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By C. O. Worden, C. A. Zapffe, F. K. Landgraf

SUMMARY FOLLOWING the discovery of Parke and Ham that deoxidation control of cast molybdenum can be predicated upon simple fractographic examination, a special study of that metal was undertaken to investigate those patterns ascribed to forgeability and nonforgeability. An elaborately developed system of cleavage patterns immediately rewarded the study; and they are reported here as a necessarily preliminary contribution calling attention to information which is both new in type and in origin. In general, the present observations confirm those of Parke and Ham, and Woodside; but they also disclose a wealth of detail and correlated phenomena which greatly expand the earlier information. For example, the oxide pattern of nonforgeability is found to be complex, perhaps involving as many as three distinctive patterns. And the nature of the carbide seems to be at least twofold. In addition, transgranular facets are here shown for the first time. Elaborately complex, but in a characteristic manner, these facets depict distortion in original crystal growth which provides truly extraordinary patterns. No carbide and oxide forms display themselves transgranularly, except in profile as exceedingly thin superficial films at the grain boundaries. Crystallographic features are also rare-a condition undoubtedly resulting from the great substructural distortion; but occasionally registrations are found of cleavage on {001}, and faulted areas believed to be Neumann-type deformation on {112}. INTRODUCTION Parke and Ham, 1 and again Woodside, 2 have reported that the forgeability of molybdenum cast by their vacuum-electric-arc process can be predicted with great dependability by a simple fractographic observation. They state that nonforgeability is the result of a grain boundary oxide which can be readily identified on the fracture facet at high magnification; and they convert the nonforgeable condition to a forgeable one by increasing the carbon content of the melt until the oxide structures subsequently observed in the fractograph become replaced by a second strongly marked pattern characteristic of carbide and coincidentally indicative of forgeability. Considerable importance immediately attaches to such observations: (I) because of their direct commercial application to one of metallurgy's inviting and relatively unexplored metals; (2) because of a general scientific curiosity regarding the nature of these characteristic markings; and (3) perhaps more important, because of

Jan 1, 1948

By Martin Weinstein

A technique is described for preparing finegrained lead telluride by ultrasonic agitation of a solidifying melt. Material prepared by this technique is dense and chemically homogeneous. N-type PbTe, containing 0.03 mole pct PbIz, has been made and its thermoelecCric Properties have been measured as a function of temperature. For comparison, the properties of similarly doped PbTe made by cold pressing and sintering, and by extrusion, have also been measured. The ultrasonically prepared material compares favorably with the others in its thermoelectric-efficiency factor. Comparison of compressive-flow curves for the three kinds of PbTe show that the ulhasonically prepared material has much superior ductility. The cleavage strength of the ultrasonic material is related to the grain size, D, by the Petch relation:Extrapolation to infinite grain diameter yields a fracture strength of 5000 psi for single-crystal PbTe. WHEN metals and semiconductors solidify in a mold they normally assume one of three cast structures illustrated in Fig. 1.' Solidification in a casting starts at the mold walls where a large number of fine crystals of random orientation can be nucleated to form the chill zone. Because of the anisot-ropy of the growth rate, those crystals whose direction of maximum linear growth is parallel to that of the heat flow grow faster and crowd out the crystals of less favorable orientation. A second zone, having a preferred orientation, called the columnar zone, thus forms adjacent to the chill zone. The speed of growth of the columnar grains will depend, in the case of limited undercooling of the melt, on the rate at which heat can be abstracted. The columnar zone can extend to the center of the casting, Fig. l(a), but it is frequently followed, in solid-solution alloys, by another zone of equiaxed randomly oriented grains in the central portion of the casting, Fig. l(b). The equiaxed structure in Fig. l(c) represents the completely grain-refined case where the equiaxed grain size is small. The third type of structure is the most desirable because it imparts a somewhat higher strength for all except high-temperature applications, it reduces segregation of the doping constituent, and it reduces the possibility of hot tearing (the separation of grains due to the melting of a low-melting point constituent in the grain boundaries). In order to obtain fine-grained castings, the nu-cleation frequency must be increased and grain growth must be restricted. Various techniques have been employed for obtaining this end, namely: rapid cooling, vibration, and inoculation of the melt. The success of these techniques depends upon the characteristics of the metal species and on factors controlled by heat transfer through the crucible walls. Recent studies2" have shown that the application of ultrasonic energy to the solidifying ingot is an extremely powerful tool in the improvement of the crystalline structure of metallic castings. Both the mechanical properties and homogeneity of the ingots are improved. Ultrasonic oscillations may affect the crystallization process by 1) permitting subcritical nuclei to agglomerate and thus form nuclei of sufficient size to cause crystallization, 2) changing the state of surface adsorption of various catalysts found in the liquid melt, 3) breaking pieces of solid from the solidified surface near the supercooled region thereby increasing the number of possible nuclei, 4) causing temperature fluctuations to occur in certain parts of the melt thereby increasing the supercooling at specific points in the liquid, and 5) decreasing the critical nucleus size by increasing the pressure at specific points in the melt.' Various investigators have concluded that the effectiveness of the ultrasonic oscillations results from cavitation which disrupts the growing solid-liquid interface The present paper describes the application of ultrasonic oscillations to the crystallization of the semiconductor N-type PbTe. The purpose of this study is to prepare crystalline

Jan 1, 1964

By G. B. Walker, S. J. Swainson, S. A. Falconer

DURING the past few years much interest and attention has been focused on a relatively new method of ore concentration, which utilizes the principles of sink and float and employs as the heavy medium a suspension in water of a finely ground solid, such as galena or ferrosilicon. Although a relatively recent development, much progress has already been made in applying heavy-media separation processes to a considerable number of ores. Eight plants in this country and abroad -are now treating approximately 10 million tons of ore annually by heavy-media separation (sink-float) processes, including lead-zinc, lead, iron, garnet, tin and tungsten. At the annual meeting of the A.I.M.E. in 1941, three interesting papers (unpublished) dealing with heavy-media separation (sink-float) processes of ore concentration as practiced in four commercial units in the United States were presented by Victor Rakowsky, Grover Holt, Elmer Isern and Robert Ammon. These papers gave an excellent exposition of the principles of sink and float, as well as the operating practice in two iron-ore-beneficiation plants, the Harrison and the Merritt, of Butler Brothers, in Minnesota; the Central mill of the Eagle Picher Mining and Smelting Co.; and the Mascot mill, of the American Zinc, Lead and Smelting Co. Augmented by pictorial descriptions and a working model demonstrating the processes, these papers evoked a great deal of interest and discussion. In fact, in reporting the high lights of the meeting in the April 1941 issue Of MINING AND METALLURGY, Professor Taggart made the statement that "preconcentration by heavy suspension was Miss A.I.M.E. 1941 so far as milling is concerned." Although to date the greatest application of heavy-media separation from the tonnage point of view has been for the treatment of lead, zinc and iron ores, these processes have a much wider field of usefulness. In this regard, it is to be noted that recently new heavy-media separation plants for treating cassiterite ore and garnet ore have been placed in successful operation. Moreover, numerous other types of ores have been found to respond well to these processes when tested on a semi-commercial scale, and it is expected that in the near future a considerable number of new plants will be erected. In view of the fact that heavy-media separation processes offer such attractive possibilities, particularly now, when the mining industry is being called on for an even larger production than ever before has been attempted, despite shortages of labor and supplies, it was felt that a description of some of the successful separations that have been worked out during the past year in the Ore Dressing Laboratory of the American Cyanamid Co. on a variety of ores of strategic importance would be of interest. The purpose of this paper, therefore, is to present the essential data relating to investigations of heavy-

Jan 1, 1943

By P. F. Gnirk, J. B. Cheatham

Single bit-tooth penetration experiments under static load were conducted on six rocks at confining pressures of O to 5,000 psi using sharp wedge-shaped teeth with included angles ranging from 30 to 120° In general, the force-displacement curves for all rocks exhibit an increasingly nonlinear and discontinuous behavior with decreasing confining pressure. The confining pressure at which a rock exhibits a macroscopic transition from predominantly ductile to predominantly brittle behavior during penetration vmies from about 500 to 1,000 psi for the limestones to greater than 5,000 psi for dolomite. The correlation between calculated values of force per unit penetration based on plasticity theory and experimental values is quite encouraging, even at confining pressures as low as 1,000 psi A qualitative correlation between volume of fragmented rock per unit energy input for a single bit-tooth and drilling rate for microbits appears to exist over a confining pressure range of 0 to 5,000 psi. INTRODUCTION Laboratory experiments utilizing a small-scale drilling apparatus have demonstrated that penetration rates are reduced considerably as a result of increasing the confining pressure from atmospheric to a few thousand psi?-3 This undesirable situation can, in general, be attributed to a combination of decreased efficiency of chip removal at the bottom of the borehole, increased rock-failure strength, and a possible change in the mechanism of chip generation and rock fragmentation with increasing confining pressure. To more fully understand the principles underlying the last circumstance, it is the purpose of this investigation to experimentally study the mechanism of single bit-tooth penetration into dry rock at low confining pressures and, in particular, to establish the confining pressure at which the penetration mechanism may undergo a brittle to ductile transition for various rock types commonly encountered in drilling. Confining pressure as used here refers to the differential pressure between the borehole fluid pressure and the formation-pore fluid pressure. EXPERIMENTAL PROCEDURE Using an experimental apparatus previously described: a single, sharp wedge-shaped tool was forced under a "statically" applied load into an effectively semi-in finite dry rock sample subjected to a prescribed confining pressure. To prevent the invasion of the con fining-pressure fluid into the pores of the rock sample during penetration, the exposed surface of the rock was jacketed with a layer of silicon putty.* Electrical instrumentation incorporated into the apparatus yielded a graphical plot of force on the tool as a function of penetration or displacement of the tool into the rock during an experiment. During the course of the experimentation the following conditions were maintained constant: (1) pore pressure — atmospheric (i.e., the rock was dry); (2) temperature — 75F; (3) rate of loading — essentially static (approximately 0.002 in./sec); (4) bit tooth — a sharp wedge-shaped tool loaded normal to the rock surface; (5) rock surface — smooth and flat; (6) drilling fluid — hydraulic oil; and (7) maximum depth of penetration — approximateiy 0.1 in. In addition, each experiment was performed on a different rock sample so the rock surface is free of a layer of cuttings and of any previous indentation craters. The influence of the corners of a borehole was neglected, since each rock sample was cemented inta a section of aLuminum tubing to simulate a semi-infinite body. Indentation experiments were made on a sandstone, two limestones, a marble, a dolomite and a schist with a 60' bit-tooth over a range of confining pressures from atmospheric to 5,000 psi and at a constant confining pressure of 1,000 psi for a variety of bit-teeth with angles ranging from 30 to

Jan 1, 1966

The following petition for amendment of the constitutional provisions relating to qualifications for membership in the Institute, signed by 75 members, of whom 27 are members of the Committee on Increase of Membership, was received by the Board of Directors, was printed on the program of the New York Meeting sent to all members early in January, and is now being voted upon by the membership: In accordance with the terms f Article X, we hereby propose the following amendment to the Constitution, Article II, Section 2: Members shall comprise all those persons who on the third Monday of February, 1918, were members of the Institute, and in addition thereto, all those thereafter, elected or transferred into the, class of Members. A person to he eligible for election or transfer into the class of Members must he at least 27 years of age and must have had at least six years' employment in the practice of engineering, mining, geology, metallurgy or chemistry, during at least three years of which he must have held positions of responsibility in one or more of these fields. Graduation from the scientific course of a college, approved by the Committee on Membership, shall be considered equivalent to two years' employment, as required in the previous sentence.

Jan 2, 1918

By S. J. Matas, R. F. Hehemann, R. H. Goodenow

The hot-stage metallographic method has been employed to determine radial growth rates of upper and lower bainite. Lower bainite appears to grow as individual plates that increase in both length and thickness while upper bainite grows as sheaves of closely spaced plates or needles. A discontinuity in the temperature dependence of the growth rate appears to be associated with the transition from upper to lower bainite and stepped quenching experiments suggest that lower bainite will not continue to grow when the temperature is raised to the upper range. Thus, a single process does not appear to control the growth of both upper and lower bainite. A tentative model based on the forces acting on a dislocation interface is proposed to account for the slow growth of bainite. It has been recognized since the early studies of Davenport and Bain that a close relationship exists between the martensite and bainite transformations in steels. However, diffusion of carbon during the transformation has lead to considerable controversy concerning the reaction mechanism.1-7 Many studies4,5,7-9 have emphasized the structura and kinetic aspects of the bainite reaction and, in particular, the difference observed between the two forms of bainite—frequently termed upper and lower bainite. A kinetic difference between the two types of bainite has been revealed in the activation energy determined from the overall reaction;4,5 however, many difficulties arise in an interpretation of these activation energies since a number of temperature dependent factors contribute to the kinetics of the overall reaction. The displacive surface relief10 accompanying the bainite reaction permits a separation of the nuclea-tion and growth contributions to the reaction and allows the kinetics of the growth process to be examined. Several investigations of this type have been conducted; however, they have been restricted to the low temperature range.3'6'11 Here, bainite plates are observed to grow slowly in both length and width. The present investigation extends such studies to include the upper bainite range. MATERIALS AND PROCEDURE Materials. The composition of the steels studied in this investigation are presented in Table I. The range of composition permitted a study of the effect of carbon content on the growth rate of upper bainite in the 9 pct Ni steels and consideration of both upper and lower bainite in the higher carbon steels. These steels were received as hot-rolled rounds and were forged to approximately 1/2 in. thick plates for preparation of metallographic specimens. In order to produce an essentially zero carbon steel, Steel A was decarburized in wet hydrogen at 1550°F for 15 days with the result tabulated as Steel AD. Experimental Procedure. In order to study the slow growth of the displacive transformation product, a commercially available Leitz hot stage was modified to permit heating of the specimen by its own resistance in a manner similar to that employed by other investigators.6 The furnace chamber was maintained at a pressure of 2 to 3 X 10-5 mm Hg prior to austenitizing at 2000° ± 12° F for 5 min. Samples could be cooled from the austenitizing to the transformation temperature in approximately 15 sec and the progress of transformation was recorded with a 9 cm by 12 cm single frame camera or a 16 mm movie camera. RESULTS AND DISCUSSION Growth Characteristics. The general growth characteristics observed in this investigation were analogous to those reported previously.3,6,11 Typical growth sequences for the high temperature and low temperature forms are illustrated in Figs. 1 to 5. In both temperature ranges, bainite plates increase in length at slow, temperature dependent rates until interrupted by a grain boundary, another plate, or

Jan 1, 1963

By R. P. Smith

IN 1937 the employees of the Hollinger Consolidated Gold Mines Ltd., at Timmins, Ont., Canada, approached organized medicine for a plan to provide themselves and their families with a complete medical service including hospitalization. This approach was made because of two conditions: (1) the necessity for some organization whereby contributions could be made in instalments to offset the sudden and large expense connected with illness for which the average employee is not prepared, and (2) the need for a more cohesive quality of service to replace a contract practice then in vogue, which did not take care of the employee's family or dependents. In different parts of the United States and Canada similar plans were in force, not only for employed groups but for numbers of people in circumscribed areas. In Europe different countries had adopted various forms of health insurance plans. It then was no surprise that these employees as a group should ask for some similar plan. With the cooperation of the management, a plan was instituted. The plan has one object only-the provision of medical services, including the accessory services such as hospitalization, X-rays, nursing, and necessary drugs and medicines. It is not concerned with cash benefits, sickness and accident payments, or any form of monetary return as the result of illness, but is simply an organization to provide medical services and pay for them from a central fund. It is a nonprofit organization and the only shareholders are the employees and their families who contribute and who in turn receive services. The Hollinger plan is limited to the employees of the Hollinger mine, who live in Timmins and the immediate vicinity. At first, the membership was voluntary. In the third year, it was made a condition of employment, with the proviso that at the end of any Association financial year an employee may withdraw if he wishes to do so. After withdrawal, he cannot again become a member until the end of the next Association year, and then only by the payment of the back dues. This step was taken to ensure continuity, and to prevent employees from withdrawing when well and reentering when faced with impending illness or operations. The employee himself is subject to medical examination on application for employment, and if accepted is subject to further examination by a specialist in chest diseases under the Workmen's Compensation Board of Ontario. Thus it is possible to exclude those who have heart disease, tuberculosis, or other disabling conditions when first employed. Wives and families of employees are not subject to medical examination but other dependents of an employee-mother, father, or other relative-who are declared by the employee to be wholly dependent upon him must be examined. The employee

Jan 1, 1944

By Clarence Zener

Theoretical considerations by one of the authors have ledl to the prediction that the dynamic internal friction of annealed metals has a broad maximum at a certain grain size. This prediction they have verified2 for alpha brass. In the present paper the theory is extended to include the precise manner in which the internal friction varies with grain size on either side of the maximum. New experimental data are presented to test this extended theory. The physical basis for the type of internal friction that is being investigated lies in the interplay between stress and temperature. Just as local fluctuations in temperature give rise to local fluctuations in stress, so likewise fluctuations in stress give rise to fluctuations in temperature. But temperature gradients give rise to necessarily irreversible thermal currents, and hence to internal friction. The theory for this type of internal friction has been developed quantitatively,³ and has been experimentally verified,4,5 for the particularly simple case of the transverse thermal currents accompanying transverse vibrations. Of more fundamental importance are the intercrystalline thermal currents accompanying all types of vibration. The variation in stress across grain boundaries arises from the elastic anisotropy and at least partial random orientation of the individual crystallites. An exact quantitative treatment of the internal friction due to these thermal currents is of course out of the question. However, much information can be obtained from general arguments.1,6 Thus when the frequency of vibration f is low, or when the grain size d is small, adjacent grains remain nearly in thermal equilibrium, and vibration proceeds isothermally with little internal friction. Again, when the frequency is high, or the grain size large, the heat flow per cycle is small, the vibration proceeds adiabatically with little internal friction. The internal friction will become a maximum in the transition region. The degree of adiabatic-

Jan 1, 1940

By Clarence Zener

Theoretical considerations by one of the authors have ledl to the prediction that the dynamic internal friction of annealed metals has a broad maximum at a certain grain size. This prediction they have verified2 for alpha brass. In the present paper the theory is extended to include the precise manner in which the internal friction varies with grain size on either side of the maximum. New experimental data are presented to test this extended theory. The physical basis for the type of internal friction that is being investigated lies in the interplay between stress and temperature. Just as local fluctuations in temperature give rise to local fluctuations in stress, so likewise fluctuations in stress give rise to fluctuations in temperature. But temperature gradients give rise to necessarily irreversible thermal currents, and hence to internal friction. The theory for this type of internal friction has been developed quantitatively,³ and has been experimentally verified,4,5 for the particularly simple case of the transverse thermal currents accompanying transverse vibrations. Of more fundamental importance are the intercrystalline thermal currents accompanying all types of vibration. The variation in stress across grain boundaries arises from the elastic anisotropy and at least partial random orientation of the individual crystallites. An exact quantitative treatment of the internal friction due to these thermal currents is of course out of the question. However, much information can be obtained from general arguments.1,6 Thus when the frequency of vibration f is low, or when the grain size d is small, adjacent grains remain nearly in thermal equilibrium, and vibration proceeds isothermally with little internal friction. Again, when the frequency is high, or the grain size large, the heat flow per cycle is small, the vibration proceeds adiabatically with little internal friction. The internal friction will become a maximum in the transition region. The degree of adiabatic-

Jan 1, 1940

By Hannon, J. W. G.

Silicosis is today's most important industrial disease and probably dates back to the Stone Age. Since the industrial revolution, increasing attention has been paid to those occupations where mineral dust is present in the air breathed by the workers. For many years it was assumed that the inhalation of all mineral dusts was hazardous. but investigations conducted in several countries pointed the statistical finger of guilt at free silica in any of its numerous physical forms as a dust of outstanding toxicity. Recognition of silica as the chief hazard has resulted in widespread use of the term "silicosis." Depending upon the concentration of finely divided silica dust to which the individual is exposed and the duration of exposure, silicosis may become a disabling condition in from one to thirty years. The structure of the lung and respiratory passages is such that only minute particles of silica can gain entry to the air cells in the lung (5 microns or under are most toxic). When these minute particles gain entry to the lung tissues they stimulate certain protective cells in the lung to multiply at an excessive rate. The cell's undergo inflammatory changes which result in nodular scars and a low-grade inflammation of the lung tissue. These progressive changes in the lung structure gradually encroach

Jan 1, 1949

By D. B. Jugle, J. B. Darby, O. J. Kleppa

A systematic study has been made of the kinetics of solution under steady state, dynamic conditions of titanium, vanadium, chromium, iron, cobalt, and nickel in liquid aluminum. It was found that the temperature dependence of the solution rate obeyed an Arrhenius-type rate equation, and that at a given temperature the rate of solution of the various solutes correlates quantitatively with the equilibrium solubility of the solute in liquid aluminum. These results are consistent with a mechanism where the rate-controlling step is the diffusion of solute atoms through a liquid boundary layer. THE present study was initially started in order to explore the feasibility of liquid-metal solution calorimetry for transition metals and alloys. Previous work1 in this field employing liquid tin as a solvent at temperatures in the 500' to 600' range had indicated that the rates of solution of most transition metals in tin are very low. Under such conditions effective solution calorimetry is difficult. The objective of the present investigation was two-fold: a) To obtain, as far as possible, quantitative data on the rates of solution of a series of transition elements in liquid aluminum. b) To explore whether liquid aluminum might be a suitable solvent for liquid-metal calorimetry. In the course of this work a comprehensive set of data was obtained on the steady state rates of solution of transition metals in a common liquid-metal solvent. The results are consistent with the boundary layer model, which assumes that the rate-controlling step consists of diffusion of solute atoms through a viscous liquid layer. EXPERIMENTAL PROCEDURE A vacuum-tight stainless steel vessel was surrounded by a resistance furnace, as shown in Fig. 1. In all experiments the temperature of the liquid solvent was controlled to 2.5' by means of a Micromax controller. A high-vacuum manifold connected to the vessel maintained a vacuum of 1 x 105 mm of Hg or better. The vacuum vessel was equipped with a charging section isolated from the working chamber by a vacuum-tight gate valve. This arrangement allowed the specimen holder to be removed or inserted into the apparatus without removal of the liquid metal bath. The specimen holder was suspended from a closed end stainless steel tube, which also served as the thermocouple protection tube. The portion of the tube that was below the solvent level was surrounded by an alumina protection tube to isolate it from the liquid metal bath. The stainless steel tube was connected through a rotary vacuum seal and a gear train to a fractional horsepower motor. For most experiments the tube was rotated at a constant

Jan 1, 1963

By AIME

Annual production of more than 4,000,000 tons of 0.74 percent copper ore and coincident handling of over 5,000,000 tons of waste at the open-pit mine of Castle Dome Copper Co. near Miami, Ariz. takes a lot of power. Manufacturers have ever co-operated with mining companies in providing the required equipment to suit the problem. Power equipment suppliers have done much to make possible the economic and profitable production of copper from low-grade ores. In the future, as mining operations will necessarily handle even lower-grade ores, the ability of the manufacturer to supply the power and mechanical equipment to produce more metal at a fair and reasonable price will be the good right arm of the miner. About 27,000 tons of concentrate is produced from the 4,000,000 tons of ore.

Jan 1, 1948

By D. R. Miller

Internal friction and elastic modulus variations in electrorefined titanium, iodide refined titanium, and alloys of the latter material with oxygen, nitrogen, aluminum, and zirconium were investigated. No oxygen peak was detected with electrorefined titanium but, provided precautions were taken to prevent increases in background damping, an oxygen peak at about 410°C could be resolved with each of the other materials. An additional partially resolved peak was observed at 500°C in a Ti-N alloy. An anomaly in the variation of rigidity modulus with temperature was observed. Possible mechanisms for the formation of any oxygen peak have been discussed. PRATT, Bratina, and Chalmersl investigated the internal friction of commercial purity titanium and alloys of this material containing 1.5, 3.5, and 4.5 at. pct O. With commercial titanium the internal friction curve consisted of two components, a background which increased steadily with temperature and a peak at about 600" C which was due to grain boundary relaxation. In the Ti-O alloys, however, an additional internal friction peak was observed at 430" to 450°C and, since this peak increased in height as the oxygen content was increased, it was thought to be associated with the presence of oxygen. The diffusion of oxygen in titanium at temperatures between 300" and 500° C is believed to have marked effects in its tensile properties2'3 and the present internal friction measurements were undertaken to obtain further information on this diffusion, using material of higher purity than that of Pratt et d. and an apparatus of very much greater sensitivity. In the course of the investigation a number of important limitations on the work of Pratt et al. were revealed and results have been obtained which emphasize the need for ensuring that in this type of experiment, internal friction is independent of strain amplitude and that the values obtained are reproducible. 1) MATERIALS AND APPARATUS The basis material from which the majority of the specimens was prepared was iodide-refined titanium, the major impurities in which were oxygen and nitrogen—the metallic impurities being present at concentrations less than 0.001 at. pct. The hardness of this material after arc melting, forging, and swaging to rods 1/4 in. diameter was Dph = 110. Specimens 10 in. long and 0.020 in. (0.51 mm) diameter were prepared from these rods by further swaging and wire drawing and were finally annealed in vacuo (5 x 10-6 mmHg) for 24 hr at 800°C. The oxygen alloys were prepared from iodide-

Jan 1, 1962

By S. H. Chauvenet

The binding of the boshes and inwalls of blast furnaces has always been an expensive piece of work. When the old stone stack was replaced by the iron shell, the brickwork was kept at a thickness of five feet or more. These five-foot walls were still too thick, and the practice now is to have as thin walls as possible and to have a free circulation of air about the brickwork of the furnace. The " basket," or lattice-work biuding, accomplishes this object, but it is expensive, m to first cost, and, if any change in the diameter of a furnace has to be made, it necessitates an alteration of the binding or of the thickness of the walls.

Jan 1, 1882

By H. C. Chang, N. J. Grant

Creep of very coarse grained high purity aluminum was studied at 400°, 700°, and 1100°F at initial stresses of 50 to 1200 psi. Local strain measurements were made across the grain boundaries and in different regions of various grains during creep, thereby permitting the drawing of component creep curves. The relative amounts of elongation as measured across a grain boundary and in the grains adjacent to the boundary depend on the temperature of testing. The significance of creep curve equations and activation energies is discussed. THIS paper presents some of the results of a research program devoted to the study of the mechanism of creep in high purity aluminum. Previous publications have dealt with the cyclic processes of alternating grain boundary sliding and migration, and the deformation in the grains caused by these processes;' the direction and the driving force of grain boundary sliding and migration;' the deformation in the grains and the restricting effects of the grain boundaries on this deformation." These previous papers were based mainly on either microscopic observations or X-ray data, or both. Sometimes creep curves across two closely spaced reference marks (about 0.6 to 0.7 mm apart) were also presented with a view to correlating the elongation values with the optical observations in general, and with certain deformation processes in particular. These curves shall henceforth be referred to as component creep curves. No attempts were made, however, to compare either the component creep curves which were obtained in different regions of a specimen, or those obtained from different specimens subjected to different creep test conditions. It is the purpose of this paper to present these component creep curves. Among the factors influencing the behaviors of these curves, those studied were stress, temperature, and grain arrangements in the specimens. It is proposed to show how greatly the deformation can vary from grain to grain and within an individual grain in a coarse grained specimen. The experimental technique and procedure have been presented.' It remains necessary to emphasize that the reference marks were produced by pressing a thin sewing needle into the surface of the specimen before the final annealing at 900°F for 24 hr and at 1150°F for 12 hr. The cold work around the needle indentations was therefore removed. The depth of these holes after electropolishing the annealed specimens was about 0.01 mm. This depth and area were negligible in comparison with the thickness of the specimens, 2.3 mm, and hence would not affect the creep behavior. Results Fig. 1 shows a development diagram of specimen P-8. The dots on the surface locate the needle point reference marks used to obtain the component creep curves. A curve obtained between two dots across a grain boundary measures not only the boundary deformation but also the deformation associated with boundary sliding occurring in the grains in the region between these indents. The original distance between two reference marks was about 0.6 to 0.7 mm. The maximum error of measurement was 0.01 mm, or in terms of percentage elongation, of the order of & 1.5 pct. Whereas the component creep curves shown in the figures to follow were drawn as a gross average of the points, in view of the fineness of some of the steps of grain boundary sliding and migration, as shown in the previous publications,¹,2 it appears logical to expect that some of the finer cycles of movement have not been delineated for the strain sensitivity of the measuring system. It seems justifiable to say that the curves are not as smooth as shown. 700°F Tests: Fig. 2 shows component creep curves across four of the grain boundaries in specimen P-8, tested at 700°F and 85 psi. These curves clearly show alternate cycles of increasing and decreasing

Jan 1, 1954

By J. E. Tobey

THERE are a lot of good things about this great industry of ours. Let us stop commiserating and consider some of the things that are right in this business. Coal is number one in the basic material industries. Our civilization owes more to it than to any other basic commodity. We are literally immersed in the benefactions of coal. In cur man-made world it is indispensable and we are constantly surrounded by objects, materials, and services which owe their existence to coal. Practically all the important materials, such as iron, steel, brick, cement, lime, rubber, glass, cotton, and wood have felt its magic touch.

Jan 1, 1939

By H. Rumfelt

Strip mining in the domestic coal industry is contributing a greater proportion bf overall production than at any time in the past. U.S. Bureau of Mines statistics show that the percentage of total production mined in 1958 by stripping methods increased to more than 30 pct, up from 22 pct in 1951. The tendency to favor strip and open pit mining exists in other mining activities, but such trends are not as clearly outlined as in the coal industry. Significantly, the depth of overburden in coal properties considered suitable for stripping is also increasing. A depth of 50 to 60 ft of overburden was once considered to be about the maximum amount that could be handled economically. Today, a depth of 80 to 100 ft is frequently taken into consideration for simple overcasting operations (i.e., excavating overburden and dumping it in the spoil position where it remains indefinitely).

Jan 5, 1961

By W. C. Lilliendahl, G. Meister

Uranium metal with a purity of about 99.9 pct was produced on a large scale by fused salt electrolysis with a material efficiency of about 90 pct. The material efficiency depends mainly on bath composition, electrolysis temperature, electrode smothering, and elutriation during washing of the powder. RESEARCH and development work on fused salt electrolysis carried on by the Westinghouse Lamp Div. Bloomfield, N. J., was done under the Manhattan District Corps of Engineers and later under the Atomic Energy Commission for the commercialization of uranium production for the first atomic pile at the University of Chicago in 1942. From the conception of the atomic bomb project it was recognized that metals with impurity levels having little metallurgical significance would be required. Permissible impurity levels were based on neutron absorption. Of particular significance was boron, which could not be present in amounts exceeding 1 ppm. The electrolytic method as developed in 1930 by Driggs and Lilliendahl,1,2 and later improved, yielded uranium of very low boron and other deleterious impurity content. No other method was capable at that time of producing uranium metal of the required purity.' The low boron content of uranium produced by the electrolytic process resulted from the availability of the reactants which were low in boron content, and from the inherent elimination of boron in the fused salt bath. Since the heart of any electrolytic process is the electrolysis cell, this paper will deal with the development of the original bath composition for the efficient production of uranium from a batch process to one of continuous operation. Emphasis also will be placed on other factors which will affect the material efficiency of the process. With the laboratory cell the material efficiency of uranium powder recovery in the early electrolysis was relatively low, about 35 pct based on the ratio of uranium recovered to uranium added. This early process also had other defects. The electro- lytic bath could not be used continuously. After three runs from a freshly charged crucible, the deposit showed a tendency to slip off the electrode as it was raised from the bath. This condition necessitated pouring the charge every fourth run and preparing a new bath. It was assumed at that time that this condition was caused by the increasing fluoride concentration with each addition of uranium salt, which adected the mobility of the uranium ions. Experimental The electrolysis cells differed in size only. They were of the floating cathode type. The laboratory cells were 21/2 in. ID and 6 in. deep and operated at 30 amp and 5 volts. Production was about 150 g metal powder per 8 hr. The plant cells (5 units) were 9 in. ID x 21 in. deep and operated at 1800 amp at 12 volts. The total production unit was designed to produce 250 lb of uranium powder per 8 hr day. Because of the tendency of uranium fines toward spontaneous combustion, material efficiencies were based only on the recovery of useful coarser metal which could be safely handled. The reported efficiencies are of particular significance only as related to the same group of experimental procedures. At the start of the project no changes were contemplated until previous data could be definitely confirmed. Therefore, the first experiments were with the 50 pct CaCl2-50 pct NaCl mixture. The material efficiency of uranium deposition as a function of the number of electrolyses is shown in Table I. In Table I, the decrease in efficiency at 800°C with number of runs is apparent and confirmed the earlier data. Operating at 900°C enabled the number of runs to be doubled, but before pouring the charge the efficiency of recovery became poor. This test indicated that the improved efficiency might have been caused by an increase in the fluidity of the bath.

Jan 1, 1958

By Paul Berggreen

LIST OF PUBLICATIONS In the Bibliography titles of publications are replaced by corresponding symbols in this list. American A-1. Transactions of the American Institute of Mining Engineers, New York. A-2. Journal of the New York Microscopical Society, New York. A-3. Journal of the Franklin Institute, Philadelphia, Pa. A-4. The Metallographist, Boston, Mass. A-5. The Electrochemical and Metallurgical Industry, New York. A-6. Bulletin of the American Institute of Mining Engineers, New York. A-7. The Iron Trade Review, Cleveland, Ohio. A-8. The Journal of Physical Chemistry, Ithaca, N. Y. A-9. The Physical Review, New York. A-10. Van Nostrand's Electric Engineering Magazine, New York. English E-1. Proceedings of the Institution of Mechanical Engineers, London. E-2. Journal of the Iron and Steel Institute, London. E3. Proceedings of the Institution of Civil Engineers, London. E-4. Journal of the Chemical Society of London, London. E-5. Philosophical Magazine, London. E-6. Proceedings of the Royal Society of Edinburgh, Edinburgh., E7. Carnegie Scholarship Memoirs, London. E-8. Proceedings of the Royal Society of London, London. E-9. Chemical News, London. E-10. Philosophical Transactions of the Royal Society of London,, London. E-11. Transactions of the North-East Coast Institution of Engineers and Shipbuilders, Newcastle-on-Tyne E-12. Iron, London. E-13. Nature, London. E14. English Mechanic and World of Science, London.

Jan 6, 1914

By C. A. Edwards

Following a brief introduction, an outline is given of the four main conditions in which gases may be associated with metals; namely, (1) adsorbed gases, (2) dissolved gases, (3) gases in chemical combination, (4) gases entrapped in blowholes or cavities. Adsorption is essentially a surface phenomenon and is regarded as the attachment of outside molecules or atoms to the exposed free valencies of the atoms comprising the surface layers. In many cases where adsorbed films of gas are formed this is accompanied by a process of diffusion of the gas into the metal itself. This is particularly true in respect to iron and hydrogen, and experiments have shown that there is no difference between the rate at which hydrogen diffuses through a single crystal of iron arid through the same material after it has been recrystal-lized into a mass of small crystals. This does not prevent a somewhat greater concentration of gas at the boundaries of adjacent crystals, nor does it mean that the effect of the gas will be the same at the boundaries as it is within the body of the crystals. Indeed, under certain conditions, iron is rendered very brittle at the crystal boundaries, as shown in experiments by Pfeil with samples of almost pure iron. Much work has been done by many investigators concerning the temperature and conditions under which dissolved hydrogen, in particular, can be at least partially removed from different metals. With iron, the hydrogen that has diffused into the metal as a result of acid attack by pickling or by electrolytic deposition of the gas on the metal is partly removed by exposing the metal to the atmosphere at ordinary temperatures. Considerably more can be eliminated by raising the temperature, and even greater quantities by jointly raising the temperature and reducing the pressure. Annealing at suitable temperatures completely removes the bad effects of excessive mounts of hydrogen dissolved in or associated with iron. This is shown by the data plotted in Fig. 1, giving values for electrolytic iron sheets after annealing at temperatures between 250" and 950" C. The hydrogen brittleness is rapidly diminished at

Jan 1, 1935