Search Documents

By DeVerle Harris

The enthusiasm with which individuals have participated in mineral exploration in the development of this country testifies to the fact that there was once a very real probability of making a worthwhile discovery. Over the years, the discovery and subsequent exploitation of the accessible ore deposits have made the finding of new deposits progressively more difficult. Present day mineral exploration has evolved from the lone prospector with the grubstaker behind him to a very costly and complex business, involving large sums of money and a staff of experts in the fields of exploration technology. Exploration today must be carried out on a large scale to be profitable. With the involvement of large amounts of capital, there has been a good deal of interest in methods of optimization of the allocation of the resources of a firm 'engaged in mineral exploration. As a step toward this, mathematical models have been formulated which are designed to quantify those variables of mineral exploration in such a manner that they can be integrated with all phases of the firms operations so as to optimize its profit objective or more simply, to make exploration more efficient and effective.

Jan 1, 1964

The methods employed for the addition of uranium to steels and cast iron in the Physical Metallurgy Division are outlined. It has been found that the segregation of? uranium is a major problem in aluminum and/or silicon killed steels and that the cooling rate is important in al-lowing the segregate to settle to one area, which can subsequently be discarded. The unsegregated areas were found to be extremely low in total oxygen, acid insoluble aluminum (AizOg) and, in some cases, slightly lower in nitrogen. Uranium recoveries, based on analyses of the unsegregated areas, were quite constant, at about 45 per cent, regardless of the type of uranium master alloy used for the addition. No segregation of carbon, manganese, silicon, sulphur, phosphorous, chromium or copper was observed in these steels. In commercial heats, the recoveries ranged from 7 to? 29 per cent for ladle additions to oxygen converted steel. When the steel was fully deoxidized prior to the uranium addition, recoveries ranged from 49 to 66 per cent, regardless of the steelmaking process.

Jan 1, 1964

By Forrest T. Moyer

The National Safety Competition was inaugurated in 1925 by the Bureau of Mines, U.S. Department of the Interior, in cooperation with the Explosives Engineer. In the first nationwide contest, 210 mines and quarries were enrolled. In 1962, the thirty-eighth anniversary of the competition, 910 mines and quarries were enrolled. These participating plants were worked a total of 133,292,989 man-hours. Of the enrolled plants, 415 achieved injury-free operations for the year, the largest number of perfect safety records in the history of the contest.

Jan 1, 1964

By E. J. Dulis, A. Kasak, R. C. Westgren

The potential of uirought tungsten- and tantaluw-rich alloys of the W-Ta-Mo-Cb system was investigated for high-strength structural applications above 2500° F. Appreciable strengthening of tung-sten and tantalum—essentially attributable to solid-solzction effects—was obtained with binary, ternary, and quaternary alloys. Tensile strengths as high as 67,000 psi were achieved at 3000 OF. ThE quest for wrought structural materials which possess good strength properties at temperatures above 2000°F has led to a considerable research effort during the past decade. In addition to exploring the potential of various high-melting-point refractory metals (such as molybdenum, columbium, tantalum, and tungsten) for very high-temperature structural applications, alloy-development programs have been undertaken to achieve greater strengths than could be achieved with unalloyed refractory metals. The methods of strengthening refractory metal alloys have included both solid-solution and dispersion strengthening. General relationships among the relevant properties (melting point, recrystallization temperature, and high-temperature strength) of refractory metals indicate that the highest strengths at temperatures of 2500°F or higher would be obtained with tungsten-or tantalum-base alloys. Therefore, the present investigation was undertaken to determine the high-temperature strength potential of solid-solution strengthened alloys based on the binary system W-Ta; to effect further strengthening, minor additions of molybdenum and columbium (at the 6 and 12 pct levels) were made. The portion of the W-Ta-Mo-Cb quaternary alloy system of interest is shown schematically in Fig. 1. The component metals—W, Ta, Mo, and Cb—have a bcc structure at all temperatures, and their binary systems are mutually completely soluble.' Complete solid solubility in the W-Ta-Mo and W-Ta-Cb alloy systems has been demonstrated,' and, therefore, it was expected that the quarternary alloys of the system would also exhibit complete solid solubility at all temperatures. In the virtual absence of contamination by interstitial elements, all the alloys would be truly solid-solution strengthened. Twenty specific compositions of this investigation included binary, ternary, and quaternary alloys of the W-Ta-Mo-Cb system as well as unalloyed tungsten and tantalum. The compositions are shown in Table I. EXPERIMENTAL PROCEDURE Consumable-electrode vacuum-arc melting with ac power was used to produce small laboratory-sized, cylindrically shaped ingots (1-1/4 in. in diameter and 2 to 3-1/2 in. long) of the twenty compositions. A furnace was specially constructed to melt as many as four electrode rods simultaneously into molds lined with tungsten or tantalum sheet. High-purity rods of tungsten, tantalum, molybdenum, and columbium were used for consumable electrodes; the diameter of each rod was determined by the desired weight percentage of the component metal in a given alloy. The details of the construction and operation of the melting furnace will be discussed in another p~blication.

Jan 1, 1964

By W. N. Carr, J. R. Biard, B. S. Reed

An analysis of the semiconductor injection laser is presented which is based on a phenomenological model using device and material parameters. The intent of the laser threshold analysis is not to predict from theory the actual threshold current density but rather to provide a logical means of interpreting experimental results. The device and material parameters have been selected such that they describe both the threshold conditions and quantum efficiency of the lasev. A technique is proposed whereby the current required to obtain a population inversion is predicted from device 1-V characteristics. Experimental data are presented which support the analysis. THIS investigation is concerned with the characteristics of GaAs lasers fabricated in this laboratory. However, the assumptions used in these calculations should not limit their application to GaAs alone. It is felt that the analysis is sufficiently general to be useful in describing the operation of other semiconductor-laser materials. ANALYSIS heavily doped semiconductors to be considered. The absorption and/or generation of optical radiation may be completely specified in terms of q(E) and the probability functions f,,(E) and f,(E) which define the occupancy of the valence-band and conduction-band levels, respectively. The symbols used in this analysis are listed at the end. Following the approach of all' it can be shown that the effective gain coefficient, g, in the plane of a forward-biased P -N junction is g(E)=-ai@)[1-fv(E)-fc(E)] [1I In particular Eq. [I] holds for the photon energy at which lasing occurs, Ep. Throughout the following discussion Eq. [I] is considered only for the lasing transition E = Ep. For simplicity the functional energy dependence of the various factors is omitted in subsequent equations. Unless otherwise stated the symbols used represent the values at Ep. If the analysis is limited to the P-type side of the laser junction, the function q(l -f,,) is recognized as the band-to-band absorption in the P-type material at thermal equilibrium. Under forward-bias conditions the function f, is determined by the electron quasi Fermi level in P-type material. For sufficiently large forward bias the second term in Eq. [3] will become dominant and net gain will result; i.e., g will become positive. In order to simplify the subsequent analysis several assumptions are in order at this point. a) No conductivity modulation occurs. /„ is independent of f, and therefore go is a constant. b) The P-type material is heavily doped such that the degeneracy of the valence band permits popu-

Jan 1, 1964

By ZJ. H. Brophy, A. L. Prill, H. W. Hayden

The effect of Group VIII transition-element additions on the sintering of tungsten powders is shown to be dependent on the phase relationships of the particular tungsten-Group VIII metal alloy system. The acceleration of sintering with nickel additions is diminished by alloying nickel with copper which is known to diminish both the tungsten solubility in nickel and the solid-vapor surface energy. In work previously published on the effects of additions of Ni, Pd, Pt, Rh, Ru, and Ir, which form solid solutions or intermediate phases of wide composition width with tungsten, sintering behavior is independent of element concentration beyond that concentration necessary to form a continuous layer on the surface of the tungsten powders employed. The sintering behavior of tungsten with additions of iron or cobalt, which form intermetallic compounds with tungsten, is highly dependent on addition-element concentration. Additions in excess of amounts necessary to form continuous layers lead to successively decreased sintering rates. The effects of certain Group VIII transition metals on the sintering rates of tungsten at temperatures below those at which a liquid phase would be predicted have recently been investigated by the present authors1-4 It was found that small additions of palladium, nickel, rhodium, platinum, and ruthenium accelerate the rate of tungsten sintering. Additions of iridium decelerated the rate of densification compared to that of pure tungsten in the same temperature range. In all cases the rate of densification changed with increasing amounts of these additions, up to those compositions at which a continuous layer was formed on the surfaces of the tungsten-powder particles. The rate of densification was then independent of further increases of the compositions of any of these addition elements. These observations were consistent with a sintering model in which the addition element formed an interface with tungsten in which tungsten dif-fusivity was either greater or less than its grain boundary self-diffusivity. Kinetic analysis of this model indicated that linear shrinkage should vary according to the relation:

Jan 1, 1964

By B. J. Dalton

The Helium Research Center, Helium Activity, Bureau of Mines, is presently engaged in a critical examination of all of the PVT data on helium that appear in the literature. The long-range objective is the development of a single equation of state for helium that will allow all of the thermodynamic properties to be calculated and will reproduce all of the data within the accuracy with which the data arc known. A preliminary objective is to obtain the best val¬ues of the second virial coefficients and to develop an equation that will reproduce the best values as a function of temperature. The method of treatment consists in expressing the PV product of a gas, for a given isotherm, in terms of a power series in either the pressure or the density and evaluating the constants by least squares solution. Associated with these functions whose coefficients have been evaluated by least squares, the following errors, or deviations, are of interest; the standard error of a single measurement; the standard error in each coefficient; and the standard error of the resulting function.

Jan 1, 1964

By K. R. Janowski, H. Conrad

As part of a program to establish the effect of crystal imperfections on laser output, a detailed study was made of the dislocation structure of ruby crystals obtained from varioius sources. Using KHSO4 as an etchant, a detailed mapping of the dislocation structure on the (0001) and the (1150) planes was carried out. A less extensive study was made of the rhombohedral planes. The average dislocation density on the basal plane was 1.5 to 3 x 106 cm&apos;2 and on the (1120) planes -5 x 10&apos; cm-2. Howe7!er, considerable variation existed between areas on a given plane. The subboundaries in the basal plane tended to lie along [1100] type directions while those on the (1120) plane tended to lie: a) parallel to the basal plane, b) along truces of the (1101) plane, and c) along normals to the traces of the (0001) planes. The orientations suggest that mang of the dislocations lie on the (0001), (1701), and (1150) planes A Laue back-rellection nnalysis Of c-axis wander in one crystal revealed a gradual increase in misorientation from me end of the crystal to the other, with a maximum variation of 1°35&apos;. Slight etching of a mechanically polished crystal revealed mumerous polishing scratches, suggesting the existence of a plastic flow layer. It is recognized that chromium concentration, lineage, and other crystalline imperfections play a role in the efficiency of ruby lasers.&apos; Consequently, it is desirable to establish in detail the imperfection structure of ruby crystals to be used as lasers. Some exploratory work along this line had already been done by Barnes&apos; and Dils and Martin.&apos;" How- referred to as the morphological system, as described by Kronberg.4 The Miller indices given in the present paper will be based on this morphological system. In this system, the three common growth planes are the (0001), the {1120}, and the {1101}.5 Since these planes are of high stability, it is expected that they are most suitable for study by the etch-pit technique. In the present investigation, a detailed mapping of the dislocation structure was carried out for the (0001) and the (1130) planes. A less extensive study was made of the etch-pit structure on rhombohedra1 planes. An analysis of dislocations in sapphire (the ruby host) was first made by kronberg,4 who postulated that slip on the (0001) plane occurred by motion of dislocations with Burgers vector 1/3 <1150> and that these dislocations might dissociate into quarter partials. An etch-pit technique using boiling phosphoric acid was developed by Scheuplein and Gibbs6, 7 for identifying dislocations intersecting the (0001) planes and the planes near (2021) in sapphire. Al-ford and Stephens8 were able to reveal dislocations on the (0001) and {1120} planes in sapphire and ruby by etching in fused potassium bisulfate (KHS04) at 675°C. The termini of basal dislocations [(000l), <1120>] were revealed by Palmour and Kriegel9 on {1120} and {1010} by thermally etching sapphire. Bond and Harvey10 were able to decorate dislocations in sapphire by adding 1 pet by weight of ZrO2 to the Al2O3 powder used in the growth of the crystals by the Verneuil technique and then heating the grown crystals for 4 hr at 1500°C. They found, using optical transmission microscopy, that many dislocations had straight segments which were parallel to one of the six [1120] directions in the basal plane. Single dislocation lines curved smoothly from one alignment to the other, turning through angles of 60 to 120 deg. Also observed were isolated hexagonal loops, approximately 10 µ in diameter, the sides of which lay along the same directions as did the longer dislocations. MATERIAL AND ETCHING PROCEDURE The ruby specimens used in this study (all containing approximately 0.04 pet Cr) had been obtained from four different sources: Linde Co., Meller Co., Valpey Crystal Corp., and those grown at Aerospace Corp.* For the initial phase of this study, several specimens were cut from the slab shown schematically in Fig. 1 which had previously been cut from a disk boule obtained from the Linde

Jan 1, 1964

By J. H. Swisher

An experimental study has been made of the possible mechanisms for foam stability in the system CaO-SiO2-Cr2O3, where Cr2O3is the foaming agent. The degree of lowering of surface tension by Cr2O3 was determined at 1600 "C for high -silica melts. Measurements were also made of foam stability under standardized conditions. The results of the two sets of measurements then were correlated by applying the Gibbs and Marangoni theories of film elasticity. It was demonstrated that the Marangoni elasticity effect is probably the largest single contributor to foam stability, although the high uiscosity of&apos; silicate melts makes some contribution in controlling the rate of drainage of liquid from bubble lamellae. ThE tendency of metallurgical slags to foam has frequently been observed during steel-refining operations. In the open-hearth furnace,this tendency is considered undesirable because it slows down the rate of heat transfer from the burners to the molten-metal bath. On the other hand, it is sometimes desirable to have a "foamy" slag in the basic oxygen converter.&apos; A more effective blanket over the steel bath is made by a "foamy" slag, and loss in yield of metal due to splashing is minimized. In addition, a flush slag can be removed more easily in this condition. Since slag-foaming problems in the field have been attacked largely on an empirical basis, it appeared desirable to obtain a better basic understanding of the mechanism of foam stability. The experimental work was directed almost entirely toward the behavior of Cr2O3 as the foaming agent in CaO-SiO,-Cr2O3 melts. In the first stage of the investigation, the degree of lowering of surface tension by Cr2O3 was determined at 1600°C. The second stage consisted of measuring foam stabilities under standardized conditions. The two sets of experimental results then were correlated by applying various theories of foam stability. For convenience in interpreting the surface-tension and foam-stability results reported here, a portion of the CaO-SiO2-Cr2O3 phase diagram2 is reproduced in Fig. 1. EXPERIMENTAL 1) Surface-Tension Measurements. Very little information is available in the literature on the lowering of surface tension of slags by foaming agents. Kozakevitch 3 mentioned that the addition of 1.5 pct Cr2O3 lowered the surface tension of FeO slightly. In another system, some data on the lowering of surface tension of foaming slags by P2O5 were reported by Cooper and Kitchener.4 The technique used for the surface-tension measurements was the maximum bubble-pressure method,&apos; using a single tube immersed to various depths in the melt. This method has been used extensively in high-temperature systems, such as in liquid metals, slags, and glasses.6,7 It has the advantage that the contact angle between the liquid and the tube material need not be known. The equation used for calculating surface-tension values from maximum bubble-pressure measurements is the Schroedinger equatioq5 which can be written as follows:

Jan 1, 1964

By Walter Kawa

Bureau of Mines research on the hydrogenation of coal has been concerned with developing processes that could be used to supplement the Nation&apos;s petroleum and natural gas resources. Motor fuel was produced in a subsidized coal hydrogenation industry in Europe prior to 1945, but the process used is still not economical and other methods of producing liquid and gaseous fuels from coal are being investigated. As an aid to the planning of coal hydrogenation research, a literature survey was made of processes or methods of hydrogenating coal that differ from the subsidized or conventional process. This report contains a bibliography of unconventional methods of hydrogenating coal and a brief discussion of the economics of the conventional method. A general discussion of unconventional methods is included, and the advantages and disadvantages are pointed out where possible. The survey supplements a previous Bureau of Mines survey3 and a comprehensive review published in 1930.4

Jan 1, 1964

By J. E. Steiner, J. M. Hodge, M. A. Orehoski

Ingots of four steels (1045, 1080, Ni-Mo-V, and Ni-Cr-Mo-V) were cast at pressures varying from about 1 to 760 mm of mercury, so as to obtain a range of hydrogen contents in each steel. The susceptibility of these steels to flaking was evaluated by cooling hot-rolled blooms at a range of cooling rates, varying from water quenching to slag cooling, and studying the occurrence of flaking as a function of cooling rate. The steels exhibited differences in susceptibility to flaking, and a tlzreshold value for hydrogen content for each steel was found, below which the susceptibility was very low and above which the susceptibility increased markedly with increasing hydrogen content. Mechanical property evaluations, metallogvaplzic exantinations, and X-my diffraction determinations o,t retained austenite were made on samples from the blooms. A mechanism of flaking which is consistent with the observed behaviors, the effects of hvdrogen content, and the differences in susceptibility among the steels investigated is postulated, based on the results of mechanical property evaluations and metallographic and X-ray diffraction studies. ThE important role of hydrogen as a factor in the occurrence of "flakes" or "hair-line cracks" in steel has now been established by many investigations. These have included investigations by steel producers and forging manufacturers, to whom the prevention of flaking is a very real and serious problem, and many research studies aimed primarily at establishing the mechanism of this behavior Several investigators3 have reported that steels cast at reduced pressures (absolute pressures of about 1 mm) not only are low in hydrogen content but are essentially insensitive to the formation of flakes. These investigations have shown that a general relationship exists between hydrogen content and susceptibility to flaking. The difficulty of obtaining suitable samples of steels of a given composition with the desired range of hydrogen contents, particularly in the relatively large sections in which flaking most commonly occurs, has been the principal obstacle to quantitative evaluations of these relationships. Steels with intermediate hydrogen contents between 1 ppm, and the 4ppm or higher of air-cast steels are generally not available in commercially produced steels. Laboratory procedures, in which the hydrogen is introduced into solid steel samples by heating in a hydrogen atmosphere under pressure, generally involve a limitation in the size of the sample which can be treated, and thus are not representative of the behaviors in large sections. The availability of a facility at the South Chicago Works of U.S. Steel, in which several ingots could be cast from a single heat of steel at total air pressures ranging from 0.25 to 760 mm of Hg, has made it possible to overcome this obstacle and to obtain ingots of a given steel covering the intermediate range of hydrogen contents desired. These ingots, furthermore, are of a size suitable for the production of product with section sizes large enough to be representative of the products in which flaking most commonly occurs in commercial production. In these experiments, this facility was used to study the relationships between hydrogen content and the susceptibility to flaking of four steels, two plain carbon steels at 0.45 and 0.80 pct C and two low-carbon alloy steels representing a medium and a rather high hardenability level. These flaking studies were supplemented by evaluations of mechanical properties and by metallographic studies on samples from the blooms, in order to obtain pertinent information on the factors other than hydrogen content which influence the susceptibilities of these steels to flaking. Based on the results of these tests, a mechanism for the initiation and propagation of the flaking cracks, which is consistent with the observed behaviors, is postulated. MATERIALS AND EXPERIMENTAL WORK Steelmaking and Conversion. To provide material for the investigation, five 29- by 35-in., hot-topped, big-end-up ingots were cast from each of four 80-ton, basic electric-furnace heats of four different steels (a 1045 steel, a 1080 steel, a Ni-Mo-V steel, and a Ni-Cr-Mo-V steel). A double-slag practice was used on all steels and the two plain carbon steels were Si-A1 deoxidized with an addition of 2 lb of A1 per ton, while the Ni-Mo-V and Ni-Cr-Mo-V steels were deoxidized only with silicon and

Jan 1, 1964

By Charles R. Boardman

Recent underground nuclear tests in tuff, alluvium, salt, and granite have yielded data essential to the evaluation of mining applications of contained nuclear detonations. The data indicate that for these media the cavity radius is predictable within ±20% without regard to the properties of the rock in the immediate shot environment. Properties of the chimney of broken rock resulting from collapse of the cavity, on the other hand, are found to be related to the properties of the rock and its preshot structural weaknesses. Seismic effects and radioactivity distribution are sufficiently documented to serve as a basis for predicting the safety conditions associated with detonations for a variety of yields.

Jan 1, 1964

By H. L. Lovell

The growing production of fly ash with the many attendant problems of economics, disposal and potential uses suggests an urgent need to consider those properties which are basic in its beneficiation. Fly ash is extremely variable and heterogeneous in all respects except its fine size. Because of its production in huge quantities, it becomes significant as a potential raw material. Detailed data are presented describing particle size and shape, density distribution and magnetic characteristics. The major components include combustible residuals, magnetite and silicates. These data are discussed in terms of beneficiation processes and uses, The results of air classification to produce a uniformly fine-sized low combustible product are encouraging. It is proposed that major increases in the future use of fly ash, must involve some form of beneficiation. Both the coal producing industries and the consuming utilities would benefit from increased utilization.

Jan 1, 1964

By R. S. Kinasevich, D. D. Crabtree, D. W. Fuerstenau, T. P. Meloy, A. L. Mular

This paper presents details of the concept that size reduction in comminution machines takes place by three mechanisms; namely impact, abrasion, and chipping grinding. Experimental evidence is presented to show that each of these comminution mechanisms produces particles of a characteristic size distribution. The actual product from a comminution device has been postulated to be the result of a composite of these three types of mechanisms. Composite curves are demonstrated for a material following the Gaudin-Schuhmann, Gaudin-Meloy, and Rosin-Rammler size distributions. About forty years ago, Gaudin1 showed that grinding may be considered a combination of impact and attrition. Since that time, major efforts have been devoted to studies, both experimental and theoretical, of impact and compression fracture, while attrition has been almost wholly neglected, at least quantitatively. A significant attempt to distinguish between attrition and impact grinding is the work of Tanaka2 in Japan. By means of an instrumented abrasion grinder and a drop weight device, he determined coefficients relating the increase in surface area of various materials to the energy expended by the two methods of comminution. He showed that physical properties of a material determine its response to attrition and impact grinding. By extending his ideas to ball milling, he concluded that to a large extent the basic comminution process in a ball mill is due to the impact of falling media. Because Tanaka used a mass of particles in his drop weight device, however, he did not obtain pure impact size reduction. The purpose of this paper is to define basic mechanisms of size reduction, to verify that each has a characteristic and meaningful distribution curve, and to show how a combination of these mechanisms results in a size distribution very like that produced by grinding mills. DEFINITION OF COMMINUTION MECHANISMS The product from a grinding device will be considered to be the sum of the contributions resulting from the action of three basic mechanisms of size reduction which operate in a ball and rod mill. These are impact grinding and two forms of attrition, namely abrasion grinding and chipping grinding. Each is defined below. Impact Grinding: If a straight line is obtained when the cumulative weight fraction finer than a given size is plotted on log-log paper as a function of that size, the slope of the line is defined as the distribution modulus. A number of investigators 3,4,5 have shown that impact fracture of single specimens of different composition and shape results in a distribution of daughter particles that exhibit a distribution modulus of unity. This has also been true for materials broken in slow compression. Moreover, under slow compression or impact fracture conditions, theoretical distribution equations6*&apos; which approximate the Gaudin-Schuhmann distribution when the distribution modulus is close to unity agree reasonably well with the experimentally obtained products. If one now considers a comminution process where many impact or compression fracture events are taking place, then any rational summation of the individual events yields, in the finer size range, a Gaudin-Schuhmann distribution whose distribution modulus is also unity. If the size distribution of the product from a mill has a distribution modulus of unity, it is implied that particles are fractured in a manner which results in a comminution event having a distribution like that obtained for the breakage of single specimens. These impact events would occur when a particle is smashed between balls or between a ball and the mill liner. Attrition, on the other hand, is that form of grinding which cannot be called impact grinding, and comprises both abrasion and chipping grinding. Abrasion Grinding: Abrasion is a form of surface wear resulting when particles rub against each other or against balls or the mill liner of a tumbling mill, somewhat like a piece of wood being rubbed over a piece of sandpaper. The surface wears at a more or

Jan 1, 1964

This paper outlines the position and capabilities of Western Canada&apos;s bituminous coal industry, and indicates the increasing importance of Japan as an export market. The use of coal in Japan is reviewed, especially as regards future trends, and an appraisal is made of Canadian coal in comparison with domestic Japanese coal and imports from other countries. The importance of maintaining a solid nucleous within the Canadian bituminous coal industry is emphasized. I N RECENT years, Japan has emerged as a valuable market for Canadian exports. The first major product exported in volume to Japan was wheat, which has become very successfully established in Japanese markets. Following this, iron ore gradually found a market in Japan, with exports usually based on long-term contracts. This iron ore was produced entirely in British Columbia In 1958, the Western Canadian bituminous coal industry -jointly with the Dominion Coal Board -sent an official mission to Japan to investigate the

Jan 1, 1964

By C. C. Herrick

The vapor pressure of indium has been measured by the torque-effusion technique, as a function of temperature between 1102o and 1422oK. For liquid indium, the vapor pressure (in atmospheres) can be represented by the equation -R In P = 5.782 x104/T - 25.29from 1000o to 1422oK. Extrapolation yields a calculated normal boiling point of 2329°K and a heat of vaporization at 298 oK of 58.09 kcal per mole by the third-law method and of 58.39 kcal per mole by the second-law method. Calculations indicate that the free-energy functions of Hultgren are to be preferred to those of Guruich. BECAUSE of the potential uses of liquid metals, it is important that convenient experimental methods be developed which will lead to a sufficient body of thermodynamic data so that reasonable estimates of properties of liquid metals can be made. Indium is particularly well-suited to investigation, since it remains liquid over a long temperature interval, it alloys readily, suitable containers for it are easily procured, and relatively few investigations of its thermodynamic properties in the region above 1000°K have been made. PREVIOUS RESEARCH The first determination of the vapor pressure of indium was made by Anderson,&apos; using the Knudsen method and silica-lines stainless-steel cells. Kohlmeyer and spandau2 determined the normal boiling point, and a mass-spectroscopic investigation has been made by Lyubimov and Lyubitov.3 (Unfortunately, only an equation representing the data of the latter investigators has been available to us.) Hultgren et al.4 and Gurvich5 have published discordant tables of the free-energy functions for indium. EXPERIMENTAL METHOD The torsion-effusion principle has been described amply in the literature.8,7 With this method, one observes the angular deflection induced by effusion of vapor from a multihole effusion cell which is suspended from a filament producing a small rotational restoring force. The pressure within the effusion cell can be computed from the relation ziaifiai where k is the torsion constant of the filament, 6 is the observed angular deflection, and ai, fi, and qi are the area, force factor, and moment arm of the ith effusion orifice. The force factor f is analogous to the Clausing factor,&apos; and corrects for the reduction in effusive force attributable to the finite geometry of the effusion orifice. Schultz and Searcy&apos; have tabulated the force factors for various tube geometries. EXPERIMENTAL APPARATUS The physical arrangement employed in this study is shown in Fig. 1. The furnace elements are six Globar heat rods with 15-in. hot zones. Temperature is maintained to * 1°K by a Beck mechanism driving two 26-amp Powerstats in parallel. A Pt (Pt, Rh 10 pct) thermocouple serves as the sensing element. Four inner tubes act as vibration isolators; the air pressure required for maximum isolation was determined empirically, and is maintained by a solenoid valve. The tungsten fiber, 9 by 0.002 in., is joined to an 0.008-in. tungsten wire or graphite rod via a machined lightweight chuck.

Jan 1, 1964

THE purpose of this chapter is to present a general outline of the basic open-hearth process for the benefit of students, practicing open-hearth operators, and metallurgists who wish to review the subject. The discussion is limited to a description of the sequence and purpose of the operations, illustrated by data and examples. Subsequent chapters deal with more detailed and fundamental studies of the subject. The function of the basic open-hearth furnace is to convert various types of ferrous material into finished steel of given com- position and quality. In comparison with other steelmaking methods, the basic open-hearth process is one of the most versa- tile, both from the standpoint of the raw materials that can be used and the types of steel that can be produced. The process can be considered as a sequence involving melting, refining, and deoxidation. With some types of liquid-metal charges, the melting stage is not present, but refining and deoxidation in varying degrees are fundamental features of the process. GENERAL DISCUSSION OF BASIC OPEN-HEARTH PROCESS The first consideration in open-hearth practice is the type of charge on which the operation is based. This consists of three components-fluxing, oxidizing, and metallic materials. Fluxes. In the basic process the fluxing material is primarily lime, added in the form of either limestone (CaC03) or burnt lime (CaO) . This is supplemented by magnesia (MgO) and lime from the furnace bottom and banks. The function of these fluxes is to form a slag with the silica (SiO2) , manganese oxide (MnO), iron oxides (FeO and Fe203), and phosphorus oxide (P205) that are produced by the oxidation of varying amounts of the silicon, manganese, iron, and phosphorus in the charge during melting and refining. The slag, composed of the basic fluxes and the neutral and acid oxides, floats on top of the steel bath when the charge is melted. The composition of this slag depends on the amount of each slag-forming element present in the charge and on the extent of oxidation of these elements during the course

Jan 1, 1964

By Koch D. F A

An electrochemical study of the dissolution of gold in aerated cyanide solution shows that the dissolution rate is determined by the nature of the surface. A passive film (probably a basic cyanide) formed at -0&#183;6 V vs a saturated calomel electrode inhibits both the anodic dissolution of gold and the cathodic reduction of oxygen. Thallium has an &quot;activating&quot; effect on these reaction mechanisms.INTRODUCTIONIn general the dissolution rate of a solid in a liquid is studied by weight loss measurements or analysis of the solution at known time intervals. However, if the solid is a metallic conductor, on which a redox reaction can occur at the metal-solution interface, it can be studied by electrochemical techniques. Electrochemical measurements have the advantage that the overall reaction can be separated into its components, in some cases by electrical measurements alone, and in others by a combination of these with analytical determinations.The overall equation for the dissolution of gold in aerated cyanide solution may be written4Au + 02+ 8CN- + 2H20 = 4Au (CN)2- + 40H- ..... (1)which can be separated into the two electrochemical componentsrepresenting the oxidation of gold and the reductionof ogygen respectively.4Au + 8CN-,= 4Au(CN)2- + 4eand O2+ 2H20 + 4e = 40H- These two reactions occur at the gold-electrolyte interface and it is the purpose of this paper to discuss the mechanism...

Jan 1, 1964

By Timo Heikkinen

We have read, with great interest, Mr. Crocker&apos;s article on "Recent Trends in Autogenous Grinding," published in the October issue of The Canadian Mining and Metallurgical Bulletin. Referring to our paper, "Two-Stage Autogenous Grinding Investigations at Outokumpu," we can now report that last August we changed to this method at the Keretti concentrator. Prior to the conversion, the Keretti plant (see flow-sheet, Figure 1) had two primary rod mills, 6 ft. in diameter and 12ft. in length, in open circuit, followed by four secondary 9-by 12-ft. pebble grate mills in closed circuit with rake classifiers. Last summer, wl1en the Since August, grinding has been successfully carried out autogenously in two stages, with two mills being employed in the primary stage and four in the secondary. The size of the pebbles in the secondary mills is about the same as earlier -l V: i to 3 inches (Figures 4 and 5). Also, we generally prefer two-stage grinding to single-stage grinding because, in the former,

Jan 1, 1964

APPROXIMATELY 90 per cent of the steel that is melted and refined in the United States and poured into ingots is made in basic open-hearth furnaces, as shown in Table 1-1. The annual ingot capacity of the steel industry reported January 1, 1950, by the American Iron and Steel Institute3* was 99,040,160 tons, of which the basic open-hearth process accounted for 85,896,580 tons, 86.7 per cent of the .total. The capacity of the individual furnaces varies over a wide range, a large majority falling within limits of 50 to 200 tons (Fig 1-1). Most of the units constructed [ ] since 1942 are in the larger size groups, between 175 and 225 tons capacity.

Jan 1, 1964