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By Lawrence Addicks

One of the properties of copper, which has done much to give it its present prominent place among the useful metals, is its electrical conductivity,—a property which has now become the chief criterion of the value of the commerical product. In pursuance of that distinctively American principle that, " the best is none too good," metal of the highest conductivity is usually called for even when such extreme purity is of no advantage ; for instance, in the making of brass and other alloys. The average brass-founder feels nervous unless his copper is so very pure that it shows a conductivity of 99 or 100 per cent., while the character of the zinc used is usually overlooked in hi s anxiety. Electrolytic refining has made it possible to produce copper

Jan 1, 1906

By Charles M. Bayer

Reading in the AIME annual reports that certain activities have been financed by the Rocky Mountain Club Fund, less senior members of the Institute may wonder. "What's the Rocky Mountain Club?" Less youthful members will not have to wonder. They will recall the Club as an intriguing, almost fantastic organization, largely of western mining men, that flared across the New York horizon, flamed brilliantly for a little more than two decades, then sputtered out of existence- glorious even in its last flash. It was the only product of its mold, a fabulous group of magnanimous men who unhesitatingly sacrificed a cherished dream for which they had raised millions of dollars so that the money, instead of creating a magnificent club house, could be used instead to save the lives of starving Belgian children in World War I.

Jan 12, 1964

By C. B. Foraker

THE Magma mine, of the Magma Copper Co., at Superior, Pinal County, Arizona, is 68 miles east of Phoenix and 21 miles west of Miami, Arizona, on highway U. S. 180. Temperatures and Underground Waters Surface Temperatures.—The average surface dry-bulb temperature at Superior is 72.4°; wet-bulb, 57.4°; with an indicated relative humidity of 38 per cent. The average yearly rainfall from 1921 to 1936, inclusive, was 18.74 in. The maximum condition of the atmosphere is in June, July and August, and the minimum is in January and February. The surface temperatures, of course, influence the temperatures of the downcast shafts; however, the variation between winter and summer causes a difference of only 2" to 3" in the stopes and working places that are not close to the intake shafts. Average atmospheric conditions are shown in Fig. 1. Rock Temperatures.—Rock temperatures on the deeper levels of the mine are as follows:

Jan 1, 1940

By C. B. Foraker

THE Magma mine, of the Magma Copper Co., at Superior, Pinal County, Arizona, is 68 miles east of Phoenix and 21 miles west of Miami, Arizona, on highway U. S. 180. Temperatures and Underground Waters Surface Temperatures.—The average surface dry-bulb temperature at Superior is 72.4°; wet-bulb, 57.4°; with an indicated relative humidity of 38 per cent. The average yearly rainfall from 1921 to 1936, inclusive, was 18.74 in. The maximum condition of the atmosphere is in June, July and August, and the minimum is in January and February. The surface temperatures, of course, influence the temperatures of the downcast shafts; however, the variation between winter and summer causes a difference of only 2" to 3" in the stopes and working places that are not close to the intake shafts. Average atmospheric conditions are shown in Fig. 1. Rock Temperatures.—Rock temperatures on the deeper levels of the mine are as follows:

Jan 1, 1940

By M. Cohen, R. J. Teitel

There is considerable interest in beryllium because of its low density (1.84 g per cu cm), high modulus of elasticity (40 X 106 psi), high melting point (1280°C), and special nuclear characteristics. Moreover, it has fair resistance to corrosion and oxidation. However, the purest beryllium known to the authors is relatively brittle at room temperature, and cannot be fabricated readily. The search for improved properties leads naturally to investigations of beryllium alloys and the phase relationships upon which they are based. The present paper is concerned with the alloys of beryllium and iron, primarily from the standpoint of the equilibrium diagram. Iron was selected (1) because of its all-round importance in metallurgy, and (2) because the beryllium-iron system is known to be quite complex. The most recent diagram in the literature is that of Gaev and Sokolov,' and covers only the iron-rich end up to 16 wt pct beryllium. Beryllium markedly restricts the austenitic field, closing the gamma loop at about 0.4 wt pct (3 at. pct). On the other hand, beryllium is soluble in a-ferrite up to a maximum of 7.5 wt pct (34 at. pct) at the eutectic temperature of 1160"C. The eutectic composition lies at 10 wt pct beryllium (42 at. pct) and corresponds to a mixture of or and FeBez (called j3 in the present paper). The solid solubility of beryllium in the a phase decreases with decreasing temperature, and makes precipitation-hardening possible. These findings substantiate the earlier work of Oester-held,2 Wever and Mueller3 and Laissus.4 In addition to the FeBe2 (ß) mentioned above, Misch6 has reported on FeBes, and indicated evidence for another compound containing still more beryllium. A preliminary diagram by Gordon,5 not hitherto published, is given in Fig 1. Besides the phases previously named, there are shown a solid solution of extended range (e), a compound of limited solubility (t), and a high temperature phase (7). Beryllium is designated as 8. The t field contains the compound composition FeBea, and the f phase undoubtedly corresponds to the beryllium-rich compound found by Misch.6 The region around the { phase was proposed by R. J. Teitel based on Gordon's data. The details of the diagram are self-explanatory. It was the unusual complexity of this system that prompted the authors to undertake the present studies. By the same token, more emphasis was placed on the beryllium-rich than the iron-rich end of the diagram. Exprimental Details RAW MATERIALS The beryllium employed in this investigation was one of the purest grades available. Its chemical analysis after vacuum melting is given in Table 1. The metal assayed 99.4 wt pct beryllium. Vacuum melted electrolytic iron of purity shown in Table 1 was the source of iron.

Jan 1, 1950

By George W. Sargent

For the experiments here described a rod was used, 0.75 in. in diameter, and rolled from one ingot. Analyses of the ingot and rod showed them to have the following composition respectively: C. Mu. Si. P. 8. Percent. Percent. Percent. Percent. Percent. Ingot,. .. 1.150 0.328 0.223 0.020 0.016 Rod,. .. 1.033 0.327 0.223 0.020 0.016 Pieces 4 in. long were heated to various temperatures in a closed porcelain tube, within a gas furnace, and allowed to cool with the same; they were then turned, threaded, and subjected to physical tests in a Riehlé testing-machine. The elastic limit was determined by the drop of the beam. The elongation was measured in two inches. From the threaded ends of the testrpieces, disks were cut, and prepared by combined polishing and etching, using parchment stretched over a wooden block and moistened with a 2-per cent. solution of ammonium nitrate. The structure, as thus developed, and the fractures, were magnified and photographed. A cooling-curve was constructed, and the critical point was located at 675º-680º C. A thermo-electric pyrometer was used to make the measurements of temperature. The micro-constituents of steel have been so frequently and thoroughly described by others that I need only say here that the theoretical micro-structural constituents of this steel were : pearlite, 95 ; ferrite, 0 ; cementite, 5 per cent. The quenched metal would be expected to consist almost entirely of martensite—provided, however, the quenching be done at or near the proper temperature. Rapid quenching from a high temperature would give rise to austenite.

Jan 1, 1902

By R. L. Orr, O. D. Sherby, J. E. Dorn

Creep data for pure metals at temperatures above those at which rapid recovery occurs (above about 0.45 the melting temperature) are correlatable by means of the equations and These correlations were applied successfully to data for aluminum, iron, nickel, copper, zinc, platinum, gold, and lead as well as for simple alloys. For a given metal, AH is a constant about equal to the activation energy for self-diffusion. THE early recognition that creep is stimulated by thermal activation prompted numerous investigators', ' to apply the same laws that are valid for the viscous behavior of liquids to analyses of creep data. To a good first approximation these laws are summarized by the equation were i is the creep rate; T, the absolute temperature; R, the gas constant in cal per degree per mol; T, the applied stress; AH, the activation energy in cal per mol; S', a constant dependent on the entropy of activation, the frequency of activation, and the contribution of each activation to the strain; and B', a constant dependent upon the size of the flow unit that is activated. Although Eq. 1 describes the flow of viscous fluids very accurately, its application to the creep of solids has been disappointing. Two reasons for the failure of Eq. 1 for creep are now known: First, the decelerating creep rates during primary creep demand that the internal structures of the metals are changing and that these changes might be reflected by changes in one or more of the three creep parameters S', AH, and B'. Consequently when the conventional methods of evaluating these parameters are employed by comparing the secondary creep rates at a series of temperatures and at a series of stresses, the true effects of temperature and stress are masked because of simultaneous changes in one or more of the creep parameters. Second, as will be illustrated more fully later, three distinctly different types of investigations have shown that the stress term for high temperature creep enters the analysis as and not as t/T. This rather unexpected result points sharply to a significant fundamental difference between the mechanisms for the viscous behavior of fluids and the high temperature creep of metals. More recent extensive investigations",'4 on the creep of high purity aluminum and several of its dilute a solid solutions have shown that where E is the total creep strain; temperature compensated time = for a constant temperature test; t, is the initial stress in a constant load test or the constant true stress in a constant stress test;" and t is the duration of test. • Eq. 2 is valid for either constant stress or constant load tests; but the total creep curve is difierent (i.e. the function, f, is differentl for each test. The fundamental origin of the validity of Eq. 2 is thought to arise from some equivalence of substructures in constant load creep tests at equal values of 0 or E. Both X-ray and metallographic examination revealed that practically identical lattice distortions and subgrain sizes are obtained for the same creep strain under the same load over wide ranges of test temperature.' Furthermore the room temperature tensile properties following equal creep strains at different temperatures under constant loads were also identical, illustrating that identical substructures were indeed obtained.' " A second type of correlation was obtained by differentiating Eq. 2 with respect to time, giving For the secondary creep rate, denoted by i,, But Eq. 2 reveals that 0, is a function of a, alone because the secondary creep rate in a given constant load test is always reached at a fixed value E,". Therefore where is the function that was introduced a number of years ago by Zener and Hollomon." Eq. 4 is not only valid for creep but will permit correlations between constant load creep and tensile data where e, is the rate of tensile straining and (TC is the engineering ultimate tensile strength.

Jan 1, 1955

By T. Glen Heslop, Dennis H. Laubscher

INTRODUCTION In all cave mining operations waste is drawn mixed in the ore, hauled, hoisted and milled. This waste usually contains some mineral which partly covers some of the costs of mining and milling it, but it still re- presents a loss of profits as the production rate from the mine is matched to the mill capacity - every tonne of waste milled replaces a tonne of profitable ore. Draw control aims to reduce the amount of waste drawn and to increase the amount of ore recovered. It is also used to regulate the grade of ore flowing to the mill and in block cave blocks to prevent potential stress build- up on the major apexes above grizzly drifts. This paper summarises what has been learnt about draw control in the forty years that cave mining methods have been used in the three largest underground chrysotile asbestos mines in the southern hemisphere. The four mining methods to which draw control has been applied are: a. Block caving. b. Shrinkage with overburden caving. c. Sublevel caving. d. Open stoping. Open stoping has been included because on a number of occasions severe falls from the back and side of these open stopes have occurred. Without full records of where and when ore is blasted, when and how much ore has been drawn from each of the drawpoints, it would be impossible to analyse the migration of ore and fallen waste in the stope. Several problems peculiar to chrysotile asbestos ore bodies affect the practice of draw control. Heterogeneous fragmentation, cavities, side pressures and the interaction of stresses in the caved ore affect the migration of ore under draw. Fibre is normally not developed uniformly throughout the ore bodies, values vary from place to place but there is usually a general decrease upwards and the hangingwall contact is an economic limit. The immediate hangingwall rock frequently looks like the ore body hostrock and is difficult to recognise in a drawpoint, and cannot be used as the marker for stopping draw. During caving or shrinkage, a large proportion of fibre becomes detached from the host rock and re- ports in the fines, which migrate differently to the larger rocks. The fines are not sticky, and flow easily if loose and dry, but compacted, the fibre and rock fines con- solidate the ore. During draw the proportion of fines in the ore varies considerably, as fines either flow relatively freely between the large rocks or become trapped and compacted above large rocks or hangups. This creates a large sampling error in drawpoint grade assessments, whether done visually or by bulk sampling, unless the assessments are done frequently. The method of draw control used is to regulate the draw rate in an attempt to lower the ore-waste interface as evenly as possible, and to finally stop working the drawpoint when a calculated tonnage has been drawn.

Jan 1, 1981

By Noel H. Stearn

To the successful functioning of the geomagnetic method of exploration in engineering and geological practice there are two prime prerequisites : the measurability and the interpretability of significant magnetic anomalies. A magnetic anomaly may be defined as a permanent distortion of the earth's magnetic field, in order to distinguish it frog the distortions, either cyclic or irregular, which vary with time. So far as known, time fluctations have no directly assignable geologic significance in terms of rock formations, while anomalies may be considered to be directly caused by the difference in the magnetic properties within and between the formations of the substances that make up the earth's outer shell. As is effectively pointed out by L. B. Slichter,1 the effects which these differences produce on the magnetic field may be extremely minute or extremely great, depending upon the magnetic properties of the formations. Thus the actual anomalies may range from the infinitesimal to a magnitude considerably greater than that of the earth's field. The geomagnetic method of exploration has shared in the deluge of experimental effort which has lately swept geophysical prospecting to its present important place in engineering and geologic practice. But to date more of this effort has been expended upon the measurability of anomalies than upon their interpretability. The tendency has been to strive for the development of instruments and especially field techniques capable of measuring minute anomalies with a precision far beyond that for which there can be any hope of adequate interpretation other than as interesting phenomena having numerous possible causes. Such efforts, of course, are highly commendable in the field of so-called pure science, which includes the accumulation of undigested detailed observations and admits of interpretation by multiple hypotheses, but in engineering practice the factor of economy must enter. Those instruments and techniques are most desirable which can most rapidly measure the interpretable range of anomalies with the precision necessary

Jan 1, 1932

By R. S. McBride

The fertilizer industry is a meeting place of mining, manufacturing and agriculture. It is an industry of dynamic change, huge tonnages, and great aggregate value. In the United States from 5,000,000 to 8,000,000 tons of fertilizer are made and used per year, with a value at the works of from $200,000,000 to $300,000,000. The world uses about 50,000,000 tons yearly with an aggregate value between two-thirds and one billion dollars. This world output contains of the essential plant-food constituents, nitrogen, phosphate, and potash, approximately 8,000,000 tons. The corresponding United States quantity, as nearly as can be estimated, is 1,400,000 tons of plant food per year in the aggregate tonnage of fertilizer. With the steady increase in the practice of scientific agriculture throughout the world there has been a corresponding growth in the consumption of fertilizers. In the United States there has, indeed, been but a small upward trend in the tonnage sold, measured in millions of tons of all classes of goods which are made and marketed. The real growth has come through the increasing concentration of the essential plant foods in the mixture. Thus it is estimated that between 1920 and 1930, although there was little increase in tonnage of fertilizer, there was an increase of fully 30 per cent in the content of nitrogen, phosphate, and potash. Hence, the American farmer has actually been using more plant-food to

Jan 1, 1932

Alfred C. Young† (communication to the Secretary): Before the appearance of Mr. Scott's paper in these Transactions we were not specially interested in the investigation which he has started; but at his request we have endeavored to collect from musty records and the recollection of our old friends a brief chronicle of the progress made by this house. As 3000 instruments were manufactured by us before any descriptive record was kept, and 2000 more before the record contained more than a statement whether the instrument was a transit or a level, and sometimes its size, we approach the task with timidity, trusting that the reader will bear the difficulties in mind, particularly as the writer's predecessors, from whom, no doubt, the information desired could have been obtained, have passed away. Instruments for surveying were manufactured by David Rittenhouse, of Philadelphia, as early as 1760; but it was not until late in the first quarter of this century that there was any American market for an instrument outside of the ordinary surveyor's compass. With the advent of canals and railroads, and the more extensive development of the Pennsylvania coalfields, arose a demand for surveying-instruments to meet problems in engineering beyond the limited field of the compass. On May 1, 1820, in which year the practical mining of anthracite coal in Pennsylvania began, William J. Young, who had served his apprenticeship with one Thomas Whitney,

Jan 1, 1901

By S. Wallden, R. Lindstrom

The electrolytic copper refining process is an excellent method for producing high-purity metal for electric conductors and other demanding applications. However, the process involves very high capital expenditure, especially the amounts of metals bound in the process. Efforts have therefore been made for many years to increase the production rate by increasing the current density, without impairing the quality of the copper. One of the approaches has been to diminish the polarization by mechanical means, while another was to "polish" the cathode surface by periodic brief reversals of the current. Reversed current electrolysis was first developed for electro- plating purposes and in 1952 Boliden AB and the Dept. of Electrochemistry at the Royal Inst. of Tech., Stockholm tested the method for copper refining with good results. However, no suitable electrical equipment for current reversal was then available. The thyristor-controlled silicon rectifier became available during the '60s and provided the scope for industrial application of the process and the first large-scale development was made by the Bulgarian copper refinery in Pirdop. Many copper refineries are now studying or adapting the reverse current process. Further lab and pilot investigations have been carried out at Boliden AB during the past 4 years and these were mainly aimed at studying the optimization of factors influencing the quality of copper. A production unit containing two tank sections with a total of 56 cells and equipped with a rectifier for cur- rent reversal has been installed and will be started during 1973.

Jan 1, 1973

By C. S. Barrett

WhEN a collimated beam of protons or other energetic particles is scattered by a single crystal, the emerging particles produce patterns that contain much crystallographic information. Calculations of the trajectories of individual particles can predict with reasonable accuracy the complete pattern (which is related reciprocally to channeling, now studied in detail6) but the task is a lengthy one which has been completed for very few cases. A many-beam dynamic diffraction calculation of the patterns would be even more difficult and in some cases may be invalid. Because of these complexities, simple methods that will predict to a rough approximation the relative intensities of the lines in films of the back-scattering patterns of a given crystal are wanted. I have found a method which, although it is not a valid computation of intensities or of film darkening by either dynamic or kinematic diffraction principles or by trajectory calculations, nevertheless is found to be useful in practice. It has been tested on several crystal types,7 and is here tested on additional ones. The method consists in first calculating the structure factor F(hk1) for the (hkl) plane, of spacing d, by the familiar equation: where the summation extends over the atoms in the unit cell and fj is the atom scattering factor of the jth atom (using tables computed for electron diffraction, preferably those computed without exchange). Then the F values are squared and summed over all the orders, n, for which F2 has an appreciable value, giving a quantity: Finally, I, is expressed as a percentage of Ic for the

Jan 1, 1970

By W. G. Fischer

This paper attempts to close the gap between extensive rock testing with field measurements and the mine operator's need for safe mine layouts and alternatives. It was found that many of the variables that influence mine geometry and worker safety are relatively unimportant while others are critical. The development of empirical relationships that tie the critical variables to the safe useful life of a trona mine layout and observations made in 140 production areas where the variables were researched over a 15-year period are discussed. The concepts presented may have applicability in mine design for other bedded deposits.

Jan 1, 1986

By Robert B. Hall, Charles W. Bauer

Alunite, KA13(SO4)2(OH)6, was used from the 15th century until early in the present century as a source of potash alum and aluminum sulfate. Since early in this century its use for this purpose has declined to virtually nil with acid treatment of bauxite or clay replacing alunite as a source of alum. During the First World War alunite served as an emergency source of potassium sulfate fertilizer in the United States and Australia. More recently, alunite has been investigated as a nonbauxite ore of aluminum, with potassium sulfate and sulfuric acid as recoverable byproducts. The Soviet Union established a commercial-scale plant in the mid-1960s producing cell-grade alumina from alunitic ore and recovering byproduct potassium sulfate and sulfuric acid. Interest in nonbauxite ores, including alunite, is expected to continue in countries that presently are dependent on imports of bauxite or alumina to support their aluminum industries. The US has the largest aluminum producing and fabricating industry in the world but imports more than 90% of its aluminum-bearing raw materials. This chapter reviews the status of alunite as a potential source of aluminum with byproduct fertilizer, and the resources available to support this industry, whenever this becomes economically feasible. Historical Background Alunite has received little attention until recently, yet for centuries it held a higher place than many of the industrial minerals considered essential today. The deposits of alunite at Tolfa, northwest of Rome, were mined almost continuously from 1462 until about the middle of the present century (DeLaunay, 1907; Lombardi, 1977). The potash alum made from the alunite, called Roman alum, was a valued commodity in international trade, being used in the making of paper, in tanning leather, and as a mordant in textile dyeing. The industry at Tolfa is said to have been controlled by the Vatican and was a source of revenue for the Papal State until fairly recent times (Lombardi et al., 1977). Since early in the present century, the preferred method for making alum has been by acid treatment of bauxite, clay, or other aluminous material, so that alunite has fallen into near-total disuse as a source of alum chemicals. Appreciable quantities of mixed alunite-kaolin rock still are quarried in the Tolfa district for use by the Italian cement industry (Lombardi and Mattias, 1979), but the role of this material in the making of Italian cement is not clear. A large deposit of alunite-bearing rock in Chekiang province, mainland China, is said to have yielded a "great quantity" of alum over a period of several centuries (Yih, 1931). During the 19th century, alunite deposits in France, Spain, Australia, and other countries were exploited as raw material for making potash alum and aluminum sulfate. Interest in alunite was revived during the First World War, not for alum, but as an emergency source of potassium sulfate fertilizer. Large veins of nearly pure alunite had just been discovered on Alunite Ridge, 11 km southwest of Marysvale in Piute County, Utah (Butler and Gale, 1912), and these were quickly brought into production for making potash fertilizer to replace supplies cut off from the famous deposits at Stassfurt, Germany. An estimated 225 kt of Marysvale alunite was mined and processed at that time (Callaghan, 1973). Similarly, Australian alunite deposits were mined as a source of potash fertilizer during both world wars (Hall, 1978).

Jan 1, 1983

By J. C. Holm

Although the main constituents of Portland cement are the oxides of calcium, silicon, aluminum, and iron, characteristics of the cement are seriously affected by such contaminants in the raw materials as magnesium, phosphorus, sodium, potassium, sulfur, and others of lesser importance. Sources of cement raw materials comprise a long list of minerals occurring in nature in various degrees of purity. The calcareous raw materials are generally limestone of purity varying from calcite to cement rock (a low-grade limestone of natural, almost correct chemical composition), chalk, marl, seashells, coral, and coral sand. The argillaceous raw materials supplying silicon, aluminum, and iron are mainly various forms of clay and shale, to which may be added silicious sand, iron ore, bauxite, or kaolin for minor adjustment of the chemical composition.

Jul 1, 1956

By F. W. Jessen, N. Mungan

The plastic flow characteristics of clay water suspensions were first recognized by Binghaml in 1916 and further studied by Ambrose and Loomis' in 1931-1932. Many physical and chemical properties of clay suspensions are deeply influenced by particle size distribution as well as by the exchange cation. Separation of a number of fractions is particularly helpful in making a detailed study of a suspension. A limited amount of work has been conducted on the effects of particle size on specific properties of mud drilling fluids. A knowledge of particle size distribution is essential for a better understanding of fundamental properties of clay suspensions, particularly viscosity and gel strength. The purpose of this investigation was to study the effect of particle size on the viscosity and gel properties of clay suspensions and to determine any changes in mineral composition accompanying variation in size. EXPERIMENTAL PROCEDURE Numerous methods may be used to fractionate a poly-dispersed clay suspension into nearly mono-dispersed systems. Particles larger than 44 micron (325-mesh) may be obtained by wet screening. For sizes from 44 to 1 micron, the fractionation may be accomplished by sedimentation, elutriation plus microscopy,' or turbidimetry.6 When dealing with systems which contain a major portion of particles below l-mi-cron size, slit ultramicroscopy,7 centrifuge methods of Svedberg,5 eams,9 and McBain,l0 and X-ray methods" may be employed. The Sharples super centrifuge has been proved suitable for the economical separation of suspended particles of submicron range.12,13,14 Three-hundred and forty-five gal of 1 per cent by weight Aquagel suspension was mixed in a high-speed 5-gallon mud mixer and the suspension was allowed to stand in 5-gal glass bottles for 30 days to assure full hydration. All particles larger than 44 microns were removed by wet screening. Five fractions in the range of 44 to 1 micron were obtained by sedimentation. The Sharples super centrifuge method described by Hauser and Reed.13 Norton and Speil,14 Ha user and Lynn,15 and Hauser and Schachman,10 as employed to yield five fractions of submicron size. A super centrifuge operation chart prepared by Fancher, Oliphant, and Houssierre12 was used to determine operating conditions for the desired particle ranges. The clay suspension, after removal of all material above 1-micron size, was centrifuged. During rotation of the bowl, the particles were deposited on a thin plastic liner which fit closely inside the bowl. After passing 5 gal of suspension through the centrifuge, the liner was removed and the particles on the liner were scraped off, remixed and recentrifuged. This was repeated five times. Thus, Fractions H, I, K, and L were obtained. The finest fraction, M, remained in an approximately 0.4 per cent suspension. Water was evaporated under reduced pressure from this suspension to yield the finest particles. Results of the fractionation are included in Table 1. In order to achieve proper orientation and humidity conditions for X-ray diffraction analysis, the following procedure was employed. The dilute suspensions were placed on glass slides and allowed to dry at room temperature. This was repeated several times. Previous to measurement each sample first was placed in a water desiccator for half an hour and then allowed to stand for 15 minutes at room temperature. thus yielding an equilibrium condition of about 52 per cent relative humidity. The relative humidity of the room in which the X-ray diffraction was carried out was maintained at approximately 50 per cent so that there was no change in the spacings during the X-ray examination. Samples

By W. O. Philbrook, H. E. Burner, F. S. Manning

The equation of continuity for the hydrogen reduction of hematite in a fixed bed of closely-sized particles is solved assuming a flat velocity profile, negligible temperature gradients, md negligible axial diffusion. A kinetic expression from the literature is used which assumes the reduction process is controlled at the oxide-metal interface. The integral fractional conversion is computed, and the importance of particle diameter, flow mte, temperature, bulk axial diffusion, and inter- and intra-particle mass trarnsfer is predicted. Comparison with experimental data suggests one or more additional undefined variable(s) is significant. Equipment modifications are suggested for fidture experimentcll work. WITH the increasing desire to "design" the ore feed of a blast furnace, it has become necessary to define more quantitatively the process variables and to evaluate the extent of their control upon the reduction process. The bulk of the work reported in the literature has centered about the reduction of single particles; however, the blast furnace process more closely resembles reduction of a fixed bed than that of single particles. To simplify this analysis, the isothermal reduction by hydrogen of a natural hematite in a fixed bed of closely-sized particles is examined. With appropriate modifications in the kinetic and flow rate expressions, the approach employed should be extensible to mixtures of carbon monoxide, hydrogen, and inert nitrogen, and to adi-abatic conditions, thus approaching the blast furnace process more closely. The fixed bed variables which are investigated in this study are particle diameter, flow rate, temperature, and bulk axial diffusion, as well as inter-and intra-particle mass transfer. Of particular interest is the effect of particle size upon fractional conversion for a bed operating under constant pressure drop. The constant pressure drop concept bears a close resemblance to the blast furnace process, where regions of larger particles may provide a greater permeability to divert most of the reducing gas flow from the regions of smaller ore particles. Under such conditions one would expect qualitatively that, for sufficiently small particle sizes where the flow rate is small and the total surface area is large, the reduction rate would be limited by the gas flow rate. Initially the gas entering the bed reacts very rapidly and the composition approaches the equilibrium conversion value a short distance from the reactor inlet. This concentration "wave-front" then moves up the bed as the flow of reducing gas is continued, leaving in its wake an ever increasing layer of reduced particles. Providing that the reducing gas leaves the bed at equilibrium concentrations, conversion is expected to increase with an increase in flow rate, and hence with an increase in particle diemater. Conversely, for sufficiently large particles the flow rate will be high but the surface area available for reaction will limit the reduction rate. Since the total surface area decreases with an increase in particle size, conversion, in this case, is expected to decrease as the particle diameter is increased. It is clear then that between these two extremes an optimum particle diameter must exist. THEORETICAL DEVELOPMENT Above the temperature where wiistite is stable (about 560°C) the reduction of hematite proceeds through the series Fe2O3/Fe3O4/FeO/Fe. On the basis of microstructural studies and earlier work, Edström1 has postulated a mechanism for the reduction of an ideal hematite lattice: 1) Iron phase formation at the boundary between wiistite, iron, and gas (for sufficiently porous iron). 2) Diffusion of iron across a wustite layer. 3) Phase boundary reaction of Fe3O4 to FeO. 4) Diffusion across a dense magnetite layer. 5) Phase-boundary reaction of Fe2O3 to Fe3O4. According to the mechanism postulated, gaseous reaction product has to be removed only at the boundaries between wüstite and iron or gas, the only possible exception being enveloped Fe3O4 specks. On this basis McKewan2,3 has proposed that one may consider the hematite reduction process as a simple two-phase system of oxide/metal. If, for FeO and Fe3O4 layers of negligible thickness, the hypothesis is made that the rate of formation of a

Jan 1, 1963

By E. Wainer, K. D. Burnham

A wet beneficiation technique for producing wollas-tonite from its ore in high yield and purity has been evaluated in a pilot plant operation at the rate of 75 tons per month. Finely crushed, unsized wollastonite ore mixed with water is passed through a high in tensity oscillating wet magnetic separator of unique design and in a single pass over 90% of the wolla-stonite exhibiting a crystal purity of 99.8% is obtained irrespective of size of feed fraction. Thereafter, the material is processed by closed cycle standard wet milling and classification techniques to yield a 1µ size product, though any mesh size up to and including 50 mesh may be obtained, if desired. Costs appear to be significantly lower than those available from dry processed techniques. Wollas tonite made by this unusual wet process appears to have potential utility in the following fields: ceramics, paints, plastics, paper, organic finishes, reinforcement of portland cement items, controlled porosity refractory ceramic foams, cinder and concrete block paint, and the like. The 1µ and certain chemically processed varieties of wollastonite may have unusual utility in the paper industry both as a filler and as a coating material and in the organic finish industry. Extensive deposits of wollastonite ore equivalent to an average tenor of 50% to 60% of this latter mineral in easily separable form exists in and around Essex County in northern New York State in reserves of the order of several tens of millions of tons. While important portions of these deposits are susceptible to open pit mining techniques, one operation near Wills-boro, N.Y., involves tunnel mining and dry milling and beneficiation techniques. This mill and tunnel mine is presently being operated by The Cabot Corp. and a variety of particle sizes are now sold into markets in the ceramic, paint, plastic finish, floor tile and in similar fields in substantial tonnages on a repetitive basis. Serious investigation and study over the past several years has indicated that, outside of the obvious economies of open pit techniques for mining purposes, wet beneficiation and milling procedures applied to the ore not only represent a potential for greater economies in the production of a superfine finished product but yields products of improved properties exhibiting increased market potential which may not be available from the dry ground product. The Lewis and Deerhead deposits, controlled by the Adirondack Development Corp., appear to be identical to the Wilisboro deposit. Utilizing ore taken from the Lewis and Deerhead deposits, a pilot plant process for the wet beneficiation, milling and classifying of wollastonite ore has been operated for several months. After scalping a marketable garnet product from a minus 16 mesh dry crushed feed on a high intensity roll magnet the balance of the material is then roll crushed in a closed cycle until it will pass a 50 mesh screen. The product constitutes the feed of the wet magnetic separator. The heart of the new beneficiation process is a cyclically operated wet magnetic separator which exhibits the unique feature that unsized feed is easily handled. Product yields of higher purity are equal to that obtained with dry magnetic separations which use closely sized dry ore and multiple passes, but only produce wollastonite of about 98% mineral purity as determined by sink float techniques. It was anticipated that the wet processing through the grinding, milling and classification stage would yield a low cost 1µ ground product which should make available greatly increased applications for the mineral beyond those presently enjoyed. The improved purity was also expected to provide coarser sizes which might be utilized as a raw material for chemical modification which again would expand the uses of wollastonite. The evidence thus far collected appears to indicate that this premise may be expected to be fulfilled. There are on the surface of wollastonite particle sites at which cheinical reactions may occur1. It is believed that wet ground material provides a better base which will allow wollastonite a deeper entree into the field of chemical raw materials. Wet ground at 20µ and finer permits with certainty a number of chemical reactions, some of which are mentioned later in this article. While well crystallized wollastonite makes up the majority of the ore, the balance consists mainly of very weakly magnetic diopside of the hedenbergite-

Jan 1, 1965

By M. L. Holzworth, Joseph C. Kremer, Paul A. Beck, L. J. Demer

FOR alloys which are in practice heat treated to obtain increased strength, such as steels, duralumin, copper-beryllium, and others, the treatment usually involves heating to a relatively high temperature. At such temperatures the grain size of the product is largely determined by grain growth. Even in metals and alloys annealed merely to relieve work hardening, recrystallization is generally followed by a certain amount of grain growth. Thus, effective grain size control, which is often of great practical importance in manufacturing processes, depends on the grain growth behavior of the material used. Despite its importance, grain growth has been the subject of few investigations of a fundamental nature. The term "grain growth" has been used to designate a group of related, but distinctly different, phenomena. The two most important and best known of this group are illustrated by the following example. Curve a in Fig r shows the increase of the average grain size of a copper-beryllium alloy, containing 2 pct Be and 0.15 pct Co, with increasing annealing temperature. The time of annealing was 2 hrs. The grain size was quite uniform in all specimens. The results of a similar experiment with an alloy containing 2 pct Be and 0.31 pct Co are shown by curve b. It is seen that for any annealing temperature below T. the grain size was smaller than in the previous case. Grain growth became slower with the higher Co content. This "inhibiting" effect of the higher Co addition was associated with the appearance in the microstructure of fine, light blue particles of the CoBe phase. Up to temperature T. the structure of the inhibited alloy (curve b) was just as uniform as the structures represented by curve a. However, after annealing at T, or at higher temperatures, the inhibited alloy showed some extremely large grains (much larger than the grain sizes developed by the uninhibited alloy with low Co content) mixed with the small grains according to curve b. The presence of these mixed or "duplex" structures is indicated in Fig 11 by the vertical lines branching off curve b. The type of grain growth occurring in uninhibited Cu-Be alloys (curve a) has has been most frequently and best investigated in brass. This type has been designated as "normal grain growth," while the grain growth phenomena occurring in inhibited materials were, at times, referred to as "abnormal grain growth." However, since the latter term has been applied occasionally to the phenomenon of critical recrystallization, which also results in large grains although by an entirely different mechanism, in the present paper a different nomenclature has been adopted in order to avoid confusion. Typical of the grain growth in uninhibited metals and alloys is the continuous

Jan 1, 1947