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By O&apos, R. G. Meara, B. W. Gandrud

In 1034 the Southern Experiment Station of the U.S. Bureau of Mines in cooperation with the University of Alabama began an investigation of the availability of kyanite ores as a source of raw material for the manufacture of refractories. Under this program, gravity concentration and flotation tests have been made on two varieties of Georgia kyariite ore, mica schist and massive. Most of the attention has been directed to the mica schist ores, as they are more widely distributed and seem to offer greater economic possibilities than the massive ores. It is evident that the preparation of kyanite for use as a refractory material involves other considerations than the mere elimination of impurities. A concentration process that eliminates impurities satisfactorily may have to be followed by some additional treatment, since the final product must be of a coarseness and size ratio that will make it suitable for refractories manufacture. So far in the investigation at the Southern Experiment Station of the U.S. Bureau of Mines only the concentration problem has been considered, and this paper is intended as an interim report. Ores The schist ores contain 1 to 9 per cent of kyanite crystals embedded in mica and quartz, with smaller amounts of graphite, garnet and iron oxide and minor amounts of other heavy minerals. The garnet content varies from a trace to a few per cent. The minerals are easily released by moderate grinding. The size of the kyanite ranges from fine needles to crystals 1 1/2 in. long, 1/2 in. wide and 1/4 in. thick. The garnet, quartz and iron oxide grains have a smaller mean mesh than most of the kyanite. The maximum size of the garnet crystals corresponds to about 14 mesh and that of the sand grains is considerably less. Most of the iron oxide is still finer, for the minus 100-mesh size is greatly enriched in Fe²O3. The massive ore consists of radiating masses of kyanite interlocked with quartz, mica, corundum and small amounts of other heavy minerals.

Jan 1, 1938

By B. W. Gandrud, R. G. Meara, O&apos

In 1034 the Southern Experiment Station of the U.S. Bureau of Mines in cooperation with the University of Alabama began an investigation of the availability of kyanite ores as a source of raw material for the manufacture of refractories. Under this program, gravity concentration and flotation tests have been made on two varieties of Georgia kyariite ore, mica schist and massive. Most of the attention has been directed to the mica schist ores, as they are more widely distributed and seem to offer greater economic possibilities than the massive ores. It is evident that the preparation of kyanite for use as a refractory material involves other considerations than the mere elimination of impurities. A concentration process that eliminates impurities satisfactorily may have to be followed by some additional treatment, since the final product must be of a coarseness and size ratio that will make it suitable for refractories manufacture. So far in the investigation at the Southern Experiment Station of the U.S. Bureau of Mines only the concentration problem has been considered, and this paper is intended as an interim report. Ores The schist ores contain 1 to 9 per cent of kyanite crystals embedded in mica and quartz, with smaller amounts of graphite, garnet and iron oxide and minor amounts of other heavy minerals. The garnet content varies from a trace to a few per cent. The minerals are easily released by moderate grinding. The size of the kyanite ranges from fine needles to crystals 1 1/2 in. long, 1/2 in. wide and 1/4 in. thick. The garnet, quartz and iron oxide grains have a smaller mean mesh than most of the kyanite. The maximum size of the garnet crystals corresponds to about 14 mesh and that of the sand grains is considerably less. Most of the iron oxide is still finer, for the minus 100-mesh size is greatly enriched in Fe²O3. The massive ore consists of radiating masses of kyanite interlocked with quartz, mica, corundum and small amounts of other heavy minerals.

Jan 1, 1938

By F. W. DeVries

The subject article is an excellent comparison between two potential oxidants, molecular oxygen and hydrogen peroxide, as used in the Palangana field at the time of the trials. The tests showed no advantage to using hydrogen peroxide; however, it would be unwise to generalize that the experience in these trials was universally true. During the time of the work cited, extremely high levels of an unusual impurity were recycling in the lixiviant, which substance was a catastrophically destructive catalyst for peroxide. Since this material was not removed before recycle, it was not surprising that much of the peroxide fed was decomposing in the feed piping and never made contact with the uranium mineralization. Under these conditions, indeed, peroxide showed no improvement over oxygen. This is, however, perhaps the most adverse environment encountered to date in US in-situ uranium leaching. In other operations, peroxide has proved advantageous where two factors have been exploited: 1.Despite the tendency for Hz02 to decompose to water and oxygen in the in-situ leach environment, its higher redox potential before decomposition has provided higher leach rates. In some formulations, overloading beyond the O2 saturation equivalent with peroxide has allowed higher oxidant levels, and higher leaching rates, when overloading with molecular O2, led to vapor-locking.

Jan 1, 1983

By AIME AIME

ON JULY 12, 1921, S. S. Arentz, representative at large from Nevada, introduced in the House of Representatives, under the number H. R. 7736, a bill to revise, amend and codify laws of the United States relating to the location of mining claims on public domain, and other purposes. This bill had been drafted by a committee of consulting engineers of the U. S. Bureau of Mines. The immediate purpose of this introduction in Congress was to make it avail- able for general information and discussion. In pursuance of this purpose Mr. Arentz issued the following circular: This proposed codification and revision of the mining laws of the United States as received from a committee of mining and metallurgical engineers appointed by the Director of the United States Bureau of Mines was introduced in the House of Representatives by the undersigned (who has operated and developed mines throughout the West for many years). It is submitted to prospectors, mine operators and mining engineers, all of whom are affected and vitally interested in the subject with the hope that they will give this bill their careful consideration and study.

Jan 1, 1921

By A. B. Young

T HE smelting industry in Utah is represented by four plants: The Midvale of the United States Smelting, Refining & Mini.ng Co., the Murray of the American Smelting and Refining Co., the Garfield of the same company and the Tooele of the Inter- na.tiona1 Smelting Co. The first two are lead smelters, the Garfield plant is a copper smelter while the last named embraces both a lead and copper smelter. A total daily smelting capacity of over 10,000 tons is represented, of which 4000 tons is lead smelting capacity. With the exception of Tooele, forty miles distant, all of these smelters are within twenty miles of Salt Lake City. Pyrometallurgical operations in this district are con- fined entirely to the production of unrefined bullion, which is shipped east to the various refineries of the respective companies. The smelting industry in this state had its beginning away back in the latter days of the Civil War, many years before the completion of the trans-continental railroad. Ox teams were still bringing their companies of better fixed Mormon emigrants across the plains to the valley of the Great Salt Lake and those in lesser circumstances were still pushing their hand- carts over the same roads to the temporary abode

Jan 1, 1925

By Eugene McAuliffe

THE heavy shrinkage in the production of bituminous coal has reflected adversely in the matter of tonnage produced by stripping arid mechanical loading machinery. The purchase of stripping and underground loading equipment has likewise been circumscribed. How- .ever a growing percentage of bituminous coal is being loaded by stripping and mechanical loading machinery. This situation is due to the fact that numerous strip pits were able to operate in Illinois and Indiana when under- cover mines were subjected to labor interference, a further advantage gained by their ability to produce and market coal at a price below that of the undercover mines. The mines equipped with mechanical loading. apparatus have enjoyed more continued operation for the double reason that the companies using coal-loading machinery are, generally speaking, more substantial and in better financial condition than many of the smaller properties who maintain hand-loading methods, and the market advantage due to lower production costs also reflects to the advantage of the undercover mines using mechanical loading equipment. Where a number of mines are con- trolled by one company, those not equipped with loading machinery and suffering from higher producing costs have often been closed, with the available tonnage concentrated in the more modernly equipped mines.

Jan 1, 1933

By AIME AIME

MICA is perhaps our No. 1. strategic mineral problem because of its large requirements in a variety of equipment for use in the military services, and because the principal source of this material has heretofore been British India, a source now threatened partly because of distance and lack of ships. [Block mica and bauxite were added to the "most critical" list published by the W.P.B. on Nov. 6.] No satisfactory substitute has yet been found for most of the uses of mica, which largely involve electrical insulation. Brazil is now our nearest and best major source of this material. No splitting plants have yet been established there but in 1941 we imported about a million pounds of block mica from that country and in 1942 that quantity will be considerably exceeded. In Brazil, mica is found almost exclusively in the pegmatite dikes along the mountain range bordering the eastern part of Minas Gerais. A belt, roughly 180 miles long by 100 miles wide, extends from Theophilo Ottoni to Carangolo. The principal mica-mining districts in this belt are the Governador Valladares area to the north and the Espera Feliz district to the south. The dikes are usually 10 to 50 meters wide and a mile or two long and intrude the old metamorphic schist formation. They are weathered and easily mined.

Jan 1, 1942

By T. J. Bosworth

The effect of hydrogen pretreatment of alumina, magnesia, and zirconia crucibles on reduced oxygen levels in iron charges has been studied. Hydrogen treatment of commercial high-purity magnesia crucibles was observed to produce as high as 70 pct reduction in oxygen content in iron melts. Hydrogen treatment of the commercial high-purity grade zirconia crucibles produced a 25 pct reduction in oxygen levels in iron melts. An average reduction of Knoop hardness of 47 pct was recorded on the iron charges melted in hydrogen-treated crucibles. On the basis of the experiments and the free-energy diagram, it appears that the major source of reducible oxygen to the iron charge is the suboxides and impurity oxides rather than the major oxide of the crucible. Suitable pretreatment of the crucibles to reduce and remove these oxides yields low oxygen levels in iron melted in the crucibles. DURING the last decade, attempts to produce more pure and uniform alloyed metals have brought about the development of many new melting techniques. Notable among these are vacuum-induction melting, inert and consumable-electrode melting, the cold-mold technique, and numerous techniques for removal of impurities by chemical reaction. However great the achievements in this field, metals must still be melted in contact with media of varying reactivity; i.e., gas, ceramic, and slag. Studies have been made to attain an understanding of the reactions that take place during melting, including slag-metal reactions and equilibria, equilibrium of hydrogen and water vapor, and carbon dioxide and carbon monoxide with oxygen in molten iron. These reactions have been treated quite thoroughly. There is one condition, however, that has been widely overlooked, and, to the author's knowledge, only cursive investigation has been made of it. This is the reaction between the ceramic crucible material and the iron charge. In recent years, Hadley and Bianchi' made a series of studies on hydrogen deoxidation of iron in magnesia crucibles. Bianchi2 studied crucible-FeO equilibria in the temperature range 1525°to 1650°C in high vacuum with, however, inconsistent results. Richardson and Jeffes3 in their series of articles on thermodynamic reactions in the making of iron and steel refer to Wentrup and Hieber's4 work on iron and aluminum deoxidation. Their pork included melting iron in alumina crucibles and measuring the aluminum and oxygen content in the iron. Because of the low values obtained, question has arisen of their analytical accuracy.3 Dastur and chipman5 obtained values on hydrogen-oxygen equilibrium in molten iron contained in alumina crucibles similar to those obtained in experiments in the present program. Hochmann6 studied removal of impurities in chromium irons in high vacuum. His results with respect to oxygen level in chromium-iron melted in magnesia crucibles are consistent with results we have obtained.

Jan 1, 1959

As described in the section on the Palabora twin crushers, the Palabora ore consists of two types: a carbonatite containing a low titanium magnetite, and a foskorite containing high titanium magnetite. As the Palabora pit was widened and deepened, more and more of the foskorite had to be mined. The 25,000 mt expansion of the Palabora plant which went into operation in early 1977 therefore takes its feed from the foskorite section of the orebody. For the expansion, a third 54 in. by 74 in. gyratory crusher was installed to crush feed for two 32 ft by 15 ft (9.75 by 4.6 m), 9000 hp (6710 kw) autogenous single -stage grinding mills. These units are located near the two existing primary crushers, and the ground ore is pumped 5277 ft (1640 m) to the expanded flotation plant by five stages of centrifugal pumps. The new gyratory is installed in a unique Figure-8 shaped enclosure with the crusher in the smaller 27 ft 11 in. (8. 5 m) diameter cylinder and the maintenance area in the 36 ft 1 in. (11 m) diameter cylinder. Cylinder walls are only 23.6 in. (600 mm) thick because their circular design permits all the concrete to be in compression. A rectangular dump pocket which sits on the smaller cylinder contains two manganese steel faced splitters to protect the crusher spider and countersunk water spray headers under the dumping positions for dust suppression. The dump pocket holds 330 st or 300 mt and is also lined with manganese steel. The crusher is mounted on a reinforced concrete diaphragm over the 363 st (400 mt) crushed ore pocket. In the back of the pocket is plastic pipe. Radioactive level control sources are lowered into this pipe from the crusher support floor. The pipe is protected by concrete covered with steel castings. Level control detectors are mounted on the front wall of the pocket. Liner plates on the crushed ore pocket walls are removed and in- stalled by the use of a circular monorail and trolley mounted on the pocket ceiling. The door in the front of the crushed ore pocket is hinged at the top rather than at the sides and is raised by an electric winch. For removal of the eccentric, rails are installed in the pocket and a unique hydraulically operated cart is moved under the eccentric. A platform is raised to receive the eccentric and lowered so that it may be removed. Crushed ore is removed from the pocket by a hydraulically powered, 8 ft

Jan 1, 1978

By H. C. Heard

The review by Professor J. C. Jaeger (Chapter 1) briefly summarizes and discusses a select group of papers by various workers dealing primarily with aspects of fracture in brittle rock materials. Professor Jaeger's treatment is primarily concerned with the correlation of phenomenological and theoretical failure criteria with empirical results from short duration tests at ambient temperatures and generally at low lithostatic and interstitial fluid pressures. As engineering rock mechanics becomes more concerned with new techniques of mineral exploration and production at increasingly greater depths in the crust, it is well to be aware of the effect of the environment -that of the superposed stress field upon the lithostatic and interstitial fluid pressure, the temperature and the duration of the loading upon the failure of rocks either by fracture or flow. All results to be discussed here are from laboratory tests on small homogeneous samples, thus caution should be used in the direct extrapolation of these results to large inhomogeneous rock masses having quite different boundary conditions in the earth. The purpose of this supplement is to briefly point out the major effects of these parameters as examined singly, with all others held constant, and to cite some recent results which apply to the main theme on the brittle failure of rocks. The total stress field imposed upon a small volume of porous and permeable rock in the earth's crust may be thought of as the sum of an applied differential stress, plus a lithostatic pressure, plus an interstitial fluid pressure. The differential stress portion may be completely specified by nine components, six shear and three normal. If the small volume element is in rotational equilibrium, by suitably choosing our coordinate axes we may resolve these nine components into the three principal com-

Jan 1, 1967

By James W. Wade

THIS discussion of the future supply of lead refers only to the next ten-year period. Beyond that no prediction can be made that would be of sufficient accuracy to serve any purpose. When any commodity is by an unsatisfied demand forced to a higher price level, and the profits of those who are able to produce the commodity are greatly increased, there is awakened a new interest in the commodity on the part of both producer and consumer. The consumer attempts to reduce his costs by developing substitutes or assisting in the development of new sources of supply. Lead is now going through this stage. The lead producer is increasing development expenditure and searching for new mines. The consumer is developing substitutes as illustrated by the increasing use of zinc oxide as a pigment, and the use of dry batteries in radio sets. The search of the Ford interests for lead, by prospecting in Missouri and Idaho, is induced by the effort to develop a new source of supply. Considering the index figures of the Department of' Commerce, it is evident that lead is on a substantially higher price level. For February, 1926, the index figure of lead is 209, while the general commodity price index is only 156, 100 being taken as the base for 1913.

Jan 1, 1926

By D. I. Bardos, Paul A. Beck

The 1100°c isothermal, sections of the V-Fe-Si, V-Co-Si, and V-Ni-Si systems were studied at silicon contents between 0 and 40 at. pct. The single-phase fields in the 30 and 50 at. pct Mn sections of the 1100°C tetrahedron of the V-'Wn-Fe-Si system were also determined. The direction of extension of the elongated O, R, D, and a-Mn Phase fields suggests that the stability of these phases is determined largely by the electron concentration. The peculiar shape of the above ternary a phase fields, as well as of the a phase fields in the V-;Mn-Si and Cr-MTZ-Si systems is accounted for on the assumption that in manganese-(iron-, coball-, nickel-) rich alloys silicon atoms do not exclude d electrons , while in alloys low in the above components they do. This assumption also leads to the expected electronconcentrations for q and ß-Mn phases formed by transition metals with aluminurn. In earlier work it was shown that in ternary alloy systems of transition elements the a a and certain other phases with complex structure, such as the p and R phases,3 form elongated phase fields extending in a direction corresponding to a constant electron concentration. Recently similar behavior was observed in manganese-rich ternary ß-Mn solid solutions with another transition element and with silicon, germanium, or tin,4 confirming earlier indications3 that ß-Mn is also an electron phase. The alloying behavior of silicon in these manganese-rich alloys sug- gested that the four outside electrons of silicon participate in the bonding and that the predominantly d-like bonding electrons are not excluded from the silicon sites. Presumably, some of the normally unoccupied 3d states associated with the silicon atoms are in these alloys lowered to the Fermi level;4 thus silicon behaves as if it, too, were a transition element. The manganese-rich boundary of the a phase in the V-Mn-Si system,4 as well as in the Cr-Mn-Si sys-tem,4,5 extends approximately parallel to the ß-Mn phase boundary, corresponding to the transition ele-mentlike behavior of silicon described above. However, at lower manganese contents (i.e., in the high-vanadium or -chromium region) the a phase field in both ternary systems mentioned extends in a direction roughly perpendicular to that of its manganese-rich boundary, a phenomenon that is apparently inconsistent with the behavior of silicon in the manganese-rich alloys. A similar, although somewhat less pronounced, extension of the a phase occurs also in the high-vanadium (low-iron) region of the V-Fe-Si system at 1175C, but reportedly not in the V-Co-Si or V-Ni-Si systems at the same temperature.5 The present work was undertaken to investigate in more detail the extension of the a phase (as well as of other electron phases that may be present) in the last three systems and to elucidate this phenomenon, which has not been satisfactorily explained previously. EXPERIMENTAL PROCEDURES Most of the alloys were melted in an arc furnace, using a water-cooled copper crucible under helium atmosphere. The transition metals were of better than 99.9 pct purity and the silicon used was 99.98 pct pure. Alloys containing less than 20 pct V were induction-melted in recrystallized alumina crucibles under argon atmosphere.

Jan 1, 1967

By G. Ostberg

OXYGEN has frequently been considered responsible for phenomena in the metallurgy of cast iron which are not sufficiently explained by the presence of other elements. Oxygen and oxides have been regarded as critical factors, particularly for the solidification process, and specifically in the formation of graphite. However, the evidence for an influence of oxygen has mostly only been indirect or qualitative. Furthermore, quantitative data on the oxygen content of cast iron presented in the literature have often been less conclusive as being apparently determined with insufficient regard for the difficulties associated with the sampling and analysis. These problems, experimental and theoretical, have been studied in this investigation. An attempt is made to bring the views on the soluble amount of oxygen in cast iron on a level with the present understanding of the thermodynamics of these types of alloys. Although there are no experimental data on the complete multicomponent cast-iron alloys some conclusions have been drawn from investigations on simpler systems. The order of magnitude of the solubility of oxygen in cast iron is considered in the first part of the paper. The second part deals with the oxygen content actually present under practical conditions. First the possible sources of errors in sampling and analyzing methods are examined. Finally some observations on the oxygen and oxide content of malleable iron during the production process are made. THERMODYNAMICS OF OXYGEN SOLUBILITY When cast iron is saturated with oxygen the saturation phase is essentially carbon monoxide or silicon dioxide depending upon the composition of the iron, the temperature, and the rates of formation of the oxides.* The latter occurs accordiw to the O + C = CO, Kc0 - a COa J 20 + Si = SiO2, Activities are used here instead of weight pct concentrations, since activities are believed to show more sensitively the effects of the interaction of all the alloying elements. Calculations involving activities are, however, seriously hampered by lack of experimental data on the interactions between the components encountered in the multi component cast-iron system Fe-O-C-Si-Mn-P-S- and so on. In order to make an estimate of the oxygen solubility reason-

Jan 1, 1959

By H. L. Gilbert, C. Travis Anderson, W. J. Kroll

IN a previous paper,1 the use of a split graphite tube resistor as a heater element for high-temperature furnaces has been described. The principal advantages of this type of construction are: I. The quadruple resistance or voltage compared with the top-bottom clamp resistor furnace. 2. Free expansion of the resistor. 3. The ease of protection from oxidation by air. 4. The firmness by which it may be held in the compact split clamp. This construction appeared to be well adapted for the fusion of high melting metals which require fusion in a vacuum. Zirconium metal had previously been melted at the Albany Laboratory of the Bureau of Mines in a vacuum arc furnace on a water-cooled plate, using a movable tungsten top electrode.2 When larger furnace capacities were desired, this type of construction proved to have its limitations as the largest tungsten rods available were about 7/8in. in diameter. The supply of direct current of high amperage for producing the . desired arc characteristics was also not available. Considerable difficulty was also found in compensating the atmospheric pressure on the flexible tubing of the movable electrode, at the same time keeping its movement sufficiently free to enable the striking of an arc on any part of the metal briquet. Among the various materials used for the electrodes in conducting experiments in the vacuum arc furnace was graphite. It was found that zirconium fused in a graphite cup with a carbon arc was contaminated to only 0.2 pct carbon. It was therefore decided to melt zirconium directly in graphite crucibles. A high-frequency furnace was first used in the attempt to melt the zirconium in graphite crucibles. The high-frequency heating coil was placed outside a silica tube which was evacuated by means of an oil diffusion pump backed up by a mechanical pump. The graphite crucible was thoroughly degassed at 1900°C before use. Considerable difficulty was experienced in operating at such temperatures in vacuo because, as shown by Zintl,3 carbon vapor formed and reacted with silica according to the reaction: Si02 + C = SiO + CO. The silicon monoxide which is volatile at these high temperatures reacted with the zirconium, thereby contaminating it with silicon and oxygen. The presence of carbon monoxide was detected by means of a gas discharge tube placed in the vacuum system as indicated by the pale blue glow of the tube as soon as carbon vapor started to react with the hot silica. The reaction between the carbon vapor and hot silica was avoided by the use of split cylindrical molybdenum shields which were inserted between the graphite crucible

Jan 1, 1948

By J. M. Seeman, R. A. Dodd

If some solution-quenched supersaturated aluminum solid solutions, e.g.., Al(Cu), are plastically deformed at room temperature and then aged at 200oC, the hardness may first decrease before increasing in the usual manner ' A similar transient softening is observed, even in the absence of plastic deformation, when a thin foil or small-diameter wire Al(Cu) specimen is rapidly quenched from the solution-treatment temperature and then aged.' Also, some solution-quenched and neutron-irradiated alloys undergo an initial hardness decrease during subsequent aging.3 The usual explanation of the transient softening in the above examples involves the effect of vacancies introduced by plastic deformation, rapid quenching, and neutron irradiation, respectively However, the mechanism of softening is not unequivo-cably established. In the first-noted case, Gane and parkins' observed that the softening was approximately proportional to the difference in the atomic diameters of solute and solvent, and it was argued that, if a large relative difference in atomic diameter promoted vacancy-assisted room-temperature solute diffusion to dislocations, dislocation climb occurring during subsequent aging at 200°C could cause transient softening. Some substantiation of this theory was offered by the additional observation that discontinuous yielding of solution-quenched polycrystalline Al(Cu) tensile specimens was suppressed by interrupting the test for a short aging treatment at 200°C. Of course, reversion (resolution of GPI) at 200°C would also cause softening, and Sil-cock4 expressed the opinion that the softening in the case of Al(Cu) must be partly associated with reversion. Also, Hirsch5 commented on the possibility that, if jogs cause hardening, an anneal at 200°C should straighten the jogged dislocations and result in softening. However, parkins' has re-expressed his belief that these mechanisms are not entirely consistent with the observed serrated stress-strain curves. Experimental. New data has now been obtained for Al(Cu), Al(Ge), Al(Mg), and Al(Zn) primary solid-solution alloys. These alloys were prepared from metals exceeding 99.99 pct purity, and specimens 4 by 4 in. diam were solution-treated, quenched, deformed 10 pct in compression at room temperature, and aged at 200'C in a cottonseed oil bath for various times. Generally, these operations could not be carried out in rapid succession, so the alloys were stored in a freezer between treatments to minimize aging. The variation in hardness with aging time, Figs. 1 to 4, was determined by microhardness testing with a 3.0-kg load. At least five readings were averaged to obtain each data point, and all measurements were taken about the center circumference of each cylinder (region of maximum deformation). Each specimen was used to obtain only one data point, i.e., specimens were not replaced in the aging bath after measurements were made. In

Jan 1, 1968

By Robert E. Ogilvie, Zvonimir Ban

Oxidation experiments were conducted above 600°C to investigate the oxidation products formed on the surface of MoSi2. Results are presented which indicate that minor iron impurities play a key role in the oxidation behavior of MoSi2 above 600 °C. Based on considerations of the crystal chemistry of the oxidation products, MoSi2 with rhenium and iron additions was found to be resistant to oxidation in the pesting temperature range. AS early as 1914, Honigschmidtl observed that some silicides of molybdenum exhibited high resistance to oxidation at elevated temperatures. This fact did not arouse much interest until 1950, when Kieffer and cerwenka2 examined this property in more detail. They found that Mo-Si alloys with approximately 70 pct Mo (by weight) could be heated to 1600°C in an oxidizing atmosphere without any significant damage. The surface was found to be protected by the formation of an extremely thin silica glass layer which had no tendency to spa11 during subsequent thermal cycling. In 1955, Fitzer3 discovered that even solid bodies made of MoSi2 completely oxidized within a relatively short time when exposed to the air in the temperature range from 300° to 600°C. To describe this phenomenon he proposed the name "molybdenum disilicide 'pest' ", clearly analogous to the previously observed "tin plague" ("tin pest") which, however, arises as the result of a phase transformation. Studies performed by Fitzer and, in particular, one published recently by Berkowitz, Blackburn, and Fel-ten,' comprise the most extensive research to date on the pest phenomenon in MoSi2, as far as the fundamen- tal mechanism of the process is concerned. The first of these studies revealed the existence of a crystalline phase which appeared at the surface at 750°C and dissolved in the glassy silica layer at 1150°C. The logical assumption was that this phase was some reaction product of MOO3 and SiO2. The formation of a reaction product of this type seemed probable since it had been mentioned by Glemser and Lutz6 in a paper describing their studies of molybdenum oxides; however, this assumption was later disproved.8 It is our belief that information concerning the exact nature of this crystalline phase may be important for a better understanding of both pesting and the protection mechanism. Therefore, since the only available general description of the pest phenomenon was that of Fitzer, it was decided to reproduce his experiments. These experiments established that, in addition to the "pest" and "nonpest" temperature range, an intermediate region exists between 600" and approximately 650°C. This region is characterized by the appearance of a variable amount of yellow to orange colored crystals. The electron-beam microanalyzer was used to qualitatively determine their composition. Iron and molybdenum were found to be major constituents. This result can be explained based on the following facts: 1) iron, according to literature data,* is the most common impurity in molybdenum powder, and its content can be as high as 0.25 pct; 2) technical silicon powder usually contains iron; 3) steel ball mills are often used for the crushing and grinding of MoSi2. In order to clarify the exact role of iron, it was deliberately added to a stoichiometric mixture of molybdenum and silicon. The observed results corroborated the previous experiment, proving that iron (probably as some silicide phase) concentrates along the grain boundaries. I) EXPERIMENTAL PROCEDURE A) Oxidation of MoSi2 with Iron Additions. 1) Specimen Preparation. Specimens were prepared by both

Jan 1, 1967

By Hsun Hu

Direct observations were made on the recrystalli-zntion of a cold-rolled (110) [001] crystal of 3 pct Si-Fe by annealing thin sections of the specimen inside the electron microscope during examination. Subgrain formation, presumably by polygonization, occurs rapidly, followed by a slow increase in the subgrain size before recrystallization can be detected. No migration of the subgrain boundaries was observed, and the formation of recrystallization nuclei by coalescence of subgrains is suggested. Re-c~ystallization characteristics of various texture components were individually examined. AS reported in a previous paper: orientations of the various deformation texture components in a 70 pct cold-rolled (110) [0011 crystal of 3 pct Si-Fe were completely confirmed by transmission electron diffraction patterns taken at various areas of the specimen. These orientations can be summarized as follows: Over most areas of the deformed crystal (111) planes are parallel to the surface. These areas correspond to either $- the two main defor: mation textures, the (111) [112] or the (111) [112].2-5 Within a few areas, (100) planes parallel to the surface are frequently found. These areas represent the minor deformation texture component, the (100) [Oll] type, which is derived from rotated Neumann bands.2'4'5 Only in very rare instances are (110) planes found parallel to the surface. This orientation corresponds to the very weak texture component of the (110) [001] type. In a pole figure, this (110) [0011 orientation is located within the orientation spread between the two main (111) [1121 type textures. Usually the electron diffraction patterns taken at various areas of the specimen are very simple ones, i.e., for any one area the pattern consists only of sharply defined spots of a single orientation. In some areas, however, more or less continuous rings of weaker intensities are superimposed on a simple pattern, indicating the presence of a wide range of additional orientations. In order to understand in detail the recrystallization of this cold-worked crystal, the recrywtallization characteristics of each of the various deformation texture components must be examined. This can best be done by using a high-temperature stage and transmission electron microscopy techniques, whereby small areas corresponding to the various texture components can be selected individually for examination. The present paper presents results obtained by this method. MATERIAL AND METHOD Specimens were prepared from a previously studied1 single crystal of a commercial grade 3 pct Si-Fe alloy with an initial orientation (110) [00l], cold-rolled 70 pct from 0.014 in. to 0.004 in. in thickness. Thin foils were prepared by electrolytic polishing as described in the earlier paper.' Specimens of this thin foil were then mounted in a high temperature stage similar to the one designed by Whelan.6 A direct current was used as the heating source. The temperature of the heating grid was calibrated by means of a Pt vs Pt-10 pct Rh thermocouple in a vacuum chamber (0.01 to 0.02µHg). Maximum variation within the temperature range of 250o to 000°C was about ± 25°C. After the desired areas were selected for examination, the specimen was heated to a low temperature for some time while the selected area was constantly watched. When no further change in structure and orientation could be observed, a higher temperature was applied. Photomicrographs and diffraction patterns were taken from time to time during examination, with the heater temporarily turned off* while the photographs were

Jan 1, 1962

By L. W. Page

PREVIOUS to the introduction of the motor vehicle the broken stone or macadam road met the conditions of rural horse-drawn traffic better than any other type of road, but under fast motor traffic it has been proved to be quite unsatisfactory, and necessitates high maintenance charges. Such a road depends for its success upon the fact that the rock dust fills the voids between the stones and acts as a cement or binder. Under ideal conditions it should be constructed of rock so suited to the volume and character of horse traffic that only enough fine dust is worn from the stones of which the road is composed to take the place of that carried off by wind and rain; and when these conditions are met, the fine dust resulting from the wear. of traffic forms with the stone a smooth, impervious shell, shedding the surface water and protecting the foundation. With increase in the number and speed of motor vehicles, however, it was soon found that the cost of maintenance also increased, until at the present day highway engineers consider the old method of constructing and maintaining broken-stone roads increasingly inadequate, and are introducing every known type of binding material other than rock dust to cement the stone together. Among the most prominent types of products in use are those produced from our various petroleums. That the value of modern methods of road preservation was appre¬ciated in this country much earlier than we have been accustomed to believe is demonstrated by the recent revival of an old patent which was granted to one John Martineau, of Elbridge, N. Y., in 1834. Petroleum had, of course, not been discovered at that time, but he claims as his invention and improvement "The application of tar, turpentine, or any of that class of tenacious, cohesive substances, reduced before use to a fluid state, and that state used as a cement, to apply to, and combine with sand, gravel, pebbles, and pulverized stone, such as is used for a Mc-Adam road, or cobble stone, the interstices of coarser material being in all cases filled, as well as may be, with sand and gravel and cemented with tar or turpentine, to form the wearing face or surface of streets,

Jan 2, 1914

By A. G. Roach

This paper deals with a plant built under joint agreement between the Canadian and United States Governments to supply the strategic mineral, corundum, at a time when African production was dwindling and war demands still increasing. The operation began in September 1944, retreating the tailings from a former mill by gravity methods, and is still in production (Sept. 1946). In 1942, when it became apparent that South African production would be insufficient to meet mounting wartime requirements of corundum, a survey was made of Canadian sources of the mineral, at the request of the Foreign Economic Administration of the U. S. Government. The investigation' indicated that the quickest and cheapest supply would be obtained by reworking the tailings deposit at Craig-mont, Ontario. Sampling of the dump by Canadian Government engineers revealed that 125,000 tons of tailings, averaging 2.96 pct corundum, was available for retreat-ment. Ore-dressing tests on representative samples of the deposit were conducted by the writer in the laboratories of the Industrial Minerals Section of the Department of Mines and Resources at Ottawa; and gravity concentration on tables was indicated as the most suitable method of treatment. Decision to proceed with the project was deferred until May 9, construction was begun on May 18, and tune-up operation of the plant begun on Sept. IS, 1944. Corundum—Its Properties and Uses Corundum is an oxide of aluminum having the formula Al2O3. Its outstanding characteristic is its great hardness; 9 in the Mohs scale. In this respect it is second only to the diamond. It usually occurs in barrel-shaped crystals in nepheline syenites and other feldspathic rocks deficient in silica. It has a specific gravity of 3.95 to 4.1 and is insoluble and infusible. In color it ranges from white, through red and green, to black. Ruby and sapphire are gem varieties of corundum. Corundum is supplied to industry as closely graded grain.= The coarser roducts (10 to 24-mesh) are used largely for snagging wheels in the steel-castings industry, while the finer grades (from 70-mesh down to flours) find a wide application in the polishing of lenses and for other uses in the optical trade. All sizes of corundum grain are in close competition with synthetic abrasives such as carborundum and alundum. In some fields of application the artificial product is superior to the natural grain but not in' all. The shape of the particle and its behavior under conditions of actual use determine its sphere of employment. The United States is the largest 'Onsumer of corundum, annual consumption in peacetime approaching 3000 tons; during the war this figure was roughly doubled. During the years 1902 to 1913, the bulk

Jan 1, 1948

By A. G. Roach

This paper deals with a plant built under joint agreement between the Canadian and United States Governments to supply the strategic mineral, corundum, at a time when African production was dwindling and war demands still increasing. The operation began in September 1944, retreating the tailings from a former mill by gravity methods, and is still in production (Sept. 1946). In 1942, when it became apparent that South African production would be insufficient to meet mounting wartime requirements of corundum, a survey was made of Canadian sources of the mineral, at the request of the Foreign Economic Administration of the U. S. Government. The investigation' indicated that the quickest and cheapest supply would be obtained by reworking the tailings deposit at Craig-mont, Ontario. Sampling of the dump by Canadian Government engineers revealed that 125,000 tons of tailings, averaging 2.96 pct corundum, was available for retreat-ment. Ore-dressing tests on representative samples of the deposit were conducted by the writer in the laboratories of the Industrial Minerals Section of the Department of Mines and Resources at Ottawa; and gravity concentration on tables was indicated as the most suitable method of treatment. Decision to proceed with the project was deferred until May 9, construction was begun on May 18, and tune-up operation of the plant begun on Sept. IS, 1944. Corundum—Its Properties and Uses Corundum is an oxide of aluminum having the formula Al2O3. Its outstanding characteristic is its great hardness; 9 in the Mohs scale. In this respect it is second only to the diamond. It usually occurs in barrel-shaped crystals in nepheline syenites and other feldspathic rocks deficient in silica. It has a specific gravity of 3.95 to 4.1 and is insoluble and infusible. In color it ranges from white, through red and green, to black. Ruby and sapphire are gem varieties of corundum. Corundum is supplied to industry as closely graded grain.= The coarser roducts (10 to 24-mesh) are used largely for snagging wheels in the steel-castings industry, while the finer grades (from 70-mesh down to flours) find a wide application in the polishing of lenses and for other uses in the optical trade. All sizes of corundum grain are in close competition with synthetic abrasives such as carborundum and alundum. In some fields of application the artificial product is superior to the natural grain but not in' all. The shape of the particle and its behavior under conditions of actual use determine its sphere of employment. The United States is the largest 'Onsumer of corundum, annual consumption in peacetime approaching 3000 tons; during the war this figure was roughly doubled. During the years 1902 to 1913, the bulk

Jan 1, 1948