Search Documents

By Alden Greninger

THAT metallographic structures analogous to the martensite of steel may be found in certain copper-aluminum and copper-tin alloys has been known for many years; similar structures recently were found in certain copper-zinc alloys.1 In all three of these alloy systems the martensite structures result from transformation of the metastable ß phase when the speed of cooling from the ß range is sufficiently high to suppress decomposition into equilibrium phases. ? In the normal decomposition of solid solutions into equilibrium phases, diffusion is needed to bring about the necessary changes in concentration, and the rate of reaction falls almost to zero at temperatures slightly above room temperature. The rates of reaction for martensite processes, however, are not dependent upon temperature; the transformation does not require readjustments of concentration. For example, the marten-site transformation in 60:40 (ß) copper-zinc does not begin until the temperature has dropped to about minus 30° C., and then continues down to minus 130° C. and probably even at lower temperatures.1 Further-more, martensite processes apparently proceed only while the tempera-ture is falling, within the proper range, and cease completely while the temperature is held constant; ? and they cannot be suppressed by extremely rapid cooling although the rate of cooling for some alloys may be increased to over 10,000 times the critical cooling velocity. Isaitschew, Kaminsky and Kurdjumow2 account for these observed behaviors of martensite processes by postulating that the mechanism " . . . consists in a regular rearrangement of the lattice in such a way

Jan 1, 1939

By Arthur F. Wendt

Introduction.—In the year 1885, the writer signed a contract to take charge of the reopening and developing of the celebrated old mines of " El Cerro Rico de Potosi." Two years earlier, an Eng- . lish firm of engineers had made a very glowing report on the property. In the summer of 1885, telegrams arrived from the parties in charge of operations at the mountain, claiming the finding of one of the old veins, with an average richness of over 200 ounces to the ton. In the fall of 1886, the author first personally visited Potosi, but found neither the English report nor the telegram borne out by the facts. After an expenditure of over half a million of dollars and more than three years of continuons hard work, the writer succeeded in unwatering and developing one of the principal old veins of the mountain. This vein, called "Cotamitos," now yields ores of about 75 ounces to the ton, and the old historic mountains of Potosi may be said to have again fairly entered the list of silver-producers. The experience of the author, during his residence in Bolivia, and data obtained from Sr. Don F. Avelino Aramayo, form the basis of this description. POTOSI. Etymology of the Name.—The Quichuá (pronounced Keechna) Indians, known to North American students as the " Incas," although the word "inca" merely signifies ''king," or "chief," of the Quichuás, called the mountain "Sumac-orcko," or the beautiful mountain." Eighty-three years before the discovery of the mountain by the Spaniards, the inca, or king, Huaina Ccapac, travelling from Cantumarca to Calque-Porco, saw the mountain of Potosf and, admiring its grandeur and beauty, said that within its bowels there was, no doubt, much silver. He ordered his vassal* to work the mines. They, having carried their mining implements to the mountain, ascended it and were on the point of commencing work, when they heard a voice of thunder, which said: " Do not take

Jan 1, 1891

By Shun-ichi Satoh

Studies by many authorities have proved that nitrogen exerts an injurious influence upon iron and steel, but in the casehardening of steel by carbon, nitrogen has the advantage of accelerating the process of cementation. Its influence upon special steels is quite remarkable; it can produce the hardest layer ever known in metallurgical products—a fact hit upon by A. Fry and studied and ascertained by L. Guillet. As there have been very few investigations on the influence of nitrogen on special steels, the writer has listed important articles dealing with this problem and has conducted experiments on nitrification. He also has tested the influence of nickel upon the penetration of nitrogen in electric-arc welding. Nitrogen Process for Surface Hardening In 1919, Siegmonl conducted an experiment known as "Versticken" by treating steel with ammonia gas and found that the steel thus treated has the properties of resisting corrosion. In 1922, L. E. Benson3 nitro-genized iron and steel by sodium nitrate. Fry3-"studied the nitrogen process for surface hardening and published the results of his studies in 1923, 1924 and 1926. Guillet tested special steels containing various elements with the current of ammonia at 500' to 510' C.10, 11, 12, and determined the hardness of some of them at various temperatures.13 He also conducted corrosion tests14 in 1927. Fry15 stated that tinplat-ing could prevent nitrogen from penetrating into steel in the course of nitrification. In 1927, Guillet 65 described the historical notes of the nitrification; and many applications of nitrification were published in the Kruppsche Monatshefte.51, 59, 62, 63, 64-74~75 H. K. Herschman66 conducted the wear test of the nitrified steel. Gunnar Hägg investigated

Jan 1, 1930

By H. A. Coy

THE Mascot mines of the American Zinc. Co. of Tennessee are situated at Mascot, Tenn., 14 miles northeast of Knoxville, on the Southern Railway. The district is centrally located in the Great Valley, or Appalachian Valley Province. Prior to 1900, a small output of zinc was obtained from oxidized ore mined in open pits. In 1900, a shaft was sunk to sulfide ore, and in 1903, a second shaft was put down, neither being as deep as 200 ft. The American Zinc Co. of Tennessee began drilling in 1911, and outlined an ore body to which its No. 1 shaft was sunk, to a depth of 365 ft. Since that time, the American Zinc Co. of Tennessee has been the only operator in. the district. The Federal mining laws have never been in operation in Tennessee and mining lands are as irregular in boundary and area as farm lands. Ownerships are generally held in fee. In most cases the surface and mineral rights, are transferred together. Electric power is supplied at 66,000 volts by the Tennessee Power do, from a hydro-electric plant at Parksville, Polk County, Tenn., 100 miles from Mascot. No other power is used, but an emergency steam plant is held ready in case of interruption of service. Labor is all native and non-union. Negroes are employed for most of the shoveling, and for a few miscellaneous jobs, but for almost, no other work.

Jan 9, 1924

By Earle Schumacher

COPPER-CALCIUM alloys are of interest as materials for use in deoxidized conductors of high conductivity. That calcium is effective in deoxidizing and degasifying copper is well known. Brandenberg and Wiens1 have described the use of calcium in the casting of sound copper and state that the deoxidation can be carried out without difficulty. The castings that they prepared were sound and sufficiently ductile to permit wire drawing. Pratt,2 in British Patent No. 1699 (1907), has claimed the use of calcium for the deoxidation and degasification of copper. Masing3

Jan 1, 1929

By William Phillips

This paper was prepared at the request of Capt. A. F. Lucas, Chairman of the Institute's Committee on Petroleum and Gas, as a preliminary discussion of the fuel oils which are used-in the Southwest, giving their composition, uses, prices, etc. Should it afterward be found desirable, these observations may be extended over a larger area. In this connection, J suggest that samples of all kinds of fuel oils, including various tars, from all over the country, be collected and sent to some testing laboratory for examination. We would be glad to extend the facilities of the laboratory of the Bureau of Economic Geology and Technology, at the University of Texas, for this purpose, and to do the work free of all expenses. After such examinations are made and the results classified and studied, it would be possible to suggest specifications under which fuel oils should be purchased, and to arrive at some conclusions respecting the uniformity of such specifications, with due allowance for climatic and other more or less local conditions. While such specifications do not now depart from a common standard anything like as much as specifications for illuminating oils do, yet there are discrepancies which should not exist. Some of these discrepancies are of lessening importance, due to the pronounced tendency to distill every crude oil that can be distilled with profit, and to send residues into the market for fuel oil. Residues from the refineries are of a more uniform chemical composition and physical nature than many of the crude oils that go direct into the fuel market. The lower flash-point oils are disappearing from the fuel trade and in place of them we are getting oils that do not flash below 220° F., nor burn under 320° F. In the Southwest, it has not been long since we had fuel oils that flashed at as low as 110° F., and the average flash point over a considerable period was 151° F. Now we are using oil that flashes at about 30° lower than the former burning point, which was 256° F. In other words, the flash point has risen, on the average, 100°; and the burning point about 75°.

Jan 6, 1914

By W. J. Carlson, S. M. Parmerter, I. Iwasaki

This article discusses the effect of physical and chemical modifications of starches on the anionic and cationic flotation of silica from oxidized iron ores and magnetite-taconite concentrates. It also deals with the results of the interaction of starch, pH, and calcium ions on the flocculation, clarification, and filtration of iron ore slimes and magnetite-taconite tailings. Starches, particularly when an-ionically modified, were found to be effective depressants in anionic silica flotation. British gums and dextrins were beneficial for oxidized iron ores, but none of the starches or starch derivatives appeared to have any effect on magnetite-taconite concentrates. The flocculation and filtration of iron ore slimes were affected most strongly by the level of starch, to a lesser degree by the pH, and virtually not at all by the level of calcium chloride. The clarification of iron ore slimes was complexly dependent on these three factors. The flocculation of magnetite-taconite tailings depended mainly on the level of starch, whereas their clarification depended on the level of lime. As previously reported in the literature, selective flocculation and partial upgrading of a semitaconite could be readily attained with starch and calcium chloride. A previous article discussed some of the parameters that are important when various corn starches are applied to the soap flotation of activated silica from iron ores and to the flocculation of iron ore slimes.' Methods of solubilizing the starches and the molecular size after mechanical and thermal treatments, as inferred from the viscosity measurements, were shown to influence the adsorption characteristics on iron ores, and the residual concentrations of both calcium ion and starch in the pulp liquor were in direct correlation with the flotation and flocculation behavior.2-4 The present article summarizes the results of more recent tests conducted to ascertain the role of starches and starch derivatives in various phases of iron ore beneficiation. The scope of this investigation has been extended to include not only anionic and cationic flotation, but also the flocculation and filtration of iron oxide slimes, the selective flocculation and partial upgrading of semitaconites, and the flocculation and clarification of magnetite-taconite tailings —all problems that are of vital importance to the iron ore industry of Minnesota. By combining a practical approach with adsorption studies and by using single-mineral systems5 in these research efforts, it is believed that the ultimate goal of developing a suitable modification of starch structure may be realized. The topics covered in this article are limited to the empirical aspects of the research program on the depressant activity of starches and products in the cationic and anionic flotation of silica and of their role in flocculation, water clarification and filtration. ANIONIC SILICA FLOTATION In the soap flotation of activated silica from iron

Jan 1, 1970

By A. M. Gaudin

The study that is presented here was undertaken in order to condense information concerning comminution, and covering a great variety of conditions, into one or several rules which would be of use in the development of a systematic theory as well as in many directly practical ways. As the result of this work, the following conclusions appear justified: 1. Rocks may be classified, from the point of view of comminution, into two general classes which are (a) structurally homogeneous, and (b) structurally heterogenous. Structurally homogeneous rocks are those in which fracture takes place through grains and grain boundaries alike; heterogeneous rocks are those in which fracture passes in preference through grain boundaries. 2. If a sized product composed of structurally homogeneous rock grains is crushed, a product results in which the relation between the percentage weight of grains of various sizes and these sizes themselves follows a definite law. This is not true of structurally heterogeneous rocks. 3. Ball milling with structurally homogeneous rocks, and under certain conditions, presents exceptions to this rule. 4. In ball milling with structurally homogeneous rocks, there exists a critical ratio of size of feed to size of balls, above which the machine operates essentially by surface wear, and below which it operates essentially by breaking across the body of the particle. 5. In ball milling, with structurally homogeneous rocks, and when the size of feed grains exceeds the critical size, the particles worn off are of a substantially definite size which depends upon the ball size. 6. In the case of a typical heterogeneous rock, such as Manhattan schist, particles are crushed in such a way that there is a greater proportion of grains of the size that is the average grain-size of the rock than there would be in that range of size with a structurally homogeneous rock. This has been found to be true with all the crushers tested. 7. Different methods of crushing produce grains of different shapes. 8. The importance of sizing the — 200-mesh portion of a crushed product, in crushing-efficiency investigations, has been greatly under-

Jan 1, 1926

By Charles P. Berkey, Joseph H. Sinclair

This paper describes the results of a visit to the Santa Elena Peninsula, Ecuador, in January and February, 1921. On account of the complicated folding and faulting of the rocks and the peculiar occurrence of petroleum, field work was possible on only a few of the many geological problems and the results here published are only a contribution to the solution of the general problem. We know of nothing published on the geology of the district, except one account, in Spanish and German, by Theodor Wolf. The Santa Elena peninsula, the most important headland of the coast of Ecuador, lies two degrees south of the equator. The chief town, Santa Elena, is about 75 miles west of Guayaquil, the main seaport of Ecuador. The nearest developed oil field is the Zorritos of northern Peru, 120 miles south across the Gulf of Guayaquil. If newspaper reports are true, viz. that the Anglo-Ecuadorian Oilfields, Ltd., has recently brought in a 700-bbl. well on the coast of the peninsula near Ancon, the district may become important in the production of petroleum. At the time of our visit, the best way to reach the peninsula was by a steamer of the Pacific Steam Navigation Go., southward from Panama and northward from Guayaquil. About once a week, one of these steamers anchored 1/2 mile off shore near the village of Salinas, an important cable station. An alternative route, in the dry season, is by automobile from Guayaquil. In February, 1921, a railway bed had been graded part way between Guayaquil and Salinas, but this was detcriorating rapidly because of lack of funds to continue construction or to keep in repair that portion already completed.

Jan 1, 1923

By D. Dever, E. S. Fisher

Measurements of the temperature dependence of the elastic moduli in single crystals of hep ruthenium, rhenium, cobalt, dysprosium, and erbium were carried out for various temperature ranges so as to investigate the correlation, suggested by prior work, between the shear anisotropy ratio, A = C44/C66, and the occurrence of the hcp — bee phase transformation. These measurements confirm the suggestion that A has a positive temperature dependence in that group of hcp metals that undergo thermally induced transfornzations to the bee structure and a negative or zero temperature dependence in the other hcp metals. It appears, from indirect evidence, that the hcp -fee transformation in cobalt is preceded by a highly negative temperature dependence of A. These results indicate that elastic anisotropy is an important factor in determining the temperatures at which martensitic phase transformations occur. Two possible roles for elastic anisotropy are proposed: 1) the shear-modulus ratio within the habit planes must be nearly similar for the two phases and 2) a large anisotropy decreases the stress necessary for the movement of the transfornzation dislocations. FUCHS' calculations of the elastic moduli in the alkali metals have shown that the high shear-anisotropy ratios, c/c', in certain bee metals and alloys are the result of large negative contributions to c' = (c11 - c12)/2 arising from the nearest-neighbor repulsive forces.' On this basis, and following Zener,2 the association between high c/c' ratios and the martensitic phase transformations that occur upon cooling certain bee metals is explained as a unique characteristic of the bee structure. Recent measurements of the elastic moduli in hcp titanium and zirconium show, however, that a high elastic anisotropy also exists in these hcp structures at the temperatures at which they transform to bee upon heating3. If there exists a direct and consistent correlation between the elastic anisotropy in close-packed structures and the occurrence of transformations to the bee phases then there is evidently a need to re-examine the conclusions of Zener theory. Elastic anisotropy may also be the result of the effects of temperature on the stability of the low-temperature close-packed structures or it may play an important role in the mech- anism of the martensitic transformations. The present measurements were aimed at establishing the phenomenological correlation between elastic shear anisotropy in hcp structures and the thermally induced hcp —bee transformations that occur in the majority of the twenty-three hcp metals, as shown in Table I. Prior to the present work the temperature dependence of the anisotropy ratio, A = c44/c66, was known at various temperatures for nine of the metals listed. The data showed a negative temperature dependence of A for cadmium, zinc, magnesium, and cobalt, which do not transform to bee, and a positive temperature dependence of A for thallium, zirconium, titanium, hafnium, and yttrium. The correlation was, however, ambiguous in that these two groups of metals are also separated with respect to the c/a ratios as noted in Table I. There remained the possibility that the temperature dependence of A is a function of c/a and not consistently associated with the transformation. The measurements of the elastic moduli in rhenium and ruthenium, in which hcp —bee transformations do not occur, were needed to help decide this question. The studies of dysprosium and erbium were undertaken to determine whether the correlation holds for the heavy rare earth metals.

Jan 1, 1968

By O. D. Gonzalez, R. A. Oriani

A thermo-osmosis technique has been used to measure the heat of transport, Q* , of hydrogen and of deuterium dissolved in a iron and in nickel, and of hydrogen in Feo.6Nio.4 in the tempevature range 400° to 600°C. For all these systems, Q* is negative and has a large temperature coefficient; an isotope effect can be established for the solutes only in nickel. The magnitude of Q* is considerably larger than the activation energy, E , for migration in the case of these isotopes in a iron, so that all variants of the Wirtz model must be rejected. The phenomenological definition of Q* is developed to show that Q* is related to the mechanisms by which the activation energy is dissipated back into the lattice, and that Q*/E is a function of the ratios of the mean free paths of electrons and of phonons to the distance of jump of the diffusing atom. A correlation is shown to exist between the sign of Q* in thermal diffusion and that of the effective charge in electro migration, and may be understood as due to the large ratio of the mean free path of electrons to that of phonons. THE study of nonisothermal diffusion in the solid state is of interest because certain aspects of the mechanism of diffusion are made manifest which remain concealed though still present in the isothermal case. The thermodynamics of irreversible processes characterizes nonisothermal diffusion, known as thermal diffusion or as the Ludwig-Soret effect, by a quantity, Q*, called the heat of transport, which essentially measures the sign and the magnitude of the steady-state concentration gradient produced by the imposed temperature gradient. The problem then is to understand the quantity Q* at the atomistic level. There does not exist a theory for the atomistic interpretation of the heat of transport. There are, however, two classes of simple models which seem to afford some physical insight into Q*. Wirtz's model1, z and its subsequent generalizations partition the activation energy, E, for the migration of the atom spatially about the region of the migrating atom, so that Q* is the difference between the portion of the activation energy centered about the original site of the jumping atom and that portion about the arrival site. Clearly, the magnitude of Q* cannot on this model be larger than the activation energy for migration. The model of Oriani3 also considers the spatial distribution of E not only before but also after the atomic jump, and Q* is related to the variation of the spatial distribution of E that is produced by the jump. The simplest kind of system with which to compare the consequences of these ideas is the interstitial solid solution, since one may easily choose a temperature at which only the interstitial component moves, the solvent lattice serving as a completely satisfactory frame of reference. Thus, one avoids complications arising when both species in a binary system move. In addition, one avoids the necessity of knowing the energy for the formation of a vacancy, something which is needed for the analysis of thermal-diffusion data on metals which diffuse by the vacancy-exchange mechanism. However, the number of well-measured interstitial systems is extremely small, and, in particular, there are almost no data in the published literature for the temperature dependence of the heat of transport. If one works with solutes which are gases in the pure state at ordinary temperatures, one may use the technique of thermo-osmosis4 which permits thermal diffusion to be measured over a small temperature difference so that the temperature dependence of Q* can be more easily determined. The choice of dissolved hydrogen in iron and nickel was based on these considerations as well as on the desire to look for an isotope effect associated with localized

Jan 1, 1965

By M. M. Rao, P. G. Winchell, R. J. Russell

A detailed analysis has been used to correlate the avalable thermodynami c da In on iron-ric11 Fe-Ni (41loys in the body-centered a, and the face-centered y phases. The inp ut injovrt~ation required by the a am lysis consists of tile heat of the a, to y transformation at 1123°K, the heat of mixing of y at 1123°K, tile specific heats of both a, and y (decomposed into Debye, electronic, and magnelic contributions), and the positional and magnetic entropies of both a, and y. PYLrrzary oirt.bul of the analysis is the free energy of each phase as a Junction of temperature and composition. FOr Fe-Ni alloys the adjustment of twenty-one parunletevs allows the accurate reproduction of enthalpy data for both phases, the heat of mixing- for y, the a/y equilibrinm compositions in the Fe-Ni phase diagram, and the usually accepted enthalpy and entropy of a and y iron. Also obtaitzed are fuirly accurate reproductions of electronic specific heat coefficients predicted from electron- to-atom ratio interpolations and To temperatuves eslimanted from transformation studies. Also considered in the calculation are the elastic constants, Curie temperatures, saturation magnlelizalion values, and indications of short- range order. The measnred activity coefficient of iron in anstetnite could not be accurately matched. The major source of uncertainty in the model is thought to be the magnetic contribution to the entropy of austenite. Calcrclations were extended to Fe-ni-C alloys using available carbon-acliuity data. The free energy of transformation from martensile to r at fixed composition was obtained as a function of nickel and carbon contetzt, and binary thetal-carbon phase diagrams Were estimaled as a function of nickel contenl. We needed thermodynamic information for Fe-Ni and Fe-Ni-C alloys at temperatures between 400" and 800°K in order to interpret the results of several phase-transformation studies. The most recent theoretical analysis of the thermodynamics of Fe-Nialloysl was based on a lumped-parameter, regular-solution model and used the Fe-Ni phase diagram available at that time.' Because significant difficulties were encountered in attempting to extend this analysis to Fe-Ni-C alloys, and because more experimental data has become available recently, we decided to attempt a new correlation. The analysis used here allows the extrapolation of measured and calculated thermodynamic values to lower temperatures and the extension of the thermodynamic analysis to Fe-Ni-C alloys. The structure of this correlation consists of expressions containing a total of twenty-one adjustable parameters. The forms of these expressions are discussed in the next section; however, a less formal summary is presented now to provide a physical overview of the model and to indicate its connections to prior work. Primary input information for this correlation is described below. The measured values of the specific heat of iron3 and its analysis475 and theoretical estimates of the specific heat of y* iron at low tempera- loys at 1123°K has been measured by solution calori-metry.7 The enthalpies of both a, and y have been measured most recently by Scheil and Saftig,B who used a dry-ice calorimeter. These data are used to formulate expressions for the heat of mixing of y and the heat of transformation of a, to y both at 1123°K. The a and y solubility limits in the Fe-Ni phase diagram have been redetermined recently9 by methods which assure a close approach to equilibrium. The a to y transformation can occur without change in nickel content or free energy at a temperature called TO; TO temperatures for various nickel contents have been estimated from transformation studies. The computed free-energy functions are adjusted by means of the parameters to fit both the phase diagram and the TO temperatures. Primary emphasis is placed on the phase diagram fit. Iron activities have been measured in Fe-Ni austenite10 between 973" and 1173°K. These activity data, which cannot be fitted accurately with our model, indicate that iron is substantially ideal in iron-rich austenite. Secondary, but helpful, information for the present correlation is provided by neutron diffraction and saturation magnetization measurements on both body-centered and face-centered Fe-Ni alloys."-'3 These results were interpreted11 in terms of composition-insensitive, localized magnetic moments on both iron

Jan 1, 1968

By Charles P. Berkey, Joseph H. Sinclair

This paper describes the results of a visit to the Santa Elena Peninsula, Ecuador, in January and February, 1921. On account of the complicated folding and faulting of the rocks and the peculiar occurrence of petroleum, field work was possible on only a few of the many geological problems and the results here published are only a contribution to the solution of the general problem. We know of nothing published on the geology of the district, except one account, in Spanish and German, by Theodor Wolf. The Santa Elena peninsula, the most important headland of the coast of Ecuador, lies two degrees south of the equator. The chief town, Santa Elena, is about 75 miles west of Guayaquil, the main seaport of Ecuador. The nearest developed oil field is the Zorritos of northern Peru, 120 miles south across the Gulf of Guayaquil. If newspaper reports are true, viz. that the Anglo-Ecuadorian Oilfields, Ltd., has recently brought in a 700-bbl. well on the coast of the peninsula near Ancon, the district may become important in the production of petroleum. At the time of our visit, the best way to reach the peninsula was by a steamer of the Pacific Steam Navigation Go., southward from Panama and northward from Guayaquil. About once a week, one of these steamers anchored 1/2 mile off shore near the village of Salinas, an important cable station. An alternative route, in the dry season, is by automobile from Guayaquil. In February, 1921, a railway bed had been graded part way between Guayaquil and Salinas, but this was detcriorating rapidly because of lack of funds to continue construction or to keep in repair that portion already completed.

Jan 1, 1923

By J. F. Kemp

CONTENTS. [ ] I. INTRODUCTION. 1. Situation.-From Monterey in the State of Nuevo Leon, the Sierra Madre mountains stretch away to the southeast and present a steep front to the northeast. The Monterey and Mexican Gulf railway, which connects Monterey with Tampico, follows their general line with its road-bed a few miles out from the foothills. At a distance of 100 miles from Monterey it passes through the town of Linares, and from Linares one can see far away to the southeast the peaks of another group of mountains

Jan 1, 1913

Jan 1, 1880

By Chester A. Rowland, David M. Kjos

Mineral ore comminution is generally a feed preparation step for subsequent processing stages. Grinding, the fine product phase of comminution, requires a large capital investment and frequently is the area of maximum usage of power and wear resistant materials. Grinding is most frequently done in rotating drums utilizing loose grinding media, lifted by the rotation of the drum, to break the ores in various combinations of impact, attrition and abrasion to produce the specified product. Grinding media can be the ore itself (autogenous grinding - primary and secondary), natural or manufactured non- metallic media (pebble milling) or manufactured metallic media - steel rods, steel or iron balls. This chapter covers rod and ball mills which utilize manufactured metallic grinding media. Fig. 1 shows the cross section of an overflow rod mill, Fig. 2 an overflow ball mill, and Fig. 3 a diaphragm (grate) discharge ball mill.

Jan 1, 1978

By C. J. Bier, J. F. O?Keefe

THIS study was carried out with copper because it represents the simplest form of sintering, in that but one metal is involved and all reactions occur in the solid state. [ ] The present work will cover three variables affecting the sintering process; namely, briquetting pressure, sintering temperature and time in hot zone. Although strength and dimensional changes were observed, this is primarily a metallographic study of the sintering process in copper. The term "sintering" should be understood to mean the process by which the metal powder particles of the compact become united into one body. MATERIAL USED The copper powder used was made from reduced copper oxide, and is typical of a grade used for the mass production of parts formed of metal powders. The screen analysis of the powder was as follows: [ ] The minus 325-mesh analysis was made by using a Roller Air Analyzer.1,2 The apparent density is here defined as the weight per cubic centimeter of the [ ] loose, unpacked powder as measured with the Hall flowmeter. The value for the powder used was 2.57 grams per cubic centimeter.

Jan 1, 1944

[United States PAGE Alabama 242 Alaska 242 Arizona 1 242 Arkansas 243 California 243 Colorado 246 Connecticut 248 Delaware 248 District of Columbia 248 Florida 248 Georgia 249 Idaho 249 Illinois 249 Indiana 250 Iowa 250] [ ]

Jan 1, 1925

By Glenn C. Waterman, Scott Hazen

3.1-1. Purpose. Development drilling is directed towards determining the grade, volume, and three-dimensional outline of a mineralized zone previously located by exploration. It is distinguished from exploration or reconnaissance drilling, which has as an objective the discovery of new mineralized areas. A development drilling and bulk sampling program should furnish the following information: 1. Geology of the mineralized zone. 2. Quantitative data on grade and tons of material within pertinent cutoff limits. 3. Physical size and shape of the deposit. Areas underlain by waste as well as ore. 4. Mineralogica1 and metallurgical characteristics of the ore. 5. I1hysical characteristics of the ore. 6. Hulk samples for metallurgical testing and grade check. 7. Data on other factors that could affect mining operations, such as ground water, ground conditions, etc. 3.1-2. Procedures. There are numerous methods and techniques that are used to acquire pertinent data on a potential ore deposit. The total cost and accuracy of a development program depends on significant evaluation of the geology, proper selection of a drilling method, thorough analysis of sample data, and accurate evaluation of all the information. Knowledge of the geology of the mineral deposit is important in planning the development testing program and in evaluating the data obtained from such a program. Exploration work usually provides some significant information on the general size, shape, thickness, grade, and geology of the deposit. In some cases no further data are needed; in many cases geological complexities suggested by the preliminary work require further geological study. Of considerable importance may be the following:

Jan 1, 1968

By Wilbur C. Helt, Joseph J. Yancik

Throughout the history of mankind, the principal use of coal has been to produce heat through combustion. The heat is used in many ways: to warm air space for our comfort; to provide heat or energy to power industrial processes, such as cement and steel production; and to produce electricity. Because it is our nation's most abundant fossil energy fuel, coal in the late 20th century is on the threshold of becoming a significant source for synthetic liquids and gas energy fuels for this country. This is made possible by conversion processes which can change solid coal into various synthetic gases and liquids. These coal-derived fuels are nearly identical to the processed fuels and chemicals provided by natural gas and crude oils, which presently provide almost all the petrochemical feedstocks and energy fuels needed for the residential, light commercial, and transportation markets. A revolution is beginning to take place, not only in the United States, but in many other countries with a return to a coal-based energy economy. Also, new combustion and conversion technologies which are compatible with national health arid environmental goals are rapidly emerging. These technologies will allow coal's use to be expanded not only in its traditional markets, but also to supply markets held by natural gas and crude oil. With the worldwide decline in natural gas and crude oil reserves, coal is being looked upon to meet the energy demand. Because of these new coal conversion technologies, coal will no longer be only a combustion fuel, but a valuable raw material for production of a variety of clean fuels and chemicals. MARKETS FOR COAL: PAST AND FUTURE A simplified diagram of the marketing network for coal is shown in Fig. 1. As shown in this figure, coal is transported to its traditional

Jan 1, 1981