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By Eugene F. Broome, Hugh A. Walls

A diffusion measurement technique based on a shear cell comprised of only two segments is described. The diffusion boundary value problem for the finite capillary geometry is solved in general for any arbitrary initial concentration profile and is subsequently specialized for the modified shear cell problem. Effects of convection and mixing at the shear interface were found to be negligible. Mercury self-diffusion coefficients were determined from -25° to 252°C. These data are in good agreement with those found by Meyer. ALTHOUGH diffusion in liquid metals has been of interest for over two centuries, the need for measurement techniques of improved accuracy and precision has become increasingly apparent as additional data have been obtained and theory has become more refined. These conditions reflect the experimental difficulties inherent in liquid diffusion measurements, in which transport by other processes, such as convection, tends to mask the diffusive transport. Frequently the disagreement between several theoretical predictions is less than that found between different sets of data obtained for a system. Moreover, as has been shown by Nachtrieb,1 diffusion data are needed over much larger temperature ranges if the functional dependence on temperature is to be known. Thus, improved techniques must be devised if experimental data are to augment fundamental understanding of the liquid state and to meet technological needs. The available techniques have been discussed elsewhere.' Of these, only the capillary-reservoir, long capillary, and shear cell techniques will be discussed briefly in terms of experimental advantages and disadvantages. These methods served to establish design criteria for the modified shear cell described here. The capillary-reservoir technique of Anderson and saddington3 has been the most widely used method in recent years. The method offers experimental simplicity relative to other methods and has been employed for high-temperature measurements. Moreover, the mathematical relationship between the measured concentration ratio and the diffusion coefficient is such that smaller values of the ratio are achieved for a specified diffusion time relative to other methods. The amplified errors between the concentration ratio and the calculated diffusion coefficient are diminished at lower values of the ratio.' The method also permits multiple determination by the simultaneous use of several capillaries. Disadvantages of the capillary-reservoir method are primarily associated with the hydrodynamic ef- fects of convection and of placing the capillary in the reservoir. These effects are most pronounced in the region near the open end of the capillary and produce an ill-defined boundary condition between the capillary and the reservoir. Such effects are not amenable to experimental or mathematical correction2 (although this has been suggested4). The long-capillary method of Careri, Paoletti, et al.5-10 involves filling one half of a small capillary tube of 150 to 200 mm total length with material of one composition or radioactivity and the other half with the second part of the diffusion couple. This arrangement eliminates the adverse hydrodynamic effects associated with the capillary-reservoir technique; however, certain other experimental difficulties are encountered in this method. The more significant of these difficulties involve the melting, expansion, contraction, and solidification of the diffusion system. The dependence in some cases of the diffusion coefficient on the capillary diameter noted by Careri et a1.7 (termed the "wall effect") has been alternatively explained by Nachtriebl as a convection effect during solidification. In mutual diffusion measurements, the convection problems associated with melting and solidification are increased because of the differences in melting points and in expansion coefficients between the halves of the diffusion couple. However, the errors caused by convection effects within this method are usually less than those in the capillary-reservoir method. Furthermore, the concentration profile needed to determine concentration-dependent diffusion coefficients by the Boltzmann-Matano analysis can be obtained from this method. Of the previous attempts to use shear cells, only the cell used by Nachtrieb and Petit11,12 appears to have yielded good data. They reduced the mechanical complexity of the conventional shear cell by using a cell comprised of only four segments. Three of these segments were filled with ordinary mercury and the fourth with radioisotopic mercury in their determination of mercury self-diffusion coefficients. The average concentration (radioactivity) was determined in each segment following a period of isothermal diffusion. These concentration values were fitted to concentration profiles obtained from the Stefan-Kawalki tables, and the diffusion coefficients were evaluated. Thus, although the number of cell segments is reduced in their method, some information about the concentration profile can be obtained in terms of the Stefan-Kawalki analysis. Moreover, their cell is suitable for measurement of diffusion coefficients at elevated pressure, as they successfully demonstrated with mercury. Consideration of the design and experimental features of the methods discussed above suggested several criteria for the new cell: 1) a ''total" capillary system, as opposed to a capillary-reservoir system, should reduce adverse convection effects; 2) such a capillary system should avoid the problems en-

Jan 1, 1969

By T. A. El-Bassyouni, Paul Gordon

Grain-gvowth data in zone-refined aluminum and in dilute alloys of copper with this aluminum have been obtained. The amounts of copper added were from 4 to 400 at. ppm. It was found that in both the unalloyed aluminum and the alloys grain growth was characterized by a high value of n in the isothermal growth equation 6n = Kt The inadvertent presence of 1 at. ppm Fe in the alloys was found to he more potent in slowing growth than the purposely added copper. Possible rationalizations of these observations and their general relevance to the theoretical use of gvain-grozvth data have been discussed. Grain growth data of Winegard and his co-workers' on zone-refined tin and dilute tin alloys were analyzed with some success2 in terms of approximate theoretical equations for boundary migration.2-4 In view of this success, experiments were carried out in an effort to obtain similar data on zone-refined aluminum and on dilute copper-in-aluminum alloys. The results obtained were anomalous in several respects and could not be used to test theory. A discussion of these anomalies is presented here; they have been attributed to impurity effects and serve to emphasize the sensitivity of grain growth in general—and the particularly high sensitivity in aluminum—to impurities. The resulting difficulties in the theoretical use of grain-growth data are also discussed. EXPERIMENTAL DETAILS An aluminum bar was zone-refined and leveled by methods similar to those described previously.' The degree of purity obtained is indicated in Table The data in Table I were determined by mass-spectrographic methods through the courtesy of Mr. Thomas A. Johnson of AIAG Metals, Inc.* Three dilute copper alloys with this aluminum were prepared also by methods described previously.' The alloys contained nominally 4, 40, and 400 at. ppm of Cu, respectively (0.001, 0.01, and 0.1 wt pct). Each material was fabricated by swaging and rolling into a round bar about 1/4 in. in diameter with an annealed penultimate grain size of approximately 0.003 to 0.007 cm. In order to minimize preferred orientation the fabrication was carried out in several steps, each consisting of a reduction of about 40 pct followed by a recrystallization anneal. Annealing temperatures for the grain-growth studies were attained by the use of boiling liquids up to 213°C and molten metal baths at higher temperatures. Temperatures were controlled to within 1°C. Samples for measurements were cylinders about 3/4 in. long and 1/4 in. in diameter cut from the fabricated rods. In the interests of sample economy a single sample was used for the grain-growth measurements at each temperature. Each sample was, thus, annealed for several successive periods of time, the grain size being measured at each annealing period on a transverse surface exposed by

Jan 1, 1965

By Coolbaugh, Franklin

CRUSHING of Climax mine-run ore is carried out in two plants: No. 1 plant (flowsheet in Fig. 1) has a capacity of approximately 5000 tons per day. It is used as a stand-by except when maximum production is required. No. 2 plant (Fig. 2) has a top capacity of approximately 17,000 tons per day. The No. 2 crusher is more efficient to operate on reduced tonnages regardless of the wide variation in peak capacities. The system of crushing is similar in both plants: Mine ore, of a size which can be drawn through 48 by 96-in. slusher openings underground, is dumped into the crusher bins from ten-ton mine cars and fed into 48 by 60-in. Buchanan jaw crushers by means of chutes and Ross chain feeders. The jaw crushers are set to discharge at approximately 9-in. size. Jaw crusher discharge is conveyed to 7-ft. Symons standard cone crushers where it is broken to minus-2-in. size,

Jan 1, 1946

By Ellsworth Daggett

The Berlin gold-quartz mine is situated in Nye county, Nevada, on the west flank of the Shoshone range, about 40 miles south and 30 miles west from the town of Austin, the county-seat of Lander county. The distance from Austin is about 60 miles by stage-road. The outcrop of the vein, at the top of the incline-shaft, is situated just at the base of the mountain proper, almost exactly at the intersection of the mountain-side with the gravelly bench that slopes for about three-quarters of a mile to the flatter sage-brush plain, or desert valley, below. The vein itself consists almost entirely of quartz, with perhaps 2 per cent. of sulphide of iron, copper, lead, zinc and antimony, and perhaps a trace of some of the compounds of tellurium with gold and silver, although none of the latter have been as yet positively identified. The relative proportion, by weight, of silver and gold in the ores, varies in different parts of the vein, from 12 silver for 1 of gold, to 7 silver for 1 of gold. The quartz vein-filling is usually frozen fast to the walls, and is very hard and compact, seldom showing the friable, fissured, or shelly structure often to be found in quartz-veins. Comparatively little evidence of relative motion of one wall of the vein upon the other is to be found—a fact indicating that during the formation of the vein, and prior to the extensive movements herein described, little disturbance had taken place. No evidence whatever of metasomatic origin has been observed. On the other hand, occasional occurrences of comby structure, in which the axes of the quartz-crystals are at right angles to the plane of the vein, rather indicate deposition from solution in a pre-existing fissure. Spurs, or branches, and small parallel veins, while not en-

Jan 1, 1908

By B. M. Larsen, T. E. Brower

THIS discussion is based on statistical manipulation and evaluation of operating data from several commercial blast furnaces which include rather wide variations in practice. We are concerned here mainly with the effect of manganese on sulphur elimination under operating conditions in commercial blast furnaces, but this effect can be outlined more clearly by including certain other variables such as silicon in iron and slag basicity, which are all in part interrelated. Real progress in understanding all of the smelting-zone reactions in this process requires more laboratory studies of slag-metal melts similar to those in the blast furnace, with careful control of oxygen pressure. Such experimental work is very difficult, however, and in the meantime, with the present scarcity of more fundamental data, such statistical trends and correlations as can be obtained from commercial furnace operating records may help in choosing laboratory test conditions as well as adding to our knowledge of operating procedures. We do not know just why the furnace data are apparently so irregular that statistical treatment of large numbers is needed to obtain accurate trends. It is partly caused, no doubt, by the many simultaneous variables present, but there are perhaps also such factors as: (I) the con- tinual swings up and down so characteristic of the process; (2) difficulty of accurate sampling of co-existing phases, as well as (3) the presence of both equilibrium and rate factors as a result of the fast driving of the process. In desulphurization, for example, the flow of thin layers of slag and metal over solid coke surfaces, plus the contact between droplets of iron falling through the slag layer in the hearth, would lead one to expect a close approach to equilibrium. On the other hand, most of the critical part of sulphur removal may occur in a short time and distance below the tuyeres with perhaps an accompanying decrease in oxygen pressure and the concurrent reduction of much of the silicon and manganese, so its degree of approach to equilibrium may be quite variable. Probable Chemistry of Desulphurization Since there is little evidence that sulphur atoms in the iron solution are aasociated to any appreciable extent in molecules such as MnS, the transfer from slag to metal and back again can be written:* (FeS) ? [FeS], [I] hence the following reactions seem most probable in the slag phase, (FeS) + (CaO) ? (CaS) + (FeO), [2] and, (FeS) + (MnO) ? (MnS) + (FeO). 131

Jan 1, 1949

By B. M. Larsen, T. E. Brower

THIS discussion is based on statistical manipulation and evaluation of operating data from several commercial blast furnaces which include rather wide variations in practice. We are concerned here mainly with the effect of manganese on sulphur elimination under operating conditions in commercial blast furnaces, but this effect can be outlined more clearly by including certain other variables such as silicon in iron and slag basicity, which are all in part interrelated. Real progress in understanding all of the smelting-zone reactions in this process requires more laboratory studies of slag-metal melts similar to those in the blast furnace, with careful control of oxygen pressure. Such experimental work is very difficult, however, and in the meantime, with the present scarcity of more fundamental data, such statistical trends and correlations as can be obtained from commercial furnace operating records may help in choosing laboratory test conditions as well as adding to our knowledge of operating procedures. We do not know just why the furnace data are apparently so irregular that statistical treatment of large numbers is needed to obtain accurate trends. It is partly caused, no doubt, by the many simultaneous variables present, but there are perhaps also such factors as: (I) the con- tinual swings up and down so characteristic of the process; (2) difficulty of accurate sampling of co-existing phases, as well as (3) the presence of both equilibrium and rate factors as a result of the fast driving of the process. In desulphurization, for example, the flow of thin layers of slag and metal over solid coke surfaces, plus the contact between droplets of iron falling through the slag layer in the hearth, would lead one to expect a close approach to equilibrium. On the other hand, most of the critical part of sulphur removal may occur in a short time and distance below the tuyeres with perhaps an accompanying decrease in oxygen pressure and the concurrent reduction of much of the silicon and manganese, so its degree of approach to equilibrium may be quite variable. Probable Chemistry of Desulphurization Since there is little evidence that sulphur atoms in the iron solution are aasociated to any appreciable extent in molecules such as MnS, the transfer from slag to metal and back again can be written:* (FeS) ? [FeS], [I] hence the following reactions seem most probable in the slag phase, (FeS) + (CaO) ? (CaS) + (FeO), [2] and, (FeS) + (MnO) ? (MnS) + (FeO). 131

Jan 1, 1949

By R. J. Lipp, I. Iwasaki, R. H. Heerema

The presence of calcium ion in iron ore pulps that are upgraded by selective desliming can result in indiscriminate flocculation of both iron oxide and siliceous gangue slimes. In order to overcome this adverse effect, deflocculation by three complexing agents, namely ethylenediaminetetzaacetate (EDTA), sodium tripolyphosphate (STPP), and sodium hexametaphosphate (SHMP), was investigated. The precipitates and complexes of these agents with calcium ion were characterized by potentiometric and conductometric titrations, and the surface properties of quartz and goethite were studied in the presence of calcium ion and of the complexing agents by means of streaming potential measurements and flotation tests. The results were then correlated with selective flocculation tests on an artificial mixture of quartz and goethite. EDTA markedly improved the selectivity of flocculation when added in near stoichiometric amounts, whereas STPP was less effective and SHMP was totally ineffective due to strong, indiscriminate dispersion. Remanent calcium polyphosphates on the goethite surface interfered with the adsorption of starch flocculant.

Jan 1, 1983

By E. W. Cawthorne, R. I. Jaffee, C. M. Craighead

SOLUTION of a solid metal or alloy in a molten metal bath is used daily in melting operations, extractive metallurgical processes, and in brazing. It is generally recognized that temperature, time, agitation, and the composition of the solute metal and the solvent bath all affect solution rate. However, there is little information available in the literature on the kinetics of the process or the relative effect that these variables have on solution rate. In connection with an aluminum brazing study, data on the solution of aluminum in an A1-Si* bath to promote rapid solidification. The chemical analyses were made on drillings taken from the cast plates. The results of this work are listed in Table I. The thermal-analysis data were obtained on 200 gram samples cooled at approximately 1.5" per min. A calibrated chromel-alumel couple was used. The thermal arrests were recorded autographically on a General Electric photoelectric potentiometer recorder. The instrument was calibrated to 22.5 pct. The thermal emf was bucked with a Leeds and Northrup semiprecision potentiometer so that 1 mv represented the full scale of the GE recorder. Referring to Table I, it will be noted that the analytical results tend to be lower than the intended compositions by about 0.3 pct Si in the higher ranges. In view of the known difficulties in obtaining accurate silicon determinations by wet analysis when the silicon content is high and in view of the care that was employed in weighing and preparing the alloys, the intended compositions are believed to be more accurate than the analyses. Furthermore, when the thermal-arrest data are plotted against the intended compositions, a smooth curve is obtained, as shown in Fig. 1. This is not the case when the data are plotted against the analytical results. It will be noted from Table I that the 12.5 pct Si alloy (melt 4) showed a primary arrest at 577.6"C and the eutectic at 576.l°C. The metallographic examination of this chill-cast plate sample showed a small amount of primary silicon. These results, Fig. 1, place the eutectic at slightly less than 12.5 pct Si and are in rather good agreement with the unpublished Hanford data. In all of the subsequent work, the composition of the A1-Si dipping baths was determined by thermal analysis (spread between the primary arrest and the eutectic temperature) employing 12.5 pct Si and 577.2 °C as the composition and temperature of the eutectic. Material Preparation and Selection of the Techniques: At the beginning of this work, it was anticipated that, owing to oxide film present on the surface of the aluminum, difficulty would be encountered in obtaining rapid uniform wetting of aluminum specimens dipped in the A1-Si bath. The following etchants were investigated as possible methods of providing a thin uniform oxide film on the specimen surface: 1—phosphoric acid (H³O4), 2—fluoboric acid (HBFI), 3—sodium hydroxide (NaOH), and 4—hydrofluoric acid (HF). Tests with sheet .specimens (2x½x0.06 in.) of 2s aluminum prepared with these etchants indicated that the fast uniform wetting required for this work could not be obtained if any oxide film existed on the specimen surface. Tests were then conducted by dipping similar specimens etched in 5 pct NaOH and given a thin

Jan 1, 1956

By John Freeman

THIS paper relates entirely to the casting of brass under fluid pressure in steel dies. Die castings of metals and alloys of low melting point have been available for many years but the development of brass die castings has been relatively recent, occurring within the past five years. The successful development of brass die castings has resulted from the availability of alloy steels that would give satisfactory life as dies and the development of suitable die-casting machines. The melting point of copper is 1084° C. (1983° F.) and of a high brass about 900° C. (1652° F.), as compared to 327.5° C. (621.5° F.) for lead, 419.4° C. (786.7° F.) for zinc and 658.7° C. (1217.7° F.) for aluminum, temperatures that are indicative of the casting temperatures required for the various types of alloys, of which the melting points are somewhat lower than those of the pure metals.

Jan 1, 1935

By Shiou-Chuan Sun

THE fact that coals of different ranks and even of the same rank differ greatly in their amenability to froth flotation is well known. In recognition of the need for an explanation of this phenomenon, two hypotheses have been suggested. Wilkins1 reported that the floatability of coals increased with an increase of the carbon content or rank. This postulate is handicapped by the fact that bituminous coals that possess moderate carbon contents are actually more floatable than anthracite coals that have high carbon contents, as shown in columns 6 and 9 of Table I. Taggart and his associates' implied that the difference of floatability between bituminous and anthracite coal was caused by the variation of carbon-hydrogen ratio. This is not applicable to the relative floatability of other coals and carbons. For example, column 11 of Table I shows that the carbon-hydrogen ratios of low-floating lignitic coal and non-floating animal charcoal are not only smaller than the moderate-floating anthracite coal, but are also similar to the high-floating bituminous coal. Furthermore, according to this hypothesis, high temperature coke-A (464), Ceylon graphite (1238), and lamp-black (357), all possessing extremely high carbon-hydrogen ratios, should be less floatable than other substances having much lower carbon- hydrogen ratios such as high volatile-B bituminous coal (11.9 to 22), anthracite coal (35.7 to 60.5), lignitic coal (15.6 to 33.6), and charcoal (13 to 26.2). However the former group is actually more floatable than the latter group.

Jan 1, 1954

By D. Harker, E. Epremian

The constitution of the nickel-tungsten system has been studied by a number of investigators, the most recent of which are Ellinger and Sykes.1 On the basis of metallography, electrical resistivity and hardness measurements and some X ray diffraction work, they constructed a consitution diagram (Fig 1). Ellinger and Sykes report a0 for the alpha face-centered cubic phase (nickel saturated with tungsten) as 3.66?.‡ The gamma phase (tungsten saturated with nickel) is given as body-centered cubic, but no value of a. is recorded. At 43 pct tungsten by weight (approximately 20 at. pct) a beta phase is reported, but structure and lattice parameter are not known. Primarily on the basis of metallographic evidence, they conclude that beta is a new phase and rule out the possibility of formation of a superlattice since they- observe a new phase in the microstructure. Grube and Schlecht2 report an ordering reaction in a system similar to the Ni-W (Ni-Mo) and Harker3 has shown that NirMo forms a superlattice upon the pre-existing face-centered cubic lattice of the alpha phase. Elliniger arid Sykes observed a change in the diffraction pattern of a 4.3 pct W alloy upon aging and attributed it to the formation of a new phase. Thus, there appears to be some question as to the character of the beta phase reported by Ellinger and Sykes. The purpose of the present work is to determine precisely the structure and nature of the beta phase in the Ni-w system of X ray diffraction methods. Experimental Procedure One inch diameter ingots of 43.66 pct, 40.15 pct and 34.06 pct .tungsten by weight (19.8, 17.6 and 14.1 at. pct respectively) were melted and cast under vacuum from electrolytic nickel and pure wire filament grade tungsten. The ingots were soaked for 16 hr at 1300°C in a hydrogen atmosphere furnace, then swaged at this temperature and finally drawn to 0.020 in. diam wire. Some of the bar stock was retained in 1/2 in. diam rod for hardness and metallographic studies. Wire samples for diffraction work were sealed in evacuated quartz tubes and subjected to the various solution and aging heat treatments in a hydrogen furnace. X ray photograms were taken in a Debeye-Slierrer camera using copper K radiation filtered by nickel foil. Results X RAY DIFFRACTION The lattice parameters of the alpha and gamma phases at saturation were determined by an X ray photogram of the 19.8 at. pct W alloy after solution heat treatment at a temperature well within the alpha-gamma range above the peritectoid temperature (17 hr at 1150°C—oil quenched). The alpha phase was found to be face-centeted cubic with a. of 3.594 ± 0.001?, while the gamma phase was determined as body-centered cubic with a. of 3.158 ± 0.001?. Exactly the same phases and parameters were ohtained with the 17.6 at. pct W alloy for the same solution heat treatment. Thorough analysis was made of an X ray photogram of a 19.8 at. pct alloy sample in the quenched and aged condition (solution treated 1T hr at

Jan 1, 1950

By R. J. Evans

THE Combined Metals Reduction Co.'s plant is at Bauer, Utah. It was built primarily to treat ore from the Combined Metals mine at Pioche, Nevada. Shortly after its completion, the company acquired the old Honerine mine, and ores from this mine, as well as custom ores from widely scattered districts, are now being treated at the Bauer plant. PIOCHE ORE The Pioche ore, which comprises about 50 per cent. of the mill feed, occurs as a replacement of an impure thin-bedded limestone. The lime beddings are separated by thin layers of micaceous shale containing appreciable quantities of sericite and graphite. The ore is an exceptionally fine-grained, dense mixture of minerals and gangue, assaying approximately 0.03 oz. gold, 7.2 oz. silver, 7 per cent. lead, 15 per cent. zinc, 16 per cent. iron, 29 per cent. insoluble and 1.5 per cent. lime. Of the total lead 7 per cent. is in the form of sulfate and carbonate. Approximately 10 per cent. of the ore consists of chert nodules impregnated with barren pyrite; the nodules average 0.8 mm. in size, and are extremely hard, compared with the other constituents of the ore. Microscopic examination of Pioche ore ground to 80 per cent. minus 150 mesh shows pyrite, sphalerite and galena still attached. EARLY ATTEMPTS AT ORE DRESSING Metallurgists, both professional and those working for private companies, have been more or less familiar with the Pioche ore since 1913; in fact, a total of 35 commercial and plant laboratories experimented with the ore between 1913 and 1921. The work during this period was decidedly negative, it being seemingly impossible to effect a satisfactory separation of the valuable minerals into marketable products. In 1913, it was recognized that fine grinding-that is, about minus 200 mesh-was required to liberate the minerals from one another, and from the gangue, but such fine grinding was not considered practicable at this time.

Jan 1, 1928

By H. E. Doerr

THE writer has been unable to find much information relative to tests made to determine the effect of forging on the specific density of steel. The opinion, however, among men engaged in the business, seems to he that forging greatly compresses or consolidates the steel. While such is doubtless the case with spongy or porous steel, the following experiments indicate that there can be little or no change in the density with steel initially free from cavities: Ten ingots of basic open-hearth steel cast as shown in Fig. 1 were used in the experiments. All the specimens were 0.53 carbon with all other elements the same, the analysis being determined from drillings taken midway between the center and outside of the upper end, as shown in Fig. 2. The specimens were selected from over one thousand ingots so that the tests could be comparative for the work done in forging only, but no two of the ingots were cast in the same heat. Each ingot remained in the mold approximately 30 min., when it was removed and air-cooled. About 12 hr. later, when the temperature had been reduced to approximately that of the surrounding atmosphere, the head was discarded and the ingot heated in an oil furnace to approximately 2250° F. (1235° C). Approximately 1 min. was required to forge under the steam hammier to 1 ¼ in. (31.75 mm.), rough diameter, as shown by the dotted lines in Fig. 2. All ingots were allowed to air-cool after forging. Cylinders ½ in. (17.7 mm.) in diameter and ½ in. high were then turned from the forged and unforged parts of the ingots and numbered. The ten pairs of specimens were submitted to Louis E. Endsley, Professor of Railway Mechanical Engineering, University of Pittsburgh; A. N. Talbot, Professor of Applied Mechanics, University of Illinois; L. Z. Slater, chief chemist, Scullin Steel Co., St. Louis, Mo. No in-formation was furnished as to which specimens were forged or unforged and each laboratory used the same specimens, submitting the average of three independent determinations, a tabulation of which is shown in the accompanying table in which the laboratories are designated by

Jan 1, 1919

E. P. Pfleider, University of Minnesota I would like to ask Bob Merrill whether he considers that horizontal concave curvature of a slope has any stabilizing effect, such as Jenike 1 suggested several years ago. R. H. Merrill, U. S. Bureau of Mines, Denver Federal Center The stabilizing effect is due to the restraint offered to radial movement by the curvature. We found in laboratory tests that if we constrained the rock with the same stresses as those measured in the pit then it would sustain a maximum stress about two or four times greater than when the same rock type was unconstrained. We are therefore definitely of the opinion that a constrained situation in a slope is favorable towards stability. G. A. Leonards, Purdue University I was interested in Mr. Lane's observations concerning the correspondence between rate of slide movement with rise of reservoir. Perhaps the most interesting feature is that the rate of movement at the time the rock slope failed was less than the rate at an earlier time when it did not fail. This is difficult to explain from current slope stability theory. K. S. Lane, U. S. Army Corps of Engineers I believe that reduced rate of movement is the result of the progressive type of failure, such as described by Patton and Deere. which occurs along the sliding surfaces. It is difficult to analytically define the progressive failure condition for inclusion in slope stability conditions, but its existence should be recognized in design. We should also realize that many apparently stable slopes undoubtedly contain overstressed regions. To design a slope with no overstressed region would be uneconomical and conservative. D. H. Deere I would pose the question-"What is the meaning of a factor of safety of one?" We were involved in the design of a large, irregularly shaped, underground cavity with an unsupported span of several hundreds of feet. Tests on rock specimens indicated a strength of 1300 lb per sq in. The RQD would have been between 90 to 100 percent indicating excellent structural continuity. In-situ stress determinations indicated an approximately hydrostatic state of stress at a level of 1400 lb per sq in. Calculation of stress concentrations at the walls indicated that the stresses there would be about 3000 to 4000 lb per sq in. Admittedly the rock is in a confined condition everywhere except at the very skin of the wall and the rock walls would thus on the average be somewhat stronger. Allowing for the effect of restraint the factor of safety was found to be less than 0.5 over a region several feet into the wall. Construction was started, using rockbolts only to support the walls. Failure around the immediate skin occurred after each

Jan 1, 1967

By C. H. Benedict

A 2000-ton ammonia leaching plant has been operated by the Calumet & Hecla Mining Co., at Lake Linden, Mich., continuously since February, 1917, except from April, 1921, to April, 1922, during the period of depression following the European war. A description of this plant has been published elsewhere.1 The present article describes the operation of the plant since 1917, together with the changes in the process that have been found to be advisable. In spite of the fact that this plant and that of the Kennecott Copper Co. are the only ones operating on a large scale, much experimental work is being done on ammonia leaching, as applied to oxidized ores, and it is to aid these and other investigators that this detailed account is given. For the benefit of those unfamiliar with the original article, the following short abstract is given, as an introduction to a more detailed account of the process and the reasons for present practice.

Jan 2, 1924

By W. R. Hibbard, J. D. Nisbet

The high temperature properties of Fe-Cr-Co-Ni base alloys and the effects of hardening element additions on these properties are rationalized on the basis of general principles of alloying. DURING the past few years the base elements in high temperature austenitic alloys have gradually been changed from iron-rich materials to nickel-rich, then to cobalt-rich and more recently to various iron, cobalt, and nickel combinations, all with an approximately constant chromium content of 20 pct. Concurrently, the hardening additions of the incongruous* elements, have been shifted from small amounts of a single element to various ratios of molybdenum, tungsten, columbium, carbon, titanium, and aluminum with the percentages of these constituents continually increasing. It has been known that the typical soft high temperature alloy (such as Inconel) consisted of face-centered cubic austenite, but the effect of varying the composition of the base elements, iron, chromium, nickel, and cobalt, has not been broadly analyzed. Therefore, it was reasoned that the first major problem in the understanding of the properties or the further development of high temperature alloys was to study systematically the effect of composition upon the mechanical properties of face-centered cubic Fe-Ni-Co-Cr austenitic solid solutions. The matrix of the strong high temperature alloys (such as Inconel X) is usually also a face-centered cubic solid solution of iron, nickel, chromium, and cobalt but with additional phases which can be generally classified as intermetallic compounds and carbides. It is usually observed that combinations of the hardening elements, tungsten, molybdenum, columbium, tantalum, titanium, aluminum, carbon, and others have been used in these strong high temperature alloys. Thus, it was reasoned that a second major problem in studying these alloys was to understand the effect on mechanical properties of adding

Jan 1, 1954

By J. M. Vonfeld, V. D. Hanson, W. K. Heinlein

TWO overfeed drum-type separators using a suspension of magnetite in water as the separating medium have been installed in the Champion No. 1 preparation plant of the Pittsburgh Coal Co., Division of the Pittsburgh Consolidation Coal Company. A simplified flow diagram of the Champion No. 1 coarse coal circuit is shown in Fig. 1. A railroad car rotary dump, capable of handling 20 cars per hr, discharges the coal into a hopper. Coal is fed from the hopper of the rotary dump to a 60-in. belt conveyor by two reciprocating pan-type feeders. The belt conveyor feeds the run of mine coal onto the main raw coal screen. The first deck is fitted with 3 in. round hole perforated plate which removes the 3x0-in. coal. The second deck of the screen is equipped with 6-in. lip screens which separate the remaining coal into +6 in. and 6x3 in. The +6 in. coal is transferred to a shaking picking table and then discharged onto the loading boom. The 6x3-in. coal is fed to the No. 2 dense medium vessel for cleaning. The clean coal from this unit flows to a vibrating screen where the medium is removed and the coal sized into 6x4 in. and 4x3 in. The 6x4-in. coal is transferred to the loading booms and the 4x3-in. is conveyed to the clean coal classifying screens to remove degradation. The 3x0-in. raw coal is blended in a system composed of three storage bins having a total capacity of 400 tons. From these bins the coal is fed onto a 48-in. flight conveyor by three reciprocating feeders. This flight conveyor delivers the coal to the Rheo plant. The 3x0-in. coal is then cleaned in two 48-in. Rheolaveur launders each equipped with two Rheo boxes. The first set of boxes removes a primary refuse and the second set produces a middling product which is recirculated in the launders. The cleaned coal and water overflows from the primary launders to two sizing and dewatering shaker screens where the water and - 3/8-in. coal are removed for further cleaning in the Rheo fine coal plant. The 3x3/8-in. clean coal is combined with the 4x3-in. coal from the No. 2 vessel, sized into 4x2 in., 2x1 1/4 in., and 11/4x3/8 in., then sent to the loading booms. The 3x0-in. refuse from the primary launders is normally fed to the No. 1 dense medium circuit, but any portion or all of this material can, as an alternate, be processed in the Rheo rewash launder. The primary refuse when fed to the dense medium circuit is screened into 3/8x0 which is cleaned in the fine coal plant and 3x3/8 for cleaning in the No. 1 vessel. The clean coal from this vessel is passed over a vibrating drainage and rinse screen, then sluiced to the rewash sizing shaker where it is dewatered and sized for loading. The installation of a pilot plant separating vessel using a suspension of magnetite in water was pro-

Jan 1, 1952

By Frederick J. McGarry, Fred Moavenzadeh

An experimental investigation of the thermal and mechanical responses of rock materials to laser radiation is described. Specifically, the following three topics have been studied in detail: 1. Temperature measurements on thin discs subjected to laser radiation. 2. Strain measurements on thin discs subjected to laser radiation. 3. Observation and evaluation of cracking and spalling phenomena in constrained and unconstrained thin discs respectively, subjected to laser radiation. In conjunction with the experimental work done, use was made of a heat flow analysis and a stress analysis program developed for this purpose. It was possible to theoretically predict the thermal and mechanical responses of a rock specimen to laser radiation and then compare them with experimental observations. Good correlations were obtained.

Jan 1, 1971

By Alfredo O. Del Campo

Copper concentrate smelting has been the subject of significant improvements during the last three decades. Several new processes are being successfully applied at industrial scale, and probably no new copper smelter will be built with the old-fashioned reverberatory furnace. However, because of financial reasons, the existing reverberatory furnaces, which smelt a significant part of the copper produced worldwide, are likely to last at least another decade. Some improvements have been introduced in reverberatory smelting practice, the best known being the use of oxyfuel burners. However, efforts to optimize the reverberatory furnace operation through automatic control have not been reported. The complex and semi-continuous nature of the process makes it dificult to find a suitable strategy for its automatic control. Many factors, like fuel economy, productivity, boiler capacity, refractory wear, converter slag return, copper losses in discard slag, etc. are interconnected. The chosen control strategy should take into account all these factors to achieve good economic results. A detailed discussion of these problems is presented.

Jan 1, 1984

OLIVIA'S recent revolution, by hindsight, seems to have been inevitable. The misery of the majority of the people, coupled with the economic crisis engendered by the refusal of the United States to meet Bolivian demands for a higher tin price, gave the National Revolutionary Movement party all the excuse it needed for overthrowing the government. Most of the mines in Bolivia are owned by three families. Precisely what it will mean to the United States is still a moot question. Argentina, with a mixture of Marxism, Fascism, and few twists created by the Perons, is in a position to grab off much of the tin we need. Because of the contingencies of geographical location, language and a natural simpatico, Argentina may be able to continue its efforts to oust the United States from its South American markets. Point Four aid was supposed to be given to Bolivia, but only for agriculture. Even this was entirely too slow. Mining, Bolivia's other major source of income was forgotten by the Washington planners. Primary aim of the new power will be to diminish its dependence on the world tin market. At a time when the free world is fighting a battle for control of metal, it stands a chance of losing an important source of supply. With the accent placed on agriculture and other industries, mining in Bolivia is certain to suffer. Argentina will be in a position to get the available supply of tin, make a strong ally in the world order of things, and add to its power play against the United States in South America. Ten labor groups have formed the Bolivian Central Workers Union. The first item on their list for immediate action is the nationalization of the mining and railroad industries. They also came out for agrarian revolution and diversification of industry. President Victor Paz Estenssoro has promised to appoint a committee for the investigation of nationalization of the mines. At least, this is indicative of a feeling for the need for caution.

Jan 1, 1952