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By K. Mukherjee

Instantaneous resistance change during martensitic transformation in Fe-30 at. pct Ni alloy has been studied using a low-noise electronic system. The smallest signals recorded in this investigation were of the order of 10 pv. These small signals did not show the initial increase reported by earlier investigators to support a double shear mechanism.&apos; A variety of pulse shapes and sizes was observed during "burst" transformations, and these signals were neither a linear function of the size of martensite plates nor of the volume fraction transformed. Even the smallest signals, presumably from single plates, showed complications resulting from elastic and/or plastic deformation, shock wave propagation, and so forth, which are inherent in the growth process of a martensite plate. The time of formation and interface velocity determined froni this experiment agree very well with the pioneering work of Bunshalz and Mehl.&apos; AN Fe-30 at. pct Ni (c0.005 pct C) alloy was used to study the time of formation of martensite plates. Martensitic transformations, unlike the nucleation and growth processes, are usually characterized by an extremely fast reaction rate. During the transformation, the crystal structure changes and this change is propagated through a finite volume of the parent crystal lattice within a very short time interval. The interface between the two phases probably consists of moving dislocations, and the time of formation of the plate depends on how fast this dislocation interface can move. Knapp and Dehlin~er or Cottrell and Bilby mechanisms, or similar dislocation models, can be used to calculate the time of formation of a martensite plate of a given size. In the past, conventional photographic technique475 as well as electrical resistivity techniques"~-" have been used to measure the time of formation of a martensite plate. The specific resistance of the martensitic phase in Fe-30 at. pct Ni alloy is lower than that of the austenite phase. Therefore if a current is passed through a small austenite sample in series with a large external resistance, then one would observe a voltage change across the sample as martensite is formed. Such dc measurements are shown in Fig. 1. The initial large voltage drop in Fig. 1, at the M, temperature, is due to a "burst" transformation where a large number of plates are formed in a cataclysmic manner within a very short interval of time. Even during the later stages of transformation as shown in Fig. 1, one can observe discontinuous voltage changes due to small bursts. In order to resolve the time scale of such discontinuous stages, the voltage signals are amplified and fed into a highspeed oscilloscope. In this investigation a low-noise amplifier was used for the first stage of amplification. The signal to noise ratio was further improved by the design of a pulse transformer. This transformer was capable of amplifying the signal by a factor of six. Voltage signals were studied over a wide time scale ranging from 2 sec to 0.1 psec. I) EXPERIMENTAL PROCEDURE A) Specimen Preparation. Specimens were cut from induction-melted Fe-30 at. pct Ni (<0.005C) alloy and cold-rolled to 0.2 by 1 mm cross section and an average length of 5 cm. During mechanical shaping, the specimens were strain-annealed at 950°C for 24 hr in vacuum. Finally the finished samples were vacuum-annealed at 1000°C for 6 hr and water-quenched to room temperature. The average grain diameter was 0.02 cm. B) Cooling System. The M, temperature of the alloy was -55°C. Fig. 2 shows the arrangement which was used to cool the specimen at a slow rate. The specimens were mounted inside a i -in.-diam hole in the 2-in.-long section of the copper specimen holder. This cavity was filled with silica gel. A dummy specimen was used under identical conditions for

Jan 1, 1969

By Charles R. Keyes

PAGE. I. IntRoduction,...........139 11. Four Phases of Primary Ore-Genesis,......141 1. Extraction of Ore-Materials from Sea-Water,....141 A. Early Views,........141 B. Metals in Sea-Water,.......142 C. Metallic Content of Sedimentary Rocks,... 142 D. Adequacy of Metal-Percentage to Form Ore-Deposits, . 143 E. Derivation of Metallic Elements in Sea-Water,.. 144 2. Metallic Content of Igneous Rocks,...... 145 A. Two-Fold Meaning of Term,.....145 B. Significance of Ordinary Rock-Analyses,... 146 C. Wide-Spread Occurrence of Rare Rock-Forming Minerals,.........146 D. Occurrence of Metalliferous Minerals in Rocks,.. 146 E. Metallic Content of Igneous Rocks Generally,.. 147 F. Metals in Volcanic Rocks,......148 G. Originality of Metal-Content of Rocks,...148 H. Physical Condition of Metallic Minerals,... 149 3. Magmatic Origin of Metals,.....,.149 A. Association of Ores with Cooled Magmas,... 149 B. Deep-Seated Origin of Metals,.....150 C. Magmatic Waters in Ore-Deposition,.... 150 D. Ore-Materials of Volcanic Emanations,... 151 E. Exportation of Metals from Magmas,.... 152 F. Ores of Magmatic Differentiation,.... 152 4. Meteoritic Derivation of the Metals,.....- 153 A. Planetesimal Hypothesis,...... 153 B. Number of Meteorites,.......154 C. Abundance of Meteorites in Desert-Regions,.. 156 D. Petrologic Character of Meteoric Falls,... 159 B. Metals in Meteorites,.......159 F. Incorporation of Meteoritic Materials in Ores, , .160 811. RecapitulatioN,..........161 I. Introduction. If the long controversy waged between those who, on the one hand, advocated a strictly deep-seated origin of ore-deposits, and, on the other hand, those who argued for an ore-genesis by

Jan 1, 1911

By M. W. Hayward

THE object of this paper is to record and tabulate the data and field observations obtained by the writers and their associates during 10 years of intensive study of lead-zinc deposits in the Cretaceous limestone areas in Northern Mexico, particularly in mines owned by the Cia. Minera de Peñoles, S. A. At the El Paso meeting of the Institute in October, 1930, J. G. Barry made the suggestion that a committee be appointed to correlate the ideas and theories which have been put forth by the numerous engineers and geologists who, during recent years, have made a study of the ore deposits in the area under consideration. The first step in a work of this nature would be to record all of the observed facts, and these facts would have to be accepted by those who attempted to formulate a theory of ore deposition. It is with this idea in mind that the writers have described as accurately as possible the actual, observed facts pertaining to the occurrence of the lead-zinc ores in dolomites or dolomitic horizons. By most writers the term "dolomite," is loosely used to designate magnesium-bearing limestones, regardless of the percentage of MgO present. Since no, true dolomites exist in the areas to be described, we shall also loosely use the terms dolomite or dolomitic limestone to designate those beds having a magnesia content of 5 per cent MgO or more. For a number of years the writers have been impressed with the fact that in areas where dolomite beds occur a large percentage of the lead ore is found in these beds, in spite of the fact that such beds may be overlain or underlain by pure limestone, which one would assume to be just as favorable for replacement as the dolomite, if not more &apos;so on account of its being more soluble in acid solutions than the dolomite. It is true that in some limestone areas, such as the Erupcion-Ahumada districts, Chihuahua, and Providencia, Zacatecas, where no dolomite beds have been found, large tonnages of lead ores have been mined. We venture to predict, however, that had there been dolomitic beds in these areas, the

Jan 1, 1931

By D. B. Robinson, J. Lukacs

A knowledge of the equilibrium water content of hydrocarbon systems under pressure is important to the natural gas industry. The information available on the solubility of water in hydrocarbon, hydrogen sulfide, and carbon dioxide systems is reviewed in this paper and the influence of the more important variables such as temperature, pressure and molecular structure on solubility in liquids and gases is discussed. A suitable cbromatographic technique has been developed for determining low concentrations of water. Tailing of the water peaks has been elim inated by adding water to the carrier gas stream The method is applicable for both gas or liquid samples and is effective in the presence of hydrogen sulfide. The experimental study of water solubility in methane-hydrogen sulfide systems at a temperature of 16oF has shown that the presence of hydrogen sulfide causes only a modest increase in water content at pressures up to 1,400 psia. Theoretical considerations and data on pure hydrogen sulfide and carbon dioxide suggest that the effect of both these compounds will be greater at higher pressures and in the liquid phase. INTRODUCTION Before transporting or processing natural gases and gas condensates, it is usually necessary to dry them using suitable dehydration equipment. The design and operation of this equipment requires a knowledge of the amount of water present in the fluid at the reservoir and operating conditions. This is influenced by temperature, pressure and composition, particular1y when certain non-hydrocarbon components are present. Field experience indicates that hydrogen sulfide and carbon dioxide, for example, alter the usual water solubility relationships appreciably. However, an extensive search of the literature does not reveal any quantitative data on such systems. For sweet natural gases, generalized empirical correlations such as the one proposed by Katz, et al,6 can be used to predict water solubility with confidence at most temperatures and pressures of interest. However, existing theoretical relationships do not permit a calculation of the deviation from these curves when polar substances like hydrogen sulfide are present in the system. Thus one must resort to an experimental approach to obtain the necessary information. The fact that laboratory experimental methods frequently involve the use of mercury which reacts with hydrogen sulfide in the presence of water, and that hydrogen sulfide interferes with many chemical reactions specific for water has contributed to the difficulty of studying water solubility in systems containing hydrogen sulfide. In this investigation the water content of a limited member of methane-hydrogen sulfide mixtures was determined using a special technique with gas chromatography. REVIEW OF PUBLISHED DATA Experimentally determined water solubility data have been reported for methane, 14 ethane, 15 propane, 9 n-butane, 16 1-butene, 11 hydrogen sulfide 18 and carbon dioxide. 19 These studies report the effect of pressure, temperature and molecular structure on water solubility in single component gases and liquids. Fig. 1 compares experimentally determined water solubilities in several hydrocarbons, carbon dioxide and hydrogen sulfide at l00F as taken from this

By G. H. Wilson

INTRODUCED in 1946 to serve a need in power-plant operation, closed-circuit TV has been used by well over 200 organizations in approximately 25 different industries. Known as industrial television, or simply ITV, it can be described as a private system wherein the television signal is restricted in distribution, usually by confinement within coaxial cable that directly connects the TV camera to one or several monitors, Figs. 1, 2. The picture is continuous and transmission is instantaneous, permitting an observer to see an operation that may be too distant, too inaccessible, or too dangerous to be viewed directly. Destructive testing or the machining of high explosives can now be conducted hundreds of feet away by personnel who still have close control through the eyes of the TV camera. It is also possible for one man to control operations formerly requiring the co-ordinated efforts of several workers. For example, at a large midwestern cement plant conveyance of limestone from primary crusher to raw mill and loading into five storage bins once necessitated the work of two men, one having little to do but prevent spilling of material by manually moving the tripper on the belt conveyor as occasion required. TV cameras mounted on the tripper now provide bin level indication to the conveyor operator at the crusher position so he is able to control the entire loading operation remotely, Fig. 3. By means of a switch, the picture from either camera is alternately available on a single viewer, or monitor, Fig. 4. Each camera is mounted on the tripper by means of a simple adjustable support and looks down into the bin, which is identified by the number of cross members on the vertical rod. Each associated power unit is located on a platform above the camera, Fig. 5. This centralized control by means of TV often has produced superior results, and in many instances saving in operating costs has been sufficient to write off equipment costs within six months to a year. Where a key portion of a process may be enclosed or otherwise inaccessible, TV again reduces the likelihood of mistakes and permits closer control by making available to the operator valuable information he might otherwise never possess. An example of this can be found at a strip mine where the coal seam lies 50 ft or more below the overburden, which is removed by a large wheel shovel. From his centrally located position the shove1 operator was unable to judge accurately to what extent the wheel buckets engaged the earth. His chief indication of efficiency was the amount of overburden on the belt conveyor as it passed his control point 75 ft from the wheel. Now, two television cameras mounted on the tip of the boom permit the operator to view the wheel from each side and provide him with a close-up view of the buckets so that he can take immediate and continuous advantage of their capacity, quickly compensating for ground irregularities and avoiding obstructions, Fig. 6. While the word television conjures up visions of highly complex and intricate apparatus such as that employed in modern TV studios and transmitting stations, the term industrial television should indicate compact, straightforward equipment. Most present-day ITV systems contain fewer than 25 tubes including camera and picture tubes. The average home television receiver alone requires at least that many tubes. Equipment like that illustrated in Fig. 1 contains only 17 tubes, of which 3 are in the camera. It can operate continuously and dependably, without protection, in any temperature from 0" to 150°F. It consumes less current than a toaster and weighs under 140 lb. Camera and monitor may be separated by 1500 to 2000 ft and by greater distance with additional amplification. This equipment is designed to withstand vibrations up to 21/16 in. and will operate successfully under more severe conditions of vibration and heat when suitable enclosures are provided. Any number of cameras may be switched to a single monitor, and any number of monitors, within reason, used simultaneously. Two types of applications in the mining industry have already been described. A third under serious consideration by several organizations will make use of ITV for remote observation of conveyor transfer points at copper concentrating plants so that evidence of belt breakdown and plugging of transfer chutes can be spotted immediately and costly overflow of material avoided. A television camera will soon be installed to view a trough conveyor near the exit of an iron-ore crusher to indicate clogging of the crusher as evidenced by reduction or absence of material on the

Jan 1, 1955

By Samuel S. Wyer

The magnitude and economic importance of the problem of correctly valuing natural-gas leaseholds become evident when me consider that: (a) Natural gas is handled in 55 per cent. of the gas distributing plants in the United States. (b) Present known natural-gas acreage forms 47 per cent. of the total known mineral-land acreage in the United States. (c) Five acres of land are now required to protect and maintain continuous service to each of the 2,000,000 domestic natural-gas consumers in the United States. (d) The cost of acquiring and maintaining this acreage of an expendible resource represents a substantial part of the cost of the natural-gas service to the consumer. (e) "The right of a citizen by means of his ownership of or his mining leases on land to draw gas from beneath its surface is property and sometimes valuable property."&apos; A large number of other court decisions have established the basic legal principle that the right to drill for gas within a given area constitutes an interest in the land itself, and is necessarily an exclusive property right. Definition of Vested Interests or Rights "Vested interests are economic interests which are legally recognized to be such that they cannot be impaired by public action, directly or indirectly, without indemnification. Vested interests are largely property interests. The recognition of an interest as a vested interest gives it some of the attributes of property, and by American courts it would be comprised in their very inclusive concept of property. Otherwise than through property, vested interests generally arise through contract."

Jan 1, 1917

By John Hillman

Reconstruction of the British mining industry began shortly after nationalization in 1947 and continued until well into the 1950s with the support of the government. This support diminished as plentiful supplies of cheap oil from the Middle East made many coal mines uneconomic. The planned rundown which followed was foreshadowed in the 1965 White Paper which outlined financial measures to speed the closure of uneconomic collieries. The decline appeared likely to continue into the 21st century as the role of coal in UK energy requirements became less and less significant. This policy was well on course in 1973 when the oil crisis led to a complete reappraisal of the position. A government examination in 1974 of the coal industry then supported the National Coal Board&apos;s general strategy of major capital investment as set out in its &apos; Plan for Coal &apos; .1

Jan 11, 1979

By S. F. Radtke, J. A. Snyder, R. M. Scriver

An automatic, continuous casting arc furnace employing a nonconsum-able electrode and a direct current arc has been constructed and operated successfully for titanium. A comparison of the properties of arc and induction-melted titanium indicates that where high ductility, formability, and toughness are required, arc-melted metal is preferable. BECAUSE of the reactivity of titanium metal with all known refractories and the common atmospheric gases, melting of the metal presents numerous problems. It is necessary to provide an inert atmosphere in the furnace as well as a crucible material that will not react with the molten metal, if a ductile ingot is to be produced. Two special furnaces have been developed that meet the requirements and one, the induction heated graphite furnace, has been described in some detail.&apos; Little information is available for sizable units wherein power is applied to the melt through an arc, and the dearth of technical information on such a furnace prompted this report. It has been demonstrated clearly that arc melting produces titanium metal with superior toughness, ductility, and formability. To produce titanium ingots with these properties, an automatic, continuous casting arc furnace has been developed and is described herein. The history of arc melting may be traced to 1800, when Sir Humphrey Davy2 first experimented with Volta&apos;s electric battery and found that light could be produced and an arc formed between two carbon points attached to the cell. The discovery of the arc was followed by the design and construction of an arc furnace by Napier," in 1845, for the reduction of metal oxides. In 1853, Pichou&apos; described a similar furnace, although it was not until the discovery of the dynamo in 1867 that the arc furnace could achieve commercial significance. In 1878, Siemens- esigned the first arc furnace intended for the melting of metals and by 1882 had melted steel and platinum successfully. . This was followed by Moissan&apos;s" classical work with the arc furnace in 1892. W. von Bolton,&apos; in 1905, found that the arc furnace was suited admirably for melting refractory metals. In his work with tantalum, no suitable refractories for retaining the molten metal were found to exist. Together with Otto Simpson, he developed an arc furnace with a water-cooled copper crucible in which tantalum could be melted without contamination. This technique proved eminently successful. In his paper on the preparation of ductile titanium, Krolle first described an application of the von Bolton furnace to the melting of this metal. The

Jan 1, 1952

By James F. Lewis

The death of Josephus Flavius Holloway, for twenty-one years an active and beloved member, and twice a Vice-President, of the Institute, cannot be allowed to pass without some expression on the part of his brethren of mingled grief and gratitude—grief that we have lost his genial and inspiring presence ; gratitude that we have been privileged to know one who lived " To make the world within his reach Somewhat the better for his being, And gladder for his human speech." The present sketch of his career and character is offered as a sincere, though inadequate, expression of these feelings. Mr. Holloway&apos;s father, Joseph T. Holloway, born, in 1796, in Sunbury, Pa., and yielding in his youthful prime to the prevailing impulse of his generation, started alone, with knapsack

Jan 1, 1897

By Kenneth Robertson

THERE is probably less known of this subject than of any other connected with the metallurgy of iron. In all the books that treat of this matter, there ore given analyses of slags, their chemical formulae, the loss of iron, etc. ; but few, if any, give the character of the iron mode at the time; none give analyses and physical characteristics of the ores and limestones used, and they present merely isolated examples from various furnaces, and consequently one is more frequently puzzled than enlightened after reading them. During two years I have had occasion to analyze the slags and many of the pig-irons from two furnaces, and for this article I hove made analyses of all the different grades of pig mode by them. A

Jan 1, 1873

By P. K. Strangway, H. U. Ross

Briquets consisting of pure artificial magnetite, pure artificial hematite, and mixtures of the two were reduced by hydrogen in a loss-in-weight furnace at temperatures in the range 500° to 1000° . The rate of reduction of the pure hematite briquets increased continuously with increased temperature. In contrast, the pure nmgnetite briquets exhibited a pronounced rate ninimutn at about 700°C. Metallographic studies of partially reduced briquets rerlealed that, at this temperature, the he.matite samples reduced in a topo-chemical manner while the magnetite ones reduced uniformly throughout, and after partial reduction their cross sections contained a mixture of iron and unreacted wustite grains. No iron shells could be detected on the surfices of any of these uwstite grains. X-ray diffraction investigations indicated that these grains had a rzinimum lattice parameter when they had been formed at the rate rninimum temperature. Also, it was found that an activation energy of 41,000 cal per mole zoas required for reduction when only these wustite grains were present. Thus, it is suggested that the overall reduction rate of the rnagnetile su?nples at temperatures in the range influenced by the rate nzinirnum phenomenon was limited by the rate qf iron ion diffusion in the unreacted wustite grains. THE rate minimum phenomenon, which has often been observed when reducing iron oxides at a temperature of about 700°C, is one of the most interesting, yet unresolved, problems in the field of reduction kinetics. Basic principles of chemical kinetics and &apos;In some instance, a second rate minimum has been observed at about 900°C. Since most investigators are in agreement that this minimum is directly related to the transformation from a to y iron (which takes place at 911°C) and since it was not encountered during the present reduction tests, it will not be referred to in this vaver. fundamental laws of diffusion all agree that, as the temperature is increased, the rate of reduction should also increase. However, with certain ores, it has been found that their reduction rate actually decreases with an increase in temperature up to some value X where a minimum reduction rate is reached. With further temperature increases beyond X the rate becomes more rapid again. Temperature X is usually referred to as the "rate minimum temperature", while the overall type of behavior constitutes the "rate minimum phenomenon". This phenomenon has been reported by numerous investigators. They have found rate minima during the reduction of both artifiial&apos; and natural374 magnetites and artificia15j6 and natural5" hematites. Rate minima have been observed when reducing high-purity material2 or low-grade ores,3&apos;4 when studying particles in the micronsize range5 or relatively large agglomerates,g10 and during reduction with either hydrogen7 or carbon monoxide.11"2 Previously, this phenomenon has been attributed to many factors; these include sintering and recrystallization of the iron formed during reduction374 changes in microporosity of the ore upon redction,"" formation of dense iron shells around retained wustite grains,11716 and chem-isorption,17 to name only a few. However, most investigators who have reported a rate minimum merely speculated as to what seemed to influence it and they did not examine the fundamental causes. Consequently, the present experimental study was initiated in order to evaluate the basic factors which could be associated with this phenomenon. MATERIALS AND METHODS The experimental techniques, followed during this investigation, are similar to those which have been described previously.18 The chemically pure magnetic powder was prepared by partially reducing Fisher reagent-grade hematite with a gaseous mixture of carbon monoxide and carbon dioxide in a rotating-drum furnace. Three-quarter-inch diam cylindrical briquets which weighed about 12 g were formed from this magnetite powder and pure hematite powder. All of the briquets were sintered while they were slowly raised through the 1200°C hot zone of a vertical tube furnace. An argon stream was continually flushed through this furnace in order to prevent oxidation of the magnetite briquets, while in the case of the pure hematite briquets sintering was carried out in air. The sintered hematite briquets had a density of 5.06 g per cu cm while the density of the sintered magnetite briquets was 4.27 g per cu cm. The sintered briquets were reduced by purified hydrogen in a loss-in-weight furnace at temperatures in the range 500" to 1000°C. In all instances, the critical reducing gas velocity was exceeded and, in order to ensure that the results were reproducible, duplicate briquets of each type were reduced under each set of experimental conditions. A continuous record of the weight loss during reduction was obtained with the aid of a Statham transducer. The present experimental setup was capable of detecting a change in weight as small as 10 mg. Since a weight loss of over 2 g usually occurred during each reduction test, an accuracy of better than 0.5 pct of the total weight loss could be achieved. RESULTS AND DISCUSSION Reducibility Tests. In the first set of experiments, pure hematite and pure magnetite briquets were used.

Jan 1, 1969

By R. H. Raring, F. E. Martin

A high speed gas quenching dilatometer useful in studying phase transformations in low alloy steels is described. Changes in specimen length are measured by means of an electrical micrometer tube. The maximum instantaneous cooling rate is approximately 5000°F per sec; the maximum average cooling rate from 1650&apos; to 950°F is approximately 2900°F per sec. Data for steels of 0.11 pct and 0.67 pct C content are included. KNOWLEDGE of phase transformations as they occur in an alloy under conditions of continuous cooling affords valuable insight into its properties. The transformation characteristics during continuous cooling of steels of high hardenability, which decompose entirely to martensite at fairly slow cool-

Jan 1, 1957

By Joseph R. Crump, Francois Ville, Frank M. Tiller

Several simplifications have been accepted in filtration theory during the past fifty years in an effort to avoid apparently intractable mathematical problems. In effect, these simplifications ignored the variation in average cake porosity and average filtration resistance with variation in pressure drop or with time. This study examines the traditional approach and shows that, in many cases, it cannot give correct design guidance. Using a set of dimensionless parameters because of the large number of significant variables, a revised theory is developed which does not require that porosity and resistance values be set constant. Graphs developed in the traditional approach (e.g., dt/dv versus v or t/v versus V) have substantial curvature near the ordinate; but this curvature is frequently ignored in theory and is easily missed in experiments. The revised theory allows more accurate design calculations, especially for compressible cakes.

Jan 1, 1980

By Paul Billingsley

The Asientos-Tepezala district is in the north of the State of Aguasca-lientes, about 30 miles north of the city of Aguascalientes, the capital. The district is reached by a standard-gage railway on the west side through the junction, Rincon de Romos, which is on the main line of the National Railways of Mexico from El Paso to Aguscalientes. The terminal is Tepezala. On the east side a narrow gage connects Asientos with the junction, San Gil, on the main line, Asientos to San Luis Potosi. Tepezala on the west side of the Asientos hills is about 2 miles from Asientos on the east side. The area between the two mining centers is separated by a low subdued divide which forms the central part of the hills. The district is in a group of isolated hills surrounded by characteristic bolsón plains. The hills rise above the surrounding plains about 6500 to 10,000 ft.; the highest peak is Alta Mira. The two mining districts lie somewhat upon the flanks of the hills at about the same elevation, 7200 ft. The district is an old one and has been known since early in the 17th Century when the mines were worked by the Franciscan Monks. Their mining operations, which were limited to the oxidized ore above the water level, consisted chiefly in extracting silver from the Santa Francisca vein. To judge from the old workings and the remains of surface plant, the operations were on a large scale. By modern mining operations since about 1900, the various mines of the district have been one of the principal sourees of ore for the smelter located at Aguascalientes. Topography The topographic features of the Asientos hills are largely controlled by the character of the underlying rocks. During the Tertiary period, the entire group of hills was probably covered by extrusive volcanic material in the form of cones and lava flows. The central part of these have since been carried away by erosion, so that remnants have been left along the borders of the hills. These remnants form rather conspicuous peaks,

Jan 1, 1927

By S. F. Emmons

Introductoy.—In view of the fact that an opportunity is to be offered to the members of the Institute present to inspect the recent developments of gold-deposits in the immediate vicinity of Washington it has seemed appropriate that some preliminary description of them should be given which may facilitate that inspection. It would have been a matter of much satisfaction to me to be able to present some general description of the gold-deposits of the Appalachian system ; but I have as yet had no opportunity of personally examining any others than those of Montgomery county, and these are still in their infancy. It is, moreover, a slower and more difficult operation to make geological observations in this region than in the more northern States; for whereas in the latter region the

Jan 1, 1890

Dr. Rausch, from your vantage point as educator, engineer, and corporate executive, what would you say is the most fundamental need that must be satisfied for the continuing welfare of our society, our industry and our profession?

Jan 3, 1977

By R. E. Ford, P. Tarassoff, P. H. Jennings

Copper oxide ore may be leached at all sizes from run-of-mine down to pulp, and consideration must be given to all available methods in determining the most economical one. Heap leaching was evaluated in a pilot plant at Gaspe Copper Mines, Ltd. which was designed to simultaneously leach two 1200-ton dumps of ore. The plant was operated for two years, in part under severe winter conditions. Two modes of leaching were investigated: acid leaching in which sulfuric acid was added externally to the leach solution, and pyritic leaching in which pyrite concentrate was added to the dump and acid was generated in situ by bacterial action. The pilot plant operation is described, and the results are compared with laboratory data obtained in 6-in.-diam columns. It is concluded that pyritic leaching offers certain operating advantages over acid leaching when copper is recovered by cementation in that iron buildup in the solution is prevented.

Jan 1, 1974

By E. J. Ripling

A NY mechanism proposed to explain hydrogen embrittlement in titanium and its alloys must, of course, be consistent with the experimental data that characterize this embrittlement. Unfortunately, however, the mechanical behavior of hydrogen-bearing titanium, at least a-ß titanium, has not been unequivocally defined. Lenning, Craighead, and Jaffee have clearly shown that hydrogen cmbrittles a-titanium by elevating its transition temperature, probably as the result of the formation of titanium hydrides. Therefore, in these alloys, hydrogen acts like at least one other interstitial contaminant, namely, nitrogen.&apos; On the other hand, ß-titanium has been shown by these same investigators to tolerate very large amounts of hydrogen without suffering severe mechanical damage.2 Mixing these two phases, however, to form the most important class of commercial alloys, the a-ß alloys, again results in severe hydrogen embrittlement, although the mechanism by which the embrittlement is produced is not of the same type as that which causes brittleness in a alloys. Ductility damage due to hydrogen increases as the strain rate is reduced in a-ß alloys, while embrittlement in a alloys increases as the strain rate is increased, since the latter is a transition temperature behavior. Steel, like the a-ß alloys, becomes more hydrogen sensitive at slow strain rates, suggesting that the mechanism producing the embrittlement in these two metals is similar. Brown and Baldwin&apos; described the hydrogen-produced ductility depression in steel as a function of testing temperature and strain rate by defining the slope of the two surfaces that produced the depression in a three dimensional chart, Fig. 1. One of these surfaces was given by the equations (de/de)4 > 0 (de/dT) < 0 [1] while the other was defined by the pair of equations Surfaces of the type given by Eq. 1 are suggested in two ways. One is an embrittlement mechanism wherein the diffusion rate of hydrogen is competitive with the rate at which the material is being deformed, as suggested by the planar pressure theory of Zapffe and his co-workers.&apos; The other is the diffusion controlled extension of Orowan&apos;s theory on delayed fracture in glass by Petch and Stables.&apos;&apos; Surfaces of the type given by Eq. 2 are also compatible with a mechanism of pressure build up in voids, according to de Kazinczy,&apos; since the solubility of hydrogen in the metal increases with testing temperature so that as the temperature is raised, the pressure in the voids is reduced. Kotfila and Erbin recently presented some data on the dependence of ductility on testing temperature and strain rate for the a-ß 3 pet Mn complex alloy at four different hydrogen levels.H Although data were presented for only three testing temperatures at three different strain rates, their results indicated that surfaces of the types defined in Eqs. 1 and 2 are produced in the alloy when the hydrogen level is sufficiently high—200 and 300 ppm—Fig. 2. Jaffee and his co-workers presented data on a number of different a-ß alloys which indicated the existence of surfaces of the type described by Eq. 2, but the ductility recovery at low temperatures as given by Eq. 1 was not found." In an attempt to aid in crystallizing this description of the ductility dependence of hydrogen-bearing a-ß alloys, tests were conducted by the author on a-ß titanium 140A with three different hydrogen contents. The tensile properties of two as-received rods and one vacuum annealed rod* were obtained over a range of testing temperatures and strain rates as shown in Figs. 3 and 4. Hydrogen analyses were made by the Battelle Memorial Institute on four pieces of the rod whose properties are shown as solid circles in Fig. 4. The hydrogen content of these pieces, taken at widely spaced intervals within the rod, were 280, 270, 289, and 270 ppm, indicating that the hydrogen content within a single as-received rod was quite uniform. One of the broken test pieces whose properties are shown in Fig. 3 as solid circles was also analyzed, and found to have a hydrogen content of 310 ppm. The analyses obtained on two of the vacuum annealed specimens were 92 and 170 ppm.

Jan 1, 1957

By R. S. Hendricks

During the past two years, Hecla Mining Co. has used shotcrete for ground support purposes with substantial cost savings. Hecla&apos;s experience indicates that shotcrete is an extremely effective ground support material which can be successfully employed in problem areas where various conventional systems would fail. To date, Hecla&apos;s use of shotcrete has been limited to openings where long-term high-quality support was required, to specific areas where exceptionally difficult ground conditions were encountered [ ] and, occasionally, to stope support. It is anticipated that when the necessary engineering and procurement of the components of an efficient materials handling system have been accomplished, shotcrete will be used on a routine basis in stoping and development situations. The real future of shotcrete is based, however, on the fact that this form of support offers greater opportunity for mechanization than rock bolt, timber or steel. Unlike all other support operations, which are cyclic, shotcrete is a continuous process, and therein lies its potential for incorporation into an efficient rapid excavation system. Hecla has obtained and operated both wet- and dry-process shotcrete application equipment. The operational characteristics of the two processes are presented and discussed below.

Jan 1, 1970

By H. Herman, C. Chiou, M. E. Fine

From variation in Young&apos;s modulus and Vicker&apos;s hardness during GPl zone formation in A1-2 at. pct Cu the following was observed: 1) the presence of grain boundaries does not have any perceptible? effect on the aging reaction; 2) the modulus charge is orientation dependent; 3) the activation energy for zone growth is confirmed to be 11 * 1 kcal per mole; 4) reaging after reversion is preceded by an incubation time that varies with temperature. An analysis is applied to the present data and to data of other workers and kinetic laws dependent on the quenching rate are determined. In Al-base Cu alloys the decomposition product of a supersaturated solid solution at low temperatures (for example 25°C) and the first product at moderate temperatures (for example 150oC) are Guinier-Preston zones of the first kind (GPI).&apos; These zones are nonideal and are thought Jo &apos;Onsist roughly of sheets of Cu atoms up to 150A in diam and one or two atoms thick.&apos; The kinetics of the reaction, ass — a2

Jan 1, 1961