Search Documents

By W. C. Leslie, R. M. Fisher, K. G. Carroll

A nitride, believed to be Si3N, has been separated from three nitrided silicon steels. Germanium nitride, Ge3N4, has been prepared from pure germanium. Comparison of the diffraction patterns indicates that the two nitrides are isomorphous; on orthorhombic structure is suggested in place of the rhombohedral structure previously reported for Ge3N4. THE possibility that a nitride of silicon may, under appropriate conditions, precipitate in silicon steels or in steels killed with silicon makes it desirable to have some positive means of identifying such a compound. One such means is the X-ray or electron diffraction pattern of the nitride. A review of the meager data in the literature indicates that the nitride most likely to form is Si3N4, a conclusion supported by the results of a study of nitrided silicon steels to be published shortly by L. S. Darken and R. P. Smith, of this Laboratory. Unfortunately, there is available no diffraction pattern for this nitride. Data have been reported, however, for Ge3N4 which, judging from the similarity between germanium and silicon, might be expected to be isomorphous with Si3N4. An effort was made, therefore, to form such a silicon nitride, to determine its composition and diffraction pattern and, if possible, its structure. To this end a series of three silicon steels was nitrided under controlled conditions with the resultant formation of nitride particles which yielded an electron diffraction pattern in situ. The particles were then extracted from the steel and an attempt was made to determine their chemical composition. X-ray and electron diffraction patterns were also obtained from the extracted particles, which indicate that the nitride is isomorphous with Ge3N4, although a complete determination of the structure has not been possible. These results show that a silicon nitride with a well-defined diffraction pattern can form in silicon steels, and they suggest that this nitride is Si3N4. Materials and Procedures The sillicon steels investigated were In the form of thin sheet or strip and had the composition shown in Table I. The 0.58 and 1.21 pct Si steels were nitrided by holding them at 1110°F in an H2-NH3 atmosphere containing 3 pct ammonia for 48 hr. The nitride particle size was increased by subsequent heating at 1500°F for 13 1/2 hr in helium. The resulting microstructure is shown in Fig. 1. The steel containing 3.20 pct Si was nitrided at 1200°F for 16 1/2 hr after which it was held in helium at 1500°F for 4 hr. Its structure as seen under the electron microscope is illustrated by Fig. 2. As would be expected from the higher silicon content and the shorter holding time at 1500 °F, the nitride particles are smaller and more numerous than those in the 1.21 pct Si steel. The ammonia-hydrogen treatment reduced the carbon content of the steels to a very low level, so no interference was encountered from carbon or carbides. In the case of the 3.2 pct Si steel, the carbon was reduced to 0.003 pct before nitriding by heating in dry hydrogen. Attempts to obtain an X-ray diffraction pattern from polished and etched surfaces of the 1.21 and the 3.20 pct Si steels were unsuccessful. However, an electron diffraction pattern was obtained from the surface of the steels. The interplanar spacings obtained from these patterns arc shown in Table 11, col. 5. The nitride particles were then extracted from all three steels by dissolving the ferrite matrix in bromine-methyl acetate, the solution used in the Beeghly method for the extraction of aluminum nitride from steel. X-ray diffraction patterns of these residues, obtained by means of a spectrometer and by a 57 mm Debye-Scherrer powder camera using filtered cobalt or chromium radiation, are given in Table II along with the pattern obtained by

Jan 1, 1953

"Acta Metallurgica" William C Ellis, Dec '57 Alfred Noble Joint Prize Committee Same as Rossiter W Raymond Award Committee AIME American Association for the Advancement of Science 0 B J Fraser, Dec '57, J T MacKenzie, Dec '58 American Geological Institute H A Meyerhoff, Oct '57, Charles F Park, Oct '58 Committee on Government Relations J L Gillson, '56 American Power Conference M Tenenbaum, '57 American Standards Association Mining Standards Board E R Borcherdt, Jan '57, Otto Herres, '57, J K Richardson, Dec '56, Alternate E W Bullard

Jan 1, 1957

By H. L. Gilbert, W. W. Stephens

Production of anhydrous zirconium tetrachloride by direct chlor- ination of a zirconium oxide carbon mixture in a silica-brick-lined chlorinator is described. Theory and thermodynamics of reactions are discussed. A pilot-model chlorinator and full-scale production equipment are described and operating data are included. ANHYDROUS zirconium tetrachloride required as a starting material in the Kroll process for production of ductile zirconium has been produced in this country principally by chlorination of the carbide or "carbonitride" made by reduction of zircon sand concentrates with carbon in the arc furnace. This process and the equipment used have been fully described.'.' It is well known that zircon or badde-leyite ores may be chlorinated directly with chlorine in the presence of carbon, and this one-step approach would seem at first glance to be preferable to the two steps involved in the carbide-chloride operation. As previously discussed1 considerations leading to adoption of the longer process were: 1—Chlorination of the carbide proceeds rapidly at temperatures below 500°C, whereas temperatures above 900°C were considered necessary for chlorination of zircon-carbon mixtures. 2—The highly exothermic nature of the carbide-chlorine reaction makes it self-sustaining, while heat must be supplied continuously in direct chlorination of the ore. 3—Silicon was thought to be chlorinated along with zirconium in the direct chlorination of zircon, leading to high chlorine consumption. In production of carbide in the arc furnace, silicon is driven off as silicon monoxide and does not enter the chlorinator. 4—For efficient direct chlorination, the ore must be finely ground and intimately mixed with carbon, and the mixture briquetted. 5—Direct chlorination requires a much larger chlorinator for a given production capacity than chlorination of carbide. Recently it has become necessary to produce large quantities of zirconium metal from a chemically purified zirconium oxide. Since the cost of the latter is high, the relatively high losses encountered in production of carbide in the arc furnace could not be tolerated, and a graphite resistor furnace5 was developed for production of carbide, which was then chlorinated in equipment previously used for chlorinating arc-furnace carbide. This method of operation was quite satisfactory, and losses in the carbid-ing step were minimized. However, operating costs were relatively high, and the process did not lend itself particularly well to large-scale operation because of the multiplicity of small units required and the hand labor needed to load, unload, and maintain the furnaces. To chlorinate the carbide, a vertical-shaft chlorinator was used in which the charge was heated with a central split graphite-rod resistor.' Operation of this chlorinator was somewhat less satisfactory with the resistor furnace carbide than it had been with the arc-furnace carbide due, principally, to the differences in physical properties of the carbide. The arc-furnace carbide is obtained as a fused metallic-appearing mass which can be crushed to -1/4 in. with production of a minimum of fines, whereas the resistor-furnace product is lightly sintered and produces a large proportion of fines in crushing and handling. These fines tend to pack in the chlorinator and promote channeling. which results in poor chlorine efficiency and low capacity. Data based on production of 22,000 lb of chloride from resistor-furnace carbide in this equipment are shown in Table I. Necessity for increasing production of chloride from about 2,000 to 15,000 lb per week led to further investigation of possible methods for direct chlorination of the oxide or oxide-carbon mixtures. Direct chlorination of the pure oxide presents much less difficulty than chlorination of zircon sand or oxide ores. The oxide is easily ground to —200 mesh, and no silica is present to cause excessive consumption of chlorine or contamination of the product. Theoretical Considerations The principal chemical reactions involved in chlorination of mixtures of zirconium oxide and carbon may be written as follows: ½ ZrO2 (c) + C(c) + Cl2(g) = ½ ZrCl,(g) + CO(g) [I] 1/2 ZrO, (c) + CO(g) + Cl2(g) = ½ ZrCl,(g) + CO2(g) 121 ½ ZrO2 (c) + ½ C(C) + Cl2(g) = 1/2 ZrCl4(g) + ½ CO2(g) [3]

Jan 1, 1953

The Howe Memorial Lecture, in memory of Henry Marion Howe, Past President of the Institute, was authorized in April, 1923, as an annual address to be delivered by invitation under the auspices of the Institute by an individual of recognized and outstanding attainment in the science and practice of iron and steel metallurgy or metallography, chosen by the Board of Directors upon recommendation of the 11on and Steel Division. The following mere the Howe lectures and lectures for the years indicated: 1924 What, is Steel? By Albert Sauveu

Jan 1, 1944

During the latter part of the Civil War an income tax was placed upon coal and the production of coal in the various collection districts during the life of this tax is shown in the tabulation that follows. The counties that include coal deposits are shown for each district. No record exists now of the production by counties, but it is calculated here on the basis of tax collected. The table, of course, does not include any territory not under the control of the northern armies, and not all of that in some cases.

Jan 1, 1942

By S. K. Bose, P. K. Sahoo, S. C. Sircar, P. K. Jena

High grade manganese ores are utilized in metallurgical, chemical, and battery industries, whereas the low grade ores are not accepted for these purposes and hence get accumulated at the minehead. In the present study an attempt was made to solubilize the manganese value as its sulfate by roasting the low grade ore with a suitable sulfatizing agent followed by water leaching. The different parameters were determined in the laboratory scale. Based on these, kilogram scale experiments were conducted where an appreciable amount of manganese goes into solution during leaching.

Jan 1, 1981

By M. Dubrovsky, J. W. Evans

A laboratory scale cell (approximately 50 amps current) equipped with a fluidized bed cathode was used in a study of the electrodeposition of cobalt from acidified aqueous sulfate solutions The effect of current density (in the range 0.1 to 1 amp/cm2 of diaphragm), cobalt concentration (4 8 to 100 glliter) and catholyte pH (1 35 to 6 2) on current efficiency and energy consumption were determined. Generally the current efficiency increased with increasing current density and cobalt concentration Current efficiencies were comparable to those reported in the literature for conventional electrowinning

Jan 1, 1981

By L. Alan Weakly

Abstract-The Bureau of Mines has pursued a program of research on mine illumination that has defined the coal miner's illumination needs. St. Joe Minerals Corporation, recognizing the need for improving the illumination of the working places in their mines, entered into a cooperative research agreement with the Bureau of Mines to utilize the Bureau's expertise in this field. Some similarity in the environment, in which coal and hard rock miners work, has allowed the application of developed coal mine illumination technology and equipment to be utilized in hard rock, room and pillar mines.

Jan 6, 1978

By G. W. Dopson, P. A. Korpi

The angular spiral lining system reduces energy consumption and grinding media consumption in grate discharge ball milk. This paper discusses the effect of this lining system on mill product size distribution. Performance comparison of a grinding circuit outfitted with angular spiral liners in ball mills are made with respect to standard double wave-liner installations. The angular spiral lining system was developed by Waagner-Biro of Austria. The installation of this lining system at Magma Copper Co. is the first of its kind in a grate discharge ball mill used for wet grinding.

Jan 1, 1983

By L. Alan Weakly

The Bureau of Mines has pursued a program of research on mine illumination that has defined the coal miner's illumination needs. St. Joe Minerals Corporation, recognizing the need for improving the illumination of the working place in their mines, entered into a cooperative research agreement with the Bureau of Mines to utilize the Bureau’s expertise in this field. Some similarity in the environment, in which coal and hard rock miners work, has allowed the application of developed coal mine illumination technology and equipment to be utilized in hard rock, room and pillar mines.

Jan 1, 1979

By C. Fairhurst, B. C. Haimson

Pink Tennessee Marble was tested for wedge bit penetration characteristics at static and dynamic (10 - 250 ft/sec) loading rates. No significant differences were found within the dynamic range as far as the energy required to remove a unit crater volume and the force used to cause a certain penetration. Under static loading, however, both the energy and the force required were significantly lower. Tests run on bits of varying width indicated that as the wedge bit narrowed to an almost conical shape, the energy used per unit crater volume became considerably lower.

Jan 1, 1971

By J. L. Hendrix, R. B. Dix

A study was made of the United States Bureau of Mines chlorine-oxygen leaching process for complex sulfide concentrates. The investigation sought to determine the kinetic order and mechanisms involved in the reactions between galena and sphalerite with chlorine. The influence of copper on the extraction rates was also studied. It has been shown that the rates of reaction of chlorine in aqueous solutions with sphalerite and galena are both zero order at 373 K with rate limiting step being the chemical reaction. Addition of cupric chloride increased the extractions of both lead and zinc.

Jan 1, 1981

By T. M. Howell

JET piercing is a licensed process developed by Linde Air Products Co. Experiments with this method lapsed during World War II, but in the decade that followed the process was expedited. Two types of drills mount the jet piercing equipment for blastholes. The turntable of one machine rotates the complete stem system as well as the blowpipe, which emits three individual flames at different levels. Depth penetrated is limited by length of the blowpipe mounted in the rotary mechanism. This machine has successfully drilled blast- holes in Minnesota taconite.

Jan 6, 1957

By H. W. Schadler

The superplastic behavior of low carbon and manganese bearing steels has been evaluated. The results of elevated-temperature stress-strain rate and elongation tests are reported which indicate that high strain rate sensitivity (>0.5) and adequate elongations are achievable in ultrafine-grained steels 1 to 2 p, but at strain rates which are not commercially attractive. It has been demonstrated that the fine grain size is retained after long times and high strains if the temperature is kept within the range of the two-phase (a + ?) field. INTEREST in superplasticity has been stimulated by the desire to: 1) understand the origin of, and mechanisms responsible for, the large uniform elongations observed, and 2) exploit this property for commercial advantage in metal forming operations. Although the Zn-22 wt pct Al alloy presently being studied as a model material1-5 may find application in sheet forming and extrusion, the potential of super-plasticity should best be realized in large tonnage materials, such as steel and aluminum alloys. The degree of superplasticity in low-carbon and manganese-bearing steels has been evaluated. The results of elevated-temperature stress-strain rate and elongation tests on ultrafine grain size material are reported. Avery and Backofen6 and Hart7 have shown that geometrically stable flow leading to extensive uniform elongation in the tension test is associated with high values of the strain rate sensitivity, m, defined: Lozinsky had reported that titanium and zirconium experience permanent deformation if subjected to a constant load and cyclic heating through the temperature range of the phase transformation. Although strain rate sensitivities in excess of about 0.2 had not been reported previously for steel, permanent deformation had been observed11-13 in a wide variety of steels subjected to a constant load and cyclic heating through the temperature range of the a-? phase transformation. Thus by analogy, steel could be expected to exhibit high strain rate sensitivity but only in the a + ? condition. High strain rate sensitivity has been observed at 650°C (a + Fe3C), but not reported as such, by Bailey, Dickenson, and pearson14 in 1931 at a strain rate of about 10-9 per min. It then remained to determine whether high tensile elongations would be observed in a rate-controlled test at constant temperature and at what strain rate strain rate sensitivity values greater than 0.5 would be observed. Since previous experience8 had indicated the importance of fine grain size to realizing high m at reasonable strain rates, it was first necessary to produce an ultrafine grain size and then keep the grains from growing during the test. The results of this investigation show that fine grain size can be readily produced16 and maintained by restricting the temperature of testing to below the ? transus. Further, superplasticity (high m and large uniform elongation) is observed. However, the strain rate range is only marginally useful for commercial forming operations with the finest grain size produced. MATERIAL The material investigated initially was a 1.9 wt pct Mn, 0.42 wt pct C, hot-rolled bar previously used by Low and Turka1015 and available in the laboratory. The 0.500-in. round was cold-rolled to a 0.090-in. flat, annealed for 4 hr at 850°C in argon, air-cooled, and cold-finished to 0.050 in. Subsequently, four additional steels of the compositions given in Table I were investigated to explore the effects of manganese, carbon, and test temperature on the observed stress-strain rate behavior. These steels were melted under argon, cast to 0.75 by 2 by 5 in. slabs, hot-rolled at 850°C, surface-finished to 0.13 in., and cold-finished to 0.050 in. Sheet tensile specimens 0.200 in. x thickness with 1- or 2-in. gage length were cut parallel to the rolling direction. Table I also includes the nominal transformation temperatures for the AISI 1340 and the four experimental steels. EXPERIMENTAL PROCEDURE Production of Fine Grain Size. Ultrafine grain size (1 to 5 p) was considered essential for this studv. Grange16 has described two techniques for producing

Jan 1, 1969

By Branko Ladanyi

In reviewing the current issues in rock mechanics, the author puts an' emphasis on problems related with the needs of extrapolation in scale and time, and of establishing proper conceptual models, especially in connection with the most recent large-scale and long-term projects such as underground disposal of nuclear waste. In such projects, where valid case histories will not be available for many years to come, the observational method can only be successful if combined with a proper framework approach, such as general rock mass classification systems and behavioral models.

Jan 1, 1982

By D. G. Osborne

Transportation cost is a key factor in both the profitability and competitiveness of coal marketing. With coal exportation growing rapidly, moisture control is important. Although in some cases, too much moisture reduction can lead to losses in transportation and pollution problems, there is normally justification for reducing moisture by mechanical means as much as possible. This paper reviews current technology of dewatering coal fines and examines the comparative capabilities of screens, filters, and centrifuges. Financial considerations are stated and implications of capital and operating costs on selection are discussed.

Jan 1, 1985

By A. J. Lynch, J. A. Holmes, F. C. Bond, D. W. Fuerstenau

This is an outstanding paper on comminution theory and represents a considerable advance in mathematical formulation. It clears the way for a discussion that should ultimately decide whether the work index should be considered as a parameter according to the Third Theory or as a constant. In the empirical differential equation dE = C dx/xn either C or n must be treated as a variable to satisfy known crushing and grinding conditions. The author has chosen the exponent n as the variable, with C as a constant.

Jan 4, 1958

ON THIS page is a photograph of a machine that has played a key role in the recent history of Kennecott's Ray mine, situated in the Mineral Creek District, Pinal County, Arizona. It is a huge, rugged, Diesel-powered, rubber-tired truck, having a capacity for carrying fifty tons of ore. It has, to a substantial degree, revolutionized the business of moving broken rock by cutting down both maintenance and operating costs. From 1911 until the end of 1954 Ray had produced 79,000,- 000 tons of ore by underground block-caving. However, in 1947 [ ]

Jan 1, 1957

By W. G. Scott

SINCE devising the incline top-slicing method in use It the Coronado mine,1 I have had numerous inquiries is to how the same system could be adapted to larger orebodies. Based upon our experience here, 1 have outlined below some suggestions for its, application to orebodies of larger size. Modifications and extensions, of course, would have to be made to take care of different dimensions and irregularities. In order that one may have a better understanding of the scheme, a brief description of the Coronado method will he given first.

Jan 11, 1917

By H. F. Yancey

COAL mine operators recognize coal as an abrasive material, because the wear of drilling, cutting, and conveying equipment is reflected as a cost item for replacement of parts. Similarly, industrial consumers of coal experience abrasive wear on all coal-handling equipment. Operators of pulverized fuel plants are doubtless most keenly aware of the abrasiveness of coal, because under the high contact pressures developed between coal and metal in pulverizers, abrasive wear is increased many fold. Moreover, experience in operating pulverized fuel plants has demonstrated that some coals are much more abrasive than others.

Jan 3, 1951