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By H. F. Bishop, F. A. Brandt, W. S. Pellini

M. S. Fisher and D. R. F. West (Imperial College of Science and Technology, London, England)—It may be of value to compare certain features of the results recorded in this very interesting paper with those of an investigation11 involving determinations of temperature gradients and rates of solidification of steel blocks of 3 in. sq section, cast horizontally in sand molds, some of which contained chills. Castings in plain carbon steels containing up to 0.8 pct C were made and, throughout this range of compositions, both inverse-rate and direct cooling curves, obtained from thermocouples placed within the mold cavity, showed a major arrest, the temperature of which was taken as the "effective liquidus" for the particular steel in question, solidifying under the conditions of the investigation. At the completion of the arrest, the curves showed a comparatively rapid de- crease in temperature. Some of the steels investigated lay within the peritectic region, and a second arrest at 1485°C was detected. In Fig. 15, which shows the effective liquidus temperatures, the limit of the 8 + liquid field has been placed at approximately 0.5 pct C. In inverse-rate curves corresponding to the thermal center of each casting, there was always a discontinuity, viz: an abrupt change of slope, at a temperature about 10 to 20°C below the "liquidus arrest," after which there seemed to be no significant irregularity in the rate of cooling. Curves corresponding to other positions in the casting generally showed some irregularities below the main arrest, probably as a result of heat flow from the solidifying interior. Even the reproducible discontinuity in the curves for the central positions appeared to have no theoretical or practical significance, though it probably corresponded to a stage in the solidification process at which only a relatively small amount of interdendritic liquid remained. Its temperature, rela-

Jan 1, 1953

By S. Beatty

RECENT experimental results' on the superconductive properties of vanadium indicate that the magnetic behavior of the metal is greatly affected by internal strains caused by mechanical work, and particularly by oxygen and nitrogen impurities. These result in an increase in the hardness of the metal such that metallurgists' have used hardness as a measure of the impurities. An increase in the impurities should also be reflected in a change of lattice parameter with increasing impurity content. The lattice parameter of vanadium prepared by the thermal decomposition of the iodide has been determined by two workers. Neuburger3 obtained a value of a, =3.0338 ± 0.0003A for the body-centered cubic lattice by means of the powder method. The work of Katelaar is referred to by van Arkel4 in which a value of a0 = 3.025 is given. Four samples were used for this investigation. Sample A, the vanadium of the highest purity in the group, was obtained by means of the thermal decomposition of vanadium diiodide and deposited on a 3 mil diam tungsten filament in the form of crystals. The second sample, labeled B, was obtained by the calcium reduction of the pentaoxide at a sufficiently high temperature to give a melt. A third sample, C, was obtained in the same manner as B but remelted in a pure argon atmosphere. The last sample, D, was prepared by the calcium reduction method and the fine powdered vanadium was then sintered by means of applied heat and pressure. Samples A, B, and C were thus essentially free of mechanical strain in their preparation. Sample D was annealed in a high vacuum at 800°C. The samples were prepared for X-ray diffraction analysis such that all additional strain by cold work or by contamination with oxygen and nitrogen was kept at a minimum. Powder obtained from filings was deemed unsuitable since this would require annealing to get rid of the cold work. A heat treatment up to 1000°C at 10-6 m pressure might still increase the impurity content by means of adsorbed oxygen from residual gas in the vacuum chamber. The most satisfactory samples were prepared for back-reflection film techniques. Samples were cut to size, etched with hydrobromic acid, and mounted in Bakelite. They were then lightly polished on 3-0 paper and lightly etched. Chemical and Hardness Analysis of Samples Spectrographic analyses were made of the four samples and indicated similar metallic impurities for the group. The major metallic impurity in each sample was iron, which was less than 0.01 pct. The sum of the other metallic impurities was approximately 0.1 pct. The carbon content was assumed low by virtue of the methods of sample preparation. The principal impurity difference between the samples was in the oxygen and nitrogen content.

Jan 1, 1953

By J. J. Gilman, T. A. Read

S URFACE effects in the cleavage of brittle crystals have been known for some oftime,1, 2 but our knowledge of surface effects in the plastic deformation of crystals is of relatively recent origin. In 1936, Roscoe9 eported his observations comparing oxidized and clean cadmium crystals. He found that cadmium crystals 1/2 mm in diam when covered by an oxide film less than 1200 atoms thick had critical shear stresses about twice those for clean crystals. This effect is anomalous in that it cannot be caused by the inherent shear strength of a normal oxide film. Either an interaction between the film and the crystal causes the large increase in strength, or the oxide film has an abnormal mechanical strength. Several authors since Roscoe have studied surface effects in crystal plasticity. A complete review of the literature will not be presented, but most of the results may be summarized as follows: 1—The critical shear stress for slip is increased markedly by very thin oxide films on zinc4 and cadmium crystals;" ' also, the entire stress-strain curve is raised by an oxide coating;3,4 both effects increase with decreasing specimen radius. 2—Surface active substances such as oleic acid destroy the hardening effect of oxide films.4, 6-8 The time required for the reduction of the hardening effect to begin increases with the viscosity of the solvent4~ 3—There has been dispute in recent years about the effects of surface active substances themselves on plastic deformation. Rehbinder, Lichtmann, and Maslenikov9 state that surface active substances reduce the strength of metal monocrystals markedly and increase the number of slip lines per unit length at a given strain. The effect varies with orientation for tin crystals being smallest for x, = 0, largest for x, = 45", and intermediate as x, + 90°.10 Several workers claim to have disproved the results of Rehbinder')"." but Rehbinder and Lichtmann9 have defended themselves and Masing with his collaborators" has confirmed some of Rehbinder's results. 4—Immersion of metal specimens in electrolytes such as sodium chloride reduces their strength12,13' and subsequent cathodic polarization increases the strength reduction. For noble metals, the strength reduction occurs for both anodic and cathodic polarization," increasing with increasing polarizing voltage. 5—Electroplated copper coatings effect the creep rates of zinc monocrystals. Poly crystals are not affected." 6—Immersion in dilute acid destroys the hardening effect of an hydroxide film. When an acid solution is applied to a steadily creeping crystal, the creep rate jumps to a very high value and then drops gradually to a steady value which is higher than the initial steady rate.*' " If the hydroxide film to be removed is very thin (about 100A thick), the creep rate does not change measurably, but a small rapid strain-increment is observed when dilute acid is applied." 7—Crystal plasticity depends on specimen dimensions. This was observed by Lichtmann and Ven-stroml" for monocrystalline tin and by Andrade and Kennedy" for polycrystalline lead. 8—Immerson of copper crystals in mercury has no effect on their stress-strain curves.'" 9—Bombardment of creeping cadmium crystals with a particles which penetrate the surface to only 0.005 mm may increase their creep rates as much as five times.''' The experiments which will be described in this paper pertain to: (a) the effect of a crystal's shape on its plastic deformation, and (b) the effect of metallic surface films on plastic deformation. For the work pertaining to (a), crystals of zinc, tin, and lead were grown which had various shapes. These were tested in simple tension. Macroscopic rotations about the tension axis which are unpredicted by the classical theory of slip were observed, and serrated edges were observed in tin crystals. For the work pertaining to (b), the effects of evaporated and electrodeposited films of copper, nickel, gold, and zinc on the mechanical properties of zinc, tin, and lead crystals were determined. The films influenced both slip and twinning of the crystals in creep and tensile tests. Experimental Details Chemically pure zinc, tin, and lead were used in this investigation. The zinc was 99.999t pct pure;

Jan 1, 1953

By J. L. Lummus, Frank O. Jones

A field procedure for determining graphite in drilling mud is presented which is sensitive to 0.25 lbs/bbl and accurate to 20 per cent. The method, utilizing oil flotation principles, is suitable for use in all oil-free water base muds except those containing ligno-sulfonates, lignites, or surface active agents. INTRODUCTION Graphite was proposed as a drilling lubricant as early as 1940, but has not been used extensively until recently.' Graphite has been substituted for oil in certain instances to avoid oil contamination of core samples since it has been found that graphite does not interfere with routine core analysis. A major difficulty in using graphite is the lack of a satisfactory field test for determining the concentration of graphite in mud. DISCUSSION OF METHOD Several possible methods of analysis were investigated, including chemical separation, density fractionation, radioactive tracers, and oil flotation.', ' The investigation indicated that a satisfactory method for field use could be devised using an oil flotation method. It was found that toluene shaken with a highly diluted mud sample would recover sufficient graphite to be apparent in the oil phase. Refinement and standardization of technique made it possible to detect as little as 0.25 lb/bbl graphite and to estimate graphite content to within 20 per cent by using a visual comparison method. The test is limited to oil-free water base muds. Quebracho, phosphates, or barytes in the mud do not interfere with the test but surface active agents, lignosulfonates' and lignites evidently render !he graphite water-wet so that none may be recovered by oil-flotation. PROCEDURE Instructions for determining graphite in mud: 1. Collect representative one gallon sample.- from mud stream. Transfer immediately 350 ml portions of this Sample into four mixing cans labeled A, B, C, and D. Measure out graphite (same as is used to treat mud) for addition to cans as indicated below, using either a specially designed scoop or a balance. Can: A B C D Grams Graphite to Add: none 2 4 6 Stir samples B, C, and D for 15 minutes with propeller type mixer. 2. Clean and rinse well with water four 250 ml volumetric flasks labeled I, 11, 111, and IV. Using a 5 ml hypodermic syringe, transfer the indicated volume of samples from cans A, B, C, and D into designated flasks as follows: From Can: A B C D To Flask: I II III IV Add This Volume of Mud: 4 ml 2 ml 2 ml 2 ml 3. Measure 100 ml fresh or distilled water to each flask and swirl gently to disperse mud. Add exactly 5 ml toluene to each flask. Stopper and shake each

Jan 1, 1953

By A. D. Mutch

IT has long been known that there are wide variations in the thermo-electric potential of pyrite. In the last few years a study of this variation and other properties of pyrite was carried out at the University of Toronto by F. G. Smith on specimens of pyrite from many loyalities. As a result of these studies the pyrite geothermometer was developed by Professor Smith. The calibration of the pyrite geothermometer is based on the assumption that "crystals of any one electronically conducting mineral species deposited at a high temperature have a more positive thermoelectric potential than crystals deposited at a low temperature, and the thermo-electric potential varies continuously between any given limits of the temperature of deposition." The cause of the variation was postulated to be crystal discontinuities, such as lineage boundaries. As yet this postulated relationship has not been established as fact. On theoretical grounds it is indicated that the thermo-electric potential of pyrite or any other partial conductor is dependent upon a number of factors as well as the temperature of formation. For this and other reasons there is ground for doubt as to the validity of the relationship postulated above. To date a large number of readings have been made with the pyrite geothermometer which have been recorded in terms of the calibration of the instrument in degrees centigrade. So far most of the pyrite tested by this technique has been in association with gold ore. The values for the temperature of formation obtained in these tests appear to be reasonable and, in relation to geological problems, to vary in the right sense. Determinations on some specimens not in association with gold ore have given readings that appear to be much too high, taking into account the probable maximum temperature of the host rock. To sum up, although many determinations made with the pyrite geothermometer appear to give reasonable values for the temperature of formation of the pyrite, there are at the same time other readings which seem anomalous. On the basis of an examination of available results of work with the pyrite geothermometer, two problems must be considered: 1—the validity of the calibration of the pyrite geothermometer; and 2— the nature of the distribution of the thermo-electric potentials of pyrite in relation to the specific problems that have been examined. In this paper the academic problem relating to the validity of the calibration of the pyrite geothermometer will not be discussed. Instead, the variations of thermo-electric potential of pyrite in association with gold veins will be discussed with regard to specific examinations. The first of these two examinations deals with the distribution of thermo-electric potentials of pyrite in association with a gold vein and was carried out in the McIntyre Porcupine Mine, Schumacher, Ont., in the summer of 1949 as part of a study with this technique. The second problem deals with variations of thermo-electric potential of pyrite in gold ore specimens from all over the world. The specimens used in this study were part of the private collection of Frank Ebbutt, geologist for Howe Sound Exploration Co. Results of Detailed and Reconnaissance Studies In discussion of the results of determinations made in these two studies the values of thermo-electric potential in millivolts will be used. It will be noted that in some of the diagrams the determinations are recorded in terms of pyrite geothermometer temperatures. Fig. 1 is a calibration chart relating pyrite geothermometer temperatures and thermoelectric potentials. A full discussion of the technique is given in the original paper by F. G. Smith.' Briefly, the determinations are made by placing two stainless steel probes, one hot and the other cold, against the surface of the pyrite crystal being tested. The thermoelectric potential that is developed is read with a null-point potentiometer that is calibrated in what

Jan 1, 1953

By F. R. Zacher

Unmined blocks in the Sewickley seam, surrounded by worked out areas, have been found to transmit overburden oads through the interval strata to the Pittsburgh seam workings 90 ft below. Operating experiences under these conditions are described in this paper. IT has always been understood, in northern West Virginia where both the Pittsburgh and Sewickley seams are mined, that pillaring or splitting in the lower Pittsburgh seam could break the interval strata and make mining in the overlying Sewickley difficult or impossible. In some instances, however, mining methods practiced in the overlying Sewickley have reversed the problem, resulting in a shifting of the intermediate layer and destroying valuable acreages of the Pittsburgh seam below. The Pittsburgh seam in this area is, on the average, 102 in. thick. About 18 in. of low-quality head coal are left for roof protection as it is mined. Immediately over the coal are two draw slates, two rider seams, and a good hard black shale, locally called black rock, which serves as a permanent roof where draw slates and riders are taken down on certain main haulroads. In most areas mined in this seam in the past the bottom has been satisfactory but soft. However, in areas now being mined by the Christopher Coal Co. in Monongalia County the bottom is very hard and unyielding. The Sewickley seam, lying 85 ft above the Pittsburgh, will average nearly 70 in. in thickness and is overlain by massive shales and sandstones. Much of the seam is mined only down to the "sheep skin," a hard band about 4 in. above the bottom, which is composed of relatively hard shale. Fig. 1 shows a typical cross-section through the Pittsburgh and Sewickley seams in the area being discussed. The thin Redstone seam is not deep-mined but is stripped in some locations where it outcrops. Most of the Sewickley seam in the Morgantown areas has been mined out from 10 to 30 years. There are at present only two large mines and five or six others of small production operating in that seam. Mining systems in the past were generally of the room and pillar type with some full pillar extraction. This seam in the Scott's Run area was operated by as many as thirty or forty different companies at one time, during an era beset with strikes, market failures, and depressions. Most of the barrier pillars along the many main haulroads were abandoned, and blocks of Sewickley coal that would be fully recovered with today's machinery were left unmined when conditions became anything less than favorable. Consequently the mined-out Sewickley is spotted throughout with solid blocks varying in size from 100x100 ft to 200x400 ft and larger. It is these unmined Sewickley blocks surrounded by worked-out portions that have caused transmissions of roof stresses to underlying Pittsburgh mining areas, see Fig. 2, resulting in untold difficulty. As the Christopher Coal Co. operates both the Pittsburgh and Sewickley seams, accurate maps of workings in both seams are readily available and are regularly consulted. The first Pittsburgh squeeze attributed to overlying Sewickley blocks occurred in the Arkwright mine, where a shuttle car crew was developing a section consisting of seven panel headings. These entries were being driven in solid coal 3400 ft from the nearest worked-out Pittsburgh area. As mining advanced it was noticed that certain ribs began to slough and certain areas to show signs

Jan 1, 1953

By J. P. Morris

PREVIOUS investigations1,2 have shown that alloying elements in liquid iron influence the thermodynamic activity of sulphur and thereby affect the partition of sulphur between metal and slag in the desulphurization process. For example, the greater efficiency of desulphurization in the blast furnace as compared to the open hearth can be attributed in part to a higher level of sulphur activity in blast-furnace metal due to the higher concentration of carbon and silicon. In the present investigation, a short study was made of the influence of manganese on the activity of sulphur in liquid iron and iron-carbon alloys. In contrast to carbon and silicon, manganese was found to decrease the activity coefficient of sulphur; and in iron-carbon alloys it counteracts to some extent the influence of carbon. However, at manganese concentrations normally present in the blast furnace or open hearth, the effect of manganese is small. Since manganese sulphide has a limited solubility in iron, manganese can act, under certain conditions as a desulphurizing agent. Considerable data on the manganese-sulphur product in carbon-saturated melts were obtained in the investigation and have been included in this report. The experimental procedure was the same as that used in the earlier investigations on the effect of silicon' and carbon' on sulphur activity. Briefly, the method was as follows: The molten alloy, contained in a graphite or sintered alumina crucible, was brought to equilibrium at a constant temperature with a mixture of hydrogen and hydrogen sulphide of constant composition by bubbling the gas through the metal. Samples of' the melt were taken for analysis at regular intervals by suction through a 2 to 3 mm bore silica tube dipped into the metal. The experiments were run in a graphite spiral resistance furnace with melts weighing 50 to 60 g. The gas bubbling tubes were made of sintered alumina and were 5/16 in. OD, 1/16 in. ID, and 24 in. long. Equilibrium was assumed to have been attained when the sulphur content of the liquid metal reached a constant value. During an experiment there was a rapid loss of manganese from the melt by volatilization. To offset this loss, small additions of manganese were made periodically. The rate of manganese addition needed to maintain a constant manganese concentration was determined in preliminary tests. In all of the experiments, deposits of manganese sulphide formed above the melts in a cooler region of the furnace. Apparently, these deposits resulted from a reaction between manganese vapor and hydrogen sulphide in the gas. To prove that manganese sulphide did not volatilize from the melts to a measurable extent, an experiment was run in which helium was bubbled through liquid iron containing both manganese and sulphur. Although manganese volatilized rapidly in this test, there was no appreciable loss of sulphur. Volatilization of manganese sulphide from a melt would have led to an apparent equilibrium condition in which the sulphur content of the metal was lower than the true equilibrium value. The experimental results are shown in the first seven columns of Table I. The data in the last two columns were obtained from the previous work on the effect of carbon' and show what the results would have been in the absence of manganese but with temperature, gas composition, and carbon content of the metal remaining the same. Comparison of the last four columns show that, in the presence of manganese, the sulphur content of the metal increased at equilibrium and the activity coefficient of sulphur decreased. However, the results show that, for manganese concentrations below 3 pct, the effect of manganese is small. The values for activity coefficient of sulphur given in Table I were calculated from the following relations: S (in liquid metal) + H2 (gas) = H2S (gas) [l] K ph2s/?s X %S X phg = 0.00251 [2] where K is the equilibrium constant for the reaction, PH2S and ph2 are the partial pressures of hydrogen sulphide and hydrogen, respectively, and ?s is the activity coefficient of sulphur. The standard state for sulphur was taken to be a 1 pct solution of sulphur in pure iron. The numerical value for K at 1600°C was determined in the earlier work. For the purpose of showing graphically the results of the tests run at 1600°C, the activity coefficients of sulphur were recalculated so as to correspond to a manganese concentration in the metal of 2 pct in each case. In the calculation it was assumed that the increase in sulphur content of the metal at equilibrium caused by the presence of manganese

Jan 1, 1953

By S. R. B. Cooke, W. Philippoff, Donald E. Cadwell

THE importance of contact angles in flotation has long been recognized, but little has been done to get quantitative relationships between the surface coverage of the mineral by the reagent, the length of the hydrocarbon chain, and the contact angle. It is well known that for a complete monolayer on the surface of a mineral the contact angle 8 is determined only by the reagent1 and principally by the chain length of the hydrocarbon radical. Although for flotation the monolayer usually is regarded as being complete, early experiments of Wark and Cox&apos; showed that at very small concentrations of potassium ethyl xanthate the contact angle on galena changed in a continuous way from 0&apos; to the equilibrium value of 60". Further, Gaudin and Vincenta showed a similar continuity using heptylic acid and sphalerite. This shows that with probably incomplete monolayers, 0 varies with the degree of surface coverage. At the time these experiments were made it was impossible to measure the actual amount of surface coverage, especially since the decrease of the collector concentration in the liquor could be influenced by chemical side reactions. Through the use of the radioactive tracer method for the measurement of the amount of collector adsorbed on the surface of the mineral, Gaudin and Bloecher&apos; were able to determine accurately the actual surface coverage of dodecylamine acetate on quartz, but they did not measure any contact angles. It is believed that the relationship between the surface coverage and the contact angle is extremely important in flotation, especially as Gaudin and Bloecher showed that a 95 pct recovery is possible with a coverage of only 5 pct. Theoretical Considerations The work of adhesion W is the energy bound (in ergs per sq cm) when an interface is formed. It is determined by the difference of the free surface energies (surface tensions) of the respective phases 7j and yZ before contact and the interfacial free surface energy y, after contact. The definition of the contact angle permits the elimination of the unknown surface energy of the solid and hence the calculation of W from the surface tension of the liquid y and the contact angle 8: W = y (1 + COS0) [1] Consider a surface consisting of two components, identified as 2 and 3, 1 being the liquid. The amount of 2 in the composite surface is x, where 0 < x < 1. The respective contact angles with 1 and air are 8, and 8.. The total work of adhesion of such a surface is the sum of the values of the components multiplied by their respective areas. A formal relation can be written: Wm = x-W2+ (l-x)-W, [2] in which W, is the work of adhesion of the composite surface. Eq 1 can be introduced into Wt and Wa, but in the case of W, some discussion is needed. If the two components are segregated, each component forming an integral part of the composite surface there is no physical meaning for a contact angle 8m calculated from W,, by using eq 1. If, on the other hand, the area of each patch of the components is small in comparison with, say, the diameter of the bubble used in measuring, it could be expected that 0m would have a physical significance, because of the action of the surface tension of the liquid-gas interface tending to smooth out sharp corners. How small these patches would have to be is difficult to predict, but by using composite surfaces with microscopically

Jan 1, 1953

By J. L. Wyatt

THE strain sensitivity, K, a property of metals defined as the unit change in electrical resistance per unit strain, was measured for commercial purity titanium wire to determine its usefulness as a strain gage material. A Kelvin double bridge, accurate to 0.000001 ohm, was used to make measurements from 0 to 1 pct total strain. A positive value of 0.17 for K was found. This compares with 2.15 for constantan and 3.5 for cold-worked invar, two of the more common strain gage materials. The effect of temperature also was determined. It was found that a change in temperature of 30°F caused the same resistance change as 1 pct strain. It is therefore concluded that titanium would have utility as a strain gage only if the thermal fluctuations in the specimen could be controlled to a high degree and in applications of very large total strain.

Jan 1, 1953

By G. H. Tausch, T. A. Huber

Very encouraging progress has been made ill the develop-ment of the permanent-type well completion which decreases considerable the cost of completions and workovers and aid-in the acquisition of reliable reservoir information at low cost. Completion and remedial operations are performed with tool,; which pass through the well tubing. Perforating and plug-hack operations can be done with the tubing in place and do not require pipe-handling equipment. Because of the many advantages afforded by this method, development work is going forward in anticipation of ultimately being able 10 use it to perform all usual well completion and workover operations. Effort is also being directed to the development of a more permanent type of lift equipment suitable for use with the permanent-type well completion. INTRODUCTION The permanent-type well completion in one in which the tubing and well-head are set in place only once in the life of the well and the completion or remedial work is performed through the tubing with a tubing-type perforator. a retrievable tubing extension. and other wire-line tools. This new type completion has made possible the saving of one to two days&apos; rig time in the completion of each of several hundred wells During the last two years, and use of equipment developed for this type of completion has resulted in a 75 per cent reduction in cost. of certain types of workovers. In addition. the more reliable indication of the commercial value of a reservoir and the more accurate general reservoir information made Possible promise to be of even greater value in oil recovery than the reduction of costs for completions and workovers Recently. several well.. were worked over by using the retrievable tubing extension suspended on a swab line to plug back with cement and then perforating a higher producing interval with the tubing-type perforator, thus opening the way for complete through-the-tubing workovers which may be performed without pipe-handling equipment or mud. Those items attendant to the use of pipe-handling equipment and mud. such as hoard matting rig substructure. and pits. were also eliminated. There are indications that the elimination of drilling mud during completion and workover operations will frequently give increased well productivity, as plugging of the perforation. will not occur. It ii now possible to perforate selectively small sections of the producing interval and to test a well through these sections prior to perforating more interval. The perforating of additional interval will not entail the costly operations of killing the well and pulling tubing, nor will the old or the new perforations be plugged. The productivity of .mall sections of a reservoir and the actual gas-oil or oil-water contacts may now be determined economically under flowing condition.. Selective completions can be made in this manner to delay gas and water problems and bring about maximum oil recovery. At the present time, gas lift appears to offer the greatest potentialities for artificial lift in the permanent-type well com"letion since it can provide full-open tubing to accommodate the through-the-tubing tools and it may be ultimately developed into a fairly permanent type of lift. With precent-day pas-lift equipment. valve or mandrel failure necessitates occacio11al removal of the tubing. thereby reducing to some extent the permanence of the completion. New gas-lift valves are now

Jan 1, 1953

By T. E. Leontis

Data are presented in this paper to show that addition of zirconium to sand-cast Mg-Th alloys effects a marked decrease in the grain size of these alloys which is accompanied by a significant increase in the mechanical properties over the entire range of thorium content investigated. The beneficial effect of zirconium on the strength properties is maintained at elevated temperatures up to 700°F. In addition the alloys exhibit exceptionally high creep resistance at temperatures up to 600°F. Zirconium does not greatly improve the strength or creep characteristics of extruded Mg-&apos;Th alloys. Cerium is not a desirable addition to Mg-Th-Zr alloys. IN a previous paper,&apos; it was shown that addition of thorium to magnesium imparts exceptionally high resistance to creep at elevated temperatures both in the sand-cast and in the extruded states. The large grain size of the sand-cast alloys, however, renders them of questionable value as engineering materials. Sauerwald² showed that the grain size can be reduced effectively by the addition of zirconium. Results of a detailed study of the properties of Mg-Th-Zr alloys over a wide range of thorium content are presented in this paper. In accordance with the preliminary findings of Sauerwald,² it is shown here that Mg-Th-Zr alloys possess the unusual combination of fine grain size and a high level of strength and creep resistance at elevated temperatures. Some information on the effect of cerium on the properties of Mg-Th-Zr alloys is presented also. Effect of Th on Solubility of Zr in Molten Mg Sand-cast test bars and 3 in. diam extrusion billets of Mg-Th-Zr and Mg-Th-Ce-Zr alloys* were pre- pared according to the procedures described in the previous paper.&apos; The zirconium was added in the form of sponge metal as supplied by the Bureau of Mines.&apos; The maximum amount of zirconium that usually can be introduced into magnesium at the customary alloying temperature of 1350° F is about 0.7 pct. The analyses in Table I clearly show that thorium in- creases the solubility of zirconium in liquid magnesium. The tabulated zirconium contents are designated as "acid soluble;" this serves to distinguish these values from the small amount of zirconium that is not dissolved when the alloy is subjected to the action of a dilute acid solution. The "acid-insoluble" zirconium is believed to be ineffective as an alloying ingredient. The acid-insoluble zirconium contents ranged between 0.03 and 0.16 pct in the present alloys, the tendency was toward higher values in alloys with higher thorium content. In contrast to the effect of thorium, cerium decreases the solubility of zirconium in magnesium. This is shown by the three Mg-Th-Ce-Zr alloyst in- cluded in Table I and stands in agreement with the observations of Nelson and Stricter".&apos; on Mg-misch-metal-Zr alloys. Effect of Zr on Grain Size of Mg-Th Alloys The potent effect of zirconium as a grain refiner has been demonstrated for many types of magnesium alloys.3-8 Of greatest importance to date are Mg-Zn-Zr alloys5,6,8 and Mg-mischmetal-Zr alloys.3,4,7 Zirconium has also been found to exert a marked grain-refining action on Mg-Th alloys. All the Mg-Th-Zr alloys cast in the form of ½ in. diam test bars have an exceedingly fine grain size (Table I). Reference to the previous paper&apos; will show that binary Mg-Th alloys containing up to 6 pct Th are almost completely columnar even in the M in. diam reduced section of a test bar, and that 10 to 50 pct Th alloys have an equiaxed grain structure of 0.03 to 0.08 in. The data in Table I also show that addition of cerium to Mg-Th-Zr alloys has no effect on the grain size. In addition to increasing the strength properties, the fine grain size of Mg-Th-Zr alloys

Jan 1, 1953

By R. W. Balluffi, B. H. Alexander

RELATIVE diffusion rates of copper and zinc in a brass have been measured in a vapor-solid type of couple with which the amounts of copper and zinc diffusing past inert Kirkendall markers can be obtained by means of a few simple experimental measurements. If inert markers are placed on the surface of copper which is then exposed to zinc vapor from a brass chips, the particles become buried due to outward diffusion of the copper, as shown in Fig. 1. A schematic diagram of such a couple after diffusion is shown in Fig. 2. Consideration of the diffusion flow of copper and zinc shows that the entire hatched area, including the cross-hatched area, is proportional to the amount of zinc diffused inward past the markers and that the smaller cross-hatched area is proportional to the amount of copper diffused outward past the markers. These areas are completely determined by the expansion of the couple, the depth of the buried particles below the surface, and the chemical composition at the specimen surface. As Darken1 has shown, the ratio of diffusivities of copper and zinc is then given by the ratio of these two areas. Polycrystalline copper and two copper single-crystals made by the Bridgman method were prepared in the form of 1.5 cm diam disks approximately 0.5 cm thick with faces plane and parallel. Tungsten particles approximately 0.001 cm in diam were bonded to the surface of each disk by heating 5 hr at 1060°C in vacuo. Each specimen was next

Jan 1, 1953

By C. E. Lesher

THE Disco* process for the production of low temperature coke and its immediate predecessor, the Wisner or Carbocite process have been described in the voluminous literature of low temperature carbonization.1 This paper will describe the development of the process from the first attempt at commercial operation by the American Gas and Electric Co. at Philo, Ohio, Yn the 1920&apos;s to the successful operation in 1949 by the Disco Co., a division of the Pittsburgh Consolidation Coal Co., of the 1000-ton per day Disco plant near Pittsburgh, see Figs. 1-2. In the 1924 coal industry depression following the hectic post World War I expansion, the northern Appalachian, unionized bituminous coal fields were affected first and foremost, and Western Pennsylvania as hard as any. Competitive market pressure was heaviest on the lower grades of steam coals, notably the from the Panhandle district where ash and sulphur are inherently higher than in the same Pittsburgh coal bed to the east along the rivers. The firm structure of Panhandle coal while favoring the prepared sizes, depressed the usefulness and value of the finer sizes. Panhandle slack and nut slack were marketed with difficulty at consistent, and at times considerable, loss. Many solutions were suggested, and the Pittsburgh Coal Co. investigated all. Lower delivered prices through lower mine costs and more advantageous freight rates were obvious goals, but equally obvious were the difficulties of self attainment of either in any substantial measure. Selling Btu&apos;s in pipes was abandoned as an idea after a thorough study of the economics of distribution of what was then, and is even now, the only developed continuous process of complete gasification of bituminous coal-producer gas. Although the coal company purchased huge blocks of electric power, it sold not a car of coal to the central power stations. Public utilities controlled the markets for electric current, and it was found that no matter at how low a cost current might be put on the bus bars by the coal company, distribution to its widely scattered coal mines made such an enterprise practically impossible. Consolidation of underground operations and a huge modernization program of mining operations in the 1920&apos;s were but preparation for the introduction of mechanical cleaning of the coal for market, particularly the smaller sizes of steam, gas, and by-

Jan 1, 1953

By M. B. Bever, J. E. Reynolds

IN several alloys of iron, copper, and lithium as well as in some pure metals, martensite formed on cooling reverts to the parent phase upon heating to a temperature below the equilibrium temperature at which the parent phase becomes stable.&apos; These martensitic transformations, therefore, are thermally reversible, although appreciable hysteresis may be involved. The martensitic reaction has long been

Jan 1, 1953

By Reginald S. Dean

THE commercial availability of electrolytic manganese has greatly changed the position of manganese as a nonferrous alloying metal. Manganese metal commercially available up to about ten years ago was reduced with either silicon or aluminum and contained substantial amounts of the oxides of these metals and other impurities. Manganese was accordingly not available as an alloy base and its addition to copper-base and nickel-base alloys was generally limited to a manganese content of a few per cent. Several special alloys like manganin contained up to 12 pct of manganese. A method for the production of electrolytic manganese was developed by the Bureau of Mines in 1936 and commercial production was begun in 1938. At the present time (June 1951), production is about 12 tons per day but appears likely to be substantially increased. Electrolytic manganese is deposited from an aqueous electrolyte containing manganese and ammonium sulphates and is marketed as cathode fragments about 1/8 in. thick. The impurities in its composition are as follows: iron, 0.0015 pct; copper, 0.001; arsenic, 0.0005; cobalt, 0.0025; lead, 0.0025; molybdenum, 0.001; sulfide sulfur, 0.017; sulfate sulfur, 0.014; insoluble, 0.002; carbon, 0.002; hydrogen, 0.015. These figures are from Bulletin 463, U. S. Bureau of Mines. From an alloying standpoint, the most important impurity is hydrogen. This can be removed by heating; 95 pct of the hydrogen can be removed in this way without introducing significant amounts of oxygen or nitrogen. Much of the commercial electrolytic manganese used in alloys is dehydrogenited by the producer, since the amount

Jan 1, 1953

By E. S. Machlin

RECENTLY, there has been much activity in the field of nucleation of martensitic transformations.&apos;- One of the problems in this field is the calculation of the rate of nucleation (number of plates nucleated per unit untransformed volume per unit time) in terms of observable parameters. Two such observable parameters are the fraction of the length of a straight line which corresponds to the portion of the total length of the line that lies in the martensitic phase and the number of plates intersected by this straight line per unit length of line. Because of the necessity of a valid answer to this problem, the following investigation was undertaken. Although this problem has been treated in the past, a derivation of the relation between the volume and linear fractions of martensite will be described to illustrate the method used in the succeeding analyses. It is assumed that the martensitic plates are in the form of a right circular cylinder having a small height relative to the radius of the base. The volume fraction of martensite is then: fr = lXNl,hjAl [1] where f, is the volume fraction of martensite, and Nij is the number of plates per unit total volume having the area Ai and the height hi. The linear fraction of martensite is obtained as follows. For the plates having the particular area A, and height h,, the fraction sin 0 dB* will have their cylinder axes between the angles 0 and 0 + d0 to the straight line along which the linear fraction of mar-

Jan 1, 1953

By F. S. Buffington, Morris Cohen

THERE is little quantitative information available concerning the effect of applied stress, in both the elastic and plastic ranges, on diffusion kinetics. Accordingly, a program has been undertaken to determine the rate of self-diffusion in high purity iron, with the specimens subjected to stress during the course of diffusion. Results are reported here for body-centered cubic iron at a diffusion temperature of 890°C. The iron used was 99.97 pct Fe, the principal impurities being 0.002 pct C, 0.008 pct 0, and 0.02 pct Si. The surface-decrease method of self-diffusion analysis was employed, and Fe55 Mn x-radiation, 2.9 years half-life) was the tracer element. Details of specimen preparation and equipment are given elsewhere.&apos; Disks of the high purity iron, % in. diam x 1/4 in. thick, were annealed at 890°C for 18 hr in dry hydrogen to produce large grains of a ferrite. The faces of the disks were then surface ground, and possible grinding stresses were relieved by annealing at 890 °C for 45 min in vacuum. A layer of radioactive iron 0.00186 cm thick was electroplated on one face of each disk. The self-diffusion coefficient was calculated from the ratio of the radiation intensities emanating from each of these faces, as measured before and after diffusion.&apos; The heating was carried out in a vacuum furnace (10-5 mm Hg) controlled to ±1.5°C. The specimens were loaded in compression between two quartz disks during the diffusion runs by means of a lever system operating through a vacuum seal. Thus one quartz disk was pressed directly against the radioactive face of the specimen, minimizing the vapor loss of radioactive iron. Steady-state creep occurred in all instances where permanent deformation could be detected, but the specimens did not exhibit appreciable transverse barreling until natural strains of 0.2 to 0.3 were attained. Essentially, the diffusion took place under uniaxial stress. The plastic strain in each case was obtained at the diffusion zone by measuring the diameter d there before and after the run: e = 2 In — do Let Du equal the self-diffusion coefficient which would have prevailed at the given temperature if no stress had been applied. This was calculated from the temperature-dependence equation which had been previously determined: —59,800 D, = 6.2 exp ( I sq cm per sec* [I]

Jan 1, 1953

By C. W. Sherman, John Chipman

IN the mathematical statement of the law of mass action, the activity of each substance consumed or produced in a reaction is used to obtain a numerical constant which is characteristic of the equilibrium of that reaction at the given temperature. The activity in many cases is equal to, or proportional to, the concentration. If this is the case, any units denoting concentrations, such as weight percentage or mol fraction, may be substituted in the equilibrium expression. It is even permissible to use mixed units provided only that each unit is that used in defining the activity of the corresponding substance. The indiscriminate use of concentration units in writing equilibrium constants sometimes leads to very erroneous results. On the other hand, what appear to be contradictory results from similar investigations often might be resolved if the activity is the quantity that is used to determine the equilibrium constant for the reaction in question. De-sulphurization serves as an important illustration. Sulphur in lron and Steel The control of the sulphur content of the finished product is one of the oldest and broadest problems in the metallurgy of iron and steel. In general, this control must be exercised through the action of a slag, and for this reason experimental studies of the distribution of sulphur between slag and metal have assumed considerable importance. Under slags of the type found in the basic open-hearth furnace the ratio (% S)/[% S] does not in general exceed about 8. Under blast-furnace conditions, however, de-sulphurization ratios of 50 to 100 are readily obtained, and under laboratory conditions using similar slags, the ratio may be as high as 400. The fact that blast-furnace metal is much more readily desulphurized than is molten steel rests upon two distinct phenomena. The first of these is connected with the slag reaction. In the open-hearth furnace, the equilibrium in the following reaction places a definite limit on the sulphur content of the slag: S + 0-- = 0 + S- - where the symbols underlined indicate elements dissolved in the liquid metal, while slag constituents are represented as ions. The high oxygen content of the open-hearth bath prevents this reaction from proceeding far enough to effect good desul-phurization. In the blast-furnace process, however, the oxygen activity is limited by the presence of carbon in the metal and in the coke bed and the controlling reaction becomes: S_+O- + C_=S- + CO(gas) [2] The second phenomenon which contributes to the easier desulphurization of blast-furnace metal is the effect of high concentrations of other elements. These elements, notably carbon, silicon, and phosphorus, increase the thermodynamic activity of sulphur several fold. As a result of this increase, the escaping tendency of sulphur from the metal phase is increased and its removal facilitated. Previous Studies It becomes, therefore, a matter of importance to determine the effects of various elements upon the activity of sulphur in the melt. The experimental approach to this problem has been made through the equilibrium between sulphur in the melt and gaseous atmospheres containing hydrogen and hydrogen sulphide. The reaction and its equilibrium constant are written as follows: S + H2(gas) =H2S(gas);K1 = -- [3] Pn2 • as where the symbol a, represents the activity of the sulphur in solution in the metal. The understanding of the chemical behavior of sulphur in steel and pig iron rests on a firm knowledge of the binary system Fe-S. A number of studies of the equilibrium have given closely agreeing results from which the activity and free energy of the dissolved sulphur may be found. The recent paper by Sherman, Elvander, and Chipman1 includes a discussion and quantitative comparison of the results of several of the significant researchesr-" on dilute solutions of sulphur in iron. The results of this study indicate that the relationship between the ratio Ph,s/p+ and the percentage of sulphur in solution is not a linear one. This

Jan 1, 1953

By F. W. Glaser

Metal-carbon-boron powder mixtures were hot pressed and the resulting specimens were studied by X-ray diffraction. It was found that regardless of the starting combination of the metal, carbon, or boron powders, a metal boride phase was always the major component in these samples. In the absence of carbon the boride phase formed on hot pressing depended only on the amount of boron present. Two new phases of the system Ti-B were found. They are Ti2B and Ti2B5. The existence of a controversial face-centered cubic phase of formula TiB was confirmed. Electrical resistivities were measured for various boride phases. It was found that the diborides are generally better conductors than the monoborides of the same metal. THE carbides and borides of the transition elements have very high melting points, in the range 2500° to 4000°C, and are therefore of interest as high temperature materials. The literature on the stability or chemical reactivity of these carbides and borides is very scarce. Various investigators&apos;-" have demonstrated a relative instability of certain carbide phases in the presence of boron or boron-containing substances. In a recent publication, Glaserl demonstrated the stability of zirconium-boride (ZrB,) in the presence of carbon at temperatures in excess of approximately 2900°C, while during a preliminary investigation of boride phases, Steinitz&apos; concluded that the diborides are stable in the presence of carbon while the monoborides of the fourth and fifth group are not, forming diborides plus carbides instead. Nelson, Willmore, and Womeldorph" have elaborated on the reaction B,C + 2TiC = 2TiB, + 3C, which was known to occur because of a relative instability of B,C and the great tendency towards TiB, formation at relatively low temperatures (approximately 1200°C). A similar study, involving as starting materials TiO, and B,C and resulting in TiB,, was recently described by Honak4, who observed the beginning of an exothermic reaction of a Ti0,-B,C powder mixture, which, when preheated in a hydrogen atmosphere to approximately 950°C, was carried to about 1600 °C by the heat of reaction. To shed more light on reactions of this type (Metal-C-B), the final product apparently always resulting in a boride phase at the expense of a carbide phase," a systematic investigation was started * Boride phases of various metals, as reported to date, are listed in Table I. and the following is an account of some of the results that were obtained. Materials, Preparation of Samples, Testing Methods The raw materials employed for this work consisted of various carbide, boride, and metal powders. as well as of boron and graphite powders. In cases where commercial grades of carbides were considered unsuitable because of low purity or excessive amounts of graphitic carbon, such carbide powders were prepared by this laboratory. The procedure for the preparation of carbide powders (zirconium carbide, titanium carbide, tantalum carbide, and niobium carbide) consisted of mixing graphite and the respective metal hydride powders in stoichio-metric proportions and subsequent heating of such mixtures in a hydrogen atmosphere in carbon crucibles. The heating was by high frequency to temperatures ranging between 1700" and 2100°C. The resulting carbide was then comminuted and screened to the desired particle size. ZrB, and TiB, powders were produced by the electrolysis of fused salt baths, according to the method described by Andriex.. The borides of niobium, vanadium, tantalum, molybdenum, chro-ium, and iron were obtained by mixing the respective metal and boron powders in the desired proportions. Such metal-boron mixtures were heated in a high frequency furnace to form boride powders. For each metal-carbon-boron group (Tables I1 through XI) a metal, its hydride, carbide or boride were mixed with carbon, boron or boron carbide powders. The additions of carbon, boron or boron carbide powders to any of these metals or metal compounds were calculated to satisfy a particular carbide or boride phase that according to the literature (Table I) had definitely been established by X-ray diffraction work. Samples of powder mixtures were hot pressed in graphite molds that were heated by direct conduction. The specimen dimensions were approximately 2.5X1X1 cm. Hot pressing temperatures were measured optically and maintained for approximately 30 sec under a constant pressure of about 1.3 ton per sq in. Wherever possible, an attempt to obtain maximum specimen density was made by temperature variation. Electrical resistivity testing was done by measuring potentiometrically the voltage drop over a length of 1.5 cm for a current of 10 amp, at room temperature. To obtain electrical resistivities for specific carbide or boride phases, values were plotted as a function of the respective sample densities

Jan 1, 1953

By J. M. Kane

IN all probability the mining and metallurgical industry as a whole can demonstrate a larger economic return from installation of dust-control equipment than any other major industrial group. This fact has partially accounted for the marked increase of dust-control installations made during the past decade. While the primary objectives for installation of dust-collecting systems are improved working and operating conditions for men and equipment, the fact that an economic return can be anticipated on salvageable materials is an added advantage which shows in partial or complete equipment write-off. The conditions apply to most phases of the mining, milling, and smelting industry, both non-metallic and metallic.

Jan 1, 1953