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By Sidney H. Haughton

FOLLOWING the discovery of diamonds in 1870 and the Witwatersrand gold fields in 1886 South Africa changed from a predominantly pastoral country with a scattered white population into a land whose economy came rapidly to be based primarily on mining. The total value of the mineral output of the Union in 1944 was approximately $493,000,000, to which gold contributed 84 per cent. Gold furnished some 33 per cent of the Union Government's total revenue in that year, and approximately half the country's population obtained its livelihood directly or indirectly from the gold mining industry. In any review of the Union's mining activities and in any consideration of the country's future, gold mining must occupy a prominent place. It is generally conceded that the present structure is not properly balanced and that an economy based on a preponderance of a single nonpermanent factor possesses potentialities of serious instability.

Jan 1, 1946

By A. P., Svenningsen

ECONOMICAL handling of a minimum of 25,000 tons of minus 3/4-in. ore per day, grinding it to 2 per cent on 65 mesh, and effecting a high recovery of the copper at the lowest possible cost were the principal aims in the design of the new Morenci concentrating plant. Dealing with a tonnage of this magnitude, it is obvious that lost motion cannot be tolerated. When ore is carried on a conveyor an unnecessarily long distance or elevated to a greater height than necessary, or when pulp flows in a launder by a circuitous route thereby losing elevation and distance, we have lost motion which is always costly both from the standpoint of construction and operation. In addition to the 25,000 tons of ore which must be handled, 100,000 tons of water per day has to be carried through the plant in the treatment of the ore. Though water is not so difficult to handle as the ore, the combined tonnage represents a figure which could easily run into a considerable monetary loss per day if all phases of the design were not carefully followed with the idea of eliminating any unnessary handing of materials.

Jan 1, 1942

By Nathaniel Hen

IN the United States, in the 2 1/2 years since the rescinding of the wartime order closing gold mines, conditions have not yet returned to normal. Shortages of man power have prevented some mines from operating at all, and most of those in operation are still at reduced capacity. This fact, combined with shortages of materials, the high cost of supplies and labor, high tax rates, and a fixed price for the product have made the past years rather rough ones for gold producers. In foreign countries conditions are rather similar. In Canada several new mines are coming into production and some others are enlarging. Costs have not increased as much as in the United States and gold production is being encouraged. Recently a bonus of 20 per cent on increased production has been proposed. In South Africa, where gold mining is of major importance in the national economy the industry is also in a favored position with government; new discoveries of major importance there will markedly increase the gold output. Demand for labor is rap-

Jan 1, 1948

By AIME AIME

DURING my senior year at college a professor said to his class that a student who failed to obtain a passing grade in that certain subject could not graduate with his class and that his diploma would be withheld until the failure had been removed. In that way for four years a diploma had been made to appear to us as the objective in attending college. We grew up to think that a diploma was the means of providing employment; consequently, a diploma could not be jeopardized and, heeding the professor's remarks, we resolved to put forth special efforts and make good. During one of our class periods this same professor digressed briefly from his prepared lecture in metallurgy and advised the boys to join a national technical society. He spoke with earnestness and sincerity. After class we students discussed those remarks. We concluded that the professor had not convinced us. We were already members of technical societies at school and saw no need of joining another. In fact, even up to that moment a society had never indicated to any of us that joining it had any relation to landing a job, and we were fully aware that joining another society meant paying out more money, for fees and dues, which money we then needed to buy food, clothes, and perhaps a new slide rule. Furthermore, we knew that joining a society was not part of the curriculum and, therefore, the diploma could not be withheld if we did not follow the advice. Our conclusion was that we would not join but would concentrate on our work that assured getting our diplomas.

Jan 1, 1936

By J. W. Sandelin, L. S. Birks

The group five metals, vanadium, niobium, and tantalum all show cold-rolled textures of {100)(011) and {112)(0ll) with a preference for the (100) in vanadium and niobium and for the {112) in tantalum. Recrys-tallization texture of (100) and (111) was reported1 for vanadium after annealing (no temperature stated). For tantal~m ,~ annealing below 1200°C strengthened the (112) texture but the (111) texture increased and was predominant as the annealing temperature was raised to 2500°C. Annealing niobium up to 1100°C strengthened the ( 100) texture and developed a weak (111) texture.' In the present work niobium has been annealed up to 2000°C. Nearly 70 pct of the grains showed {111) texture with only a weak (112) component and an insignificant (100) component remaining. In addition, double-crystal rocking curves were used to follow the increase in crystal perfection of the grains with increased annealing time. Material and Treatment. Samples i by 4 in. were sawed from & -in.-thick cold-rolled niobium sheet obtained from Wah Chang. Chemical analysis of the material showed it to be 99.4 pct pure with tantalum as the major impurity. Individual pieces were annealed for 2, 15, 30, and 60 rnin in a vacuum of 10'* Torr using an rf generator. They were etched until the grain boundaries were well-defined, Fig. 1. Average grain size varied from 1 mm for 2 min annealing to 2 mm for 60 rnin annealing. Experimental Results. Preferred Orientation. The orientations of 97 of the 117 grains in the specimens of Fig. 1 were determined by back-reflect ion Laue patterns. A General Electric 10-cm-diam cylindrical camera was used rather than the conventional flat camera in order to record more of the low-index spots. The method proposed by Forest, Barton, and schieltz4 was used to transform the cylindrical film patterns to standard stereographic projections. Table I gives the compilation of data. Even 2 rnin anneal at 2000°C is sufficient to yield a strong (111) preferred orientation, and the percentage of grains with this orientation increases steadily with annealing time at the expense of all other orientations. Crystal Perfection. X-ray topographs were taken of each specimen in both the (111) and (112) orientation using the method described by Birks and Grant.' As the anneal time increases, the grains become larger and the individual reflections become slightly more uniform in intensity, indicating an increase in crystal perfection. For a more quantitative measure of crystal perfection, it was necessary to measure the double-crystal rocking curve. The spectrometer employed was a Gaertner instrument of Compton design. LiF was chosen for the first crystal because the (400) reflection with d spacing of 1.05 AU is a good match to the (222) niobium reflection with d spacing of 0.95 AU. CuKp radiation was used in order to further reduce the d spacing mixmatch correction.' A variable aperture was placed between the LiF and the niobium specimen so that a single grain or even a small portion of a grain could be examined. Fig. 2 shows typical rocking curves for the four annealing times. For the 2-min specimen, a single peak is observed with 10' of arc full-breadth at half maximum. As the annealing time is increased to 15 or 30 min, several sharper peaks of 40 to 80" breadth can be seen within a single grain. After 60 rnin anneal only a single peak of about 30" is observed. Table I1 shows the corrected rocking curve breadths and the dislocation densities, ND. The latter were calculated from the equation7 where W is the corrected rocking curve breadth at half maximum in radians and b is the effective Burger's vector. For (110)(111) slip in niobium, b is 2.86 AU. Discussion. The annealing of cold-rolled niobium at 2000°C causes rapid preferential growth of grains with {ill} orientation. After only 2 rnin annealing time, 35 pct of the grains have the (111) orientation, and after

Jan 1, 1968

By H. L. Gilbert, W. W. Stephens

Production of anhydrous zirconium tetrachloride by direct chlor- ination of a zirconium oxide carbon mixture in a silica-brick-lined chlorinator is described. Theory and thermodynamics of reactions are discussed. A pilot-model chlorinator and full-scale production equipment are described and operating data are included. ANHYDROUS zirconium tetrachloride required as a starting material in the Kroll process for production of ductile zirconium has been produced in this country principally by chlorination of the carbide or "carbonitride" made by reduction of zircon sand concentrates with carbon in the arc furnace. This process and the equipment used have been fully described.'.' It is well known that zircon or badde-leyite ores may be chlorinated directly with chlorine in the presence of carbon, and this one-step approach would seem at first glance to be preferable to the two steps involved in the carbide-chloride operation. As previously discussed1 considerations leading to adoption of the longer process were: 1—Chlorination of the carbide proceeds rapidly at temperatures below 500°C, whereas temperatures above 900°C were considered necessary for chlorination of zircon-carbon mixtures. 2—The highly exothermic nature of the carbide-chlorine reaction makes it self-sustaining, while heat must be supplied continuously in direct chlorination of the ore. 3—Silicon was thought to be chlorinated along with zirconium in the direct chlorination of zircon, leading to high chlorine consumption. In production of carbide in the arc furnace, silicon is driven off as silicon monoxide and does not enter the chlorinator. 4—For efficient direct chlorination, the ore must be finely ground and intimately mixed with carbon, and the mixture briquetted. 5—Direct chlorination requires a much larger chlorinator for a given production capacity than chlorination of carbide. Recently it has become necessary to produce large quantities of zirconium metal from a chemically purified zirconium oxide. Since the cost of the latter is high, the relatively high losses encountered in production of carbide in the arc furnace could not be tolerated, and a graphite resistor furnace5 was developed for production of carbide, which was then chlorinated in equipment previously used for chlorinating arc-furnace carbide. This method of operation was quite satisfactory, and losses in the carbid-ing step were minimized. However, operating costs were relatively high, and the process did not lend itself particularly well to large-scale operation because of the multiplicity of small units required and the hand labor needed to load, unload, and maintain the furnaces. To chlorinate the carbide, a vertical-shaft chlorinator was used in which the charge was heated with a central split graphite-rod resistor.' Operation of this chlorinator was somewhat less satisfactory with the resistor furnace carbide than it had been with the arc-furnace carbide due, principally, to the differences in physical properties of the carbide. The arc-furnace carbide is obtained as a fused metallic-appearing mass which can be crushed to -1/4 in. with production of a minimum of fines, whereas the resistor-furnace product is lightly sintered and produces a large proportion of fines in crushing and handling. These fines tend to pack in the chlorinator and promote channeling. which results in poor chlorine efficiency and low capacity. Data based on production of 22,000 lb of chloride from resistor-furnace carbide in this equipment are shown in Table I. Necessity for increasing production of chloride from about 2,000 to 15,000 lb per week led to further investigation of possible methods for direct chlorination of the oxide or oxide-carbon mixtures. Direct chlorination of the pure oxide presents much less difficulty than chlorination of zircon sand or oxide ores. The oxide is easily ground to —200 mesh, and no silica is present to cause excessive consumption of chlorine or contamination of the product. Theoretical Considerations The principal chemical reactions involved in chlorination of mixtures of zirconium oxide and carbon may be written as follows: ½ ZrO2 (c) + C(c) + Cl2(g) = ½ ZrCl,(g) + CO(g) [I] 1/2 ZrO, (c) + CO(g) + Cl2(g) = ½ ZrCl,(g) + CO2(g) 121 ½ ZrO2 (c) + ½ C(C) + Cl2(g) = 1/2 ZrCl4(g) + ½ CO2(g) [3]

Jan 1, 1953

By J. R. Hauber, N. R. Borch

A study uras made on the creep behavior of cast and extruded SR grade beryllium. It is shown that, for stresses below about 1000 psi in the temperature range 760" to 85o° c, the creep behatior is nearly exactly described by the Nabarro-Herring mechanism. The activation energy is apparently that for self-diffusion, 42 2 kcal per mole, below 1000 psi, but it rises to 88.6' kcal per mole at higher stresses. The slress exponent is 4.5 at the higher stresses. Tertiary creep in this material is clearly related to void formation apparently caused by grain boundary sliding. BERYLLIUM is becoming an increasingly important technological material. A search of the literature has revealed a lack of fundamental studies on the creep of beryllium. This investigation was therefore undertaken to gain insight into the creep behavior of this material. EXPERIMENTAL PROCEDURE Tensile creep samples were prepared from cast and extruded SR grade beryllium. The vendor's chemical analysis of the beryllium tested is shown in Table I. The test specimens were machined as shown in Fig. 1 from i -in.-diam rods. The machined creep specimens were annealed to remove surface damage and to establish a variation in grain size. The heat treatments and their resulting grain diameters are shown in Table 11. The average grain diameters were determined by the intercept method. True average grain diameters were estimated by multiplying the measured average grain diameters by 1.5.' The creep tests were performed at temperatures from 700" to 850°C in a vacuum of 105 Torr or better in a tantalum-element resistance furnace. Loads were applied by an Instron testing machine such that the stress was held constant to within 20 psi. The test temperature was measured by thermocouples on the sample. With one exception the deviation from the desired test temperature was 2"C, and in that case the deviation was 4"C. Elongations were measured by an extensometer within the vacuum chamber which was fastened to the creep specimens at the grooves in the grip ends, as shown in Fig. 1. The precision of measurement of elongation was 1 X loe4 in. The creep tests were begun only after thermal equilibrium had been established in the sample and the extensometer to insure that there was no strain rate component due to transient thermal effects. Two kinds of creep experiments were performed. First, at constant grain size, the effects of varying stress and temperature were studied. In the second set of experiments, the temperature was held constant and the grain size was varied. The activation energy for creep was determined by varying the temperature at constant stress, as described by orn, during the first set of experiments. The variable grain size experiments revealed that creep at low stress apparently occurred by the abarro-errin' mechanism. In all of the creep tests, the stress was held constant only until sufficient strain had occurred to accurately determine the creep rate. The stress was then raised to a new value and the new creep rate determined. This process was reported until tertiary creep occurred. In this manner several data points were obtained from each specimen. The assumption was made that the structure was not changing appreciably between the incremental stress levels. This was verified by reducing stresses to previously tested levels and comparing the creep rates with the creep rates obtained at the lower strains. The re-producibility was within experimental error over strains on the order of 1 pct. EXPERIMENTAL RESULTS A typical series of creep tests is shown in Fig. 2. Primary creep was not observed in any test. Transient creep, which we define as creep rates that are nonlinear with time, was not observed for any change in stress except where tertiary creep occurred. The absence of both primary and transient creep has been previously reported for hot-pressed powder beryllium.= The data for the creep behavior at constant grain size are summarized in Fig. 3. The data show two distinctly different stress dependencies. At stresses below about 1000 psi, in the equation:

Jan 1, 1969

By G. Britsianes, T. L. Joseph

THE reduction of a lump of iron ore is a complicated sequence of up to three reactions proceeding simultaneously in a gas-solid system. As the ore moves down the blast furnace into zones of higher temperature and higher reducing power, it is successively reduced through the three oxides of iron into metallic iron. The reduction process involves much more than chemical problems. Physical factors add to the complexity of the overall process. Under optimum conditions, reduction of the ore is completed at a level about one-half way down the blast furnace stock column. At this point, the ore undergoing reduction has attained a temperature of about 1000°C and has been in the furnace for about 6 hr. On the practical side, the behavior of the ore during smelting has been of great interest to operators. Unsatisfactory blast furnace operation on burdens containing magnetite ore or badly slagged sinter has often been attributed to poor re-ducibility. The question of reducibility has also been raised in formulating quality standards for agglomerates such as nodules, briquettes, and pellets. In the present investigation, the solid phases formed during reduction were studied as a step toward a better understanding of the overall process. Equilibrium Studies The iron-oxygen equilibrium diagram shown in Fig. 1 reveal; a number of facts pertinent to the gaseous reduction of iron ores. This diagram is from the work of Darken and Gurryl, 2 and represents a correlation of the best available data. Four solid phases may exist during the complete reduction of hematite to metallic iron. These are hematite (Fe2O3), magnetite (Fe3O4), wustite (FeO), and iron (Fe). The wustite phase is a solid solution which is not stable below 570°C. At this temperature the solid solution undergoes a eutectoid-type of decomposition into the phases, magnetite and iron. Thus above 570°C, the diagram dictates that a hematitic ore should pass through a four-phase sequence on reduction to metallic iron. Below 570°C, only hematite, magnetite, and iron should appear. Information on the iron-oxygen system has been derived largely from CO and H2 reduction equilibria. The Fe-C-0 relationships have been studied extensively by R. Schenck and his coworkers and well summarized by H. Schenck.3 More recent studies have been made by Darken and Gurry.1, 2 Data from these sources have been combined and plotted in Fig. 2. With respect to the Fe-H-O system, the works of Emmett and Schultz4 seem the most reliable, and these data have also been included in Fig. 2. Certain physical properties of the solid phases of the iron-oxygen system are summarized in Table I. The crystallographic information is of special interest as much of the present work has been concerned with the X-ray analysis of the products of reduction. Reduction with Hydrogen The reduction of ore with hydrogen is the net result of two or more gas-solid reactions. Above 570°C, the reaction sequence may be represented by stoichiometric stages as follows: 3Fe203+ H2e2Fe,O, + H20 [1] 2Fe3O, + 2H2 6FeOw + 2H2O [2] 6FeOw + 6H3 ^ 6Fe + 6H=O [3] Fe2O3 + 3H2 ^ 2Fe + 3H,O. [4] These reduction reactions follow the general form: A (solid) + B (gas) e C (solid) + D (gas). This type of gas-solid reaction has been investigated by Langmuirl' who has shown that such reactions can occur only at the boundary between the two solid phases. Furthermore, a nucleus of the second phase must initiate the reaction. Once such an interface exists, the reaction proceeds through a layer of the solid reaction product (C). The specific mechanisms involved will depend a great deal on the properties and condition of this particular layer. A number of heterogeneous reactions such as the dehydration of single crystals of copper penta-hydrate and the calcination of limestone follow this type of process. It should be noted that the inter-facial type of reaction also occurs even in dense polycrystalline material which simulates a mono-crystalline behavior.

Jan 1, 1954

By L. W. Casteel, E. A. Jones

MINING the lead deposits of Southeast east Missouri has reached a high stage of technical development dictated by the scattered occurrences of low-grade ore through favorable horizons in the Bonne Terre formation. The rock-breaking, handling, and related practices described here have evolved as the best way of mining these particular deposits. These methods are applied in the production of about 19,000 tons of lead ore per operating day from four mines in Southeast Missouri. Development drilling Drifts 10 ft wide and either 8 or 9 ft high are driven in this district on contract. Miners are guaranteed standard wages plus a bonus on the footage advanced, if earned. Labor, fuse, caps, wire, and dynamite used are charged against the contract. Normally the cycle of operations in drifting is performed by a two-man crew, a motor operator and a shovel operator who first load out the rock broken by the preceding shift. The drift crew then sets up two vertical column and mounts the drills. Cleveland HC-10's are used which have a steel lug integral with the cylinder for connection with the air feed. All drilling in drifts is wet. Air pressure is 85 to 100 lb at the face. From 28 to 32 holes are drilled per swing in a pyramid cut. Cut holes

Jan 1, 1947

By B. E. Field

Cobalt is a silvery white metal with a slight bluish cast. It strongly resembles nickel in its appearance and properties, notably its resistance to corrosion, although its alloys with other metals differ decidedly in their properties from those of nickel. The name "cobalt" was derived from the German Kobold, meaning goblin, and this came to be applied to the cobalt minerals which, although they resembled ores, did not readily yield metal when smelted by the primitive processes available in the Middle Ages. Cobalt minerals were used as pigments by potters and glass workers before the Christian era. Cobalt blue glass was found in the tombs of the Egyptians and in the ruins of Troy, and many colors used by the ancient Greeks and Romans contained cobalt. The ancients were entirely unaware that the colors they used were caused by cobalt and the metal itself was not isolated until about the middle of the eighteenth century, by Brandt, although the preparation of cobalt compounds had been carried on in a small way ever since the opening of the silver-cobalt deposits at Schneeberg, Germany, in 1470.

Jan 1, 1935

By Tilden Cummings

The extractive mineral industries share a number of common characteristics and basic problems which are completely different from those associated with manufacturing and mercantile operations. These industries now supply about 95% of the inanimate energy consumed in this country, and share with agriculture in providing virtually all of our basic raw materials. Mineral producers, like farmers, are subject to the economic hazards of fluctuating markets and prices. Unlike farmers, however, they cannot renew the productivity of the earth, but must seek continually for new sources of supply. The necessity for exploration and development of new reserves, to replace those used up by production, introduces additional factors of economic risk. These operations require the expenditure of large amounts of capital, often well in advance of any assurance of profitability. Commercial banks that understand these special problems can provide a variety of constructive financial services to the mineral industries. The history of cooperation between banks and mining enterprises has yet to be written, but there is every indication that it would encompass a period of hundreds of years. Records refer to depository and lending services by the early European private bankers involving precious metals and jewels. Many of the exploratory voyages to the Far East and the New World were organized with the financial backing of wealthy syndicates, some of which also provided banking services, in the hope of finding new sources of gold and other precious minerals. In the United States many large banks are closely identified with the development of some of the larger mineral deposits such as the Mesabi Range and the gold fields of California.

Jan 5, 1965

By M. E. Glicksman, G. S. Ansel

It has been shown by Walton and Chalmers,&apos; that the mechanism of the development of solidification textures in castings involves the preferential growth of dendrites along certain crystallographic directions as determined by the influence of prevailing heat-transfer conditions. Specifically, this growth is parallel to the direction of heat flow. The purpose of the present investigation was to determine the applicability of this mechanism to: 1) commercially pure aluminum (99.75 pct) solidified to coarse columnar crystals, 2) an aluminum-silicon casting alloy (5.25 Si, 0.38 Fe, 0.02 Cu, 0.10 Ti, 0.002 S) cast to a fine-grained structure under complex and reproducible heat transfer conditions. PROCEDURE AND RESULTS 1) Specimen Preparation—Using a technique similar to that employed by Northcott and Thomas,2 samples were melted in the directional solidification mold, Fig. 1, by heating the entire assembly to 670° C. The mold was then end cooled using a water jet. From considerations of harmonic analysis, the likely distribution of isotherm normals encountered by the growing crystals is shown in Fig. 1. 2) Orientation Analysis—The pure aluminum sample froze to large columnar crystals, nucleated close to the metal diaphragm, with the growth direction parallel to the mold axis. Using the back-reflection Laue technique, the growth direction of these crystals was determined to be a <100>, which coincided within 53 deg to the mold axis. Metallographic examination of the relatively fine-grained aluminum-silicon sample revealed a dendritic mode of growth having its primary dendrite arms along isotherm normals. Back-reflection Debye-Scherrer patterns, taken with the specimen rotating about its cylinder axis, yielded rings displaying symmetrical arcing, thus proving that the sample did, indeed, possess the solidification texture inferred from the preliminary metallographic examination. To determine the extent and orientation of the texture in the aluminum-silicon alloy, a density distribution of the (111) poles of the sample was plotted using the transmission Debge-Scherrer

Jan 1, 1960

By William G., Pariseau

There are important phenomena in rock and soil mechanics that cannot be explained in terms of theories of homogeneous, isotropic materials. Subsidence of strata about mine openings is an example. In-situ stress measurements in nonisotropic sedimentary, and metamorphic rocks is another. Patterns of joints, faults, fractures, and similar geologic features impart directional mechanical properties to rock masses that are locally isotropic or anisotropic. On the geologic scale, the non-homogeneity of composite rock masses may, in certain instances, be dealt with as homogeneous anisotropy. The mechanics of large rock masses can, therefore, be expected to involve considerations of anisotropy. The source of the anisotropy is not relevant. Once the scale of observation is selected and the material is defined accordingly, the analysis of stress and deformation proceeds without regard to the numerical values of the material constants. There are also important phenomena in rock and soil mechanics that cannot be explained in terms of linear elasticity, theory. For the mechanical description of anisotropic geologic materials capable of de- forming beyond the limit of purely elastic strains, a plasticity theory is required.

Jan 1, 1972

By A. D. Schwope, L. R. Jackson, K. F. Smith

Burghoff and Blank1 have pointed out that the creep properties of hard-drawn coppers are closely associated with their individual softening characteristics and have further shown that the creep resistance of various types of copper is improved, under certain circumstances, by cold stretching. In the design of certain types of electrical machinery, it is important to have the creep resistance as high as possible; furthermore, short-time creep strength is important since in many cases stresses are large only during warming-up and cooling-down periods. In this paper, data are presented showing the effect of cold work on the short time creep strengths of various types of commercial copper under several conditions. It is shown that trends from short-time creep tests are evident at longer times. Materials Used in the Investigation The coppers used in this investigation were commercial grade and of two basic types, oxygen free high conductivity (OFHC) and tough pitch. Additions of silver in amounts of 15 and 25 oz per ton were added to each of the two coppers. The analyses of these six coppers are given in Table 1. Originally, they started as wire bars 4 X 4 X 54 in. A. square rod was made by hot rolling the wire bars to 9/16-in. rod in 8 passes. This rod was then cold drawn to 0.445-in.-diam rod and annealed for 3 1/2 hr at 1000°F. It was then cold drawn to 0.325-in. rod and again annealed at 1000°F for 3 1/2 hr. Hard square rods were then made by cold rolling to 0.257 X 0.257-in. rod. Soft wire was made from the hard- drawn material by annealing at 650°F for 3 hr. The final rolling was performed using a set of 9-in. grooved rolls revolving at 30 rpm, which produced square wires. Reductions of approximately 5, 20, 30, and 40 pct were obtained using several passes in the same direction for the large reductions. The 5 pct reduction by drawing was accomplished using a steel die having 2 parallel bearing surfaces. The die angle was 7 1/2 degrees and the wires were lubricated with a paste of ceresin wax dissolved in carbon tetrachloride. The speed of drawing was 13 fpm. Since work was done on only two sides of the wire simultaneously, it was necessary to rotate it 90 degrees each pass to insure uniform deformation. The room-temperature tensile properties of the various tempers are given in Table 2. The grain size of the an- nealed 0.257-in. wires was uniform and averaged about 0.035-0.045 mm. Experimental Procedures for Short-time Creep Tests Standard creep-test frames (Fig 1) were used for the testing. Special fixtures were designed to apply axial compressive and tensile loads to the copper wires. The compression specimens were 1 in. long and the ends were ground flat and parallel. The creep in compression was indicated by the movement of reference marks s-ratched on intersliding platinum strips attached to the moving heads of the fixture. The movement was measured with an optical micrometer fitted with a filar eyepiece on which the smallest division was 0.00005 in. The tensile creep specirriens were 4 in. long which provided ample gripping surface for the jaw-type grips. The platinum strips were attached to a one-inch gauge length of the wire and the creep measured as previously described. The single-specimen furnaces were connected to individual power and control sources. The controlling equipment consisted of Foxboro controllers

Jan 1, 1950

By J. W. Rutter, K. T. Aust

THE object of the experiments to be described in this report was to determine, first, which grains, out of a large number introduced into a sample in which their growth could proceed, were able to grow most successfully; and, second, the factors which control their growth selection. In an earlier study of grain boundary migration in high-purity lead,&apos; it was found that, under some conditions, the most successful grain in an experiment of this type bears a special orientation relationship to the grain into which it is growing. The present work represents an extension of the previous study, directed at the determination of the orientation relationships which appear under a wider variety of conditions. Experiments of this general type have been done using commercial aluminum2 with somewhat conflicting results. In the present experiments, in contrast to the above,&apos; the sample composition was a principal controlled variable, resulting in a considerable clarification of the phenomena observed. EXPERIMENTAL TECHNIQUE The experimental technique used in this investigation was essentially that employed previously in studies of grain boundary migration kinetics.1&apos;3 The material used was zone-refined lead with various small amounts of tin or silver added to study the effect of varying the sample composition. The specimens were in the form of single crystals, about 1/4 in. 1/4 in cross section by 3 to 4 in. in length, grown from the melt in a horizontal graphite boat. A crystal grown in this way generally contained a lineage or "striation" substructure of the type shown in Fig. 1 of Ref. 1. This substructure consists of an array of low-angle boundaries which partition the crystal into regions misoriented from each other by a few degrees. The substructure constitutes a source of driving energy, estimated to be about 4000 ergs per cc, for the migration of a large-angle grain boundary into the striated crystal. New grains were introduced by plastic deformation in compression of a localized reglon at one end of the sample. Re-crystallization occurs at room temperature in the deformed region, introducing a large number of new, striation-free grains into the specimen. These grains are able to grow into the melt-grown crystal on annealing at a suitable temperature. The stria-tions are removed by passage of the grain boundary, as the substructure energy is utilized to produce the boundary migration. Usually, only one or two of the recrystallized grains persist after growth has occurred for about 1 cm out of the deformed region. Laue back-reflection X-ray photographs were obtained to determine the orientation relationship between the melt-grown crystal and the recrystallized grain or grains which grew most successfully in each specimen. EXPERIMENTAL OBSERVATIONS Fig. 1 shows the results obtained for a series of specimens to which had been added tin in the range from 0 to 5 ppm by weight. In this figure is plotted, in the standard stereographic triangle, the single axis about which the most successful recrystallized grain or grains are related to the starting, melt-grown crystal by the smallest rotation. The range of angular rotations observed about such axes is indicated beside each stereographic triangle. The results shown in the stereographic triangle on the left, Fig. l(a), were obtained by localized deformation at one end of each specimen at room temperature, followed by annealing in a furnace which had been preheated to 300°C. The furnace atmosphere was argon. It will be seen that the orientation relationships observed between the melt-grown and recrystallized grains are quite random. On the right, Fig. l(b), are shown results for samples in which the de-

Jan 1, 1961

By Rex B. McLellan, W. A. Oates, William W. Dunn

Vapor transport experiments have been carried out in order to determine the saturation solubility of carbon in cobalt and nickel with respect to graphite over a large temperature range. Some of the uncertainty existing in the thermodynamics of these systems has been removed and accurate estimates of the heat and entropy of solution of carbon in nickel and cobalt have been deduced. The relatitle partial entropies of carbon are considered to be predominantly vibrational in origin. ALTHOUGH the thermodynamic properties of solid solutions of carbon in cobalt and in nickel have been investigated previously, the results of these investigations show a marked lack of agreement amongst themselves. In this investigation simple vapor transport experiments have been undertaken in order to measure the temperature variation of the saturation solubility of carbon in nickel and cobalt with the object of removing to some degree the uncertainties in the thermodynamics of these systems. In the case of the C-Co system, early measurements of the saturation solubility of graphite in Co show results at the same temperature differing by almost an order of magnitude.1-5 Recently Schenck, Frohberg, and Jaspert6 measured the equilibrium between CH4-H2 mixtures and C-Co solid solutions at five temperatures ranging from 850° to 1050°C. Their values of the activity of carbon in the solid solution, deduced from a knowledge of the chemical potential of carbon atoms in the gas, varies linearly with composition at each temperature and the authors concluded that the solutions were Henryan. The saturation solubilities deduced from Schenck, Frohberg, and Jaspert&apos;s measurements are in good agreement with the solubility determined at 1000°C by Rao and Nicholson7 and the value at 1000°C deduced from the measurements of smith8 on the equilibrium between CO/CO2 mixtures and C-Co solutions. The object of this investigation was to check the results of Schenck, Frohberg, and Jaspert and also to extend the range of solubility data to higher temperatures. In the case of the C-Ni system, there is fairly good agreement between the values given by schaefer9 for the saturation solubility of carbon C, in nickel, the value given at 1000°C by Rao and Nicholson,7 and that deduced from Smith&apos;s8 measurements of the equilibrium between C-Ni solutions and CO/CO2 mixtures at 1000°C. The values of C, deduced from Schenck, Frohberg, and Jaspert&apos;s6 measurements of the carbon activity in nickel are also in fairly good agreement. However, there is a large discrepancy between the above set of measurements and those of Lander, Kern, and Beach," who measured the carbon solubility of nickel in equilibrium with graphite by depositing an excess of graphite on the surface of Ni-foils from a gaseous mixture and subsequently diffusing in the carbon. These results are considerably higher than those mentioned above. The determinations6 of carbon activity a, in nickel from the CH4-H2 equilibrium showed that at all the temperatures investigated, the ac-values varied linearly with concentration up to about a, = 0.6 and then began to increase with concentration much more rapidly. On the basis of auxiliary experiments in which C-Ni solutions were equilibrated with graphite, Schenck, Frohberg, and Jaspert concluded that their CH4-H2 solid equilibrations at high values of a, were spurious and a, behaved linearly with composition up to the saturation limit (a, = 1). The short linear extrapolations of Schenck, Frohberg, and Jaspert&apos;s a, data yield values of C, in good agreement with those of Lander, Kern, and Beach." The solubility data for nickel discussed here is presented in Fig. 1 in the form of plots of ln[Cc/(l - 2cc)] vs 1/T. The discrepancies mentioned are clearly seen. In this investigation a vapor transport method is used to measure C, over as wide a temperature range

Jan 1, 1969

By P. S. Kotval, H. Hahell

PRECIPITATION of M23C6 carbides at grain boundaries in austenitic steels and nickel base superalloys has received considerable attention. Hatwell and Berghezan,1 in a study using carbon extraction replicas, observed that dendritic growth of the M23C6 carbide phase occurred at grain boundaries in austenitic steels. Merrick and Nicholson2 have observed that in thin foils of "Nimonic 75" alloy the precipitation of M23C6 carbide was discontinuous at grain boundaries. Lewis and Hattersley3 have suggested that the type of M23C6 precipitation observed in Ni-Cr austenites represented the early stages of discontinuous precipitation. In a more recent study, Singhal and Martin4 have concluded that grain boundary M23C6 precipitation involves the migration of an austenite grain boundary by a mechanism very similar to that proposed by Tu and Turnbull.5 Tu and Turnbull&apos;s suggestion essentially involves grain boundary migration under the driving force arising from the difference between the surface free energies of the opposite sides of the plate. Thus, Singhal and Martin&apos;s observation4 implies that the first stage of discontinuous precipitation has taken place and that the grain boundary has provided a diffusion short circuit for the sub-stitutional solute atoms (principally chromium) which assist the preferential growth of the M23C6 plate in contact with the grain boundary. However, no evidence of the characteristic cellular morphology typical of discontinuous precipitation was found in Singhal and Martin&apos;s studies. Presumably, this is due to the low volume fraction (i.e., low supersaturation of solute) of the precipitating carbide reported by Singhal and Martin.4 Recently, Raymond6 has studied precipitation of the M23C6 carbide in Incoloy alloy 825 and shown that the growth of this phase is perpendicular to grain boundaries at 1400°F and in the plane of the grain boundary at 1700°F. The former aging condition resulting in discontinuous or "cellular" precipitation. Raymond has suggested an explanation for this behavior based on the relative rates of chromium diffusion by volume and grain boundary diffusion at the two different aging temperatures. In the course of a recent investigation on precipitation behavior in several &apos; strengthened superalloys, precipitation of M23C6 carbide at grain boundaries was studied. Under conditions of a high degree of supersaturation, the M23C6 carbide precipitates in the discontinuous or cellular morphology in Waspalloy (Ni-18.51 Cr-2.0 Fe-3.53 Mo-1.16 Al-2.78 Ti-0.09 C). This note presents electron microscopy observations of this mode of precipitation and its effect on mechanical properties. Specimens of Waspalloy after "solution" heat treatment at 1950°F show essentially single phase matrix with a few residual particles of "primary" MC carbide. In normal commercial heat treatments, precipitation of Ni3(Al,Ti) ordered fcc r&apos; phase occurs throughout the matrix and M23C6 precipitates as globular particles at the grain boundaries. In these commercial heat treatments the degree of supersaturation during precipitation is low. However, if specimens of Waspalloy are quenched from the solution heat treatment temperature of 1950°F and then aged at an aging temperature where the degree of supersaturation is high, discontinuous precipitation of M23C6 occurs. Figs. 1 and 2 show thin foil micrographs of Waspalloy, solution heat treated at 1950°F, water quenched, and aged at 1292° and 1598°F, respectively, for 500 Fig. 1—Thin foil of Waspalloy, solution heat treated at 1950°F for 1 hr, water quenched, and aged for 500 hr at 1292°F. Magnification 15,500 times. Fig. 2—Thin foil of Waspalloy, solution heat treated at 1950°F for 1 hr, water quenched, and aged for 114 hr at 1598° F. Magnification 13,000 times.

Jan 1, 1970

By W. T. Isbell

Although the pressure to meet the heavy demand for lead still took precedence over new metallurgical developments in the field of roasting, smelting, and refining of lead in 1948 there nevertheless has been considerable activity in the experimental development of new processes and improvements as well as plans for the modernization of many plants both here and abroad. Increasing labor and material costs have stimulated the trend to greater mechanization, revamping of flow sheets, and construction of larger units wherever possible. Although there have been many serious labor stoppages in the United States, Mexico, and Europe, labor supply has improved in most plants even if it has fallen off in efficiency.

Jan 1, 1949

By H. M. Shepard

THE copper industry operated at high capacity throughout 1947, with no serious tie-ups in operation as was the case in 1946, when almost the entire industry was shut down by a four-month strike. Refined copper production in the United States averaged 94,250 tons for the first eleven months and deliveries to domestic consumers, including foreign copper for domestic consumption, averaged 114,000 tons per month. On April 29 the import duty of 4d per lb was suspended until March 31, 1949. Copper prices fluctuated considerably for a short time thereafter. Over the year the price of domestic electrolytic copper at refineries on the Atlantic seaboard advanced from 19.225¢ on Jan. 2 to 21.200d on Dec. 24.

Jan 1, 1948

By Frederick Bacorn

THE paper of Reno H.. Sales on Ore Deposits at Butte, Mont.,&apos; is a careful and painstaking work, an important contribution to the literature of the subject. As is almost inevitable in a work of such magnitude, a few misstatements occur; and some of these I shall endeavor to point out. Mr. Sales has also fallen into error, as I think, in the application of his theory of ore deposition; and while the modification which I venture to suggest is a minor one geologically, it is of great economic importance. I refer to Mr. Sales&apos;s idea of an outward migration of mineralizing solutions from a supposed central copper zone. In order that I may make myself plain, I must first epitomize the theory as a whole, which I understand to be this: All of the Butte ore deposits (save those along the Continental fault, not herein considered) are derived from solutions of magmatic origin, which, at the beginning of their ascent from a great depth, were, acid in reaction, hot, and were carriers of copper, zinc, manganese and other metals. As they departed from their point of origin they lost heat, and, because of reactions with the wall rock, became more and more alkaline. The metal deposited from these solutions in their hot condition was principally copper; and, as they cooled, they deposited less and less copper and more and more manganese and zinc, until the copper practically disappeared. With this theory in general I have no fault to find, nor have I, it must be stated, the qualifications necessary to enable me to pass upon it critically; but it seems to me to be reasonable and probable, and is one which I am quite willing to accept.

Jan 8, 1914