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Approximately half of all the fuel energy used in the United states is now pro-vided by oil and natural gas. A persistent and rapid growth in energy demand during the last 3 decades has been absorbed largely by the liquid and gaseous rather than solid fuels. In 1948 the energy provided by coal was substantially the same as in 1920. Meanwhile, the use of oil and natural gas each had increased fivefold. On a per capita basis, the change is more significant. Coal consumption has dropped from about 6 tons per person to 4-1/2 tons, while oil has increased from 4-1/3 barrels to 14-1/3, and natural gas from 7,500 cubic feet to about 35,000. These facts would have only academic interest if the United States had unlimited supplies of all fuels. However, while the Nation's reserves of coal are adequate to meet our needs for centuries, those of oil and natural gas appear limited. It is obvious, therefore, that the security of our liquid-fuel position would be greatly enhanced if the supply could be based in an increasing degree on solid fuels, such as coal and oil shale, which make up more than 95 percent of our fuel reserves, instead of natural oil and gas. In addition, this would create new employment and help to stabilize the market for coal, which may be facing comparatively bleak prospects in the near future unless its position with respect to other fuels is improved.

Jan 1, 1950

By H. Sigurdson, T. V. Cherian, C. H. Moore

The phenomenon of recovery of cold-worked metals is interesting not only because of its practical importance but also because of its fundamental significance in solid state reactions. Although extensive investigations1,2 have already been made in an attempt to discover the mechanics of the recovery process, many of the observations have not yet been satisfactorily correlated to provide a completely consistent model for the process. The wide differences in the recovery rates of various properties can be cited as a typical example of one of the difficulties that are encountered. Frequently, for example, the electrical resistance will have almost completely recovered before any recovery in tensile strength can be detected. Of course, such differences in the recovery rates of different properties might be explained by assuming that each property is a unique function of the work-hardened state, and consequently each property exhibits its own unique recovery rate. The assumption that different properties are uniquely related to the work-hardened state cannot be denied. On the other hand, the properties that recover at different rates often exhibit more or less parallel changes upon work-hardening. This suggests that the microstructural changes attending recovery are not exactly the reverse of the changes attending work-hardening. Several types of imperfections must be postulated in order to account for this apparent anomaly. The different recovery rates for various properties, then, are due to the different recovery rales of the type of imperfection to which each property is most sensitive as well as the unique dependence of each property on the cold- worked state. This concept assumes that a simple model of the work-hardened state consisting only of one type of imperfection, such as Taylor's type of dislocation patterns, is inadequate to cope with the diversified phenomena attending work-hardening and recovery. Although current models for the work-hardened state are not useful for describing all aspects of the recovery process, the general trends of the recovery of each postulated type of imperfection as a function of time and temperature should be at least qualitatively deducible from the rather well developed laws of kinetics of reactions in the solid state. Consequently, recovery data might prove useful for elucidating some aspects of the complexities of the work-hardened state of metals. A preliminary attempt to study work-hardening by investigating recovery rates of cold-worked metals is outlined in the following pages of this report. Experimental Procedure Many properties recover when cold-worked metals are annealed below their recrystallization temperature. Therefore, electrical resistivity, thermal electromotive force, X ray diffraction line widths, X ray diffraction line intensities, elastic spring back, density and other physical and chemical properties have been used to study the recovery process. Major interest, however, has generally been directed toward the recovery of the mechanical properties such as hardness, yield strength, and tensile strength. But a search of the literature suggests that the effect of recovery on the true stress-true strain curve has been neglected, in spite of the current recognition of the fundamental importance of such an investigation. An investigation on the effect of recovery treatment on the true stress-true strain curves in tension, therefore, was undertaken in the present study. Commercially pure aluminum (99. + pet Al) in the form of 0.100 in. thick rolled sheet of 2S-O aluminum alloy was selected as the material for this investigation because rather extensive correlatable data are already available on the recovery of some of its properties. Tensile specimens having a 6 in. long gauge section and a uniform reduced section width of 0.500 in. were machined from the sheet in accordance with a design that has previously been reported.3 All specimens were selected with their axes aligned in the rolling direction. In order to eliminate the effects of previous work-hardening and the effects of machining, the specimens were annealed for 15 min. at 750°F before testing. During tensile testing the loads were measured by means of a proving ring (sensitive to 1/2 lb) in series with the specimen.4 Strains were determined from the extension of a rack and pinion strain gauge sensitive to a strain of + 0.0001. The stress was recorded as the true stress, namely

Jan 1, 1950

By J. K. Stanley

Knowledge of the diffusivity of carbon in the low temperature form of iron (alpha iron existing below 910°C) is at the moment of considerable interest in the study of the decomposition of austenite and martensite, the elastic after-effect,123 the magnetic after-effect4 and the decarburization of steel below 910°C. Information on the solubility of carbon in iron, and to a lesser extent its diffusion, is also important in consideration of such phenomena as blue-brittleness, temper-brittleness, "magnetic" aging, quench-aging, strain-aging, and possibly the yield point. In order to obtain more information on these subjects more fundamental knowledge is necessary. It is the purpose of this work to present data on the diffusion and solubility of carbon in the alpha iron. The high temperature form of iron (gamma; face-centered cubic) existing above 910°C is capable of dissolving relatively large amounts of carbon, up to 1.7 pet at 1130°C, while the low temperature form (alpha, body-centered cubic) existing below 910° dissolves only a limited maximum amount of less than 0.02 pet carbon at 725°C, according to data obtained here. Since the solubility of carbon in the face-centered or gamma iron is large, relatively speaking, no great analytical difficulties have been encountered in the determination of the solubility lines5 or of the diffusion of carbon.0 The limited solubility of carbon in alpha iron offers difficulties because experimental procedures and analytical methods for low carbon contents below say 0.01 pet have to be more refined than techniques used for work with gamma iron. Because of the difficulties of applying conventional methods to the determination of the diffusion of carbon in alpha iron, virtually no work has been done on this subject. However, by proper refinement of the analytical method for small amounts of carbon, the determination of the diffusion coefficient can be made readily using modified procedures. The solubility of carbon in alpha iron has been determined over a temperature range by various investigators, but the agreement among them is poor. The present investigation establishes the limits quite accurately. Information of this kind is useful in establishing the correctness of equilibrium diagrams but, more significantly, such information on maximum solubilities, especially when extended to alloyed ferrites, should be extremely important in the study of aging and related phenomena. Literature The literature existing on the diffusion, in particular, and on the solubility of carbon in alpha iron is not extensive. The data which exist are not of a high order of accuracy, much of them being in the realm of conjecture. THE DIFFUSION OF CARBON IN ALPHA IRON Whiteley7 made the qualitative ob- servation, using metallographic techniques, that the rate of diffusion of carbon at the A1 (725°C) point was very rapid and that its diffusion was still rapid at 550°C. Snoek,4 studying the magnetic aftereffect in high purity iron, arrived at the conclusion that the after-effect could be explained by the presence of small amounts of carbon diffusing under the influence of magnetostrictive strain (lattice distortion due to magnetic interaction). In later work, Snoek8 made an estimate of the ratio of carbon diffusion in alpha to its diffusion in gamma iron, and concluded that for a temperature of 910°C the ratio of Da/D? was 2600. Polder,9 basing his calculations of D on relaxation phenomena in the elastic after-effect, estimated that Da is about 1/3 of D? at 910°C (1183°K) and is about 1/12 of Dy at 727°C (1000°K). Polder's equation for the diffusion of carbon in alpha iron was calculated to be 18000 D = 5.2 X 10-4 e-RT cm2 per sec Ham10 obtained data for the diffusion and solid solubility of carbon in alpha iron at two temperatures by using one technique similar to that employed in this study. He found a D of 8.0 X 10-7 cm2 per sec at 702°C and of 2.7 X 10-7 at 648°C. THE SOLUBILITY OF CARBON IN ALPHA IRON Although pearlite is absent in steels containing 0.06 pet,11 0.05 pet,12 or 0.045 pet C,13 it appears that the carbon in these steels cannot be in solution in ferrite. The solubility of carbon at the A1 (725°C) point was first determined by Scott14 on the basis of cooling curves, and was found to be between 0.03 and 0.04 pet C. Tamura15 by interpolating between the solubility of carbon in delta iron at 1400°C and in alpha at room temperature (assuming zero solubility) ar-

Jan 1, 1950

By J. J. Jakosky

The strategic importance of the metallic minerals in our industrial economy, and the declining rates of discovery have focused attention on means of exploration for new mineral deposits. A consideration of exploration techniques leads to an attempt to evaluate the effectiveness of geophysics as a tool for mining exploration. One means of evaluation will be to compare the use of geophysics in petroleum exploration with its possible uses in mining. Geophysics in Petroleum Exploration During the past twenty years, the petroleum industry has established an effective exploration technique. Geology is the basic tool in those areas where reliable predictions can be made from surface conditions. In the other areas, where the geological studies are inadequate, they must be supplemented with geophysics or direct exploration, such as drilling. Since geophysical work is far less costly than any form of direct explbration, it is used almost exclusively as the means for obtaining the desired subsurface information. The geological and geophysical techniques are credited with locating sites which yielded one producer for three dry holes during the year 1947.' For the wells located without geology or geophysics, there is a ratio of one producing well to sixteen dry holes. From these figures it is seen that the geological and geophysical techniques are more than four times as successful as the nontechnical exploration. It will be in order to consider further this ratio of one producer to three dry holes. The geophysical methods in use today† do not pretend to locate oil directly; their function is to locate anomalies or structures favorable for the accumulation of oil. For a producing oil well we must have not only structure, but also other favorable conditions, namely: petroliferous source beds, the required porosity and permeability in the reservoir rocks, an impermeable cap rock over the reser- voir, and the necessary water or gravity drive to force the oil into the bore hole. Since the geophysical work can only detect and sometimes delimit the anomaly, these other necessary conditions can be determined only by direct exploration. The success of modern geophysical work in locating and limiting the structure itself is remarkably high, probably over 95 pct accurate. Geophysical work renders an important service in the delineation of the structurally unfavorable areas and their elimination from the drilling phase of the exploration program. When attempting to locate any material of scarce occurrence in the earth, it is of paramount importance to know where not to dig. This elimination of barren areas is the least appreciated but is of great economic importance. For illustration, the difference between one producer to three dry holes, and one producer to sixteen dry holes, represents a saving of thirteen drilled wells, which would require an expenditure many times the cost of the geophysical work that might have revealed the nonfavorable structural conditions. The percentage of geophysically-located wells necessarily will continue to increase in the statistics of future years, as the search for oil is extended

Jan 1, 1950

By J. D. Lubahn

The influence of precipitation from solid solution on the subsequent deformation resistance of alloys is well known. However, the influence of precipitation or aging that occurs simultaneously with deformation may be entirely different and of considerable importance. It is thought1 that the presence or absence of a yield point jog in impure iron at room temperature and the presence or absence of discontinuous flow at higher temperatures may be directly related to aging phenomena, particularly since the yield point jog is absent when the carbon and nitrogen are sufficiently removed.2 As a preliminary attack on the problem of simultaneous aging and deformation, three kinds of tests—constant strain rate tensile tests, constant load creep tests, and variable strain rate tensile tests—were carried out on an age hardenahle aluminum alloy. Constant Strain Rate Tensile Tests Stress-strain curves at a strain rale of about 0.001 min-1 were obtained for specimens of 61S that had been quenched into liquid nitrogen after a one-hour solution treatment at 521°C, then aged at room temperature 10 min., 20 min., 4 hr, and 26.5 hr before testing. Strain-time curves were obtained on the same chart with the stress-strain curve by means of an auxiliary pen, driven parallel to the axis of the chart drum at constant speed by a synchronous motor and gear chain. The angle of rotation of the chart drum was proportional to strain. The strain rates reported are the measured slopes of the strain time curves. Constant strain rate was approximated (within a factor of 2) by manual adjustment of the oil inlet valve of the hydraulic testing machine in such a way that the course of the recorder pen was parallel to pre-drawn strain-time lines of the desired slope. The specimens were machined from 9/16 in. rod. The cylindrical portion was 0.357 in. in diam by 13/4 in. long and

Jan 1, 1950

By R. P. Carreker, J. C. Fisher

Cheep tests are normally constant load tests. Such tests approximate some types of service conditions and therefore are justified from the engineering point of view. Coupled with this consideration is the advantage of simplicity inherent in constant load tests, as contrasted with the comparatively complex requirements of a constant stress test. It is not surprising that the vast majority of creep tests reported are of the constant load type. Despite the enormous amount of accumulated creep test data, plastic flow is by no means completely understood. The widespread use of constant load tests is at least partly responsible for this lack of understanding. Any attempt to analyze deformation must involve the more fundamental quantity stress, rather than load. It is possible to predict constant load behavior from known constant stress data, but the reverse is much more difficult. When a metal specimen elongates, as in a creep test, the cross section decreases, maintaining constant volume. Thus For a constant stress test the force on the specimen must be decreased as the cross section decreases, that is, this force must be inversely proportional to the elongation of the specimen. An-drade has described three methods of obtaining the constant stress condition,l-3 each of which is relatively complex. The most recent proposal,³ suggests a major simplification which maintains the simplicity of the constant load test while approximating quite closely the desirable condition of constant stress. Andrade's device is admittedly more accurate but the method described below has definite advantages Consider a specimen in the form of a "V" supported at its ends. If a weight be applied at the vertex of the angle, the stress in each leg of the "V" If this stress causes an elongation ?1 in each leg of the "V," the angle decreases from a. to a smaller angle a1. The quantity sec — thus decreases with specimen elongation while the quantity 1/A increases. By selecting proper initial conditions it should be possible to hold S/So very nearly constant at unity. The proper initial conditions are realized when a0 is made equal to approximately 90°. Fig 1 compares the ratios of S/S0 for a0 = 85, 90, 95, 100°, with a0 = 0, that is, a straight speci- men, for true strains up to e = 0.10. It may prove convenient to measure X, the movement of the vertex, rather than the true elongation 1. Contour lines of X/lo are also plotted in Fig 1. The method for obtaining constant stress described above is especially suited to the testing of small wires, but may easily be extended to rods of any diameter through the use of a suitable grip which serves as the vertex joining two identical rods forming the legs of the "V." References 1. E. N. da C. Andrade: On the Viscous Flow in Metals, and Allied Phenomena. Proc. Roy. Soc., A, 84, 1, (1910-11). 2. E. N. da C. Andrade and B. Chalmers: The Resistivity of Polycrystalline Wires in Relation to Plastic Deformation, and the Mechanism of Plastic Flow. Proc. Roy. Soc., A, 138, 348, (1932). 3. E. N. da C. Andrade: A New Device for Maintaining Constant Stress in a Rod Undergoing Plastic Extension. Proc. Phys. Soc., 60, (3). 304, (March, 1948).

Jan 1, 1950

By G. H. Anderson

Cadmium-coppeR precipitate, a byproduct of the purification stage of the zinc plant, is composed mainly of zinc, cadmium and copper in varying amounts depending on the efficiency of precipitation and the cadmium and copper contents of the impure solution treated. The composition range is approximately: cadmium 10-12 pct, copper 6-8 pct, and zinc 3&35 pct. As received at the cadmium plant, the precipitate is a dark gray to black press cake produced by filter pressing the flocculent cadmium-copper precipitate formed when impure zinc solution is agitated with zinc dust. The details of the cadmium-copper precipitation are to be found in the paper "Electrolytic Zinc at Risdon, Tasmania," by W. C. Snow. Transactions AIME, 121, 501. The treatment, in addition to recovering cadmium as metal, yields a copper product as a residue for realization and recovers in solution for return to the zinc plant, the excess of zinc dust used during purification. The recovery of cadmium metal is approximately 200 tons† per year, but, with the amount of copper residue recovered, varies with the zinc production tonnage, composition of the original concentrates, degree of roasting and other operational factors. The operations involved in the recovery of the foregoing materials are carried out in a building adjacent to the purification section of the zinc plant and can best be described by dividing the process into the following stages: 1. Oxidation and Grinding of the cadmium-copper precipitate. 2. Leaching and Filtering. 3. Precipitation of cadmium. 4. Oxidation and Grinding of the precipitated cadmium. 5. Leaching oxidized cadmium precipitate and Purification of leach solution. 6. Electrolysis. 7. Melting, Casting and Packing. A feature of the process is the use of two distinct solution circuits. Spent electrolyte from the zinc plant circuit containing about 10 pct sulphuric acid is used as the primary solvent of the cadmium and zinc present in the oxidized precipitate. When the cadmium is later separated by precipitation and filtering, the filtrate, originally zinc plant spent electrolyte and now fortified in zinc, is returned to the zinc plant. The precipitated cadmium, after oxidation, is redissolved in spent electrolyte from cadmium electrolysis which solution is in closed circuit within the cadmium plant except for discards to the zinc plant circuit as mentioned in Section 5 hereinafter. (Fig 1.) Details of the various operations follow. I. Oxidation and Grinding of the Cadminm-copper Precipitate The precipitate having had a preliminary drying by compressed air in Dehne filter presses in the zinc plant is trucked to a storage platform of sufiicient length to store 3 to 4 days' production separately. After 48 hr exposure to atmosphere, oxidation is sufficient to enable all cadmium and zinc but only a portion of the copper to be dissolved in dilute sulphuric acid. The oxidized precipitate is shovelled into trucks and, after weighing and sampling, is broken in size by means of

Jan 1, 1950

By Herbert Clark Hoover, Lou Henry Hoover

PREVIOUSLY I have dealt with the methods of separating silver from copper. There now remains the portion which treats of solidified juices ; and whereas they might be considered as alien to things metallic, nevertheless, the reasons why they should not be separated from it I have explained in the second book. Solidified juices are either prepared from waters in which nature or art has infused them, or they are produced from the liquid juices themselves, or from stony minerals. Sagacious people, at first observing the waters of some lakes to be naturally full of juices which thickened on being dried up by the heat of the sun and thus became solidified juices, drew such waters into other places, or diverted them into low-lying places adjoining hills, so that the heat of the sun should likewise cause them to condense. Subsequently, because they observed that in this wise the solidified juices could be made only in summer, and then not in all countries, but only in hot and temperate regions in which it seldom rains in summer, they boiled them in vessels over a fire until they began to thicken. In this manner, at all times of the year, in all regions, even the coldest, solidified juices could be obtained from solutions of such juices, whether made by nature or by art. Afterward, when they saw juices drip from some roasted stones, they cooked these in pots in order to obtain solidified juices in this wise also. It is worth the trouble to learn the pro- portions and the methods by which these are made. I will therefore began with salt, which is made from water either salty by nature, or by the labour of man, or else from a solution of salt, or from lye, likewise salty. Water which is salty by nature, is condensed and converted into salt in salt-pits by the heat of the sun, or else by the heat of a fire in pans or pts or trenches. That which is made salty by art, is also condensed by fire and changed into salt. There should be as many salt-pits dug as the circumstance of the place permits, but there should not be more made than can be used, although we ought to make as much salt as we can sell. The depth of salt-pits should be moderate, and the bottom should be level, so that all the water is evaporated from the salt by the heat of the sun. The salt-pits should first be encrusted with salt, so that they may not suck up the water. The method of pouring or leading sea-water into salt-pits is very old, and is still in use in many places. The method is not less old, but less common, to pour well-water into salt-pits, as was done in Babylon, for which Pliny is the authority, and in Cappadocia, where they used not only well-water, but also spring-water. In all hot countries salt-water and lake-water are conducted, poured or carried into salt-pits, and, being dried by the heat of the sun, are converted into

Jan 1, 1950

By I. C. Brown, J. F. Henderson

"IntroductionThe Yellowknife greenstone belt lies along the west side of Yellowknife bay on the north shore of Great Slave lake, some 600 miles north of Edmonton, Alberta. The producing gold mines along the belt include the Con-Rycon and Negus which came into production in 1938 and 1939, and the Giant Yellowknife, which followed in 1948. In addition to these, the Akaitcho and Crestaurum mines are potential producers and there are several promising prospects.Early geological work along the belt was done by A. W. Jolliffe who first recognized a number of great faults, the largest of which is the West Bay fault with a horizontal movement of more than 3 miles. In 1943, A. S. Dadson, following an examination of the Giant-Yellowknife property, advanced the hypothesis that Baker Creek valley was underlain by a series of major gold-bearing shear zones. Subsequent diamond drilling in 1944 bore out the correctness of this view and outlined the great ore-bearing shear zones that are now being developed and mined by Giant Yellowknife Gold Mines. Near the south boundary of the Giant property, the shear zones are cut off by the West Bay fault. This prompted Neil Campbell, District Geologist for the Consolidated Mining and Smelting Company, to make a detailed study of the geology along the West Bay fault in the hope of finding the faulted extension of the Giant shear-zone system on the west side of this fault. In this he was entirely successful. By careful geological mapping he matched several faulted diabase dykes on both sides of the fault and, knowing their dip, determined the horizontal and vertical components of movement along the fault. Subsequent •diamond drilling based on Campbell's work located the presumed correlative of the Giant shear-zone system on the Con-Rycon and Negus properties, where it has been named the Campbell zone or system. At the present time, all production at the Negus Mines property is coming from orebodies along the Campbell zone."

Jan 1, 1950

By Charles H. Moore, H. Sigurdson

When lime and magnesia are used as fluxes in the smelting of titaniferous ores fluid, digestible slags low in iron oxide and high in titanium dioxide are produced. The mineral phases present in such slags are (Fe,Mg)O.ZTiOp, CaTiO3, and minor amounts of silicate glass (or its devitrification products). The flux additions are added to the ore in relative amounts to crystallize a ratio of (Fe,Mg)O.2TiO2 to CaTiO, of near the eutectic proportions of 60 pct (Fe,Mg)O.2TiO2 and 40 pct CaTiOl. FeO.TiOz (ilmenite) remains present in the slag until the FeO content is reduced to approximately 8 pct. Optimum slag composition is obtained by reducing the FeO content to between 2 and 6 pct. Continued reduction shifts the (Fe,Mg)O.2TiO2 to oxygen deficient structures classified as MgTi306 and MgTi2O.. Further reduction yields titanium oxycarbides and freezes the melts. The(Fe,Mg)0.2TiO2 structure shows a complete isomorphous replacement of iron by magnesium. It also forms a solid solution compound with as high as 12 mols of TiO2 under reducing conditions without the occurrence of rutile or reduced titanium oxides in the slag.

Jan 1, 1950

By Russell G. Haworth

Three companies, United States Potash Company, Potash Company of America, and International Minerals and Chemical Corporation, are now operating potash mines and reGneries in the Carlsbad, New Mexico, area. The three mines are located approximately twenty miles east of Car1sbad. The deposits have been found ideal for mechanized mining methods. This summary has been compiled from information made available by the three operating companies. Prospecting Since outcrops of potash are nonexistent, prospecting is accomplished by drilling and coring of the salt section to establish the grade, thickness, and outline of the potash beds contained in the salt deposits. Information regarding the nature of the formations in the cover of 400 to 600 ft thick over the salt and potash beds is also obtained from drill cuttings in the same operation. By proper interpretation of assembled data the best location for shafts may be determined. The overburden varies in character but consists in general of interbedded shales, sand, gravels, limestones, and anhydrite beds. Water, in unpleasant quantities, especially in the sands and limestones, often completes the geologic section. Some of the shaftas in the area have been sunk without undue difficulties, others have been delayed by flows of water. Most of the shafts are concreted from the surface to the salt section. Each of the three mines in the Carlsbad area has one shaft for hoisting ore and one for hoisting men and supplies. Mining Methods Information acquired from initial drilling and prospecting affected the choice of mining methods. Since the tabular, slightly rolling deposits were similar to coal seams, the room-and-pillar system used in coal mining was adopted by all the companies. Pillars have not been removed in any of the mines on a large scale. One company has conducted experimental robbing of pillars in one restricted area. Where it is known that overlying strata contain water in large amounts, it is not considered practical to risk flooding of the mines by removing pillars without fill. Some thought is now being directed toward development of economical methods of filling for pillar recovery. The problem is not identical at the three mines and local conditions will govern the methods employed for eventual pillar recovery. The important point is that, with large reserves, it has not been necessary to resort to mining of pillars for adequate production. The ore deposits are laterally extensive but are irregular in shape and lie at a depth of 700 to 1100 ft below the surface. The major operations of all mines are on the same bed strati-graphically, except for the langbeinite level at International Minerals and Chemical Corporation. The deposits are apparently not connected and in many parts of the deposits being mined, "salt horses" or barren zones occur. From 400 to 700 ft of salt with minor beds of polyhalite and anhydrite lie immediately above the ore horizon. The ore differs from the salt only in the potassium chloride content and color due to small amounts of iron associated with the sylvite, giving the ore a somewhat mottled red and white cast. Thickness of the ore varies from 5 to 14 ft. Rooms and break-throughs in the mines vary from 24 to 40 ft in width, the overlying salt forming an excellent roof and providing safe mining conditions. Almost no timber is used in any of the mines for roof support. Drilling is normally the first step in mining the face of a room. Electric motor driven auger drills are used in the area. Jack hammers were used to some extent when the mines were first opened but the ore is easily drilled if bits are sharp and the coal type

Jan 1, 1950

By P. R. Sperry, P. A. Beck, J. Towers

Dahl and Pawlek1 found that electrolytic copper develops extremely coarse grains at 1000°C after about 90 pct reduction by rolling. This coarsening occurs only under conditions of penultimate grain size, deformation, and alloying which lead to the "cube" recrystallization texture.l,2,3,5 The peculiar angular shapes and straight grain boundaries of the coarse grains were noted by several investigator.1,4,5 On the other hand, coarsening in Fe-containing aluminum or in AI-Mn alloys8 does not depend on a "cube" (or any well developed) recrystallization texture. It is true that increasing deformation by rolling, and, therefore, an increasingly well developed re-crystallization texture, are associated with decreasing incubation periods of coarsening.6-7-8 Nevertheless, coarsening readily develops in aluminum even after only 30 pct reduction by rolling, where the recrystallization texture is very weak.6,8 Also, coarsening was observed by Jeffries9 many years ago in sintered thoriated tungsten, which presumably has no preferred orientation. In all these cases coarsening is associated with grain growth inhibition by a dispersed second phase.8,9 The annealing temperature has to be suficiently high to overcome the inhibition at a few locations. But if it is too high, growth starts at many points, and the resulting grain size becomes much smaller.9 Normally, the coarse grains are more or less equiaxed, and the boundaries have a typical ragged appearance.6.8 Cook and Macquarie4 demonstrated that, in addition to the texture-dependent coarsening previously found at 1000°C,l electrolytic tough pitch copper may also coarsen at 800°C after 50 pct reduction by cross rolling. The coarse grains formed under such conditions have rounded shapes and ragged boundaries, like those in aluminum. When the annealing temperature is higher, the tendency for their formation decreases. All these observations suggest that the coarsening at 800°C is associated with inhibition by a second phase. Actually, coarsening at 800°C after 50 pct reduction by cross rolling was observed only in tough pitch copper,4 which contains Cu2O particles. On the other hand, the texture-dependent 1000°C coarsening occurs in both tough pitch and oxygen-free copper;4 it does not appear to depend on the presence of a dispersed second phase. However, the interpretation of the 800°C coarsening in Cu after 50 pct rolling as an inhibition-dependent process, similar to the coarsening in A1-Mn alloys, is somewhat weakened by the fact that this coarsening was reported4 to occur only after cross rolling, and not after straight rolling. It was, therefore, decided to re-examine this question. A 1 in. diam electrolytic tough pitch copper rod, No. 2 hard drawn, was annealed for 20 min at 700°C, rolled to 0.5 in., annealed 10 min at 700°C, and straight rolled to 0.064 in. It was then given a penultimate anneal of 20 min at 500°C and it was cut into four sections, which were given final reductions by straight rolling as follows: A 30 pct reduction of area B 50 pct reduction of area C 70 pct reduction of area D 90 pct reduction of area Specimens cut from the four sections were finally annealed at 800°C in an oxidizing atmosphere. Strip A remained fine grained up to 10 hr, but the specimen annealed 12 hr consisted of only 2 large grains. Strip B had a few scattered large (1/2 to 3/4 mm) grains after 1 min, although the balance of the specimen consisted of fine grains of about 0.02 mm. After 5 min there were several 10 to 15 mm grains present, and after 1 hr strip B was completely coarsened. The coarse grains had the same characteristics (see Fig 1) as those obtained by Cook and Macquarie at 800°C after cross rolling. Strip C had several grains of 0.05 to 1 mm after 1 min, but it was still largely fine grained after 12 hr. After 48 hr it consisted entirely of grains of about 0.5 to 4 mm, with an extraordinarily large number of twin bands. Strip D remained com- pletely fine grained after 4 hr at 800°C. These results indicate that, in the deformation range of 30 to 70 pct reduction, the incubation period for coarsening as well as the rate of growth and the final size of the coarse grains decreases with increasing deformation. Similar

Jan 1, 1950

By A. Ignatieff

This is the second review of developments in coal mining engineering (see C.I.M .M. Transactions, Vol. LI, 1948, pp. 262- 264) and covers the period from October, 1948, to January, 1950. Mechanization The period under review was characterized by the intensive development of appliances providing for complete mechanization of coal-face operations. A variety of machines are being evolved or have already been placed on the market which embody the principle of 'continuous mining'. This trend can be observed in all coal producing countries. In the United States, two continuous mining machines have been developed for entry and room application and by the end of 1 949 were being used in a number of mines. These are the Joy Continuous Miner in which the coal is ripped from the face by means of multiple cutter chains, and the Jeffrey Colmol employing cutters on rotating arms for chipping the coal from the face. The Joy machine is made in tw6l models, 34-in. and 48-in. high and designed for a range of seam thicknesses from 3-ft. -t-in. to 4-ft. 6-in. and from 4-ft. 6-in. to 8ft., respectively. Some experience has been gained with this machine and accounts of its performance are already appearing in the technical literature. The Jeffrey-Colmol has a more limited range of working height. The first model, 38-in. high, was designed for seams about 4 feet in thick11ess but more recently the 28-in. low model has been placed on the market for seams 2-ft. 6-in, to 3-ft. 4-in. in thickness. Conventional mobile loading machines of the gathering-arm type are continuing to yield high production under suitable conditions, and improvements or modifications of the basic principle are embodied in new machines as, for example, the Jeffrey mobile (conveyor) loader with extensible (gathering-arm) head developed for conveyor mining.

Jan 1, 1950

By Holt. Grover J.

"IntroductionThe history of iron ore production in the United States has followed a pattern not far different from that set in the production of non-ferrous ores; the first interest of the prospector and miner being the discovery and development of high-grade ores. In the early stages of development of most mining districts, high-cost low-grade ores are usually of slight interest due to the additional capital investment required in concentrating plants, as well as the increased requirements of •power and other facilities. As the reserves of higher grade ores are depleted and the technical knowledge of ore beneficiation is broadened, production of concentrates from the lower grade ores is stimulated.The real stimulus necessary to arouse serious consideration of beneficiated iron ore in the Lake Superior district has been provided by the serious inroads made in the high-grade ore reserves by two World Wars.The first shipment of high-grade iron ore from the Mesabi range in Minnesota was recorded in 1892, and the first token shipment of concentrates was made 15 years later, in 1907. Not until 1910 did the production of concentrates assume any great importance. A steady increase in concentrate production over the years is shown by the fact that, in 1910, concentrates accounted for 8 per cent of the total shipments from the State, whereas by the time of World War II this percentage had increased to 22 per cent and by 1948 had risen to 26 per cent. It seems a safe assumption that the shipment of concentrated iron ore, from the Mesabi range in particular, will continue to increase even more rapidly from now on, with other iron ranges of the Lake Superior district following this lead."

Jan 1, 1950

By Bernard Lewis

This report summarizes the fundamental research and technical studies conducted by the Explosives Branch of the Bureau of Mines from July 1, 1943, to June 30, 1949. It is the thirteenth of a series of annual reports, which have aimed to bring to the reader a resume of the research results that have appeared in published form during each fiscal year. The work of the Explosives Branch covers a number of activities - explosives research, explosives testing, flame and combustion research, flammability of gases and vapors, dust-explosions research, and technical studies in the experimental mine. An important part of the work of the branch is fundamental research to advance our knowledge and understanding of explosion processes. Considerable emphasis has been placed on studies of ignition and flame stabilization, as it is felt that an understanding of these processes should assist materially in alleviating explosion hazards in coal mines. The results are also finding important application in the development of jet propulsion. Studies of the explosibility of gases, vapors, and dusts saving thousands of lives and are preventing the destruction of much property. In innumerable instances in which potential explosion hazards exist, safe operating procedures have been recommended from data taken in the Laboratory. Aware of the value to national security of research results of combustion, flame, and explosion, the Army, Navy, and Air Forces are actively supporting important phases of this fundamental research.

Jan 1, 1950

By Louis Moyd

In the preparation of illustrations to accompany reports of investigations concerning particle shapes of various natural and manufactured materials proposed for use as he aggretates in concrete structures, it was found that stereoscopic views of such materials presented the information much more effectively than the usual two-dimensional photographs. With the whole-hearted cooperation of the Photographic Section, a technique was developed in the petro-graphic laboratory of the Concrete Research Division, U.S. Corps of Engineers, at Clinton, Miss., for simple and rapid preparation of paired stereoscopic photographs and micrographs. The method requires only equipment which is usually part of the general stock of any laboratory, and it is adaptable for all purposes in which three-dimensional views would be found superior to ordinary photographs. Stereoscopic Photographs Where the subject or subjects to be photographed are small but not of microscopic size, an ordinary camera having a ground-glass focusing screen is set up vertically over the field. The material to be photographed is placed on a card, the surface of which is suitable as a background. The card is mounted so that it can be tilted about 5' above and below the horizontal plane, on an axis that coincides with the north-south diameter of the viewing screen. A simple way of achieving this is to mount the card on an object having a convex lower surface. In our laboratory, a watch-glass has been used, with plasticene as the mounting medium. The convex surface should be mounted on a support having a round opening on top and a flat bottom. A roll of tape, a petri dish, a beaker, or any other piece of equipment having the proper shape to give stability to the setup will be satisfactory. The arrangement of the required equipment is shown in Fig 1. For the best results, the subject to be photographed should be mounted in the plane of the axis of rotation. To achieve this effect, the depth of the mass of plasticene between the background and the watch-glass is varied so that when the watch-glass is tilted back and forth on the axis, the subject to be photographed does not appear to move back and forth across the viewing screen. A permanent piece of equipment, embodying an adjustable vertical screw, with lock-nuts, could be made for this purpose. The subject may be illuminated in any manner desired. It was found that the presence of shadows intensifies the effect of depth. In taking the photographs, the concave surface is mounted so that one side of the background card is about 5' below the horizontal, while the axis remains in the horizontal plane. The subject is focused carefully on the ground glass and a picture is taken. The card is then tilted so that the opposite side is about 5' below the horizontal, while the axis still remains in the horizontal plane. The subject is again put in focus and another picture is taken. After both pictures are developed and printed, they are placed side by side in the same orientation and examined with a stereoscopic viewer. If depressions appear where there ought

Jan 1, 1950

By F. W. Glaser

Iron-silicon alloys have had a great influence, in many ways, in modern industry. Silicon steels have been used almost exclusively for the construction of electrical machinery, but have also become an important material for structures which benefit by the high tensile and yield strengths of this material. In elaborating on the early history of work done on iron-silicon alloys, Greiner, Marsh and Stoughton1 went back as far as 1808, and pointed to Berzelius as the first producer of ferrosilicon. During the last twenty years some very important contributions in the form of studies of the iron-silicon system, as well as of the physical properties of these alloys, have been published. In consideration of the brit-tleness and poor machinability of alloys containing more than 5-6 pct Si, commercial interests have stimulated the research done on iron-silicon alloys, but mainly in the range of 0 to 6 pct Si. Yensen2 has shown the influence of im- purities, such as carbon, sulphur and phosphorus on the magnetic properties of 2, 4, and 6 pct Si alloys. Corson3 extended his investigation of physical properties to approximately 32 pct Si, and attributed the brittleness of the high-silicon material to the particular constitutional features of the alloys. Though mentioned earlier in the literature, the effect of nitrogen on crystal growth and magnetic permeability of iron-silicon alloys has been demonstrated recently by Morrill4 and Rostoker,5 respectively. In all the above quoted investigations, except that of Rostoker,5 sand or chill casting processes were employed for the preparation of samples. A major advantage of the powder metallurgy process is that it does away with time-consuming machining in many applications. The powder metal industry is always interested in pro- ducing a finished product employing a material which has presented considerably greater difficulties in manufacture by other methods. Steinit26 described preparation and testing of various Fe-Si alloys which were produced by the powder metallurgy process for the manufacture of armatures for small electric motors or generators. While Steinitz investigated alloys up to 6 pct Si, Rostoker5 went as high as 9 pct Si. The author7 previously discussed the diffusion of iron-silicon compacts containing 6 and 10 pct silicon. It is the object of this paper to study the progress of diffusion occurring in iron-silicon alloys by electrical resistivity measurements. All samples were prepared by pressing and sintering of compacts. Iron, silicon, and Fe-Si powders of various mesh size and compositions were employed to obtain test samples. It was assumed that complete diffusion had been obtained when the electrical resistivity reached a constant value characteristic for that particular alloy. To this end, electrical resistance measurements were used to follow the progress of alloying under various conditions.

Jan 1, 1950

By C. G. Dunn

The measurement of interfacial teusions or grain boundary energies in metals is an important metallurgical problem, especially since it bears on growth and nucleation processes. Statistical methods of measuring equilibrium grain boundary angles, which relate interfacial tensions, have been used by some investigators1'2 but more direct methods would be preferred. A direct way, based on a simple extension of a successful method of growing single crystals of silicon ferrite to predetermined orientations in flat specimens,3 is to produce three-grain specimens in such a way that the equilibrium common grain boundary will be perpendicular to the surface of the specimen. The angles to be measured then appear as the grain boundary angles in the surface of the specimen. The method of producing a single crystal specimen with a predetermined orientation is basically the same as that employed by Yoshida and Fuji-wara4 in their work on aluminum wires. The specimen, prior to any single crystal transformation, must have a matrix which will support the growth of a crystal of the desired orientation. Growth may occur through exaggerated grain growth or, if the matrix is strained a critical amount. by normal recrystallization. In either case the matrix must have stability at the temperature used to effect the transformation, this stability appearing as a long induction period for exaggerated grain growth or for the formation of recrystallization nuclei. Additional control is gained by using a high temperature gradient through which the specimen is moved at a suitable rate. To obtain the desired orientation, the specimen is fed a short way into the furnace producing one or more crystals in the hot end. After the specimen is removed from the furnace, the orientation of a crystal is determined, so that this crystal may be reoriented by properly deforming a narrow piece of the matrix between the end crystal and the rest of the specimen. This part of the specimen in the case of silicon ferrite is preferably held at red heat during the reorienting process. Fig 1 shows a specimen which is ready to be transformed into a single crystal through growth of a reoriented "seed" crystal. When the method just described is applied to the production of a three-grain specimen two crystals are grown first side by side in one end, the specimen is then reversed and the third grain grown from the opposite end. A suitable group of grains each of different orientation is one where all three grains have the same crystallo-graphic plane in the plane of the specimen. Fig 2 shows a photograph of a three-grain group prepared as described. The notches are introduced in the open ends of the grain boundaries to anchor them during the final annealing operations which ultimately should bring the grain boundaries to the lowest energy configuration. Two-grain groups with different crystallographic planes in the plane of the specimen can be similarly prepared and treated. If the two grains have different surface (gas to metal) energies per unit area, the equilibrium condition leads to a curved grain boundary.* * This feature of the problem was pointed out by J. c. Fisher. References 1. Cyril Stanley Smith: Grains. Phases and Interfaces: An Interpretation of Microstructure. Trans. AIME 175, 15. Met. Tech. TP 2387, June 1948. 2. D. Harker and E. Parker: Grain Shape and Grain Growth. Trans. A.S.M. (194,5) 34, 156-195. 3. C. G. Dunn, A. Seddon, and R. Wylie: Unpublished Work, 1946-1947. 4. Takeo Fujiwara: A Method of Producing A Long Single-Crystal Wire of Aluminum with any Desired Crystallographic Axis. Jnl. of Sci. Horoshima Univ. A, (1939) 9, No. 3, 227.

Jan 1, 1950

By C. G. Dunn, F. Lionetti

The energy associated with grain boundaries in polycrystalline aggregates is believed to play a major role in grain growth processes and, when growth ceases, to determine the final equilibrium grain boundary angles. Further, the energy of grain boundaries of recrystallization nuclei is a factor in nucleation processes. It is important to know, therefore, how the energy per unit area of a grain boundary, that is, the grain boundary surface tension y, depends on the difference in orientation of the two lattices of the grains producing the boundary. Although the problem is important, surprisingly little has been done toward a quantitative evaluation of the effect of orientation difference on grain boundary energies. C. S. Smith1 recently has discussed this problem and in addition to showing effects of orientation difference on equilibrium angles has shown a variety of interesting effects of surface tension on the appearance of microstructures. Fig 1 and the following relations expressed in Eq 1, which connect equilibrium grain boundary angles and surface tensions, illustrate equilibrium conditions which are believed to hold true in metals. ?l2 _ ?23 _ ?l3 [1] sin ?3 sin ?1 sin ?2 Clearly any two of these surface tensions can be expressed in terms of the third when the equilibrium angles ?1, ?2, and ?3 are known. Applied to the present problem for solid state equilibrium of three grains, the angles ?1,?2 and ?3 must be measured in a plane perpendicular to the line of junction of the three grains. Normally a direct determination of these angles from random microsections is impossible. Consequently Harker and Parker2 and Smith1 (except for some measurements on flat specimens) resorted to a statistical method to determine equilibrium grain boundary angles. Smith reported that grain boundaries meet the surface of a piece of metal nearly perpendicularly. He reported also, in connection with direct angle measurements on flat specimens with grains extending through the thickness, that angles varied appreciably from 120" and concluded that there was a measurable effect of orientation difference on surface tension. Another direct way of determining equilibrium angles and a method adaptable to studying particular configurations, recently suggested by Dunn,³ is to use a three-grain flat specimen with orientations of grains so chosen that the junction line of the three grains will be straight throughout the thickness and perpendicular to the surface of the specimen. Choice of orientations is possible when individual grains of each group can be grown to predetermined orientations through the reorienting and growth of " seed crystals " as described.³ Not only is it possible, for example, to have grains with the same crystallographic plane in the plane of the specimen, but a given orientation difference between two grains can be made a common factor to an unlimited number of three-grain groups while a series of orientation differences is investigated. Any effect of anisotropy of gas-solid surface tension due to grain orientation should be minimized by having all gains oriented the same with regard to crystallographic plane in the plane of the specimen. Another feature of the three-grain group is the notched grain boundaries as shown in Fig 2 for one specimen (S4). The notches serve to anchor the end positions of the grain boundaries (especially at high temperatures) while the central and junction point of the grains moves toward an equilibrium position. Final equilibrium should produce straight grain boundaries if the notches are very narrow and if changes in orientation* of the grain boundary do not alter the surface tension.† If one assumes the straight line condition and no change of surface tension with small changes in grain boundary orientation and finds the equilibrium configuration by a minimization of the grain boundary energy, one obtains the relations given in Eq 1. The approach to straight line boundaries or to minimum energy configurations in specimens containing large grains, such as those used in the present investigation, may be very slow compared with the approach to equilibrium conditions for the grain boundary angles. It may be desirable, as proved to be the case in the present investiga-

Jan 1, 1950

By A. L. Bailey, B. A. Landry

All who are even generally aware of the tremendous rate of increase in coal washing operations must realize the growing importance of the float-and-sink test. I believe it is conservative to estimate that, in the past decade, the dollar volume of float-and-sink testing has increased tenfold. It is a simple matter of economy, then, to examine the factors that determine the cost of adequate float-and-sink testing. When the Coal Preparation Section of the Bureau of Mines entered upon a greatly expanded program of such work in connection with the synthetic liquid fuels investigations, it seemed advisable to examine these factors experimentally. The principal consideration that differentiates float-and-sink test sampling from general purpose sampling, is that the original particle size must be preserved. Therefore, the total cost of the test will be directly affected by any standard that might be proposed to limit sample bulk reduction at any given particle size. For this reason, the relationship of sample size to variability of results was the first factor to be studied experimentally. Of course, the matter is rendered complex by the circumstance that the float-and-sink test, not a simple analytical measurement but a process test, comprehends a number of more-or-less independent items of fundamental data; and as shown in the report, the' variability of the samples differs with respect to these different items. This condition and the wide variety of situations in which float-and-sink test data are used, in combination with other factors, to study complex process operations, indicate the difficulty of setting up fixed standards for float-and-sink sampling and testing. At this stage at least, it is the intent rather to obtain experimental data on the principal Factors involved so that the reader may arrive more intelligently at a procedure adapted to his problem. The authors of this paper have presented experimental data showing the relationship between size of sample and particle size for different variability tolerances with respect to percentage of sink. In further studies, data are being collected to appraise also the variability of the samples with respect to float-ash content and size consist. The scope of this work will be broadened to cover particle sizes up to 4 in., and a third series of tests has yielded similar data for a much cleaner type of raw coal. Thus, the further studies will make available a fairly comprehensive meas- ure of variability with respect to size consist, percentage of sink, percentage of middlings, and percentage of ash in the float, for three coals ranging from 3.87 to 17.68 pct in refuse content (heavy sink material) and from 4.18 to 17.52 pct in middlings. Introduction At present there are no published standards for float-and-sink test sampling. During the rapid expansion of float-and-sink test work, varying procedures have been based on adaptations of the ASTM standards for sampling coal for analyses. For this reason, a special study of gross sample reduction has been undertaken to determine the limits for this step in the operation where no reduction in particle size is to be made before testing. Float-and-sink tests are made whenever a thorough study of coal characteristics is desired. The tests may be made on samples from coal-cleaning units such as jigs or tables, or coal samples may be tested which are taken from a loading boom, railroad car, or the coal seam itself. The resultant gross sample may be large and pose a problem of sample reduction. The question is, then, how much can the sample be reduced and still fall within preassigned limits of accuracy of the original gross sample of coal? Coal from channel samples may be crushed to liberate impurities and then separated into various gravity fractions from which washability curves are drawn; from these curves, it is possible to determine the cleaning characteristics of the coal. However, coal samples from coal-cleaning units cannot be

Jan 1, 1950