Search Documents

OPEN-HEARTH refractories are not merely an accessory to the furnace. They are the furnace, to all intents and purposes. The steel work of the main structure is merely an open frame which helps to support the refractories; and the regenerators, a necessary part of the furnace system, consist almost entirely of refractories. Not only do refractories constitute the essential part of the furnace, but they also carry the liquid steel all the way 'to the point where it begins to solidify. On leaving the furnace the liquid passes through a refractory runner into a refractory-lined ladle, then through a refractory nozzle closed by a refractory stopper on the end of a rod protected by refractory sleeve bricks. The liquid is sometimes sent through an additional refractory- lined tundish, a supplementary ladle, or a refractory runner for bottom pouring, until it finally enters the iron mold in which it solidifies. Even in the mold, refractory materials are sometimes used to provide a nonconducting "hot top." This series, from runner and ladle to hot top, inclusive, is often referred to collectively as the "pouring-pit refractories." REFRACTORY RAW MATERIALS The raw materials available are best classified into basic and acid types. The principal basic raw materials are magnesite, dolomite, and chrome ore. The principal acid materials are silica in various natural forms, and fireclay. Magnesite. Austria was the principal source of magnesite (MgC03) until recent years, when the Province of Quebec, in Canada, and the states of Nevada and Washington became important sources for the American steel industry. More recently these natural sources have been supplemented by the so-called "sea-water magnesite"-which is the name somewhat incorrectly given to magnesium hydroxide obtained as one of the products

Jan 1, 1951

By R. Priestner, R. F. Krause

Solid, cylindrical crystals of a iron have been fractured at 10°K by the simultaneous application of tension and torsion stresses. Thus, a complex distribution of normal (sN) and shear (ss) stresses existed in a cleavage plane at fracture. In every crystal the clearage-plane normal was inclined to the specimen axis, so that a unique point, M*, in the operative cleavage plane was defined where the quantities sn and s2 N + s2 S) were maximized. It is shown that the maxirrzum resolved normal stress on the cleavage plane at fracture decreased as the resolved shear stress in the cleavage plane at M* increased. Thus, a normal stress la?*! for fracture was not satisfied. A fracture law which takes shear stress into account. and which predicts that (s2 N +s2S) should be constant, is to be preferred. However, the data is best represented by a linear dependence of sN on sS, sS which 110 physical significance can be attached. It is suggested that the fracture-nucleating -mechanism is a short-range one. A critical stress law has not yet been unequivocally established for the propagation of cracks in metals. Measurements of the tensile fracture stresses of variously oriented zinc single crystals1 failed to establish the normal stress law expressed by In Eq. [1], sN is the fracture stress, P, resolved normal to the fracture plane, and 0 is the angle between the fracture -plane normal and the stress axis. Similarly, a comprehensive investigation failed to verify the normal stress law for the tensile fracture of a-iron single crystals.' However, a subsequent investigation,3 using iron from the same ingot, presented fracture data which obeyed the normal stress law. It has been shown previously4,5 that the Griffith criterion for fracture6 does not predict such a normal stress law. This result is of particular significance in considering the fracture of metals, such as zinc and iron, which may fail by cleavage. In these metals fracture propagates in a well-defined "cleavage" plane, whether or not an applied stress is normal to it. When the cleavage-plane normal deviates from the direction of application of a uniaxial stress, for example, the crack propagates under the combined action of normal (sN) and shear (ss) stresses. When the presence of a resolved shear stress in the crack plane is taken into account, the Griffith criterion is expressed by4

Jan 1, 1967

By E. Wainer, K. D. Burnham

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

Jan 1, 1965

By R. M. Hudson

A study has been made of the decarburization of low-carbon sheet steels at temperatures from 1100" to 1475°F in mixtures containing hydrogen, nitrogen, water vapor, and in some instances carbon monoxide. Decarburization occurs principally by the reaction C (in steel) + H20 = CO + H2 and follows a first-order rate law. The decarburization rate appreciably increases with an increase in temperature up to about 1325°F, but the increase in rate is small with fur- Use of a dry hydrogen atmosphere results in a relatively slow decarburization of steel and use of a wet hydrogen atmosphere results in relatively rapid decarburization. It is now generally recognized' that the reaction C (in steel) + H2O = H2 + CO [l] accounts for most of the decarburization that occurs in wet hydrogen-containing atmospheres. The present article is concerned with the decarburization of low-carbon sheet steel in H2-N2 atmospheres ther increase in temperature. The limiting rate of decarburization can be predicted from a knowledge of the solid solubility and diffusivity of carbon and this rate is approached as the water-vapor content of an atmosphere is increased. Hydrogen contents above about 8 pct are beneficial only in that they permit higher levels of water vapor to be used without oxidation of the steel. A buildup of CO in the atmosphere lowers the rate of decarburization. containing various amounts of water vapor and carbon monoxide. The effectiveness of these atmospheres and the influence of temperature on decarburization rate will be considered. EXPERIMENTAL WORK The chemical compositions of the three steels used in decarburization-rate studies are listed in Table I. Steel A was a commercially hot-rolled rimmed steel that was cold-reduced at the Laboratory to furnish specimens 0.025, 0.041, and 0.059 in. thick. Most of the experiments in which this steel was used were made on the 0.041-in.-thick material. Steel B and Steel C were cut from 0.010-in.-thick commercially cold-reduced coils that were

Jan 1, 1963

By A. Berthet

In the past two decades, of the successive steps leading from iron ore to finished steel, the production of liquid steel and its preparation for the casting operation has probably undergone the most drastic evolution. The reason for this is the development of oxygen converters (top blown and later on bottom blown) and UHP arc furnaces which are replacing the conventional processes such as the open hearth and basic Bessemer processes. These new processes have been great advances, but it would certainly be quite hazardous to assert that the situation will remain the same for the coming decades. In fact, with the advent of continuous steelmaking a new generation of processes has now arrived. The research and development programme at IRSID on continuous an a steelmaking began ten years ago has progressed systematically in the following stages : First a comparison was made on a small pilot scale of various techniques : for example, refining in a runner by top or bottom blowing, pulverizing the metal stream by oxygen, using the mixing effect of a vortex, etc. but for various reasons these processes proved unsatisfactory and were abandoned in favour of a method using the so -called "emulsion refining".

Jan 1, 1972

By C. G. Southmayd

Anyone who has been confronted with the problem of predicting the performance of a sand-pump installation is vitally aware of the dearth of precise information that has been published on this important subject. Such data as have been collected are not readily available in a concise and readily usable form, so that many operators would find it a considerable chore to find the pertinent information required to undertake a detailed study. The purpose of this paper is to assemble such established data, correlate them with field experience and outline the factors that must be appraised in the determination of a satisfactory pump installation. The transportation of solids in solution is of vital interest to every mill superintendent and operator, and many of the factors that are involved in this hydraulic problem vary widely from installation to installation, and in some cases even from time to time on any one installation. These include: type of solids (including shape of particles), size of solids (grind), percentages of fines (slimes), dilution of pulp, contour of pipe line, type of pipe, age of pipe line, effect that diameter of pipe has on characteristic flow conditions, and other factors. Some of these have been fairly well determined by experimental work but many still must be established through interpolating or extrapolating between values that have been derived from known field conditions. Most problems primarily concern the transportation of a definite weight of dry solids from one specific location to another. The type of material, shape of particles, grind and percentages of fines are established and very often the dilution at which the solids must be handled as well. The problem then evolves into a determination of the size, type and contour of the pipe line and the net effective head against which the pump must operate. Before discussing the determination of the head, it might be well to review the interrelationship between the pump discharge (capacity), the head developed by the pump and the pump speed, which will apply to any centrifugal pump installation. Effect of Pump Speed Basically, the head developed by a centrifugal pump varies as the square of the pump speed and the discharge as the first power of the speed. However, even at constant speed a centrifugal pump will operate over a wide range of capacities, depending upon the head that must be developed to deliver the liquid or pulp to the end of the pipe line. This is shown graphically in Fig. I. If the pump in question is being driven at a constant speed of goo r.p.m. it will deliver 500 U. S. gal. per min. against a head of 56 ft., 800 U. S. gal. per min. against a head of 50 ft., and so on. In other words, at this speed the capacity of the pump will be determined and limited by

Jan 1, 1947

By C. G. Southmayd

Anyone who has been confronted with the problem of predicting the performance of a sand-pump installation is vitally aware of the dearth of precise information that has been published on this important subject. Such data as have been collected are not readily available in a concise and readily usable form, so that many operators would find it a considerable chore to find the pertinent information required to undertake a detailed study. The purpose of this paper is to assemble such established data, correlate them with field experience and outline the factors that must be appraised in the determination of a satisfactory pump installation. The transportation of solids in solution is of vital interest to every mill superintendent and operator, and many of the factors that are involved in this hydraulic problem vary widely from installation to installation, and in some cases even from time to time on any one installation. These include: type of solids (including shape of particles), size of solids (grind), percentages of fines (slimes), dilution of pulp, contour of pipe line, type of pipe, age of pipe line, effect that diameter of pipe has on characteristic flow conditions, and other factors. Some of these have been fairly well determined by experimental work but many still must be established through interpolating or extrapolating between values that have been derived from known field conditions. Most problems primarily concern the transportation of a definite weight of dry solids from one specific location to another. The type of material, shape of particles, grind and percentages of fines are established and very often the dilution at which the solids must be handled as well. The problem then evolves into a determination of the size, type and contour of the pipe line and the net effective head against which the pump must operate. Before discussing the determination of the head, it might be well to review the interrelationship between the pump discharge (capacity), the head developed by the pump and the pump speed, which will apply to any centrifugal pump installation. Effect of Pump Speed Basically, the head developed by a centrifugal pump varies as the square of the pump speed and the discharge as the first power of the speed. However, even at constant speed a centrifugal pump will operate over a wide range of capacities, depending upon the head that must be developed to deliver the liquid or pulp to the end of the pipe line. This is shown graphically in Fig. I. If the pump in question is being driven at a constant speed of goo r.p.m. it will deliver 500 U. S. gal. per min. against a head of 56 ft., 800 U. S. gal. per min. against a head of 50 ft., and so on. In other words, at this speed the capacity of the pump will be determined and limited by

Jan 1, 1947

By G. E. McElroy

Much attention has been directed to mine-air flow in recent years, more especially in Great Britian where there is frequent reference to a theory of fluid flow developed by English engineers. Briefly stated, this theory is that for similar passages of the same relative roughness, in which fluid flow occurs, the conditions of flow are exactly the same for W D V equal values of the product where W = density of the fluid, D = diameter of the passage through which flow occurs, V = mean velocity of flow, and p = absolute viscosity of the fluid flowing. This, the "Reynolds Criterion" of fluid flow, had its origin in the work of Reynolds1 more than 40 years ago. Later, Rayleigh2 amplified the theory which has been conclusively proved for small pipes by the experiments of Stanton and Panne13 over a large flow range, and by Lacey4 over a somewhat more limited range. Concordant results on small pipes have also been obtained by numerous other investigators with single fluids over more or less limited ranges of flow. According to this theory, results in one medium, such as water, are immediately applicable to another, such as air; and experimental results on models are (theoretically, at least) applicable to full-scale designs. This is of great importance in aeronautics and can be of considerable value in mine ventilation research. Hodgson, in a recent paper,6 has outlined the application of this theory to mine-air flow and recent English experiments6 on the resistance of a timbered mine airway have been expressed in this form.

Jan 1, 1927

By Henry P. Ehrlinger, James C. Bradbury

Tripoli is a naturally occurring, very finely divided form of silica found chiefly in some midwestern and southeastern states and used commercially as fillers and abrasives. Definitions Tripoli is a microcrystalline, finely particulate, more or less friable form of silica that appears to be the product of leaching of siliceous limestone or calcareous chert. The term was originally applied to a deposit near Seneca, Mo., that resembled material of that name found near Tripoli in North Africa (Hovey, 1894). The two deposits were subsequently found to have different physical characteristics -the North African tripoli, now called tripolite, is a diatomite, composed of the siliceous skeletons of microscopic marine plants called diatoms, and the Missouri tripoli contains no diatom remains; the term tripoli, however, continued to be used for the Missouri material and is now applied in a general way to most silica deposits similar to it in characteristics and geologic origin. In commercial trade tripoli is commonly understood to designate material from the Missouri-Oklahoma field; silica from southern Illinois, the other major producing area, is referred to commercially as amorphous silica. Each term, however, may be used commercially for material, regardless of place of origin, that has the characteristics or uses commonly ascribed to the material from one or the other major producing area. For example, in the commodity price listings, Engineering and Mining Journal routinely lists under Tripoli, prices "f.0.b. Elco, III." and "f.0.b. Seneca, Mo., and Rogers, Ark.," and under Silica, amorphous, prices "f .o.b. Ill.," and "f .o.b. Dierks, Ark." Amorphous silica, the commercial designation given to southern Illinois tripoli, is, like the term tripoli, a misnomer. Mineralogically, the southern Illinois deposits are composed of microcrystalline quartz, and no amorphous material has been detected during X-ray and scanning electron microscope investigations (Leamnson, Thomas, and Ehrlinger, 1969; Thomas et al., 1970). Soft silica is another term that has been applied to Illinois and Tennessee tripoli, presumably to distinguish it from the more compact Missouri material. It has also been used in the ceramic trade to distinguish tripoli from "hard" silica, or silica flour, produced by pulverizing silica sand (Heinz, 1937). Rottenstone, produced commercially in Pennsylvania, is similar to tripoli in that a major constituent is finely particulate silica, and its uses are much the same as those of tripoli- as abrasives and fillers. The origin of rottenstone also is similar to that of tripoli-decomposition of a siliceous sedimentary rock. The parent rock is defined as a siliceous limestone (Gary, McAfee, and Wolf, 1972; Thrush, 1968) or as shale (personal communication). Heinz (1937) quotes a brief statement describ-

Jan 1, 1975

By J. L. McK. Yardley

There are two general classes of problems in connection with electric furnaces. First, those relating to the best utilization of the electrical power inside the furnace; second, those connected with the bringing of the electrical power to the point where it is to be utilized. Referring particularly to the latter class of problems, many calculations have been made, covering a wide variety of furnaces, to check the electrical capacity and power factor found from test. The following analysis, made for the purpose of determining the maximum capacity and approximate performance of a new furnace, to operate at 160 volts on a 60-cycle circuit, may be of interest. The first characteristic necessary to determine is the inductance, since this is the factor that limits the amount of power which can be put into the furnace. Inductance is calculated from the dimensions of the furnace, according to formulas of the U. S. Bureau of Standardsll as follows. Formula 99, for mutual inductance, is: M = 2l [log 2l/d-1 +d/l] Formula 103, for self-inductance, is: Both of these formulas are approximations which are nearly correct when 1 is great compared to d or R. 1 = length of circuit, in centimeters, d = separation between the conductors, in centimeters, R = geometric mean radius of conductors. For a circular tube, R = the radius of the circle. For a solid circular conductor, R = 0.7788 X the radius of the conductor. For a rectangular conductor, R = 0.2235 X (a + b), a being the length, and b being the width of the rectangle. To calculate the inductance of a three-phase circuit, it is customary to figure the inductance of one leg. In circuits where the three conductors

Jan 1, 1920

By J. L. Jones

1. Brinell tests at progressively increasing temperatures are given for a representative lead-base and a representative tin-base babbitt, showing that the former has superior resistance to deformation at the working temperatures of bearings. 2. Small squares of bearing bronze, tinned and then babbitted with a representative lead-base babbitt and a representative tin-base babbitt were subjected to compressive loading. The lead-base babbitt showed less average compression than the tin-base babbitt. Compression did not materially increase the Brinell hardness of the babbitts. 3. A process and a tool are described for giving smoother and more accurate surfaces to bearings than has heretofore been possible. The following experiments have recently been carried out in the chemical laboratory of the Westinghouse Electric and Manufacturing Co., Pittsburgh, Pa. While the work is incomplete, it is described at the present time because data on the comparative merits of lead-base and tin-base babbitts are of interest in connection with the present shortage of tin. BRinell Habdness of Babbitt at Increasing Temperatures Bearings fail because of wiping, or deformation. Hence tenacity is desirable in a bearing metal, especially tenacity at high temperatures. The Brinell test is commonly regarded as a measure of tenacity. In fact, it has recently been proposed to substitute for Brinell hardness number the expression " tenacity number."l It seemed, therefore, that the Brinell test was especially adapted for the tests described. Disks, 4 in. (101 mm.) in diameter and 1.5 in. (38 mm.) thick, were made of the babbitts to be studied, designated A, B, C. They were poured into metal molds, pyrometer leads being soldered in the center of each disk. The composition of the babbitts was as follows:

Jan 1, 1919

By A. L. Field

WOOLSEY McA. JOHNSON, Hartford, Conn. (written discussion).¬When ;we regard the number of British thermal units running into the billions that-must be applied to metallurgical slags in the United States, we cannot but conclude that the physical chemistry of-slags is a very important subject when measured in dollars and cents. A further contemplation of the subject shows us that it has been hitherto treated in too purely a practical manner. It is needless to comment at length on the cost of these heat units and on the cost of fluxes to produce these metallurgical slags, for, it amounts to tens of millions of dollars annually. Accordingly, this research is of value to the country. But we must,all balance our results against our efforts. Therefore, while the speaker is unwilling to criticise unduly this meritorious research, lie does criticise it in the interest of the profession for the reason that it seems to him too highly theoretical. The article is much too, scientific to produce results at a minimum cost. Let us explain our meaning. It has been said that there are always two sides to a question. It may be further said that there are always three sides to a question, the two extremes and the middle ground. In any industrial research there are the highly theoretical side, the purely practical side, and the theoretico-practical side. To study a slag and be practical in the studying, there is something needed that represents in the laboratory (or in microcosm) what actually happens macrocosmically in the blast furnace. There is such a thing as the art of metallurgical research occupying the middle ground between theory and practice.

Jan 4, 1917

By Ernest Kirkendall

THE amount of research done in the last few years on the subject of diffusion in solid metals is significant of the importance of this problem. To review the literature dealing with diffusion is unnecessary here. Desch1 in 1912 reviewed the work that had been done on diffusion in solids and gave a bibliography of the literature published before that time. Mehl's paper in 1936 2 is an excellent review of diffusion in metals and contains a large bibliography. Of importance also for its review and bibliography is an article by A. I. Krynitsky.3 While considerable material has appeared in the literature on diffusion in brass, the amount of information is not great compared to that pertain-ing to some of the other alloys. Most of the information published is of a qualitative nature; that which is quantitative varies considerably. Thus the quantitative determination of the rates of diffusion of copper and zinc in alpha brass by a new method appeared worth while. In the present investigation the rate of diffusion of zinc in approxi-mately the same composition alpha brass has been determined at three temperatures.

Jan 1, 1938

By W. F. Hergert, L. H. Banning

Experimental production of Al-Si alloys, containing from 33 to 55 pct Al, by direct reduction of aluminum silicates in a three-phase arc furnace is described. Advantages of a smelting technique utilizing hogged wood waste as part of the reductant and for temperature control are discussed. WORK on the problem of producing aluminum by smelting has been in progress since the middle of the eighteenth century. Early work met with little success and in 1782 Lavoisier, an eminent French chemist, expressed the belief that alumina could not be reduced by carbon. It was almost a century later when the Cowles brothers developed a process for the production of aluminum alloys by reducing alumina coincident with the reduction of other metal oxides. In practice, the other metal oxide was usually copper. In 1907 it was first shown that alumina alone could be reduced by carbon at a temperature of 2200°C. The metal produced was volatilized and lost or recombined with the oxides of carbon formed in the reaction.' For a number of years after the Cowles brothers abandoned production of Cu-A1 alloys because their product was not commercially competitive with the aluminum produced by the Hall process, there was little interest in thermal reduction processes. After World War I interest in such processes was renewed and a number of patents were issued on processes for the production of A1-Si alloys.' , "he function of the silicon in these processes was the same as the function of the copper in the Cowles brothers process, namely, to prevent the reduced aluminum from recombining with the oxides of carbon and to promote absorption of the aluminum vapors set free at the high temperature required for the reduction reaction. The advantage of using silicon in place of copper for this function is that silicon has a higher boiling point (2600"C) than copper (2310"C) and its oxides, combined with aluminum oxides, occur in nature in almost unlimited quantities. No A1-Si alloys have been produced commercially in the United States, as far as is known. However, considerable experimental smelting of aluminum silicate materials has been done by the TVA at Wilson Dam, Ala.' The most extensive development and commercialization of the electrothermal production of A1-Si alloys took place in Germany before and during World War II.V he furnaces used in the

Jan 1, 1956

Discussion of the paper of Dorsey A. Lyon and Robert M. Keeney, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 80, August, 1913, pp. 2117 to 2149. C. D. WOODWARD, Butte, Mont.:-We constructed a small blast furnace, and used first carbon electrodes and an alternating current of about 50 to 75 volts. We were able to smelt the material which was fed to the furnace, but we did not carry on experiments far enough to see just exactly what the power consumption was and compare it with the amount of material treated. We found that the blast seemed to help materially in reducing our charge and cutting down our power consumption. There were several other experiments tried at the time, and I do not call to mind now just what they were. We were trying to do away with the carbon electrode and replace it with an iron one, and it also seems to me we tried to use the ore for an electrode; but I believe that the electric furnace in the reducing end is simply a question of British thermal units per kilowatt-hour compared with British thermal units in a pound of coke. Now, if a pound of coke costs us 0.5 c. and a kilowatt-hour costs us in the neighborhood of 1.5 c., I think there is a big advantage in using coke instead of the electrical current for copper reducing. We tried steam, and a number of other methods, to throw copper down, but it has been some time ago and I am not very familiar with them now. The outlook of the experiments did not seem to be very promising, and we took it more as a thermal problem than an electrical one. PROF. JOSEPH W. RICHARDS, South Bethlehem, Pa.:-Mr. Woodward has spoken of the question as a thermal problem. I would call attention to the fact that electric furnaces usually utilize the heat of the electric current at from four to ten times the efficiency with which the heat generated by fuel is utilized; so it will not do simply to compare by thermal units generated. Your total thermal units may cost much less from coke than from electricity, yet you will find the electrically generated thermal units utilized in a properly designed furnace from three to ten times more efficiently than in the combustion furnace. You must make that allowance is comparing the cost of thermal units generated electrically and thermal units from coke.

Jan 11, 1913

By W. H. Howard

As the result of a series of analyses and volume determinations of gases discharged from the converters at the Garfield Smelting Co.'s smelter at Garfield, Utah, it was found that a considerable amount of lead fume was escaping from the stacks of the converter plant, and that if this lead could be recovered at a reasonable expense an attempt should be made to collect it. Two methods suggested themselves: (1) filtration through bags; (2) electrical precipitation of the condensed fume by a Cottrell plant. Filtration through Bags Tests were made in filtering converter gases through the ordinary woolen bags of lead-smelter bag houses to determine how long such material could withstand the corrosive action of the gases. While blowing on white metal only, the fabric was usually destroyed in 10 to 14 hr. In tests conducted in filtering gases when blowing on matte or slagging stage exclusively and when relatively considerable lead was being volatilizcd, bags in one instance lasted 60.5 hr. It therefore was evident that the Garfield converter gases did not contain in themselves sufficient neutralizing elements for the purpose of direct bag filtration, even during the slagging stage. Such results were more or less anticipated, but it was thus proved that under all conditions of blowing Garfield mattes a very considerable amount of neutralizing agent, zinc oxide or lime, or both combined, as in the Sprague process, would be required to render bag filtration possible. Again, owing to the constantly changing quantities of SO3 from a given battery of converters, depending on the number blowing at a given time and on the stages of the blow, it would be practically impossible to feed automatically the required amount of neutralizer. In order to safeguard the bags sufficient neutralizer would have to be continuously added to meet the maximum SO3 output, thus wasting neutralizers and giving an undesirably diluted final product. Such a condition is entirely different

Jan 1, 1915

By E. A. Gulbransen, W. S. Wysong, K. Andrew

INTRODUCTION THE reaction of carbon in solid solution in a metal with the surface oxide film on many metals may be inferred from thermodynamic calculations for high vacua and high temperature conditions. Holm1 has recently shown that oxide films may be removed from ferrous materials by heating in a vacuum at high temperatures and that carbon is the essential element in the reaction. Considerable work has been described in the literature on the decarburization reaction. Several general references may be noted.2,3,4 However, the nature of the mechanism involved in the decarburization is not well understood. Our interest in this reaction resulted from many attempts to degas and to reduce by pure and dry hydrogen the surface oxides 0n strips of various types of chrome-nickel alloys. Some of the early experiments on the behavior of 13 pct chrome-iron in vacua of the order of 5 X 106 mm and at a temperature of 600°C have been reported.5 These experiments showed a slow reaction with the residual oxygen or water vapor in the system and no reaction with hydrogen. This is in accord with thermodynamic data which would lead to the prediction that it is extremely difficult to maintain a hydrogen atmosphere at 600°C pure enough to reduce Cr203 formed on the surface. The crystal structure of the superficial oxide film formed on 13 pct chrome iron and Nichrome V has been investigated in the thin film range by Gulbransen, Phelps and Hickman,6 and shown to be Cr203. It was surprising to us to note that when a specimen of Nichrome V containing approximately 80 pct nickel and 20 pct chromium was heated to 850°C in a high vacuum, the specimen' lost weight. The rate of weight loss was very temperature sensitive. A study of this reaction in vacua and in a hydrogen atmosphere is the subject of this communication. TYPE REACTIONS Let us consider the various reactions which may occur when a metal is heated in vacua, in a hydrogen atmosphere, or in an oxygen atmosphere. The number and kind of reactions will depend upon the chemical nature, of the metal, its alloying constituents and the location of the alloying constituents. The metals used in this study are chrome-nickel alloys of the heater type. They consist essentially of chromium, nickel and iron, small amounts of carbon, silicon and manganese and traces of zirconium, calcium, aluminum and magnesium. The trace elements are added to improve the lifetime and other characteristics of the alloy when used as a heater. Seven of the more important reactions with which we are going to be concerned here are as follows: [I. Metal • (gas) ;--* metal + gas - degassing of the metal 2. xM(s) + y ½ 02(g) tom- M.0„ (s) – oxidation]

Jan 1, 1948

By F. E. Rizzo, L. R. Bidwell, D. F. Frank

THE use of galvanic cells for the determination of oxygen activities has spread rapidly since the suitability of calcia-stabilized zirconia as a solid electrolyte material was first demonstrated by Kiukkola and Wagner.' In many of these investigations:-7 including several at ARL, the free-energy changes for various oxidation-reduction reactions involving the oxides FexO, NiO, and Cu2O have been measured as a means of assuring that a cell apparatus is functioning properly. As a result, a large quantity of data pertinent to the calculation of the high-temperature standard free energy of formation (?GO) of these oxides has been accumulated. AGFexo has been carefully measured in many independent investigations, using a variety of techniques, and consequently is accurately known. chipmans has used this informa-

Jan 1, 1968

By Henry Rumfelt

8.1-1. History and Description of Shovels. The history of excavating machinery is not clearly defined but the machines seem to have been originally developed for dredging activities, principally involving rivers and harbors. The first, as far as can be determined, was a steam "spoon dredge" developed by Grimshaw of Boulton and Watt of Sunderland, England, in 1796. The land machine forerunner of the present-day power shovel was not developed until 1835. It was invented by William Smith Otis, a young partner of a Philadelphia contracting firm by the name of Carmichael and Fairbanks. The moving force behind this invention was the heavy activity in railroad construction. From this early start the power shovel has developed from steam powering to internal-combution-engine powering and to electric powering. In both directions it has developed to its present state of a finely engineered and precision-built tool. Through the interim the railroad-type shovel, about a half-swing arrangement designed especially for making railroad cuts and mounted on rails, was developed. The rail-mounted shovel gradually gave way to the full revolving shovel. It was high on the list in 1912 and was practically extinct by 1927. From the beginning, a few of the small revolving shovels designed primarily for the general contractors' market had found their way into quarry and mining operations. During this same period, the stripping shovel had been introduced-a 2 ½ cu. yd., 100-ton, full revolving stripping machine with a 41 ft boom. Although this shovel was designed especially for stripping, it was also used for heavy-duty, open pit mining service. In 1925 the heavy-duty, full revolving quarry and mine machine was developed. Strip mining shovels evolved through a somewhat separate path. Hand digging plows and mule-drawn slip scrapers were first reported used by Kirkland, Blakeney and Groves near Danville, Illinois for strip mining

Jan 1, 1968

By Walter S. Weeks

In this paper the effect of natural ventilation pressures is considered a part of the mine resistance and it is shown that their effect on the mine resistance is not the same as the total natural ventilation pressure of the shafts if the mine has several levels. It is shown that increasing the fan pressure causes the division of the air to approach the condition that would obtain if there were no natural ventilation pressure present. It is shown that if an appreciable difference in pressure is maintained between the beginning and end of a group of splits, the value of the integrated effect of the natural ventilation pressures on the individual splits does not change substantially with moderate changes of this pressure. A method is outlined for determining the resistance factor of the mine and the value of the effect of natural ventilation with the fan operating; also a method for determining this factor when circulation is caused by natural ventilation alone. Natural Ventilation Pressure Natural ventilation pressure (N.V.P.) is caused by the difference in weight of the air in two similar columns between two horizontal planes, and the difference in weight is caused principally by the difference in temperature of the two columns. The fan pressure causes some variation in density, but, since it is usually small and affects both columns, its effect is relatively unimportant. It has been suggested that "N.V.P." be called "stack effect"; but, since the term N.V.P. was used in a previous Institute paper,' applied in exactly the same manner, the term will be used. Frictional Resistance The frictional resistance to flow in a mine without natural ventilation may be expressed as RQ2 where R is a constant for a given air density and Q is the rate of flow. This frictional resistance plus the effect of velocity changes will be called the F pressure (F.P.) and a curve of F.P. against Q, the F characteristic of the mine. If a pressure is applied to a mine by a fan, the air flow so adjusts itself that the drop in pressure through any path from entrance to exit of mine, due to frictional resistances and velocity changes, is the same as that in any other path. The mine resistance varies as the square of the quantity. The air distribution without N.V.P. will be called "normal." Natural Ventilation Present When N.V.P. is irregularly distributed in a mine, it is more convenient in analysis to consider the N.V.P. as a part of the duct resistance. If it is so considered the resistance no longer varies as the square of the quantity, and if N.V.P. exists between levels the distribution of the air is no longer normal. The total N.V.P. of the mine is the pressure caused by the full length of the shafts. If a mine has several levels, N.V.P. exists

Jan 1, 1946