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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 Augustus Locke

I WISH to urge on this Committee the task of evaluating mining geology. -My motive is as follows: It, is a. duty of the Institute from time to5 time, to establish the social perspective of the professions grouped within it, not simply to promote their use, but to determine with engineering definiteness their true powers and functions. This becomes the delegated duty, therefore, of this committee in respect to geology. Be- cause my own subject is mining, I shall confine my remarks to mining geology. But I believe that the evaluation should be made to include all of that geology termed economic. The perspective for such evaluation is shown in the nature of the public support given to geology. The federal Geological Survey, the leading organization on the economic side, is actuated by the zeal of a small group of devoted professionals who consider its work valuable, ' It proceeds, however, on a starvation ration of appropriations, and that implies that neither the corporations, the voters nor the vote getters consider it important. Altogether, in' the public consciousness, geology is negligible. That, at the same moment, .the profession should act with full confidence, while everyone else should act' with opposite motives, is not fitting. For us, as a committee, to remain incurious regarding such a disparity of beliefs is quite impossible.

Jan 1, 1931

By Reno Sales

INTRODUCTION. THE geology of Butte possesses especial interest on account of the magnitude of the ore deposits, their extraordinary richness and persistence in depth. Since its discovery in the early 60's the district .has yielded, in round numbers, 6,000,000,000 lb. of copper, 260,000,000 oz. of silver, 1,250,000 oz. of gold, and a large but not definitely known number of pounds of zinc. This enormous metal production has been derived from an ore tonnage estimated roughly at 65,000,000 tons. At the present day, most of the important mine shafts have reached a depth of. 2,400 ft., while several are more than 3,000 ft., deep. At these-great depths rich bodies of copper ore are being exploited, showing no diminution in metal content as compared with the ores of the higher levels. The present (1913) daily rate of production is approximately 14,000 tons, of which 13,250 tons may be regarded as copper ore, although a small percentage of this is minable only because of the presence of

Jan 8, 1913

By W. B. Daly, A. S. Richardson

The application of artificial refrigeration, or air-conditioning, to the ventilation of deep, hot mines has long been a subject of interest to the operators of such properties. Artificial cooling of the air in theaters, railroad coaches, and various industrial plants has been so successful within recent years that it has been natural to assume that the adoption of similar methods would afford a ready solution to the difficult problem of mine ventilation. It should however, be obvious, that although there may be nothing technically impossible in the application of this process to mine ventilation there is a great economic distinction between the maintenance of a high standard of comfort for a large number of people in a relatively small space such as a theater and the cooling of air to improve working conditions for miners scattered throughout the extensive workings of a large mine. Many methods of air-conditioning have been considered by the management of the Anaconda Copper Mining Co. at various times, but until the development of the process to be described in this paper none has seemed economically practicable. The Ventilating Problem at Butte The main obstacle to satisfactory ventilation in the Butte mines is the normally high temperature of the granite country rock. In the present operating zone, rock temperatures as high as 120' F. have been noted, and in some parts of the district the rate of increase of temperature with depth has ranged as high as 3.5" F. per 100 ft. Other factors, such as the decay of mine timber and the oxidation of sulfide minerals in the ore bodies, contribute to raise the temperature of the air in the working places but, particularly in the development of the mines to greater depth, the naturally high temperature of the rock is of predominant importance. In few other places, probably, are the ordinary ventilating measures more hindered than at Butte. At an operating depth now exceeding 3000 ft., all of the air required for ventilation must pass through timbered shafts which, because of heavy ground, are of small size and offer great resistance to the flow of air. Shaft compartments are rarely more than 4.5 X 5 ft., and the shaft area open to the flow of air usually does not exceed 65 sq. ft.; in only two shafts is the area as great as 85 sq. feet.

Jan 1, 1934

In connection with the recent visit of the Special Mission of British Ministry of Munitions to the United States, the United Engineering Societies gave a dinner to the members of the. Mission on Tuesday evening, Nov. 13. This was the only public function on behalf of the visiting commissioners while they were in New York. During the remainder of their visit they were in daily conference with bankers, merchants' associations, labor federations, and other organizations. The result of these conferences will doubtless have an important influence on the manufacture of war supplies in the United States, since it will enable our business men and manufacturers to avoid a good many of the mistakes that unfortunately occurred in England at the beginning of the war. At present, fully 90 per cent. of the employees of British munition factories are omen, and the problem of employing women in the industries of the United States will doubtless soon be encountered with increasing frequency.

Jan 1, 1918

By Francis S. Peabody

This paper will not be a technical paper, because, although I have been in the business of mining and selling coal for 30 odd years, I am neither a mining engineer nor a practical miner. If I digress from time to time from my thesis, I must be forgiven by the expert engineers and highly technical gentlemen for whose proceedings this article is written. Waste of the wonderful store of power that the Creator placed at our disposal appears to have been the theory and the basis of our methods of extracting this power—waste from the time the coal is mined to the time it is consumed. Let us consider the prime causes of this wastage which has been the heritage of the coal mining industry. In the early days—about 150 years after " Stone Cole" was discovered in Illinois by Joliet and Marquette, and Father Hennepin noted a "cole" mine on his map—the mode of mining prevalent among farmer landowners, on whose property coal was discovered near the surface or outcropping on the hillsides, was to enter the seam by a shallow shaft or drift into the hillside and remove the coal by wedging it down until a large room was left. The roof without support would fall and our primitive coal operator would then sink another shaft or drive another drift. In these early operations only the large lumps were taken and all small pieces and screenings were left to be covered by the fall of the roof—in fact this condition prevailed in Illinois up to about 1885. Gradually the method of mining changed from the open chamber, to a single entry with rooms turned to the right and left. Later, as the demand for coal increased and the necessity for larger mines became evident, the "room and pillar" system grew to be regular practice. The room and pillar system of mining consisted of starting away from the shaft bottom or drift mouth, with a pair of entries usually 12 to 15 ft. wide and about 30 ft. center to center, one entry being used for the air intake and the other for the return air and haulage; from each entry rooms or chambers were turned, narrow at the mouth and widening

Jan 1, 1918

By AIME AIME

IN ORDER to carry on its work most effectively, the Committee on Industrial Organization (now known as the Committee on Industrial Relations) consists, of .a number of sub-committees, each composed of a chairman and members who are especially fitted to carry out the work designated by its title. With only one or two exceptions, all of these committees made reports at the New York meeting of the Institute, in February of this year, abstracts of which follow.

Jan 1, 1920

By J. W. Rutter, K. T. Aust

The temperature dependence of the rate of grain boundary migration was measured in bicrystals of zone-refined lead containing from 20 to less than 1 ppm by wezght of tin. The apparent activation energy in the temperature range from 320" to 200oC is markedly dependent upon the solute tin concentration and upon the orientation relationship of the grains adjacent to the grain boundavy. The quantitative experimental observat~ons are compared with the predictions of various theories of grain boundary migration. In previous work.&apos;?&apos; the mobility of individual grain boundaries was studied as a function of impurity concentration and type of boundary. Grain boundary migration occurred at the expense of dislocation arrays which were introduced into the specimen during solidification. Boundary mobility in zone-refined lead at 300°C was markedly decreased by small additions of tin. 0.004 wt pct being sufficient to decrease the rate of grain boundary migration by a factor of 1000. The mobility of grain boundaries having polar orientation relationships near 38 and 22 deg about <Ill>, and 28 deg about <100>, was much less sensitive to tin concentration in the range studied. As a result, these boundaries have relatively high mobilities. The present paper is a continuation of the above study. Data are now presented on the temperature dependence of the motion of individual grain boundaries in zone-refined lead as a function of solute tin concentration and orientation relationship of adjacent grains at the grain boundary. The experimental observations are compared with the predictions of a number of theories of grain boundary migration3-8 which, prior to the present experimental investigation, could not be critically evaluated. EXPERIMENTAL PROCEDURE The striation or lineage structure of melt-grown single crystals of zone-refined lead, containing various additions of tin, was utilized to provide a driving force for grain boundary migration, as previously described.1,2 Each grain boundary under study separated the striated single crystal from another grain which was introduced by localized plastic deformation and recrystallization of a small region of the sample. The speed of migration of grain boundaries in dilute alloys of tin in zone-refined lead was investigated as a function of 1) tin concentration from < 0.0001 to 0.002 wt pct, 2) temperature in the range of 200" to 320°C, and 3) orientation relationship of the adjacent grains at the grain boundary. The substructure driving energy available for grain boundary migration was estimated to be about 4000 ergs per cu cm, within a factor of two, from specimen to specimen.&apos; The specimen dimensions, and growth and alloying procedures for the preparation of striated single crystals of lead of known tin composition, were as described previously.&apos; Each bicrystal was carefully wrapped in aluminum foil, and annealed in a well-stirred salt bath consisting of 50 pct NaNO2 and 50 pct KNO3, for known periods of time at a series of constant temperatures (*2°C). The grain boundary positions, before and after each anneal, were determined by etching lightly in a solution of 5 pct nitric acid in methyl alcohol, in order to follow the motion of the boundary and determine its rate of migration. Thus, the rate of motion of the grain boundary in a single specimen was measured at various temperatures. The above procedure was carried out for each grain boundary in seventeen different bicrystal specimens.

Jan 1, 1960

By J. W. H. Clare

An equilibrium isotherm at 550°C is given for ternary alloys rich in aluminum containing 0 to 15 wt pct Cr and 0 to 20 wt pct Mn. Phases encountered are: aluminum solid solution; stable temary compound G; and MnAl8,. In addition, a limited number of alloys were annealed at 450°C to check for differences from the 550°C isotherm. These experiments limited the composition of the G phase at 550°C and further experiments established that the G Dhase is not stable above 590 ± 1 °C. RAYNOR and Little1 established several equilibrium isotherms using aluminum-rich alloys containing up to 5 pct of the elements chromium and manganese. These isotherms showed that, in addition to an a solid solution and the two binary intermediate compounds 8 and MnAl6, a stable ternary compound ex-isted in the system. This phase was called the G phase because of its ghostly appearance in micro-sections. Little, Raynor, and Hume-Rothery2 found a similar phase in binary aluminum-manganese alloys and, as a result of their experiments, concluded that the G phase was a metastable phase existing in the aluminum-manganese system. This phase was stabilized by the addition of chromium. The constitutional work of Raynor and Little,&apos; although showing the existence of the G phase in the aluminum-chromium-manganese system, did not establish precisely the composition limits of the phase or the temperature above which the phase became unstable and disappeared from the system. The work described in this paper was undertaken to provide this information. An examination of the previous work&apos; showed that an isotherm at 550°C would provide the required data regarding composition in the shortest possible time, as the (a + G) phase field narrows considerably at higher temperatures. The same work showed that the G phase ceased to exist between 580° and 595°C. A more precise estimate of the transformation temperature would therefore be obtained by annealing selected alloys at successively higher temperatures beginning at 580°C. EXPERIMENTAL PROCEDURE 1) Materials Used—The experimental alloys were prepared from four master alloys containing 15.00 w pct Cr, 15.28 wt pct Cr, 19.80 wt pct Mn, and 19.38 wt pct Mn which were made from super-purity aluminum, electrolytic chromium, and electrolytic manganese. The aluminum was of 99.996 pct purity, the principal impurities being copper, iron, and silicon. The chromium and manganese were 99.9 pct pure, the principal impurities being antimony, calcium, and magnesium. 2) Preparation of the Experimental Alloys—The alloys were prepared in 20-g quantities by melting together the requisite amounts of master alloy and aluminum in an alumina-lined crucible and, after thorough stirring with an alumina rod, cast into a cold copper mold to give ingots 1/4 in. in diam and 3 in. in length.

Jan 1, 1960

By W. M. Brown

SEQUACHEE Valley includes portions of the counties of Marion, Sequachee, Bledsoe and Cumberland. It extends in a general direction parallel with the Great Valley of East Tennessee, some 75 miles northward from the Alabama state line. It is separated from the Valley of East Tennessee by a mountain arm about a dozen miles wide, known as Wallen&apos;s or Walden&apos;s Ridge. The genesis of the valley, geologically speaking, is simple. It is an erosion-valley along the axis of an anticlinal. The point of the wedge remains in a row of low "saw-tooth" hills, running up the center of the valley. These hills are of Lower Silurian age, and consist of Trenton limestone, covered and protected in some measure by chert. Walls of Carboniferous age form the inclosing mountains on either side; whilst a magnificent arch of Hudson River, Niagara, Hamilton and Subcarboniferous strata closes the valley at the

Jan 1, 1886

By E. C. Burke, W. R. Hibbard

Plastic deformation in magnesium single crystals was studied by tensile tests at room temperature utilizing an improved preparation and testing technique. Consistent critical resolved shear stress values for basal slip were obtained. The advent of pyramidal slip at room temperature was rationalized upon the basis of grip constraints. A bend-twinning hypothesis was advanced as an explanation of mechanical twinning which occurs as a complex stress-relief mechanism. INVESTIGATIONS of the plastic deformation of magnesium have been limited to the determination of the fundamental kinetics which may be summarized as follows: 1—Twinning on the {102).l 2— Slip on the (001) plane in the [loo] direction at room temperature.&apos; 3—Slip on the {101) or {102) plane in the [loo] direction above 225°C." 4—Critical resolved shear stresses for basal slip in tension at room temperature of 83 g per sq mm with a variation from 57 to 127 g per sq mm." Bakarian&apos; studied the compression of thin wafers of magnesium single crystals and classified the components of the deformation mechanisms as follows: 1—The Basal field: (001) at an angle of less than 20" to the compression surface. Fracture along {101} or slip on (001) followed by {101} fracture. 2—The prism field: (001) at an angle greater than 60" to the compression surface. Twinning on the {102) generally occurring during the early stages of loading, basal slip in the areas of original orientation and (001) slip within twins. 3—The central field: (001) at angles greater than 20" but less than 60" to the compression surface. Slip on the (001). 4—The critical resolved shearing stress for {101} slip above 225°C was 400 g per sq mm. Observations of mechanical twins in hexagonal close-packed metals have been summarized by numerous investigatorsb-&apos; emphasizing a lateral or rotational atomic adjustment, in addition to the pure twinning shear, and the importance of reorienting the basal plane to a position more favorable for continued slip, rather than the resulting small dimensional changes. Criterion for the operative twinning planes has not been clearly established. Schmid and Boas hurmised that an energy condition related to the atom movements is the determining factor. MillerQ bserved that twinning stresses in zinc crystals decreased as the amount of prior deformation increased. Preparation of Specimens Magnesium single crystals % in. in diam x 8 in. long were grown from the melt under an argon atmosphere in a gradient furnace similar to that described by Jillson." Magnesium containing 0.018

Jan 1, 1953

By J. G. Morlet, A. R. Troiano, H. H. Johnson

Delayed failure in steel occurs by controlled initiation and growth of a crack. The incubation period for crack initiation was measured. Crack initiation and Propagation are controlled by interaction between hydrogen concentration and triaxial stress state. The incubation period results from stress-induced diffusion of hydrogen to the point of crack initiation. THIS paper describes the phenomenon of delayed failureland the kinetics of crack initiation and propagation in uniformly hydrogenated steel. The investigation was prompted by service failures of high-strength-steel components at applied stresses far below the conventional yield strength, after the part had successfully sustained equal or higher stresses for an extended time interval. This delayed failure phenomenon, often termed static fatigue, is associated1 with the presence of hydrogen. This is not surprising, since the voluminous literature on flaking and hydrogen embrit-tlement demonstrates that hydrogen may exert a potent embrittling influence. Flakes, or internal hairline cracks in alloy-steel forgings, are related to the presence of hydrogen retained from the steel-making process.2 On the other hand, embrit-tlement arises from hydrogen introduced during surface treatments such as acid pickling or electroplating. Laboratory delayed failures have been induced in notch specimens of 4340 steel by electrolytic charging of the specimen surface with hydrogen and subsequent static stressing.l,4,5 Static fatigue was observed over a wide range of applied stresses; however, failure did not occur below a critical applied stress, designated as the static fatigue limit. In this instance the extended time for failure resulted primarily from the macroscopic redistribution of hydrogen. A crack formed to the depth of the hydrogen enriched "case* upon loading; further crack growth naturally awaited diffusion of hydrogen into the material ahead of the crack. The crack-propagation rate was therefore controlled primarily by the macroscopic diffusion of hydrogen into the specimen interior during the test. Thus, in this instance static fatigue was associated with the movement of a gross concentration gradient. However, delayed failure in steel of uniform hydrogen concentration is of greater fundamental interest, as well as commercial significance. With a homogeneous hydrogen distribution a different mode of delayed failure might be expected. As the heterogeneous hydrogen distribution became more uniform,4,5 the initial crack-propagation rate decreased markedly and, in fact, what appeared to be an incubation period for crack initiation was observed. However, the macroscopic concentration gradient precluded an accurate evaluation of these observations. Although the existence of an incubation period, up to this time, has not been established definitely, it is not amiss to point out some implications of the concept. It is of interest in all hydrogen-induced embrittlement phenomena, such as flaking, delayed failure, and hydrogen embrittlement. Much discussion has centered around the possibility of an

Jan 1, 1959

By E. H. Wells, A. Andreas

New Mexico retained its position as the sixth largest oil-producing state for the year 1937 with a total production of 38,484,630 bbl. This was an increase of 11,680,184 bbl. over the 1936 production of 26,804,446 bbl., or a gain of 43 per cent. The production for Lea County during 1937 was 35,961,056 bbl.; for Eddy County, 2,136,251 bbl.; and for northwestern New Mexico (San Juan and McKinley Counties), 387,323 bbl. The average daily non-marginal well allowable for Lea County on Jan. 1, 1937, was 92 bbl.; at the close of the year it was 67 bbl. The average daily pipe-line runs were less than the allocations of the New Mexico Oil Conservation Commission, but slightly in excess of the state allowables recommended by the United States Bureau of Mines. The average daily production for the year was 105,437 barrels. The total number of completions in the state was 742, of which 638 were oil wells; 19 hydrocarbon gas wells; 5 carbon dioxide gas wells and 80 dry holes. Of the dry holes, 46 were in proven fields. Of these 46 dry holes, 13 were in the Artesia-Grayburg-Jackson-Maljamar area, Eddy County, two in the Getty Extension field, Eddy County, 11 in the Red Mountain field, McKinley County, three in the Rattlesnake field, San Juan County, and nine in the Aztec-Bloomfield area, San Juan County. There were only eight dry holes in the proven fields in Lea County. Southeastern New Mexico Lea County.—The Monument field was the largest producing field in Lea County, with 10,945,788 bbl., closely followed by the Eunice field with 10,927,929 bbl. The Hobbs field, formerly the largest producing field in Lea County, was relegated to third .place, with 7,292,522 barrels. Drjlling during the year closed the gap between the northern part of the Eunice field and the southern part of the Monument field. The wells in this area were relatively small, because of decreased porosity in the lime. The greatest activity in Lea County was in the Monument pool, with 199 completions, 197 being oil wells, one a gas well and one a dry hole.

Jan 1, 1938

By B. F. Tillson, C. M. Haight

I. General Remarks..........................723 1. Location............................723 2. Characteristics of the Orebody..................725 (a) Mineralogical (b) Shape, Strike, Dip, Size, Etc. (1) Ore (2) Country Rock 3. Historical Sketch........................725 11. Mining Method..........................726 1. Outline of Methods Now in Operation............... 726 (a) Stopes (b) Fill . (c) Pillars (d) Slices (e) Transportation (f) Miscellaneous 111. Mining Operations........................727 1. Shaft..............................727 (a) Sinking (b) Dimensions and Equipment, Sketches (1) Size, Inclination. Direction, Etc. (2) Timbering (3) Stations (4) Track (5) Hoisting Equipment (a) Skips (b) Engines and Ropes (c) Idlers (d) Man Cars (6) Loading Pockets (a) Operating Figures (7) Headframe

Jan 1, 1918

By S. B. Christy

The fact that many millions of gold have been extracted by the cyanide process, during the last five or six years, from South African tailings which could not be profitably worked by any other method previously tried upon them, lends a peculiar practical interest to this branch&apos; of metallurgy. Numerous writers have recently made valuable contributions on the process without exhausting the many complexities of the subject. Among the first American writers on the subject in its modern aspect were two former students of the University of California, Mr. Louis Janin, Jr., and Mr. Charles Butters. Young Janin was one of the first to enter this field, and performed much useful experimental work in the early stages of the history of the process. At about the same time, Mr. Charles Butters, who had left California to erect chlorination works for the Robinson mine at Johannesburg, became interested in the cyanide process, and, after getting the chlorination plant in working order, put up, for working the tailings from the Robinson mine, a cyanide plant which achieved the first large-scale success ever made with this process. The papers which Charles Butters, together with John E. Clennell and Edgar Smart, have contributed on the chemistry of the process, were among the first to give any adequate idea of its nature.* Another important contribution to the literature of the subject is the paper of Dr. A. Scheidell, published in 1894 as a " Bulletin of the California State Mining Bureau." This contains an admirable summary of the state of the art at the time of its publication.

Jan 1, 1897

By William Gilman

IN the past five years, and without much fanfare, Turkey has emerged as a significant figure in the world mining picture. This has been accomplished by a five-year plan now in its last year. A second five-year plan is already under way, ahead of schedule. It will concentrate even more than the first in developing Turkish mines in order to increase present exports of coal, chrome ore, and copper, and to develop new mineral exports as well. To be fully understand the republicic?s mining program should be considered as something more than merely tapping rich resources in the East along the Aegean Sea, in the North among the mountains descending to the Black Sea, and in the West at the foot of the Taurus Mountains. It should also be viewed in the light of a strong nationalist policy with many aspects of state socialism. Turkey declares frankly that all mineral re- sources belong to the nation and all exploitation should be by the state for the twin purpose of modernizing the state and securing foreign exchange for the state by exports. Accordingly, the principal mines are state-operated and a few lesser enterprises, although not state-owned, have at least been put in the hands of Turkish capital.

Jan 1, 1938

By C. K. Gupta, P. K. Jena

Niobium (columbium) metal in the form of a button has been produced by calciothermic reduction of niobium pentoxide using sulfur as the heat booster. In these experiments with 50 g of niobium pentoxide per batch, the influence of percentage of calcium in excess of the stoichiometric, the percentage of sulfur by weight of the niobium oxide, and the outer-wall temperature of the bomb on the quality and yield of the metal has been studied. The maximum yield on this scale was 78 pct using 50 pct excess Ca and 20 pct of S and at a bomb-wall temperature of 600°C. In experiments conducted on 500 g of niobium pentoxide, reduction with 40 pct excess Ca and 20 pct of S, and at a bomb-wall temperature of 500°C, the.yield of the metal improved to 82 to 84 pct. Some of the reduced-metal samples have been electron-beam melted and the button melts thus obtained have been observed to be extremely ductile and capable of cold reduction to 98 pct without intermediate annealing. NIOBIUM, because of its high melting point (2468oC), its ductility, its resistance to corrosion especially in liquid metals, its high-temperature mechanical properties, and its relatively low capture cross section (1.1 barns) for thermal neutrons, has potentialities as a structural material in the field of nuclear engineering. Niobium and its alloys are also gaining importance in high-temperature technology as components in aircrafts, jet engines, and missiles, electronics, chemical engineering, and surgery. In 1904 Weiss and Aichel 1 produced niobium by reduction of its pentoxide by misch-metal. Since then a large number of investigations have been carried out for the extraction of niobium from its compounds. The various routes through which the metal niobium has been extracted from its compounds can broadely be classified into the following groups: a) reduction of its halides, oxides, and fluo-salts with metals like calcium, magnesium, sodium, and aluminum;2-10 b) reduction of its halides with hydrogen and oxides with carbon or carbides;11-18 c) electrolytic winning from its halides and fluo salts;19-25 and d) thermal decomposition and disproportion ion of its halides26-30 Among the processes in commercial use at present are sodium reduction or fused-salt electrolysis of potassium niobium fluoride, carbide or carbon reduction of the oxide, and hydrogen or metallothermic reduction of the chlorides. In 1907 Von Bolton2 prepared niobium by reducing niobium pentoxide with aluminum. Dennis and Adam-sona attempted reducing the oxide with magnesium powder in argon atmosphere and the resulting metal contained as much as 5 pct O. Mondolfo8 claimed a method for the reduction of the oxides with aluminum. In the case of both magnesium and aluminum reduction, it has been stated31 that by-product oxides such as MgO or A12O3 would involve a major separation problem. Further, in the case of alumino-thermic reduction, the solubility of aluminum in niobium and intermetallic formation have to be reckoned with. In 1922 Bridge3 produced niobium by calcium reduction of niobium pentoxide. Dennis and pdamson&apos; obtained the metal by a similar method with an oxygen content of 0.2 pct. In most of the cases of metallothermic reduction of niobium oxides mentioned above, the metal niobium is obtained in the form of powder. In an attempt to produce massive niobium metal, lock&apos; used iodine as the thermal booster in the bomb reduction of niobium pentoxide by calcium. Massive niobium metal was obtained with a maximum yield of 75 pct containing 0.1 pct 0. Joly32 carried out experiments on calcium reduction of niobium pentoxide on a 2-kg scale using sulfur as the heat booster in a sealed bomb filled with argon. In his experiments, the reaction was initiated by passing a current through niobium spiral wire embedded in the charge. In a typical run consisting of 2000 g of niobium pentoxide, 3100 g of calcium, and 800 g of sulfur (S/Nb2O5 = 3.3), he obtained massive metal in the form of a very uneven mass with a yield of -57 pct. With lower amounts of sulfur and calcium, powder niobium mixed with small metal globules was obtained and the yield was also poor. From these experiments he concluded that this method is not a suitable one for industrial development considering the quality and yield of metal obtainable and the possible hazards with higher ratios of sulfur to niobium pentoxide in the -~charere. In the present work, a detailed investigation on the calciothermic reduction of niobium pentoxide in a stainless-steel bomb in presence of sulfur as the heat booster was undertaken on a laboratory scale.

Jan 1, 1964

The General Committee met in the Treasury Building at Washington on Oct. 6 and 7. At the first meeting, Cornelius P. Kelley was appointed chairman, and Paul Armitage, secretary. Sub-committees were ap-pointed on Invested Capital, Mine Valuation, and Depletion and De-preciation. On Oct. 7, the reports of these committees were submitted to the General Committee and were referred to the Executive Committee. A motion was carried that the Executive Committee he constituted a permanent committee to continue the work of the Committee, with full power to acid to and increase its membership, that. as thus increased, it should constitute a permanent organization to act- and cooperate with the Treasury Department in matters of mining taxation under the Federal Income and Excess Profits Tax Laws. Thereafter the Executive Com-mittee met and formed a permanent committee as follows: Cornelius F. Kelley, chairman, 42 Broadway, New York City. J. L. Darnell, office of the Commissioner of Internal Revenue, Wash-ington, D. C. J. Parke Channing, 61 Broadway, New York City. Walter Douglas, 99 John St., New York City. R. V. Norris, 542 Second National Bank Bldg., Wilkes-Barre, Pa. J. E. Spurr, Engineering and Mining Journal, 10th Ave., and 36th St., New York City. W. G. Swart, 808 Selwood Bldg., Duluth, Minn. J. P. Finley, 45 Cedar St., New York City. W. A. Williams, Bartlesville, Okla. F. S. Peabody, Peabody Coal Co., McCormick Bldg., Chicago, Ill. Matthew C. Fleming, 71 Broadway, New York City. H. B. Fernald, 54 Wall St., New York City. William G. Mather, Cleveland, Ohio. Walter Fitch, Eureka, Utah. Arthur Thacher, 900 Security Bldg., St. Louis, Mo. John P. Gray, Coeur d&apos;Alene, Idaho. Paul Armitage, secretary, 233 Broadway, New York City.

Jan 12, 1919

By W. D. Sylwestrowicz

In tests on polycrystalline copper and aluminum, the ratio of the yield stress to modulus of elasticity was found to be strongly dependent on tempemture. Also, it was shown that the change of the yield stress with temperature of a material at a given temperature and deformed to a given yield stress, but not necessarily to the same strain, does not depend on previous mechanical thermal history. Likewise, for a material at a given temperature and deformed to a given yield stress, the rate of work hardening is independent of the temperature of prior stressing. It has been shown by Los and Orowan1 and by Dorn, Goldberg, and Tietz2 that the temperature dependence of the yield stress-strain curves of crystalline materials reflects two effects: not only does the yield stress of a material in a given structural state depend on the temperature, but the structural state (and the corresponding strain hardening) after a given amount of plastic straining also depends on the temperature at which the pre-straining has been carried out. Thus, for instance, if a specimen of a ductile metal has been strained along the stress-strain curve 1 at room temperature to point A, Fig. 1, and then the straining continued in liquid nitrogen along curve NR, the yield stress A&apos; immediately after lowering the temperature is lower than the yield stress A" of a specimen that has been strained by the same amount in liquid nitrogen (along curve 3). AA&apos; represents the effect of the temperature change upon the yield stress of the specimen pre-strained at room temperature; A&apos; A" is the excess strain hardening acquired if the pre-straining has been carried out in liquid nitrogen instead of at room temperature. The dependence of the yield stress (i.e., of the structural state acquired during preceding straining) upon the conditions (speed, temperature) of a pre-straining is the reason for the nonexistence of a so-called "mechanical equation of state" for plastic deformation. A &apos;mechanical equation of state" is a relationship of the form F(s,E, e, T) = 0, or s = f(E, E, T) [1] It was first suggested by Ludwik3 that plastic deformation might obey such an equation; this, however, was conclusively disproved by experiments of Kochendorfer.4 Additional disproofs were given in

Jan 1, 1959

By A. B. Kinzel

Precise knowledge regarding the effect of heat treatment on the properties of steel has made possible the detailed specifications and instructions covering optimum heat-treating temperatures and practices that are in current use. A distinct contrast is presented by the metallurgical treatment of steel adjacent to a fusion weld, as such steel is subjected to each temperature from room temperature to fusion temperature, and cooled at a rate that is not generally controllable but is predetermined by the nature of the assembly to be welded, the kind of welding used, and the surrounding conditions. This is true regardless of the type of fusion welding: oxyacetylene, electric arc, thermit or flash resistance. Therefore it seemed desirable to investigate the effect of this metallurgical treatment on the characteristics of carbon steels commonly used for welding, by a detailed study of metal subjected to each temperature range; i.e., each heat-affected zone. Oxyacetylene welding was chosen for the investigation because of the experimental facility of accurately segregating and studying each temperature zone. The nature of the zones produced by other types of welding is the same. The difference is primarily a matter of dimensions of each of the temperature zones involved. The advantages and disadvantages of the extent of the zone are of prime moment, and are discussed after the presentation of the detailed zone study. No mention is made of the fused metal proper, as this has been the subject of much published research and the nature of the solidified metal is fairly .ell known. General Method The scheme of procedure in the work herein reported involved the testing of the metal of each temperature zone adjacent to the weld in so

Jan 1, 1935