing iron in mattes, but rather that Cu-Ni alloys behave as a single metal during the matte converting operation. The laws which govern the converting of Cu-Ni alloys were found to be the same laws as those that govern the conventional converting of copper alone. Although considerable information has been reported on the theoretical aspects of copper smelting, little data is available on the smelting of Cu-Ni ores except for phase diagrams and process descriptions. The available information on the Cu-Fe-S ternary and related systems prior to 1953 has been summarized by Ruddle.2 Since Ruddle's publication, Rosenqvist and coworkers have completed phase equilibria investigations of the Fe-S, Co-S, and Ni-S binaries,3 the Fe-S-O ternary,4 and the Cu-Fe-S-O quaternary.4 An extensive investigation of the Cu-Fe-S ternary system at smelting temperatures has been made by Krivsky and Schuhmann.5 At these temperatures, the Cu-Fe-S system is very similar to the Cu-Ni-S ternary with respect to the location of the single-phase and two-phase liquid matte regions. In the former, however, the area of immiscibility is more extensive and the region of liquid matte-liquid metal-solid metal equilibria is much more extensive. Krivsky and Schumann observed that the Cu2S-FeS pseudobinary system is, for practical purposes, an ideal mixture. This investigation has served as a valuable guide in analyzing the Cu-Ni-S ternary. EXPERIMENTAL The experimental procedure employed in this investigation was the conventional technique of equilibration of the sulfide matte with gaseous mixtures of hydrogen and hydrogen sulfide at 1200°C. The thermodynamic properties of sulfur (S2) in the gas phase are determined by means of Eq. [I] and the activity of sulfur in the matte by Eq. [2].

Jan 1, 1963

By R. D. Taylor, Jim Douglas Jr., H. H. Rachford Jr., P. M. Dyke

A major obstacle to the use of wetting agents in .secondary recovery by water flooding is the adsorption of the agents on the sand. As a result of adsorption, the surfactant always lags behind the floodwater front. Consideration of the chromatographic theory of adsorption indicates that the detergents will not lag as much if used in very high concentrations. An investigation was made of the possibility of using high concentrations economically by flowing slugs of wetting agents followed by normal flood water. The experiments consisted of adsorption studies on Alundum powder and Berea sandstone. Flow rests on a 12-in. Alundum core and 22-in. Berea core were used to determine rate of detergent movement. The results of the flow experiments indicate that the relative rate of surfactant advance is, indeed, sensitive to the concentration of the agent. A 10 per cent slug moved with a rate that war 78 to 95 per cent as fast as the rate of advance of the flood water. By contrast, one with 25 ppm (the number of parts of commercial detergent in a million parts of water on a weight basis) concentration moved less than one-fourth as fast as the flood water, and calculations indicate that in very long porous systems the rate of movement of the lower concentrations will be a small fraction of the rate of advance of the flood front. The results. of the adsorption studies were utilized to calculate the rate of advance of the detergent when only the initial concentration was known. The calculated rates showed substantial agreement with the experimental flow tests in the high concentration ranges. The adsorption results were also used to estimate the cost of the materials for a slug-type surfactant flood in the field. In addition to the faster rates of movement, the concentrated detergent slugs removed much more oil than the dilute solutions. However, the effectiveness of the slug process depends on many variables. The quantity of oil removed is increased markedly by increasing the flooding rate. The efficiency is also influenced by the type of crude, type of reservoir rock and initial water saturation. Therefore, a careful analysis of each reservoir system is required before the economic value of the process can be determined. INTRODUCTION It is well known that the displacement of oil by invading water during water flooding is far from complete. It is generally agreed that the unrecovered oil is retained in the porous medium by the capillary forces which may be relatively large compared to the forces generated by the flowing water. Therefore, it was logical that some early workers should turn to surface-active materials to reduce the capillary forces to facilitate the release of oil. As early as 1927,' a patent was granted for the use of surface-active materials in water flooding. In 1932, when soap solutions were passed through Bradford and Venango sands, it was reported that the results were inconclusive, erratic and that "further investigation is needed to determine exactly the function of the solution and to obtain a clearer insight into the phenomena involved."' Some of the modern scientific reports conclude with a similar statement,' showing that the lack of agreement on the mechanism of oil removal by wetting agents is still very widespread even though several comprehensive studies have been reported.'." Although there is a lack of agreement as to the general effectiveness of the detergents for water flooding, most investigators do agree that all of the common detergents are strongly adsorbed onto the solid surfaces of the reservoir. In the early calculations it appeared that all additives would be lost before reaching much of the formation area which contained the additional oil to be removed. Experiments indicated that if the usual small waterflood concentrations of wetting agents were used, the rate of advance of detergent through the formation would be only a small fraction of the rate of advance of the flood front. Indeed, some investigators4 felt that the use of wetting agents would never be economically feasible because of their adsorption. For example, DunningG estimated that the wetting agent in concentrations of 25 ppm, would advance only 0.05 times as fast as the flood front. Ojeda, et al,' found that a surfactant in a concentration of 10 ppm moved less than 0.01 times as fast as the flood front. It is significant, however, that both investigators found that increased concentrations of wetting agents moved faster, relative to the flood front, than solutions at the lower concentrations. Ojeda showed that an extrapolation of his data indicated a relative rate of 0.5 at 1 per cent concentration, while Dunning6 estimated a relative rate of 0.46 for a 1 per cent concentration. It was obvious that these concentrations could not be used for continuous injection because the cost of the injected detergent would far exceed the value of additional oil produced. Traditionally, detergents are used in very low concentrations for they show good

By E. L. Dougherty

A phenomenological theory for a one-dimensional unstable miscible displacement similar in type to the Buckley-Leverett model but including the effects of mixing is proposed An equation giving the fractional flow of pure solvent through an oil phase containing dissolved solvent is derived including the effects of gravity and nonbomogeneities. Numer ical integration of the resulting pair of nonlinear hyperbolic partial differential equations gives volumes of dissolved and undissolved solvent as functions of space and time. Parameters in the model which characterize mixing due to dispersion were determined from experimental data; the parmeters correlated with viscosity ratio. The results indicate that the rate of dispersive mixing is proportional to volumetric flow rate Incorporated into our equations were Koval's heterogeneity factor H. which characterizes mixing due to channeling. This allowed satisfactory predictions of displacement behavior observed in horizontal floods in nonhomo-geneous cores; but in most cases the values of H which we used were considerably larger than those used by Koval. INTRODUCTION It has been shownl,2,3 that for favorable viscosity ratios, the diffusion equation with convection satisfactorily describes the behavior of a miscible displacement in a porous media. Numerous attempts to develop a satisfactory mathematical description for the case of unfavorable viscosity ratio have been reported, but they have met with only partial success. These attempts, which are reviewed by oval! have taken two approaches: (1) development of a flow model akin to the Buckley-Leverett approach for immiscible displacement neglecting the effects of mixing5,6 and (2) simultaneous application of Darcy's Law for flow and the diffusion equation with a convection term for mass transfer.7,8,9 We set out to construct a mathematical model of Type 1 including, though, the effects of mixing. Based upon a set of hypotheses, we derived a pair of nonlinear hyperbolic partial differential equations which describe in a one-dimensional system the combined effects of flow and mixing. To work with these equations it was necessary to develop a fractional flow formula. The combined system was integrated numerically using the method of characteristics. In our equations the mixing process is characterized by four parameters. Three of these, labeled ß, P1 and P2, account for dispersive type mixing. The fourth is the heterogeneity factor H, proposed by Koval to account for channeling due to nonhomogeneities in the porous media. Values of the parameters which would cause agreement between theory and experiment were determined by trial-and-error for miscible floods conducted in horizontal cores of both homogeneous and heterogeneous materials. Calculations were also performed for vertical floods in homogeneous cores. The purpose of this paper is (1) to present the details of the mathematical analysis, (2) to present the results of the calculations, (3) to consider what light the results shed on the mixing process in an unstable miscible displacement, and (4) to provide a firmer foundation for the correlation technique developed by Koval for predicting the behavior of unstable miscible floods. STATEMENT OF PROBLEM The problem is to construct a mathematical model which describes in one dimension the observed behavior in an unstable miscible displacement. The approach is phenomenological in that the equations are based on assumptions which violate certain physical precepts known to apply to the displacement phenomenon. However, the assumptions do allow us to account mathematically for the more essential phenomena. The work is of value if we can quantitatively predict experimental results which heretofore could not be predicted, even though the synthetic nature of the model belies complete explanation of the observations. We assume that the system is comprised of two contiguous flowing phases. One phase, which we call free solvent, has the properties of pure solvent. We call the fraction of the pore volume occupied by this phase the solvent saturation, designated s. The oil phase consists of oil containing dissolved

By W. Crafts, J. L. Lamont

Secondary hardening in tempering has long been recognized as a typical characteristic of steels containing large amounts of carbide-forming alloys. These steels, when quenched and tempered, tend to soften somewhat after tempering at low temperatures, and to reharden at intermediate tempering temperatures before finally softening to low hardness. This behavior in tempering has been studied by many investigators, chiefly with respect to thc secondary hardening of high-speed steels. The initial softening has usually been ascribed to decomposition of martensite and growth of iron carbide particles. The secondary hardening has been explained by formation of fresh martensite from residual austenite, formation of very fine alloy carbide particles and by precipitation hardening of metallic compounds in the ferritic matrix. However, factors derived for the calculation of tempered hardness in low-alloy steels1 indicated only a tendency toward retarded softening rather than a discontinuous rehardening. A study was, therefore, made to determine whether fresh martensite from residual austenite and precipitation hardening are essential to rehardening and the degree to which tempered martensite could be rehardened by precipitation of alloy carbides. The mechanism of carbide rehardening was also investigated to determine the nature of the process. The causes of secondary hardening in high-speed steel have received serious consideration for about thirty years. Among the earlier workers Bain and Jeffries2 in 1923 recognized residual austenite as a significant factor, but in addition, emphasized the effect of the formation of alloy carbide particles of "critical" size. They conceived that freshly quenched martensite forms low-alloy iron carbide at low tempering temperatures; with further tempering the iron carbide is then modified by alloying elements that can diffuse most readily at intermediate temperatures (850°F); and that the iron carbides grow in size by coalescence so that the steel tends to lose hardness. At higher tempering temperatures carbide stability rather than alloy availability becomes the controlling influence and in high-speed steel "iron-tungsten carbide is the most stable one and forms to the elimination of the earlier formed carbides. . . . The iron-tungsten carbide particles reach approximately the size for critical dispersion after a short reheat at II00 F." This concept, the formation of alloy carbide nuclei, redissolving of the iron carbide, and diffusion of carbon to the alloy carbide, was restated for vanadium steel in 1932 by Houdremont, Bennek, and Schrader. Subsequent studies have confirmed that iron carbide changes to alloy carbide at 1000 to IIOOOF, but the mechanism of the process has received little consideration.

Jan 1, 1949

By G. R. Leverant, C. P. Sullivan

To evaluate the effect of a dispersion of nondeform-able, incoherent, second-phase particles on high-strain cyclic deformation and fracture, recrystallized TD-nickel (Ni-2ThO2) and a commercially pure nickel, Ni-200, were fatigued under strain control at total strain ranges varying from 0.009 to 0.036. Relative to the Ni-200, the slip at the surface of the TD-nickel was more wavy and discontinuous due to the presence of the thoria particles. This made crevice formation (incipient cracking) within slip bands more difficult in TD-nickel than in Ni-200. Both materials cyclically hardened to a constant (saturation) flow stress which increased with increasing plastic strain amplitude. Cellular substructures were developed in both materials during cycling. The cell size in TD-nickel was controlled by the thoria particle distribution and was independent of plastic strain amplitude over the range investigated. The cell size in Ni-ZOO was larger than that in TD-nickel at similar plastic strain amplitudes and was a function of plastic strain amplitude. These results, together with the cyclic stress-strain curves for both materials, are discussed in terms of a model for fatigue strain accommodation at saturation recently proposed by Feltner and Laird. NUMEROUS fatigue investigations have considered the interrelation of slip character, dislocation substructure, and cracking in pure metals and solid-solution alloys. However, except for the studies of the low-strain fatigue of internally oxidized copper alloys1 and cast, dispersion-strengthened lead,&apos; little is known about the effects which small, incoherent, nondeform-able, second-phase particles have on cyclic deformation and cracking processes. Effects due to the particles alone are often obscured by a dislocation substructure introduced during thermomechanical processing of dispersion-strengthened metals. In the present study, recrystallized TD-nickel and a commercially pure nickel, Ni-200, were employed to evaluate the effect of a thoria dispersion on high-strai fatigue deformation and cracking at room temperature. I) MATERIAL AND EXPERIMENTAL PROCEDURE The TD-nickel was supplied by DuPont as a 5/8-in.-thick stress-relieved plate which had been subjected to a proprietary schedule of thermomechanical treatments, and the Ni-200 as 3/4-in. bar which was subsequently annealed for 2 hr at 850°C in argon resulting in an average grain diameter of 0.05 mm. The compositions of these materials are given in Table I. The microstructure of the TD-nickel consisted of elongated grains parallel to the primary working direction with an average width of 0.16 mm, Fig. l(a). Many fine annealing twins were present indicating that the starting material was in a recrystallized condition; this supposition was confirmed by the absence of of any extensive dislocation substructure, Fig. l(b). Sheetlike stringers parallel to the rolling direction were occasionally seen both within grains and at grain boundaries. Some approximately spherical particles about 2 in diam, which may correspond to exceptionally large thoria particle aggregates, were also present. The average Young&apos;s modulus of the plate material in the rolling direction was 21.8 X 106 psi which is consistent with a {100}<001>recrystalliza-tion texture3&apos;* being prominent. In transmission microscopy, the 2.3 vol pct of thoria particles generally appeared to be uniformly distributed although some clusters, 0.1 to 0.3 in diam, of larger particles were observed as previously reported for TD-nickel sheet,5 and stringering of particles was present in some areas as welt. The average diameter of the thoria particles was 450A with a calculated mean planar center-to-center spacing of 2100A, as determined by quantitative metallographic analysis.= The 0.2 pct offset yield stress was 36,000 psi which agrees with the value predicted by the modified Orowan relation7 for edge dislocations bowing between thoria particles of the size and spacing observed in the present investigation. Fig. 2 illustrates the specimen design employed for the axial high-strain fatigue testing. Adapters were screwed onto the threaded portions of each specimen so that testing could be performed in the same manner as that reported for buttonhead specimens.8 Stressing was coincident with the working direction for both materials. The gage section of each specimen was electropolished and lightly etched prior to testing. The total strain was controlled, being varied between zero and a maximum tensile strain ranging from 0.009 to 0.036. In addition to these tests, a circum-ferentially notched TD-nickel specimen was cycled over a total strain range of 0.0075. The same strain

Jan 1, 1969

By A. Kenneth Schellinger, O. Cutler Shepard

Overgrinding, Or the breaking of ore particles into sizes smaller than required for liberation, is a first-magnitude problem in grinding for concentration processes. The conventional ball mill-classifier circuit used in commercial grinding produces mineral particles that are all ground to pass an upper size limit, while the proportion of very fine sizes, or slimes, is uncon rolled. Calculations based on measurements made in commercial plants which were grinding ore for flotation concentration indicate that about go pct of the energy used in grinding is consumed in useless overgrinding.1 In addition to accounting for the consumption of a large amount of energy, over-grinding is detrimental to the flotation process. Overground slime coats larger partitles and inhibits selective action by the flotation reagents on particles which by themselves could be separated very well. A further difficulty is that extremely finely ground minerals do not respond satisfactorily to flotation-collecting reagents, and both selection and recovery decrease markedly with particles finer than 5 to 10 microns.2 conventional classifier-ball mill circuits inherently tend to overgrind the valuable minerals more than the gangue minerals because most valuable minerals are of higher density and are softer and more friable than the gangue minerals. The rem- edy to this situation would seem to be a separating mechanism which would separate free valuable mineral particles regardless of size and density considerations and a mechanism which would operate in the grinding mill so that valuable mineral grains would be removed from the grinding machine as soon as they are freed. A consideration of these ideas led the authors to the conception of a simultaneous grinding and flotation mechanism. So far as the authors are aware, such a machine has never been tried, even on a laboratory scale. Development oF Apparatus and Experimental Method Apparatus development went through several stages before a really workable machine was devised. Work was started with a large cast-iron mortar 7½ in. in diameter and 8 in- deep. A cast-iron disk Was mounted on the end of a vertical shaft SO that it fitted loosely into the bottom of the mortar. On top of the disk four radial cleats ¼ in. high were bolted to agitate the ball charge as the disk, or impeller, rotated. The vertical shaft was driven at 100 rpm by a mechanism improvised from an old coffee-mill type of grinder. A hole was drilled into the bottom of the mortar through which compressed air was introduced for frothing. In operation, more charges of Ore which had been crushed to pass an 8-mesh screen were placed in the bowl along with water and suitable reagents. The impeller was then started and the compressed air turned On so that the ore was ground while being exposed to air bubbles. Mineralized froth was

Jan 1, 1949

By J. S. McNeil, J. U. Messenger

In the drilling of oil wells the control and prevention of lost circulation of the drilling- fluid is a oroblem which is frequently encountered; in many cases existing materials and methods for alleviating this condition have not been adequate. For severe cases of lost circulation in which the simpler methods, such as application of various bridging materials to the mud system, have proven unsatisfactory. a new material and method for applying to the loss zones have been developed which appear to he superior to existing techniques in many respects. The material, called a clay cement, is capable of being handled as a drilling fluid after initial mixing of the solitl ingredients with water and may be pumped down the drill pipe and squeezed into loss zones. After a short period, the material develops a very high gel strength which seals off the zone against further losses of the drilling fluid. In field tests, the process has been demonstrated to be a very effective method for combatting lost circulation. INTRODUCTION Methods of treating lost circulation in rotary-drilled wells by the addition of special materials to drilling fluids have long been in the process of development and are continuing to improve.&apos; However, the annual drilling costs which can be traced directly to lost circulation difficulties still run into the millions of dollars. The loss of mud materials into highly permeable zones may range up to $50,000 per well in some areas. In addition to mud costs, excessive requirements of casing, cement; rig time, and the attendant blowout hazards further emphasize the importance of the need for improved methods of combatting lost circulation. The shortcomings of presently-used materials and methods have led to the development of a new lost returns material in the form of a time-setting clay cement. In field tests this material has proven very successful in plugging off loss zones. which other more conventional materials had failed to do. REVIEW OF PRESENT CORRECTIVE MEASURES The proper control of such operating factors as pump pressure, clearance between pipe and hole, and speed of running pipe in a holez is of primary importance in preventing and minimizing lost circulation problems. These factors, however, concern matters of drilling technique and do not directly involve lost circulation materials. Aside from setting casing past loss zones, three principal methods are generally employed for the purpose of avoiding or combatting lost circulation: (1) adjustment in properties (principally density) of the drilling fluid, (2) addition of fibrous, flaky, granular or other types of bridging materials to the mud system, and (3) the application of cements to the loss zones. The latter method is usually employed only after the first two have proven unsuccessful. In Table I are listed some advantages and disadvantages of the common corrective measures. Frequently, a combination of bridging material and cementing material is used." This combination is based on the premise that a bridge will

Jan 1, 1952

By R. P. Smith

The carbon content of a number of alloys ranging (before carburitation) from purified iron to purified cobalt was determined for fixed activities of carbon by equilibration with each of six CO-CO2 atmosphere at 1000°C. At fixed carbon activity, the carbon content decreases continuously with increasing cobalt content. For concentrations of 0 to 50 at. pct Co the results can be expressed by a linear interaction equation of the type In y2 = 7.76n2/(n1+n3)+ 2.30 n3/(n1+n3) where y2 is the activity coefficient of carbon (standard state such that y2— 1 as n2 — 0 in the Fe-C binary) and n1, n2, and n3 are the number of atoms of iron, carbon, and cobalt per unit weight of alloy. The results are also given in terms of the a functions. In the same concentration range, the results are in accord with the regular solution theory of Alcock and Richardson. THE carbon content of Fe-Si, Fe-Mn, and Fe-Ni alloys at fixed activities of carbon has been reported previously.&apos;-, The present work extends R. P. SMITH, Member AIME, is Research Chemist, E. C. Bain Laboratory for Fundamental Research, United States Steel Corp., Research Center, Monroeville, Pa. these measurements to a series of Fe-Co alloys. These alloys, like the Fe-Ni alloys, are fcc ("aus-tenitic") over the entire range of composition at 1000°C. EXPERIMENTAL PROCEDURE The alloys were made from electrolytic cobalt and Plast-Iron in a small vacuum-melting furnace. A small amount of graphite was added to each melt to keep the oxygen content low. The ingots were analyzed for iron and carbon: the amount of cobalt was obtained by difference. Analysis of the top and bottom of the ingots indicated that they were uniform in alloy content. Except for the pure cobalt the ingots were hot-rolled to approximately 0.15 cm thickness, cleaned by sandblasting, then cold-rolled to about 0.045 cm. We were not successful in cold rolling the pure cobalt; therefore it was hot-rolled to the final thickness. The last traces of surface oxide were removed by acid pickel, then the samples were treated in a hydrogen-2 pct water vapor mixture at 1100°C to remove carbon and most of the oxygen. The carburizing procedure was similar to that previously described.1,2,4 The alloys in the form of strips about 1.7 cm wide, 7.5 cm long, and 0.04 cm thick, together with a similar specimen of purified iron, were equilibrated with each of six CO-CO2 mixtures of fixed composition, then quenched in the

Jan 1, 1965

By S. T. Wlodek

The surface and subscale oxidation reactions were followed by means of continuous weight-gain and metallographic techniques over the range 1600" to 2200°F (871° to 1204 °C) for up to 400 hr. Full identification of all scale and subscale reaction products was obtained by electron and X-ray diffraction. At or below 1800°F (982°C) a linear rate of reaction (QL = 46.0 kcal per mole) governed the oxidation process, extending for up to 100 hr at 1600°F (871 "C). During linear oxidation the surface scale consisted of an amorphous SiO2 film overgrown with Cr 2O 3 and NiCr204. This initial linear process was followed, and above 1800°F completely replaced, by two successive parabolic rate laws (Qp = 60 and 57 kcal per mole). This parabolic reaction involved the formation of a complex scale consisting of Cr2 O3 and smaller amounts of NiCr2O4. Parabolic oxidation appeared to coincide with the disruplion of the silica film present during linear oxidation and was followed by subscale (internal) oxidation of crystobalite and NiCr2O4. The balance between the subscale and surface oxidation reactions controls the oxidation of this commercial alloy. The amorphous silica film appears to result in the linear rate and diffusion through Cr2O3 is the more likely rate-limiting step during parabolic oxidation. THE oxidation of a multicomponent composition is a complex phenomenon not presently amenable to a rigorous classical interpretation. Nevertheless, even a qualitative understanding of the scaling and subscale reactions that occur in a commercial composition can illuminate the reactions that limit its high-temperature stability in an oxidizing environment. This study of the oxidation of Hastelloy Alloy X presents the first of a series of studies with the above approach in mind. Hastelloy X exhibits one of the best combinations of strength and oxidation resistance available in a wrought, solution-strengthened, nickel-base alloy. Although during long time exposure some precipitation of M6C and M23C8 carbides as well as a complex Laves phase occurs, the amounts are probably small enough to have no appreciable effect on the chemistry of the matrix. Radavich has identified the oxidation products on Hastelloy X oxidized for 5 min to 10 hr at 1115°F as NiO and the NiCr2O4 spinel. Oxidation for 5 to 15 min at 1500°F produced a scale of spinel, NiO, and a rhombohedra1 phase, probably Cr2Os. Sannier et 2. have reported continuous weight-gain data for Hastelloy X at 1650" and 2010°F and internal-oxidation measurements after 150 hr at 2010°F. In addition, much of the data on binary Ni-Cr alloys recently reviewed by Kubaschewski and okins&apos; and Ignatov and Shamgunova4 as well as studies of binary Ni-Mo alloys5 are also pertinent to the oxidation of this composition. EXPERIMENTAL Continuous weight-gain measurements and metallographic measurements of subscale reactions were the main experimental techniques used in this study. X-ray and electron diffraction backed up by a limited amount of electron-microprobe analysis served to characterize the nature of the scale- and subscale-reaction products. Two heats of commercial sheet of the composition given in Table I and identified as A and B were used in the bulk of this study. Internal-oxidation measurements were made on a third heat of material in the form of a 0.5-in.-diam bar. In order to assure homogeneity, all heats were reannealed 4 hr at 2175°F prior to sample preparation. weight-Gain Measurement. All specimens (1.5 by 0.4 by 0.03 in.) were abraded through 600 paper, electropolished, and lightly etched in an alcohol-10 pct HCl solution. An electrolyte of 150 cu cm H,O, 500 cu cm HsPO4 (85 pct conc), and 3 g CrO3 at a current density of 0.9 amp per sq cm or a solution of 10 pct HaW4 in alcohol used at 4 v and 0.3 amp per sq cm was used for electropolishing. The resultant surface exhibited a finish of 3 ± 1 p rms. Continuous weight-gain tests were made at 1600°, 1700°, 1800°, 1900°, 2000", and 2200°F on auer&apos; type balances capable of recording a total weight change of 110 mg with an accuracy of k0.1 mg. All tests were made in air dried to a dew point of -70°F and metered into the 2-in.-diam reaction

Jan 1, 1964

By W. M. Albrecht, M. W. Mallett

The solubilities of hydrogen in titanium and several of its alloys were determined at 600 to 1000°C and pressures of 0.05 to 10µ of mercury. Solubility increases with increasing beta phase in the alloys. Factors found to affect degassing rates are specimen size and presence of thick surficial oxide. Removal of hydrogen by heating in vacuum and in flowing inert atmospheres was studied. Practical curves predicting minimum degassing times are presented. THE presence of hydrogen in titanium and titanium alloys has detrimental effects on the mechanical properties of the metal.&apos;"," The hydrogen content of commercial titanium is sometimes of the order of 200 ppm by weight&apos; and varies with alloy composition. As a consequence, titanium and some titanium alloys as normally processed are sometimes not ductile unless treated to lower the hydrogen content. The best known hydrogen-removal treatment is heating the material in a vacuum. The rate of removal (degassing) at a give temperature determines the duration of the treatment required to attain a satisfactory low hydrogen level.

Jan 1, 1959

By R. E. Cech

Metallographic observations on hydrogen-reduced nickel oxide crystals suggest that nucleation of nickel occurs at structural singularities in the oxide. The fully reduced structure contains micron-diameter, worm-like voids occupying 40 to 50 pct of the volume. The crystallographic orientation relationships between nickel oxide and nickel resulting from oxide reduction are recorded and discussed. THE process of reduction of oxide to metal is one of considerable complexity involving a chemical reduction reaction, mass transport of reducing agent to the point of reaction and of reaction product away from it, and finally a transformation whereby metal atoms released from the oxide rearrange to form a stable reduced phase. In addition, nucleation of the reduced phase affects the overall reaction kinetics. Thus far only the thermodynamic aspect of reduction has received the attention warranted by the importance of

Jan 1, 1960

By C. E. Cottrell, G. W. Preckshot, N. D. Delisle, D. L. Katz

Most crude oils contain asphaltic substances that may be naturally or artificially precipitated. In the Greeley field, California, this asphaltic bitumen is precipitated during the flow of the oil from the reservoir to the stock tank The mechanism of such precipitation is not well understood. This paper presents the progress that has been made by using the electron microscope as a new tool and by observing the effects of the streaming potential on the formation of bitumen particles. Crude oils at atmospheric pressure viewed in the electron microscope in very thin films under a vacuum showed no asphaltic particles. A technique of preparing slides of thin films by dilution of the oil with benzene and washing in petroleum ether was used at first, and these observations showed that the solvents caused the formation of the particles, varying from 0.01 to 0.2 micron in diameter. The electrical effects of fluids flowing through porous solid were studied, with emphasis on the formation of colloidal particles by the streaming potential. The streaming potential of crude oil flowing through sand was measured and was shown to be responsible for the formation of bitumen particles. These results bring out a new phenomenon, which may occur when crude oil flows through the porous oil reservoir. mechanisms. Asphalt has been the subject of widespread investigation but, owing to the complexity of the substances being considered, progress has been slow. Investigators working primarily with the asphaltic substances have treated the subject from the colloidal standpoint and have developed theories that picture the asphaltic particles as surrounded by adsorbed materia1s.14,15,17,24 The deasphaltization of lubricating oil by the use of solvents treats the subject primarily from the standpoint of liquid-liquid equilibria.&apos;&apos; A complete understanding of asphaltic substances would make possible the following of the material from its initial state in the crude oil through precipitation processes to the final plastic stage, the most common form of which is used in asphaltic pavements. Since these asphaltic particles are very small, it appears &apos;hat the electron microscope4 might be a useful tool in studying the precipitation processes. Specimens are examined by the electron microscope in a vacuum and as very thin films, requiring special techniques in preparation of samples. A brief description of the electron microscope and its operation will bring out the difficulties and advantages of its use for this problem. The first work was done with crude oils that had been diluted with solvents for the preparation of the film to be examined. Later a technique was developed by which the undiluted oil film could be made thin enough for direct examination. These two techniques show vastly different results Asphaltic particles have been precipitated from crude oils by a variety of

Jan 1, 1943