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By F. E. Jaumot, R. L. Smith

Self-diffusion in zinc has been used as an instrument for comparison of the absorption and sectioning techniques as a means of studying diffusion. Single crystal as well as poly-crystal samples were used asanda the temperature range of diffusion extended from 200° to 415°C. For temperatures above 200°C, the data indicate that the results obtained from the absorption technique agree with those obtained from the sectioning technique. The effect on the values of the diffusion coefficient of electroplating vs evaporation as a means of applying the tracer was investigated and no significant difference observed. It was found that an excess or deficiency of tracer did not materially affect the results obtained from the sectioning technique, but invariably caused errors with the absorption technique. NEARLY all self-diffusion experiments and many alloy diffusion experiments have employed radioisotopes as the instrument for following the diffusion. Of the various techniques in which radioisotopes are applicable, the two most widely used are the sectioning and absorption techniques. In the former, the diffusion coefficient is obtained from a curve of log concentration vs the square of the mean penetration depth. In the latter, the diffusion coefficient is calculated from a knowledge of the decrease in activity at the surface after diffusion. In spite of the importance of knowing the reliability of the diffusion data and the widespread use of these two techniques, they had not been directly compared experimentally on the same samples. Thus, such a comparison was worthwhile. The specific system chosen for this comparison was the self-diffusion of zinc, since the metal was readily obtainable in high purity, single crystals were easily grown, and the anisotropic features of the diffusion added an additional factor of interest to the comparison. Self-diffusion in both single and polycrystals was investigated, since the possibility existed that grain boundaries and grain boundary diffusion might produce different effects for the different techniques. Also, the effects of electroplating vs evaporation as a means of applying the radioactive tracer, and the effects of applying an excess or deficiency of tracer material were studied. The general experimental procedures and the mathematical analyses of both techniques have been described previously in some detail, and only those points essential to an understanding of the present work will be discussed here. The mathematical analysis of the sectioning data requires only a knowledge of the solution of Fick's equation. where C,, is the initial concentration, C is the concentration at depth x, D is the diffusion coefficient, and p is the absorption coefficient of the solvent metal for the radiation from the solute. Having obtained F from the experiment, the value of z can be read from a plot of F vs In z, and D can then be calculated if is known. The necessity of knowing the absorption coefficient causes most of the criticism of the absorption technique. It is very difficult to measure accurately under the conditions existing in the diffusion experiment, but it is absolutely necessary, as will be indicated briefly later. Portions of this problem have been discussed in detail elsewhere." The difficulties involved in the measurement of the absorption coefficient arise from three principle factors: the physical characteristics of the absorber, the geometry, and complex radiation spectra. The first two are heavily dependent upon the third. If

Jan 1, 1957

By AIME AIME

AS director of Battelle Memorial Institute and as Chairman of the important O.P.M. advisory committee on metals and minerals, Clyde E. Williams numbers his acquaintances in the mineral industries by the thousands and h because his principal hobby is liking human beings, most of his acquaintancs are also his friends. Clyde is one of the many outstanding metallurgist, in the United States who started as a chemist. After graduating from the University of Utah in 1915 he was successively chemist for U.S. Smelting Refining and Mining Co., and at the Bureau of Mines station at Ithaca, N.Y. He then got into, metallurgical work and in 1920 he was appointed superintendent of the Northwest Station of the Bureau of Mines at, Seattle. Subsequently he was assistant to H. Foster Bain in metallugical work for the

Jan 1, 1942

By Mark Sheppard

DURING the winter of 1937, the writer visited a West Virginia stone, quarry at which the overburden is stripped hydraulically. The quarry is in a bed of limestone, about 200 ft. thick, which outcrops on a hillside above a small river; the quarry face is 175 ft. high. The top of the stone is cut in all directions by erosion channels, which are filled with a tough, red clay. Some of the larger channels are 30 ft. deep and 8 ft. wide, The thickness of the clay overburden ranges from a few inches to 10 ft., the average being estimated as less than 3 feet. The topography of the district is rugged, and the hillside above the quarry face is not suited to the use of the usual mechanical methods of moving dirt. Until hydraulicking was started 10 years ago, the over-burden was dug by hand labor, dumped to the quarry floor and trans-ported to the dump in quarry cars, Cleaning deep channels was a slow and expensive process. When hydraulicking was started, the top of the quarry face was over 200 ft. above the level of the river. The pipe line was carried in a semi-circle around the top of the quarry about 200 ft. from the face and about 50 ft, above it. As there is no adequate supply of water above the quarry, the water must be pumped from the river: As quarrying pro-gressed the pipe line was moved until the discharge points are now over 300 ft. above the river. Water is pumped from the river by a four-stage centrifugal pump having a 5-in. intake and a 4-in. discharge. It is direct-connected to a 200-hp,, 2300-volt, 1760-r.p.m. induction motor. At 1760 r.p.m. the rated capacity of the pump is 750 gal. per minute under a head of 600 ft. The pump is installed in a house of frame construction on the river bank, about 10 ft, above normal water level, which also houses the pump for the mill-water supply. Above the pumps are hoisting hays into which the motors are raised whenever the river reaches flood stage.

Jan 1, 1938

By A. G. H. Anderson, A. W. Kingsbury

Silicon bronzes containing ken are used to a considerable extent in industry, under the trade name of P.M.G. alloys. Various classes of wrought alloys fall in the composition range 1.5 to 3.5 per cent silicon, and 0.5 to 2.5 per cent iron. Castings may contain as much as 6 per cent silicon and 3 per cent iron at present. The constitutional diagrams of these alloys are thus of considerable practical importance. Copper-silicon-binary alloys have been thoroughly investigated by a number of workers, the latest reports being those of C. S. Smith1 and of A. G. H. Andersen.2 Although much work has been done on iron-copper alloys,3 recorded investigations on the copper-rich copper-iron binary constitutional diagram are not numerous. Tammann and Oelsen4 etermined the solubility limits of iron in copper by means of magnetic measurements, and found that the solubility of iron in copper amounts to a fraction of one per cent at 400°C., increasing slowly to one per cent at 800°C. From 800°C., the solubility increases rapidly and attains 4 per cent at iioo°C. Hanson and Ford,5 using electrical resistivity measurements and the microscope, determined a somewhat different solubility limit. of earlier X-ray works on the copper-iron system, very little has been published. The work by Bradley and Goldschmidt6 on copper-iron-aluminum alloys includes some information on the copper-iron binary. These investigators conclude that substitution of iron in the copper lattice decreases the spacings, which is contrary to the evidence of the present work. Hanson and West? have investigated the ternary alloys of copper with iron and silicon. Although their diagrams are valuable contributions to the understanding of these alloys, they did not recognize the kappa phase,l,2,7,8 and their diagrams do not everywhere conform to the phase rule. The present work contains a check by means of X-rays of the solid solubility limit of iron in copper, and an X-ray investigation of the ternary-phase diagram, which, owing to present conditions, it became necessary to curtail considerably. Preparation of Samples Castings weighing about 75 grams were melted under vacuum. The charges were made up of ingot iron, copper cathodes from Laurel Hill, and refined silicon supplied by the Electrometallurgical Co. Alundum crucibles were generally used. The exceptions were alloys 77 and 78, which were melted in graphite crucibles. The ingots were annealed at 800°C. for one week, then samples were cut for chemical analysis. Longitudinal sections of the binary alloy ingots were hammered into plates 1/8 in. thick. Wherever possible, these plates were homogenized at temperatures ensuring

Jan 1, 1943

By A. G. H. Anderson, A. W. Kingsbury

Silicon bronzes containing ken are used to a considerable extent in industry, under the trade name of P.M.G. alloys. Various classes of wrought alloys fall in the composition range 1.5 to 3.5 per cent silicon, and 0.5 to 2.5 per cent iron. Castings may contain as much as 6 per cent silicon and 3 per cent iron at present. The constitutional diagrams of these alloys are thus of considerable practical importance. Copper-silicon-binary alloys have been thoroughly investigated by a number of workers, the latest reports being those of C. S. Smith1 and of A. G. H. Andersen.2 Although much work has been done on iron-copper alloys,3 recorded investigations on the copper-rich copper-iron binary constitutional diagram are not numerous. Tammann and Oelsen4 etermined the solubility limits of iron in copper by means of magnetic measurements, and found that the solubility of iron in copper amounts to a fraction of one per cent at 400°C., increasing slowly to one per cent at 800°C. From 800°C., the solubility increases rapidly and attains 4 per cent at iioo°C. Hanson and Ford,5 using electrical resistivity measurements and the microscope, determined a somewhat different solubility limit. of earlier X-ray works on the copper-iron system, very little has been published. The work by Bradley and Goldschmidt6 on copper-iron-aluminum alloys includes some information on the copper-iron binary. These investigators conclude that substitution of iron in the copper lattice decreases the spacings, which is contrary to the evidence of the present work. Hanson and West? have investigated the ternary alloys of copper with iron and silicon. Although their diagrams are valuable contributions to the understanding of these alloys, they did not recognize the kappa phase,l,2,7,8 and their diagrams do not everywhere conform to the phase rule. The present work contains a check by means of X-rays of the solid solubility limit of iron in copper, and an X-ray investigation of the ternary-phase diagram, which, owing to present conditions, it became necessary to curtail considerably. Preparation of Samples Castings weighing about 75 grams were melted under vacuum. The charges were made up of ingot iron, copper cathodes from Laurel Hill, and refined silicon supplied by the Electrometallurgical Co. Alundum crucibles were generally used. The exceptions were alloys 77 and 78, which were melted in graphite crucibles. The ingots were annealed at 800°C. for one week, then samples were cut for chemical analysis. Longitudinal sections of the binary alloy ingots were hammered into plates 1/8 in. thick. Wherever possible, these plates were homogenized at temperatures ensuring

Jan 1, 1943

EXECUTIVE COMMITTEES OF LOCAL SECTIONS New York Meets first Wednesday after first Tuesday of each month. DAVID H. BROWNE, Chairman, JOHN H. JANE WAY, Vice-Chairman. F. E. PIERCE, Secretary, 35 Nassau St., New York, N. Y. P. A. MOSMAN, Treasurer. Boston Meets first Monday of each winter month. HENRY L. SMYTH, Chairman. ALFRED C. LANE, Vice-Chairman. HENRY A. WENTWORTH, Secretary-Treasurer, 60 India St., Boston, Mass. ROBERT H. RICHARDS, ALBERT SAUVEUR. Columbia Holds four sessions during year. Annual meeting in September or October. FRANK A. ROSS, Chairman. RUSH J. WHITE, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. FREDERIC KEFFER, FRANCIS A. THOMSON.

Jan 6, 1915

THE paper on "Specific Efficiency of the Blast Furnace" by Richard Franchot, which was pub-lished in the September issue of MINING AND METALLURGY, was presented for discussion at the Pitts-burgh meeting. The session opened with a discussion among S. P. Kinney, Mr. Franchot, and J. N. Reese as to the methods and results in sampling for cyanides in the blast furnace. This is covered in detail in writ-ten discussion below. T. T. Read objected to the use of the term specific efficiency as likely to be confusing. The blast furnace has to perform the function of reducing Fe, 03 to Fe as well as that of fusing the metal and, since the reduc-tion of Fe, 0? involves a CO equilibrium, it seems mis-leading to calculate efficiency on the basis of burning the , all carbon to CO? since it is not possible. Mr. Franchot replied that he used the term in the sense defined by Richards in his "Metallurgical Calculations;" but a subsequent search failed to reveal the term in Richards, who says (page 245, 1st edition): The practical conclusion is that a blast furnace generates in itself not much over 40 per cent of the calorific power of the fuel used, and rejects nearly 60 per cent; by using part of the waste gases to heat the blast, however, some of this rejected heat, to an amount representing net 5 to 10 per cent of the calorific power of the fuel used, is returned to and injected bodily into the furnace, thus rendering available for the purpose of running the furnace about 50 per cent of the calorific power of the fuel as a maximum. The efficiency with which the furnace applies this 50 per cent usefully to the objects of the reducing and smelting is another question for investigation.

Jan 2, 1927

By G.A. Moore, C. E. Sims

In previous publications of the writers4-7 it has been shown that vacuum extraction of steel can be carried as close to quantitative completion as desired provided the steel is in the austenitic state and sufficiellt time is allowed. For precise work, the method claims preference because the equipmelit for holding and heating the sample can be made simple, and because crucibles, boats, and other unnecessary materials can be eliminated and the blanks thus made very small. It is well known that the evolution rate of hydrogen is smaller just above the trans. formation than immediately below, as would be expected from the increase in solubility when passing into the gamma state. Many attempts have been made to obtain analyses by extraction just below the transition, using times of approxi. mately 2 hr. while it is true that the rate of evolution drops nearly to zero under these conditions, it has repeatedly been shown that the process is incomplete since on raising the temperature into the austenitic range, evolution will be resumed, usually after a, considerable induction period. The low-temperature evolution process appears to be useful in some cases for comparative tests where the residual crror may be more or less constant between samples, For general use, however, there is no guarantee that the error caused by incomplete extraction is constant; hence, the more laborious but more reliable high-temPe'atu'e Process must be used. At high temperature, an original flash evolution, similar to that at lower temperature, is first observed. After not more than an hour, the flash subsides and cvolution settles down to a regular first-order reaction rate for which the half-life* is usually of the order of a few hours for the 5/8-in. diam cylinder at 1050°C. The regular evolution may be followed for whatever period appears justified, after which the residual gas may be estimated as equal to that which was evolved in the last observed half-life period. Tests have shown that the composition of the evolved gas does not vary greatly during the progress of evolution; therefore the residual gas may safely be taken to have the same composition as the portion col-

Jan 1, 1949

By C. E. Sims, G. A. Moore

In previous publications of the writers4-7 it has been shown that vacuum extraction of steel can be carried as close to quantitative completion as desired provided the steel is in the austenitic state and sufficiellt time is allowed. For precise work, the method claims preference because the equipmelit for holding and heating the sample can be made simple, and because crucibles, boats, and other unnecessary materials can be eliminated and the blanks thus made very small. It is well known that the evolution rate of hydrogen is smaller just above the trans. formation than immediately below, as would be expected from the increase in solubility when passing into the gamma state. Many attempts have been made to obtain analyses by extraction just below the transition, using times of approxi. mately 2 hr. while it is true that the rate of evolution drops nearly to zero under these conditions, it has repeatedly been shown that the process is incomplete since on raising the temperature into the austenitic range, evolution will be resumed, usually after a, considerable induction period. The low-temperature evolution process appears to be useful in some cases for comparative tests where the residual crror may be more or less constant between samples, For general use, however, there is no guarantee that the error caused by incomplete extraction is constant; hence, the more laborious but more reliable high-temPe'atu'e Process must be used. At high temperature, an original flash evolution, similar to that at lower temperature, is first observed. After not more than an hour, the flash subsides and cvolution settles down to a regular first-order reaction rate for which the half-life* is usually of the order of a few hours for the 5/8-in. diam cylinder at 1050°C. The regular evolution may be followed for whatever period appears justified, after which the residual gas may be estimated as equal to that which was evolved in the last observed half-life period. Tests have shown that the composition of the evolved gas does not vary greatly during the progress of evolution; therefore the residual gas may safely be taken to have the same composition as the portion col-

Jan 1, 1949

New York Meets first Wednesday after first Tuesday of each month. DAVID H. BROWNE, Chairman, JOHN H. JANEWAY, Vice-Chairman. F. E. PIERCE. Secretary, 35 Nassau St., New York, N. Y. P. A. MOSMAN, Treasurer. LEWIS W. FRANCIS. Boston Meets first Monday of each winter month. HENRY L. SMYTH, Chairman. ALFRED C. LANE, Vice-Chairman. HENRY A. WENTWORTH, Secretary-Treasurer, 60 India St., Boston, Mass. ROBERT H. RICHARDS, ALBERT SAUVEUR. Columbia Holds four sessions during year. Annual meeting in September or October. FRANK A. ROSS, Chairman. RUSH J. WHITE, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. FREDERIC KEFFER, FRANCIS A. THOMSON.

Jan 8, 1915

New York Meets first Wednesday after first Tuesday of each month. DAVID H. BROWNE, Chairman, JOHN H. JANEWAY, Vice-Chairman. F. E. PIERCE, Secretary, 35 Nassau St., New York, N. Y. P. A, MOSMAN, Treasurer. Boston Meets first Monday of each winter month. HENRY L. SMYTH, Chairman. ALFRED C. LANE, Vice-Chairman. HENRY A. WENTWORTH, Secretary-Treasurer, 60 India St., Boston, Mass. ROBERT H. RICHARDS,- ALBERT SAUVEUR. Columbia Holds four sessions during year. Annual meeting in September or October. FRANK A. ROSS, Chairman. RUSH J. WHITE, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. FREDERIC KEFFER, FRANCIS A. THOMSON.

Jan 7, 1915

By Ove Sandberg, Olav Bowitz

The operational characteristics of the Soderberg vertical spike anode are briefly discussed stressing the importance of the flow properties of paste in the fluid zone, the thermal shrinkage in the carbonizing zone, and the surface disintegration in the consumption zone. The requirements for paste recipe and binder quality are combined with design and operation of cell. A low temperature susceptibility of viscosity and low thermal shrinkage of paste together with a low microporosity of the binder coke are important properties. PRACTICAL application of Soderberg's idea of a selfbaking carbon electrode proved successful just before 1920. Shortly after, experimental work was started with the aim of developing a continuous electrode that could be adopted as anode in aluminium reduction cells. The intermittent operation of a large number of small prebaked anodes made the idea of developing a continuous anode for electrolytic production of aluminium especially tempting. Moreover, the electrode consumption in this process, even on a theoretical basis, is very high. Many installations were carried out in the 1930's and during the Second World War. During the tremendous post-war expansion of the aluminium industry, the Soderberg electrode has been steadily more widely adopted. Thus, today more than 60 pct of the Western World's output of aluminium is produced in cells with selfbaking anodes, see Big. 1. The quality of the anode paste of Sfiderberg elec- trodes is considered a major factor influencing the specific carbon consumption. The purpose of this paper is to survey the fundamental requirements which must be met in order to obtain good anode operation. We have limited this paper to a discussion of Elektrokemisk's research on the vertical spike type anode. I) FUNDAMEKI'TALS OF ANODE CARBON PERFORMANCE A) Brief Introduction. The only practical method for producing a conductive carbon anode of the size required is to form and carbonize a mixture of a carbonaceous binder and a precalcined dry aggregate coke. In the Soderberg electrode, the forming and carbonization take place in the electrolytic cell

Jan 1, 1962

The following is an incomplete list of members and guests who called at Institute headquarters during the period Sept. 10, 19188 to Oct. 10, 1918. Thomas J. Adams, Rahway, N. J. A. N. Mackay, London, England. Henry M. Ami, Washington, D. C. A. W. MacNichol, San Francisco, Cal. Chester Atkinson, Peru, South America. Ernest Marquardt, Casper, Wyo. Bennett R. Bates, Berkeley, Cal. Lieut. S. A. Mewhirter, Denver, Colo. Robert S. Botsford, Petrograd, Russia. William A. Nelson, Nashville, Tenn. Juan Felix Brandes, Santa Barbara, Cal. Robert W. Olinger, Bahia, Brazil, So. G. A. Collins, Seattle, Wash. Amer. C. V. Corless, Coniston, Ont., Canada. G. Preumont, La Paz, Bolivia, So. Amer. F. T. Eddingfield, Washington, D. C. William H. Rettie, Yonkers, N. Y. C. Mason Farnham, Barre Plains, Mass. . Julius Segall, Minneapolis, Minn. F. N. Flynn, Trail, B. C., Canada. Robert Y. Seip, Franklin, N. J. Duncan D. Forbes, Humboldt, Ariz. H. M. Schleicher, Boston, Mass. Alexandre Gouvy, Paris, France. Chester Steinem, Ft. Monroe, Va. Henry G. Granger, Cartagena, Colombia, A. L. Sweetser, Pittsburgh, Pa. So. Amer. . H: E. Treichler, Creighton Mine, Ont., E. Harms, El Paso, Tex. Canada. Alfred G. Heggem, Tulsa, Okla. Frank A. W. Tullock, Yumbo, Colombia, H. B. Henegar, Mascot Tenn. So. Amer. A. M. Kivari, Denver, Edward I. Williams, Ft. Monroe, Va. T. M. Kniffin, Brookline, Mass. Alfred W. G. Wilson, Ottawa, Canada. Charles Lehman, London, England. Donald H. McLaughlin, Camp Meade,Md. C. E. Addams, who recently resigned as general manager for the Arizona Hercules Copper Co., has leased the Ray silver-lead property three miles from Ray, Ariz. Bennett R. Bates has resigned his position as general superintendent of the Cubo Mining & Milling Co., in order that he may take the examination for an officer of engineers.

Jan 11, 1918

The Committee on Technical Nomenclature, of which John T. Faig, Professor of Mechanical Engineering at the University of Cincinnati, is Chairman, appointed by the Society for the Promotion of Engineering Education, has recently issued a report advocating uniformity in the use of symbols to designate engineering and mathematical terms: The selection of the symbols was based upon a canvas of a considerable number of engineers, editors of engineering papers, and professors of engineering throughout the United States. The list, as finally accepted by the Committee and recommended for universal adoption, is as follows: Concept Symbol I Concept Symbol Acceleration due to gravity 'g Length L Acceleration, linear a Mass m Area A Modulus of section Z Breadth b Modulus of elasticity, Young's... E Center of rotation 0 Moment of force M Coefficients and constants C, K Moment of inertia, polar J Deflection of beam y Moment of inertia, rectangular.. I Depth : d Quantity of liquid flowing Q Diameter D . Radius r Distance passed over s Radius of gyration k Distance of extreme fiber from Reactions R neutral aids C Revolutions per unit of time.... N Eccentricity of application of load e Stress, unit S Efficiency (hydr., mech., vol.)...er,.em, e9 Time t Force F Torque T Friction, coefficient of f Velocity, angular :. W Head H 'Velocity, linear V Height h Volume V Horsepower : Hp Weight W Hydraulic radius Re Previous lists of symbols have not secured wide acceptance in, this country; some that have been proposed by prominent writers are familiar to very few engineers. The above list is presented in the hope that it will assist in the evolution of a standard list. It is short; it contains no Greek letters; it is mnemonic to a considerable degree, though not by

Jan 1, 1918

By J. Szekely, V. Stanek

Heat and gas flow interactions in nonisothermal packed beds were examined in the paper. A study was made of the response of the system to a step or pulse change in the inlet gas temperature, with a fixed value of the overall pressure drop across the bed. Under these conditions the heat flow and fluid flow transients are coupled because the convective heat transfer rate is alfected by the mass flow rate of the gas which, in turn, for a fixed pressure drop will depend on the temperature profile in the system. The Problem was stated in terms of differential equations, which were integrated numerically. The parameters used in the computation were so chosen to reflect the operation of the stack region of blast furnaces and sinterbeds. The computed results showed that the pressure drop-flou1 relationships and the rate of progress of the temperature fronts (waves) were strongly interrelated and were also markedly affected by variations in particle size and in void fraction. MANY metallurgical processes involve the contact of solid particles with a gas stream in a packed bed arrangement under nonisothermal conditions. Examples are shaft furnaces, regenerators, pebble heaters, and the sinter process. Although the heat and mass transfer aspects of packed bed processing have been extensively studied, the associated flow phenomena and in particular the effects of nonisothermality on the flow, have received little attention to date. :In fact, most of the previous workers considered the flow rate of the carrier gas time invariant and independent of the heat or mass transfer processSzekely and carr2 have shown that the pressure drop-flow relationships in nonisothermal packed beds may be strongly affected by the temperature profile within the system. These authors have devised a method for relating the pressure drop to flow for a given temperature profile. thus providing an extension of the Ergun equation to steady nonisothermal systems. Finally, in a recent paper willmot3 examined the response of regenerators to externally imposed changes in the gas flow rate. Both these investigations were somewhat specialized since, in general, neither the temperature distribution nor the gas flow rate may be regarded as truly independent variables, thus the heat transfer and the fluid flow problems have to be solved simultaneously. The work reported here is divided into two parts: in Part 1 the general formulation is given and a detailed discussion is presented of fixed bed systems. Part is devoted to systems in which a gas and particulate solids are contacted in a counter flow arrangement. FORMULATION Consider a nonisothermal fixed packed bed, extending from through which a gas is flowing. The problem is to develop a relationship between pressure drop and gas flow (with the gas flow being the dependent variable) and to evaluate the rate at which a change in the gas temperature, imposed at the inlet, travels through the system. Let us consider an infinitesimal section of the bed and establish differential heat, mass, and mechanical energy balances over this region. In addition, relationships are needed describing the temperature dependence of gas density (equation of state) and the temperature dependence of viscosity. These may be written as: where c, and are constants. It is noted that in this formulation we neglected any temperature gradients within the solid particles, thus assuming these to be either sufficiently small or of sufficiently high thermal conductivity to meet this condition. The justification and consequences of this assumption will be mentioned in the discussion.

Jan 1, 1970

Teamwork: The famous first sentence of an essay en- titled Aphorisms, by Hippocrates, is as follows: "Life is short, the Art long, opportunity fleeting, experience treacherous, judgment difficult." The future of science does not depend so much on the number of scientists or the number of colleges, but rather on the individual qualities and the degree of perfection of a limited group of leading scientists and colleges. These are individual factors which require inherent talent which in turn is a condition evolved after generations of culture. Thus, very elaborate higher education for indiscriminate masses of humanity or students may not necessarily show the expected results. In other words, it is possible that higher specialized education should be given only to the few talented individuals, and their capacity and worth should be judged by as highly qualified and talented teachers. Quality is the greatest of all competitive aids. An essential qualification that must be possessed by a quality mineral industries college is a high caliber teaching staff, for the mineral sciences will advance in the coming years only if the leading minds of today are made avail- able as the mental springboards for our scientists of tomorrow. Mineral industries schools are finding it increasingly difficult to maintain a high caliber staff of instructors and administrators in competition with private business and governmental demands for similar

Jan 1, 1950

By R. D. Carnahan, J. E. White

A study of dispersion strengthening in TD-Nickel (nickel plus 2 vol pct Tho2) was conducted employing microstrain techniques at ambient room temperature. It was found that optimum strength was due primarily to the incorporation of stored energy developed by a variety of thermal-mechanical treatments. The relatively low strength of the recrys-tallized condition implies that the dispersed particles themselves offer only token resistance to deformation. The development of resistance to large-scale recovery or recrystallization at temperatures near the melting point requires a more extensive sequence of strain-anneal cycles than does the development of optimum strength. A micro-Bauschinger effect was observed which appears to be related to the lattice resistance to the movement of free dislocations. The effect was nearly identical to that in pure nickel indicating that the presence of the dispersed phase and considerably increased dislocation density (stored energy) only alters the number or effectiveness of barriers. THE early stages of deformation of engineering materials can be conveniently studied by utilizing strain-gage techniques which permit resolution of strains less than 5 X 10-7 in. per in. for testing in four-point bending (Carnahan and white1). The present investigation, part of a continuing study on the very early stages of deformation, was designed to reveal the true role of a dispersed phase in promoting high strength in a commercially available dispersion-strengthened alloy. Although this technique has been used for some time to study microdeformation in pure metals and alloys, it has just recently received attention as a means of investigating dispersion strengthening. Studying the very early stages of deformation in alloys which depend upon a finely dispersed inert phase for strength may prove to be a very important method for a better understanding of these materials. It is essential to obtain considerable clarification of actual dislocation movement and the kinds of deformation barriers which exist before optimum properties can be designed into this type of material with any degree of confidence. Considerable research on a variety of dispersion-strengthened materials has resulted in two different schools of thought regarding the strengthening mechanism. One faction2-4 favors the idea that the particles themselves resist the motion of dislocations. The criterion for yielding is the fracture of the dispersed second-phase particles due to an array of piled-up dislocations. Other invesfigators5-a have shown that particles are effective primarily by allowing a greater buildup of stored energy or dislocation density through thermal-mechanical treatments in the composite than the pure matrix material. The particles themselves, then, are not exclusive obstacles, but the complex network of particles, dislocation tangles, subboundaries, and grain boundaries are strength determining. The development of such a complex dislocation network in SAP has been studied recently in some detail by Goodrich and Ansell. The ability of dispersion-strengthened alloys to resist softening or recrystallization is also of considerable importance; however, the criteria for maximum stability may not necessarily be those for maximum strength. In this study, in addition to the evaluation of the microstrain properties of TD-Nickel, it is felt that considerable clarification of the true dependence of strength and stability on the dispersed phase is shown. I) MATERIAL AND PROCEDURE TD-Nickel is a dispersion-strengthened alloy developed by the E. I. DuPont de Nemours Co., which contains 2 vol pct thoria (Tho2) in a pure-nickel matrix. The average ThO2 particle size is approximately 0.1 p and the interparticle spacing is less than 1 u. The material was supplied by DuPont in two conditions: hot-extruded bar stock, and stress-relieved cold-rolled sheet 0.025 in. in thickness. The bar was extruded at 2200°F from a cold-pressed and sintered billet. The sheet stock was prepared from the extruded material by a process involving ten or more 50-pct cold reductions by rolling with intermediate anneals at 1800° to 2000°F. Test specimens used in this study were prepared in the form of rectangular parallelepipeds measuring 0.375 by 1.375 in. in thicknesses ranging from 0.025 to 0.040 in. Samples prepared from sheet and extruded stock were mechanically polished before heat treatment and were handled with extreme

Jan 1, 1964

By N. Brown, R. Kossowsky

Plain carbon steels with 0.48 and 0.95 pct C were quenched and tempered at 705°C to produce carbide dispersions with spacings on the order of 1 p. The morphology of the structure consisted of a carbide-dislocation network. The strengthening due to the dispersion was found to vary linearly with M-½ where M is the mean free-ferrite path determined by the entire network. No preyield microstrain preceded the upper yield point. After prestraining, the lowest stress at which dislocation movement could be detected was 104 psi; this frictional stress was independent of the dispersion and prestrains up to 6.5 pct. The Cottrell-Petch equation for grain-size strengthening was used to discuss the dispersion strengthening in this investigation. The results support an impurity mechanism for the upper yield point rather than one based on the Johns ton- Gilman theory. IT was pointed out by Gensamerl that the mean free path in the matrix is the important variable which controls the degree of dispersion strengthening. Gensamer's data on steels showed a linear relationship between the yield point and the logarithm of the mean free-ferrite path. The first theory was by Orowan,2 who suggested the mechanism of dislocations bowing between particles, with the resulting relationship that where a is the yield point, P is the distance between particles, and G is the shear modulus. The Orowan equation applies to that range of dispersion where P is large compared to the particle size and the particles are not coherent, so that the matrix is essentially free of internal stresses. As was pointed out by Orowan, there are different degrees of dispersion which, in turn, will influence the strength-controlling mechanism. However, in this investigation, we wish to confine ourselves to the region of coarse dispersion, where the Orowan mechanism should, intuitively, be applicable. It was soon evident that the data, which existed at about the time that the Orowan theory was proposed, did not agree with the Orowan equation in that the actual strengthening was always greater than the theoretical predictions. Thus, Fisher, Hart, and pry3 modified the Orowan theory by suggesting that the Orowan process took place in the microstrain region preceding macroscopic yielding and the subsequent, rapid work hardening in the form of residual dislocation loops around the particles largely determined the observed macroscopic yield point. The F-H-P theory stated that the increment of strengthening due to the work-hardening mechanism was proportional to f3/2 where f is the volume fraction of the precipitate. F-H-P used data by Shaw, Shepard, Starr, and Dorn4 on A1 3-5 pct Cu to support their theory. Roberts, Carruthers, and Averbach5 were the first to make a microstrain study of dispersion strengthening, and they found that for steel the Gensamer relationship was obeyed. Hayman and Nutting6 suggested that in the case of tempered steel 1) the ferrite grain boundary was the primary obstacle and 2) the carbide particles simply formed part of the grain boundary obstacles. They found that the strength varied as G"" where G is the ferrite grain size. Turkalo and LOW' determined the structure of quenched and tempered plain carbon steel using a replica technique; they concluded that the carbide particles did not necessarily lie in the ferrite grain boundaries. When they defined the mean free-ferrite path as being determined by both particles and the ferrite path boundaries, their data obeyed the Gensamer relationship. Meiklejohn and skoda8 showed that the strengthening from iron particles in mercury was a function of the particle size and the distance between particles. Dew-Hughes9 explained the Meiklejohn and Skoda results by the following theory: 1) grown-in dislocations which surrounded the particles were produced by the thermal stresses during the time the material was cooled to the testing temperature, and 2) the observed strengthening was associated with the cutting of the grown-in dislocations by the glide dislocations. Ansell and Lenel10 proposed a theory in which the glide dislocations pile-up or surround the particle until the number of dislocations in the pile-up is sufficient to yield or fracture the particle. The resulting theory says that the yield point varies as p-1/2, where P is the distance between particles. The Ansell-Lenel theory is almost identical to the

Jan 1, 1965

By C. A. Czako

INTRODUCTION In recent decades sintering and pelletizing of finely divided materials have become the primary tonnage producing modes of agglomeration. This statement is especially true in the iron and steel industry and, to a lesser degree, in the nonferrous, chemical and non-metallic minerals processing industries. In every industry the main objectives in agglomerating fines are essentially the same, namely to convert ores, minerals and chemicals of undesirable fineness into agglomerates characterized by a size consistency desirable for subsequent use or processing. Depending on the type of agglomeration process selected and the conditions maintained during agglomeration, the physical process of increasing size is complemented by a number of other unit processes. These processes can occur simultaneously, consecutively or in an overlapping manner. Some of these additional unit processes are incidental to the agglomeration operation, but at the same time can be critical, depending upon the subsequent use of the product. Accordingly, during processing, conditions have to be controlled to either suppress or enhance the extent of completion of these unit processes. The purpose of this report is to review laboratory testing as the basis for engineering modern sintering and pelletizing plants. Considering that most typical applications are for the iron and steel industry, agglomeration of ferrous materials is reviewed and discussed. When these total processes are adapted to suit non- ferrous materials, chemicals, or non-metallic substances, the over- all approach remains the same; only the processing parameters are affected as necessitated by the different nature of the materials.

Jan 1, 1977

By H. E. McKinstry

Movement on a fracture of irregular shape can cause local widening of the fissure and thereby offer freer channelways for circulation of ore-depositing solutions. This influence: coupled with large areas of wall rock available for reacting with ore solutions in brecciated and shattered ground can account for locally active deposition of metals and the resulting ore shoots. Such irregularities in the fracture system may be caused by local variations in the strength of rocks and by pre-existing lines of weakness, especially if these stand at favorable angles to certain components of the fracturing stress. Therefore correct interpretation of the mechanics of fracturing should permit deductions as to structurally favorable places on unexplored portions of the vein system. Introduction It has long been recognized that movement on a curved or irregular fault surface is capable of separating the walls in certain portions of the fault, but until very recent years the importance of this mechanism as a factor in localizing ore shoots has escaped proper recognition. A short time ago W. H. Newhouse' presented a careful analytical study of displacements and their corresponding open spaces. For reasons that will be discussed later, it frequently happens that portions of the vein which are favorably oriented are not merely wider but also richer than the average. In many cases the widening with its accompanying richness coincides with very minor changes in the dip or strike of the vein, irregularities that commonly escape notice unless the vein is mapped in detail and a careful geometrical analysis made. While the relationship between the width of the vein and the changes in dip or strike has been recognized as a matter of observation, the irregularities have been accepted as more or less the result of accident. There has been very little effort except in isolated cases to find out the causes of these changes in dip or strike. Yet it is clear that if the causes can be recognized and expressed in terms of geologic structure the geologist will know where to look for repetitions of these favorable conditions either on extensions of the same vein or on adjoining veins. Any lack of understanding of the causes is due to the limitations of our ability to interpret our observations and not to the sheer capriciousness of

Jan 1, 1941