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By M. C. Udy, P. C. Rosenthal

THE use of minute boron additions to steel has been given considerable attention in recent years. Comparisons made between boron-free and boron-containing heats of otherwise identical analysis have indicated, beyond a doubt, the potent effect of boron for increasing hardenability. The actual hardenability increase has been expressed as a multiplying factor, or in terms of the percentage of other alloying elements boron might replace, The present study presents the results of a systematic survey of. the use of boron as an addition to two types of alloyed steels and as a replacement for various percentages of molybdenum in these steels, Both cast and wrought steels of the two basic compositions were prepared. Molybdenum, because of its scarcity at the time the investigation was started, was selected as the element to be replaced by boron. Attention was also given to the effects of boron on other properties of the steels, particularly their notched-bar toughness, to investigate other advantages or limitations of this element as an alloy addition. EXPERIMENTAL WORK Steels Investigated The two basic compositions used in this survey of boron as a replacement for molybdenum are given in Table I. The cast steels were higher than the wrought steels in silicon content to improve the casting quality. [ ] Each of these base steels, both cast and wrought, was made with molybdenum contents of o, 0.10, 0.20, 0.30, or 0.40 per cent, the total comprising 20 steels. In addition, each of these 20 compositions . was prepared with boron additions in amounts of 0.0015, 0.003, and o,006 per cent as ferroboron; and in amounts of 0.002 and 0.005 per cent as two com¬mercial intensifier alloys, designated alloys A and B. The boron-treated steels totaled 100, and the entire series 120, Test Procedure Each steel was melted as an individual heat in a 50-lb., magnesia-lined induction furnace. Ingot iron scrap or mixtures of ingot iron and steel scrap were used for melting stock. Deoxidation was carried out in the furnace with o.10 per cent aluminum. The aluminum addition was

Jan 1, 1946

By AIME AIME

In taking account of stock, on the occasion of the recent removal of the office of the Institute, it was found that pamphlet copies of the papers named in the list given below were on hand, in excess of the average number deemed adequate for future casual demand. Special reduced rates will be made for these surplus copies to members applying promptly. "First come; first Served." Author. Title. Ref. No. ASHBURNER, C. A. " Petroleum and Natural Gas in New York State." 273 MARTENS, A. "The Microstructure of Ingot¬ Iron and Cast Ingots." 626

Jan 1, 1907

By Clyde Williams

IN this war as in no former one, the use of metals has been the major factor governing success. For building new plants, new transport facilities whether by land, sea, or air, for our mechanized army, and for nearly all weapons, iron and steel has provided the basic material. Being the world leader in iron and steel production in peacetime, we soon adapted plants to production for war. Starting with a production of 66,000,000 tons of steel ingots in 1940 from a rated capacity of 80,000,000 tons which only could be reached by straining every productive device available, our industry expanded to 86,000,000 tons in 1942, and ultimately to 96,000,000 tons. To do so required expansion of every unit operation including mining, rail and water transportation, blast-furnace and steelmaking facilities, and rolling mills. New plants not only had to be built in record time but more output for each operation was essential. This performance required skillful operation and engineering techniques and also a better understanding of the physics and chemistry underlying such complex operations as the working of a big blast furnace. A vastly increased pig iron production made possible the great output of steel by an industry that had depended on scrap for its basic raw material even though sufficient scrap was unavailable. This was done by conversion of pig iron in the Bessemer either into steel or into a low-carbon product that was subsequently used in place of scrap in the open¬hearth steel furnace. Furthermore, by duplexing from the open-hearth to the electric furnace, and the construction of many new electric furnaces, our output of electric-furnace alloy steel was greatly increased. Moreover, techniques were developed by which alloy steel could be made in the open hearth with the result that our production of alloy steel reached the fantastic figure of 15,000,000 tons a year.

Jan 1, 1945

By C. E. Barnett, G. R. Durland

LUMINESCENT materials have been used in an increasing variety of ways in recent years. Such uses range from the screens on which the picture or image is presented in television and other cathode ray tubes to fluorescent lamps, fluorescent effects in decorative, theatrical, and display lighting, and the many applications of phosphorescence in paints, textiles, paper, and plastics. During the war the screens for a radar set or the "night-seeing" devices were not fundamentally different from those in other cathode ray tubes, but nevertheless they presented special problems for the phosphor manufacturer. It was essential that the "pips" on a radar screen continue to glow after the exciting beam had swept on, but this afterglow would be ruinous to a television screen. In the image tube used for seeing at night with infrared instead of visible light, electrons emitted by an infrared-sensitive receiving surface were amplified and converted to visible light after striking a fluorescent screen. The small size of the screen caused special problems in reducing the grain size of the phosphor to obtain adequate resolution. Other devices used phosphor surfaces which could be stimulated directly by infrared radiation to emit visible light. Energy was stored in the phosphors by prior excitation with short-wave-length radiation, and the stored energy released on subsequent exposure to infrared radiation. Maps, navigational charts, bombing manuals, and computers of various sorts were printed on fluorescent paper or lettered with fluorescent inks. Fluorescent markings excited by small ultraviolet lamps were used on airplane instrument dials. A large amount of research was done to determine the best color for the emitted light and other properties for the fluorescent materials, and on the best methods for their fabrication into the items listed above. Phosphorescent materials found wide use during blackout restrictions to mark safe passageways, to delineate traffic hazards, to identify packages, and to mark tools and other items of equipment.

Jan 1, 1948

By Walter C. Lawson

THE primary objective in laying track in panel sections is to reduce the number of track laborers required. This is possible because the work is mechanized. Moreover, because the work is mechanized and each of the operations needs only a few men, and each is self-contained, the work can be carried on at night as well as in daylight; therefore, the method provides a means of preparing tracks on more than one shift. The laying of tracks in open pits and quarries in panel sections is not new but new methods have been made possible by the introduction of new types of equipment. The purpose of this paper is to describe the methods that are followed in' the Morenci open pit. GENERAL MINING OPERATIONS Full-scale ore production at Morenci is about 50,000 tons daily. The normal yearly output of ore and waste is 32,000,000 tons, of which 30,000,000 tons is handled by rail haulage. This requires the building of approximately 47 miles of loading and other temporary tracks during a 12 months' period (Fig I). Broken ore and waste, is loaded., into 90-ton capacity dump cars with 5-cu-yd full-revolving electric shovels. Shovel banks are uniformly 50 ft high:. They are blasted- with churn drill holes, and the broken material from a blast is loaded out with two shovel cuts, the first one being called (locally) the "splatter" cut and the second one the "clean-up" or "face-up" cut. When a shovel is making its clean-up cut, the loading track is about 70 ft from the toe of the bank and, under normal conditions, a bank is blasted against it without removing the track. It is thus evident that each track is used for two shovel cuts before relocation is necessary, inasmuch as a single position serves for both the clean-up cut prior to blasting and for the splatter cut following the blast. The normal advance of a solid bench by a single blast is 40 ft (Fig 2). PREPARATION OF PANEL GRADE In preparation of panel grades bulldozers and rooters are used for the bulk of the work and an auto-patrol road grader for the final stage. At Morenci, bulldozers have always been used for track-grade preparation, but before the introduction of the other two types of equipment grades were uneven and irregular at best, and always necessitated a big gang of track laborers to hand-block under the ties with rocks after a track was laid into place. High blocking also made poor track because of instability and caused frequent derailments. Under these conditions derailments were generally bad as re-railing became difficult. Much track was torn up and many ties broken in the process. The inadequacy of the hand-blocked track, together with the inefficiency of hand blocking, constantly pointed to the desirability of reducing the amount of labor required, so various means were tried to improve conditions, such as wood

Jan 1, 1947

By R. W. Jordan, J. Winter, A. J. Goldman

Kirkendall diffusion of copper and nickel atoms across the bond interfaces, as well as oxygen diffusion in the core to the interfaces, are the mechanisms which control the variation in bond strength with annealing time at 1600°to 1800°F in the cupro-nickel clad copper Mint composite. The unequal mass transfer resulting from the high diffusion rate of copper in cupro-nickel compared with that of nickel in copper caused void formation in the core. Small voids also formed in the cladding after short annealing times. These may have been nucleated by nickel oxide particles which are formed by the dissociation of the cuprous oxide in the core and the movement of oxygen to the cupro-nickel interfaces. The bond strength drops to very low values for annealing time up to 3 hr when the void density is greatest. The increase in bond strength after 16 to 72 hr at 1600°F is a result of the decrease in the void density in the cupro-nickel cladding and the growth of grains across the interface. The void density decrease is attributable to grain boundary diffusion of vacancies to the surface. The abnormally large grains in the copper preclude a similar process from taking place in the core. THE solution to many engineering materials problems that cannot be satisfied by using a single metal or alloy is often attained by combining two or more metals in such a way that each component performs a different function, while the composite meets the overall requirements. The Coinage Act of 1965 authorized a changeover from the traditional 90 Ag-10 Cu dimes and quarters to a bimetallic laminate of 75 Cu-25 Ni clad on a copper core. Economic considerations as well as physical, chemical, and mechanical properties provided a basis for the selection of this composite as a substitute for the silver-bearing alloy. An extensive survey of alloys suitable for use as coinage was prepared by Battelle Memorial Institute for the U.S. Mint.1 It was found that the cupro-nickel/cop-per/cupro-nickel composite satisfied the required color, density, mechanical properties, corrosion resistance, electrical properties, and magnetic properties to make it completely acceptable to the general public and the vending machine industry. This investigation is part of a program to determine the feasibility of reclaiming composite scrap by thermally degrading the bond strength of the cupro-nickel clad copper laminate. The composite exhibits bond degradation and subsequent bond improvement during annealing in the temperature range 1600" to 1800°F. A study of the operative diffusion processes and the resultant structural changes was made in order to explain the observed variations in bond strength with annealing time. EXPERIMENTAL PROCEDURES AND RESULTS Bond Degradation. A measurement of the forces required to peel the cupro-nickel cladding from the

Jan 1, 1969

By W. W. Schmittroth, A. Y. Bethune

The commercial analysis of Special High-Grade zinc usually involves the determination of lead, iron, copper and cadmium as impurities in the base metal. Over the past 20 years, as the result of metallurgical improvements in the art of producing Special High-Grade zinc metal there has taken place a gradual exclusion of almost all extraneous elements, and the few that do remain in the final product have been virtually reduced to the vanishing point. Thousands of tons of zinc are now commercially produced annually and made available to the trade, in which impurities are present only in the order of 0.0010 per cent or less and the sum total of all impurities does not exceed 0.0025 per cent. To such zinc the term "super-purity" might well be applied without undue exaggeration. The techniques used for production control and final analysis of Special High-Grade zinc by means of emission spectra in the laboratories of the electrolytic zinc plant of the Sullivan Mining Co. are based on the premise that self-electrodes are to be preferred over all other forms for the examination of the zinc in question. Furthermore, after a survey of the literature and considerable experimental work,' it was decided that the spectrographic method of internal control, the principle of which was first announced by Gerlach,2 using a modification of the high-voltage alternating-current arc source introduced by Duffendack and Thompson,3 with the calibration of each photographic plate as recommended by Wolfe,4 would yield the most accurate and reproducible results. Self-electrodes were chosen in order to make use of one of the unique advantages inherent in spectrographic analysis; namely, the rapid and almost effortless detection of elements other than those being quantified by the analyst; or conversely, the proof that the zinc is free from such impurities if no spectral line of the suspected element appears. This fact was verified for certain elements, and will be discussed later. Carbon electrodes impregnated or packed with zinc salts chemically prepared from the zinc to be assayed were avoided for a number of reasons. First, the chemical manipulation was another time-consuming step, which increased the chances for contamination. Second, none of the common zinc salts, such as the chloride, nitrate or sulphate, yielded reproducible results under our conditions, nor did the spectral line of the impurity appear as readily in the low concentrations as when using zinc metal. Third, no commercial carbon, except the very expensive, was pure enough to use with this grade of zinc and the continued time, effort and expense incurred in the purification of carbon were not desirable. The use of special High-Grade zinc self-electrodes introduces certain complications with regard to obtaining satisfactory excitation conditions, because it seems necessary to raise the temperature

Jan 1, 1949

By J. R. Long, C. E. Armantrout, A. H. Roberson, T. R. Graham

The preparation and fabrication of copper-manganese-zinc alloys and the evaluation of their engineering properties have for some time been an integral part of a research program of the Federal Bureau of Mines. In this project, the use of electrolytic manganese, along with high purity copper and zinc, has permitted the preparation of alloys which contain a minimum of impurities which are capable of producing detectable effects in the properties studied. The initial work on the physical properties of wrought alpha solid solution alloys and a general outline of the alpha solid solution area for alloys containing up to 40 pct manganese have been presented in previous reports. 1,2,3,4,5 The evidence accumulated in these investigations clearly showed that additions of manganese to the copper-zinc alloys improve the strength properties of the brasses without seriously reducing their characteristic ductility and that considerable quantities of manganese could be added to the copper-zinc alloys without exceeding the mutual solubilities of manganese and zinc in copper. In continuation of these studies, additional data have been obtained in a more extensive investigation of the phase relationships of the copper-manganese-zinc ternary system. The present report delineates the solid phase boundaries of the ternary system from the copper-zinc binary to the manganese-zinc binary for alloys containing up to 50 pct zinc. Summary The alloys used in this investigation were conditioned by working schedules designed to homogenize the structures prior to heat treatments required for the equilibrium phase sludy. The treated alloys were examined by metallographic methods including hardness and X ray data for confirmation. The composite data of the investigation are summarily presented in a series of isothermal sections of the ternary system at 1100, 1200, 1300, 1200, and 1500°F. The salient features of the system as outlined by these data are: (1) the continuous alpha solid solution which extends across the diagram to the gamma-manganese phase of the manganese-zinc system at temperatures of 1200°F and higher, (2) the beta phase of the copper-zinc system similarly forms a continuous solid solution with its counterpart the beta field of the manganese-zinc binary, (3) at 1100°F (593°C) these alpha and beta fields are greatly restricted by complications arising from the allotropic transitions of manganese and the decreasing solubility of manganese in the alpha solid solution. The alpha + beta fields intersect the alpha + alpha manganese field to produce the beta + alpha manganese field and two adjacent three phase fields consisting of alpha + beta + alpha manganese and gamma + beta + alpha manganese. Typical microstructures representative of the various phase areas at each temperature are also presented. Review of Previous Work The copper-manganese-zinc alloys have periodically been the subject of numerous investigatioris of both prac-

Jan 1, 1950

By H. A. Bedworth

ALLOYS of copper and silicon have been known for one hundred years or more but the commercial development of this type of alloy has taken place during the past few years. In 1905, Sperry1 proposed the use of copper-silicon alloys for springs and other purposes for which copper-tin bronzes were used. Some attention was given to this proposal at the time but no one succeeded in producing a practical alloy containing more than a fraction of a per cent. of silicon. The equilibrium relations of the copper-silicon system were studied first by Rudolfi2 and later by Sanfourche3 and Corson.4 The constitution of the system has also been recently investigated by Matuyama,5 and in the laboratories of the American Brass Co. by Smith.6 Some of the physical properties of the copper-silicon alloys have been investigated by Norbury7 and by Geiss and Van Liempt.8 Summarizing the results of various investigators of, the constitution of copper-silicon alloys, the solubility reaches its maximum value, 6.7 per cent. silicon, between 721° and 782° C. At 852° C. the solubility is 5.25 per cent., while at 400° C. it is only 4.1 percent. silicon. The copper-silicon alloy begins to get so hard at about 3 per cent. silicon that it is difficult to manage. It was found by Jacobs that the addition of manganese to this alloy considerably improved the working

Jan 1, 1929

By C. R. Watts

The feasibility of producing composites containing nickel or molybdenum fibers in a beryllium matrix was inrestigated. The composties studied were jabricaled by powder mallurgical techniques. The 1-mil-diarr nickel fibers reacled completely below 900°C, converling the fibers .from nickel to Ni5Be2,. As the /LO/-pressing temperalure as raised above 1110oC, tlie nickel diffused outward from the beryllide fibers. The solid solubility of nickel in beryllium was clboul 20 wt pet at the 1100°C pressing temperature a1 the zone-fiber interface. The 1.5-mil-diam molybdenum fibers slzolred no evidence of reaction and little evidence of diffitsion after pressing at 900°C. Between 1000° and 1050°C pressing conditions, the fibers began lo react , producing 1ayers of MoBe2 and MoBe12, respectively surrounding the molybdenurn core. The struture remained the same at 1100°C with no evidenre of solid solubility of the molybdenum in the berylium or vice versa. In recent years a considerable amount of attention has been devoted to the determination of methods for improving the mechanical properties of materials through the use of fiber or whisker reinforcement. Previous work with metal matrix composites indicates that the study of the chemical compatibility of the fiber and matrix is an area requiring greater understanding. The metal-metal or ceramic-metal interface is frequently subject to chemical reactions that may result in the formation of hard brittle intermetal-lic compounds and/or low melting point eutectic compositions. The reaction products may reduce both the low-temperature and elevated-temperature strength of the composite by weakening the fiber-matrix bond, producing premature failure at the interface. It is well-known that most metal-metal systems and many metal-ceramic systems of interest for structural composites are thermodynamically unstable,'-" particularly at elevated temperatures. If, however, the rate of reaction under the conditions of fabrication is sufficiently low. composites can be fabricated that can be used efficiently for indefinite periods at low temperatures and for short periods at elevated temperatures. This paper presents the results of a series of tests to determine the compatibility of nickel and molybdenum fibers with beryllium at various hot-pressing temperatures. Nickel was selected as a candidate fiber material primarily because the relatively ductile fibers might be useful as crack arresters in applications such as ballistic impact where crack growth can result in catastrophic failure. The high density and the reactivity of nickel were primary factors detracting from its selection as a possible reinforcement. Molybdenum with a modulus of elasticity of 52 Xlo6 psi is one of the few metallic materials having a modulus higher than beryllium (42 X lo6). Its high modulus, coupled with its refractory characteristics, made molybdenum an attractive candidate for a relatively stable fiber reinforcement for beryllium. Its density, being higher than that of nickel and over five times that of beryllium: detracted from its other characteristics. EXPERIMENTAL PROCEDURE The specimens were prepared from beryllium powder with a dispersed phase of fibers by powder metallurgical techniques. P-20 grade powder, Table I, from Berylco was used as the matrix material. Short lengths of 0.001-in.-nominal-diam nickel fibers supplied by the Sigmund Cohn Corp. and 0.0015-in.-nominal-diam molvbdenum fibers obtained from the General Electric Co. were used as the dispersed phase. The composite constituents were combined under an argon atmosphere by mechanically mixing the powders and fibers. The compositions used were nominally 1 vol pct fibers. After mixing. the composites were hot-pressed into a-in.-diam pellets under an argon atmosphere at 900°, 1000". 1050". and 1100°C at a pressure of 6000 psi with no hold time at these temperatures so that a comparison could be made between the resultant microstructure and hot-pressing temperature. The billet was heated at a rate on the order of 30°C per min to the desired temperature and then cooled at a somewhat slower rate. The microstructure obtained should be considered as characteristic of the integrated time-temperature history of the sample, as well as the maximum temperature attained. Upon removal from the hot-pressing dies. the specimens were cut. mounted. and polished by standard procedures. No etchant was used in specimen preparation. Photomicrographs, electron microprobe scans, and electron back-scatter pictures were made. X-ray dif-fractometer patterns were made of several of the specimens. but only the lines for beryllium could be resolved. Specimens for optical and electron microprobe examination were selected partially for the roundness of the cross section. A round cross section was taken to indicate that the body of the fiber was approximately normal to the surface and that therefore effects due to fiber material immediately below the surface could be neglected. RESULTS AND DISCUSSION The microprobe scans indicated that nickel reacted as low as 900°C, converting the entire fiber cross section to NisBe21. Fig. l(a). There was no evidence of further reaction from the optical or the back-scatter pictures, Figs. 2(n) and 3(a).

Jan 1, 1970

By George W. King

The yield strength of a dispersion-hardened W-3.8 vol pct Tho,alloy, in both the recovered and recrys-tallized condition, was investigated and cornpared with that ofrecrystallized pure tungsten over the temperature range of 325" to 2400°C. It is deduced that the Orowan mechanism is obeyed in the recrystallized alloy. In the recovered alloy, a further enhancement of the yield strength results from the retained substructure which is stable up to temperatures in excess of 2700°C. Temperature and strain rate cycling tests were also performed, and the apparent activation energy for the deformation process was derived. This activation energy, - 3 ev, for the recovered and also the recrystallized alloy was about the same as that for re crystallized pure tungsten. However, the activation volume of the recovered alloy, -10-2 cu cm, was about an order of magnitude lower than that of the recrystallized alloy or pure tungsten. This fact accounts for an enhancement oj- the temperature dependence of the yield stress of the recovered alloy. A dislocation velocity exponent of about 4 to 13 was deduced frorn the strain rate cycling tests , which is in good agreement with values reported for tungsten single crystals. VARIOUS theories have been developed to explain the enhanced yield strength of a metal containing a dispersed second phase of small hard particles. These theories are thoroughly reviewed by Kelly and Nicholson.' The theoretical models can be separated into two types. The first type assumes direct interactions between moving dislocations and dispersoids. One of the most widely investigated models for this mechanism is the bowing out of dislocations between the dis-persoids and their subsequent pinching off in order to bypass the obstacles. This is the well-known Orowan mechanism.' The second type is an indirect effect of the dispersion because of its ability to stabilize to high temperatures the substructure introduced by cold working. In this instance, the increment in the yield strength is expected to be inversely proportional to the square root of the subgrain diameter. In the present work, a quantitative study was made of the strengthening effect caused by a thoria dispersion in a recrystallized W-3.8 vol pct Thoz alloy over the temperature range 325" to 2400°C. The results are compared with the increment predicted for the Orowan mechanism based on the calculations by ~shb~.~ In addition, the alloy was tested in the recovered state so that any additional strengthening resulting from the substructure produced during fabrication could be measured. The respective contributions can be separated in this manner, provided that the particle size distribution of the dispersion remains the same in both the work-hardened and the recrystallized state. Particle size distribution measurements showed that this condition was met in the present work. I) EXPERIMENTAL PROCEDURES A) Material Production and Fabrication. The alloy investigated is essentially the same as that reported much earlier by ~effries,~ who also found the strength of tungsten to be improved by the thoria dispersion. The procedure for producing the alloy consisted of mechanically blending a thorium nitrate solution in proper concentration with tungsten oxide (WO3) powder, followed by hydrogen reduction to metal powder. After reduction, the dispersed second phase is present as thoria (Thoz). The pure tungsten powder used for comparison was produced in the same manner except that the thoria doping step was omitted. The powders were consolidated by cold pressing and self-resistance sintering in hydrogen. The resulting ingot had a cross section about 0.6 sq in. and a density about 93 pct of theoretical. The ingot was swaged to 0.174-in.-diam rod at temperatures varying from 1650°C initially to -1200°C near final rod sizes. Two intermediate recrystallization anneals were employed during fabrication. Analysis of the swaged rods is reported in Table I. B) Electron Microscopy Techniques. Carbon extraction rrPxcas prepared by a technique reported by ~00' were used to quantitatively evaluate the thoria particle size and distribution. Electron nlicrographs of extraction replicas were taken at 20,000 times but were then enlarged two to three times in printing. The areas photographed were randomly selected. A Zeiss Particle Size Analyzer (Model TGZ3) was used to count and measure the sizes of all particles present on the print. About three thousand particles were counted in determining a distribution curve. Electron transmission microscopy was used to determine the effect of annealing on the substructures of the materials. Thin foils were produced by a two-stage thinning process. The rods were first ground on emery paper to ribbons about 10 mils thick and then a jet of 5 pct KOH was used to electrolytically reduce a portion of the cross section of the ribbon. Final perforation was achieved by immersing the specimen in a 5 pct KOH solution and electrolytically polishing at a current density of about 0.3 amp cm-'. The foils were examined with a Hitachi HU-11A electron microscope. C) Tensile Testing. Tensile testing was performed in an Instron Testing Machine equipped with a radiation-type vacuum furnace which operates at about 1O"S torr at temperatures as high as 2400 °C. The same furnace was used for annealing the tensile specimens.

Jan 1, 1970

By Stephen Krickovic

THERE is today no proven continuous mining machine that can be used under all the varying conditions found in most bituminous coal mines. During the last five years, however, both the machines and methods of using them have been improved. Coal operators can now exercise a fair degree of selectivity, except those who must struggle with thick and hard partings and operate in seams less than 40 in. thick. It must be realized, then, that more than one type of continuous miner may be used advantageously in the same coal mine. Although this appears to violate the standardization generally sought after, the gain can more than offset added maintenance and, to a lesser degree, operating problems. It is equally important to realize that most coal mines will require one or more conventional loader setups in the plan of total mechanization. Seam variations, adverse physical conditions, and special designs of main headings for haulage and ventilation, to name only three reasons, may render 100 pct use of continuous miners uneconomical. Of course, this situation may change. In one mine, prior to 1954, machines that ripped coal from the face achieved only average results, as compared to the impressive performance of boring-type units in another coal mine. A boring-type unit was therefore selected for the first mine in the belief that the chance of success would be greater if it were used in a combined cutting and wedging operation, cutting a full face in its forward movement. The miner was located in a part of the mine where a special projection could be readily developed, a solid area scheduled for mining according to the overall progress plan. All openings surrounding the particular area were carefully investigated for the presence of sulfur balls. Fig. 1 (opposite) shows the representative seam section, containing the several pyritic bands 1/4 to 1/2 in. thick; a characteristic Pittsburgh seam parting averaging 5 to 6 in. of slate, coal, and slate; and the occasional py-rite lenses 2 to 3 in. thick. Under normal conventional mining methods, the top 10 or 12 in. and the bottom 4 in. are left in place to offer roof protection

Jan 1, 1958

By R. J. Brison, R. D. MacDonald

This chapter is written primarily from the standpoint of development of flotation processes for treatment of specific ores. However, most of the principles and techniques discussed are equally applicable to other forms of applied flotation research such as improvement of procedures in existing plants and development of new reagents or methods without reference to specific ores. Because it is not possible to cover this subject in detail here, much of the material presented is in the form of a guide to the literature, with emphasis on readily available, English language publications. Details are included only if considered to be widely applicable or not readily accessible in the literature. Related subjects which are covered elsewhere in this volume, such as flowsheet design and statistical techniques, are not emphasized in this chapter. The material presented is intended primarily for those familiar with the theory and practice of flotation, but with limited experience in applied flotation research. It may be of value to the experienced investigator as well, by calling to his attention some useful viewpoints or techniques that he may have overlooked. It has often been said that flotation is more of an art than a science. In- deed much of the knowledge of flotation behavior is empirical. However, the unsystematic, artisan approach to flotation problems results only in an ac- cumulation of unrelated data. Like any other physical or chemical process, flotation is amenable to investigation by systematic experimental methods. The experiments should be based, as far as possible, on an understanding of the natural laws that govern the process and on good experimental procedures. SAMPLING OF A DEPOSIT In working out a flotation process for a mineral deposit, no step is more important than that of obtaining a suitable sample or samples. Experimental procedures cannot compensate for the lack of a representative sample. Methods of sampling a deposit have been published elsewhere,l-4 but a few points are of special importance from the standpoint of flotation. First, the sample should be representative of the deposit, not only in respect to chemical composition, but also in respect to mineralogical composition and degree of dissemination of the valuable minerals. To help ensure

Jan 1, 1962

By H. G. Moulton

THE INCREASING scale of mining operations over the past decade, particularly in connection with the exploitation of large bodies of comparatively low-grade copper ores, has made necessary the study of the behavior of rock under failure. When extractions of as high as 40,000 tons a day are reached in steam-shovel operations and as high as 20,000 tons per day in underground mining operations, it is evident that excavations soon become of such size that the behavior of the rock will often be dependent on fundamental principles applicable to more or less homogeneous materials under stress, rather than on weathering or local planes of weakness. In the ordinary rock excavations encountered in civil-engineering practice, such as excavations for subways, highways, railroads, etc., rock faces are not carried to depths sufficient to develop any pressures, or consequently any failures, except those due to loose masses resulting from local planes of weakness. When, however, orebodies whose tonnage is measured by hundreds of thousands are to be extracted by steam-shovel operations in open pits, it is necessary to determine if possible in advance the slopes that the sides of the pits will assume, for these slopes influence the shape of the excavations and thereby the amount of ore that may be extracted by the open-pit method. When large orebodies are mined underground at depths of 300 to 500 ft. (91 to 152 m.) by caving methods, the surface subsiding as the ore is withdrawn, it is necessary to determine in advance the outermost limits of fracture in the subsiding surface, for on the delineation of these limits depends the location of surface improvements, mills, smelters, etc. and also the location of development work, such as hoisting shafts, main haulage levels, and all other underground openings that must remain undisturbed during the period of ore extraction. Heretofore, in civil-engineering practice, it has been assumed that earth and rock behave differently in failure. For the calculation of earth

Jan 2, 1920

By Robert H. Richards

Walter Renton Ingalls recently gave a very interesting talk before the student mining society of the Massachusetts Institute of Technology. In it he showed the present status of mining as he sees it. In the talk he explained that, while discoveries of great mining districts are still pssible, they are being made less and less often; that the great mining companies, although there are large numbers of mines offered for sale, are finding it less and less possible to find new mines that are up to the standard of richness that they wish for purchase. The natural conclusion is that better, cheaper, and more efficient methods of mining, concentrating, and smelting are needed if the lower-grade mines are to be worked at a profit. This is true also if the high-grade mines are to yield their greatest profit. This paper deals only with the concentrating or ore-dressing problem, and gives some thoughts which point towards greater profit. In a paper on The Development of Hindered-Settling Apparatus the writer showed that there were two main lines of work that would lead to greater saving, lower tailing assay, and, therefore, greater profit. The first is the recrushing of middling or tailing products for the saving of the contained values. This is well understood and largely carried out in existing mills. The second is the saving of fine free mineral at the first opportunity. This is a matter less well understood in the mills, and to dwell upon this the present paper is written. The writer is himself convinced and hopes to convince the reader that, for obtaining the above result, not only is better classification needed, but also more classification; that is, there should be more spigots or pockets to the classifier. His attention was recently called to a small mill which had a three-pocket cone classifier fed with from 2 to 0 mm. stuff, supplying feed to four Wilfley tables. The first spigot had about all the

Jan 1, 1914

By Lewis E. Dr. Young

MINING engineers in the United States understand that mining conditions in the British coalfields are much more difficult than in most of the mines now being operated in the United States. We realize also that in the near future we must face some of these same difficult problems. Early Mechanization The progress made in mechanical loading in the United States is the result of a long struggle in many coalfields to mine with power tools safely and to increase output per man-shift. Attempts to use power to loosen coal and to transport broken coal in the U. S. may be said to date from the Stanly Header, or Entry-Driver brought from England in 1888. The principle of this boring machine was used in the McKinlay Entry-Driver, almost continuously used in the U. S. since 1920. Since 1888 experimental loaders, scrapers, and conveyors were installed with more or less success. Beginning in 1918, considerable progress was made with mobile loaders, and in 1920 the first wage agreement for the operation of mechanical loaders was made in Indiana. In 1923 the Pocahontas Fuel Co. loaded nearly 1 million tons of coal using 23 Coloders. Labor Policy The United Mine Workers of America have never officially opposed the Mechanization movement. On December 10, 1945, in a statement before the House of Representatives Labor Committee, John L. Lewis said, regarding the policy of the United Mine Workers of America: "We have welcomed progress; we have welcomed machines. We have told our people that they had to accept that condition; that it was the process of progress, and that they would have to take their chances." Recent Development In 1951 about 71 pct of the tonnage mined underground was mechanically loaded. Over 4000 shuttle cars are in service and it is estimated that much more than half of the tonnage loaded underground is produced by trackless mining. In 1947 roof-bolting was introduced extensively and it is estimated that more than 2 ½ million bolts are now being used per month in about 600 mines. The use of roof bolts has permitted the more effective and safer use of loaders and shuttle-cars. Continuous Mining The McKinlay Entry-Driver could have been used for continuous mining, but for many years it was used only .for entry driving. In 1946 the Silver machine was developed in Colorado, and in 1947 this was acquired by the Joy Mfg. Co. and called the Joy Continuous Miner. Other types of combination mining-loading machines which eliminate drilling and blasting operations are the Marietta Miner, the Colmol, the Lee-Norse Miner, the Junior Miner, the Goodman and the Konnerth machines. There are several other types in the process of development. Probably by January 1953 there will be about 250 continuous miners in operation in the U. S. Payment of Mine Labor One of the most important problems in mechanizing was the establishing of rates of pay that would be attractive to the best men. Prior to the installation of mobile loaders the hand loaders and cutters have been paid by the ton. It was felt that a system of a day's pay should be established and that piece and tonnage rates should be abolished completely. Without exception, all coal loaded in mines equipped with mobile loaders is prepared and loaded by men paid an hourly rate. Trends in Mining Research There are two diverse approaches in coal production research; to try to design a mining machine to fit current methods, or to adapt mining practice to take advantage of proven machines. A great deal of credit must go to the mine operators who have been enterprising and dynamic enough to use available equipment intensively and to discard it as soon as an improved or new machine is available. Effect of Changing Markets Formerly there was an important demand for lump and prepared coal in the larger sizes for domestic use. The use of bituminous coal for house heating has decreased so that not more than 19 pct of the annual tonnage goes to retail trade, only 12 pct is used by the railroads, and much of the retail and most of the railroad coal is in stoker size. As a result of this decline in the market for coarse coal most of the large mining operations have crushers installed in the tipples or preparation plants. Mass production at the face requires increased preparation facilities. Another important trend is in connection with complete seam mining with mechanical loading. In many mines where the immediate roof is apt to fall with the coal no effort is made to separate roof material from coal prior to

Jan 1, 1952

By C. N. Garman

Homestake-New Mexico Partners operate a 750-tpd carbonate leach uranium concentrate mill near Grants, N.M. The highly mineralized water available as process water leaves much to be desired. The 628 ppm as CaCO 3 makes the use of raw water very troublesome in pipes and on filter cloths. However, the residual sodium carbonate in the final filter cake going to tails makes an ideal softening agent. To take advantage of this fact, all makeup water used in the mill is first used as tailing slurry dilution water and comes to the mill from the tailings pond. The 5-acre tailings pond serves as a thickener and 100 to 150 gpm of nearly clear solution is decanted to a pump to be returned to the mill. Since this tailings water has small quantities of uranium in the solution an ion exchange scavenger unit was installed to remove as much uranium as possible. The ion exchange raffinate is then used as final filter wash ahead of the tailings slurrying step. In spite of the large settling area this return water is not clean enough for ion exchange feed. The solids present are very fine and composed of approximately 15 pct (by weight) burnable carbonaceous material common to the sandstone uranium ores in the area, 40 pct SiOz plus 45 pct CaC03. Laboratory work showed that this material responds very well to flotation. Before deciding to use flotation, various clarifying systems such as pressure leaf filters, sand filters, and continuous vacuum pre-coat filters, were considered. Each of these could have solved the problem but with much more operating labor, more reagents and greater installation costs than the flotation step. About 100 to 150 gpm of fouled water is fed to two 66-in. Fagergren cells, in series. Reagents used at the beginning were Arquad 2HT75 and Arquad C50, at the rate of about 1% lb per 8-hr shift, or about 0.0053 lb each per ton of ore. This did not completely remove the solids but does an acceptable job. Approximately 75 pct of the slimes are a size that can be caught on a 41-Whatman Paper are removed. Removal of these slimes also allows much better settling of the coarse nonfloatable material. Advantage is also taken of this fact in a small settling tank ahead of precipitation. Removal of this amount of the slimes makes the ion t:xchange feasible. PREGNANT SOLUTION CIRCUIT The carbonate? leach-caustic precipitation method of uranium concertration does not provide for any process purification step ahead of precipitation. Therefore, any fine solids getting into the pregnant solution through the filter cloth show up in the final concentrate. This, of course, lowers the grade, and, at times, the slimy nature of these very fine solids rendered final filtration of the concentrate difficult if not impossible At Homestake-New Mexico Partners a 75-ft thickener was available for gravity clarification of 100 to 120 gpm of this pregnant solution. However this did not sufficiently remove the slimes. Laboratory investigation of the whole range of flocculants that were suggested by literature, salesmen, and friends failed to turn up anything of consequence. A continuous vacuum pre-coat filter would do the job and was investigated. The capital cost and the operating labor and materials made this a last chance choice. Following work done in the metallurgical laboratory on the tailings return water, it was found that some changes in the reagent strengths and combinations made a very definite decrease in the solids in the pregnant solution. Concentrate grade improved about 5 pct anti the final product after drying had an appreciably greater bulk density. Compared to a cost of about 2.2e per ton for pre-coat filter opelation for cleaning just one circuit, flotation costs less than 1.0 per ton of ore for cleaning two circuits. While a pre-coat filter would do a more thorough job, the flotation does all that is required for either circuit. Gravity causes the froth produced to run back into the leach circuit. This does not appear to result in a build-up of objectionable slime. No extra manpower is required; the operators in the separate areas can observe the operation of the cells and mix the small quantities of reagents as needed. Normally the 66-in. Fagergren cell requires 15 hp per cell, but this very dilute slurry needs only 10 hp for both cells. Originally, a combination of the two Arquads mentioned previously served as frothers and promoters. As further testing

Jan 1, 1962

By R. Wild, F. A. Wright

When a blast furnace has a certain defined burden and is operated under fixed conditions of blast temperature, etc., the fuel efficiency is determined by the extent to which the reducing gases can remove oxygen from the burden in the furnace stack. This is determined by two distinct factors: 1) The uniformity of gas-solid contact, and 2) The ease with which oxygen can be removed from individual pieces of burden. This latter is often called burden reducibility. When burdens were poorly prepared the first factor was by far the most important and a study of the reducibility of individual lumps was of rather academic interest. In recent years good burden preparation with emphasis on uniformly sized material has led to greatly improved gas distribution in the stack, and thus the second factor has become much more important and there has been a marked increase in interest in methods of measuring reducibility. This paper explores the Linder method of measuring such reducibility. The measurement of reducibility of burden materials must be carried out under conditions duplicating, as nearly as possible, those of the blast furnace stack. This is very difficult since the blast furnace process is a counter-current one, and thus the initial conditions encountered by the solid (gas temperature, composition, etc.) are the result of heat and mass transfer occurring lower down the stack. Any method of burden testing which does not take this into account is, at least to some extent, based on arbitrary assumptions. In an attempt to study blast furnace reactions under non-arbitrary conditions BISRA adopted the SCICE technique as a method of investigation. This technique has been used with a measure of success.' The SCICE technique, however, was found to be too slow for use as a routine test for burden materials and it was decided to construct additional equipment for burden testing. A test was required which would: 1) Be as realistic as possible. 2) Be quick and easy to operate. 3) Give some indication of the breakdown likely to take place during reduction in addition to a reducibility index. After a critical assessment of the reducibility tests which have been proposed it was decided to adopt the Linder test equipment and procedure as a basis for burden testing. THE LINDER TEST APPARATUS AND PROCEDURE The apparatus which was constructed (Fig. 1) was the same as that described by Linder2 except for minor changes in design. Linder also laid down a test procedure which he had derived from the results of investigations on Swedish blast furnaces. The variations of temperature and gas composition during the test were defined; these are shown diagram-matically in Fig. 2. BISRA's intention was to use the standard temperature and gas composition programmes for testing a variety of burden materials and also to investigate the influence of different programmes on standard burden materials, making use of information from the SCICE apparatus wherever this is possible. Up to the present, effort has been concentrated on the first part of the programme, and work on the second part has only just commenced. For each test 200 g of coke and 500 g of burden material were used. Linder had recommended that the coke and burden material should be between 1 and 1 1/2 in. and this was adhered to in early experiments on ores and sinters. Since the eventual aim of this work was to relate the test results to blast furnace operation, it was decided to carry out subsequent experiments using burden material in the size range used in the blast furnace, as far as this was possible. If the main interest was, for example, a comparison of the products resulting from different methods of agglomeration, then there would be advantages in using burden materials as close as possible to a standard size. After the charge had been placed in the reaction tube and this had been connected to the gas supply, rotation of the reaction tube at 30 rpm was started and the reduction programme was commenced, the gas temperature and composition being manually controlled according to the programme shown in Fig. 2. After the reduction test the charge was cooled in a nitrogen atmosphere. It was then removed from the reaction tube, the coke and burden separated, and the extent of burden breakdown assessed by screening it at 10 and 30 mesh. The extent of reduction was then

Jan 1, 1964

By F. R. Archibald, C. M. Nicholson

The present paper may be considered complementary to an earlier contribution on the same subject by F. R. Archibald and C. F. Jackson.1 It is particularly concerned with engineering and technological aspects of the operations at the Harleyville Alumina Plant during its period of operation from January 1945 to July 1946. The plant was built for and operated by Ancor Corporation, at Harleyville, South Carolina, as part of the government sponsored wartime program related to alumina production from domestic raw materials. The main purpose of the program was to secure technical and engineering data, based on actual plant experience, that might serve as a foundation for large scale production of alumina from raw materials other than bauxite. The Harleyville plant was directed specifically to treatment of clays found in very extensive deposits in the Carolinas and Georgia using the lime-sinter process developed by Ancor Corporation. It is considered that the purpose stated above has been served and this paper is to record and discuss some of the more important findings. The main factor in location of the plant at Harleyville was the presence in that locality of a rather remarkable deposit of high calcium limestone. The clay mining operation was centered near Aiken, S. C., and although a rail haul of ninety miles was involved there were, at the time, factors favorable to the Harleyville location offsetting, in part, the cost of transportation of clay, There are, no doubt, locations in the general area where clay and limestone deposits may be found in closer proximity hut they had not been proven up when the project was undertaken. Availability of power from the Santee-Copper development whose high tension line skirted the Property; ready access to rail and highway transportation; the promise, realized in actuality, of ample supply of soft water; and availability of labor supply were other factors of importance. Moreover, the general area has the decided advantage, for this type of operation, of a mild climate. Construction was begun in August 1943, and although stopped for a time priding review of the general situation that fall, it was resumed, albeit with less urgency, and substantially completed by the end of 1944. The total capital cost was approximately $3,460,000 The first alumina was turned out in April 1945 and from then until the plant was closed down in July 1946, the operations followed a succession of periods of production alternating with periods in which minor alterations were made in conformity with experience. Steady improvement was made and at the time Operations were discontinued it was considered that experience and the necessary engineering were in shape for removal of the remaining bottlenecks and a somewhat major revision in one section of the plant. Unfortunately this could not be carried out and it was necessary to discontinue the

Jan 1, 1949

By W. W. Schmittroth, A. Y. Bethune

THE commercial analysis of Special High-Grade zinc usually involves the determination of lead, iron, copper and cadmium as impurities in the base metal. Over the past 20 years, as the result of metallurgical improvements in the art of producing Special High-Grade zinc metal there has taken place a gradual exclusion of almost all extraneous elements, and the few that do remain in the final product have been virtually reduced to the vanishing point. Thousands of tons of zinc .are now commercially produced annually and made available to the trade, in which impurities are present only in the order of 0.0010 per cent or less and the sum total of all impurities does not exceed 0.0025 per cent. To such zinc the term "superpurity" might well be applied without undue exaggeration. The techniques used for production control and final analysis of Special High-Grade zinc by means of emission spectra in the laboratories of the electrolytic zinc plant of the Sullivan Mining Co. are based on the premise that self-electrodes are to be preferred over all other forms for the examination of the zinc in question. Furthermore, after a survey of the literature and considerable experimental work,1 it was decided that the spectrographic method of internal control, the principle of which was first announced by Gerlach,2 using a modification of the high-voltage alternating-current arc source introduced by Duffendack and Thompson,3 with the calibration of each photographic plate as recommended by Wolfe,4 would yield the most accurate and reproducible results. Self-electrodes were chosen in order to make use of one of the unique advantages inherent in spectrographic analysis; namely, the rapid and almost effortless detection of elements other than those being quantified by the analyst; or conversely, the proof that the zinc is free from such impurities if no spectral line of the suspected element appears. This fact was verified for certain elements, and will be discussed later. Carbon electrodes impregnated or packed with zinc salts chemically prepared from the zinc to be assayed were avoided for a number of reasons. First, the chemical manipulation was another time-consuming step, which increased the chances for contamination. Second, none of the common zinc salts, such as the chloride, nitrate or sulphate, yielded reproducible results under our conditions, nor did the spectral line of the impurity appear as readily in the low concentrations as when using zinc metal. Third, no commercial carbon, except the very expensive, was pure enough to use with this grade of zinc and the continued time, effort and expense incurred in the purification of carbon was not desirable. The use of Special High-Grade zinc self-electrodes introduces certain complications with regard to obtaining satisfactory excitation conditions, because it seems necessary to raise the temperature

Jan 1, 1946