Search Documents

By R. B. Sosman, J. C. Hostetter

It is well known that ferric oxide, Fe2O3, is paramagnetic, while magnetite, Fe3o4, is classed among the highly ferromagnetic substances. But magnetic data on oxides intermediate in composition between Fe2o3 and Fe3O4 have been almost completely lacking. Fe2O3 and Fe3O4 form a solid-solution series, according to present evidence.' In this series the properties change continuously from Fe2O3 toward Fe3O4, as the percentage of FeO increases from zero toward 31.03, which is the percentage in magnetite. It is possible that there is a break in the series near Fe3O4, but it has not yet been possible to establish the existence of such a break experimentally. The occurrence of solid solution in this series is shown by the dissociation pressure, or oxygen pressure in equilibrium with the oxides, which falls continuously over the range from Fe2O3 to Fe3O4. The oxygen-pressure curves at 1100" and 1200" are shown in Fig. 1. The existence of solid solution is also demonstrated by the continuous change in optical properties from Fe2O3 over to a composition containing about 18 per cent. FeO, at which point the opacity of the oxide becomes so great that it is impossible to obtain measurements at higher percentages of ferrous iron. Natural oxides of iron intermediate in composition between Fe2O3 and Fe3O4 are much more common than is generally supposed. If a mineral oxide is not strongly attracted by a small hand magnet and if it gives a red streak, it is usually labeled "hematite." If it is strongly attracted by the hand magnet it is usually labeled "magnetite" without further tests. As we shall show later, oxides containing from 1 up to 31 per cent. FeO can be thus erroneously lumped together as "magnetite." It is a fact, nevertheless, that the great bulk of natural oxides of iron lie fairly near either Fe2O3 or Fe3O4 in composition. The reason will be

Jan 1, 1918

By E. W. Filer, R. P. Smith, L. S. Darken

The solubility of nitrogen gas in purified iron and low alloy steels is determined for the y region (930° to 1350°C). The diffusivtiy of nitrogen is estimated from the rate of approach to equilibrium. The investigation of aluminum-killed steels, held in nitrogen, discloses precipitation of aluminum nitride, the solubility of which is determined. ALTHOUGH several investigations of the solu-bility of nitrogen gas in y iron have been reported, all have made use of the method adopted by Sieverts in his classic work, whereby the solubility is determined by the pressure or volume change of the gas. The agreement between different investigators* is rather poor, particularly as compared to the self-consistency of results of several individual investigators. The present report represents a portion of our investigation of the equilibrium of nitrogen and nitrogenous atmospheres with iron and steels. The method adopted in this temperature region (910" to 1400°C) consists of holding the specimen in gaseous nitrogen, quenching (or cooling), and determining the nitrogen content by direct analysis (solution in acid followed by distillation and titra-tion of the ammonia).** Up to 1050°C a 20 in. vertical wire-wound (Kan-thal) furnace was used; this was wound in three sections so that by proper adjustment of relative currents, and use of a modulator1 and a commercial controller (using a chromel-alumel control couple), a zone almost 6 in. long could be maintained uniform within a few tenths of a degree. Since the temperature coefficient of the nitrogen solubility is low, the full precision was not utilized and a variation of l° to 2" was tolerated; a variation of a similar amount also occurred occasionally between the beginning and end of the experiment. At higher temperature a vertically mounted, tubular Globar furnace and control unit was used; the zone of uniformity (l° to 2"C) was here limited to about 2 in.; fluctuations with time were comparable to those in the wire-wound furnace. Reported temperatures were measured by use of a platinum-platinum-rhodium thermocouple, which was frequently com- pared with a similar standard couple which was calibrated at the gold and palladium points and also compared with one certified by the Bureau of Standards; error from this source is believed to be less than 1 "C. Nitrogen gas from a commercial cylinder was mixed with slightly over 1 pct H by use of a gas mixer described previously.' This mixture was passed over hot copper and through ascarite and phosphorus pentoxide to remove oxygen and water vapor. The purified gas contained 1.05 pct H. This procedure was adopted to prevent the formation on the specimens of oxide film, which is well known to be nearly impervious to nitrogen; its success was attested by

Jan 1, 1952

By G. Thodos, R. B. Grieves

A method has been developed For predicting the critical temperatures and critical pressures of binary mixtures of carbon dioxide, hydrogen sulfide, nitrogen, hydrogen, carbon monoxide and oxygen with the normal paraffin hydrocarbons. For carbon-dioxide and hydrogen-sulfide systems, relations are presented that take into account the peculiar behavior of mixtures with closely boiling components, such as carbon dioxide-ethane and hydrogen sulfide-propane mixtures which exhibit minimum critical temperature points. For hydrogen, nitrogen and carbon-monoxide systems, the extreme critical behavior caused by wide differences in pure component properties is established In addition, those fixed gas-paraffin systems which resemble paraffin-paraffin systems are also accounted for. For a mixture of known composition, the pure component critical temperatures, critical pressures and normal boiling points are all that are required to determine its critical point. Graphical relations are presented relating Tc and PC , of the mixture to the pure component properties. From the treatment of 12 carbon-dioxide and hydrogen-sulfide systems reported in the literature (74 mixtures), the expected error lor the critical temperature is approximately 1.5 per cent, and for the critical pressure, approximately 2 per cent. From the treatment of six hydrogen, nitrogen and carbon-monoxide systems reported in the literature (30 mixtures), the expected error for both the critical temperature and critical pressure is approximately 2.5 per cent. The relationships, which have been developed with only normal paraffins as the hydrocarbon components, may be extended to those isoparaffins and olefins which fall within the allowable volatility ranges. INTRODUCTION Many of the fixed gases — carbon dioxide, hydrogen sulfide, nitrogen, hydrogen, carbon monoxide and oxygen — occur in natural mixtures with hydrocarbons. Carbon dioxide and hydrogen sulfide are frequent components of the fluids produced from underground petroleum reservoirs. Nitrogen, carbon dioxide and hydrogen sulfide are present in varying quantities in most natural gases and gas-condensate well effluents. Hydrogen mixtures are of considerable interest in many phases of refining processes of petroleum. The determination of the critical temperatures and critical pressures of such mixtures is of value in vapor-liquid equilibrium studies, for the prediction of the characteristics of underground reservoirs, and for reduced-state correlations of PVT, transport and thermodynamic properties. The accurate estimation of the critical point for binary mixtures is an important initial step toward a complete analysis for the establishment of the critical temperatures and pressures of multi-component mixtures. Methods for predicting the critical temperatures and critical pressures of binary hydrocarbon systems have already been presented in the literature.8 It is possible to apply these existing methods to fixed gas-paraffin mixtures, but due to their unusual critical behavior, values calculated deviate considerably from experimental values. For systems containing trace quantities of the fixed gases, these methods are acceptable; however, for systems containing more than 5 mol per cent of the fixed gases, these utterly fail to produce reasonable critical values. Consequently, in this study a method has been developed for handling such binary mixtures over the entire composition range. CARBON-DIOXIDE AND HYDROGEN-SULFIDE SYSTEMS The critical behavior and the vapor pressure behavior of mixtures of carbon dioxide and hydrogen sulfide with paraffinic hydrocarbons may be quite similar or quite dissimilar to that of paraffin-paraffin mixtures, depending on the volatilities of the components involved. The critical temperature and normal boiling point of carbon dioxide are very close to the corresponding values for ethane, while its critical pressure is considerably higher than that of ethane. The normal boiling point of

By Paul B. Crawford, Bobby L. Landrum

Electrical model studies have been made of the effect of drainhole drilling on production capacity. Drain holes are those lateral holes which are sometimes drilled to assist in increasing the oil drainage into the main wellbore. The studies indicate that if the drainhole length i.r near 0.2 of the drainage radius, the increase in production capacity may be approximately 1.8, 2.08, trnd 2.33 for the case of one, two and four drain holes, respectively. If multiple drain holes are drilled, shorter holes are required to achieve a specific increase in production capacity than if one or two holes are drilled. To achieve increases in production capacities by factors near three it is shown that the drainhole lengths divided by the drainage radii must be approximately 0.64, 0.48, cnd 0.37 for the case of one, two and four drain holes, respectively. IN T RO DUCTION Kecent developments in drilling techniques have permitted the drilling of lateral or horizontal holes to increase the rate of production. The number of these drain holes may vary from 1 to 10, and they have been drilled laterally as much as 100 ft. Drainhole drilling at substantial depths is of recent origin but has been used in the Spraberry field of West Texas, the La Pas field in Western Venezuela, and certain fields in California. The diameter of the drain holes has been approximately 6 in. In drilling drain holes it is desired to know how much increase in production capacity may be expected, what additional benefit may be gained by drilling more than one drain hole, and what increase in production capacity may be brought about by lengthening the existing drain holes. In realization of the importance of lateral drilling, electrical model studies were made to provide quantitative estimates on the effect of drain holes on production capacity. ANALYSIS An electrical model was used in studying this problem. A wooden circular reservoir approximately 30 in. in diameter and 2 in. deep was filled with a dilute salt solution to a depth of 1 in. A copper band formed the periphery of the tank, and a copper wire was inserted in the center of the tank to represent the well. The drainage radius divided by the well radius was equal to 500. A diagram of this type model is shown in the inset of Fig. 1. An electrical potential was applied to the wire well and copper band at the periphery to determine the flow of current. Following this measurement copper wires of various length were soldered to the vertical wire well in such a manner as to simulate lateral wells drilled into the reservoir. Multiple lateral holes of various lengths were studied by varying the number and length of copper wires soldered to the vertical wire well. All multiple lateral wells were located symmetrically about the vertical well. The effect on production capacity by drilling an infinite number of lateral holes was studied by replacing the lateral hole with a copper disk. For each condition the flow of current was measured and compared with the flow of the vertical well only. The model which is thus described provides the steady state increases in production capacity which may be expected in some cases. The data conform to those which would be observed for a uniform homogeneous reservoir. The data may have primary application to those reservoirs producing above the bubble point. It is realized that few lateral holes are drilled in reservoirs of this type, but the data may be of some value in guiding future work or aiding to explain observed phenomena.

Jan 1, 1956

By H. H. Spain, R. C. Rumble, H. E. Stamm

This paper presents a reservoir analyzer study of the performance of the Woodbine formation in the East Texas basin. The study was made possible by the compilation of available information on the configuration. thickness and the pressure drawdown of the formation. The investigation was made of the pressure variations in the basin incident to production from the several Woodbine reservoirs. In addition, the apparent compressibility of Woodbine water was evaluated so that the potential water yield of the formation could be determined. The distribution of permeability of the Woodbine sand and the interference between producing areas were also investigated. In conjunction with this basic study of the Woodbine sand, an acceptable match of the production-pressure relationship in the East Texas Field was established on the analyzer. INTRODUCTION When production is taken from a reservoir contiguous to an aquifer, the resultant pressure gradient causes a water influx into the reservoir. For some years it has been the practice to predict the performance of water drive reservoirs with mathematical equations that relate the water influx into reservoirs to their pressure behavior. A rigorous solution of these equations is quite complex: hence, the conventional method requires the simplifying assumptions that the formation have constant thickness, permeability and poiosity, and that it have a known and regular shape. It is necessary to use performance records of the reservoir in question to determine the equation constants that make the results of the mathematical calculations duplicate the reservoir history. The values of the constants determined in this manner sometimes differ so greatly from theoretical or measured values that the constants appear unreasonable. The equation constants comprise such factors as the thickness, porosity and permeability of the formation, and the viscosity and compressibility of water. Usually the thickness, porosity and viscosity are known within a reasonable degree of certainty. whereas the formation permeability and the water compressibility are known with considerably less certainty. Hence. permeability and compressibility values are arbitrarily selected that will make the mathematical equations duplicate the reservoir behavior. In many reservoir studies the value of the compressibility of water thus selected has exceeded the reported value by a factor of from severalfold to manyfold. Whether this excessive value results from the inadequacy of the mathematical approach to take into account the shape irregularities and the heterogeneities of the aquifer, or is due to some type of formation compaction and decrease of porosity has not been established. Because of the significance of the potential water yield of formations with reference not only to oil reservoirs but to water resources as well, it is very important that a representative value for the effective water compressibility be determined. One of the best known examples of a field for which it has been possible in the past to predict the future reservoir pressure is the East Texas Field. Until about 1943 it was possible by means of mathematical equations to duplicate past pressure behavior and to predict with a high degree of accuracy the reservoir pressure of the field. Since 1943, however, the calculated pressures have deviated progressively from the observed pressures to such a degree that in recent years, it has

Jan 1, 1951

By W. H. Moore, E. T. Powell

IN the early days of mining in the Anthracite field, only the thicker and better seams of coal were mined, because of the limited mining and coal-cleaning facilities, therefore many of the thinner and less productive seams were permitted to remain unmined. With improvements in mining methods, the introduction of modem preparation plants, and the increased market demand for small-size coal, the thinner and more laminated seams have now become assets. In many instances these seams overlie the mined-out beds of the thicker and better seams, from which all recoverable coal was removed by the conventional breast-and-pillar method of mining. Some collieries in certain sections of the Anthracite field are now relying on these thinner and laminated seams. For the purpose of illustration, a large area in the Hickory Swamp-Ridge Basin of the western middle coal field has been selected, where as early as 1898 the No. 4, or Little Buck Mountain, seam was mined and pillars removed. The No. 5, or Buck Mountain, seam lying on a comparatively light pitch and with intervening strata of but 55 ft. of rock was not mined until 1935. Farther east, in the same basin the Nos. 8 and 9 seams, which are two splits of the Mammoth seam, have been mined and robbed and the workings have been abandoned since 1896. The overlying No. 9½ seam, or the upper split of the Mam- moth, and the No. 9¾ or 4-ft. seam remained virgin, with only an interval of 50 ft. of rock separating them, and with 40 to so ft. of rock strata separating the No. 9½ seam from the completely mined area of the Nos. 8 and 9 seams. These seams lie on a pitch of 45° on the south side of the basin and on 75° on the north side of the basin. Mining has been carried on in the 9½ and 9¾ seams for 3 years on both dips of the basin, for a distance of 3500 ft. In some sections the overlying strata of the thicker seams previously mined have settled without any apparent breaks in the upper strata, as indications have shown in the top split of the Mammoth; while in other areas the roof and bottom of this top split of the Mammoth have settled unevenly, thereby causing the bottom and roof to break into blocks. In attempting to mine over a large area of the No. 5 or Buck Mountain seam, a similar settlement has been encountered; the roof of the seam has been broken and a considerable amount of timbering has been necessary in order to make the mining of the seam possible. The conventional breast-and-pillar method, using shaker conveyors, has been used in the No. 5 seam, and a slant-breast method in the mining of Nos. 9½ and 9¾ seams. Mining OF Light-pitch Seams The No. 4 seam was mined and robbed by the conventional breast-and-pillar system. In this area the seam pitched from 5° to 25° on the north dip, averaged 8 ft. in thickness and had a slate bottom and a

Jan 1, 1942

By H. A. Wahl

This paper presents methods of designing hydraulic fracture treatments in formations saturated with slightly compressible liquids. Howard and Fast describe the fluid-loss control resulting from the viscosity and compressibility effects of the reservoir fluid in terms of a fracturing fluid coefficient. However, for horizontal fractures, this coefficient is applicable to infinitely thick reservoirs. These methods of evaluating fluid loss from horizontal fractures during treatment differ from previous methods in that: (I) formation thickness is incorporated in the velocity function describing the rate of fluid loss to the formation; and (2) for a given thickness the relative position of the fracture to the horizontal boundaries of the reservoir or any interrnediate permeability barrier is incorporated in the design procedure. This theory is applied to several actual and hypothetical field cases. The results of these calculations demonstrate that the eflect of formation thickness on fluid loss from horizontal fractures may result in fractures several times larger than predicted by other methods. INTRODUCTION Hydraulic fracturing has been the dominating well-stimulation technique during the last decade. From the time it was commercially available, fracturing has had a very favorable success ratio compared to other stimulation methods. However, numerous wells that were successfully stimulated remained economic failures. Only in the last few years has the oil industry recognized the importance of designing treatments for each well which will yield the maximum profit. This implies that for a given set of treatment conditions the size and general physical characteristics of the fracture can be determined. One of the outstanding contributions in the field of fracture design was presented by Howard and Fast.' In their paper, three flow mechanisms that control fluid loss from the fracture to the formation are defined: (1) viscosity effects of the fracturing fluid, (2) viscosity and compressibility effects of the reservoir fluid, and (3) wall-building effects of a treated fracturing fluid. The rate of fluid loss to the formation adjacent to a fracture is shown to be a function of time. For each flow mechanism the velocity function v(t) is expressed as a constant or fracturing fluid coefficient divided by the square root of time. This form of v(t) can be used in the Carter equation, as developed in the Howard and Fasc paper, to estimate the areal extent of fractures. This equation may be written as In the following sections the effect of formation thickness on fluid loss from horizontal fractures is evaluated when the controlling flow mechanism is the viscosity and compressibility of the reservoir fluids. The major assumptions inherent in the Carter equation are brought out in subsequent mathematical developments. THE EFFECT OF RESERVOIR FLUIDS ON FRACTURE EXTENSION When a fracture treatment is performed using a fracturing fluid identical to the reservoir fluid, the only flow mechanism controlling fluid loss is the viscosity and compressibility effects of the reservoir fluids. In developing a fracturing fluid coefficient for this mechanism, Howard and Fast considered a segment of the formation bounded by a unit area on the fracture face and extending to infinity in the direction of leak-off as shown in Fig. 1(a). The direction of leak-off z is normal to the fracture face. The equation governing the linear isothermal flow of fluid into this segment is where a = Eq. 2 is a form of the diffusivity equation. It is derived from the equation of continuity, Darcy's law and Eq. 3

By Gordon M. Yocom

A PROPER consideration of the subject of this paper should include economic aspects as well as the technical phases of the metallurgy, production, and properties of the product. The metallurgical phases of the processing and properties of the product will be considered only from practical aspects and within the scope of the writer's experience with tonnage production. The Bessemer process was invented 85 years ago and became important because it put steel manufacture upon a larger and less costly basis. In America the Bessemer production has declined for many years and has not maintained its proportionate place with the rapid advances of the open hearth. The achievements in the open-hearth field were attained by the greater number of technical people attracted to that branch of the industry. The antipathy of technical students for the older and less popular Bessemer field gradually weakened the forces defending it and retarded the development of new and better methods. In Europe the economic advantage of the basic Bessemer process has not been overlooked and the tonnage usually is greater than that of the open hearth. The acid process has been the subject of renewed attention in America during the past few years and those who are more familiar with it are striving to show that the method is too valuable to abandon. A considerable tonnage of Bessemer-blown metal, in both molten and ingot forms, used in connection with the open-hearth practice makes it an important auxiliary unit to the industry. This practice aids in modifying the price level of heavy remelting scrap in addition to speeding up the open-hearth operation. The use of Bessemer steel has continued not only because of periodic economic advantages but also because of certain inherent qualities of machinability, weldability and stiffness, which are valuable for many applications. The properties of stiffness and rather high reaction to cold-work require some modification in order to meet the demands of modern methods of processing, which involve cold-reduction and cold-forming. At least one factor contributing to the stiffness of this steel is the relatively high phosphorus content of the acid product. The phosphorus content of the Thomas or basic Bessemer steel of Europe is considerably lower than the normal acid product in America. The American industry has continued the use of the acid process chiefly for the reason that the available ores are more easily adapted to this process from both metallurgical and economic standpoints. In European practice the basic process is necessary with the highly phosphoric ores available and it is sustained to some degree by the sale of the rich phosphate slag as a by-product. The basic process was used in this country at several plants many years ago, but was abandoned for economic reasons. A part of the past history of these trials is given here because the author believes it has not been published and it has some bearing on the subject of this paper. The information is authentic to the extent that

Jan 1, 1941

By S. Leber

Pole figures and pole distributions were used for the quantitative detevinination of the preferred orientations in swaged tungsten rods and the effect of subsequent wire drawing on the texture. In the swaged rod, the preferred orientation could best be described as a pseudo (111-112) [110] cylindrical texture. A secondary component was assigned the indices (110) [001]. Further reduction by swaging retained these cylindrical textures. Wire drawing caused lattice rotations about the wire axis, converting the cylindrical texture into a normal fiber texture. The conversion was initiated and proceeded lnost rapidly in the center of the wire. The (110) /001] component was converted into a (110) fiber texture by wire drawing. The effective rotations were about axes contained in the lransverse plane. The preferred orientation associated with tungsten wire usually has been assumed to consist of a (110) fiber texture. This implies rotational randomness around the wire axis. Leber1 has shown that rotation about the wire axis may be restricted resulting in a preferred orientation designated as a cylindrical texture. Specific crystal planes tended to remain aligned parallel to the wire surface. This texture seemed to be the result of the swaging operation used in the intermediate stages of fabrication. Bhandary and cullity2 detected similar textures in swaged iron wires. Peck and Thomas3 suggested that the preferential alignment of crystal planes parallel to the wire surface was the result of tangential flow, characteristic of swaging. Wire drawing, following swaging, twisted the crystals about axes parallel to the wire axis, converting the cylindrical texture into a normal fiber texture.4 In this investigation, quantitative techniques were used to more accurately characterize the cylindrical texture and to study its conversion into a normal fiber texture. PROCEDURE The material investigated was lamp-quality tungsten. Three ingots were rod-rolled and swaged to 112 mils diameter, and were then drawn to 10-mil wire. Samples were obtained after each drawing pass. (110) and (200) pole figures were obtained from samples prepared as shown in Fig. 1. To form the sample shown in Fig. l(a), l-in. lengths of wire were glued side by side to form a l-in. square. The composite was ground and electropolished to form a diametral reference surface. For certain specific tests, samples were prepared as shown in Fig. l(b). This composite was made from 10-mil-thick strips prepared by grinding on parallel longitudinal planes. The polished reference surface in this case was, in essence, the wire surface. The two forms of samples [~igs. l(a) and l(b)] were related by a 90-deg rotation around the wire axis. Because of ease in preparation, most data was obtained from the diametral samples. The X-ray data were obtained using a Siemen's pole-figure goniometer. These data were not corrected for absorption or defocusing effects, since only the angular locations of the intensity maxima were of interest. Regions of the pole figure more than 80 deg from the center were not investigated. Partial monochromatization was achieved by the use of unfiltered copper radiation and a krypton-filled proportional counter. No evidence of spurious white radiation effects5 could be detected. Therefore, more elaborate X-ray techniques were not required. Intensity levels were chosen to show all pertinent details of the orientation distributions. The reference plane for the pole figures was the diametral section. The orthogonal reference directions, shown in Fig. 1, were the wire axis, the radial axis per-

Jan 1, 1965

By Pol Duwez, Spencer R. Baen

A LTHOUGH the practical importance of Fe-Cr--iV Mo alloys has long been recognized, constitution studies have been limited to a few alloys within rather narrow ranges of composition. The purpose of the present study was to establish the phase boundaries in the ternary diagram at a temperature of 1200°F (650°C).* The identification of phases and the determination of phase boundaries were based primarily on X-ray diffraction measurements and occasionally on microscopic observation. The methods used for locating the phase boundaries were essentially those described in detail by Andersen and Jette,' and by others.', The compositions of 180 alloys, prepared by powder metallurgy techniques, are shown in Fig. 1. The chemical analysis and mesh size of the powders which were used for the preparation of the alloys are given in Table I. The powders were mixed for 48 hr or longer, then compacted under 80,000 psi in a %-in. diam steel die. Each specimen weighed approximately 5 g. The compacts were sintered for 4 hr at 2500°F (1371°C) in an atmosphere of pure dry hydrogen (dew point near the temperature of liquid nitrogen). An open tray of chromium powder was placed upstream of the compacts to act as a "getter" for the last traces of oxygen or water vapor. In many cases this chromium powder was bright after sintering. Occasionally the upstream side of the powder was slightly greenish, but in all cases the downstream side was metallic. Some of the alloys contracted during sintering and some expanded as much as 20 pct. The latter alloys, which in all cases were brittle, were crushed in a tool steel mortar, repressed, and resintered for 4 hr at 2500°F. After sintering, the alloys were aged for ten days at 1200°F (650°C) in evacuated (105 mm Hg or better) fused silica tubes and were cooled rapidly to room temperature following the aging treatment. The use of the powder metallurgy technique in preparing alloys for structural investigation offers a simple method 'of avoiding contamination or non-homogeniety which could result from a melting operation. It is very often possible to dispense with chemical analysis of the alloys which have been prepared by the powder metallurgy method. In lieu of chemical analysis, it is necessary to determine the weight of the compact before and after sintering. The chemical composition of the alloy may be considered as that of the green compact, within the limits of accuracy determined by the loss of weight during sintering. In phase-diagram studies it is important to achieve homogeniety in structure, whether the alloys are prepared by powder metallurgy or by melting. Homogeniety means complete diffusion during the sintering of the alloys which are prepared by powder metallurgy. It has been found from experience that the best criterion for establishing the completeness of diffusion is the sharpness of the X-ray diffraction patterns. This criterion has been used throughout the present study. The X-ray diffraction data were obtained using powder cameras of either 214.86 or 71.62 mm diam. Copper, cobalt, or chromium Ka. radiation was used, the choice being based on the alloy composition. The powder samples were obtained by filing or crushing, depending on whether the alloy was ductile or brittle. In some cases, the powder was annealed for 4 to 6 hr at 1200°F in vacuum. The measurements were corrected for film shrinkage and absorption. The large camera, in which the film is mounted

Jan 1, 1952

By John Wulff, Robert Kamm, M. A. Steinberg

IN a previous paper1 from this laboratory, the development of a lead grid method for exploring the distribution of strain and density within metal powder compacts was described, In that work thin lead foil with rectangular holes cut at regular intervals was inserted with the powder fill, the arrangement pressed and then radiographed to permit measurement of the deformation of the lead grid. Densities at each grid element obtained in this manner were plotted as a function of the die dimensions. From such plots it was, found that the densest part of a compact pressed from one side (the top) is at the top outer region and the least dense at the bottom outer region -of the specimen. The axial density maximum occurs more often nearer the bottom than at the top. As a result of such exploratory measurements, it appeared reasonable to conclude that variations in density could be attributed in the main to die wall friction. Thus compacts of large diameter appeared relatively uniform in density except where the die fill had been uneven. Finally it was found that lubrication of the finely finished die cavity contributed more to magnitude and uniformity of density within the compact than interparticle lubrication. Since publication of the above results, it was found that circular-hole grids could be more accurately made and, when deformed within the powder, more readily measured and analyzed. Much of the former work was repeated and new results which include the effect of lubrication, compact height, pressure, speed of pressing and vacuum pressing are reported in the present paper. CIRCULAR-HOLE GRIDS AND ANALYSES OF RADIOGRAPHS Commercial lead sheet 0.008 in. in thickness was used in all the work reported. The 0.0938-in. diam holes were punched in the sheet on 1/8-in, centers to an accuracy of 0.001 in. The finished grid used contained eight or more holes in a row and from I to 24 rows. The lead sheet was clamped between two pairs of brass strips bolted to a small milling machine table which was itself bolted to a bench in correct position near a vise which held the punch. Travel of the lead grid in two dimensions was controlled by two steel lead screws calibrated in 0.001-in. divisions. A stripper plate was used on the punch to avoid distortion of the lead foil. A high carbon-high chromium (chrocar) one-piece steel die was used throughout the work. The die cavity was 1,125 in. in diam and the clearance between plungers and die wall was 0.001 in, The die was also used for pressing from both ends with two long plungers. Finally, lapping of die and plungers gave a surface whose rms value on an Abbot profilometer was 5 micro-in. The die walls and plungers were, except where otherwise noted, lubricated with a stearic acid suspension in benzene. This was put on in multiple layers and allowed to dry before filling the die.

Jan 1, 1948

By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By J. H. Hollomon, J. C. Fisher

THE fundamental problem concerning the fracture of both crystalline and noncrystalline solids is the divergence between the actual and the theoretically computed fracture stresses; the stress required for fracture, computed from the forces between atoms, is many times that actually observed with commercially available materials. Computations have been made1, 2 indicating that the theoretical fracture stress should be from 100 to 1000 times that actually observed. There are other incidental problems that have arisen, perhaps the most important of which is the problem of size effect often observed in the measurement of the fracture stress of non-metallic solids, such as glass. Another effect concerns the relation between deformation and the stress required for fracture. Experiments recently made with pearlitic steels indicate that the tensile fracture stress increases with increasing tensile deformation and decreases with increasing prior compressive deformation. This marked anisotropy of the effect of deformation on the fracture stress is in contrast with the essential isotropy of the flow stress. Early experiments on rock salt crystals by Joffé, et a13 have illustrated the effect of tensile strain in increasing the tensile stress required for fracture. A consistent theory must be constructed that will explain not only the divergence of the measured fracture stress from the theoretical value, the size effect, and the effect of deformation; but will also explain and predict the effects of combined stress, of temperature, of strain rate, and of metallurgical structure. With respect to this last variable, it has now been relatively well established that the carbide particle is the element of structure controlling the fracture of steels. In steels carbide particles vary in shape from plates to spheroids. It has been found that not only does the magnitude of the fracture stress depend upon the size and shape of these particles, but also its dependence upon strain is affected by changes in shape and size of the particles. The precipitate resulting from the age hardening of duralumin also modifies the fracture stress of this alloy. Nonmetallic inclusions greatly lower the fracture stress of all metals. The magnitude of the lowering depends on the size and shape of the included particles. In glass, the major source of the low fracture stress has been fairly conclusively demonstrated by Griffith4 to arise from real flaws or cracks present in the material. He showed that the stress concentration at the end of a defect was of sufficient magnitude to raise the stress at this location to a value comparable with the theoretical strength of the material. If the cracks were reduced in size, Griffith showed that the observed fracture strength increased by virtue of the decrease in stress concentration. He also pointed out that cracks disposed perpendicularly to the applied tensile stress would be more effective in lowering the fracture

Jan 1, 1947

By J. S. Crump, H. L. Stone

Laboratory studies have indicated that displacement of oil from a reservoir by means of a condensing gas drive results in extremely high oil recovery, approaching 100 per cent under the most favorable circumstances. A condensing gas drive is defined as a gas drive in which the gas utilized is appreciably soluble in the oil it is displacing. The laboratory studies consisted of a number of gas drive displacement experiments, all using a horizontal, sand-packed, steel tube as the laboratory reservoir. The experimental results indicate that the more soluble a gas is in the oil to he displaced, the more efficient that gar is as a displacing fluid. Experiments were conducted utilizing both a light, volatile crude and a heavy, asphalt crude as the in-place oil. In both cases, oil recovery was appreciably enhanced by solubility of the displacing gas. It is believed that the use of condensing gas drives would result in increased oil recovery from many reservoirs during either primary or secondary phases of production. INTRODUCTION Since the early days of the oil industry there has been an increasing awareness of the problems of oil recovery. During the last few decades particularly a growing recognition of the problems has led to widespread attempts on the part of the industry to increase oil recovery by improved technology. One method which has been used to increase recovery is the maintenance of reservoir pressure by injection of gas. Part of the beneficial effect resulting from this gas injection was to prevent evolution of the gas dissolved in the reservoir oil, since such evolution would cause the oil to shrink and become more viscous, thereby adversely affecting oil recovery. In most instances, the gas injected was predomillantly methane, and so the possibility of oil recovery by retrograde vaporization existed. Laboratory investigations of displacement of reservoir oils by methane, carried out at high pressure, have indicated that considerable additional recovery of light oils could be effected by vaporization, but only at the cost of a severe volumetric shrinkage of the residual oil which would cause a decrease in relative permeability to oil in the reservoir. Consequently, recovery of oil by physical displacement would be impaired. The study suggested, therefore, that recovery of oil might be enhanced by injecting into the reservoir a gas known to be appreciably soluble in the oil at reservoir conditions. Swelling of the oil due to solution of gas should result and yield a consequent increase in the relative permeability to oil. The work described in the following sections was, therefore, undertaken to investigate the possibility of increased recovery by this mechanism. Research similar to that reported in this paper has been conducted by The Atlantic Refining Co.1,2,3 In these studies, Whorton, et al, and Slobod, et al, used methane-rich gas to displace oil from model reservoirs. Solubility of the gas was achieved by keeping the reservoir pressure greater than the saturation pressure of the original oil, and the degree of this solubility was varied by operating at different reservoir pressures. Thus the Atlantic project was primarily a study of the effect of reservoir pressure upon oil recovery by gas drive. The objective of the work reported in this paper was to study the effect of gas composition upon oil recovery while holding the reservoir pressure constant. DESCRIPTION OF EXPERIMENTS The discussion of the preceding section suggests that

Jan 1, 1957

By M. H. Pilkuhn, H. Rupprecht

p layers on n-type substrates of GaAs were prepared by difhsion of zinc into these substrates. Experimental details about the diffusion technique will be presented. It will be shown that inhomogeneity in the substrate doping level and crystal shucture defects cause nonplanarity in the junction plane. These nonplanarities give rise to high threshold current densities. From incremental sheet-conductivity measurements the zinc profile is derived. Data about surface concentration and gradient of the zinc concentration at the junction are presented. Finally, some results of laser diodes, which were made of wafers with extremely planar diffusion fronts, are discussed. ThE investigations reported here are part of a program concerned with the materials aspect in the fabrication of GaAs laser diodes. This includes studies of the influence of crystal defects introduced both during the growth of the crystal and as a consequence of subsequent diffusion. Compared with the progress made in the investigation of structure defects, for instance by X-ray microscopy in materials like silicon, no similar results are known so far for the case of GaAs. The further progress in laser diodes will depend very much upon our knowledge of these structure defects and subsequently upon our ability to avoid them. Laser diodes of GaAs had been made mostly by diffusing an acceptor impurity, normally zinc, into an n-type substrate. This procedure was found more convenient than the inverse one for various technical reasons. We will follow this line and restrict ourselves to zinc diffusion only in this paper. DIFFUSION TECHNIQUES AND EXPERIMENTAL DETAIL In order to set a refgrence for our experiments, we used a standard procedure for the diffusion runs. The diffusions were carried out in a sealed quartz tube for 2-1/2 hr at 850°C. One milligram zinc arsenide (ZnAsz) per cu cm of the tube volume served as zinc source. Under these conditions the junction depth was between 25 and 30 p. It is assumed, according to the investigations of the zinc arsenide system by V. Lyons and V. ilvestri,' that ZnAs2 dissociates completely at 850°C into ZnsAsz and Asg. Since there is a condensed phase of ZnsAs2 in the tube at 850°C, the partial pressure of zinc is controlled by the pressure of the arsenic formed by the dissociation of ZnAs2. Due to the fact that the zinc partial pressure resulting from the dissociation of ZnsAsz is only a weak function of the partial pressure of arsenic, the amount of the initial ZnAs2 is not very critical. Experimentally, we found that the junction depth, as well as the surface concentration, was practically the same, if the ingots of ZnAs2 varied between 0.2 and 5.0 mg per cu cm. The wafers were oriented with the main faces in (100). Surface damage due to cutting and lapping was removed by a chemical-etch treatment in a rotating beaker (etch solution: HzSOr, H202, and HzO in a ratio 3:l:l). The GaAs substrate material was n type and doped with tellurium, selenium, silicon, or germanium. It was grown by means of horizontal or Czochralski techniques. After the diffusion process, junction depth and planarity were checked either by grooving with a

Jan 1, 1964

By Irving Cadoff, Richard Nolder

An analysis oj a series of samples of single -crystal silicon grown on sapphire shows that ,four distinct orientation relations exist. There are at least thirteen crystallographic planes which serve as substrates ,for epitaxial growth The model which assumes that silicon substitutes for aluminium and bonds with the oxygen atoms of the sapphire to form the first later for subsequent growth can account for the epitaxial geometry in all four cases. Multiplici-ties 01 specific orientations are found which are explained by the symmetry of both the sapphire and silicon crystal structures. It was reported in the previous paper' that single-crystal silicon films can be deposited on single-crystal a A1,03 (sapphire) with a wide variety of orientations. The silicon films, however, were found to deposit in only four different orientation relationships with respect to the sapphire substrate. The X-ray data have been analyzed to determine the plane and direction of atomic fit and an atomic model to account for the epitaxial relationships at the silicon-sapphire interface has been developed. These results are described in the present paper. EXPERIMENTAL The Laue X-ray data described in the previous paper were reduced to stereographic projections in a standard manner. These data were supplemented with X-ray reflection data obtained with -& E and A Full-Circle Goniometer (Electronics and Alloys, Inc.) mounted on a Phillips diffractometer unit. The silicon films were thin enough to result in characteristic reflections from the substrate as well as the silicon. The superimposed stereographic projections were analyzed to determine the orientation relationships. Ambiguities were resolved by referring to constructed models of various lattice planes for both silicon and sapphire. These lattice models were also used to develop the model for atom fit at the interface. DATA AND ANALYSIS 1) Crystal Structures. The crystallography of silico-n, which is of the diamond cubic class with a. = 5.4~, is straightforward. The sapphire structure is more complex and generally difficult to represent in pictorial form. It is of the rhombohedra1 class but usually referred to hexagonal axes. The transformation of indices between these two systems can lead to ambiguities which will have bearing on the analysis presented herein. Therefore, the basis used in this paper is described in the appendix. Referred to the hexagonal system, the parameters of sapphire are co = 12.95.&, a, = 4.75~, c/a = 2.73. All parameters are for room temperature. Figs. 1 and 2 illustrate schematically the hexagonal unit cell model of sapphire used for this analysis. The oxygen atoms are assumed to occupy positions in an idealized hexagonal array on basal planes. Their actual positions are in a slightly distorted hexagonal array. The aluminum-atom positions are scaled to their actual positions in the lattice with respect to the basal layers of oxygen atoms. It was found that an idealized model where the aluminum atoms are assumed to lie exactly at the octahedral interstices of the oxygen lattice, similar to that used by ~ronberg,' was not adequate for this study.

Jan 1, 1965

By R. W. Kraft, F. D. George, F. D. Lemkey

From a conszderation of the geometrically possible ways in which an array of lines or linear features in three-dimensional space can depart from a statistically random arrangement, a system was developed to describe and measure different types of anisotrypic arrangements of lines in opaque solids. The technique was applied to a specimen of unidirectionally solidified Al-Cwll, eutectic which contained microstructural imperfections termed lamellar faults. Experimental data obtained from photomicrographs of different facets of a grain of this alloy were then analyzed using this system. It was deduced that the defects, which are essentially linear in natuve, were predominantly parallel to one another but not parallel to the nominal growth direction probably because of some lateral heat flow during solidification. InGOTS of lamellar eutectic alloys which have been unidirectionally solidified under growth conditions which prevent colony formation consist of large elongated grains in which the lamellae are approximately parallel to one another. Deviations from a parallel lamellar structure within a grain are caused by extra lamellae which form occasionally during the solidification process. Three-dimensional analyses of such specimens have revealed that one extra platelet produces two defects, termed 1amellar faults, which can and do grow more or less independently of one another.' The faults are analogous in many ways to edge dislocations in crystals. If a lamella of one phase is considered to be basically two-dimensional, e.g., a surface, then a fault can be defined as the locus of points which delineates an edge (or half the periphery) of one extra lamella as it grows and forms bridges and saddles in an otherwise parallel arrangement oi lamellae, Fig. 1. Were it not for the fact that bridges and saddles occur in the structure, the extra platelet could be defined as the unit defect and the concept of linear faults of positive and negative character around the periphery of the extra platelet would be unnecessary. If an extra platelet is merely inserted (actually it is grown in) between other parallel platelets, the fault line around the periphery of the extra platelet would circumscribe one and only one platelet, namely the extra one, and the faults would lie in a plane parallel to the lamellae. But when an extra platelet merges with adjacent ones and each side grows independently of the other, it is no longer topologically possible to delineate "the extra plate." A fault circuit which either closes on itself or passes out of the specimen still occurs although it no longer will be coplanar with the lamellae. In fact, it is usually not even Planar even if the lamellae are. Under these conditions a concept that a specimen contains N extra platelets of a given size per unit volume would be very artificial and consequently meaningless. Therefore, because of the topological complexity of the alloys, it was deemed necessary to define one-dimensional

Jan 1, 1962

By R. T. Hukki

The purpose of this paper is to present an analysis of the unit operation of grinding and the circulating load, of the unit operation of classification and the circulating load, and of the two superimposed into one operation to clarify the overall trend of events relating the circulating load to the capacity of the closed circuit grinding system, to the specific surface area of the final fine product, and to the energy consumption in the closed circuit grinding process. The capacity of the closed circuit is frequently, if not always, determined by the classifier, not by the mill." With these words a startling idea was expressed in 1934 by Dorr and Anable.1 Today, some 30 years later, grinding in closed circuit is universally accepted. The basic curve presenting the capacity factor versus circulating load by Dorr and Anable has obviously been so convincing that not a single authoritative investigation regarding its validity seems to have been conducted. The only major subject of discussion appears to have been the relative merits of the 'high' and 'low' circulating loads. It seems to be universally agreed that much still remains to be hoped for regarding sharpness of classification. BASIC CURVES FOR CONSTANT MILL LOADING Fig. 1 presents a series of basic curves for constant mill loadings in function of new feed rate and circulating load. The mill loading indicated by each curve is the sum of hourly tonnages of new feed and circulating load. For example, at point 0 where the new feed rate is 100 t/h and the circulating load 300%, or 300 t/h, the mill loading is 400 t/h. In closed circuit grinding, the new feed rate corresponds to the rate of finished classified material produced. Although at this stage the effect of classification is excluded in construction of the basic curves, the trend indicated by these curves is strongly in favor of closed circuit operation under relatively small circulating loads. A study of the curves reveals that, e.g., a mill operating under a load of 200 t/h at point P where the new feed rate is 50 t/h and the circulating load 300% will also operate under the same total load at point Q where the new feed rate is 100 t/h and the circulating load 100%. In other words, a reduction of circulating load from 300% to 100% would lead to doubling of the new feed rate and doubling of the rate of production of finished material, without a change in the total mill loading. The obvious question is, is it also possible by a reduction of the circulating load in a closed industrial grinding circuit to increase the production of finished classified material and, if so, how and to what extent? GRINDING TESTS BY DORR AND ANABLE In a series of open circuit grinding tests reported by Dorr and Anable1 limestone was ground at various feed rates in a 3-ft ball mill. The original data are reproduced in Table I. It can be seen that with the increased feed rate production of -65-mesh material increased and the energy consumption per unit weight of the -65-mesh product decreased in the reverse ratio. The data shown in Table I have been reproduced for our purposes in Table II for a scale corresponding to grinding in a large industrial mill. This reproduction

Jan 1, 1968

By W. S. Keyes

The State of Nevada, known par excellence as " the Silver State," occupies the major portion of the wide plateau, or so-called Great Basin, lying between the Sierra Nevada range on the west and the Wahsatch range of the Rocky Mountains on the east. It extends from the 114th degree to the 120th degree of longitude, west of Greenwich. It is limited, on the north, by the 42d degree of latitude, and on the extreme south by the 35th degree of latitude. Its general shape is that of an irregular parallelogram, from which the lower or southwestern portion has been cut off by a diagonal southeasterly line; the missing portion forms a part of the State of California on the west. The Great Basin is made up of a succession of low hills, or minor mountain ranges, running very nearly north and south, with long valleys between them. All of these mountains are more or less metalliferous. On the westcrn rim, marking the eastern flank or foothills of the Sierra, we find granites, porphyries, and propylites. Here we note the great Comstock lode, with its free-milling gold and silver ores, and still further south the once prominent and the now reviving gold and silver-bearing districts of Esmeralda County, Nevada, and of Morro County, California. Next, at some distance to the east, we find the mining districts at and near Unionville, in Humboldt County. Still further to the east we find the Battle Mountain copper-silver district, north from the railroad, and southerly therefrom the Austin or Reese Ever, Belmont, and other districts. Still further east and north of the railroad, we find the Tuscarora, a new district of very

Jan 1, 1879

By Robert Maddin

The application of electrolytic polishing of metals introduced a new technique for preparing surfaces, especially for single crystals. This procedure generallv has been assumed to eliminate the strain introduced by mechanical polishing and to result in a more truly representative surface, particularly in the case of soft metallic materials. However, apparently little information is available concerning specific characteristics of a surface prepared electrolytically. The conventional method of mechanical polishing is known to produce a layer of distorted metal which is usually removed by a suitable chemical etchant. To what depth the strain introduced by mechanical polishing penetrates into the lattice is still obscure. The present investigation illustrates the apparently anomalous appearances of glide ellipses on electrolytically polished surfaces of aluminum single crystals. Experimental Procedure and Results Aluminum single crystals, 99.975 pct pure, remaining from the investigation of Found,' were polished electrolytically using a solution of fluoboric acid and a low current density. Laue back-reflection technique, interpreted after the manner of Greninger,2 was used to determine the orientation and the specimen axis rotation of the crystals. Three flat surfaces about 4 mm wide parallel to the specimen axis, one perpendicular to the theoretical slip direction and the other two 120° apart, were polished mechanically and repolished electrolytically. A tensile load was applied using a Southwark-Emery tensile machine at a rate of about 40 lb per min. Elongation was measured by noting the initial and final gauge lengths. X ray diffraction was used to obtain the usual x and X values in order to calculate the elongation and shear by plotting stereographically the specimen axis rotation by means of the Schmid-Boas formula.³ In Table I may be found the value of the gauge diameter, measured elongation, calculated elongation and shear for the crystals investigated. Fig I shows the initial and final positions of the specimen axes of the crystals. At a low magnification the slip lines developed on specimen Al-I appeared straight and rather evenly spaced. However, at a high magnification, the slip lines were seen to be composed of small markings which were present throughout the length of the specimen (Fig 2). The distance between the markings was fairly constant and their directions all parallel to One another' Fig 3-57 photographed On different surfaces of the specimen, illustrate the interesting appearance of these lines. It may be noticed from Fig 4 that the markings, which present the appearance of

Jan 1, 1949