Search Documents

By E. C. Wright

The following article is based on observation of college graduates entering the steel industry in technical work made during the Past 25 Years, the first five of which were spent as a college instructor in two engineering schools, and the last 20 in the employ of a large steel company that has hired hundreds of engineering graduates for steel-mill operations. The college graduates encountered during this period have come from many colleges representing schools in Eastern States, Midwestern Universities, many Southern colleges, and many smaller colleges and normal training schools mostly in western Pennsylvania and Ohio. The college training of these students for engineering work naturally has varied widely and the educational qualifications of the entrants have been in many ways different. It was found at an early date that graduates of standard engineering colleges were much more adaptable than graduates in science from nontechnical schools. The engineering students seemed to be more suited to actual work in steel plants and in general were better able to grasp a knowledge of the operations they observed. However, although the graduates of engineering schools have had somewhat better training in physics, mathematics, and engineering, it has been a general and continual observation that most of the students employed have had inadequate training in the fundamental sciences. Since this discussion relates entirely to metallurgical engineers it should be emphasized that students taking metallurgical engineering courses in college seem to be poorly trained in organic chemistry-physics, physical chemistry, thermodynamics, and any higher form of mathematics than simple calculus. It has been noted frequently that young engineers faced with problems in a mill that involve some mathematics generally flounder badly, and that they have little conception of physical chemistry. Another common deficiency lies in the young graduate's lack of knowledge of where to look for the more detailed literature on any subject. He reverts instinctively to some college textbook whose coverage is usually very elementary. It is recommended that such textbooks contain a bibliography of the source literature. and that students be taught to use the original data. Many of the students had had previous courses in college dealing with metallurgical work such as steel melting, metallograhy, etc.r but it was found that their grasp of these subjects was extremely sketchy. It was soon realized that an ordinary engineering graduate could be taught more about steel melting and manufacturing processes in a few weeks in a plant than he could learn in a college course on such subjects. A similar statement may be made regarding the ability of students to conduct laboratory work. Their lack of technique and skill in handling equipment and setting up experiments was soon apparent. It became neces-

Jan 1, 1948

By Rossiter W. Ph. D. Raymond

(From the President's Address at St. Louis, 1874.) IN the course of this address, President Raymond referred to the law, said to have been discovered at the French works of Terrenoire, that the amount of phosphorus may be increased without injury to steel, if the amount of carbon be proportionately decreased. The works named have been for more than a year, it is said, manufacturing in the open hearth, by the Martin process, steel rails containing as high as 0.35 per cent. of phosphorus, with about 0.15 per cent. of carbon, which were not found inferior to Bessemer rails. It is not claimed by the manager of the works that phosphorus is an ingredient to be preferred, or purposely introduced; but only that materials containing it (such as old iron rails, etc.), can be succesfully employed. Other parties have apparently a higher opinion still of the new manipulation, and are prepared to claim for "phosphorus steel" superior qualities. Mr. I. Lowthian Bell alluded to the subject in his recent address as President of the British Iron and Steel Institute, but without expressing a positive opinion. After pointing out that the commercial value of the process turned on the cheap manufacture of ferro-manganese, by means of which only could the necessary amount of manganese be introduced into the Martin bath, without increasing its contents of carbon, Mr. Raymond proceeded to say that the principle alleged to have been discovered at Terrenoire was already known years ago, in this country, at least. Not only had steel been manufactured here, containing high percentages of phosphorus, coupled with low percentages of carbon, and suitable for use in rails, boiler-plates, etc., but the reason of its surprising qualities had been distinctly surmised, if not widely proclaimed. The following analyses and extracts from private letters prove these assertions. Some of them assert a similar principle in -the case of wrought iron ; but the analyses, and the remarks based upon them, have reference solely to the steel manufactured under the superintendence of Mr. Slade, at the works of the New Jersey Steel and Iron Company in Trenton.

Jan 1, 1875

[ ]

Jan 1, 1938

By M. R. Hatfield, F. J. Vosburgh

In a recent article, it was shown that in the blast furnaces in Germany that are lined with carbon blocks no cooling plates are used, and that shower cooling is employed on the hearth and bosh sections. While one of the authors was in Germany he was told that one furnace was being operated without even the shower cooling on the bosh section, though the hearth section was shower-cooled. In discussion of this interesting situation with a number of blast-furnace operators in this country, it was made clearly and promptly evident that shower cooling was very unpopular, probably because of its messiness and its ineffectiveness. Both of the causes for the dislike of shower coolings are reasonable ones. Shower cooling can be and frequently is messy, but the present cooling of blast furnaces leaves much to be desired on that score. Shower cooling is ineffective as compared with plate cooling, so far as its usefulness in keeping the bricks cool enough not to melt or fall to pieces is concerned. However, the introduction of carbon linings changes the situation. No one is concerned with keeping a carbon lining cool, for no temperature in the blast furnace has any effect on carbon, which is just as stable at 3000°F. as it is at 70°F. The only concern is for the shell—to keep it cool enough for safety and comfort— and for that shower cooling is sufficient. Of course, with only the shell to cool, instead of the shell plus all the refractory material, much less water would be required, and the necessity for constant attention to the flow would be lessened, as the hundreds of inlets and outlets would be eliminated. Probably half of the water used in cooling a blast furnace is used for cooling the shaft and tuyeres and the remainder for the bosh and hearth sections. However, in view of the dislike of shower cooling in the United States, and particularly because at least one German blast furnace is operated with no cooling of the bosh section, thought was given to the possibility that a carbon-lined blast furnace might be operated without any cooling of the entire carbon-lined portion. For that reason a series of experiments was performed to determine what might be the temperature of the shell of a blast furnace protected by a carbon lining and operated under varying conditions up to a maximum inside temperature of 3000°F. Experimental Procedure A schematic diagram of the experimental setup is shown in Fig. I and a photograph of the entire assembly in Fig. 2. The heating element was a a tubc nominally 25/8 in. 0.d. by 2 in. i.d. by 30 in., used as a resistor. Power was furnished by a I5-kva. transformer operating

Jan 1, 1942

By M. R. Hatfield, F. J. Vosburgh

In a recent article, it was shown that in the blast furnaces in Germany that are lined with carbon blocks no cooling plates are used, and that shower cooling is employed on the hearth and bosh sections. While one of the authors was in Germany he was told that one furnace was being operated without even the shower cooling on the bosh section, though the hearth section was shower-cooled. In discussion of this interesting situation with a number of blast-furnace operators in this country, it was made clearly and promptly evident that shower cooling was very unpopular, probably because of its messiness and its ineffectiveness. Both of the causes for the dislike of shower coolings are reasonable ones. Shower cooling can be and frequently is messy, but the present cooling of blast furnaces leaves much to be desired on that score. Shower cooling is ineffective as compared with plate cooling, so far as its usefulness in keeping the bricks cool enough not to melt or fall to pieces is concerned. However, the introduction of carbon linings changes the situation. No one is concerned with keeping a carbon lining cool, for no temperature in the blast furnace has any effect on carbon, which is just as stable at 3000°F. as it is at 70°F. The only concern is for the shell—to keep it cool enough for safety and comfort— and for that shower cooling is sufficient. Of course, with only the shell to cool, instead of the shell plus all the refractory material, much less water would be required, and the necessity for constant attention to the flow would be lessened, as the hundreds of inlets and outlets would be eliminated. Probably half of the water used in cooling a blast furnace is used for cooling the shaft and tuyeres and the remainder for the bosh and hearth sections. However, in view of the dislike of shower cooling in the United States, and particularly because at least one German blast furnace is operated with no cooling of the bosh section, thought was given to the possibility that a carbon-lined blast furnace might be operated without any cooling of the entire carbon-lined portion. For that reason a series of experiments was performed to determine what might be the temperature of the shell of a blast furnace protected by a carbon lining and operated under varying conditions up to a maximum inside temperature of 3000°F. Experimental Procedure A schematic diagram of the experimental setup is shown in Fig. I and a photograph of the entire assembly in Fig. 2. The heating element was a a tubc nominally 25/8 in. 0.d. by 2 in. i.d. by 30 in., used as a resistor. Power was furnished by a I5-kva. transformer operating

Jan 1, 1942

By L. R. Woodyatt, H. J. Beattie, C. T. Sims

Theories correlating the formation of u and related intermetallic compounds to the electron-per-atom density of binary and ternary alloys have appeared regularly in recent technical literature. These same principles can be modified and applied to complex precipitation-strengthened alloys such as the iron-, cobalt-, and nickel-base superalloys and the stainless steels. Since these complex alloys contain carbides and other phases that normally precipitate before the U-type phases, the nature and amount of the precipitated phases must be calculated first. The following general formula is then applied to the residual matrix composition of the alloy: element. The magnitude of the resulting number is indicative of whether the alloy will form a a -type phase. When these calculations (which are computerized) are systematically applied to alloys of knoun phase analysis, a breakoff in average electron-vacancy number is noted between U-free and U-prone alloys. Alloys with an average electron-vacancy number higher than the breakoff form a-type phases, while those with lower ones do not form these phases. This method could then be used to eliminate from consideration all experimental compositions that would precipitate undesirable phases. It also is useful in evaluating analyzed heats of alloys where minor heat-to-heat variations determine whether the alloy is o-free or o-prone. THE highly significant development of strong, ductile superalloys to provide reliable construction materials in the 1000" to 2500° F temperature range has been due principally to unremitting application of Edisonian techniques and logic by the dedicated physical metallurgists who have shouldered this responsibility. Tools such as the electron microscope, phase analysis, and computers to accomplish regression analyses have been used heavily, but the effort has been essentially practice of an art, rather than a science. The objective of this paper is to describe and illustrate application of some relatively fundamental principles to certain of these alloy systems in an attempt to remove some of the empiricism from the technology. Specifically, the work presented here deals with the use of periodic-group relationships to predict the formation of intermetallic phases which can occur in primarily austenitic (fcc) structures. Calculations that have been developed might be applied in the design of new alloys and the evaluation of known alloys, and thus have the potential of eliminating vast areas of unnecessary alloy preparation and evaluation. ALLOYING CONCEPTS AND STRUCTURAL FEATURES OF SUPERALLOYS Strength is produced in austenitic superalloys by three principle mechanisms: 1) precipitation of y'; 2) formation of carbides; 3) solid-solution hardening by soluble refractory metals. The first mechanism requires the addition of aluminum and titanium, the second requires carbon and carbide-forming elements, while the third calls for the addition of molybdenum and/or tungsten. A considerable concentration of chromium is usually maintained to resist oxidation/corrosion, but it is also an important carbide-forming element. Fig. 1 shows a sketch and electron micrograph of the structure of a typical wrought nickel-base super-

Jan 1, 1967

By W. O. Philbrook, R. H. Spitzer, F. S. Manning

The steady-state operation of an isothermal, counter-current reactor in which a mouing bed of hematite particles is reduced by hydrogen has been modeled mathematically using a generalized single-particle kinetic formulation for topochemical reduction with formation of the intermediate oxides, wustite and magnetite. Reduction prof iles have been generated for various oper- REDUCTION of iron ore, as practiced industrially, approaches counter current, granular-bed operation. The total process is extremely complex. Quite under- ating conditions selected to demonstrate the influence of major variables such as gas and solid flow rates, bed length, and particle size. These profiles illustrate , among other things, that the reducing-gas requirement in a countercurrent bed hinges upon the iron-wüstite equilibrium or 'pinch-point" in much the same way as in a staged reactor. standably, nearly all research has been focused on reduction of single particles of oxide under controlled conditions. While this approach simplifies the problem by eliminating interparticle interactions, the remaining intraparticle transport and kinetic processes still constitute a most formidable challenge. Only within the last few years has knowledge of single-particle reactions been developed sufficiently to make modeling of counter current-bed reduction a realistic and useful study of process behavior. The authors have analyzed1"3 extensive laboratory

Jan 1, 1969

By H. W. Hardinge

Disregarding for the present the economic side of a new device, let us turn to that feature of the conical pebble-mill which is of interest from a scientific point of view, and consider the device as a puzzle in which the theories of the cylindrical type of mill have been increased. Many articles have been written on the theory of the tube-mill, and explanations have been made which do not explain ; but these have evolved suggestions of practice which have resulted in changes in the tube as to length, diameter, feed, discharge, speed of rotation, rotation on hollow trunnions, rotation on rings, and changes in the operation as to quantity and size of pebbles, charge of load above or below the axis, crushing by causing the larger pieces of the material of the charge to act as grinders, whether crushing is abrasive or impactive, etc. The practical worker in crushing. is first interested in the endeavor to reach an econonlic means of accomplishing a desired end; but the improvements in crushing-practice have been largely left to the manufacturer of machinery, who, as a rule, has little, if any, knowledge of the specific requirements— such as granulation, sizing for concentration without pulverizing the metals, instead of pulverizing the rock or gangue; the metals being the more friable, while the rock is tough and not so easily disintegrated. A reversal of this practice is the aim of sliming direct for cyanidation or pulverizing for cement, etc. In the ordinary cylindrical mill, having a diameter of 4 or

Jan 1, 1909

By MERLE HOWARD GUISE

WHEN I was a boy I walked into Fairbanks in 1905. I was but a soft chechako, and arrived with blisters covering my feet, as a result of "mushing" the 400-mile trail on foot. Because of them, the display windows of the trading posts were first to catch my eye-dog and horse collars, harness and sled parts! And because of my enthusiasm for things adventurous, I looked long upon the prospectors' gold pans, shovels, rifles, camp equipment, and what not. Today those windows are filled with motor car accessories, tires and repair parts; yes, even thermos bottles and vacuum cleaners! There were many chance meetings with little parties of prospectors in my youth, and it always set my blood to tingling. Sometimes it was a 70-year-old sun-baked son of the Arizona desert, wrangling his stubborn, faithful jenny away from some outfitting store, at others a shovel-ended poling b0at in northern Canada, \vith the partners and the dogs towing upstream along the bank, or an old sourdough, with tug-rope around neck and hand on the spruce sapling gee-pole, mushing along behind his two or three old, plodding malamutes, dragging a little Yukon sled piled high with rusty sheet-iron stove, pick and shovel, cross-cut saw and axe, rifle, bales of dog salmon, and other paraphernalia. These meetings envisioned the panning of old creek beds and draws in the search for as yet undiscovered pay-channels; they meant the toughest kind of work sinking a hole to bedrock in some far-away valley of promise; they suggested wood fires to thaw the frozen muck and gravel and crude windlass and hand-made tub to hoist the water and the mud; but loudest of all they spoke of Adventure.

Jan 1, 1929

By Frank C. Greene

Drilling for oil and gas in Missouri continued at a slightly lower rate than has been prevailing. A summary of operations for the past few years as compiled and published by the Missouri Geological Survey and Water Resources is as follows: Two oil pools are being developed in Cass County. Neither area has been drilled completely, and detailed descriptions will not be given at this time. In the Endicott pool in the southern part of T. 44 N., R. 33 W., oil is found in the Warrensburg sand, which is now considered to be the Big Lake sand of eastern Kansas. The top of the sand is about 125 ft. below the Herthalimestone. The best well is reported to have made 14 bbl. per day for the first four days. The oil is 30" to 32' BB. gravity. This is the only pool in the state, aside from the older areas on the east and west edges of Lees Summit, Jackson County, that is producing oil from the Warrensburg sand. Drilling continues in the Knoche pool in the central part of T. 46 N., R. 33 W., where the oil is found in the Squirrel sand. The oil produced by both these pools is sold by truck in Kansas City.

Jan 1, 1937

By J. A. Bownocker

THE Pittsburgh is one of the most important coal beds of Ohio. It was the last of the great coal beds to be worked extensively in that State, has the largest area of virgin coal, and will in all probability be the last of the great deposits to be exhausted. The line of outcrop sweeps nearly southwest in a sinuous line from Jefferson County on the north to Lawrence on the south, a distance on a bee-line of at least 150 miles. (Fig. 1.) The maximum width of the area under which this coal is due is about 55 miles, but in most places it is less than half that and in the two southern counties it is in places restricted to narrow ridges. Here as elsewhere the Pittsburgh coal forms the base of the Monongahela formation, and the following section taken from Condit shows the position of this bed with reference to certain higher ones in this field:1 FEET INCHES Shales and thin beds of limestone 24 5 Coal, Meigs Creek, No. 9 4 0 Shale, sandy 11 0 Coal 0 8 Shale, clayey 6 0 Coal, Lower Meigs Creek 3 0 Shales,clayey 2 0 Limestones and thin layers of clay 25 0 Unseen 11 0 Coal, Redstone 2 0 Unseen 11 0 Coal, Pittsburgh, No. 8 8 0 Clay 5 0 Limestone 4 0 From the standpoint of continuity the Pittsburgh coal of Ohio must be classed with the patchy type. As the map shows, the coal is thin or wanting along many miles of the line of outcrop. The large deposits form three separate areas, which, in order of their importance, are generally known as (1) the Belmont, (2) the Federal Creek, and (3) the Gallia fields.

Jan 10, 1926

By G. F. Dillion, A. F. Armington

THE present method for the ultrapurification of boron involves the formation, distillation, and decomposition of boron tribromide.' However, the boron tribromide prepared contains several impurities in the ppm range, even after distillation. Some of these impurities, notably carbon, can be reduced after decomposition by zone refining. In this study, a comparison of the purity of boron tribromide at various formation temperatures is presented. The apparatus employed consisted of a bromine flask connected to a 22 mm ID horizontal quartz reaction tube packed with amorphous boron powder, which was in turn connected to a receiving flask cooled with an ice bath. Argon was used as a carrier gas. The approximate rate of passage of bromine to the reaction tube was 25 g per hr. The reaction was first investigated at several temperatures in order to determine the lowest temperature necessary to produce a colorless product which was assumed to be an indication of complete reaction of the bromine. The lowest temperature found in this study was 420oC. The amount of impurities found in the boron tribromide at various formation temperatures is shown in Table I. The data presented are emission spectroscopic results of boric oxide produced by the hydrolysis of 2 to 3 g of boron tribromide in 10 ml of distilled water. After hydrolysis, the samples were dried several hours on a hot plate. Assuming equilibrium conditions in the reactor, one can make approximate thermodynamic calculations estimatling the completeness of reaction of bromine with boron and its impurities at various temperatures. Data for these calculations were taken from Rossini,3 and must be taken as approximations since the T?S factor was not included in the calculations. The results of such calculations indicate that, with the exception of carbon bromina-tion, all impurities would react almost to completeness (> 99 pet) at all temperatures between 400" and 900oC. In the case of carbon, which cannot be accurately analyzed spectroscopically, it is estimated that only about one sixth as much carbon tetrabromide would be formed at 400" than at 900°C. Since some marked reductions in impurity content were observed at the lower reaction temperature which would not be predicted by thermo-

Jan 1, 1962

By D. W. Hutchinson, W. W. Wen, A. A. Terchick, J. C. Anderson

It is estimated that approximately 3% of the raw coal processed today in coal preparation plants throughout the nation will ultimately report to slurry-tailing disposal (Anderson, 1975). The usual disposal method is to pump refuse slurry containing - 48 mesh (300 pm) refuse into dams or impoundments constructed of coarse refuse. The failure of an impoundment at Buffalo Creek, Saunders, WV (Anon., 1972) resulted in an evaluation of refuse disposal methods by various regulatory agencies as well as coal producers. The result of this evaluation was the promulgation of federal regulations dealing with the construction, operation, and final abandonment of coal refuse disposal area. As a consequence of these regulations, the use of the landfill/impoundment method of disposal became in some cases economically unfeasible or technically impossible. US Steel has studied a number of alternative methods of refuse disposal. During an investigation of mechanical dewatering with a pressure filter, portland cement was added to the slurry to solidify the filter cake. Because of the success of the cement addition, it was decided to study the stabilization of fine coal refuse slurry through use of cement-type additives. The goal of the investigation is to develop a process that will use cement-type additives to solidify the refuse slurry into a form that can be handled and stacked with the coarse refuse, thus eliminating the need for slurry impoundments.

Jan 1, 1982

By J. G. Bartram

Jan 1, 1934

By P. W. Neurath, R. E. Waite

INFORMATION is available on the effect of stress on permeability, coercive force, and hysteresis for a variety of materials' but for the technically important grain-oriented 3 pct Si-Fe' the stress effects are not adequately covered in the literature; in addition, most of the stress data do not permit estimation of what would happen to the 60 cycle watt losses of the material under stress. Direct measurement of these effects therefore has been made and appears to be of considerable theoretical as well as practical interest. Losses were measured on the central 25 cm portion of 40~3~0.035 cm samples which could be stressed in a small tensile machine built for this purpose. Under tension the following effects, illustrated in the figures by a particular example, were observed: 1—"Unstrained" material of commercially acceptable loss level shows no change or a small increase in loss at low elastic stresses. For the sample shown in the figures, this is illustrated during the initial run, where a 7 pct increase is observed (Fig. 1). 2—There is no additional change in loss when the sample is further strained up to the elastic limit (Fig. 1). Within that limit the loss-stress curve is reversible. This is not illustrated in Fig. 1. 3—Even in the plastic range only small increases in loss are observed as long as the sample is kept under stress (Fig. 2, point N); often no increase can be observed (Fig. 1). 4—A large increase in watt losses is observed after removal of the stress subsequent to plastic deformation (Figs. 1 and 2). 5—All, or nearly all, of the foregoing increase in loss due to plastic deformation can be eliminated by a reapplication of tensile stress but returns upon removal of this stress. This is illustrated in the third run (Fig. 3). This run remains within the elastic limit and shows the reversibility of the stress-loss curve under this condition. These findings have been confirmed on large Samples (approximately 200~10~0.035 cm and larger) except that under 1 no initial increase in loss was ever observed on these. The accuracy of the watt loss measurements is of the order of 1 pct. Neither bending of the sample in the tensioning device nor a redistribution of flux along the width of the sample accounts for these results. They therefore must be explained on the basis of either a change in the domain configuration due to stress or a change in the domain wall mobility. Acknowledgment The assistance of Mr. Robert L. TenBroeck with the instrumentation is gratefully acknowledged.

Jan 1, 1956

By Wm. E. Milligan

LEAD stocks at the beginning of 1943 were comfortable when compared with those of other base metals such as copper, zinc and tin. This situation was early recognized by W.P.B. and other Governmental agencies and every effort was made to encourage the substitution of lead for these latter metals in all essential uses. Despite this apparently healthy condition, lead was not denied participation in the various measures inaugurated by the Government to relieve metal shortages. Thus in the Mexican trade agreement, effective Jan. 20, the tariff on two important classes of lead importss was halved. Similarly, in the setting up of B quota premiums, a B base was allotted to lead, with all pro¬duction above this figure receiving an additional payment of 2.75c. per lb., or a total payment of 11.75c. per lb. At about the same time it was announced that all quota transactions would be based upon the lead content as shown by the smelter settlement sheets. This basis was 86 percent of the lead content for all ores shipped to custom milling plants and 95 per cent for ores and concentrates shipped to custom smelting plants. The importance of this action can be appreciated when in the Coeur d'Alene it was estimated as equivalent to a 5 per cent increase compared to the previous base.

Jan 1, 1944

By Harlan A. Walker

Rock-drill steel has an important bearing on costs in many mining operations, both directly and indirectly. Direct factors include such items as shop expense, steel consumed per ton of ore produced, cost of distribution and the dust hazard. The latter, although no specific amount may be assigned to it, is an ever-present problem, and is receiving increased attention as the science of mining progresses. Indirectly drill-steel performance affects consumption of compressed air, maintenance of drills and drilling speed. The latter, in turn, increases or retards the tempo of mining and development. These factors, while not all inclusive, are preponderant in their importance. Thus it is evident that in an extensive operation drill-steel expense may run to many thousands of dollars and that thoughtful research leading toward more efficient practice is warranted. Experimental Work During the late spring of 1939, experiments were undertaken at Homestake in reducing changes in drill-steel gauge from ? in. to 1/16 in. In drifts and crosscut headings mounted machines were set up and holes were drilled with ?-in. bit-gauge changes and other holes a few inches

Jan 1, 1940

By Harlan A. Walker

Rock-drill steel has an important bearing on costs in many mining operations, both directly and indirectly. Direct factors include such items as shop expense, steel consumed per ton of ore produced, cost of distribution and the dust hazard. The latter, although no specific amount may be assigned to it, is an ever-present problem, and is receiving increased attention as the science of mining progresses. Indirectly drill-steel performance affects consumption of compressed air, maintenance of drills and drilling speed. The latter, in turn, increases or retards the tempo of mining and development. These factors, while not all inclusive, are preponderant in their importance. Thus it is evident that in an extensive operation drill-steel expense may run to many thousands of dollars and that thoughtful research leading toward more efficient practice is warranted. Experimental Work During the late spring of 1939, experiments were undertaken at Homestake in reducing changes in drill-steel gauge from ? in. to 1/16 in. In drifts and crosscut headings mounted machines were set up and holes were drilled with ?-in. bit-gauge changes and other holes a few inches

Jan 1, 1940

By Harold M. Feder, Robert V. Schablaske, Irving Johnson, Ewald Veleckis

The stoichiometry, structure, and stability of the internzediate phases formed between zinc and some of the rare earth (RE) metals were systematically exarnined by means of a recording effusion balance and X-ray diffraction analyses. In the La-, Ce-, PY-, Nd-, and Y-Zu systems, at or below about 600 C, the following sequences of phases (REZnx) were found: La, x = 1, 2, 4.0, 5.25, 7.3, 17/2, 11, and 13.0;' Ce, x = 1, 2, 3, 11/3, 4.3, 5.25, 7.0, 17/2,* and 11; Pr,x = 1,2, 3, 11/3 ,* 4.3, 5.3(?), 7.0, 17/2,* and 11; Nd,x = 1,2, 3,* 11/3,* 4.3, 6.5, 8.5,* and 11; Y,x = 1,2,3, 11/3, 4.5, 5.0, 17/2,* and 12.* The structure types of all these phases were classified. In addition, lattice parameters were obtained for the first time for the pluses denoted by asterisks. In the absence of de tectable valency or electronegativity effects the systesnatic trends in the results have been ascribed to the effects of' the lanthanide contraction. For example, the maximum number of zinc atoms in the coordination polyhedron surrounding the RE atom decreases from twenty-four to twenty-two to twenty as the size of the RE atom decreases. THE structures and compositions of a great many intermetallic phases (e.g., the Laves phases) are known to be based primarily, but not exclusively, on the space-filling efficiency of various modes of packing together atoms of different sizes. The valencies and electronegativities of the constituent atoms are, however, also influential. In extreme cases hypothetical intermetallic phases which fulfill the efficient spacefilling requirements may not be present in the constitutional diagram because of thermodynamic instability brought about by the operation of valency or electronegativity factors. Hence, for a detailed study of the influence of atomic size on alloy structure and composition, it would be desirable to minimize variations of valency and electronegativity. The intermetallic phases formed by the rave earths (RE) with some common partner offer an excellent opportunity for isolating the effects of size from those of valency and electronegativity. The rare earths exhibit a large, but smooth, decrease in size (the lanthanide contraction) in the series from lanthanum to lutetium when inter comparison is made for a common valence state, e.g., isolated atoms or trivalent ions. The elements yttrium and scandium are frequently included as pseudo rare earths; their sizes place them in the vicinity of dysprosium and lutetium, respectively. The electronegativities of RE elements vary by less than 10 pet. The trivalent state is the most common; however, the well-known tendency of cerium, praseodymium, and terbium to achieve higher valencies, and of samarium, europium, and ytterbium to seek lower valencies, requires that caution be exercised in the assumption of equal valencies. In the present study the existence, constitution, and structure of each of the numerous intermediate phases formed by zinc with lanthanum, cerium, praseodymium, neodymium, or yttrium were examined systematically and in detail. The investigation was conducted by a recording effusion balance technique and by X-ray diffraction analysis. The results enrich our knowledge of the phase diagrams of these systems. In addition, they present some clear-cut evidences of the operation of the size factor alone. EXPERIMENTAL PROCEDURE Apparatus. The mode of operation of the recording effusion balance and its application to phase studies have been discussed in detail elsewhere.' In this work, an effusion cell containing a finely divided alloy was suspended within an evacuated tube from the beam of an analytical balance. The tube was immersed in a massive molten salt bath whose temperature was controlled to within 0.5o C during each experiment. The loss in weight of the alloy owing to effusion of zinc* was continuously recorded. Two effusion cells, 1/2 in. diam by 1 in. high, were machined from tantalum rods. Two orifices were drilled laterally into the walls of each cell. The orifice areas were determined by calibration with pure zinc: cell A had a total orifice area of 6.5 x 10-41 sq cm, and cell B an orifice area of 9.8 x 10-3 sq cm. By appropriate choices of orifice area and temperature the wide range of volatilities from pure zinc to pure rare earth metal could be investigated. X-ray diffraction powder photographs were made at room temperature with a 114.6-mm Debye-Scherrer camera with both filtered CuKa radiation and filtered CrKa radiation. Lattice parameters were refined by a computer-programmed least-squares analytical treatment which incorporated appropriate extrapolation techniques.2 Frequent use was also made of a special computer program3 designed to generate a powder pattern from an assumed structure in order to verify structural assignments. Materials. Lanthanum, neodymium, and yttrium were purchased from the Lunex Co., cerium from the Cerium Metals Corp., and praseodymium from the St.

Jan 1, 1968

By Stanley F. French

ELECTRICAL power and distribution for the sulphide ore plant is an addition and extension of the existing power system which has served the oxide reduction plant since its inception in 1914. The power plant is located at Tocopilla on the west coast of Chile, some 90 miles from Chuquicamata. A brief description of this plant and the existing transmission system is necessary to an understanding of the problems involved in the provision for the sulphide plant load. Originally the Tocopilla power plant consisted of four Escher Wyss turbines driving Siemens Schuckert generators, each rated 10,000 kw. At various times, units of 10,000 and 20,000 kw were added, all of which operated at 215 psi and 600°F at throttle. In order to improve the economy of the station, a Topping unit was installed in 1938 together with a high-pressure steam generator of 360,000 lb per hr capacity. This unit is rated at 11,000 kw and was designed for 750 psi, 880°F. The exhaust from this turbine passes to the low pressure station header for operation of part of the low pressure turbines. Total kw generated by the high pressure boiler, topping turbine and associated low pressure turbines totals 33,000 kw and the total station capacity is 113,000 kw. This installation proved one of the most successful of its kind, operating almost continuously. The original plant was of German design and consequently European characteristics were incorporated into the system, the frequency being 50 cycles and voltages of 500, 5000 and 100,000 were used for low, generator, and transmission voltages,

Jan 1, 1952