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The Tuscarora mining district, which has been highly productive of gold and silver ores in past years, is situated about 50 miles north- west of Elko, Nevada. The town of Tuscarora lies at an altitude of about 6,000 ft on the west side of the Independence Valley. Precipitation, particularly the winter snowfall, is considerably greater than in many other parts of Nevada, and temperatures are lower. From Tuscarora can be seen-across Independence Valley in the mountains to the east, a distance of about 12 miles, the Freeport Minerals Jerritt Canyon mine, which seems to be-destined to become one of the great gold mines in the western hemisphere. Tuscarora, a gold and silver camp, was active from the early 1870s to 1903 and produced about $10 million in those 30 years. Ten major mines and several smaller ones were operated in an area of about 1.45 square kilometers (one-half squaremile). The deepest shafts were only 230 m (750 ft) but most of the ore came from about the 105 m (350 ft) levels. Mineralization above the water table, at about 30 m (100 ft), was mostly native silver and cerargerite with free gold. Below the water table the ore was rich in sulfides including argentite, stephanite, proustite, pyrargyrite, enargite, arsenopyrite, bornite, chalcopyrite, pyrite, sphalerite and galena. A number of the properties contain sizeable dumps of what was con- sidered waste rock when it was mined. These dumps aggregate over 408,000 mt (450,000 st) with one dump, the Navajo, containing over one-third of the total. A few grab samples taken in the summer of 1978 from some of the dumps indicated interesting silver values with minor gold content. AgAu Exploration Ltd., was organized to explore and develop these dumps into a heap leaching operation. In the fall of 1978 a campaign was started to lease, with front money payments on a royalty basis, three groups of claims on which were located a few hundred thousand tons of dumps. In September and October of 1978, a systematic program of sampling was started on the Navajo dump which was most favorably situated in that it was near to an area which would furnish good sites for heap leaching pads. At the time it was fully recognized that sampling of dumps was a most difficult problem. Because of the topography on which they were situated and the manner in which they were formed, each dump required its own special sampling technique.

Jan 1, 1981

By B. D. Thomas

GRAVITY concentration is a general term designating processes for separating and sorting granular material by means of forces that depend on the density, size and shape of the particles. When these forces are applied to the particles the latter are caused to move, those of a given density along one path and those of a different density along another, until ultimately they are sufficiently separated to be removed from the operation of the process. The forces producing this separation are in general complex and, unfortunately, no completely rigorous analysis of them has as yet been devised. The science of the hydrodynamics of viscous fluids deals with the little that is known about the problem. Every observer of nature is familiar with the fact that an object moving in a fluid encounters a force of resistance. We have only to walk against a brisk wind or stir a cup of coffee, or observe the slow fall of a grain of sand in water, to experience directly the fact that such forces exist. The exchange of force between an object and a fluid in which it is moving operates on the fluid as well as on the object. Thus a sailboat may be set in motion by the force exerted by the wind on the sail; but the sail also deflects the wind-furthermore, the water in which the boat floats is set in motion by the force exerted by the boat as it cleaves through the water. The wind is thus enabled to do work on the water through the intermediary of the boat. In general, an object moving through a fluid encounters a force that opposes the motion and also acts to change the motion of the fluid. In gravity concentration we are dealing with this force of resistance acting - on the granular particles that are to be separated. Furthermore, the motion induced in the fluid by a particle will in turn affect the motion of a neighboring particle. This effect will be reciprocated and in consequence there will be an exchange of forces between all the particles in the material. These effects are complex and the most that can be expected is that we may be able to determine in a qualitative way how they operate. In gravity concentration, then, the following types of forces may be distinguished as acting on the particles: 1. The force of gravity, which acts on every particle in the system in proportion to its mass. 2. Buoyant forces, which arise from the force of gravity acting on the fluid.

Jan 1, 1950

By F. Milton Lewis, Roshan B. Bhappu

The methods for preparing operating cost estimates for a proposed mining venture are outlined. The procedures for estimating the direct and indirect operating cost for proposed mining and ore processing facilities are reviewed. Profits from the by-products are credits to the total operating cost, direct plus indirect, and are subtracted to obtain the total net operating cost. The non-operating costs which are a part of the total expenses are defined but are not considered in this manuscript. A method for developing the operating cost for a typical copper concentrator in the southwest is described in detail.

Jan 1, 1978

By Francis R. Conley, John A. Sievert, John N. Dew

A brief review is presented of the past performance of a number of large, thin, highly permeable reservoirs with low dips in the Bolivar Coastal fields of Venezuela. The performance of these reservoirs indicates that the fluids are segregated vertically within the sand section by gravity. With this assumption, equations are developed which describe the performance under pressure maintenance operations. Methods of solving these equations and results of simple example calculations are presented. Example calculations indicate that under pressure maintenance conditions injected gas tends to {tow preferentially along the top of the sands and that encroaching water has a tendency to flow preferentially along the bottom. The expected performance of segregated fluids is discussed and compared with that of fluids which are uniformly distributed in any sand section. INTRODUCTION The field performance of a number of reservoirs described herein indicates that the fluids are segregated vertically within the sand section by the force of gravity. Thus, it was felt that any method used to predict the future performance of these reservoirs should consider the effects of segregation in the sand sections. A study of the available information on some of the reservoirs suggests that increased recoveries may be expected if the reservoir pressure is maintained by either crestal gas injection or flank water injection. To predict future performance of reservoirs under pressure maintenance operations, a method of analysis was needed which would account for segregation of fluids in the sand sections. Several methods of analysis have been developed to take into account the segregation of fluids in the reservoir as a whole1,3 To our knowledge no method considers segregation of the fluids within sand sections in the manner indicated by the past performance of several reservoirs in the Mara-caibo Basin. This paper outlines part of the work done in studying some of these reservoirs and contains a description of their performance characteristics. The analysis presented is restricted to pressure maintenance conditions, since space limitations prevent a full discus- sion of the development of the mathematical relations and the various methods of solving them. Only a sketch of the development of the mathematical relations is given. The various methods of solving these relations are pointed out, but the actual determination of solutions to various problems are omitted except for one example. It is felt that these results may aid in the study of reservoirs outside the Maracaibo Basin. Some concepts on which the present analysis is based are outlined by D. N. Dietz. However, the analysis presented herein includes several factors not considered by Dietz: (1) variations in permeability and in the cross section, (2) various shapes of the cross section, and (3) the production of fluids. Also, the mathematical development presented by Dietz differs considerably from our corresponding analysis. RESERVOIR CHARACTERISTICS The reservoirs under consideration, large and thin, with low dip and high permeability, are large to the extent that they contain from 0.5 to over four billion bbl of oil initially in place. The section thicknesses vary from 100 to 400 ft and the lengths from 10,000 to 40,000 ft. Thus, a length-wise cross section of the producing formation appears to be long and thin. The dip angles vary from 0 to 6 degrees and the average permeabilities vary from 0.5 to over three darcies. The reservoirs contain from 20 to 50 per cent shale inter-laminated with the productive sands. Most shale breaks within the major sands do not correlate from one well to the next, and correlation is often difficult, even between wells drilled from the same location. However, it is often possible to correlate the shale breaks between major sands for some distance. Herein we are concerned with the performance of reservoirs containing oil of gravities over 20" API. Past reservoir performance indicates good pressure communication and, in cases where pressure sinks have developed, large amounts of fluid migration have occurred. Few of the reservoirs have had initial gas caps, but also, few have been found to be highly under-saturated. Due to gravity segregation, secondary gas caps usually form before the pressure has been reduced more than 25 per cent of its initial value. The effect of gravity has not only been apparent on a reservoir-wide basis, but has also caused segregation of the reservoir fluids in productive sections. Proof of this is found from the results of selective well tests, workovers, and electric and various other types of logs. Evidence that

By F. E. Werner, B. L. Averbach, Morris Cohen

THAT bainite formed near the M, temperature bears a striking r esemblance to martensite tempered at the same temperature has been shown by the electron microscope.' By means of electron diffraction,' it has been established that carbide and cementite are present in bainite formed at 500°F (260°C); these carbides are also found in martensite tempered at 500°F (260°C).' The investigation reported here is concerned with an X-ray study of the matrix phases in lower bainite and tempered martensite. These phases have turned out to be dissimilar in structure; the matrix of bainite is body-centered-cubic while that of tempered martensite is body-centered-tetragonal. A vacuum-melted Fe-C alloy containing 1.43 pct C was studied. Specimens of 16 in. diam were sealed in evacuated silica tubing and austenitized at 2300°F (1260°C) for 24 hr. One specimen was quenched into a salt bath at 410°+7 °F (210°+4°C), held for 16 hr, and cooled to room temperature. The structure consisted of about 90 to 95 pct bainite, the re: mainder being martensite and retained austenite. A second specimen was quenched from the austen-itizing temperature into iced brine and then into liquid nitrogen. It consisted of about 90 pct martensite and 10 pct retained austenite. The latter specimen was tempered for 10 hr at 410°+2°F (210°+1°C). The specimens were then fractured along prior austenite grain boundaries (grain size about 2 mm diam) by light tapping with a hammer. Single aus-tenite grains, mostly transformed, were etched to about 0.5 mm diam and mounted in a Unicam single crystal goniometer, which allowed both rotation and oscillation of the sample. Lattice parameters were measured by the technique of Kurdjumov and Lyssak. This method takes advantage of the fact that martensite and lower bainite are related to austenite by the Kurdjumov-sachs orientation relationships Thus, the (002) and the (200) (020) reflections can be recorded separately, permitting the c and a parameters to be determined without interference from overlapping reflections. According to these findings, the matrix phase in bainite is body-centered-cubic and, within experimental error, has the same lattice parameter as ferrite (2.866A). On the other hand, martensite, tempered as above, retains some tetragonality, with a c/a ratio of 1.005t0.002. Most workers in the past have assumed that bainite is generated from austenite as a supersaturated phase, but the nature of this product has not been established. The question arises as to whether bainite initially has a tetragonal structure and then tempers to cubic, or if it forms directly as a cubic structure. If it forms with a tetragonal lattice, it might well be expected to temper to the cubic phase at about the same rate as tetragonal martensite. The martensitic specimen used here was given approximately the same tempering exposure, 10 hr at 410°F, as suffered by the greater part of the bainite during the isothermal transformation. About 50 pct bainite was formed in 6 hr at 410°F. On tempering at this temperature, martensite reduces its tetragonality within a few minutes to a value corresponding to 0.30 pct C.' Further decomposition proceeds slowly, and after 10 hr the c/a ratio is still appreciable, i.e., 1.005. Thus, even if the bainite were to form as a tetragonal phase with a tetragonality corresponding to only 0.30 pct C, which might be assumed to coexist with e carbide, it would not be expected to become cubic in this time. It seems very likely, therefore, that bainite forms irom austenite as a body-centered-cubic phase and does not pass through a tetragonal transition. The carbon content of the cubic phase has not been determined, but it could easily be as high as 0.1 pct, within the experimental uncertainty of the lattice-parameter measurements. It has been postulated that retained austenite decomposes on tempering into the same product as martensite tempered at the same temperature. There is now considerable doubt on this point. The isothermal transformation product of both primary and retained austenite at the temperature in question here is bainite," and the present findings show that bainite and tempered martensite do not have the same matrix. Acknowledgments The authors would like to acknowledge the financial support of the Instrumentation Laboratory, Massachusetts Institute of Technology, and the United States Air Force.

Jan 1, 1957

By J. E. Graham, A. H. Glenn

Oil operators engaged in drilling on the Continental Shelf of Louisiana and Texas are in agreement that adverse weather and wave action are two of the greatest hazards to the safety and efficiency of their work. It was ami-pated when the offshore operations commenced that such would be the case, and experience to date has verified this assumption. Because atmospheric conditions and wave action involve tremendous amounts of energy it is highly unlikely that it will be possible to control any but the most localized weather and wave phenomena within the foreseeable future. Thus. as long as the offshore operations involve the movement of small craft and barges over exposed waters, and the transfer of personnel and heavy equipment from these craft to either fixed structures or larger craft at close quarters, the weather and wave problem will remain. Taking into consideration the persistence of the wave and weather problem and the improbability of achieving a direct solution, the Humble Oil & Refining Company, in planning its offshore campaign investigated the possibility of forecasting wave and weather conditions in order to provide warnings of dangerous conditions and increase efficiency in day-to-day planning of work. It was recognized that predictions of wave and weather conditions based on meteorology and oceanography, both geophysical sciences, are not 100 per cent accurate and application of forecasts in the offshore work was dependent on whether they provided information which was sufficiently greater in accuracy than the layman's guess to be worth the expenditure involved. During World War 11. meteorology and oceanography were used with success in reducing danger resulting from environmental conditions and increasing efficiency of operations exposed to the elements. This success was partially the result. of improvement in the scientific techniques involved and the procurement and distribution of observational data, and partially due to the large scope of the military operations which meant that a reduction of losses of a relatively small percentage of the total cost amounted to a large figure expressed in terms of dollars. Since the offshore drilling involves an extremely large financial investment, it was considered that the experience of the Armed Services in successfully employing meteorology and oceanography might be duplicated in the oil industry. In addition. the oil industry's successful experience in utilizing seismology, geology, and terrestrial magnetism; all geophysical sciences, indicated that meteorology and oceanography, also of the family of geophysical sciences and sharing their scientific assets and liabilities, might be profitably put to use. Since the immediate problem involving the sciences of meteorology and oceanography in the offshore campaign is wave action, a program was inaugurated within the Humble Oil & Refining Company during June 1947. the purpose of which was to ascertain the applicability and limitations of wave forecasting in the offshore campaign. A summary of the effective wave forecasting techniques developed during the war was prepared in the form of a forecasting manual for the Continental Shelf off Grand Isle, Louisiana, by Bates and Glenn. After completion of this manual, experimental forecasts were prepared daily over a two-month period by Graham and Thompson to determine the accuracy of the forecasts. It was considered that the accuracy of the experimental forecasts justified a more extensive test under actual operating conditions in the offshore work and the firm of A. H. Glenn and Associates was set up under the sponsorship of the Humble Oil & Refining Company to work with the Humble Grand Isle District in providing forecasts of wave and weather conditions over a one-year period. This paper discusses the service now provided to the Grand Isle District, its applicability and limitations. TYPE OF FORECASTS REQUIRED It was apparent before the commence-mence of the forecasting service that a specialized type of forecast was required. Many of the weather elements of interest to the general public, such as rain and temperature, are of minor concern to offshore operators. On the other hand, such elements as wave height and wind speed and direction are of great concern in the offshore operations since variations in wave height of a few feet in the critical range divide safe from hazardous working conditions. To be of utility. a forecasting service for the offshore work must provide detailed forecasts of the elements which affect the operation. With this in mind, it was decided that forecasts would include the following information: average wave heights to the nearest foot, wind speeds within a range of approximately 5 miles per hour, and wind directions within 221 degrees. Since the procedure for forecasting these elements involves thorough analysis of weather data, it was decided to include a generalized forecast of weather conditions such as rain and cloud cover, although these are of secondary importance.

Jan 1, 1949

By C. Laird, C. E. Feltner

May different kinds of dislocation structures have been observed in strain-cycled metals and alloys. In order to understand their pattern and causes, an experimental program has been carried out to determine the influence on the dislocation structures of the three variables: 1) slip character of the material, 2) test temperature, and 3) strain amplitude. The results show that at high strain amplitudes cell structures me formed when the slip character is wavy, and that these are progressively replaced by uniform distributions of dislocations as the stacking fault energy is decreased. At lower strains, dislocation debris is formed which consists primarily of dipoles in wavy slip mode materials and multipoles in planar slip mode materials. Temperature merely acts to change the scale of the structure, smaller cells, and clumps of dislocation debris being associated with lower temperatures. It is shown that the results for many metals fit this pattern, which Parallels that occurring in unidirectional deformation. DISLOCATION structures produced by cyclic strain (fatigue) have been examined in a number of metals by transmission electron microscopy. These studies have produced a variety of interesting and often seemingly conflicting results. For example, different investigators have reported such structural features as cells.le4 bands of tangled dislocations,4'5 dense patches or clusters of prismatic dislocation loops, planar arrays,4'10 and various combinations or mixtures of these different structures. Most of these observations have been made on materials which were initially annealed and cyclically strained at low amplitudes resulting in long lives. Recently we have reported observations of the dislocation structures produced in copper and Cu-7.5 pct Al cycled at large amplitudes, resulting in lives of less than 104 cycles.4 These results, examined in combination with those in the literature, have suggested that a common or consistent structural pattern exists. Variations in this pattern appear to be determined chiefly by the three variables, namely, the slip character of the material,4,11 test temperature. and the strain amplitude. To verify this interpretation, we have studied [he influence of the above three variables (in different combinations) on the resultant structures in cyclically strained metals. Copper, fatigued at room temperature, was chosen as a reference state to which all other observations can be compared. The effect of slip character has been investigated by employing fcc metals of different stacking fault energy. Thus aluminum which has a more wavy slip character than copper, and Cu-2.5 pct A1 having a more planar slip char- acter, have been examined. The aluminum samples were fatigued at 210°K thus making their homologous temperature equal to that of copper at room temperature. The influence of temperature has been evaluated by examining the structures in copper at room temperature and 78°K. Finally the effect of strain amplitude was studied by looking at the structures at amplitudes giving lives ranging from 104 to 107 cycles. All of the specimens were examined at the 50 pct life level at which stage the structures have reached a stable configuration.12 I) EXPERIMENTAL PROCEDURE Strip specimens, 0.006 in. in thickness, were prepared from base elements of 99.99 pct purity or greater. Specimens were fatigued by cementing the strips to a lucite substrate which was subjected to reverse plane bending. This method of testing has been described e1sewhere.7 After fatiguing, specimens were thinned and examined in a Philips EM 200 which was equipped with a goniometer stage capable of ±30-deg tilt and 330-deg rotation of the specimen. On the basis of separate calibrations,13 allowances were made for the relative rotation and inversions between the bright-field images and the diffraction patterns. II) RESULTS AND DISCUSSION The life behavior of the materials under different test conditions is shown in Fig. 1 in the form of plots of total strain range vs cycles to failure. Comparisons of structures produced in the different materials were made at amplitudes which produced equal numbers of cycles to failure. The influence of strain amplitude on the structures produced in the reference state material (copper tested at room temperature) is shown in Fig. 2. At the 104 life level the structure produced comprises cells similar to those previously observed.3,4 They are approximately 0.5 p in diam and the cell walls are generally more regular or sharper than those produced by unidirectional deformation.14 At the 10' life level the

Jan 1, 1969

By A. H. Glenn, J. E. Graham

Oil operators engaged in drilling on the Continental Shelf of Louisiana and Texas are in agreement that adverse weather and wave action are two of the greatest hazards to the safety and efficiency of their work. It was ami-pated when the offshore operations commenced that such would be the case, and experience to date has verified this assumption. Because atmospheric conditions and wave action involve tremendous amounts of energy it is highly unlikely that it will be possible to control any but the most localized weather and wave phenomena within the foreseeable future. Thus. as long as the offshore operations involve the movement of small craft and barges over exposed waters, and the transfer of personnel and heavy equipment from these craft to either fixed structures or larger craft at close quarters, the weather and wave problem will remain. Taking into consideration the persistence of the wave and weather problem and the improbability of achieving a direct solution, the Humble Oil & Refining Company, in planning its offshore campaign investigated the possibility of forecasting wave and weather conditions in order to provide warnings of dangerous conditions and increase efficiency in day-to-day planning of work. It was recognized that predictions of wave and weather conditions based on meteorology and oceanography, both geophysical sciences, are not 100 per cent accurate and application of forecasts in the offshore work was dependent on whether they provided information which was sufficiently greater in accuracy than the layman's guess to be worth the expenditure involved. During World War 11. meteorology and oceanography were used with success in reducing danger resulting from environmental conditions and increasing efficiency of operations exposed to the elements. This success was partially the result. of improvement in the scientific techniques involved and the procurement and distribution of observational data, and partially due to the large scope of the military operations which meant that a reduction of losses of a relatively small percentage of the total cost amounted to a large figure expressed in terms of dollars. Since the offshore drilling involves an extremely large financial investment, it was considered that the experience of the Armed Services in successfully employing meteorology and oceanography might be duplicated in the oil industry. In addition. the oil industry's successful experience in utilizing seismology, geology, and terrestrial magnetism; all geophysical sciences, indicated that meteorology and oceanography, also of the family of geophysical sciences and sharing their scientific assets and liabilities, might be profitably put to use. Since the immediate problem involving the sciences of meteorology and oceanography in the offshore campaign is wave action, a program was inaugurated within the Humble Oil & Refining Company during June 1947. the purpose of which was to ascertain the applicability and limitations of wave forecasting in the offshore campaign. A summary of the effective wave forecasting techniques developed during the war was prepared in the form of a forecasting manual for the Continental Shelf off Grand Isle, Louisiana, by Bates and Glenn. After completion of this manual, experimental forecasts were prepared daily over a two-month period by Graham and Thompson to determine the accuracy of the forecasts. It was considered that the accuracy of the experimental forecasts justified a more extensive test under actual operating conditions in the offshore work and the firm of A. H. Glenn and Associates was set up under the sponsorship of the Humble Oil & Refining Company to work with the Humble Grand Isle District in providing forecasts of wave and weather conditions over a one-year period. This paper discusses the service now provided to the Grand Isle District, its applicability and limitations. TYPE OF FORECASTS REQUIRED It was apparent before the commence-mence of the forecasting service that a specialized type of forecast was required. Many of the weather elements of interest to the general public, such as rain and temperature, are of minor concern to offshore operators. On the other hand, such elements as wave height and wind speed and direction are of great concern in the offshore operations since variations in wave height of a few feet in the critical range divide safe from hazardous working conditions. To be of utility. a forecasting service for the offshore work must provide detailed forecasts of the elements which affect the operation. With this in mind, it was decided that forecasts would include the following information: average wave heights to the nearest foot, wind speeds within a range of approximately 5 miles per hour, and wind directions within 221 degrees. Since the procedure for forecasting these elements involves thorough analysis of weather data, it was decided to include a generalized forecast of weather conditions such as rain and cloud cover, although these are of secondary importance.

Jan 1, 1949

By G. L. F. Powell

g samples of Cu-20 wt pct Ag alloy have been mdercooled to a maximum of 197°C by melting under a slag of commercial soda-lime glass in a vitreous silica crucible. No grain refinement of the primary copper was observed in samples undercooled to the maximum of 197°C. When the samples contained a small amount of oxygen, the copper dendrites were partially recrystallized at undercoolings greater than 97°C. In previous papers'-3 reporting the grain structure of undercooled silver and copper, it was observed that grain refinement was dependent on both undercooling and oxygen content. Grain refinement occurred in undercooled silver when the degree of undercooling exceeded the range 153" to 175"C, while in Ag-0 alloys (0.12 wt pct) fine equiaxed grains were exhibited when undercooling was greater than 50°C. Similarly, copper samples undercooled as much as 208°C displayed fan-shaped growth from a single nucleation site, while the grain structure of Cu-O alloys (0.08 wt pct) was fine and equiaxed at undercoolings larger than 150°C. Thus the presence of oxygen greatly reduced the undercooling at which grain refinement occurred. It was also observed that the change in grain size resulted from recrystallization and was not due to an enhanced nucleation rate in the liquid-solid transformation. It is possible that the influence of oxygen on recrystallization is due primarily to its presence as a solute element. walker4,' reported that, although a grain size change did not occur in pure nickel until the undercooling exceeded 150°C, small grains were observed in samples of Ni-Cu alloy solidified at small and large degrees of undercooling. Jackson et al.6 suggested that the fine grained structure of the Ni-Cu alloy resulted from the melting off of dendrite arms during recalescence. This remelting process may occur in alloys as a result of segregation during freezing which causes a variation in liquidus temperature from point to point within a dendrite. It was therefore decided to undercool copper with a metallic alloying element to ascertain whether the presence of a metallic solute would have a similar effect to oxygen in inducing grain refinement. A Cu-Ag alloy was chosen, since both metals had been shown to behave similarly on undercooling. The alloy Cu-20 wt pct Ag was selected since the eutectic constituent outlines the initial growth form of the primary copper, so that the as-frozen grain structure is not obscured if subsequent recrystallization occurs. This paper describes the results of undercooling experiments carried out with Cu-20 pct Ag samples undercooled to a maximum of 197°C and the effect of oxygen content on the grain structure of the undercooled samples. EXPERIMENTAL Melting was carried out in a small cylindrical resistance furnace using "fine" silver granulate and oxygen-free high conductivity copper. The procedure adopted was to melt the required quantity of silver in air in a clean vitreous silica crucible for approximately 15 min, freeze, and add granulated commercial soda-lime glass to form a complete surface slag cover, after which the sample was melted and frozen several times to reduce the oxygen content. The glass slag cover was approximately 3 in. thick. Pieces of copper (=50 g) were added to the crucible until the required quantity to make 350-g samples of alloy had been charged. Each piece was added quickly to the crucible which was held at a temperature slightly above the melting point of silver. The piece was quickly pushed beneath the glass to minimize oxidation and any oxide coating usually decomposed before the piece had settled down into the silver. After the full quantity of copper had been added, the melt was stirred with a silica rod to hasten homogenization and a Pt/Pt 13 pct Rh thermocouple enclosed in a vitreous silica sheath inserted for temperature measurement. Heating and cooling curves were recorded on a potentiometric chart recorder fitted with a zero suppression unit. The milli-voltage range of the recorder was adjusted so that temperatures could be read to 1°C. Heating and cooling curves were taken every hour until three consecutive readings gave the same solidus-liquidus range, consistent with the solidus-liquidus range for this alloy composition by reference to Hansen and Anderko.7 Metallographic examination of samples frozen at this stage, failed to show any variation in composition from bottom to top of the ingot. Consequently, it was considered that the melt was homogeneous at this stage and undercooling experiments were then car-

Jan 1, 1970

By R. P. Laforce, ZJ. R. Low, A. M. Turkalo, D. F. Stein

The interaction of the crlloying eletnenls, nickel and chromium, with the impurity elements, antimony, pIzosphorus, tin, and arsenic, to producse reversible temper brittleness in a series of high-purity steels containing 0.40 wt pct C has been investigated. The alloyed steels contained approximately 3.5 pcl Ni, 1.7 pct Cr, and 0.05 to 0.08 pct of the particular irnpurity to be investigated. Susceptibility to teirlper embrittlement was measured by comparing the notched-bar transition temperature of each steel after quenching from the final temper and after very slow cooling (step cooling;) following the final temper. A plain carbon steel without alloying elements, bu/ ud/h 0.08 pel Sh, does not embrittle when step-cooled through the emzbrittling range of temperatures. The same embrittling treatment, applied to a steel with about the same antinzony content but with nickel and chvonziunz added, causes a 700°C increase in transition temperature. If chromium or nickel is the only alloying element, the increase in transition temperature is only 50%, again with antimony present. A carbon-free iron containing nickel, chromium, and antimony shou~s a 200°C shift in transition temperature for the same thermal treatment. Specific alloy-impurily interactions are also observed for the other impurity elements, phosphorus, tin, and arsenic. Additional investigations involving electron microscopy, trzicrohard-ness tests of vain boundaries, minor additions of zirconiutn and the rare earth and noble metals, nzainly with negative results, are also described. HE particular type of embrittlement investigated is that which is encountered in alloy steels tempered in the temperature range from about 350" to 525'C or slowly cooled through this range of temperatures when tempered above this range. This type of embrittlement is sometimes called reversible temper brittleness to distinguish it from the embrittlement indicated by a minimum in the room-temperature V -notch Charpy energy vs tempering-temperature curve encountered in the range 28 0" to 350°C. Temper brittle-ness seriously restricts the use of many alloy steels since it precludes tempering or use in the embrittling range of temperatures and may significantly raise the ductile-brittle transition temperature of heavy-section forgings and castings tempered above the embrittling range, since such sections cannot be sufficiently rapidly cooled after tempering to avoid embrittlement. The very voluminous literature of temper brittle-ness up to about 1960 has been reviewed by woodfine' and LOW.' Of particular significance to the present investigation was the demonstration by Balajiva, Cook, and worn3 that high-purity Ni-Cr steel does not exhibit temper brittleness and the subsequent detailed and systematic study by Steven and Balajiva~ of the effect of impurity additions on the susceptibility to embrittlement of Ni-Cr steels. Steven and Balajiva showed that, of the impurities which may be found in commercial steels, Sb, As, P, Sn, Mn, and Si could all produce temper brittleness in a high-purity Ni-Cr steel. The principal purpose of the present investigation was to study the effects of particular alloy-impurity combinations on susceptibility to temper embrittlement. The steels used were high-purity 0.30 to 0.40 wt pct C steels containing 3.5 wt pct Ni and 1.7 wt pct Cr, separately or in combination. The susceptibility of these steels was then determined when approximately 500 ppm by weight of antimony, arsenic, phosphorus, or tin were added as an impurity. The melting, casting, and forging practices used in the preparation of the materials investigated are described in Appendix A. Table A-I in this appendix shows the analysis of all steels to be discussed. The steels were produced as 20- or 2-lb heats. The smaller heats were used after it had been demonstrated (see Appendix B) that a small, round, notched test specimen could be used to measure the shift in the ductile-brittle transition temperature caused by temper brittleness with about the same result as that obtained by Charpy testing. HEAT TREATMENT Unless otherwise noted, all steels were tested for embrittlement in the tempered martensitic condition. A typical heat treatment for a 0.40 C, 3.5 Ni, 1.7 Cr steel was: 1 hr at 870"C, in argon, quench into oil at 100"C, quench into liquid nitrogen, temper 1 hr at 625"C, and water-quench. The warm oil quench was used where quench-cracking was encountered; otherwise the initial quench was into room-temperature oil or water. For other compositions austenitizing temperatures were 50°C above Acs with the remainder of the thermal cycle the same. Steels in this condition, with no further heat treatment, are designated as non-embrittled. The above quenching and tempering cycle for the 0.40 pct C steels resulted in as-quenched hardnesses of 48 to 53 RC and as-tempered hardnesses of 24 to 31 Rc except in the case of the plain nickel or plain carbon steels. In these, the as-tempered hardness was as low as 80 to 90 Rg. No attempt was made to adjust the tempering temperature to obtain the same hardness in ali steels since it was felt that a uniform thermal cycle was more important than exactly equivalent hardness values. Pro- the standard quench and temper described above, the standard embrittling treatment was "step-cooling". For this the thermal cycle was: 593"C, 1 hr; furnace-cool to 538"C, hold 15 hr; cool to 524"C, hold 24 hr; cool to 496"C, hold 48 hr; cool to 468'C, hold 72

Jan 1, 1969

By John C. Calhoun, R. C. Newman

A report is made of experimental work performed on the capillary retention of water within porous solid systems, the displacement being accomplished with air and various organic liquids. A portion of the experiments were designed to measure the lowering of vapor pressure of water within a porous solid with subsequent conversion of such vapor pressure data to capillary pressure values. The form of the capillary pressure curve at high capillary pressures has been elucidated from this data. Certain theoretical approaches are presented to indicate the correlation between work done by previous investigators. The present work is correlated also with theory. Surface area values are calculated for the various core systems studied. INTRODUCTION Leverettl in 1941 presented a paper which gave the essential concepts of capillary behavior in porous solids. His presentation included both theoretical and experimental aspects of the problem. He defined the term "capillary pressure" and applied it to an ideal porous system. His work included the definition of a dimensionless quantity which was a function of fluid saturation and which could be correlated with porosity and permeability for clean, unconsolidated sands. His experimental work was performed by the drainage of water from packed columns of unconsolidated sands. Subsequently, other authors have presented experimental techniques which permit the determination of capillary pressure data on small core samples. Data have been presented on porous systems other than unconsolidated sand and with the use of liquids other than water. Notable among these are the works of Hassler, Brunner and Deahl,2 Bruce and Welge,³ Amyx and Yuster, and Purcell. Others have indicated the applicability of such data to field problems without regard to the theoretical aspects of the capillary pressure saturation function. Within the recent published literature there have also been reported studies of the correlations between capillary pressure data and other fundamental properties of porous solids. It was the intent of the present reported work to investigate the behavior noted by water and various other liquids within porous systems in an attempt to amplify existing correlations between capillary properties, surface properties, and other fundamental characteristics of porous systems. The experimental work described here was performed as two different investigations but due to its nature it is reported as separate phases of the same general topic. CAPILLARY PRESSURE AND VAPOR PRESSURE LOWERING It has long been recognized that the vapor pressure above the curved surface of a liquid is a function of the curvature of the liquid surface." The capillary pressure is also a function of the curvature of the liquid surface. Both capillary pressure values and vapor pressure lowering are, therefore, functions of the liquid saturation of a porous solid. A quantitative relationship between the vapor pressure lowering and the capillary pressure can be simply developed by considering a porous solid system containing water in equilibrium with its vapor. The capillary pressure at any height within the system is defined as Pc= Pv -P1.......(1) where PI is the pressure in the vapor phase and PI is the pressure in the liquid phase. Consider that both the water and its vapor are continuous phases within the system and that at any point the two phases are in equilibrium. The gradients in the liquid and vapor columns within the porous system are: PI = plgdh dPv = pvgdh By integrating these gradients from the point where h = 0 to the height h, values of PI and PI at the point h are found. Let the point where h = 0 be that where Pc = 0. At this point also Pv is equal to Pve, the equilibrium vapor pressure of the liquid above a flat surface. From the first of these integrations since p is independent of height: P = p1gh + P, From the second, by substituting pv = PvM/RT, where M is the molecular RT weight: Pv M Pvo- RT gh By combining the two last equations to eliminate h, one obtains: P1 RT Pv Substituting, values for Pv and Pi in equation (1) gives PyRT RT Pv which is approximately Pc=RT/Mp1 In Pvo/Pv .......(2) This equation relates the vapor pressure above a curved surface with the capillary pressure across the curved surface in terms of measurable quantities. The equivalent of this equation is given by Freundlich."

Jan 1, 1949

By John C. Calhoun, R. C. Newman

A report is made of experimental work performed on the capillary retention of water within porous solid systems, the displacement being accomplished with air and various organic liquids. A portion of the experiments were designed to measure the lowering of vapor pressure of water within a porous solid with subsequent conversion of such vapor pressure data to capillary pressure values. The form of the capillary pressure curve at high capillary pressures has been elucidated from this data. Certain theoretical approaches are presented to indicate the correlation between work done by previous investigators. The present work is correlated also with theory. Surface area values are calculated for the various core systems studied. INTRODUCTION Leverettl in 1941 presented a paper which gave the essential concepts of capillary behavior in porous solids. His presentation included both theoretical and experimental aspects of the problem. He defined the term "capillary pressure" and applied it to an ideal porous system. His work included the definition of a dimensionless quantity which was a function of fluid saturation and which could be correlated with porosity and permeability for clean, unconsolidated sands. His experimental work was performed by the drainage of water from packed columns of unconsolidated sands. Subsequently, other authors have presented experimental techniques which permit the determination of capillary pressure data on small core samples. Data have been presented on porous systems other than unconsolidated sand and with the use of liquids other than water. Notable among these are the works of Hassler, Brunner and Deahl,2 Bruce and Welge,³ Amyx and Yuster, and Purcell. Others have indicated the applicability of such data to field problems without regard to the theoretical aspects of the capillary pressure saturation function. Within the recent published literature there have also been reported studies of the correlations between capillary pressure data and other fundamental properties of porous solids. It was the intent of the present reported work to investigate the behavior noted by water and various other liquids within porous systems in an attempt to amplify existing correlations between capillary properties, surface properties, and other fundamental characteristics of porous systems. The experimental work described here was performed as two different investigations but due to its nature it is reported as separate phases of the same general topic. CAPILLARY PRESSURE AND VAPOR PRESSURE LOWERING It has long been recognized that the vapor pressure above the curved surface of a liquid is a function of the curvature of the liquid surface." The capillary pressure is also a function of the curvature of the liquid surface. Both capillary pressure values and vapor pressure lowering are, therefore, functions of the liquid saturation of a porous solid. A quantitative relationship between the vapor pressure lowering and the capillary pressure can be simply developed by considering a porous solid system containing water in equilibrium with its vapor. The capillary pressure at any height within the system is defined as Pc= Pv -P1.......(1) where PI is the pressure in the vapor phase and PI is the pressure in the liquid phase. Consider that both the water and its vapor are continuous phases within the system and that at any point the two phases are in equilibrium. The gradients in the liquid and vapor columns within the porous system are: PI = plgdh dPv = pvgdh By integrating these gradients from the point where h = 0 to the height h, values of PI and PI at the point h are found. Let the point where h = 0 be that where Pc = 0. At this point also Pv is equal to Pve, the equilibrium vapor pressure of the liquid above a flat surface. From the first of these integrations since p is independent of height: P = p1gh + P, From the second, by substituting pv = PvM/RT, where M is the molecular RT weight: Pv M Pvo- RT gh By combining the two last equations to eliminate h, one obtains: P1 RT Pv Substituting, values for Pv and Pi in equation (1) gives PyRT RT Pv which is approximately Pc=RT/Mp1 In Pvo/Pv .......(2) This equation relates the vapor pressure above a curved surface with the capillary pressure across the curved surface in terms of measurable quantities. The equivalent of this equation is given by Freundlich."

Jan 1, 1949

By B. H. Caudle, L. H. Silberberg

Reservoir depletion by natural water drive is typified by the movement of water from an aquifer into the adjacent oil-bearing formation. Prior studies of this type 01 water movement have generally neglected the resistance to flow in the aquifer and its effect on the movement of water into the oil bearing zone. A method for designing and operating scaled models of such reservoir systems is presented. Experimental data on a model of an edge-water-drive reservoir are shown and discussed. INTRODUCTION Most petroleum reservoirs derive at least a part of their productive capacity from water influx. This water may be injected from the surface or it may come from an aquifer adjacent to the oil zone. In either case, the reservoir engineer must be able to estimate the advance of the water as a function of either the elapsed time or the fluid produced. This paper describes a type of fluid flow model which includes the effect of viscous and gravitational forces in the reservoir and the surrounding aquifer. Natural water influx can be divided into three general (but widely overlapping) categories according to the direction of flow in the aquifer. These are shown schematically in Fig. 1. Fig. l(a) illustrates an edge-water-drive mechanism. In this case, water advances updip along the stratum but the movement of water is essentially horizontal and very little of the oil is actually underlain by water. The bottom-water drive (Fig. l(b)) is characterized by a thick aquifer underlying the oil zone. The water movement is generally vertical in the aquifer. The third category is illustrated in l(c). Referred to as the "thin oil column", this type of oil accumulation consists of oil over water in a relatively thin stratum. Fluid movement is horizontal in both the oil and water zones, except close to the producing well. One characteristic which all three of these types have in common is that part of the water flow takes place in the water invaded region of the oil reservoir while the remainder of the water flow occurs in the aquifer. The resistance to the flow of water usually will not be the same in these two regions. This occurs because the porous rock normally contains only water in the aquifer, while the water-invaded region always contains microscopic globules of bypassed oil (residual oil) which interfere with the flow of water through the rock. The production history of any type of a water-drive system is a function of two phenomena — where the water goes, and how it displaces the oil in the area invaded by the water. It is usually impractical to study these two phenomena at the same time. In most cases one type of analysis is used to predict the gross movement of water in the reservoir, while a different type of analysis is employed to determine the amount of oil to be recovered from the gross volume contacted by the water. The portion of the oil reservoir which is invaded by water is mainly a function of the resistances to fluid flow in the several parts of the flow system. This gross water influx in the three types of natural water drive typically results in water cusping to the production wells either from the side or from below (water coning). In 1747, Muskat described a greatly simplified mathematical model for predicting the area invaded by water in a bottom-water-drive reservoir.1 This model used the Laplace equation and suitable boundary conditions to describe the isopotentials and streamlines in the flow system. The use of this model assumes that (1) the reservoir rock is homogeneous in nature, (2) the oil and water mobilities are equal, (3) there is no oil flowing in the water invaded region, and (4) external forces — such as gravity — do not affect the flow. This method has been used for both natural water drives and water injection projects. In this, as in most models, the method of images is used to reduce the size of the model necessary to describe the reservoir. The assumption of equal viscosities and permea-

Jan 1, 1966

By R. O. Leach, O. W. Wagner

Because of unfavorable wetting conditions much residual oil is left when a porous material is Pushed by water. Methods suggested to change reservoir wetting to improve oil displncernrnt efficiency are generally expensitlr. The present 1aborator.y study was undertaken to gain an under.standinx of the factors which determine reservoir wettability, arid to find out if oil displacement efficiency might be improved by a wettahility change accomplished at low cost in on oil reservoir. Contact angle measurements were made on mineral surfaces using sevc.r~zl sets of reservoir oil and water samp1es. Results of the contact angle studies suggest that reservoir wetta-hility may he primarily determined by natural surface-active substances present in the reservoir fluids. The effect of changing sa1inity and pH of the water phase was studied. The re.suits suggest that gross changes in preferential wettability might be acc~o~npli.shed by injection of water containing simple chernicnls to alter pH or salinity in the reservoir. Such treatment could he much less expensive than injection of commercial surface-active agents. Waterflood tests have also been made using synthetic cores and oil and water having wening characteristics similar to those of reservoir fluids. Cores initially oil-wet were flooded in such a way that they were made prefermtial1y water-wct by the advancing flood water. This reversal in preferential wettability achieved greater oil displacement efficiency than when either oil-wet or water-wet conditions were maintained throughout the flood. For the systems studied, the higher the oil viscosity the greater the percentage improvement obtained over conventional waterflood recovery. This suggests that a flooding process making use of wettability-reversal may extend the oil viscosity range over which water flooding is attractive. Because a precise adjustment of reservoir wettability does not seem to be required, and because altering the pH or salinity in some reservoirs may be inexpensive, it appears that a waterflooding process employing wet-[ability-reversal could find .succesful field application. I NTRODUCTION The efficiency with which water will displace oil from a porous material is related to the nature of the capillary forces present. These in turn are controlled by the preferential wetting of the solid by the two fluids. Because of unfavorable wetting conditions, 30 per cent or more of the original oil in place may remain unrecovered in that portion of a reservoir flushed by water. This paper is concerned with the possibility of improving waterflood oil displacement efficiency by alterations in the wettability of the porous material. A laboratory study was made to gain a better understanding of the factors which control reservoir wettability, and to determine if the oil displacement efficiency could be improved by some inexpensive means of manipulating wettability of the porous medium. Contact angle measurements were made with several natural and synthetic oil, water and solid systems (1) to obtain a better understanding of how to duplicate reservoir wettability in the laboratory, and (2) to discover possible means for changing preferential wettability of natural reservoir systems. Flooding tests were also made in synthetic systems to determine if oil displacement efficiency could be improved by those wettability manipulations suggested by the contact angle measurements. Based on these studies a possible method for improving waterflood oil displacement efficiency is presented. This method involves causing an originally oil-wet porous material to become preferentially water-wet during the course of a water flood. The purpose of this paper is to present results of the laboratory studies. THEORY Rock surfaces in some oil reservoirs are believed to be covered with a firmly attached bituminous or other organic coating. Such surfaces would be preferentially oil-wet in the presence of both oil and water, regardless of composition of reservoir fluids. Other reservoirs are believed to contain rock surfaces not permanently coated with such materials, and which would be preferentially wet by water in the presence of water and oil free from surface-active substances. However, when the reservoir fluids do contain certain natural surface-active materials in sufficient quantity, rock surfaces acquire a degree of preferential oil wettability caused by adsorption of these natural surface-active materials on the solid. The equilibrium amount of these materials adsorbed per unit surface area is believed to depend upon their concentration in the bulk liquid phases.

By John E. Willson, Ben L. Seegmiller

A portable electronic instrument was designed and constructed to detect unknown stress magnitudes in rocks. The principle used to detect stress is based on the propagation velocity method. This method allows the stress in a rock subjected to a load of unknown magnitude to be determined, provided that the wave velocity-stress relationship for similar rock is known. This is accomplished by measuring the travel time of longitudinal mechanical waves passing between two points a set distance apart in a rock. The velocity of the wave is calculated and the stress determined from the wave velocity-stress relationship. If the sending and receiving transducer spacing is constant, a time vs. stress relationship rather than the velocity-stress relationship may be used. The method is nondestructive and tests can be made without drilling or otherwise disturbing the rocks. The first studies undertaken in the United States to determine stress in rocks using propagation velocity techniques were reported by Obert1,2 in 1939 and 1940. The Soviet Union first reported using propagation methods to study rock pressures in 1951.8 Success of the method led to the development of a pulse-type ultrasonic seismoscope4 in 1953. Using this instrument, Ivanov and Betaneli5,6 in 1963 succeeded in devising and testing under field conditions a method of investigating coal pillar stresses. In 1967 Osipova7 reported results of similar studies in the Nakhichevan salt mines. In France, Tincelin8 has used the propagation velocity method to study the stress distribution in iron ore pillars. Uhlmann9 has investigated stresses in salt and potash pillars in Germany, using velocity techniques. Determination of uniaxial stress by propagation velocity methods is limited to rocks which have readily detectable wave velocity-stress variations. The present stress detection instrument is restricted in application to rocks which have a velocity change under stress of at least 300 fps. Examples of rocks which meet this requirement are sandstones, coal, and possibly some limestones. Testing of this instrument was limited to a laboratory study and the results may or may not be indicative of what would be found in a field test. A program of field experiments to study the feasibility of using this instrument to determine mine pillar and tunnel stresses is in progress. Instrument Design The instrument has two main components: A probe and a control-display unit. The probe is a hand-held device to which two identical rodlike transducers are rigidly mounted. Coaxial cable connects the probe to the control-display unit which is mounted in an enclosed carrying case measuring 7 % x 9 x 13 in. The instrument is designed so it may be carried and operated by one man. Weight of the probe and enclosed control-display unit is approximately 20.1b. The probe consists of two transducers identical in construction. One transducer is used to convert electronic pulses to mechanical waves and transmit these waves into a rock. The other detects the transmitted waves in the rock and converts them back into electronic signals. The basic element in both transducers is a piezoelectric crystal. The crystal is a disk made of lead titanate zirconate and has a natural resonant frequency of 400 kHz ±1% in the thickness mode. A schematic of one of the two identical transducing elements is shown in [Fig. 1.] A spacing of 6 in. between sending and receiving transducers has been found to be most satisfactory. The control-display unit consists of a pulse generator and a 1-in. oscilloscope. Various electronic devices are used for the power supply, amplification, and calibration. The amplitude of the square wave from the pulse generator can be continuously varied between 0 and +20 vdc. Pulse width can be set at 1, 2, 3, or 4 µsec. The repetition rate of the pulse can have the following values: 50, 75, 100, 150, 200, 250, 300, 400, 500, 750, and 1000 Hz. The oscilloscope delay system allows the travel time of the longitudinal wave passing through a rock to be measured to an accuracy ±0.1 µsec in the range from 0 to 995 µsec. Fig. 2 is a schematic of the various electronic sections in the control-display unit. Laboratory Testing The first step in using the instrument is to develop a velocity-stress or a time-stress curve for the par-

Jan 1, 1972

By T. S. Plaskett

A striated structure perpendicular to the growth axis was observed by the copper-decoration tech-nique in dislocation-free, .float-zoned silicon crystals. The striations, which were spaced about 100 p apart, fitted the relationship d = f/u , where d is the spacing, f is the growth rate, and u is the crystal rotation rate. Each stria was resolved into an UNDOPED silicon crystals pulled from quartz crucibles by the Czochralski technique usually exhibit a striated structure perpendicular to the growth axis.'-' This structure has been attributed to oxygen segregation, with the oxygen being introduced from the quartz crucible. If the crucible is rotated, the level of oxygen contamination has been reported as high as 10° atoms per cu cm.10 These striations are similar to solute striations commonly observed in doped Czochralski-grown crystals. The periodic nature of the striations is caused by a periodic variation in the growth rate",12 which is attributed mainly to thermal gradients in the melt.13 A finer striated structure14 attributed to constitutional supercooling is sometimes observed between the coarse striae. The oxygen striations have been observed by infrared transmission techniques,' by the copper-decoration technique,' by X-ray diffraction microscopy,6-8 and by 9 p absorption measurements3 on crystals pulled from the melt both with and without dislocations. In this investigation float-zoned dislocation-free crystals were examined by the copper-decoration technique. The level of oxygen for float-zone material is less than 1016 atoms per cu cm the lower limit of detection by 9 p absorption measurement. EXPERIMENTAL TECHNIQUE The crystals were grown by the float-zone process with the rf heating coil outside of the quartz envelope containing the silicon. All float zoning was done under an atmosphere of purified helium. The Dash technique15 was used to grow the crystal dislocation-free. This involves growing the crystal initially with a diameter between 2 and 3 mm and at array of starlike precipitates of copper. The strucLure was not .found at the surface tor a depth of about 1.5 mm, or in a region of similar width ahead of a dislocation network. The structure is postulated to consist of vacancy clusterings or dislocation loops. very rapid rates, about 20 mm per min, for a distance of about 3 cm. The diameter of the crystal is then increased to the diameter of the source of silicon, which in this case was about 19 mm. Because of the arrangement of the apparatus, the zone was passed downward rather than upward, contrary to the standard float-zoning practice. Also, the source was rotated rather than the seed. ziegler17 has made dislocation-free crystals by a similar technique but has passed the zone upwards. The starting material was zone-refined and had a p-type resistivity of 150 ohm-cm. The major impurity was boron; the total impurity excluding the boron was reported by the supplier (Dow-Corning) to be typically less than 2 x 1013 atoms per cu cm. The crystals were examined by the Dash copper-decoration technique18'19—a method in which about 10" atoms per cu cm of copper are diffused at a temperature between 900" and 1000°C into silicon which is then quenched to room temperature. On quenching, the copper precipitates on crystalline defects which are then visible when viewed by transmission infrared microscopy. The photomicrographs shown were taken either of the infrared image tube screen or directly on infrared film. All sections prior to decorating were chemically polished and, for some sections, given a sirtlZ0 dislocation etch-pit examination. After decorating, the samples were mechanically polished. RESULTS A photomicrograph, taken in transmission of a decorated cross section, is shown in Fig. 1. The portion of the section shown is near the surface of the crystal. The entire cross section showed no dislocation etch pits after being given a Sirtl etch treatment. It is seen that the copper precipitated randomly. Each precipitate, as has been reported by others, was found to have a starlike structure.

Jan 1, 1965

By M. Bevis, E. O. Fearon, P. C. Rowlands

Fe-Ni and Fe-Ni-C martensite specimens have been deformed in compression at room temperature and the habit planes of operative deformation twins determined by two-surface optical trace analysis. The full orientations of the martensite crystals were determined from divergent X-ray beam diffraction patterns. The experimental results are in excelled agreement with predicted twinning modes. In particular, the habit planes of some deformation twins in bcc martensites are consistent with a "Type XI compound'' twinning mode with Kl, Kz, 71, 77~ elements given by {5, 8, 11) {ioi}, (33) (ill) Tetragonal derivatives of this mode are operative in bct martensites. UnUSUAL deformation twinning modes have been reported by Richman' to occur in Fe-Ni-C martensites with bcc and bct structures. The twin habit planes were determined by single-surface trace analysis (pole locus method) and the remaining twinning elements were determined from the geometry of twin-twin intersections. The indices assigned to the observed habit planes are (3 101, "(089)" and "{0, 1,13)" or "{1,2,7} ", and only in the first case do the twinning elements correspond to a predicted twinning mode. This is mode 1.4 in the paper by Bevis et al. The results presented in Ref. 2 indicate that previously unpublished bcc and bct modes should be operative in preference to the (130) mode and anomalous modes reported by Richman. In view of these results and the uncertainties involved in determining habit planes from single-surface trace analysis and twinning elements from twin-twin intersections5 a two-surface trace analysis of deformation twins in Fe-Ni and Fe-Ni-C martensites has been carried out. EXPERIMENTAL PROCEDURES Two alloys with compositions Fe-23 pct Ni-0.6 pct C and Fe-30.4 pct Ni were prepared from 4N pure materials by induction melting under a vacuum of 10"5 mm Hg. The alloys were homogenized at 1350'~ for 5 days. Both of these alloys are austenitic at room temperature with M, temperature - — 50"C. The aus-tenite grain size of the Fe-Ni-C alloy was approximately 300 to 400 p. The Fe-Ni alloy was remelted in a vertical tube furnace and the melt lowered slowly from the hot zone of the furnace to produce s ingle -crystal austenite specimens. Specimens approximately 10 by 5 by 5 mm were cut from the ingots and quenched to various temperatures below the Ms temperature. The specimens were elec-tropolished in a 10 pct perchloric acetic electrolyte before being deformed in compression at room temperature. Martensite plates which exhibited profuse deformation twinning were selected for analysis and the specimen polished on a second surface such that the two surfaces which contained the martensite plate enclosed an obtuse angle of approximately 145 deg. The specimens were then electropolished to reveal the traces of the deformation twins on both surfaces. The full orientations of the martensite crystals were determined using a divergent X-ray beam technique (Kossel line technique) employing an AEI SEM2 electron probe microanalyzer. Details of this technique which include a detailed description of the Kossel camera attachment to the microanalyzer used in the present experiments have been discussed elsewhere.3 Only additional details relevant to this investigation are discussed here. The specimens were mounted with one surface normal to the incident electron beam as illustrated schematically in Fig. 1. The martensite plates to be analyzed were located using the normal scanning equipment of the microanalyzer. The position of the electron beam and hence the position of the source of divergent X-rays generated within the crystal could be located to within 1 p. Exposure times of approximately 8 to 10 min were required for back-reflection Kossel patterns and it was found that useful diffraction patterns could be obtained consistently from heavily deformed martensite plates. A reference line (carbon contamination mark) produced on the two surfaces of the specimen by scanning the electron beam in a direction having a known relationship with the reference !ine in the X-ray camera enabled the full orientation of the crystals to be determined. Martensite plates with widths as small as 8 p could be oriented using this procedure. The Kossel line patterns were interpreted using the charts developed by Rowlands and ~evis~ as generally

Jan 1, 1969

By David S. Bolin

INTRODUCTION This paper is directed toward those companies or individuals who may be considering the possibility of tin exploration or development projects in South America. Although tin deposits are known in many countries of Latin-America including Argentina, Peru, and Mexico, the majority of the deposits are located in Bolivia and Brazil. These two countries also account for virtually all the current production. Many factors affect the economic decisions related to mining and exploration projects in this region including the following: 1) Types of deposits 2) Anticipated size and grade of deposits 3) Deposit geometry and ore distribution as it affects the selection of a mining method 4) Metallurgical amenability 5) Governmental policies 6) Taxation 7) Anticipated capital and operating costs 8) Marketing costs This discussion will be directed toward each of these points. The majority of the presentation will be concentrated on Bolivia as this country is the principal producer in the region, however, the potential for further tin development in Brazil is excellent. Due to the remote and previously almost inaccessible location of the stanniferous districts of Brazil, little is known with respect to size and type of non-alluvial deposits which may exist in this vast country. TYPES OF DEPOSITS Two major types of deposits are currently being exploited in Bolivia; alluvial, and hard rock or lode deposits. Bolivia produces substantial tin from both types of deposit whereas virtually all Brazilian production to date has been from alluvial sources. Alluvial Deposits Brazil: The alluvial tin deposits of Brazil are located in river channels and flood plains adjacent to low mountain ranges. The terrain containing the tin placers is flat, marshy, and generally jungle covered. The major controls of alluvial cassiterite concentration are the ancient and present stream channels. The average tin concentration in the placers varies from 500 grams to approximately 1.0 kilograms per cubic meter. Tin reserves in the Rondonia field of Brazil have been estimated at 600,000 tons of fine tin. A bucketwheel suction dredge went into production in the Rondonia district in 1979, and four others have since been ordered. Several other gravel pump, and hand mining operations are also in production in this field. In addition to the Rondonia district, tin occurrences are known from Xingu, in Para state, and in the state of Minas Gerais. Bolivia: The alluvial deposits of Bolivia are somewhat more complex due to the variable geomorphology and abrupt topography. Conventional placer accumulations of cassiterite are found in many stream channels and intermontane basins surrounding the major lode tin producing regions. In addition to stream and valley placers, a group of deposits locally referred to as "Pallacos" or "Llamperas" which consist of colluvium, landslide debris and glacial moraine material, contain substantial tin reserves in some areas. The stream channel and intermontane basins contain the only deposits which are presently being exploited by mechanized methods. One dredge is working the stream channel below Cerro Rico de Potosi and another is operating in an intermontane basin southeast of the city of Oruro. Both of these dredges are operated by private companies. The average grade for these operations varies from 250 to 500 grams per cubic meter. The largest of the intermontane basin placers known at present is the Centenario deposit located adjacent to the Catavi lode deposit. This deposit contains approximately 170 million cubic meters of material with an average grade of about 150 grams per cubic meter. The "Pallacos" deposits are found on the slopes of mineralized areas and in glacial moraine. The mineralized material is generally completely unsorted, with tin and sometimes tungsten values distributed erratically throughout the entire mass. Most of these deposits are worked by small leasors or cooperatives; however, at least one mechanized washing plant is in operation southeast of Oruro. The size of these deposits may reach up to several million cubic yards. Grades are very erratic, but may range from 200 to 500 grams per cubic yard. In addition to the formal mining operations, virtually every drainage surrounding the major mines is being worked by independent' miners utilizing hand mining and jig or pan concentration. The aggregate production from these operations is substantial. The

Jan 1, 1982

By H. E. Cline, E. F. Koch, J. L. Walter

It has been postulated and, in a few instances shown, that some kind of dislocation structure will be present at semicoherent interfaces to accommodate small lattice mismatches. In the present study of the NiAl-Cr eutectic, regular arrays of interface dislocations are observed at the boundary between the chromium-rich rods and the NiAl-rich matrix. The networks were examined by transmission electron microscopy and selected area diffraction. The rods and the matrix have a crystallographic relationship in which all directions and planes of the two phases are parallel. The dislocation networks are cmposed of a<100> dislocations lying on the intersections of the cylinders with (100) planes. Dislocations forming hexagonal rather than square arrays are also observed at certain areas of the network. The morphology of the network is consistent with the interpretation of mismatch being accommodated by interface dislocations in the cylindrical geometry. The measured spacing between dislocations was used to calculate an apparent lattice mismatch between the phases (˜0.35 PCt)interface network energy (-140 ergs per sq cm), and network strengthening (-10,000 psi). It has been proposed by Frank and Van der Merwe1 that dislocations should be present at the boundary between two semicoherent crystallographically related phases. The role of the interface dislocations would be to reduce the internal stresses, caused by the mismatch in atomic spacing across the interface. Such dislocations have been observed at the interface between expitaxially grown films and Substrates.2-4 Interfacial dislocations have also been observed at precipitate-matrix interfaces.&apos;-&apos; Directionally solidified eutectics have been shown to have semicoherent phases1&apos; and would, therefore, be expected to have interfacial dislocations as found by Weatherly at a lamellar fault in A1-A12Cu.11 The NiAl-Cr eutectic appeared to be a promising system to examine because both phases are cubic, the lattice mismatch is small, and the phases are crys-tallographically related. Furthermore, the eutectic is easily thinned for transmission microscopy. Indeed, interfacial dislocations were observed and this report describes the nature of the dislocation networks in the boundary between the NiAl-rich ma-trix-phase and the fine chromium-rich rods.21 I) EXPERIMENTAL PROCEDURE Ingots, 3/4 in. in diam and 6 in. long were made by melting in vacuum and casting under argon using 99.9 pct pure material. The composition, in at. pct, was 33 pct Ni, 33 pct Al, and 34 pct Cr. The ingots were then placed in A1203 crucibles on a water-cooled base, melted by means of induction, and withdrawn from the hot zone at the rate of 1 in per hr under argon.* * T his material was first directionally solidified in this laboratory by E. R. Stover Slices were taken perpendicular to the growth direction of the directionally solidified ingot for metallography and for transmission electron microscopy. The electron transmission samples were thinned mechanically, then thinned electrolytically in A-2 electrolyte* *A-2 electrolyte: 62 ml perchloric acid, 700 ml ethanol, 100 ml butylcellosolve, 137 ml distilled H20. until a hole appeared in the foil. 11) EXPERIMENTAL RESULTS A) Optical Microscopy. The microstructure, viewed on a plane perpendicular to the growth direction, is shown in Fig. 1. The structure consists of cells or colonies of parallel chromium-rich rods in the NiAl matrix. The cells occur when there are impurities present12 or, in a ternary eutectic, if the composition is slightly off the eutectic composition. The axis of the chromium-rich rods is parallel to the growth direction except near the cell boundaries. Here the rods may assume angles to the growth direction; however, examination shows that the crystallographic relationship between the rod and the matrix remains the same. Fig. 1 includes cell boundaries where the rods formed at a large angle to the growth direction. The variation of rod position across the cells made it possible to Fig. 1-Structure on plane perpendicular to growth direction. Rods near cell walls are at large angle to growth direction. Magnification 315 times.

Jan 1, 1970

By R. B. Full

DURING the summer of 1949, the United Nations Scientific Conference on the Conservation and Utilization of Resources met at Lake Success. As summed up by one writer, the purpose was: "That everyone will try to learn how to feed more people from an acre of land." That objective is a stimulus to the phosphate rock industry as well as other industries. Phosphate rock was mined first in the Canadian province of Quebec where it was found as an apatite in pockets. In 1863, mining began near the Rideau Canal, first in open trenches and quarries until shafts were sunk. These operations were difficult since hard rock had to be drilled and blasted. Steam was the source of power. The phosphate rock was hand-selected and recovery ranged from 6 to 10 pct, averaging 70 pct to 85 pct bpl (bone phosphate of lime). Costs, f.O.b. Montreal, were $14 a ton, and selling prices averaged $17 a ton. In 1885, about 29,-000 tons were sold on this basis, but by 1892 the output fell to 8000 tons at an average price of $15 a ton at Montreal. South Carolina Deposits Phosphate rock was first discovered in South Carolina in 1837, but a mining company was not formed until 1867. It was immediately successful, and the industry continued to develop and ship an increased tonnage of land and river rock, shipments increasing from approximately 20,000 tons in 1868 to 537,000 tons in 1890, when the shipments began to decrease. In 1892 only 350,000 tons were shipped. In this field there were two types of deposits: land rock and river rock. More land rock tonnage was mined until about 1887 when river rock production began to equal it. The land rock was mined adjacent to and in the river marshes by pick, shovel, and wheelbarrow. Each worker dug daily a space 6 ft wide, 15 ft long and 6 ft deep, which was overburden, and then loaded about 3 cu yd of phosphate rock into wheelbarrows. His helper would wheel the barrows to small steam railroads up to 250 ft distant. Water was kept from the pits by steam pumps connected to railway cars. The phosphate rock was loaded into railroad cars, hauled and dumped into a log washer to which water was added, and run over trommel screens to eliminate the clay and loose sand. Steam shovels for loading were introduced about 1891. River rock was mined by floating dipper dredges and at low tide was loaded into barges by laborers using oyster tongs, the large lumps being hand-loaded. Barges and bateaus were unloaded by wheelbarrows which were wheeled to the same type of land rock washers. The washer product was piled with stacked pine cordwood in alternate layers and fired for drying. Usually this was done under sheds along the river bank. The dried rock then was transferred to ships, usually three or four-masted schooners. Cost of production of both land and river rock, including $1 a ton royalty paid to the state for state-owned property, was approximately $4.25 a ton averaging 60 pct bpl. The selling price was approximately $7 a ton f.O.b. In 1886 the courts handed down a decision permitting anyone to mine, and many additional companies were organized immediately. As a result, the selling price was lowered to a profit margin of 50Ø or less per ton. The South Carolina mines were eventually shut down when a more profitable source of phosphate rock was discovered in Florida. Florida Deposits Phosphate rock was discovered in Florida in 1882, and in 1883 a small quarry was opened near Hawthorne. In 1886 phosphate rock of good grade was discovered on Peace River, and the Arcadia Phosphate Co. was formed. In 1888 the company began shipments amounting to 3000 tons that year. During the latter part of 1888, hard-rock phosphate was discovered near Dunnellon. Exploration extended rapidly, and deposits of hard-rock phosphate were mined over a wide area so that shortly after 1900

Jan 1, 1952