Search Documents

By Fred D. DeVaney and

The coercimeter, as its name implies, is an instrument for measuring the coercive forcet of magnetic substances. It was developed by Davis and Hartenheim in the Special Studies Section, Metallurgical Division. A detailed description of this apparatus may be found elsewhere.2 The coercive force determinations of magnetic materials are interesting because of the relationship established by Gottschalk,4 who showed a linear relationship between the magnetization coercive force and the specific surface of comminuted particles. The value of this relationship in determining grinding efficiency has been shown by Dean.3 The determination of the surface contained in the subsieve sizes has always been a difficult problem for investigators. They made approximate measurements of the surface of coarse materials by sizing on screens, but for the determination of the surface of the sub-sieve sizes it was necessary to make detailed grain counts or elutriation tests, or to study dissolution rates. The technical literature contains many references to other methods for determining these surfaces, either by some special apparatus or by mathematical calculations based on distribution lines. Many of the methods are long and tedious, and the results of some, at least, are questionable. he turbidimeter gives quick results on ground cement. By using magnetite as the material to be ground, a simple determination of its coercive force by the coercimeter, requiring 10 minutes or less, can be transposed directly and accurately into units of relative surface. This subject has been pursued further by the U. S. Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., and the following is a description of the results.

Jan 1, 1939

By Fred D. DeVaney and

The coercimeter, as its name implies, is an instrument for measuring the coercive forcet of magnetic substances. It was developed by Davis and Hartenheim in the Special Studies Section, Metallurgical Division. A detailed description of this apparatus may be found elsewhere.2 The coercive force determinations of magnetic materials are interesting because of the relationship established by Gottschalk,4 who showed a linear relationship between the magnetization coercive force and the specific surface of comminuted particles. The value of this relationship in determining grinding efficiency has been shown by Dean.3 The determination of the surface contained in the subsieve sizes has always been a difficult problem for investigators. They made approximate measurements of the surface of coarse materials by sizing on screens, but for the determination of the surface of the sub-sieve sizes it was necessary to make detailed grain counts or elutriation tests, or to study dissolution rates. The technical literature contains many references to other methods for determining these surfaces, either by some special apparatus or by mathematical calculations based on distribution lines. Many of the methods are long and tedious, and the results of some, at least, are questionable. he turbidimeter gives quick results on ground cement. By using magnetite as the material to be ground, a simple determination of its coercive force by the coercimeter, requiring 10 minutes or less, can be transposed directly and accurately into units of relative surface. This subject has been pursued further by the U. S. Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., and the following is a description of the results.

Jan 1, 1939

By John W. Lane, Richard A. Ronzio, Frederick N. Bender

Climax Molybdenum Co. operated a hydrometallurgical plant at Climax, Colo., from August 1966 to August 1968 to recover molybdenum from an oxidized ore. The feed, tailings from sulfide flotation, was first upgraded by cycloning. The concentration plant handled 6000 tpd of feed and produced 2000 tpd of slime concentrate. The concentrate was leached by a sulfuric-sulfurous acid solution at 65°C. The molybdenum was solubilized in the form of "molybdenum blue." Activated charcoal was added to the leach tailings in a resin-in-pulp type circuit. Molybdenum was adsorbed on the charcoal. The charcoal was screened from the pulp and washed. The washed charcoal was pumped to columns where it was ammoniated and air-blown. The oxidized molybdate then was washed from the charcoal. The eluate was evaporated until ammonium dimolybdate crystallized out. The ammonium dimolybdate was calcined to molybdenum trioxide.

Jan 1, 1973

By M. Semchyshen, G. A. Timmons

The predominant orientation in both straight-rolled and cross-rolled molybdenum is the {100} [110] texture. Upon complete recrystallization, this same texture predominates, but there is less spread about the ideal orientation. A secondary orientation about the [111] direction as the axis develops in cross-rolled sheet. Compression-rolled sheet exhibits random orientation in the plane of the sheet. Some mechanical properties were measured at varying angles to the rolling direction to determine the effect of preferred orientation on anisotropy in molybdenum sheet which had been straight, cross, or compression rolled. THE development of the arc-cast process has made available large ingots of molybdenum from which it is possible to roll sheet of considerable size. It is anticipated that such sheet will be further fabricated by spinning, drawing, stamping, or forming. Anisotropy of physical properties caused by the preferred orientation developed in the sheet during rolling may be expected to affect the behavior of the metal when subjected to these fabricating operations. To produce a sheet which will be most amenable to the fabrication of a given shape by a particular operation, consideration should be given to the directions and magnitudes of plastic deformations produced in the operation. When possible, the rolling schedule should be controlled to develop a texture which favors the required deformation. The existence of preferred orientations in rolled molybdenum sheet has been reported by Jeffries,' Konobejewsky,' Fujiwara," Goss,' and Ransley and Rooksby." None of these investigators obtained sufficient X-ray data to permit the construction of pole figures; instead, they based their conclusions upon Debye-Scherrer patterns of a limited number of positions. Ransley and Rooksby devoted some attention to transcrystalline cleavage at 45" to the rolling direction, indicating that it is appreciable in polycrystalline material only when the crystals are in the ideally preferred condition, and that this condition is only approached if the metal has been rolled successively in two perpendicular directions. In a recent paper, Custers and Riemersmao introduced the first pole figures to describe the textures of straight-rolled and cross-rolled molybdenum sheet. To increase the knowledge concerning the generation and effects of preferred orientations in molybdenum sheet, an investigation was undertaken to determine the effects of variations in rolling schedule and annealing treatments on preferred orientation, and to correlate preferred orientations with some mechanical properties. The orientations of straight-rolled, cross-rolled, and compression-rolled sheet have been determined by X-ray analysis, both as-rolled and after recrystallization. Pole figures have been constructed to describe the textures produced by these various rolling procedures. Texture of Cast Molybdenum Ingots In the arc-cast process, molybdenum powder is pressed into a vertical column which is sintered to increase its strength as it proceeds downward into a water-cooled mold, where the metal is melted in an alternating-current arc established between the end of the formed powder electrode and the metal bath at the top of the growing ingot. Since the solid-liquid interface moves continuously upward in the mold, the crystal axes are not normal to the cold surface of the mold but have the curvature shown in Fig. la. X-ray analysis reveals that the cube axis is the fiber axis and that it is normal to the cold surface of the mold; that is, the [loo] direction is parallel to the longitudinal axis of the ingot. This substantiates recent work by

Jan 1, 1953

By J. K. Kerver, J. S. Osoba, J. G. Richardson, J. A. Hafford

A detailed study of a number of methods of relative permea-abilitv measurement has been made in a search for the tech-niqrle most suited to routine analysis of cores taken from reservoir rock. It has been found from tests run on the same samples of core material by a number of techniques that the Penn State, Hassler, Hafford, and dispersed feed techniques all yield results which are felt to be reliable. Conditions under which the faster single core dynamic technique may be used are described. Further work on the calculation of relative permeabilities to oil from data obtained by the gas drive method is needed before this latter rapid method can be utilized. Correlations between theoretical studies and experimental results have been obtained in studies of the boundary effect. pressure distribution in two-phase flow, and gas expansion effects. Previous conclusions that the effects of the outflow boundary could be made negligibly small have been substantiated. Results of experimentally determined oil and gas pressure distributions along a core sample during flow are presented. Further studies of the effects of rate of flow in the measurement of relative permeability-saturation relations have shown that results are independent of the rate of flow as long as the flow rate is below the point where inertial effects commence. An analysis of the effects of a severalfold expansion of gas along the flow path indicates that while saturation gradients are induced in the test sample, the errors caused by this phenomenon in relative permeability measurements are small. INTRODUCTION Many pages of literature have been devoted to pointing out the need for relative permeability-saturation relations in reservoir engineering. One of the most attractive ways of obtaining this information is by the analysis of samples of core material taken from the formation in question, and again literature has described man); methods for obtaining these data. It is the purpose of this paper to present the work that has been done in the study of some of these published methods together with some other methods that have been recently developed in this laboratory. Also, a study of some of the factors that influence the laburatory determination of relative permeability-saturation relations is presented. FACTORS WHICH AFFECT LABORATORY STUDY OF FLUID FLOW THROUGH RESERVOIR ROCK To determine relative permeability-saturation relations of samples of reservoir rock in the laboratory, it is important to know what factors affect these measurements in order that the magnitude of these effects can be ascertained and steps then can be taken to eliminate or, in some cases, to minimize them. The factors that have been investigated are the boundary effect, the effect of gas expansion. and the rate effect. Boundary Effect In laboratory experiments in which two immiscible fluids are flowed through a porous medium, there exists a discontinuity of capillary properties at the outflow face. This discontinuity exists became the fluids pass from a region of finite capillary pressure in the sample to a region of zero capillary pressure in an open receiving vessel. The capillary forces existing in the core caupe the rock to tend to retain

Jan 1, 1952

By G. Krauss, J. M. Thompson, H. Y. Kumagai

Boron-doped p-type and arsenic-doped n-type source materials were used to deposit thin silicon films on amorphous fused quartz substrates by cathodic sputtering in argon atmospheres. All as-sputtered films were found to have high electrical resistivities of about 104 ohm-cm, despite controlled variation of the substrate temperature from 50O to 400°C. The high resistivity of the n-type films persisted even after postdeposition heat treatments as high as 1000°C, while p-type films showed a sharp decrease in re-sistivity to values on the order of 1 ohm-cm or lower after heat treatments above 650°C. X-ray and electron diffraction, together with transmission electron microscopy of the p-type films, revealed that the improved electrical properties resulted from two distinct processes. A primary crystallization or recovery within the pains, which were approximately 200Å diam in the as-sputtered films, accompanied the initial sharp drop in resistivity at 650°C. Following this process, a secondary recrystallization or discontinuous grain growth was nucleated in films heated at 1000°C. The resulting significantly increased size of certain grains and the corresponding decrease in grain boundary area accompanied an additional decrease in resistivity after heat treatment at 1000°C. The properties of thin silicon films are of interest because of their possible application in device technology. Although evaporated silicon films on amorphous substrates1-3 and both sputtered and evaporated germanium films4-' have been studied in some detail, sputtered silicon films have not been widely investigated. It has been observed that evaporated silicon films deposited at substrate temperatures below approximately 600°C are amorphous.1,3,9,10 At substrate temperatures higher than this, the films are polycrys-talline, sometimes exhibiting a fiber texture with the fiber axis normal to the substrate surface.' Similar results have been obtained with germanium films, although in this case the substrate temperature for the amorphous to crystalline transformation is reported to be as low as 150OC.5 The mechanism of film deposition by cathodic sputtering differs markedly from that of thermal evaporation. It might be expected, therefore, that the properties of sputtered and evaporated silicon films would also differ. The purpose of our study was to determine the effects of deposition conditions and heat treatments on the electrical resistivity, structure, and composition of thin silicon films sputtered on fused quartz substrates. EXPERIMENTAL DETAILS Apparatus. A schematic diagram of the sputtering apparatus is shown in Fig. 1. The vacuum chamber was enclosed by an 18-in.-diam by 12-in.-high Pyrex bell jar mounted on a stainless-steel base plate. Access holes in the base plate were used to supply argon gas to the chamber, to allow for various electrical feedthroughs, and to provide mechanical motion to the shutter between the source material and substrate. The chamber was evacuated by a pumping system consisting of a 720 liter per sec oil diffusion pump backed by a 13 cu ft per min mechanical pump. Ultimate pressures of less than 1 x 10-6 torr could be achieved. The substrates were securely mounted on the stainless-steel substrate holder by quartz tabs held in place by stainless-steel screws. Temperatures of the substrate holder were measured by a thermocouple inserted within the holder. A quartz lamp was used to heat the holder and temperatures as high as 420°C could be maintained. Deposition Conditions and Procedure. The substrates used were polished fused quartz slides 116 by 1-12 by 3 in. and were outgassed at 200°C for 1 hr at a pressure less than 1 x 10-5 torr before film deposition. This was followed by a presputtering period of 2 hr during which the movable stainless-steel shutter was so positioned that deposition on the substrate was prevented. At a sputtering voltage of 5000 v dc and an argon pressure of 0.03 torr, the cathode cur-

Jan 1, 1967

By Herbert Banks Johnson

DURING the past 10 or 12 years very little information has been made generally available concerning the commercial possibilities of separating materials by means of static electricity; and yet during that same period important improvements have been made in various branches of the science of electricity, which, when taken together, and applied to electrostatic separation, have resulted in important improvements in that art as well. For example, much improvement has been made in high-voltage electrical equipment such as full-wave vacuum-tube rectification and improved mechanical rectification. Great strides have likewise been made in the development of insulators for high-voltage work, not only in the materials used but also in the design of the insulators themselves. Again, in another field, the development of air-conditioning equipment has improved the technique of controlling the surface condition, through drying or humidifying, of the various materials that are passed through the electrostatic separator. In many authoritative publications and textbooks, the electrostatic separation process is declared to require a balance far too sensitive for general commercial application. For example, one publication1 in the past has referred to an unfavorable effect on the process caused by varying atmospheric conditions such as humidity. Some2 have even gone so far as to state that sunlight and shadows may seriously affect the separating efficiency of the process. Such statements may have been true in the early development of the art, when the source of static electricity was derived from a friction disk machine, such as the Wimshurst. The Blake Mosher equipment and the work of Huff in applying motor- generator sets, transformers and mechanical rectification overcame much of this kind of objection to the commercial application of the electrostatic separating process. Another objection made periodically is that it is generally considered necessary to feed the particles into the electrostatic field in a stream that

Jan 1, 1938

By Paul Weaver

DURING 1932 the amount of geophysical surveying carried out as a part of oil-field development in¬creased, particularly in the Gulf Coast of Texas and Louisiana. Here the most intensive geophysical activity was displayed in the discovery of domes and prospects several years ago, after which there was a period of relative inactivity. This year many of the leases required development and geophysical methods were used to obtain pictures of the detailed structures. These were almost exclusively gravity and reflection-seismograph surveys and for the first time this latter method was generally used by oil operators to construct subsurface contours. The total number of geophysical troops in this territory increased from 16 to 40 during the year.

Jan 1, 1933

By John Brownson

Ge-Si N-N heterodiodes hare been built recently which show promise as high-speed logic devices. Low-resistivity germanium is deposited on silicon substrates held at temperatures above the germanium melting point and an alloyed heterojunction formed. The diodes are fabricated from this material using conventional mesa techniques. Over-all device qualify has been greatly improved by the use of epitaxial silicon substrates, that is, a subsirale consisting of a film of thin, high -resistivity silicon on a thicker Piece of low-resistirily silicon crystal. A semimpirical device design equation has been devised which predicts switching performance fairly well within the range of resistivitics and geometries employed. Switching times 01 0.9 ns and PIV 's of —20 v are typical of the better 10-ma diodes. Switching times as low as 0.5 ns have been observed for 10-ma diodes and as low as 2.8 ns for 200-ma diodes. With further development it should be possible to improve switching speed by a factor of four. IN our laboratory, Ge-Si heterodiodes have been built recently which show promise as high-speed logic devices. The diodes have been built using a process reported in some detail in an earlier publication.' The process in short involves alloying a thin film of low-resistivity germanium into a silicon substrate. the germanium having been transported and deposited by the well-known Theuerer halide reduction process.2 This process contrasts with that reported earlier by Oldham who used an essentially conventional direct epitaxial deposition technique.3 Oldham's process, unlike ours, requires cleavage of the silicon sample inside the reactor furnace the instant prior to deposition. Our process has the advantage of yielding large-area macro-scopically plane heterojunctions. Heterodiodes in general have several interesting properties. Without attempting to summarize the theory of heterojunctions.4 two of these properties which have direct relevance should be mentioned. First, N-.V and P-P heterojunction diodes rectify alternating current. Provided that either the band gap or the electron affinity of the two materials is different (which in general is the case), electronic barriers will exist in the junction band structure. When the device is sufficiently forward-biased, the barriers shift so as to permit current flow, and when it is reverse-biased. the barriers block current flow. Second, for N-N and P-P heterodiodes. the foward-conduction process involves majority carriers only. Consequently. when such a device is turned off. there is no minority-carrier storage and hence the diodes switch on and off quite rapidly. As we have reported earlier. N-P and N-N Ge-Si heterodiodes have been built in this laboratory. As one would predict from theory, the N-P heterodiodes were rather slow in turning off while the N-N's were quite fast. Similarly, the turn-off time of the N-P's increased rapidly with forward current while that of the N-N's was independent of forward current. Both N-N's and N-P's were moderately photosensitive. Photocurrents resulting from normal room illumination were as high as 1 µa at 1 v for small-area devices. The most disappointing parameter of the early N-N devices was reverse leakage.' The reverse characteristic was invariably "soft" and leakage at only several volts reverse bias was intolerable. The reverse characteristic was greatly improved by using higher-resistivity silicon substrates. Leakage becomes large at voltages about one third of the avalanche voltage one would expect of a P-N homo-junction formed on silicon of the same resistivity. Thus leakage could be reduced to reasonable limits by using unconventionally high-resistivity silicon. Medium-power diodes formed on 30 ohm-cm substrates leaked typically 15 to 50 µa at 100 v reverse bias. The use of high-resistivity silicon substrate material, however, created a new problem. In order to have an acceptable forward-conductance characteristic. the area of the diodes had to be increased. With this increase in area, the capacitance increased. Switching time for N-N heterodiodes is essentially a linear function of capacitance. Thus when the resistivity was raised. so was the switching time. A SEMIEMPIRICAL HETERODIODE DESIGN EQUATION As a result of our experiments with a limited range of diode geometries and resistivities. a semi-

Jan 1, 1965

By R. W. Heckel

The densification of molybdenum powder by hot pressing has been studied as a function of time (up to about 3 x 104 sec) at pressures of 5000, 15,000, and 30,000 psi in the temperature range from 3700o to 1200°C. Excluding results below 2 to 5 x 10 sec, the density (D) - pressure (P) - time (t) data followed the general form:

Jan 1, 1965

By Arthur Notman

IN VIEW of the wide publicity given to the charges by the Couzens Committee of the United States Senate of discrimination by the Bureau of Internal Revenue in favor of the copper companies, it becomes a matter of interest to consider the basis for these charges. The point to be determined is whether they rest on a foundation of fact or are purely and simply matters of opinion. The whole question boils down to the purpose of the Tax Law as applied to mines, which is to afford the same protection to them as provided for all other taxpayers, namely: that they were to be allowed to pay back as depletion to their owners the values of their properties as they existed or were estimated to exist on May 1, 1913, free from tax. To determine these valuations it was? necessary to select from a wide range of possibilities a set of values for a number of essential factors.

Jan 1, 1925

By Cyril Stanley Smith, Earl W. Palmer

STRIP of any of the metals used for deep drawing operations occasionally yields cups that are defective because of a rim that varies in height around the cup in a wave-like manner Some such defects are traceable to tools or other press factors, but when the protuberances formed (usually four in number on brass and other copper alloys) are symmetrically disposed with respect to the rolling direction of the strip, they are invariably attributable to the metal The effect is known as "caring" and the protuberances are called "ears" Other terms frequently heard are "tips," "scallops," and "corners " It is recognized that the effect is most commonly a result of a directional crystal structure produced by rolling and annealing operations in the manufacture of the metal strip Numerous papers dealing with various aspects of the caring effect have appeared in the literature, those listed in the references' being especially interesting and valuable An investigation of the factors influencing caring of brass cups has been in progress in the laboratories of the American Brass Co for several years, and it was thought desirable to make some of the results generally available in summarized form The present paper discusses many factors that do and do not contribute to ear formation In addition, a section is devoted to methods of minimizing the caring tendency of brass sheet by proper selection of the cold-rolling and annealing schedule by which it is produced In the space available, it is impossible to quote detailed experimental procedures and numerical results However, the authors make no statement that they do not believe to be properly substantiated, either by experimental evidence obtained under laboratory conditions or by experience in the actual production of deep-drawing brass in the brass mill MECHANISM OF EAR FORMATION It must be clearly understood that the formation on cups of symmetrical ears, four or more in number, is attributable solely to the strip metal, and results from the strip having different deformation characteristics in different directions The tools used in the drawing process, or the type and completeness of lubrication of the strip, have nothing to do with the problem of ears, although they do, of course, greatly affect the "drawing quality" of the strip and the general appearance of the cup A single tip may be drawn up on the rim of a cup because of misalignment of the tools, or because the gauge of metal varies from side to side of the strip The two-ear form that sometimes appears is also traceable to gauge variations However, the four-ear and six-ear symmetrical forms that we are concerned with here are caused by factors inherent in the structure of the metal itself

Jan 1, 1942

By A. E. Harnsberger

IT is obvious that details such as the physical and chemical properties and methods of heat-treating of the materials mentioned must be omitted in a paper on the subject of materials used in oil-refinery pumps1. Only sufficient identification is given to enable the reader to find additional information from already published data. Also, the subject covers many operating conditions, but only the most important services can be discussed here. To the oil refiner, the pumping equipment is of vital interest. Practi-cally every refinery operation, from the charging of crude oil to a dis-tillation unit to the shipping of refined products, involves some form of pumping machinery. Intermediate refining stages involve a great variety of pumping machinery to carry out successfully the aims of the refinery technologist. Temperatures at which oils are handled vary from -50° F. to 900° F. Pressure may vary from subatmospheric to 2000 lb. per, sq. inch. The selection of the proper materials involves a careful consideration of the conditions under which the particular pump must operate. The four most important considerations are temperature, pressure, corrosion, and abrasion or wear. Consideration of temperature may be divided into three parts: (1) extremely low temperatures of the order of -50° F.; (2) temperatures at atmospheric or slightly above; (3) temperatures from 200° to 900° F. Pressures fall into two groups: (1) pressures reached by ordinary trade pumps of the order of 200 lb. per sq. in., (2) extreme pressure conditions involving pressures as high as 2000 lb. Noncorrosive and corrosive oils can be treated differently. Under the latter falls corrosion in the presence of water, which will occur up to 250° F. The second type of corrosion occurs in high-temperature pump-ing equipment, with temperatures from 450° to 900° F., largely caused by sulfur compounds. There are also other corrosive conditions met with

Jan 1, 1935

By Dorsey Lyon

INTRODUCTION THE electric furnace has always been found to be especially adapted to melting, refining, and finishing processes throughout its gradual acceptance by metallurgists, as a practical apparatus for conducting metallurgical operations. In the steel industry, the electric furnace is firmly established in the manufacture of steel of the highest grade, equal to crucible steel. For the production of the cheaper grades of steel in large tonnage, the electric furnace gives a higher-grade product than the open-hearth or converter, but due to the high cost of power prevailing in steel centers, considered from the electric furnace standpoint, it is not economical to produce tonnage steel in the electric furnace. As a refining and finishing agent for open-hearth or Bessemer steel, the electric furnace has had some degree of success in the production of tonnage steel. After a study of the use of the electric furnace in the steel industry, it appears that there may be a possibility of its use to advantage for the melting of cathode copper. In the case of copper the problem is not one of actual refining, because the copper if refined properly y the electrolytic method needs no further refining; it needs simply to be cast into a marketable shape. The name" refining". is applied to the present finishing process, because in the operation oxygen and other impurities are removed, which the electrolytic copper absorbs in being melted in the reverberatory furnace. Considering that processes may be positive, negative, and neutral; the electrolytic method would be positive; reverberatory melting of cathode copper, negative; and electric furnace melting, neutral. The electrolytic method produces about as pure a copper as is possible, if operated properly and the anodes are not too impure. The final reverberatory melting of this cathode copper lowers the grade of the final product, due to the absorption of gases and impurities.

Jan 8, 1914

By R. L. Wiegel

The generation of operating information for mineral beneficiation processes has become more sophisticated as a result of the use of improved laboratory analytical techniques, some of which provide multiple component assays, as well as the introduction and gradual industrial acceptance of process sensors for the measurement of flow, density, size, and chemical composition. In general, however, the mineral processing engineer's ability to tie together this wealth of information has not kept pace with these developments. In fact, in almost all existing plants, the metallurgical inflow-output balance, wed to indicate current process performance, is still being calculated from only a small portion of the information routinely available. There is substantial activity in the development of techniques for using all available process information to significantly improve the reliability of the metallurgical balance. While the use of these improved techniques does require access to computing facilities and a slight change in perspective on the part of the mineral processing engineer regarding the inviolability of process information, there are numerous practical benefits to be derived from their application. In addition to summarizing some of the concepts basic to these techniques, this paper describes the experience of the author in applying one of these advanced metallurgical balance techniques to a variety of pilot plant and commercial plant flowsheets during the past eight years.

Jan 1, 1983

By C. S. Smith, L. W. Kempf, C. S. Taylor

The thermal conductivity of aluminum alloys is of considerable industrial importance. This is particularly true in such applications as internal-combustion engines where one of the principal reasons for the use of these alloys is their relatively higher thermal conductivity. In spite of this, relatively few data are available on this property of aluminum alloys. The reason is quite apparent to anyone concerned with the experimental determination of coefficients of thermal conductivity. This determination, in theory so simple, is extraordinarily difficult if any high degree of precision is desired. Fortunately, some .knowledge of the relationship between thermal and electrical conductivity has permitted the use of the latter physical property in deducing the relative approximate values of the thermal conductivities of metals. This fundamental relationship, first enunciated by Wiedemann and Franz' as applying to metallic elements and later shown by Lorenz2 to be applicable to alloys within a single metallic system, has been of service in the industrial application of metals. The electrical conductivity of metals is easily determined with a high degree of precision. It is, therefore, quite desirable that the relationship between electrical and thermal characteristics be determined with the greatest possible precision. This paper presents data on the electrical and thermal conductivities of a number of aluminum alloys of industrial importance. Literature on Thermal Conductivity of Aluminum Alloys Masumoto3 determined the electrical and thermal conductivities of 18 aluminum alloys. His results indicated a relatively constant relationship between thermal and electrical conductivity.

Jan 1, 1937

By R. G. Wheeler, J. W. Goffard

The Larson-Miller parameter was used to correlate time, temperature, and indentation creep of magnesium, aluminum, and some of their alloys. In the temperature range 300" to 450°C, the short-time Meyer hardness of pure magnesium was less than that of the magnesium alloys tested, but for long times the pure magnesium has greater indentation creep resistance. Aluminum (1100 alloy) had 1.5 to 2.5 times more indentation creep resistance than magnesium at 300" and 450oC, respectively. Hardening of aluminum with a dispersion of Al2O3 was effective in the time and temperature ranges studied. New technologies have required the development of new materials and the utilization of the more familiar materials for new and unusual applications. The use of magnesium and aluminum and some of their alloys, because of their desirable nuclear characteristics, light weight, low cost, and ready availability, has been extended to the 300" to 450°C temperature range. In this temperature range the basic consideration of these materials must be their rate of plastic flow rather than offset yield strengths. The indentation testing reported here arose from a need for design data for the load-holding ability of supports made of these materials. Test Procedure—Hardness indents were made with a 0.275-in.-diam quartz indentor and a 10.65-lb load. The indentor was made by fire-polishing a spherical surface on the end of a fused quartz rod. The samples were held at temperature in a graphite crucible controlled to ±2°C. A thermocouple was attached to the sample and test temperatures were recorded. The diameter of the spherical indentation was measured at the end of a test period and the compression stress (Meyer Hardness) was determined by: H___________load__________ m = projected area of indent Samples were 1 in. in diam and at least 1/4 in. thick. It was observed that at the higher temperatures and longer times, the quartz indentor would stick to the magnesium sample. The quartz indentor was, therefore, frequently inspected and fire-polishing repeated when necessary. The area of sticking was always a small fraction of the area of indent and was therefore considered to have an insignificant effect on results. Correlation of Hot-Indentation Test Data with Time-Temperature Parameter—Sherby and Dorn' have correlated creep or tensile data of a' solid solutions of aluminum with a temperature and strain-rate parameter suggested by Zener and Holloman. underwood2 used this parameter to correlate creep properties of some steels with hot hardness, and upon the basis of this correlation a means of obtaining creep properties from short-time (and inexpensive) hot hardness tests has been demonstrated. Since the validity of the correlation of creep properties with a time-temperature parameter and the correlation of creep properties with hot hardness have been shown, it follows that hot hardness may correlate with the time-temperature parameter. The hot-indentation data obtained was expressed as Meyer hardness, and was shown to be time and temperature dependent. Correlation of Meyer hardness, time, and temperature with the parameter was made using the relationship: Hm = Meyer hardness t = time, hours T = absolute temperature, OK K = constant A value for the constant K was calculated by equating In l/t + K/T at different temperatures and times but at the same hardness. The correlation was tested by plotting Hm vs the parameter, In 1/t +K/T. Since materials are being sought which have high hardness at low indentation creep, i.e., a high Meyer hardness for long time at high temperatures, low values of the parameter are ofthe most interest. TEST RESULTS Magnesium—Pure magnesium (99.98 pct) cut from extruded rod was indentation tested perpendicular to the rod axis at temperatures of 300°, 350°, 400°, and 450°C for times ranging from 6 sec to 112 hr. Fig. 1 shows the time dependency of Meyer hardness at the four constant temperatures. Fig. 2 shows the correlation of the Meyer hardness of pure magnesium with the time-temperature parameter using a K of 22,720 in Eq. [I]. At the bottom of Fig. 2, the effect of doubling the time of indentation t2 = 2(t1), on the abscissa for any time is shown graphically. This effect is of constant magnitude. Also shown graphically are the magnitudes of the effects on the

Jan 1, 1960

By W. E. Keck, Paul Jasberg

The flotative properties of the principal minerals in Michigan's potential iron ores have been investigated to develop methods of bene-ficiation for the ores. One of these minerals, magnetite, is of considerable importance as a source of iron. Study of its flotation was similar to that of hematite1, another iron mineral in these potential ores. The present research consisted essentially of: (1) a survey of the literature on magnetite flotation, (2) the preparation of pure magnetite, (3) the development of laboratory procedure and (4) flotation experimentation. Literature on Magnetite Flotation.—For the purpose of this discussion, the results of previous work on the flotation of magnetite can be summarized as follows. The mineral has been floated with pine oil2, and it has also been separated from synthetic mixtures with silicates by the use of the same reagent2. Magnetite and apatite in iron-ore slimes have been separated by flotation of apatite with sodium palmitate3. These data were utilized in the present investigation. Preparation of Magnetite.—The pure mineral was prepared from the magnetic-separator concentrate of an iron ore (obtained from the Wither-bee Sherman Corporation, Port Henry, N. Y.). This concentrate was slowly comminuted with laboratory rolls and pulverizer to pass 65-mesh and was then tabled several times. Tabling yielded a relatively coarse magnetite concentrate, tailing and slimes. The two latter materials were rejected insofar as the present work is concerned, and treatment of the magnetite (table concentrate) was continued by separating it into — 65 + 200 and — 200-mesh sizes. Separation of the sizes was made by first dry screening and then wet screening. The —200-mesh material was rejected to eliminate possible introduction of error into flotation

Jan 1, 1939

By W. E. Keck, Paul Jasberg

The flotative properties of the principal minerals in Michigan's potential iron ores have been investigated to develop methods of bene-ficiation for the ores. One of these minerals, magnetite, is of considerable importance as a source of iron. Study of its flotation was similar to that of hematite1, another iron mineral in these potential ores. The present research consisted essentially of: (1) a survey of the literature on magnetite flotation, (2) the preparation of pure magnetite, (3) the development of laboratory procedure and (4) flotation experimentation. Literature on Magnetite Flotation.—For the purpose of this discussion, the results of previous work on the flotation of magnetite can be summarized as follows. The mineral has been floated with pine oil2, and it has also been separated from synthetic mixtures with silicates by the use of the same reagent2. Magnetite and apatite in iron-ore slimes have been separated by flotation of apatite with sodium palmitate3. These data were utilized in the present investigation. Preparation of Magnetite.—The pure mineral was prepared from the magnetic-separator concentrate of an iron ore (obtained from the Wither-bee Sherman Corporation, Port Henry, N. Y.). This concentrate was slowly comminuted with laboratory rolls and pulverizer to pass 65-mesh and was then tabled several times. Tabling yielded a relatively coarse magnetite concentrate, tailing and slimes. The two latter materials were rejected insofar as the present work is concerned, and treatment of the magnetite (table concentrate) was continued by separating it into — 65 + 200 and — 200-mesh sizes. Separation of the sizes was made by first dry screening and then wet screening. The —200-mesh material was rejected to eliminate possible introduction of error into flotation

Jan 1, 1939

By E. I. Salkovitz, F. W. von Batchelder

DURING the last few years several papers1-' have been published in which internal friction measurements have been used to determine the quantity of carbon or nitrogen dissolved in a iron. This method is based on the fact that, in pure Fe-N and Fe-C alloys, nitrogen and carbon cause peaks in the internal friction vs. temperature curve; at a frequency of 1 cycle per sec (cps) these peaks appear at $-200 and +360C, respectively, and if internal friction is expressed as Q-1, which is equal to times the logarithmic decrement, this figure will, by coincidence, give the weight percentage of nitrogen or carbon in solid solution.' In most of the studies published, very pure iron (Puron) was used. In one case the influence of manganese on the behavior of nitrogen in a iron was mentioned.4 It would be of great value, especially for the study of aging and related phenomena, if this method could be applied to commercial mild steel with norrnal percentages of manganese, phosphorus, sulphur, etc. As a rule, in such steels carbon and nitrogen are present together, and the amounts of these elements in solid solution should preferably be determined separately. The fact that their internal friction peaks appear at different temperatures (+36° and + 20°C in pure iron) seems promising for such a selective determination. It is necessary, however, that the peaks are narrow enough not to interfere with one another, and further, that there is no effect from carbon on the behavior of nitrogen in stress induced diffusion, and vice versa. According to Fast,' however, in the presence of manganese the nitrogen peak gets wider and appears at a higher temperature nearer the carbon peak, and thus the prospects for selective determination are reduced. (The carbon peak was not affected by the presence of manganese.) But even if fully quantitative de- terminations of the two elements are not attained, some relative figures on the sum of them and an indication of which one is the predominant one, would be of value. Some results from experiments along these lines will be reported here. An internal friction measuring device was assembled mainly following a description by KG." The measurements were also carried out as reported in that paper. Table I gives the chemical compositions of the four different materials used in this investigation. All materials were drawn to wires with diameter about 0.8 mm, and the analyses refer to these final shapes. Determination of Nitrogen Peak Wires from steels A, B, and C were decarburized in wet hydrogen (about 30 pct H2O) at 700°C until no carbon or nitrogen could be found by chemical analysis. No peak was then found in the internal friction. The wires were further annealed at 580°C for 16 hr in hydrogen bubbled through a solution of 6.8 pct NH3 in distilled water. Chemical analyses gave 0.04 pct N in A and C, and 0.06 pct in B. After annealing at 580°C for 15 min in a lead bath and water quenching, the internal friction was immediately measured. The resulting curves are shown in Fig. 1. At these high values of the internal friction the accuracy is comparatively poor; at Q-1 - 0.030 it is estimated to be 0.002. In order to make possible a calculation of the activation energy for diffusion of nitrogen, measurements were made at two different frequencies. Steel A shows rather broad peaks, and their temperatures can hardly be expected to be very accurate. Steels B and especially C are better in this respect. The finding of Fast' that manganese broadens the nitrogen peak is con-

Jan 1, 1953