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By H. B. Pulsifer

ABOUT 15 varieties, or modifications, of the best magnesium available were prepared and subjected to etching tests, then examined for microstructure. Of the 30-odd etching reagents that were tried, nearly half, mostly ammonium salts, etched the metal satisfactorily. The surfacing and etching of magnesium is shown to be a very simple and quick operation. The density and hardness of magnesium were determined. The most interesting new observations relate to the finding of the hexagonal etch figures, the crystal laminations, and the fact that the metal is plastic, cold, when restrained or quickly deformed. Under slowly applied pressure cold metal deforms slightly, then shears to fracture without plastic flow. The chief structural features of magnesium are presented in two reduced photographs and 30 photomicrographs. MATERIALS TESTED There are only two sources in the United States from which new metal can be procured: the American Magnesium Corpn. and the Dow Chemical Co. No pronounced structural or property differences in the metals from these two companies were disclosed by the work of this investigation. The following materials were obtained from the manufacturers: 1. Massive crystals of distilled metal (American Magnesium Corpn.). 2. Rods of hot-extruded metal, ½ -in. squares and 5/8-in. rounds (American Magnesium Corpn.). 3. Sheet magnesium, 0.005-in. thick (American Magnesium Corpn.). 4. Cast stick metal, 1 3/8-in. dia. (Dow Chemical Co.). 5. Magnesium-aluminum alloy, hot-rolled plate, ½ in. thick (American Magnesium Corpn.). From these materials, were prepared: 6. Sections from a furnace-cooled ingot made from distilled crystal. 7. Cold-strained pieces from (6), (4) and (2). 8. Pieces cold-squeezed to fracture from (6), (4) and (2). 9. Hammer-struck pieces from (6), (4) and (2). 10. Steam-hammer struck pieces from (6), (4) and (2). 11. Sections from furnace-cooled ingot of the magnesium-aluminum alloy.

Jan 1, 1928

By K. H. Ribe

Water often enters an oil reservoir during completion or workover operations on a well and forms a partial "water block" to oil production. A mathematical study of radial two-phase flow, neglecting capillary effects, has been employed to study the formation of such a water block and subsequent re-moval by production from the well. The effects of reduced oil permeability about the well on the well productivity were studied. The fluid saturation distributions about the well during formation and removal of the water block have also been computed. Several relative permeability relations and viscosity ratios were employed. If water has invaded the formation, its influence through relative permeability effects alone can cause the following. 1. Oil productivity will be depressed for extended periods after production is resumed and will build up only gradually as the water is removed. 2. Oil injected for treatment of water blocking will delay rather than promote restoration of full well productivity by enlarging the region invaded by water. Thus, unless the specific action of chemicals contained in the oil is needed, oil injection appears undesirable. INTRODUCTION During oilwell workover operations, water may enter the oil-bearing formation from the wellbore. When production is resumed, oil must flow through the region invaded by this water. The presence of this region can cause both well productivity and oil production rate to be low and oil to be produced with high water-oil ratio for some time after production is initiated. This situation is sometimes described as a water block. The introduction of water into the formation may result in other actions which also lead to reduction in well productivity and which are also usually included in the connotation of the broad term, water block. Often considered, for example, are the possibilities of clay swelling by contact with fresh water and the formation of emulsions with the formation oil. If it is suspected that such specific actions have taken place, remedial treatments are undertaken which usually involve the injection of chemicals in oil. Since the introduction of water, even in the absence of specific interactions with the formation or oil, will cause a temporary water block (which might be misinterpreted as evidence of a more severe situation), it is of importance to evaluate the magnitude and duration of this blocking which results purely from the reduction in relative permeability to oil in the vicinity of the wellbore. It is also of interest to evaluate the effect of oil injection on the productivity of a well blocked by water in this manner. Inasmuch as this unfavorable condition may persist for some time, it may lead to premature condemnation of a workover or premature abandonment of a potentially productive pay zone. A quantitative evaluation of the influence of water entry on the oil productivity through changes in relative permeability was made by solving a radial form of the Buckley-Leverett equation. The distribution of water saturation around the wellbore during the entry of water was calculated and was followed by a similar calculation of the saturation distribution during the period of resuming production. At any stage in the removal of the invading water, knowledge of the distribution of its saturation permitted calculating the attendant loss in oil productivity. The influence of the shape of the relative permeability relationships was also evaluated by carrying out the calculations for two hypothetical cases. Further, the effect of the oil-water viscosity ratio was examined by repeating the calculations, for several ratios of unity and greater, with the same relative permeabilities. Fi-nally, results are presented to show how the length of time a well must be swabbed to resume production depends on the length of time it has been subjected to invasion by water. STATEMENT OF THEORY Differential Equations Water is assumed to enter a producing formation which is initially at the connate-water saturation and contains no gas. The water and oil are treated as in-

By Eugene McAuliffe

TWO years ago the American Institute of Mining and Metallurgical Engineers made a memorable contribution toward a better understanding of the problems that have for many years confronted the coal industry. Specific suggestions toward betterment were then advanced, certain of which were taken up, amplified and endorsed by men who were conscien-tiously interested in the work of lifting this great industry out of the morass it has lain in for years. Two certain suggestions then made-provision for seasonal variations in railroad freight rates that would tend to encourage the purchase and movement of coal during the low summer production period, and provi-sion for the collection by the United States Government of all the facts surrounding the industry-were intro-duced in the form of legislation in the United States Senate by a member of that body, a man whose personal character, antecedents and business training put him above and beyond all suspicion of demagoguery; however, as the result of the insistent, vindictive opposition of the industry itself, these two bills, con-structive in their nature, were buried under an ava-lanche of misrepresentation. Today, with all mines that employ union labor at a stand still, the work of stabilizing the industry is yet before us. As aptly stated by Herbert Hoover, in March, 1920, when he was president of the Institute; An engineering organization is particularly the body to under-take this work. It is an economic problem, an engineering pro-blem within the ken of our experience; it is a problem that requires not only constructive thought but quantitative thought and wise social thought. The engineers of the United States occupy a position midway between capital and labor. They enter upon problems of this kind without prejudice either way, and they have that faculty of mind for quantitative thought, as distinguished from qualitative thought, that takes such problems as this out of the region of politics into the region of matter-of-fact solution.

Jan 5, 1922

By M. G. Fowler

A GENERAL decline in copper production for most American producers occurred during the past year as a result of shortage in available labor. Few noteworthy technical developments have been reported; undoubtedly, many changes and improvements have been made but have not been reported because of lack of time. During the war years through 1944 the pressure for sustained high production has been of prime importance and during 1945, with slackening of production, many operators were faced with the problem of catching up on repairs and maintenance of plants, with inadequate labor supply. In hydrometallurgy there were some important developments that undoubtedly will be reported during 1946. Several operators in the Southwest have instituted experimental leaching programs to exploit low-grade oxidized and mixed ore bodies. The Bureau of Mines is conducting pilot-plant experimental work to determine the possibility of producing a satisfactory sponge iron at an attractive cost from deposits of iron ore and coal in Arizona. The sponge iron would be used for the production of cement cop¬per. The cell house of the Inspiration Consolidated Copper Co. at Inspiration,

Jan 1, 1946

By W. A. Dunkley, W. W. Odell

The sulfur content of coal is perhaps more important in the manufacture of illuminating gas than in any other coal-using industry. Whether the gas is made by the distillation of coal in retorts or ovens or by steaming incandescent coal or coke in the water-gas process, a portion of the sulfur present in the fuel always passes into the crude gas. Practically all the sulfur that remains in the finished gas is transformed into sulfur dioxide (SO2) when the gas is burned. Sulfur dioxide is a pungent suffocating gas and, if present in the air in any perceptible amount, is deleterious to health and comfort and damaging to house furnishings. SO universally is this recognized that laws regulating the amount of sulfur that may be permitted to remain in the gas are very generally in force. The capacity of a plant to purify gas frequently limits the selection of coal for gas making. This condition may arise from different causes. Some plants were originally designed to handle a certain grade of low-sulfur gas coal, and very little leeway was allowed for growth or for the use of inferior coals. Other plants, when built, had ample capacity to purify gas from relatively higher sulfur coals, but their output has grown so rapidly that their purifying capacity is now limited and only the low-sulfur coals can be handled. There is a great quantity of coal in the United States that would satisfy the requirements of the gas manufacturer, were it not for the high sulfur content. The coals containing less than 1 per cent. sulfur are becoming scarcer year by year and, in time, the gas industry will probably be compelled to use coals that are now considered out of the question. Sulfur Compounds in CRude Gas Sulfur exists in unpurified illuminating gas in a variety of compounds; chief of these are hydrogen sulfide (H2S) and carbon disulfide (CS2). In crude coal gas H2S is usually present to the extent of 0.5 to 2.0 per cent., by volume, equivalent to about 300 to 1200 gr. per 100 cu. ft. of gas. In carbureted water gas, the amount of sulfur compounds depends not only on the sulfur content of the coal or coke used, but also upon cite

Jan 1, 1920

By A. M. Gaudin

The flotation process has been applied extensively in the mineral and chemical fields. This paper reveals results obtained by an exploration of an application to the biological field. In many ways this study was indeed an exploration since so many factors are different. In the mineral field, the particles, both those floated and those not floated, cover a wide range of sizes and shapes; in the biological field, the particles of one population are primarily of one or two sizes and one or two shapes. This identity in size and in shape gives biological systems the advantage of homogeneity. In the mineral field the particles may be as coarse as a millimeter; in the biological field the size may be a micron, or less. In the mineral field the particles may have a gravity several times that of water so that their apparent gravity is quite substantial. Microorganisms, on the other hand, may have a gravity so near that of the liquor that their settling velocity in the liquor is vanishingly small. These two facts conspire to make bubble-particle encounter in the pulp-body less likely. Finally, microorganisms are living, reproducing, and dying-all of which does not help the experimenter get a balance of materials. The analytical problems, too, are extraordinarily difficult, for the organisms can contain only elements that occur in their environment, although at a different level of concentration. The chemical composition of the surface of microorganisms is readily altered. In spite of these areas of difficulty, microorganisms can be floated to leave practically water-clear tailing, they can be floated from each other and, in fact, the same organism can be fractionated into a float that differs from the sink. SIZES AND SHAPES OF ORGANISMS Most ore pulps are described with reference to the percentage of the pulp that is fine enough to pass a 200-mesh sieve. Thus a copper-ore pulp may be 80% -200 mesh. Since 200 mesh equals 74 µ, a 2000-mesh particle would be 7.4 µ in diameter, and a 20,000-mesh particle would be 0.74 µ. The microorganisms with which this work is concerned are of the order of magnitude of 20,000 mesh. We have worked with Escherichia coli, the colon bacillus, Bacillus cereus, Bacillus subtilis, Bacillus megaterium, and Serratia marcescens. In some pioneer work, Dognonl,2 reported the use

Jan 1, 1962

By V. Patarini, D. Kuehl, F. Galasso, M. Salkind

In recent years, a great deal of research has been directed toward the production of continuous low-density, high-strength, high-modulus boron fibers for aerospace applications. A technique which has proven to be quite successful for forming these fibers involves the reaction of boron trichloride and hydrogen on a hot tungsten wire. In this process, a boron fiber is produced which consists of a tungsten boride core covered with amorphous or crystalline boron depending on the temperature of the preparation.2,3 The purpose of this paper is to present the properties which have been obtained to date from measurements and observations on these fibers. Selected samples of boron filament produced by reacting boron trichloride and hydrogen on a 0.5 by 10-3 in. diam tungsten wire substrate using different reacting temperatures were cross-sectioned, polished, and photomicrographed with cross-polarized light. The temperature of the wire was measured using a two-color optical pyrometer. Photomicrographs of these samples are shown in Fig. 1. Three general types of boron, in addition to the tungsten borides, have been identified by means of X-ray powder diffraction techniques: a) at low temperatures (below 1400°C) the boron is deposited in the amorphous form; b) at temperatures between 1400° and 1500°C the boron is deposited in the ß tetragonal form; and, c) above 1500°C the boron is deposited in the B rhom-bohedral form. In the depositing range of 1400" to 1500°C the boron initially deposits as amorphous and becomes crystalline as evidenced by the large equi-axed grains which then merge into columnar grains in later stages of boron deposition. This can be seen in Fig. 1 and has been observed in the X-ray patterns of these fibers, which contain both halos from the amorphous boron and lines from the ß tetragonal form. Above 1500°C the only boron reflections observed in the X-ray patterns were those of the ß rhombohedral form and only columnar grains are seen in the photomicrographs. Photomicrographs of the surface in Fig. 2 show the smooth-surface kernal-type deposition which corresponds to the amorphous form and the rougher surfaces which correspond to the crystalline form. Mechanical measurements were made on amorphous boron produced at 1300°C rather than the crystalline boron because the strengths of these filaments were greater and were more consistent. A tensile tester consisting of a fixed crosshead containing a double

Jan 1, 1967

By H. F. Easter

(San Francisco Meeting, September, 1915) THE lead department of the El Paso Smelting Works at El Paso, Tex., is operated strictly oil a custom basis. The ores treated are drawn from the surrounding territory, comprising New Mexico, Arizona, western Texas, and northern Mexico. Ores received from the last-named section originally amounted to a very large tonnage, but of recent years have dwindled into comparative insignificance so far as this plant is concerned. This has been clue partly to the establishment of a lead-smelting plant at Chihuahua, which is much closer than El Paso to most of the important mines, and partly to the recent revolutionary troubles in Mexico. There are no mines of either lead or copper in the immediate vicinity of El Paso. In general, it may be said that the lead-ore supply of recent years has been uncertain and precarious, with a general tendency toward an excess of silica and a shortage of iron. This latter requirement has been met in large part by the use in El Paso lead furnaces of considerable amounts of roasted heady copper matte from the Chihuahua smeltery and of converter slag from the El Paso converters. These two materials, coupled with complex lead-copper ores from Bisbee, Ariz., have introduced into the lead-smelting operations a most unusual amount of copper, which has had an important bearing upon the smelting practice of the plant. This matter will be discussed later. The ore, loaded in either box cars or gondolas, enters the storage yard on four tracks elevated about 8 ft. above the ground. As all unloading is clone by hand, unloading platforms at the height of the car floor parallel the tracks on each side to afford a runway for wheelbarrows. At frequent intervals these lengthwise platforms are joined together by others running crosswise to facilitate the distribution of the ores evenly over the beds, which are located below and between the tracks. At present much of the bedding space formerly used for lead ores is given over to the copper department, but 20 bins of various sizes are retained for the use of the lead furnaces and the Huntington & Heberlein roasting plant. The largest of these holds about 1,000 tons, while the smallest holds not over

Jan 8, 1915

The early history of coal in West Virginia is all included with that of Virginia in the few records available but for present-day readers it is much more convenient that the account of this area prior to the Civil War be grouped with that since then. West Virginia shares with Maryland in the first record of coal noted in the Appalachian fields. This was along the upper Potomac River, in the fall of 1736, and the data about it are given under Maryland, as most' of the development of the area was in that state. The next record of coal was left by John Peter Salley in his account of the expedition he made with Howard and others in 1742. (See p. 17.) The next reference found is that of Dr. Thomas Walker, in 1750, when he passed through the Pocahontas coal field. This has been described on page 18. Six years later, in March 1756, Capt. William Preston, who was with Major Lewis in his expedition down Big Sandy River, wrote in his journal: "Tuesday 2.... Moved down the branch and- came to the main creek where we camped. Put on half rations. Came into the Cole land; crossed the river 8 times."1 The party crossed from the head of Clinch River to Horse Pen Creek, then to Jacob's Fork and down it to Dry Fork of Tug River; the coal was seen in what is now McDowell County. The early settlers must have known of the presence of the great Pittsburgh bed in the northern part of the state, both along the Monongahela River and elsewhere, because the outcrops could easily be seen along streams in many. places. The report of the Commissioners for Adjusting Claims to Unpatented Lands, made in 1789, contains several references to coal in the names of streams, made years earlier. The earliest is one for 1,000 acres to James Walker, in Monongalia County, "adjoining his settlement on a branch of the right hand fork of Pappaw known by the name of the Stone Cole Lick made in the year 1773."2 Another of 400 acres in the same locality was settled upon in 1777.2 A third spoke of a tract "on the left hand fork of Stone Cole about three miles from the mouth," in 1783.1 Monongalia County then covered all of the northern

Jan 1, 1942

By T. Cameron Kenney

INTRODUCTION Whereas the design of rock slopes in open-pit mines is done largely by mining engineers and geologists, the design of slopes in overburden at this point in time is a problem for which civil engineers or geotechnical engineers are best prepared to deal. The reasons for this situation are to be found in the educational curricula and the technical journals of the two groups, where soil mechanics has received little attention by mining engineers and geologists, and rock mechanics has similarly received little attention by civil engineers. In ten years' time this paper will hopefully be considered by young mining engineers to be a repeat of the material that they studied at university. However, even in ten years time I believe that the civil (or geotechnical) engineers will be extensively used as consultants on overburden- slope problems of open pit mines because mining companies will find this more expedient than maintaining their own geotechnical staff, special field equipment and special testing laboratories. For this reason, the purpose of this paper is not to condense several university soil mechanics courses into a twenty-page text for mining engineers and geologists. Rather, the purpose of the paper is to offer a general explanation of various factors affecting slope stability so that mining engineers and geologists will have a better understanding of the behaviour of overburden soils in slopes. A great deal has been written in soil mechanics literature on the subject of slope stability. No attempt will be made to reference all this material but rather only a selected number of references will be cited. Excellent general treatments of the subject of stability of overburden slopes are available (1,2,3,4). Further information of a more specialized nature is to be found in such publications as the Journal of the Soil Mechanics and Foundation Division of the American Society of Civil Engineers, Geotechnique (printed by the Institution of Civil Engineers, England), Canadian Geotechnical Journal, and the proceedings of the conferences of the International Society for Soil Mechanics and Foundation Engineering. FACTORS INFLUENCING SLOPE STABILITY There are two general scales of slope-stability problems, gross stability and local stability. Gross stability refers to large volumes of soil, and gross instability would involve large rotational-type shear failures. Local stability refers to something much smaller and examples

Jan 1, 1972

By R. L. Skaggs, D. T. Peterson

The effect of carbon in solid solution on the plastic behavior of thorium was studied by measuring the flow stress of Th-C alloys from 4.2" to 573°K and at several strain rates. Carbon was found to strengthen thorium primarily by increasing the thermally activated component of the flow stress. The strengthening due to carbon was directly proportional to the carbon content and decreased rapidly with increasing temperature up to 423" K. The flow stress also increased with increasing strain rate. The strengthening appears to be due to a strong short-range interaction between carbon atoms and dislocations. A yield point was observed in the Th-C alloys which increased with increasing carbon content. JTREVIOUS study of the mechanical properties of thorium has been confined largely to the measurement of the engineering properties. Work prior to 1956 has been summarized by Milko et al.1 who reported that additions of carbon to thorium sharply increased the room-temperature strength. In addition, the yield strength was observed to decrease rapidly over the temperature range from 25" to 500°C. In 1960, Klieven-eit2 measured the flow stress of thorium containing 400 ppm C. He found that over the temperature range from 78" to 470°K the flow stress was strongly dependent on temperature and rate of deformation. A drop in the load-elongation curve, or a yield point, was observed over most of the above temperature range. Above 470°K, the flow stress was nearly independent of temperature and strain rate. This strong temperature and strain rate dependence of flow stress is not generally observed in fcc metals. It is, in fact, more typical of the behavior reported for bcc metals. Bechtold,3 Wessel,4 and conrad5 have pointed out the striking difference between the commonly studied bcc metals and fcc metals in regard to the effect of temperature and strain rate on the flow stress. Zerwekh and scott6 studied the plastic deformation of thorium reported to contain 12 ppm C. They found that this material did not obey the Cottrell-Stokes law as expected for fcc metals. In addition, they found values of the activation volume smaller by an order of magnitude than expected for an fcc metal. They concluded that thorium was strengthened by a randomly dispersed solute. Thorium differs from many other fcc metals that have been studied extensively in that it shows a relatively high carbon solubility at room temperature. Mickleson and peterson7 report the solubility limit at room temperature to be 3500 ppm C. The lowest value reported is that of Smith and Honeycombe8 who report the limit to be 2000 ppm C at 350°C. The pres- ent investigation was a systematic study of the flow stress and yield point phenomenon of thorium over a broad range of carbon content, temperature, and strain rate. EXPERIMENTAL PROCEDURE The thorium used in this investigation was produced by the reduction of thorium tetrachloride with magnesium as described by Peterson et a1.' Chemical analysis of the original ingot after arc melting and electron beam melting is shown in Table I. Alloys were prepared by arc melting this thorium with high-purity spectrographic graphite. Threaded specimens with a gage length 0.252 in. diam by 1.6 in. long were used for the constant stress or creep measurements. These specimens were machined from rod which had been cold-rolled and swaged to % in. diam. Tensile specimens were prepared by swaging annealed 3/8 -in.-diam rod to 0.102 *0.001 in. The as-swaged wire was cut to lengths of 2 in., annealed, and the center 1-in. gage length elec-tropolished to 0.100 ±0.001 in. The specimens were gripped for a length of 3 in. at each end by a serrated four-jaw collet which was tightened by a tapered compression nut. No slipping occurred in the grips and negligible deformation was observed outside the 1-in. gage length. Both the creep and tensile specimens were annealed at 730°C under a vacuum of 1 x X Torr. The resulting structures consisted of equiaxed recrystallized grains with a grain size of 3200 grains per sq mm for the tensile specimens and 2200 grains per sq mm for the creep specimens. After the specimens were prepared, samples were analyzed for nitrogen, oxygen, and hydrogen. The results of these analyses are given in Table 11.

Jan 1, 1969

By L. Delisle

This work represents the first step of an attempt to test the applicability of the electron microscope to the study of subgrain structures in copper. Observations on annealed and deformed single crystals and polycrystalline samples of copper are described. IN the course of study of the structure of fine tungsten wires and tungsten rods with the electron microscope, well defined subgrain structures were observed. The size, size distribution, and orientation uniformity of the etch figures varied widely in different samples. Figs. 1 and 2, electron micrographs of a tungsten wire and of a tungsten rod, respectively, are illustrations of the difference in size and size distribution of the etch figures in different samples of the same metal. The observed differences, as pointed out in a previous paper,' appeared to be related to the heat and mechanical treatments of the samples. They were also consistent with the results reported in the literature on the mosaic structure of metals.' For that reason a program of research was initiated in an effort to obtain more systematic evidence of the possible relation of heat and mechanical treatments to the subgrain structure of metals as observed in the electron microscope. The purpose of this paper is to present observations made on the effect of cold work on the subgrain structure of copper. Procedure Starting Materials: Copper was the metal studied because it can be obtained in a high degree of purity, much information is available in the literature on its properties and its response to cold work and heat treatment, it shows no allotropic change, and it is sufficiently hard to be handled without great difficulty. Two groups of specimens were used: 1—single crystals cast from spectroscopically pure copper and 2—polycrystalline samples of oxygen-free high conductivity copper. Single crystals were studied because it was hoped that the elimination of a number of variables, such as grain boundaries, orientation differences, degree of purity, would simplify the problem and perhaps permit a better understanding of the phenomena that would be observed. The polycrystalline samples were designed to give a general picture of the changes considered. The single crystals were made of copper which analyzed spectroscopically to better than 99.999 pct Cu. They were cast in vacuum, by the Bridgman method, in crucibles made of graphite with a maximum ash content of 0.06 pct. The mold design is shown in Fig. 3. It permitted casting crystals of the size and shape required for the experiments, so that the danger of introducing cold work in the original samples by cutting or other machining would be eliminated. The polycrystalline samples were pieces, 3/4 in. long, cut from a rod of oxygen-free high conductivity copper, % in. in diameter. A flat surface, 1/4 in. wide, was milled along the rods, polished, and etched. The samples were then annealed in vacuum at 850°C for 1 hr. Polishing and Etching: Work previously done on tungsten,' polished mechanically and etched chemically," had shown that: 1—the general appearance of the etch figures of a given sample was not altered by repeated polishings and etchings under similar conditions; 2—variations in the time of etching and the concentration of the etchant changed the definition of the etch figures, but did not alter their general size nor orientation distribution within the limits of observation. Further work confirmed the reproducibility of the subgrain structures observed in, 1—single crystals and polycrystalline samples of copper when polishing and etching were repeated under similar conditions, and 2—specimens of tungsten and polycrystalline copper when electrolytic polishing and etching were substituted for mechanical polishing and chemical etching, respectively. On the strength of these observations, it was felt that, if conditions of polishing and etching were kept constant, changes observed in the subgrain structure of a sample upon deformation and annealing would be attributable to such treatments. For that reason the conditions of polishing and etching were kept as constant as possible. The single crystals were polished electrolytically in a bath of orthophosphoric acid in water, in the ratio of 1000 g of acid of density 1.75 g per cc to 1000 cc of solution, under a potential drop of 1.6 to 1.8 V. Electrolytic polishing was selected to prevent the formation of distorted metal in polishing. The same samples were etched by immersion in a 10 pct aque-

Jan 1, 1954

By Glen R. Neighbors, Sylvan Cromer

HIGH subsurface temperatures and pressures are making cementing operations more difficult as deeper producing horizons are being sought. Recorded bottom-hole temperatures above 200°F. and pressures in excess of 12,000 Ib. per sq. in., obtained by combining hydrostatic and pump pressures, are not uncommon. Insufficient time is available for proper placement of standard Portland cement, because of the shortened setting time produced by these excessive temperatures and pressures, therefore special types of cements have been developed to overcome these difficulties. From the standpoint of placement, the ideal slurry would be one that would remain fluid long enough to be placed, then harden rapidly, so that there would be a limited amount of contamination and the well could be placed on production in a minimum of time. It is highly desirable, therefore, that some method be devised to measure accurately the time that any slurry will remain in a fluid state while being pumped into the well. To study the effect of elevated temperature and pressure on fluidity, the authors have developed the pressure-type consistometer (Figs. I and 2) described below, and are presenting data obtained with it, using slurries of both quick-setting and slow-setting cements. Studies were made over a temperature range from 110° to 270°F., and a pressure range from atmospheric to 3000 lb. per sq. inch. APPARATUS The fluidity of cement slurries at atmospheric pressure is usually determined with the Halliburton consistometer1 or the Thickening Time Tester.2 These instruments are similar, in many respects, to an ordinary ice-cream freezer. The slurry to be tested is placed in a container that is rotated at a constant speed with an electric motor. Constant temperature is maintained by surrounding the container with a thermostatically controlled bath. The torque on the paddles, which is proportional to the force needed to shear the slurry, is indicated on a scale. The Halliburton instrument is calibrated from 0 to 100 poises against fluids of known viscosity. To permit direct correlation of observed elevated pressure data with those published at atmospheric pressure, the authors' designs of the slurry container, paddle, and torque indicator closely resemble those used on the Halliburton instrument. Duplicate results may be obtained at atmospheric pressure in either instrument. Instead of the atmospheric constant-temperature bath, one was built from a high-pressure steel bull plug. A Uni-Bolt union equipped with a blanking plug serves as the top, permiting the instrument to be opened or closed in less than one minute. The slurry container is built from Shelby steel tubing. A wrench socket welded to the bottom of the container engages a hexagonal nut on the top of the steel shaft that rotates it. This acts as a universal

Jan 1, 1941

By R. A. Pallanch

Probably one of the most perplexing problems with which a mill operator contends is the proper evaluation of his mill results. True, he accurately determines his recoveries of metals and grades of products monthly, weekly, and often daily. These figures do not of themselves directly translate to mill economics. When one figure is unusually good there may be an offsetting circumstance. The advantage of high lead or zinc concentrate grade may be offset by poorer recovery; high lead recovery may be offset by poorer zinc recovery, or vice versa; and so on. Besides, grades or recoveries may not of themselves mean more than a reflection of the grade and character of the ore during the period under study. What the operator sorely needs is some one measuring stick that tells him when he has achieved his greatest return, regardless of grades or recoveries—for if he knows his methods and practices are yielding the optimum return he need no longer concern himself with the assays of products and tailings, or the corresponding distribution of metal values. At first blush it would appear that the obvious answer to this is the actual money return to the mill. Paradoxical as it may seem, however, money return does not make a dependable yardstick any more than do grades and recoveries, as ore condi- tions would vary enough to bring about greater money return during periods when the actual metallurgical work is not as good. The mill operator, of course, should always aim for the greatest return on the ore, once it is in the mill bins, with proper attention always to mill treatment cost. The need of a proper yardstick becomes more imperative with the increasing complexity of the problem. In the case of a simple, single-product operation on a fairly uniform ore, in which only one metal is of significant importance, the need is not great, as grade and recovery pretty well tell their own story. At the other extreme is the operation that makes three or four separate marketable products from a complex mixture of heterogeneous ores that vary tremendously in individual metal contents and ratios, degree of oxidation, and other characteristics, and in which gold, silver, copper, lead and zinc are all significant values. Economic Recovery The first attempt at obtaining a proper single yardstick for a fairly complex ore with which I am familiar is the use of the ''Economic Recovery" term at the lead-zinc flotation mill of the Sunnyside Mining and Milling Co., Eureka, Colorado. This method had been applied there early in Sunnyside flotation-mill history (not later than 1920) and credit for the innovation I believe belongs to Messrs. Kuryla and Marquand. The term "Economic Re-

Jan 1, 1949

By W. E. Remmers

The fact that gray iron increases in volume, cracks and distorts upon repeated heating and cooling is rather conlmon knowledge. In ingot molds, Diesel engine pistons, carburizing boxes, continuous furnace parts, grate bars, stoker parts, and all castings that are subjected repeatedly to high and low temperatures, the phenomenon of growth presents a vital problem. Ingot molds distort and produce cracks which result in seams or laps and later appear as defects in the finished product. The heads of Diesel pistons frequently fail by cracking in a stellar shape. This is attributed usually to the result of permanent growth. Distortion and change of dimension of furnace parts frequently renders them entirely unusable. In chain grate stokers, mechanical difficulties frequently are caused by the growth of the links. In proper operation these links should never attain a temperature sufficiently high to start growth; nevertheless, some have grown in. on an 8-in. length when improperly operated. Even though the phenomenon is generally known there still exists a deficiency in the explanation of the mechanism of this growth. The field of investigators of this subject has a decided variation in opinion concerning the causes. The problem is of sufficient importance therefore to warrant further consideration. Review of Published Work Since the published work, particularly the European, contains much detail, only the outstanding results and conclusions of the investigators will be reviewed. The pioneering investigations of Outerbridge in 1904 and 1905 brought forth the conclusion that growth was not a function of chemical or crystallographic changes but was a result of the formation of fine hair cracks. These cracks are supposedly due to a nonuniformity of thermal expansion and contraction which ruptures the structure of the material. More recently Benedicks and Lofquist presented a purely mechanical theory, which is similar to that of Outerbridge. These investigators believe the temperature gradient from the outside to the center of the cast piece causes a contraction of the outer layers on passing

Jan 1, 1931

By D. B. Grove

THE heavy media separation process plays an outstanding role in the concentration of 4000 tons of zinc ore per day at the Mascot mill of the American Zinc Co. of Tennessee. Of the total tonnage, 72 pct is treated in the heavy media separation plant to reject 56 pct of the ore as a coarse tailing, which has a ready market. Concentrates from this separation are beneficiated further by jigging and flotation. Approximately 25 pct of the total zinc concentrate production is made in the jig mill. Jig tailings are ground and pumped to the flotation circuit where the balance of the production is made. Fig. 1 shows a generalized flowsheet of the mill.

Jan 8, 1951

By Bernard G. Carbajal

The dielectric properties and thermal stability of glow-discharge polytnerized films of styrene, chloro-benzene, and other organics and photoresist filrns are presented. Variations in the glow-discharge polymerization procedure are related to thermal stability. Thermal treatwzents to improve the dielectric properties of both positive (A2 340) and negative (KMER) photoresists are given. THIS study of the dielectric properties of thin organic polymer films is part of a program to investigate the electronic applications of organic materials. Thin organic polymer films have been produced in an ac glow discharge,13 with a low-energy electron-beam process,4 and in an rf dicharge. A process has been developed during the course of this program for forming thin organic polymer films in a dc glow discharge. These glow-discharge polymerized (GDP) films exhibit some useful dielectric and insulative properties. Variations in the properties of the GDP films can be induced by changes in the source material (monomer) andor in the conditions of the glow discharge. Thin organic polymer films can also be produced from typical positive and negative photoresists. Some variations in the properties of the photoresist films can be induced by suitable post-application treatments such as thermal crosslinking. The properties of interest in this study are dielectric constant, dielectric strength, resistivity, and thermal stability. POLYMER FILM PREPARATION I) GDP Films. The GDP films were prepared in a dc glow discharge in an atmosphere of organic monomer vapor. The details of the glow-discharge procedure have been presented previously.6 Briefly, under the influence of a dc glow discharge organic vapors can be polymerized in the vapor phase and the resultant polymer (GDP film) deposits on and in the vicinity of the cathode. Substrates placed behind a screen cathode can be uniformly coated over all exposed areas. Pattern definition can be achieved using normal mask stencil techniques. Table I presents the pertinent parameters in the preparation of GDP styrene. Conditions of Forrrzation of GDP Styrene. The rate of deposition for GDP films was monitored using a current-time integrator. The thickness of the deposited film for a given set of experimental conditions was a function of the current-time integral. The fifth row in Table I is a compilation of the deposition rate of GDP styrene films. Other organic monomers behave in a similar fashion. With the exception of the highly halogenated saturated hydrocarbons, all organics subjected to the conditions of the glow discharge form GDP films. 11) Photoresist Films. Photoresists are normally recognized to exist in two forms, a low molecular weight, soluble polymer form (A) and a high molecular weight, crosslinked insoluble form (B). Typical negative photoresists are applied in the low molecular weight form A and converted to the high molecular weight form B by the action of light. (Positive photoresists are applied in form B and converted to form A by the action of light.) Eastman Kodak Metal Etch Resist (KMER) has been chosen as a typical negative photoresist. Polymer film samples were prepared in the same configuration used for GDP films. The KMER was applied in the usual fashion using a 120°C drying step (infrared-lamp heating) and a 180°C post-bake. Care must be taken to completely remove the solvent in the drying step and to properly develop and postbake to exposed photoresist. If the photoresist film is not properly dried and postbaked, severe blistering and peeling will occur during subsequent elevated-temperature exposure. Thickness can be controlled by varying the viscosity of the form A photoresist and the spin rate at application. AZ 340 was chosen as a typical positive photore-

Jan 1, 1967

By Harlowe Hardinge

THE sound made by ball, pebble and rod mills has long been used by the operator as the "telltale " of their operation. The nature of this sound depends upon local conditions and the type of mill used. By experience an operator can tell whether the mill is running properly or not. Some operators are able to detect the difference in sound much better than others and get better results running the same mill under the same conditions. The automatic operation of a mill using sound as the fundamental means for maintaining control presents many problems. The satisfactory solution of these problems requires, for given operating conditions, a greater average output, with improved product for subsequent processing, than can be obtained by manual control. RELATION OF SOUND TO USEFUL GRINDING ENERGY Experience has taught us that there is a difference in character as well as in intensity of sound between a mill grinding wet and one grinding dry, in open or closed circuit, to obtain a coarse or fine product, on the same material, to say nothing of the effect with a variety of different materials. Broadly speaking, a wet-grinding mill operates best at a lower sound level than the same mill grinding dry, with other conditions the same. Several reasons for this variation in sound intensity under these conditions can be advanced, but the important point is that there is a difference, based upon practical results. Since these reasons may be more or less involved, and may be subject to much discussion, only one will be considered here. It is apparent that two balls hitting together or a ball striking the lining, if there is no intervening material, will produce the maximum sound. If a complete cushion of material is placed between the balls or ball and liner, so that the energy is dissipated without doing useful work, the balls will be unable to create enough pressure or force to fracture the particles, and the sound will be at a minimum. At some point in between-that is, where there is sufficient material between the balls or ball and liner so that the ball will fracture the particles without mashing them unduly-the sound

Jan 1, 1939

By D. H. Davis

HAND picking was the earliest form of coal preparation, first practiced to improve the outward appearance of the coal being loaded and to remove any pieces that might appear objection- able to the buyer. It is still extensively practiced on the plus 1-in. sizes, and particularly on the plus 4-in. and larger sizes. The percentage of ash reduction that can be obtained by hand picking depends entirely upon the amount of free impurity occurring in the coal. In a particularly dirty seam, where a considerable quantity of rock occurs with the coal as mined, hand picking produces sizable reductions in ash. If the coal is prepared clean at the working face hand picking is a final check; in some cases, on the smaller sizes, it is practiced only to show that an effort is being made to prepare a clean product. Because of the variety and different methods of handling coal, the early plants were not always adapted for efficient hand picking. At most mines an attempt is made to remove the visual impurities at one or more of the following places in the surface plant:2 (1) in the tipple during screening; (2) on picking band, belt, or shaking conveyors;. (3) during the loading of the coal as it goes into the railroad car. Whatever the physical arrangements of the plant may be, the usual practice is to run the coal over the screen, picking table or boom at such a rate that each-piece of impurity is exposed to the view of the picker. Coal should be uniformly sized and spread out on the table so as not to exceed one particle in depth. The flow should be even in tonnage and the speed of travel should be from 30 to 60 ft. per minute and not 'exceed 80 ft. per minute. The dirtier the coal, the slower the speed required for a fixed number of pickers. Actually, picking capacity depends on the number of particles per minute that can be picked out and-rejected. The percentage of impurity removed is determined by this and the average weight of piece rejected. Handling a mixture of sizes from nut to the largest lump over the same picking table or conveyor is not conducive to efficient separation by hand picking because the lump hides the smaller impurities. Picking tables should not exceed 5 ft, in width, so that a picker on either side will be able to remove impurities from the center of

Jan 1, 1943

The Climax Molybdenum Company' s newest operation is the Henderson project, which is located on the east side of the Continental Divide. Ore reserves are estimated at more than 300 million tons at a grade of 0.49% MoS2. For mining the ore a modified panel caving system is used. The ore is transported to the Henderson mill on the west side of the Continental Divide on a 42 in. (1.07 m) gauge railroad through 9.6 miles (15.4 km) of tunnel and 4. 8 miles (7.7 km) of surface track, a total distance of 14.4 miles (23. 2 km). Each train consists of 30 ore cars with capacity of 22 st (20 mt) of ore or 660 st (599 mt) per train. The unmanned trains operate completely automatically. At the 54 in. by 84 in. primary gyratory crusher, the bottom dump ore cars pass over a dump scroll to discharge at a maximum rate of 100 st (91 mt) per minute. Dumped ore falls onto a rock box before passing over a 17 ft long by 46 ft wide (5. 2 m by 14 m) grizzly set at a 40° angle with bar spacings of 7 ½ and 8 ½ in. (191 mm and 216 mm) openings. An estimated 30 to 50% of the ore (which at times is wet and sticky) passes through the grizzly. The operators report that a shallower angle on the grizzly, perhaps 35º to 37º, would have been sufficient and would have prevented impact on the back of the crusher pocket by large boulders. This pocket as well as the crushed ore pocket under the crusher is lined with AR plate. The accompanying drawings show a "future splitter" and the operators are planning the installation of this unit to prevent impact and subsequent damage to the crusher spider. Crushed ore at an 8 to 9 in. (203 mm to 229 mm) size joins the grizzly undersize in the pocket beneath the crusher. This pocket is sized at 660 live st (599 mt) so that it will accept an entire trainload of ore. Crushed ore is removed from the pocket by a four-speed, 84 in. (2. 1 m) apron feeder operating at 9.6 to 29. 3 fpm (2.9 to 8.9 mpm). A 60 in. (1.5 m) takeaway conveyor operating at 480 fpm (146 mpm) delivers the crushed ore to a 58,000 st live and 193,000 st total (52,600 and 175, 100 mt) open stockpile under an A -frame supported tripper gallery. Impact idlers on the takeaway conveyor under the apron feeder discharge are mounted on wood blocks for a cushioning effect and ripped belt detecting bars are located behind each impact idler. The conveyor tunnel is of corrugated and galvanized steel construction rather than concrete. The concrete crusher enclosure is circular in design from its lowest level at elevation minus 110 ft 4 in. (minus 33. 6 m) to elevation

Jan 1, 1978