Search Documents

By Harry H. Power

INDUSTRY has the right to expect the petroleum engineering schools to supply more than the minimum technical qualifications necessary to obtain or discharge the responsibilities of a particular job. The basic training, social and economic orientation, should go far beyond these minimum requirements. Petroleum engineering students should also be well grounded in the history of the oil business so that they may understand the industry's progress since the advent of the Drake well. Furthermore, according to P. H. Bohart, the schools "have a definite duty to help the students form a workable philosophy of life, which includes an appreciation of the service of science to mankind, and a belief in the obligation of the individual who enters a profession to exalt himself by continuing his studies and growth so that he may never cease making contributions to the advancement of science and industry."

Jan 1, 1948

By Edward W. Parker

(Toronto Meeting, July, 1907.) NOTE.-The material from which this paper has been prepared was collected for the U. S. Geological Survey Bulletin, Contributions to Economic Geology, 1906, and appears also, though in somewhat more extended form without illustrations, in that publication. ALTHOUGH the briquetting of coals and lignites has been carried on for many years in Europe, and has reached a particularly high state of development in France, Belgium, and Germany, it has made comparatively little progress in the United States. The causes for the backwardness of the United States in this regard are several, and first among them has been the abundant supply of cheap raw fuel with which the manufactured article has to compete. With our millions of acres of coal-productive territory, from which the product can in most cases be cheaply extracted, it has appeared in many districts more economical to waste the slack or culm, which con¬stitutes a considerable percentage -of the product, than to attempt to save it at the additional expense required for briquetting. It is for this reason that the view in all sections of the anthracite-region of Pennsylvania is marred by the unsightly culm-banks which encumber the ground, and that in some of the bituminous-districts one sees huge piles of unmarketable- slack allowed to burn up in order to get rid of them. When the coal is of a coking quality, or when the slack can be used for steaming-purposes, these losses are not sustained, but many thousands of tons of what might be converted into usable fuel have been wasted every year simply because of the increased expense involved in its preparation.

Sep 1, 1907

By Louis Moyd

In the preparation of illustrations to accompany reports of investigations concerning particle shapes of various natural and manufactured materials proposed for use as fine aggretates in concrete structures, it was found that stereoscopic views of such materials presented the information much more effectively than the usual two-dimensional photographs. With the whole-hearted cooperation of the Photographic Section, a technique was developed in the petrographic laboratory of the Concrete Research Division, U.S. Corps of Engineers, at Clinton, Miss., for simple and rapid preparation of paired stereoscopic photographs and micrographs. The method requires only equipment which is usually part of the general stock of any laboratory, and it is adaptable for all purposes in which three-dimensional views would be found superior to ordinary photographs.

Jan 1, 1949

By E. B. Brauer, W. Hurst, J. D. Clark

Because of drilling, completion, and workover practices, the permeability around a wellbore generally is different from the permeability of the formation. The zone with the altered permeability is called "skin" and its effect on the pressure or flow behavior of the well is called "skin effect". Hawkinsl has shown that the radius and the permeability of this zone are related to the skin by: If the permeability in the skin zone is less than that of the formation, the skin is positive; if it is more than that of the formation, the skin is negative. If the two permeabilities are equal, s is zero; that is, there is no skin. Van Everdingen2 and Hurst3 have given mathematical solutions to the case of a zone of reduced permeability around the wellbore. This skin effect is illustrated in Fig. 1. They treat the positive skin as a zone of reduced permeability of infinitesimal thickness around the wellbore. When applied to a well with negative skin, however, their solutions lead to the calculated flowing well pressure which is smaller than the formation pressure, i.e., an injection situation. This is a physical contradiction. In this paper, it is shown that this mathematical difficulty can be overcome by assuming an effective wellbore radius larger than the actual wellbore. Existing solutions2"4 are modified to include the effect of an enlarged wellbore radius, and thus enable the engineer to deal with negative as well as positive skins. Theoretical Development Van Everdingen and Hurst,4 through the use of Laplace transformation, obtained the following expression for transient fluid influx into a wellbore: The values for QtD, reported extensively by van Everdingen and Hurst,4 are obtained from the following integral:

Jan 1, 1970

By J. E. Harris

By elimination of other possible nucleation processes, it has been demonstrated, for commercially pure magnesium and a Mg-Al alloy, that at stresses less than that necessary for triple-point cracking creep cavities are most probably nucleated heterogeneously at second-phase particles. Evidence for the existence of such particles is presented and the role of grain boundary sliding in the nucleation process is examined quantitatively. DURING creep deformation of polycrystalline magnesium and its dilute alloys in the temperature range 0.45 to 0.7 Tm (Tm = absolute melting temperature) cavities form mainly along grain boundaries oriented normal to the stress axis and failure eventually occurs by their growth and impingement.' The possibility of low-ductility creep failure of magnesium-alloy reactor cans during service has prompted a number of studies of cavity formation in these materials.2-5 In this paper divergent theories of cavity nucleation6-10 are examined critically and conclusions drawn regarding the most probable mechanism of formation of cavities in magnesium. The paper is divided into two parts. The first section consists of the review and quantitative assessment of the possible role of grain boundary sliding in the nucleation process. In the second part an experimental program is described where an electron-microscope technique has been used to determine if second-phase particles exist in as-received commercially pure magnesium and in a magnesium alloy 1) THEORETICAL REVIEW Possible nucleation sites for creep cavities are: a) high-angle grain boundary triple points,11-14 b) subboundary/grain boundary intersections,15-18 c) ledges in the grain boundary, 19-25 d) second-phase particles. 9,26-30 Each of these possibilities is now considered with special reference to deformation of magnesium. 1.1) Triple-Point Cracking. The stroh31 condition to nucleate fracture is: " > vr [1] where ss = applied shear stress, ? = surface energy, C = shear modulus, L = length of sliding interface. This relationship is independent of the nature of the interface and it is possible to calculate the stress concentration at the end of a sliding high-angle grain boundary and thus deduce, approximately,* the minimum applied stress necessary to nucleate triple-point cracking. Such theoretical predictions for Nimonic alloys have been made by McLean13 and found to agree quite closely with the minimum stress determined by experiment. Stresses capable of nucleating triple-point cracking should also be sufficient to nucleate fracture at a grain boundary due to intragranular slip, for the lengths of sliding interface in the two cases are approximately equal. Thus the minimum stress for triple-point cracking should represent a demarcation between failure due to general "cracking" and that due to cavitation. Hauser, Landon, and Dorn32 have demonstrated that for polycrystalline magnesium in the temperature range 78° to 298°K the fracture stress is inversely proportional to the square root of the mean grain diameter. As pointed out by stroh31 this result indicates that Eq. [I] describes the fracture characteristics of magnesium at low temperatures. Heal3 has reported that for rapid deformation (112 pct hr-1) of polycrystalline magnesium the transition from cracking to cavitation occurs in the temperature range 175" to 275°C. He also presented the fracture-stress values for the same material tested under similar conditions. From Eq. [I] taking G = 1.3 x 10" dynes , ? = 600 ergs . cm-2,33 and L = 0.017 cm, a Stroh-McLean13,31 tensile stress of -266 kg. cm-2 is calculated, corresponding to a transition temperature of -190°C; this is in

Jan 1, 1965

By Clinton M. Young

(Pittsburg Meeting, March, 1910.) I. INTRODUCTION. THE experiments herein. described were carried on in 1908-9 . by the State Geological Survey of Kansas. Some months before taking up work on black powder the Survey had resumed work on an interrupted investigation of explosions in coal-mines, a subject which is engaging the attention. of numerous investigators. An unusual number of serious disasters has directed to. the subject a study which discloses the disquieting fact that, in the. United States, the ratio of lives lost per ton of coal mined has been on the increase. Methods of coal-mining have changed to some extent with the great increase of output, attained in, comparatively recent years. These changes involve the working of very extensive mines, with increased difficulty of ventilation, increased accumulation of coal-dust, and. a very great increase in the amount of explosive used.. . This last point assumes truly startling proportions when it is carefully observed. In the fields of the Middle. West it is not now uncommon for a miner to use six ,kegs (150 lb.) of black powder in a "pay" of two weeks, while within the memory. of men still active, one keg (25 .lb.) would last two men for a " pay." So. great has . the use of explosives become in some fields that the skilled coal-miner is hard to find, and the coal is not mined, but blasted. A preliminary study of the subject. of explosions in coal-mines has. led to the belief . that the use of, large -quantities of explosives, in some cases by slightly-trained men, had not been * Associate Professor- of Mining Engineering, University of Kansas, Lawrence, Ran.

Aug 1, 1910

By A. G. Rozner

TRANSVERSE rupture tests have been commonly used in mechanical investigations of brittle materials. The specimens are simple, easy to prepare, and loading presents no difficulty. Owing to the complexity of stress distribution in bending1 one can determine stresses rigorously only for the elastic range. The bend-test results, however, are at times converted into tensile-strength data, determined as maximum fiber stress. The assumption is made that for small plastic deformations the linear stress-strain relation applies. This problem was experimentally investigated by Bach3 who tested cast iron in bending and in tension and found that the maximum fiber strength obtained in bending exceeded the experimental tensile strength by a factor depending on the geometry of the tested piece. The factor varied from 1.57 for a rectangular cross section to 2.12 for a circular cross section of the tested beam. Since this work was carried out 60 years ago, the cast iron used could be expected to have been highly brittle, thus the extent of plastic deformation prior to fracture very small. We have therefore carried out a number of tests on magnesium-modified cast iron with an average elongation of -5 pct. It was hoped that the data obtained from the tests would serve as a guideline for comparing data obtained in tension and bending for brittle materials. Mechanical properties were measured at room temperature on an Instron tensile machine at a crosshead speed of 0.05 in. per min. The three-point bend test employed cylindrical bars 0.20 in. in diameter with a 1.0-in. span. For the tensile test, cylindrical tensile specimens with a gage length of 0.85 in. and a diameter of 0.160 in. were used. Results are summarized in Table I. From Table I one can see that fracture strength

Jan 1, 1965

By B. C. Craft

Oil and gas development in Mississippi during the year 1933 was rather active and a number of important wildcat wells were drilled throughout the state. Mississippi showed an increase in drilling operations during 1933. There were 58 completions from 22 counties during this period, compared with 53 completions in 10 counties during 1932. The Jackson gas field in Hinds and Rankin counties continued to be the most active area with 26 completions, resulting in 17 gas wells, 2 oil wells, and 7 dry holes, compared with 38 gas wells, 1 oil well and 5 dry holes during 1932. A further attempt to extend the producing limits of the Amory gas field resulted in a dry hole. Extensive exploration in south Mississippi has proved the existence of ample source beds and presence of an extensive sandbody near the top of Cockfield. Core tests, supplemented by extensive geophysical work, have been carried on in Jackson, George, Harrison, Pearl River and Stone counties. Exploration will be continued in 1934. The most important deep test drilled in 1933, and the deepest well ever drilled in a southeastern state, was the Eastman Gardner et al., Bank of Seminary No. 1, sec. 26-8N.-15W., Covington County. This well went through about 1300 ft. of Selma chalk, and was abandoned in the Eutaw at 8004 ft. Another interesting operation during the past year was the Foster Creek Oil Corporation's Foster Creek Lumber Co. No. 1, sec. 14-2N.-2W., in the "Eastern Conroe Trend." This test is shut down at 3687 ft. in the Catahoula sandstone and has not encountered any important shows of oil or gas. A total of 107 of the 117 gas wells completed in the Jackson gas field since its discovery in 1930 are still producing, and have a combined open flow of approximately 3,724,896,000 cu. ft. It is reasonable to assume that this area will be rather inactive during 1934 as the maximum daily production during 1933 was 3,476,000 cu. ft. The 10 wells that have gone dead were edge wells. The water level is now between the sub-sea depths of 2190 and 2195 ft. The Gulf Refining Company's Rainey No. 1, sec. 13-5N.-lE., one of the early wells in the field, had gas and water at —2225 ft. That the field is under hydraulic control is

Jan 1, 1934

By H. 0. HOFMAN AND W. MOSTOWITSCH

I. INTRODUCTION. THE mineral gypsum, CaSO, + 2 H2O, has been used for many years as a sulphurizing and basic flux in several smelting¬operations. Thus, in smelting oxide nickel-ore in the blast furnace, it is commonly added to the charge to furnish the sulphur necessary for collecting the metal in a matte, and a base for slagging the siliceous gangue. In the concentration of lead-copper matte in the reverberatory furnace it has been used for years at Freiberg, Saxony1 for a similar purpose, and for producing at the same time a copper-matte with less than 0.15 per cent. Fe. The latest use gypsum has been put to is in the blast-roasting process of Carmichael-Bradford.2 The term "blast-roasting," given by A. S. Dwight3 to the Dwight-Lloyd method of roasting and agglomerating ,I is a happy generic term which covers the ground better than the " lime-roasting" of Ingalls' or the " pot-roasting " of Austin,6 in that it leaves the operation independent of the character of the flux and the form of apparatus, and retains the characteristic feature of this class of processes-namely, that of using forced draft. In the Carmichael-Bradford process the dehydrated material, mixed with galena-concentrate, acts as a diluent and a flux. The process differs in this from the Huntington-Heberlein7 and the Savelsberg8 processes, in both of which limestone is used.

Jan 1, 1909

Jan 1, 1910

By JAMES J. PURDY

The great majority of stokers used in residential heating installations are of the clinkering type. Because of inherent characteristics of the under- feed combustion process as it occurs in these small stokers, and because of the wide range of operating conditions encountered in residential heating schedules, not all bituminous coals can be used successfully in residential underfeed units. The problem of providing consumer satisfaction has been attacked by the joint efforts of the stoker manufacturers and the coal industry; the stoker manufacturers have been concerned with improving their product to permit the use of a wider range of coals, and coal operators have made every effort to market selected and better prepared coals. In view of the wide range of physical characteristics and chemical properties of bituminous coals, the problems are real and are receiving increased attention.

Jan 1, 1949

By C. E. Abbott

THE Birmingham district, Alabama, is distinctive in the proximity to one another of its deposits of iron ore, coal and flux. These three basic requisites for the making of iron and steel are found within a radius of 10 miles. Both dolomite and limestone are produced, the former for blast-furnace flux and the latter for basic open-hearth operations. The Tennessee Coal, Iron and Railroad Co., a subsidiary of the United States Steel Corporation, operates a limestone mine at Muscoda, near Bessemer, 12 miles southwest of Birmingham, served by its own railroad transportation system. The mine has a capacity of 130 tons per hour. Average analyses of a recent month's production are as follows: Fe2O3 Si02 A12O3 CAC03 MGCO Lump, per cent 0.51 0.22 98.63 0.14 Crushed and washed, percent 0.70 0.26 98.36 0.18 Lump stone, 2 1/2 to 7 1/2 in., is used in open-hearth operations at Fairfield Steel Works. Fine crushed and washed stone, 1 ¼ to 0.063 in., is calcined at the, lime-burning plant and used for lime charges at the Ensley open hearths.

Jan 1, 1936

By P. Nicholls

THOUGH the burning of fuels extends far back into antiquity, and though fuel beds are the most common and widely distributed example of chemical actions and engineering practice, there has been little attempt to group fuel beds by types or to define the principles associated with them. This paper does not profess to cover completely the subject of fuel beds. It suggests some of the over-all principles of the two more com-mon types. No new investigational data are included, but the deduc-tions are largely based on a recent publication of the U.S. Bureau of Mines1. DEFINITION OF TYPES There are three primary types of fuel beds: (1) Underfeed, in which the fuel and the air move in the same direction; (2) overfeed, in which the fuel and the air move in opposite directions; (3) crossfeed, in .which the fuel and the air move at right angles to each other. The principle that fixes the type is the relation between directions of the flow of fuel and of air. Fig. 1 shows the three types diagrammatically. All other types are compounded of these three in a simple or more or less complex manner. It does not follow that these three type designations are limited to the methods used in representing them in Fig. 1; they may be turned in any direction, and as long as the relative directions of the fuel and air are the same the type is not changed. For example, A as shown resembles a pot-type stoker, but the air and fuel can move downward as in the so-called smokeless heating boiler furnace. Also, C can be placed hori-zontal, as in chain-grate stokers. For this reason, the terms used to designate the three types are not all that could be desired; more logical ones could be coined, but those used probably are satisfactory until the discussion of fuel-bed types becomes more common.

Jan 1, 1935

By JOHN W., E. C. SARCENT

The South Texas area discussed herein represents districts 2 and 4 of the Texas Railroad Commission. It extends from Jackson, Lavaca and Gonzales Counties on the northeast to the Rio Grande River, and comprises a total of 26 counties.

Jan 1, 1946

By J. C. Borland, J. H. Rogerson

Jan 1, 1963

By K. G. Gorling, S. J. Wallden, N. B. Lindvall

It is the policy of The Metollurgical Society to provide, in the TRANSACTIONS OF THE METALLURGICAL SOCIETY OF AIME, a prompt and accurate medium for publication of reports of significant new research in both the scientific and engineering aspects of metallurgy. Papers submitted to the Society are judged by competent reviewers according to established criteria for technical merit, accuracy, originality, and presentation. STAFF: Editorial Director, Rixford A. Beals; Associate Editor, James J. Burke; Assistants, L. Capria and R. K. Larkin. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: A. W. Thornton, Choirmon; Dennis Carney, John Chipman, J. C. Fulton, J. H. Hollomon, H. tl. Kellogg, A. E. Lee, R. Maddin, J. D. Sullivan, and O. Swan. Review and selection of manuscripts is under the supervision of the following Publications Committees: Extractive Metallurgy Division T. B. King. Cha~rmon; S. J. Dickenson, R. P. Hermsdorf, R. Schuhmann, Jr.. and P. T. Stroup. Institute of Metals Division: Robert Maddin, Chairman. F. Lincoln Vogel, Jr., Vice-chairman, W. A. Backofen, R. W. Balluffi, J. H. Bechtold, M. B. Bever, R. S. Busk, C. G. Goetzel, Paul Gordon, C. D. Graham. Jr., Robert F. Hehe-mann, R. I. Jaffee, F. E. Jaumot, Jr., lrving R. Kramer, A. J. Leno, Horold Margolin, C. J. McHorgue, Russell A. Meussner, J. 6. Newkirk, H. W. Paxton, G. E. Pell~ssier, I. S. Servi, Alan U. Seybolt, A. J. Sholer, and Sack Wahsburn. Iron and Steel Division: J. C. Fulton, Chairman; T. B King, F. C. Langenberg, W. O. Philbrook, and T. B. Winkler. Published bimonthly by the American Institute of Mining Metallurgical and Petroleum Engineers Inc., 29 West 39th Street, New York 18, N. Y. Telephonne pennsylvania 6-9220.Petroleum Subscription Engineers$20 per year for non-AIME members in United States and North South and Central 6-9220.SubscriptionAmerica $25 toreign; $5 for AIME members. Single copies, $4.00, iinalo copies Southfpr;ign,andCentral $5 00. The AIME 'is $25not responsible for any statement made or opinion expressed in its publications Copyright 1958 1958 by the American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. . Registered coble address, AIME New York . . . Indexed in Engineering Index, Industrial Arts Index, ...and Chemical Abstracts . . . Application for second class mail privileges IS pending at New Yark, N. Y. Volume 212, Number 2.

Jan 1, 1959

By J. J. Lillie

Sublevel stoping was first developed in the Michigan iron mines many years ago. Since that time this method, and modifications with long hole drilling, have been used in a number of non-ferrous mines and have been described in various papers and articles. With a few exceptions, the operations where sublevel methods have been applied are producers of large daily tonnages from ore bodies of considerable size. In selecting mining methods for small properties or relatively small detached ore bodies, sublevel methods often have been overlooked. The method has been used success- fully in relatively small operations at Copper Canyon, Nevada, and, more recently, in mining small ore bodies at Darwin, Calif. As a result of this experience, we believe that a review of the general procedure, the advantages noted, and the results obtained will be of interest to many operators of relatively small mines.

Jan 1, 1949

By Frank G. Snyder

The Precambrian of Midcontinent United States includes a metamorphic belt of probable Middle Precambrian age, a belt of Keweenawan volcanics and sediments, and widespread igneous activity that extended from Iowa to Texas. Most of the present structural configuration of the Midcontinent was developed by epeirogenic movements during the Paleozoic. The dominant elements are basins and arches. Three major metallogenic provinces occur in the Midcontinent. They include the Missouri Precambrian iron ores, the Lake Superior copper ores, and the Mississippi Valley lead-zincbarite- fluorite deposits. Several large iron deposits, occurring in rhyolite and andesite host rocks, are known. Both discordant massive bodies and replacement- type bodies occur. The iron deposits are believed to have been formed during the period of igneous activity. They are essentially the same age as the volcanics and older than the granites that intrude the volcanics. The Lake Superior copper ores include two established districts, the Keweenawan district and White Pine, and the copper-nickel deposits in the Duluth gabbro. The lead-zinc-barite-fluorite deposits include four major districts, Southeast Missouri, Upper Mississippi Valley, Tri-State, and Illinois-Kentucky, and at least eight minor districts. Ore may occur in stratiform deposits and in veins. The major districts all contain stratiform deposits, but several have produced appreciable quantities of vein ore. Only vein deposits are known in some of the smaller districts. The major features of all districts can be catalogued in terms of host rocks, structural patterns of districts, types of ore-bearing structures, and mineralogical characteristics. From these features, a Mississippi Valley type ore body, in its type area, can be defined.

Jan 1, 1968

By G. V. Smith, C. O. Tarr, R. F. Miller

Metallurgists have long recognized that the Fe3C type of carbide is not a stable phase in steel and that, given sufficient time, it will decompose with formation of graphite, at least at temperatures below about 205o°F.l This slow graphitization has never been of much concern to users of hypoeutectoid steels, for in such steels it occurs only during prolonged exposure at elevated temperature. In I935, Kinzel and Moore2 reported complete graphitization of the carbide of a 0. I5 per cent carbon steel that had been in service for about 26,000 hr. at a temperature of about IIOO° to 12oo°F. In discussing this paper, both Mathews and Sauveur reported graphitization of slightly hypereutectoid steels. In an extensive investigation of graphitization of high-purity iron-carbon alloys, Wells1 produced graphite at 7oo°C. (I29o°F.) in an alloy containing as little as 0.13 per cent carbon, and showed that graphite may precipitate either directly from austenite or from decomposition of Fe3C, also that the rate of graphitization tends to increase with increase of temperature, at least up to a certain point, and with the presence of graphite nuclei. Jenkins, Mellor and Jenkinson,3 studying the structural changes in carbon steels ranging from 0.17 to 1.14 per cent carbon during stress-rupture tests at elevated temperature, observed graphite in an aluminum-killed 0.40 per cent carbon steel after fracture in 4340 hr. under a stress of 17,900 lb. per sq. in. at 840°F. and in many of the steels after stress-rupture test at 12oo°F. Unstressed samples of 0.60, 0.86 and I.I4 per cent carbon steels graphitized almost completely in 360 hr. at I200°F., while samples of 0.90 and 1.10 per cent carbon steels were somewhat graphitized, and steels containing 0.24, 0.40 and 0.57 per cent carbon showed no sign of graphite. Their results indicate that graphite precipitates the more readily the higher the carbon content, though this tendency is influenced to some extent by deoxidation practice, and that graphitization is accelerated by plastic deformation. In a recent study of the graphitization of 0.4 and 0.6 per cent carbon steel strip, made by M. A. Hughes,4 it was found that at I2oo°F. graphite appeared after 72 hr. in aluminum-killed but not in silicon-killed steel, and that the rate of graphitization was increased by slow cooling from I6oo°F. and by cold-working prior to annealing. In creep tests of normalized 0.15 per cent carbon steel killed with 2.5 Ib. of aluminum per ton, at the U. S. Steel Corporation laboratory at Kearny, spheroidization and some graphitization were found after 3000 hr. at Iooo°F. under a stress as low as 1500 lb. per sq. inch. .

Jan 1, 1944

By C. O. Tarr, G. V. Smith, R. F. Miller

Metallurgists have long recognized that the Fe3C type of carbide is not a stable phase in steel and that, given sufficient time, it will decompose with formation of graphite, at least at temperatures below about 205o°F.l This slow graphitization has never been of much concern to users of hypoeutectoid steels, for in such steels it occurs only during prolonged exposure at elevated temperature. In I935, Kinzel and Moore2 reported complete graphitization of the carbide of a 0. I5 per cent carbon steel that had been in service for about 26,000 hr. at a temperature of about IIOO° to 12oo°F. In discussing this paper, both Mathews and Sauveur reported graphitization of slightly hypereutectoid steels. In an extensive investigation of graphitization of high-purity iron-carbon alloys, Wells1 produced graphite at 7oo°C. (I29o°F.) in an alloy containing as little as 0.13 per cent carbon, and showed that graphite may precipitate either directly from austenite or from decomposition of Fe3C, also that the rate of graphitization tends to increase with increase of temperature, at least up to a certain point, and with the presence of graphite nuclei. Jenkins, Mellor and Jenkinson,3 studying the structural changes in carbon steels ranging from 0.17 to 1.14 per cent carbon during stress-rupture tests at elevated temperature, observed graphite in an aluminum-killed 0.40 per cent carbon steel after fracture in 4340 hr. under a stress of 17,900 lb. per sq. in. at 840°F. and in many of the steels after stress-rupture test at 12oo°F. Unstressed samples of 0.60, 0.86 and I.I4 per cent carbon steels graphitized almost completely in 360 hr. at I200°F., while samples of 0.90 and 1.10 per cent carbon steels were somewhat graphitized, and steels containing 0.24, 0.40 and 0.57 per cent carbon showed no sign of graphite. Their results indicate that graphite precipitates the more readily the higher the carbon content, though this tendency is influenced to some extent by deoxidation practice, and that graphitization is accelerated by plastic deformation. In a recent study of the graphitization of 0.4 and 0.6 per cent carbon steel strip, made by M. A. Hughes,4 it was found that at I2oo°F. graphite appeared after 72 hr. in aluminum-killed but not in silicon-killed steel, and that the rate of graphitization was increased by slow cooling from I6oo°F. and by cold-working prior to annealing. In creep tests of normalized 0.15 per cent carbon steel killed with 2.5 Ib. of aluminum per ton, at the U. S. Steel Corporation laboratory at Kearny, spheroidization and some graphitization were found after 3000 hr. at Iooo°F. under a stress as low as 1500 lb. per sq. inch. .

Jan 1, 1944