Search Documents

By Leah L. Naugle, H. H. Lowry, H. G. Landua

Evidence has been accumulating in recent years, in part from the work of the Coal Research Laboratory, that coals belong to a family of natural polymers and that even in complex reactions the differences between coals are quantitative and not qualitative. This point of view leads to the expectation that if a series of coals were subjected to a closely controlled set of experimental conditions the results obtained should be related to the chemical analyses of the individual coals. The data accumulated over the past 10 years by the Bureau of Mines in its ('Survey of Coke-, Gas-, and By-Product-Making Properties of American Coals," in what has come to be recognized as the Bureau of Mines-American Gas Association (BM-AGA) carbonization assay test,l-l2 offer an unusual opportunity to check this conclusion. The present paper reports an analysis of the data on the first go coals and coal blends— including coals numbered I to 55B, inclusive —which have been carbonized according to a standard procedure at intervals of 100°C. from 500° to 1100° in either or both 13 or 18-in. cylindrical retorts.13 In Table I are given the name of the seam from which the sample was obtained, the analytical data used, and the reference to the original publication of the Bureau of Mines. The coals range in fixed carbon from 46.2 to 79.0 per cent, in volatile matter from 15.4 to 41.3 per cent, in ash from 2.1 to 15.9 per cent, in moisture from 0.8 to 19.7 per cent, and in total sulphur from 0.40 to 4.44 per cent; therefore the entire gamut of bituminous coals is represented. The petrographic nature of the individual coals is not considered in the following analysis, although both "normal" bright coals and splint coals are included in the samples studied. For information on the petrography of the coals and for further information characterizing the coals the original papers should be consulted. Although the coals that are included extend over the whole range of bituminous coals, they do not cover this range entirely adequately. In particular, only 13 of the 90 coals have moisture contents greater than 3 per cent. This concentration at low moisture values means that the effect of moisture, which is an important factor, cannot be determined with as much certainty as would be desirable. All the coals were not tested at every temperature and in both retort sizes. Only the first 30 coals were tested at 1100°, and only about 50 at the other temperatures, except at 900°, where nearly all of them were included. In the accompanying tables the actual number of observations entering into each correlation is given. In this study equations are given for calculating analyses, yields, and properties of coke and by-products from the coal analyses. To decide whether these equations are satisfactory it is necessary to know the accuracy with which these quantities were measured in the assay tests.

Jan 1, 1942

By ROBERT. RICHARDS

I. INTRODUCTION The object of this paper is to enlarge the field of settling velocities treated by me in my former papers, Close Sizing Before Jigging, and Sorting Before Sizing.' There seemed need of work both on coarser and on finer sizes. Messrs. A. Sidney Warren and M. L. Nagel undertook the investigation for the coarser sizes, from 12.85 mm. down to 2.05 mm. diameter. Their work, because of the closer spacing and because of the increased number of observations and consequent stronger averages, called for a revision of the former work. Messrs. G., A. Barnaby and Ralph Hayden undertook this part of the work, from 2.49 mm. down to 0.28 mm., which is near the limit of sifting. Their work covers the ground much more minutely and comprehensively than the former papers. There remained to be covered the portion of the field too fine for investigation with the sieves. This part, covering the range of grains from 0.48 to 0.03 mm., was undertaken by Mr. E. S. Bardwell. For it he used the elutriation method. II. THE FIRST, OR COARSEST, SECTION OF THE FIELD. The first desideratum in this investigation was a series of sieves for sizing the sands preparatory to making the tests. It became necessary, therefore, to decide on a sieve-scale for this purpose. A sieve-scale is a series of sieves in which the dimensions of the holes of the successive members form a series increasing by a. definite ratio. There are three natural sieve-scales : 1, progressing by doubling the width of the hole for each suc-

May 1, 1907

By Lawrence H. Van Vlack, Otto K. Riegger, Gerald I. Madden

The microstructural variations of periclase (MgO) in the presence of oxide liquids are examined under the steelmaking variables of: 1) temperature, 2) liquid composition, and 3) FeO additions under different oxidation levels. Attention is given to the distribution of the phases, both liquid and solid, and to the growth of individual crystalline grains. Silicate liquids penetrate more extensively between individual periclase grains than do liquids containing high percentages of Fe2O3 Higher MgO solubilities in the liquid and lower MgO contents of the solid favor more rapid grain growth. The presence of a second solid phase reduces the periclase grain growth rate and increases the amount of the solid-to-solid contact within the oxide microstructures at high temperatures. The service suitability of a refractory depends on many factors. Two are of major importance and include 1) the thermal resistance to melting, and 2) the mechanical resistance to loads at service temperatures. Neither is a simple consequence of the service temperatures because service conditions will alter compositions, produce partial melting, and induee phase changes. Consequently, the equilibrium phase relationships have been rather thoroughly studied and give a knowledge of the thermal resistance to melting, but do not give full information about the mechanical properties because two refractories with the same types and quantities of phase may have different microstructures. Although variations of microstructures with time, temperature, and composition have been subjects for extensive investigation in metals, only a limited amount of comparable microstructural work has been performed for refractory materials.' This study was an attempt to evaluate some of the consequences of service parameters upon the microstructures of refractories so that bases may be established for the analyzing of high temperature mechanical properties. Periclase (MgO) was chosen as the refractory oxide; variables included those which are encountered under steelmaking conditions such as 1) temperature, 2) liquid composition, and 3) FeO additions under various oxidation levels. Specific attention was given to the distribution of the phases, both liquid and solid, and to the growth of individual crystalline grains. The most closely related work on microstructures of polyphase materials is that of Van Vlack and Rieg-ger2 on the microstructure of magnesiowüstite [(Mg,Fe)O] in the presence of silica. In that work which pertained to solid solutions with less than 40 pct MgO, most of the quantitative work was performed on FeO microstructures. The chief conclusions concerning these relatively low-melting oxide solids were as follows: 1) the rate of crystalline grain growth is inversely proportional to the grain diameter, 2) grain growth proceeds more rapidly at higher temperatures but is slightly retarded by additional liquid content, and 3) a Silicate-containing liquid penetrates as a film between the individual magnesiowüstite grains independent of time, temperature, amount of liquid, or the MgO/ FeO ratio. The above observations are in contrast to prior work3 on the microstructure of silica in the presence of iron oxide-containing liquids where the liquid does not penetrate as a complete film between solid grains. The phase relationships for the compositions of the present work are shown in Fig. 1 which is a summary of the work of several investigators.4 Of importance is the fact that CaO forms a more stable structure with SiO2 and Al2O3 than do either MgO or FeO. The oxygen potential has little effect on periclase unless iron oxide is also present. The iron oxide is ferrous at moderately low oxygen levels, changing to ferric as the Oxygen potential is increased so the spinels, magnetite, and magesioferrite are formed.5 These two phases are relatively stable in air at steelmaking temperatures. I) EXPERIMENTAL PROCEDURE ractory were made with reagent grade Oxides. The magnesium oxide used was 99 pct MgO after ignition, and the iron oxide raw material had a minimum content of 99 pet Fe2O3. The CaO, SiO2, and A12O3 were also reagent grade raw materials. After mixing, the required compositions were pressed into pellets at a minimum pressure of 5000 psi to insure compaction of the raw materials and prevent excess void content. A silicon carbide element tube furnace was used with thermocouple control for sin-

Jan 1, 1963

OFFICERS AND DIRECTORS For the year ending February, 1932 PRESIDENT ROBERT E. TALLY JEROME, ARIZ. FREDERICK W. BRADLEY SAN FRANCISCO, CAL. WILLIAM H. BASSETT,P WATERBURY, CONN KARL EILERS NEW YORK N. Y.

Jan 1, 1929

By Christian F. Baiz

INTRODUCTION Industrial minerals can have similar financing requirements to those needs of metaliferrous and coal mining projects. One of the outstanding differences is the understanding of the many different markets that these industrial minerals represent. There are in excess of 30 principal industrial minerals ranging in terms of annual production from the largest quantity such as sand and gravel, to possibly the smallest quantity of production of a legitimate industrial mineral which may be defined as industrial and rough gem diamond. (See Tables 1 and 2) Project finance techniques, analytical methods, and information requirements are covered elsewhere in this Chapter and Chapter 10. Some comments on equity finance aspects follow. EQUITY AMOUNT The amount of equity in a financing transaction provides a cushion to the lender in case the project runs into trouble. Generally speaking, the greater the amount of risk in a project, the more equity a lender will require. The amount of cash equity in a project financing transaction is between 25 and 40 percent. The amount of leverage (debt/equity) is negotiable based on such factors as the strength and extent of the sponsor's undertakings, of the project's economics, and the term of a strong sales contract. Naturally, a borrower seeks to obtain d loan with as little equity required as can be negotiated. Zero percent equity is usually associated with a take-or-pay contract (a hell-or-high- water unconditional commitment under which the purchaser must pay for the commodity as though it were shipped regardless of whether it is actually mined or shipped) with a financially strong corporate entity i.e., the parent company or an end user. As a take-or-pay contract is tantamount to a guarantee of payment, the banker views the credit basis of the loan as being other than the borrower's mining operation and therefore will analyze the creditworthiness of the institution purchasing the commodity on the basis of its corporate balance sheet. Do not confuse a take-or-pay contract with a take-if- tendered or take-and-pay contract. Another means in the United States of obtaining zero percent equity is the carved out production payment financing, typical of coal mine financing. This involves the sale, or conveyance, by the owner of the mineral property of a production payment to a nominally capitalized company. The nominally capitalized company is formed solely to buy the production payment and usually borrows 100 percent of the purchase price from a lender. Equity amounts of 10 to 20 percent generally are found in transactions which employ techniques such as an advance sale or a subordinated lease/loan. These agreements are viewed as quasi equity by most banks for several reasons. First, the proceeds represent a cash infusion early in the project's life - usually prior to the bank lending any funds. Thus, the repayment schedule is "behind" that of the bank debt. In the case of an advance sale, repayment is in the form of a long-term supply contract with favorable terms, usually priced close to the mining operation's costs. There is also usually a requirement that all costs of the project be paid for by the loan or equity, often making the sponsors financially responsible for any cost overruns. Cost overruns are a major risk in any project, large or small, and are often due to unforeseen factors such as wildcat strikes, a piece of faulty equipment, or any event which delays completion, e.g., remote location, weather, etc.. . The question of how overruns are covered can be negotiated. For example, in addition to the original debt/equity ratio of the project, there can also be a cost overrun ratio that will

Jan 1, 1985

By C. A. Heiland

Measurements of gravity with gravimeters have come into increased use in this country and abroad in the past five years. Probably 100 to 125 gravimeter parties are working in the United States alone. In oil exploration, gravimeter methods have relegated the gravity pendulum definitely to second place, if not third, and now closely rival and possibly surpass the torsion balance in many applications. Gravimeters have lately been applied in mining, although it is doubtful whether they will ever replace electrical or magnetic methods in this work. Notwithstanding the widespread application of gravimeters, there has been no article covering the entire field in the domestic or foreign literature. The purpose of this paper is to meet the demand for comprehensive engineering information on the subject. The working principles of a number of gravimeters will be illustrated and treated in relation to the action of corresponding seismometers and astatization methods. The mathematical discussion of theory has been confined to the most necessary fundamentals and been given in as elementary form as possible. A description of calibration methods constitutes the last part of the paper. The symbols shown at the top of page 197 will be used in equations throughout the paper. Dynamic and Static Gravity Methods Methods of measuring gravity fall into two groups: dynamic and static methods. The first group involves the measurement of time. Examples are: determinations of the period of oscillation of a pendulum, measurements involving the free fall of a body, and comparisons of gravity with the centrifugal force of a rotating body. Measurements in the second group of gravity methods are concerned with deflections of certain indicators when the force of gravity is in equilibrium with another comparison force.

Jan 1, 1940

By C. A. Heiland

Measurements of gravity with gravimeters have come into increased use in this country and abroad in the past five years. Probably 100 to 125 gravimeter parties are working in the United States alone. In oil exploration, gravimeter methods have relegated the gravity pendulum definitely to second place, if not third, and now closely rival and possibly surpass the torsion balance in many applications. Gravimeters have lately been applied in mining, although it is doubtful whether they will ever replace electrical or magnetic methods in this work. Notwithstanding the widespread application of gravimeters, there has been no article covering the entire field in the domestic or foreign literature. The purpose of this paper is to meet the demand for comprehensive engineering information on the subject. The working principles of a number of gravimeters will be illustrated and treated in relation to the action of corresponding seismometers and astatization methods. The mathematical discussion of theory has been confined to the most necessary fundamentals and been given in as elementary form as possible. A description of calibration methods constitutes the last part of the paper. The symbols shown at the top of page 197 will be used in equations throughout the paper. Dynamic and Static Gravity Methods Methods of measuring gravity fall into two groups: dynamic and static methods. The first group involves the measurement of time. Examples are: determinations of the period of oscillation of a pendulum, measurements involving the free fall of a body, and comparisons of gravity with the centrifugal force of a rotating body. Measurements in the second group of gravity methods are concerned with deflections of certain indicators when the force of gravity is in equilibrium with another comparison force.

Jan 1, 1940

By M. E. Glicksman, G. S. Ansel

It has been shown by Walton and Chalmers,&apos; that the mechanism of the development of solidification textures in castings involves the preferential growth of dendrites along certain crystallographic directions as determined by the influence of prevailing heat-transfer conditions. Specifically, this growth is parallel to the direction of heat flow. The purpose of the present investigation was to determine the applicability of this mechanism to: 1) commercially pure aluminum (99.75 pct) solidified to coarse columnar crystals, 2) an aluminum-silicon casting alloy (5.25 Si, 0.38 Fe, 0.02 Cu, 0.10 Ti, 0.002 S) cast to a fine-grained structure under complex and reproducible heat transfer conditions. PROCEDURE AND RESULTS 1) Specimen Preparation—Using a technique similar to that employed by Northcott and Thomas,2 samples were melted in the directional solidification mold, Fig. 1, by heating the entire assembly to 670° C. The mold was then end cooled using a water jet. From considerations of harmonic analysis, the likely distribution of isotherm normals encountered by the growing crystals is shown in Fig. 1. 2) Orientation Analysis—The pure aluminum sample froze to large columnar crystals, nucleated close to the metal diaphragm, with the growth direction parallel to the mold axis. Using the back-reflection Laue technique, the growth direction of these crystals was determined to be a <100>, which coincided within 53 deg to the mold axis. Metallographic examination of the relatively fine-grained aluminum-silicon sample revealed a dendritic mode of growth having its primary dendrite arms along isotherm normals. Back-reflection Debye-Scherrer patterns, taken with the specimen rotating about its cylinder axis, yielded rings displaying symmetrical arcing, thus proving that the sample did, indeed, possess the solidification texture inferred from the preliminary metallographic examination. To determine the extent and orientation of the texture in the aluminum-silicon alloy, a density distribution of the (111) poles of the sample was plotted using the transmission Debge-Scherrer

Jan 1, 1960

By C. C. Wright, T. S. Spicer, R. G. Bowman

In recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation&apos;s fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. Production of Fly-ash The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air

Jan 1, 1944

By T. S. Spicer, C. C. Wright, R. G. Bowman

In recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation&apos;s fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. Production of Fly-ash The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air

Jan 1, 1944

By Richard A. Conkling

A shale layer, buried beneath two or three thousand feet of strata, in some instances, will upon folding become thicker in the synelines and thinner on top of the anticlines. This can be accounted for, in part, by the stretching on the crests of the fold and the compressing in the troughs; but this will by no means account for all of it, as is shown in the example herein set forth. It is my firm belief that the rest of the thickness is due to flow. What causes the movement, however, does not concern us here, SO long as there is movement, for this article purposes to show its effect upon the producing area of different sands. It is the author&apos;s hope, in this way, to drop a hint or two that may be valuable to the oil geologist, in making estimates of future productions and values of oil properties. An example will be given from property in the famous Gushing Pool in northeastern Oklahoma, where the author has had occasion to make a detailed study before recommending some property to his company, and has then been able to watch the results of this work. The author never mapped the surface structure in this pool, as this had been done by Frank Buttram when he was with the Oklahoma Geological Survey. We are using, therefore, a section of his map in this article for our surface contours. The main east dip comes farther east than this section shows. From the 10-ft. contours in Fig. 1, it will be seen that the surface folding is very slight, but in the contour map of the Bartlesville sand (Fig. 2), which was the greatest producing sand, we see much more complex folding. It seems that the folding becomes greater with the depth. Folding may have started in Middle Pennsylvanian times and continued through the Upper Pennsylvanian which is found at the surface. This may, or may not, have been the cause of the increase of folding with depth. However, the fact that mostly concerns us is the interval of shale between the Bartlesville sand and the Tucker sand. The Tucker is the next productive sand below the Bartlesville. Not enough wells have been drilled to the Tucker sand to make a contour map of it, but

Jan 1, 1917

By Glenn C. Waterman

THE diamond drill is a very important tool in exploration and development testing and its use is increasing. In almost all cases results of diamond drilling are analyzed on the basis of grade and tons. A proper evaluation of core and sludge assays is important if drilling results are to be acceptable as a basis for geologic and engineering appraisal. The relatively wide variation in assay averages as calculated by various well-known combining methods indicates that the engineering choice of a method may affect the outcome of the drilling in terms of ore and waste. The problem of combining assay results from core and sludge samples has been discussed many times in conference and in the literature.&apos;-&apos; Most writers agree that the field of disagreement in methods is large and that the engineer on the job must consider features unique to his drilling, pick one of several combining methods, and depart from the rules when abnormal results come in. All the discussion to date can be summed up by the admission that as yet there is no fairly simple, generally acceptable combining method that is practicable over a wide range of drilling conditions, ground conditions, and ore occurrence. The combining problem is important in evaluating drilling results at Chuquicamata. Recently a reappraisal has been made of recovery variables and their effect on assays, with the result that a new combining method is offered which fits average drilling conditions and is mathematically reasonable. It is simple in application, fundamentally correct, and an improvement over most combining methods. At Chuquicamata diamond drillholes are used to outline the grade and position of blocks of normal and marginal grade oxide, mixed, and sulphide ore. Most holes penetrate all classes of material (and waste), and it is important for mining programs as well as ore reserves to know almost precisely the soluble and insoluble copper content of mineralized ground. At present three classes of ore are mined and treated differently. For an orderly sequence of mining operations which can provide regular daily tonnages of all three ore types and keep grade at certain levels with minimum variation, ore type and its grade must be predicted. Diamond drilling plus geologic mapping and bench sampling are tools for prediction. And drilling data are largely used to calculate grade of material more than a few meters away from bench faces. The orebody at Chuquicamata" is criss-crossed by millions of barren or mineralized weak to fairly strong slips and fault fissures. Mineralization is diverse and encompasses many quartz and oxide or sulphide-bearing copper veins, as well as seams and disseminated grains. Copper occurs in oxide or sulphide minerals or mixtures of these two mineral types. Rock conditions vary from intensely seri-citized (soft and porous) through clay-altered ground to almost fresh granodiorite. The result is an orebody which offers many obstacles to good and consistent core recovery in diamond drilling. Recovery varies considerably in the several alteration zones, the various types of oxide and sulphide ores, and the position and inclination of the drillhole within the complex fracture pattern. As core recovery drops sludge samples must be used with core samples to calculate grade. Many years of drilling at Chuquicamata indicate that in good grade oxide zones and in the sulphide areas core recovery is good and the ground uniformly mineralized. Moderate loss of core, therefore, does not markedly affect grade calculations based on core assays. An early core-sludge combining method used core assays at face value as indicating grade down to 50 pct core recovery, but below this recovery percentage sludge samples were used and weighted according to the standard Longyear chart. This method apparently did not introduce serious errors, but it abruptly used sludge assays with high weighting factors representing 100 pct return irrespective of actual percentage of sludge recovered. Recent drilling activities have been directed toward outlining the marginal ore areas. The non-uniform mineralization and generally poorer core recovery in such ground indicated that a more exact core-sludge combining method was required to equate wide differences between core and sludge assays and recovery. In fringe ore areas at Chuquicamata core recovery averages about 50 pct, from a minimum of 10 to 15 pct to a maximum of 100 pct. Sludge recovery is likewise variable and averages perhaps 80 pct even though holes are cemented as water return falls off. In a homogeneously mineralized area cut by many slips and faults, with hard and soft ribs, loss of core is loss of ground which has a grade similar to that of core recovered, and core assays approximate true grade. In this case sludge samples need not be used. However, it would be unusual to know beforehand that an area is uniformly mineralized, and in fact this condition is probably uncommon. Generally the distribution of valuable minerals in the ground does not exactly compare with their recoverability in core. Thus, in the usual case, loss of core decreases the

Jan 1, 1956

The Industrial Minerals div. has been forging ahead in formulating a program for the February Annual Meeting in Los Angeles. Several papers have been listed and more are being worked into the program. For the cement, lime and gypsum part of the sessions, papers on Gypsum in the Aircraft Industry, Geology of San Marcos Island Gypsum Deposit, and Status of New Dry Rotary Blast Hole Drills, are expected. The Chemical Raw Materials sessions will feature a symposium on potash, with 13 papers as the anticipated number to be presented. Airborne and Ground Magnetometer Work has been suggested. Eight papers have been set for Mining Geology, Four papers, Mining Phosphate Rock, Idaho Phosphorous, and Geology of Carlsbad Potash and Geology of Pearlite will be on the program. Sessions on Dimension stone and slate have been tentatively worked out with papers on Geologic Factors Affecting the Dimension Stone Industry of California, A Quarter Century of Granite Quarrying in Massachusetts, Rock Bursting and Other Geologic Problems in the Granite Quarries of Barre, Vt., Quarry Practices in the Indiana Building Stone Industry, Stratigraphy and Composition of the Salem Limestone, and Dimension Stone in the U. S. in 1952. The Rare Minerals Committee is aiming for six papers with two papers now definitely on the program.

Jan 1, 1952

By J. W. Spretnak, G. W. Powell, J. H. Bucher

Tlze room-temperature tensile fracture oj smooth, round specitnens of three ultrnhigh- strength steels tempered to a wide range of strength levels was studied by means by light and electron-microscopic examination of the fracture surfaces. The fracture of AISI 4340 and 300 M at all the strength levels studied, and H-11, except after tempering at 1200° and 1300°F, occurs in three stages. The initiation of fracture is internal (except in some lightly tcmpeved specimers in which fracture is initiated at surface flaws), and is nucleated largely by separation at metal-second phase intevjaces. TIze voids grow and, coalesce to form a crack. When the crack has reached a sufficienl size, rapid propngutio~z ensues. Failure in this stage of fracture usually occurs by dimpled rupture of inicroshear stefis. In the case of H-11 tempered in the 1125° to 1300°F range, fracture in the shear steps is predominantly by concentrated deformation without void formation. The termination of fracture is usually occomplished by the formation of a shear lib in which fracture occurs by shear dimpled rupture. In the case of H-11 tempered at 1200° and 1300°F, no shear lip was obserued, and the radial elelments extend to the surface—a true termination slage does not exist. ThE tensile fracture of several metals and alloys has been investigated.2-4 In the case of polycrystal-line materials, cup-cone fracture usually results. The mechanism of cup-cone fracture may be summarized as follows.5 Cavities are formed in the necked region of the specimen. They usually are initiated by inclusions or second-phase particles. The cavities extend outwards by means of internal necking, and a crack lying about perpendicular to the length of the specimen is formed in the necked region. Subsequent crack growth occurs by the spread of bands of concentrated plastic deformation inclined at an angle of 30 to 40 deg to the tensile axis. Cavities are formed in the bands of concentrated deformation. The deformation bands zigzag across the bar with the net result that mac-roscopically the crack extends about perpendicular to the specimen axis. The final separation, or cone formation, appears to occur by continued crack propagation along one of the deformation bands out to the surface of the specimen. The micromechanics of the tensile fracture of ultrahigh-strength steels have not been thoroughly investigated. Larson and carr6,7 studied the tensile-fracture surfaces of AISI 4340 with a low-power microscope and reported that three stages of fracture could be observed in general. A centrally located region characterized by circumferential ridges, an annular region characterized by radial surface striations, and a peripheral shear lip were found. It was first pointed out by 1rwin8 that the central region is very probably one of fracture initiation and slow growth, and that the annular, radially striated region is one of rapid crack growth. Presumably the crack grows slowly, assuming roughly a lenticular shape, until it is large enough for the initiation of rapid propagation. In this investigation, it was attempted to determine the fine-scale aspects of the room-temperature tensile fracture of some ultrahigh-strength steels, and to relate the variation in fracture mode with microstructure. The steels studied were AISI 4340, 300M, and H-11 tempered to a wide range of strength levels. I) EXPERIMENTAL PROCEDURE The compositions of the steels studied are given in Table I. The steel was received in the form of hot-rolled bar stock 5/8 to 1 in. in diameter from which oversized specimens were machined and heat-treated. The heat treatments employed are given in Table 11. Subsequent to heat treatment, the specimens were ground to the final dimensions and stress-relieved by heating for 1 hr at 350°F (with the exception of the as-quenched steel). Standard smooth round specimens of 0.252-in. diameter and 1-in. gage length were tested in a Tinius Olsen Universal Testing Machine using a cross-head speed of 0.025 in. per min. The relatively coarse aspects of the fracture topography were determined by light-microscopic examination of sections through the fracture surface of nickel-plated specimens. A direct carbon-replication technique9 was used in the electron-microscopic study of the fracture surfaces. The replicas were examined in the electron microscope, and stereo pairs of electron micrographs were taken. The stereo pairs were then examined using a Wild ST4 Mirror Stereoscope. Carbide and inclusion particles extracted in the replicas were analyzed by selected-area electron diffraction. II) EXPERIMENTAL RESULTS The mechanical testing data are summarized in Table 111. The values reported are the average of

Jan 1, 1965

By W. M. Raynor

LARGE quantities of "midnight oil" have been consumed by researchers in attempting to develop a process to produce cold ductile zirconium at low cost. The tantalizing facts that zirconium is a bright, silvery, tarnish-proof metal and is 2 1/2 times as abundant in the earth&apos;s crust as copper, and thirteen times as plentiful as lead have resulted in much speculation on uses, ranging from automobile radiator grills to kitchen sinks. but unfortunately no low-cost process of producing it has so far been found. In the case of zirconium, we cannot say that "virtue is its own reward" for the principal virtues of the metal, namely, corrosion resistance at ordinary temperatures and ability to absorb gases at high temperature, are the very characteristics that defeat all of the usual recovery methods such as sintering, plating, or direct chemical reduction. The only method giving a pure metal sufficiently low in oxides, nitrides, etc. to be truly cold-malleable is the one developed by Van Arkel and DeBoer in 1925. This process involves decomposition of zirconium tetraiodide in contact with a hot filament and pre

Jan 1, 1947

By R. W. Baldwin

As used in geophysical exploration, the term overvoltage applies to secondary voltages set up by a current into the earth which decay when the current is interrupted. These secondary effects may be measured by pick-up electrodes. The term induced polarization has often been employed to describe this same phenomenon. In its own operations Newmont Exploration Ltd. commonly uses the word pulse. The basis of this method in prospecting is that metallic particles, sulfides in particular, give a high response, whereas barren rock, with certain exceptions, gives a low response. Overvoltage has been tried in searching for many types of mineral occurrence but has been most successful in outlining the widespread disseminated mineralization associated with porphyry coppers. History:&apos; Newmont Mining Corp. has been interested in overvoltage since 1946, when Radio Frequency Laboratories of Boonton, N. J.. drew the company&apos;s attention to phenomena observed in the laboratory. At the instigation of A. A. Brant further model studies were undertaken, and the first tests were performed in 1947. Tests at San Manuel, Ariz., in 1948 were very encouraging, clearly demonstrating that the method could be used to distinguish scattered sulfides at depth. H. 0. Seigel followed up the San Manuel work with a study to determine the phenomena involved.&apos;

Jan 1, 1960

By A. R. Calawa, T. C. Harman, M. Finn, P. Youtz

A study has been made of the growing, annealing, and diffusion parameters in PbSe, Pb1-ySnySe, and Pb1-xSnxTe. Single crystals of these materials have been grown using the Bridgman technique. For all of the above materials the as-grown crystals are p type with high carrier densities. To reduce the carrier concentration and increase the carrier mobility, the samples are annealed either isothermally or by a two-zone method. From isothermal anneals, the liquidus-solidus boundary on the metal-rich side of the stoichiometric composition has been obtained for some alloys of Pb1-xSnxTe and on both the metal- and seleniunz-rich sides for PbSe and alloys of Pbl-ySnySe. In Pbo.935 Sno.065 Se carrier concentrations as low as 5 x1016 Cm-3 and mobilities as high as 44,000 sq cm v-1 sec-1 at 77°K have been obtained. Inter diffusion parameters mere also studied. The ddiffusion experiments mere identical to the isothermal or two-zone annealing experiments except that the samples were removed prior to complete equilibration. The resulting p-n junction depths were determined by sectioning and thermal probing. Inter diffusion coefficients for various temperatures were calculated for both PbSe and Pb0.93Sn0.0,Se. RECENTLY, there has been considerable interest in the PbTe-SnTe and PbSe-SnSe alloys with the rock salt crystal structure. The unusual feature of these systems is the variation of energy gap EG with composition. Several investigations1-3 have shown that EG for the lead chalcogenides decreases as the tin content increases, goes through zero, and then increases again with further increase in tin content. The possibility of obtaining an arbitrary energy gap by selecting the composition is an especially attractive feature of these alloys for applications involving long-wavelength infrared detectors and lasers. In addition, some unusual magneto-optical, galvanomagnetic, and thermomag-netic effects should occur for alloys with low band gaps. If uncompensated low carrier density crystals can be obtained, then a small carrier effective mass, a large dielectric constant, and the resultant high carrier mobility should yield enormous effects at low temperature in a magnetic field. The relative variation of the energy gap with pressure should also be very large for these low gap materials. The primary purpose of this paper is to provide some information concerning the preparation of low carrier concentra- tion, high carrier mobility, and homogeneous single crystals with a predetermined alloy composition. I) DETERMINATION OF ALLOY COMPOSITIONS In all of the work described in this paper, the composition of lead and tin chalcogenides in the alloys was determined by electron microprobe analysis. Separate X-ray spectrometers are used to make simultaneous intensity measurements of the Pb La1 and Sn La1 lines emitted by the sample under excitation by a beam of 25 kev electrons focused to a spot about 2 µm in diam. These intensities are compared to the intensities of the same lines emitted by standards under the same conditions. The standards used are the terminal compounds of each pseudobinary system, i.e., PbTe and SnTe for Pbl-xSnxTe alloys, PbSe and SnSe for Pbl-ySnySe alloys. The composition of the sample is then obtained from theoretical calibration curves which relate the weight fractions of lead and tin in the alloy to the measured ratios of X-ray intensities for the sample and the standards. The lead and tin calibration curves for each alloy system were calculated by using corrections for backscattered electrons,4 ionization,5 and absorption,6 and assuming that the atom fraction of tellurium or selenium in the sample and standards is exactly +. Results obtained by using the microprobe are in good agreement with those obtained by wet chemical analysis. II) CRYSTAL GROWTH FROM THE VAPOR Early work on the vapor growth of PbSe was carried out by Prior.7 He used small chips of Bridgman-grown single crystals as the source material and frequently converted the whole charge of a few grams into one crystal. In the present work, vapor growth occurred using a metal-rich or chalcogenide-rich two-phased alloy powder as the source material. Small, nearly stoichiometric crystals are formed on the walls of the quartz tube. The procedure will now be described in detail. Initially, a 100-g charge containing (metal)o.51(chalco-genide)o 49 proportions or (metal)o.49(chalcogenide)o. 51 proportions of the as-received elements in chunk form are placed in a fused silica ampoule. After the ampoule is loaded, it is evacuated with a diffusion pump and sealed. The sealed ampoule is placed in the center of a vertical resistance furnace. The region containing the ampoule is heated to about 50°C above the liquidus temper-ature for the particular composition used. After about one-half hour at temperature, the elements are reacted and the molten material homogenized. The ampoule is quenched in water. The quenched ingot is crushed to a coarse powder for vapor growth experiments and to a fine powder for the isothermal annealing experiments which are discussed in a later section. Vapor growth experiments were carried out using the powdered, metal-rich or chalcogenide-rich alloys

Jan 1, 1969

By W. B. Clark

IN OPERATING the Alpha mine of the Consolidated Coppermines Corp., Kimberly, Nev., it was necessary to pump out approximately 1200 gallons of waiter per minute to prevent the mine being flooded. There were three levels in the mine at which water accumulated and from which it was pumped, the 1200, 1400 and the 1800- ft. levels. At each, the pumping equipment was installed in duplicate so that if for any reason one unit was out of commission the other would be available to prevent flooding. The two centrifugal pumps at the 1200-ft. level were 600 hp. each; at the 1400-ft. level, 100 hp. each; and at the 1800-ft. level, 300 hp. each.

Jan 1, 1933

By R. E. H. Pomeroy

Early in 1917, it became evident, owing to existing and pending market conditions, that a substitute for crude petroleum must be found for firing the smelter furnaces. After a review of the plants then existing, it was deemed advisable to depart from their practice and to adopt the following described system of distributing pulverized coal to the furnaces. The principal advantages of the proposed system, which influenced this decision, were: (I) Equal safety; no pulverized coal is stored at the furnaces; (2) greater ease of operation, furnace fires being controlled by regulating valves in burner branches, as in gas firing; (3) better organization; all machinery, including pulverized coal feed, is under one roof, and the organization is separate from the furnace department; (4) greater cleanliness; all machinery is under vacuum; (5) greater flexibility of application, the coal and air mixture can be piped where needcd. The design of the plant is the result of the combined efforts of the local engineering staff and of the machinery manufacturers. Many new features were embodied in this design to insure greater safety, cleanliness, and efficiency of handling. After 14 months of continuous operation, the plant has proved entirely satisfactory. The building is of structural steel, covered with corrugated steel, with many windows and is painted light gray inside and out. The building floor is of concrete with ample drains to the sewer, and the building is equipped with fire and service water piping. Fig. 1 shows the east side of the building and the incline conveyor from the raw-coal bins. The plant is operated entirely by electric power. All alternating current is 550 volts, 3-phase, 60 cycles. The pulverized-coal feeding niotors and control mechanism are operated by 220-volt direct current supplied by motor-generator sets in the building. Autamatic push-

Jan 1, 1921

By H. Y. Hunsicker

A graphic method has been devised for three-di-mensional analysis of hot deformation and for correlating the amount and directionality of the deformation with resulting directional properties. Deformation is evaluated in terms of dimensional change ratios referred to three orthogonal axes. Since all combinations of the three ratios can be represented in a triangular coordinate field with logarithmic scales, a two-dimensional chart of extent of deformation and degree of asymetry is possible. The entire gamut of shape changes from upsetting through flat-rolling to rod-rolling is accommodated. The resulting coordinate system is a base upon which can be represented the properties of the wrought products measured in the directions of the axes employed fir evaluating the deformation. When property data are available for many types and amounts of deformation, a three-dimensional figure can be constructed, and the projection of this figure is referred to as a &apos;&apos;3d&apos;&apos; chart. Experience in using such charts to plan fabricating operations for a variety of thick-section forged and rolled products of heat-treated aluminum alloys has verified its practical value for optimizing directionality relationships. MechANICAL anisotropy of thick section products of heat-treatable aluminum alloys is recognized by producers and users of these products, and the extent of the directional differences is apparent in property tabulations included in handbooks, standards, and specifications.&apos; Attention has also been directed to the existence of important directional differences in the resistance of these products to stress-corrosion cracking. Metallurgical structure factors responsible for these directional differences include, among other possibilities, shape and alignment of grains, voids and nonmetallic inclusions (when present), volume fraction and spatial distribution of secondary phase particles and solid-state precipitates, crystal-lographic textures, and Bauschinger effect. The contributions of the individual factors vary with alloy composition, heat-treated temper, type of working process (forging, rolling, extrusion), and the amount and directional nature of the deformation. In general, the cast ingot used as the starting material for producing these wrought products exhibits only a modest degree of directionality. A monotonic and continuous transition from this nearly isotropic state with progressive hot deformation would appear probable, assuming that the working temperature is sufficiently high to cause continuous dynamic recovery. Several years ago a project was undertaken to evaluate the effects of hot deformation and metallurgical structures on the directionality of thick wrought aluminum alloy products, and the method to be described was developed as an analytical tool in this investigation. DIRECTION NOMENCLATURE The nomenclature system adopted by industry for the three mutually perpendicular directions employed in testing aluminum alloy products includes four terms: "longitudinal", "transverse", "long transverse", and "short transverse". These terms are conventionally related to the external geometry of the product but also by implication to the deformation and resulting metallurgical structure. Occasions arise in which through use of unusual fabricating methods, intentional or otherwise, the structure does not have the usual relationship to external geometry or may be very complex because of inhomogeneity of deformation throughout the piece. The longitudinal direction is generally parallel to the primary rolling direction or to the direction of extrusion. In the case of forging, it is parallel to the direction of maximum extension (not maximum "working" or "flow", as frequently stated). The term transverse is applied to any direction perpendicular to the longitudinal direction in a product having symmetry about the longitudinal axis, and generally, although not always, the deformation to produce these forms is nearly symmetrical in the transverse plane. This term then may be applied to a round, square, hexagon, or other polygonal, symmetrical shape produced by extrusion or rolling or by forging, if produced by a simple, symmetrical drawing procedure. The type of microstructure generally associated

Jan 1, 1970