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By A. P. Herring, S. F. Ravitz

Manganese dioxide reacts with sulfur dioxide solution in the absence of oxygen to form manganous ion and dithionate ion, together with a small amount of sulfate ion. The effects of SO, concentration, hydrogen ion concentration, stirring speed, and temperature on the rate of the reaction were studied. If it is assumed that undissociated SO2 molecules react rapidly with MnO, at active surface sites and that bisulfite ions react slowly, an equation can be derived that satisfactorily represents the observed reaction rates. For solutions in which the reaction with undissociated SO2 predominates, reaction rates and activation energies estimated from diffusion theory agree well with those found experimentally. Manganese dioxide dissolves readily in aqueous solutions of sulfur dioxide. The nature of the dissolution reaction was first investigated by Gay-Lussac and welter1 in 1819; they identified a new oxysulfur radical, the dithionate ion, S2O6, as one of the reaction products. Since then, the reaction has become a standard method of preparing dithionates in the laboratory and one of the more promising methods of leaching manganese from low-grade ores. In the "dithionate process" developed by the U.S. Bureau of Mines2,3, manganese-dioxide ore is suspended in a solution of calcium dithionate and leached with gas containing sulfur dioxide. The manganese is dissolved and the sulfur dioxide is oxidized according to the reactions:

Jan 1, 1965

By W. R. Phibbs

The blast furnace of the Columbia Steel Corpn., at Ironton, Utah, was put in blast April 30, 1024, and its operation has presented some interesting problems. The coke for the furnace is furnished by 33 Koppers Becker type ovens of 15 tons capacity each. The coal is shipped from the company's mine at Columbia, Utah, which is approximately 123 miles from Ironton, and is probably the highest volatile coal that is being coked for blast furnace use in this country. The analysis of the coal is: PeR Cent. Moisture................................................. 3.90 Volatile.................................................. 39.00 Fixed carbon............................................ 51.10 Ash............................................... 6.00 Sulfur................................................. 1.07 The analysis of the coke is: PeR Cent. Volatile.................................................. 0.55 Fixed carbon............................................. 89.70 Ash...................................................... 9.75 Sulfur................................................... 1.05 The coke is light and of a fingery construction, but is very fast burning. A screen test of the coke as loaded into the skip tubs at the furnace shows the following: Per Cent. On 2 in.................................................. 17.90 On 11/2 in................................................ 41.78 On 1 in.................................................. 27.80 Through 1 in............................................. 12.52 The by-product yields are as follows: Gas................................. 11,000 cu. ft. per ton of coal Sulfate............................... 30 Ib. per ton of coal Tar.................................. 12.65 gal. per ton of coal Motor fuel........................... 3.00 gal. per ton of coal Average B. t. u. in gas................. 567

By Kenneth K. Humphreys, Joseph W. Leonard, Robert L. Llewellyn, William F. Lawrence

INTRODUCTION Cleaning fine coal sizes utilizing air currents in machines as the primary separating medium is called dry concentration or pneumatic cleaning. In 1947 approximately 18 million tons (16.38 million mt) of bituminous coal were cleaned by air machines; in 1965, 25.4 million tons (23.1 14 million mt); but in 1975, only 7 million tons (6.37 million mt). Table 11-1 shows the tonnages cleaned of bituminous coal and lignite in the United States by various types of equipment from 1938-1963. Table 11-2 shows only tonnages cleaned by pneumatic methods from 1964-1975. The decrease in tonnage to approximately 7 million tons (6.3 million mt) is due to a higher moisture content in the mined coal and the greater difficulty in cleaning the coal by air. There also was a definite trend to load raw coal at the mines, especially the slack which is the most expensive to clean due to the dewatering and drying requirements. While there have not been any applications of pneumatic cleaning in the anthracite field, its use has not been fully explored. The same is true for lignite and subbituminous coals.

Jan 1, 1979

By Michael Perch, Charles C. Russell

Nearly 75 per cent of the total coke production in the United States in 1940 was consumed in blast furnaces. In 1939 the percentage was 69.9, and in 1938 it was 61.3. To produce a net ton of pig iron 1757 lb. of coke was required in 1940 and 1760 lb. in 1939. These figures indicate how dependent the production of pig iron is upon the production of coke. The rate of iron production is in some measure influenced by the physical and chemical characteristics of the coke. Blast-furnace operators believe that the physical properties of coke profoundly influence the operation of the furnace. Although it is true that coke of a wide variety of physical properties is used in American blast furnaces, the periodic fluctuation of these properties is one of the causes of irregularity of blast-furnace operation. The purpose of this paper is to present a broad picture of the physical properties of by-product coke that are generally considered to be important by coke-oven and blast-furnace operators. Effects of the kind of coal used, the preparation of the coal, the rate of coking, and other factors will be considered. Of all these variables, the kind of coal used is by far the most important. In this discussion use will be made of the method of coal classification by rank1 standardized by the American Society for Testing Materials. Although this method of classification has been an American standard for several years, it has not been given the attention it deserves, especially in connection with the selection of coal for production of coke. Despite the fact that many producers of blast-furnace coke are limited to some particular source or sources of coal, a good understanding of the principles involved in setting up the standard method of classification may lead to a better appreciation of the causes of changes in coke characteristics. Furthermore, where it is necessary to select new coals as a substitute for the original supply, this method of classification can be of great assistance. The data presented have been gathered from many sources, but no attempt has been made to cover the vast literature. Instead, some of the more important data have been selected to show how coals and their carbonization affect some of the physical properties of coke. It must be emphasized that generalizations concerning the behavior of coking coals are presented and that individual coals may vary widely from the specific behavior depicted. Nevertheless, it is believed that the data illustrate certain typical behaviors. Neither was it possible to cover completely all the factors involved; for example, the macroscopic constituents of coal are believed to have important effects on the physical properties of coke, but since there is little information available for such study, and since vitrain, clarain, and durain are neither

Jan 1, 1942

By Hans Lundberq

WHEN geophysical methods were first employed in the search for ore deposits and oil accumulations, it was hoped that they would provide a direct means of locating such concentrations. Magnetized needles were used long ago in prospecting for magnetic iron ore, and soon after the discovery of galvanism in about 1790 attempts were made to find concentrations of valuable minerals electrically. Evidence indicating that the early geophyeical instruments were regarded merely as improved divining or dowsing rods is to be seen in the names "mineral finders," "ore finders," etc., that were applied to them. Today, appellations of this kind raise serious doubts in informed minds as to the intelligence and integrity of individuals advocating the use of such euphemistically named methods or instruments, for experience and research have shown that, geophysical, it is never a question of directly locating a given mineral but merely of delimiting its possible occurrence.

Jan 1, 1939

By E. Buehler, J. E. Kunzler

High-pu.1-ity molybdenum has been heat treated, melted, and zone refined and the physical and chemical changes that are produced by these processes have been studied by making resistance ratio measurements. Pronounced effects are observed that are associated with recrystalliza-tion at about 1200°C and with melting. Melting alone is found to result in a substantial purification by the evaporation of impurities such as iron. Zone refining is found to be reasonably effective with four passes producing a three-fold decrease in resistance ratio and a minimum ratio of 0.0003. With the aid of low temperature measurenzents, it has been shown that the build-up of a deposit of the material being zone refined on the radio frequency coil used for heating can lead to contamination of the sample. CONSIDERABLE interest in high-purity refractory metals for the study of mechanical properties has developed during recent years. Also the need for highly pure metals in certain fundamental studies, such as electronic band structure, has become quite widely appreciated. Molybdenum can now be produced with sufficiently high purity to make it attractive for such investigations. The most suitable measure of chemical purity of metals used for many of these studies is its resistance ratio, R,.,o,/Ro, During the purification of molybdenum by zone refining and its subsequent evaluation by this technique, a number of informative observations were made. These observations concern the effectiveness of zone refining, the volatilization of impurities at the melting point, and the recrystallization of molybdenum and appear to be pertinent to other refractory metals. Also, the usefulness of low-temperature resistance measurements as an analytical tool for evaluating the presence of chemical impurities and physical defects in metals is again illustrated. Samples of high-purity molybdenum of known mechanical history were heated to various temperatures between 800°c and their melting point. Resistance ratios of the samples were measured after they had been given a specified treatment. The data were used, along with mass spectrographic analysis, as an aid in interpreting the nature of the processes that occurred in conjunction with each treatment. Changes in the concentrations of chemical impurities and physical defects are typical of things that effect the low-temperature resistivity. SAMPLES The starting material was obtained from Westing-house Corp., Bloomfield, N.J. It was in the form of molybdenum rods, usually 1/8 or 3/16 in. in diameter. These had been previously processed from bars, 5/8 in, in diameter, originally reduced from 4 in. diam arc-cast ingots, by hot swaging at about 1300°c. In the final step, the temperature was lowered to about l lOO°C which resulted in the production of elongated grains. Typical grains were about 0.03 mm thick and 0.6 mm long. The molybdenum was quite pure as is indicated by the results of mass spectro-scopic analysis1 given in Column 2 of Table I. Other nongaseous elements not listed in the table were not detected. ZONE REFINING AND THERMAL TREATMENT OF SAMPLES Several sample rods, 8 to 10 in. long, were zone refined or were heat treated at several temperatures. Both types of operations were performed using 3 me-

Jan 1, 1962

By S. Lipson, H. W. Antes, H. Rosenthal

A study was made of the effect of ingot structure on the strength and ductility of high-strength wrought-aluminum alloys. It was found that a fine-cast structure facilitated complete homogenization which, in turn, resulted in significant increases in ductility and strength. A completely homogenized 7075-T6 alloy developed tensile properties of 85,000 psi UTS, 75,000 psi YS, with 40 pct RA. Completely homogenized 7001-T6 alloy tensile properties were 102,000 psi UTS, 99,000 psi YS, with 19 pct Ra. A method was devised for making small ingots having secondary dendrite arm spacing of less than 10 u. This method involved multiple-pass arc melting of commercial rolled plate with a tungsten electvode. This material could be completely homogenized after 3 hr at 900°F; homogenization of the original plate material was not complete after 120 hv at 900°F. Degree of homogeneity was determined by use of metallographic and electron-microprobe analyses. The electron-micro-probe study also showed the preferential segregation of solutes in the microstructure. HIGH-strength aluminum alloys, such as those of the 7000 series, usually freeze by the formation and growth of dendrites. The dendrite arm spacing (DAS) depends on the rate of solidification.' Commercial ingots are usually direct chill-cast to promote more rapid solidification, but, due to the large mass of the ingot, localized solidification times are long and a large DAS results. During solidification, solute elements are rejected by the solid as it forms, causing enrichment of the liquid and ultimately solute-rich interdendritic regions. In order to attain a homogeneous ingot, the segregated solutes must diffuse across the dendrite arms. The larger the DM, the longer the time for complete homogenization. In the case of commercial ingots, the DAS is so large that the time for complete homogenization is prohibitively long and, therefore, second phases or compounds are always present. These un-dissolved phases are carried over to the wrought material during processing, resulting in an impairment of strength and ductility. In addition, the mechanical fibering of the undissolved second phases or compounds during working results in mechanical property anisotropy. If complete homogenization could be attained, higher ductility could be expected. The realization of higher ductility at current strength levels is a desirable objective; however, if higher-strength alloys were wanted, it might be possible to sacrifice some of this ductility by adding more solute elements and produce even higher-strength alloys than are currently available. Further, if complete homogenization leads to more efficient utilization of solute elements, then more dilute alloys should have relatively high strengths with very high ductility. In all instances, it would be expected that the degree of mechanical property anisotropy due to mechanical fibering would be reduced. Therefore, it was the purpose of this investigation to produce cast structures that would facilitate homogenization and to determine the effect of homogenization on the properties of high-strength, wrought-aluminum alloys. MATERIAL CLASSIFICATION Commercial Alloys. In order to illustrate the non-homogeneous condition that exists in commercial high-strength, wrought-aluminum alloys, typical micro-structures of 7001, 7075, and 7178 are shown in Fig. 1. The chemical compositional specifications of these alloys are given in Table I. It can be seen in Fig. 1 that a considerable amount of undissolved second-phase material is present in each of these alloys. The solute elements associated with the undissolved phases were identified by electron microanalyses. Back-scattered electron images and characteristic X-ray images of the three commercial alloys are shown in Figs. 2, 3, and 4. These data indicate that the second phases are regions of high copper and high iron-copper concentrations. The second-phase material also was analyzed for magnesium, zinc, manganese, chromium, and silicon, but no significant enrichment above that of the matrix was found. Therefore, the problem of homogenization resolved itself into one of dissolving the copper-rich and the iron-copper-rich second phases. In order to accomplish this objective, two approaches were made. The first was to reduce the iron as low as possible since this element has a maximum solid solubility of 0.03 pct in aluminum. The second was to produce cast structures with finer DAS to facilitate dissolving the second phases. Commercially Produced High-Purity Alloys. A special high-purity, 2000-lb ingot of 7075 alloy was made by a commercial producer. This alloy contained the following weight percentages of solutes: 5.63 Zn, 2.48 Mg, 1.49 Cu, and 0.21 Cr. All other elements combined were less than 0.02 pct by wt including iron and silicon at less than 0.01 pct each. The ingot was cast and processed into rolled plate using standard commercial techniques. Microstructures of standard commercial 7075 and the special high-purity 7075 are shown in Fig. 5. It can be seen from this figure that the high-purity alloy has less undissolved second-phase material, but a significant amount was still present. The second phase in the high-purity material did not contain iron but it was found to be enriched with copper. The slight effects of the increased purity and de-

Jan 1, 1968

By Don M. Jackson, Robert W. Howard

Techniques for the epilaxial growth of single -crystal silicon carbide films on silicon were developed. The vapor-phase decomposition and bydrogen reduction of silicon tetrachloride (SiC14) and Propane (C3H8) resulted in clear films of silicon carbide, lip to seveval microns in thickness. The growth took place in a horizontal . silicon epilaxial reactor at 1100°C (pyrometer) at a rate of- 3000Å per minute. Electron diffraction and X-ray diffraction studies demonstrated that the films were single-cyrstal, ß -phase, or cubic silicon carbide. SiO2 film were used to mask areas of the silicon sur-lace in order that the silicon carbide might be grown in controlled geometries. Both n- and p-type films were grown on p-type silicon waters.. Heavily doped silicon films of the same conductivity type as the silicon carbide films were deposited over the silicon carbide in order to affect better probe contact to the structures. when n-type silicon carbide mesas were grown on p-type silicon substrates the de vollage-current relationships between films and substrates were that of junction diodes. These diodes showed a sensitivity to while light ill that the incident light increased forward- and reverse-satro,ation currents, P-type silicon carbide mesas grown on p-type silicon were ohmic rather than rectifying in their voltage -current relationship. No conclusions could he reached concerning heterojunc-tiou rectification in the structure. SILICON carbide is a semiconductor with many interesting properties. It decomposes at temperatures above 2200°C.1 It occurs in two general crys-tallographic forms—hexagonal (a Sic) and cubic (ß Sic)—with the cubic form having a forbidden-gap energy of 2.32 ev and the hexagonal form (specifically the 6H polytype) a gap energy of 2.86 ev.3 It behaves as an extrinsic semiconductor at temperatures approaching 5003C. It has been shown to have a high resistance to radiation damage4 and p-n junctions formed in Sic have been shown to radiate visible light under forward- or reverse-bias conditions. Epitaxial silicon carbide on silicon carbide has been successfully grown through the use of a variety of techniques, such as gaseous cracking of SiCL4 and CC4, nearly all of which require a deposition temperature above 1500°C.6 This paper will cover very recent work on the gas-phase deposition of highly ordered films of silicon carbide on high-quality silicon single-crystal substrates. The films have been shown to ex- hibit junction-rectification properties when geometrically isolated regions are electrically biased with reference to the silicon substrate. There will be no discussion of the mechanism of heterojunction rectification, but the methods of film fabrication, geometry control, and structural evaluations will be covered in detail. Electron diffraction, X-ray diffraction, and diode electrical properties were used to characterize the films and the junctions. GAS-PHASE DEPOSITION OF Sic The techniques for the deposition of silicon carbide films were a logical outgrowth of the standard silicon epitaxial process. The major premise followed was that, for any film to nucleate in an ordered fashion where there is considerable mismatch in lattice parameters (in this case 22 pct), an extremely clean, damage-free substrate surface must be presented to the gas stream. Thus a standard gas-phase HCl etching step was used to prepare the substrates for growth. A minimum of 5 µ of substrate-surface material was removed prior to the deposition of Sic overgrowth films. The techniques used for growing silicon carbide films were those of growing silicon alone, with the added injection of a hydrocarbon gas into the hydrogen and silicon tetrachloride gas stream. The hydrocarbon gases used thus far have been research-grade (99.99 pct) methane (CH4) and propane (C3H8). Propane ultimately gave the best results. The gas flows were controlled through a panel shown schematically in Fig. 1. A hydrogen main stream of 30 liters per min passed through the horizontal quartz-tube epitaxial reactor, while SiC14, C3H8, HC1, and doping gases were injected as side streams. The

Jan 1, 1965

By L. R. Woodyatt, H. J. Beattie, C. T. Sims

Theories correlating the formation of u and related intermetallic compounds to the electron-per-atom density of binary and ternary alloys have appeared regularly in recent technical literature. These same principles can be modified and applied to complex precipitation-strengthened alloys such as the iron-, cobalt-, and nickel-base superalloys and the stainless steels. Since these complex alloys contain carbides and other phases that normally precipitate before the U-type phases, the nature and amount of the precipitated phases must be calculated first. The following general formula is then applied to the residual matrix composition of the alloy: element. The magnitude of the resulting number is indicative of whether the alloy will form a a -type phase. When these calculations (which are computerized) are systematically applied to alloys of knoun phase analysis, a breakoff in average electron-vacancy number is noted between U-free and U-prone alloys. Alloys with an average electron-vacancy number higher than the breakoff form a-type phases, while those with lower ones do not form these phases. This method could then be used to eliminate from consideration all experimental compositions that would precipitate undesirable phases. It also is useful in evaluating analyzed heats of alloys where minor heat-to-heat variations determine whether the alloy is o-free or o-prone. THE highly significant development of strong, ductile superalloys to provide reliable construction materials in the 1000" to 2500° F temperature range has been due principally to unremitting application of Edisonian techniques and logic by the dedicated physical metallurgists who have shouldered this responsibility. Tools such as the electron microscope, phase analysis, and computers to accomplish regression analyses have been used heavily, but the effort has been essentially practice of an art, rather than a science. The objective of this paper is to describe and illustrate application of some relatively fundamental principles to certain of these alloy systems in an attempt to remove some of the empiricism from the technology. Specifically, the work presented here deals with the use of periodic-group relationships to predict the formation of intermetallic phases which can occur in primarily austenitic (fcc) structures. Calculations that have been developed might be applied in the design of new alloys and the evaluation of known alloys, and thus have the potential of eliminating vast areas of unnecessary alloy preparation and evaluation. ALLOYING CONCEPTS AND STRUCTURAL FEATURES OF SUPERALLOYS Strength is produced in austenitic superalloys by three principle mechanisms: 1) precipitation of y'; 2) formation of carbides; 3) solid-solution hardening by soluble refractory metals. The first mechanism requires the addition of aluminum and titanium, the second requires carbon and carbide-forming elements, while the third calls for the addition of molybdenum and/or tungsten. A considerable concentration of chromium is usually maintained to resist oxidation/corrosion, but it is also an important carbide-forming element. Fig. 1 shows a sketch and electron micrograph of the structure of a typical wrought nickel-base super-

Jan 1, 1967

By Frank S. McKenna, Myron A. Pugacz, Clarence E. Jackson

THE notched-bar impact test has proved worth while in certain applications as a test for control of the quality or the heat- . treatment of steel. In view of the serious thought that even so simple a test as the tensile test, has evoked during the past years, it is not surprising that the notched- bar impact test should have inspired much experimental work. The correlation of the great number of data has not been successful, although steady progress has been made toward a better understanding of this test. Progress has been made, especially, in the isolation of the effects of the many variables that control the results. The stress system imposed on a specimen with a notch is so complicated and un- predictable that no simple evaluation of the test has been possible. Because of this uncertainty, many engineers hesitate to use the notched-bar impact test, and this attitude may well continue until a better understanding of the effects of the variables in the test are available. Without doubt, any additional data that may be presented should be accompanied by as complete a description of the details of test as possible, so that it may be added to the general fund of information that is to serve as the basis for the theory of the notched-bar impact test. The many factors that may control the test results have been pointed out repeatedly. The importance of the effect of the type and dimensions of the specimen has been recognized. Most of the work reported by American investigators has been limited to small- size (Charpy) specimens tested as a simple beam; two types of notches (Fig. I) have been commonly used. Considerable data have also been presented by many investigators using a small specimen tested as a cantilever beam; this commonly being called the Izod test. Here, however, a shear component of stress makes the stress system even mare complex than that present in the simple beam type of test, hence a critical analysis is difficult. Much work has also been reported by investigators using the tension type of specimen. A second variable that must be con- trolled is the testing temperature. An indication that the tests were performed at room temperature is not sufficient, since in many steels a variation of a few degrees in the actual testing temperature may be sufficient to give an entirely different range of results. Other factors. such as the com- position and condition of the material being tested and the speed of test, should also be considered. Many investigators have contributed data and theoretical discussions on the problems encountered in notched-bar test-

Jan 1, 1944

By Howard Eavenson

EARLY in 1917, the United States Coal & Coke Co. secured options on several tracts in Harlan County, Ky., aggregating about 1.9,000 acres in area, and after careful prospecting by outcrop openings and diamond drilling, completed the purchase late in July of that year. This property is situated in the eastern end of Harlan County, south of the Poor Fork f Cumberland River, and extending across Big Black Mountain to the Clover Fork of Cumberland River, a distance of about 7 mi. (11.3 kg.). It extends from the Kentucky-Virginia line westward for about 6 mi. Looney Creek, which empties into Poor Fork, crosses the property for about 4 mi. (6.4 kg.), and as several of the seams within the property outcrop along this stream, it afforded an easy, and the logical, place for development. The property is on the northern side of the geological trough formed by the uplifting of Stone Mountain, on the southern, and Pine Mountain, on the northern side; the northern boundary along Poor Fork is practically at the base of Pine Mountain. This, area has been described in various geological reports.1 The main seam on this property is the one known variously as the "C," Benham, Keokee, Taggart, and Roda; it is, also called, by the Kentucky Geological Survey, the Kellioka seam of the western portion of Harlan County. This seam averages, in this property, about 5 ft. (1.5 m.) in thickness, although local rolls reduce this thickness considerably over small areas; and at the extreme western end of the property the seam splits. It is usually clean, although occasionally a small parting occurs within a few inches f the bottom f the seam; it is one f the best

Jan 9, 1921

By Eric Jette

THE alloys of gold and iron were investigated in 1907 by Isaac and Tammann,1 who determined the thermal diagram for the entire system by thermal analysis and microscopic examination. They also reviewed the previous literature. Since that time the present authors have been able to find only two additional references. Guertler and Schulze2 examined the electrical resistance of iron alloys containing up to 40 per cent by weight of gold between 0° and 200° C.; the alloys were in the form of wires. The main result of this work was to confirm the solid solubility limit found by Isaac and Tammann; namely, about 20 per cent Au. More recently, Shih3 has examined the magnetic properties of gold alloys containing up to 10 weight per cent iron and particularly the range below 5 per cent. The alloys in the lower range were found to be paramagnetic; the 10 per cent alloy was ferromagnetic. The present investigation was undertaken to determine the solid solubility limits at various temperatures, particularly below the a-y transformation point of iron, since these solubilities are of some impor-tance in connection with the working of the alloys in the manufacture of certain "grey" and "blue" golds.

Jan 1, 1934

By R. Taggart, J. W. Barton, G. R. Purdy, J. G. Parr

The constitution and mechanical properties of heat-treated alloys containing up to 10 pct* Ni in Ti have been investigated. The effects of quenching and of various isothermal treatments ale described, and C-curves are presented. The production of the precipitated and the martensitic hexagonal phases on quenching is discussed. MARGOLIN, Ence, and Nielsenl have determined the titanium-nickel phase diagram. A study of the transformations in gas-quenched and tempered powder specimens was made by Polonis and Parr.' Some isothermal transformation work was carried out by Margolin and ~unshah, who determined transformation curves for 4 and 6 wt pct alloys, while Robinson et al.investigated the formation of the w phase in a quenched and tempered alloy, Margolin and Bunshah showed that while a martensitic transformation could be obtained on quench- ing thin sections of a 4 wt pct alloy, a 6 wt pct alloy precipitated a nonmartensitic phase. The present investigation was undertaken to obtain more information on the transformations in quenched, quenched and tempered, and isothermally transformed lump specimens of alloys containing up to 10 pct Ni. Isothermal transformation curves have been determined for 7 and 10 pct alloys and cooling curves have been obtained for quenched alloys containing up to 7 pct Ni. The mechanical properties of 2, 5, and 10 pct alloys were studied, with the object of relating properties to microstructures. EXPERIMENTAL METHODS Alloys containing up to 10 pct Ni were prepared from sponge titanium and spectrographic standard nickel by levitation-melting and chill-casting in a split copper mold. The 5 and 10 pet alloys were prepared from sponge Ti having an as-melted hardness of 115 Vpn. The other alloys were made from a sec-

Jan 1, 1961

By E. T. Turkdogan, M. T. Hepworth, R. P. Smith

The permeability of oxygen in 0 iron in the tempera-ture range 700" to 900 C and in 6 iron at 1450°C was determined by the rate of internal oxidation of iron, containing -0.1 pct Al. The solubility of oxygen in zone-refined iron was determined by equilibration with hydrogen-water vapor gas mixtures at 1450" and 1510°C; oxygen solubilities , for iron in equi1ibriu.rn with molten oxide, are found to be 66 and 83 ppm for these two temperatures, respectively. The diffusivity of oxygen in iron at 14500C3 as calculated from the permeability and solubility data, is (4.1 * 0.6) x 10 "B sq cm per sec. OXYGEN is one of the most common impurities present in iron or steel, mainly in the form of oxide inclusions. In the study of many metallurgical problems concerning solid iron, it is often desirable to know with a reasonable accuracy the solubility and diffusivity of oxygen over a wide temperature range. The solubility of oxygen in solid iron has been the subject of numerous studies yielding highly discordant results as seen for example from the literature surveys made by Meijering &apos; and Schenck et a1.&apos; As shown by Kitchener et aL3 and by Sifferlen, the high oxygen solubilities reported by many investigators are the result of oxidizable impurities which are often present in iron. In addition, there have been experimental problems associated with icaccuracy of oxygen analysis of iron containing less than 100 ppm 0. A number of studies have been made on the permeability of oxygen in a and y iron using Fe-Si, Fe-Mn, and Fe-A1 alloys in the internal-oxidation experiments.1&apos;2&apos;5&apos;6 However, no direct measurements have been made of the diffusivity of oxygen in iron. In the present work two sets of experimental measurements were made: permeability and solubility studies at 1450" and 1510°C and permeability studies only in the range 700 to 900°C. In both sets of permeability measurements slab-shaped specimens containing small predetermined amounts of aluminum in solution were exposed at constant temperature to gas mixtures of hydrogen, water vapor, and argon for varying times. These specimens were quenched, sectioned, and examined for oxygen penetration by metallographic observation of aluminum oxide particles which formed. From these data, it is possible to calculate the ratio of the diffusivity of oxygen in iron, D, to the equilibrium constant K for the reaction Hz(g) * O (dissolved in iron) = H,O(g). EXPERIMENTAL Permeability Measurements at 1450°C. An ingot of vacuum-carbon deoxidized iron containing 0.086 pct A1 was prepared, using commercial "Type lO4A Plas-tiron"; after hot rolling, specimens were machined into slabs a by 2 by 2 in. The impurity contents were: S, P < 0.002 pct; C, Mn < 0.01 pct; each of all other Usual impurities < 0.004 pet. The amount of oxide inclusions in this material, determined by a bromine-methyl acetate extraction, corresponded to about 20 ppm 0 in the iron which agreed well with the results of vacuum-fusion analysis. Each specimen was annealed at 1450°C for 1 hr in purified hydrogen, polished to a smooth surface, and then introduced into a controlled oxidizing atmosphere in a recrystallized alumina tube at 1450°C. The constant temperature zone (*3"C) was about 3 in. in length. The gas composition was controlled by mixing argon with hydrogen (using calibrated constant-head flow meters) and passing the mixture through a column of a mixture of oxalic acid dihydrate and 10 pct anhydrous oxalic acid, to establish a required water-vapor content in the gas mixture. The temperature of the oxalic acid dihydrate column was controlled by a thermostat. The total gas flow was in the range 800 to 1000 cu cm per min. The exit gas from the reaction tube was passed through a weighing bottle containing a desiccant, to cross-check the degree of water-vapor saturation, which for all experiments was about 97 pct of those derived from the data of Baxter and Lansing.1 For a typical experiment, a specimen was introduced into the furnace in a stream of dry argon and hydrogen. The specimen was then rapidly raised by a Pt-Rh alloy wire into the hot zone and allowed to reach the reaction temperature, at which time the oxidizing gas mixture was introduced. The oxygen potentials employed were sufficient to oxidize aluminum but not to cause liquid iron oxide to form. After a specified time, the experiment was ended by dropping the specimen onto a water-cooled copper block at the bottom of the reaction tube. The depth of the internally oxidized zone, hereafter called the "case", was determined by sectioning the specimen at right angles to the long direction. The section was then examined under a microscope equipped with a micrometer stage. In general, the oxide particles were fairly uniform in size and distribution, forming a reasonably well-defined interface between the oxidized and unoxidized region. A typical cross section as observed at X30 is shown in Fig. 1. A thermal macroetch was used in one selected specimen to delineate the case. A cross section of a previously oxidized slab was polished and reheated at 1450°C in a hydrogen atmosphere for about 10 min. Upon quenching, the surface relief shown in Fig. 2 was produced; causes of this effect are unknown. Permeability Measurements Below 900°C. A slightly

Jan 1, 1967

By Gordon S. Duncan

(New York Meeting, February, 1912 THE U. S. Geological Survey, I believe, has almost completed a study of the Harney Peak quadrangle, preliminary to the publication of a report on that, district. As I was engaged for some months on an investigation of the mode of occurrence of the ore-bearing formation in this area, it has seemed to me timely to make public the results of my study, as a contribution to the consideration of this subject. It seems scarcely necessary to describe the locality and general geology of the Black hills of South Dakota, for since 1846 many have contributed information concerning this region, some of the reports bearing such well-known names as those of Walter P. Jenney, Henry Newton, S. F. Emmons, and C. R. Van Hise, while we have only to glance at Bulletin No. 4 of the South Dakota School of Mines, in which Prof. C. C. O&apos;Harra, of that institution, has given us a bibliography of contributions to the geography and geology of the section, to find that other well-known men have studied the district, and have given us the benefit of their researches. The U. S. Geological Survey has made geological maps of nearly the whole of the Black hills, the only quadrangle yet to be completed being, as stated, the Harney Peak district. During the late summer and autnmn of 1910, it was my lot to examine and report. on a considerable area in this neighborhood, which once had been prospected, and in some cases exploited, for tin. This paper gives an account of certain geological phenomena, noted at that time, which greatly influenced my conclnsions. The predominating formation of the district is pre-Cambrian, represented by a highly-cleaved mica-schist, usually very garnetiferous, and sometimes hornblendic. Rising like an island from the surrounding schist is a large mass of granite, known as

Jul 1, 1912

By W. M. Bertholf

To establish the minimum or break-even efficiency of a preparation plant it is necessary to determine the ratio of production costs per ton of run-of-mine coal to sale price per ton of clean coal. This ratio is then divided by the percentage of plant recovery. Assume, for example, that washability data indicate that 80 pct of the run-of-mine coal may be recovered as clean coal selling for $5.50 per ton. If the same plant incurs $4.00 per ton mining costs and $0.25 per ton preparation costs, the cost to sale price ratio would be 4.25/5.50, or 77.3 pct. Since the plant is capable of recovering 80 pct of the run-of-mine coal the minimum plant efficiency would be 77.3/80, or 96.6 pct. If the plant efficiency were increased to 100 pct the limit on preparation costs would be increased to $0.40. Therefore, the washing operation must be accomplished at a cost of $0.25 to $0.40 per ton and the efficiency must be 96.6 pct or higher. By plotting a curve of efficiency vs preparation costs and taking into consideration the plant cost, feed rate, operating costs, and yields of the various flowsheets it is possible to select a financially sound process. Table I classifies preparation processes according to their nature of separation. It must be remembered that what is thought to be ideal does not always prove practical under actual operation. An outstanding example is the work done on the plunger-type jig. It was determined by the law of equivalence that this unit could treat satisfactorily only sizes differing by no more than a ratio of 2. Yet these same plunger-type jigs are successfully treating sizes considerably greater than this ratio.

Jan 12, 1957

By D. D. Homer, R. H. Cromwell

The Minas de Matahambre No. 2 shaft, vertical, four-compartment lined with steel sets and hardwood lagging, has been sunk 2057 ft. On account of rock structure, over-all cross-section dimensions are 23 by 6 ft. Certain sections have been concreted. Two compartments are for handling ore and men, one for supplies and men, and one for manway, cables and counterweight. Two 250-ton capacity skip pockets with air-operated gates and steel cartridge pockets have been installed underground. A steel "A" headframe, a 250-ton steel receiving bin, and skip-to-man-cage changing equipment have been provided. Skip capacity is 102½ cu. ft. The hoist is a Nordberg double-drum 10 ft. by 6 ft. 6 in. geared, electrically driven, with parallel grooving for 1-?in. cables. Maximum hoisting speed is 1600 ft. per minute. The motor-generator set, control panel, slip regulator and hoist accumulator are housed in the basement of the hoist house. The electrical equipment is General Electric. The direct-current hoist motor is 800 hp. Control is of the Ward-Leonard-Ilgner type. The motor-generator flywheel set, normal speed 720 r.p.m., consists of an 800-hp. induction motor, a 22-ton flywheel (dia. 117 in.) and a 650-kw. generator.

Jan 1, 1934

By E. J. Rapperport, E. D. Levine

The boundaries of the (a +ß) field in the Al-Li system were determined between 150°and 550°C utilizing quantitative metallography and lattice-parameter measurements. The solubility of lithium in aluminum decreases from 12.0at. pct Li at 550°C to 5.5 at. pct Li at 150°C. P Al-Li is saturated with aluminum at 45.8 at. pct Li and has this boundary value constant over the temperature range 150°to 550°C. THE solid solubility of lithium in aluminum has been determined by several investigators, 1-6 but, as shown in Fig. 1, there is little agreement among the various determinations. The earliest investiga-tions&apos;-&apos; are suspect because of the use of impure materials. Although high-purity materials were employed in more recent work,4&apos;5 the experimental techniques may have led to contamination of the specimens. Probably the best work has been that of Costas and Marshall,6 who obtained close agreement between results obtained by two independent phase-boundary techniques: electrical resistivity and mi-crohardness. No detailed studies of the solubility of aluminum in the bcc ß phase, Al-Li, have been reported. Cursory investigations1,2,6 have indicated only that the (a+ß) -p boundary lies between 40 and 50 at. pct Li and is relatively independent of temperature. The present work was undertaken in order to provide an independent check on Costas and Marshall&apos;s determination of the solubility of lithium in aluminum, to extend knowledge of this solubility limit to temperatures below 225°C, and to make an accurate determination of the solubility of aluminum in Al-Li. EXPEFUMENTAL Alloy Preparation. In view of the difficulties encountered in previous investigations of the A1-Li system, close attention was paid to the use of methods of alloy preparation and treatment that would minimize contamination. Aluminum sheet (99.99 + pct Al) was vacuum-induction melted in a beryllia crucible to remove hydrogen. Lithium (99.9 pct Li) was charged with pre-melted aluminum into a beryllia crucible, in a helium-filled drybox. The crucible was sealed in a Vycor tube and transferred from the drybox to an induction furnace. Melting of alloys was performed by induction heating in a helium atmosphere. Solidification was accomplished by means of a suction apparatus, shown in Fig. 2, in which the alloy was forced by changes of pressure into a 3/16-in. inside diam closed-end beryllia tube. This technique produced rapid solidification of a small portion of the melt, resulting in alloys with a high degree of homogeneity. Typical lithium distributions are presented in Table I. Transverse sections 1/8 in. long were cut from the alloy rods, and each section was split in half longitudinally. One half of each section was analyzed for lithium, and the opposing halves were employed for phase-boundary determinations. Lithium contents were determined by flame photometry with an accuracy of 1 pct of the amount of lithium present. Thermal Treatments. Homogenization and equilibration heat treatments were performed in electrical-resistance furnaces with temperatures controlled to ± 2OC. Calibrated chromel-alumel thermocouples were employed to measure temperature. Homogenization was performed in helium-filled l?yrex tubes for 1 hr at 565°C. The encapsulated specimens were then transferred directly to furnaces maintained at lower temperatures for equilibration. Equilibration times were 2 hr at 550°C, 8 hr at 450°C, 27 hr at 350°c, 90 hr at 250°c, and 285 hr at 150"~. These times were chosen on the basis of conditions employed by previous investigators. Alloys were quenched from the equilibration temperatures by breaking the capsules into a silicone oil bath. By performing all possible operations either in sealed capsules or in a helium-filled drybox, the specimens were given minimum exposure to the atmosphere. Quantitative Metallography. Metallography of Al-Li alloys is difficult because of the atmospheric reactivity of the ß phase. It was found possible, however, to prepare surfaces of good metallographic quality by preventing contact with moisture during preparation. Grinding through 4/0 paper was performed in the drybox. The specimens were then transferred under kerosene to the polishing wheel. Three polishing stages were employed: 25-p alundum with kerosene lubricant on billiard cloth, 1-µ diamond paste on Microcloth, and 1/4-p diamond paste on Microcloth. Between stages the samples were cleaned by rinsing in trichloroethylene and buffing

Jan 1, 1963

By J. O. Betterton, D. S. Easton

A detailed investigation was made of the phase diagram of silver-zirconium, particularly in the region 0 to 36 at. pct Ag. The system was found to be characterized by two intermediate phases Zr2Ag and ZrAg and a eutectoid reaction in which the -zirconium solid solution decomposes into a-zirconium and Zr2Ag. It was found that impurities in the range 0.05 pct from the iodide-type zirconium were sufficient to introduce deviations from binary behavior, and that with partial removal of these impurities an increase in the a-phase solid solubility limit from 0.1 to 1.1 at. pct Ag was observed. The phase diagram of the silver-zirconium system is of interest as an example of alloying a transition metal from the left side of the Periodic Table with a Group IB element. Silver would normally act as a univalent metal, its filled 4d-shell remaining undisturbed during the alloying. However, there is a possibility that some of the 4d electrons might transfer to the zirconium. An insight into such a question can occasionally be obtained by comparison of phase diagrams. The silver-zirconium system forms part of a more complete review of various solutes in zirconium in which these valency effects were studied.&apos; Earlier work on the silver-zirconium system was done by Raub and Enge1,2 who investigated the silver-rich alloys. After the start of the present experhents, work on this system was reported by Kemper3 and by Karlsson4 which for the most part agrees with the phase diagram presented here. EXPERIMENTAL PROCEDURE The alloys were prepared by arc casting on a water-cooled, copper hearth with a tungsten electrode and in a pure argon atmosphere. Uniform solute composition was attained by multiple melting on alternate sides of the same ingot. Progressive improvements in the vacuum conditions inside the apparatus during the course of the experiments reduced the Vickers hardness increase of the pure zirconium control ingot from 10 to 20 points, observed initially, to negligible amounts at the end of the experiments. Such hardness changes in zirconium are a well known indication of purity. For example, -01 wt pct additions of oxygen, nitrogen, and carbon increase hardness by 6, 10, and 3 VPN respectively. &apos;9&apos; Further verification that the final casting technique did not add a significant quantity of impurities was obtained when pure zirconium was arc cast and then isothermally annealed in the vicinity of the allotropic transition. The transition was always observed to take place over the same temperature range as in the original crystal bar. The alloy ingots were annealed in sealed silica capsules for times and temperatures which varied between 1 day at 1300°C and 60 days at 700°C. The best method found to prevent the reaction of the zirconium with the silica was foil wrapping of molybdenum or tantalum. With this method, samples of pure zirconium were found to be unchanged in hardness after annealing for 3 days at 1200°C. In most of the experiments the protection of these foils was supplemented by an additional layer of zirconium foil inside the molybdenum or tantalum foil. The alloys, foil, and the capsule were outgassed at pressures in the range 10 to l0-7mm Hg in the temperature range 800" to 1100°C before each anneal in order to remove hydrogen and other impurities, and to provide a suitable container for the high purity, inert atmosphere, which is essential in the annealing of zirconium. The temperature measurements were made with Pt/Pt + 10 pct Rh thermocouples calibrated frequently during the experiments against the melting points of zinc, aluminum, silver, gold, and palladium. For the longer anneals the sum of various temperature errors was generally well within ± 2°C. For short-time anneals and during thermal analysis the overall temperature error is considered to be within ± 0.5°C. The compositions of the alloys from the quenching experiments were determined by chemical analysis at Johnson Matthey and Company, Ltd., under the direction of Mr. F. M. Lever. The actual metallo-graphic samples were individually analyzed in every case, and prior to the analyses two or more sides of each specimen were examined to insure that the specimen was not segregated. The sum of the solute and solvent analyses was in each case within the range 99.9 to 100.1 pct. In the course of the experiments, minor impurities in the range 0 to 500 ppm were found to have significant effects on the zirconium-rich portion of the phase diagram. Similar effects had been encountered previously in other zirconium phase-

Jan 1, 1959

By L. F. Mondolfo, B. E. Sundquist

The undercooling associated with the nucleation of the secondary phase from the liquid by the solid primary phase was studied in sixty binary alloys by means of a hot-stage microscope. It was found that in a system of a and ß, a usually nucleates ß at low undercoolings, but ß does not nucleate a, except possibly at undercoolings approaching homogeneous nucleation. This behavior can be explained in terms of relative interfacial energies and shows that crystallographic disregistry is only a minor factor in heterogeneous nucleation from metallic liquids. PREVIOUS experimental work1-6 on nucleation of solids from liquids has shown that normally nucleation is heterogeneous, and that small solid particles present in the liquid are responsible for the nucleation. These experiments and the theory that has evolved from them have made apparent that there is a "characteristic undercooling" associated with the nucleation of the solid from a given liquid by a given impurity. Little is known, however, about the chemical and structural relationships between the nucleating agent and nucleated solid that control the effectiveness of the nucleating agent in catalyzing the nucleation, as measured by the required undercooling. A review of the literature has yielded seventeen undercoolingsL-6 for the nucleation of solid from liquid metals by "known" nucleating agents. All values come from experiments in which the metal studied was divided into a number of particles (10 to 300 pin diam.) much larger than the number of extraneous impurity particles so as to obtain a large number of particles free of foreign nucleating catalysts. Known nucleating agents are then introduced by coating the droplets with particles or a thin film of the catalyst. Six of the seventeen undercooling values referred to cases where, for various reasons, the identity of the nucleating species was not at all certain. Another six cases involved nucleating agents with a crystal structure that was not known. Four other cases involved undercoolings listed as greater than or equal to undercoolings which were very likely those for homogeneous nucleation. One investigation3 involved adding to droplets powdered oxides, carbides, and so forth that were doubtlessly covered with adsorbed oxide or nitride films. The highly variable nature of these films resulted in highly variable undercooling (as was also found in preliminary work in this investigation). It is apparent that the information on heterogeneous nucleation in liquid metals is too limited to give rise to any definite conclusions on the nature of the catalytic process. With these problems in mind a new method was

Jan 1, 1962