Search Documents

By H. Reginald Hardy, Y. S. Kim

Recent studies of inelastic behavior and acoustic emission in geologic materials further validate the concept that such materials may be considered to consist of an elastic media containing an array of pores and cracks. In the present paper this concept is investigated further by experiments in which the mechanical behavior of a number of geologic materials were studied in detail at low stress levels using ultrasonic pulse methods. Experiments were carried out on cylindrical test specimens of Indiana Limestone, Tennessee Sand- stone and Barre Granite under relatively low confining pressures (0-5000 psi). Analysis of data from these experiments indicated that there existed a low-level critical stress at which there appeared to be a transition in the mechanical behavior of the material. Under triaxial stress, results indicated that the differential critical stress was relatively independent of confining pressure, i.e., the mechanism responsible for the transition in mechanical behavior was governed by a maximum shear stress criteria.

Jan 1, 1971

By Y. C. Liu, W. R. Hibbard

An aluminum single crystal cold-rolled from (110) [1121 essentially retains its initial orientation after 99.6 pct reduction in thickness. The orientation of the recrys-tallized grains of this material can be described in terms of crystallographic rotations about principal poles of deformation texture. DURING the study of the recrystallization of a copper single crystal cold-rolled from a (110) [112] initial orientation, the orientation of the re-crystallized grains could be derived by a 30" rotation of the orientation of the cold-rolled matrix about its <111> poles.&apos; The present investigation was undertaken to extend the work done on copper&apos; to an aluminum crystal also cold-rolled from a (110) [112] initial orientation. Experimental Procedure The procedure of this experiment was similar to that reported for copper.&apos; An aluminum (99.998 pct) single crystal rod* 1 % in. in diameter was grown in back-reflection technique.&apos; The specimen (1.20x 1.004x0.6787 in. thick) was then rolled along the [112] direction. The final thickness was 0.0028 in., giving a reduction in thickness of about 99.6 pet. Specimens were cut from the rolled strip with scissors, and approximately in. of disturbed metal was removed with Tucker&apos;s reagent. The rolling edge remained intact. The specimens were sandwiched between two graphite plates and annealed in a lead or lead alloy bath which was electrically heated. Pole figures were constructed using the techniques previously described.&apos; Specimens were electrolytically polished4 and etched with 47 pct HNO8, 50 pct HC1, and 3 pct of 48 pct HF. The electrolytic polishing method and etching reagent employed for aluminum specimens were not entirely satisfactory and the microstruc-tures could not be studied in any detail. Results and Discussion The octahedral pole figure of cold-rolled aluminum strip is plotted in Fig. 1. The <111> poles spread in the transverse direction approximately 8" for the highest intensity areas. The spread in the transverse direction can be related to a rotation about two <110> directions lying in a plane containing the rolling direction and rolling plane normal. The two <110> directions and a scale of rotation for the <111> poles are shown in Fig. 2. The amount of rotation is consistent for three of the four <111> poles, about 35" to 40". The discrepancy for the fourth pole is believed to be due to limitations of the film technique. Alternate inter-

Jan 1, 1956

By P. G. Shewmon, J. Y. Choi

The surface-diffusion coefficient for , has been measured on (111) and (100) surfaces of copper from 1000" to 620°C. D,(Ge) on the (111) is two to three times that on the (100) as was found earlier for copper and gold on copper. D, (Ge) on both (111) and (100) is about thirty times that found for gold or copper tracers on the same surfaces, while in the temperature range where both D,(Ge) and Ds(Au) have been measured the activation energy for germanium is the same as that for gold. The apparent activation energy for Ds(Ge) is not a constant, but decreases with temperature. In a recent paper we reported on the application of a new tracer technique to the determination of the surface-diffusion coefficient (D,) for gold and copper on (111) and (100) surfaces of copper.&apos; In this paper, we shall give the results obtained when the same technique was used to measure Ds for germanium on the (111) and (100) surfaces of copper. In addition to providing data on D., for an additional element on copper, the longer half-life of germanium (275 days) meant that Ds could be measured down to a much lower temperature and thus over a much wider temperature range (1000" to 620°C) than was used in our gold-tracer work (1060" to 780°C) or copper mass-transport studies (1060" to 800). The apparent activation energy for D, (Ge) is essentially the same as that found for gold or copper in the same temperature range, though the values of D, (Ge) are thirty times greater than those found for gold or copper tracers. The most interesting new result found is that the apparent activation energy for Ds(Ge), and thus Do, definitely increases with temperature. Such a trend was much more apparent in Gjostein&apos;s mass-transport work on copper than in our own, though in an earlier paper we mentioned the difficulty of fitting all of our points with one straight line:= No real explanation of this is given though experiments done on grain boundary groove growth at various ambient pressures demonstrate unequivocally that vapor transport plays no part in the increase in activation energy with temperature.

Jan 1, 1964

By B. Ramaswami, Y. Nakada, R. Schaefer

EARLY investigations1 of the tensile properties of fcc single crystals did not reveal the easy glide region of crystals with axial orientations inside the standard stereographic triangle. With the production of high-purity metal, a region of easy glide became known1 Consequently, modern work of fcc single crystals ordinarily uses high-purity metal. In order to determine whether further purification of aluminum beyond 99.992 pct purity would result in significant alteration of the tensile properties of single-crystal specimens, metal was zone-refined and crystals grown from the purified material were compared to crystals grown from the original material. Some similar studies were made of gold and silver crystals. Aluminum. The material to be zone-refined was cast into bars 1/4 by 1/2 by 8 in. A zone, approximately 1-1/2 in. in length, was passed over each bar eighteen times at a rate of 6 in. per hr. Melting and stirring were carried out by an induction heater under a vacuum of approximately 10"5 mm Hg, the metal being held in a graphite container. he last 3 in. of each processed bar were then cut off and discarded. No quantitative determination of purity was made, but the effectiveness of the zone refining was tested by a method first suggested by Walton, Tiller, Rutter, and winegard3 depending on the relation between cell structure and impurity content. Rutter and Chalmers4 have shown that a cellular substructure is associated with the presence of impurities during solidificatibn, and have shown how solute rejection at the freezing interface can lead to such an association. Thus the observation of cells gives evidence of impurities being present. To look for cells, the last quarter of a zone-refined bar was cut off, remelted, and grown rapidly into a single crystal. It was then heavily electropolished and thermally etched.~ Cells were revealed by the presence of many parallel rows of etch pits. The same process was carried out with material from the first half of the bar, but no cells were detected. These observations give evidence that a significant amount of impurity material was moved to the "dirty" end of the zone-refined bars. Further indication of purification was obtained from recrystallization experiments. It was found that, after cold rolling to a 97 pct reduction in thickness, the material from the pure end of the bar re-crystallized at room temperature, but the material from the "dirty" end did not. Other investigators6 have previously reported that zone-refined aluminum recrystallized at room temperature. The purified material was cast into 1/4 by 1/4 in. bars, and seeded crystals were grown in a (100) orientation and in a single slip orientation where the Schmid factor is m =2. The crystals were then cut to the desired length, annealed for 24 hr at 610°C, furnace-cooled, and etched in Tucker&apos;s etch. The crystals were tested in a floor-model Instron machine, using a gage length of 4 in. and a strain rate of 1/2 pct per min. The resulting curves are shown in Fig. 1. It is seen that the differences between the curves for zone-refined and original-purity materials are small. These differences are within the scatter observed for crystals of the original purity. In particular, the zone refining does not significantly affect the onset of the different "stages" of the curves.

Jan 1, 1964

By G. Y. Chin, W. F. Hosford

It has long been recognized that, for a crystal to undergo an arbitrary shape change by crystallographic shear, at least five independent shear systems must be activated. Taylor1 analyzed the deformation of fcc crystals by {111}<110> slip and showed that the principle of minimum work could be used to determine which combination of slip systems might act to produce a given shape change. Later Bishop and Hi112 attacked the same problem by first identifying the state of stress which could physically activate five or more {111)(110) systems simultaneously and then invoking the principle of maximum virtual work to determine which combination would act for a given shape change. Taylor&apos;s general approach has been used to calculate the active slip systems and the relative strengths during axisymmetric flow of cubic crystals with other deformation modes, including {112}<111> slip3 and {111}<112> twinning.&apos; It is the purpose of this note to identify the stress states capable of activating simultaneously five or more of these systems. {111}<112> Twinning. The {111}<112> systems are defined in Table I and illustrated in Fig. 1. The sense of the shears are those for twinning in fcc crystals. The shear stress on any system may be written in terms of the stress components expressed relative to the 1,2,3 cube axes. For example, the stress For five or more of the systems ij to be activated simultaneously, it is necessary that Tij/T be equal to unity in at least five of the expressions [3], while Tij < T for the remainder. (These restrictions assume that the same shear stress T is required to activate each system and that the shear stress on any system cannot exceed that for its activation.) The discrete values of the stress components A through H which can satisfy these restrictions are listed in Table II together with the values of Tij/T for all systems. It may be noted that Tij/ T is not necessarily zero on all nonactive systems as found by Bishop and Hill for <110> {111} slip. In fact, for the case of twinning Tij/T may reach negative values as large as -2 for shear stress in the reverse direction, Table 11. This means that, if those stress states are to be valid, the shear stress to activate reverse twinning must be greater than twice that for forward twinning. Such stress states are probably valid in view of the directionality of the twinning process. There has been no documentation of reverse twinning thus far. It may be noted that the stress states fall into four classes, which may simultaneously activate eight, six, six, and five twin systems respectively. These solutions may be applied to the {112}(111)

Jan 1, 1970

By Y. Kondo, S. Yamazaki, Z. Asaki

Thermal deco7nposition of Pyrite particles in a fluidized bed with inert gas stream was studied. Assuming that heat transfer from the surroundings to the fluidized particles controls the overall decomposition rate, rate equations for the batch process and for the continuous process were derived. In the batch experiment, a linear rate equation satisfies the experimental results and the overall heat transfer coefficient calculated from the rate constant agrees fairly well with that obtained by Leva.l1 For the continuous process, two rate equations were derived, one on the assumption of complete mixing of particles and another on the upward piston flow of particles in a fluidized bed. The former holds for a bed containing a higher fraction of decomposed pyrite realized at lower feeding rates. The latter can be applied for a bed at higher feeding rates. Thus, segregation of particles in the fluidized bed was indicated at higher feeding rates. Bed temperatures also correspond to these conditions. ThERMAL decomposition of pyrite may be represented by Eq. [I]. The pressure of diatomic sulfur gas reaches 1 atm at about 690°C. The thermodynamics,&apos; kinetics,2&apos;3 composition, and properties3-5 of decomposed products of such a reaction have been studied. Pyrite is a very common sul-fide mineral and is often accompanied with other sul-fides. It is of basic interest in nonferrous metallurgy to clarify the behavior of pyrite in the pyrometallur-gical processes of sulfide minerals of metals such as copper, lead, zinc, nickel, and so forth. Interest in this reaction increased recently because of possible elimination of arsenic from pyrite in processing highly purified iron oxide pellets. Producing elemental sulfur from pyrite, instead of sulfuric acid, also aroused interest in this reaction. It is indicated that the thermal decomposition of solid particles, such as calcium carbonate, proceeds through three major sequential steps: heat transfer, interfacial chemical reaction, and mass transfer.637 It is known that the decomposed product of pyrite is very porous2, 3 and the diatomic sulfur gas evolved can easily escape through this layer of decomposed product. It depends upon the circumstances, therefore, whether the heat transfer to the interface within particles or the chemical reaction at the interface determines the overall decomposition rate. The enthalpy change in the decomposition of pyrite is about 33 kcal per mole FeS2 which is comparable to that of calcium carbonate. The decomposition of calcium car- bonate becomes more and more dependent on the rate of transport of heat when reaction temperature increases, such as occurs in a fluidized bed.6&apos;7 It is reasonable to presume, therefore, that the thermal decomposition of pyrite, an endothermic process, carried out in a fluidized bed may be analyzed according to the heat transfer controlling model. This work intends, first, to propose a mathematical model that determines the overall rate in a fluidized bed for the decomposition process and, second, to investigate a few characteristics of the fluidized bed based upon the experimental results obtained. KINETICS OF THERMAL DECOMPOSITION IN A FLUIDIZED BED It is intended in this section to obtain rate equations for thermal decomposition of pyrite in a fluidized bed by assuming that the overall rate is determined by heat transfer from the surroundings to the particles. Both batch and continuous processes are considered. 1) Batch Process. To obtain the rate equation in the batch process, the following two additional assumptions are made. First, the temperature of preheated inert gas, tg, blown into the fluidized bed is assumed to be the same as the temperature of the fluidized bed, tf. Thus, no heat exchange occurs between the gas and particles in the bed and only the heat transfer from the reactor wall kept at tw to the particles is to be considered. Second, the decomposition is assumed to start at the outer surface of the particles and to proceed toward the center. At any given time during decomposition, undecomposed pyrite remains in the tori at a temperature: td. The decomposed shell is composed of FeS1+x whose outer surface is at tp Diatomic sulfur gas evolving at the interface is heated to tf during its escape through the decomposed shell. This is illustrated in Fig. 1. With the above-mentioned assumptions of heat transfer, we have:

Jan 1, 1969

By William Y. Holland, Roger M. Cook

In view of the increasingly widespread deterioration of concrete structures as the result of the interaction of the alkalies sodium and potassium released by hydration of portland cement and susceptible rocks and minerals in aggregates, it is believed that a paper summarizing the geographic distribution of these aggregates will be of interest to producers and users of concrete, concrete products, and concrete-making materials. THIS paper reviews the problem of alkali-aggre-gate reaction in concrete and describes the geologic and geographic occurrence and distribution of alkali-reactive sand and gravel in western United States. It includes no discussion of crushed stone or synthetic aggregates. Most deposits of sand and gravel are accumulations of particles of rocks and minerals from a variety of sources, and it is not unusual for at least one or two varieties of the rocks to contain some form of reactive material. Examination by petro-graphic methods of many sands and gravels, as well as manufactured aggregates, has shown that a comparatively high proportion of the deposits does contain, in greater or lesser degree, rocks and minerals known to be deleteriously reactive with the alkalies of cement. Fortunately the amount of reactive materials is commonly less than that necessary to cause deleterious effects in concrete. As investigation of unsound concrete structures progresses, it becomes evident that the alkali-aggre-gate reaction is even more widespread than supposed, Figs. 1 and 2. Even though some parts of the country appear at present to be immune, further investigations will probably show that the effects of alkali-aggregate reaction can be seen in many structures in these areas, although only on a small scale in most of them. Many concrete structures will, of course, have lived their useful life before disintegration from this cause is serious, and in others the alkali-aggregate reaction may never become significant even though the microscopic evidence of reaction is present. The alkali-aggregate reaction first was reported to be a cause of deterioration of concrete in 1940 when Stanton1 described expansion of concrete pavements in California. Similar expansion and deterioration of concrete was recognized during succeeding years in concrete structures located in many parts of the country, but particularly in the western states. A number of concrete laboratories2 became interested in the problem. It was soon determined that only certain combinations of aggregate and cement caused the alkali-aggregate reaction to take place, and moreover that the reaction progresses only in the presence of water. Further research proved that cements containing more than 0.60 pct total alkalies (pct Na,O + 0.658 x pct K2O), when used with aggregates containing appreciable amounts of reactive ingredients, caused the reaction to take place, usually with subsequent deterioration of the concrete. During the last few years this limitation has been adhered to in both government and private construction as the maximum allowable alkali content of cement to be used with aggregates of known alkali reactivity. Because of this limitation, it appears that deleterious reaction either has been reduced or eliminated in many recently built structures in which it probably would otherwise have occurred. Recent tests have shown that the degree of expansion obtained with any particular cement-aggre-gate combination depends not only on the alkali content of the cement but also upon the relation of this alkali content to the amount and degree of reactivity of reactive constituents in the aggregate.&apos; In laboratory mortar bars, opal and cements with alkali content of as low as 0.2 pct (as equivalent of Na2O) have produced deleterious expansion as the result of alkali-aggregate reaction. These experiments demonstrate that aggregates containing even 0.1 pct of opal are deleteriously reactive. It was soon determined that alkali-silica gels were formed by the interaction of the alkalies of the cement and the reactive aggregate, Figs. 3 and 4. Osmotic or swelling pressures produced by the continued hydration of these gels cause expansion of the concrete with resulting cracking, warping, and dislocation. Evidence of the alkali-aggregate reaction can be seen by a petrographic study of the deteriorated concrete. Among the first structures studied by this method was Parker Dam on the Colorado River, California-Arizona. In the concrete from this dam pebbles of rhyolite, andesite, siliceous limestone, and chalcedonic chert were found to be reactive.

Jan 1, 1954

By Y. C. Liu, G. A. Alers

The effect of rolling reduction on the textures of Cu-A1 alloys has been investigated both by pole figure and by modulus methods. In alloys which exhibit complete copper or brass types of rolling texture, the rolling reduction has little effect on the texture except to increase the degree of preferred orientation. In alloys which exhibit a transition texture, however, increased rolling reduction increases the amount of brass-type texture at the expense of the copper-type texture. The present experimental results show that there is no one-to-one correspondence between the SFE and the rolling texture of fcc metals. Additional data taken from the literature for fcc metals also support this conclusion. On the other hand, the present and previous experimental results are shown to be in good agreement with the suggestion that the texture transition occurs at a critical value for the separation distance between two partial dislocations—a consequence of the "dislocation interaction" hypothesis for texture. formation. This critical separation occurs when the parameter .r/ub is 3.75 x 10&apos;3. From this, a value for the SFE of 39 ergs per sq cm may be deduced for a Cu-2.85 at. pct A1 alloy. ThE correlation between the rolling texture of fcc metals and the stacking fault energy, SFE, was one of the first attempts to relate atomistic properties with the type of rolling texture.&apos; This correlation gives a qualitative explanation for the experimental observation that the addition of alloying elements, which generally lower the SFE, changes the copper-type texture to a brass-type texture. The simplicity of this correlation had led to its general acceptance and even its quantitative use.&apos; However, it is only a correlation and is largely based on descriptive features of pole figures, and on the poorly known SFE values in dilute alloys. Quantitative verification of this phenomenologi-cal correlation is, in fact, completely lacking. One purpose of the present study is to test this correlation. Another atomistic description for the formation of rolling texture is the "dislocation interaction" hypothesis of texture formation.3 In this hypothesis, the factor controlling the type of rolling texture depends on whether or not the separation distance between two partial dislocations exceeds a critical value. Materials having a separation of less than the critical value are supposed to exhibit a copper-type texture while those with a separation above the critical value are supposed to have a brass-type texture. At the critical value, it is expected that the material should show equal amounts of copper- arid brass-type orientations in their textures, i.e., a 50 pct transition texture. The SFE appears in this hypothesis as only one of several factors which determine the separation distance between partial dislocations. It is possible to test the validity of these two concepts by studying the rolling texture as a function of rolling reduction. Since the SFE per se is an intrinsic property of the metal, it should not, by definition, be influenced by local irregularities, such as variable stress conditions. Thus, no change in texture-type is expected to occur with changes in rolling reduction. On the other hand, according to the "dislocation interaction" hypothesis, any factor that effectively influences the separation distance of partial dislocations would be expected to change the rolling texture. Since the separation distance between partial dislocations is known to depend upon local stresses,4-6 it is anticipated that there would be an effect of the degree of reduction on the texture-type. Also, since applied stresses are more likely to increase, rather than to decrease, the separation between partials,4&apos;5 the overall effect would be to increase the amount of material in the brass-type orientations as rolling reduction is increased. Furthermore, this reduction dependence would be most prominent in alloys exhibiting the transition texture since the distance between partials in those alloys is thought to be close to the critical value. Experimental data in the literature is insufficient to distinguish between these two alternatives. Haessner studied the effect of rolling reduction on textures in a series of Ni-Co alloys by means of the X-ray intensity-ratio technique,&apos; and found that while one texture parameter indicated no reduction dependence the other indicated a slight dependence of the rolling texture on reduction in the range of 96 to 99 pct. As has been noticed previously, the intensity-ratio technique is a convenient but controversial method7 because there is no a priori reason to suggest which intensity-ratio would describe the texture most meaningfully. A more quantitative method of describing textures is found in terms of the orientation dependence of Young&apos;s modulus. Here, the type of modulus aniso-tropy associated with the copper-type texture is sufficiently different from that observed for the brass-type texture to allow the two types to be easily distinguishable and a quantitative measure of the amount of each can be deduced from the numerical results. This ability to provide quantitative data is particularly valuable when the two textures occur simultaneously in one alloy as is the case for the transition textures. In this paper the modulus method, supplemented by pole figure data, is used to look for an effect of roll: ing reduction the texture. Also by combining the texture measurements with recent determinations of the SFE in Cu-A1 alloys&apos;0&apos;" it should be possible to test for a relationship between the SFE and textures.

Jan 1, 1970

By J. Ruben Velasco, Roland B. Mulchay

CANANEA has long been recognized as a remarkable field for geologic study. The copper deposits and rocks of the district have been described by many geologists and engineers, but only the most general correlations have been made between Can-anea sedimentary rocks and other known sedimentary sections in the southwestern United States and northern Mexico. The present paper describes the Cananea sediments in greater detail than has been done before and attempts to fit the Cananea sedimentary section more closely into the geologic time table. The lack of well-preserved fossils has made it difficult to date the sediments accurately in geologic time, but it is possible to make tentative correlations between the Cananea sediments and the southeastern Arizona sections, based largely upon lithology and general position in the geologic column. It appears that sedimentation at Cananea and Bisbee may have been closely similar during Paleozoic time. Even such generalized correlations, however, may be subject to considerable modification in the future. The present study has led to the recognition of other problems of age and mineralization relationships in the Cananea district. Cananea is located in the north-central part of the state of Sonora, Mexico, at an elevation of 5270 ft. It is about 135 miles northeast of Hermosillo, the state capital, and 25 miles south of the international boundary. By road Cananea is 40 miles from the twin towns of Naco, Ariz., and Naco, Sonora, and about 50 miles from Bisbee, Ariz. It is served by the Nogales-Naco branch of the railroad, F.C. Pacifico, and is connected with Chihuahua and Mexico City by the Aeronaves airline. The headwaters of three rivers flowing to the Gulf of California are located in the Cananea Mountains: the San Pedro River, flowing to the north; the Sonora River, flowing south and west; and the Mag-dalena River, flowing west. Elenita Mountain, the highest point in the district, has an elevation of 8140 ft. The Cananea Mountains extend in a series of north-south to northwest-southeast spurs and ridges and are surrounded by gently sloping gravel plains. The mineralized area, lying across the southern and central parts of the range, is about 6 miles long and at most 2 miles wide. Elevations at the mines vary from 5300 ft at Cananea-Duluth mine at the southeast end of the district to between 6000 and 7000 ft at the west end of the mineralized area at Puertecitos-Elenita mines. Principal production has been from the intensely mineralized and altered area of Capote Basin in the central part of the district and the immediately surrounding area to the southeast. The district has produced over 2 billion lb of copper, substantial molybdenum, and minor amounts of lead, zinc, silver, and gold. Total production through 1949 is estimated at more than $300 million. In 1900 large-scale development was started at Cananea by W. C. Greene. Until World War II only high-grade ores were exploited; low-grade ores were extracted after the installation of a large concentrator in the early 1940&apos;s, and subsequent operations have been based upon mining and processing ores containing less than 1.0 pct copper from open-pit and underground workings. Mining and concentration of such low-grade ores, however, are made possible only by continued high copper prices, and active exploration for high-grade orebodies has been continued throughout the important mineralized areas. General Geology Study of the involved rock pattern at Cananea has indicated a complex geologic history for the district. Widespread alteration and mineralization have masked many of the salient features and have led to widely varying geologic interpretations over the years. Further work will probably disclose new information which will modify current beliefs. At Cananea a conformable series of sediments of probable Paleozoic age was deposited on an unknown basement. Following Paleozoic time there was an extended period of erosion common to many districts in the southwestern U. S., and there is no present evidence of marine sedimentation at Cananea after the Paleozoic. The eroded surface was eventually covered with a great thickness of extrusive volcanic rocks. The entire series of sediments and volcanic rocks was later intruded by a variety of deep-seated igneous rocks. These included the Cananea granite, the Cuitaca granodiorite, the El Torre syenite, the Tinaja diorite, the Campana diabase and gabbro and the Colorada rhyolite quartz porphyry. Faulting of early age, probably prior to the deposition of the volcanic rocks, may have been responsible for the present position of some of the intrusive rock masses. In the Capote mine on the third and fourth levels the northwest-striking Rick-etts fault zone, with apparent offset of about 800 ft, has been sealed by a dike-like mass of Cananea granite which gradually increases in size with depth. In lower levels of the mine the granite forms a large southeast-plunging mass generally following the course of the Ricketts zone. The granite is not known southeast of the Capote-Oversight mine areas and the Ricketts fault does not appear in the vol-canic~ southeast of Capote Basin, but several plugs of Colorada quartz porphyry cut the volcanics along the assumed general southeast trend of the Ricketts zone. These porphyritic intrusives may be the up-

Jan 1, 1955

By L. Thomassen, N. Spooner, J. M. Thomas

NI-CR and some Ni-Cr-Fc alloys, when used as electrical resistance heating elements in reducing atmospheres, at times suffer rapid breakdowns due to so-called "green rot." These reducing atmospheres are most frequently used in bright annealing and heat-treating furnaces which are kept for long periods of time at 1500&apos; to 1800°F. The green rot is a preferential oxidation of the chromium in the alloy to such an extent that the remaining metal frequently becomes ferromagnetic. The Curie point (magnetic transition point) at room temperature for a pure Ni-Cr alloy is known to be at about 7 pct Cr.¹ This represents a severe loss in chromium for one popular grade of resistance alloy, which is nominally 80 pct Ni-20 pct Cr. The formation of oxides along the grain boundaries makes the ribbon brittle and gives the fracture a green, earthy appearance—hence the name. The authors have studied this phenomenon, simulating the industrial conditions by heating resistance ribbons in various reducing atmospheres, such as moist hydrogen or the atmosphere specified in the ASTM test.² This atmosphere contains 16 pct H2, 10 pct CO, 4 pct C02, 1 pct CH1, 1.5 to 2.5 pct H2O, balance N2. Little success was had in producing severe corrosion with the commercial 80 pct Ni-20 pct Cr alloys. It had been noticed, however, that 90 pct Ni-10 pct Cr alloy wires deteriorated very rapidly when placed in the bottom of narrow thermocouple protection tubes. The bottoms of the tubes with the wires were heated in air. This took place both in porcelain tubes and in Inconel* tubes either with the cold end open or loosely stoppered with asbestos. On examination the wires showed microstructures which would be classified as green-rot corrosion. Subsequent investigations with various alloy wires confirmed the observation that corrosion occurred in some wires, including 80 pct Ni-20 pct Cr alloys, much more rapidly in such tubes than had occurred previously in test atmospheres mentioned above. When 90 pct Ni-10 pct Cr alloys are oxidized with an abundant air supply, the oxide coat consists of both nickel and chromium oxides. In this case thermodynamic equilibrium between the oxides is not established. However, when oxidized 90 pct Ni-10 pct Cr alloy specimens were heated to 1500" to 1800°F inside small diameter tubes, the oxide coat transformed to a bright metallic outer layer of nickel or nickel-rich alloy, beneath which appeared a green oxide, followed by intergranularly attacked metal. The obvious explanation is that in the narrow tubes, thermodynamic equilibrium is being established according to the equation NiO + Cr (in alloy) ? Ni + Cr2O3 This reaction is favored due to the fact that the oxygen pressure over nickel oxide is more than 10"&apos; times the oxygen pressure over the green chromium oxide. The initial oxygen in the tubes is depleted very rapidly by oxidation of the wire and of the tube, if it is metallic. A confirmation of the occurrence of the reaction, reduction of NiO by the chromium in the alloy, was obtained by putting oxidized nickel foil into an evacuated quartz tube along with a piece of bright 90 pct Ni-10 pct Cr alloy ribbon, and heating the tube at 1820°F for a number of hours. The nickel oxide on the foil was completely reduced to pure nickel, leaving a bright foil. The 90 pct Ni-10 pct Cr alloy became strongly magnetic and showed the typical green-rot structure. Weights of the samples before and after testing showed the weight loss of the foil to approximately equal the weight gain of the ribbon. Evidently the bottom of long, narrow protection tubes, stoppered or not, may under certain conditions act just as the sealed quartz tubes in respect to being a confined space in which oxygen is not freely replenished. This condition of oxygen depletion can be prevented by introducing a small amount of air into the bottom of the tube. Many conditions becloud the green-rot phenomenon, such as carburization, sulphidization, and the presence of other corrosive agents. However, these experiments have shown that the basic reaction is a case of internal oxidation which can occur simply by adjusting the oxygen pressure to a low enough level so that the atmosphere will leave the nickel intact and oxidize the chromium. The action of the other agents in commercial atmospheres can then be taken up as individual cases. From these and numerous other tests completed to date or still in progress, it is believed that a more critical evaluation of electrical resistance alloys for their resistance to green-rot corrosion can be made. A much better understanding of the mechanism for this type of corrosion should also result. A more complete report on these experiments will be published later. In the May 1953 issue: TP 35213 Discussion: Solubility of Carbon and Oxygen in Molybdenum by W. E. Few and G. K. Manning, discussion by N. A. Gokcen: p. 747, first column, the fifth, sixth, and seventh lines should be the first, second, and third lines, followed by the present first, second, third, fourth, eighth, ninth, and tenth lines.

Jan 1, 1954

By Richard W. Lodge

Ix the crucible-method of assaying ores for silver a certain amount of litharge is essential to supply sufficient lead to collect the precious metals. The object of this paper is to point out that the use of a .large excess of litharge in the assay of some ores will give results for silver that are uneven as well as low. So far as I know, however, an excess of litharge does not affect the results obtained in the crucible-assay of ores for gold. The main reasons for using, in the crucible-assay, much more litharge than is required to give the necessary lead button are : 1, its action as a flux; 2, its action as a desulphurizer; and 3, its action as an oxidizer, especially on metals like copper and nickel, whereby they are forced into the slag as oxides and thus prevented from passing into the lead button. Hence, by the use of much litharge in the crucible-assay more-ore can often be taken than in the scorification-process, and a lead button obtained which can possibly be cupelled at once or after a single scorification. The method is specially advantageous with an ore carrying much copper or similar impurity and poor in silver, when the assayer does not wish to resort to a wet-analysis for the determination of the silver. It is well known that some ores give better results when assayed by the scorification-method, while others give better results by the crucible-method. For several years I have noticed that, when much litharge was used with certain sulphide and arsenical ores, the results were considerably lower than when the scorification-method was used. This fact was more forcibly brought out in connection with certain work carried on this year by Messrs. H. A. Frame and

Sep 1, 1907

By Y. C. Kim, S. L. Barua

M. Armstrong&apos;s paper is very interesting and can be regarded as a pioneering work of applying geostatistics on washed coal. The density levels used in her study are uniformly spaced, which facilitated curve fitting through a proper experimental design. Most of the existing coal washing plants in the US, however, gather washability data at non-uniform intervals which, in turn, affects the goodness of curve fitting. We would like to emphasize the importance of having a proper experimental design, if a similar geostatistical application is to be conducted on washed coal. We, at the University of Arizona, tried the variogram on recovery (Kim, Barua, and Baafi, 1982, SME preprint 82-143) which showed a similar pattern as Fig. 4 of Armstrong&apos;s paper. In both cases, the first experimental variogram value is invariably and inexplicably higher than the second variogram value. Although Armstrong ignores the first point because of "small number of sample points," we did not do so because there were 17 sample pairs. As a consequence, we concluded that the obtained experimental variogram was unsatisfactory and that further research is warranted. In other words, this disagreement in variogram interpretation between M. Armstrong and the University of Arizona begs the question whether the experimental variogram of Fig. 4 truly reflects the spatial correlation in washed coal, assuming there is such a correlation. Finally, we wish that Armstrong could have done a similar study on clean sulfur, which is a vital interest to the coal mines in the US. Her implied remark on sulfur in the concluding section of the paper may turn out to be incorrect because our experimental variograms on clean sulfur at different density levels were even less satisfactory than those on recovery. ?

Jan 1, 1986

By Jan M. Mutmansky, Y. J. Wang

Mine ventilation analysis is an engineering discipline that can be considered a branch of the body of science known as network analysis. Likewise, the group of engineering procedures known as the critical- path method (CPM) is considered a branch of network analysis. It is therefore not surprising that mine ventilation network analysis and CPM have many similarities. These similarities are useful in analyzing several types of mine ventilation problems and will be utilized in this paper. The analogy between the free split in a ventilation circuit and the critical path in a scheduling network has been recognized by Owili-Eger (1973). While this was recognized as a property of a general ventilation network, many important applications to controlled- splitting problems also exist. The mathematical procedures necessary to apply CPM and network methods have previously been presented (Wang, 1981; Wang, 1982). This paper will illustrate the implementation of these methods by application to mine ventilation networks.

Jan 1, 1982

By P. A. Witherspoon, Y. W. Tsang

Normal stress-fracture closure variation and stress-dependent fluid flow rates were calculated for rock fractures of different aperture distributions. This study shows that both the mechanical and hydraulic properties of the fracture are controlled by the large-scale roughness of the rock fracture. Hence the typical large-scale undulation wavelength of the rock joint dictates the suitable sample size to be used in normal stress and fluid-flow measurements, if results due purely to sample size are to be avoided.

Jan 1, 1982

By Leon Y. Sadler, E. K. Landis

Froth flotation has been described by several authors" as being analogous to a first-order rate process. Although a few investigators"," have found orders other than one fit their data best, the rate is described most often by the first-order equation, [ ] where r is rate of disappearance of floatable mineral by flotation, C(t) is concentration of floatable mineral in the cell, t is time, and k is first-order flotation rate constant. One of the difficulties in using this rate equation to develop a mathematical description of an actual flotation process is the determination of a suitable value of the constant k. The value of k, which reflects the floatability of the floatable mineral, is dependent on the hydrodynamic conditions in the cell, type and concentration of flotation reagents used, pulp density, and pH, method of froth removal, aeration rate, particle characteristics, and many other factors. Therefore, it is reasonable to expect that each particle of floatable material has a distinct value of k and that a unique distribution of k values exists for given feed and cell conditions. This has been observed and discussed by several investigators, and mathematical descriptions of the batch cell and steady-state continuous cell with distributed flotation rate constant have been developed." The mathematical description in the form of a transfer function of the continuous or flow cell under unsteady-state conditions with a distributed flotation rate constant has not been presented in the literature. The purpose of this note is to make such a presentation. The basic features of the perfectly mixed continuous

Jan 1, 1974

By Y. Ueda, F. Noguchi, T. Yanagase

The rate of CaO dissolution into slag melts is of great importance in the field of pyrometallurgy. In this study the mechanism of CaO dissolution has been investigated by observing the melt heated on Pt-filament directly through microscope together with a help of X-ray micro analyser to find out a distribution of each element around CaO crystal. The direct observation reveals that the CaO dissolution tends to proceed by the action of molten slag entering between CaO crystal and newly formed 2Ca0. Si02 layer through cracks. The effect of slag composition on the formation of 2CaO- SiO2 layer will be shown as well as the effect of halogenides addition on the destruction of this compound layer.

Jan 1, 1976

ALABAMA Anniston.-Bretz, J. A. Carrington, F. G. Gerber, A. B. Klugh, B. G. Semple, R. A. Ashland.-Barton, .J. Bessemer.-Abbott, C. E&apos;. Ball, T. L. Beaver, J. J. Ferguson, V. Salmon, H. S. Sehaber, C. F. Whatley, W. J.

Jan 1, 1923

By Henry M. Rowe

Professor Ruff&apos;s most illuminating paper&apos; describing his extremely valuable investigation of the carbon-iron equilibrium diagram assigns definite temperatures to certain very important lines in the diagram, viz.: the eutectic temperature EB (Fig. 1) and the " near-eutectic " temperature E&apos;B&apos;, but without indicating clearly enough the reasoning which warrants these assignments. These temperatures are of such primary importance that it is well to indicate the apparent gaps in the reasoning, in the hope that they may be filled in. In his diagram, Fig. 1, the point X and the liues B&apos;D&apos;lII represent the experimental results reached by Ruff and Goecke;a AB, AEB, and SE represent the liquidus, the solidus, and the solubility of the carbon in solid austenite in the absence of graphite according to Gutowsky,3 AB being also in accordance with Spiecker&apos;s data; S&apos;E&apos; the solubility of carbon in solid austenite in the presence of graphite according to Ruer and Iljin;5 GS the line A3 after Ooerens and Meyer; 6 and EBC the true eutectic line as inferred by Prof. Ruff from Gutowsky&apos;s data. B&apos;D&apos; is the carbon content found in cast-iron which had apparently saturated itself with carbon in the presence of the graphite of the enclosing graphite crucibles in which the determinations were made. From its straightiiess and its sharp inflection near 6.67 per cent. of carbon, the carbon content of

Jan 1, 1913

By J. S. Harris

AS a result of the study of social problems to which so much thought has been given in this country and Europe in the last half century, many employers of labor have come to think that some provision should be made for their workingmen in case of injury. There has been a growing tendency so to administer the laws governing industrial pursuits in these countries as to add self-interest on the part of capitalists, to the plea urged by humanity, that every possible care should be taken to guard the workers from accident; but as no care can guarantee immunity, there is a necessity to supplement these precautions by some method of providing pecuniary aid that shall be available when disabling accidents do occur. It was once a favorite idea of theorists on political economy, that in the ideal state of society every man should take care of himself, and that the less care or control there was assumed by any man over others&apos; private affairs, the better; but this gospel of selfishness has had its day, and it is now generally recognized that in the existing state of affairs the stronger and richer cannot escape the duty of being to some extent, the keepers of their less fortunate brethren ; and, on the other hand, that an assumption of care for them involving to some extent an exercise of authority, is not a thing to he necessarily and always resisted. Out of these convictions, many efforts for the amelioration of the condition of workingmen have grown—which or one result have produced various plans which combine the con-

Jan 1, 1884

By Clair Upthegrove, E. S. Rowland

The widespread interest in the alloys of beryllium with copper is due principally to the fact that certain compositions show very favorable precipitation-hardening characteristics and are, in fact, the stronges nonferrous alloys known at the present time. Investigations have been conducted by Masing and Dahl and others on the physical characteristics of ternary beryllium alloys, in an attempt to produce precipitation hardening effects with a smaller amount of beryllium than that required in the binary copper-beryllium alloys (2.0 to 2.5 per cent Be). The results of these investigations show that ternary alloys of beryllium with Cu-Sn, Cu-A1 and Cu-Zn, among others, exhibit promising improrcmc~nts in physical properties after precipitation-hardening treatment and, while the increases in properties obtained are not as high as those reahzed from the binary copper-beryllium alloys, excellent properties arc obtaincd with beryllium contents averagirlg about one-half the amount reqnired in the binary alloys. This paper presents the results of an investigation of the equilibriun relations of certain alloys containing copper, tin and beryllium. The alpha-phase boundary of the ternary system is given for alloys containing from 0 to 1 per cent beryllium. The equilibrium conditions beyond the alpha-phase boundary are presented for alloys containing up to 32 per cent tin and 1 per cent beryllium. The data were collected by means of quenching experiments, microscopic examination and thermal analysis The results of some powder-method X-ray determiniations on the alloys, conducted by Mr. William Mikulas and Prof. Lars Thomassen at the University of Michigan, are used as evidence in this paper. The con

Jan 1, 1935