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By D. V. Edmonds, C. J. Beevers

Tensile tests were carried out on a! titanium containing 850, 1250, and 2700 ppm 0, and up to -500 ppm H. The tests were performed at -196", -78", 20°, 150°, and 300°C at a strain rate of -1.0 x 10??3 sec-1. Increasing oxygen content, increasing grain size, and decreasing test temperature resulted in enhanced embrittlement of the a titanium by the hydrogen additions. Metallographic observations showed that this can be correlated with the influence of these parameters on the introduction of cracks into the a! titanium by fracture of titanium hydride precipitates. CRAIGHEAD et al.1 reported that the hydrogen content normally found in commercial-purity a! titanium (60 to 100 ppm) was sufficient to cause a substantial lowering of the impact strength, and they attributed this embrittling effect of hydrogen to the precipitation of titanium hydride. Lenning et al.&apos; found that in commercial-purity a titanium there is an almost complete loss of impact strength at about 200 pprn H, which is approximately half the value needed to eliminate the impact strength of high-purity a titanium. They also showed that the presence of 3000 ppm hydrogen reduces the room-temperature tensile ductility of commercial-purity material to a value of the order of 10 pct; the corresponding hydrogen concentration for high-purity titanium is over 9000 ppm. It thus appears that the detrimental effect of hydrogen on the mechanical properties of commercial-purity titanium becomes evident at much lower hydrogen contents than for high-purity titanium. The main difference between the two types of a titanium might be expected to be the higher level of interstitial impurity in the commercial-purity grade. Jaffee et a1.3 studied the influence of temperature and strain rate on the hydrogen embrittlement of high-purity and commercial-purity ! titanium. In general, the behavior was the same for both materials; embrittlement was enhanced by decreasing temperature and increasing strain rate. Recent results from tests on commercial-purity a titanium containing 850 ppm O and varying amounts of hydrogen up to -500 ppm showed that the degree of embrittlement by hydrogen is intimately related to the fracture characteristics of titanium hydride precipitates.4 The present paper considers the interrelationship between the mechanical properties and micro-structural features of commercial-purity a! titanium containing 850, 1250, and 2700 ppm 0 and varying amounts of hydrogen up to -500 ppm. 1. EXPERIMENTAL PROCEDURE Three types of commercial-purity titanium supplied by IMI* were used in the investigation, and for the *Address: Witton, Birmingham 6, United Kingdom. purpose of this paper are designated Ti 115, Ti 130, and Ti 160. The principal impurity elements are given in Table I. The material was received in the form of 12.7 mm diam bars having a fully recrystallized structure. Tensile specimens with a round cross-section of 4.5 mm diam and a gage length of 15.2 mm were machined from the bars. In order to develop the same grain size (mean linear intercept of grain boundaries) in each of the three types the specimens were annealed under a dynamic vacuum of <10?5 mm Hg, Table 11. Specimen hydriding was carried out in a modified Sieverts apparatus;&apos; hydrogen was taken into solution at 450°C and after holding the specimens at this temperature for 24 hr they were furnace-cooled to room temperature at an average rate of -100 C deg per hr. By this method nominal hydrogen contents of 0, 50, 100, 250, and 500 ppm were introduced into specimens of Ti 115, Ti 130, and Ti 160 (100 ppm (wt) -0.5 at. pct). The actual hydrogen contents were calculated from the weight differences obtained by weighing the specimens before and after the hydriding treatment. Tensile tests were carried out at temperatures of -196", -78", 20°, 150°, and 300°C on a 10,000 kg In-stron machine at a nominal strain rate of -1.0 x 10-3 sec-1. Fractured specimens were sectioned in planes parallel to the tensile axis, mechanically polished to 0.25 µm grade of diamond paste, and then attack polished using a solution containing by volume 99 parts H2O, 1 part HF, and 1 part HNO3. Although the latter treatment unavoidably opened out cracks and voids visible after mechanical polishing, it did reveal the grain structure, titanium hydride morphology, and deformation twinning structure.

Jan 1, 1970

By Frank C. Aplleyard

The two calcium sulfate minerals-gypsum and anhydrite-occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO4•2H2O) and anhydrite, the anhydrous form (CaSO4) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the largest part of total calcium sulfate reserves. However, it has very minor economic use, and most of the following discussion will be devoted to gypsum. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [Sulfur Combined Lime Trioxide Water (CaO) (SO,) (H2O) Gypsum 32.6% 46.5% 20.9% Anhydrite 41.2% 58.8% -] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have never been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. As a result most mine production of gypsum will range between 85 and 95% pure. Often it is used as mined, although in certain cases, one or more forms of mineral beneficiation are employed to upgrade the product. End Uses The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris (the hemihydrate of calcium sulfate, CaSO4 ½ H2O) which when mixed with water will set or harden as the calcium sulfate returns to the dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uncalcined uses of gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in less developed countries where construction and other industrial uses may be quite limited, the use of uncalcined gypsum for portland cement retarder may well be the dominant-if not the only-market for the mineral. It has often been noted that calcium sulfate constitutes the world&apos;s largest reserve of sulfur, and minor use of both anhydrite and gypsum has been made to produce sulfuric acid or other sulfur compounds such as ammonium sulfate. However, because sulfur is readily available at lower cost from other sources, use of calcium sulfate has been limited to only a few locations where it could compete economically. No such use is reported in the United States at this time. Mineralogy Anhydrite, CaSO4 because of its geologically rapid conversion to gypsum, and relatively high solubility (about 0.2 g per 100 g H2O) is not often found outcropping in climates wet enough to support abundant vegetation except on steeply dipping slopes or other places where hydrated material is continuously removed. Anhydrite rock is most often light to bluish gray in color, and under the microscope, varies

Jan 1, 1983

By K. E. Brown, F. W. Jessen

By utilizing an 8,000-ft experimental field well equipped with 10 gas-lift valves and 10 Maihak pressure recorders, gas-lift tests were conducted with port sizes ranging from 5/16 through I in. The well was equipped to provide accurate means of measuring surface pressures, temperatures, quantity of injection gas and fluid production. The tests were conducted in 2%-in. OD tubing, and the well was making 95 per cent water. A complete evaluation of gas-lift-valve port sizes shows the relationship of per cent recovery, gas-liquid ratios, minimum pressure created at the operating valve and horsepower requirements for each port. The length of time necessary for the fluid in the tubing to reach equilib.rium conditions after each cycle was recorded. Fallback of fluid at depths of 477, 969, 1,685, 2,493 and 4,290 ft was noted. For each port size, pressure loads of 2.50, 300, 350, 400 and 450 psi were lifted with a valve operating at approximately 550 psi at 6,000 ft. Gas-liquid ratios for each load were varied from excess gas to a gas volume per cycle whereby the load failed to reach the surface. Numerous curves are presented in evaluating the accumulated dara. The results show a 1-in. port to be the most efficient under all conditions. The production of intermittent liquid slugs against different-sized surface chokes was evaluated. These tests were conducted from a 7/16-in. ported valve at 4,072 ft. Tests indicate that, when possible, a %-in. in diameter choke or larger should be used at the surface. In the past few years most of the advancement in gas-lift operations has been made in continuous-flow operations. Yet, it is estimated that at least 70 per cent of the wells on gas lift in the United States are of the intermittent type. Since the term "slug flow" is sometimes used in both intermittent- and continuous-flow operations, it would be well to distinguish between the two types of flow. Continuous-flow gas lift is defined as a method whereby the fluids are produced at a continuous rate at the surface. This generally requires a continuous injection of gas through a surface choke; however, various other control devices sometimes are installed to eliminate freezing, to shut-off gas during natural flow periods, etc. The actual flow of fluids in the tubing may be of the slug type (one of many flow patterns known to exist in continuous flow). Intermittent flow is defined as a method of gas lift whereby the liquid is produced in separate piston-type slugs. Perhaps this type of flow could best be thought of as a ballistic-type flow where the liquid leaves bottom as a piston, propelled by a slug of expanding gas. Gas generally is injected through some type of control at the surface at predetermined intervals. However, the valve may have characteristics whereby gas can be injected through a small choke and still result in a ballistic-type flow. The purpose of the experimental work was to evaluate the most efficient port size to be used on the operating valve for the ballistic type of lift and, in addition, to establish the importance of utilizing a surface choke large enough to allow slugs to be produced without detrimental effects. This work is part of a compre- hensive study of both intermittent-and continuous-flow gas lift, representing a joint project conducted by the Ohio Oil Co., the Sun Oil Co., Otis Engineering Corp, and The U. of Texas. The problem of evaluating port sizes has been given little previous attention. Some work undoubtedly has been done which has not been published to date. Some tests were conducted when the wireline, mechanically-opened valve (Nixon) first came on the market. This valve was capable of utilizing full tubing area as its port size. It is known that this was a very efficient valve, but to the authors&apos; knowledge the results of tests have never been published. EXPERIMENTAL EQUIPMENT These tests were conducted on an actual field well, the Ohio-Sun Unit Well No. 2-E, in the North Markham-North Bay City field, Matagorda County, Tex. The well incorporated 23/8-in. OD tubing and produced 95 per cent water. Since the running of equipment was to be quite elaborate and expensive, a well was selected in which both intermittent- and continuous-flow tests could be conducted. This particular well was capable of producing in excess of 1,000 B/D of liquid (95 per cent salt water), yet with a 3/64-in. in diameter bottom-hole choke, production was controlled to 82 B/D. Most of the intermittent tests were conducted at this low rate. Figs. 1 and 2 show all the surface and down-hole equipment. As can be seen, every attempt was made to insure that ample equipment was available for reliable testing procedures. Fig. 1 shows the surface testing equipment. The input gas was controlled first by a regulator, then

By S. N. Singh, M. C. Flemings

Results are presented of a study on the combined influences of ingot dendrite am spacing and thermo-mechanical treatments on the fracture behavior and mechanical properties of high purity 7075 aluminum alloy. The most important single variable influencing mechanical properties was found to be undissolved alloy second Phase (microsegregation inherited from the original ingot). Ultimate and yield strengths were found to increase linearly with decreasing amount of alloy second phase while ductility increased markedly. At low amounts of second phase, transverse properties were approximately equal to longitudinal properties. In tensile testing, microcracks and holes were invariably found to originate in or around second phase particles. Fracture occurred both by propagation of cracks and coalescence of holes, depending on the distribution and amount of second phase. IN most commercial wrought alloys, second phase particles are present that are inherited from the original cast ingot. These include, for example, non-equilibrium alloy second phases such as CuAl2 and impurity second phases such as FeA13 and Cr2A1, in aluminum alloys. A previous paper1 has dealt with the morphology of these second phases in cast and wrought aluminum 7075 alloy, and with their behavior during various thermomechanical treatments. In this paper we discuss the influence of the particles on mechanical properties and fracture behavior of the alloy. Previous experimental work indicating a direct and major effect of second phase particles on mechanical properties (especially on ductility) includes the work of Edelson and Baldwin on pure copper.&apos; Also relevant are the many studies demonstrating the important effect of nonmetallic inclusions on the fracture of. steel.3&apos;4 Work on aluminum includes that of Antes, Lipson, and Rosenthal5 who showed that a dramatic improvement in ductility of wrought aluminum alloys of the 7000 series is achieved by eliminating second phases. It now seems well established that included second phases play a dominant role in controlling ductility (as measured, for example, by reduction in area in a tensile test) of a variety of materials. There is, therefore, considerable current interest in the mechanisms by which second phase particles affect ductile fracture. Experiments done by various workers have shown that second phase particles or discontinuities in the microstructure are potential sites for nuclea-tion of microcracks and of holes,6-l3 which then grow and cause premature fracture and the loss of ductility. Theoretical attempts have been made to explain the observed phenomena; most are able to explain observations qualitatively, but lack quantitative agreement. Much experimental work needs to be done to aid extension of theoretical models. A recent review article by Rosenfield summarizes work in this general area.14 PROCEDURE Material used in the previously described study on solution kinetics of cast and wrought 7075 alloy1 was also used in this study. Procedures for ingot casting, solution treating, and working were described in detail in that paper. Test bars were obtained for material of 76 initial dendrite arm spacing (11/2 in. from the ingot base) and 95 µ initial dendrite arm spacing (51/2 in. from the ingot base) for the following thermomechanical treatments (solution temperature 860°F; reduction by cold rolling). a) Solution treated 12 hr, reduced 2/1, 4/1, and 16/1. b) Solution treated 12 hr, reduced 16/1, solution treated approximately 5 hr after reduction. c) Same as a) except solution treated 24 hr prior to reduction. d) Same as b) except solution treated 24 hr prior to reduction. e) Same as d) except solution treated 20 hr after reduction. Test bars were taken both longitudinally and transverse to the rolling direction. Transverse properties are in the long transverse direction; since the final product was sheet (0.030 in. thick), properties in the short transverse direction could not be obtained. Test bars were flat specimens, of gage cross section1/-| in. by 0.030 in. and 1/2 in. gage length. After machining the test bars, they were given an additional 1/2 hr solution treatment of 860°F and aged 24 hr at 250°F. Three bars were tested for each location and thermomechanical treatment, after rejection of mechanically flawed bars. The average results of these three bars are reported. Elongation was measured using a $ in. extensometer and reduction in area was determined using a profilometer to measure the area after fracture. INFLUENCE OF THERMOMECHANICAL TREATMENTS AND SECOND PHASE ON MECHANICAL PROPERTIES Results of mechanical testing are presented in Figs. 1 to 4 and in tabular form in the Appendix. A general conclusion from results obtained is that details of the thermomechanical treatments studied were important only insofar as they influenced the amount of residual second phase. Figs. 1 and 4 show the longitudinal properties obtained (regardless of thermomechanical

Jan 1, 1970

By P. W. Gilles, B. D. Pollock

THE pioneering work of Steinitz1 and Steinitz, Binder, and Moskowitz2 has shown conclusively the existence at high temperature of two additional phases in the molybdenum-boron system and thus brings to a total of six the number of structures appearing in this system. To the structures Mo2B, MOB, and Mo2B5 they have added MO3B2, a new -MOB form, and have shown that MOB,, which has the same range of composition as Mo2B5, is only a high temperature structure of the latter. This solid solution, interestingly enough, includes neither of the compositions corresponding to the stoichiomet-ric compounds, MOB, or Mo2B5, but rather at all temperatures has intermediate values of composition. These workers have also, in the course of their work, measured melting points, transition temperatures, eutectic and peritectic points in the system and have shown that Mo3B2, because of its dispro-portionation at low temperature to Mo2B and MOB, is stable only in a limited high temperature range. During the course of the present work on the vaporization properties of the molybdenum-boron compounds, a few transition temperatures were observed. When the report of the other workers appeared, it was decided to repeat, in part, their study of the system. As a result, considerable evidence has been obtained that substantiates the specific kinds of melting processes they report as well as the general features of their diagram. However, a marked difference was found between the temperatures they report and the ones observed in this study, with the latter being higher. The purposes of this paper are to present the evidence obtained in this laboratory that verifies their diagram of the system, to give some important temperatures in the system, to compare them with those previously published, and to seek an explanation of the difference. Samples The metal starting material was 400 mesh molybdenum powder with a purity stated by the manufacturer to be 99.9 pct. The initial treatment, designed to remove volatile contamination, consisted of heating in a vacuum for 10 min to a temperature of from 800" to 1000°C during which a loss of 0.3 to 0.4 pct occurred. An assay following this treatment showed it to be 99.4 pct pure, with the principal impurity probably being oxygen. The boron starting material was obtained from the Cooper Metallurgical Laboratories and the Fair-mount Chemical Co. as 325 mesh powder with manufacturers&apos; analyses of 99 pct or better. Initial treatment consisted of heating in molybdenum in a vacuum at about 1700°C for 10 min. During this time a loss of 3.5 pct occurred. An assay following this treatment showed the different samples to have purities ranging from 95.5 to 99.0 pct with iron and carbon as the principal impurities. Following the initial treatment, the elements were combined to form stocks of Mo2B and MOB by heating pressed mixtures in a vacuum to 1100" to 1200°C to accomplish reaction and to 1500" to 1900°C for a few minutes to evaporate the more volatile impurities. Analysis of the two compounds for boron by a modification of the method of Blumenthal3 and for molybdenum by the lead-molybdate method indicated them to have purities greater than 99 pct. The individual samples to be studied had compositions in the Mo2B-MOB range and consisted of mixtures of the stock compounds. Procedure As is usually the case in high temperature work the selection of containers for the samples posed some problems. For vapor pressure studies tantalum crucibles, allowing little contact with the pressed samples, were used and some of the observations made during these experiments are pertinent to the study of the phase diagram. Most of the experiments, however, were performed in graphite containers, as were those of the previous authors. Two kinds of spectroscopic grade graphite crucibles were used. One was a % in. cylinder, 3/4 in. high, containing seven 3/16 in. holes drilled 1/2 in. deep into which were packed samples of the different mixtures weighing 250 to 500 milligrams. The other, consisting of separate crucibles, was prepared by drilling 3/16 in. holes, 1/2 in. deep into 1/4 in. graphite rods % in. long. The 7/8 in. cylinder was heated directly by induction while the small crucibles were packed in a tantalum heating element for induction heating. All heating was done in a high vacuum system in which the pressure was generally less than 1x10-5mm and never rose above 2x10-5mm when the samples were hot. The general pattern of the heating in graphite was to heat rapidly to a temperature somewhat below the desired one, then to raise the temperature slowly. The samples were held for 2 to 5 min at the maximum temperature, which in all cases was far higher than that needed to produce reaction. The short time was employed to reduce possible contamination by the crucible material and to reduce composition changes that would occur because of vaporization. After examination following the heating, the samples were reheated to a higher temperature. Temperatures were measured with a Leeds and Northrup disappearing filament optical pyrometer, certified by the National Bureau of Standards, by sighting through a window at the top of the vacuum

Jan 1, 1954

By E. C. W. Perryman

The recovery and recrystallization characteristics of superpurity aluminum have been investigated using electrical resistivity, X-ray line breadth, and hardness measurements for the former and the micrographic method for the latter. The three different properties recover at different rates and have different activation energies. The recrystallization results agree well with Avrami&apos;s theory and furthermore indicate that the perfect subgrains formed during recovery are not the nuclei for re-crystallization. WHEN a metal is plastically deformed, its physical and mechanical properties generally undergo considerable changes and by subsequent annealing these changes are partly or wholly annihilated. Thus, a recovery process can be discussed, taking this term in its general sense. In practice, however, there is reason to discriminate between two apparently different processes, one most easily followed at low temperatures, in which the properties return to an almost constant value between that of the cold worked and fully annealed material, and a second process in which the properties return to their original values before cold working and which is accompanied by the formation and growth of new grains having an orientation different from that of the matrix. In this paper the word recovery will be taken to mean the changes in some property as a function of annealing time which occur either without the appearance of new grains or under conditions such that the new re-crystallized grains are very small (= 2 microns), are very few in number, and substantially do not affect the property being measured. This definition is rather abitrary, for it will depend upon the sensitivity of the technique used for the observation of new recrystallized grains, which in the present work was about 1 to 2 microns. However, it is helpful to use the term recovery in this sense and to reserve the term recrystallization for the processes of nucle-ation and growth of new grains in the cold worked matrix. Although considerable work has been done on recovery and recrystallization, most workers have based their study on the measurement of one or perhaps two parameters. Since very small amounts of impurities have such a profound effect on the recrystallization characteristics of a pure metal, it becomes extremely difficult to correlate one piece of work with another. With this in mind, the present work on recovery and recrystallization was done on the same material. Experimental Procedure Material Used and Fabrication: The composition of the superpurity aluminum used throughout this investigation was 0.002 pct Cu, 0.003 pct Fe, 0.003 pct Si, and <0.001 pct Mg. The ingot was hot rolled to 0.250 in., annealed, and cold rolled to 0.034 in. A large number of reductions and intermediate anneals were carried out so as to produce material with a minimum of preferred orientation and maximum homogeneity. For the recovery part of the investigation, the final cold reduction was 20 and 80 pct and for the recrystallization part, 20 pct. After each pass in the cold rolling process, the material was quenched in cold water in order to keep the rolling temperature as near room temperature as possible. Annealing Procedure: For the recrystallization work, specimens 1x1 in. were cut from the 0.034 in. cold rolled sheet and a hole was drilled in each through which a wire was threaded to support it in the salt bath. The temperature of the salt bath was controlled to +2°C and the time taken for a specimen to reach temperature was approximately 5 sec. These 1 in. squares were then divided into three groups, one of which was given 5 min at 318°C and another 2 hr at 244°C. These treatments were such that recovery was almost complete and a well defined subgrain structure produced. Separate specimens of each group were annealed for different times at 301°, 318°, 355°, and 373°C, i.e., three specimens for each annealing time. The delay between finish of cold working and start of annealing was about 1 hr. For the recovery work, strips 0.062 in. thick were cut from the cold worked sheet, annealed, and then given the last cold rolling operation. This was done for each annealing temperature. By this means it was possible to minimize the delay between cold working and annealing. In general, all measurements were carried out within 1 hr of the last cold rolling operation. Annealing at low temperatures was done in an oil bath the temperature of which was maintained constant to +1°C. Electrical Resistivity Measurements: Strips 20x0.5x0.05 in. were machined and the electrical resistance measured using a Kelvin double bridge. Measurements were made in an oil bath maintained at 20rt0.1°C. The same specimen was used for the complete isothermal annealing curve.

Jan 1, 1956

By F. C. Langenberg

IT is the purpose of this paper to present a limited amount of experimental data obtained on the Charpy impact machine. Several concrete examples will be given showing the relation existing between the results obtained upon the Charpy impact machine and the behavior of the parts tested when in service. Although it is pointed out by G. Charpy and A. Cornu-Thenard1 that it is first necessary to determine a satisfactory working process before studying the correlation between the results of these tests and the behavior of the parts tested in service, this ideal course cannot be strictly adhered to. If a certain part repeatedly fails in service and the available tests give no indication of its cause, advantage must be taken of any possible means that will solve the problem; therefore, even though the reliability of the results obtained by the Charpy impact machine have been questioned by many, it was necessary to use this instrument without giving careful consideration to its possible sources of error. It would seem that the conclusions arrived at by Charpy and Cornu-Thénard justify the assumption that the precision obtained by this machine is comparable to that obtained by, the other more common forms of testing. The second general conclusion arrived at by them, namely, that the impact test upon notching does not offer any direct correlation to the ordinary tests, is also borne out by many hundred determinations made in the laboratories at Watertown Arsenal. This statement, however, should be qualified as follows: Other ordinary tests include the static tensile test from bars taken in a longitudinal .direction and the Brinell hardness. The author agrees that no law is yet known for the computation of the energy absorbed in the rupture of bars of the same material but of different dimensions. Although Charpy and Cornu-Thénard do not refer in their valuable article to the use of the Charpy machine in industrial practice, it should be stated that this instrument has been in constant use in the laboratory at Watertown Arsenal for several

Jan 8, 1919

By A. William Johnson

It was pointed out in an earlier paper1 that our understanding of the atomic mechanism by which diffusion occurs in metallic alloys is scarcely in an advanced state. This unsatisfactory condition is the result not of any lack of interest, but of the difficulty of designing experiments that .will yield suitable data. The diffusion coefficient of an alloy, measured in the usual way, is simply a number specifying the rate of homogenization of a nonhomo-geneous metal; this number, of itself, can furnish neither the rate at which the individual atoms move nor information as to the mechanism by which they move. It does not necessarily follow, however, that such information cannot be obtained, even if the path to be followed is still not clear. Much success has been attained in the study of diffusion in ionic crystals. A number of experiments, for which there are few counterparts in connection with metals, yield information often indicating a detailed mechanism by which diffusion probably occurs. From such work, quite acceptable theories of lattice imperfections have been developed by Wagner, Schottky, Frenkel, Jost and others.2 It is postulated that real crystals of stoichiometric composition contain, in equilibrium, certain imperfections of which the most importarlt types are: (I) vacant cation sites, with an equal number of interstitial ions; (2) vacant anion sites, with an equal number of interstitial ions; (3) equal numbers of anions and cations in interstitial positions; (4) equal numbers of vacant anion and cation sites. The classification of a particular crystal according to this scheme then follows from studies of the variation of electrical conductivity with pressure of the electronegative component surrounding the crystal, with ion size, and with temperature; other physical phenomena, such as the Hall effect, have aided in establishing the classification. The relative mobility of the anion and cation may be determined by chemical analysis of the salt at the electrodes following electrolysis. With such information, and knowing that one ion never occupies the lattice site normally belonging to an ion of opposite sign, it is usually possible to ascertain the diffusion mechanism. It is clear that the same experiments are not applicable to metal crystals, and substitute experiments that yield as much information have not yet been devised. Much can be learned, however, about the mobilities of the two* kinds of atoms in alloys by the use of radioactive metals as indicators. Only one such experiment has been performed in the past. In 1933, Seith and Keil,3 in an effort to explain the great difference between the rate of diffusion of gold in lead and of lead in lead, measured the rate of diffusion of radioactive lead in 3 gold-lead

Jan 1, 1942

By A. William Johnson

It was pointed out in an earlier paper1 that our understanding of the atomic mechanism by which diffusion occurs in metallic alloys is scarcely in an advanced state. This unsatisfactory condition is the result not of any lack of interest, but of the difficulty of designing experiments that .will yield suitable data. The diffusion coefficient of an alloy, measured in the usual way, is simply a number specifying the rate of homogenization of a nonhomo-geneous metal; this number, of itself, can furnish neither the rate at which the individual atoms move nor information as to the mechanism by which they move. It does not necessarily follow, however, that such information cannot be obtained, even if the path to be followed is still not clear. Much success has been attained in the study of diffusion in ionic crystals. A number of experiments, for which there are few counterparts in connection with metals, yield information often indicating a detailed mechanism by which diffusion probably occurs. From such work, quite acceptable theories of lattice imperfections have been developed by Wagner, Schottky, Frenkel, Jost and others.2 It is postulated that real crystals of stoichiometric composition contain, in equilibrium, certain imperfections of which the most importarlt types are: (I) vacant cation sites, with an equal number of interstitial ions; (2) vacant anion sites, with an equal number of interstitial ions; (3) equal numbers of anions and cations in interstitial positions; (4) equal numbers of vacant anion and cation sites. The classification of a particular crystal according to this scheme then follows from studies of the variation of electrical conductivity with pressure of the electronegative component surrounding the crystal, with ion size, and with temperature; other physical phenomena, such as the Hall effect, have aided in establishing the classification. The relative mobility of the anion and cation may be determined by chemical analysis of the salt at the electrodes following electrolysis. With such information, and knowing that one ion never occupies the lattice site normally belonging to an ion of opposite sign, it is usually possible to ascertain the diffusion mechanism. It is clear that the same experiments are not applicable to metal crystals, and substitute experiments that yield as much information have not yet been devised. Much can be learned, however, about the mobilities of the two* kinds of atoms in alloys by the use of radioactive metals as indicators. Only one such experiment has been performed in the past. In 1933, Seith and Keil,3 in an effort to explain the great difference between the rate of diffusion of gold in lead and of lead in lead, measured the rate of diffusion of radioactive lead in 3 gold-lead

Jan 1, 1942

By Arthur F. Taggart

PROGRESS in a technical art is of several kinds. It springs .from many diverse sources. It comprises invention, mechanical improvement, operating advance, analytical study, education. Invention is, by definition, a relatively great, essentially individual step, taken quickly. Operating advance is the slow, cumulated march of practice; in contrast, it moves at the pace of the tortoise, but over, the years its effects rival and, in some cases, surpass those of invention. Mechanical improvement- is a usual concomitant of the reduction of invention. to operating practice; thereafter it is a primary tool of operating advance. Analytical study is the process of mental digestion of the fruits of invention and practice. Its purpose is to render these into a form assimilable by the art as a whole, and by the perennial crop of would be practitioners. Education, disseminating the results of such study, consolidates and maintains the positions gained. Thus, slowly at first, but continuously accelerating, the tide of progress grows- to flood. Such growth, in mathematical parlance, is expressible in the general form y = mxn, where x is time, n is some positive number greater than one, m is another positive number, and y is the state of the action at instant x. When n is 2, the readers will recognize the graph of the equation as one branch of the familiar square parabola, whose property it is to become parallel to the y-axis; i.e., to move at an infinite rate, in that never-never

Jan 1, 1947

By H. W. McQuaid

IT IS usually assumed that chemical specifications are sufficient for steel to be used for case carburizing, and if the steel analyzes within the ordinary limits specified for steel for this purpose, no difficulty traceable to the steel used should be encountered in obtaining satisfactory results in the case carburizing and hardening. Much work has been done to determine the effect of various alloying elements on the rate of carbon penetration, etc. but, to our knowledge, little if anything has been published in regard to the effect of the quality of the steel on the final results in the hardening of case-carburized steel parts. The writers believe that the structure of the case both before and after quenching is greatly affected by the actual condition of the steel itself as made, and that for good results in the case-carburizing and hardening departments, the steel should be of the best possible quality as regards non-metallic impurities. It is the purpose of this paper to prove that the presence of excess dissolved oxides in the steel, as made in the melting furnace, affects permanently the results obtained in carburizing and hardening and that it is possible that the presence of dissolved oxide can result in total unfitness of low-carbon steel for, case hardening purposes. When races and rolls for roller bearings are made from a low-carbon steel, case carburized and hardened, it is of primary importance that the results of this treatment be of the highest quality. It is necessary, therefore, that in the case-carburizing work each detail be rigorously checked to avoid any defects which would cause the loss of much time and material. The case carburizing with which this paper deals was done in under-fired oil furnaces. The temperature of each furnace is controlled by means of a platinum platinum-rhodium thermocouple, in connection with a potentiometer indicator and potentiometer recorder. The temperature of each furnace is registered every 15 min. by an operator, who is continually checked by the automatic recorders.

Jan 2, 1922

The Pueblo plant receives its principal supply of iron ore from the Sunrise mine, located in Platte County, Wyo., and Iron Mountain, southwest of Cedar City, Utah. Limestone from Monarch quarry located on the continental divide above Salida, Colo., is shipped into Pueblo to be used as a flux. Of importance to the successful operation of the blast furnace plant is the ore preparation unit at Pueblo. Due to the geologic structure of both the Utah and Wyoming deposits, the ores, both high in grade, are quite variable in chemical and physical nature.

Jan 11, 1953

By B. C. Allen

Grain boundary grooving has been studied in chromium, molybdenum, and tungsten under a variety of conditions using high vacuum techniques and tantalum -gettered argon. The average surface free energy of solid chromium, and the chromium-liquid silver interface free energy were respectively found to be 2200 ± 250 and 500 i 130 ergs per sq cm from groove formation kinetics and estimates of pertinent volume difffusion coefficients. The results for chromium were unffected by variations in interstitial content ranging from 0.003 to 0.09 pct C, or 0.003 to 0.03 pct O. Surface diffusion is the primary mechanism of groove formation in chromium under 1 atm argon at 1200" to 140O°C, and is essentially unaffected by 0.003 to 0.09 pct C, 0.003 to 0.03 pct O , metastable nitrogen contents up to -0.01 pct, and up to 2 torr Ag vapor. At higher temperatures, the major mechanism is volume diffusion in argon or evaporation-condensation in stutic vacuum. Surface diffusion occurs in molybdenum at 0.5 to 0.96 and in tungsten at 0.5 to 0.9 of the absolute melting tempera -ture by a single mechanism, possibly by the migration of single adatoms or vacancies. Results were slightly affected by up to 23 tory Sn vapor, and in molybdenum were essentially unaffected by 0.5 Ti or carbon in the range 0.002 to 0.02 pct. Volume difffusion through the liquid is the mechanism of groove formation in chromium-liquid silver at 1200" to 1400°C and in molybdenum-, Mo-0.5Ti-, and tungsten-liquid tin at 1200" to 2000°C. The solid-liquid interface free energies involved were estimated from grooving kanetics. WHEN a grain boundary intersects a solid surface, a groove tends to form along the line of intersection at temperatures above about half the absolute melting point (0.5 TM). The groove progressively grows by preferential atomic migration either by diffusion or evaporation. Establishment of a groove angle occurs in accordance with the grain boundary and surface free energies involved. The motivation for groove formation is a reduction in the total surface free energy of the system. This study is a continuation of previous work on thermal grooving of chromium, molybdenum, and tungsten.&apos; The temperature ranges were extended, and the effect of metallic and interstitial impurities was evaluated. The results were such that certain interface free energies and surface self-diffusion coefficients were deduced from the grooving kinetics. EXPERIMENTAL WORK Materials and Preparation. As indicated in Table I, the 0.05-0.08-cm-thick chromium, molybdenum, and tungsten sheet used was nominally 99.99 pct after recrystallization. Two lots of molybdenum with about the same analysis, Mo-0.5Ti,* and tungsten were ob- *Alloy compsitions are expressed in weight percent . tained commercially. Extruded chromium rod,&apos; prepared from iodide process crystals, was warm rolled to sheet at 700°C. Sheet of three Cr-0 impurity alloys containing up to 0.03 pct 0 was prepared by warm rolling arc melted, extruded, and swaged rod. Two Cr-C impurity alloys containing up to 0.09 pct C were made by equilibrating unalloyed chromium with a known amount of CH4 for 24 hr at 1150°C in previously evacuated quartz capsules. Chromium containing nominally 0.015 and 0.06 pct N was similarly prepared by equilibration with NH3. The sheet was recrystallized to give a stable grain size about equal to the sheet thickness. Molybdenum and Mo-O.5Ti were recrystallized in a tantalum resistance furnace 1 hr at 1 x lo-5 torr at 2300" and 220O°C, respectively. Tungsten was similarly annealed for 1 hr at 2500°C. Chromium and its impurity alloys were outgassed at 1100°C and recrystallized 1 hr at 1700°C under 1 atm Ar. Except for nitrogen, the impurity content stayed roughly constant. Nitrogen in both alloys was reduced to <0.001 pct. In fact, over 80 pct of the added nitrogen was lost after outgassing at llOO°C and annealing sheet 1 hr at 1300°C in argon in the presence of tantalum. Such a rapid loss can be rationalized since -2 torr N are required for equilibrium with 0.04 pct N in solution,3 while the equilibrium pressure is ~10-5 torr over tantalum at 1300°C.4 The recrystallized sheet was cut into small coupons which were metallographically ground and polished on one side with a minimum of grain boundary relief. The surface roughness was on the order of 0.01 µ. The tin and silver used were nominally 99.999 spec-trographically pure. After being outgassed at 1100°C and equilibrated in a molybdenum crucible for 0.5 hr at 1800°C in argon, the tin contained 3 ppm 0, <0.3 ppm N, and 0.1 ppm H. Following outgassing at 900°C and equilibration in a chromium crucible 1 hr at 1400°C in argon, the gas content of the silver was 1 ppm O, <0.5 ppm N, and 0.3 ppm H. Grooving Under Argon or Vacuum. All specimens were placed in unsealed containers made from rod or sheet of the same alloy, thereby enabling the polished surface to achieve gas-solid equilibrium. The annealing fixtures are shown in Fig. 1. The specimen was placed in a resistance furnace with a tantalum or Ta-10W heating element plus tantalum fixtures or radiation shields. Chromium was outgassed at 1100°C, and molybdenum and tungsten were outgassed at 1900°C to 1 x l0-5 torr or at the grooving temperature, whichever was lower. In vacuum anneals, the specimen was then heated directly to the intended grooving temperature. In argon anneals, 99.996 Ar was admitted

Jan 1, 1970

By Charles H. Thurman

THE data given herein were first included in a paper read before San Francisco Section, A.I.M.E., in October 1940, and are applicable to conditions existing until the gold-dredging industry was temporarily suspended by Order L-208 of the War Production Board in the fall of 1942. There is no doubt that gold dredging will be resumed at some future time, and on a scale equivalent to that of the recent past, but the cost data given herein will be affected to some extent by conditions existing at that time, and by labor rates and prices for materials then prevailing. DRAGLINE VS. BUCKET-LINE Dragline dredges should not be considered for mining large areas of low-grade placer gravel. In such deposits a dragline operator with a 5-cu. yd. dragline would be doing well to maintain an operating cost of 6¢ per cu. yd., while a bucket-line dredge with buckets no smaller than 7 cu. ft. each could be operated for less than 4¢ per cu. yd. By operating costs, I mean only field charges such as direct operating and overhead, which includes pay roll, power or fuel, repairs and maintenance, insurance, land clearing and general expenses, but not including such items as prospecting, depletion, depreciation of equipment, State Franchise Tax, or Federal Income Tax. It is not to be inferred that a dragline dredge cannot make a profit in small low-grade deposits, where the extent of a given property is too small to justify the use of the more costly bucket-line dredge. Consider small deposits of 10¢ gravel. It is obvious that a deposit of 5,000,000 cu. yd. of such gravel could not be mined profitably with a new, 7-cu. ft. bucket-line dredge, costing upward of $250,000, and with operation costs at 4¢ per cu. yd., paying for land or royalties out of earnings; nor could a new combination 5-cu. yd. dragline and washing plant, worth upward of $125,000 and working at 6¢ per cu. yd., make a profit. These comparisons are made because the hourly capacity of both types of dredges is nearly the same. The bucket-line dredge averages 93 per cent operating time in 24 hr., as against about 80 per cent or less for the dragline dredge. These percentages of operating time are important factors in making a comparison of this kind. The bucket-line dredge has greater efficiency in cleaning soft bedrock, usually characteristic of dredging deposits, and a 7-cu. ft. bucket-line dredge can be efficient to a total digging depth of 80 ft. (65 ft. below water, 15 ft. above). A 5-cu. yd. dragline dredge is limited to about 30 ft. of efficient digging depth, 5 ft. of which could be above water. In small areas of gravel not over 30 ft. deep, a 5-cu. yd. dragline dredge could make a profit where a bucket-line dredge could not do so. As an example: compare the dredging of 3,000,000 cu. yd. of 10¢ gravel 28 ft. deep with bucket line, costing 4¢ per cu. yd., and with a 5-cu. yd. dragline dredge operating at 6¢ per cu. yd. Because of small yardage, new equipment is not warranted, therefore we can assume that the dredges of both types are used equipment, fully depreciated. Dismantling, mov-

Jan 1, 1945

By Richard R. Bains

"When l hear - I normally remember 10 percent When I hear and see - I can remember 15 to 25 percent When I hear, see, and do - I usually remember up to 50 percent" While this is not a truism in relation to each and every individual; on the average, this is the case. If we use this as a premise in training operator and maintenance personnel, then it must be obvious that we can&apos;t rely on a mere presentation, even one which includes the needed classroom participation and/or hands on work, to do a thorough job and to make this personnel totally proficient - 100 percent proficient. We have to have some other device some other means to make this a continuing process, a process wherein the people can grow in knowledge while performing their normal duties. We have to feel that the words "normal duties" are the key to the whole program. If you would ask a crusher operator what his duty is, he might say "To run this crusher so that we produce 250 tons per hour of a minus 13mm (minus 1/2 ") product." A maintenance man could say "To fix the unit when there is a problem." Both of these answers are legitimate but, they are only a part of the total picture. In order for each of these individuals to do the best job, he must know not just the specifics about the machine he works with or on - he must know the interrelation of all the machinery in the crushing circuit - how the efficiency of each machine affects the others - why a minor problem on one piece of equipment can generate a major problem for another unit which follows it or precedes it. In short, you cannot separate machine operation and maintenance from the application of the equipment in the crushing circuit - and obtaining this knowledge must be a part of the normal duty of crushing plant personnel. As an example a crusher - any crusher - is designed to crush oversize material. It is not designed to accept feed which is already at or less than the required product size. If sized material goes to the crusher, increase wear results by using the crusher as a chute or the crushing chamber can be clogged up with the fines. This latter point is particularly true with cone crushers, especially in the third (Short Head) stage of crushing. When a Gyradisc is used (fourth stage crushing) it is even more critical that the product be removed before the material goes to the crusher. The crusher cannot control this - the screen ahead of the crusher does. The screen must be of adequate size and be functioning properly to allow the crusher to work at optimum. Screening is both an art and a science. Since there are so many variables which affect the output of the screen, it is always best to have a screen which is larger than the sizing calculations dictate. The screens are the most important elements in the circuit. Without screens, specification materials cannot be made and the size of the screen will ultimately aid or hinder your ability to get the most production possible out of the plant. There is a formula available from all screen manufacturers which is designed to calculate the proper screen size. It takes into consideration the

Jan 1, 1982

Jan 1, 1900

NEW MEMBERS The following list comprises the names of those persons who became members during the period Mar. 10, 1916 to Apr. 10, 1916. ALLEN, P. R., Pres., McAlester Coal & Coke Co., Knight Templar Bldg., McAlester, Okla. BERNARD, CLINTON PERCIVAL, Min. Engr., Care Forminiere Mission Kasai, Tschikapa, Congo Belge, W. Africa. CARPENTER, GEORGE 0., Vice-Pres National Lead Co. St. Louis Mo. CLARK, WILLIAM ANDREWS, JR., Min. Engr., Pres., Elm Orlu Mining Co., Butte, Mont. CLAYTON, CHARLES YANCEY, Asst. PrOf. of Metallurgy and Ore Dressing, Missouri School of Mines, Rolla, Mo. COHEN, JULIUS MILTON, Mgr. Croesus Gold Mines, Ltd., Matheson, Ont., Canada. CRAMER, WILLIAM BRONSON, Met. at Concentrator, Old Dominion Copper Min. & Smelt. Co., Globe, Ariz. DAHL, SIMEON H., Mill Supt., Messina Transvaal Dev. Co., Messina, Transvaal S. Africa.

Jan 5, 1916

By Percival Roberts

I DESIRE to present this evening a few notes from the standpoint of a manufacturer upon the subject of tests of iron for structural purposes; not that I have any new facts to which to call your attention, but rather a statement of a few of the objectionable features of the present modes of operation, showing the absolute necessity of important and very radical changes. At the present time, as most of you are well aware, proposals for materials are accompanied by certain specifications as to quality and tests to which the manufactured article must conform. Evolved in many cases from the inner consciousness of some one more expert in theory than in practice, we find a few of the specifications to be good, many bad, and some indifferent. Appended are specimens of specifications of the most prominent engineers and railroad companies, which may be taken as representing the best and most intelligently framed specifications which we now have, arid yet in some pints scarcely satisfactory, owing to misunderstanding of tests as now made. To show the very varied opinions held as to proper quality of iron for bridge-work, I give the tests of two lots of fron made by inspectors with the results, which were referred to the maker with the following commensts : Lot No. 1. Teat of Iron for Eyebars. Reduced area. Elongation. Size. Per cent. Per cent. Breaking load. 4" x 1 3/8 26 25 68,500 Bent 120° around 1 1/2" bar with fracture. Reduced area. Elongation. Size. Percent. Percent. Breaking load. 6" x 1 7/15 24 24 48,820 Bent 110° around 2" bar. This iron should bend 180° without fracture, and is therefore rejected. Lot No. 2. Test of Iron for Brirlye. All measurements taken upon a parallel section of 10". Iron for tension members. Breaking load Elongation. size. per aquare inch. Percent. 1 5/8 49,600 20 14 61,600 27

Jan 1, 1882

By Eugene McAuliffe

The term "mechanical mining" carries an ambiguity which justifies a preliminary word of explanation. . All mining activity conducted in this day is more or less mechanical; that is to say, power expressed in the form of electricity, steam or compressed air is used in some portion of practically every mining activity of consequence. "Mechanical loading" is more nearly correct than "mechanical mining" in reference to present practice. The first substantial effort made in the direction of mechanical mining, subsequent to the application of steam for hoisting and underground pumping purposes, was that of substituting for hand labor undercutting and shearing by power-driven machines. The undercutting of coal by hand represented at one time the most arduous task confronting the miner. Occupying a kneeling position in the thicker beds, or lying on his side in the thinner coal, the task was tedious and exhausting. The first attempt to substitute crude air-driven, and later electrically driven, "punchers," as the percussion type of machine was called, met with much the same opposition on the part of the workers as was expressed by workers in the other industries when any innovation, whether labor-saving or otherwise, was introduced. We should not be too critical of this attitude of mind shown by the mine workers. The peculiarly isolated character of the work carried on in semidarkness by a class of men who to a large extent lived and held themselves aloof from the other branches of society led long ago to the development of a craft consciousness which they have found difficult to surrender. It was not until 1891 that a definite record of the results obtained by the use of undercutting machines of all types was made available, the quantity undercut in that year totaling 6,211,732 tons of bituminous coal from all American mines. The volume of bituminous coal undercut by machines in 1928 totaled 369,687,007 tons, or 73.8 per cent. of the nation&apos;s production. In the light of this experience, we can properly feel that the work of introducing the coal-loading machine as a substitute for hand shoveling is making substantial progress.

Jan 1, 1931

By B. C. Craft, Murray F. Hawkins, John R. Rayne

A reservoir mechanism of sulfur recovery by the Frasch process is presented. Improving the economic, of recovery appears to be largely a well, rather than a reservoir problem. A most important factor is the limitation of the lateral extraction of .sulfur about the wells due to the almost vertical .flow of the injected hot water. Model studies are described which confirin the mechanism of sulfur recovery by presently used methods. Studies on a five-spot system indicate improved econo171ics regarding recovery, recovery rate, therinal efficiency, and well spacing. INTRODUCTION Sulfur mining by the Frasch process is one of the most important methods of sulfur production. Developed by Herman Frasch in 1894, it enjoyed a rapid growth and presently supplies 40 per cent of the world&apos;s sulfur and about 80 per cent of the U. S. sulfur." The Frasch process of mining the underground native sulfur deposits involves melting the sulfur in place by introducing super-heated water into the sulfur bearing formations, and producing the sulfur as a liquid. Many problems are encountered in mining these native sulfur deposits, and sulfur production depends chiefly upon the nature of the sulfur deposit and the underground thermal efficiency of the heat transfer system. THE RECOVERY MECHANISM Sulfur is typically found in salt dome cap rock as crystal aggregates occurring within the cavities, seams, and pores of limestone and gypsum formations.&apos; Sulfur-bearing limestone is typically cavernous, vugular, and fractured. Porosity averages about 20 per cent and sulfur saturation averages approximately 25 per cent by weight.1,15 Vhe sulfur bearing formations are very heterogeneous in nature and physical characteristics vary widely within small distances. Total cap rock thickness may vary from 50 to more than 1,000 ft, and net productive thicknesses from a few feet to a few hundred feet. In most cases the upper portion of the limestone formation is barren of sulfur, varying from 5 to 200 ft in thickness.1,15,33 The immediately overlying sediments and the underlying dense anhydrite formation provide permeability barriers to the flow of water from the cap rock section.&apos;" Sulfur wells are drilled with conventional oilfield drilling rigs. Fig. 1 illustrates the casing program of a completed sulfur well. The cap rock sections are drilled with core bits and continuous core logs are recorded. After coring, the cap rock section is underreamed to a diameter of 9 7/8 in. The bottom of the 8-in. casing is welded closed and rests on the bottom of the drill hole, which extends through the cap rock to a few feet above the bottom of the sulfur-bearing formation. The 8-in. pipe contains 5 ft of 3/4-in. perforations on 6-in. centers and 15 ft of 1-in. perforations on 1-ft centers. The 20-ft perforated section is set opposite the lower 20 ft of the sulfur-bearing formation. The 4-in. sulfur pipe is set inside the 8-in. water line on a seat ring at the top of the 5-ft section of 3/4-in. perforations. The mining water, heated to about 330°F under a pressure of 250 psi, is forced down the annulus between the 8-in. and 441-1. pipes and through the 1-in. perforations to the sulfur-bearing formation. Compressed air, at 400 psi pressure, is supplied through a 1-in. air line near the bottom of the well to provide air-lift of the liquid

Jan 1, 1957