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By Herbert H. Kellogg, Hugo Vasquez- Rosas

Recently the long-chain primary amines have been used extensively for the flotation of silicate minerals. The use of amines to float sulphide minerals has been investigated by several authorsl-5-l8 but most of this work has been done with the short-chain (less than six carbon atoms) primary amine compounds or the more expensive secondary, tertiary and quaternary amines. Perhaps the fact that the long-chain amines are good collectors for the common gangue minerals has led investigators to omit them from consideration as collectors for the selective flotation of metallic sulphides. The work reported in this paper was designed to investigate the use of a typical long-chain amine salt, laurylamine hydro-chloride, as a collector for the flotation of galena-sphalerite ores. The results show that laurylamine hydrochloride (LAmHCl), when used in small amounts, is a good collector for the selective flotation of sphalerite and galena from the common gangue minerals. The differential flotation of sphalerite from galena was not accomplished but the amine flotation of sphalerite after the standard xanthate flotation of galena is possible. The experimental work reported herein is not complete enough to be able to say whether amine flotation of lead-zinc ores would prove superior to xanthate flotation, or whether the method is even applicable to a more complex ore than the one used for this work. However, the apparent reagent costs for the flotation operations described in this paper seem to be less than for xanthate flotation. This fact alone should be sufficient to encourage the millman to investigate the use of these amine reagents, especially as these reagents are available on a commercial scale at a reasonable price. This paper has as its secondary purposes to illustrate how contact-angle measurements have aided in this investigation, and to bring forward some evidence concerning the mechanism of the collecting action of primary amines. Contact-angle Tests The contact-angle measurements were made by the method described by del Giudice6 and used in recent work by Taggart and his collaborators.7-9 The mineral specimens for the contact-angle tests were carefully chosen, to avoid cracks and inclusions of other minerals. All specimens were mounted in "transoptic" plastic mounts and the surfaces were cleaned by polishing with levigated alumina on a cloth-coverkd glass polishing wheel. Distilled water was used on the lap during the polishing and at all subsequent steps in the contact-angle tests. The mounted mineral specimens were handled with glass forceps and special care was exercised to prevent exposure of the clean surface to air or any other source of contamination.

Jan 1, 1947

By R. W. Smith

There are many inconsistencies and gaps in available information concerning the mechanism whereby dodecylamine acts as a collector for quartz. The author compares the studies which have been made in correlating the contact angle with adsorption density on quartz over all pH ranges, and attempts to resolve some of the inconsistencies. In recent years much information has been obtained concerning the mechanism whereby dodecylamine acts as a collector for quartz. Fuerstenau,1 for ex- ample, has shown that adsorption density and zeta potential under some conditions, at least, can be correlated with contact angle and flotation rate. There appear, however, to be several inconsistencies and gaps in information available. One inconsistency involves trying to correlate contact angle with adsorption density on quartz over all pH ranges. Fuerstenau's correlation at a collector concentration of 4x10-5 moles per liter dodecylamine acetate and about pH 10 shows a contact angle of about 80 degrees occurring at approximately monolayer coverage. If Gaudin and Morrow's2 and Morrow's3 contact angle data for near neutrality (pH 6 to 7) are now compared with deBruyn's4,5 adsorption data on quartz in a similar pH range, it will be noticed that a contact angle of 38 to 40 degrees corresponds to complete monolayer coverage (at an amine concentration of approximately 10"3 molar). In fact even at an amine

Jan 1, 1963

By Bruce W. Gonser, Robert J. Nekervis

EACH metal has a unique combination of properties that distinguishes it from other metal;. Su& a combination may account for applications that cannot be met very well by anything else. This is particularly true of tin, one of the earliest metals used by man. Table i shows the consumption of tin in the United States by usage for the years 1949 and 1950, which may be considered to be generally typical of current usage. The major applications-tinplate, solders, bronze, and babbitt-were well established a century ago. Applications for the metal and (probably later) of tin alloys started more than 5000 years ago. Fortunately for the ancients, tin is one of the metals whose oxide is easily reduced by carbon. Nature further simplified the refining problem by providing only one ore of commercial importance, cassiterite (SnO2). Tin is easily reduced from cassiterite. All that is necessary is high heat in the presence of carbon. It is quite possible that back in the dawn of history, tin was discovered when black alluvial sand was thrown on a fire, either to bank it or to put it out. SOURCES OF TIN All the important tin-producing centers are in the southern hemisphere, far away from the' industrial consuming centers. Fig 1 shows their location and 1950 production. Reserves are adequate, and the industry is able to produce considerably more tin than is

Jan 1, 1953

By AIME AIME

PROBABLY no man has been of greater service to the Institute and has kept more in the background than Henry Krumb. A Vice-President continuously) for the last eleven years, apparently neither his picture nor a biographical sketch ever have adorned these pages and were he forewarned in the present instance he would order us to "forget it." He is a Columbia School of Mines man, Class of '98. He worked underground at Rossland, B. C. for a time, then for a year and a half a. chief engineer of the famous Camp Bird at Ouray, Colo. For three wars he was examining engineer for the Guggenheims and since 1901 has been an independent consulting engineer with experience throughout the Americas.

Jan 1, 1939

By K. C. Hong, R. B. Jensen

The problem of determining the optimum set of steam volumes and cycle lengths for a single well undergoing multicycle steam stimulation in order to maximize the cumulative discounted net income has been formulated mathematically and programmed for a digital computer. The mathematical fonnulation of the problem and the method for its solution are discussed in this paper. The oil production performance during each stimulation cycle was simulated by either a constant percentage or a harmonic decline. Using simple analytical expressions for production performance, the cumulative discounted net income and cumulative time of operation were related to the pertinent process and cost parameters and two principal process control variables (cycle length and steam injection volume). The discrete maximum principles was used to transform the equations for cumulative time of operation and cumulative discounted net income into a set of simultaneous equations. The simultaneous equations then were solved by trial and error on a digital computer to determine the set of cycle lengths and stem injection volumes that gives maximum cumulative discounted net income over the project life. INTRODUCTION Steam stimulation is a process for improving the oil recovery rate from wells producing high-viscosity crudes. The process is applied on an individual well basis and is executed in a series of cycles, each consisting of three phases: steam injection, soaking (steam condensation), and production. Significant increases in production rate following the stimulation operation result from heating the reservoir around the wellbore. As heat is removed with produced fluids and dissipated into nonproductive formations, the production rate declines, usually to near the prestimulation value. Typical production responses are given in case histories reported by Owens and Suter,l and are depicted in Fig. 1. Duration of the production phase is equal to the time for the oil production rate to decline to some specified value and is called the cycle length. (Cycle length is defined as the producing portion of the cycle and does not include the downtime required for steam injection and soaking operations.) Termination of the production phase coincides with the start of steaming for the next cycle. The process is continued, cycle by cycle, until it becomes unprofitable. Models 2-4 have been developed to simulate behavior of a single well during one cycle of steam stimulation and have been used to investigate the effects of system and operating conditions on the production responses. However, these investigations have not shown how the models can be used to determine a most profitable set of operating conditions for a multicycle stimulation project. Perhaps these models are too complicated mathematically to be adapted readily to an optimization study. This paper presents a method for optimizing a multicycle steam stimulation project based on simple production performance models. First, the performance of a steam-stimulated well during each cycle was simulated by either a constant percentage or a harmonic decline model. Using these simple analytical expressions for production performance, the cumulative discounted net income (before tax) and cumulative time of operation for each cycle were related to the pertinent process and cost parameters and two process control variables—the cycle length and the steam injection volume. Finally, the profit function to be maximized was formed. The analogy between the above problem and problems of optimizing multistage decision processes that have been reported extensively in the chemical engineering literatures5-10 in recent years has led this investigation to the use of the discrete maximum principle.5-7 This principle was used to transform the equations for cumulative discounted net income and cumulative time of operation into a set of simultaneous equations characterizing the optimum operating conditions in terms of the two control variables. These equations

Jan 1, 1970

By W. J. Houk, F. C. Hull

To clarify interpretations of grain structures and to assist in calculations of spatial grain size distributions, plane distribution curves have been determined for random sections through four regular polyhedrons approximating the shapes of metal grains. The characteristics of the distribution curve for the average metal grain are predicted. IT was realized early in the history of metallurgy that metals are polycrystalline aggregates and that the size and shape of crystals affects the properties of the material. Reaumur1 in 1722 employed the microscope to examine the fractured surfaces of steel and of white and gray cast iron and suggested a polyhedral arrangement of the crystals. The first extensive investigation of the form of crystal grains was carried out by Desch.2 He examined the disintegrated grains from a ß brass sample and noted that the number of faces per grain ranged from eleven to twenty and that the number of edges per face varied from three to eight and the maximum occurred at five. While it has been found practical to examine isolated grains only in exceptional cases, it is always possible to make a plane section through the metal and examine the shape of the grain sections on the plane of polish. Desch2 tried to determine the relation between the form of a polyhedron and that of its plane sections for comparison with distribution curves of numbers of sides per grain section of actual metal samples. The polyhedrons investigated were the rhombic and pentagonal dodecahedrons and the orthic tetrakaidecahedron. However, the frequency distributions of the number of sides of plane intersections were not sufficiently characteristic to decide which polyhedron most closely approximated the average grain in a metal. Determination of Statistical Shape of Grain in Space Scheil3 was interested in the problem of calculating the distribution of grain sizes in space from the easily measured distribution of grain section sizes on the plane of polish. Assuming that the grains were spheres and using the plane distribution curve for a sphere shown in Fig. 1, he employed a successive subtraction method to calculate the spatial distribution. In order to evaluate the accuracy of these calculations, Scheil and Wurst4 determined the actual distribution of grain sizes in space in their sample of ingot iron by polishing off successive layers and following every individual grain in a series of micrographs. From curves of mean radius of intersection of a given grain vs thickness of metal removed in polishing, Scheil and Wurst attempted to derive the statistical shape of a grain in space. Their calculated plane distribution curve for this shape is compared with the distribution curve for a sphere in Fig. 1. A table of values based on this curve was prepared for calculating spatial distributions of grains. The calculated and measured spatial distributions of their sample then agreed much better than when a spherical shape had been assumed. In the present paper, an attempt has been made to learn something about the average metal grain by studying in detail the effect of the shape of regular polyhedrons on the plane distribution of areas and shapes of areas produced by random sections through them. From the data presented below, it can be concluded that the plane distribution curve for the average metal grain differs in three fundamental respects from the curve derived by Scheil and Wurst. Polyhedrons Selected for Study The polyhedrons selected for the statistical study are illustrated in Fig. 2 and consisted of a cube, a figure formed by cutting off the corners of a cube at the midpoints of the original edges, a tetrakaidecahedron, and a pentagonal dodecahedron. The length of edge on any one figure is a constant. For the above models the edge lengths were 3.50, 4.00, 2.00, and 2.08 in., respectively. A cube was selected for one of the polyhedrons because of its simple geometry, because it is a form that by repetition can completely fill space, and because it represents a convenient degree of departure from compactness beyond which the shape of

Jan 1, 1954

By P. L. Lavery

A numerical method to derive approximate solutions for stress intensity factors for rectilinearly anisotropic bodies without resolving to complex variable approach is presented. The method is based on the assumption that the crack opening profile can be simulated by a simple curve such as an elliptic function and a relationship is found for the stress intensity factor in terms of near tip displacements. An example solution is derived for a transversely isotropic body and the results are verified with Westergaard's stress function approach. The proposed model has a great potential for the applications to fracture mechanics of anisotropic rock materials.

Jan 1, 1984

By William D. Manly, John Towers, Paul A. Beck

RECENT work on grain growth in high purity aluminum and in a solid solution type alloy of aluminum and magnesium' showed that the isothermal increase of the average grain diameter D with time follows the equation [D = K(to + A)-Eq I] Here [to] is that portion of the total annealing time [t], which is available for grain growth, i.e. the annealing time less the time necessary for complete recrystallization. The parameters A and n depend only on the temperature. A has the dimension of time, and is usually of the same order of magnitude as the time for recrystallization: R. In some instances R may be substituted for A in Eq I. This is the case for example at long periods of annealing or at high temperatures, where both A and R become small in comparison with t. In such instances Eq I is simplified to [D-K-tnEq2] For high purity aluminum the exponent n increases in the ratio of about 1 to 5 in the temperature range of 350° to 600°C. 70-30 brass has been long known to exhibit grain growth of the continuous type, such as occurs in pure metals. For this reason, it was of interest to determine whether grain growth in brass also follows Eq I and 2 as it does in aluminum. Isothermal grain growth data for 70-30 brass were published in recent years by R. S. French2 and by H. L. Walker3 Fig I shows a log D vs. log t plot of French's data, together with the 500, 600 and 100°C data by Walker for 42.8 pct reduction by rolling. In such a log D vs. log t plot Eq 2 corresponds to a straight line with a slope of n. As seen in Fig I, the data of French and the 600°C data of Walker can be represented by straight lines. However, the 500 and 700°C data of Walker give curved lines and the average slope of his 500°C line is very different from the slope of the line representing French's data for the same temperature. Furthermore the curvature of the 700°C line suggests a tendency for grain growth to stop after 8 hr. If confirmed, this would constitute a definite deviation from Eq 2, not explainable on the basis of the specimen thickness effect found in high purity aluminum.1 Walker's specimens were 0.125 in., i.e. 3.18 mm thick, while the deviation occurs at a grain size of approximately 0.4 mm. A further point of divergence arose recently, when J. E. Burke suggested4 on the basis of Walker's data, that, instead of Eq 2, grain growth in 70-30 brass follows the equation [D-D. =K• t,Eq3] Here D, is the grain size as recrystallized at the temperature in question. Although it was possible to show5 that, for pure aluminum, for which isothermal grain growth has been carefully investigated, Eq 3 is incompatible with the experimental facts, the situation remained somewhat obscure with respect to 70-30 brass. In view of the discrepancies between the

Jan 1, 1948

By Erkki Laurila

INVESTIGATION of the methods of analyses for magnetite and ilmenite in the Otanmäki iron-titanium ore and respective mill products has resulted in certain improvements in the methods conventionally employed. The outcome of the investigations is summarized as follows: 1-Development of a diamond-drill core analyser for the determination of magnetic susceptibility of drill cores containing magnetic minerals. 2-Development of a magnetite-ilmenite analyser for pulverized products. 3-Development of a potentiometric method of chemical analysis for the determination of iron, vanadium, and titanium in succeeding steps from one test sample. 4-Proposal for a continuous and automatic magnetite assay method.

Jan 9, 1951

By R. W. Smith, C. Schroeder, R. Haddenham

Amphoteric surfactants are heteropolar organic compounds which possess at least two functional (ionic) oppositely charged groups per molecule. The ones studied are manufactured by General Mills and possess one or more long hydrocarbon chains plus a carboxyl group (s) and an amino or imino group. Hallimond tube and M. C. Fuerstenau micro flotation cell flotation tests were performed on quartz and hematite as a function of pH using amphoteric, cationic, and anionic surfactants as collectors. For the most part, flotation could be correlated with an interaction of charged groups on the collectors with oppositely charged sites on the minerals plus association of hydrocarbon chains. The comparison of flotation in a Hallimond tube and an M.C. Fuerstenau cell shows that one should use care in using the latter if one excludes an additional frother from the system. Also, it is interesting to note that sometimes greater collector concentrations are required in the Fuerstenau cell for comparable flotation recoveries.

Jan 1, 1974

By G. F. Leaming

The paper by R.V. Ramani and R.J. Sweigard is a wonderful description of the labyrinthine web that has been spun about the mining industry by energetic bureaucrats and politicians over the past 50 years. The remedy for the problem, however, is not more of the same, but less. That may be difficult for the industry to achieve, for it is not a technical solution but a political one. And the current fervor for more detailed planning at all levels of government and private enterprise has become deeply ingrained. The authors recommend the provision of more information about mining and mineral resources to "macro" (i.e., government) land use planners. They apparently overlook, however, the already strong tendency on the part of most government land use planners to consider themselves omniscient. Thus, giving them more information about the technical problems of mining will only make them want to get more and more involved in the "micro" (private, site specific) mine development and production plans of the individual mining firm. In fact, this has already happened at all levels of jurisdiction from municipal to federal government. Examples are legion. The most effective way to ameliorate the adverse impacts of government land use planning on existing and potential mining operations is to: (1) introduce greater flexibility in the definition of land use zones by local and state governments; (2) adopt realistic and relevant ambient environmental performance standards in governing relationships between mineral land uses and concurrent or subsequent nonmining land uses; (3) allow greater leeway for economic considerations in land use decisions in contrast to the explicit legalistic approach now in vogue; (4) recognize that all minerals are not the same and that sand and gravel mining should not be treated the same as underground metal mining, coal stripping, oil field production, or in situ leaching; and (5) eliminate the notion that mining operators should be responsible for determining in detail the use of land by subsequent owners of mined land. This last bit of conventional ethic really makes no more sense than requiring the builders of every shopping center or government office complex to provide detailed plans for the use of that land when its use for shopping or government is ended. Did the builder of Ebbetts Field plan for Brooklyn after the Dodgers went to Los Angeles? Should the developer of the Bingham Pit plan for suburban Salt Lake City after the copper mining goes to Chile? The nation's mining industry must address these questions before further bankrupting itself to provide more data to planners and spending thousands of dollars per acre to create land that when reclaimed is worth only a few hundred dollars per acre. ? Reply by R.V. Ramani and R.J. Sweigard We thank Mr. Learning for his valuable contribution. His views on the problems of land use planning and mineral resources are most welcome additions to our paper. As the title indicates, our paper was more concerned with the impacts of land use planning on mineral resource conservation than with the details of the planning process. On the whole, his five recommendations would be helpful for mineral resource conservation. However, we would suggest that the argument he presents for his final recommendation does not address the differences between mining as a land use and commercial or institutional uses. We believe that this difference is the crux of the issue. We share Mr. Learning's desire to ameliorate the adverse impacts of land use planning. Possibly the most detrimental impact is the loss of mineral resources. Any development, whether mineral or community, that does not give proper consideration to other resources can result in permanent loss or sterilization of resources. With proper planning, some of these losses can be avoided. As our paper indicated, one factor that limits the consideration of mineral resources, and ultimately leads to their sterilization, is the generally inadequate levels of resource characterization and understanding of the unique nature of mineral resources and mining operations. The last point raised by Mr. Learning is also important. In terms of reclamation and land use planning in mining districts, we certainly do not advocate spending more than what the results are worth. The main thrust of the paper was to explore the avenues for conserving the mineral resources so that, at some appropriate time, the issue of mining and reclamation can still be addressed. ?

Jan 1, 1986

By R. I. Jaffee, R. M. Evans

IN recent years, the interest in liquid metals as heat-transfer media for power plants has been very great. The possibility of the development of nuclear power plants has increased this interest and served as the impetus behind much research on low melting metals and alloys for such purposes. The principal reasons for consideration of liquid metals as heat-transfer media lie in their high thermal conductivity and consequent high heat-transfer coefficients, stability at high temperatures, and the high ranges of temperature possible. The element gallium possesses some of the requisite properties for a heat-transfer liquid. It is a unique material, having a low melting point and a high boiling point. Pure gallium melts at 29.78oC, and suitable alloying will produce a metal which melts below room temperature. The boiling point is about 2000°C. As it is a liquid metal, the heat-transfer characteristics would be good. Gallium is not now readily available, due in part to a lack of uses for the metal. Nevertheless, it is not a rare element, and a sufficient supply of gallium exists to permit its consideration for this use. Since gallium has some promise as a heat-transfer liquid, owing to its unique properties, research on the subject was carried on at Battelle Memorial Institute at the request of the Bureau of Ships, U.S.N. The research had as its objectives the determination of the effect of alloying on the melting point of gallium, and the study of the corrosion of possible container materials. In this research, alloys were found which had significantly lower melting points than pure gallium, but none which simultaneously fulfilled other additional requirements, chiefly the corrosion problem. Neither was it found possible to reduce the melting point of certain otherwise suitable alloys appreciably by small additions of gallium or gallium alloys. The results gave little hope that gallium alloys can be developed which enhance the good properties and minimize the undesirable characteristics of elemental gallium. Thus, gallium now appears less promising than other metallic heat-transfer media. The experimental thermal-analysis techniques used in this work have been described.' Experimental Results As a first approximation, the development of low melting gallium alloys was based on alloying elements suitable for use in a nuclear power plant, which also lowered the melting point of gallium. Information from the literature, summarized in Table I, indicates that. tin, aluminum, and zinc are the only suitable elements which cause a lowering of the melting point of gallium. Indium and silver also lower the melting point of gallium, but are of little interest for use in nuclear power plants. Of the elements reported not to lower the melting point of gallium, there is some ambiguity on the behavior of copper. Weibke3 obtained solidus arrest temperatures of 29°C for Cu-Ga alloys from 60 to 90 pct Ga, 0.8C lower than the generally accepted melting point. This may be the effect of a eutectic close to gallium, or, more likely, the result of impurities, or experimental error. The seven elements listed in Table I whose effects were not known were of potential interest if they lowered the melting point of gallium. Their effects were determined experimentally for this reason. Binary alloys containing nominally 2 pct of each of these elements were prepared in the form of 2-g melts by placing the components in a graphite crucible and holding them in an argon atmosphere at 370°C for 5 hr. These melts were then subjected to thermal analysis. In all cases. the solidus temperature was the melting point of gallium. Since these elements (As, Ca, Ce, Mg. Sb, Si, and T1) did not lower the melting point of gallium, they were not considered further as components of a eutectic-type alloy. Ga-Sn-Zn Alloys Preliminary considerations of this system for low-melting alloys were encouraging. All three binary systems were of the simple eutectic type. The composition and melting points of the eutectics were as follows: Sn-9 pct Zn (199°C), Ga-8 pct Sn (20°C), and Ga-5 pct Zn (25°C). Therefore, the probability of a ternary eutectic was high. For reasons to be discussed later, aluminum could not be used as an alloying constituent, leaving the Ga-Sn-Zn system as the only one of interest for low-melting gallium-

Jan 1, 1953

By Chikaosa Tanimoto

INTRODUCTION The committee on Rock Mechanics, Japanese Society for Civil Engineers, has been discussing 'soft rock engineering in Japan' and presented several papers concerning dam, tunnel, bridge and slope constructions to International Symposium on Weak Rock, Tokyo 1981. This is the summarized paper based on References of Okamoto et a1 (1981), Iida et a1 (1981), Working Group on Tunneling-JSCE (1981), Working Group on Bridge Foundations-JSCE (1951) and Kikuchi et a1 (1981), which can convey general view on engineering experiences with weak rocks in Japan. From the point of view to the origin and/or distinctive physical properties, weak rocks in Japan may be classified into (1) sedimentary, (2) weathered, (3) low welded-pyroclastic and (4) fractured ones. Their typical characteristics are summarized in the following section. Concerning dam foundations on soft rock, several hundreds have already been constructed and, at present, nearly one hundred are under construction or at planning stage. These dams, almost without exception, have some problems such as site selection, material selection for fill-type and concrete dams, design of dam and its foundation, and construction procedures, requiring special ingeneous and cautious measures to cope with the local geotechnical difficult situations. In tunneling, for the decade of 1970s, the number of tunnels in soft rock either completed or under construction was at least 160, including Seikan Tunnel of 53.9 km long, Nakayama Tunnel of 14.8 km long and so on. Most of these tunnels are distributed in the northern half of Mainland, consisting of a basement of Paleozoic strata and Plutonic rocks, overlayed by Neogene Tertiary formations which include large

Jan 1, 1982

PITTSBURG MEETING The One Hundred and Ninth Meeting of the Institute, for the presentation and discussion of technical papers, will be held at Pittsburg, Pa., Oct. 8, 9 and 10, 1914. This meeting is to be under the auspices of the Iron and Steel Committee, the Committee on Petroleum and Gas, the Committee on Coal and Coke, and the Committee on Non-metallic Minerals. Thirty papers have been secured by these Committees and will be presented at the meeting. These papers will be published in the September and October Bulletins. The Local Committee of Arrangements for this meeting is as follows: SAMUEL A. TAYLOR, Chairman. FRANCIS C. PHILLIPS. GEORGE S. RICE. C. F. V. Rys. KENNETH SEAVER. JOHN S. UNGER.

Jan 9, 1914

By I. Sheinhartz, H. M. McCullough

DURING the course of a lubrication study in relation to the compacting of metal powders, it became desirable to measure the thickness of sprayed graphite coatings on steel dies for hot pressing. The thickness of these lubricant coatings ranged between 0.0001 and 0.002 in. In their particular case, the authors were interested in a method for measuring the lubricant thickness on tapered die inserts having curved surfaces. The lubricant was sprayed on the inserts at an elevated temperature and it was desirable to measure the thickness as soon as possible after application. Various standard types of commercial equipment were tried. Most of the available devices operated on either a mechanical or magnetic principle. The mechanical devices, such as micrometers, dial indi-

Jan 1, 1956

By Joseph P. Brennan, Robert L. Vines

A historical comparison of the frequency of fatal coal mining accidents occurring underground in mines of various size ranges in the United States and in member countries of the Commission of the European Communities is presented. Frequencies are normalized on hours-worked and tons-produced bases. The comparisons rely on published and confirmed data and on theory for selective treatment of data in an effort to overcome reporting differences and basic differences in the mining conditions and system employed. Trends are identified ad projections made of the effect on accident records of various industry growth patterns. Conclusions are drawn regarding the reasons for differences between the records of U.S. underground coal mines and the records of those mines in European countries.

Jan 1, 1984

By Samuel Hoyt

THIS paper gives a brief description of an investigation made several years ago on the diffusion of zinc into copper. The material for that study was furnished in the form of thin copper strips coated with zinc. The result was required rather quickly and at not too great an expense, and especially information was desired as to the rate at which zinc would diffuse from the zinc coating into the copper and the temperature at which the operation should be carried out. A study of the requirements of this problem indicated that the solution might be secured by means of six determinations. This is the smallest number that will give the information desired and, at the same time, furnish checks on the accuracy of the determinations which justify an abbreviated experimental program. This does not count a preliminary test which was designed to give some idea of the correct temperature to use. The minimum number of temperatures that can be used is two. Knowing the rates of diffusion of zinc into copper at two properly chosen temperatures, it is possible to calculate the rate for any other temperature, and also to check the accuracy of the determination by means of the heat of diffusion, which is calculated from the effect of temperature on the rate of diffusion. The minimum number of determinations at any one temperature is three. The amount of diffusion which occurs at a fixed temperature is definitely related to the time of diffusion, so that by determining the amount of diffusion for three different time intervals, this relationship may be established and possibly a check on the accuracy may be secured. This accounts for the six determinations or experiments, and suggests the logical plan of the work. The check used here is not generally applicable to diffusion phenomena, but it seems to hold closely enough for the limited amount of diffusion in this investigation to justify its use.

Jan 1, 1928

By James Ferguson

THE fact that little if anything has appeared in the technical press or in the Transactions of the Institute on the subject of roll shells proper, used in various grinding appliances such as Cornish rolls or Chilean mills, may be taken as an incentive, if not an excuse, for the present article. No attempt is made to enter into a. discussion as to the theory or mathematics of crushing as performed by rolls, the subject being treated in a general way with respect to the manufacture of roll shells 'and some salient points touching on their adaptability and wear in service. While it stands to reason that skill coupled with judgment in the mechanical design of rolls, Chilean mills or other types of grinding machinery, with special reference to strength of parts, nicety of adjustment and other mechanical features, stand for efficiency in their operation .and satisfaction in service, the exceedingly important item. of roll shells or other wearing parts entering into their construction should not be lost sight of. In other words, a well-designed piece of grinding machinery is just as inefficient in service, when equipped with poor roll shells or shells made of the wrong or an inferior grade of metal, as good roll shells made according to the best practice the steel maker knows, working on an old or antiquated set of rolls. Unfortunately there is a tendency occasionally for the machinery builder to blame the steel maker or vice versa if roll shells do not wear well or evenly, or if they break before being worn down to their ultimate thin point. There is no occasion for this attitude, as the product, of each must stand on its own merits. But it is essential that the two work in harmony since the machinery builder usually does not furnish the shells for his rolls or grinding mills, but depends on the steel maker, who makes a specialty of this rolled product, to give the particular needed element of efficiency to his machine.

Jan 9, 1914

By Percy Barbour

The town of Goldfield, Nevada, with the exception of six stone buildings, was burned to the ground to-day. One man is dead from causes attributed to the fire. A woman is missing and is believed to have perished and several persons were treated for burns as the result of the conflagration believed to have been of incendiary origin which started in the old Tenderloin District. The water supply was not sufficient and dynamite only scattered the frame structures and added kindling to the flames which were fanned by a forty-mile wind. Newspaper Dispatch, July 6. No former Goldfield resident could read that dispatch with unmixed feelings. About two o'clock one morning the crowded train from San Francisco landed me in Goldfield no more hours late than it habitually was. The desert air was clear and crisp and bracing but the pandemonium of cab and bus drivers did not drown out the sounds of music and merriment which floated from the blaze of light which was Goldfield about three-quarters of a mile from the station. As I stood in the ferry house, at the foot of Market Street, awaiting the Oakland Ferry, an old friend of mine, down to see who was departing for the greatest boom town of this generation, informed me that if I had made no reservation for quarters in Goldfield, I would be unable to obtain any, even chairs in the hotel lobbies were renting for $4 per night, and volun-teered the use of his room there for my convenience until his return. He described the house and location, which I identified without difficulty, but found no one to direct me to the room. I peered through a glass door into a room which seemed to be unoccupied and timorously entered and turned on the electric light., I found mail on the dresser addressed to my friend,

Jan 8, 1923

By C. Y. Cheng

THE purpose of this note is to show that the dislocation mechanism controlling the creep of Fe-4 pet Si alloy1 may equally account for the behavior of a-Fe2 over the same temperature range. A recent study of the creep behavior of a-Fe has been made by Ishida et al.2 Their results were in agreement with the mechanism of nonconservative motion of jogged screw dislocations over the entire range of temperatures investigated, from 480° to 1045°K. However, the observed creep rate was much higher than that which could be accounted for by the above model unless the authors assumed that pipe diffusion became significant below 775°K. More recently, Cheng et al.1 inves-gated the creep of Fe-4 pet Si alloy over about the same temperature range and found that the results could be correlated fairly well with a dislocation climb mechanism as represented by Eq. [l]. Proceeding as shown previously,1 if creep is controlled by a single climb mechanism, at intermediate stresses, the shear creep rate, y, can be represented by where n and K are material constants {K is independent of the temperature but dependent on the structure, that is, K decreases during the primary stage and reaches a steady-state value over the secondary stage of creep), t is the applied shear stress, G is the shear modulus, gc is the free energy of activation for creep (usually equal to that for self-diffusion, gd), and RT has the usual meaning. By solving for y, the apparent activation energy for creep, Q which can be determined experimentally, is given by where hc is the enthalpy of activation for creep which usually is also equal to that for self-diffusion, h^. By using Eq. [2], the data in Fig. 2 of Ref. 2 can be re-plotted as shown in Fig. 1. By comparing the two figures, it is seen that the slight increase in the apparent activation for creep over Region II, as noted in Fig. 2 of Ref. 2, is due to the influence of temperature on the shear modulus rather than of the stress on the

Jan 1, 1969