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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'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'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'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 ' 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' 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 E. J. Koval

Practical miscible displacement processes will be characterized by lingering of the solvent into the oil. The lingering process is brought on by viscosity differences, and can be accentuated by channeling and longitudinal dispersion. The effects of these factors on the efficiency of unstable completely miscible displacements are combined in what is called the K-factor method. This method, analogous to the Buckley-Leverett method, predicts recovery and solvent cut as a function of pore volumes of solvent injected. Experimental data are included and show excellent agreement with theory for a wide variety of sandstone cores and viscosity ratios. INTRODUCTION Theoretical considerations,1 laboratory experiments,2 and pilot tests3 lead to the conclusion that miscible displacements in the field will be unstable In an unstable miscible displacement, the solvent fingers through the oil. This fingering leads to early breakthrough of the solvent and an extended period during which both oil and solvent are produced. For such a system, there appear to be four principal factors which bring about or accentuate the effects of instability: longitudinal dispersion (including geometrical effects), channeling, viscosity differences and gravity differences. Other factors, such as diffusion and flooding rate, can also influence the effects of instability, but at the flooding rates considered in this report, circa 15 ft/D, they are unimportant. Longitudinal dispersion can be thought of as a spreading of the solvent front caused by the presence of microscopic inhomogeneities. Channeling of the solvent occurs when a porous medium has macroscopic inhomogeneities; i.e., gross permeability variations. Viscosity differences lead to fingering of the less viscous solvent. This difference in viscosity accelerates the growth of fingers along paths previously developed because of permeability variations. Gravity differences lead to overriding by the usually less dense solvent. Al- though gravity effects are generally small at a flooding rate of 15 ft/D, they would, nevertheless, unnecessarily complicate the interpretation of flooding experiments. For this reason, all the experiments reported herein were done with matched density fluids. Fingering and the resultant poor areal sweep were recognized early as the dominant influences on the efficiency and the economics of miscible displacement processes. Much research effort has been spent on ways to minimize fingering and increase areal sweep such as the use of graded viscosity slugs4 or water slugs. Some researchers attempted to work out ways to prevent fingering completely; i.e., to achieve a stable displacement through gravity or latitudinal dispersion stabilization. l Others did not attempt to control fingering but obtained an economic process by merely recycling the solvent and sweeping pattern by pattern.6 During this period, all aspects of fingering came under close scrutiny. Some researchers reported on how fingering looks2 and how it is affected by viscosity ratio,7 geometry,7 and slug size.2,* Peaceman and Rachfordg suggested a mathematical approach to the prediction of unstable miscible displacements in relatively homogeneous sand packs, but their work cannot be extended conveniently to heterogeneous systems. Hence for a heterogeneous system, no method is presently available for predicting solvent cut and recovery as functions of pore volumes of solvent injected. The purpose of this investigation was to attempt to fill in the gap in our knowledge concerning the prediction of performance of unstable miscible dis placements. Necessarily, the system selected for study was a relatively simple one. The restrictions placed on the system were: (1) The system was linear; (2) The solvent was miscible in all proportions with the oil in place; (3) The solvent was continuously injected into the porous medium; (4) Gravitational effects were eliminated by matching densities and (5) All the flood rates were high and constant at 15 ft/D to avoid any small rate effect and to minimize any diffusion effects. To simplify and to indicate that both longitudinal dispersion and channeling arise from permeability variations, the effects which they cause or influence have been termed heterogeneity effects. The use of

By D. F. Lascelles

D. F. Lascelles (School of Earth Sciences, MacQuarie University, North Ryde, N. S. W., Australia)- The paper contains many misconceptions commonly held by both geologists and soil scientists with regard to soil processes. The analogy between supergene copper enrichment and "nickel laterite" deposits is quite apt and the use of nomenclature from the former in describing supergene nickel deposits is justified. However, care must be exercised with regard to the notable differences in

Jan 1, 1974

By Howard A. Meyerhoff

In western Argentina, in the Province of Mendoza and the Territory of Neuquen, there is a series of solid bitumen deposits which are claimed to be the most extensive in the world. In a linear belt 500 km (311 miles) long, roughly paralleling the axis of the Andes but occupying a variety of positions with respect to the orogenic structures, more than 100 outcrops have been reported. Approximately 70 of these have been prospected, and some mining has been planned or attempted for about half this number. Limited tonnage, high sulphur content, inaccessibility, labor shortages, and disastrous fires have taken a heavy toll among these operations, and in 1947, only 4 deposits were being actively mined, but 8 more were being explored and developed with a view to placing them in production. Inasmuch as these deposits are currently yielding a substantial fraction of Argentina's limited domestic supply of solid fuels, a brief account of the deposits and of the small industry based upon them will provide a commentary on Argentina's fuel problem. Character of Solid Bitumens The solid bitumens of Mendoza and Neuquen are petroleum derivatives, as is indicated by the following ultimate analysis : Constituents Per Cent Hydrogen.................... 6.8 Carbon...................... 82.4 Nitrogen..................... 1.6 Oxygen...................... 2.7 Sulphur...................... 2.2 Ash.......................... 4.3 100. 0 In physical appearance they bear a close resemblance to coal and are commonly called carbon. Their specific gravity has an extreme range of 1.10 to 1.777 in 36 samples weighed, but the average is between 1.14 and 1.24. The material is black, lustrous to dull, with blocky to sub-con-choidal fracture. Though brittle, the purest material is softer than anthracite and exhibits slightly more cohesion. This bituminous material is generally known as asfaltita or asphaltite, but definitive chemical studies indicate that the term asphaltite or grahamite can be applied correctly only to the exceptionally pure material of the Auca Mahuida district in Neuquen. Some other name should be used for the chemically variable bitumens found in all other districts, and the designation "asphaltitic pyrobitumen" has been proposed by Carlos A. S. Piscione.1 At the present time these bitumens are finding favor as solid fuel and as a gas-producing medium. They yield heat values of 8650 to 9750 cal,2 or 14,500 to 16,750 Btu per pound, and in consequence of their excellent heating qualities and the scarcity of imported coal, they are marketed as far away as Buenos Aires at a price of go to 95 pesos, or approximately $22 to 23, per metric ton. In burning, the material swells and decomposes into solid, fluid, and gaseous fractions which burn violently though nonexplosively. Its combustibility has been responsible for disasters and virtually complete destruction at Mina La Es-peranza and Mina Santa Marta, and for minor mishaps elsewhere, as at Mina Escondida in August 1947.

Jan 1, 1949

By Howard S. Lee

In central Colorado is a great belt of intrusive porphyry nearly 100 miles long (160 km.), extending from the Clear Creek district on the north to Aspen on the south, which includes many of the well known mining camps of the state. Near the southern end of this belt, at Leadville, the occurrence of these intrusives is most marked, resulting in intensive mineralization and the formation of a great variety of large orebodies. During the past 40 years, Leadville has been a steady producer of gold, silver, lead, zinc, manganese, iron, and bismuth, in the forms of sulfide, carbonate and oxide ores. It is the purpose of this paper to discuss pyrite alone, which, under present economic conditions, is valuable chiefly for its sulfur contents. The ore-bearing formation of the Leadville district consists of two beds of limestone separated by a layer of quartzite. The upper limeatone is carbonaceous, and is known locally as the blue limestone. It varies in thickness from 50 to 300 ft. (15 to 91 m.). The lower limestone is Silurian, known locally as white limestone, and is about the same thickness as the upper bed. Underneath the Silurian limestone is a layer of Cambrian quartzite from 100 to 250 ft. (30 to 76 m.) thick resting on Archean granite, which forms the limit of ore deposition. As a rule, there is a sheet of white porphyry above the upper, or blue limestone; a sheet of gray porphyry is associated with the blue limestone, either in or below it, but the porphyries are not so regular as the quartzites and limestones and are not always found in their expected positions. Throughout the district there is an elaborate system of faults and intrusive porphyry dikes, which have an important bearing on ore deposits. The writer has seen two or three orebodies which were not closely associated with either a fault or a porphyry dike, but if the minor fractures and water courses are considered as part of the fault system it is safe to say that all orebodies are directly traceable to one or both of these causes. The distribution of pyrite in the Leadville district is quite general; but, eliminating the smaller bodies and those containing prohibitive quantities of zinc or lead, and considering only the larger deposits commercially valuable for their sulfur, we find the chief pyritic ore-bodies extending in a zone approximately 6000 ft. (1828 m.) long and several hundred feet wide, from the Yak and Moyer, on the south; through the Louisville, Greenback, Mahala, Adams, and Wolftone, on Carbonate Hill; across Yankee Hill, and into the Quadrilateral, Denver City, and Tip Top, on Fryer Hill.

Jan 1, 1920

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By Alexander B. Morris

Studies such as the investigations into the solubility of gases in crude oil under various conditions, which have been carried on during the past three or four years, are very interesting from an academic point of view, but this consideration alone is hardly sufficient to warrant the large contributions from the industry necessary to maintain them. Some definite benefit to the industry as a whole should be forthcoming. The purpose of this paper is to direct the attention of company engineers, and company executives, to some of the ways in which the information gained from these studies can be made directly profitable. This work has two principal economic aspects. One affects the investment budget, and through it the financial requirements of the companies. The other affects operations, and through this course is reflected in current earnings. It will be shown that, as a direct result of the investigations into gas solubility, undertaken in the recent past by various investigators, it is now possible: 1. To determine more accurately the amount of reservoir oil originally present. 2. To obtain closer control on operating conditions, to effect more economical recovery. 3. To predict earlier and more dependably when and how much surface lifting equipment will be needed. 4. To reduce, or entirely avoid the very large investment in gasoline recovery equipment now frequently found necessary. 5. To control the gravity of the pipe-line oil so as to secure the greatest possible revenue from the products of the well. 6. To effect the recovery of a large amount of gasoline now wasted while the practicability of a gasoline recovery system is being decided. 7. To plan operations, by comparison with the history of old properties operated without this new information, so as to avoid the mistakes of ignorance made in the past. These points will be discussed in the following pages, though not necessarily in the order stated. There is so much overlapping of the points themselves, and of the data from which they have been drawn as conclusions, that to treat them in any particular order would require

Jan 1, 1935

By A. J. Opinsky

MANY investigators, in their discussions, have reasoned that the ductile-brittle transition in iron could be explained by the intrusion of cleavage into the normal slip process. The purpose of this note is to apply the laws of critical normal stress for cleavage and critical shear stress for slip to explain the orientation and temperature dependence of the ductile-brittle transition in body-centered cubic metals. It will be found that within a certain temperature range, single crystals tested in tension will cleave or slip, depending on their orientation. Some data recently appearing in the literature will be analyzed from this standpoint. For a single crystal with [uvw] parallel to the tensile axis, the resolved shear stress on the slip

Jan 1, 1954

By H. F. Webster, C. G. Dunn

Rolling md annealing procedures are described for developing the (110) preferred orientation in tantalum for use as a thermionic-emission materinl where electrodes of a uniform high work function are needed. The development of a (110) [001] annealing texture is also reported. A preferential growth process due to low (110) gas-metal surface energy is considered in explanation of the observed growth of (110) grains. ThE growth of (110)-oriented grains in thin strips of rolled zone-refined tantalum, previously discussed briefly,' is reported together with more recent information on the formation of a (110)[001.] annealing texture, i.e., one where the [001] direction of each grain lies close to the rolling direction. The development of tantalum sheet with a (110) preferred orientation (position of [001 ] directions unspecified) is of importance as a thermionic-emission material in thermionic-energy converters. Since therm ionic-emission properties of cesium-coated crystals vary over a wide range depending on (hkl) a2-7 a single (hkl) preferred orientation is more useful than either several preferred orientations or none. Furthermore, the (110) preferred orientation yields the highest thermionic-emission density for a cesium coverage of less than a monolayer.5-7 A consideration of the stability of the grain structure needed at high operating temperatures suggests that the preferred orientation itself should be produced by annealing processes. Information on annealing textures in tantalum, however, is rather limited. Pugh and Hibbard 8 obtained (111)[112] and (lll)[112] components in a 1400°C recrystallization texture in 95 pct cold-rolled foil; these components were enhanced on annealing at 2500°C. Muller9 rolled 99.97 Ta to 90 pct reduction in thickness in the final stage and noted only a slight sharpening of the rolling texture, with some intensification of the (111)[112] component upon annealing at 1200°C. The experimental procedure followed in the present work stemmed from the idea of using possible differences in (hkl) surface energies to provide a small driving force for growth of grains having the lowest (hkl) surface energy.l0* This would mean using high-purity tantalum processed into thin sheet form and annealed at high temperatures either in a noncontaminating atmosphere or in one producing additional sample purification. EXPERIMENTAL Zone-Refined Tantalum. National Research Corp. tantalum in the form of 1/8-in.-diam rod and of 99.98 purity (53 ppm 0, 15 ppm N, and 8 ppm C) was zone-melted four times. The traversing speed was 4 mm per min. Such treatment increased the resistance ratio, R293k/R20K , where R293K is the resistance of the specimen at 20°C and R20K the re-resistance at liquid-hydrogen temperature, from a value of 25 for the initial rod to 175 for the zone-refined rod (the increase in the resistance ratio provides a measure of purification11,12). Part of a zone-refined rod was rolled unidirec-tionally to a strip 0.003 in. thick and 0.28 in. wide. Samples were given anneals in the range 1300" to 2100°C using ac conduction heating in an oil-free vacuum system. Recrystallization to small grains appeared to be complete at 1300°C. Large grains were formed at higher temperatures, but these were not entirely strain-free, some grains showing asterism in Laue X-ray patterns and some displaying a range in orientation. Part of the difficulty was caused by thermal expansion of the tantalum strip as it was held between fixed supports. However, in a different arrangement with the tantalum freely suspended in a tantalum can, high-frequency induction heating in vacuo at about l0-6 Torr produced

Jan 1, 1964

By A. D. Marlin, A. J. Gentile, E. F. Jordan

Metallurgical changes in SAE 52100 ball-bearing components resulting from overload testing are described. Changes in microstructure, hardness, and resiclctal stresses crre discussed zuitlz re.ference to material cleanliness obtained by various steel-melting practices and are compared with work by otlzer investigators. Evidence is presented to show that the initialion and development of microstruc-tural alterations are characterized by two separate reactions: the appeavance of a "dark etchingJ' constituent, and "gray lines" or a light etclzing constituent. The dependency of these tzvo reactions on material cleunliness, running tirne, and contact stresses is discussed and a failure mode related to material cleanliness and microstructural transformation is proposed. THE study of ball- and roller-bearing contact fatigue has been paced by a strong emphasis on bears ing application performance. Particular attention has been paid to conditions that effect the spalling-type failure that is characteristic of rolling contact fatigue in through-hardened components. Some of the conditions investigated are lubrication and atmosphere,1-3 material characteristics and finish,475 and speed and design fa~tors."~ A typical spalling-type failure is shown in Fig. 1. The arrow shows the motion of the ball relative to the inner-ring race surface. The leading edge of the spall is usually sharper than the trailing edge. The race surface near the trailing edge also shows small dents caused by debris from the spall. In this type of testing very little metallurgical investigation is done on failed bearings. Emphasis is placed on test conditions and statistical analyses of endurance data. More basic work has been done relating micro-structural changes to fatigue performance. Dyer" and Wood, Cousland, and sargant9 have used mostly simple materials, such as single crystals and single-phase polycrystalline specimens, under simple alternating strain to identify a systematic process of fatigue damage. drutowski" was concerned primarily with the relationship between steel structure, contact stress, and energy losses in rolling contact. dones11 and Bush, Grube, and Robinson12 utilized changes in microstructure and residual stress in overload-tested rolling contact elements as a means of investigating the fatigue process. Work is being done on an ASME-sponsored contract,13 using both simple and complex materials, but there is still a long way to go before such theories as pore and void growth in simple structures can be applied to the relatively complex bearing steel microstructure. The purpose of this paper is to report on an investigation into the effect of steel cleanliness on the structural alteration and residual stress changes found in overload-tested ball bearings. Using these results and those of previous investigators, we will propose probable failure mechanisms in both overload- and normal load-tested ball bearings.14,15 PROCEDURE Ball bearings? 3208 size, were fabricated from SAE 52100 steel obtained by five different melting practices. The melting practices, chemistry, and inclusion ratings for the five lots of steel are summarized in Tables I and 11. The nonmetallic inclusion ratings were determined by the Jernkontoret method described in ASTM E45-51 Method A. This technique consists of microscopically examining a series of polished samples taken from specified locations in the ingots, billets, or bars. Each sample is surveyed at XlOO magnification and the inclusion types and sizes are compared to standard fields. Because of the nature of these ratings all values in Table I1 are rounded to the nearest half. The elec-

Jan 1, 1965

By H. I. Aaronson, H. A. Domian, A. D. Brailsford

A current study of the growth kinetics of k (hcp) plates in a Cu-Si (fcc)' has generated a requirement for data 02 the chemical interdiffusion coefficient in a (termed D,) as a function of temperature at the composition of the a/a + k pJase boundary. Rhines and Mehl 2 have determined D, as a function of composition at lower silicon contents by making Matano analyses of concentration-penetration curves. However, the accelerating increase in B, which they demonstrated as the phase boundary composition is approached at constant temperature and the rapidly diminishing accuracy of this analysis as the limiting compositions of a diffusion couple are approached (the silicon-rich component of their couples contained appreciably less silicon than is permitted by the solubility limit) indicate that the required information cannot be safely obtained by extrapolation of their data. Although the quite different method employed in this study is not exact, it will be shown that the approximations made are not serious ones, particularly from the viewpoint of the prgcipal application anticipated for these data. D, was determined from the migration kinetics of the a :k boundaries formed in sandwich-type diffusion couples produced by welding a block of high-purity copper to opposite sides of a cube (* in. on edge) of homogenized high-purity Cu-5.82 wt pct Si alloy. The alloy is pure k in the temperature range employed. The surfaces of the couple components which were normal to the diffusion direction were machined accurately flat and parallel, lightly polished, and carefully cleaned. Welding was then accomplished by means of the vacuum-encapsulated pressure jig technique previously employed.3 Welding was always conducted at the intended diffusion temperature; thus the welding anneal also served as the first diffusion anneal. Subsequent diffusion anneals were performed in evacuated Vycor capsules. Following the welding anneal, one of the surfaces parallel to the diffusion direction was machined, ground, and polished flat; additional material was removed from this surface after each diffusion anneal in order to avoid any effects of composition changes. After etching,4 the average distance between a : k boundaries was measured by means of a traveling microscope with an accuracy (per measurement) of better than 1 p. Satisfactory results were obtained at four temperatures in the range 775° to 655°C; attempts to obtain data at two lower temperatures were unsuccessful, evidently as the result of the interference of surface contamination during the welding process.

Jan 1, 1969

By Robert Glass Cleland

[PARTIAL LIST OF DIRECTORS OF THE NICHOLS CHEMICAL COMPANY AND NICHOLS COPPER COMPANY: G. H. Nichols William H. Nichols, Sr. William H. Nichols, Jr. Charles W. Nichols E. Remington Nichols George Martin Luther John Brown Francis Herreshoff]

Jan 1, 1952

By R. S. Montgomery

Laboratory experiments simulating rock drilling were conducted on a number of commercial grades of tungsten carbide in order to determine their wear rates when they are used as inserts in percussive rock drill bits. The test rock was Barre granite and tests were made at conditions similar to those of the carbide buttons near the periphery of a large, down-hole, button bit. In addition, some wear rate measurements were made at a low blow energy. Wear rates of these carbide buttons were an extremely sensitive function of their cobalt contents and hardnesses and were proportional to e-°.57Hup to a hardness of about 91 RA. The point of minimum wear rate, which occurs at about 92 RA, corresponds to the point of maximum compressive strength. Modern percussive rock drill bits have inserts of cemented tungsten carbide on their wear faces. These inserts have drastically reduced bit wear in comparison to that of earlier all steel bits. The most common cemented carbide grade used in percussive rock drill bits contains about ten weight percent cobalt, although grades containing more or less cobalt are also used. Contrary to the case with carbide in metal-cutting tools, alloying materials are rarely used in mining grades. There are a number of designs of rock bits in current use. The most common form is an X bit which has four chisel-form radial wings. The button bit is another important design and one which has been recently developed. This design uses a flat steel face studded with relatively small hemispherically tipped carbide buttons. These types are illustrated in Fig. 1. Studies have been made of the sliding wear of cemented tungsten carbide on rock 1-4 and multiple-impact fracture', 5-6, b~t there has been comparatively little published on the percussive wear of this material although the wear of the impact face is the most important. There is some available data on the rate of dulling of rock bit inserts in actual drilling 7 but no laboratory studies. Sliding wear studies are useful for understanding the wear of coal and mineral cutting tools and gauge wear of percussive drill bits. but the

Jan 1, 1970

By T. P. Papazoglou, N. A. D. Parlee, W. C. Phelps

HE high vapor pressures of metals such as lead, calcium, lithium, bismuth, and magnesium at steel-making temperatures present experimental problems which have thus far rendered it almost impossible to obtain really reliable data for their solubilities in liquid iron. Many investigators have attempted to equilibrate liquid iron in the same crucible with the undissolved liquid phase of such volatile metals. The published results,l-6 although useful, are often questionable on the grounds of not being obtained under true equilibrium conditions. Such information is not always of practical value in any case since the equilibrium vapor pressure is often several atmospheres and steel is not currently made at these pressures. Solubility measurements at lower partial pressures (< 1 atm) appeared to be more practical and easier to make. These data could be used to calculate solubilities at other pressures where Henry&apos;s Law is obeyed, and to estimate solubilities under other conditions of temperature and pressure with useful accuracy. This note outlines the development of a general technique for the measurement of solubilities in systems of this kind. The method involves equilibration of the high-boiling metal at known temperatures with the vapors of a low-boiling metal at known partial pressures. Analyses of quenched samples provide vapor pressure-solubility data and make calculations of alloy thermodynamics possible. The principle involved is similar to the closed-system diffusion-transport method which is difficult to apply with most high-melting liquid metals like iron, due to closure problems. A two-zone horizontal (molybdenum wire element) tube furnace, Fig. 1, provides two constant-temperature zones in a reaction tuve (3/4 in. ID by 1 in. OD by 36 in.). A high-boiling metal sample, 9, introduced in the higher-temperature zone, is maintained at temperature T1, and a volatile metal sample, 7, in the lower-temperature zone, is held at T2. A stream of argon with 10 pct hydrogen is passed via flowmeters, 1, and mixing-drying towers, 2 and 3. through the reaction tube at a favorable flowrate and acts as a carrier gas which entrains vapor from the volatile liquid metal at a specific constant partial pressure. The gas mixture passes through a system of constrictions, 6 and 8, to the higher-temperature zone, establishes intimate contact with the high-boiling liquid sample, 9, and exits through a small condenser tube. The entire system is at (nearly) atmospheric pressure and the volume of carrier gas passed is measured with a wet gas meter. When the high-boiling sample attains equilibrium with the vapor phase, both samples are removed and quenched. Analysis of the high-boiling sample for solute content reveals its solubility for the low-boiling metal at a vapor pressure calculated from carrier-gas volume and either a) weight loss of volatile metal or 6) weight gain of high-boiling sample plus condenser (which collects the undissolved vapors). To test the capabilities of the method, liquid silver at 1403&apos;C was equilibrated with lead vapor at various partial pressures. The relatively simple Pb-Ag system was particularly suitable for uncovering experimental problems and providing the first step toward investigations with more volatile metals and more difficult combinations.

Jan 1, 1965

By D. W. Levinson, L. E. Tanner

DURING the course of an investigation of the zirconium-iron-tin system the zirconium-iron system was reexamined up to 55 pct* Fe. The alloys pre- visible melting3 and X-ray diffraction studies were made of samples of the alloys. The ferromagnetic properties of ZrFe2were determined by Professor P. W. Selwood* using a modified Faraday balance.4 The zirconium-rich portion of the phase diagram is presented in Fig. 1 and compared with the work of Hayes et al.1 The maximum solubility of iron in ß is somewhat decreased while the eutectic temperature is raised. There seemed to be no change in the eutectic composition of 16 pct Fe. Since the base material was so low in iron content, it was possible to establish the maximum solubility in a between 0.017 and 0.025 pct Fe at the eutectoid temperature. The observation of fine ZrFe, particles in the micro structure of a specimen of 0.012 pct Fe alloy quenched from 700°C indicated that the solubility drops below this composition at 700° C and lower. Further study was made of the intermediate phase ZrFe2. wallbaum5 identified the compound initially as ZrFe2 with a C 15 (MgCu2) structure, placing it at 55 pct Fe stoichiometrically. Hayes et al.1 believed they found the phase at about 47.2 pct Fe and called it Zr2Fe3 but reverted to ZrFe, in the discussion of their paper.6 Jordan and Duwez7 confirmed Wallbaum&apos;s work as well as finding the same single-phase structure to about 62.3 pct Fe or Zr0-61 Fe2-18. In order to establish the ternary phase relations in the zirconium-iron-tin systema the exact position of this phase had to be known. This was accomplished by X-ray diffraction, visible melting, and metallographic techniques. Elliott8 obtained a single-phase ZrFe2 X-ray diffraction pattern from an alloy of about 55 pct Fe. This was confirmed in the present study with an alloy of 54.81 pct Fe. However, extra lines (attributable to a or ß zirconium) were found in diffraction patterns of the 47.42 and 49.83 pct Fe alloys. The melting characteristics of these same alloys were studied by suspending 47.42, 49.83, and 54.81 pct

Jan 1, 1960

By R. C. Gifkins

R. C. Gifkins (CSIRO)—In this paper evidence is put forward to support the idea of grain boundary shearing in aluminum at 4.2°K and the phenomenon is explained in terms of a low-temperature "equicohesive temperature". It is stated that these findings show that grain boundary shear cannot be ruled out in any situation by temperature arguments alone. We believe, from our own recent study of "apparent grain boundary sliding&apos;&apos; at temperatures below 0.45 Tm, that it can be ruled out on temperature arguments alone.45 Our experiments were made principally with magnesium and a Ms-A1 alloy ("Magnox A12"). Careful examination of offsets of marker lines or steps at grain boundaries produced by deformation at room temperature (-0.3 Tm) showed many of these to result from curvature over narrow zones along the grain boundaries. A significant residuum did, however, appear as a sharp offset or step. It was found that the mean value of this step rose to a small value during the first 0.5 to 1 pct strain and then remained at this level with further strain. Moreover, exactly the same values were obtained (at the same stress) at 75°C instead of 21°C. That is, in this range of temperature the "apparent sliding" was not temperature-sensitive. At 125°C and above there was sliding which increased with strain and which was temperature-dependent. When this temperature-dependent sliding was used to calculate the sliding to be expected at room temperature, this underestimated the "apparent sliding" by a factor of 104. The conclusion drawn is that the "apparent sliding" consists of shear localized in a zone of a width measured perhaps in microns, whereas it seems that true sliding occurs on the boundary surface.46 A model for such localized shear has been developed in general terms, following a similar model of Urie and Wain.47 Other strong evidence for low-temper- ature sliding has been based on the offsets of marker lines consisting of a substructure seen using the electron microscope to resolve these.48 We have repeated this work and found that the effects can be accounted for in terms of cracks in an oxide film which is produced when the substructure is etched up; these cracks form over zones of shear rather than at actual interfaces. However, in aluminum at room temperature (-0.3 Tm) there is no "apparent sliding" which is optically detectable. We suggest that, when the temperature is much lower (and possibly the rate of strain higher, too), as in the experiments of Chin et al., then aluminum behaves like magnesium at room temperature, and a narrow zone of shear develops to accommodate differences in strain across the grain boundary. Such a zone could well give rise to triple-point cracks. It is hoped to investigate these suggestions further. B. Y. Chin, W. F. Hosford, Jr., and W. A. Backofen (authors&apos; reply)—It is interesting to have Dr. Gif-kin&apos;s comments, although it is somewhat difficult to reply in detail without the reference containing the work that he describes. Apparently though, he does find a low-temperature temperature-independent sliding that would seem to be related to the observations reported here. Perhaps some of the difficulty has semantic origins, growing out of the distinction between (&apos;true sliding" and "apparent sliding".

Jan 1, 1965

By J. B. Dilworth

I. INTRODUCTION. THE purpose of this paper is, first, to give a general account of a little-known coal-district of SE. Kentucky, its topography, drainage, and mineral resources, for those who may be interested in its economic development; and secondly, so to describe the geologic features of the field as to furnish available data to those engaged on the broader problems of Appalachian coal-geology. The data from which the major portion of the paper has been prepared were obtained, in professional investigations for private individuals and corporations, within the last decade. The area under review, defined by a heavy line on the map, Fig. 1, lies between Little Black and Pine mountains, and extends from Harlan on the west to a N-S. line crossing Looney creek 3 miles from its mouth on the east. This area can be divided for description into a Western and an Eastern Division. The character of investigation pursued in the Western Division, below Fugitt creek, was very different from that employed in the Eastern. In the former, only a rapid reconnoissance was attempted : such coal-openings as had been made by prospectors or by citizens in obtaining fuel were visited, their sections measured and, in many instances, sampled. Elevations were obtained barometrically and approximate locations sketched on a small-scale map. In a field where the coals are so well opened, the reconnoissance method gives a very fair idea of the number and character of the principal beds and their relative positions, and affords much evidence for their correlation over wide areas, without permitting the more refined work required to discover all the seams of the measures and to determine the details of geologic structure.

Feb 1, 1912

By R. P. Aikman, F. G. Miller, J. M. Podgursky

As part of a larger study of the mechanism of froth flotation of coal, the rates at which coal particles of various size and specific gravity react to froth flotation were investigated. Results of this study show that in flotation: I) recovery rate increases, but selectivity decreases with a decrease in particle size down to 100 mesh, and 2) recovery rate is constant for all sizes between 100M and 325M. n response to the growing demand for low-sulfur coking coal for iron making, the coal industry is continually striving to perfect methods for cleaning coal to acceptable ash and sulfur levels while maintaining maximum product yield. By present standards the industry has adequate processes for cleaning coarse coal, i.e., + 28 mesh, at almost any desired specific gravity. However, in the case of fine coal, i.e., —28 mesh, neither of the two existing processes - froth flotation or hydrocycloning — in its present state of development yields products that are comparable in ash and/or sulfur content to products normally obtained from coarse coal processes. The work outlined in this paper is part of a larger study directed toward maximum exploitation of froth flotation for fine coal processing. The concepts and data presented are now serving as a basis for designing fine-coal circuits in which improved efficiency is obtained by optimum use of froth flotation with other fine-coal processing methods. The paper includes: 1) A discussion of the value of a detailed wash-ability study as a method of assessing the problems associated with fine coal processing, 2) A general discussion of hydrocyclone principles, included to serve as a basis for understanding the mechanism of coal flotation, and 3) A detailed discussion of the mechanism of coal flotation, as well as the research leading to the optimum use of froth flotation in combination with other fine-coal cleaning methods to provide efficient fine-coal processing. Our study of the rates at which coal particles of various size and specific gravity react to flotation shows that in flotation: 1) recovery rate increases but selectivity decreases with a decrease in particle size down to 100 mesh, 2) recovery rate is constant for all sizes between 100 mesh and 325 mesh, and 3) the flotation process effectively rejects only those extremely fine particles which do not contain surface carbon. (Because of this feature, froth flotation is an excellent method for rejecting clays - the only extreme fines in - 325-mesh coal that are always carbon free.) Washability studies of flotation products are used to assess flotation efficiency. These studies show that: 1) the increase in percent sulfur in flotation products above the theoretical sulfur content as defined by the washability study is due almost entirely to flotation of fine high-specific-gravity particles that are part coal and part pyrite, and 2) in a given size range particle floatability decreases with an increase in particle specific gravity. Error curves are explained and are used to compare the mechanisms of coal flotation and hydrocycloning. These comparisons show that hydrocyclone performance is affected primarily by particle mass, i.e., particle specific gravity and size, whereas coal flotation performance is dependent on both the particle mass and the coal surface available for bubble attachment. Since the error curve is a basic tool for rating the efficiency of any coal processing system, it will be useful to quickly review the principles of error curve construction. RATING COAL-PROCESSING EFFICIENCY BY THE ERROR CURVE The organic component of coal is of lower specific gravity than its impurities, and the most effective principle for coal concentration is therefore separation on the basis of specific gravity. However, since there is no sharp dividing line between pure coal and pure ash components, specific gravity must be closely controlled if the product is to have acceptable quality at maximum yields. In turn, the basis for close control in any coal processing system is the reference standard provided by precise laboratory washability studies. In these studies, coal is carefully separated into a series of progressively higher specific gravity fractions to establish a relationship

Jan 1, 1968

By O. R. Morris, G. L. Hawkes

A galvanic cell, using as electrolyte a fused salt solution of calcium carbide and as electrodes carbon and a Fe-C alloy of known composition, has been set up to study the thermodynamics of Fe-C alloys in the temperature rmzge 800" to 1000°C. Time independence and reproducibility of the cell electromotive force were taken as evidence of the reversible behavior of the cell. Carbon was believed to be present in the electrolyte as the so-called acetylide ion, C;-. The plots of the cell electromotive force us temperature for a specific alloy composition were straight lines within the limits of experimental error. The average Partial molar enthalpy of carbon in iron relative to pure carbon was found to be +10,610 i 93 cal per g-atom C. Thermodynamic analysis of the data has led to the following equation for the carbon activity, ac, based upon pure carbon as the standard state: In ac = In Zc + 10,560/RT + (10.02 + 77O/T)ZC - 2.350 where ZC is the lattice ratio [nC/(nF, - nc )] and T is the absolute temperature. This equalion gives carbon activity values generally slightly lower than those from gas equilibration studies reported in the literature. METAL LOGRAPHIC examination of a polished cross section of the steel anode used in the electrolysis studies of fused salt solutions of calcium carbide by Morris and Harry revealed extensive carburization of the steel by the electrodeposited carbon. This carburization was reflected in the variability, with time, of the applied potential to the electrolysis cell, necessary to maintain a constant current density at the electrodes. This observation suggested the setting up of a galvanic cell of the "alloy concentration" type to study the thermodynamics of some metal-carbon alloys. Cells of this general type have been widely used for the study of alloy systems.2 In view of the availability of published data in respect of the austenite phase of the Fe-C system, it was decided to carry out measurements upon these alloys before proceeding to studies of less well documented systems. The galvanic cell may be written: where [C] is carbon dissolved in iron. The electrolyte was a fused salt solution of calcium carbide, containing some 5 to 10 mol pct of carbide. The cell reaction is believed to be: C(s)-[CI [I1 Carbon forms an interstitial solid solution in iron, with the atoms located in the octahedral interstices. In the fcc crystal structure of austenite there is one octahedral interstice per iron atom. Thus, the lattice ratio, ZC, shown by Gurney3 to be the fundamental concentration parameter in the context of interstitial solutions, is given by: where nc and nFe are the number of carbon and iron atoms, respectively. chipman4 has recently shown empirically the advantages of using this concentration parameter instead of the more usual atom ratio or atom fraction. The cell electromotive force, E, assuming reversible behavior, is related to the carbon potential or the partial molar free energy of carbon in the solid solution relative to pure carbon at the same temperature and pressure, GP at the composition ZC, by the equation: where z is the carbide ion valency and F is the Faraday constant. An activity of carbon, ac, in the solution relative to the value of unity assigned to pure carbon, and an activity coefficient, qC , are defined such that: where R is the gas constant and T the absolute temperature. GF is further related to the relative partial molar enthalpy Hm, and the temperature coefficient of the cell electromotive force, (aE/aT)Zc, by the equations: Measurement of the cell electromotive force thus enables calculation of the relative partial molar thermodynamic properties of carbon in iron, if z is known. At E = 0, the solid solution is in equilibrium with pure carbon. More convenient for many purposes is the standard state based upon the infinitely dilute solution, Henry&apos;s law. The relationship between the activity coefficient of carbon based upon this standard state, and that based upon the pure carbon standard state, qC , may be obtained by considering the free energy of transfer of carbon from the latter standard state to the former. The relationship is: where +:H is the activity coefficient of carbon in the hypothetical standard state based on a reference of

Jan 1, 1969