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By A. W. Asman

The problem of balanced design in a belt conveyor has been under constant study. Increased use of this method of transport in recent years has stimulated investigations. Conveyor belt, power transmission and other machinery should be adequate to perform the required service. All components of the belt conveyor should work as an efficient unit moving its load continuously between terminals. As part of a long term research project on belt conveyors, Hewitt-Robins established in 1954 a 2-year grant at Pennsylvania State University. Under terms of the grant, certain fundamental phenomena were to be studied. This work evolved a new concept in belt conveyor power determination based on the principle of belt tension. The Penn State contract furnished the foundation for later more detailed studies. From these most recent investigations, more specific factors were defined. In the final analysis, all of the data collected has been worthwhile in belt conveyor design. Units now operate over long distances at speeds of over 800 fpm. Long high lifts are commonplace. Where vertical or inclined shafts were the rule, belt conveyors receive first consideration. Although belt conveyors have moved forward rapidly, the future will see a tremendous gain in their use. The ideal test belt conveyor would be several thousand feet in length and have a maximum tension of at least 70,000 lb., Also, this conveyor should be horizontai and have a variable feed rate of more than one material. Data from such a field belt conveyor combined with laboratory information would permit accurate analysis. Since this type of conveyor was not available, many field locations were visited: An alternate would have been to erect a closed circuit system in the laboratory. Either method had limitations and the first was selected as having the best possibilities. Manufacturers of conveyor belting and machinery basically have been using the same horsepower formula. As more information became available from field installations, factors in the basic formula were modified. Practically all conveyors are designed today by adding together the horsepowers required to move the empty belt, move the load horizontally, and elevate the load. In selecting size of drive motor, the first two elements are relatively unimportant if the last is large. However, it is the combination of

Jan 1, 1961

By J. M. Toguri, K. Grjotheim

It is known 1,2 that the equilibrium between titanium metal, TiCl2 , and TiCl3, in a solvent of molten metal chlorides, is influenced both by the total amount of dissolved titanium and by the type of solvent. Assuming that the trivalent titanium forms the complex ion Ti111 Cl4, the equilibrium reaction may be expressed by the following equation, (Me) TiIII cl4+ 1/2 Ti = 3/2 TiII cl2+ (Me) Cl The ideal ionic equilibrium constant for this reaction is, Where the N's are the molar ionic fractions in the equilibrium melt, and (Me) the different types of cations present in the equilibrium mixture. The following thermodynamic relation is derived between Kand the concentration of cations in the equilibrium melt, mix The N"S are the equivalent ionic fractions, and so forth are constants corresponding to the standard changes in free energy for reactions in melts where only the cation indicated is present, and f (y1) is a function of the activity coefficients in the equilibrium mixture. When this term vanishes, a simplified linear relationship between In Kideal and the concentration is obtained. The simplified relationship has been applied with satisfactory results to the experimental data of Mellgren and pie,' and Kreye and Kellogg.2 MANY existing methods for the production of light metals involve the reduction of their respective metal halides in the presence of salt melts composed of alkali or alkaline earth chlorides. In such a solution phase, the light-metal halide may undergo stepwise reduction from a higher, to a lower valence, and finally to a zero valent state. In this connection, the disproportionation equilibrium is of great interest. In the case where the higher valence is three and the lower valence is two, the disproportionation equilibrium may be written as follows, 3 Me11 = 2 Me111 + Me [I] If this equilibrium occurs in a salt melt containing a large excess of alkali chlorides, a typical ionic melt is obtained. It is then possible to formulate the cation equilibrium: 2 Me+h' + Me = 3 Me++ [II] Reaction [11] is analogous to a cation exchange reaction. It has been shown thermodynamically that the equilibrium constant for such a reaction in 2

Jan 1, 1960

By L. W. Berger, R. I. Jaffee, D. N. Williams

The effects of hydrogen on the properties of binary Ti-A1 alloys containing 2.5, 5, and 7 pct aluminum and ternary alloys of the same compositions with added interstitial elements oxygen, nihrogen, and carbon were studied. Aluminum increases the apparent hydrogen solubility of the a-phase, resulting in a marked increase in resistance to impact embrittlement. In the Ti-5Al and Ti-7Al alloys, for example, the addition of 180 and 305 ppm hydrogen, respectively, did not cause embrittlement, while unalloyed titanium was embrittled by as little as 75 ppm. The role of aluminum in increasing hydrogen solubility of the a-phase probably accounts for the excellent hydrogen tolerance of a-ß alloys containing considerable amounts of aluminum. There is some evidence that aluminum retards the rate of hydride precipitation. If so, these alloys may be susceptible to slow-strain embrittlement. UNALLOYED a-titanium is extremely sensitive to small amounts of added hydrogen in that there is a marked decrease in notch properties. For example, as little as 100 ppm hydrogen is sufficient to lower the room-temperature notch-impact strength from over 100 to less than 20 in.-lb.' This loss of impact Strength has been associated with the Presence of hydride phase in the microstructure. Hydrogen in the amounts encountered in commercial practice

Jan 1, 1959

By Cloyd M. Smith

A FEW years ago, the Ventilation Committee established the practice of presenting one topic each year for discussion at the annual meeting. The practice has met good response on the part of committee members and I suggest that it be continued. The topic chosen for this year, "Underground Anemometry," is a topic which has bothered me for more than 20 years. It seems to me that the coal industry is content to rely on slipshod methods for measuring the rate of flow of air underground, so I prefaced my discussional charge to committee members with the statement that I regard air measurements made in the usual way, with hand held anemometer, as no good. Agreements and disagreements came in from more than a dozen engineers, some of whom are with operating companies, coal and metal; some with manufacturers; others with government agencies.

Jan 1, 1949

By Oliver Bowles

STRIKING new developments in the field of industrial minerals include the employment of lime, salt, coal, and air for the manufacture of stockings, and the substitution of paper for granite and marble in making tombstones. Certain minerals that have heretofore been regarded as valueless except as museum or laboratory specimens, are now being applied commercially. Serpentine, in forms neither fibrous nor ornamental, massive topaz, pinite, and zoisite are examples. For certain other minerals, notably pyrophyllite, bentonite, vermiculite, and sulphur, extension of established uses into new fields has occurred. Substitution takes a toll in many industries, but producers of industrial minerals as a class have gained more than they have lost in recent years. Encouraging progress has been made in developing at long last a suitable substitute for certain of the uses of mica, the only industrial mineral on the strategic list of commodities established by the War. and Navy Munitions Board. Some of the more important developments in process, equipment, and use .that have come

Jan 1, 1940

By H. H. Power

THE PETROLEUM DIVISION of the A.I.M.E. continued with its diversified activities during 1.935. Sessions at the New York meeting in February were devoted to production engineering, domestic and foreign oil production, and petroleum economics. The symposiums on domestic and foreign production proved their increased usefulness. The data accumulated for 1935 were added to those published during prior years in "Petroleum Development and Technology." A joint session on the use of metals in the petroleum industry was held by the Institute of Metals, Iron and Steel, and Petroleum Divisions. W. S. Farish, chairman of the board of the Standard Oil Co. (N. J.), was the principal speaker at the annual dinner. The October meeting, held in Hous¬ton, was characterized by an excellent program and large attendance. Four sessions were devoted to problems in estimating reserves, reservoir energy, properties of drilling muds, electrical logging, water flooding, and other subsurface studies. Foreign representatives of the Anglo-Persian Oil Co. presented a paper on surface tension and specific gravity of crude oil under reservoir conditions. The address by President Buehler, the dinner at San Jacinto Inn, a trip to various lo

Jan 1, 1936

By George M. Fowler, J. P. LYDEN

T HE relationship of geological structure to orebodies and to the great masses of chert in the Tri-State mining district is of such significance that it prompts a brief recital of the existing information regarding the various periods of structural deformation. We began to note a relationship between structure and orebodies early in our studies of the field, and further work revealed a like relationship of structure to the great masses of chert so commonly associated with the ore-

Jan 1, 1934

By C. A. Stiles, J. W. Nyhus

Erie Mining Co. is a 10.3-million-tpy pellet producer on the east end of the Mesabi Range 60 miles north of Duluth. Its complex includes facilities for mining, crushing, grinding and beneficiation in addition to a pellet plant and power plant. A 74-mile railroad links the mine and plant to Taconite Harbor on the shore of Lake Superior. The concentrate recovery ratio at Erie is about 1: 3, and this, along with stripping activity, makes it necessary for the company to mine nearly a million tons of material a week. At the outset, all crude ore mined at Erie was hauled entirely by rail, but with expansion into additional mining areas, the company made a gradual transition towards truck-to-rail haulage. Today, in Erie's 11th year of operation, over 50% of all crude taconite mined is transported by truck to loading pockets where it is transferred to rail cars. Future years will see more taconite moved in this manner. Thus, the company has an increasing interest in tire performance.

Jan 6, 1969

By A. S. Odeh

During the last few years, several authors1-6 have advanced mathematical solutions, both exact and approximate, to the pressure behavior of a well producing from a region bounded by a circular discontinuity. The most recent solutions were reported by Carter, and by Bixel and van Poollen. Varter solved the appropriate equations analytically. Bixel and van Poollen reported a numerical solution and provided correlation charts for the interpretation of flow tests; their method uses an overlay technique and is valid for wide ranges of mobility and storage capacity ratios. The mobility ratio is defined as the ratio between k/p of the two zones, and the capacity ratio is defined as the ratio between $c of the two zones. We have developed independently an analytic solution, programmed for the CDC 1604, that agreed with Carter's.'1 The same differential equation, assumptions, boundary, and initial conditions were used. We ran 30 drawdowns and 30 buildups of a unit capacity ratio and of varied mobility ratios. We also varied the radial distances to the discontinuity, and the radii of drainage. We examined the results and obtained correlations that were simple to apply and useful in flow test interpretation. The results and the correlations reported here in graphical form allow the determination of the mobility of the two zones and the radial distance to the discontinuity. They eliminate the need to fit field data to a curve as is required in the overlay technique.6 Thus, the advantages of the present correlations are that they require less effort and they provide a unique answer. They also provide guidelines for selecting the parts of the flow test plot to be used in the interpretations. Moreover, the results obtained from the programmed analytic solution define the time intervals where the approximate solution reported by Hurstl and discussed by Larkin2 are applicable. Normal buildup and drawdown plots resulted in an early straight line, a long transition zone and a late (second) straight line. However, the second straight line will not occur if the drainage radius is not at least 10 times the radial distance to the discontinuity. The mobility of the imer and outer zones can be calculated from the slopes of the first and second straight lines, respectively, by the normal methods of the flow test analysis. We found that the radial distance to the discontinuity may be determined from the abscissa value for the point of intersection of the extensions of the two straight lines. Results similar to some of these were reported by Adams et aL7 The approximate solution compared favorably with the exact one during the first and second straight-line periods. However, during the transition zone, deviation occurred between the two solutions. Discussion of Figures Figs. 1 through 7 summarize the results of this investigation. On Figs. 3 through 7 there appears the equation of each respective plot. In this paper the mobility ratio M is defined as klp2/kzpl, where subscripts 1 and 2 refer respectively to the inner and outer zones, and dimensionless time = t, = 6.32 X In the investigation, M ranged from 0.25 to 50;

Jan 1, 1970

By AIME

After an adventurous past-four changes of government in thirty years -the whole of Silesia and attached coal territories have become part of the Polish State. The coal resources of this area are the biggest among the European countries. Under a surface area of 5700 sq km are about 100 coal seams, with a total thickness of 150 meters. According to German estimates, there are some 150 billion metric tons of coal ranging in thickness up to 14 m within a depth of 1500 m. The seams are mostly level, free from faults, with good top and bottom; the coal is of excellent quality, hard and clean; and mining conditions are favorable. The mines are worked at considerable depth by means of vertical shafts and operate with cage and skip hoisting. Before the war, the mines were up to date, equipped with modern machines. Among the European countries, output per man shift was the highest ? 1.9 to 2.1 metric tons ? and cost of production was the lowest.

Jan 1, 1949

By H. H. Dreissen, F. J. Fontein

The operating principle of the classifying cyclone has been described often but some special aspects of the cyclone receive further clarification here. In addition, several uses of the classifiers are summarized and made clear by means of practical examples. In coal and ore washeries, the washing cyclone is widely used for the separation by specific gravity of sizes up to about 12 mm. This application has lately been extended to the separation by specific gravity of particles up to about 50 mm. This use makes special demands on the construction and wear resistance of the cyclone. The sieve bend, a development of the Dutch State Mines which is less well known than the hydrocy-clone, is dealt with at some length. The sieve bend is an apparatus designed for wet screening. Attention is given to the variables influencing the performance of the sieve bend. Hydrocyclones are now so widely applied that it would be difficult to find an industry not, directly or indirectly, using them or knowing how to use them since publications on this subject abound.1-3,5,9-11,13-15 However, because of the large number of variables influencing the operation of classifying cyclones, it is not entirely possible to calculate the results of this type of cyclone. Therefore, a number of lesser known variables will be discussed here along with some special applications of the classifying cyclone. FACTORS INFLUENCING CYCLONE CLASSIFICATION Shape of Particles: The shape of particles may cause a much coarser classification than the one expected, considering the sieve analysis and the cyclone dimensions chosen. This was clearly shown by feeding a mixture of spheres and disks in water into a cyclone. The spheres were 0.36 mm diam and the disks, 3 mm diam and 0.03 mm thick. These dimensions were chosen in order that the disks and spheres might have the same rates of fall under gravity. Both spheres and disks had a specific gravity of 1.05. The results obtained with these particles in a cyclone are summarized in Table I. Test No. 2 shows that the catch of spheres was

Jan 1, 1963

By M. Mortada

Nonsteady-state flow of slightly compressible liquids in porous media of non-uniform properties has been the subject of a number of recent studies. Most of these studies considered one-dimensional flow in systems with cylindrical geometry and with the properties of the porous medium varying with radial distance only. A. Houpeurt' studied the problem in its general form by examining the solutions of the differential equation, In Eq. 1, the permeability k and the porosity + are arbitrary functions of radial distance. Houpeurt concluded that, except for special forms of the functions k and the problem is not well suited for mathematical treatment, but lends itself to high-speed digital computation. Carslaw and Jaeger' discussed the solution of Eq. 1 for the case in which the permeability varies as a power of the radial distance. P. Albert3 studied analytically the pseudo steady-state solutions in systems of finite radial extent and non-uniform properties. He also obtained some numerical solutions for nonsteady-state flow using a high-speed computer. William Hurst4 examined the interference pressure drop due to a point sink located in an infinite system consisting of two permeability regions in series. In this case, the permeability changed at a radial distance r from the point sink. INTERFERENCE BETWEEN OIL FIELDS IN A NON-UNIFORM AQUIFER The interference pressure drop for oil fields located in an extensive aquifer of uniform properties is discussed in a number of places in the literature. This work considers the interference pressure drop for oil fields located in a non-uniform extensive aquifer comprising two regions of different properties as shown in Fig. 1. Region I of the aquifer extends from which is the radius of Oil Field A, to ar,,, where a>1. It has permeability k,, porosity +, and effective compressibility c,. Oil Field B is located in Region II which extends from ar, to infinity and has different properties from those of Region I, but the same formation thickness h. Region II has permeability k2, porosity and effective compressibility c2. The choice of this type of aquifer should not imply that it is of frequent occurrence. It is chosen primarily to illustrate the effects of non-uniform aquifer properties on oilfield interference. It is of interest to point out that a non-uniform radial aquifer in which both the permeability and the porosity are inversely proportional to the radial distance can be treated in a manner similar to a linear aquifer of uniform properties. The situation where only the permeability varies as the inverse of the radial distance is also amenable to analytical treatment. Both aquifers behave quite differently from a radial aquifer with uniform properties so far as the water influx and the interference pressure drop are concerned. METHOD OF SOLUTION The expression for the interference pressure drop in Oil Field B due to a constant rate of water influx in Oil Field A is developed in the Appendix. This is accomplished by the simultaneous solution of two partial differential equations describing the pressure in Regions I and 11. The two differential equations are solved subject to the following conditions: (1) at r,, the pressure gradient is constant; (2) at ar the pressure and

By A. G. Rozner

TRANSVERSE rupture tests have been commonly used in mechanical investigations of brittle materials. The specimens are simple, easy to prepare, and loading presents no difficulty. Owing to the complexity of stress distribution in bending1 one can determine stresses rigorously only for the elastic range. The bend-test results, however, are at times converted into tensile-strength data, determined as maximum fiber stress. The assumption is made that for small plastic deformations the linear stress-strain relation applies. This problem was experimentally investigated by Bach3 who tested cast iron in bending and in tension and found that the maximum fiber strength obtained in bending exceeded the experimental tensile strength by a factor depending on the geometry of the tested piece. The factor varied from 1.57 for a rectangular cross section to 2.12 for a circular cross section of the tested beam. Since this work was carried out 60 years ago, the cast iron used could be expected to have been highly brittle, thus the extent of plastic deformation prior to fracture very small. We have therefore carried out a number of tests on magnesium-modified cast iron with an average elongation of -5 pct. It was hoped that the data obtained from the tests would serve as a guideline for comparing data obtained in tension and bending for brittle materials. Mechanical properties were measured at room temperature on an Instron tensile machine at a crosshead speed of 0.05 in. per min. The three-point bend test employed cylindrical bars 0.20 in. in diameter with a 1.0-in. span. For the tensile test, cylindrical tensile specimens with a gage length of 0.85 in. and a diameter of 0.160 in. were used. Results are summarized in Table I. From Table I one can see that fracture strength

Jan 1, 1965

By J. Jones-Parra, R. S. Reytor

The porosities of fractured limestone reservoirs can be divided into two broad types in accordance with their effects on fluid distribution and fluid flow. In the coarse porosity, gravity segregation lakes place freely and the resistance to fluid flow is very small. In the fine porosity there is no segregation and a high resistance to flow, and it has relative permeability characteristics similar to tight sandstones. By analyzing the affect of the two porosities it is concluded that in some cases to recover the maximum amount of oil it is necessary to remove large quantities of gas from the reservoir by producing at high gas-oil ratios. In this manner the fine porosity is drained of its oil and the gas-oil contact drops slowly permitting higher production rates from the oil leg. Since this conclusion is contrary to widely accepted principles of conservation, a mathematical model (Fig. I) was constructed to duplicate the conditions desired. The behavior of the model indicates that under certain conditions it is possible to recover more oil by producing at high gas-oil ratios than by production at low gas-oil ratios, and that the rate of production is affected more by gas shut-offs than by the decrease in pressure (Figs. 2, 3, 4 and 5). INTRODUCTION It has been noted that certain limestone reservoirs behave in such a way as to indicate that there are two distinct types of porous spaces available for fluid storage and fluid flow. Regardless of the nature of these porous spaces the distinguishing characteristic is that in one type of porous space there is definite gravity segregation between the oil and the gas; while in the other, the gas evolved tends to remain distributed equally throughout the reservoir. For the sake of simplicity the porosity in which gravity segregation takes place at a fast enough rate to affect the behavior will be called "coarse po- rosity", while that in which this is not so will be termed "fine porosity". The behavior of a reservoir of this type would be different than that of a sandstone reservoir, especially if most of the oil is in the fine porosity. It has been observed that fluid flow to the wells takes place mostly through the coarse porosity. The large fractures which

By Malcolm T. Hepworth

RECENT interest in thermoelectric devices has been directed toward studies of the properties of thermoelectric materials of semiconducting solid compounds with little attention given to ionic and semiconducting liquids such as aqueous solutions, fused salts, and mattes. One type of thermoelectric system is the thermocell: a nonisothermal galvanic cell with two identical electrodes at different temperatures connected by an electrolyte bridge. An electromotive force, v, is generated which is a function of the electrode reactions and the properties of the electrolyte according to the Eastman' equation: where S* is the entropy change of the system arising from the electrode reactions and by heat transferred by ion migration and by thermal conduction. The quantity nF is the product of equivalents passed and Faraday's constant. A value of S* of 23.06 cal per "C is equivalent to 1 mv-Faraday per "C. The symbol, a, is used for dV/dT in analog to the See-beck coefficient of solid-state thermoelements. de Bethune2 has calculated the temperature coefficients of the electromotive force of a large number of nonisothermal aqueous cells from measurements on the nonisothermal temperature coefficients of the standard hydrogen electrode, combined with data on the isothermal temperature coefficients of half-cells tabulated in the literature. Values of these coefficients (a) in de Bethune's compilation ranged up to 3 mv per C. In particular he reported a value of +2.059 mv per "C at 25'C for the cell: Fe (aqueous, unit activity) (aqueous, unit activity) written for the hot-electrode reaction. The positive sign indicates that the hot electrode is positive (an "n-type thermocell"). In analog to a solid-state p-n system, it would be possible to couple two thermocells together to form a system in which the figure of merit could be calculated by adding the temperature coefficients according to the relationship described by offee:' where a is the Seebeck coefficient in volts per "C, p is the specific resistivity in ohm-cm, and K is the thermal conductivity in watts per cm "C. Even though ionic systems have rather high electrical resistivities compared with semiconducting and metallic systems, it was felt that a preliminary study of one ionic system should be made to establish some basis for evaluating the possibility of a p-n thermocell for energy conversion. Accordingly the Fe", Fe"' system was studied as a possible component for a p-n system. A glass system was constructed consisting of two vertical water-jacketed tubes connected by a horizontal tube, Fig. 1. Platinum-black electrodes 1 cm by 1 cm in dimension were inserted in each vertical tube with thermometers to register the electrode-compartment temperatures. The temperature of the electrode compartments was controlled by circulating water from thermostatted baths around the electrode compartments. The electromotive force of the cell was then read by a potentiometer for zero current as a function of the temperature of the hotter electrode. Current output of the cell for varying external loads was also measured. The cell resistance was measured by means of a bridge circuit with 10,000 cps signal and oscilloscope. Resistance measurements were converted to specific resistivity by calibrating the cell with a solution of known conductivity.

Jan 1, 1965

By C. W. Goodale

TOMBSTONE, a name not exactly full of cheerful suggestion, has a great record as a mineral producer and a colorful history as a frontier mining camp. The only practical route to Tombstone in the early 80's was by way of San Francisco and Los Angeles. The Southern Pacific was building across Arizona, and a sleeper was attached to a construction and freight train at Los Angeles, and was trailed slowly across the Colorado Desert to Benson in the San Pedro Valley. Thence one staged 26 miles to Tombstone, which is located near the foot of a range of hills at an altitude of about 4500 ft.

Jan 1, 1925

By F. W. Schaller

TETRAGONALITY is an important aspect of the models of transformation, strengthening, and tempering of ferrous martensite. When the c/a

Jan 1, 1963

By R. G. Turner, M. G. Hubbard, A. E. Dukler

Gas phase hydrocarbons produced from underground reservoirs will, in many instances, have liquid phase material associated with them, the presence of which can affect the flowing characteristics of the well. Liquids can come from condensation of hydrocarbon gas (condensate) or from interstitial water in the reservoir matrix. In either case, the higher density liquid phase, being essentially discontinuous, must be transported to the surface by the gas. In the event the gas phase does not provide sufficient transport energy to lift the liquids out of the well, the liquids will accumulate in the wellbore. The accumulation of the liquid will impose an additional back pressure on the formation that can significantly affect the production capacity of the well. In low pressure wells the liquid may completely kill the well; and in the higher pressure wells there can occur a variable degree of slugging or churning of the liquids, which can affect calculations used in routine well tests. Specifically, the calculated bottom-hole pressures used in multirate backpressure tests will be erroneous if the well is not removing liquids on a continuous basis, and gas:liquid ratios observed during such a test may not be correct. Several authors1,3,8,14 have suggested methods to determine if the flow rate of a well is sufficient to remove liquid phase material. Vitter14 and Duggan' proposed that wellhead velocities observed in the field would be adequate for keeping wells unloaded. Jones8 and Dukler3 presented analytical treatments resulting in equations for calculating, from physical properties, the minimum necessary flow rate. An analysis of these studies indicates the existence of two proposed physical models for the removal of gas well liquids: (1) liquid film movement along the walls of the pipe and (2) liquid droplets entrained in the high velocity gas core. Although there probably is a continuous exchange of liquid between the gas core and the film, they will be treated separately for the purposes of this study. The development and comparison of these separate models with experimental data will permit the determination of which, if either, is the controlling mechanism for the removal of liquids from gas wells. The Continuous Film Model Liquid phase accumulation on the walls of a conduit during two-phase gas/liquid flow is inevitable due to the impingement of entrained liquid drops and the condensation of vapors. The movement of the liquid on the wall is therefore of interest in the analysis of liquid removal from gas wells. If the annular liquid film must be moved upward along the walls in order to keep a gas well from loading up, then the minimum gas flow rate necessary to accomplish this is of primary interest. The analysis technique used follows Dukler2 and Hewitt5 and involves describing the profile of the velocity of a liquid film moving upward on the inside of a tube. The minimum rate of gas flow required to move the film upward is then calculated.

Jan 1, 1970

By J. P. Neumann, L. Raymond

At temperatures near 1000°C, only the (112) (111) slip systems are operatire in tungsten. Therefore, the substructure introduced into the billet upon rleforming a single crystal by rolling at 1000 "C can be controlled by proper selection 01. processing ral'iubles. Using a reduction of 10 pct pel- pass, the (001)[110] and the (110)[001] crystals will deform by duplex slip rip to a 50 pet reduction in thickuess. These rolled single-crystal sheels are characlerized by anisotropic hardening, retention of ductility with warm working, lattice bending which is related to the conlacl (angle, and macroscopic dimensional changecs in the length bid not the width of the billet. When several slip systems become operative, a greater degree of work hardening is itztvoducetl into the crystal. This rolling- condition is characlerized by isotropic hardening, loss of ductilily with warm working, complex lattice distortions, and macro-scopic dimensional changes in both the length rind Width of the billel. IN tungsten, the {1 10}(111) slip systems are operative below room temperature,' while above 700°C only the {112{ (111) slip systems are observed.2,3 In the transition region, i.e., room temperature. both systems appear. It is the purpose of this investigation to show that tungsten single crystals deformed by rolling at a temperature where only one slip system is operative generate dislocation substructure which depends on the crystal orientation. For a specific crystal orientation. the resulting dislocation substructure can be further influenced by modifying the rolling procedure. Crystals oriented for multiple slip display less substructural sensi- tivity to modifications in processing techniques than do single crystals oriented for duplex slip. Under simple slip modes of deformation, very little work hardening is introduced into a rolled single-crystal sheet. Mechanical properties such as room-temperature strength. ductility, and hardness are used to confirm the existence of the different work-hardened conditions generated within the crystal by modified warm-rolling techniques. EXPERIMENTAL PROCEDURE Material. Single-crystal billets of four different crystal orientations. grown by the Arc-Verneuil technique. were ground to a size of 0.25 by 0.375 by 3 in. In terms of their rolling plane and rolling direction, the billets had the following orientations: (1101 [001 ] (110) [110] (001) [110] (001) [100] The actual orientation of all crystals was within 5 deg of the ideal orientations. The typical impurity content of the crystals is given in Table I. Polishing and Etching. Polishing was done elec-trolytically in a 20 g per liter aqueous solution of NaOH at approximately 10 v. It was established by the Laue back-reflection X-ray technique that the surface damage due to grinding and cutting operations with a diamond wheel did not exceed 0.001 in. Therefore after each cutting or grinding operation at least 0.002 in. was removed electrolytically from the surface in order to eliminate surface effects. By lowering the voltage to 3 v, subgrain boundaries and individual dislocations are identified in agreement with Berlec 4 where the etch-pit traces on a cubic plane form a square. The etching time was about 5 sec at room temperature. Rolling. Rolling was carried out on a Loma 2-high mill (Model 600). The peripheral velocity of the 6-in.-diameter rolls was 500 in. per min, with the surface temperature of the rolls about 400° to 450° C The billets were heated before each pass for 30 min in argon to 1000 C. Oxidation of the crystals during rolling in air resulted in a thin layer of greenish-yellow WO 3 This oxide was removed after each pass by immersing the crystals for a few minutes in a boiling NaOH solution. Prior to the initial rolling pass, a surface layer of 0.001 in. was removed by polishing. The crystals were then annealed in vacuum (10-4 torr) at 2400 C for 30 min. All crystals were rolled in the same direction; i.e., the same end was always introduced into the rolls. The rolling program was conducted in

Jan 1, 1965

By H. J. Modi, D. W. Fuerstenau

pH effectively regulates the flotation of corundum through its control of the surface charge. Since collector ions function as counter ions in the double layer, the collector must be anionic when corundum is positively charged and cationic when it is negatively charged. Even a long-chained xanthate will float positively charged corundum. Association of the hydrocarbon chains of the adsorbed collector ions gives rise to increased adsorption and increased rate of flotation. Because of this phenomenon, neutral organic molecules aid flotation although the unionized collector cannot promote flotation independently. Na2SO4 was found to depress the flotation of corundum with animic collectors through ionic competition whereas the same salt activates corundum for flotation with cationic collectors. A close connection between ion association, electrokinetic behavior, and floatability is suggested. As part of the increasing interest in the physical chemistry of flotation, strong experimental evidence has been obtained which indicates that organic ions are adsorbed as counter ions by non-metallic oxide minerals mainly because of the electrical forces which exist at interfaces(1-3). Thus flotation of such minerals without activation should then be appreciable only when the mineral and the collector are oppositely charged. Since only limited work has been reported on the effect of surface charge upon flotation behavior(3) this general hypothesis on the flotation of insoluble oxide minerals has not been tested thoroughly. Investigating the flotation of a mineral for which extensive electrokinetic data exist yields a way to test this hypothesis more extensively. The electrokinetic behavior of corundum in solutions containing both organic and inorganic electrolytes has been studied quite thoroughly' Electro-kinetic measurements have shown that in the case of corundum, simply by controlling pH the solid surface can be charged either positively or negatively. For this reason corundum was chosen for study. The object of this paper is to present a study of the flotation of corundum and to explain the results in the light of our knowledge of adsorption mechanisms gained from streaming potential investigations. This paper is concerned mainly with the effect of surface charge on flotation with anionic and cationic collectors, but in addition such flotation phenomena as collector hydrolysis, Van der Waals attraction between hydrocarbon chains, ionic competition, and activation are discussed. While the present paper is confined to a reporting of the data obtained and some of the more immediate conclusions, it will be seen that the results, in combination with those on other systems, do promise a

Jan 1, 1961