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By G. D. Oxx, L. F. Coffin

The concept of using a phase that is liquid at service temperatures as a component of coatings for refractory metals has been described. The liquid, an alloy of gold and silicon, is retained on a molybdemum surface by a capillary system made of molybdenum disilicide. The coating has the advantage of good thermal shock and has a self-henling chracteristic. In order for highly stressed structures to exceed a service temperature of 2000°F, it has become apparent that a development that does not depend on the traditional iron, cobalt, or nickel-base alloy is needed. Alloys of the refractory metals, i.e., molybdenum, tungsten, tantalum. niobium (colum-bium), and rhenium are potentially useful at extremely high temperatures that more conventional alloys would never be expected to achieve. A new alloy of molybdenum has become available that has a 100-hr rupture strength of 35,000 psi at 2200°F.1 As a result of this work, it may be assumed that a material with adequate mechanical properties at 2200?F is now available. Unfortunately, this alloy and all other known alloys of the refractory metals suffer from not being; serviceable in an oxidizing atmosphere for a very long time. In order to permit general use of refractory metals at high temperatures, it is necessary to prevent destructive oxidation by appropriate alloying or by protective coatings. The liquid phase coating reported here is representative of a concept for the protection of metals that permits higher service temperatures and introduces a new group of materials for selection as coatings. Coating Requirements—Service conditions that represent potential applications for refractory metals vary considerably: however, it is possible to consider two conditions that are usually present. The refractory metal1 component must be heated to the service temperature at least once and usually frequently. When a solid coating is used, usually the coating and basis metal do not have the same coefficient of expansion. This difference causes thermal stress in the coating that is aggravated by rapid heating and cooling and eventually causes coating failure. The second consideration is the probability that there will be damage to the coating by some environmental condition. In jet engines, for example, it is expected that large particles, stones, metal parts, and so forth, will strike a bucket at high speed and cut a hole in the coating. In addition to the above considerations, the coating must also have other fundamental properties. Obviously, it must be oxidation resistant. In addi- tion, it must prevent permeation of oxygen and subsequent oxidation of the basis metal at the interface. Also, diffusion of the basis metal to the outside surface and subsequent oxidation there must be prevented. Finally, the coating must not react with the basis metal to form a weak bond at the interface. It should be noted that the coating need not support a load: it must only remain intact. Liquid Phase Coating Design Factors—In the use of a liquid as a principal coating constituent, it would be expected that the two service conditions mentioned above would be satisfied. A liquid would flow under the influence of the thermal strain developed by coating-basis metal expansion mismatch such that failure from this source would not be expected to occur. It is also probable that the ability of a liquid to flow would provide a self-healing effect. Thus, damage caused by particles in the atmosphere would be repaired. A third advantage is evident in that vapor pressure rather than melting point limits the service temperature. This latter advantage permits use of low melting but oxidation resistant metals such as gold or copper that would be quite useless if the solid state was required. A low viscosity liquid alone. however, is a totally unsuitable coating because it will simply flow off a component, particularly under the influence of a high acceleration field. A method of preventing liquid loss must be devised. In this case, it is desired that the liquid have a low viscosity so that it may easily flow into flaws; thus, raising the viscosity is not a satisfactory solution. One other inherent difficulty is caused by the high mobility of atoms in the liquid state as compared to the solid state. Because of this mobility, it would be expected that gases would diffuse more rapidly through a liquid. It is also probable that the solubility of oxygen in the liquid would be comparatively high. These factors would tend toward rapid permeation of oxygen and oxidation of the substrate. It is most reasonable that this problem could be solved by incorporating a solid phase, which is impermeable to gases, as a component of the coating. To overcome the tendency of a liquid to flow easily, it is possible to use surface tension to advantage. If the surface were made up of a large number of capillary tubes of sufficiently small diameter, then surface tension would hold the liquid even against the acceleration of a centrifugal field.

Jan 1, 1961

By O. B. Bennett

WHEN diamond drilling was introduced in the Rhokana mines in 1939 it was used principally for pillar removal and for completion of the upper portions of shrinkage stopes which were being affected by increasing pressure. This method of drilling long blastholes proved so successful that it was extended gradually to cover stoping, pillar recovery, and hanging cave work. BY 1949 virtually all the ~roduction of Mindola and Nkana was being obtained by this method. At the present time 87,500 ft are drilled each month by the 80 diamond drills in daily operation. Responsibility for control and issue of diamond drilling equipment and crowns, as well as tabulation of all performance figures, was taken over by a sPecially formed Roto drill department, which also investigated the problems encountered with this new method. To assist this department a fully equipped test chamber, Fig. 1, was established underground where performances of various types of machines and equipment could be studied under conditions as nearly uniform as possible. Since the establishment of this department, which was eventually taken over and incorporated into the study department, considerable experimental work has been done on every aspect of the subject. The problems can be classified broadly under four headings: improvement of drilling equipment, crown design, machines, and stoping layouts. One of the major problems with drilling equipment has been to eliminate vibration. Owing to flexing of rods in the hole, severe friction is set up on the back end of the 'Ore barrel and On any high spots in the rods, inducing harmonic vibration in the string of rods and causing the crown to chatter against the face. This not only causes premature crown failure but also reduces penetration speeds and increases wear on the machines and rods used. In the early days, when only holes of EX size were drilled, vibration was largely overcome by periodic greasing of rods and core barrel during each run, but with the change-over to the larger BX hole it became obvious that application of grease by hand was inefficient and time-consuming, and attempts were made to perfect a self-lubricating core barrel. A series of these core barrels was made up and tested and a number of the latest type were used under normal operating conditions, but although footages up to 120 ft were drilled without refilling the overall performance was inconsistent, and the idea was shelved in view of the success of the stabilizer rods referred to later in this paper. At the same time tests were made with barrels 5 ft and later 6 ft long instead of the normal 2 ft. Although a slight improvement was noticed, greasing was still necessary. It was found that rod vibration increased as the core barrel became worn, and in an early test chamber experiment crowns drilled with a worn core barrel averaged 95 ft with a diamond loss of 4.76 carats, whereas the same type of crowns with a new barrel averaged 228 ft with a diamond loss of 3.13 carats. until then all BX drilling had been done with B-sized rods, but during a test on a string of BX-sized rods it was noticed that vibration was negligible. Because of the larger surface area of metal bearing on the sides of the hole, however, the friction and resistance of rods of this size rendered them impracticable on any but the most powerful of the machines, The use of stabilizers spaced evenly along the rods was the next logical step, and for this B couplings, see Fig. 2, were set with three tungsten carbide inserts 1 in. long placed around the periphery equidistantly and at an angle of 45" with a right hand lead. These were placed immediately behind the core barrel and then at 12-ft intervals, as it was found that vibration still occurred when the stabilizers were more than 15 ft apart. The effect of these stabilizers was immediately noticeable; holes were drilled with a minimum of vibration, penetration speeds were improved, and as it was no longer necessary to grease the rods there was a marked decrease in the overall drilling time for each hole. While tests were being made with the stabilizer comeb periodic were taking place with a set of tapered threaded rods, and because there was marked improvement in efficiency it was decided to incorporate the stabilizers and tapered threading in all new rods ordered for Rhokana. The feature of these rods is that only four full turns are required to tighten the coupling as against nine for the present type of B rods. Also, as they are self-centering it is virtually impossible to crossthread them. Each rod has a male 5" tapered Acme thread, Fig, 3, on one end and a female at the other, so that separate couplings are unnecessary, and every fifth rod has an

Jan 1, 1955

By J. B. Newkirk, W. G. Martin

Oxidized cobalt powder is known to have a magnetic hysteresis loop which is asymmetric with respect to the magnetization axis. The experiment described herein shows that the orientation relationship between the basal plane of hexagonal cobalt and the oxide which forms upon it at 400°C is {111}ux//{100.1 }co <110>ux//<11.O> This orientation relationship allows a magnetic interaction between the antiferromagnetic oxide and the ferromagnetic substrate which could account for the offset hysteresis loop. Oxidized nickel powder has a symmetrical hysteresis loop and so is apparently not influenced by any magnetic interaction between metal and oxide. The orientation of the oxide (cubic) was found to be identical with that of the nickel substrate when the oxide forms on a polished surface parallel with {111} Ni. IN 1956 W. H. Meiklejohn and C. P. Bean discovered that fine particles of cobalt which had been prepared in a certain way have a magnetic hysteresis loop which in a strong field is asymmetric relative to the magnetization axis.&apos; The cobalt powder exhibited this unusual magnetic property only after it had been oxidized in air or oxygen; it lost the shifted hysteresis loop when the oxide was reduced in hydrogen. X-ray and neutron diffraction&apos; experiments showed the presence of cobaltous oxide (COO) and hexagonal cobalt in samples exhibiting the biased hysteresis loop and specifically showed no indication of any other compound with the exception of mercuric oxide.* The magnetic hysteresis loop becomes symmetrical above the Nee1 temperature (paramagnetic state) of COO. Therefore, it was concluded that the anomalous magnetic behavior is associated with the influence of cobaltous oxide upon the metallic cobalt. It has been proposed that crystallographic coherency may exist between the cobalt and a plane of some antiferromagnetic material which has unbalanced spin distribution and sufficient magnetic anisotropy to hold its spin in the direction which existed when the specimen was cooled. COO has these properties. Therefore, Roth&apos; has suggested that cobaltous oxide may form with a {111} plane parallel and coherent with the basal plane of the hexagonal cobalt metal and proposed that, as consequence of the antiferromagnetic interaction between COO and the underlying cobalt, the magnetization direction in oxidized fine Co particles may be ro-lated from the easy c-direction.2 Such a relationship, he proposed, would explain the observed magnetic effect in oxidized cobalt powder. The main purpose of this study was to determine the orientation relationship, if any, between the basal plane of cobalt and the oxide which forms upon it. Attempts to produce a film of COO which was strong enough to be handled were not successful. However we did succeed in making a film of CoCo2O, which was strong enough to be removed from the cobalt substrate and mounted on an electron-microscope grid. Because of the close structural similarity of COO and CoCo2O, we believe the orientation relation found for CoCo2O, on cobalt probably also holds for COO on cobalt. The epitaxial relationship of NiO and Ni also was investigated. To date no shifted hysteresis loop has been observed with nickel powder. However, the similarity of atomic array in cobalt and nickel leads to the prediction that a {111} of NiO may be parallel with a (111} of nickel. Experimental Method Cobalt-Cobalt Oxide—A coarse-grained specimen of a (hexagonal) cobalt was prepared by allowing a large crystal of fee cobalt to transform slowly at 400°C. The crystal was then cut to expose a surface parallel with the basal plane. A back reflection Laue X-ray photograph showed that the 00.1 plane was within 2" of the cut surface. The surface was mechanically polished and then electro polished in 85 pet orthophosphoric acid after which the crystal was held for 30 min at 400°C in air. During this heat-treatment the surface darkened slightly due to the oxide film which formed. The film was not thick enough to give an X-ray diffraction pattern, even by a glancing-angle technique. Glancing-angle electron diffraction was not possible either, owing to the interference of the electron beam with the high magnetic fields which exist at the 00.1 surface of the cobalt. However, it was possible to make an electron-diffraction photograph of the oxide film by stripping it from the cobalt substrate using the method described later. By maintaining reference marks carefully, it was possible to preserve the orientation relationship between the stripped film and the substrate on which it was formed. The oxidized surface of the crystal was first covered with a 1 pet solution of collodion (cellulose nitrate) in amyl acetate. When the film was dry, small rectangles were scored on the surface with a needle point. The specimen was then repolished

Jan 1, 1959

By R. R. Judd, H. W. Paxton

The rate of dissolution of cementite was studied in three low-carbon materials: a zone-refined Fe-C alloy, an Fe-0.5pct Mn-C alloy, and a commercial low-carbon steel. The materials were spheroidized, ad then held isothermally at temperatures above the Al. The isothermal anneal was interrupted periodically by a water quench and the specimens were analyzed by quantitative metallography for the amount of aus-tenite formed during the anneal. The results of this study were compared with an analytical model for the process, which assumes that carbon diffusion in aus-tenite is the rate-controlling step for the cementite dissolution process. The correlation between the model and the experimental data is excellent for the zone-refined Fe-C alloys; however, the Fe-0.5 pct Mn-C alloys and the commercial steel deviate from the calculated model. This deviation is thought to be a result of manganese segregation between the carbide and the matrix. The rate of nucleation of austenite at carbide interfaces was reduced by the manganese addition and enhanced by the presence of ferrite-ferrite grain boundaries. PREVIOUS investigations of the nucleation and growth of austenite from ferrite-carbide aggregates are not entirely satisfying for at least one of several reasons. The most prevalent of these is a lack of quantitative data. Engineering studies have been run on many steels with little control over important parameters such as composition and initial aggregate structure. The data obtained are valid only for material with identical chemistry and thermal history. A more informative approach to the problem of aus-tenitization would be to determine the mechanism that controls the rate of solution of carbide in austenite and how it is modified by alloying elements. This information could then be used to calculate an austeniti-zation rate for any material, provided its composition and structure are known. The object of the present work is to establish the rate-controlling step for cementite dissolution in Fe-C austenite and to investigate the modification of this rate by small manganese additions. The composition and structure of the material used were carefully controlled and all measurements were designed to allow a quantitative analysis of the kinetic process that controls the austenitization rate. A MODEL FOR DISSOLUTION OF CEMENTITE Cementite dissolution has been analyzed mathematically by a model that approximates the material used in the experiments. This model postulates a regular ar-array of identical cementite spheroids with 4 C( diam, embedded in a grain boundary- free ferrite matrix. The analysis provides a detailed description of the dissolution of one carbide spheroid and a generalization of the solution by summation over all the carbides in the material. The carbides may be isolated by defining identical, space-filling cells of ferrite around them. If the cell dimensions are greater than the diameter of the austenite sphere resulting from complete dissolution of the carbide, and no interaction (through diffusion in ferrite) takes place between cells during the dissolution process, the model need concern only one cell, since the solution in each cell is identical. In the experimental material, the dimensions of the cell, the carbide, and the final austenite sphere are approximately 24, 4, and 8 p, respectively; use of the single cell is therefore justified. The experimental observations are made on the austenite nodules that form around each carbide during the dissolution process. The model concerns the growth of these austenite nodules. The attendant shrinking of the carbide can be obtained from the same analysis by an extension of the calculations. Several a priori assumptions are necessary to make the analysis of the growth problem tractable. They are: 1) carbon diffusion through the austenite nodule is the rate-controlling process; 2) local equilibrium exists at all interfaces, 3) the austenite nucleus that forms on each carbide instantaneously envelops the carbide; 4) during the austenite growth process, the diffusion flux of carbon in ferrite is insignificant; 5) a quasi-steady state exists in the austenite concentration field; that is, at any instant during the dissolution process, the austenite carbon concentration gradient closely approximates that for a steady-state solution; and 6) the effects of capillarity on the dissolution rate of the carbides can be neglected. Referring to Fig. 1, a mass balance at the y-a interface for an infinitesimal boundary movement gives: Where rb is the outer radius of the austenite shell, C1 and C are carbon concentrations at the interface in austenite and ferrite, respectively, see Fig. 2, is the diffusion coefficient of carbon in austenite for the concentration of carbon at the interface, and t is time. The fifth assumption permits the austenite carbon concentration to be approximated by the Laplace solution for the spherical case. Therefore, where C(Y) is the carbon concentration at r, and A and B are constants. Local interfacial equilibrium fixes the boundary conditions for the diffusion problem. They are:

Jan 1, 1969

By Jerome J. English, Gordon W. Powell

An experimental investigation and mathematical analysis of the thermal-dilation behavior of the titanium alloy Ti-7Al-3Cb have shown that the linear dimensional changes associated with the polymorphic transformation need not be isotropic. The absolute magnitude of the linear dimensional change, which may be either positiue or negative, associated with the cr-p transformation is dependent upon the relutzve volumes of different orientations of the transformation product. It is hypothesized that the dilation irregulati-ties that have been observed during the polymorphic transformation of pure, coarse-grained titanium and other titanium-base alloys can be explained in the same manner. When titanium is heated above about 165O°F, the hcp a structure transforms to bcc 0. Thermal-dilatioh measurements have shown that the transformation is accompanied by a decrease in length of 0.16 pct.&apos; Such dilation behavior would be expected because the volume of the hcp unit cell is about 0.3 to 0.4 pct greater than that of the bcc unit cell. A recent investigation2 of the thermal-dilation behavior of an experimental a-p* titanium alloy, Ti- 7A1-3Cb, containing 0.06 wt pct 0 showed that its dilation behavior during the polymorphic transformation differed substantially from that reported for unalloyed titanium. The first time the alloy was cycled through the transformation, the dilation curve closely duplicated that of unalloyed titanium. However, upon repeated cycling through the transformation temperature range, both the magnitude and the sign of the dimensional change associated with the transformation were observed to vary with each cycle. This investigation was undertaken to obtain additional data on the dimensional changes associated with the polymorphic transformation in the Ti-7A1-3Cb alloy and to determine the cause of the dimensional irregularities. After testing, the specimens were examined metallo-graphically. In addition, Laue back-reflection patterns were obtained from selected sections taken perpendicular to the specimen axes to determine the a orientations present in these sections. White radiation from a tungsten target and a 0.1-mm-diam collimator were used to produce the diffraction patterns. RESULTS Dilation Curves. Three types of thermal-dilation curves were obtained when the a-8 titanium alloy was heated and cooled through the transformation temperature range. These three types of curves are illustrated in Fig. 1. The type I curve represents what is considered normal behavior, because the dilation change is what would be expected on the basis of the volumes of the unit cells of a and p. The Type I1 curve is the inverse of Type I. Normal behavior is characterized by an expansion on cooling through the transformation, whereas a contraction takes place in the Type 11 curve. With Type ni behavior, no clearly distinguishable length change occurs during the transformation. No other anomalies that might be indicative of other phase transformations were observed in the dilation curves at lower temperatures. Apparently, the cooling rate was low enough for equilibrium to be reached during the 0 to a transformation. Table I lists the types of dilation curves observed during the polymorphic transformation as a function of the direction of measurement and cycle number. The A1 value was determined by extrapolating the low-temperature (a + 5 pct p) and high-temperature (100 pct p) segments of the dilation curves to a common temperature and measuring the difference in the or-dinates at that temperature, see Fig. 1. The transformation occurs over a temperature range in this alloy, so the magnitude of A1 is not an absolute value but depends on the choice of temperature. A mean temperature, T,, within the transformation temperature range was selected for the measurement. T, on cooling occurred about 100°C lower than T, on heating. The first time each of the three dilation specimens was heated to above the temperature, that is, Cycle 2, normal Type I behavior was observed. In Cycle 3, two deviations from normal behavior occurred. First, during cooling of the longitudinal specimen, a substantially larger expansion, +0.21 pct, was measured as 0 transformed to a compared with +0.03 pct in Cycle 2. Second, the thickness specimen was observed to undergo a contraction instead of the anticipated expansion on cooling. Continued cycling of the three specimens from room temperature to 2500°F produced additional changes in the dilation behavior. These changes did not seem to be related to the fabrication direction of the alloy because the values of a1 for the longitudinal, transverse, and thickness specimens varied unpredictably in magnitude and sign. Furthermore, both the longitudinal and transverse specimens showed all three types of dilation curves at least once during the six cycles that they received. Fig. 2 is a sketch of the transverse specimen after

Jan 1, 1967

By P. G. Shewmon, H. E. Collins

A study has been made to determine the sites at which sulfur adsorption occurs on copper surfaces. measurements were made of the relative torques, Ys, at the intersection of twin boundaries with surfaces near the three low-index orientations, i.e., (100), @lo), and 011), over a range of H2S/H2 ratios. HZS concerztvations j&apos;ro~n 3 to 1500pp)n between 830" and 1050°C were used. It is concluded that sulfur adsorption occurved preferentially though not exclusively at edge sites near the (100) and (110) surfaces in the HzS range — 700 Ppm giving rise to negative torques near these orientations. Beyond this HzS range, adsorption occurred at all sites. Near the (111) surface, 7/y little with HzS concentration up to approxiwzately 75pptn. Above this range, the results indicate adsorption is occurring OH both terrace and edge sites. SCIENTIFIC interest in surfaces and their interactions with a gaseous environment dates back to the beginning of the 19th century. The scientific luminaries of that period—Faraday, Maxwell, Rayleigh, Dewar, and Gibbs—were already concerned about such processes. However, it has only been within the past several decades that adsorption on metal surfaces has been actively studied. This increased interest in adsorption has been brought about by the advent of new and improved experimental techniques and apparatus, e.g., ultrahigh vacuum, and field-emission and ion microscopes. However, most of the work done using these techniques has been carried out at low temperatures. When adsorption studies have been made at either low or high temperatures, they usually gave no indication of the particular surface orientations or type of sites on which adsorption was occurring. In the last few years, there have been a series of studies in which the surface tension, y,, and/or its derivative with respect to orientation, 7, have been studied as a function of orientation and atmosphere.&apos;-7 Nearly all of the work on the relative torque,* ~/y, silver annealed in hydrogen and air.6 Recently Winterbottom and Gjostein" have used a modified and more accurate Mykurian method to determine the y plot of gold in hydrogen The only work in which T/~, has been measured over a range of chemical potentials for a given solute, p2, is that of Robertson and shewmon7 on the Cu-0 system. They measured T/Y, vs Po, (10"" to 10- l3 atm) at 1000°C in various mixtures of Hz0 and HZ. From this work they estimated the value of p2 at which one half of the surface sites are occupied with oxygen, pg, as being in the range 10- l6 to 10- l5 atm of oxygen. They also found that increasing Pa increased the magnitude of ~/y, near the (111) and (100) orientations. This indicates that oxygen is not adsorbed preferentially at step edges, but uniformly over all surface sites. In addition, they did one experiment on sulfur adsorption on copper surfaces, which indicated that sulfur adsorption decreases ~/y, near the (100) orientation, while not affecting ~/y, near the (111). This could be interpreted as indicating that sulfur adsorbs preferentially at step edges near the (100). In this paper the primary objective of the work has been to carry out a study of sulfur adsorption on copper surfaces over a range of temperatures and p,. In conjunction with this work, thermal grooving at grain boundaries has been examined as a method of determining the effect of sulfur adsorption on y,. METHODS Ideally, one would like to have information on the quantity of solute adsorbed on a surface and the types of sites at which it is absorbed as a function of p2. The total quantity adsorbed or the surface excess is given by the thermodynamic equation Thus data on the variation of y, with pz indicates the value of p2 at which adsorption becomes appreciable and the quantity adsorbed. The type of adsorption site is more difficult to deduce but information on this can be obtained from the variation of rz with 8, the angular deviation of the surface orientation. This is obtained from the thermodynamic equationlg Data on t and ys as functions of p2 have been obtained by the following methods. 1) Twin Boundary Grooving—By determining the effect of adsorption on the torque, 7, where T is the variation of surface energy, y,, with orientation, it is possible to obtain some indication as to the preferred sites of adsorption. Experimentally, the torque value measured is the relative torque, 7/ys The twin boundary grooving technique suggested by Mykura&apos;&apos; was used in this study to determine near the three low-index orientations— (loo), (110), and (111). Mykura&apos;s equation relates 7 /yS to measurements of the di-

Jan 1, 1967

By Henry R. Linden

The demand for natural gas continues to increase at higher than anticipated rates, partly because of its widening price advantage over most other fossil fuels when the cost of air-pollution control is included. However, there are clear indications that the natural gas supply from the conliguous 48 states and continental shelves will not keep up with this rapid growth in demand indefinitely. Projections are presented which define the extent of potential deficiencies from the 1970&apos;s to the year 2000. Among the sources of supplemental gas - imported pipeline natural gas from Canada and Mexico, tanker import of liquefied natural gas, and synthetic pipeline gas from coal and oil shale -by far the most abundant at potentially competitive costs is pipeline gas from coal. The state of development and relative economics of the various coal gasification processes are reviewed. It is shown that synthetic pipeline gas could become a very substantial market for bituminous coal and lignite at current mine-mouth prices - 60-70 million tons of coal for each trillion cubic feet of synthetic pipeline gas produced. This corresponds to only slightly more than the current annual increase in gas demand. Although annual discoveries (gross additions to proved reserves) of natural gas in the United States are still on a general upward trend from the current level of 22 trillion cu ft annually, most forecasters do not expect this to increase substantially in the foreseeable future. For example, the updated (to include 1966 and 1967 data) mathematical model of natural gas discovery and production in the U.S. developed by the Institute of Gas Technology (IGT)&apos; projects that discoveries will level out at about 25 trillion cu ft annually in the late 1970&apos;s and during the 1980&apos;s and then decline to about 21 trillion cu ft by the year 2000 (Fig. 1). This adds up to a new supply for the period 1968-2000 of about 790 trillion cu ft. Experts who usually reflect the producers&apos; viewpoint, such as Radford L. Schantz of Foster Associates,* are relatively more pessimistic. In contrast, a forecast just made by the U.S. Dept. of the Interior is much more optimistic.3 It assumes an increase in gas discoveries of 2.2% per year over the period 1965-80, reaching about 30 trillion cu ft in 1980. If this rate of increase were extended to the year 2000, annual discoveries would reach 46 trillion cu ft at that time, for a total over the period 1968-2000 of about 1100 trillion cu ft. To these forecasts of new gas discoveries must be added proved reserves of roughly 290 trillion cu ft,4 bringing total U.S. supplies for the rest of the century to nearly 1100 trillion cu ft (IGT) and possibly as high as 1400 trillion cu ft (U.S. Dept. of the Interior). This is approximately the same range as that of two estimates of total remaining recoverable natural gas supply: Potential Gas Committee, 980 trillion cu ft5 and IGT, 1450 trillion cu ft.6 Only the 1965 estimate by the U.S. Geological Survey7 suggests that economically recoverable natural gas supplies will not be exhausted around the end of the century. These forecasts are, naturally, based on the assumption that changes in technological, economic, and regulatory environment as they affect the gas industry will be of an evolutionary, not revolutionary, nature. The various forecasts of potential natural gas supply must now be compared to forecasts of natural gas demand (Table I). The general consensus is that the recent Future Requirements Committee projection to 1990&apos; (extended to the year 2000 by the most recent U.S. Bureau of Mines (USBM) projection9) represents the minimum gas requirements (Table 11). They add up to a total of 1030 trillion cu ft for the period 1968-2000. Even this minimum anticipated gas demand exceeds the total remaining supply estimate by the Potential Gas Committee and would nearly exhaust the proved reserves plus new discoveries projected by IGT. The supply situation would appear much tighter if the demand projections of the Texas Eastern Transmission Gorp.10 and the American Gas Assn.(A.GA.)&apos;&apos; were used (Table I). Yet, these higher forecasts probably do not include the effects of such new markets as gas fuel cells, use of liquefied natural gas as a transport fuel, etc. They also may not fully reflect the impact of air quality control on the fuel market. Obviously, the probable discrepancy between projected supply and demand can only be accommodated in four ways. 1) Rapid increase in exploration and drilling activity to provide new supplies in the amount projected by the optimistic U.S. Dept. of the Interior forecast, coupled with an increase in net pipeline imports from Canada and Mexico from the present 0.5 trillion cu ft per year

Jan 1, 1970

By Clarence E. Sims

An effort has been made to give both a comprehensive and simplified picture of the origin, modes of formation, and characteristics of nonmetallic inclusions in steel. Exogenous inclusions, those formed by mechanical entrainment or heterogeneous reaction, have their principal source in ladle refractories. Mechanical emulsion is not considered a likely mechanism. Endogenous inclusions, resulting from homogeneous reactions, are formed mainly during cooling and freezing. They are principally oxides and sulfides but include some nitrides and carbides. Deoxidation affects both the quantity and character of such oxide inclusions and significantly affects the size and shape of sulfides. The importance of inclusions is largely in their effect on mechanical properties. It is fitting and proper that we should honor the memory of those technical giants who have left such a rich heritage to our profession. Today, according to annual custom, we pay tribute to such a man. To have been chosen to play a part in this observance prompts in me an inordinate pride while I am humble before the responsibilities of my task. The ranks are growing thin of those who had the good fortune to come under the personal influence of Professor Howe, but the number who continue to benefit from his legacy of technical wisdom con-stantly increases. I am among the latter. One has only to read his works to appreciate his unusual ability to take data and observations from many sources and give them a clear and comprehensive

Jan 1, 1960

By Albert Burch

AN analysis of this subject demands a study of the theory and practice of the present system, conclusions as to its merits, and recommendations for remedying its defects if any be found. Theory of the Present Law The theory of the present law with reference to lode locations contemplates the existence upon the surface of mineral-bearing veins which have clearly marked boundaries, and which can be so readily traced that a locator may immediately mark the boundaries of his 600 by 1,500 ft. claim in such a way that the vein will pass through both of its end-lines. It also supposes that, having discovered such a mineral-bearing vein, the locator will at once post a notice upon such discovery, mark the boundaries of his location in such a manner that they can be readily traced, and from that time forward have absolute title to the ground embraced within such boundaries, as against every person except the United States. For initiating title to placer ground, the law presupposes the discovery of a valuable mineral deposit; but not necessarily in place, as in the case of lode claims; and the location must be made to conform "as nearly as may be" to the legal subdivisions of the United States public land survey. When the placer law was extended to include the acquisition of title to oil lands, no exception was made as to the necessity for the discovery of valuable mineral in advance of location!

Jan 6, 1914

C. Le Neve FosteR, Llandudno, Wales: I regret that Prof. Clowes is not here, and also that I cannot produce one of his lamps for inspection. The lamp has but just passed the experimental stage, and is now on sale in England for the purpose of testing it in practice. The only complaint I have heard made against it is the high price. It costs six or seven guineas. Possibly that would not frighten you on this side of the water as much as it does us. R. W. RaymonD, Brooklyn, N. Y.: So far as my obsrvations and experience go, we have not yet reached a state of affairs in the coal-mines of this country which calls for the general use of safetylamps by common miners. Certainly such a practice is to be avoided if possible, on account of the recklessness of miners, which it seems almost impossible to control by warning or discipliue. It is much better, if practicable, to confine the use of safety-lamps to inspectors or " fire-bosses," and not to permit the miners to work or to go where naked lights cannot be carried. In a colliery near Pottsville, Pa., with which I was connected for five years, and which had the reputation of being highly "fiery " (jets of fire-damp bubbled continually through the puddles in the gangways, and a thin sheet of it lay along the roof), we managed to avoid all serious

Jan 1, 1894

By Ernest A. Kaarsberg

This paper presents the results of studies of the elasticity of some isotropic and anisotropic rock samples based on longitudinal- and shear-wave pulse velocity measurements. Experimental evidence from velocity measurements on isotropic steel samples is also presented to show, within error limits, that any two of the elastic constants required to completely describe the elasticity of an isotropic solid can be obtained from any two of the following four velocity measurements: longitudinal "rod,&apos; "plate," extended medium (infinite medium equivalent), or shear wave. Measurements of three of these velocities in an approximately isotropic basaltic rock sample are used to illustrate this application to this type of rock. For the anisotropic study, a suite of Colorado oil shale samples is used. These rocks exhibited transverse isotropy. The five elastic constants required to completely specify this type of anisotropy are obtained from longitudinal- and shear-wave pulse velocity measurements made in directions parallel, perpen-dicular, and at 45° to the bedding plane. Density, velocity, and elastic modulus relationships among these shales are also given. Duvall 1 has described a method for determining the elastic constants of isotropic and, in two cases, anisotropic rock samples. This method is based on ultrasonic pulse techniques and on resonance-frequency measurements of rock samples in the shape of rods (diamond drill cores). Rock samples, however, are not always available in rod form. When this is the case, other methods can be used to study their

Jan 1, 1969

By David Sinclair, Philip B. Bucky

The dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests. § None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their application in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I The Photoelastic Method The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution. General Explanation The stress at any point 0 in a structure (Fig. I), may be resolved into two components, P and Q, each a pure tension or compression, at right angles to each other, called principal stresses.&apos; To fully identify the stress, the values of P and Q and their directions or angle F must be known.

Jan 1, 1940

By David Sinclair, Philip B. Bucky

The dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests. § None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their application in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I The Photoelastic Method The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution. General Explanation The stress at any point 0 in a structure (Fig. I), may be resolved into two components, P and Q, each a pure tension or compression, at right angles to each other, called principal stresses.&apos; To fully identify the stress, the values of P and Q and their directions or angle F must be known.

Jan 1, 1940

The following communication was recently sent President Wilson by J. Parke Channing, Chairman of the Engineering Council: The transportation systems of our country are largely the creations of its professional Engineers. This statement can be made without disparagement to the statesmen, the financiers, the manufacturers, the lawers, the educators, the mechanics, the laborers and many others, who, with the Engineers, have contributed to the development of transportation. Through all stages of preliminary exploration, final survey, construction, upkeep and operation, in financial management, and in adjustment of the relations of transportation to the public, the genius and knowledge of the Engineer are essential. Not only in technical physical matters, but also in determinations of policy, his contributions have supplemented and must ever supplement those of other men. These declarations hold good for all the carriers of commerce, by rail, by highway, by water, by pipe-line, by wire, or by air. Hence, it follows that the body established by Government to regulate the commerce, the carriers and the ways of communication, embracing so many engineering features, should number among its nine members, men of engineering training and experience. Engineering Council, being aware of a vacancy on the Interstate Commerce Commission, begs leave to request the Chief Executive that in filling this vacancy, he give earnest thought to the selection of a man who, to his other qualifications, adds the training and experience of an engineer familiar with transportation problems.

Jan 9, 1919

The President was authorized to appoint. a liaison committee to cooperate with the American Mining Congress in respect to the establishment of a Secretary of Mines and Mining in the President&apos;s Cabinet. He appointed Edwin Ludlow, Chairman; Mark L. Requa, and J. E. Johnson, Jr. It was resolved to accept the invitation from the Chicago Section to hold the. 120th meeting of the Institute in Chicago during the week of Sept. 15, 1919. The action of the Executive Committee in appointing Past President E. Gybbon Spilsbury as representative of this Institute to visit France upon the invitation of the Société des Ingénieurs Civils de France was approved. The final budget for 1918 was approved. Tile President was authorized to appoint a committee, of three members, on the Development of Activities of the Institute. The committee was requested to report at the February meeting of the Institute, and the Secretary was requested to invite each local section to have a member present to discuss the subject. The President appointed J. W. Richards, Chairman; P. N. Moore, and Allen H. Rogers. Thirty-six members, ten associates, and five junior associates were elected; one change of status from associate to member was granted; two members were reinstated; and eight resignations were accepted. An extension of time was granted to nine members. The dues of eight members were suspended on account of their being in active service.

Jan 2, 1919

By Myron Rodgers

IN rock- or ore-crushing tests all data, in order to be valuable for study and comparison, should be obtained and tabulated under conditions as uniform as possible. The results of many such tests have no value for comparison, because of incomplete data and the lack of uniform conditions, screens and scale of sizing, etc. The purpose of this paper is to suggest a form of standard specifications which may be developed by the Milling Committee and approved by the A. I. M. E. for rock-crushing tests. It is not intended to discuss any theories of rock crushing. Reports of rock-crushing tests should include the following details: 1. Description of the machine employed (jaw or gyratory crushers, rolls, stamps, tube mills, Chilean mills, etc.). 2. Method and material (timber, concrete, etc.) of foundation. Much power is dissipated in the vibration of poor foundations. 3. Locality from which the rock or ore was obtained, and geological, mineralogical, and physical characters of the material. 4. The power consumption of the machine running with no load and with full load, the unit of power being 1 hp, per 24 hr. 5. The capacity of the machine in tons (of 2000 lb.) per 24 hr. 6. The duty in tons per horsepower-day. 7. The screen analysis of feed and product by the proposed A. I. M. E. standard screen scale. On the foregoing statement, the following remarks are offered.

Jan 9, 1915

By David Sinclair, Philip B. Bucky

THE dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests.§ None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their application in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I THE PHOTOELASTIC METHOD The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution. GENERAL EXPLANATION The stress at any point 0 in a structure (Fig. 1), may be resolved into two components, P and Q, each a pure tension or compression, at right angles to each other, called principal stresses.1 To fully identify the stress, the values of P and Q and their directions or angle [0] must be known.

Jan 1, 1940

By John V. Beall

Probably it won&apos;t happen to us again in a thousand years, but it was very embarassing at the time. It is only because of certain matters that have come up this month that we tell you at all about it. At the beginning of our trip to Peru and Chile last summer, we were flying with Bill Haddon from Lima to Tacna aboard Fawcett. Being an old hand at foreign travel, particularly in South America, we felt obliged to explain some of the special features of travel in Latin America and the niceties of etiquette in particular and were so engaged when the plane landed at the airport. We led the way briskly into the terminal, expecting at any moment to have a representative of Southern Peru Copper pop up and present himself. However, this didn&apos;t happen so we repaired to the baggage arrival station to wait. All the bags were quickly picked up, but ours were no where to be seen. Bill was slightly agitated because the plane was being buttoned up for take off. However, rising to the emergency with our usual aplomb, we took charge of the situation. Brandishing the claim checks under the nose of the porter who pointed to them and said, "si, Tacna," we nodded briskly and in our serviceable Spanish said "si se[n]or, vayase viejo, rapido." He was off and back with our suitcases quickly enough.

Jan 1, 1970

By P. A. Toynbee

An experimental air-slide classifier1 has been applied to the de-dusting of ground dolomite in an attempt to produce a grade of -30 +150 mesh (B. S. Sieves) material from a raw material containing 30-35% of the -150 mesh fraction. Air flows varying between 1.5 and 2.5 cu ft/sec sq ft of screen area were used. The throughput of dolomite was between 80 and 100 lbs/h. inch of screen width. The size analyses of the de-dusted material and of the original dolomite are shown in table at right. The proportions of the +100 mesh material in the feed and in the de-dusted products have been used to calculate materials balances, on the assumption that there is no loss, as dust, of this +100 mesh fraction. By interpolation, it can be shown that a de-dusted product recovery of 68.5% will be obtained at an air flow of 2.13 cu ft/sec sq ft of screen area. The feed material contains 68.5% of +150 mesh material, so that if the de-dusting gave a perfectly sharp cut, the product would contain no material less than 150 mesh. Further calculations based on the size analyses, show that, at an air flow of 2.13 cu ft/sec sq ft of screen air, the -150 mesh fraction in the de-dusted product will fall just below the specified maximum limit of 5%.

Jan 1, 1964

By Thomas H. Sheehan

The purpose of this paper is to present an application of computer technology to assist the mineral company financial executive in assessing exchange risks. The paper is divided into five parts: Background, Translation Approaches, Theory, Empirical Validation, and Conclusion. BACKGROUND Exchange risk results from a change in the rate of exchange between a host and a home country&apos;s currencies. Legitimate reasons exist for changes in the currency exchange rates among countries in a world with over a hundred different currencies. These reasons include: different economic growth rates, social factors, cultural heritages, and political motivations. The problem of exchange rate changes are perennial and exist whether the world operates on exchange rates or floating exchange rate practices. The cause of the problem is trade and international payment imbalances. If one accepts the premise that exchange rates fluctuate over time, then the mineral company financial executive faces a continual process of reassessment of the impact of exchange rate changes on the financial worth of his company. (1) The mineral company financial executive prepares balance sheets and income statements that are audited by certified public account- ants annually for shareholders, bankers, and tax authorities. The financial executive translates assets and equities denominated in foreign currencies into domestic dollars, e.g., Japanese firms convert to Yen, French firms convert to Francs, and so on. When figures from foreign subsidiary operations are consolidated into the balance sheets of the parent corporation, estimates of the company&apos;s finan-

Jan 1, 1977