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By L. F. Marek, G. W. King, A. Bogrow

The purpose of this paper is to present the data and some interpretation of the results of a laboratory study of the reduction of iron ore and the deposition of carbon from the reducing gas mixtures in such reductions. One major object of the study was to determine the effect of gas pressures on these chemical processes. Effort was made to approximate the conditions of temperature, gas composition, linear and mass gas velocities, pressure range, and extent of reduction prevailing in commercial blast furnaces. The results show that the reduction of Fe203 proceeds by two steps, largely consecutive under the conditions used herein: reduction of Fe203 to FeO, and reduction of FeO to Fe. Unless the gas has a CO!CO, ratio greater than 2.1 only the first step occurs under these conditions (850°C) but the following generalizations apply to either step or to the combination. The rate of reduction of relatively fine ore particles .at any time is proportional to the mass rate of supply of CO (provided some of it is thermodynamically available): the rate therefore is proportional to the linear velocity at constant pressure, or to the pressure at constant linear velocity. Thus, the rate of reduction may be increased without increase in linear velocity of the reducing gas by increasing the mass velocity of the gas and increasing the pressure correspondingly to avoid any increase in the linear velocity. The rate "constants"—i.e., the efficiency of conversion of the "available" CO supplied— is not actually constant but decreases as the reduction proceeds, and is a function only of the state of the ore; i.e., of the amount of reduction already accomplished and hence of the amount of CO passed. The particle size of ore used in nearly all the experiments was relatively small (8 to 14-mesh). The rate of reduction in run 16 with 3 to 8-mesh ore particles is within experimental error the same as with the finer ore. Although this would indicate an absence of effect due to particle size in this range of ore particles, it is desirable to have more data on other ore sizes and on ore of different densities before arriving at any generalizations on this point. Although it is possible to extend the analysis of these results to consideration of the more detailed kinetics and mechanism of iron oxide reduction, such extension is beyond the scope of the present paper. From the experiments on carbon deposition, it was evident that if carbon deposition is increased at all by the application of pressures up to 10 psi ga., such increase appears to be less than the experimental and analytical error. It appears safe to conclude that at top pressures on the order

Jan 1, 1948

By H. Eyring, J. W. Fredrickson

Many theories have been advanced to explain the phenomena of elastic and plastic deformation. The object of this report is to present a mechanism for deformation, not radically differing from existing theories, but embodying.certain principles and concepts of these theories. This proposed theory cannot be the complete answer to the age-old problem of deformation but it is believed that it will be a step further in the proper direction. The plastic properties of solids have recently been reviewed by Seitz and Read.' ZenerZ has reviewed and correlated the existing work on the anelasticity of metals. With these and others3'4'5 resent theories of deformation are well-known. Of the many theories now extant, those receiving most attention have been proffered by Griffith,6 Becker,l Smekal,8 Polanyilg Orowanlo and Taylor.'' Although differing quite widely in details, these theories are based more or less on a common principle of flaws or dislocations that exist in the crystal lattice. The effect of stress concentrations surrounding a flaw or crack has been treated most recently by Fisher and Hollomon.12 The various authors differ as to the exact nature of the flaws or dislocations, the causes of their appearance, or the manner in which they initiate slip. All of the theories agree that the number of dislocations increases with progressing deformation. It is universally agreed that the shearing process is not a simple gliding of ideally perfect atomic lattice planes. It is also agreed that the "macroscopic" process of gliding, or slip, is brought about by the spreading of a large number of locally initiated "glide steps" through the whole crystal. The occurrence of these "glide steps" is closely related to the presence of some kind of deviations from the "ideal" lattice structure, even in the undeformed crystal. These deviations are overcome ''one at a time," in a manner of speaking, due to some stress-concentrating effect.13 Proposed Theory Many solids show a continuously increasing deformation if subjected to a constant load of suitable magnitude in an extended range of temperature for a sufficient time. This deformation, or flow, may be said to be due, in general, to the tendency of the atoms or molecules in an elastically stressed body to readjust themselves in such a way that if the deformation were kept constant, a release of stress would take place. If rupture does not occur, this process of relaxation causes the rate of flow to obtain a final constant value, as shown in the curve (Fig I) obtained by Taylor and Quinney.14 In this state the release of stress by relaxation exactly counterbalances the increase due to the elastic strain on the test pieces.

Jan 1, 1949

By Joseph J. Yancik, Leonard L. Felts, George B. Clark

LITTLE information has been published concerning the actual or useful amount of energy obtained from explosives when they are used for blasting. To provide more data on this subject, 8-in. neet cement cubes were blasted in a steel plate box and the breakage energy evaluated by comparison with drop crusher results using Rittinger's,1,2 Kick's: and Bond's' theories. Theories by Bond and Wang," Lineau," Hatch,' Roller,' and others0-11 were not considered applicable. Those used in this investigation may be expressed mathematically as follows: Rittinger Theory E = KrS2, pet,—--------------- [1] 40 d1 d0 Kick Theory TV 1 1 E = =K, [S pct. log1/d+ 100 log d0] [2] 40 d1 L. L. FELTS, Junior Member AIME, was formerly a Graduate Assistant, University of Illinois. G. B. CLARK, Member AIME, was formerly Professor of Mining Engineering, University of Illinois, and is now Chairman, Dept. of Mining Engineering, Missouri School of Mines and Metallurgy. J. YANCIK, Junior Member AIME, is a Graduate Assistant, Missouri School of Mines and Metallurgy. This paper, TP 4213A. is revised from a thesis submitted by L. L. Felts in partial fulfillment of the M.S. degree in Mining Engineering, University of Illinois, 1954. Discussion may be sent (2 copies) to AIME before May 31, 1956. Manuscript, Dec. 27, 1954. Bond's Third Theory E = Kb [S pct. log1/d1+ 100 log d0] where E — energy used in breakage, d, = average diameters of screen fractions of broken cement particles, pct, = percent weight of diameter d;, and 2 pct, = 100 pct. The above equations were employed to determine values of Kr, Kk, Kb for particle size distributions similar to those obtained from the blasting curves. These values were in turn used as a means of approximating the specific energy of the blasted material. The efficiency of crushing by blasting was then determined by dividing this specific energy by the maximum available work of the explosive per gram of cement. Knowledge of the failure of solids under static loads is developing very rapidly. Their failure under impact loads has been investigated and reported in the literature only to a limited extent. Theories of failure' hnder static loading include 1) the maximum stress theory, 2) the maximum strain theory, 3) the theory of constant elastic strain, 4) theory of maximum shearing stress, and 5) Mohr's theory of strength. All of these have elements of usefulness in establishing an applicable theory for blasting. For highly strained and compressed material such as that surrounding a detonating charge of high explosive, the Mohr theory and its implications appear to be the

Jan 1, 1957

By W. R. Seyfried

THE -problem of extracting alumina from clay and low-grade bauxites has been the subject of considerable interest for some time. The basic reason, of course, lies in the fact that known reserves of high-grade bauxite are not inexhaustible and that the present commercial process cannot successfully cope with low-grade bauxites or clay. Ultimately it may be necessary to use these poorer raw materials for all commercial operations, An unprecedented demand for aluminum during the war emergency and the constantly threatened shortage of imported bauxite caused the United States Government to take an active role in this problem. Through the National Academy of Sciences, the War Production Board and the Defense Plant Corporation, it investigated processes and finally selected four to be used in the construction and operation of four experimental plants. Each plant was to be designed in such a way as to facilitate its incorporation into a larger commercial plant should the need arise. The Chemical Construction Corporation process, or "Chemico" ammonium sulphate process as it is better known, was one of the four selected. The extensive literature and patents on record before the war generally follow one of two process-types depending upon the extracting reagent used. One group uses an acid reagent, the other an alkali. The Chemico process uses an acid reagent. For those interested in other processes described in literature, there is a short bibliography at the end of this paper, The basic steps of all acid extraction processes are: (I) to make the aluminum silicates acid soluble, (2) to separate the released alumina from impurities and insoluble gangue, and (3) to recover the reaent for re-use. THE PROCESS AS PLANNED In April 1941, a group of chemists and engineers of the Chemical Construction Corp, became interested in the problem of extracting alumina from clays and low-grade bauxites and, under the leadership of Mr. Blakeslee Barnes, Vice President and General Manager of the Company, first drafted a process in July of that year-five months prior to Pearl Harbor. The work continued in our research laboratories and with a small pilot plant, By June 1943, the work had progressed to a point where it was possible to apply for a patent on the process which was U.S. patent 2,405,426, granted August 6, 1946. Immediately prior to the development of the Salem plant, the process was envisaged to be as follows: I. The first step was to make the aluminum silicates acid soluble. It was planned: (a) Clay or low-grade bauxite would be roasted at 700 to 800°C (1292° to 1492°F). (b) The roasted ore would then be leached .with hot aqueous ammonium bisulphate to form a slurry. In this way the

Jan 1, 1948

By W. E. Horst

Flotation feed was hell constant for batch laboratory tests and continuous pilot and commercial plant tests on a spodumene ore to determine the relation.ship between flotation behavior and the size and type of flotation machine. Results. showed that additional retention time would be needed in the plant flotation circuit to duplicate laboratory or pilot plant performance when operating Dariables of the. plant flotation machines remained unchanged. During the past few years of operation at Kings Mountain, N. C., full-scale flotation has generally yielded poorer metallurgical results than those obtained in the laboratory or pilot plant. After 2 min in each size of Denver flotation machine in the spodumene rougher circuit, pilot recovery (41.7 pct) was almost three times that of the plant (13.6 pct) and about twice that of the laboratory (21.0 pct). Pilot and commercial plant data are based on continuous operation, and laboratory results on batch testing of rougher performance. The ore is a pegmatite containing spodumene, feldspar, quartz, mica, and amphibolite. Data were accumulated to evaluate the scale-up relationships between laboratory, pilot plant, and plant flotation cells. Flotation rate constants and dimensional analysis were used to define the relationship existing between flotation behavior and scale of operation. Measuring Flotation Rates: Efficiency of the rougher stage was measured by flotation rate, defined as the recovery that can be attained within a given time." • The problem of measuring flotation rates has been studied by many investigators, whose methods have varied. Published studies an flotation kinetics have been summarized recently by Gaudin.l When comparing flotation rates, it is more satisfactory to compare straight line relationships between recovery and flotation time than exponential curves resulting from plotting cumulative recovery vs cumulative flotation time. To convert the exponential curves into straight line relationships, rate equations were applied similar to those used in chemical kinetics to study the velocity of chemical reactions. Two rate equations have been used in this investigation to measure efficiency of the various cells: 1.5 order Rate Equation dR/dt=k (A-R)1.0 [Eq.1] Second Order Rate Equation dR ---- - K(A - R)2 [Eq. 2] dt Upon integration Eq. 1 becomes 1/(A-R)1/2=k/2 t+1/A1/2 [Eq. 3] and Eq 2 becomes: or fEq. 4] t/R=1/A2K+t/A [Eq. 4] where R = cumulative recovery [percent recovery of total value (spodumene) in flotation feed]. A = initial concentration, pct (100 pct of mineral to be separated). t = flotation time (minutes). k = flotation rate constant for 1.5 order rate equation [units: 1/(percent) 0.5 (min)1. K = flotation rate constant for second order rate equation [units: 1/(percent) (min) 1.

Jan 1, 1959

By Morris Muskat

A general theory has been developed for the effect of permeability stratification on the efficiency of the gas-injection phase of cycling operations. It has been applied to three special types of permeability variation; namely, exponential, probability, and linear. In the case of the exponential permeability distribution the effect of areal pattern sweep efficiency was also taken into account. The exponential permeability distribution can be characterized by the ratio of the maximum to minimum permeability, which has been termed the stratification constant. Curves were calculated for the variation in total wet gas recovery and total gas throughflow, to give that recovery to various abandonment limits of the wet gas content in the produced gas, as a function of the stratification constant. The cumulative wet gas recovery decreases monotonically as the stratification constant increases and is generally higher at the lower values of the wet gas content abandonment limits. The total gas throughflow first rises to a maximum as the stratification increases, and then ultimately declines. The effect of the areal sweep pattern efficiency is relatively minor as compared to that of the stratification constant, except in the region of low values of the latter where the formation is substantially uniform. The probability distribution can be characterized by a "variation" parameter varying from o to I as the formation changes from strict uniformity to extreme variability. The curves of total wet gas recovery and total gas throughflow to different abandonment limits of wet gas content versus the variation parameter have the same general characteristics as for the exponential permeability distribution. In the linear permeability distribution the ratio of maximum to minimum permeability also serves as a stratification constant index defining the distribution. The curves of total wet gas recovery and gas throughflow to fixed abandonment limits versus the stratification constant are similar to those for the exponential permeability distribution. However, for the higher values of the stratification constant the recoveries and throughflows do not asymptotically fall to o as in the latter, but approach constant values determined by the abandonment limit of wet gas content in the produced gas. Introduction It is becoming generally recognized that one of the most important factors determining the economic feasibility of cycling operations is the areal continuity and permeability distribution of the producing formation. While the effects of areal variations in permeability, porosity, thickness, and well pattern on the sweep efficiency can be evaluated by electrical model studies,' those due to permeability stratification require separate treatment. Several studies have been reported2,3 on the' influence of permeability variations on the wet gas recovery by cycling. In these, however, discontinuous permeability variations either have been assumed explicitly, or the analysis has been carried through as if they were discontinuous. While, in fact, the actual permeability profiles will undoubtedly be discontinuous, recent develop-

Jan 1, 1949

By Donald T. Hawkins, Ralph Hultgren

The lorsion effusion method has been used to measure the vapor pressure of lead over pure lead and eight Pb-Sn alloys ranging from 9.1 to 87.9 at. pct Pb in the temperature range 950° to 1125°K. The resulting ?H°y 298 = 46,630 ± 200 cal per g-atow for pure lead is in excellent agreement with previous work. Deriued ?Gph values for the alloys were smoothed and correlated with previous heat of formation data to obtain entropies for the liquid alloys. values for the tin component were calculated by Gibbs-Duhem integmtion. Surfhce depletion of these liquid alloys was found to be absent, as shown by the fact that the measured pressure remained substantially constant with time in contrast with previous measurements on iron-rich solid Fe-Mn alloys. The activities and Gibbs (free) energies of the liquid Pb-Sn system are not well known although the heats of formation have been accurately determined by K1eppa.l Vapor pressure determinations of the activity of lead by Voronin and Evseev2 disagree with those of Predel.3 Elliott and chipman4 measured activities by the electromotive -force technique in the ternary Pb-Sn-Cd system. From the resulting values of the activity of cadmium, they were able to calculate the activities of lead and tin for the binary Pb-Sn system at the compositions xsn = 0.33 and 0.67. Atarashiya, Uta, Shimoji, and Niwa5 determined the activity of tin from Hz-H2O equilibrium measurements, but their results are subject to question due to uncertainty in the final state of their samples. To resolve these differences, measurements of the activity of lead were made using a torsion-effusion apparatus. Among other advantages, this apparatus rapidly detects errors caused by surface depletion, which tends to reduce the apparent vapor pressure of the more volatile component. If the measured torques remain nearly constant with time, only bulk depletion is occurring. This contrasts with the rapid decrease in torque found in solid Fe-Mn alloys at high temperatures and low manganese contents.6 EXPERIMENTAL 99.999+ pct Pb was obtained from the American Smelting and Refining Co. and 99.999 pct Sn from Vulcan Detinning Co. Eight Pb-Sn alloys were prepared by melting together weighed amounts of the pure metals in evacuated Pyrex tubes and quenching the melts in water. Loss of weight in preparation was less than 0.02 pct in all cases. The effusion cells were made from high-purity, nonporous graphite. Graphite was chosen because of its resistance to reaction with lead and tin and because it can be accurately machined with precision orifices. Two cells were used with overall dimensions as shown in Fig. 1. The orifices of cells 1 and 2 were, respectively, 1 and 1.5 mm in diam.

Jan 1, 1968

By M. G. Driessen

For a number of years the cyclone, familiar to Americans as a dust collector, has been used as a thickener of suspensions at one of the coal-preparation plants of the Netherland State Mines in Limburg. The plant treats nut-size coal at 120 tons an hour in a heavy-medium washer. The diluted medium from the rinsing screens is thickened in cyclones. More recently the cyclone has been adapted to act as a coal cleaner. The principle of the cyclone thickener is the same as that of the cyclones used in industry for catching dust or fine particles suspended in the air or in gases. Generally the latter are more efficient in this respect—the smallest particles that can be caught with reasonable efficiency are considerably smaller than with the cyclone thickeners. The reason is obvious; the ratio of specific gravities between the dust particles in a gas and the gas itself is about 800 times larger than the ratio between, for instance, the specific gravities of shale particles and water. The ratio of the velocities of fall of shale particles (? = 2.5)† in air and in water is as follows: In the range of Stokes: ?air = 93?water In the range of Allen: Wair = 49Wwater In the range of Newton-Rittinger: ?air = 36.6?water The same ratios apply for the velocities in the centrifugal field, from which it follows that it is especially difficult to catch the very fine suspension particles in a liquid. The efficiency of a cyclone thickener depends mainly on the circumferential velocity of the liquid at its innermost radius, because here the centrifugal forces are the highest. However, these velocities cannot easily be calculated, as the flow is three-dimensional, and thus the axial components cannot be neglected .(p. 252, condition 3). We believe that at first a spiral tangential motion along the cyclone wall is created, which causes the inner vortex ascending from the apex of the cyclone (Fig I). At the same time the inner vortex is strengthened by the individual vortices in horizontal planes, and thus a part of the total flow can find another and perhaps quicker way to the outlet. In any case, the exact motion, not only of the fluid but especially of the suspended particles, is so difficult that we have to refer to the experiments to find the exact behavior of this kind of apparatus. Method of Judging PerforMance of Coal Washer Geologists, rather than mechanical en-gineers, would be able to describe the separating or stratifying effect in nature, but even a bather on the shore lying on the soft sand near the sea wonders why all the small sand grains have approximately the same size. A child playing on the border of the river could easily

Jan 1, 1949

By Alfred H. Hesse, Edwin T. Myskowski

The development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly IOO per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposi-tion is accompanied by a change in volume of as much as ; per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson3 found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potter6 have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to go per cent Mn is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparalion of Alloys.—The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 CU-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced go per cent when forged to 1/2-in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.—The tensile specimens, 0.313-in. diameter (1.25-in. gauge length),

Jan 1, 1942

By Edwin T. Myskowski, Alfred H. Hesse

The development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly IOO per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposi-tion is accompanied by a change in volume of as much as ; per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson3 found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potter6 have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to go per cent Mn is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparalion of Alloys.—The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 CU-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced go per cent when forged to 1/2-in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.—The tensile specimens, 0.313-in. diameter (1.25-in. gauge length),

Jan 1, 1942

By J. Murray Riddell, George A. Morrison

THIS paper is a companion to the one by George A. Morrison on Mining a Deep Limestone Mine in Ohio.[+] Barberton is 8 miles west of Akron, Ohio, and 23 miles south of Cleveland. The underground mining of limestone at Barberton constitutes the world's deepest limestone mine. The stratigraphy is as follows: 0-20 ft. Loam, clay, sand and gravel. Water bearing. 20-40 ft. Fractured. sandstone. Water bearing. 40-110 ft. Sandstone with interbedded shale, slightly fractured. Water bearing. 110-314 ft. Sandstone with interbedded shale, slightly fractured. Water carrying. 314-2197 ft. Shale with occasional seams of sandstone, which varies in thickness from a few inches to 4 feet. Dry. 2197-2247 ft. Limestone. Dry. 2247-2742 ft. Dolomitic limestone. Dry. 2742-2767 ft. Salt. Dry. 2767- Dolomitic limestone. Dry. All of the strata dip to the southeast, about 0.5 per cent from the horizontal. The top 110 ft. of the crust is water-bearing. The rock strata are naturally fractured to a depth of 314 ft., sufficient to allow the passage of water. In the shaft-sinking operations, a stra was encountered at a depth of 520 ft., and flows of methane gas were pierced at depths of 1350 and 1952 feet. Specifications for the mine plant called for, in part, the sinking of two vertical shafts and a hoisting plant capable of producing at the rate of 300 tons per hour. No. I shaft is 550 ft. west of No. 2 shaft. Each shaft measures 8 by 17 ft. outside of steel. General features of the design (Fig. I) are: Principal set members, 6-in. H-section; connecting angles (studdles), 3/8 by 4 by 4-in. angle irons; spacing of sets, 8 ft. centers; spacing of bearer sets, generally, 160 ft.; bearers, of 12-in. I-beams. Each bearing set featured a concrete ring about the periphery of the shaft, steel to rock, and 8 ft. in height; permanent guides, 6 by 10-in. long-leaf yellow pine, 85 per cent heart. THE SHAFT-SINKING OPERATION The preliminary shaft-sinking work consisted of driving interlocked steel piling about the exterior of the shafts to depths of 35 and 32 ft., respectively, and of such horizontal dimensions as to ultimately permit the pouring of a concrete collar 2 ft. in horizontal thickness. Following the pouring of a shaft collar, a temporary wooden headframe for shaft-sinking purposes was erected. The head-frame, while ordinary, featured: (I) a storage pocket of 300 cu. ft. capacity with truck servicing facilities, and (2) pneumatically operated dump doors, which were actuated by the hoistman, thus caring for the dumping of the "ball-and-chain"

Jan 1, 1944

By A. H. Daane, B. J. Beaudry

The Sc-Ti system was studied by thermal, metal-lographic, and X-ray methods. Scandium was found to transform at 1334 °C from a (hexagonal) to ß which was concluded to be bee since a continuous series of solid solutions is formed between ß scandium and ß titanium at elevated temperatures. There is a minimum in the solidus at 51 wt pet Ti and 1300°C, a monotectoid at 1050°C and 49 wt pet Ti, and a eutectoid at 875°C and 91.5 wt pet Ti. The maximum solubility of titanium in a scandium is 13.5 wt pet at the monotectoid temperature, while the maximum solubility of scandium in a titanium is 6.5 wt pet at 875°C. SCANDIUM, a member of Group 111 A of the periodic table, and now called a rare-earth metal,' has become of interest recently due to its low density (2.99 g per cc) and relatively high melting point (1539°C).Spedding,' et al. have described a method of preparation of pure scandium metal and have made a study of its basic properties. Since scandium is approximately 10 to 12 pet smaller in at. diam than the other rare earths while its electronegativity and valence are the same, a knowledge of its alloying behavior in contrast to these elements should be very helpful to fundamental alloy theory. Since scandium is quite scarce and difficult to prepare in pure form, its use as a structural material by itself seems quite unlikely. However, its use in special cases as an alloying addi- tive to other low-density materials is a possible application; the Sc-Ti system was chosen for this reason and for others of fundamental interest. Scandium was suspected of having a high temperature bee form as do some of the other rare-earth metals.3'4 Since titanium has a high-temperature bee form, a continuous series of solid solutions at elevated temperatures between ß scandium and ß titanium would prove the existence and structure of the high-temperature form of scandium. The existence of a continuous series of hexagonal solid solutions at room temperature was predicted by Burkhanov and Savitskiy,5 but Hias shown to be incorrect in early X-ray studies. EXPERIMENTAL METHODS Materials. The metals employed in this investigation were crystal bar titanium and distilled scandium prepared by the method described by Spedding,2 et al. The major impurities are listed in Table I in PPm. Alloy Preparation. All the alloys examined were initially formed in a nonconsumable electrode are-melting furnace under an atmosphere of purified helium or argon. A curve based on the observed weight loss of 0.6 pet* when titanium was melted

Jan 1, 1962

By S. Isserow

RECENTLY, a description of the wartime work in this laboratory on the U-Si phase diagram was published. This diagram was available earlier in the open literature; as were Zachariasen's crystal structure identifications for the compounds in the system. The uranium end of the phase diagram is shown in Fig. 1. The most recent work on this system has emphasized the peritectoid E phase, of particular interest for a number of reasons. The early work provided evidence of this phase's resistance to corrosion in water and of its slight ductility. Further information on these properties has been obtained here. Work elsewhere4 has provided evidence of stability under irradiation. This body-centered-tetragonal phase is relatively isotropic compared to the more usually applied a or ? uranium phases. Unlike the other compounds in this system, it contains no Si-Si covalent bonds.3 In addition, consideration on the basis of Pauling's concepts leads to the conclusion that in the E phase, uranium has a higher valence than in any of the other phases. Definition of the composition of the ? phase has been of prime concern in the study of this alloy. Evidence is presented below that its silicon content is slightly higher than that of stoichiometric U8Si, the composition frequently assigned this phase on the basis of Zachariasen's identification. This work on the composition required careful attention to the method of dissolving the alloy for analysis, since apparently low silicon contents could be found under certain conditions, see Appendix. Preparation: Melting, Casting, and Heat Treatment—Almost all the samples were from castings with a diameter of 13/4 or 2 in. and about 1 ft long, weighing 10 to 15 lb. The U-Si charge was melted by heating to about 1650°C in an induction heated vacuum furnace. Beryllia crucibles were used at first, but were replaced by zirconia-washed graphite as the technique of keeping the carbon content low enough (about 500 ppm) was mastered. The alloy was bottom-poured at about 1650°C into graphite molds. A few small buttons, weighing no more than 50 g, were prepared in a small arc melting unit.' Since cast material has a preponderance of uranium and U8Si2, heat treatment is necessary to ob-tain the ? phase by the solid-solid peritectoid reaetion. Once obtained, the ? phase is stable to room temperature, obviating the need for speeial attention to the method of cooling after epsilonization, see Fig. 1. It was found desirable to epsilonize at 800°C for a week. For some purposes, in which residual uranium and/or U8Si2 are tolerable, shorter periods may be adequate. The temperature of 800°C is not critical, since essentially the same results were obtained from 785° to 825°C. Further departure from this epsilonization range is inadvisable.

Jan 1, 1958

By R. T. DeHoff

A new approach to the measurement of the size distribution of particulate structures imbedded in opaque bodies is developed. The method is based upon the assumption of a general two-parameter distribution curve, and the estimation of these two parameters from three well-known counting measurements made upon metallogvaphic sections. The total number of particles in the system is also a product of the analysis. Application of the method with the assumption of the logarithmiconorma1 disfribution function is developed in detail. A complete description of the geometry of a particulate structure requires the determination of the size distribution of particles. The problem of estimating the size distribution of particles of a particular phase in a multiphase system, or the grain-size distribution in a homogeneous system, has been approached by many investigators.'-'0 All of the solutions proposed by these investigators share the following characteristics. a) A minimum of several hundred particle sections in the microstructure must be examined, and some characteristic dimension recorded, such as area,3'5 intercept length,6"9 or diameter.1'2'4'10 b) The resulting data must undergo a series of fairly complex calculations to generate the empirical histogram which describes the size distribution in three dimensions. c) In order to manipulate the result, the histogram must be fitted to some assumed mathematical formula, using the attendant statistical procedures. d) With two notable exceptions,8,10 the particles must be spherical. The measurements and calculations involved are in general very tedious and time-consuming, with the logical result that much effort has been expended in the development of equipment which will perform these tasks automatically and semiautomati-cally.9,11-15 considerable success has been achieved in this area, but the equipment is in general expensive, and usually places stringent requirements On the quality of microstructure which can be reliably analyzed. In laboratories which do not possess such equip- ment, the analysis of geometry is usually limited to measuring total properties of the microstructures, such as volume fraction and interfacial area, because the measurements required are much simpler to make. The determination of size distributions rarely is undertaken. The development which is presented in this paper permits the estimation of size distributions of three-dimensional structures from the same simple counting measurements which are required to determine the surface area and volume fraction of the particulate structure, and one other counting measurement. The basic approach that is used is to assume a general mathematical form for the distribution, which is described by two parameters (as the normal distribution is described by assigning values to the mean and the standard deviation), and then estimate these two parameters from the results of the counting measurements. The introduction of a third counting measurement also permits the evaluation of the number of particles per unit volume, Nv.

Jan 1, 1965

By H. l. Burghoff, C. H. Mathewson

THE study of the creep of metals under conditions of prolonged loading has received the attention of many investigators for several years and almost innumerable papers have been published on the various aspects of the subject. As it appeared that much could still be learned from a study of single crystals, the present work was carried out to study the effects of temperature and conditions of loading upon the properties and deformation in tension of single crystals of alpha brass containing about 70 per cent copper and 30 per cent zinc. In particular, it was hoped to obtain information from tests below and above the recrystallization temperature of the material, so that properties such as elastic limit, yield point or critical stress, and manner of deformation might be compared for tensile tests at an ordinary loading rate and for prolonged. loading. Accordingly, short-time tensile tests and creep tests were made at room temperature, 300º, 500° and 700°F. The two latter temperatures are above the lowest possible recrystallization temperature of polycrystalline 70-30 brass. PREVIOUS WORK Clarke and White1 have made creep tests of some copper-zinc alloys, including 70-30 brass, and copper-zinc-tin alloys at temperatures both below and above the recrystallization temperature of the materials considered. Hanson and Wheeler have studied the flow and fracture of single crystals of aluminum for short-time and prolonged tensile loading over a range of temperature extending from room temperature to 400°F., their experiments being made without consideration of the orientations of the test specimens. Extensive creep and fracture tests on single crystals of lead at room temperature have been made by Betty3 and by Baker, Betty & Moore.4 Results of the last-named investigation were published while the present work was in progress. Millers examined the elastic limit of zinc single crystals at and above room temperature by means of creep tests, while Miller and Milligan6 reported the results of tests designed to show the influence of temperature on elastic limit of single crystals of aluminum, silver and zinc. The behavior, of iron crystals under static tensile loading at room temperature was reported by Gensamer and Mehl7 while the present investigation was in progress. Their specimens exhibited a well-defined yield point, below which no appreciable creep could be detected. The manner of yielding proved interesting, as the shape of the creep-time curve for the iron crystals differed from the common type of creep curves. Elongation did not begin immediately, or at least was initially very slow. The rate of elongation then increased continuously and finally decreased to zero. This S-shaped type of elongation-time

Jan 1, 1941

By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By Robert I. Jaffee, Bruce W. Gonser, Eugene M. Smith

There has been little investigation of the gold-germanium binary alloys. Haughtonl does not mention any work on the system. In a review article commemorating the fiftieth anniversary of the discovery of germanium, E. Einecke2 mentioned a gold-germanium eutectic at 24 atomic per cent Ge (10.4 weight per cent) melting at 359°C., but did not give the source of his information. From measurements of electrical conductivity, J. 0. Linde3 estimated that at least 0.6 weight per cent germanium is soluble in gold. The recent availability of germanium in this country in commercial quantities has led to interest in its properties and its alloys. This study is part of a program of investigation on germanium alloys; work on ternary alloys involving germanium and gold will be reported later. In this investigation, the composition and melting point of the Au-Ge eutectic reported by Einecke has been found to be substantially correct. Eutectic composition has been placed at I2.0 per cent germanium, however. An alloy of 10.4 per cent Ge, Einecke's value, was found to have a few gold dendrites in it. The cutectic temperature has been determined as 356.0 6 ± 0.5°C., slightly less than the temperature of 359°C. reported by Einecke. The liquidus curves and the solid solubility of ger- manium in gold have been determined, and are shown in Fig. I. Materials and Alloying The germanium used in this investigation was prepared by the Eagle-Picher Lead Co. from pure germanium oxide, by reduction in clay crucibles with sodium cyanide. The regulus is quite pure, assaying over 99.9 per cent Ge. High-purity gold obtained from Handy and Harmon was used. Alloying was carried out in graphite crucibles in an atmosphere of purified hydrogen. The temperature was brought up to 1050" to iioo°C., and the metal was allowed to freeze in the crucible. Prepared in this way, the gold dendrites in hypoeutectic alloys were somewhat segregated at the bottom and sides of the ingot, and on the hyper-eutectic side the lighter primary germanium tended to gather at the top. Most of the alloys were made from virgin metal. Low-germanium heats were made by alloying pure gold with the eutectic. Melting losses were consistently a few milligrams or less, and the composition could safely be taken from the intended analysis. The 30 per cent and 50 per cent germanium heats for thermal analysis were made in part from remelted higher germanium heats, and they may be OR composition as much as one per cent. Because of the high cost of materials, the weight of heats for thermal analysis were 15 to 20 grams and heats for metallo-graphic, X-ray, and hardness specimens were 2 to 4 grams.

Jan 1, 1945

By Robert T. Pring

In addition to the humanitarian aspects of a dust-control program, certain economic benefits are becoming more fully recognized and now furnish a greater incentive to the mill operator to eliminate the dust from his plant. It is well known that a favorable working environment promotes increased efficiency and improves the morale of employees, with a consequent decrease in labor turnover rates. One progressive mining company' estimates its direct and indirect labor turnover costs at from $40 to $50 per man; for skilled labor, such as machine operators, the cost may approach $100 per man. While these figures may not be typical of every plant, they do indicate a potential savings in operating costs. Dust signifies waste; its elimination decreases maintenance costs of mechanical and electrical equipment; its recovery is often justified from the standpoint of values contained in the collected material, although in large-scale milling operations handling low-grade ore this may not be an important factor, Perhaps the most significant trend in industrial sanitation is that dust-control equipment and procedures are becoming recognized as integral parts of the mill flowsheet. Exhaust ventilating systems are now afforded equal care in design and maintenance to that given other machinery more closely related to the Process. Methods of Dust Control "Dust control" is a general term descriptive of a number of methods used singly or together to prevent particulate atmospheric contamination. These methods are: in order .of their desirability, as follows: 1. Change of process. 2. Isolation of process. 3. Wet methods. 4. Ventilation. a. Local exhaust ventilation. b. General ventilation. 5. Personal respiratory protection. In ore-concentration plants it is seldom prac tical to change a process to eliminate the dust it creates It is possible in some cases to isolate a particular dust-producing operation from the rest of the plant, provided that constant attention on the part of the operators is not required. Frequently water is used in fine crushing and fine grinding, primarily to facilitate the processing of the ore and incidentally to allay the dust produced. Wet methods, however, are not feasible in coarse and secondary crushing operations, because of the relatively great volume of water required in instantly wetting each freshly fractured rock surface. Such quantities of water would entail conveying and storage difficulties. Local exhaust ventilation is the most effective and most commonly applied control measure, wherein directional air currents through the zone of dust production draw the contaminants into a duct system. Unfortunately, only a limited amount of reliable information on exhaust ventilation is available.2-5 of necessity these publications are rather general, being primarily concerned with engineering fundamentals. While many organizations have successfully

Jan 1, 1943

By Robert I. Jaffee, Bruce W. Gonser, Eugene M. Smith

THERE has been little investigation of the gold-germanium binary alloys. Haughton1 does not mention any work on the system. In a review article commemorating the fiftieth anniversary of the discovery of germanium, E. Einecke2 mentioned a gold germanium eutectic at 24 atomic per cent Ge (10.4 weight per cent) melting at 359°C., but did not give the source of his information. From measurements of electrical conductivity, J. 0. Linde3 estimated that at least o.6 weight per cent germanium is soluble in gold. The recent availability of germanium in this country in commercial quantities has led to interest in its properties and its alloys. This study is part of a program of investigation on germanium alloys; work on ternary alloys involving germanium and gold will be reported later. In this investigation, the composition and melting point of the Au-Ge eutectic reported by Einecke has been found to be substantially correct. Eutectic composition has been placed at 12,0 per cent germanium, however. An alloy of 10.4 per cent Ge, Einecke's value, was found to have a few gold dendrites in it. The eutectic temperature has been determined as 356.0 ± 0.5°C., slightly less than the temperature of 359°C reported by Einecke. The liquidus curves and the solid solubility of germanium in gold have been determined, and are shown in Fig. I. MATERIALS AND ALLOYING The germanium used in this investigation was prepared by the Eagle-Picher Lead Co. from pure germanium oxide, by reduction in clay crucibles with sodium cyanide. The regulus is quite pure, assaying over 99.9 per cent Ge. High-purity gold obtained from Handy and Harmon was used. Alloying was carried out in graphite crucibles in an atmosphere of purified hydrogen. The temperature was brought up to 1050° to 1100°C., and the metal was allowed to freeze in the crucible. Prepared in this way, the gold dendrites in hypoeutectic alloys were somewhat segregated at the bottom and sides of the ingot, and on the hypereutectic side the lighter primary germanium tended to gather at the top. Most of the alloys were made from virgin metal. Low-germanium heats were made by alloying pure gold with the eutectic. Melting losses were consistently a few milligrams or less, and the composition could safely be taken from the intended analysis. The 30 per cent and 50 per cent germanium heats for thermal analysis were made in part from remelted higher germanium heats, and they may be off composition as much as one per cent. Because of the high cost of materials, the weight of heats for thermal analysis were 15 to 20 grams and heats for metallographic, X-ray, and hardness specimens were 2 to 4 grams.

Jan 1, 1945

By M. R. Geer, H. F. Yancey

WITH the exception of pneumatic processes and ii few special beneficiation methods of comparatively limited application, all mechanical coal-cleaning and mineral- dressing processes involve the admixture of solid particles with a liquid, generally water. Upon completion of the beneficiation process the solids must be reclaimed from the water. With coarse particles separation of solids from water is accomplished readily by the simple expedient of screening, but recovery of fine solids presents a much more difficult problem. Thickening and dewatering are practiced so generally, both within the mineral industry and else- where, that they have been the subject of study through the years and a number of processes for making the solid-liquid separation have been developed. Dorr-type thickeners have been standard equipment for many years, and more recently driers employing centrifugal force have gained in popularity. 1 A cyclone device employed to thicken the loess suspension is a novel feature of the loess heavy-medium coal-cleaning process developed by the Netherlands State Mines in the thirties. The cyclone thickener was first mentioned by Driessen2 in 1939 in a paper describing the loess process and has been the subject of two more recent reports by the same author.3 The cyclone does not differ greatly from cyclone dust collectors used in this country for years, except that it is operated wet rather than dry. Advantages of the cyclone over other thickening devices are its simplicity of construction, high capacity, and the fact that, having no moving parts, it is simple and inexpensive to operate. The Bureau of Mines became interested in the cyclone after one of the present authors observed it in operation in the Netherlands in 1945. The first experimental work with the cyclone conducted by the Bureau of Mines was an investigation of the unit functioning as a heavy-medium cleaner for fine coal-a use for the cyclone that was conceived long after it had been perfected as a thickener. The results of this investigation were published last year.4 The present investigation deals exclusively with operation of the cyclone as a thickener. OBJECT AND SCOPE OF INVESTIGATION Although the cyclone thickener has been dealt with in three reports by Driessen, its use as a thickener was not the principal subject of any of these reports and therefore neither the cyclone itself nor its operation was described completely. The design of the cyclone was described only in a very general way, only limited operating results were given, and virtually nothing was disclosed about the influence of the various possible operating variables. Moreover, the Netherlanders apparently had employed the cyclone exclusively for thickening loess and had not employed it on coal slurries. One English colliery has used a cyclone to thicken coal slurry,5 and as it appeared that

Jan 1, 1948