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By R. W. Gurry

In a series of charts this paper presents the composition of all gas mixtures, composed of the elements carbon, hydrogen, oxygen and nitrogen, which at temperatures from 1000° to 1800°F are in equilibrium with (1) austenite of various carbon contents, (2) iron and iron carbide, (3) graphite, (4) iron and its oxide. THIS paper presents the results of calculations made to determine the proportions of CO, CO2, CH4, H2, H2O and N2 in gas mixtures which, at temperatures from 1000" to 1800°F, satisfy, individually, the following conditions: (1) equilibrium with carbon steel of specified carbon content throughout the stable 7 iron region; (2) equilibrium with iron and iron carbide, both above and below the eutectoid temperature; (3) equilibrium with graphite; (4) equilibrium with iron and its oxide. From these data a new type of chart has been prepared which permits one to determine, from a room-temperature analysis of the furnace gas in question, the effect of the gas upon the steel at furnace temperature. Thus a guide is provided as to the carbon content which will result and as to the possibility of oxidation or sooting. All of the atmospheres commonly used in the commercial heat treatment of steel are composed of some or all of the simple constituents CO, CO2, CH4, H2, H2O and N2, and also in some cases oxygen or higher hydrocarbons. As the gas mixture is heated certain alterations in the proportions of the constituents take place, and at the temperature of the furnace the composition is, in general, not at all that of the entering gas. If equilibrium in the gas phase is presumed a calculation involving the use of certain fundamental data predicts for a certain temperature the carburizing, decarburizing, or sooting characteristics of a given atmosphere, and, upon the additional assumption of equilibrium between gas and metal, also the oxidizing ability of the gas and the ultimate carbon content of the steel. The extent to which these predictions are fulfilled will depend upon how closely the assumptions of equilibrium are realized in any particular case. Although at lower temperatures equilibrium is often not reached, there is considerable evidence indicating that above about 1000°F the approach to equilibrium in the gas phase is generally substantially complete, particularly in the vicinity of the steel which acts as a powerful catalyst in promoting reactions in the gas phase. The extent of the gas-metal reactions is commonly affected essentially by the sojourn at temperature; equilibrium with respect to carbon, for example, is accomplished simply by continuing the treatment long enough. However close the approximation of equilibrium may be in any instance, the above mentioned calculation indicates the condition of the steel at equilibrium, and at the present time this is the only basis of control of a furnace atmosphere. The effect at elevated temperature of a gas of a certain composition at room temperature upon a given steel has customarily been judged by first calculating from gas equilibrium constants the proportions of the gas constituents at the temperature of the steel, then comparing certain of these with the proportions known to be in carbon or oxygen equilibrium. This process is tedious and time-consuming, in particular because the calculation generally involves a series of successive approximations; and since some knowledge and familiarity with this type of computation are required, not everyone needing the information has been, in the past, in a position to obtain it. By making a series of equilibrium calculations, combining with fundamental data for gas-metal reactions, and plotting the results in a special way, a chart has been prepared which enables anyone

Jan 1, 1951

By T. S. Lundy, R. E. Pawel, F. R. Winslow, C. J. McHargue

The volume-diffusion coefficients of Nb-95 and Ta-182 in niobium have been measured over the temperature range 878° to 2400°C. High-temperature specimens (T 21500°C) were sectioned by conventional lathe and grinding techniques while low-temperature specimens were sectioned by an anodizing and stripping technique previously described. Over a range of more than ten orders of magnitude in diffusivity, the self-diffusion data is well-represented by the equation: D = (1.1+ 0.2) exp [- (96,000 * 900)/RT ] cm2/sec Upward deviations from this line are explained by short-circuit diffusion in combination with the loss of resolution of the sectioning techniques. Oxygen contamination within the range 100 to 450 ppm was found to have little or no effect on the self-diffusivitj 01 niobium. In a limited number of measurements, the diffusivity of Ta-182 in niobium was found to be about half that of Nb-95 in niobium. These data may be described by D = (I.0+0.90.5)exp [- (99,300 * 2400) /RT ] PREVIOUSLY reported studies of self-diffusion in niobium were by Resnick and Castleman1 and Peart, Graham, and Tomlin.2 The data of Resnick and Castleman over a temperature range 1585" to 2120°C show considerable scatter but. can be represented by D = (12.4 *0.8) exp [-(105,000+3OOO)/RT] cm2/sec The limited data of Peart, Graham, and Tomlin follow the equation D = 1.3 exp (-95,00O/RT) cm2/sec In view of recent diffusion data for ß zirconium3 and 0 titanium4 in which Arrhenius-type plots do not yield straight lines and of the potential high- temperature uses of niobium and its alloys, we thought it important to investigate the diffusion behavior of this bcc refractory metal over a large temperature range. This has recently been done for molybdenum,5 chromium,6 vanadium,"" and tantalum.9 Niobium was a particularly suitable material for this study largely because of the development of an anodizing and stripping sectioning technique which enables diffusivities as small as l0-19' sq cm per sec to be determined accurately.10 In addition to self-diffusion data, data were obtained for the diffusion of Ta-182 in niobium and for the effect of varying oxygen content on self-diffusion. I) EXPERIMENTAL PROCEDURE Materials. The niobium was obtained from three sources: 1) melting stock from Shieldalloy Corp., 2) electron-beam melted single crystals, 1/2 in. diameter, from Semi-Elements, Inc., and 3) oxygen-doped, electron-beam melted single crystals from Materials Research Corp. The melting stock was electron-beam melted and specimens 5/8 in. diameter by 1/2 in. long were machined from the center of the bar. The analysis supplied by the vendor and an interstitial analysis of one of the specimens are given in Table I. The single crystals (type 2 above) were cut with a jeweler's saw to specimens about 3/8 in. long. The interstitial analysis of this material is given in Table 11. This material was used

Jan 1, 1965

THE metal iron has physical and chemical properties which are somewhat different from those of steels, but a knowledge of the pure metal is a useful starting point in studying the behavior of steels. Solid iron exists in two different crystalline forms, called alpha (a) and gamma (?) iron, the former being the ordinary form at room temperature. When heated above the "A2 point," 768 C (1414 F), the metal becomes nonmagnetic, and at the "A, point," 910 C (1670 F), it undergoes a change in crystalline form to become gamma iron. In the range 768 to 910 C, it is sometimes called beta (ß) iron to distinguish it from the magnetic alpha, but the two are identical in crystal structure. When gamma iron is further heated to 1400 C (2552 E), it changes into delta (d) iron, which is identical with beta or non- magnetic alpha iron. Pure iron melts (in an inert atmosphere) at 1537 C (2800 F); the melting point is generally lowered by alloys or impurities. PROPERTIES OF IRON AT HIGH TEMPERATURES Many of the properties of iron undergo abrupt changes at the transition temperatures.1 For example, in heating through the A, point, a sudden shrinkage in volume occurs. Similarly, melting is attended by sharp physical changes such as an increase in volume. Table 16-1 contains a summary of the measured physical properties of pure iron at several temperatures. Usually the properties change smoothly within the range of stability of a given form, but this is not always true. For example, the specific heat reaches a sharp maximum at the A2 point although no trans- formation occurs. (See Fig 14-1.) Solvent Powers of Liquid Iron. Liquid iron is capable of dissolving most of the other metals and many nonmetallic elements as well. Of the metals that are liquid at the melting point of iron, only lead, silver, and bismuth refuse to dissolve to an ap-

Jan 1, 1951

By H. W. Russell, Paul D. MILLER

IT is known that austenitic chromium-nickel steels that have free carbide in the grain boundaries are subject to intergranular corrosion. It is difficult to detect such a susceptible condition in a fabricated article because present test methods require a sample section for examination and in most cases this is difficult to obtain. The question of the nature and prevention of intergranular corrosion in austenitic stainless steels have been ably discussed by Bain and co-workers1-3 and by other investigators.4-10 The present methods of study subject samples to corrosive conditions in such reagents as the Strauss solution, a. mixture of copper sulphate and sulphuric acid. Such tests usually require at least 72 hr. to run. Various methods of measuring the degree of sensitization have been employed, such as the measurement of electrical resistivity, magnetic measurements, measurement of the degree of cracking produced on bending over a mandrel, and microscopic studies. The detection of carbides at the grain boundaries by metallographic polishing and etching methods is tedious and requires a skilled operator. A recent report on such methods of carbide detection is given by the American Society for Testing Materials Subcommittee VI of Committee A-10 11 and by Arness.12 The present investigation was undertaken to develop a simple test procedure for detecting carbide precipitation or susceptibility to intergranular corrosion. The test is designed for use in the plant and for the testing of fabricated structures. Carbide precipitation, the factor leading to susceptibility to corrosion, is produced by heating the alloy in the temperature range 800° to 1600°F., as in welding, in improper annealing or in service where such temperatures are met. The connection between such precipitation and susceptibility to corrosion has been thoroughly discussed, as has been the use of stabilizing addition elements to prevent precipitation. EXPERIMENTAL METHOD A small area of the steel under test is subjected to an anodic treatment in a cell that can be clamped onto a sample or an actual structure. The cell and electrical circuit used are illustrated in Fig. I. The cell C is lead, joined to the steel plate D and insulated from it by a short piece of rubber tubing E. The cell is forced tightly against the steel plate by a spring or clamping device. The seal formed by the rubber against the steel plate is sufficient to retain the liquid bath inside the cell. The spot treated can be made any shape desired, depending on the shape of the rubber gasket. The cell illustrated polishes a circular spot about 3/8-in. diameter. The bath consists of 60 per cent (by weight) sulphuric acid to which is added 5 ml. per liter of Glycyrrhiza extract (U.S.P.). The cell requires about 2 to 2.5

Jan 1, 1941

By M. Van Weyenbergh, G. Van Esbroeck

The copper mines of the Katanga region in the Belgian Congo lie along the same mineralized belt as those of Northern Rhodesia. There are two distinct types of deposits in that belt, the dolomitic and the quartzitic. In the dolomitic type the metallic minerals are found in a dolomitic limestone country rock. Through oxidation and enrichment, large deposits of high-grade oxidized copper ores were formed, some of which are being worked by the Union Minière du Haut Katanga. Such deposits are all in Katanga. The quartzitic deposits are found in Katanga and Northern Rhodesia. Here the primary mineralization occurred in sandstones and quartzites, in horizons stratigraphically lower than the dolomites. These rocks are not favorable to secondary enrichment and the oxidized zone is poorer than the sulphide zone, which alone contains the ore. There are also in Katanga a few ore-bearing veins. One of them is being worked in the Prince Leopold mine at Kipushi. Prince Leopold Mine The Kipushi ore body fills a fault vein and invades the wall rocks more or less extensively by metasomatic replacement. The vein strikes north-northeast and south-southwest and dips to the west. The variable dip averages 60' to a depth of 300 ft., and more uniformly 80' below 400 ft. In the upper section the average width is 200 ft. and below the width is about 150 ft. The length of the ore body is 2300 feet. The eastern side of the vein—the footwall—is dolomitic and contains irregular masses of ore sometimes extending 100 ft. or more from the main

Jan 1, 1940

By Frederick Beckett

WIDESPREAD experimentation has been conducted in recent years to devise a means of preventing intergranular corrosion in austenitic chromium-nickel steels of the 18 per cent chromium-8 per cent nickel type. Additions of titanium to these steels have been used commercially to overcome this difficulty, as advocated by Krupp of Germany, and the latest literature reference concerning improved details of this method is the article by Bain, Aborn and Rutherford.1 Extensive work by the present authors has shown columbium also to be a particularly valuable agent for inhibiting intergranular corrosion. This paper does not deal with steels that are largely or wholly aus-tenitic ; it is limited to a discussion of the results obtained through the use of titanium and columbium in plain high-chromium steels. For many years titanium has been used commercially by some steelmakers as a cleanser, and to a lesser extent as a hardener, but then in greater per-centages. The results of the work to be described disclose that titanium and columbium in proper proportions act as effective softeners in the high-chromium steels. It is well known that chromium intensifies the hardening effect of carbon in steel; it imparts pronounced air-hardening properties within a rather wide range of chromium content; it provides increased ductility in steels of given strength and hardness; and it enhances resistance to corrosion and oxidation at elevated temperatures to a marked degree. However, in applications requiring a combination of some of these valu-able properties great hardness is frequently a detriment rather than a merit. When the objective is a soft and ductile steel having optimum corrosion resistance, the producer strives for a carbon content as low as commercially practicable.

Jan 1, 1933

By Rex B. McLellan, M. L. Rudee, T. Ishibachi

A modelfor dilute quasi-regular interstitial solid solutions is proposed in which the solute atoms can occupy both the octahedral and tetrahedral interstices in the bee solvent lattice. The distribution function, according to which the solute atoms are apportioned between the two kinds of sites, is calculated. The partial thermodynamic functions of the solution are calculated from the distribution function. It is shown that such a solution model can explain the deviation from linearity of the Arrhenius plot of the temperature variation of the diffusivity of carbon through a iron. The published difiusivity data is analyzed to obtain numerical values for the distribution function. Finally it is shown from the numerical values of the distribution function that the possibility of dual-site occupancy will have a negligible effect on the solution thermodynamics for this system. DeSPITE the large amount of experimental data available on the thermodynamics and diffusion kinetics of dilute solid solutions of carbon in a iron, many of the elementary properties of these solutions are not understood due to real or apparent discrepancies in the experimental data. Basically there is a lack of agreement between the solubility and diffusion data obtained by anelastic damping techniques and by bulk chemical thermodynamic methods. SPecifically the heat of solution of cementite in ferrite estimated from thermodynamic measurement1, 2 is about twice as high as that determined from anelastic damping measurements.3 Furthermore the diffusion coefficient D of carbon in a iron in the range -40" to about 150°C (covering about ten orders of magnitude) determined from anelastic damping techniques is such that an Arrhenius plot of In D vs 1/T is linear. However in the range of about 300o to 850°C where mass flow measurements of D have been made (covering about four orders of magnitude), although the data merges with the low-temperature data, the Arrhenius plot departs from linearity. The object of this paper is to present a more refined model of dilute ferrite solutions in which the solute atoms can occupy two kinds of interstitial sites. The experimental data is analyzed in the light of this model and it is believed that thereby some of the anomalies can be resolved. snoek4 explained the room-temperature internal-friction peak (usually referred to as the Snoek peak) in iron as the stress-induced ordering of interstitial carbon and nitrogen atoms occupying the octahedral (0, 0, 1/2) interstices in the bee lattice. From the consideration of a hard-sphere lattice model the (0, 1/4, 1/4) tetrahedral interstices are larger than the octahedrons but their symmetry would not produce the strain dipole necessary to give rise to the Snoek peak. Thus the presence of the Snoek peak is direct evidence that the octahedrons are occupied. Since the publication of Snoek's explanation, most workers have assumed that all of the carbon and nitrogen in the a solid solution was located in the octahedral sites. This assumption of universal octahedral occupancy has been implicit in the theory of wert5 for interstitial

Jan 1, 1965

By G. Cartaud, F. Osmond

We have already devoted two previous memoirs to this question. In the firstL we collated and discussed the existing literature on the subject; in the second: we described the crystalline forms obtained by the reduction, at different temperatures, of ferrous chloride by hydrogen or by zinc-vapor. The conclusion from these researches was that the three allo-tropic states of iron—a, stable below A2; , stable between A2 and A3; and , stable above A3—all crystallize in the cubic system. The differences observed were such as are customarily encountered in the crystallographic records of many minerals of which allotropic varieties or isomerides are not known, and did not conform to the ordinary definition of polymorphism. It is, however, improbable that allotropic transformations, which are placed beyond doubt by a series of positive facts, do not involve some changes in the intimate structure. As a matter of fact, the crystals we did obtain were too small to allow of a precise examination, and this might introduce an element of uncertainty in the firm establishment of our conclusions. Professor H. Le Chatelier mas even led to think from some of our results that r-iron could very well be a rhom-bohedron simulating a cube, and not a true cube, and it will be remembered that the crystalline form of bismuth was for a long time incorrectly regarded as cubic. Allotropy does not, however, necessarily involve such a deduction. Without departing from the cubic system at all, a whole

Jan 1, 1907

By Francis C. Krauskopf, Carl E. Swartz

Metallurgists differ considerably in their opinions regarding the effect, if any, of small amounts of iron pyrites, or other iron compounds on zinc sulfide ores during the roasting operation. As a result, the literature on this subject expresses many conflicting ideas. The ore, previously crushed to pass through a 1-mm. screen, dries in the roasting kiln, losing water up to 200° to 300° C. At 150° C. iron pyrites begin to lose sulfur. As the temperature increases, while the ore is passing to the hotter part of the furnace, the sulfur burns to sulfur dioxide, leaving the metals as zinc oxide and ferric oxide. These two substances then interact to form zinc ferrite, a compound, yellow brown in color, having the general characteristics of a spinel. Like magnetite, another spinel, zinc ferrite is insoluble in alkalis and dilute acids. As a result, when leached with 10 per cent. sulfuric acid solution, zinc values tied up in this compound remain behind History In the electrolytic recovery of zinc from its ores, the roasted ores are usually leached with a 10 per cent. sulfuric acid solution. When the zinc ore contains iron pyrites as an impurity in an appreciable amount, the actual yield of metallic zinc is much lower than a theoretical calculation would indicate. Further, losses of zinc are, in a rough way, directly proportional to the amount of iron pyrites or other iron compounds present. When the iron is present in the ore in an isomorphous relation to the zinc, as in the case of a marmatite, a greater amount of zinc remains insoluble than when present as a true pyrite or marcasite. Work on the insoluble residues obtained from leaching of the calcines shows that the zinc lost is intimately tied up in this residue. Some investigators have suggested a definite compound, such as zinc ferrite; others merely a mixture of zinc and iron compounds. As early as 1851, Pelouze(')' prepared calcium ferrite by fusion of calcium oxide and ferric oxide. Ebelman, 2) about the same time, prepared

Jan 1, 1928

By Millard K. Shaler, Sydney H. Ball

During the past 50 years the attention of mining-men has been turned to Africa, and within the past decade prospecting-expeditions sent into Central Africa have resulted in the open-ing-up of several mines. Having recently spent two years in the Belgian Congo for the Societe Internationale Forestiere et Miniere du Congo, it is our purpose to outline briefly the mining-conditions in that part of Central Africa. Before it became, in 1908, a Belgian colony, this region was known as the Congo Free State. 11. Location and Area. The Belgian Congo lies in southwestern Central Africa, west of the continental divide, as illustrated in Fig. 1. It has a coastline of but 20 miles on the Atlantic, but widens rapidly eastward to points 5 north and 14 south of the equator. Its area is 908,000 sq. miles, which is almost one-quarter that of the United States and Alaska, or more than one and one-half times that of Alaska. Stated in other terms, its area is nearly one-third that of the United States, exclusive of Alaska and the insular possessions, or more than that of all the United States east of the Mississippi river. III. Topography and Drainage. From north to south, Africa is made up of three topographic elements: 1, the Atlas mountains, a highly-accentuated region

Jan 1, 1911

By Å. Sterten, R. Tunold, J. Brun, K. Dalatun

The subjects of this study are two corrosion phenomena familiar to operators of aluminum plants employing Soderberg anodes of the vertical type, namely the sul-fide scale formation observed at the steel contact spikes and the corrosion wear observed at the lower edge of the gas collecting skirts. The causes of these corrosion phenomena are discussed on the basis of observations from practice and measurements on commercial cells as well as on laboratory experiments. It is concluded that the anode spike corrosion is mainly due to the attack by sulfur compounds contained in the anodically evolved gases and that this attack is greatly promoted by cracks and pores in the anode carbon embedding the lower spike ends. The corrosion of the gas collecting skirt is mainly attributed to anodic dissolution of the iron during occasional contacts with the melt. ANODE SPIKE CORROSION The visible result of this corrosion is the formation of a brittle loosely adherent scale on the lower ends of the mild steel spikes maintaining the electric contact to the carbon anode, Fig. 1. The thickness of the scale usually varies from 0.5 to 3 mm, but in some cases scale of about 10 mm thickness has been observed by the writers. During the spike pulling, usually repeated every 3 weeks, part of the scale often loosens and remains in the anode carbon, resulting in contamination of the aluminum with iron. This corrosion has been attributed to reaction of the iron with gaseous sulfur compounds originating from the anode paste materials.'-4 This paste usually consists of 70 pct precalcined petroleum coke with 1.2 to 1.4 pct S and 30 pct coal tar pitch containing 0.5 to 0.7 pct S. During operation the gasification of the anode materials takes place in two ways: First, gases are evolved by the gradual baking of the anode paste added on top of the anode. Due to the sealing effected by the upper semifluid zone of the paste, these gases, containing sulfur compounds from the pitch, are forced downward through pores and cracks in the rigid anode carbon. At the temperatures of the zone of the lower ends of the spikes, 700" to 900°C, the original components of the baking gas must undergo decomposition, similar to that taking place with the production of coal gas, resulting in a gas mixture consisting mainly of H2 and CH4 with small percentages of H2S as the main sulfur compound.5 Second, the anodic reaction results in a mixture of C02 and CO, the total quantity of which is about 15 times that of the baking gas. These anode gases must carry the entire sulfur content of the carbon gasified by the anodic reaction. Henry and Holliday6 have shown that COS is the main sulfurous component of the anode gases from Soderberg cells. Soderberg anodes usually exhibit a network of vertical cracks, frequently traversing from one spike to the next one and to the outside of the block and widening downward to the working face of the anode. In addition the anode carbon, particularly that below the spike ends, is rather porous, as indicated in Fig. 1. It therefore seems probable that the anode gases also may partly penetrate to the spike ends. As the anode is partly immersed in the melt, the static pressure of this must forward this penetration. I) SPIKE SCALE COMPOSITION A great number of freshly extracted spikes from industrial plants were inspected and samples of the scale collected for examination. Before analyzing the samples a thin iron oxide layer, formed by air oxidation of the outside of the red hot scale immediately after spike pulling, was removed. On the average the Fe/S ratio found by these analyses corresponded to I the composition FeSl. oo7. X-ray powder patterns showed no oxide and otherwise agreed with those found by Haraldsen7 for iron sulfide with 50.00 at. Pct

Jan 1, 1970

By W. H. Bassett, J. C. Bradley

Beads of metal frequently appear at the ends of cast-copper wire bars and on the sides of wedge cakes near the top. These are richer in cuprous-oxide than the rest of the casting. A micrographical study of these exudations has been made. 11 is suggested that the materical is forced through the surface while the copper is solidifying. If not eliminated in process of manufacture, it shows on the finished polished sheet copper in patches differing in color from the main body of the shad. Figures 1 to 4 show the copper exudations, at different magnifications, as they appear on the ends of cast wire bars, and on the sides, usually near the top, of wedge cakes. Sometimes the exudations are in fine "drops;" at other times, large masses of the material are found. Microscopic examination of the copper exudation indicates that it is high in oxide and of eutectic proportions. Because of the difficulty of securing a suitable sample, the protuberances have not been analyzed chemically; but the spectroscope shows no indication that there are any more metallic impurities present than in the balance of the copper. The lowest copper plus silver content of the coppers studied for this paper was 99.914 per cent.; the highest, 99.966 per cent.; so the oxygen content of the whole casting would be well under 0.07 per cent. Structure of Protuberances The segregation of oxide between grains in the interior of the cast bar, not far from the "set," is shown in Figs. 5 and 6. In general, the amount of cuprous oxide begins to increase at a point about 0.01 in. below the normal surface of the casting, i. e., the base of the drop; but it does not attain maximum concentration in the main body of the metal. Vertical sections, Figs. 7 to 12, show that there is a definite line of large cuprous-oxide globules at the base of the drops. Horizontal sections at this place show that these large globules lie in a thin billowy

Jan 1, 1926

By John D. Sullivan

Leaching of copper ores is a comparatively old art, probably dating back to medieval times. The leaching of mixed oxidized-sulfide ores, however, is modern. The first modern plant leaching mixed ores was at Ajo, Ariz., where commercial operations commenced in 1917. While the ore at Ajo was primarily oxidized there was always some sulfide present. The Inspiration leaching plant, which was put in operation in 1926, may be considered the first plant constructed for the extraction of both sulfide and oxidized copper. The pioneers in leaching mixed ores had a difficult task before them since they had very little fundamental data on the chemical and physical factors of leaching. For the very large amount of painstaking experimental work that was done before building the Ajo and Inspiration leaching plants the reader is referred to the original articles.' For a period of several years the writer worked on problems connected with the chemistry and physics of leaching mixed oxidized-sulfide ores. This paper summarizes the experimental work and discusses various factors involved in leaching ores. It also presents many data heretofore unpublished. Among the new data are those on chrysocolla, pages 518 to 519, inclusive; dioptase, page 519; covellite, page 529; virtually all those on chalcopyrite, pages 531 to 533, inclusive; enargite, page 533; and tetrahedrite and tennantite, pages 534 and 533. The oxidized copper minerals of commercial importance in American ores are azurite, Cu3(OH)2(CO3)2; malachite, Cu2(OH)2CO3; chrysocolla, CuSi03.2H2O; tenorite (or melaconite), CuO; and cuprite, Cu2O. Dioptase, CuSiO3.H2O is less common. Brochantite, CuSO4.3Cu(OH)2, while the chief mineral in the ore at Chuquicamata, is not of major importance in the United States. Metallic copper, while chemically not so, is frequently classed as an oxidized mineral of copper. The most important sulfide minerals are chalcocite, Cu2s; covellite, CuS; bornite, Cu5FeS4; and chalcopyrite, CuFeS2. Less important complex sulfides are enargite,

Jan 1, 1934

By D. Geoffry Minnes, Ray Blair, Stanley J. LeFond

Nepheline syenite is a silica deficient crystal-line rock consisting of albite and microcline feldspars and nepheline, together with varying but small amounts of mafic silicates and other accessory minerals. Nepheline-bearing rocks are widely distributed around the world but only in Canada, Norway, the Union of Soviet Socialist Republics, and the United States are deposits worked commercially, Because of its low melting point and fluxing ability, nepheline syenite was investigated in the early 1900s by many students of glass and ceramics. Although the nepheline syenite deposits in Methuen Township, Ont., Canada, were discovered as early as 1897 it wasn't until 1935 that the first mill was erected to produce nepheline syenite products. In Canada, nepheline syenite deposits are worked by Indusmin Ltd. and International Minerals and Chemical Corp. (Canada) Ltd. who have combined production capacity in excess of 1800 stpd. Between 1935 and 1972 seven million tons valued at $78 million were produced from the Methuen Township deposits. In Norway, the Norsk Nefelin Div. of Elkem Spigerverket has produced nepheline syenite from a deposit on Stjernöy Island in western Finland since early 1960. Production has increased from 8 kt in 1961 to over 200 kt in 1980. Nepheline syenite has been under investigation in the Union of Soviet Socialist Republics (USSR) since at least 1928. In 1951 the first commercial alumina works was brought on stream at Volkhov, near Leningrad, utilizing nepheline concentrates from the Kola peninsula as mill feed. Since then two others have been completed and more are planned. Large quantities of portland cement, sodium carbonate, and potassium carbonate are produced in conjunction with the alumina. A material called nepheline syenite, but actually a pulaskite, is produced in Pulaski County, Arkansas, by the McGeorge Construction Co. for construction aggregates and by the 3M Co. for roofing granules. The Dome Fill Co. purchases the fines and uses them in the preparation of enclosed construction fill. Production is over 2,000,000 stpy. Chap. 16 on "Feldspar, Nepheline Syenite, and Aplite" in the 3rd ed. of Industrial Minerals and Rocks (Castle and Gillson, 1960) and Nepheline Syenite Deposits of Southern Ontario (Hewitt, 1960) contain excellent accounts of earlier commercial development of nepheline syenite as a glass and ceramic material. As in the 4th ed., this chapter deals mostly with the period since 1960 and with matters not previously reported in detail. An English monograph on Nepheline-Syenite and Phonolite (Allen et al., 1968) is a complete survey, at the time, of nepheline syenite which, with its very complete list of references, is an excellent source book. End Uses Nepheline syenite from the Canadian and Norwegian producers finds use primarily in the manufacture of glass and ceramics. One producer also makes several grades of nephellne syenite that are useful as extender pigments and fillers in paint, plastics, and rubber. In the Soviet Union nepheline is used in increasing quantities in the manufacture of alumina, alkali carbonates, and portland cement and to a lesser degree it is used in the manufacture of colored container glass.

Jan 1, 1983

By W. D. Sylwestrowicz

In tests on polycrystalline copper and aluminum, the ratio of the yield stress to modulus of elasticity was found to be strongly dependent on tempemture. Also, it was shown that the change of the yield stress with temperature of a material at a given temperature and deformed to a given yield stress, but not necessarily to the same strain, does not depend on previous mechanical thermal history. Likewise, for a material at a given temperature and deformed to a given yield stress, the rate of work hardening is independent of the temperature of prior stressing. It has been shown by Los and Orowan1 and by Dorn, Goldberg, and Tietz2 that the temperature dependence of the yield stress-strain curves of crystalline materials reflects two effects: not only does the yield stress of a material in a given structural state depend on the temperature, but the structural state (and the corresponding strain hardening) after a given amount of plastic straining also depends on the temperature at which the pre-straining has been carried out. Thus, for instance, if a specimen of a ductile metal has been strained along the stress-strain curve 1 at room temperature to point A, Fig. 1, and then the straining continued in liquid nitrogen along curve NR, the yield stress A' immediately after lowering the temperature is lower than the yield stress A" of a specimen that has been strained by the same amount in liquid nitrogen (along curve 3). AA' represents the effect of the temperature change upon the yield stress of the specimen pre-strained at room temperature; A' A" is the excess strain hardening acquired if the pre-straining has been carried out in liquid nitrogen instead of at room temperature. The dependence of the yield stress (i.e., of the structural state acquired during preceding straining) upon the conditions (speed, temperature) of a pre-straining is the reason for the nonexistence of a so-called "mechanical equation of state" for plastic deformation. A 'mechanical equation of state" is a relationship of the form F(s,E, e, T) = 0, or s = f(E, E, T) [1] It was first suggested by Ludwik3 that plastic deformation might obey such an equation; this, however, was conclusively disproved by experiments of Kochendorfer.4 Additional disproofs were given in

Jan 1, 1959

By Horace Mann

A FEW years ago, it was generally thought that from 15 to 18 per, cent. of zinc oxide was the upper limit of a workable lead blast-furnace slag. With slags above this zinc-oxide content, the furnaces gave so much trouble because of hearth, wall, and crucible accretions that the campaign was very short. The time lost in cleaning out the frozen furnaces, for it was seldom possible to blow them out, and blowing in was so great that it was considered uneconomical to attempt the running of high-zinc slags, even if this were metallurgically possible. It is true that there are, references to one or two slags much higher in zinc than the foregoing,1 but the average smelterman regarded these, as freaks and not to be considered for regular furnace work. One or two plants, notably the plant of the United States Smelting Co, at Canyon City, Colo., ran charges, higher in zinc. At this plant, the zinc-oxide content of the charge was frequently 20 per cent. and higher but the slags from these furnace's seldom ran over 10 to 12 per. cent. zinc oxide. The furnaces were run with a large volume of air under a relatively low pressure, a low smelting column, and a very hot top; as a result, a large amount of zinc was volatilized. Even with the low smelting column and hot top, accretions caused much trouble and barring, down was a daily occurrence. At the time most of the theories on lead blast-furnace work were promulgated or worked out, it was necessary to run a furnace with a cold top in order to avoid an excessive loss due to fines and fume. At the same time, the smelting conditions had to be such that the lead and silver would be reduced and would enter the bullion. The slag had to be liquid but the charge must not give excessive accretions either in the hearth or on the walls of the furnace. This forced the operators to run the furnaces with a comparatively low blast, which, in turn, caused a small fuel consumption per unit of time with the accompanying result of a low working temperature.

Jan 8, 1925

By C. G. Dunn, P. K. Koh

Microstructure, magnetic torque, and texture data before and after grain growth were obtained on two 3.25 pet Si-Fe specimens having initially the same cold-rolled textures and the same primary recrystallization textures. The latter textures consisted of four components, two only of which were strong; the strong components were near (120) [001] and (320) [001]. The textures of the two specimens obtained by grain growth were different. In one specimen the two weak components were converted into strong components by a secondary recrystallization process; in the other specimen the primary recrystallization texture was retained by a normal grain-growth process. The difference in behavior of the two specimens was interpreted in terms of a difference in the relative grain sizes between weak and strong components; i.e., in terms of a geometrical factor that would alter the early growth rates of grains belonging to the two weak components of the texture. Specifically the growth rate was considered as the product of two terms: a driving force and a boundary mobility. The texture changes observed are considered to favor the oriented-nucleation growth-selectivity theory more than the oriented-growth theory. WHEN primary recrystallization and grain-growth textures form as a result of annealing deformed metals or alloys, the fundamental processes involved are nucleation and growth. Knowledge, therefore, about nuclei and the factors influencing their growth is required not only for the understanding of texture development but also for its control. In the oriented-growth theory of texture formation1, 2, 3 the problem of nuclei is generally disposed of by the assumption that nuclei are available in all orientations; the theory then has to explain the final texture from the initial texture and the way boundary mobility depends on orientation. In the oriented nucleation theory of texture formation"' nuclei are considered to be present only in certain orientations but the importance of growth selectivity is still recognized. For example, the mobility of boundaries of approximately the same orientation and of the coherent type in twins is believed to be low while that of high-angle boundaries, in general, is high. Because of this the theory may be described as an oriented-nucleation growth-selectivity theory. The main feature of the oriented-nucleation theory, however, is the importance given to nuclei; i.e., how they form in specific orientations and how they grow. In the present investigation two cold-rolled single crystals were used to study the effects of growth after primary recrystallization. The cold-rolled textures and the primary recrystallization textures were determined from portions of these specimens and reported earlier.",' The two cold-rolled crystals were in the (111) [112] stable end orientation, the recrystallization textures were nearly identical and consisted of two strong components, designated M and M', which were near (120) [00l] and (320) [00l], respectively, and also some specific weak components near (111) [110] and (111) [110]. It is well recognized that a single strong component in the primary recrystallization texture may be needed for secondary recrystallization3, 5, 8 but unfortunately when this is the case the amount of material left in deviating orientation may be too small either for growth or for positive identification. The present samples proved to be almost ideal for the study of minor components and their influence on texture changes produced by growth after primary recrystallization. The results obtained are interpreted in terms of present knowledge of grain-growth processes. Experimental Procedure Two lots of silicon-iron alloy of essentially the same composition, namely, 3.25 pet Si, 0.004 C, 0.009 P, 0.010 S, 0.035 Mn, 0.070 Ni, 0.090 Cu, 0.009 Sn, with traces of A1 and Cr and the balance Fe, were converted into single crystals 0.025 in. thick and 1.25 in. wide. The orientations were predetermined by the method of reorienting a seed crystal as described elsewhere.3 pecimen 1 from one lot had the (335) [556] orientation while specimen 2 from the second lot had the (111) [112] orientation.* Both crystals were cold rolled to a reduction in thickness of 70 pet while widening approximately 20 pet. Samples of each were selected for determining 1) the cold-rolled texture, 2) the time required at

Jan 1, 1959

By E. C. Harder, D. F. Hewitt

Since early in 1916, when it became apparent that the steel industry of the United States could not depend for the duration of the war on several important foreign sources of manganese and might have to depend entirely on domestic ores, the U. S. Geological Survey, with the assistance of several cooperating organizations, has made a comprehensive investigation of domestic manganese resources. The work has included field studies in a number of states well as annual, quarterly, and monthly canvasses among operators concerning current and future production. In order that the interested public might have access to the important results of the studies, preliminary reports concerning the field work as well as periodic summaries of production were issued as promptly as possible. Although numerous summaries of production l2, l3, l4 have been prepared from time to time for the use of the several boards and committees responsible for the conduct of the war, it has been thought for some months that those engaged in the industry, as well as others, might be interested in a preliminary summary of the accumulated geologic and production data. The cessation of hostilities, in November, 1918, probably detracts from the usefulness of much of the material that is here presented, but apart from the historic interest in the performance of an important industry in war time, there is a possibility that some of the conclusions may be helpful to those who continue to exploit domestic deposits, as well as to those who wish to measure the country's independence in mineral supplies. Appropriate final geologic reports are being prepared by the geologists who did the field work. The present authors, having done but a small part of the recent field work, acknowledge with great appreciation the use of preliminary and unpublished reports and the cordial informal cooperation of the following geologists in the preparation of this paper: F. L. Ransome, G. W. Stose, F. C. Schrader, J. T. Pardee, E. L. Jones, Jr., H. D. Miser, Laurence LaForge, J. B. Umpleby, Arthur Keith, F. J. Katz, and E. S. Larsen, of the U. S. Geological Survey. Field work in Virginia was carried out in cooperation with the Virginia Geological Survey, T. L. Watson, State Geologist; in Georgia, with the Georgia

Jan 1, 1920

By Thomas J. Menner

Jan 1, 1983

By A. B. Calhoun

These mines, which belong to the Burma Corporation, Ltd., formerly a London company now incorporated in Rangoon, Burma, are situated in the semi-independent state of Tawng-Peng, one of the small divisions comprising the northern Shan states and erroneously known as part of Upper Burma. Bawdwin is approximately 23' 6' N. latitude and 97" 20' E. longitude, 450 miles north of Rangoon, 169 miles northcast of Mandalay and 50 miles south and west of the Province of Yunnan, China (see Fig. 1). Although the mines were worked by the Chinese during the Ming Dynasty, 1412 A. D., the most extensive operations took place between 1796 and 1851, when the mines contributed largely to the silver market of China. During the reign of Tung Chik, 1868 A. D., they were abandoned partly because of the Mohammedan rebellion in Yunnan, which made life and property insecure, but largely because of the difficulty of operating the mines on account of water and poor ventilation. Since that time practically nothing was done, although the Burmese kings are said to have made several sporadic attempts to work the mines, until 1891 when Europeans were attracted by the great slag dumps (assaying about 40 per cent. lead) which the Chinese had left after extracting the silver. After a railroad and smelter had been built and 200,000 to 300,000 tons of slag smelted for lead, exploration work was started and old workings cleaned out in order to locate the remnants of the orebody that it was supposed the Chinese had left. After two years of most discouraging work, the remains of a large orebody was discovered by the Dead Chinaman Tunnel or what is the 171-ft., or No. 2 level adit. From then on the development was rapid and today the Chinaman is considered one of

Jan 1, 1923