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By C. J. Frosch, J. A. May, H. G. White, C. D. Thurmond

Gallium phosphide epitaxial layers were grown from the vapor phase on undoped single-crystal galliurn arsenide substrates in silica tubes by an open-tube wet-hydrogen process. The epitaxial layers were grown over a range of water pressures at three substrate temperatures. Excess donor concentrations were determined by surface barvier capacitance measurelrzents without removing the layers from the substrates. The excess dmlor concentration, ND-NA, is fo~ind to vary approxilnately inversely with the pressure of water added to the hydrogen carrier gas. This is the relationship that would be expected for singly ionized silicon donors on gallium sites in extrinsic galliunz phosphide, with the silicon coming from the SiO generated by the reaction of hydrogen with the silica tube. An increase in the partial pressure of water in the hydrogen stream decreases the SiO pressure. The results indicate that ni, the intrinsic hole and electrmt concentration for gallium phosphide at the three substrate temperatures, is smaller than the concentration estimated from available data for the density of states effective masses and the energy gap. Mass-spectrographic measurements confirm that the dono?, introduced into gallium phosphide is silicon. The equilibrium concentrations of silicon in vapor-flown gallium Phosphide have been estimated from available thernzodynamic information that includes the solubility measurements of silicon in gallium phosphide in equilibrium with a gallium-rich liquid phase. Satisfactory agreement with the measured silicon concentrations is obtained. FROSCH1 has described an open-tube process for growing single-crystal Gap from the vapor phase by a GazO transport mechanism. The method depends upon the reaction of H20 in an H2 carrier gas with a heated source of polycrystalline Gap which provides the necessary vapor species. When the temperature of these vapor species is lowered, super saturation occurs and single-crystal Gap will deposit on a suitable substrate. Unintentionally doped single crystals of Gap grown by the wet H2 process in silica tubes are n type. Evidence is presented to show that the donor introduced is silicon, and that a qua si-equilibrium model accounts for the inverse dependence of the donor concentration on the water partial pressure and predicts the magnitude of the donor concentrations. Ainslie et al. experimentally showed a similar inverse relationship between the carrier density and oxygen pressure for GaAs. Emission-spectrographic analyses showed a decrease in the silicon concentration with increasing oxygen overpressure for GaAs. Cochran and Foster suggested the theoretical possibility of suppressing silicon contamination by using Ga20 generated by the reaction of gallium with water vapor. 1) EXPERIMENTAL The apparatus and procedures are essentially the same as those described by Frosch.' The apparatus consists of a 25-mm-ID SiO2 tube extending through a controlled high-temperature flat zone for the location of the polycrystalline Gap source and a downstream temperature gradient falling at a rate of about 14°C per cm. The latter provides the region of super saturation for the location of the single-crystal substrate. The partial pressure of water in the inflowing hydrogen stream, pA2, O was controlled by mixing me-tered proportions of dry H2 with H2 saturated with H2O vapor at 0°C. The total gas flows were about 200 cu cm per min in all experiments. The Gap sources were prepared by pulverizing boat-grown polycrystalline ingots to pass a 20-mesh sieve. The substrates were cut from an undoped single-crystal boat-grown GaAs ingot purchased from Monsanto. This ingot had a carrier concentration of about 1015 atoms per cu cm, a resistivity of about 5 ohm-cm, and a mobility of about 5000 sq cm per v sec at 25°C. Substrates with dimensions of 1 by 1 by 5 x lo-' cm were employed. The growth faces were chemically polished (111) arsenic faces. Epitaxial layers, at least 7.5 x 10-3 cm thick, were grown,. This required from 1 to 24 hr depending upon the Pii2Q values and the temperatures. In all of the runs, the source temperatures were 50°C higher than the substrate temperatures. Samples were prepared

Jan 1, 1968

Taking the Long View THE present international situation has serious implications for this nation. The possibility of total war is no more appalling than the threat of making the United States permanently into an armed camp. A period of ten years under such conditions could mean a Communist victory without firing a shot-if the present trend toward statism is allowed to continue. As individual citizens and as members of the mining profession we have the power to oppose the march toward socialism. We must not adopt shortsighted policies dictated by self-interest, but must endeavor to size up the situation as a whole and act according to what will be best in the national interest. The economic picture for the metal mining industry under present emergency conditions is apparently bright. Demand for metals exceeds supply. But there is danger that fluctuating prices will bring Government regulation. Care must be exercised in our pricing policies, or the calamity of Government intervention will be inevitable. President Truman's "loophole" reference to percentage depletion early in the year caused a brief flurry of excitement, but now that the immediate threat is over the industry has lapsed into sommolence on this subject. Special tax privileges accorded the mining industry because of inherent risks should be guarded by a continuing propaganda campaign to educate Congress and the public. If this is not done we may find ourselves losing the necessary tax protection which we now possess by a capricious act of legislation. Stockpiling minerals from abroad certainly lengthens the life of our own mineral resources. The present consumer demand for the base metals indicates foreign sources of supply for stockpiling. However, this is only one facet of the problem. For strategic military reasons it is necessary that the United States have quick sources of all minerals within our national boundaries. Undeveloped mineral deposits do not meet this need so that where it is possible to encourage our own mineral development by stockpile purchases, it should be done. A need exists for an overall controlling agency that would make purchases for the stockpile according to military necessity, current metal market conditions, and so as to strengthen the mining industry. In the course of the history of the United States we have been engulfed in several wars by the necessity of protecting our economic rights abroad trading privileges-and also because of moral obligations. Disregarding the moral side, it is difficult to reconcile fighting wars to protect world freedom of trade when in peacetime we attempt to restrain such trade by tariff barriers. When it comes to accepting subsidies from the Government in one form or another it is difficult to overlook the immediate personal gains and see in the future that where the Government lays out capital it becomes a partner in the business and not a silent one. It is apparent that hope for the traditional American way of life cannot be bought without some self-sacrifice; and we cannot wait for the other fellow to start it because it is the responsibility of each individual citizen. By taking the long view our course should be apparent and not diverge sharply from our own personal benefit.

Jan 10, 1950

By R. Rocca, M. B. Bever

THE adiabatic elastic deformation of a body is accompanied by a change in temperature. This phenomenon is known as the thermoelastic effect. Under adiabatic conditions the temperature of a metal bar is decreased by an elastic elongation and is increased by an elastic compression. All materials which elongate on heating behave in this manner. The sign of the thermoelastic temperature change is reversed for the few materials which have a negative coefficient of thermal expansion. The following equation for the thermoelastic effect can be derived from fundamental thermody-namic theorems, as shown in the Appendix: dT8 =-a1/cs T dss [1] Cs In this equation, T is the absolute temperature, S is the entropy, a, is the coefficient of linear thermal expansion, cs' is the heat capacity per unit volume at constant stress and s is the stress (positive in tension). Eq 1 can be applied to small, but finite changes in stress in the following form: ?Ts =- a1/cs T?ss [2] The sign of the temperature change AT is opposite to that of the change in stress s for materials which have a positive coefficient of thermal expansion. Eq 2 has been verified for many different materials and stresses at room temperature. No previous publication appears to have been devoted to an in- vestigation of the thermoelastic effect over a range of temperatures. Review of Literature Lord Kelvin (W. Thomson) presented a general theory of the thermoelastic effect in 1851' and later applied it to a solid, subject to an arbitrary system of stresses'. His analysis was based on a cycle of isothermal and constant-strain transformations and led to Eq 2 above. Even today, one of the clearest expositions of the thermoelastic effect is found in Lord Kelvin's article on elasticity in the Ninth Edition of the Encyclopedia Britannica (1878). R. ROCCA, Junior Member, and M. B. BEVER, Member AIME, are Research Assistant in Metallurgy and Associate Professor of Metallurgy, respectiuely, Massachusetts Institute of Technology, Cambridge, Mass. AIME New York Meeting, Feb. 1950. TP 2760 E. Discussion (2 copies) may be sent to Transactions AIME before APT. 1, 1950, and is scheduled for publication Nov. 1950. Manuscript received Oct. 15, 1949.

Jan 1, 1951

By J. D. Miller, M. Misra

The processing strategy for the effective separation of bitumen from low grade (<l0 weight percent bitumen) Utah tar sands by a hot water process differs significantly from that used for the processing of high grade (> 10 weight percent bitumen) Utah tar sands. Excellent separations (coefficient of separation = 0.9) can be achieved for high grade Utah tar sands by intense hot water digestion followed by a modified froth flotation step. Such a technique is ineffective for low grade tar sands. In order to change the characteristics of the low grade tar sand an attempt was made to enrich the bitumen content of the feed to greater than 10 weight percent by recycle of bitumen concentrate to the digestion stage. However, the quality of the separation was not improved under these circumstances. Similarly feed enrichment by heat treating the low grade feed with recycled concentrate prior to digestion did not improve the separation. More successful separations of low grade Utah tar sands were finally achieved by modification of the viscosity of the low grade bitumen with controlled addition of diluent. These results of the hot water separation tests and variations in the quality of separation are interpreted in terms of the physical properties of the bitumen and the surface bonding forces operative at the bitumen-sand interface.

Jan 1, 1981

By R. G. Knickerbocker

THE copper smelter and refinery of The Messina (Transvaal) Development Co. Ltd., at Messina, South Africa, was erected in 1920 and 1921, but initial operations were deferred until late in 1922 on account of the collapse of the copper market in the interim. Because the anticipated production was to be only 20 tons of copper per day from a high-grade matte containing 60 per cent copper, and because the ore did not contain gold or silver in quantities sufficient to pay for separation from the copper bullion, it was decided to design the plant along lines quite different from the modern smelteries treating large quantities of sulfide ores carrying appreciable amounts of gold and silver. The plant was built, therefore, for the production of copper by the Nicholls-James process. By this method two-thirds of the copper matte produced was roasted in a Merton calciner and charged into a bath of the remaining one-third portion of unroasted matte in a reaction furnace. The original design was not only novel in providing for the Nicholls-James process, but also in comparison with new plants built elsewhere, because of factors inherent in the locality. Sources of supply for machinery were very remote; it takes three months after the placing of an order to accomplish delivery of machinery into Messina from the United States. Native labor was available at 30 to 40¢ per 8-hr. shift. These factors permitted plant design which provided no overhead cranes, no matte ladles, no slag pots or other usual mechanical means of transportation between departments. The design resulted in a compact simple plant with furnaces arranged close together and. terraced so as to provide for gravity transfer of molten material from one furnace to another and for manual disposal of products. Fig. 1 shows the relative location of furnaces. The three furnaces are parallel on successively decreasing elevations. A superimposed feed floor was provided above the furnaces. All three furnaces were provided with coal-dust burners served from a Bonnot system of coal-dust transportation, and the waste gases were discharged into waste-heat boilers.

Jan 1, 1932

NEW MEMBERS The following list comprises the names of those persons who became members during the period of May 10, 1918, to June 10, 1918. ABEEL, GEORGE H., JR., Cons. Min. Engr., .4111 Lafayette Ave., St. Louis, Mo. ALLEN, CARL A Metal Min. Engr., U. S. Bureau of Mines, Butte, Mont. BECKER P. FRANK Engr., Lightner Min. Co., 35 Nassau St., New York, N. Y. BOCK, JAMES H., Steam Shovel Foreman, Chino Copper Co., Santa Rita, N. M. CARRON, FRANK X., Civ. and Min. Engr Rock Springs, Wyo. CROWE, THOMAS B., Mill Supt., Portland Mill, Portland Gold Min. Co., Victor, Colo. DOBSON, PERCY GRENSIDE, Min. Engr. and Geol., Crow&apos;s Nest Pass Coal Co., Fernie B. C., Canada. ESTABROOK, W. H., Capt., 3d Bat. 20th Engineers, A. E. F., Care postmaster, N.Y. FRASER, 0. B. J., Engr., International Nickel Co. of Canada, Ltd., Port Colborne, Ont., Canada. GARRIDO,. MANUEL F., Min. Engr 109 W. Myrtle St., San Antonio, Tex. GRODSKY, VLADIMIR ALEXANDROVITCH, Cons. Engr., Motor Products Corpn., Detroit, Mich.

Jan 7, 1918

By T. L. Joseph

Blast furnaces are most efficient thermally when the CO2 in the top gas is highest. Oxygen introduced in the air blast is converted to CO in the combustion zones. The extent to which CO, generated in front of the tuyeres, is converted later to CO2 depends upon the ratio of ore to coke in the charge and the degree to which CO2, formed by reduction of iron oxides with CO, reverts to CO by the secondary reaction C + CO2 = 2CO. About 300 to 400 lb. of carbon&apos; per ton of pig iron is normally involved in the solution-loss reaction or direct reduction of FeO with carbon, which produces the same over-all results; that is, lower CO2 in the top gas. Rich2 has recently reported a reduction in fuel consumption at slower rates of blowing on two furnaces in spite of higher heat losses per ton of iron. Lower fuel consumption at slow operating rates was due to more complete reduction of the ore that resulted in higher CO2 in the top gas and consequently more efficient use of carbon. Kinney3 has reported substantial savings in fuel as a result of crushing and sizing the ore charge. Improvements in practice brought about by sintering magnetite concentrates, flue dust and fine ores have been due to the establishment of conditions favoring more complete reduction of the ore in the upper part of the furnace. The extent to which oxides and fluctuations in composition in pig iron affect the quality of steel and finished product needs further study. There is evidence that more thorough preheating and reduction of the ore in the upper part of the furnace tend to give a better quality of iron. Bogatzkii4 found from laboratory work that the amount of oxygen entering electrolytic iron, melted under various slags, was directly proportional to the concentration of free FeO in the slag and inversely proportional to the basicity of the slag. Herty and Gaines5 concluded that the silicate content of open-hearth steel before deoxidation is related to the concentration of silica in the pig-iron charge, indicating that most of the persistent inclusions are silica from the iron. They also found that

Jan 1, 1936

By T. L. Joseph

Blast furnaces are most efficient thermally when the CO2 in the top gas is highest. Oxygen introduced in the air blast is converted to CO in the combustion zones. The extent to which CO, generated in front of the tuyeres, is converted later to CO2 depends upon the ratio of ore to coke in the charge and the degree to which CO2, formed by reduction of iron oxides with CO, reverts to CO by the secondary reaction C + CO2 = 2CO. About 300 to 400 lb. of carbon&apos; per ton of pig iron is normally involved in the solution-loss reaction or direct reduction of FeO with carbon, which produces the same over-all results; that is, lower CO2 in the top gas. Rich2 has recently reported a reduction in fuel consumption at slower rates of blowing on two furnaces in spite of higher heat losses per ton of iron. Lower fuel consumption at slow operating rates was due to more complete reduction of the ore that resulted in higher CO2 in the top gas and consequently more efficient use of carbon. Kinney3 has reported substantial savings in fuel as a result of crushing and sizing the ore charge. Improvements in practice brought about by sintering magnetite concentrates, flue dust and fine ores have been due to the establishment of conditions favoring more complete reduction of the ore in the upper part of the furnace. The extent to which oxides and fluctuations in composition in pig iron affect the quality of steel and finished product needs further study. There is evidence that more thorough preheating and reduction of the ore in the upper part of the furnace tend to give a better quality of iron. Bogatzkii4 found from laboratory work that the amount of oxygen entering electrolytic iron, melted under various slags, was directly proportional to the concentration of free FeO in the slag and inversely proportional to the basicity of the slag. Herty and Gaines5 concluded that the silicate content of open-hearth steel before deoxidation is related to the concentration of silica in the pig-iron charge, indicating that most of the persistent inclusions are silica from the iron. They also found that

Jan 1, 1936

By R. P. Aikman, F. G. Miller, J. M. Podgursky

In response to the growing demand for low-sulfur coking coal for iron-making, the coal industry is continually striving to perfect methods for cleaning coal to acceptable ash and sulfur levels while maintaining maximum product yield. By present standards the industry has adequate processes for cleaning coarse coal, (i.e., +28 mesh) at almost any desired specific gravity. However, in the case of fine coal (i.e., -28 mesh) neither of the two existing processes-froth flotation and hydrocycloning-in its present state of development yields products that are comparable in ash and/or sulfur content to products normally obtained from coarse coal processes. The work outlined in this article is part of a larger study directed toward maximum exploitation of froth flotation for fine coal processing. The concepts and data presented are now serving as a basis for designing fine-coal circuits in which improved efficiency is obtained by optimum use of froth flotation with other fine-coal processing methods.

Jan 7, 1967

By J. Quigley

As the outcrop mines in the West developed into underground operations, systems of ground support were gradually evolved. In the early coal mines there was little need for support except near the dirt line in portals, where stone masonry was common. Where the top was shaley or broken, native pine props with light cross bars and legs furnished enough support even in Utah&apos;s 25-ft coal seams. As depth of workings increased. roofs and backs of the same general nature as those near the surface became more and more unstable and required more and more support. Some coal airways show this tendency very clearly. From the surface down the same type of roof shows deterioration which an experienced eye can translate into a measure of depth under surface rather than change in rock characteristics. Rock bolts, developed by various companies and by the U. S. Bureau of Mines, have become an effective substitute for timber in sections of some metal and nonmetal mines formerly requiring escessive timber support, and further use of war surplus landing mats, chain link fencing, and a new punched channel developed by one of the steel companies has enabled other mines to operate deposits where costs of timber and lack of clearance for timber support would have prohibited mining. The block caving mines have made extensive use of reinforced concrete underground to achieve similar ends under difficult conditions. Steel sets are standard in many Bureau of Reclamation projects, although these are usually covered in with concrete to make the permanent structures the Bureau&apos;s reclamation projects require. But the use of steel in mining operations is limited and has been confined principally to the iron ore mines of Michigan, Wisconsin, and Minnesota. Some mines have installed used rail as posts, caps, and crossbars, but a rail section is not suited for load carrying, and used rails are generally brittle. having a tendency to fail without warning when overloaded. European mines were the first to reach the size of worked out areas and depths of cover resulting in major roof problems. The Europeans resorted to pack walls and masonry walls, in conjunction with timber arched sets. rail arches, and combination timber and rail and steel arches. The give in these pack walls and wooden blocking was supplemented by a hinge in the center of the arch. This design is called an articulated arch Through various refinements of this principle of the support giving graduallv with the load. Toussaint-Heintzmann developed the yielding or sliding arches, in which yield is accomplished by friction in the overlapping joints of the arch. This type has gained widespread acceptance in the Ruhr and Lorraine Basin and is being manufactured by Bethlehem Steel for sale in this country. In North America the anthracite mines in Pennsylvania, followed by certain iron ore mines in upper Michigan and Canada, were the first to employ these arches to any extent. The practice was later adopted by Kennecott at Ruth, Nev., and by others. Despite high initial cost, the use of these arches is growing in many parts of the country because of their suitability in heavy ground. In its present form of manufacture the yield-able arch consists of open U-shaped rolled section with heavy beads on the edge. The open edge of the U is placed toward the wall. The section nests in another section of the same dimensions, and an arch can be built up from rolled radii and tangents of various weights and lengths. Sections are fastened together by U bolts and saddles. The lap on the joint varies from 12 to 24 in., and ordinarily the bolts are tightened with a 1-in. drive air wrench. The arches are spaced with channel struts held by J bolts and saddles. Sections can also be obtained that are composed of various combinations of radii and tangents and true circles. The joints can be placed to bear against anticipated loads and asymmetrical loads imposed by dipping strata. In the arches now being manufactured clearance widths up to 19 ft are obtainable in weights of sections from 9 to 30 lb per ft. The circular cross sections are available in the same weights ranging from 8 to 16 ft diam. At present most of the arches sold are supplied only in carload lots. It is hoped that demand will grow so that distributors can stock various weights and sections to give small operators a chance to try this new type of rock support under their own particular conditions. Several excellent papers have discussed the properties of various sections now manufactured, the dimensions of the sets obtainable, and their application under widely differing conditions. The present article will describe the methods and results of a special use of the arches at Kaiser Steel mine No. 3. Sunnyside, Utah. Problem at Mine No. 3 : In 1953 Kaiser Steel Corp. laid out Sunnyside mine No. 3 to recover coking coal left by the previous operator, Utah Fuel Co.. below workings that had been abandoned in 1928. Two seams had been worked, the upper and lower, separated by 30 to 42 ft of rock. Approximately 10 million tons of coal had been extracted from this area some 3000 ft down the itch from the outcrop to a 1500-ft depth of cover. The mine had been opened by slopes in both upper and lower seams. Sometime in the late 1920&apos;s the lower slope

Jan 1, 1960

Twelve Directors, the Secretary, and ten guests were present. It was unanimously resolved that the sense of this body is that the name of the Institute should be changed to American Institute of Mining and Metallurgical Engineers. Messrs. J. W. Richards and Bradley Stoughton were appointed a committee to formulate the necessary steps for bringing the matter to a vote. The committee in charge of the New York meeting, with Allen Rogers, Chairman, was appointed. The rules of the American Engineering Standards Committee were approved. The Bulletin was presented to the Springfield Arsenal. The sum of $250 was appropriated to the Southern California Section. The By-laws were changed to increase the Secretary&apos;s cash from $500 to $1000. The report of the Treasurer was accepted. Sixty-eight members, thirteen associates, and forty-eight junior associates were elected. Four members were reinstated. The resignations of seven members were accepted. Thirteen members on active duty at the front had their dues remitted. Upon the recommendation of the Finance Committee, it was resolved that the clues of any members who have attained the age of seventy (70) years and have been members for a continuous period of at least thirty (30) years shall be remitted.

Jan 7, 1918

By Allan T. Gwathmey, J. Bruce Wagner, Kenneth R. Lawless

Between 250°and 550°C in oxygen pressures of 10 to 760 mm Hg, the relative oxide thicknesses formed per unit time on the (100), (111), (110), and (320), decreased in this order. The predominant oxide orientation was (001)Fe3O4 and [110] Fe304 A small amount of a-Fe2O3 which exhibited a fiber pattern was observed in all oxides except those formed at 250°c in low oxygen pressures. IN order to understand the properties and behavior of thin films, particularly their role in oxidation reactions, there is needed more experimental information on their structure, composition, and kinetics of formation on clean surfaces of known geometry. The present study was undertaken to obtain such information for thin oxide films formed on single crystals of a body centered cubic metal, iron. Crystals in the form of spheres were used in order to expose all possible crystal planes to the reactant gases simultaneously. Using this procedure the relative rates of oxidation of all planes could be estimated, and those exhibiting, maximum or minimum oxidation rates could be selected for a more intensive study of composition and expitaxy. Since the three types of information were obtained from the same experiment using a single crystal substrate, any differences between rate, composition, and expitaxy on the several planes may be attributed to the influence of the substrate structure. EXPERIMENTAL The starting material for this study was Armco iron rods, 6 in. long and 3/8 or 1/2 in. in diam. The analysis was reported to be 99.8 pct Fe, with major impurities listed as carbon 0.018 pct, manganese 0.027 pct, phosphorous 0.005 pct, sulfur 0.029 pct, silicon 0.005 pct, and copper 0.11 pct. These rods were cleaned with ether and heated in an atmosphere of moist hydrogen at 950°C for three days. The purpose of this treatment was to decarburize the iron and to provide a consistent, uniform grain size for the growth of single crystals. Crystals in the form of rods, up to 1/2 in. in diam and 2 in. long, were prepared by a method similar to that reported by Leidheiser and Buck.2 Spherical crystals, 3/8 and 1/2 in. in diam and having a handle about 1/4 in. in diam by 112 in. long, were machined from the single-crystal rods. After machining, each crystal was etched in aqueous nitric acid to remove the cold-worked metal at the surface. Before each experiment, the crystal was polished mechanically with metallographic papers through number 4/0, and electropolished in a perchloric acid-acetic anhydride mixture by the method of Jacquet and Rocquet.3 The crystal was washed in running distilled water for at least 5 min. The excess water was blotted with a soft paper tissue, and the crystal was placed in an all-glass reaction vessel (See Fig. 1). The crystal was heated at 550°C in hydrogen for at least 8 hr prior to the oxidation in order to reduce any surface oxides and to help relieve any stresses in the metal. For the structure and composition studies, flat faces were cut parallel to (loo), (111), and (110) planes on the iron crystal spheres. The orientation of these faces was checked by a back-reflection X-ray diffraction technique. The faces were within 2 deg of the desired orientation. The flat faces were treated as described above except that prior to electropolishing they were given an additional polish on metallographic felt saturated with twenty-minute levigated alumina. After the crystal was heated in hydrogen for at least 8 hr, the temperature was adjusted to the desired value, and the hydrogen was evacuated. Commercial oxygen which had been purified by successively passing through tubes containing magnesium perchlorate, Ascarite and magnesium perchlorate was admitted to the desired pressure as measured by a mercury manometer. A resistance-wound furnace surrounded the oxidation chamber, and a temperature controller maintained the temperature within ±3°C. The furnace was provided with a small window for observing the crystal. The changes in thickness of the oxide films were followed by observing the interference colors. The oxidation was allowed to proceed until the desired oxide thickness was attained on a given crystal plane. The experiment was terminated by evacuating the oxidation

Jan 1, 1962

Discussion of the paper of Robert R. Abbott, presented at the New York Meeting, October, 1913, and printed in Bulletin No. 82, October, 1913, pp. 2389 to 2400. ALBERT SAUVEUR, Cambridge, Mass.:-Mr. Abbott has certainly made a strenuous effort to ascertain the influence of the various elements on the absorption of carbon by steel-a subject of great importance to those dealing with the case hardening of that metal. Because of the extensive and careful character of Mr. Abbott&apos;s experiments, one is all the more disappointed that his results, as he himself recognizes, are not more satisfactory; for, indeed they leave us just about where we were,-still entertaining uncertain views in regard to the carbon-absorbing power of various alloy steels. It might be asked whether Mr. Abbott&apos;s method of estimating the amount of carbon absorbed-namely, by weighing the specimens before and after the carburizing treatment-was the best one to select. Are not serious sources of error. inherent to such procedure because of the difficulty of satisfactorily removing the earburizing material attached to the specimen ? The method of least squares has certainly failed to solve the problem satisfactorily. By manipulating Mr. Abbott&apos;s results in a different manner I have obtained the following expression: P = 100 - 50 C - 7 Ni + 20 Cr, in which P represents the carbon-absorbing power; C, the percentage of carbon; Ni, that of nickel; and Cr, that of chromium. It is assumed that the carbon-absorbing power of pure iron, or what might be called its carburizability, is represented by 100. Applying the formula, for instance, to a steel containing 0.15 per cent. C, 3 per cent. nickel, and 0.50 per cent. chromium, its carbon-absorbing power would be 100-50X0.15-7X3+20X0.50=81.50; that is, 81.50 per cent. of the carbon-absorbing power of pure iron.

Jan 12, 1913

By W. T. Lundy

THE forms in which sulphur is commonly found-native sulphur, sulphides of many metals and sulphates-are widely distributed throughout the world. The two first mentioned are the principal sources of sulphur. Substantial amounts of sulphur in some form are recovered from gases from industrial plants and from gases from smelters treating other minerals. In recent years, plants have been installed in the United States to recover sulphur in elemental form from sour gases."&apos; The amount of sulphur so produced is small at the present time but undoubtedly will increase in the future. The recovery of sulphur from gases is not covered in this chapter, which is confined to: (1) native sulphur deposits of Texas and Louisiana; (2) those of Italy; (3) other scattered deposits of native sulphur; and (4) pyrites deposits found in many countries of the world.30 Sulphur, a nonmetallic element, occurs normally in well developed bipyramidal or tabular crystals of the orthorhombic system, as well as in stalactitic and earthy masses. The mineral has a distinctive yellow color, which may be dark and discolored by impurities; the streak is white; the luster is resinous; and the fracture is conchoidal to uneven. Sulphur is translucent to opaque; has a hardness of 1.5 to 2.5, a specific gravity of 2.05, and an atomic weight of 32.06.16 The molecular weight of the solid is expressed by the symbol SS and that of the liquid and vapor ranges from S2 to S8, depending on the temperature. Sulphur melts at a temperature between 2340 and 248°F, depending on its crystalline state, to a liquid of dark amber color, the boiling point of which is 832°F. The viscosity near the melting point is about that of water and increases to 50,000 times that of water at a temperature of 380°F, subsequently falling rapidly to a low figure at the boiling point. Crystallization changes slowly from rhombic to monoclinic above 205 °F and in cooling the transformation is reversed. The mineral is a very poor conductor of heat and electricity; it is insoluble in water and nearly all acids and is soluble in cold carbon bisulphide and carbon tetrachloride. It ignites in air at a temperature of 478°F, burning with a distinctive blue flame with evolution of sulphur dioxide.47

Jan 1, 1949

By Robert H. Richards

This truly remarkable machine was built on a preliminary scale in May, 1895. The first full-sized table was built by Mr. A. R. Wilfley, and was used in his own mill in Kokomo Colo., in May, 1896. The first table sold for installation was placed in the Puzzle mill, Breckinridge, Summit county, Colo., in August, 1896. The mill enthusiasts at first hailed it as the cure for all the ills that flesh is heir to in the milling line. A little later it was found to make losses which were serious, and on this account the table succeeded only to a limited extent in displacing the vanners of the gold-mills. Still later, mill-men in a number of districts throughout the country made special studies of the faults of the machine, and devised a number of ways of grouping supplementary machines to overcome as far as possible the losses, and at the same time retain the benefit of the extraordinarily large capacity accompanied by the production of clean concentrates for which the machine has become so justly famous. I hope to make an exhibit of some of these methods in an appendix to my book on ore-dressing which is now in preparation. These experimenters have not written up the subject, and if they possess all the facts they have not given them out for the benefit of the mining profession at large. The object of this paper is to obtain the facts and to present them so clearly that their bearing can be seen by all. To this end two complete series of tests have been planned. One (the present paper), to study concentration of galena in presence of quartz; the other (to follow shortly), to study concentration of chalcopyrite in presence of quartz. Some authorities claim that the table does its best work when treating natural products; by this phrase I mean products which have been crushed to pass through a limiting

Jan 1, 1908

By Alfred E. Hunt

Tars paper is suggested by the appointment on the part of the American Societies of Mechanical and of Civil Engineers of committees upon the subjects of " Standard Tests and Methods of Testing," and " Uniform Methods of Tests of Material used in Metallic Structures," respectively, and by a study of the report of one of these committees, and other papers. Moreover, the writer has had frequent occasion to hear the complahts of tnanufacturers who furnish structural material subject to specifications, that in the tests prescribed, the number of tests required, and the methods of making

Jan 1, 1892

By Neils Hansen

The microstructure of dispersion-strengthened aluminum aluminum-oxide products containing from 0.2 to 4.7 wt pct of aluminum oxide has been examined by optical and transmission electron microscopy, and the flow stress has been determined at room temperature and at 400C by tensile testing. Products were examined as recrystallized and as high-temperature extruded, and the microstructures consisted of a fine dispersion of oxide particles in a matrix divided by respectively recrystallized grain boundaries and subgrain boundaries. The flow stress (0.2 pct offset) at room temperature of recrystallized dispersion strengthened aluminum aluminum-oxide products is the superposition of dispersion strengthening and grain boundary strengthening. This superposition has been found to be linear. The flow stress (a) can be related to the grain size (t) by the Petch equation: ing content of oxide and k is a constant independent of the oxide content. For extruded products a similar relation has been found by replacing the grain size by the subgrain size. The k-value is of the same order for the two types of structure, which shows that the subgrain boundaries are as effective slip barriers as grain boundaries. Tensile testing at 400C of re-crystallized and extruded products shows that oxide dispersion strengthening is very effective, whereas the strengthening effect of grain boundaries and subgrain boundaries is small. THE microstructure of dispersion-strengthened products consists of hard particles finely distributed in a metal matrix. The strengthening effect of the dispersed phase has been fairly well established,1 and it has been found that the size and volume fractions of the dispersed particles are important structural parameters. However, in many dispersion-strengthened products which have been worked and heat-treated during manufacture the matrix is divided into well-defined grains or sub-grains, which may also have a strengthening effect. A model of the matrix strengthening in dispersed products worked during manufacture has been proposed,2 introducing the energy of the structure as a strengthening factor, especially at low temperatures. A difficulty in this model is, however, to relate this (stored) energy to the structural parameters directly observable as for instance grain size. The strengthening effect of the matrix grain size after recrystallization has been in- vestigated for nickel-thoria (TD-Nickel) products3 and for copper aluminum-oxide products. Conclusive results were, however, not obtained as the grain size of TD-nickel was constant. 5 to II , after recrystallization at temperatures from 700 to 1200°C and as the copper products containing 5 to 1 wt pct of aluminum oxide could not be recrystallized even after severe cold reduction and heat treatment at 1050C. For aluminum aluminum-oxide products containing from 1 to 5 wt pct of aluminum oxide it has been shown that the tensile strength at room temperature decreases when an extruded product is cold-worked and recrystallized. The matrix in the extruded products is divided into well-defined subgrains of micron size, and as the grain size of the recrystallized products is about two orders of magnitude higher, it is obvious that grain boundary strengthening occurs. Preliminary results8 have indicated that the flow stress containing no grain boundaries, A is a constant and t is the subgrain size. At elevated temperatures the effect of boundaries is more complex; it has been shown11 that recrystallized products having an oxide content of about 3 wt pct are more creep resistant than extruded material in the temperature range 400° to 600°C, whereas on application of a higher strain rate the tensile flow stress (0.2 pct offset) is higher in extruded than in recrystallized aluminum—5 wt pct aluminum oxide products at temperatures from room temperature to 427°C (800), Finally it has been shown12 that the Brinell hardness at 350°C of extruded products having about the same content of aluminum oxide increases with decreasing grain size, determined by X-ray line-width measurements. The present study was undertaken to obtain a quantitative relationship between the tensile strength and the grain size of aluminum aluminum-oxide products in the recrystallized as well as in the extruded state. The tensile testing was performed at room temperature and at 400uC. The grain size of the recrystallized products was varied by changing the degree of cold-work preceding the recrystallization heat treatment. In extruded products grain (or subgrain) size variations were obtained by high-temperature heat treatment after extrusion. EXPERIMENTAL a) Materials. Aluminum aluminum-oxide products have been manufactured by consolidation of aluminum powder covered with a layer of aluminum oxide formed during powder manufacturing. The products examined were manufactured from atomized powder containing

Jan 1, 1970

By A. L. Holley

THERE is a growing demand for pure and cheap material for fine open-hearth steel ; a material not only very free from phosphorus, but from carbon and silicon; so that it may he rapidly converted into steel. Iron and steel scrap are not trustworthy as to quality, and they are often dear. There are three methods of purifying cheap materials for the open hearth. 1. Mechanical puddling, as done at Creusot, which removes 90&apos; per cent. of the phosphorus from the pig iron. 2. Krupp&apos;s washing process (the conduct and results of which I fully described in a former paper*), which eliminates 70 to 80 per cent. of the phosphorus and most of the sulphur and silicon from pig iron. Neither of these processes would sufficiently purify, for very fine steel, those very impure pigs which are cheapest in many parts of the United States: 3. The process of producing directly from the ore an iron which is practically pure chemically, although mechanically mixed with the impurities of the ore. This is the oldest of iron processes ; one form of it, the Catalan forge, employed to produce charcoal blooms, is still in use, but its great cost is rapidly throwing it out of competition. Among the modern attempts to produce iron direct from the one, on a large scale and at a cheap rate, several have been in various respects successful. Dr. Siemens&apos;s process of treating a ton and a half or more of ore and the coal to deoxidize it, in a rotating gas furnace, and bringing out, in some four hours, a ball of chemically pure iron so soft that the fluid and impure slag may be squeezed out of it, is the most attractive and the most highly developed of all the modern direct processes. I have watched it, from time to time, since 1874, and have noted a steady improvement. It may now be said to have passed the experimental stage, although, like older processes, it must be adapted by practice to special materials. The cause which has been more potent than all others, including the defects of the best direct processes, to bring these processes into disrepute, is the waste-ful treatment of the direct product. With one or two exceptions (when failure was due to other and obvious causes), the direct product has been made into wrought iron (weld iron). Even Dr. Siemens has, at Towcester, in England, and at Park, Bro. & Co.&apos;s, in Pittsburg, set up his apparatus for this purpose. Is it likely that

Jan 1, 1880

By William A. Johnson

THE fundamental role of diffusion in many reactions occurring in solid metals has long been recognized, and there have been careful measurements of rates of diffusion in numerous alloy systems, but our understanding of the atomic mechanism by which diffusion occurs is scarcely in an advanced state 1-3 It is doubtful that this mechanism can ever he directly ascertained, rather, all imaginable mechanisms must be examined and the one that is in best accord with such data as can be obtained from suitably chosen experiments should be selected Because of its relative simplicity, diffusion in a system containing only one kind of atomic species-commonly called self-diffusion-is of considerable theoretical interest It may be expected that diffusion theory will not be advanced appreciably until a wide variety of diffusion experiments-of which diffusion in a chemical concentration gradient and self-diffusion are two important types-are carefully performed and inter-compared Aside from the purely theoretical interest in self-diffusion measurements, such studies will be of considerable engineering importance The rate of any process in a pure metal requiring the movement of atoms, of which recrystallization and creep are two familiar examples, will be understood more readily with the aid of self-diffusion data † Self-diffusion implies the diffusion of something into its exact counterpart, the detection of such a process is patently impossible, and it is-necessary to substitute for it the diffusion of one isotope (in this case radioactive) into another isotope (in this case stable) of the same chemical element There is, however, no reason to suppose that a radioactive atom will not diffuse at the same rate as its stable isotope, for all of the isotopes of the same element have exactly the same chemical properties, neither the difference in nuclear energy nor the difference in mass would be expected to exercise an important influence in this phenomenon In this sense, self-diffusion may be thought of as the diffusion of radioactive atoms down a radioactivity concentration gradient, just as usual diffusion is the diffusion of one kind of atone down its chemical concentration gradient The first measurements of self-diffusion ii ere made by von Hevesy4-6 using the radioactive lead isotope thorium B in ordinary lead The recent development of means for producing artificial radioactive elements has made possible similar measurements on gold,7,8 copper,2,9 and zinc 10 11 Many of the data that have been obtained are rather poor, and no adequate reason has been given for their poorness, it appears, however, that the unsatisfactory results are characteristic of the particular experimental procedure employed, and not of self-diffusion measurements in themselves The experimental technique that has yielded the poorer results is the deposition of a thin layer of radioactive atoms on the surface of a specimen and the determination of the rate of inward diffusion

Jan 1, 1941

By J. T. Eash, E. M. Wise

In a previous communication1 the improvement in slrength, harden-ability and color, occasioned by replacing gold in a typical gold-silver-copper alloy by various amounts of platinum, or palladium, was discussed. In the present paper the results of further studies upon the constitution and the nature of the hardening transformation in these alloys are presented. This research may be summarized as follows: 1. The liquidus and solidus have been determined for the alloys of the palladium and platinum series. Cooling curves were utilized for determining the liquidus of the palladium alloys but this method proved unsuitable for the platinum alloys so that a novel quenching method was utilized for the latter. Both the liquidus and solidus of the palladium alloys increase steadily with the palladium content. The liquidus of the platinum alloys increases rapidly with the platinum content, while the solidus temperature increases with the platinum content up to about 14 atomic per cent platinum, but suffers no further increase with additional increments of platinum up to 20 atomic per cent at least, owing to a peritectic reaction. 2. Palladium, and even more effectively platinum, reduces the rate of grain growth. Owing to this fact and to the increase in the solidus temperature, "overheating" does little or no damage to alloys containing reasonable quantities of these elements. This is confirmed both by tensile tests and metallographic examination. 3. The excess phase present in one of the high-platinum-content alloys has been isolated and chemically analyzed and was found to consist almost wholly of platinum, gold, and copper, evidently derived from the compound AuCu, by the partial replacement of gold by platinum. 4. The variation in the solubility of this platinum-content phase in the alpha solid solution with the temperature has been determined. This

Jan 1, 1933