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By B. D. Crawford, S. A. Falconer

ONE of the outstanding achievements in connection with this country's war efforts has been the ability of our mining industry to supply from domestic sources many of the minerals of strategic importance that formerly were obtained principally from abroad. In order to meet the war-born demands for these scarce minerals, it has frequently been necessary to develop special methods for treating ores and waste products hitherto considered too low-grade to be workable; and to improve the efficiency of older beneficiation processes. Important in this respect have been the recent technological advances in the field of froth flotation of nonsulphide minerals. Because of the refractory nature of many of these domestic ores, and, in many cases, the limited available technical data regarding their treatment, much research work has been necessary. The following examples describe the procedures and reagents used, and the results obtained, in certain laboratory flotation investigations conducted by American Cyanamid Company's engineers at the Cyanamid Ore Dressing Laboratory on ores containing such minerals as scheelite, manganese oxides and carbonate, ilmenite, brookite, kyanite, garnet, spodumene, mica, feldspar, celestite, fluorite, chromite, corundum, and cassiterite. In presenting these data, we wish to point out that many of the minerals listed have previously been tested, and their amenability to flotation reported, by other investigators-notably those of the United States Bureau of Mines. In some instances the procedures and reagents used in the treatment of some of the following described ores follow rather well-established lines, and with one or two exceptions, the reagents used were well known. However, many of the ores tested did not respond well to simple conventional procedures and it was necessary to adopt special methods of conditioning and desliming, reversal of the usual order of floatability of some of the minerals, multiple cleaning, etc., in order to secure separations. Except where otherwise noted, all numbered and trade-marked reagents mentioned in this paper are marketed by the American Cyanamid Co. or the American Cyanamid and Chemical Corporation. TUNGSTEN ORES Tungsten minerals, vitally important in the war industries of the United States, rank high in the list of those we formerly had to import in order to supply our needs. Most of our domestic ores of tungsten contain scheelite as the valuable mineral. Today there are in the neighborhood of twelve tungsten operations in this country where flotation is used as the main or accessory form of benefication. It has, of course, been known for some time that scheelite and other tungsten minerals respond to treatment by flotation.

Jan 1, 1944

By Edward Wisser

The environment of an ore body is taken to mean not only its physical surroundings but every factor, passive or active, that conditioned the ore shoot, saving only the original composition of the solutions that formed the shoot. Collection of data related to the shape and characteristics of veins should be followed by correlation of the data and the formulation of generalizations regarding ore formation. The nature of the criteria used in arriving at these generalizations is discussed. Certain of the criteria, when used with an understanding of their underlying causes, become "ore- guides." In the course of his study the geologist must not confine himself to the immediate surroundings of the veins, but should attempt to work out the geologic history of events culminating in the crucial epoch for any mining district, the period of mineralization. The work may involve study of features far removed from the veins and related to them only indirectly. It commonly means thorough study of the geology of the entire region surrounding the ore deposits. THE following question has been suggested for discussion: [t] "Are there any criteria by which one can determine when mining operations have reached the roots of an ore deposit?" The question deals less with the roots of a particular ore body than with the lower limit of the vertical range within which ore bodies may be expected. It concerns a critical line upon the longitudinal vertical projection of a vein.[t] Below this line it is useless to look for ore shoots; above the line exploration below the bottoms of individual ore shoots may be justified. Can we learn to determine the position of such a line? In some multivein districts the line for any given vein may be approximated by simple interpolation or extrapolation. Where this is possible the bottoms of the lowest ore shoots in the various veins are points on an imaginary, gently rolling surface. The trace of this surface upon the vein is our critical line for that vein. The imaginary surface rolls so gently that it may be projected from two or more known veins to an unexplored vein near by. Here is a criterion for the bottoming of ore that has nothing to do with changes in the appearance of the vein in question; it rests solely on the depth at which the ore bottomed in adjacent veins. The method is not applicable in districts only slightly explored in depth, nor where the lower limit of the ore-bearing horizons

Jan 1, 1939

By Nicholas J. Grant, Henry Epstein, John Chipman

FOR many years steel producers have been concerned with the presence of hydrogen in steel. Hydrogen dissolved in excess of its solid solubility at the melting point may cause bleeding and gross unsoundness in ingots and castings. In fully-killed steels the hydrogen content which results in these difficulties varies with the alloy content1 and may range from 6 to 12 ppm.* It is also recognized that of heat treatment diminishes rapidly as the size of the part to be treated increases. The time required to remove a specified fraction of the hydrogen present increases as the square of the diameter of the section, making the treatment of large- sizes impractical. In order to prevent bleeding and gross unsound-ness due to hydrogen, and in view of the inadequacy of corrective heat treatment alone to provide optimum properties when hydrogen is present in large sections, efforts to limit the hydrogen content must be taken while the steel is still liquid. The main subject of this paper is a discussion of the factors affecting the hydrogen content of liquid steel in acid and basic open hearth, and basic electric two-slag furnace processing. Literature Survey Because many of the results and observations reported in the literature have a direct bearing on the results obtained in the present research and form part of the basis for conclusions reached, a brief summary of the findings is necessary. Methods for experimental investigation of hydrogen in liquid steel are comparatively new. The first attempts to estimate the hydrogen content of the open hearth bath were by Kalling and Rudberg,6 who devised a method for collecting gases evolved from the boiling bath of a basic open hearth furnace. They found that the gas during the boil generally contained 2 to 3 pct H2. From this and Sieverts'

Jan 1, 1958

By W. H. Craigue

THE scope of this article covers only the mathematical principles involved in discounting to present worth future expected profits and it is believed answers definitely two questions, which were raised at a recent meeting of the Committee on Methods of Valuing Coal Properties, as follows: 1. The accumulative effect of carrying charges on the value of coal mines showing definitely the number of years beyond which the coal may not be mined at a profit and subsequent to which the possession of any unmined coal will be a liability rather than an asset. 2. The effect on the valuation of coal mines, in the presence of the carrying charges described in question 1, of an increase in plant capacity and production. In general, in considering these questions, it may be stated that the consideration of an increase in plant capacity and production follows as a matter of course after a determination has been made of the year beyond which no profits are to be realized (giving the carrying. charges accumulative effect, or in other words capitalizing the carrying charges, as shown hereinafter). For example, if it is determined that any coal that is unmined after 45 years will have no value or less than no value, the question immediately arises as to whether or not a plant should be constructed that would result in a yearly production great enough to extract the entire tonnage in a time less than 45 years, and if so the number 'of years less than 45 years that would, from a financial stand-point, be the most desirable, all under the assumption that the market for the product or the transportation facilities are such that the yearly production can be increased to the desired amount.

Jan 1, 1933

By J. Geertsma

In order to obtain a better insight into the pressure-volume relationship of reservoir rocks a theory of pore and rock bulk volume variations is presented. The theory is independent of the shape of the pores but is restricted to isotropic porous media built up of continuous homogeneous matrix material. The main conclusion obtained from this theory is that only three elastic constants and three viscous constants are required for describing pore and rock bulk volume variations if the porosity is explicitly introduced into the treatment. In addition, reasonable approximations are introduced for various types of reservoir rock, e.g., sandstones, limestones, and shales, which lead to further simplifications of the basic formulas. In consequence there is then a further reduction in the number of deformation constants which have to be determined experimentally. It is shown how measurements of these remaining deformation constants can be performed most conveniently. Finally the application of the theory to reservoir studies is discussed and the translation of experimental results obtained in the laboratory into reservoir behavior is considered. INTRODUCTION The decline of fluid pressure in connection with the withdrawal of fluid from an underground reservoir gives rise to a change in volume of both reservoir fluids and reservoir rock. The volume variation of the reservoir rock results in a decrease of both the pore volume and the total volume of the fluid-filled formation. Whereas the variation in volume of the reservoir fluids with pressure is usually known from PVT analysis, that in the volume of the porous medium is rarely measured, as it is considered of minor importance in reservoir engineering. Nevertheless, certain experimental results' suggest that in a number of cases the neglection of the variation in pore volume may introduce errors into material balance calculations of reservoirs producing above the bubble point. Only a few experimental results on the compressibility of porous rocks have been published. The compressibility of pure quartz and of calcite can be found in a paper by Adams and Williamson'. Botset and Reed' carried out some experiments on the compressibility of loose sands, while Carpenter and Spencer' measured the compressibility of a number of consolidated sandstones, which data were supplemented by Hughes and Cooke5. Hall' finally reported a number of experiments designed to study the influence of the porosity on the compressibility of oil-bearing formations, from which it appeared that, particularly in the low porosity range, the compressibility of the pore volume is important enough to be taken into account. Difficulties, however, arise in applying these experimental results to field cases. This is partly due to the fragmentary nature of the published data. Yet even if more complete data were available, the need for a theoretical background would be strongly felt. Such a background can be partially found in studies carried out by Biot,6,7 who published a theory of elastic deformations of porous materials and their influence on fluid displacement within the pores, by Lubinski8, who studied the stress distribution in an elastic porous medium neglecting pore compressibility, and by Gass-mann" who mathematically analysed the elasticity of packings of spheres. The contributions of Biot intro-duce a number of deformation constants which are impractical for reservoir rocks from an aspect of experi-mental determination. The theory developed by dass-mann is correct but difficult to read. It appeared, how-

Jan 1, 1958

By Dr. O’Neil Thomas J., Donald W. Gentry

Introduction “A Western mine is a hole in the ground owned by a liar. . ." -Mark Twain THE CAPITAL INVESTMENT DECISION Decisions pertaining to a firm's proposed capital investments can have vital short- and long-term consequences on the organization's ability to compete, and even survive.Capita1 investment decisions, in general, center around two fundamental activities: (1) allocating capital funds to specific investment projects or assets, and (2) obtaining necessary financing in such proportion as to increase the overall value of the firm. In essence these activities or decisions describe the science of finance (as contrasted with economics). Fimnce has been described in general terms as the study of how a present, known amount of cash is converted into a future, perhaps unknown, amount of cash (Archer, Choate, and Racette, 1979). Fundamental to understanding the science of finance and the capital investment decision process in general are the basic concepts relating to cash flow transactions, time, income generation (markets), expected returns, and risk. The functions of finance may be segregated into three fundamental decisions which a firm must address: (1) the dividend decision, (2) the financing decision, and (3) the investment decision. These decisions are interdependent and their joint impact on the objective of the firm must be considered. This book primarily addresses the concepts and components associated with the investment and financing decisions as they affect the practice of mine valuation. Responsibilities of Management A primary assumption incorporated in this book is that the fundamental objective of any firm is to maximize its value, or wealth of its owners (stock- holders). Here, the term wealth refers to the total current market value of the firm's assets. In the case of corporations, the wealth or value is considered to be represented by the market price of the firm's common stock. The price of the firm's common stock obviously will be affected by its investment, financing, and dividend decisions. Consequently, an optimal combination of these three decisions should maximize the value of the firm to its stockholders. It is important to point out that wealth maximization is a more appropriate and inclusive goal for the firm than profit maximization. Indeed, there is a difference between the two objectives in most situations. For instance, a firm can always raise profits by selling stock and investing the proceeds in treasury bills or certificates of deposit. This type of activity, however, would rarely cause net shareholder wealth

Jan 1, 1984

By W. H. Emmons

The exploration of deposits of the metals will never become an exact science. There will always be an element of uncertainty in prospecting and developing mines. In countries where the surface has been closely scrutinized, most of the deposits whose outcrops contain valuable metals have probably been discovered. Many metalliferous deposits, however, are normally so much altered at the surface that the true significance of their outcrops is likely to be obscured. If a deposit is not exposed, its presence may become known by some one of its characteristics that is different in kind or in degree from a similar feature of the associated rock. Thus, a deposit that is not exposed may be discovered because of its magnetic property. So few minerals are strongly magnetic that the value of magnetic surveys is limited, but the dip needle has nevertheless proved of great aid in locating magnetic belts, and these in some regions are associated with workable iron ores. The Cuyuna Iron Range of Minnesota, which does not exhibit any outcrop of iron ore, was discovered by drilling "areas of attraction" that are due to belts of magnetic rocks associated with the iron ores. In some regions the use of the dip needle is justified, even if it does no more than reveal the strike of the rocks, since a knowledge of the latter enables the driller to locate and point his holes to advantage. The measures of gravity by the use of the pendulum are so accurate, or the limit of error is so small, that one might detect the presence of a concealed tabular deposit approximately at the surface, 34 ft. (10.36 m.) thick, having a density double that of the surrounding rocks. However, not many deposits have a density twice that of ordinary rocks and a thickness as great as 34 ft.; if they lie a short distance below the surface the density or the thickness must be even greater. Consequently, there is not much hope of sufficiently developing the gravity method of detecting deposits of heavy ores to make it of practical value. If the limit of error could be reduced to about one-tenth the present factor, and if the rather tedious and painstaking methods of determining gravity that are now in use could be simplified, the method would promise some degree

Jan 1, 1918

F. J. DE WILDE, Galena, Ill. (written discussion *) .-As it is impossible to spare the time for a lengthy discusson of this excellent paper, I am dwelling only on points where either the information is not clear or opinion differs radically from that of the authors. On page 1218, relative to oil rock, the authors state that the presence of oil rock is always taken as a favorable indication of proximity to ore. As thick, highly carbonaceous, oil rock has been found quite often in isolated patches outside of the district proper, the mere presence of oil rock is not always an indication of the propinquity to ore deposits. Regarding glass rock, I agree with the authors, that, generally speak-ing, sphalerite in the glass rock is spotty; however, they fail to mention that nearly all mines contain more or less ore in the glass rock, the usual location being near the toe of the pitch. On page 1220, they say that disseminated deposits are only found in, or close to, the oil rock. To refute this statement, I refer them to a typical disseminated deposit situated at the Adam and Eve shaft of the Frontier Mining Co. This deposit is located in the central horizon of the Galena dolomite, that is, in those sedimentaries containing flint nodules. Perfect crystals of sphalerite are found disseminated through-out the rock, and are commonly known by the miners as strawberry jack. I believe all top runs, or upper deposits as described above, should be classed as disseminated; physically the ore makes its occurrence in just such a manner.

Jan 11, 1919

By J. R. CAIN

SAMUEL L. HOYT, ? Nela Park, Cleveland, Ohio (written discussion?). The work that Dr. Cain is doing on gases in steel should have a highly important bearing on investigational work in connection with steel-making practice. We found, for example, in our work in connection with the use of manganese in open-hearth practice that we needed expressions for the manganese efficiency and the "condition" of the steel. To get these figures we assumed that we would need to know the amount of FeO at different stages of the heat and the amounts of the gases present. This required simultaneous analyses of our samples for FeO and the gases and Dr. Cain seems to be the only investigator who has considered the analytical work from this point of view. That he has done so is very encouraging and it is to be hoped that his work will solve the mys-teries now surrounding this neglected phase of steel metallurgy. Those interested in the Ledebur method for use in connection with the efficiency of manganese as a "deoxidizing " agent will he disappointed to learn that more recent work at the Bureau indicates that Ledebur determinations are not reliable. The principal source of error seems to be due to the partial reduction of the ferrous oxide by the carbon present in the steel. However, it seems like an unnecessary criticism of the Ledebur method to state (p. 1319) that it proved of little value because it showed little differences in oxygen for a series of steels treated with ,various reagents and showing variations in physical properties and free-

Jan 12, 1919

By C. R. Hayward, H. O. Hofman

I. INTRODUCTION. THE aim of instruction in a metallurgical laboratory is to make real the principles on which metallurgical processes and operations are based, and to foster the spirit of investigation: The materials with which experiments are carried out are ores, metals, and metallic compounds. The method varies with the end sought. A class may work as a whole, each member contributing his share to the solution of a problem, or the students may carry on investigations independently; the former exemplifies class-research; the latter, individual research. It is with a branch of the former, with special reference to ore-treatment that the present paper intends to deal. In smelting an ore by a well-established process, the result is shown by analyzing the products to see whether their compositions correspond to those calculated in making up the charge; by taking account of stock to show the distribution of metal in the different products made and the losses from dust and volatilization, by casting a thermal balance to find the ,distribution and losses of heat; and by making a cost-sheet to ascertain, as far as possible, the necessary outlay of money. In, lixiviation and amalgamation, the mode of operating has to be varied to adapt a process to the individual ore. Here a number of tests become necessary. Each will consist of a series of experiments with one variable, in order to find the conditions under which the variable gives the best result; a. summary of several tests will give the best method of operating.. Working a number of charges with the best method will furnish the data desired for ascertaining the recovery of metal,

Jun 1, 1909

By C. L. Baker

The total production of petroleum in the Gulf Coast in 1927 was 54.541.180 bbl., .5.655.665 bbl. more than in 1926. The Texas total was 49.129.910 bbl. (Table 1) and the Louisiana tota1 5.411.270 bbl. (Table 2). Louisiana production decreased 278.028 bbl., compared with that of 1926. Spindletop produced nearly 44 per cent. of the Texas total. Initial production in Louisiana amounted to 62.865 bbl. and in Texas to 352.955 bbl.' The Oil and Gas Journal gives a total of 1145 wells

Jan 1, 1928

By S. C. Das. Gupta, B. S. Lement

isothermal formation of martensite occurs in the range of —65o to —197oC and is always preceded by some athermal transformation. By rapid cooling the isothermal, but not the athermal, component of transformation can be suppressed. Stabilization against isothermal transformation can be induced by cycling from below M. to room temperature. A LTHOUGH the transformation of austenite to XV martensite is generally believed to occur only on cooling, recent evidence indicates that this reaction can also occur at constant temperature. Isothermal formation of martensite was observed in tool steel by Fletcher, Averbach, and Cohen.'. They found that the hardening reaction that occurs during the quenching of a plain carbon or low carbon alloy tool steel does not stop immediately when room temperature is reached; instead austenite continues S. C. DAS GUPTA is Research Fellow, Department of Metallurgy, University of Notre Dame, Notre Dame, Ind. B. S. LEMENT, Associate Member AIME, is on the Research Staff, Department of Metallurgy, Massachusetts Institute of Technology, Cambridge, Mass. Discussion on this paper, TP 3123E, may be sent, 2 copies, to AIME by Dec. 1, 1951. Manuscript, April 16, 1951. Detroit Meeting, October 1951. This paper represents part of a thesis by S. C. Das Gupta submitted in partial fulfillment of requirements for the degree of Doctor of Philosophy in Metallurgy to the University of Notre Dame. to transform at room temperature although at a decreasing rate. Since only a small amount of austenite transforms in this fashion, isothermal formation of martensite was considered to be merely a "tailing off" effect of the main hardening reaction. Another point of view was advanced by Kurd-jumov and Maksimova"' * who reported that the austenite-martensite reaction could be suppressed by rapid cooling of a 6 pct Mn-0.6 pct C steel in liquid nitrogen and that as much as 25 pct martensite could be formed by reheating to and holding at subzero temperatures above that of liquid nitrogen. These investigators came to the conclusion that martensite is thermally nucleated at certain special regions in the austenite and subsequently grows to observable dimensions. Isothermal transformation of austenite to martensite was cited by Fisher, Hollomon, and Turnbull" as evidence supporting another nucleation and growth theory of martensite formation. According

Jan 1, 1952

By E. W. Parker

Anthracite, as sent to market, comes under three general terms of description: characteristics, source and size. Anthracite is generally classified as white ash, red ash, or Lykens Valley. The white ash coals are sometimes further described as "hard" or "free-burning." Lehigh white ash would come under the former description and Shamokin white ash under the latter. As a rule, it may be said that the nearer the origin of the coal to the western extremity of the anthracite region, the softer and more free-burning it is. Indeed, for many years the coal from Trevorton, at the western tip of the Middle Western field, was classified as "semianthracite" in the shipment reports. Lykens Valley coal is always a red ash coal, with a higher volatile content than the general run of anthracite, and consequently free-burning. The name does not exclusively indicate the neighborhood in which the coal is dug, but rather refers to the beds from which it is obtained. These beds lie, not above the Pottsville conglomerate, as is the rule, but encased in it. The extreme eastern limit of the Lykens Valley beds would seem to be about Tremont, in Schuylkill County, and the Natalie mine, near Mount Carmel. There are, of course, traces of these beds farther to the east, but they do not seem to be workable. There are as many as six of the Lykens Valley measures found in the conglomerate at some points, but to a large extent they are unworkable. Whether this coal is obtained in the Lykens Valley proper, where the beds were first identified, or from the Shamokin Valley, it is always Lykens Valley coal, and it has long been considered a premium coal, especially desirable for domestic use, particularly when a quick, hot kitchen fire is desired. Coals are, of course, frequently marketed under special names—Jeddo, Scranton, Kingston, Old Company Lehigh, Famous Reading, Lacka-wanna, etc.—which, of course, have the trade significance which their producers and vendors have built up. General Description of the Various Coals, with Name of Seam and Producing District This is partly covered in the paragraphs above. Lykens Valley coal is produced from one or another of the six Lykens Valley beds lying within

Jan 1, 1930

By J. V. Emmons

THE processes of hardening and tempering steel tools within the past 15 or 20 years have been so developed that the forward strides of the industry can scarcely be followed by the average observer. No small part of the credit for this phenomenal advancement is due to the improved methods of measuring the high temperatures necessary. Pyrometry has made possible the discovery and use of the many special alloy steels the wonderful properties of which are revolutionizing the industrial world. So sensitive are these steels to changes of temperature that often a variation of only 10° F. at a critical point of the heat treatment will cause the failure of the tool. In the tool-manufacturing industry today, accurate control of the many heating operations is imperative. The principal processes in the manufacture of tools that require accurate high-temperature measurements are annealing, carburizing, hardening, tempering, and laboratory research. Several other operations, such as forging and straightening, use rougher and correspondingly less accurate methods. These operations are usually performed in the following approximate ranges of temperature: DEGREES F. DEGREES F. Annealing 1000 to 1700 Tempering 200 to 1200 Carburizing 1400 to 1000 Forging 1400 to 1800 Hardening 1400 to 2500 Straightening 300 to 1300 Laboratory research covers the entire range. Annealing and carburizing are usually done in muffle or semi-muffle furnaces, heated with coal, coke, oil, gas, or electricity. Many of them are of large size, holding several tons of steel at one charge. Both indicating and recording pyrometers are used. The recording instruments are generally of the thermoelectric type, while for the indicating, both optical and thermoelectric are used.

Jan 9, 1919

By S. Wiederhorn

The energy and force of interaction between a crack and a slip band have been calculated. When the distance between the crack and the slip band is greater than the dislocation spacing of- the slip band, the force on the cgrack is perpendicular to the slip band. The energy needed to propagate a crack against this force can be lawe enough to pevmit crack propagation parallel to noncleavage planes. SEVERAL recent experiments have demonstrated the occurrence of crack-slip band interaction in ionic crystals having a NaC1-type structure. Stokes, Johnston, and Lil have studied the nucleation and growth of cracks in MgO. From their observations, they conclude that slip bands have the ability to halt and stabilize cleavage crack nuclei. Gilman2 has shown that a crack, propagating along a (100) cleavage plane in a previously deformed LiF crystal, tends, at certain points within the crystal, to switch to (110) planes. He reasons that plastic deformation reduces the cohesive energy of the (110) planes below that of the (1130) planes, making possible (110) crack propagation. Keh3 has demonstrated that when indentations are made in MgO, crkcks form along (110) planes at the indentations. Gilman2 attributes the formation of these cracks to plastic cieformation. There is some doubt as to the formation of cracks on (110) planes. Kuznetsov4 in his discussion of crack propagation in rock salt, shows that splitting along (110) planes requires 1.76 times as much energy as splitting along a stepped (100) surface. Therefore, the observed (110) cracking in LiF and

Jan 1, 1962

By Michael Hoch, Walter C. Wyder

The Cr-Ni system was investigated between 900" and 1400°C and 45 to 100 wt pct Cr. The Cr-Fe system was studied between 1200" and 1385°C and 70 to 100 wt pct Cr. Powdered alloy compacts were produced from high-purity chromium, nickel, and iron poulders. The compacts were sintered in an argon atmosphere and then machined into small, 0.030-in. diam cylindrical specimens. These were then heated by induction in the high-temperature X-ray diJfractwn camem under a helium atmosphere and irradiated with copper Ka radiation. From the results of the high-temperature X-ray diffraction patterns it can be concluded that chromium exists only in the bcc form, and that no eutectoid reaction occurs in the Cr-Ni system in the temperature interval 900" to 1400°C. The X-ray diffraction patterns are in agreement with the Cr-Ni phase diagram of Bechtoldt and Vacher, and Williams. It is possible that chromium undergoes one or more allotropic transformations between room temperature and its melting point. Most of the evidence was gathered from the study of the chromium-rich ends of the Cr-Ni and Cr-Fe binary systems. All the investigations rely heavily on indirect methods: thermal analysis, electrical resistivity, and micro-graphic inspection of quenched samples. In the present work the chromium-rich side of the Cr-Ni and Cr-Fe binary systems is studied, using high-temperature X-ray diffraction techniques. Thus the coexistent structures can be observed directly at temperature. PREVIOUS INVESTIGATIONS ~ansenl shows two possible Cr-Ni phase diagrams 1) a simple eutectic [Liquid =a-Cr(bcc) + y-Ni(fcc)], 2) a eutectic [Liquid+ P-Cr(fcc) + y-Ni(fcc)] and euctectoid [p-Cr(fcc) ==a-Cr(bcc) + yNi(fcc)]. The latter is based on the work of Grant and co-workers.2 Stein and rant'" placed the eutectoid composition at 1215°C and 68 wt pct Cr; their diagram is shown in Fig. l. Similarly, Sully3 also discusses the two proposed diagrams. Price and Grant,4 working on an isothermal section of the Cr-Ni- Fe ternary diagram at 1300°C, made no mention of a ß-chromium phase (fcc). The ß-chromium structure was also reported by Misencik 5 in the Cr-Nb(Cb) system. Williams 6 studied the Cr-Ni system using precipitation techniques. His work included the chromium and nickel solvus lines below 1250°C. He reported no ß structure nor any eutectoid reaction. The solvus lines which he produced were very similar to those of Jette, et al 7 below 1000°C. He concluded that Grant and coworkers2 had misinterpreted their data, and that effects which they had reported were actually due to the rapid and extensive precipitation of the nickel-rich phase. Bechtoldt and vacher8 used sintered powdered alloy compacts in an attempt to find the ß phase. They used metallographic and room-temperature X-ray diffraction techniques and also failed to detect the fcc chromium phase. They attributed the low slope of the chromium solvus at approximately 1150°C as the probable cause of the abundant precipitation obtained. They also stated that the precipitation was the probable cause for the abrupt discontinuities in the thermal analysis and electrical resistivity data which led to the conclusion that a eutectoid reaction existed. Fig. 1 also shows their diagram. Grigor'ev and coworkers9 investigated the polymorphic changes of chromium in the Cr-Ni phase diagram. Using standard microstructural and thermal analysis techniques, they published a phase diagram which contained five polymorphic forms of pure chromium and four eutectoid reactions. They stated that the room-temperature bcc chromium transformed to a fcc structure at 930°C, to bcc at 1300°C, to hcp at 1650oC, and then finally to bcc at 1830°C. The eutectoid reactions were placed at 850°, 960o, 1140°, and 1220°C. Also to be noted was the fact that the uppermost phase, the bcc above 1830°C, was different from the upper phase of Grant and coworkers,2 the fcc above 1840°C. Their eutectoid reactions, temperatures and compositions fall

Jan 1, 1963

By Richard S. McCaffery

This paper considers certain aspects of the acid bessemer process, particularly in its relations to the duplex process—that combination in which the pig iron is first desiliconized and decarburized in acid bessemer converters and then dephosphorized in basic open-hearth furnaces. The acid bessemer process employs an acid-lined converter and produces an acid slag. The blow is usually thought to eliminate the silicon and manganese as oxides and then to burn off the carbon as carbon monoxide On account, however, of the relatively large amount of metallic iron present in the converter, compared with the relatively small amount of the impurities it is desired to oxidize, the first reaction in the converter probably is the formation of iron oxide, which dissolves in the bath and acts as an oxygen carrier for the silicon and carbon. As soon as iron oxide is dissolved throughout the bath, the oxidation of silicon commences; but in the early stages of the blow the mass law would indicate that iron oxide must form first, and this oxide probably increases up to some saturation point. The molten metal in the converter from the early stages of the blow right through to its completion remains basic, while the slag produced is siliceous. This fact is shown by the corrosion of the acid bottom and the tuyeres, which is greatest at the tuyere orifice where oxidation is most active and where there is the most iron oxide. Why does this acid bottom corrode? Because it is attacked by a base. The thought, therefore, suggests itself, why not. make the bottoms of basic or neutral material?' As the converter slag is acid, those parts of the converter coming in contact with the slag should be acid; but those parts of the converter that are in contact with the molten metal saturated with metallic oxides should be basic. or neutral. Bessemer operators have for some time tacitly admitted this condition, for the blast pressures have steadily increased with the object of keeping the metal in suspension, and so preventing bottom corrosion; if the molten metal were not basic, it would not attack an acid bottom. In addition, the tuyeres are bunched together at the middle of the bottom and a clear space is left around the outside of the bottom; if tuyeres are placed too near the side walls the

Jan 1, 1922

By Richard S. McCaffery

This paper considers certain aspects of the acid bessemer process, particularly in its relations to the duplex process—that combination in which the pig iron is first desiliconized and decarburized in acid bessemer converters and then dephosphorized in basic open-hearth furnaces. The acid bessemer process employs an acid-lined converter and produces an acid slag. The blow is usually thought to eliminate the silicon and manganese as oxides and then to burn off the carbon as carbon monoxide On account, however, of the relatively large amount of metallic iron present in the converter, compared with the relatively small amount of the impurities it is desired to oxidize, the first reaction in the converter probably is the formation of iron oxide, which dissolves in the bath and acts as an oxygen carrier for the silicon and carbon. As soon as iron oxide is dissolved throughout the bath, the oxidation of silicon commences; but in the early stages of the blow the mass law would indicate that iron oxide must form first, and this oxide probably increases up to some saturation point. The molten metal in the converter from the early stages of the blow right through to its completion remains basic, while the slag produced is siliceous. This fact is shown by the corrosion of the acid bottom and the tuyeres, which is greatest at the tuyere orifice where oxidation is most active and where there is the most iron oxide. Why does this acid bottom corrode? Because it is attacked by a base. The thought, therefore, suggests itself, why not. make the bottoms of basic or neutral material?' As the converter slag is acid, those parts of the converter coming in contact with the slag should be acid; but those parts of the converter that are in contact with the molten metal saturated with metallic oxides should be basic. or neutral. Bessemer operators have for some time tacitly admitted this condition, for the blast pressures have steadily increased with the object of keeping the metal in suspension, and so preventing bottom corrosion; if the molten metal were not basic, it would not attack an acid bottom. In addition, the tuyeres are bunched together at the middle of the bottom and a clear space is left around the outside of the bottom; if tuyeres are placed too near the side walls the

Jan 1, 1922

By R. T. Hukki

THE accepted basis of comparisons between mills of different diameter is the percentage critical speed. If n = actual mill speed, rpm, nc = calculated critical speed, rpm, np = calculated percentage critical speed, and D == inside diameter of the mill in feet, then n, In the following analysis capacity, T, is expressed in short tons per hour, tph, and power consumption, P, in kilowatts, kw. Accordingly power consumption per unit of capacity, P will be expressed in kilowatt hours per short ton, or kw-hr per ton. In all equations D refers to the inside diameter of the mill in feet and v to the peripheral speed of the mill in feet per minute inside the liners. ' Comparison between separate mills must be based on equivalent grinding conditions, i.e., same feed, same size distribution of feed, same size distribution of product, and same percentage of solids. In addition, comparisons between separate rod mills must be based on the same rods, same type of liners, and same percentage rod load. Comparisons between separate ball mills presuppose the same balls, similar liners, and same relative ball load. The practical np-range through which the equations apply varies, being narrower for fine grinding in ball mills and wider for coarse crushing in rod mills. The Relationship between Capacity and Speed It is the general belief that the capacity, T, of a tumbling mill is directly proportional to the speed of the mill, other things remaining constant.' Mathematically this is represented by the equation T - c¹ n tph [4] where c, is a factor related with the grinding characteristics of the ore, method of reduction, and the units chosen. It is proposed here that the general equation relating mill capacity and speed should be of the form T = c¹ nm tph [5] In other words, the capacity should be proportional to the mill speed raised to power m, the numerical value of the exponent being 1 5 m 5 1.5, depending on the circumstances. Eq. 5 can also be written in the following forms: T = c, (np)m tph, and [6] T=Ca vm tph, [71 where v = peripheral speed of the mill in feet per minute. If the observed capacity of a mill at speed n¹ is = T¹ tph, the capacity T² of the same mill at speed n² should be T² = T¹ (n²/n¹)tph [8] The Relationship between Power Consumption, Mill Diameter, and Speed The only well known theoretical deduction relating power consumption, P, and mill diameter appears to be the formula of duPont introduced by Gow, Guggenheim, Campbell, and Coghill.' According to duPont, the power required to operate a mill is a function of the mass of the balls, of the lever arm of the ball mass, and of the speed of the mill. The ball mass per unit of mill length is proportional to the square of the diameter, the lever arm is directly proportional to the diameter, and the critical mill speed or any percentage thereof is inversely proportional to the square root of the mill diameter. Following this reasoning, the original duPont formula is of the form P = c4D² c D • c6D-0.5 = c7D2.5 [9] If the mill speed in the above equation is expressed in terms of Eq. 3, the duPont formula may be written as follows: P=f1(D2) f2(D) f³(—np) or [10] vD P = c np D2.5 kw [11] Eq. 11 may also be derived from the mechanical principle of force, which is equal to mass x acceleration. Power necessary to operate a mill may be considered to be an homogeneous linear function of the force developed. Ball or rod mass per unit of mill length is a function of D2. The acceleration factor of the ball or rod mass is a function of the peripheral speed of the mill. Thus P = f4(F) = /x(D2) f5(v) Indicating that v = nDn, and n = c9 np /vD, the above equation becomes P = f2 (D2) -fa (D ca np/vD

Jan 1, 1955

By W. Denham Verschoyle

In designing a pocket instrumeut whereby any giver1 horizontal or vertical angle may be closely approximated, the following points should be kept in view, if general utility is aimed at : 1. The instrnment should be light and compact, so that it can be carried in the pocket, or in a sling. 2. It should be capable of observing any angle whatever, horizontal or vertical. 3. Since time is often an important consideration in making a preliminary survey, it should be capable of giving the horizontal and vertical angle at one observation. I do not know of any instrunlent that will fulfill these requirements, except the one here described. Where the depression- or elevation-angle of the distant object, whose bearing is required, exceeds 50 or 60 degrees, it becomes difficult or impossible with a prismatic compass, for instance, to obtain accurate results; and since it frequently happens, particularly in mining, that much work requires to be done beyond that limit, it is obvious that an instrument which can be used to observe a high angle just as easily as a low one, if not absolutely a necessity, will at least be a great convenience. How this a pocket transit" attains to the required degree of universality will be understood from the diagram, Fig. 1, in which B is a beveled, graduated circle, attached to and freely revolving about the center of the magnet A. Light falling on B is reflected through a window in F (the compass-box), along the line AC, and is again reflected back to the eye at D by the prism C. By a simple arrangement, the tight-line BCE call be completely revolved in the vertical plane DE, which is normal to AC. It is clear, then, that no matter through what vertical

Jan 1, 1908