Search Documents

By H. T. Clark

NO previous determinations of the deformation or recrystallization textures of titanium or of titanium-base alloys have been reported in the literature. The room-temperature structure of titanium is hexagonal close-packed with a c/a ratio less than 1.633. It would be expected, therefore, to have a rolling texture similar to that of other hexagonal close-packed metals, namely (0001) [1010]. Burgers and Jacobs1 have shown that zirconium, a metal isomorphous with titanium in its structure and similar in many of its properties, has such a texture with a scatter of the basal plane toward the transverse direction. This scatter is in the opposite direction from that found in magnesium by Bakarian2 but similar to that reported by Smigelskas and Barrett3 or beryllium. The rolling and annealing textures reported here for high-purity iodide titanium are significantly different from the . textures of any other hexagonal close-packed metal. All titanium used during this investigation was prepared by the iodode process." The annealed hardness of this material varied from 73 (material used for sample No. 2) to 97 Vickers hardness number. An estimate of the chemical composition of this grade of titanium has been reported by Finlay and Snyder.5 With one exception, shown in table I, the as-deposited titanium was cast into 10 to 20 g ingots in an electric arc furnace in purified argon before being rolled to sheet. The cast ingots were forged and ground until their cross-section was approximately rectangular, annealed 1 hr at 700°C in vacuum and cold rolled. Rolling was carried out in a two-high, 4 in. diam mill, using reductions no greater than 10 pct per pass. The direction of rolling was reversed after each pass, and, in order to avoid temperature effects, the sheet was allowed to cool after each pass. Unless the rolled sheet was sufficiently thin for X-ray penetration (about 0.004 in.), it was reduced to this thickness by pickling. Because of the possibility of introducing twinning or other deformation during grinding, no attempt was made to maintain uniform thickness of the sample during pickling by intermediate grinding or sanding operations. Those samples to be used for determining the annealed texture were recrystallized by vacuum annealing the cold-rolled sheet for 1 hr at 500°C. These thin samples were held between thick titanium sheets during annealing to prevent distortion. Table I outlines the rolling and annealing schedule of those samples for which photograms or texture patterns are shown. X-ray Techniques The usual techniques for determining textures were employed during this work. Molybdenum radiation was used for the transmission exposures and copper radiation for the glancing angle ones. Since titanium fluoresces under these conditions, it is necessary to employ a filter between the sample and the film. The Kß radiation filters are very satisfactory for this purpose. Sufficient grains having favorable orientation were present in both the cold-worked and in the cold-worked—500°C annealed samples to provide satisfactory patterns with the samples stationary. Because of the difficulties of comparing intensities of transmission photograms with those obtained

Jan 1, 1951

By Frank C. Appleyard

Gypsum, the dihydrate form of calcium sulfate, has a history of usefulness to man dating back several thousand years, and a worldwide industry has been built on the mining and processing of this versatile industrial mineral. However, anhydrite, the other principal calcium sulfate mineral has very limited use, so much so that separate statistics for it are not always kept, but are usually included with those for gypsum. Although often found in close association, the two minerals have important chemical differences in that anhydrite is the anhydrous form of calcium sulfate (CaSO,) whereas gypsum is the dihydrate (CAS0;2H20). These two molecules of combined water result in significant differences in hardness, density, and solubility of the two minerals. However, of most importance is the difference in thermal properties wherein gypsum, upon the application of a modest amount of heat, can be converted to the hemihydrate of calcium sulfate (CaS0;Vi H,O) or plaster of paris, an intermediate product upon which is based over 90% of the value of all calcium sulfate end products. Anhydrite, on the other hand, is inert at these temperatures and its uses have been limited to only those few cases where calcium sulfate in the anhydrous form may have an advantage. The earliest known use of gypsum plaster dates back some 5000 years to the time of the Pharaohs of Egypt who had discovered that gypsum rock, when exposed to fire, broke down into a powder which when mixed with water would form a putty that could be "plastered" on a rough mud brick or stone wall to make a smooth finish. It was used down through the centuries in a limited way for ornamental purposes, but did not achieve wide acceptance because of its quick (25 to 30 min) setting or hardening time which made it difficult to use. The first real understanding of gypsum chemistry was developed in France about 1755, and the gradual growth of its present utilization dates from that time. In the United States, the first utilization of gypsum was to grind it to a fine material for use as a soil conditioner at about the time of the Revolutionary War, and the term "land plaster" for ground gypsum has remained in use. Another cementituous material-lime or calcium oxide-had become the usual plastering material, but by about 1870 a method for retarding the set of gypsum plaster was discovered and it has today almost completely replaced lime as a plastering material. In recent years, gypsum products sold in the United States have reached a total valuation of approximately $500 million per year as illustrated in [Table 1].

Jan 1, 1975

By Maurice Cook

NORMALLY the grain size of cold-rolled and annealed copper sheet is of the order of 0.02 to 0.06 mm., and 0.1 min., for example, would, for many purposes, he regarded as undesirably large. The occurrence of very large grain sizes in a few isolated cases of copper sheet led the authors to inquire into the causes giving rise to such unusual results. During the course of this work a very large number of experiments have been carried out to determine the effect of varying the conditions of the final and penultimate rolling and annealing operations, as well as of earlier rolling and annealing treatments. A correspondingly large number of observations have been made, but within the space of one paper it is possible only to outline relatively briefly what appear to be the more important of these experiments and observations. The presentation of the results does not follow chronologically the order in which the experiments were carried out and they have been rearranged for the sake of simplicity. In recent years a considerable amount of work has been done in connection with the recrystallization and grain growth in metals and alloys that take place on annealing, and a number of generalizations have been reached. It is known that the crystal size in wrought material in the annealed condition depends on a number of factors, including the time and temperature of the annealing operations and the nature and amount of cold-work to which the material has been subjected. Results, however, that are not covered by these generalizations can be obtained, which, in some instances, may even appear to he contradictory to them. According to these generalizations gradual changes in grain size are effected by progressive variation of the factors involved in annealing or cold-working. The work recorded in the present paper, however, relates to the development of grain sizes which are far beyond those normally encountered in ordinary annealing operations and far in excess of grain sizes which, according to ordinary standards, would be classified as coarse or large.

Jan 1, 1938

By Claus G. Goetzel

Pressing of powdered metal parts is best done in the direction of the shortest extension of the piece, to avoid too great a loss of pressing force through internal iriction. As long as curved surfaces, re-cessej, or offsets occur only parallel to this shortest axis of pressure, no special difficulties arise: the cross sections, perpendicular to the pressure, do not vary, nor does the shape of the parts change during compression except for a gradually reduced thickness (Fig. IA). The problem becomes more dificult, however, when the curved surfaces or recesses are perpendicular to the shortest axis of the part (Fig. IB) Two processes for molding uniformly dense parts with complicated shapes from powdered metals are described in detail in this paper. Both can be employed successfully by those trained in the art. The first refers to curved parts; the second is especially adapted to parts having one or more recesses or steps. Both methods, as set forth here, are applied under the condition that presents the more difficult problem. For clarity, before description of the two practical methods, the variable factors in molding powdered metal parts will be reviewed, then an idealized procedure will be considered briefly. Variable Factors in Molding Powdered Metal Parts Compression Ratio Compression ratio is defined as the proportion of the final relative density of the compact to the apparent density of the powder. For iron powder of an apparent density of 3.0, for example, a compression ratio of 2 1/2:1 would be required to produce a compressed compact of 7.5 density; whereas for another iron powder having an apparent density of only 1.5, a compression ratio of 5:1 would be required to produce the same density. The lower the powder's apparent density, the greater must be the compression ratio for pressing compacts of high density.

Jan 1, 1946

By Claus G. Goetzel

Pressing of powdered metal parts is best done in the direction of the shortest extension of the piece, to avoid too great a loss of pressing force through internal iriction. As long as curved surfaces, re-cessej, or offsets occur only parallel to this shortest axis of pressure, no special difficulties arise: the cross sections, perpendicular to the pressure, do not vary, nor does the shape of the parts change during compression except for a gradually reduced thickness (Fig. IA). The problem becomes more dificult, however, when the curved surfaces or recesses are perpendicular to the shortest axis of the part (Fig. IB) Two processes for molding uniformly dense parts with complicated shapes from powdered metals are described in detail in this paper. Both can be employed successfully by those trained in the art. The first refers to curved parts; the second is especially adapted to parts having one or more recesses or steps. Both methods, as set forth here, are applied under the condition that presents the more difficult problem. For clarity, before description of the two practical methods, the variable factors in molding powdered metal parts will be reviewed, then an idealized procedure will be considered briefly. Variable Factors in Molding Powdered Metal Parts Compression Ratio Compression ratio is defined as the proportion of the final relative density of the compact to the apparent density of the powder. For iron powder of an apparent density of 3.0, for example, a compression ratio of 2 1/2:1 would be required to produce a compressed compact of 7.5 density; whereas for another iron powder having an apparent density of only 1.5, a compression ratio of 5:1 would be required to produce the same density. The lower the powder's apparent density, the greater must be the compression ratio for pressing compacts of high density.

Jan 1, 1946

By Alden B. Greninger

The study of mosaic structure of crystals1 has been confined until recently to the field of theoretical physics. Crystallographers, in general, have neglected the subject, although X-ray crystallographers constantly make use of formulas for intensities of X-ray reflection as modified by mosaic structure. Work on mosaic structure has centered chiefly on the task of proving or disproving the secondary-structure theory of Zwicky,² and very little attention has been paid to the visible imperfections of crystals. A. Goetz has been responsible for most of the supposed experimental confirmations of Zwicky's theory.3 On the other hand, Smckal,4 and Orowan,5 among others, maintain that there is neither theoretical nor experimental evidence to substantiate Zwicky's secondary structure. Lately the subject has been intensively investigated by Buerger,6 one of whose recent papers led to a symposium on mosaic structures.'

Jan 1, 1935

By Alden B. Greninger

The study of mosaic structure of crystals1 has been confined until recently to the field of theoretical physics. Crystallographers, in general, have neglected the subject, although X-ray crystallographers constantly make use of formulas for intensities of X-ray reflection as modified by mosaic structure. Work on mosaic structure has centered chiefly on the task of proving or disproving the secondary-structure theory of Zwicky,² and very little attention has been paid to the visible imperfections of crystals. A. Goetz has been responsible for most of the supposed experimental confirmations of Zwicky's theory.3 On the other hand, Smckal,4 and Orowan,5 among others, maintain that there is neither theoretical nor experimental evidence to substantiate Zwicky's secondary structure. Lately the subject has been intensively investigated by Buerger,6 one of whose recent papers led to a symposium on mosaic structures.'

Jan 1, 1935

By Theodore H. Eyde

The Superior Oil Co. drilled two holes, 4720 and 5940 ft, respectively, using conventional oilfield rotary drilling equipment. The results indicated that large rotary drills can be adapted to mineral exploration purposes with few modifications. The principal advantages are: a large hole diameter, excellent samples of cuttings, a geolograph which is a constant drilling record, rapid penetration even in hard rocks, and the ability to use electric logs for measuring the properties of the rock being penetrated. The disadvantages are the high cost of mobilization, drilling, and oilfield service at remote locations. Though the oilfield sampling techniques are adequate for identifying lithology, improvements are necessary to obtain representative samples for analytical purposes. As deeper targets are explored, mineral exploration organizations will have to resort to rotary drilling.

Jan 1, 1975

By G. Bruggeman, K. G. Kreider

Grain boundary dij]usion coefficienls were measured in tungsten between 1400° and 2200° C and can be expressed by the equation sq cm per sec This activation energy confirms some eavlier estimates made .from tungsten sintering experiments. Grain boundary diffusion was found to occur in sub-bozrndavies having -misorientations of less than 10 deg. The actiuation energy for this subboundavy diffusion is equal to that for dijjusion in incoherent grain boundaries with in the limits of error. This is shown to be consistent with the dislocation model of Low-angle boundaries wheve diffusion occlcvs along- the dislocation 'YPipes" comprising -tile boundary. RECENT investigations of the sintering of tungsten powders all report activation energies which are considerably less than the activation energy for tungsten volume diffusion. Kothari' reports a value of 100 * 5 kcal per mole, Hayden and Brophy' obtained 90 kcal per mole, and Vasilos and smith3 found 110.7 kcal per mole from their sintering studies. Since most determinations of the activation energy for volume diffu-sion4-' fall between 120 and 160 kcal per mole (the true value seems most likely to be nearer 150 kcal per mole), the conclusion is drawn that the mass transport leading to densification during sintering is accomplished by grain boundary diffusion. This interpretation is consistent with various diffusion models of the sintering process. 10-12 Vasilos and Smith calculate diffusion coefficients from their data which fit the equation D * 1.36 x 10* exp(-llO,700/HD However, no direct measurements of tungsten grain boundary diffusion have been made. Furthermore, considerable disagreement exists between the directly measured values of tungsten volume diffusion.'-' In order to corroborate the inferred results of the sintering experiments concerning grain boundary diffusion and to provide accurate diffusion data essential to the analysis of the kinetics of creep, oxidation, precipitation, and so forth, the present work was undertaken to measure self-diffusion in single-crystal and polycrystalline tungsten between 1400" and 2200°C. It is within this temperature range that tungsten sintering is done, the re crystallization of tungsten occurs, and the widest application of tungsten as a high-temperature material will probably be made. EXPERIMENTAL PROCEDURE Radioactive WlE5 was produced by irradiating tungstic acid in a neutron flux of 1.2 x 1012 neutrons per sq cm per sec for 36 hr. A 2-week waiting period was allowed for the decay of w"~ also produced by the irradiation. (w"~ has a half-life of 24 hr.) The half-life of the remaining isotope was determined to be 75 days confirming the presence of w lE5 and the absence of any undesired radionuclide. Specimens 4 in. in diam and $ in. thick were cut from polycrystalline swaged tungsten rods (recrystal-lized) and from Linde single-crystal rods. Chemical analyses of these materials appear in Table I. Actually upon closer examination, the single-crystal specimens were found to consist of several subgrains separated primarily by tilt boundaries in which the misor-ientation ranged from 3 to 10 deg. Thus, it was possible to measure boundary diffusion coefficients in these low-angle subboundaries as well as in the incoherent boundaries of the polycrystalline specimens. The two faces of each specimen were ground flat and parallel within 0.0001 in. The radioactive tungstic acid was dissolved in concentrated ammonium hydroxide, placed on the ground flat of the specimen, and evaporated to dryness. The oxide was then reduced in hydrogen at 1000°C resulting in a layer of wlE5 approximately 1 p thick. The diffusion anneals were performed in vacuum in a tantalum resistance furnace. Time at temperature ranged from 10 hr at 1400°C to 2 hr at 2200°C. The penetration profile was determined by measuring the residual activity after successive removal of surface layers by grinding on metallographic polishing paper. Extreme care was exercised to insure that sections were always taken normal to the diffusion direction; this was verified repeatedly by checking that front and back surfaces of the specimen remained parallel. The activity was measured with an end-window Geiger-Mueller counter. The sides and edges of the specimen were well-shielded to eliminate possible effects due to surface diffusion. The weight of the

Jan 1, 1968

By J. J. Kramer, W. A. Tiller, G. F. Bolling

THE axial orientations of columnar crystals in unidirectionally solidified ingots of zone-refined zinc and tin have been examined using the techniques recently described by us.' Both metals had an initial purity of 99.999+ pct before zone refining and satisfied all qualitative guides for very high purity after zone refining. Fig. 1 presents the orientations of the columnar crystals for tin and zinc, respectively. For tin, there is a preference for grains growing in the [I101 direction, i.e., the dendrite direction.' For zinc, a weak preference for the [0001] direction is seen (a random population in the unit triangle would give equal density on either side of the 60-deg circle centered on [0001]).' There was no apparent evidence for dendritic growth in either metal. These results, and those previously reported,' confirm the recent investigation by Hellawell and Herbert of casting textures observed for zone-refined lead, zinc, and tin.4 The preferred casting orientations for these metals in both the impure and zone-refined states are given in Table I. In the experiments on zone-refined lead,' it was shown that two separate textures existed: a preferred (111) nucleation texture existed at the chill surface and a preferred (111) texture developed during solidification. Either effect is sufficient to produce the result recorded in Table I. Similarly the results recorded for tin and zinc may be attributable to either a preferred nucleation or a preferred growth phenomenon and additional experiments are required to separate these two possible explanations. Hellawell and Herbert' attribute their results to a preferred growth process and account for it on the basis of a "layer-growth" model proposed much earlier by one of the present authors.5 An equally satisfactory growth model would be that based upon anisotropic surface energies. However, both of these growth models would indicate that the preferred growth direction for very pure metals should be normal to the plane of closest packing in the metal. This is consistent for zinc but, contrary to the conclusion of Hellawell and Herbert, it is not consistent for tin since here the (100) is expected to exhibit a greater density of packing than the (110). Although tin is expected to exhibit an anisotropy of thermal conductivity, we would expect the thermal conductivity to be the same in the [1101 as the [l00]

Jan 1, 1963

By M. G. Driessen

For a number of years the cyclone, familiar to Americans as a dust collector, has been used as a thickener of suspensions at one of the coal-preparation plants of the Netherland State Mines in Limburg. The plant treats nut-size coal at 120 tons an hour in a heavy-medium washer. The diluted medium from the rinsing screens is thickened in cyclones. More recently the cyclone has been adapted to act as a coal cleaner. The principle of the cyclone thickener is the same as that of the cyclones used in industry for catching dust or fine particles suspended in the air or in gases. Generally the latter are more efficient in this respect—the smallest particles that can be caught with reasonable efficiency are considerably smaller than with the cyclone thickeners. The reason is obvious; the ratio of specific gravities between the dust particles in a gas and the gas itself is about 800 times larger than the ratio between, for instance, the specific gravities of shale particles and water. The ratio of the velocities of fall of shale particles (? = 2.5)† in air and in water is as follows: In the range of Stokes: ?air = 93?water In the range of Allen: Wair = 49Wwater In the range of Newton-Rittinger: ?air = 36.6?water The same ratios apply for the velocities in the centrifugal field, from which it follows that it is especially difficult to catch the very fine suspension particles in a liquid. The efficiency of a cyclone thickener depends mainly on the circumferential velocity of the liquid at its innermost radius, because here the centrifugal forces are the highest. However, these velocities cannot easily be calculated, as the flow is three-dimensional, and thus the axial components cannot be neglected .(p. 252, condition 3). We believe that at first a spiral tangential motion along the cyclone wall is created, which causes the inner vortex ascending from the apex of the cyclone (Fig I). At the same time the inner vortex is strengthened by the individual vortices in horizontal planes, and thus a part of the total flow can find another and perhaps quicker way to the outlet. In any case, the exact motion, not only of the fluid but especially of the suspended particles, is so difficult that we have to refer to the experiments to find the exact behavior of this kind of apparatus. Method of Judging PerforMance of Coal Washer Geologists, rather than mechanical en-gineers, would be able to describe the separating or stratifying effect in nature, but even a bather on the shore lying on the soft sand near the sea wonders why all the small sand grains have approximately the same size. A child playing on the border of the river could easily

Jan 1, 1949

By W. L. Martin, J. N. Dew, H. B. Steves, M. L. Powers

This paper presents and discusses the results obtained during a pilot test in the Loco field in southern Okla homa. The test was conducted in a 2%-acre pattern that was part of a 20-acre conventional waterflood pilot area. The conventional flood was well past its economic limit when the hot waterflood was initiated to obtain technical information and operating experience. Temperature data from nine observation wells showed that about 75 percent of the pattern was affected by heat, and that heat losses were severe in the pilot pattern. About 60 percent of the injected heat was lost to overburden and underburden zones during hot-water injection. Wellbore heat losses were held at tolerable levels at the shallow depth of the test by providing a low-pressure air annulus between the injection tubing and well casing. Hot water provided water injectivity increases of 200 to 400 percent. The hot water channeled across the lower portion of the oil sand in three directions through zones of relatively high water saturation. There was no conclusive evidence that natural fractures or pressure partings aflected the flow of fluids in the pilot pattern; however response undoubtedly was aflected by localized pressure gradients and by injection-production rate ratios. The results showed that hot waterflooding increased oil recovery in a reservoir containing 600 cp oil. The total tertiary oil production from the pilot pattern area was 3,896 bbl or about 156 bbl/acre-ft swept by heat. The corre.sponding WOR was about 34:I. Description of the Hot Waterflood Process To hot waterflood an oil reservoir, water is injected that has been heated to a temperature substantially higher than the original reservoir temperature, but lower than the vaporization temperature of water at the prevailing pressures. In the reservoir the hot water flows continuously into cooler sand and rapidly loses heat to the sand until it has been cooled to the original reservoir temperature. Thus, a heated zone and a region or "bank" of cooled water begins to accumulate immediately after hot water injection is started. This bank of cooled water continues to grow ahead of the heated zone, which also grows, but at a slower rate. This occurs because heat transfer is almost instantaneous, and the ratio of heat capacities of water to rock is such that two or three unit PV of hot water must be injected to heat a given unit bulk volume of the reservoir. The primary displacement mechanism is the same for both hot and conventional cold waterfloods; i.e., "piston" displacement occurs at the original reservoir temperature. The incremental benefits of hot waterflooding usually occur long after the breakthrough of cold water at producing wells, and the increased oil recovery necessarily is accomplished with high WOR's (water-oil ratios). Heat decreases the viscosity and density of oil and water. These effects result in more rapid and increased recovery of secondary or tertiary oil. If the cost of the required heat is low enough, the ultimate oil recovery of a hot waterflood should be increased substantially over what would be expected at the economic limit of a conventional cold waterflood. The economic benefits of any hot-fluid injection project depend primarily upon the cost of the heat required to produce more oil at an increased rate. This cost depends in part upon the amount of heat lost to surrounding formations. Heat loss depends upon reservoir thickness, water injection rate and temperature, the depth of the formation, well spacing, and the characteristics of the reservoir rock and surrounding formations. In general, percentage heat losses decrease as injection rate and reservoir thickness increase. Although it is an old idea, hot-water injection has not received widespread field application in the oil industry as a drive process. Much of the original field work with hot water was done in Pennsylvania fields where water permeabilities and injection rates are low. In these cases, hot-water injection was used primarily as a means of increasing in-jectivities — not as a recovery process. Ramey' recently has published an excellent review of the development of hot fluid injection processes. Recent publications"' and our own experiences now indicate that hot water or steam injection also can effectively increase the oil recovery from reservoirs containing viscous crudes. However, the economics of these methods as displacement processes have not been established. Several theoretical predictive techniques have been published (for a review see Ramey'), but simplifying assumptions make

Jan 1, 1969

By J. H. Wernick, J. E. Kunzler

HIGHLY pure metals are needed for low-temperature electron transport studies in progress. Recent improvements in purification techniques, such as zone refining, have made it possible to obtain metals with improved purity. For some metals, the improvement has been to the extent that ordinary analytical techniques are inadequate and special methods are needed.1 For other metals purification is more difficult, so that simple but rapid analytical methods are desirable as an aid in evaluating the effectiveness of purification procedures. Furthermore, it is desirable to be able to determine the impurity level of the sample or ingot with the minimum of physical disturbance of the material. In order to aid in the preparation of purer metals, techniques involving the measurement of electrical resistance at liquid-helium temperatures have been devised for studying impurity distributions in zone-refined ingots and other bulk samples without destroying the ingot or its geometry. The method yields information on the variations in purity along the length of the ingot or sample and provides a measure of the overall purity of the material. Compared with ordinary analytical methods, the resistivity method is rapid, sensitive, and does not require significant physical disturbance of samples with reasonable shapes. It has the disadvantage that resistance measurements are not specific, i.e., they do not identify the impurity. However, this disadvantage is offset by the advantage of being able to establish a measure of the overall purity so far as electrically active" impurities are concerned. METHOD AND ITS BASIS The method is based on the well-known fact that the resistivity, at Liquid helium temperatures, of a reasonably pure metal containing no regions with additional phases decreases with increasing chemical purity or a decrease in the number of physical defects. It is convenient to separate the total resistivity into three parts: where is the resistivity due to the scattering of the conduction electrons by the lattice vibrations or phonons, p is the contribution due to physical defects, and originates from the effect of chemical impurities in the metal. Insofar as Matthiessen's rule is obeyed,2 pphys and pchem are independent of temperature. Except possiblyin the very purest metals, ptherm is negligible at liquid helium temperatures and For zone-refined metals, which normally are well annealed and consist of large grains, at the chemical purity levels thus far attained the available data indicate that pphys is negligibly small or at least constant throughout the ingot. Assuming that the effect of physical defects is negligible for isotropic metals, This assumption appears consistent with most of

Jan 1, 1959

By Clarence Wright

THE average lead and zinc content of the ores mined and milled in the Joplin district is low as compared with that of other lead and zinc deposits throughout the United States. Because of this fact and of the high grade of the concentrates, the ratio of concentration is unusually high. Most of the operating companies have aimed to produce as high a grade of concentrate as possible in order to obtain the highest price for their product. They have done this at the sacrifice of the percentage of zinc recovered. The average percentage of zinc recovery is from 60 to 70 per cent. For percentage of recoveries from actual mill tests, see tables. The concentration is commonly effected by crushing the ore to h-in. (12.7 mm.) size and subjecting it to a roughing and cleaning over two or more large Cooley jigs, of the Harz type, the finer sands being treated on the usual types of sand and slime tables. The treatment of slimes by flotation is being tested at several of the larger mills. COARSE CONCENTRATION When the ore. has been hoisted from the mine it is dumped onto a chute leading to a grizzly made of iron bars, usually heavy rails, spaced 4 to -5 in. (101 to 127 mm.) apart. The oversize is caught on the grizzly, the mineralized pieces are broken with sledge hammers so as to pass through, and the boulders that are practically barren are sorted out by hand and trammed to the waste-rock pile. The proportion of waste rock thus sorted out varies from a fraction of 1 per cent to 15 per cent., depending on the nature of the rock.

Jan 10, 1917

By R. Kerby, T. R. lngraham

The rates of cadmiuln cementation from buffered solutions were studied on both the cylindrical and circular faces of a rotating zinc disk. The activation energies are equivalent on both surfaces, but the rate is more rapid on the cylindrical face. At higher temperatures and at pH values above 6.4, the rate of deposition increases because of an increase in the cathodic area of the deposit. The rate may also be increased by decreasing the thickness of the diffusion layer by rapid stirring. The presence of small amounts of copper, cadmium, lead, iron, or aluminum in the zinc does not affect the cementation rate, but when srnall amounts of copper, cobalt, and arsenic were present in the solution cadmium deposition ceased shortly after it started. Small amounts of copper in solution become cemented with the cadmium to form a coarse deposit of Cd3Cu. When zinc ores containing cadmium are processed for electrolysis, the cadmium appears with the zinc in the leach liquors. Because of the discharge potential of the cadmium ion and the hydrogen overvoltage on metallic cadmium, the cadmium ion must be removed prior to zinc electrolysis to prevent its codeposition. Cadmium is usually removed from acidic zinc sulfate solutions by cementation on zinc. When zinc sheets are used with the appropriate conditions of pH and temperature, a finely divided, high-purity cadmium powder is obtained; it floats to the surface with attached hydrogen bubbles and, after careful washing, may be processed directly to a marketable product.' The reaction on zinc sheets is relatively slow because of the limited amount of exposed cathodic area on the sheets. A much more rapid reaction is obtained when zinc powders are stirred into the solution, but this procedure does have a potential disadvantage: some unreacted zinc may be trapped in the cemented cadmium and thus lower its grade.1 The equilibrium constant at 25°C for the displacement of cadmium by zinc is of the order of lo", which indicates that at equilibrium the displacement would be essentially quantitative and no back reaction need be considered. This indication is not entirely true, however, because in the presence of oxygen any loose cadmium which is out of contact with metallic zinc tends to redissolve after cementation.' The overall effect is much the same as that to be expected if the equilibrium constant were much smaller. Previous experimental work on cementation reac- tions3 is in general agreement that the rates of cementation usually follow first-order kinetics. The metal on which cementation occurs is considered to consist of anodic areas from which metal dissolves and cathodic areas onto which the reactive metal is cemented. For the reaction to continue, the cemented deposit must remain open and porous for the removal of ions. Usually, the deposited metal influences the rate of cementation; when it blocks the pores in the deposit, the rate of cementation will be decreased. Alternatively, when the cemented metal grows as den-drites or as coarse powder the cathodic area is correspondingly increased and the rate of cementation increases,3 Thus, it is only during the initial stages of cementation, prior to the development of deposit effects, that the kinetic behavior of the reaction may be studied without ambiguity. In this paper, experiments will be described for cementation of cadmium from dilute solutions onto the surface of a rapidly spinning zinc cylinder. The effects of ionic concentration, disk rotation speed, temperature, and impurities will be described. APPARATUS AND PROCEDURE The apparatus used for the experiments was described in a previous paper.4 It consisted of a 2-liter vessel in which the contents were protected, against oxidation, by a stream of prepurified nitrogen. The vessel was immersed in a water bath which controlled

Jan 1, 1970

By N. H. Harrison, J. K. Rodgers, S. Regier

This paper presents comparisons of data obtained from a laboratory reservoir study and from a calculated behavior prediction with the actual production history of a condensate reservoir. A small non-commercial discovery was depleted under closely controlled conditions and the well fluids were sampled at frequent intervals. Data on the reservoir and production variables were accumulated on a fixed schedule. A laboratory reservoir study war made using the initial well fluid samples as charging stock. The production procedures and operating conditions were held constant throughout the study wherever possible and in general paralleled the field work. The well fluid compositions and the cumulative recoveries ar a function of the reservoir pressure were also calculated using conventional flash vaporization procedures and equilibrium constants. Comparisons based on the composition of the well fluid show good agreement, the laboratory study agreeing within experimental accuracy with the field work and the calculated data comparing equally well. The gas-oil ratios are also in good agreement, but with somewhat greater deviations at the higher pressures. In the overall picture, it is believed that a model st,~tiy can predict within experimental accuracy the production history of a condensate reservoir. Better equilibrium constants for the heavier hydrocarbons are needed in order to attain improved composition accuracy by calculation. INTRODUCTION In Aug., 1955, a gas condensate well was completed in San Juan County, Utah, that was initially thought capable of good commercial production. These conclusions were derived principally from core data and electric logs, which indicated good permeability, porosity and gas content. However, after the usual series of potential tests it was found that the reservoir pressure had declined some 22 per cent, and it was obvious that the zone tapped was but a small pocket or trap. It became apparent that, with a controlled depletion of a small reservoir, a unique opportunity was available to compare laboratory and calculated studies with an actual field depletion and to further the present knowledge of condensate reservoirs. FIELD WORK The Coalbed Canyon Well No. 1 was conventionally completed in the Paradox limestone formation to a total depth of 5,912 ft. The producing zone from 5,762 to 5,806 ft was perforated with four jet shots per ft. The wellhead and field equipment were also conventional, the major items consisting of a two-pass indirect fired line heater, a high- and a low-pressure separator with the necessary controls and accessories, gas meters, back-pressure regulators, flare stacks and condensate stock tanks. The initial testing of this well con-sisted of a series of flow potential and pressure build-up tests during which some 30 MMcf of gas was produced. The reservoir pressure declined from an estimated 2,300 to 1,782 psig during this period, from which it was concluded that the reservoir was very small. In order to approach steady-state conditions in the reservoir and so provide optimum conditions for making comparisons, the field depletion was programmed to approach, if possible, constant production conditions. Bi-hourly readings were taken of the tubing pressure, the pressure and temperature of the separators, oil and gas rates, and other pertinent operating data. The gas rate, as indicated by the orifice meter, was held constant by the adjustment of the choke in the line heater. The temperature of the first stage separator was held constant by adjustment of the line heater jacket temperature. Practical considerations of production made the maintenance oi a constant gas rate impossible. The test started with a gas rate of 4 MMcf/D and a separator pressure of 250 psig. This rate was maintained until the choke was fully opened. The gas rate then declined with the falling tubing pressure and production was continued until the rate was about 2

By S. Shapiro, G. Krauss

RECENT investigations1 3 of the products of marten-sitic transformation in Fe-Ni and Fe-Ni-C alloys have made use of light microscopy to describe mar-tensitic fine structure. The application of conventional metallographic techniques to this problem was possible because of the similarity of distributions of parallel striations developed by etching polished surfaces to distributions of transformation twins which are positively identified in thin films by transmission electron microscopy. The surface striations frequently are not well-defined, and could also be due to, for example, rows of etch pits which are not resolved by the light microscope. This note describes the etching effects revealed by examination of surface replicas of mar-tensite in the electron microscope. The application of a replica technique both extends the observations of fine structure made with the light microscope and allows the results of conventional metallography to be used with more confidence. Samples of an Fe-33 wt pct Ni alloy were used for this study because of the detailed knowledge of the fine structure of martensite which has been developed'-4 for alloys of about this composition. Samples transformed to martensite at -120°C, and transformed samples heated to 340°C to effect a small amount of reversal of martensite to austenite, were examined. Surfaces were first prepared for replication by elec-tropolishing in a chromium oxide-acetic acid electrolyte at a current density of 0.1 amp per sq cm and a temperature of 15°C or a perchloric acid-acetic acid electrolyte at a current density of approximately 2 amps per sq cm and a temperature of 15°C. The polished surfaces were then etched for 4 to 7 sec by immersion in a solution of equal parts HC1, HNO,, and H20. Application of the etchant for this period of time produced discrete attack of certain features without loss of resolution due to overlapping of areas most susceptible to etching. The etched surfaces were replicated by 1) preshadowing with Pt-Pd alloy at an angle of 20 to 30 deg, 2) depositing a thin carbon film, and 3) stripping the film and shadowing material by immersion in a 5 pct nital solution. Two types of etching effects were observed by examination of the surface replicas in the electron microscope: l) continuous striations centered at the bottom of long grooves or the tops of pyramidal elevations on the sample surface, and 2) high densities of fine etch pits. Examples of both types of features are shown in Figs. 1 to 4. The striations are in each case continuous and have the same characteristic configurations as do transformation twins in martensite. Fig. 1 shows that the density of grooves decreases toward the edge of a martensite plate and Fig. 2 shows a region where the striations are of varying length. Similar examples of transformation twin arrangements determined by transmission electron microscopy of thinned foils of martensite have been shown in the literature,'~ and, based on these similarities, the striations and their associated grooves or mounds are considered to be evidence for the presence of transformation twins. The transf~rmation twins in martensite are on the order of l00 A thick, much too fine for resolution by the light microscope. It appears that orientation-dependent etching of the matrix martensite about the twins results in grooves or surface elevations which

Jan 1, 1967

By D. L. Abata

This paper discusses recent technology dealing with the use of computer graphics in the mining industry. It presents a newly developed computer software package specifically designed for use in underground mining operations. This software package, developed under a US Bureau of Mines contract, 1) displays mine ventilation schematics and other representative illustrations for a real time data acquisition system and 2) uses the Bureau-owned Minefire and Ventilation Code for display of ventilation and contamination predictions on the microprocessor system. The package uses a unique system of display indexing that provides a simple yet efficient method of recalling a series of mine schematics detailing an underground operation and an alarm acknowledgment scheme that provides an effective method of identifying problem areas that may exist in the mine network. The package was written in Fortran for a 64-kilobyte, Z80-based microprocessor computer.

Jan 1, 1986

By R. O. Williams

A study utilizing neutron diffraction, electrical resistance, and chemical extraction has been carried out to clarify the chromium-rich part of the miscibility gap previously proposed for this system. This gap appears to be more symmetrical than previously supposed and is very flat. This flatness is believed to be the result of a cooperative phenomenon perhaps of magnetic origin; in particular, it is believed that the chromium-rich phase is antiferromagnetic. The presence of antiferromagnetism is believed to result in an additional strengthening mechanism very sinzilar to that for ordered precipitates. Likewise, it is proposed that the quenched alloys which are known to be ferromagnetic have antiferromagnetic regions which accounts for the maximum in hardness around 75 pct Cr. It is also believed that the existence of antiferromagnetism in other alloys of transition elements might explain some of their anomolous characteristics. THE iron-chromium phase diagram at low temper atures has recently been constructed as shown in Fig. 1(a)1 based upon that work and the work of Fisher, et al2 This system exhibits a number of extraordinary features but perhaps the most striking is the odd shape of the miscibility gap (in the

Jan 1, 1959

By Alden B. Greninger

That metallographic structures analogous to the martensite of steel may be found in certain copper-aluminum and copper-tin alloys has been known for many years; similar structures recently were found in certain copper-zinc a1loys.l In all three of these alloy systems the martensite structures result from transformation of the metastable fi phase when the speed of cooling from the B range is sufficiently high to suppress decomposition into equilibrium phases. In the normal decomposition of solid solutions into equilibrium phases, diffusion is needed to bring about the necessary changes in concentration, and the rate of reaction falls almost to zero at temperatures slightly above room temperature. The rates of reaction for martensite processes, however, are not dependent upon temperature; the transformation does not require rendjustments of concentration. For example, the martensite transformation in 60:40 (B) copper-zinc does not begin until the temperature has dropped to about minus 30" C., and then continues down to minus 130" C. and probably even at lower temperatures.' Furthermore, martensite processes apparently proceed only while the tempcrature is falling, within the proper range, and cease completely while the temperature is held constant ;$ and they cannot be suppressed by extremely rapid cooling although the rate of cooling for some alloys may be increased to over 10,000 times the critical cooling velocity. Isaitschew, Kaminsky and Kurdjumow2 account for these observed behaviors of rnartensite processes by postulating that the mechanism 6I... consists in a regular rearrangement of the lattice in such a way

Jan 1, 1939