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By E. C. Truesdale, Gerald Edmunds

A few years ago H. M. Cyr, working in the Research Laboratories of The New Jersey Zinc Co., produced a few pounds of zinc1 of such purity that no other elements were detected in it by spectrographic analysis, using the facilities then available. This zinc contained less than one ten-thousandth of one per cent of metallic impurities.&apos; During the decade that followed upon the laboratory production of this "spectro-graphically pure" zinc, commercial developments brought about the production of large tonnages of zinc of purity exceeding 99.99 per cent, and today zinc of 99.999 per cent purity is produced and marketed as "chemically pure" zinc. Typical analyses of present supplies of high-purity zinc are given in Table 1. Table 1.—Typical Analyses Percentnge by Weight Sum of Zinc Fe, Ib1 Fe Cd 1A1 cd Special High Grade*.......... 0.007b 0.005b 0.005b none O.OIOb C.P. (chemically pure)......... < 0.0002 0.0005c 0.000052 S.P. (spectrographically pure).. <0.0002d <0.00005d a A.S.T.M. Standard Specification for Special High Grade Slab Zinc (A.S.T.M. Designation: B 637). b Maximum. &apos; Fe chemically determined. Pb and Cd are spectrographically determined. d Differences between composition of C.P. and S.P. zinc are discussed later in this paper. The availability of commercial tonnages of special high-grade zinc has been the basis for the development of the zinc-base die-casting alloy industry which, in the year 1936, consumed one-eighth of the zinc used in the United States for all purposes. This and the C.P. and S.P. grades have given impetus to scientific investigations into the properties of pure

Jan 1, 1939

By D. J. Jr. McAdam

PART I.-OUTLINE OF INVESTIGATION, DESCRIPTION OF METHODS AND MATERIAL Previous Investigation of the Influence of Stress on Corrosion IN 1917 Haigh1 presented evidence that under simultaneous corrosion and cyclic stress metals may fail at lower stresses than if the corrosion is prior to the cyclic stress. In 1926 the author, while investigating the cooling effect of water on the fatigue resistance of metals, found that under these conditions steel specimens fail at stresses far below the endurance limit.2 (By "endurance limit" is here meant the fatigue limit obtained with specimens as free as possible from stress concentration and corrosive influences.) This led to an investigation (at the Naval Engineering Experiment Station, Annapolis, Md.) of the influence of cyclic stress on corrosion. This investigation maybe divided into three parts. The first part was a general survey of the conditions necessary to cause complete failure under corrosion and cyclic stress of relatively high frequency. The entire process by which metals fail under these conditions was-called "corrosion-fatigue." "Corrosion-fatigue limits" for a large number of metals were determined and the relationships of these limits to chemical composition, heat treatment and physical properties were established. The conclusion was reached that corrosion-fatigue is due to the accelerating influence of cyclic stress on corrosion. Results of this part of the investigation were presented in five papers.2-6 The second part of the investigation was a preliminary study of the influence of cyclic stress on corrosion. Each experiment was conducted in two stages. The first was a corrosion stage in which the specimen was corroded under cyclic stress; the second was a fatigue stage, in which the previously corroded specimen was tested (without further corrosion) to determine its fatigue limit. The difference between this fatigue limit and the endurance limit was used as a criterion of the "damage" due to

Jan 1, 1931

By C. T. Malcomson

An elaborate series of experiments has been conducted during the past three years at Irvington, N. J., which has resulted in the perfection of a process for the manufacture of smokeless fuel from high-volatile coals, and for the recovery and refinement of the coal-tar products derived therefrom. These experiments have been financed by Messrs. Blair & Co., of New York, and were conducted under the direction of Charles H. Smith, a member of this Institute, and the inventor of the process. The low-temperature distillation of coal has interested investigators for many years. Sporadic attempts have been made to solve the mechanical problems, but until the Smith process was developed, they were not carried to conclusions of economic value. The present coal shortage and the increasing demand for smokeless fuels make this subject one of timely interest. DescRiption of Plant The following equipment was installed and operated during the experimental period: Four horizontal and two vertical units of commercial size for the low-temperature distillation of the coal; two vertical, two horizontal, and two inclined benches for distillation of the briquets at medium and higher temperatures; presses and auxiliary equipment necessary for making briquets; and a complete byproduct recovery and tar-refining plant. This commercial equipment is provided with gas and electric meters, pyrometers and other apparatus for recording accurately the results of all experiments. There is, in addition to the commercial equipment, a complete chemical laboratory with distillation and recovery apparatus, including facilities far refining and cracking the tar and measuring the yields and calorific value of the gas. This apparatus makes possible a study on a small scale, of the various problems involved in the process. Description of Process Mr. Smith&apos;s experiments have resulted in the production on a commercial scale of: 1. A fuel, called Carbocoal, which, for convenience in handling, is prepared in briquet form.

Jan 1, 1920

By Wilson Blake

A mathematical model based on the finite element method of stress analysis has been used to describe the behavior of the western wall of the Kimbley Pit as its slope was steepened from 45° to 57°. Theoretical stress changes because of slope modification are slight except at the toe of the modified slope. Magnitudes of stress created are small when compared with the strength of a competent rock. Resulting displacement patterns point out the need for determining the in-situ state of stress at a site prior to excavation or modification. A comparison of model results with field measurements shows that, in general, the model has described the measured behavior of the west wall of the Kimbley Pit remarkably well. The Bureau of Mines and the Kennecott Copper Corp. began joint research on open-pit slope stability at the Kimbley Pit, Ely, Nev., in 1961. The initial or planning phase of this research dealt with a detailed geologic study of the Kimbley Pit, determination of in-situ stresses in the district, laboratory and field tests to determine rock properties, and the design of a full-scale experiment to study the behavior of this pit as its western wall was steepened from 45° to 57°. Fig. 1 shows a cross-section of the original pit outline, the steepened pit outline, major geologic features, and the two instrumentation adits. After the final or slope modification phase of the research began, a laboratory research program was initiated to develop a mathematical model that would analytically describe the behavior of the pit as its western slope was steepened. This theoretical model study of the slope modification at the Kimbley Pit was conducted with the finite element method of stress analysis. The results are described in this report.

Jan 1, 1969

By S. N. Kesten, Richard Murphy, A. H. Land, W. F. James

Introduction—by W. F. James and A. H. Lang This paper describes the geology and present state of development of uranium and thorium deposits in Canada. It is expected that this information will be added to that now being assembled from available American and British data to provide a background for engineers and others who may be called upon in the future to examine or search for radioactive deposits. Some generaliza- tions regarding the Canadian deposits are included, but many of these are necessarily tentative. The information contained in the paper is up to date for the end of 1948. The information contained in this paper has been derived from many sources. Much of it is from the records of the Canadian government-owned Eldorado Mining and Refining (1944) Limited and from examinations of government and private properties made by officers of the Geological Survey of Canada. Some information on privately-owned properties has been quoted from other sources mentioned in the text. The information has been assembled by W. F. James of Eldorado Mining and Refining (1944) Limited and A. H. Lang of the Geological Survey of Canada, who have written the sections for which they are credited. The description of the Eldorado mine is based on reports by Richard Murphy, formerly chief geologist for Eldorado; the report by Mr. Murphy was published previously by the Canadian Institute of Mining and Metallurgy,&apos; to whom the writers are indebted for permission to repub-lish. The section dealing with the geology of and development work in the Goldfields area, where Eldorado has important holdings, is by S. N. Kesten, field geologist for Eldorado. The geological diagram of the Goldfields area (fig. 2) was kindly supplied by A. M. Christie of the Geological Survey of Can-

Jan 1, 1951

By C. A. Heiland W. E. Pugh

The principle underlying the majority of magnetic intensity variometers is a comparison of the force to be measured with another force of known magnitude. The known force may be (a) of a magnetic nature, such as magnetic fields produced by magnets or coils, or (b) of a mechanical nature, such as (1) the elastic forces of wires, or (2) the force of gravity, such as employed in bifilar magnetometers and magnetic balances. In instruments of such type, usually a magnetic system is employed, free to move about either a horizontal or vertical axis, on some sort of a suspension. If the earth&apos;s magnetic field alone were present, such a system would adjust itself into the direction of the field or that of its components. Owing to the simultaneous action of the comparison force, however, the magnetic needle assumes a position that differs from the direction of the magnetic force; for all such instruments, the angle of deflection is given by tan = FIX, where F is the known and X the unknown earth magnetic force component. In other words, the magnetic system merely serves as an "indicator" for the position of balance of the two forces. Considering the matter from this point of view, it is not immediately obvious why the temperature of such a magnetic system should modify the results. In magnetic instruments, we may distinguish two different effects of temperature: (1) a magnetic effect and (2) a mechanical effect. The first is due to the fact that the magnetic moment of a magnet drops with an increase in temperature. This drop is characterized by the temperature coefficient of the magnetic moment (see equation 1). The second effect is due to the change in the torsion of suspension wires with temperature or to the expansion of lever arms of masses acting on magnetic balances.

Jan 1, 1934

By Earl Bardwell

THE structural relations existing between cuprous oxide and copper -were first systematically studied by Heyn1&apos;, who suggested that a study of the microstructure of refined copper might be substituted for the analytical methods in vogue for determining the oxygen content of copper coming from the refining furnace. Hofman, Green and Yerxa,2 in their paper A Laboratory Study of the Stages in the Refining of Copper, working along the lines suggested by Heyn, showed that a study of the microstructure could be made to yield a correct estimate of the oxygen content of the specimen of refined copper under examination. In order to determine the oxygen content of the specimen of refined copper under. examination a photomicrograph was first made. From the relative areas of copper and eutectic, the percentage of cuprous oxide and the corresponding percentage of oxygen were then readily calculated. It was found that the values for oxygen thus obtained corresponded closely with the analytical results. With the idea of utilizing this method of determining the oxygen content of each charge dipped from the refining furnaces at the Boston & Montana Reduction Plant, the physical testing laboratory was equipped with suitable apparatus for carrying out the work. It may be of interest to describe certain of the methods which have been worked out in this connection and give such data as have been obtained bearing on the effect of the oxygen content of refined copper upon its conductivity. Apparatus.-For the benefit of those who may be unfamiliar with metallographical apparatus and methods and may be interested to know what equipment is required, a few words with regard to the apparatus is in place at this point.

Jan 7, 1913

By H. I. Althulee

The mines operated by the Compañía de Real del Monte y Pachuca, Pachuca, Mexico, are in two districts, the Pachuca, and Real del Monte. The principal area of mineralization is within a rectangle roughly 10 miles from east to west and 6 miles from north to south. It contains a number of veins from 2 to 20 ft. wide, which are exploited by this mining company. The scattered position of the producing mines led to the construction of two mills between 1906 and 1908; the Loreto mill, in Pachuca, averaged 2600 tons daily, and the Guerrero mill, in Real del Monte, milled 1270 tons daily. On Feb. 1, 1929, the management decided to enlarge the Loreto mill to take the combined tonnage of both mills at that time. This economic measure required the centralization of ore delivery, which would also afford a material saving in the cost of ore transport. The centralization would give the company the following advantages over the former system of operation: 1. Beneficiation at a single mill, closer to source of materials and supplies than the abandoned Guerrero mill. The refinery is also in the Loreto patio. 2. Ore delivery to surface at one point (San Juan Pachuca shaft) instead of at four. 3. Elimination of aerial tramways. To show what would be required to effect this centralization, it is necessary to describe the means by which the ore was delivered to the two mills, prior to centralization. The heart of the Real del Monte district is roughly four miles from that of the Pachuca section. The producing mines in these two districts were: Pachuca district: Real del Monte district: Santa Ana mine La Rica group Camelia group Purisima group Santa Margarita mine

Jan 1, 1934

By J. W. Leonard, J. C. Anderson, C. T. Holland

PREPARATION CONTROL IN UNDERGROUND MINING Selective Mining According to district Depending upon the particular geographic loca- tion or seam characteristics, modern raw coal preparation practices can be used to obtain improved product quality and uniformity. Nevertheless, certain coal markets may require only marginal quality while others may require very high quality, and these objectives may be sought by commencing the preparation of coal underground at the "working face." Under- ground preparation involves choosing those portions of the seam which can be cleaned to satisfy predetermined market requirements involving ( 1 ) maintenance of uniformity in chemical quality, (2) elimination of removable impurities, (3) control of sizes and size ratios, and (4) control of moisture. The methods employed to attain these objectives vary widely with the (1 ) seam under development, (2) mining equipment available, and (3) changing trends in the consuming markets. When a mining property is opened and development progresses from one section to another, the (1) petrography of the coal in the seam does not remain uniform, (2) character of roof and floor are subject to change, and (3) character and prevalence of mineral impurities are subject to considerable variation. The quality of coal shipped to market from any mine depends upon intelligent foresight, planning, execution, and supervision. Mining becomes a highly technical art. The quality of coal as determined by chemical and petrographic analysis is without question one of the most important considerations in the development and life of any coal-mining property. Variations in such proper- ties as volatile matter, ash, sulfur, Btu content, and petrography are of considerable interest, and to a limited extent so are such properties as phosphorous content, free swelling index, plasticity, hardness, pressure formation during coking, and ash composition. The maximum and minimum specifications of these characteristics as established by competitive market conditions place definite limits on the marketability of a coal.

Jan 1, 1979

By W. F. James, Richard Murphy, S. N. Kesten, A. H. Land

Introduction—by W. F. James and A. H. Lang This paper describes the geology and present state of development of uranium and thorium deposits in Canada. It is expected that this information will be added to that now being assembled from available American and British data to provide a background for engineers and others who may be called upon in the future to examine or search for radioactive deposits. Some generaliza- tions regarding the Canadian deposits are included, but many of these are necessarily tentative. The information contained in the paper is up to date for the end of 1948. The information contained in this paper has been derived from many sources. Much of it is from the records of the Canadian government-owned Eldorado Mining and Refining (1944) Limited and from examinations of government and private properties made by officers of the Geological Survey of Canada. Some information on privately-owned properties has been quoted from other sources mentioned in the text. The information has been assembled by W. F. James of Eldorado Mining and Refining (1944) Limited and A. H. Lang of the Geological Survey of Canada, who have written the sections for which they are credited. The description of the Eldorado mine is based on reports by Richard Murphy, formerly chief geologist for Eldorado; the report by Mr. Murphy was published previously by the Canadian Institute of Mining and Metallurgy,&apos; to whom the writers are indebted for permission to repub-lish. The section dealing with the geology of and development work in the Goldfields area, where Eldorado has important holdings, is by S. N. Kesten, field geologist for Eldorado. The geological diagram of the Goldfields area (fig. 2) was kindly supplied by A. M. Christie of the Geological Survey of Can-

Jan 1, 1951

By D. J. McAdam

In 1917 Haighl presented evidence that under simultaneous corrosion and cyclic stress metals may fail at lower stresses than if the corrosion is prior to the cyclic stress. In 1926 the author, while investigating the cooling effect of water on the fatigue resistance of metals, found that under these conditions steel specimens fail at stresses far below the endurance limit.2 (By "endurance limit" is here meant the fatigue limit obtained with specimens as free as possible from stress concentration and corrosive influences.) This led to an investigation (at the Naval Engineering Experiment Station, Annapolis, Md.) of the influence of cyclic stress on corrosion. This investigation may be divided into three parts. The first part was a general survey of the conditions necessary to cause complete failure under corrosion and cyclic stress of relatively high frequency. The entire process by which metals fail under these conditions was called LLcorrosion-fatigue." Corrosion-fatigue limits" for a large number of metals were determined and the relationships of these limits to chemical composition, heat treatment and physical properties were established. The conclusion was reached that corrosion-fatigue is due to the accelerating influence of cyclic stress on corrosion. Results of this part of the investigation were presented in five papers.*-= The second part of the investigation was a preliminary study of the influence of cyclic stress on corrosion. Each experiment was conducted in two stages. The first was a corrosion stage in which the specimen was corroded under cyclic stress; the second was a fatigue stage, in which the previously corroded specimen was tested (without further corrosion) to determine its fatigue limit. The difference between this fatigue limit and the endurance limit was used as a criterion of the "damage" due to

Jan 1, 1932

By George H. Eldridge

The existence of phosphate of lime within the State of Florida has been known for over a decade; but until the spring of 1887, the extent and value of its deposit.;, possibly with one exception, were unsuspected. In that year Col. T. S. Moorehead, induced by a statement made by Mr. J. F. Le Baron, examined the gravels of the Peace river, recognized the importance of the deposits, acquired such tracts as were regarded as desirable, and established the pebble-phosphate industry, making his first shipment in May, 1888, to the Scott Manufacturing Company, of Atlanta, Ga. The establishment of the pebble-phosphate industry upon Peace river was followed, a year later, by the discovery in Marion county of an entirely different class of phosphate, now commonly known as hard-rock phosphate. This discovery was made early in June, 1889, by Mr. Albertus Voght, in a well which he was sinking upon his place near the site of the present town of Donnellon, about 20 miles southwest of Ocala. To it, more than to any other cause, is due the rapid and remarkable development of the present great industry of the State. It was, however, Mr. John F. Dunn, of Ocala, who turned to advantage the accidental discovery of Mr. Voght. After acquiring a knowledge as to the chemical composition and value of the material, Mr. Dunn and hid associates purchased several thousand acres of land and organized the Dunnellon Phosphate Company for active operations. From Dunnellon as a center, prospecting rapidly extended in all directions, until at the present day important mines have been opened over a well-defined tract more than 200 miles long and about 6 miles wide. This tract lies par-

Jan 1, 1893

By W. A. Koehler, W. L. Eaton, Reynold Q. Shotts, M. E. Hinkle, M. R. Geer, Ralph M. Hunter, H. F. Yancey, Andrew B. Crichton, E. Zimmerman, S. H. Ash

R. Maize and H. P. Greenwald presiding) E. T. POWELL*-I would like to ask either Mr. Ash or Mr. Eaton if they know of any place where the Mine Inspectors&apos; for¬mula has been used that water has flowed from one colliery to the other. W. L. EATON (authors&apos; reply)-We have made considerable study but we have not gotten around to very many of the barrier pillars. I would not say that any or all of them have been designed to the strict figures of this formula. Most of those ex¬amined will not hold back the water that they are supposed to hold back. E. T. POWELL-If the pillar remains ac¬cording to the Mine Inspectors&apos; formula? W. L. EATON-We have not found very many where the provisions were followed. E. T. POWELL-Where the Mine Inspec¬tors&apos; formula has been fully complied with, have there been failures or not? W. L. EATON-I cannot say. Most of these barrier pillars probably were designed in accordance with this formula, but most of them, if they were so designed, are not in that shape now because a large number of them will not hold back the water; they have been reinforced, and they are punc¬tured in various places. Holes have been driven through them to relieve the hydro¬static pressure to avoid a failure. They do not dare to have a failure. In many instances, the barrier is punc¬tured to avoid a failure. In order to mine their coal safely, many companies must pump water from mines that were aban¬doned many years ago. R. MAIZE-That is true, Mr. Eaton, but do you know of any case where a barrier pillar actually failed and flooded an ad¬joining mine when the pillar had been left in accordance with the Mine Inspectors formula?

Jan 1, 1948

By Claus G. Goetzel

Pressing of powdered metal parts is best done in the direction of the shortest extension of the piece, to avoid too great a loss of pressing force through internal iriction. As long as curved surfaces, re-cessej, or offsets occur only parallel to this shortest axis of pressure, no special difficulties arise: the cross sections, perpendicular to the pressure, do not vary, nor does the shape of the parts change during compression except for a gradually reduced thickness (Fig. IA). The problem becomes more dificult, however, when the curved surfaces or recesses are perpendicular to the shortest axis of the part (Fig. IB) Two processes for molding uniformly dense parts with complicated shapes from powdered metals are described in detail in this paper. Both can be employed successfully by those trained in the art. The first refers to curved parts; the second is especially adapted to parts having one or more recesses or steps. Both methods, as set forth here, are applied under the condition that presents the more difficult problem. For clarity, before description of the two practical methods, the variable factors in molding powdered metal parts will be reviewed, then an idealized procedure will be considered briefly. Variable Factors in Molding Powdered Metal Parts Compression Ratio Compression ratio is defined as the proportion of the final relative density of the compact to the apparent density of the powder. For iron powder of an apparent density of 3.0, for example, a compression ratio of 2 1/2:1 would be required to produce a compressed compact of 7.5 density; whereas for another iron powder having an apparent density of only 1.5, a compression ratio of 5:1 would be required to produce the same density. The lower the powder&apos;s apparent density, the greater must be the compression ratio for pressing compacts of high density.

Jan 1, 1946

By Claus G. Goetzel

Pressing of powdered metal parts is best done in the direction of the shortest extension of the piece, to avoid too great a loss of pressing force through internal iriction. As long as curved surfaces, re-cessej, or offsets occur only parallel to this shortest axis of pressure, no special difficulties arise: the cross sections, perpendicular to the pressure, do not vary, nor does the shape of the parts change during compression except for a gradually reduced thickness (Fig. IA). The problem becomes more dificult, however, when the curved surfaces or recesses are perpendicular to the shortest axis of the part (Fig. IB) Two processes for molding uniformly dense parts with complicated shapes from powdered metals are described in detail in this paper. Both can be employed successfully by those trained in the art. The first refers to curved parts; the second is especially adapted to parts having one or more recesses or steps. Both methods, as set forth here, are applied under the condition that presents the more difficult problem. For clarity, before description of the two practical methods, the variable factors in molding powdered metal parts will be reviewed, then an idealized procedure will be considered briefly. Variable Factors in Molding Powdered Metal Parts Compression Ratio Compression ratio is defined as the proportion of the final relative density of the compact to the apparent density of the powder. For iron powder of an apparent density of 3.0, for example, a compression ratio of 2 1/2:1 would be required to produce a compressed compact of 7.5 density; whereas for another iron powder having an apparent density of only 1.5, a compression ratio of 5:1 would be required to produce the same density. The lower the powder&apos;s apparent density, the greater must be the compression ratio for pressing compacts of high density.

Jan 1, 1946

By Wayne P. Myers

Electricity, as normally thought of by a layman&apos;s definition, is a manmade force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man&apos;s safety, are rigidly enforced by the U.S. Bureau of Mines, as well as the various state departments of mines. BACKGROUND Until recent years most underground coal mines used direct current exclusively for all movable and for some stationary equipment. Exceptions were for permanent pumps, tipple, fan, and outside buildings where alternating current was normally employed. However, over 60 years ago there were mines with dual systems. Alternating current was used for cutting machines, drills, and pumps, direct current for locomotives. There were no other machines as these were hand-loading mines. Later, during early mechanization in the 1920s, alternating current was also applied to loading machines at some mines. Use of dual electric systems then declined until fairly recently when

Jan 1, 1973

By T. Egleston

FOR a great part of the progress of the world we are indebted to the works of engineers. It is to them that we owe our means of rapid transportation, our canals, our railroads, our bridges, many of our automatic machines, and most of those appliances which, by facili tating or decreasing the amount of human labor to be expended and by utilizing the great forces of nature, have made the present progress of the world possible. Their education is a matter of momentous interest to the whole civilized world. I have, therefore, thought that some discussion of the theory upon which their education should be based would be of interest to this body, and have ventured a few reflections and suggestions upon the subject. The word education, in its original signification, meant the draw ing out of a man what there was in him. In our common schools the practical work of education consists in putting into the brain a larger number of facts than can be retained, which are consequently more or less understood and digested. It ordinarily consists simply of teaching a round of abstractions or facts which when not assim ilated are not only useless to the individual, but generate careless habits of thought and make more or less untruthful, unfaithful or unsuccessful men. In most of our schools a procrustean system is adopted; all are made to advance upon one general plan, the quick being kept back and the slow dragged on at a rate too great for their power of comprehension. Until within a very few years it has been a theory in common school education that the brain alone should be developed, and that little or no attention need be paid to the train-

Jan 1, 1888

By R. W. Kraft, L. D. Graham

The process of&apos; spheroidization, or more properly coarsening, of Al-CuAl,eutectic alloy specimens with various initial microstructures was studied by quantitative metallographic and X-ray diffraction techniques. By measuring the rale at which specimens with a very fine dispersion of phases (produced by quenching molten droplets of the alloy in water) coarsened it uias determined that the rate-controlling mechanism for coarsening was diffusion, probably of aluminum in the aluminum-rich phase. The lamellae in specimens with a high degree of microstructural and cr-ystallog/uphic anisotropy (produced hy unidirectional solidification of ingots) thickened during heat treatment by recession of the CuAl, platelets from jaulted regzons, yet the specinlens retained a very high degree of. anisotropy after prolonged heat treatments at a temperature within 8°C of the eutectic temperature. In such specimens the crystallographic orientation relationship between the phases remained constant and no change in the crystallographic substructure occurred. Based on these observations a model was developed for the coarsening—or rate of&apos; thicken-ing—oj- the lamellar structures which predicts that the rate of decrease of interface area is proportional to the square of lamellar interface area. Experiments with degenerate and very coarse lamellar microstruc -tures preduced by extremely slow unidirectional solidification) indicate that initial microstructure is a most important factor governing the final micro-structure after heat treatment. The particle size and shape of dispersed phases are important parameters affecting the properties of a wide variety of two-phase materials. As is well-known, varietythe dispersed-phase particles tend to coarsen at appropriately high temperatures because the interface energy of the system is reduced by the concomitant reduction in interface area. The phenomenon of

Jan 1, 1967

By Oscar Marzke

STUDIES on the precipitation of a face-centered from a body-centered structure-a common occurrence in alloy systems-are essential to the development of a theory for the formation of segregate structures. The separation of the alpha phase from the beta of the copper-zinc system is an example of this type of precipitation. EARLIER STUDIES ON THE SUBJECT R. F. Mehl and 0. T. Marzke1 in 1931 presented a paper giving the results of some investigations carried out by them on the segregate structures produced when the alpha and gamma phases of the copper-zinc system and the alpha phase of the copper-aluminum system precipi-tate from the beta phases of these systems. They showed that the alpha phase precipitates as needles close to the [111] directions of the beta phase. In the discussion of that paper some doubt was expressed about the nature of the segregate. More investigations were undertaken to determine the character of the precipitate in the copper-zinc system and also the orientation relationship between the matrix and precipitate. The present paper gives the results of these investigations. Since the publication of the earlier paper, several other papers on this subject have been published in this country and abroad. Haneman and Schroder2 reported that the alpha phase precipitates as needles along the [111] directions of the beta phase and that these needles align themselves to form plates on the {111} planes of the matrix. Mathewson and Smith3 pointed out that the {111} plane does not contain the [111] direction and that it would be quite impossible, therefore, for needles in the [111] direction to form plates on the {111} plane. They suggested

Jan 1, 1933

By W. R. Shimer, F. O. Kichline

The investigation herein described was carried out for the purpose of studying, both by chemical and metallographical means, the extent of over-oxidation of steel that can be accomplished by excessive overblowing in a Bessemer converter. 111 addition there are appended some results of basic open-hearth and crucible steels. Remarks on Chemical Methods. The test block used was hemispherical in shape, 4.5 in. in diameter and 2 in. thick. Drillings for analysis were obtained by drilling through the entire solid part of the block, carefully avoiding all cracks and blow-holes and mixing these drillings thoroughly. Drillinga were carefully examined for scale and the finest were gone over with a microscope to be sure all scale from whatever source had been removed. Oxygen was determined by the well-known method of Ledebur, modified according to Cushman,1 with, however, the removal of the preheating tube, which was found unnecessary. This method has been found to give concordant results. Blanks run from 0.0003 to 0.0006 g. Duplicate determinations varied not more than 0.001 to 0.003 per cent. It seems to be generally supposed that the hydrogen method gives only that oxygen which is combined with iron. Whether this be true or not, the content of oxygen existing as iron oxide no doubt predominates sufficiently, so that the result obtained is sufficient to indicate whether the steel is over-oxidized or not. We are well aware that the oxides of manganese and chromium, when existing alone, are not reduced by hydrogen at a red heat. To learn of their action in steel the following work was carried out: A sample of ferro-manganese and of ferro-chrome were each exposed

Jan 1, 1914