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By J. Gurland

The effects of variations of carbon content on the constitution and properties of sintered WC-Co alloys were studied. The grain growth of tungsten carbide during sintering was measured and it was shown that it takes place mainly by solution and reprecipitation of the carbide in and from the binder at the sintering temperature. It was found that the decomposition of W3C03C by carburization during sintering is responsible for the formation of very large grains. THE properties of sintered WC-Co alloys are critically dependent upon their final composition and structure. Slight changes of cobalt and carbon contents and small variations of grain size result in marked changes of mechanical properties and performance of products. Previous investigators have studied the microstructure as a function of composition' and have dealt with the influence of cobalt upon properties.' The present work is concerned with the effect of carbon content upon constitution, microstructure, and grain growth during sintering, as well as upon the physical properties of sintered compacts. Phase Boundaries at the Sintering Temperature The WC-Co section through the ternary diagram W-Co-C has been studied by Wyman and Kelley,' Takeda,V andford and Trent," and Rautala and Norton." Two phases, namely WC and a cobalt-rich solid solution (P), appear in the sintered structure if the carbon composition corresponds very nearly to the theoretical carbon content of WC (6.12 pct C). But small deviations from the ideal carbon content will bring about the occurrence of either graphite or the double carbide W,Co3C (7) . The 7 phase was long believed to be metastable, this conclusion being based mainly on the work of Takeda. More recent studies have shown that it is a stable phase of the ternary system,"5 but the actual phase boundaries have not been established and there has been some discussion as to whether or not the 7 phase occurs at some stage of sintering in the fully carburized alloys." In view of this uncertainty it was thought advisable to undertake an investigation of the phases present during the sintering of WC-Co alloys. Commercially available tungsten, cobalt, and carbon powders were used in the present study. A typical analysis of impurities in a sintered compact is reported in Table I. The desired carbon compositions were attained by varying the amount of carbon added to the tungsten during carburization and controlling the composition during sintering by packing the compacts into beds of mixed alundum-carbon powders of suitably selected ratios. The alloys were sintered in a hydrogen tube furnace at 1400°C, then brought to equilibrium at the temperature under investigation and quenched in water. The high temperature phases were identified by metallographic and X-ray diffraction techniques. The samples were etched with a 10 pct solution of alkaline potassium ferricyanide. The phase boundaries, established by metallo-graphic examination, are shown in Fig. 1, which is a vertical section through the ternary diagram at 16 pct Co. The temperatures of the invariant planes, at 1298" and 1357°C were established by Rautala and Norton. The vertical section shows that the three-phase field, WC + 7 + L, extends into the two-phase field, WC + L, but does not include the stoichiometric composition of WC. In practice this means that the 7

Jan 1, 1955

By T. D. Yensen

IN the investigation of the magnetic properties of iron-nickel alloys,1 it was found necessary in order to make the alloys forgeable, or malleable, to add small quantities of some other element. Iron-nickel alloys have been known for nearly a century, but have been made in commercial quantities only since 1885. Their remarkable mechanical properties were disclosed by Riley in 1889 and from that time on a large amount of research work has been done both to discover new properties and to correlate the results obtained.2 Lately the Bureau of Standards has collected the published data in a special circular3 giving in compact form an account of the properties of the iron-nickel alloys. It also contains a clear historical sketch of the development as well as a selected bibliography. The chief difficulty with the development of iron-nickel alloys was that the "pure" alloys do not forge readily. The addition of small amounts of manganese, however, made the alloys forgeable, and manganese has therefore come to be regarded as a necessary constituent of nickel steels. The present paper shows to what extent manganese is needed for various nickel contents and also what is the effect of other alloying elements on the forgeability. It also touches upon the cause of forgeability but refers to other sources for more exhaustive treatises, on the subject. The alloys were prepared by melting electrolytic iron and electrolytic nickel with of without other alloying elements in the desired proportions in a magnesia crucible in a vacuum furnace under a. pressure of 1 mm. mercury. The ingots weighing about 2 kg. were allowed to cool in vacuo. If pipes or blowholes were present, the ingots were cut in such

Jan 1, 1920

By T. H. Oxnam

The predominating value of the ores now being treated by the Palmarejo and Mexican Gold Fields, Ltd., is silver, although some gold also is carried. The present method of treatment consists of wet-crushing and concentrating, followed by the cyanidation of the un-roasted sands and slimes. The sands are treated by leaching, and the so-called " accumulated slimes " by a system of agitation and decantation. It is only within very recent years that the cyanidation of unroasted silver-ores has been commercially successful. In fact, at the time operations were begun at the cyanide-plant at Chinipas, February, 1902, I knew of no other leaching-plant treating similar ores successfully. The cyanide treatment of the Palmarejo ores differs but little from the ordinary practice in cyaniding gold-ores; and perhaps but little, if any, new information concerning the metallurgy of silver is to be gleaned from it. Palmarejo Mines. The Palmarejo mines are located in the southwestern part of the State of Chihuahua, Mexico, on the foothills of the Sierra Madre mountains, at an elevation of 3,200 feet. The mills, 12 miles distant, are situated on the Chinipas river, near the town of Chinipas, which is about 150 miles northeast of Agiabampo, on the Gulf of California. Supplies are shipped via this port as this route is the best and most direct to the property. The ore-bodies in the Palmarejo mines have been deposited along a series of rock-fractures, caused by an intrusion of eruptive rock. The most important of these fractures or fissures, both in width and value, are the Prieta and Blanca veins, which

Jan 1, 1906

By I. W. Alcorn

THE cost of drilling in the past few years of proration and ever decreasing allowables has received increasing thought and study. It seems to parallel the strides made with respect to pumping problems in 1932 and 1933. Low profit margins stimulate the search for economies. Any discussion of slim-hole drilling involves a multitude of abstract values, and the problem can be attacked only by a study of records and rational thinking. In a measure, traditional methods must be studied with a questioning attitude. The words "slim hole" may be somewhat misleading, as the term is entirely relative. For that reason I wish to define it as used in this discussion. On the Gulf Coast, I would define a normal hole as one in which 10 3/4-in. surface casing has been set and below which a 9 7/8-in. hole is dug. With this as a datum, holes of larger diameter below surface would be called "large holes," with 12 1/4 in. as the "extra large" class and holes of smaller diameter classed in the slim-hole range, 6 1/4 in. representing about the minimum size. The optimum size has not been definitely determined, but the preference is for a program that would call for setting 8 5/8-in. surface casing and digging a 7 3/4-in. hole. Different sections of the country might very properly deviate from this practice because of differences in depth, formations, regulations, or other factors. This paper will be confined to a discussion of the drilling of exploratory wells, as the drilling of this class of wells is quite a different problem from that of drilling a proven field, although many of the same considerations apply in both cases, as will be apparent. Although for many years shallow slim-hole and core-test holes of small diameter had been dug, it was not, I believe, until the fall of 1937 that serious consideration was given to its application in drilling wells 7000 ft., 8000 ft. and 9000 ft. deep on the Gulf Coast. This does not mean that nearly all such wells drilled on the Gulf Coast now are of the slim-hole variety, but only that efforts have been aimed in that direction with very encouraging results and there has been a very definite trend to reduce the size of holes, a trend that probably will continue. As to exploration policy, there appear to be two distinct and opposite views. The one usually followed in the past was more or less designed to "shoot the works" on one well. Generally on the Gulf Coast, the depth at which production might be obtained is limited by the drilling equipment and economics. With this thought in mind, wildcat wells are often planned with the idea of carrying the depth to 10,000 ft., or even 15,000 ft. All of the possible hazards are anticipated and the general drilling and casing programs are so predicated. Such wells contemplate the drilling of large-diameter holes; the setting of at least one protective string of casing and an extensive coring policy, all of which finally adds up to an expensive well. As opposed to this general policy is the slim hole. This, on the Gulf Coast, recognizes that new discoveries represent gam-

Jan 1, 1941

By R. D. Mollison, C. F. Fogarty

Sulfur is widely distributed in nature. It is present in the earth's crust, the ocean, the meteorites that come to us from cosmic space and in practically all animal and plant life. According to Clarke,9 the earth's crust contains 0.06 pct sulfur. Large quantities of free or combined sulfur are found in coal, natural gas and petroleum. Mineral waters contain sulfates and hydrogen sulfide. Sulfur is rather plentiful in the crust of the earth; however, only under special circumstances can it be produced profitably. Sulfur is one of the cheapest raw materials used by industry; and, therefore, the economic feasibility of a given deposit is strongly dictated by the law of supply and demand on local as well as world-wide levels. The forms which are commercially important are elemental sulfur or brimstone, and the sulfides such as pyrite (FeS2), pyrrhotite (FenSn+1), chalcocite (Cu2S), sphalerite (ZnS), and galena (PbS); the sulfates such as gypsum (CaSO4,2H2O), anhydrite (CaSO4), and kieserite (MgSO4,H2O). Elemental Sulfur Elemental sulfur is found in many localities, generally in solfataras and gypsum type deposits. The solfatara deposits are found commonly in the neighborhood of active or extinct volcanoes as in Italy, Japan and Chile, or fumaroles associated with mineral springs such as the Mammoth Hot Springs in Yellowstone Park. Here the sulfur is deposited in tufas or other porous host rocks. This type of sulfur deposit probably results from the oxidation of hydrogen sulfide or the reaction of hydrogen sulfide with sulfur dioxide. Most of the world's supply of elemental sulfur comes from the gypsum-type deposits. Here the mineral occurs as either crystalline or amorphous sulfur in sedimentary rocks in close association with gypsum and limestone. This association is characteristic and occurs in almost all the great gypsum beds of the world, although sulfur is not always present in quantities of economic importance. Various theories have been advanced to account for this association. Bischof5 suggested that the sulfur came from hydrogen sulfide which resulted from the reduction of calcium sulfate by carbon or methane in accordance with the following reactions: CaSO4 + 2C= CaS + 2CO2 CaS + C02+ H2O = CaCO3 + H2S CaSO4 + CH4= CaS + C02+ 2H20 2H2S + 02= 2H20 + 2S All of the sulfur-bearing domes on the Gulf Coast have calcium sulfate in great quantity in the cap. They all show the presence of hydrocarbons. The oxygen for the final reaction could have been supplied by circulating ground waters. The principal objection to this theory is that temperatures of 700° to 1000°C are needed to reduce the sulfate to sulfide with carbon compounds. The geologic evidence is that the temperature of the sulfur-bearing domes of Texas did not exceed 100°C. Proponents of the theory say that geologic time or a catalyst replaced temperature. According to another theory the sulfur in the salt domes is the result of bacterial action. Sulfate reducing bacteria have been detected in sulfur cores and in the formation water issuing from salt domes. It has, therefore, been suggested that these bacteria converted the sulfate to sulfide which subsequently was converted to elemental sulfur.

Jan 1, 1960

By M. W. Legatski, D. L. Katz

The best currently available description of the longitudinal mixing properties of a porous medium is an equation of the form which relates the effective longitudinal dispersion coefficient Dp to the molecular diffusion coefficient Do, the electrical resistivity factor F, the porosity <f> and a Peclet number. If the parameters dpa and m are determined for a porous medium of known porosity and electrical resistivity factor, then a dispersion coefficient may be estimated for a given flow rate and a given gas pair. A new method, featuring on-line gas analysis by thermal conductivity and on-line data reduction by analog computation, was developed and used to determine these mixing parameters for eight naturally occurring sandstones and two dolomite samples. The exponent m of the above equation was found to vary between 1.0 and 1.5. The characteristic length dpa in the above equation was found to vary between 0.25 and 1.9 cm, with an average value of 0.4 cm for sandstones. Measurements were made on two cores in which paraffin wax had been deposited by evaporation from a pentane solution. They indicated that the presence of an immobile phase such as connate water could increase the dispersion coefficients significantly. INTRODUCTION While the petroleum and chemical industries have studied the mixing of miscible liquids flowing in consolidated porous media and of miscible gases flowing in unconsolidated porous media, relatively little data have been presented to describe the mixing of gases flowing through consolidated porous media. Such data are of particular interest to the gas storage industry. For instance, the U. S. Bureau of Mines is storing large quantities of a rich helium-nitrogen gas in contact with a natural gas in a dolomite reservoir. Since the rich gas occupies only 15 percent of the total reservoir volume, it is essential that the extent of rich gas-natural gas mixing be predicted and understood as a function of rock properties, pressure and rate of movement. This investigation was concerned only with the determination of longitudinal dispersion coefficients. It is understood that a transverse dispersion coefficient, which characterizes mixing perpendicular to the direction of flow, may be an order of magnitude less than the coefficient characterizing mixing in the direction of bulk flow.5719 It should also be recognized that the use of any dispersion coefficient is in itself a simplification. It is necessary to assume that mixing in a porous medium may be characterized by the equation for flow in a single direction. A number of authors1 l8,19 have pursued the mixing problem, not in terms of the so-called "dispersion model" described by Eq. 1, but in terms of a "mixing cell model". This model supposes that a porous medium is constructed of a large number of small mixing chambers and that the concentration of the diffusing component within each mixing chamber is uniform. Fick&apos;s law (Eq. 1) assumes that there is no gross by-passing of one fluid by another, and that there are not stagnant pockets of gas in the system under consideration as discussed by Coats and Smith.8 These assumptions are not always valid for flow through porous media and it is important to recognize the limitations upon Eq. 1. The most serious limitation upon the assumption of Fick&apos;s law mixing in a porous medium is

By Hans Lundberg

FOR the last 20 years, geophysical methods have been in practical use. The results accumulated during this time have been broad enough to enable us to formulate some general rules for conducting geophysical surveys to the best advantage. It is a well established fact that electrical and magnetic methods have aided the geologist to outline bodies of ore, to differentiate between various types of rocks hidden from view and also to determine the thick-ness of the layer of drift that covers the bedrock. Fundamental require-ments for a successful solution of a geophysical problem is the existence of physical differences between the various formations under investiga-tion. If such conditions exist, our problem becomes a physical, mathe-matical and geological analysis of the effects of these differences upon the structure of an arbitrarily produced, or already existing, field of force. Experience has shown that reliable and consistent results in analyzing such fields of force are obtained only if: (1) the methods and apparatus used are scientifically sound and designed to provide information with a maximum amount of accuracy, reliability, sensitivity, simplicity and speed of operation, and (2) the interpretation of the results of such an investigation is guided not only by rigid mathematical rules but also by common sense, based upon sound geological knowledge and imagination. Today, a number of methods are based upon sound principles, are highly sensitive and are well suited for field work. The instrumental developments have resulted in self-contained instruments, which permit the determination of field ratios and intensities with great accuracy. Magnetic surveys have almost become standardized. The electrical methods, mostly based on the determination of potential-drop ratios, or electromagnetic field ratios, are built as bridge circuits and it is easy to determine amplitude, as well as phase relationship of the various electrical and electromagnetic fields.

Jan 1, 1938

By C. A. Heiland

Geophysical methods are playing an ever increasing part in various engineering fields. About ten years ago, geophysical exploration was first applied in civil engineering to the study of foundations and the location of construction materials and water. Its usefulness is now being extended into the field of structural engineering. Almost every structure has to be so designed that it will withstand any force to which it may be subjected. Such forces may result from its own weight, applied loads, pressures of various kinds, including those due to wind and water, ground subsidence and vibrations. The last two, problems involving the nature and dynamic behavior of surface and subsurface formations, are within the scope of geophysical investigations. In the design of any structure, the disposition and dimensions of its members as well as their materials must be so selected that they will withstand any or all of the forces enumerated above. In other words, its "resistance" to such forces must be sufficient, allowing for a definite margin of safety. Often a static treatment of the problem leads to satisfactory results, but the static method entails serious errors when vibrations are involved, as in resonance with an impressed vibration the displacements of a structure or parts thereof may dangerously exceed the allowable values. The principle of "dynamic design"† is, therefore, avoiding or reducing resonance by suitable selection of the natural frequency of a structure, or by the provision of damping. Methods of Investigation Dynamic design of structures is required where ground vibrations occur naturally or are produced artificially. Earthquake regions fall in the first group; areas of industrial activity where vibrations are produced by machinery, blasting, etc., fall in the second. In either case, dynamic

Jan 1, 1940

By J. M. Lommel, B. Chalmers

The transfer of material from the solid to the liquid states can be accomplished in several ways. It occurs by the application of heat in the more familiar metallurgical operations of melting but it can also be accomplished by solution in a liquid, as can occur in systems using liquid metals for heat-transfer media. The kinetics of this reaction were studied to learn more of the separate steps in the process. In the case of a pure material at its melting temperature, Te,A,, thermal energy must be supplied to the solid in an amount equal to the latent heat of fusion in order for the solid-to-liquid transfer to occur. The rate at which heat is supplied, and hence the rate of melting, is a function of the temperature gradients in the system. This phase transfer can also occur in the absence of temperature gradients in the system illustrated in Fig. 1, which is a partial phase diagram between the components A and B. A solid of composition CI will

Jan 1, 1960

By C. A. Heiland

Geophysical methods are playing an ever increasing part in various engineering fields. About ten years ago, geophysical exploration was first applied in civil engineering to the study of foundations and the location of construction materials and water. Its usefulness is now being extended into the field of structural engineering. Almost every structure has to be so designed that it will withstand any force to which it may be subjected. Such forces may result from its own weight, applied loads, pressures of various kinds, including those due to wind and water, ground subsidence and vibrations. The last two, problems involving the nature and dynamic behavior of surface and subsurface formations, are within the scope of geophysical investigations. In the design of any structure, the disposition and dimensions of its members as well as their materials must be so selected that they will withstand any or all of the forces enumerated above. In other words, its "resistance" to such forces must be sufficient, allowing for a definite margin of safety. Often a static treatment of the problem leads to satisfactory results, but the static method entails serious errors when vibrations are involved, as in resonance with an impressed vibration the displacements of a structure or parts thereof may dangerously exceed the allowable values. The principle of "dynamic design"† is, therefore, avoiding or reducing resonance by suitable selection of the natural frequency of a structure, or by the provision of damping. Methods of Investigation Dynamic design of structures is required where ground vibrations occur naturally or are produced artificially. Earthquake regions fall in the first group; areas of industrial activity where vibrations are produced by machinery, blasting, etc., fall in the second. In either case, dynamic

Jan 1, 1940

By J. H. Nead, J. W. Halley

The new low-alloy high-strength steels are obviously here to stay. With 75 per cent higher yield strength and 50 per cent higher tensile strength than plain carbon structural steel, they permit 20 to 40 per cent weight savings and 10 per cent or more increase in pay load in the construction of railroad cars, buses, trucks, and a great variety of material-handling equipment. Their cost is low enough so that the extra cost of the new lighter construction over that with carbon steel offers an attractive self-liquidating investment; in some instances new construction with these low-alloy steels may even be as cheap as with plain carbon steel. A considerable and rapidly growing demand for the low-alloy steels has already sprung up. The many steel compositions that have appeared on the market lately18, 27, 28, 29, 30 to meet this demand would seem to indicate that no single composition is uniquely fitted for the purpose. However, no doubt some compositions are more suitable than others. The purpose of this study was, therefore, to compare the effects of the various alloying elements that might be used in the low-alloy steels in order to choose the metallurgically most logical composition, paying due regard, of course, to the economic aspects involved. Properties Desired in Low-alloy Steel A distinction between the new low-alloy steels and the common alloy steels is that the latter are generally used in the heat-treated (that is, quenched and tempered) conditions, whereas the new low-alloy steels are not only not heat-treated but are not susceptible to heat-treatment in the ordinary sense of the term. In this lies one of their chief advantages. Their properties can be obtained in the as-rolled, air-cooled, or annealed condition, just as with mild plain carbon structural steel. There is no need for heat-treating. Such steels can be readily formed hot or cold, and their properties are not appreciably changed by hot

Jan 1, 1936

By J. H. Nead, J. W. Halley

The new low-alloy high-strength steels are obviously here to stay. With 75 per cent higher yield strength and 50 per cent higher tensile strength than plain carbon structural steel, they permit 20 to 40 per cent weight savings and 10 per cent or more increase in pay load in the construction of railroad cars, buses, trucks, and a great variety of material-handling equipment. Their cost is low enough so that the extra cost of the new lighter construction over that with carbon steel offers an attractive self-liquidating investment; in some instances new construction with these low-alloy steels may even be as cheap as with plain carbon steel. A considerable and rapidly growing demand for the low-alloy steels has already sprung up. The many steel compositions that have appeared on the market lately18, 27, 28, 29, 30 to meet this demand would seem to indicate that no single composition is uniquely fitted for the purpose. However, no doubt some compositions are more suitable than others. The purpose of this study was, therefore, to compare the effects of the various alloying elements that might be used in the low-alloy steels in order to choose the metallurgically most logical composition, paying due regard, of course, to the economic aspects involved. Properties Desired in Low-alloy Steel A distinction between the new low-alloy steels and the common alloy steels is that the latter are generally used in the heat-treated (that is, quenched and tempered) conditions, whereas the new low-alloy steels are not only not heat-treated but are not susceptible to heat-treatment in the ordinary sense of the term. In this lies one of their chief advantages. Their properties can be obtained in the as-rolled, air-cooled, or annealed condition, just as with mild plain carbon structural steel. There is no need for heat-treating. Such steels can be readily formed hot or cold, and their properties are not appreciably changed by hot

Jan 1, 1936

By Ta M. Li

A change in priorities is perhaps the underlying motivation reflective of governments and people in the Far East nations of the Philippines, Indonesia, and Thailand. While in the past, local governments have focused on feeding their large populations, the transfer of modern technology to the agricultural sector has produced record crop years in many of these countries. As a result, agricultural objectives have become more manageable, prompting governments to shift priorities to the accelerated development of their industrial sectors. The basis of any sustained industrialization program, the governments concede, is the development of a vibrant minerals sector.

Jan 8, 1979

By Charles C. Templeton

Any explanation of the nature of multiphase fluid flow through porous media must ultimately involve a knowledge of the mechanism of such flow through the individual pores of the medium. To provide quantitative information of the latter type, a study was made of gas-liquid and liquid-liquid displacements in single uniform Pyrex capillaries with diameters as small as 4 microns. Quantitative observation of air-liquid displacements with zero contact. angle indicates the adequacy of a model based on Poiseuille&apos;s Law and the independence of capillary pressure and interfacial velocity. Consequently, this work discounts previous claims that flow is abnormally retarded in very small capillaries. For the displacement of a very viscous oil by water in a capillary initially filled with water, flow is faster than predicted by the above model. This behavior is probably due to the existence of a thin annular film of water between the oil column and the capi1lary wall as postulated by Yuster. INTRODUCTION The need for experimental observation of the microscopic nature of multiphase fluid flow, to further the understanding of the results of macroscopic flow investigations, has been previously recognized. Chatenever and Calhoun1 in connection with the API Project 47B have extensively studied the flow of fluids through layers of glass or lucite spheres between glass or lucite plates. Lowman2 prepared an interesting film concerning flow in a single capillary, using an apparatus which made a moving interface appear stationary in the field of a microscope. The purpose of the present investigation was to deter- mine what contribution might be made to this field by comprehensive quantitative observation of gas-liquid and liquid-liquid displacements in single capillaries of uniform, very small diameter. The techniques used are similar to those of Lowman but incorporate improvements necessary for quantitative work. Quantitative observations must begin with fluids of simple chemical composition to provide a basis for analyzing the more complex behavior that may be expected with natural reservoir fluids. However, some qualitative observations on systems involving crude oils are presented. Experiments of this sort involve the observation of the velocity of the interface separating two fluids, and have been performed in horizontal or vertical capillaries by several investigators.3,4,5,6,7,8 The most general treatment of their mechanics, by Brittin,9 involves forces due to capillarity, viscous resistance, gravity, an "end-drag" effect, and the rate of change of momentum of the capillary contents. Since the range of pore diameters of interest in petroleum reservoirs is about 0.1 to 100 microns, it was desired to perform these experiments in the smallest capillaries possible, to ascertain whether capillary diameter had any effect on the existing theory based on data from larger capillaries.* It was also important to be able more systematically to vary the direction and rate of displacement than was done by previous investigators. Finally, to concentrate attention on viscous and capillary forces by eliminating gravity as a parameter, this study involves only horizontal capillaries. The work of Eley and Pepper&apos; with a "large" (0.766-mm diameter) horizontal capillary is the previous investigation which is most similar to the present method of quantitative observation. Here capillaries with diameters as small as 4 microns will be studied.

Jan 1, 1955

By C. M. Wayman, G. R. Srinivasan

A metallographic study of the isothermal products formed between 750° and 285°C was made in an Fe-7.9 wt pct Cr-1.11 wt pct C alloy, and a time-temperature-transformation diagram was determined. The study shows that the austenite decomposes into three different products: pearlite above 540°C, ferrite and carbide between 540° and 300°C, and lenticular bainite below 300°C. No upper bainite forms in this alloy. The results are discussed in terms of carbon diffusion models for upper bainite formation. AUSTENITE transforms into several products depending on the temperature, composition, and rate of cooling, and the various transformation products have been a source of controversy for a long time. Since the classical study of Davenport and ~ain&apos; extensive work has been carried out. The present study concerns the isothermal transformations in an alloy which was used for a detailed investigation of bainite crystallography and provides information supplementary to the work of Lyman and Troiano who studied austenite decomposition in steels containing 1 pct C and varying amounts of chromium. Their work showed that increasing the amount of chromium in high-carbon steels had the effect of depressing the B, temperature and of shifting the TTT curves to longer times and lower temperatures. They further found that if the chromium content is increased in a 1 pct steel to about 9 pct no bainite would form even after a period of 100 days. However, a preliminary investigation by the present authors showed that bainite plates do form in steels containing about 8 pct Cr and 1 pct C. In view of this and some results from a thin-foil electron microscope investigation of the bainite formed in the present alloy: it was considered desirable to investigate the other isothermal products as well. EXPERIMENTAL PROCEDURE The alloy used in the present investigation was obtained from a triply vacuum-melted ingot prepared from high-purity materials. Chemical analysis for the alloy verified the composition to be Fe-7.9 wt pct Cr-1.11 wt pct C. Metallographic observations were made on i by i by « in. specimens which were aus-tenitized at 12 50°C for 50 to 60 hr in evacuated quartz capsules and then water-quenched. Since the M, temperature for this alloy is below room temperature, the homogenizing treatment produced a completely austenitic structure consisting of very coarse austenite grains (ASTM #0-1). Several samples of the austenitized specimens were metallographically prepared and observed for any proeutectoid carbide separation. It was found that all the carbon was in solution. The water-quenched specimens were upquenched and given isothermal treatments at temperatures between 285" and 750°C for varying periods in molten salt or lead baths. The specimens were then water-quenched, and those showing less than 5 pct transformation were used for plotting the beginning of the austenite decomposition. To ensure the removal of the disturbed layer, the mechanically prepared specimens were electropolished in a 1:6 HzS04, CHSOH solution for 10 to 15 sec at 20 v. Final polishing was done with a vibratory polisher using 0.05-p alumina. Various etchants including nital, ferric chloride, and hot ferricyanide (Murakami&apos;s reagent) were used to bring out details in the different transformation products. The ferricyanide etch was used whenever the preferential etching of carbides was desired.

Jan 1, 1969

By W. O. Philbrook, K. Natesan

A mathematical model was derived for the temperature change in a particle undergoing heterogeneous chemical reaction and heal exchange with a stream of fluid. The model has been applied specifically to the exothermic oxidation of spherical particles of zinc sulfide. Very good agreement was obtained between the theoretical prediclion and experimental observation. It was found that at no stage of the reaction was the particle subjected to a state of thermal instability. In studies of gas-solid reactions, it is generally assumed that the gaseous and the solid phases are at the same temperature throughout the reaction period. This is not strictly true since most of the reactions are either exothermic or endothermic in nature. This paper deals only with heterogeneous gas-solid reactions of noncatalytic type. In the case of exothermic reactions (e.g., roasting of sulfides), there may result an increase in temperature of the particle due to the release of the heat of reaction, and this increase in temperature may enhance the reaction rate and thus cause further release of heat. Such a "spiralling" effect may lead to a thermally unstable situation within the particle. On the other hand, in the case of endothermic reactions (e.g., calcination of limestone), there may occur a decrease in temperature of the particle as the reaction proceeds, leading to a virtual "quenching" of the reaction front. A general discussion of autothermic processes with emphasis on properties and reactor design is given by Van Heerden. 1 Levesque and cubicciotti 2 observed self heating of the sample in the oxidation of thorium. Anous et al. 3 observed self cooling of the sample in their dehydration studies on chrome alum. Cannon and Denbigh, 4 and Ong et al.5 reported self heating of the sample in their studies of the kinetics of oxidation of zinc sulfide. A typical plot of heat generation and heat loss rates with reaction temperature is shown in Fig. 1.&apos;14 The Sigmoid curve represents the heat generation rate while the straight lines represent the heat loss rate. The main objectives of this analysis are to estimate the temperature increase of a single particle undergoing an exothermic reaction and to study the possibility of a thermally unstable situation within the particle. Also, a study of the dependence of the tempera- ture increase on different process variables has been attempted. A "she ll-by-shell" method has been proposed to analyze the problem. The shells may be made as small as necessary, and equations may be set up for heat transfer by various mechanisms. Such equations will have to be solved for each shell, with the boundary conditions for ith shell being obtained from the (i - 1)th shell, using a high speed digital computer. The oxidation of spherical particles of zinc sulfide is considered for this analysis, but the treatment is general enough to be applicable to other reactions and particle shapes. The oxidation reaction can be written as AH =« -115 kcal/mole ZnS [1] Such a reaction has been found to proceed in a topo-chemical manner; i.e., as the reaction proceeds, a progressively thicker outer shell of zinc oxide is formed, while the inner core of unreacted sulfide decreases. It has been found experimentally, both in the present work and in the previous investigations,4-6 that the particle retains its original dimensions. Therefore, at any given time, the particle may be

Jan 1, 1970

By H. R. Brannon, F. M. Perkins, Weldon O. Winsauer

Both the abnormal resistivity exhibited by shaly reservoir materials and their potential are due to adsorption of ions. Interrelationships between the two have been derived and verified by laboratory results. These relations which have resulted from this work may be used in a qualitative manner to estimate whether or not a particular shaly reservoir contains hydrocarbons, and also to estimate the porosity of shaly sands. INTRODUCTION In spite of the progress which has been made in the last decade toward a better understanding and utilization of the electric log, there remain a number of problems in the interpretation of the log. One of these which is often troublesome is that of divining the nature of the fluids in sandstones or carbonate rocks which contain appreciable amounts of shale. It was shown by Patnode and Wylliel in 1949 that shaly rocks exhibit an abnormally low resistivity when saturated with solutions of low ionic concentrations. This phenomenon has been demonstrated to be due to the adsorptive properties of shale or clay in the rock.&apos; In estimating the fluid content of shaly sands or carbonates from the electric log, it is desirable and sometimes necessary to correct for the abnormally low resistivity. A similar correction is likewise often necessary if attempts are made to estimate the porosity of a stratum from resistivity measurements. The correction may be made from data obtained on core samples and from information on salinity of interstitial water. Cores, however, are not always available. Moreover, even if cores are at hand, their examination is time-consuming. It would be most desirable, therefore, to make corrections of this nature from the log itself. Since both the abnormal resistivity and the potential&apos; are consequences of the adsorption of ions on shale, it should be possible to utilize the potential curve to give better interpretation of resistivity data obtained in logging shaly materials. The work described in following sections was directed toward this end. THEORY Relation of Resistivity of Shaly Reservoir Rock to Adsorpttve Properties In discussing the effect which the presence of shale or clay exerts on the resistivity of a reservoir rock, it is convenient to make use of the resistivity factor.4,5 This quantity has been defined as the ratio of the resistivity of the rock when it is completely saturated with an electrolyte to the resistivity of the electrolyte itself. When the rock, such as a clean sand or carbonate, is free of shale the resistivity factor is virtually independent of the ionic concentration of the electrolyte used to saturate the sample, so that F = R0/Rw = constant for a clean rock . . (1) where F is the resistivity factor, R0 is the resistivity of the rock saturated with electrolyte, and Rw is the resistivity of the electrolyte. When the rock contains argillaceous material, the resistivity factor as defined above is no longer independent of the concentration of the electrolyte used to saturate the rock, but decreases as the ionic concentration of the electrolyte decreases. In explanation of this behavior, it is instructive to consider a sample of shaly porous rock placed in contact with a large volume of a dilute electrolyte. The sample is considered to become saturated with the electrolyte, and to attain equilibrium with it. As a result of adsorption by the shale surfaces within the rock, there is a greater concentration of ions in the solution adjacent to the shale particles in the interstices of the sample than there is in the external solution with which the

Jan 1, 1955

By R. J. Stokes

This paper compares the room-temperature mechanical behavior of magnesium oxide crystals containing &apos;fresh&apos; and &apos;grown in&apos; sources. &apos;Fresh&apos; dislocation sources introduced by cleavage or mechanical contact move and multiply to generate slip bands at 3000 psi. Macroscopically the crystals yield smoothly at 6000 psi and can be quite ductile. When &apos;fresh&apos; sources are eliminated by chemical polishing the crystals have to rely on &apos;grown in&apos; sources to initiate slip. They then deform elastically up to extremely high stresses (-30 to 50,000 psi) yielding with a sharp stress drop down to the level at which Ifresh&apos; sources operate. Grown in&apos; sources are considered to be associated with impurity wecipitate particles or inclusions. Annealing crystals at 2000°C dissolves these particles thereby eliminating sources for slip. The crystals then become consistently stronger (> 70,000 psi) approaching within 1/10 of the theoretical strength. Dislocations of the grown-in network do not move under stress to nucleate slip. It is proposed that they are locked electrostatically. DISLOCATIONS were originally conceived to resolve the large discrepency between the theoretical and real strength of solids. The idea that slip propagates by the movement of dislocations is now well confirmed both by electron transmission and etch pit studies. But this by itself is not sufficient to explain the low yield strength of crystals for there is still the need to understand where slip dislocations originally come from. Theoretical estimates place the stress to generate dislocations homogeneously in the lattice at approximately 1/30 of the shear modulus,&apos; a value 104 to 105 times greater than the stress at which the very first manifestations of plastic deformation have been observed. Only an special cases can the theoretical strength be approached; in crystals of high perfection such as whiskers2 where dislocation sources do not preexist and in covalent crystals where the dislocations present at room temperature are almost completely immobilized by the bond character of the solid.3,4 For the most part it is necessary to assume that the yield strength of ionic and metallic solids corresponds to the motivation and multiplication of dislocation sources present beforehand. The question as to their origin appeared to be answered by the suggestion of Frank and Read5 that dislocations forming part of the grown-in structure could operate as a mill for the large scale production of dislocations. The Frank-Read mechanism is still widely accepted as the source of dislocations but a number of observations have been reported which are in serious disagreement with it. One of the most intriguing of these is that under normal testing conditions dislocations of the grown-in network appear to play no role in the plastic deformation of rock salt structure ionic solids. This was first reported in the etch pit studies on lithium fluoride by Gilman and Johnston6 and is true also for magnesium oxide. To explain the comparatively low yield stress of lithium fluoride it was proposed by a number of authors7,9 that small unresolved prismatic loops formed by vacancy condensation were acting either directly or indirectly as the dislocation sources. This proposal led Gilman10 to perform a series of detailed and careful experiments on lithium fluoride to try to identify the sources responsible for the initiation of slip. He concluded that prismatic loops played no general role and that other sources were more important. Dislocation sources in ionic crystals can be divided into two general categories. First, there

Jan 1, 1962

By Richard H. Jahns

Terminology and Basic Specifications Minerals and closely allied natural substances that are used for personal adornment, as raw stock for the fashioning of ornamental objects, or for other decorative purposes can be referred to collectively as gem materials. Industrial gem materials are those employed directly in various areas of industry. Substances that are manufactured for gem or industrial uses are termed synthetic gem materials; most of these correspond in composition and crystal structure to certain minerals found in nature. Imitation materials are those whose use is based upon their resemblance to substances of different composition and greater value. Gem stone is a designation commonly restricted to those materials suitable for personal adornment, and the complementary term ornamental stone is applied to the remaining materials not used industrially. This distinction is arbitrary and somewhat inconstant, owing to numerous geographic differences and historical shifts in end uses. Further, there is a complete gradation between the category of ornamental stones and that of dimension stone. Although many building and monumental stones are undeniably ornamental in their uses, treatment of such material is beyond the scope of this chapter. Substances that lose their identity in use are excluded from the gem category. Thus a transparent crystal of beryl would not be classed as a gem stone if it were treated as a source of beryllium metal. The adjectives precious and semiprecious have been employed as a means of distinguishing different gem materials on the basis of their recognized value. Diamond, emerald, ruby, and sapphire consistently have been regarded as precious stones, and in cut form they commonly are referred to as the noble gems. Opal, pearl, turquois, and chrysoberyl also have been classed as precious at various times. In recent years, however, it has been increasingly recognized that no satisfactory distinction can be based upon assessed value or any group of intrinsic properties, and at the present time all gem stones normally are referred to as precious. Indeed, the tendency is to extend this term to include many of the so-called ornamental stones, and the designation semiprecious has been essentially discontinued. Unlike most mineral commodities of economic value, gem materials are little altered in processing for end uses. Some stones are used in essentially their natural form, and most are reshaped and polished without significant changes in their fundamental properties. Thus the preparation of gem and ornamental stones is intended chiefly to emphasize or enhance desirable characteristics that are present initially. The worth of most synthetic gem stones is founded upon the identity between their major properties and the natural characteristics of the corresponding minerals, just as the pleasing qualities of imitation stones depend upon how well certain of their properties simulate those of more valuable substances. The most important specifications of gem materials represent four basic factors: beauty, durability, rarity, and portability. Beauty, whether expressed as splendor, "purity," attractiveness, or in some other way, is mainly a function of personal response to optical properties such as color, transparency, indices of refraction, and dispersion. Freedom from visible imperfections is important for transparent stones. For some substances beauty depends also upon asterism, opalescence, textural and

Jan 1, 1960

By Walter P. Jenkey

[ ] I. THE REDUCING ACTION OF CARBON AND OF HYDROCARBONS. Carbon has long been recognized as one of the most powerful reducing agents in the deposition of ores. Investigations, made by myself, of the zinc- and lead-deposits in Southwest Missouri, in the region centering about Joplin, where the formation of the metallic sulphides has been due to the action of bitumen, carbonaceous shales and bituminous coal, Lace afforded abundant evidence that the solid oxygenated hydrocarbons, particularly, when in fine powder and in suspension in the waters circulating through the ore-bodies, are the most energetic and powerful reducing agents known. Bitumen, liberated by the decomposition of the ore-bearing limestone, is found in the Joplin mines in all degrees of fluidity and hardness, dependent on the amount of oxidation it has undergone. From semi-fluid maltha it grades into partly oxidized mineral-pitch, which, by further oxidation, changes to hard asphalt, finally breaking up, from continued absorption of oxygen, into a fine powder resembling in appearance powdered coal. In this condition oxidized bitumen, from its light gravity, is transported readily in suspension in the underground circulating-waters. Bituminous coal and black carbonaceous clays and shales occur as surface formations, often in intimate association with

Jan 1, 1913