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By George Gardner

THE application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous dis-charge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condi-tion often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies consid-erable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, there-fore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially pre-pared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation.

Jan 1, 1939

By Eugene McAuliffe

TWO years ago the American Institute of Mining and Metallurgical Engineers made a memorable contribution toward a better understanding of the problems that have for many years confronted the coal industry. Specific suggestions toward betterment were then advanced, certain of which were taken up, amplified and endorsed by men who were conscien-tiously interested in the work of lifting this great industry out of the morass it has lain in for years. Two certain suggestions then made-provision for seasonal variations in railroad freight rates that would tend to encourage the purchase and movement of coal during the low summer production period, and provi-sion for the collection by the United States Government of all the facts surrounding the industry-were intro-duced in the form of legislation in the United States Senate by a member of that body, a man whose personal character, antecedents and business training put him above and beyond all suspicion of demagoguery; however, as the result of the insistent, vindictive opposition of the industry itself, these two bills, con-structive in their nature, were buried under an ava-lanche of misrepresentation. Today, with all mines that employ union labor at a stand still, the work of stabilizing the industry is yet before us. As aptly stated by Herbert Hoover, in March, 1920, when he was president of the Institute; An engineering organization is particularly the body to under-take this work. It is an economic problem, an engineering pro-blem within the ken of our experience; it is a problem that requires not only constructive thought but quantitative thought and wise social thought. The engineers of the United States occupy a position midway between capital and labor. They enter upon problems of this kind without prejudice either way, and they have that faculty of mind for quantitative thought, as distinguished from qualitative thought, that takes such problems as this out of the region of politics into the region of matter-of-fact solution.

Jan 5, 1922

Jan 1, 1970

By S. Floreen

Measurements have been mode of the effects of tempering and austenitizing heat treatments, the work-hardening characteristics, and the effects of test temperature and strain rate on the properties of a low-carbon Fe-18 pet Ni martensitic alloy. In many respects the alloy behaved quite similarly to cold-worked iron. One notable quality was the excellent ductility at temperatures as low as 20°K. Many of the qualities of the maraging steels could he related to the properties of the Fe-Ni matrix. THE 18 pet Ni maraging steels have demonstrated that unusual combinations of strength and toughness may be obtained by age hardening a low-carbon Fe-Ni martensite matrix.' These properties must, to some extent, reflect the properties of this Fe-Ni matrix, and therefore an understanding of the properties of this matrix is a prerequisite to a complete understanding of the steels. There have been several recent studies of Fe-Ni-C martensites, but not much attention has been paid to alloys with very low carbon contents. At low carbon levels the crystal structure of these alloys is essentially bee.2 Electron transmission microscopic examination of a 20 pet Ni binary alloy showed martensite platelets separated by low angle boundaries.3 Plastic deformation of the low-carbon alloys has been shown to proceed by wavy glide.4 The hardness of these martensites is typically RC 28, and their yield strengths are 70 to 80 kg per sq mm.2, 5 Their ductility is excellent. Room-temperature tensile elongations of 18 pet and reductions of area of 70 pet have been observed in an Fe-18 pet Ni binary alloy.5 These observations have provided a qualitative understanding of the flow characteristics of these alloys. To date, however, no thorough study of their properties has been made. In particular, it is not known to what extent the deformation characteristics of low-carbon martensites are similar or dissimilar to those of pure iron or other bee metals. The present work was undertaken to provide more detailed information on the flow characteristics of a low-carbon Fe-18 pet Ni martensite. PROCEDURES, RESULTS, AND DISCUSSION Materials. A 40-lb heat of the Fe-18 pet Ni alloy used in this study was made by vacuum-induction melting. The charge materials were electrolytic iron and electrolytic nickel. A carbon boil was used to achieve deoxidation. After the boil the heat was refined by additions of 0.1 wt pet Ti and Al. These additions are commonly used in the maraging steels to keep the carbon and nitrogen contents in solid solution at a minimum. After casting, the heat was

Jan 1, 1964

By Wm. I. Weisman, C. W. Tandy

Consumption of fluorspar in the United States in the last ten years has doubled to 1.34 million tons. One main, reason for the increase has been the use of the basic oxygen furnace to produce steel which requires considerably more fluorspar than the open hearth. The increasing consumption of aluminum and fluorocarbon chemicals will require more fluorspar, Since 1964 domestic fluorspar prices have advanced over 70%. Maximum prices were attained in 1971 and remain stable. These higher prices have brought about the expansion of production capacity at many of the present mines and mills. Exploration has been intensified, resulting in new discoveries, which are being brought into production. Many deposits, heretofore considered uneconomical, are being reappraised for possible development. Companies who have not previously mined fluorspar are actively seeking and acquiring new properties. The outlook for the continued health of the domestic fluorspar industries is favorable at present prices; however, it is doubtful that production will be greatly increased. New production will have to come from presently inaccessible areas of much greater distance from consuming centers. Prices will have to be higher to support this production. Domestic fluorspar production meets only 20% of domestic consumption. Thus, reliance on imports on fluorspar in the future will become increasingly more critical.

Jan 1, 1975

By Bhudeo N. Sinha, Paul Dean Proctor

Heavy metal contents in stream waters, sediments, and selected aquatic algae were determined for the upper Meramec River basin, Missouri, of 3905 km2 (1508 sq mi) area and site of the proposed and controversial Meramec dam and reservoir. Six distinct drainage areas within the basin are: (1) a lightly industrialized and farm area, (2) a primitive forested- ranch area, (3) an area which includes the Northern New Lead Belt, (4) the westward drainage of an old and extensive barite mining area, (5) the main trunk of the Meramec River, and (6) short north-divide tributaries of the Meramec River. Lower Paleozoic sediments rest nonconformably upon eroded and hilly Precambrian igneous basement. This locally rises as major inliers and also makes up the St. Francois Mountains to the east. Major lead, and lesser zinc, copper, cobalt, and nickel mineralization occurs in the buried Cambrian Bonneterre dolomite. Residual barite is present along the eastern fringe of the basin and is derived from the Potosi formation. Some 62 water samples, active stream sediments (AS), bank samples (BS), and 11 selected aquatic algae samples were collected in the various drainage areas and analyzed for copper, lead, zinc, cadmium, nickel, arsenic, and mercury contents. Heavy metals in water have a maximum range of 1-120 ppb (parts per billion), and this for zinc. The AS and BS sediments have orders of magnitude greater acid leachable metal contents in the -80 mesh fraction, with lead hawing the greatest range of 11-1028 ppm. Heavy metal content of stream-algae approaches that of the sediments in which they grow. Most anomalous heavy metal accumulations occur near mining and milling activities and in the streams draining such areas. Significant distortions of the primary dispersion pattern militate against geochemical exploration for hidden ore zones, but do demonstrate the mining, milling, and smelting activities of man, and sporadic mineral occurrences in younger horizons.

Jan 1, 1980

By Frank D. Hoyt

BY far the most conspicuous of the Pennsylvania slate districts is that extending from the New Jersey line at the Delaware Water Gap westward almost to the Schuylkill River. This covers parts of three counties in east-central Pennsylvania: Northampton, Lehigh, and Berks. The most important development, both in geographic size and product importance, is in Lehigh and Northampton counties. The greater part of the region is underlain by only one formation-the Martinsburg, consisting of slates, clay slates, and sandy shales, all of the Ordovician period. The slate-bearing Martinsburg formation is underlain by Cambro-Ordovician limestones. Immediately overlying the Martinsburg formation is the Tuscarora quartzite of the Silurian period. The Martinsburg formation itself is divided into three distinct divisions, termed simply: the upper, the middle, and the lower members. Commercial slate has been extracted from all of these members, but the formation of greatest importance is the upper member, representing 2600 ft of the total formation thickness of nearly 11,000 ft. The upper member is commonly referred to as the "soft slate" and consists of three facies: 1) beds of blue-gray, very sandy, almost quartzitic slate, in many places, approximately a medium-coarse sand- stone with calcareous cement; 2) blue-gray sericitic slat-the dominant rock type of this member-with occasional chloritic beds; and 3) dark gray or virtually black, highly carbonaceous beds, referred to locally as "ribbons."

Jan 8, 1958

By Arthur L. Christenson, Clarence E. Jackson

IN the establishment of the relationship between weldability and hardenability, two methods have been employed in correcting for the grain growth produced in the heat-affected zone: first, the hardenability calculated from chemical composition1 may be corrected to the grain size observed in an actual weld,2 or, second, a hardenability test may be made on the steel quenched from a temperature high enough to produce a grain size comparable to that found in the heat-affected zone.3 In order to obtain grain sizes in the end-quench hardenability bar comparable to those resulting in the base metal from the welding cycle, a quenching temperature of 2100°F. has been used. In studies of the end-quench hardenability specimen quenched from 2100°F. instead of from a lower temperature of 1700°F., it is important to ascertain the relative cooling rates for various distances along the bar. It is a question as to whether the cooling occurs at the same rate or whether there is any significant difference from the standard cooling-rate curve published by Jominy and confirmed by others.4,5 This paper reports experimental evidence concerning the effect of quenching temperature on the cooling rates in the end-quench hardenability test. The effect of quenching temperatures on cooling rates has been studied by a number of investigators.6,7 French has considered this effect from both theoretical and experimental aspects. In French's studies on complete quenching of spheres and rounds, an increase in the quenching temperature caused an increase in the cooling rate at 720°C. at the center of the specimen. The center cooling velocity also has been shown to be dependent upon the surface per unit volume for the type of specimens studied; the velocity of cooling increases with an increase in the surface per unit volume. Three methods of indicating the rapidity of cooling of a body of metal during a quenching operation have been proposed: I. The time it takes for the metal to cool from the quenching temperature to a temperature halfway between the quenching. temperature and the temperature of the quenching medium (half-temperature time): Grossmann, Asimow and Urban7 justify the use of this criterion by the fact that the half-temperature time includes the temperature and time of incubation as well as the zone of formation of pearlite and, further, the data so derived accord very closely with experimental values. 2. The time interval the metal remains in a given temperature range; for example,

Jan 1, 1943

By Samuel Daniels

Aluminum-base alloys containing small amounts of copper and magnesium possess but ordinary physical properties as sand cast, but may be treated to give a remarkable range of tensile values and of Brinell hardness. The high-copper (4.5 per cent.) duralumins must be given a protracted treatment which in nature resembles the malleableizing of white cast iron; the low-copper (2.25 per cent.) duralumins develop an excellent combination of strength and ductility with a treatment which requires a maximum of 5 hr. to be completed. THE wrought alloys of aluminum with small amounts of copper and of magnesium have, with the development of the automotive and aircraft industries, sprung into prominence through the medium of duralumin; but the cast alloys remained in the background because their possibilities in the heat-treated condition were either not recognized or not fully investigated. In 1919, the Bureau of Standards published a preliminary survey1 of this field, which pointed out that, in general, the ultimate strength and the percentage of elongation of the alloys of aluminum with and without magnesium could be improved by so simple a treatment as heating to 932° F. (500° C.) for 2 hr., cooling in, air, and aging at room temperature for several days. British investigators, too, working with chill-cast material, found that " considerable improvement in the mechanical properties of copper-aluminum alloys' may be obtained from suitable heat treatment applied to castings."2 Jeffries and Gibson3 made the first contribution to the literature dealing exclusively with the heat treatment of sand-cast aluminum-base alloys, describing the effect of small additions or of combinations of copper, magnesium, and iron on the response to a short heat treatment comprising heating at 932° F. in a

Jan 7, 1924

By Alexander Squire

A brief study of the effects of material and processing variations upon the tensile properties of steel formed from mixtures of iron and carbon was made in order to provide information regarding the properties obtainable in iron-carbon compacts as influenced by forming pressure, sintering temperature, and graphite particle size. Sintered steels formed from mixtures of iron and graphite have been studied by Stern,' who investigated the effect of various percentages of graphite on compacts formed from electrolytic iron that were repressed and heat-treated after sintering. A further study, by Stern and Greenberg,l is concerned with the heat-treatment of steels formed by the car-burization of iron compacts, and Margolies3 has reported work on the simultaneous sintering and carburization of iron-powder parts. Glauch4 investigated the effect of various types of graphite on the properties of iron-carbon powder alloys but did not determine the effect of different particle sizes of the same graphite alloyed with different types of powder. In the investigation reported in this paper, powders typical of those produced by electrolytic deposition and the decar-burization of shotted steel scrap were used. The powders were mixed by tumbling in a jar mill with graphite powder ground to an average particle diameter of 2, 4, 6, and 16 microns (as determined by microscopic measurement). The properties of the iron and graphite powders are presented in tabular form as Table I. In order to obtain the maximum information from a minimum number of test specimens, the study was divided into two sections with one set of specimens treated identically in each section as a basis for comparison. In the first section, iron powder produced by the shotting and subsequent decarburization of scrap steel was mixed with 2-micron graphite powder, pressed at 50,000, 100,-000, and 200,000 psi, and sintered in hydrogen at 1200°C for the periods of time ranging from 15 to 120 minutes. In the second section of the investigation, electrolytic iron powder was mixed with graphite of an average particle diameter of 2, 4, 6, and 16 microns, pressed at 100,000 psi, and sintered at temperatures ranging from 1000° to r200°C'. for periods of time of 30 to 180 minutes. By following this procedure an indication of the effect of the following variables upon the density and tensile properties of iron-carbon powder compacts was obtained: (I) forming pressure, (2) sintering time, (3) particle size of graphite powder, (4) sintering temperature, (4) type of iron powder.

Jan 1, 1947

By Alexander Squire

A brief study of the effects of material and processing variations upon the tensile properties of steel formed from mixtures of iron and carbon was made in order to provide information regarding the properties obtainable in iron-carbon compacts as influenced by forming pressure, sintering temperature, and graphite particle size. Sintered steels formed from mixtures of iron and graphite have been studied by Stern,' who investigated the effect of various percentages of graphite on compacts formed from electrolytic iron that were repressed and heat-treated after sintering. A further study, by Stern and Greenberg,l is concerned with the heat-treatment of steels formed by the car-burization of iron compacts, and Margolies3 has reported work on the simultaneous sintering and carburization of iron-powder parts. Glauch4 investigated the effect of various types of graphite on the properties of iron-carbon powder alloys but did not determine the effect of different particle sizes of the same graphite alloyed with different types of powder. In the investigation reported in this paper, powders typical of those produced by electrolytic deposition and the decar-burization of shotted steel scrap were used. The powders were mixed by tumbling in a jar mill with graphite powder ground to an average particle diameter of 2, 4, 6, and 16 microns (as determined by microscopic measurement). The properties of the iron and graphite powders are presented in tabular form as Table I. In order to obtain the maximum information from a minimum number of test specimens, the study was divided into two sections with one set of specimens treated identically in each section as a basis for comparison. In the first section, iron powder produced by the shotting and subsequent decarburization of scrap steel was mixed with 2-micron graphite powder, pressed at 50,000, 100,-000, and 200,000 psi, and sintered in hydrogen at 1200°C for the periods of time ranging from 15 to 120 minutes. In the second section of the investigation, electrolytic iron powder was mixed with graphite of an average particle diameter of 2, 4, 6, and 16 microns, pressed at 100,000 psi, and sintered at temperatures ranging from 1000° to r200°C'. for periods of time of 30 to 180 minutes. By following this procedure an indication of the effect of the following variables upon the density and tensile properties of iron-carbon powder compacts was obtained: (I) forming pressure, (2) sintering time, (3) particle size of graphite powder, (4) sintering temperature, (4) type of iron powder.

Jan 1, 1947

By Frank H. Reed, P. W. Henline, Harold W. Jackman

A SUMMARY of the consumption of coal in 1945 shows that the coke industry accounted for 17 pct of the total coal used. No substitute for coke and the blast furnace in the reduction of iron ore has gained sufficient prominence so far to be given serious consideration. However, while the same slot-type ovens are being built and used now as were in use a few years ago, the problem of obtaining suitable coking coals, both high- and low-volatile, has forced many operators to revamp coal-blending facilities. Until the beginning of World War II, high-temperature coke plants were able to secure the required high-volatile and low-volatile coals from two or three seams and from three or four mines. Thus, many of our coke oven plants were able to operate with storage bins for two coals only. The variance in raw materials was not great, and uniformity of blend was a relatively simple problem. Since the beginning of World War II, many and important changes have taken place. Demand for all coals increased greatly. Production, though kept as near maximum capacity as possible, could not meet the demands for coal generally, and particularly for the various kinds of coal which have proved to be satisfactory for specialized uses; coals were allocated as nearly as possible in the order of greatest need; storage piling was reduced to the minimum necessary to keep plants in operation; uniformity of quality could not be maintained, and with this last, uniformity of composition of blends for coking could not be maintained. Whereas before the war producers of metallurgical coke could fill their needs from three or four mines, by the end of the war it was not unusual to find shipments to a single coke oven plant coming from as many as 30 different mines, in a single month. Since many of the mines producing both high- and low-volatile coal for high-grade metallurgical coke are rapidly nearing depletion, the problem of seeking new sources and of blending a number of coals in each plant for the production of high-temperature coke is facing practically every producer in the United States at the present time, and is one which will probably continue for many years to come. Midwestern by-product coke ovens in the Chicago and St. Louis areas use annually from 12 to 15 million tons of bituminous coals which are transported 500 to 700 miles from the Appalachian coal fields of Pennsylvania, West Virginia, and eastern Kentucky. Approximately two-thirds of this coal is high-volatile bituminous. The critical transportation problem confronting the nation in 1943, and the growing scarcity of the best Appalachian coking coals, prompted the Illinois Geological Survey to propose a research program in which would be studied the coking properties of blends of low-sulphur, high-volatile Illinois coal with the high- and low-volatile coals from the eastern fields. Such blends containing Illinois coal, if substituted for the all-eastern blends normally coked,

Jan 1, 1948

THE SECRETARY The year 1917 has been a notable one in Institute affairs. The usual activities, including meetings, publications, local section interests, library service, and so-forth, have been continued on at least the same scale as previously, and in addition the resources of the Institute have been placed without stint at the service of the Nation, not only for the active prosecution of the military side of the war, but even more especially in the industrial operations which form the very basis of modern warfare. The officers and directors of the Institute have labored both officially and individually, while the Institute as a body, through committees of, prominent members, and through many individual members, has given freely. Finally, Institute funds have been appropriated to an amount exceeding $5000 to accomplish the cooperation with Government bureaus, and provide committee expenses necessary for performing the services that have been given. The President of the Institute had a very large personal share in many of these activities, which will be described in the following pages, as well as in the President's own report. Many of the Institute's members are giving their whole time for. $1 a year, or less, and especial mention should be made of Herbert C. Hoover, Food Administrator, W. L. Honnold, Head of the Commission for Relief in Belgium, Mark L. Requa, Petroleum Administrator, Edgar Rickard and Charles W. Merrill of the Food Administration, S. A. Taylor of the Fuel Administration, W. L. Saunders, B. B. Thayer and Joseph W. Richards who .are giving a. large share of their time to the Naval Consulting Board, W. Y. Westervelt, W.0. Hotchkiss and Harvey S. Mud of the War Minerals Committee, David W. Brunton of the War Committee of Technical Societies, and hundreds of others whose names are mentioned in the Honor Roll of Members. It has also been a notable year in cooperation with sister-societies. The most important event under this head was the accession of the American Society of Civil Engineers into the fraternity of Founder Societies.

Jan 2, 1918

By R. A. Wood, R. I. Jaffee, H. R. Ogden, D. N. Williams

The tensile properties, creep resistance. and thermal stability of highly alloyed Ti-Al-Zr alloys were examined. On the basis of these studies, the Ti-7Al-1ZZr composition was selected for more complete evaluation. The alloy was found to be weldable and free from excessive directionality. In addition, it developed maximum properties without requiring heat treatment other than an annealing operation in the alpha field. The alloy was recommended for scale up and is presently being investigated on a production-level basis. One of the more attractive properties of titanium alloys is their ability to withstand stress at moderately high temperatures, and a considerable amount of effort has been devoted to increasing the maximum service temperature of titanium alloys. This work has suggested that the optimum alloys for high-temperature service will be single-phase a (close-packed hexagonal) alloys containing significant amounts of aluminum. However, the maximum amount of aluminum which can be alloyed with titanium is between 6 and 8 pct,l since at high-aluminum contents an embrittlement reaction occurs in the anticipated service temperature range, 800" to 1100°F. It has been shown that the embrittlement reaction involves decomposition of the high-aluminum a phase to one or more new phases.' Since this reaction does not occur at intermediate or low-aluminum contents, it was felt that intermediate Ti-A1 alloys might be strengthened by a-soluble ternary additions without inducing the embrittlement reaction. The first alloying addition considered was tin, which shows extensive solubility in a titanium and has moderate strengthening tendencies. Unfortunately, it was soon apparent that tin also promoted the embrittlement reaction, and that to obtain a stable alloy, the aluminum content had to be reduced as the tin content was increased. The second alloying addition considered was zirconium, which is similar to tin in its effects on titanium. This element did not contribute to the embrittlement reaction and, in fact, appeared to increase the maximum amount of aluminum which could be alloyed with titanium without inducing instability. This paper describes an investigation of the Ti-A1-Zr a alloy region. Alloys containing from 4 to 12 pct A1 and from 6 to 15 pct Zr were examined. The properties of these alloys are described and the bases for selecting an optimum composition is outlined. This composition, Ti-7A1-12Zr, is presently being scaled up in tonnage quantities, and is being evaluated extensively throughout the industry. In addition to presenting the basis for its selection, this paper presents a description of the properties developed in laboratory material as determined during the alloy investigation. These properties suggest that this alloy can fill an important position in applications requiring light weight, fabrica-bility, weldability, and strength to 1000oF or higher. EXPERIMENTAL PROCEDURES Titanium alloy ingots were prepared by inert electrode arc melting under an argon atmosphere. Alloying elements used were 110 Bhn titanium sponge, high-purity aluminum, and reactor-grade zirconium. Pancake-shaped ingots were prepared weighing approximately 300 g. The composition of the ingots was checked by weight measurements before and after melting. The pancake ingots were forged at 2000°F to approximately half their original thickness to give a flat plate roughly 1/2 in. thick. This plate was then rolled at 1800' to 1600°F to 0.250 in. thick. All of the alloys examined fabricated well. However, alloys containing 15 pct Zr tended to overheat due to exothermic oxidation, and scaling was excessive. As might be anticipated from its effect in decreasing the ß transus, increased zirconium appeared to improve fabricability somewhat, especially during rolling at lower temperatures. Except for a limited study of heat-treatment response, all alloys were examined in the a-annealed condition. Prior to heat treatment the a and ß tran-sus temperatures were determined by metallo-graphic examination of samples quenched after annealing at 50-deg intervals in the transformation region. These data are shown in Fig. 1. Recrystal-lization appeared to occur in about 1 hr in the range 1300º to 1500ºF. Therefore, alloys were annealed for 1 hr at 1550ºF (4 and 5 pct Al), 1600ºF (6 through 7-1/2 pct Al), or 1650°F (8 or more pct Al). This produced an equiaxed a grain structure. In most alloys, a "ghost" structure was visible after the a-annealing treatment, as shown in Fig. 2. This structure apparently resulted from the acicular

Jan 1, 1963

By J. Szekely, G. P. Martins

A formulation is given and a general analytical solution is presented for the problem of spherical phase growth in multicomponent systems. The results are valid for describing the rate of bubble growth in the absence of translational motion and, therefore, should be relevant to heterogeneous nucleation processes. Typical worked examples are given, which include bubble growth due to the simultaneous diffusion of hydrogen and nitrogen in molten steel, and the growth of CO bubbles in steel, due to the reaction: C + 0 = CO. The calculations predict that the presence of additional components would enhance the growth rate and also increase the absolute rate at which the individual components are transferred into the bubble. These findings should be relevant to degassing processes. THE problem of spherical bubble growth in the absence of translational motion is appropriate to the description of the heterogeneous nucleation and subsequent growth of gas bubbles while attached to a solid surface. Such problems are of considerable practical relevance to various vacuum degassing and steelmaking processes where bubble nucleation and subsequent growth play an important part in the overall reaction mechanism. A definitive formulation of spherical phase growth has been given in the now classical paper by Scriven1 and the analogous problem for solid phase growth has been discussed by Horvay,2 furthermore a thorough review of the relevant literature has also become available.3 All this previous work was concerned with one component or binary systems. The purpose of this paper is to show that the technique developed by Scriven may be generalized to alow the consideration of multicomponent systems. The results of this generalization would be particularly relevant, as gas bubble nucleation in the metallurgical systems previously mentioned frequently involves the simultaneous diffusion of several components. In the following a general formulation is given and typical worked examples are presented. FORMULATION Consider the growth of a spherical gas bubble due to diffusion in a quiescent liquid of infinite extent, as sketched in Fig. 1. The formulation of such problems requires the statement of the following conservation equations relating to the liquid phase: Equation of continuity Equation of motion Conservation of the diffusing species—Diffusion Equation. The following assumptions are made: a) The fluid is incompressible, quiescent, and of infinite extent b) The bubble is stationary, i.e., it undergoes no translational motion c) Spherical symmetry is observed throughout d) The mass diffusivity is constant e) Chemical equilibrium exists at the surface of the bubble, and any reactions occurring there are fast compared to the diffusion process f) Inertia and surface tension effects are neglected. Equations derived on the basis of these assumptions by previous investigators were found to provide a reasonable representation of bubble growth while attached to a surface in organic and aqueous systems4,5 For gas bubble growth in molten metal systems assumptions a) to d) chould hold reasonably well. The exclusion of chemical kinetics as a possible rate limiting step may not be universally valid, but should hold for many systems operating at high temperatures. The effect of hydrodynamic inertia may be neglected for moderate growth rates; finally, the assumption neglecting the effect of interfacial tension on the bubble growth was made for the sake of mathematical convenience; its inclusion would have required the use of quite cumbersome numerical techniques. While surface tension effects could be appreciable on the initial values of the overall growth rate, especially at low absolute pressures and in case of small bubbles, they are not thought to modify the relative effects present in multicomponent systems, the study of which is the objective of this paper. Within the framework of the above assumptions

Jan 1, 1970

General discussion on the above subject, presented at the Pittsburgh meeting, October, 1914. GEORGE S. Rice, Pittsburgh,. Pa.-Undoubtedly there is a serious problem through the juxtaposition of gas and oil wells and coal mines, not only at the present time, but possibly of far more serious import for the future. If one examines a map of the coal fields on which is superposed the oil and gas fields of the country, one finds that they overlap to a very great extent. I may say at the beginning that we have not, so far as I know, had any very large number, of accidents growing out of this situation causing loss of life. Such accidents, or rather incidents, that have occurred have all been rather potential possibilities for disasters due to the leakage of gas from wells into the adjacent coal mines. The condition has been most acute in the Fairmont district of West Virginia, and in the general coal fields southwest of Pittsburgh in Pennsylvania. The accidents which have actually occurred were summarized in Bulletin No. 65 (Oil and Gas Wells through Workable Coal Beds) issued by the U. S. Bureau of Mines, reporting the transactions of several meetings in Pittsburgh, February, 1913, of oil and gas well representives, State geologists, State mine inspectors, coal-mine operators, and representatives of the U. S. Bureau of Mines. This conference was partly brought about through a case in which the Pennsylvania State inspection department had brought suit to restrain a gas company from completing a well through a certain mine. The office of the Attorney General of Pennsylvania asked the opinion of the Bureau of Mines upon the matter; about the same time the Association of State Geologists, at its New Haven meeting, asked the Bureau to take up the problem. Accordingly, it was thought advisable to bring together the several, interests. For the most part the danger is, I think, greater in the future, than at the present time Many parts of the coal fields of Pennsylvania, in Greene County particularly, have been penetrated by numerous wells very close together, and with the present practice of having a large coal pillar around each well, has made or will make the mining of many areas difficult or pro-

Jan 4, 1915

PRECEDING chapters on thermochemistry, and the reactions in and between metal and slag phases in the bath of the furnace tend to emphasize the equilibrium or "static" conditions in the furnace and process, such as the total amounts of heat from fuel combustion or from certain bath reactions, the concentration relationships between slag and metal at the steady state for certain reactions, and the like. Such data are obtained essentially by means of the logic of thermo- dynamics, which helps to determine the energy change between initial and final states in a process as well as to define its equilibrium or steady-state condition, but which is not concerned with the rate of change in the process or with the mechanisms or path followed between initial and final states. These questions of just "how it works" and "how fast" belong to the kinetic aspect of any process; their answers are helpful in speeding up or slowing down and thus controlling intelligently its operation, and also to understand certain natural limitations which are especially important in many high-temperature processes. The kinetic aspects of interest here comprise mainly (1) the flow of gases through the furnace system, (2) the flow of heat in the system, and (3) the mechanisms and rate factors in the various chemical reactions. A really adequate discussion of the first two subjects would require at least three or four times the space available here; it has been tried, therefore, in this and the next chapter to outline but a few fundamentals necessary to an intelligent approach and to indicate some of the conditions of heat and gas flow more or less peculiar to the open hearth, since several good general discussions on these subjects may be found in the literature.(1) For the designer of open-hearth furnaces, the principles of gas flow are of paramount importance.(2,3,4,5) They are also important to the operation of the process, however, at least to the extent of a general qualitative picture of the movement of gases in the system, which is all that is attempted here.

Jan 1, 1944

By Arthur Fleischer

THE Kalunite process? for the production of metal-grade alumina from alumina-containing ores is applicable, considered from a general point of view, to any aluminous raw material that can be converted to potassium alum or equivalent normal alum. This result of modern technology has been the subject of a continuous study and development since 1929, on a laboratory and test-plant scale, with initial emphasis on the utilization of alunite as the raw material. The research and developmental program was carried out by the Kalunite Company and its successor, Kalunite, Inc., an affiliate of the Olin Corporation of East Alton, Illinois. The process is now approaching the time for a major test in its history with the completion of construction of a plant having a capacity of zoo tons of alumina per day in Salt Lake City for the conversion of Marysvale, Utah, alunite ores to alumina and potassium sulphate. The Salt Lake Alumina Plant is a Defense Plant Corporation project. PRODUCTION OF ALUMINUM The known existence of alunite deposits, especially in the Marysvale district, furnished the motive for the original inquiry into the utilization of this raw material for aluminum production. The deposits in this region were actively explored during World War I and utilized for the production of potassium sulphate, an essential fertilizer, of which a shortage of monumental proportions then existed. Up to the twentieth century for alunite is a mineral with an ancient history-it was used in Europe and in China as a source of potassium alum. It never had been used successfully in. this country as a source of oxide for reduction to metal. Although the known reserves of this ore, which undoubtedly will be greatly expanded with a commercial outlet for this ore, are recognized to be sufficient for only a part of the present-day needs of aluminum, it has a definite place in the aluminum industry. Academically it points the way for future raw materials. The aluminum industry has undergone a remarkable growth in the past few years as a result of defense and war requirements. Its expansion in many ways has been beyond belief and prediction, both in volume and location. This wartime status of the industry has accelerated the consumption of bauxite to such an extent, that a re-evaluation of the raw material reserves for the future peacetime industry and for eventual wartime reserves is seemingly of concern. The generally accepted picture of bauxite ore reserves in the United States, especially in raw material suitable for treatment by the Bayer process, focuses attention on other possible sources of raw material of metal-grade oxide. The perspective for the development of a suitable process may have changed in the interim

Jan 1, 1944

By A. Gatti, R. L. Fullman

A very fine dispersion of aluminum oxide is produced by internal oxidation of solid-solution alloy of 0.14 pet A1 in Ag. The particle size of the aluminum oxide is approximntely 50 to 100A in radius. The yield strength of the alloy is increased markedly by internal oxidation. A further increase in strength is produced by cold working the internally oxidized alloy. Recrystallization is retarded by the finely dispessed aluminum oxide particles, so that the strength increase resulting from cold work is retained on annealing at temperatures 14 to about 700°C. MANY workers'-3 in the past have studied various aspects of the internal oxidation of aluminum-silver alloys. This paper is an extension of these studies with emphasis placed on the effect of time and temperature of annealing on the strength of these alloys after oxidation and subsequent cold working. Two general conditions are necessary to internally oxidize an alloy. First, oxygen must diffuse through the base material more rapidly than does the addition; otherwise oxidation will take place as a surface layer. Secondly, the affinity of oxygen for the addition must be greater than for the base material. After internal oxidation of certain alloys takes place, a marked increase in hardness accompanied by higher yield stress and improved creep properties is noted, presumably as a result of the highly dispersed oxide within the base material. Meijering and Druyvesteyn1 also noted that the internally oxidized portion of a partly oxidized alloy failed to recrys-tallize under annealing conditions that led to coinplete recrystallization of the unoxidized part. EXPERIMENTAL-METHODS AND PROCEDURES Few alloys can be made to contain a second phase that is extremely stable at high temperatures. Silver plus aluminum in solid solution was chosen for these internal oxidation studies because of the high rate of oxygen diffusion through silver and the very stable nature of aluminum oxide. Two alloys were vacuum cast. The nominal compositions were: Alloy A—1 pct Al, balance Ag; Alloy B—0.1 pct Al, balance Ag. Chemical analysis, which does not distinguish between aluminum and aluminum oxide, showed the conlposition to be: Alloy A—1.6 pct Al, and Alloy B—0.14 pct Al. The ingots were machined for surface cleaning, swaged and drawn to 0.020-in. diam wire. A sample 20 ft long of the 0.020-in. dianl wire of each composition was annealed 24 hr at 800°C in pure dry hydrogen. Each wire was then cut into two equal pieces. Photomicrographs of the 0.14 pct A1 alloy are shown in Fig. 1, the annealed 0.020-in. wire at the left and the oxidized wire to the right. The oxidation treatment for the first set of data was 1000 hr at 800°C in air. After this treatment the 1 pct A1 proved to be brittle. It is assumed that high alunlinum oxide concentration at the grain boundaries was responsible. The 0.14 pct Al wire remained ductile and all further data were derived using this alloy. One-half of this wire, about 5 ft, plus 5 ft of as-homogenized wire, was then drawn cold to 0.005 in. diam. All tensile tests were conducted with an Instron Engineering Corp. tensile-testing machine, Model TT-B. Unless otherwise indicated, the tests were made at room temperature with a strain rate of 0.1 per min. All metallographic samples were etched with an aqueous solution of 2 pct each of CrO3 and H2SO4 . EXPERIMENTAL RESULTS AND DISCUSSION PARTICLE SIZE DETERMINATION A study was made of the particle size of the aluminum oxide produced in the samples of Ag + 0.14 pct Al, oxidized 1000 hr at 800°C. A cross section of the as-oxidized wire was mounted in bakelite, polished, and etched with an aqueous solution of 2 pct each of CrO3 and H2SO4. The specimen was then thoroughly cleaned by stripping successive coatings made by applying 10 pct nitrocellulose in amyl acetate. The final replica of the cross section was made by applying 2 pct nitrocellulose in amyl acetate. The replica was stripped, transferred to a copper screen, shadow cast with chromium at 10 deg and photographs taken using a Phillips Metallix electron microscope at an accelerating potential of 100 kv. A photograph of an etched sample of the as-oxidized material is shown in Fig. 2. We believe the pits in the photograph are places were A12O3 inclusions were sitting in the matrix. By inspection, it appears that the volume fraction ob-

Jan 1, 1960

By Robert Palmer

So MUCH has already been written on this vast subject of ground movement and subsidence, and so many data collected and commented upon, that in this paper the author proposes to confine himself to the submission of some plans showing what has actually occurred in the mining of several of the orebodies which have, come under his direction during the last 20 years or so at Rio Tinto, Spain. Some notes are added for the purpose of describing the plans. The author does not attempt to give his opinion as to the reasons why the subsidences have occurred in the manner in which they are found, but confines himself to giving as true a picture as possible of the movements that have taken place.

Jan 1, 1930