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By Donald D. Smythe

Tars paper describes briefly the topography and geology of the region where the mica-bearing pegmatites are found and discusses prospecting, the quality of the mica, its preparation, and evaluation of the deposits. Muscovite mica occurs in a number of widely separated localities in Brazil, but production has come largely from deposits in the southeastern and eastern part of the State of Minas Gerais (Fig. I). There the deposits form a discontinuous zone, which starts at a point 90 km. north of the city of Rio de Janeiro and extends north for some 500 km., roughly parallel to the coast. A maximum width of 180 km. is reached along the Rio Doce. To the west in Minas Gerais, and extending east into the states of Espirito Santo and Rio de Janeiro, the mica zone proper is fringed by areas in which there are scattered occurrences of mica-bearing pegmatites. A few of these outlying deposits have produced commercial mica, but most of them are unimportant. To the southwest, in the State of São Paulo, there are a number of mines, which at one time produced a very considerable amount of sheet mica, largely as a by-product of kaolin mining. These deposits, and, a few others lying between them and the main productive areas to the northeast, appear to be the southwestern continuation of the strong Minas Gerais mica zone. In the vicinity of Conquista, just north of the Minas Gerais boundary in the State of Bahia, and still farther north, near Jacobina, there are several known mica deposits. Their location indicates that they may be the northern continuation of the main mica zone. The major part of Brazilian mica production has come from four areas within the mica zone proper; from north to south, Governador Valadares, Raul Soares, Espera Feliz, and Muriaé. The first is 190 km. from north to south and reaches a maximum width of 180 km. The Raul Soares area extends 135 km. from northeast to southwest, and in places is 80 km. wide. The Espera Feliz area is 100 km. from north to south, and reaches a width of 35 km. The Muriaé area extends 150 km. from northeast to southwest and its width reaches 40 kilometers. Between the known productive areas, and in the areas directly to the southwest and to the north of them, little mica has been produced. These gaps, as well as certain irregularities in the outline of the mica zone itself, are to be ascribed either to lack of prospecting or to conditions preventing the discovery of mica, rather than to its nonexistence. Elsewhere in Brazil mica has been reported from eastern Goiaz, Ceará, Pernambuco, Rio Grande do Sul, Matto

Jan 1, 1946

By G. Derge, W. Peifer, J. H. Richards

INTRODUCTION A WIDE variety of metallurgical defects in steel have commonly been attributed to the presence of excessive amounts of hydrogen. These defects include flakes in rails and forgings, cracks in welds, and blisters in enameled ware. They have been related to hydrogen largely by circumstantial evidence because the proper sampling and analysis of steel for hydrogen has been known to be difficult and because no general agreement has existed with regard to the relative suitability and accuracy of available methods. The need for a direct approach to these problems has been widely recognized. This general situation has been well described in the publications of the British Committee on the Heterogeneity of Steel Ingots,1 and current approaches to the problem were reviewed in a recent symposium of the AIME.12 The plans described by the present authors at that meeting have now matured satisfactorily and will form the basis of this paper. The principle object of this paper will be to describe the methods of sampling and analysis which have been developed and to illustrate the usefulness and limitations of these methods by citing their application to a specific problem. The first problem selected for investigation was the behavior of hydrogen in rail steel. This was chosen because the occurrence of shatter cracks in rails has received a great deal of study over a long period of time. The defect can be controlled by the expensive procedure of slow cooling. However, it may be hoped that a better understanding of the factors influencing the hydrogen content of rails will lead to a more efficient control of this problem. Rails provide a good starting point for a more general study of hydrogen in steel because they provide a cross section large enough to develop cracks, yet small enough for convenient handling and sampling. Rails were also selected because they are made from plain carbon steel and it was felt that the initial work should not be complicated by the effects introduced by alloying elements. The considerations which determined the original planning of this study should be reviewed. The inherently complex nature of most hydrogen problems requires that a large amount of data must be collected for any particular case. This in turn means that any analytical procedure should be as rapid and simple as possible. The same objective of speed is indicated by the fact that it may finally become desirable to use hydrogen analysis in process control. It is also known that hydrogen is highly fugitive and that any procedure which facilitates early analysis of the sample without prolonged or irregular storage has distinct advantages. The most important previously reported methods of analysis may be classified into three general groups: (I) Vacuum fusion. (2) Vacuum extraction (without melting). (3) Total combustion.

Jan 1, 1948

By John Brownson

Ge-Si N-N heterodiodes hare been built recently which show promise as high-speed logic devices. Low-resistivity germanium is deposited on silicon substrates held at temperatures above the germanium melting point and an alloyed heterojunction formed. The diodes are fabricated from this material using conventional mesa techniques. Over-all device qualify has been greatly improved by the use of epitaxial silicon substrates, that is, a subsirale consisting of a film of thin, high -resistivity silicon on a thicker Piece of low-resistirily silicon crystal. A semimpirical device design equation has been devised which predicts switching performance fairly well within the range of resistivitics and geometries employed. Switching times 01 0.9 ns and PIV 's of —20 v are typical of the better 10-ma diodes. Switching times as low as 0.5 ns have been observed for 10-ma diodes and as low as 2.8 ns for 200-ma diodes. With further development it should be possible to improve switching speed by a factor of four. IN our laboratory, Ge-Si heterodiodes have been built recently which show promise as high-speed logic devices. The diodes have been built using a process reported in some detail in an earlier publication.' The process in short involves alloying a thin film of low-resistivity germanium into a silicon substrate. the germanium having been transported and deposited by the well-known Theuerer halide reduction process.2 This process contrasts with that reported earlier by Oldham who used an essentially conventional direct epitaxial deposition technique.3 Oldham's process, unlike ours, requires cleavage of the silicon sample inside the reactor furnace the instant prior to deposition. Our process has the advantage of yielding large-area macro-scopically plane heterojunctions. Heterodiodes in general have several interesting properties. Without attempting to summarize the theory of heterojunctions.4 two of these properties which have direct relevance should be mentioned. First, N-.V and P-P heterojunction diodes rectify alternating current. Provided that either the band gap or the electron affinity of the two materials is different (which in general is the case), electronic barriers will exist in the junction band structure. When the device is sufficiently forward-biased, the barriers shift so as to permit current flow, and when it is reverse-biased. the barriers block current flow. Second, for N-N and P-P heterodiodes. the foward-conduction process involves majority carriers only. Consequently. when such a device is turned off. there is no minority-carrier storage and hence the diodes switch on and off quite rapidly. As we have reported earlier. N-P and N-N Ge-Si heterodiodes have been built in this laboratory. As one would predict from theory, the N-P heterodiodes were rather slow in turning off while the N-N's were quite fast. Similarly, the turn-off time of the N-P's increased rapidly with forward current while that of the N-N's was independent of forward current. Both N-N's and N-P's were moderately photosensitive. Photocurrents resulting from normal room illumination were as high as 1 µa at 1 v for small-area devices. The most disappointing parameter of the early N-N devices was reverse leakage.' The reverse characteristic was invariably "soft" and leakage at only several volts reverse bias was intolerable. The reverse characteristic was greatly improved by using higher-resistivity silicon substrates. Leakage becomes large at voltages about one third of the avalanche voltage one would expect of a P-N homo-junction formed on silicon of the same resistivity. Thus leakage could be reduced to reasonable limits by using unconventionally high-resistivity silicon. Medium-power diodes formed on 30 ohm-cm substrates leaked typically 15 to 50 µa at 100 v reverse bias. The use of high-resistivity silicon substrate material, however, created a new problem. In order to have an acceptable forward-conductance characteristic. the area of the diodes had to be increased. With this increase in area, the capacitance increased. Switching time for N-N heterodiodes is essentially a linear function of capacitance. Thus when the resistivity was raised. so was the switching time. A SEMIEMPIRICAL HETERODIODE DESIGN EQUATION As a result of our experiments with a limited range of diode geometries and resistivities. a semi-

Jan 1, 1965

By H. B. Hunter, F. G. Stone, F. J. Dunkerley

Introduction and Literature Survey This is the second in a series of papers coming from this laboratory on the correlation of the low temperature tensile properties of tin-binary alloys with microstructure. These engineering data and those of the previous paper1 were obtained as the initial part of a long-range program to determine the changes in the fundamental mechanical properties accompanying the beta to alpha phase change in tin and its binary alloys below 13.2°C. Since it appears now that the more fundamental studies will be delayed,* and since no summary of the low temperature properties of these tin-base white bearing alloys was found in the literature, it was decided to publish all the engineering data thus far obtained. Accordingly, the tensile properties of thirteen binary alloys containing from 0.1 to 60 pet cadmium and 0.1 to 10.43 pet antimony measured at six temperatures from —196 to +23°C are presented here and their variations rationalized in terms of microstructure. A literature search showed that these systems had not been investigated at low temperatures, although both the tin-cadmium and tin-antimony2,3,4,5 and the tin-rich corner of the ternary system67 have been studied at room temperature. Hanson and Pell-Wal-pole5 and Homer and Plummer4 determined the tensile properties of alloys containing from 0 to 10 pet cadmium. The same authors3 determined the tensile strength and elongation in the tin-antimony system from 2 to 18 pet antimony at room temperature while Pell-Walpole et al.6,7 studied the properties of high tin and tin-antimony-cadmium alloys. Since there were many variables besides composition in these tests, it was difficult to make a valid comparison with the room temperature data of the present study, but in general the tensile strength and ductility values are in reasonable agreement. Pell-Walpole2 also determined the effect of grain size on the tensile strength of pure tin and 1 pet alloys of both antimony and cadmium. The true maximum stress was found to decrease exponentially as the number of grains in the cross-section increased. This effect of grain size was strikingly revealed in the present work, as indicated in a later section. Hanson and Pell-Walpole8 placed the solid solubility limit of antimony in tin at 3.5 pet at 20°C, increasing to 4 pet at 190°C, and then sharply increasing to 10.3 pet at 246°C (the latter being a peritectic point). Their results are in disagreement with those of previous investigators,9 and the discrepancy seems to lie in the micro-graphic observation of the second phase

Jan 1, 1950

By J. Serra, M. Turpin, R. Alberny

A new method is proposed to obtain automatically an unbiased estimate of the interdendritic spacing A. It is shown that the structure can be built by a random distribution of a rectangular basic unit. The usual definition of the interdendritic spacing yields a value 1 which, coupled with A, gives the shape of the basic rectangular unit. A study of the relationship between dendrite arm spacing and solidification rate was conducted as a part of a research program on dendritic solidification. For any comparison between theory and experiments to be meaningful, it is necessary to measure reproducible and clearly defined spacings. Fig. 1 shows clearly that even in a fairly simple structure such measurements are difficult. if we compare photos (a) and (b), we can hardly assess which one shows the larger spacing. Moreover, the quantity to be measured can be defined in several ways. On a small scale, dendrites seem to be distributed in a very regular and ordered way. However, on a larger scale, this regularity no longer exists. The usual way to measure spacings is to pick up some rows of dendrite stalks; such measurements are obviously biased since less orderly regions are not taken into account. A more objective method is to section the picture with randomly oriented straight lines and average the measured interdendritic spacings. The purpose of this paper is to show that such measurements, which can be conducted automatically, yield objective and reproducible results which are directly related to characteristic features of the dendritic structure. I) THEORETICAL ANALYSIS 1-1) Mathematical Morphology and Function of Co-variance. Matheronl and Serra2 enlarced- the definition and geometrical meaning of the notion of covariance to encompass problems in mathematical morphology. A brief review of part of their theory can be stated as follows. Let A' be an isolated particle, and let us consider a group of two scanning points h is the vector joinlng these points, h its modulus, and a its direction. Let us also define a boolean function, k(x), whose value is 1 if x lies inside the particle and 0 if it 1s outside. The total number of events in which both points are inside A' IS the covariance Ii',(h): is the measure of the intersection of A' with the particle ALh obtained by translating A' of -h Obviously K,(O) is the volume of the particle A', or its area if A' is a two-dimensional body. The average value of K,(h), when the direction of a vector h of constant modulus is rotated, is: An important property of the covariance is illustrated on Fig. 2: if the shape of a particle shows some regularity along a direction a, K,(h) generally presents a maximum. We now consider a group A, made of many particles A' distributed in space; then k(x) is taken as the realization of a stationary random f~nction.~ The volume fraction (or fraction of area if the problem is two-dimensional) occupied by A equals the average value q of k(x): meaning "average value of"). We also replace

Jan 1, 1970

It is always the case with heavy and cheap materials that the area within which they can be economically used depends upon the cost of transportation, and in those days of poor roads and no mechanical means of haulage on them, coal could only be moved a few miles from the mine by any other means than water. The need of better means of transport to the areas west of the mountains had been urged by Washington and many other leaders, but the first turnpike over the Alleghenies only reached the Ohio River at Wheeling, W. Va. in 1818. The James River and Kanawha road reached the Ohio in 1831, that from Winchester, Va. to Parkersburg in 1838, and the road through the Cumberland Gap was completed in 1797. None of these affected the coal industry excepting indirectly by building up some of the river towns which coal could reach. The inadequacy of roads alone to carry the traffic of the rapidly growing interior communities was demonstrated only a few years after the National Pike was completed, and in the early 1820's several of the states embarked upon the construction of a canal system, which had been under discussion for some years. The Erie Canal was opened in 1825 from Lake Erie to the Hudson River through New York; Pennsylvania, Virginia and Maryland had already started similar projects designed to bring traffic to their principal cities from the interior. The Pennsylvania Canal was started from Columbia, as a railroad extended from Philadelphia to that point, and it followed the Susquehanna and Juniata Rivers to Hollidaysburg; thence to Johnstown, a distance of 36 miles, where it consisted of partly railroad and partly inclined planes, the boats being hauled up, and lowered down the planes; from Johnstown the canal followed the Conemaugh, Kiskiminitas and Allegheny Rivers to Pittsburgh, 104 miles. Boats first reached Pittsburgh by this route in 1834. The Chesapeake and Potomac Canal followed the Potomac River from a point above Alexandria above the falls, to Cumberland. This canal was chartered in the eighteenth century and a portion of it was used by traffic in 1800. It was too small to be of much use and was abandoned, and later after many legal and financial vicissitudes was completed to Cumberland, traffic from there starting late in 1850. This date, however, was long after the Baltimore and Ohio Railroad had been completed to

Jan 1, 1942

By Francis Lucas

EACH year we gather in this auditorium to honor the memory of a . distinguished American metallurgist and educator. I cannot bring to you reminiscences of Prof. Henry Marion Howe as other lecturers have done. It was not my good fortune to enjoy the privilege of studying and ,working under his direction. As I have reflected on the published works of Professor Howe, it has seemed to me that his mind was trained on the nature of metals and on the mechanism which produced known but unexplained effects. He was interested in controlling and regulating the causes so as to produce specific effects, useful in serving mankind. I recall an afternoon in May, 1925, when, at the invitation of Mrs. Howe, I visited his former home, Green Peace at Bedford Hills, N. Y. The purpose of my visit was to receive at the hands of the widow -an engraving of Professor Howe, a reproduction of a painting from life. Mrs. Howe showed me his study. The walls of this large attractive room, brilliantly illuminated by the spring sunshine, were literally covered with the scrolls of honors and of decorations which had been conferred on Professor Howe by governments, academies, universities, societies and. institutions the world over. As we walked about the room, she pointed out the significance of each honor and recited a few details of each occasion. I sensed the pride with which Mrs. Howe, then in the late autumn of her life, told me of her husbands' achievements, of his struggles, of his disappointments and of his successes. There was a surprisingly familiar note in the recital to which I was listening. I have found the same theme running as a disconnected thread through the written accounts of the lives of most men of science. We then went to the drawing room to chat for a few minutes before I said my farewells. As we seated ourselves, Mrs. Howe turned to me and asked: "Mr. Lucas, what of this great microscope of yours? Cannot it be applied to the study of disease? What a great blessing it would be if it could be directed to relieve the suffering of mankind."

Jan 1, 1931

By J. Chipman, H. A. Wriedt

DURING the past twenty years, a considerable background of knowledge has been built up on the chemical behavior of oxygen in liquid iron. Little is known regarding oxygen in liquid nickel or the effect of nickel as an alloying element on the behavior of oxygen in liquid steel. The solubility of oxygen in liquid iron was determined by Fetters and Chipman' and, more precisely, by Taylor and Chipman.' The Ni-NiO eutectic was placed by Merica and Waltenberg"' * at 1438°C and 0.24 pct 0, and this point has been confirmed by others." O It was reported by von Bohlen und Halbach and LeitgebelT that nickel and its oxide are miscible in all proportions at 1600°C, but this report is discredited by observations of others. The melting point of NiO according to von Wartenberg and ReuschV s 1990°C. Approximate values of oxygen solubility at several temperatures were reported by Hensel and Sc0tt.O The data of Krupowski and Balickil0 are inconsistent with those of Hensel and Scott and indicate a solubility less than half that found in the present study. For oxygen solubility in Fe-Ni alloys under pure iron oxide-nickel oxide slags, only the scattered data of von Bohlen und Halbach and LeitgebelT are avail- able. The careful work of Bardenheuer and Brauns" involved silica-saturated slags. The equilibrium between Fe-Ni alloys and iron oxide-nickel oxide slags was studied by zur Strassenu and by Jander and Senf,u but no oxygen analyses were reported. Oxygen in Pure Nickel Apparatus and Nlethod: Samples were taken with a "Taylor sampler" from a bath of molten electrolytic nickel held under an air atmosphere in a magnesia-lined 30 lb induction furnace. Saturation of the melt with oxygen was effected partly by the addition of chemically pure black nickel oxide and partly by the air atmosphere. Samples were taken only when there was a clearly visible oxide phase present. To avoid contamination of this oxide phase, the silica-sheathed Pt—Pt-10 pct Rh thermocouples, by means of which temperatures were measured, were immersed in the melt for the minimum time consistent with accurate reading. Samples and temperature readings were taken only after the furnace had been

Jan 1, 1956

By John W. Langley

In the summer of 1888 it was the fortune of the writer to present the subject of the desirability of establishing a set of samples of steel, which should be analyzed with extreme care, in order that they might become standards to which scientific and commercial analyses of iron and steel could be subsequently referred; also, that greater uniformity in the results of analyses might be brought about, since these standards would bear towards analytical methods somewhat the position which the original units of weight and length, the gramme and meter, or the pound and yard, preserved in Paris, London, and Washington, do to the mechanical arts. The plan met with hearty co-operation, with the result that com mittees were appointed in Sweden, Germany, France, England, and America, to receive the material and to see that the necessary au alyses were executed. In England, the British Association for the Advancement of Science appointed a committee, which subsequently published a plan

Jan 1, 1891

By J. F. Abel, F. T. Lee

Subsidence is controlled by a complex com¬bination of mining and geologic factors. For example, a compilation of worldwide data shows that, as the percentage of shale in the overlying rock mass decreases and the amount of sandstone increases, the angle of draw (and the area affected by subsidence) decreases. Limestone in the over¬burden appears to cause a more than twofold decrease in the angle of draw compared to a like amount of sandstone. Increased amounts of sandstone were accompanied by a greater surface subsidence relative to the mining height. The total thickness of overburden did not appear to influence the subsidence magnitude above super-critical panels. The greater the thickness extracted, the smaller percentage of that thickness shows up at the surface as subsidence. The greater the percent of the seam extracted, the greater the subsidence reaching the surface. The maximum subsidence above room-and-pillar panels de¬pends on the pillar height and minimum width as well as the other factors listed.

Jan 1, 1984

By E. Peters

As in other fields of Extractive Metallurgy, Hydrometallurgy is preoccupied with separation processes and with oxidation-reduction processes. The physical chemistry of each type of process can be described in terms of thermodynamic equilibria and in terms of reaction kinetics. Reaction kinetics are much more important at the low temperatures limiting hydrometallurgical processes than in com- parable pyrometallurgical operations and the number of cases in which the kinetics can be described by simple liquid-phase mass-transfer models are sharply limited. It is convenient to subdivide the applicable rate phenomena into processes in which (a) interface reactions control the rate,(b) mass transfer processes control the rate, (c) solid state process affect the rate, (d) thermodynamically predicted phase changes or molecular reactions fail to take place, (d) metastable substances or supersaturated phases persist, and (elchomogeneous reactions in solution affect the chemistry and the kinetics. Examples are drawn from the unit steps of leaching, cementation, hydrogen reduction, and electrowinning.

Jan 1, 1973

By E. Hein, R. A. Dodd

The fatigue softening of prior strain-hardened poly crystalline copper has been determined by measuring changes inflow stress resulting from fatigue treatments. Tensile fatigue does not soften the metal, while the softening due to reversed stress fatigue depends on the extent to which fully reversed stressing is approached. True tensile fatigue is shown to be possible only in the case of long wire specimens. Annealing following fatiguing of strain-hardened metal shows that tensile fatigue is very effective in modifying normal recovery and recrys-tallization. OBSERVATIONS by Ludwik and Scheu,' Kenyon,' Polakowski and Palchoudhuri, Kemsley, and Broom and Ham,596 have shown beyond doubt that strain-hardened metals are softened by reversed-stress fatigue. To some extent the softening might be associated with a rearrangement of dislocations, but the results of Broom and Ham5 on the temperature dependency of the fatigue hardening of annealed copper, and those of McCammon and Rosenberg7 on the partial recovery at 100'C of fatigue-hardened copper suggest that point defects may be involved. Since lattice vacancies are the only species of point defect present in appreciable quantities in thermody-namic equilibrium, most attention has been accorded them in the various theories advanced to explain hardening and softening effects resulting from fatigue. Precise mechanisms remain uncertain, and while some effects may be due to single vacancies, defects arising from vacancy clusters may also contribute to the changes in properties. All types of plastic deformation result in point-defect formation, one frequently invoked formation mechanism involving the nonconservative motion of jogs formed by the intersection of, for example, mixed dislocations. But since fatigue deformation is thought to be a particularly effective way of forming point defects, additional mechanisms peculiar to fatigue must be sought. One possibility is that jogged loops contract during the unloading cycle to give rows of vacancies. A local high-vacancy concentration could conceivably promote polygonization and recovery by climb, and, therefore, could explain the fatigue softening of strain-hardened metals under appropriate conditions of temperature. Conversely, the experiments by Broom and Ham6 on the fatigue hardening of copper single crystals involving subsequent tensile testing of previously fatigued specimens, resulted in the observation of distinctly lowered yield points. This could be due to vacancy atmospheres associated with dislocations, possibly augmented by jogs on dislocations. In addition to the yield-point phenomenon, a post-yield hardening was observed, with a temperature-dependence resembling the friction-hardening of irradiated metals,9 this again suggesting a point-defect mechanism. An important development in this field has been the observation,10 by transmission electron microscopy, of high concentrations of prismatic loops in fatigued aluminum. By analogy with quenched aluminum filmso11 it seems certain that these loops originate in the collapse of vacancy clusters formed during deformation. Metals, such as copper, having a relatively low-stacking fault energy would tend to produce Frank sessile loops (in practice tetrahedral defects with stacking faults on all (111) planes) rather than the glissile prismatic loops observed in aluminum. The manner in which these various defects affect the different aspects of fatigue behavior has not yet been fully investigated. The present work was designed principally to indicate whether tensile fatigue gives rise to hardening and softening effects similar to those associated with reversed stress fatigue, and with the hope of providing additional information on the contribution of point defects to fatigue deformation. Despite the uncertain ty often associated with the interpretation of resistivity data, i.e., the relative contribution of stacking faults and other defects, such measurements are conveniently employed to study point defect pheno-

Jan 1, 1962

By S. L. Hoyt

ABOUT three years ago eight standard steels were prepared for the cooperative investigation of methods for oxygen analysis, sponsored by the Iron and Steel Division of the American Institute of Mining and Metallurgical Engineers and by the National Bureau of Standards. A preliminary report of the results was made at the annual meeting of the A.I.M.E. in February, 1936. ? This report showed the reliability of vacuum-fusion methods and further brought out certain advantages of the fractional vacuum-fusion method. The results obtained by the authors with the latter method will be discussed here, with some com-ments on the procedure for those who are interested in determinations of gases in steel. Some additional comments are offered on the use of the polarizing microscope for identifying the inclusions in the steel to check and amplify the findings of the fractional vacuum-fusion analysis. For details of the fractional method, see the paper by L. Reeve1.

Jan 1, 1937

Jan 1, 1932

By J. L. Lamon, W. Crafts

P. Coheur and L. Habraken—We read this paper with great interest and are glad to congratulate the authors for their valuable work, supplying an important contribution to the mechanism of tempering on the carbides in vanadium steels. We are in a good position to appreciate this work since we have been studying, for more than a year, Cr-Mo steels of a composition similar, but less highly alloyed (namely 0.1 pct C, 3 pct Cr, 1 pct Mo). Our results are quite in concordance with the authors', however, we wish to point out that it is very interesting to use equally the electron microscope in order to observe the variations of microstructure in steels. We have studied simultaneouslv the evolution of the carbides in situ with the electron microscope, and, after extraction, again with the electron microscope, and then with X-rays. The first results which we have obtained have been communicated at the Congress of Delft (July 1949) and at the "Journbes de la Metallurgie" in Paris (October 1949). These may be summarized as follows: After tempering with varying either the tempering temperatures or the tempering times, the carbides show two evolutions. The first one is connected to the carbides existing in the steels, principally in the boundaries of the grains. For some groups of steels these carbides may coalesce and for other groups they may

Jan 1, 1951

THE Institute of Metals Division opened its series of meetings by a session* on lead, R. S. Dean be-ing in the chair and G. 0. Hiers acting as vice-chairman. A large and representative audience listened to the papers in the abstract and contributed an inter-esting and fruitful discussion. The main points of these papers and discussion are given below: In the absence of Carl E. Swartz, the summary and conclusions of his paper, "A Study of the Lead-Tin-Cadmium System with Reference to Their Use as Solders," were read. Swartz investigated a number of alloys in the lead-tin-cadmium system and prepared a diagram representing the solidification ranges of these alloys. He also made tensile strength tests of joints made with these alloys, and compared these with joints made with ordinary lead-tin solder. The tests showed solders containing cadmium were equally strong as the lead-tin series and that the cadmium alloys were suit-able in other respects for use as solders. In general, solders of the composition near to the ternary lead-tin-cadmium eutectic appeared to be the best for most soldering work although compositions widely differing are desirable for special purposes. The lead-tin-cad-mium solders are finding a market particularly in the fields requiring lower solidification temperatures than common solders. Mr. Darby opened the discussion and asked whether it was a fact that the lead-tin-cadmium solders were more useful than ordinary solders on galvanized and tin-plated sheet. C. Smith said he thought it to be a fact that galvanized sheet was more easily soldered by the lead-tin-cadmium solders than common lead-tin-solder. Continuing, Mr. Smith showed lantern slides of his own investigation of the thermal diagram and recommended the 70 per cent lead, 20 per cent cadmium, and 10 per cent tin for general employment. He thought the author did not differentiate between wetting and alloying and pointed out that wetting was more a ques-tion of the flux than the metal. In some cases a definite alloy was formed by soldering and in some no evidences of alloying were found. Illustrating the former case he showed slides and demonstrated that failures always took place longitudinal with the brittle compound alloy and transversely across the solder itself.

Jan 3, 1928

By K. E. Brown, J. P. Brill, T. C. Doerr

A wide range of intermittent gas-lift tests way conducted in a 1,500-ft experimental well through 11/4- and 11/2-in, nominal size tubing. The well was equipped with two gas-lift valves, four Maihak electronic pressure transmitters and surface facilities to measure casing and tubing pressures, temperature, liquid production and the rate and volume of gas injected. For each tubing size, tests were conducted varying the slug length, gas volume injected and liquid viscosity and surface tension. From these tests, an empirical "fallback" or liquid loss correlation has been developed. No general fallback correlation could be obtained, and the correlation is presented in the form of one curve for each slug length of a given liquid and lubing size. A conceptual model has been developed which combines the fallback correlation with equarions which govern liquid slug pow. A mathematical simulation of the model in the form of a digital computer program is used to calculate total recovery, gas volume used and clearance time for a given test. Tubing pressures at the gas-lift valve and at the gm-slug interface are calculated as a function of time. Tubing pressures at the surface during slug clearance ore also calculated. The results compare favorably with the test data and verify the conceptual model. The extent to which the model can be used for other tubing sizes, depths, liquids and gas-lift valves can only be determined with additional experimental data. Data are also necessary so that a fallback curve can be constructed for the particular test conditions studied. INTRODUCTION The flow of liquid slugs in vertical conduits has long been an established production method in the petroleum industry. Under the name "intermittent gas lift", many advances have been made in engineering design. However, the unsteady-state nature of liquid slug flow has discouraged attempts to describe the problem analytically. The result has been that intermittent gas lift is dominated by rules-of-thumb engineering practices developed over many years. The advent of slim-hole completions has increased the demand for a more rigorous solution to the intermittent problem. Small-diameter conduits offer more frictional per intermittent cycle. Small-diameter conduits are defined to be 1%-in. nominal size tubing or smaller. When oil is produced from the reservoir in which it is found, and transported to surface tanks by intermittent gas lift, three separate flow stages are encountered: flow of the fluids to the wellbore through a porous medium, vertical flow of a liquid slug from the point of gas injection to the surface, and horizontal flow of the liquid slug through the surface flowlines from the wellhead to the surface tanks. The three stages are depicted schematically in Fig. 1. The present study deals with liquid slug flow in both the vertical and horizontal conduits, ending when the bottom of the liquid slug reaches the surface. Due to the large number of variables involved, the analytical study of intermittent gas lift is extremely complex. The possibility of flow regimes other than slug type, the nature of the force fields acting on the system, the interfacial instabilities involved, the varying operational principles of existing gas-lift valves and the complete unsteady-state nature of the physical phenomena occurring in an intermittent gas-lift cycle relate some of the difficulties encountered.

By AIME AIME

AWIDE variety of subjects was discussed at the Wednesday sessions on Non-metallic Minerals. W. M. Weigel as chairman, presided at the morning session, and W. M. Myers, vice-chairman, in the afternoon. In the morning session a paper by W. N. Logan on "Mineral Wool Resources of Indiana" was read by H. H. Hughes. Mr. Logan explained that as Indiana is the principal source of mineral wool, the paper might well he entitled "Mineral Wool Resources of the United States."

Jan 1, 1932

By E. A. Cappelen Smith

FOR distinguished service in the art of hydrometallurgy, the Mining and Metallurgical Society of America presented its gold medal to E. A. Cappelen Smith, at a dinner held in the Hotel Commodore, New York, on Nov.' 10, 1920. Prof. Waldemar Lindgren, president of the society, in giving the medal, said: "By the advancement of the science of hydrometallurgy, by the construction of plants on a scale audacious in their conception, by the successful overcoming of all sorts of difficulties, you have placed your name among those who occupy the very front rank among the hydrometallurgists. In recognition of this distinguished contribution to the science of metallurgy, the Mining and Metallurgical Society of America now awards you its gold medal."

Jan 1, 1920

THE CHAIRMAN (F. K. COPELAND,* Chicago, Ill.).-At this particular time conditions existing in this, country, and elsewhere, make all questions of milling or smelting or mining, or anything else, absolutely secondary to the one question of labor. We have always devoted our attention largely to the efficiency of machinery, and to reductions in costs, etc., and have let this tremendous problem of our relation to labor more or less take its own chances. There has never been a time when those who are responsible for the operation of business of different kinds were as com-pletely at a loss as they are now, so that anything that can be brought out that relates to labor is, to my mind, of utmost importance. T. T. READ, Washington, D. C.-This formulation of a method of curtailing forces at the Copper Queen is a notable step in advance of our treatment of personnel in the mining industry. So far as I know, it is the

Jan 12, 1919