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By William H. Bassett

COPPER is the world's most important non-ferrous metal, and brass is the most widely used non- ferrous alloy. Much of the utility of each may be credited to the work of metallurgists who have constantly improved the quality of the metals and alloys and the methods of fabrication. Standing in the front rank among these is William Hastings Bassett, the newly elected president of the Institute. Mr. Bassett, ,who is technical superintendent and metallurgist for the American Brass Co.,

Jan 1, 1930

By W. F. Chiao

Ultrasonic attenuation, a, measurements in the frequency range of 5 to 55 mc per sec have been studied to determine their quantitative relationship with the following three variables of mixed microstructures in steels: 1) the volume percent, XF, of polygonal fer-rite in mixed structures of martensite and polygonal ferrite in Fe-Mo-B alloys: 2) volume percent, XA, of retained austenite plus martensite aggregates in high-carbon steel; and 3) substructural differences between 100 pct bainitic ferrite structures formed at various temperatures. The quantitative relationship obtained in the first two conditions by plotting a us the known structural parameters can be expressed, respectively, as: where al, a 2 and C1, Cz are constants. In the third condition the nature of the attenuation depends on the state of dislocations generated at the transformation temperatures and also on the alloy composition. From these measured results, the mechanism of ultrasonic attenuation caused by these mixed microstructures can also be studied. MUCH interest has recently been shown in the application of ultrasonic attenuation and wave velocity measurements to the study of the microstructural characteristics of steels. The general aims of most of the investigations in this field can be grouped into two categories: one is to study the mechanisms of ultrasonic losses caused by the characteristic phases in the microstructure of steel,''' and the other is to develop nondestructive test methods and applications for quality control.~' 4 Apparently no work has been done on the evaluation of ultrasonic attenuation meas -urements as a means of quantitative determination of a given phase in the microstructure of a steel. It is well-established that the decomposition of austenite results in four main microstructural constituents—polygonal ferrite, pearlite, bainite, and martensite—and that each phase has different mechanical properties. Thus, when a steel consists of mixed microstructures, the mechanical properties can often be related to a quantitative measure of the volume percent of each phase present. This study relates ultrasonic attenuation measurements to: 1) the volume percent of polygonal ferrite in mixtures of martensite and polygonal ferrite in Fe-Mo-B alloys; 2) the substructural differences between 100 pct bainitic ferrite structures formed at various temperatures; and 3) the vol- ume percent of austenite in austenite plus martensite aggregates in a high-carbon steel. The choice of the specimen materials was based on the laboratory stocks which were suitable to produce the required mixed microstructures for this study. EXPERIMENTAL PROCEDURES Materials and Heat Treatment. Polygonal Ferrite Plus Martensite Structures. This mixture of phases was produced in a vacuum-melted Fe-Mo-B alloy. The alloy was hammer-forged at 1900" ~ to a -f-in.-sq bar. By isothermally heat treating the alloy at 1300° F for various times and then water quenching, variations in the amount of polygonal (or proeutectoid) ferrite can be controlled in a microstructure in which the balance of the material is martensite. In the present work, four different times of isothermal transformation were adopted; after heat treatment, the four specimens were machined for ultrasonic measurements. The compositions, heat treatments, and dimensions of the four specimens are listed in Table I. 100 pct Bainite Structures Formed at Different Temperatures. It has been well-established by Irvine et al.= that the presence of molybdenum and boron in ferrous alloys can retard the formation of polygonal proeutectoid ferrite and expose the bainitic transformation bay, so that a more acicular or bainitic ferrite can be obtained over a wide range of cooling rates. Their investigation6 also showed that the mechanical properties of fully bainitic steels are usually closely dependent on the substructural characteristics of the steels. For studying the substructural characteristics in completely bainitic structures, six Fe-Ni-Mo alloys, of which five were free from carbon addition and one with 0.055 pct C addition, were selected so that a wide range of hardness values for 100 pct bainitic ferrite structures could be produced by normalizing at 1900" F followed by air cooling. The different bainitic transformation temperatures were recorded during air cooling. All of the alloys were vacuum-melted and then forged at 1900" F to square bars. Data on the six specimens of these structure series are summarized in Table 11. Austenite Plus Martensite Structures. The high-carbon steel used to study austenite plus martensite structures was vacuum-melted and then forged into Q-in.-sq bar. The series of mixed structures of austenite plus martensite was produced by quenching the specimens from the austenitizing temperature to room temperature and then refrigerating them at various temperatures within the range of martensite transformation to produce different amounts of retained austenite. Data on the four specimens of this series are listed in Table 111. Quantitative Analysis of the Microstructures. The microstructures containing martensite plus polygonal ferrite were analyzed by the point-counting technique.

Jan 1, 1969

An ore search for commercial titanium-bearing ore deposits is in progress by the Crane Co., manufacturers of valves, because they expect this metal to be important in valve manufacturing in the future. The company will eventually be mining and making titanium sponge. At present they are buying titanium tetrachloride from the Stauffer Chemical Co, at Niagara Falls and making titanium by reaction with magnesium. Production from the Babbitt concentrator of Reserve Mining Co. is scheduled to begin in late 1951 or early 1952. The capacity is to be 300,000 tons of pellets per year made from magnetic taconite concentrates.

Jan 7, 1951

By D. M. Thayer, P. B. Linkson

High intensity wet magnetic separation methods have received much attention in the search for alternative and effective methods to treat weakly magnetic minerals. This paper examines the incorporation of such techniques in the beneficiation of a non-sliming specular Michigan Hematite. The dependence of separation efficiency and beneficiation of specular hematite on various parameters controlling the operation of such a device is investigated experimentally. Particular attention is focused on particle size limitations imposed in these separations. In light of these data, metallurgical balances are presented and an attempt made to rationalize the various models suggested in the literature.

Jan 1, 1982

By H. R. Deeth

NEPHELINE syenite is a sodium, potassium, aluminum silicate rock occurring in many countries. Large deposits have been investigated in Russia, India, and Norway and in the U. S., where it is known to occur in Arkansas, New Jersey, and Wisconsin. There are extensive areas containing nepheline syenite in south-central Ontario, a region surveyed in 1905 by Adams and Barlow. By 1925 considerable interest had developed in searching for aluminous raw materials that could be used by the glass industry. This finally focused attention on the nepheline syenite described by Adams and Barlow in 1910.1

Jan 11, 1957

By N. F. Schulz, H. A. Lex, J. D. Zetterstrom

A green ball of iron ore faces many perils from the time it is formed until it finally emerges from the pelletizing furnace as a hardened pellet. For instance, if the rate of heat transfer into a ball is sufficient to produce vapor from either the free or combined water more rapidly than it can escape at a tolerable pressure, the ball may split, spall, or even explode, a failure commonly known as decrepitation. To avoid such failures, one must either limit the rate of heat transfer during the drying and preheating stages, at the expense of production rates, or improve the decrepitation resistance of the green balls. The latter remedy may often be accomplished through changes in ore preparation, balling procedures, or the judicious use of binders or other additives. INTRODUCTION Pelletization has become established as an especially desirable method for the agglomeration of fine taconite concentrates and it promises to be equally satisfactory for improving the physical structures of certain natural ores. A high-quality pelletized iron ore consists of uniformly sized spheres, usually about 1/2-in. diam, which are strong enough to resist abrasion and breakage during handling and which reduce well without disintegration in the blast furnace. The unfired agglomerates, "green balls", are subject to several destructive effects that must be avoided or minimized if a high-quality product is to be obtained by pelletization. Among these are abrasion and impact deformation or breakage during handling of the wet green balls, deformation and breakage by compressive forces in the bed of ore in the pel-letizing furnace, decrepitation during drying and preheating, wind erosion, and radial cracking at firing temperatures. Moisture condensation from the warm saturated gases downstream from the drying zone on wet, cool balls may cause bed collapse if it becomes excessive. Decrepitation is defined as the sudden disintegration of green balls, usually with an audible pop, that occurs when they are heated too rapidly during the drying or preheating stages of the pelletization process. The extent of ball disintegration may vary from merely splitting off a small fragment to almost total disintegration into the original ore particles making up the ball. Such ball destruction results in a decreased yield of pellets, and the fragments, which also tend to interfere by obstructing the gas flow through the bed, must eventually be screened from the fired product and recycled. The closely related type of ball failure that sometimes occurs during the high temperature firing stage, resulting in radial cracks without fragmentation, was not considered to be decrepitation for the purpose of this investigation. Failure by decrepitation is not usually a serious problem in the pelletization of taconite concentrates. The problem is significant, however, in the pelletization of some natural ores, especially those containing hydrous iron oxides. In some instances, economicd production rates cannot be maintained if the drying and preheating rates are slowed down enough to avoid decrepitation. OBJECTIVES This investigation was undertaken to: (1) Develop a practical laboratory means for quantitatively measuring the tendency for green balls to decrepitate in iron ore pelletizing furnaces, and (2) Investigate the causes and cures of ball decrepitation. MATERIALS Two iron ores were used in the work reported here: a taconite concentrate at 90% minus 325 mesh, containing 65.0% Fe, 8.4% SiO2, and no loss-on-ignition; and a crude oxidized ore at 54% minus 325 mesh, containing 59.1% Fe, 3.6% SiO2, 1.1% A12O3, and 9.5% loss-on-ignition. For a special test of effect of particle size distribution on decrepitation, two other

Jan 1, 1967

By K. F. G. Hosking

I read Professor Gaudin&apos;s paper with great interest and pleasure because for some time I have held that the chemical aspect of comminution is a subject of considerable importance to the mineral dresser and deserves to be thoroughly investigated. It does seem appropriate, however, to emphasize the fact that "fresh" edges and corners produced by the grinding of solids display enhanced reactivity has been recognized and utilized in the development of certain mineral identification techniques. Some of these techniques are worth noting, not only because they might facilitate research in the aspect of mineral dressing under discussion, but also because they emphasize the fact that many mineral species commonly regarded as being very inert can display a surprising reactivity when in the freshly ground state. In 1951 Isakov6 published a number of tests for the components of certain mineral species which depend essentially on grinding in a mortar a mixture of the material under investigation with a solid reagent. Thus when stibnite, 4(Sb2S3), is ground with sodium or potassium hydroxide. the antimony is revealed by a momentary development of a yellow color which changes in air to orange-red. Other antimony minerals need a preliminary treatment before the test can be carried out. This consists of grinding with aluminium sulfate, ferric sulfate or potassium bisulfate, and breathing upon the resultant mixture. I have employed a similar technique to determine the approximate magnesia content of certain limestones.&apos; The method depends essentially on the fact that when a sample of limestone is ground under controlled conditions with solutions of sodium hydroxide and Titan yellow the color of the final product is, within limits, a function of the amount of magnesia present. I have also shown that the components of a wide range of minerals can be identified by applying chemicals to their streaks on portions of vitrified, unglazed floor tiles, etc. Under such circumstances the diversity of the reactions which take place in the cold (because of the reactivity of fresh corners and edges) is surprising. Thus, for example, if a garnierite, (Ni,Mg)3Si2O5(OH)1, streak is treated first with a drop of 0.880 ammonia and then with a drop of a 1 pct alcoholic dimethyl-glyoxime it immediately becomes red, indicating the presence of nickel.&apos; Stevens and Carron9 have evolved a simple field test for distinguishing minerals by "abrasion pH." A soft nonabsorbent mineral is scratched in a drop of water on a streak plate until a milky suspension is formed. A piece of pH indicator paper is dipped into the suspension, after which it is removed and the maximum deviation from neutrality noted. When a hard mineral or one which absorbs water is being tested, fragments are first ground for 1 min with a few drops of water in a mortar to make a heavy suspension. The importance of the findings of such tests to mineral dressing may be judged by the abrasion pH values, Table 11, recorded by Stevens and Carron for certain species usually regarded as comparatively inert. The combined results Of the above researches clearly indicate that comminution is capable of altering the pH of a pulp and of causing the chemical nature of the surfaces of some of the components to be profoundly changed&apos; Depending On circumstances such surface alterations may have a beneficial or an adverse effect if these products are subsequently subjected to flotation. The tests also suggest that by grinding "inert" minerals with appropriate solid or liquid reagents "reactive" surfaces may be developed which might facilitate separations by flotation. It is an interesting and instructive problem to determine the reactions that are likely to take place when dry solid substances are subjected to comminution and to the unavoidable heat liberated during the process. To do this it is theoretically necessary to know the free energy values of the reactants and possible resultants, but unfortunately there is a dearth of such data! However, the heats of formation of many substances are known, and generally speaking, if in a reaction of the type AB + CD = AD + CB the sum of the heats of formation of AB and CD is less than that of AD and CB the reaction will probably proceed to the right. Thus, according to a note I have (the author of which I cannot name) if PbS (black) is warmed with CdSO, (white), PbSO., (white) and CdS (yellow) are formed, and that the reaction does, in fact, take place is indicated by the change in color of the mixture. The reaction is expected, as the sum of the heats of formation of PbS and CdSO, is less than that of PbSO, and CdS (as shown below). PbS + CdSO4 = PbSO4 + CdS 22.2 + 218.0 < 216.2 + 33.9 Finally, certain other aspects of the chemistry of comminution, which are neither mentioned by Professor Gaudin nor referred to by me are to be found in a paper by Welsh" and in the printed discussion thereof. A. M. Gaudin (author&apos;s reply)—The observations contributed by Dr. Hosking are indeed welcome, as they add to our experimental knowledge of a topic which is believed to be of the first importance. In connection with the experiments cited it should be kept in mind that oxidation, hydration, and carbonation at various rates should always be deemed to be possibilities when grinding is done in water or in air, even in "industrially dry" air. Special precautions might lead to sufficient minimizing of these reactions and to the assertion, instead, of deliberately-created reactions. The author wishes to thank Dr. Hosking for his contribution.

Jan 1, 1957

By H. P. Reid

Portland cement is manufactured under either of two general processes, the wet or the dry. The raw materials in general consist of limestone, shells, marl, cement rock, clay, shale, blast-furnace slag, etc., so proportioned that when calcined the desired composition will be obtained. In the wet process the combined raw materials are ground to extreme fineness in the presence of water, to a resulting slurry of from 30 to 50 per cent moisture content. The moisture of the slurry may be reduced by thickening or filtering processes for feed to the cement kiln or the slurry may be fed to the kiln with its full percentage of water. The dry process differs from the wet in that the surface moisture of the raw materials is removed prior to grinding. For the drying of these materials heat is required and in most cases is produced by burning of raw fuel either on grates or stokers before the dryers or in suspension in the form of pulverized coal, oil or gaseous fuel. The power required for making the cement is sometimes purchased from outside sources; sometimes it is generated from the heat in the waste gases leaving the cement kilns, or generated at the plants direct from raw fuel. We have, then, as the possible requirements of fuel in the cement industry: (1) fuel for power generation, (2) fuel for drying raw materials, including coal before pulverizing, and (3) fuel for burning the raw materials to cement clinker. There is no essential difference in quality required in fuel for burning the materials by the wet and,dry processes. Fuel fob Power Generation As there is nothing peculiar to steam generation in a cement mill power plant as compared with other power plants this use classification of such fuel will be found in other reports of the Technical Committee. Fuel for Drying Raw Materials and Coal Any fuels capable of producing moderate temperature gases may be used for drying raw materials. There is no problem of material contamination from fuels at this part of the cement manufacture to be guarded against.

Jan 1, 1932

By L. D. Rickets

The principles on which an art is founded are usually few and necessarily basic in nature, but he who wishes to achieve the power to select his aides and give success to important undertakings that may be entrusted to him in the future must ordinarily undergo years of drudgery in order to gain the experience that will enable him to distinguish such fundamentals through the haze of reenforcing detail that clothes and tends to disguise them. This especially applies to those who would dream dreams that may come partly true. Professor Henry B. Cornwall of Princeton was a graduate of Freiberg with mining experience in Mexico. He was my friend and mentor during my college life. In 1883 I finished my postgraduate course and had two offers of work to consider. His advice is very clear in my mind today. It was essentially as follows: I know something of the mines of Mexico and have crossed through the mountains of the West. The West possesses a vast area of mountain and valley. California has long had its gold mines, the Comstock and Gilpin County followed and now comes the discovery of Leadville. I believe the West, will become a great mining country. You can choose now to teach here or go to the mountains. Were I in your place I would go West and identify myself with mining.

Jan 1, 1932

By George Otis Smith

A PHILOSOPHER has pointed out that inventive genius, in substituting mechanical power for human brawn, leaves&apos; man the intellectual factor in the industrial life. "Almost human" is the description sometimes applied to the automatic machine, yet the true characteristic of the perfect machine is its unquestioning obedience. "Its not to reason why." The human operator, not the mechanism of gears and levers, has freedom of choice: he wills; the machine obeys: There map be a grinding monotony, a tiring rhythm, that passes from machine to man, but the responsibility resides in the man. In no proper sense call the machine worker be called the slave: whether he guides an electric shovel or tends a group of automatic 1athes.in the machine shop.

Jan 1, 1930

By Gerald Greene

Tan various lead producers have given the subject of lead drosses much attention in recent years but the problem of their economical treatment is yet to be solved. Formerly the copper in the furnace feed was removed from the furnace in the form of matte. The speiss at that time consisted principally of the iron arsenide. The practice today is to roast off most of the sulfur and the copper in the feed forms a dross in the furnace, which is removed from the furnace with the lead. This material is poured into the drossing kettles and allowed to cool down to but slightly above the freezing point of lead. The copper dross, containing almost all of the arsenic and part of the antimony, is skimmed off and treated in a small reverberatory furnace at most plants. This is essentially a liquation process. The skimmed dross contains from 70 to 80 per cent lead, and much of this lead is liquated out. The products from this treatment are: (1) impure lead, (2) speiss and (3) matte. The speiss from the reverberatory furnace was studied in this research. The literature on the subject is of very little assistance, as almost no work has been done on the problem of establishing the exact identity of the various phases present. One author(1) states that speiss consists of a series of isomorphous compounds of the general formula FexAsy in which the Fe may be replaced by Ni, Co, Cu, Pb, Ag, Au, Pt, Zn, Cd and the As replaced by Sb, S and Bi. Hofman(2) states that the iron arsenide present is Fe5As.

Jan 1, 1935

By William P. Shinn

IT seems proper to present in the Transactions of the Institute, from time to time, formal record of the advances made in the arts and sciences to which our organization is devoted-milestones in the highway of progress-from which our successors may measure what they in their turn have gained. The admirable address of the Hon. Abram S. Hewitt, then president elect of the Institute, on "A Century of Mining and Metallurgy in the United States," read at the opening of the meeting held in this hall in June, 1876, forms a point of departure, and the conclusion of the eighth decade of the nineteenth century and the end of the first five years of our country&apos;s second century seem to offer a fitting time for again making up our record. The period since 1875 has been marked by a degree of activity in mining and metallurgical industry never before equalled in our history, while the progress made in the science and art has been, if possible, still more noticeable. Whether we consider the mining of iron, ore, and coal, or of the precious metals,-the advances made in smelting the former and in reducing the latter, the extraordinary increase in the production of Bessemer steel, or the science of Thomas and. Gilchrist, which makes the hitherto rejected phosphorus the corner-stone of success,-the past five years are alike memorable for the progress they have shown and to some of the most marked features of this progress I will now oriefly call your attention. It may be of interest in this connection to note the following figures, showing the growth of the population of the United-States during the last three decades :

Jan 1, 1881

By F. C. Schora, H. P. Meissner

Both a graphical and an analytical technique are presented for calculating stream compositions and temperatures in adiabatic staged systems in which solids travel countercurrently to a gas stream. Such a system might be a tower containing several plates, on each of which the descending solid is fluidized by the rising gas stream. Examples are presented in which chemical reactions occur, including the oxidation of SO, by a solid catalyst and the gaseous reduction of iron oxides. COUNTERCURRENT staged processes involving reactions between solid and gas streams are becoming more common. These operations are generally carried out in a series of beds of fluidized solids, with each bed or "plate" acting as a stage. Fig. 1 is a schematic diagram of such a series of stages located in a column, down through which a solids stream moves from stage to stage counter to a rising gas stream. Typical reactions carried out in such systems are the dehydration of aluminum trihydrate, the calcining of limestone, and the gaseous reduction of iron oxides. Calculation of the performance of these counter-current systems rapidly becomes more complex with increases in the number of stages and in the number of chemical reactions occurring. Calcula-tional procedures for isothermal operations of such systems have been described.4 Actual tower operations, however, are generally adiabatic, and in consequence far from isothermal. The object here is to present both graphical and analytical techniques applicable to such adiabatic towers operating continuously and in steady state. In this introductory discussion, the graphical techniques presented are of the McCabe-Thiele type, rather than of the Pon-chon type. In all the examples presented, it will be assumed that both thermal and chemical equilibrium are attained in each bed. The assumption that the gas and solid streams leaving each bed are at the same temperature as the bed is in accordance with the familiar behavior of actual fluidized solid systems. Chemical equilibrium, on the other hand, is not necessarily attained in any given stage between these two streams, even with deep beds, since reaction rates may be slow. In the last section of this paper, discussion is presented of methods suitable for use when chemical equilibrium is not attained. The adiabatic tower in Fig. 1 has "n" stages numbered from 1 to n, starting with the bottom stage as number 1. In analyzing this tower&apos;s performance, it is important to express gas flow rates in terms of a key component or element which remains completely within the gas stream throughout the tower. Similarly, solid flow is best expressed in terms of a key compound or element which remains within the solid phase throughout the tower. Thus, in burning limestone with a hot flue gas, the gas flow might be expressed as G, the pound mols of nitrogen flowing through the tower per unit time, while solid flow might be expressed as S, the pound atoms of calcium in all forms in the solid stream per unit of time. Defined in this way, both G and S are constant throughout the tower. The enthalpy of the gas and solid streams are now best expressed in terms of these key components. That is, the gas stream enthalpy H is expressed as Btu in the total gas per mol of the key component in the gas. Similarly, the solids stream enthalpy h is expressed as Btu in the total solid stream per pound mol (or pound atom) of the key component in this stream.

Jan 1, 1962

By L. R. Weisberg, E. A. Miller

Single-crystalline films of silicon of good quality were vacuum-deposited on sapphire. The improved crystallinity was achieved by the strict exclusion of oxygen from the evaporation system, including the use of a "oxygen-free" silicon source. To minimize possible contamination of the source, the silicon was sublimed from the solid at about 1390° C. using a simple electron bombardment system to heat the silicon. This resulted in deposition rates of about 5 to 7 µ per hr and film thicknesses of 4 to 20 µ. The vacuum during deposition was ordinarily about 5x 10-8 Torr, DESPITE the success achieved in the chemical vapor deposition of silicon on sapphire using Silane,1-4 vacuum deposition has not provided comparable properties. For example, Chu et a1.5 vacuum-deposited silicon on single-crystalline substrates of A12O3, Sic, ThO2, and other compounds, and, although some epi- but the use of ultrahigh vacuum (about 1 to 3 x10-9 Torr) during deposition did not significantly improve the results in the oxygen-free system. The crystalline quality of films deposited on (0001) sapphire was found to be considerably superior to (1102) sapphire surfaces. Using (0001) sapphire, single-crystalline films were deposited at temperatures as low as 780° C and as high as 1075°C, with the best crystalline quality obtained at about 1000°C. At this temperature, hole mobilities over 250 sq cm per v-sec were achieved. taxy was indicated, single-crystalline films were not produced. More recently, Salama, Tucker, and young6 evaporated silicon on single-crystalline sapphire, but only poor crystallinity was observed, and low carrier mobilities were measured. In the present experiments, good-quality single-crystalline films of silicon on sapphire have been achieved by specifically excluding oxygen from the evaporation. This included not only the use of a "clean" vacuum system but, of special importance, the use of an oxygen-free silicon source. This has also been shown to provide a dramatic improvement in silicon homoepi-taxy.7 As a result, silicon-on-sapphire films with hole mobilities over 250 sq cm per v-set were achieved, and single-crystal films were grown as low as 780°C and as

Jan 1, 1969

By Richard Kunter

INTRODUCTION Additional work has been done on the CIP circuit at Creede, and a brief description of this work is presented in this paper. DREDGE The original dredge for the Bulldog was built by Al Hack, Inc. of Denver. The dredge cutter head is mounted on a boom made of 6-inch diameter pipe which is raised and lowered by a cable-pulley system. Maximum cutting depth is 8 feet. Slurry from the dredge flows through a floating 6-inch diameter pipe supported on 55-gallon drums which runs from the dredge to the shore and then to a trash screen and pumping system. See Figures 1 and 2. The cutter head, suction pump, winches for dredge movement, and all other operations are controlled from a small operations house located toward the rear of the dredge. All of the basic dredge equipment is mounted on a chassis about 8 ft x 16 ft in size. Additional buoyancy was originally provided by sealed 55-gallon drums supported along the sides of the chassis by a small wooden framework. Additional framework and barrels on the front of the chassis on either side of the cutter boom provided additional stability, particularly when digging in hard material. The dredge was quite stable, but two problems were apparent. For one, it could have been sunk by someone from the shore firing a rifle into all of the barrels. In prime deer-hunting and sportsman country

Jan 1, 1983

By Benny Langston, Frank M. Stephens

Although little information is available concerning small-scale equipment for dust collection in laboratories, it is possible to adapt standard equipment for laboratory use. Dust from laboratory processes may be collected by cyclone separators, filters, electrostatic separators, scrubbers, and settling chambers. IN recent years much attention has been given to recovery, treatment, and disposal of dusts discharged into the atmosphere from operations of industry. considerable data has been accumulated on both operation and design of dust-collector equipment for commercial installations. On the other hand, there is almost no published data on design and construction of small-scale equipment to handle dust problems that arise in the ore-dressing laboratory. Dust-collection equipment such as multiclones, single-cyclones, scrubbers, chemical and mechanical filters, settling chambers, and electrostatic separators has proved its efficiency for collecting dust in industry. In the laboratory, however, the engineer is faced with the problem of collecting small quantities of dust, inexpensively, without diverting the major effort from the metallurgical problem to the problem of collecting dust produced by the process. For most applications standard dust-collection equipment is too large for use in the laboratory; however, for control of dust in large working areas it is often possible to use a standard dust collector, such as an air filter, with branch ducts to eliminate a health hazard. For example, the well-furnished sample-preparation room containing small jaw crushers, rolls, and pulverizers, in addition to the riffles and screens necessary for preparation of samples, presents a perennial source of dust. The authors&apos; experience has shown that a combination system consisting of overhead branch ducts to the individual equipment and floor ducts with grills, where applicable, connected to a central dust collector effectively removes dust generated in preparation of samples. Fig. 1 is a sketch of a downdraft dust-collector for table installation. Similar systems can be built with floor grids. For portable equipment such as laboratory vibrating screens this type of installation with a steel grill to support the heavy load is reasonably efficient. Overhead branch ducts to individual crushing and grinding equipment, although efficient, must be carefully controlled by dampers to prevent excess loss or a change in the composition of the sample. Change in sample composition can result from excess velocity, which causes selective removal of constituents of low specific gravity. Fig. 2&apos; shows the theoretical effect of terminal velocity on spherical particles of different specific gravities in air and water under action of gravity. Fig. 3 shows the effect of air velocity on composition of CaCO, coal mixtures. Although the entrainment of dust particles in a moving air stream is the basic mechanism by which all dust-collection equipment functions, usually intake velocity of the dust-collection system must be controlled to prevent loss of part of the sample. As an example of what may happen when excess velocities are used, a mixture of 50 pct coal and 50 pct limestone was crushed to —10 mesh and fed to a pulverizer equipped with an overhead dust-collection system. Fig. 4 shows the overhead dust-collection equipment used in this test. The pulverizer was set to give a product 95 pct —100 mesh in two stages. Velocity of air passing over the lip of the pulverizer was measured with an anemometer. After grinding, the finished product was analyzed to show the amount of calcium carbonate present. Fig. 3 shows graphically the increase in calcium carbonate as velocity through the dust-collection duct was increased. These data show that at a velocity of 1 ft per sec little if any of the coal was entrained by the overhead draft. At the maximum velocity, about 6.5 ft per sec, approximately 7 pct more coal was entrained than calcium carbonate. From an operating standpoint, this problem can be remedied easily by dampering the line to control velocity. The lowest velocity commensurate with satisfactory dust control should be used to prevent excess loss and, in some cases, selective dust loss. Collection of Dust in Laboratory Processes As in industry, the engineer desires to collect efficiently the dust produced by processes being investigated on a laboratory scale. However, in the collection of laboratory dusts he is faced with two additional problems: 1—The volumes of gas and the quantity of dust that must be recovered are small when compared with the capacity of standard dust-collector equipment, which must be scaled down in design except for collection of dust from large pilot-plant operations. 2—In addition, because of the variety of problems studied in the process laboratory, the engineer cannot design today a dust collector that will meet the conditions imposed by the processes of tomorrow. Sometimes, therefore, he must compromise collection efficiency to minimize the cost of fabrication and the amount of time diverted from the metallurgical to the dust-control problem. For collection of dust from laboratory processes a cyclone separator, filters, electrostatic separators, scrubbers, and settling chambers can usually be adapted for small-scale operations. The following

Jan 1, 1955

By H. A. Schwartz

By analyzing cementite separated electrolytically from white cast iron of known composition and history, the distribution of silicon between austenite and cementite during and after freezing has been followed. The results constitute a contribution to our knowledge of equilibria in the ternary (metastable) system iron-carbon-silicon. Incidental information was obtained, also, with respect to the distribution of manganese, silicon, and phosphorus, when only relatively small amounts of each are present. The major conclusion of the paper is that during solidification, equilibrium is attained when the silicon is all rejected to the liquid phase, permitting silicon-free austenite to separate. OF THE outstanding investigators of the system iron-carbon-silicon, Gontermann,1 Charpy and Cornu-Thenard,2 and Honda,3 only the first touched on the chemical composition of the solid and liquid phases in equilibrium with one another. He concluded that his data did not permit a decision as to which of an indefinitely large number of pairs of compositions of liquid and solid would be found in any given case. If through the three dimensional equilibrium diagram of the iron-carbon-silicon system an isothermal plane is passed in the region of partial solidification, two lines of intersection with the liquidus and solidus, respectively, are obtained, also a point marking the alloys&apos; composition. If, in this, plane, a straight line is drawn through the point, and intersecting both the liquidus and solidus isothermals, the two intersections mark a liquid and a solid alloy that may be chemically in equilibrium at the chosen temperature. From thermal data alone, Gontermann could not assign any particular direction to the line and, hence, could not determine which pair of conjugate points to choose.

Jan 7, 1924

William B. Phillips, Birmingham, Ala.: The analysis of Pratt coal made by myself, and given by Mr. Ormsbee in his paper (p. 113), is likely to mislead the reader as to the real nature of this coal. It represents the very purest coal that I have been able to get, and does not represent the average composition of the lump-coal as prepared for market. I wish it were true that the coal had no more than 2.50 ash and 0.83 sulphur. The analysis of McCalley is nearer the real figures than any of the others. There is no use in giving an

Jan 1, 1896

Greater automation of facilities is probably the best hope of the mining industry in its efforts to surmount continually rising labor costs. Underground mining, with its inherently low unit labor output, is especially vulnerable to rising costs, and here maximum automation is becoming increasingly important. One area of such operations that has been receiving a great deal of investigation is that of ore haulage and hoisting, two steps that often account for 10-35% of underground operating costs. Innovations and experimentation by mining firms and manufacturers over the past few years have resulted in larger, faster and more efficient tramming and hoisting equipment, but the White Pine Copper Co., at its operation in the Upper Peninsula of Michigan, is preparing to start up an entirely new concept in haulage later this summer. Known as the Dashaveyor System, it consists of individually powered modules (cars) that run on tracks inside a rectangular tube or on an open trackway at predetermined speeds up to 50 mph. At White Pine the Dashaveyor will be used to carry ore (crushed underground to -10 in.) from the mine to the concentrator. Dr. James Boyd, president of Copper Range Co., which is a 25% shareholder in The Dashaveyor Co., has indicated that if the Dashaveyor meets the expectations for surface operation, it will also be used underground for ore transport in place of the several miles of conveyor belts currently in use (Business Week, July 29, 1967).

Jan 7, 1968

By T. D. Yensen, R. K. McGeary

While we have not been primarily interested in the determination of hydrogen in the alloys that we have been dealing with, we arc very glad to cooperate in this symposium on sampling and analysis for hydrogen, as we can never tell when we may find it desirable to perform such analyses. Vacuum-fusion Method Our primary interest has been oxygen and carbon, in the analysis of which we think we have become very proficient. Our oxygen-analyzing apparatus is of the vacuum-fusion type (Fig. I). This employs Dr. Derge&apos;s type of graphite cruciblc and slit sleeve, with graphite powder between, for heat insulation (Fig. 2) supported in a clear quartz bulb connected to the Pyrex glass system by means of a carefully made ground joint. The latter is kept cool by means of an air blast from a circular copper tube surrounding the joint. The crucible is heated by high-frequency induction and the 24 one-gram samples successively dropped in from the horizontal tube at the top by means of a magnet. The gases (H², CO, N2) are passed through the CuO catalyst held at 300°C. (converting CO to CO²I, H² to H²O) and the CO² and H2O frozen out in the main liquid air trap, while N2 is evacuated. At the end of the operation, shown by the termocouple vacuum gauge indicating a pressure of 10-4 mm. Hg, the analyzing system is isolated by means of the mercury cutoffs, and the CO² and H2oare determined by transferring first the CO2 and then the HzO to the small trap at the right. This is done by placing liquid air on the small trap, then removing the liquid air from the large trap for one minute, which is sufficient to evaporate the Co2 and transfer it to the small trap. The CO2 is then measured by closing the mercury cutoff at the extreme right, removing the liquid air from the small trap, warming it up to room temperature, adjusting the mercury level to one of the three marks on the glass tube (corresponding to three volumes calibrated so that I mm. Hg of CO² corresponds to 0.001, 0.002 and 0.010 mg., respectively, of oxygen) and finally reading the pressure. Liquid air is now replaced on the large trap, the mercury cutoff at the right opened, transferring the COz back to the large trap. The cutoff to the pumps is then opened, the liquid air removed for one minute, thus evacuating the CO², the pumps again cut off and the H2 O transferred to the small trap as before, except that it is now necessary to warm the large trap with a Bunsen burner in order to evaporate all the H2O. This requires about three minutes, as the inner tube must be heated to at least 100°C. In order to prevent H²O from being adsorbed on the glass walls, the glass tubing beyond the catalyst (i.e., to the right in Figs. I and 3) is kept heated to about 150°C. by means of Nichrome ribbon as shown in Fig. 3. For a I-gram sample the above amounts of oxygen (0.001, 0.002 and 0.010 mg.) 35

Jan 1, 1945