Search Documents

By J. L. Humphrey

The origin of roof bolting is obscure, but is believed to have begun some 40 years ago in the mines of St. Joseph Lead Co. in southern Missouri. It was not until after World War II, and more particularly after 1949, as a result of the concentrated effort of the USBM, that roof bolting attracted widespread interest. It is estimated that at the end of 1954, 26 pct of all bituminous coal mining in the U. S. was being done under roof bolts. Those mines alone use nearly 2,000,000 roof bolts per month, according to USBM statistics. Uses in metal mines are increasing rapidly, as confidence and knowledge grow. The application has found equal success in other fields, such as tunneling work for dam and waterway construction and right of way maintenance on highways and railroads.

May 1, 1956

BULLETIN 177. The decline and ultimate production of oil wells with notes on the valuation of oil properties, by C. H.- Beal. 1919. 84 pp., 4pls., 80 figs. BULLETIN 179. Abstracts of current decisions on mines and mining, reported from September to December, 1918, by J. W. Thompson. 1919. 166 pp. TECHNICAL PAPER 214. Motor gasoline; properties, laboratory methods of testing, and practical specifications, by E. W. Dean. 1919. 33 pp., 2 figs. TECHNICAL PAPER 219. Combustion and flue-gas analysis, by U. S. Fuel Administration. 1919. 12 pp., 5 figs. TECHNICAL PAPER 223. Cost-keeping for small metal mines, by J. C. Pickering. 1919. 46 pp. Only a limited supply of these publications is available for free distribution. Publications should be ordered by number and title. Applications should be addressed to the Director of the Bureau of Mines, Washington, D. C.

Jan 7, 1919

By AIME AIME

RECENT experiments in reflected sunlight photography in mine shaft's' and. slopes in the McAlester, Oklahoma, coal-mining district have been so satisfactory as to indicate that such a method has definite scientific value. The entrances to abandoned deep shafts and slopes on Choctaw and Chickasaw Indian coal lands in Oklahoma are being filled or bulk-headed by the U. S. Geological Survey under Public Works Project F. P. 63-C&C. Inasmuch as these mines may be reopened at some future time when there is a demand for coal, H. I. Smith, Chief of the Mining Division, suggested that photographs of deep shafts would be of value. Such photographs would show timber details and the general condition of the walls. Photographic records of the exact status of shafts when filled will facilitate operations in reopening.

Jan 1, 1936

By William M. Huang, T. Carl Shelton

There are undoubtedly many factors that affect the emission of gas from coal but the permeability of coal to gas flow would seem to be fundamental. However, there is very little information on coal permeability to gas flow available in the U.S. at the present time, despite the fact that such knowledge would appear to be significant in any degasification effort. Studies made recently in the mining engineering laboratories at Virginia Polytechnic Institute have determined values of permeability on one-inch cubes of selected coals. COAL PERMEABILITY The permeability values given in this paper are based on adaptations of Darcy's Law formulated by Henry Darcy in 1856 from experiments with fluid flow in porous media.' Using air as the gaseous fiuid, they were obtained by employing similar methods as are used to determine the permeability of petroleum and gas reservoir rock specimens.

Jan 5, 1962

By D. A. Dukelow

By using the U. S. Steel oxygen sensor to measure the oxygen content of the steel, deoxidation practices have been developed for silicon-killed fine-grain steel produced by the basic oxygen process. Measurements of oxygen content taken at final turndown are related to the amount of the aluminum addition to the ladle necessary to obtain the desired aluminum analysis for proper grain refinement. In comparison with heats deoxidized by the standard approach, which is based on carbon content, the heats deoxidized according to the oxygen-sensor-based schedule showed a 25 percent decrease in variability from the desired aluminum content. As more heats of a particular grade are made, it is expected that improved quality will result in decreased rejections and better analysis control. Sensor-based deoxidation schedules are also being developed for semikilled, rimmed, and capped steels.

Jan 1, 1972

By A. V. Henry

THE kaolins of the southeastern United States were known to civiliza-tion as early as the latter part of the eighteenth century-and yet the GEORGIA PRODUCTION UNITED STATES PRODUCTION IMPORTS Fig. 1.-KAOLIN PRODUCTION AND IMPORTS. commercial history of Georgia kaolins may be said to begin in the year 1900. The U. S. Bureau of Mines reported for that year a production of 6885 tons of "miscellaneous" clays in Georgia. A comparison of these figures with those of 1934, when the production rose to 284,556 tons (65 per cent of the domestic production), indicates the growing economic and technologic importance of this raw material. Fig. 1 clearly shows that a part of the increase is due to a normal growth in the use of kaolinitic clays and a part is due to replacement of clays formerly imported.

Jan 1, 1937

By AIME AIME

THE second blast furnace of the Azov steel mill was blown in on Feb. 17, says the Economic Review of the Soviet Union. This furnace, the 111th in the U. S. S. R., has a volume of 930 cubic meters, and a daily output of 775 tons of pig iron. The 1934 program at the Azov plant includes three 250-ton-open-hearth furnaces, two coke-oven batteries, a repair shop, mine and agglomeration plant at Gamysh-Burum, and two ports, one at the latter town and one at Mariupol. On Feb. 21 the sixth open-hearth furnace of the Stalinsk (Kuznetsk) mill started operations; on Feb. 12 the fourth open-hearth furnace at the Liebknecht mill at Dniepropetrovsk, produced its, first steel, 47 tons of high-grade boring steel. The fourth open-hearth furnace

Jan 1, 1934

EXPLORATION U.S. 4,065,972 - Exploration for subsurface ore bodies of uranium. mercury or other inorganic or organic minerals having specific gases associated thereto Small gas sample containers are planted in a plurality of shallow holes in the surface of the earth in a predetermined pattern and left in place for a period of time sufficient to collect migrating gases. Each container includes a gas collection chamber and means for admitting gases at a predetermined flow rate. Strips of detector material which is sensitive to specific gases are mounted in the collection chamber. Recovered containers are subjected to qualitative and quantitative analysis. F. W Holub and H. W. Alter, assigned to Terradex Corp Jan. 3, 1978. 9 pp (73-421 5R) Filed 5-24-76 (689,710) Same. British 1,498,737, dated Jan. 25, 1978

Jan 1, 1979

By J. E. Schaffer

Drilling activity in Ohio increased slightly in 1939. There were 1020 completions as compared to 910 in 1938. During the past six years the number of completions has varied little (Table 1). Oil production in Ohio has been gradually declining since 1896, when the peak production of 23,941,000 bbl. was reached (Fig. 1). Since that date production has slowly declined to an estimated production in 1939 of 3,144,134 bbl., the lowest in 53 years. This total production is divided approximately into the following grades of crude oil: Pennsylvania, 1,185,456 bbl.; Corning, 1,261,615 Flg 1. bbl.; Lima, 578,500 bbl.; Lodi, Based on figures of U. S. .Bureau of 104,740 bbl.; Cleveland, 13,823 Mines and Oil andGas Journal bbl. Table 2 shows the prices paid for the various grades of crude oil.

Jan 1, 1940

By Robert D. Thomson

Listed among strategic and critical minerals for stockpiling, mica is an important raw material in electronic and electrical equipment industries. Each year large quantities are consumed in the manufacture of television and radio tubes, radar sets, generators, transformers, electric toasters, and irons. Crude mica, which comes from the mine in crystals or in rough books of various shapes and sizes, is known as run-of-mine or book mica. Structural imperfections, impurities, rough edges, and defective laminae are removed by cobbing, rifting, and trimming to produce a marketable block mica or film mica. After the rough books have been hand-cobbed to remove adhering rock, dirt, and crushed or defective mica they are rifted, or split. In the U.S. a straight-bladed knife is generally used for rifting. Products of this operation are classed broadly as untrimmed sheet mica and scrap.

May 1, 1956

By J. E. Schaffer

Drilling activity in Ohio increased slightly in 1939. There were 1020 completions as compared to 910 in 1938. During the past six years the number of completions has varied little (Table 1). Oil production in Ohio has been gradually declining since 1896, when the peak production of 23,941,000 bbl. was reached (Fig. 1). Since that date production has slowly declined to an estimated production in 1939 of 3,144,134 bbl., the lowest in 53 years. This total production is divided approximately into the following grades of crude oil: Pennsylvania, 1,185,456 bbl.; Corning, 1,261,615 Flg 1. bbl.; Lima, 578,500 bbl.; Lodi, Based on figures of U. S. .Bureau of 104,740 bbl.; Cleveland, 13,823 Mines and Oil andGas Journal bbl. Table 2 shows the prices paid for the various grades of crude oil.

Jan 1, 1940

By E. J. Efsic, C. M. Wayman

The fcc to bcc y to a transformation in an Fe-24.5 at. pct Pt alloy was studied and found to be martensitic. Large martensite plates are formed in this alloy which are ideal for crystallographic studies; the Ms temperature is about -5°C. Ordering of the parent phase prior to transformation to martensite causes a pronounced lowering of the Ms temperature. For the first time in the case of alloys of iron, measurements of the habit plune, orientation relationship, and magnitude and direction of the shape stvain have been obtained on preselected martensite plates. It is shown that by measuring the initial and displaced (as a result of the shape strain) positions of three or more non-parallel fiducial scratches on one reference surfice the maguitude and direction of the shape strain and the state of distovtion at the parent-mavtensite interface can be determined with a reasonable degree of accuvacy. The agreement between the phenomenolog-cal crystallographic theory of martensitic transformations and the experimental results habit plune, orientation relationship, and nlagnitude and direction of the shape strain) is essentially perfect, and is thought to be the best reported to date for iron alloys. THE comparatively few investigations on binary Fe-Pt alloys have been concerned with magnetic properties, ordered phases, and the equilibrium diagram itself. Various investigations have shown that the equilibrium diagram is of the open y field type; in addition there is a peritectic transformation, a minimum melting point, and three ordered phases: Fe3Pt, FePt, and FePt3. The results of a number of investigators1-6 have shown that the temperature dependence of the y to a (and reverse) transformation in iron-rich alloys is reasonably well-established. The Fe3Pt phase was first noted by Kussman and Rittberg,7 and its existence was later confirmed by Franklin et al,8 Steijn and Donahoe,9 and Berkowitz et al.10 The FePt phase was reported by Isaac and amman' and later confirmed by a host of others.3,6,7,12,13 Kussman and Rittberg7 noted the existence of the superlattice FePt3. Prior to 1956, the 1 to a transformation in iron-rich Fe-Pt alloys was termed "irreversible". In 1957 Klokholm and Donahoe" termed this transformation martensitic, presumably because of its occurrence at temperatures well below those where diffusion normally takes place. This observation served as a point of departure for the present investigation, and in the very early stages of the work to be discussed it was readily verified that the y to a transformation in iron-rich Fe-Pt alloys is indeed martensitic. Quite large martensite plates exhibiting the well-known surface tilt were observed. These plates are ideal in the sense that the boundaries between the parent and product phases were usually very straight. It thus appeared that Fe-Pt martensites would be ideal for crystallographic studies, and this was the purpose of the present investigation. Details of the crystallography of martensitic transformations (particularly for iron alloys) and the phe-nomenological crystallographic theories15-l7 have been discussed many times and thus will require very little elaboration here. The end result of these theories, given in matrix form, is

Jan 1, 1968

By W. Ivanick, Frank W. Glaser

ORDERING reactions of Fe-Si compositions in the a region have been mentioned in a number of review articles.7-8 However, little is known in regard to the critical temperature, T at which this transformation takes place. Greiner and Stoughton,' in a study of the constitution of iron-rich Fe-Si alloys below 800°C, placed the onset of order at a composition of about 4 to 5 wt pct (7.5 to 9.5 atomic pct) Si. They observed that at this composition the ductility and strength begin to decrease sharply and brittleness develops. During X-ray studies they observed only the appearance of superlattice lines for compositions containing 12.5 atomic pct Si. More recent X-ray diffraction studies- etected the appearance of superstructure lines (corresponding to the calculated positions of [Ill] and [ZOO] reflections) for alloys containing 9.5 atomic pct. This fact confirms Greiner and Stoughton's original hypothesis in regard to the onset of order at compositions containing about 7.5 to 9.5 atomic pct Si. The physical properties.of Fe-Si alloys containing more than 10 atomic pct Si have been studied only to a limited extent. Their extreme brittleness and difficulties of sample preparation render them of little industrial use in comparison with alloys in the 0 to 10 atomic pct Si range. The properties of Fe-Si alloys reported to date are mostly properties measured at room temperature on ordered compositions It appears that because of experimental difficulties fully disordered alloys could not be produced in the critical composition ranges and their properties could therefore not be reported. In Figs. la, lb, and lc, a summary of physical properties of Fe-Si alloys, measured during recent investigations of the influence of silicon additions to iron, is presented. No mention of determination of the critical temperature, T for disorder could be found in the literature. The following is an account of work done in an attempt to: 1) produce the disordered state of various Fe-Si alloys and establish the critical temperature, T for disordering, and 2) compare the electrical and thermal conductivity characteristics of the ordered and disordered phases as functions of composition. Materials, Preparation of Test Samples, and Testing Methods Fe-Si alloys with high silicon contents (about 10 atomic pct) are usually prepared using powder metallurgy techniques. This method insures accurate compositions and high purity through the use of protective atmospheres during solid state diffusion alloying of the mixed powders."" Iron and silicon powders were mixed in the desired proportions, cold or hot pressed, and then homogenized at 1150°C for periods ranging from 6 to 12 hr under a protective getter and in a hydrogen atmosphere. Fully homogenized samples were quenched in water from various and successively higher temperatures to establish the critical temperature for disorder. Temperatures were determined using Pt—Pt-Rh thermocouples in contact with the test samples. Test bars were approximately 0.6x1.25x7.5 cm. Electrical measurements were made at room temperature by determining the potential drop over a 1.5 cm span for a current of 10 amp. Densities of the samples were determined by immersion. High temperature electrical resistivities were measured using previously described techniques.'" Specific heat conductivity up to 200°C was measured by heating one end of the test bar and water-cooling the other; heat conductivity was then obtained by subtracting the rate at which heat entered the water from the

Jan 1, 1957

By P. S. Roller

P. S. ROLLER,* College Park, Md.-The author introduces the idea of a grind limit, or lower size limit of the particles formed directly by grinding, and this is stipulated to be 0.70 micron. I wonder where all the particles come from that lie between the resolving power of the microscope and 0.7 micron, which are seen under a microscope in examining a sample of grind? There is also introduced the idea of excess fines; this is all right in itself but the author's quantitative definition seems to be virtually impossible to justify, and, moreover, is obscure. Just why E, the excess fines, should be defined as the distance between an F line and a y line is hard to follow, and just where the distance should be measured does not appear to be stated, as it should be since the F and y lines intersect and the distance between will depend upon where that distance is measured. The basis of the presentation is the relation of log weight against log size that was "discovered" by Schuhmann. While this relation is implied to fit, the only evidence that I can see is a slightly irregular line in Fig. I between 2 per cent and 18 per cent by weight and then a precipitous drop at 18 per cent away from any sort of straight line. Some of the conclusions are rather startling, It is stated that E, the excess fines, remains constant for all the comminution products of any particular material, except that it may decrease for some coarse crusher products. No reason is given for this assertion. One would, on the contrary, expect that excess fines, if such a concept is permissible, would generally vary with different conditions instead of being constant. Again, "as much net energy is required to reduce a ton of quartz to particles of the grind-limit diameter (namely, of course, 0.7 micron) by grinding as is required to melt the quartz." This would require many data to prove, but no proof is given; any consideration would reveal the impossibility of such a result. Still further, ore samples "ground to widely different sizes, and with different circulating loads and different size distributions or product, show the same production of new surface area per revolution of the mill, when this grind limit is used." This statement is confuted by ordinary experience, which teaches that grinding efficiency varies generally with the condition of material. For example, the cushioning effect of fines is widely accepted, while the inefficiency of a ball mill when the feed is too coarse is also well known. R. SCHUHMANN, JR.,* Cambridge, Mass.-Contrary to Mr. Bond's stand, there is a great deal of miscellaneous experimental evidence that comminution does not stop at around 0.7 micron, nor does it cease consuming energy at that point. Comminution is in fact recognized as an important method of producing colloids.5 Mechanical comminution methods were used by von Weimarn6 to produce colloidal dispersions of a variety of solids, including the minerals chalcocite, galena, hematite, stibnite. Utzino7 gives average particle sizes ranging from 0.02 to 0.09 micron for colloids produced by mechanical comminution of several crystal-line solids. Andreasen and Berg8 have ground

Jan 1, 1941

By P. S. Roller

P. S. ROLLER,*College Park, Md.-The author introduces the idea of a grind limit, or lower size limit of the particles formed directly by grinding, and this is stipulated to be 0.70 micron. I wonder where all the particles come from that lie between the resolving power of the microscope and 0.7 micron, which are seen under a microscope in examining a sample of grind? There is also introduced the idea of excess fines; this is all right in itself but the author's quantitative definition seems to be virtually impossible to justify, and, moreover, is obscure. Just why E, the excess fines, should he defined as the distance between an F line and a y line is hard to follow, and just where the distance should be measured does not appear to be stated, as it should be since the F and y lines intersect and the distance between will depend upon where that distance is measured. The basis of the presentation is the relation of log weight against log size that was "discovered" by Schuhmann. While this relation is implied to fit, the only evidence that I can see is a slightly irregular line in Fig. x between 2 per cent and 18 per cent by weight and then a precipitous drop at 18 per cent away from any sort of straight line. Some of the conclusions are rather startling. It is stated that E, the excess fines, remains constant for all the comminution products of any particular material, except that it may decrease for some coarse crusher products. No reason is given for this assertion. One would, on the contrary, expect that excess fines, if such a concept is permissible, would generally vary with different conditions instead of being constant. Again, "as much net energy is required to reduce a ton of quartz to particles of the grind-limit diameter (namely, of course, 0.7 micron) by grinding as is required to melt the quartz." This would require many data to prove, but no proof is given; any consideration would reveal the impossibility of such a result. Still further, ore samples "ground to widely different sizes, and with different circulating loads and different size distributions or product, show the same production of new surface area per revolution of the mill, when this grind limit is used." This statement is confuted by ordinary experience, which teaches that grinding efficiency varies generally with the condition of material. For example, the cushioning effect of fines is widely accepted, while the inefficiency of a ball mill when the feed is too coarse is also well known. R. SCHUHMANN, JR.," Cambridge, Mass. Contrary to Mr. Bond's stand, there is a great deal of miscellaneous experimental evidence that comminution does not stop at around 0.7 micron, nor does it cease consuming energy at that point. Comminution is in fact recognized as an important method of producing colloids., Mechanical comminution methods were used by von Weimarn6 to produce colloidal dispersions of a variety of solids, including the minerals chalcocite, galena, hematite, stibnite. Utzino7 gives average particle sizes ranging from 0.02 to 0.09 micron for colloids produced by mechanical comminution of several crystalline solids. Andreasen and Berg' have ground

Jan 1, 1941

By P. S. Roller

P. S. ROLLER,* College Park, Md.-The author introduces the idea of a grind limit, or lower size limit of the particles formed directly by grinding, and this is stipulated to be 0.70 micron. I wonder where all the particles come from that lie between the resolving power of the microscope and 0.7 micron, which are seen under a microscope in examining a sample of grind? There is also introduced the idea of excess fines; this is all right in itself but the author's quantitative definition seems to be virtually impossible to justify, and, moreover, is obscure. Just why E, the excess fines, should be defined as the distance between an F line and a [?] line is hard to follow, and just where the distance should be measured does not appear to be stated, as it should be since the F and [?] lines intersect and the distance between will depend upon where that distance is measured. The basis of the presentation is the relation of log weight against log size that was "discovered" by Schuhmann. While this relation is implied to fit, the only evidence that I can see is a slightly irregular line in Fig. I between 2 per cent and 18 per cent by weight and then a precipitous drop at 18 per cent away from any sort of straight line. Some of the conclusions are rather startling. It is stated that E, the excess fines, remains constant for all the comminution products of any particular material, except that it may decrease for some coarse crusher products. No reason is given for this assertion. One would, on the contrary, expect that excess fines, if such a concept is permissible, would generally vary with different conditions instead of being constant. Again, "as much net energy is required to reduce a ton of quartz to particles of the grind-limit diameter (namely, of course, 0.7 micron) by grinding as is required to melt the quartz," This would require many data to prove, but no proof is given; any considera¬tion would reveal the impossibility of such a result. Still further, ore samples "ground to widely different sizes, and with different circulating loads and different size distributions or product, show the same production of new surface area per revolution of the mill, when this grind limit is used." This statement is confuted by ordinary experience, which teaches that grinding efficiency varies generally with the condition of material. For example, the cushioning effect of fines is widely accepted, while the inefficiency of a ball mill when the feed is too coarse is also well known. R. SCHUHMANN, JR.,* Cambridge, Mass.¬Contrary to Mr. Bond's stand, there is a great deal of miscellaneous experimental evidence that comminution does not stop at around 0.7 micron, nor does it cease consuming energy at that point. Comminution is in fact recognized as an important method of producing colloids.5 Mechanical comminution methods were used by von Weimarn6 to produce colloidal dispersions of a variety of solids, including the minerals chalcocite, galena, hematite, stibnite. Utzino7 gives average particle sizes ranging from 0.02 to 0.09 micron for colloids produced by mechanical comminution of several crystalline solids. Andreasen and Berg8 have ground

Jan 1, 1941

By J. C. Martin

Stmplified equations are developed for the flow of fluids in gas drive reservoirs in which the effects of gravity can be neglected. The results show that the pressure distribution is governed by a nonlinear heat flow type of equation, and the saturation distributions are related to the pressure by the same equations QS those developed by Muskat for the average pressure and saturations in gas drive reservoirs. Unrler certain conditions the equation for the pressure can be approximated by the linear form of the heat flow equatlon. This equation tk analogous to the equation for the pressure in single-phase compressible flow The analysis reveals that the equation for the pressure in n~ultiphase flows can be obtained directly from the equation for the pressure in slngle-phase flows by simply replacing the single-phase compressibility by the total compressibility and the single-phase mobility by the sum of the mobilities of all the fluids present. Perrine's method of pressure buildup analysis for multiphme flows is based on these same substitutions. Thus, the development presented in this paper constitutes a theoretical justification for Perrine's method of pressure buildup analysis. One of the most difficult problems associated with the production of oil is the determination of the flow of the fluids within the reservoirs. One purpose of this paper is to present the development of simplified equations for the flow in gas drive reservoirs. The other purpose is to present some of the needed theoretical foundation for the methods currently being used in the analysis of multiphase pressure buildup data. The analysis presented in this paper makes use of a partial linearization of the equations governing multiphase flows. It is felt that the process of linearizing or partially linearizing the nonlinear equations of multiphase flows can lead to useful results since this process has proved extremely valuable in the study of other fields of science and engineering where nonlinear equations are encountered. Pressure buildup data of shut-in wells have been used for many years to estimate the static reservoir pressure. These data have also been used in studying the aver- age permeability both away from and close to the well-bores. The majority of the buildup data are obtained from wells producing two or three fluids. As yet the theoretical foundations for the methods of buildup analysis used in connection with rnultiphase buildup data have not been established. A number of methods of analysis of pressure buildup data have been developed." Most of these methods apply only to single-phase flows, and almost all of the theoretical analysis is confined to single-phase flows. Perrine' developed a method of analysis for rnultiphase flows from the method for single-phase flows of Miller, Dyes, and Hutchinson.' He did this by simply replacing the single-phase compressibility by the multiphase compressibility and replacing the single-phase mobility by the sum of the mobilities of the fluids in the rnultiphase flows. Obviously, such a procedure lacks a certain amount of theoretical justification, and such practices can lead to erroneous results. Fortunately, Perrine's results have a theoretical justification, and this justification is presented in the following discussion. It is assumed that gravitational effects and the cornpressibility of the rock can be neglected. Under these assumptions the equations governing the simultaneous flow of gas, oil and water in porous media areo* The preceding equations can be expanded into the following expressions.

By A. T. Yu

On March 18, 1964, the 52,000 dwt ore carrier M/S Houn Maru called at the port of Coquimbo, Chile, on its maiden voyage to take iron ore to Japan. This marked the first time a vessel of this size ever arrived at Coquimbo, and the event promises to drastically accelerate henceforth iron ore exports from Coquimbo province. This was made possible by the use of a versatile shiploading system recently installed by Cia. Minera Santa Fe. Coquimbo has no mechanized loading facilities other than six conventional 5-ton cargo cranes. Limited space on shore further complicates the stocking problems. To make the best of what is available, a meticulously organized semi-hand-loading system has been developed through the years.

Jan 5, 1964

By B. A. Wilcox

ThERE are several reports in the literature which indicate that both solid-solution hydrogen and hydride precipitates can promote low-temperature em-brittlement of tantalum.1-3 For example, Imgram et al.2 showed that hydrogen additions in the range of 140 to 580 ppm promoted a ductile-to-brittle transition at slightly above room temperature in both wrought and recrystallized tantalum. This contrasts with the observation that tantalum of norma1 purity is very ductile, even at liquid-nitrogen temperature. Imgram et al. also found that hydrogen additions caused a deterioration of notch tensile properties of tantalum. The purpose of this communication is to present some limited evidence that hydrogen can also cause fatigue embrittlement of tantalum. The material used in this investigation was wrought, stress-relieved (1000°C, 1 hr), are-melted tantalum rod (5/8-in. diameter) containing the following impurities in weight percent: 0.005 C, 0.007 02, 0.0005 H2, 0.003 N2, 0.08 Cb, 0.01 W, and 0.01 Fe. Hydrogen charging was done in an atmosphere of flowing dry hydrogen for 3 hr at 600°C, followed by an homogenizing anneal in purified argon for 15 min at 600°C, and cooling in an argon atmosphere. Typical micro-structures of the hydrogen-free and the hydrogen-charged materials are shown in Fig. 1(a) and Fig. 1(b), respectively. Fig. 1(b) shows the appearance of hydride precipitates which, in many cases, formed preferentially parallel to the rod axis. The hydride dispersion was uniform across the diameter of the specimen. The fact that the precipitate was a tantalum hydride was tentatively confirmed by X-ray diffraction on a metallographically prepared surface. After hydrogen charging, chemical analyses by vacuum fusion revealed the hydrogen content to be 0.0295 wt pct. In addition, the oxygen and nitrogen contents were slightly raised to 0.0095 O2 and 0.005 N2.

Jan 1, 1964

By J. A. Berger, R. J. Towner

The pjPocesses of polygonization and subgrain growth were followed in slightly stretched 99.99 pct A1 single crystals heated for cumulative times at 400°, 500°, and 600°C. Changes in sub-grain size and boundary angle were determined from measurements on X-ray micrographs. CAHN1, 2 studied polygonization in stretched and heated aluminum single crystals of 99.99 pct A1 using various techniques, including etch pits, Laue patterns, and a slight restretching of heated specimens to reveal small changes in lattice orientation by the direction of new slip lines. He found that kink bands, which had well-defined boundaries lying in a plane perpendicular to the slip direction (at least in the early stages of deformation), formed during stretching. Also, he noted that bending occurred about the <211> axis lying in the (111) slip plane perpendicular to the <110> slip direction. His studies of polygonization were largely confined to the kink bands rather than to the weakly bent matrix regions between bands. The minimum temperature required to bring about polygonization was established at about 450 "C. Guinier and Tenevin used a focusing Laue X-ray diffraction technique to study polygonization in aluminum single-crystal specimens of 99.99 pct purity. Stretching the crystals 5 pct in tension caused a widening of the focused Laue spots. After heating for 4 hr at 450°C, their method revealed no change in the specimen. Above 450°C polygonization was detected and further annealing near 600°C led to subgrain growth. They concluded that the orientation of the crystal relative to the axis of deformation had no marked effect on polygonization. Gay and Honey-combe4 using an X-ray microbeam technique found that polygonization did not occur in a stretched aluminum crystal heated at 250oC, although some decrease in the yield strength occurred. When the temperature was raised to 475oC, the asterism became broken up as a result of polygonization. Honeycombe5 noted that reflections on X-ray mi-

Jan 1, 1961