Search Documents

By E. H. Greener, M. E. Fine

The internal friction (1/Q) of cobalt Fig. 1 (measured by an electrostatic dynamic method1) near 250°C begins to increase rapidly on heating and continues to increase until 560°C, the highest tem- perature measured. In the plot of log of 1/Q against 1/T, above 250°C the data nearly fit two straight lines intersecting at 400°C, approximately the temperature of the hexagonal-cubic transformation. The higher temperature branch corresponds to an effective activation energy of 6500 cal per mole, the lower temperature branch 11,000 cal per mole. Young's modulus Fig. 2 increases approximately

Jan 1, 1959

By F. C. Langenberg, J. Chipman

New data on the distribution of silicon between slag and carbon-saturated iron at 1600oand 1700oC are presented which, in combination with previously published data, permit the determination of silica activities over a broad range of compositions in the CaO-Al2O3-SiO2 system. The distribution of silicon between graphite-saturated Fe-Si-C alloys and blast furnace-type slags in equilibrium with CO has been described in previous publications.1"3 In this past work the silica-silicon relation was established at temperatures of 1425" to 1700°C for slags containing up to 20 pct Al2O3. This paper presents the results of additional studies at 1600" and 1700° C which extend the silicon distribution data at these temperatures for CaO-A1203-SiO2 slags over a range from zero pct A12O3 to saturation with A12O3, or CaO.2A12O3. The upper limit of SiO, is set by the occurrence of Sic as a stable phase when the metal contains 23.0 or 23.7 pct Si at 1600" or 1700°C, respectively. The activity of silica over the expanded range is determined directly from the distribution data.3 Recently, 4-7 other investigators have studied the activities of SiO, and CaO, principally in the binary system, using different methods and obtaining somewhat different results. EXPERIMENTAL STUDY The experimental apparatus and procedure have been fully described in previous publications.1, 3 Six new series of experimental heats have been made, four at 1600° and two at 1700°C. Master slags of several fixed CaO/A12O3 ratios were pre-melted in graphite crucibles, and these were used with additions of silica to prepare the initial slag for each experiment. Slag and metal were stirred at 100 rpm and CO was passed through the furnace at 150 cc per min. The initial sample was taken 1 hr after addition of slag at 1600°C or 1/2 hr after addition at 1700°C. The run was normally continued for 8 hr at 1600°C or 7 hr at 1700°C, and the final sample was taken at the end of this period. Changes in Si and SiO2 content indicate the direction of approach to equilibrium, and in a series of runs where the approach is from both sides this permits approximate location of the equilibrium line. Fig. 1 shows the results of such a series of 15 runs at 1600°C for slags of CaO/Al2O3 = 1.50 by weight. Figs. 2 and 3 record other series at 1600°C and Fig. 5 a series at 1700°C with fixed CaO/Al2O3 ratios. The results of the experiments at 162003°C have been reported in part in a preliminary note.3 In the experiments recorded in Figs. 4 and 6, the slags were saturated with A12O3 (or with CaO.2A12O3 within its field of stability) by suspending a pure alumina tube in the melt during the course of the run. The final slag analyses were used to establish the liquidus boundaries8 in the stability fields of CaO.2Al,O3 and of A120,. ACTIVITY OF SILICA The free-energy change in the reaction has been calculated by Fulton and chipman2 from recent and trustworthy data including heats of formation, entropies, and heat capacities. The more recent determination by Olette of the high-temperature enthalpy of liquid silicon is in satisfactory agreement with the values used and therefore requires no revision of the result which is expressed in the equation: SiO, (crist) + 2C (graph) = Si + 2CO(g.) [1] &F° = + 161,500 - 87.4T The standard state for silica is taken as pure cristobalite and that of Si as the pure liquid metal. Since the melts were made under 1 atm of CO and were graphite-saturated, the equilibrium constant for Eq. [I] reduces to K1 = asi /asio2 The value of this constant is 1.77 at 1600°C and 16.2 at 1700°C. Through K1, the activity of silica in the slag is directly related to the activity of silicon in the equilibrium metal.

Jan 1, 1960

By Herbert H. Kellogg

Graphs representing the standard free-energy of formation as a function of temperature for 21 fluorides are presented, along with estimated values for the standard free-energy of formation of 20 atedadditional fluorides. A few of the many possible uses of these data in metallurgical calculations are discussed, including the fluorination of oxides, sulphides, metallurgicaland chlorides, and the reduction of metal fluorides. RECENT papers which have presented free-energy data for oxides, sulphides, chlorides, carbonates, sulphates, and silicates in the form of free energy vs. temperature plots,1-5 have found important uses in teaching and metallurgical development work. This method of presentation of thermo-dynamic data serves to make available in readily usable form thermodynamic constants which are scattered throughout the literature, and to show by graphical means the stability relations which exist between the compounds of a given type. It is certainly desirable to have these free-energy-temperature diagrams for as many types of compounds as are of present or potential use in metallurgical processes. Thus, even though there are but few uses of metallic fluorides in extractive metallurgy today, the potential uses of fluorine processes are of great importance and serve as the principal justification of this paper. Recent developments in the production of fluoro-carbons have resulted in vastly improved methods for the production and handling of fluorine and corrosive fluorides, with consequent reduction in costs.".' The extractive metallurgist should no longer overlook possible fluorine processes when development of a new process for a relatively high unit-price metal is being considered. In a previous paperv he author outlined in some detail the importance and use of free-energy data in metallurgical calculations and also discussed the properties of a standard free-energy vs. temperature diagram. The same method of presentation is adopted in this paper, and the reader is referred to the earlier work for explanations of the use of free-energy data. Thermodynamic Data This paper presents standard free-energy vs. temperature diagrams, Figs. 1 and 2, for those fluorides for which the major thermodynamic constants are known. In the calculations of the standard free-energy of formation (AGO), values of the enthalpy of formation at 298°K (?Ho,) were taken from "Selected Values of Thermodynamic Constants"8 most of the values of standard entropy at 298°K (S°298) were taken from "Selected Values"," but in a few cases the values given by Kelley9 ere preferred; data for the Phase changes came from "selected Values" and several of Kellley's publics- tions;0-12 and most of the specific-heat data were taken from Kelley.l0 The appendix gives a detailed list of the sources of the data. As explained in an earlier paper,6 he accuracy of some of the standard free-energy relationships is not high. An error of +1 kcal at 1000°C is expected in most of the curves of Figs. 1 and 2. The error may be as high as +3 kcal in some of the curves. Rather than attempt to estimate the reliability of each curve, the source of the data used is reported in the appendix, and the reader may compare these data with newer values as they become available. Figs. 1 and 2 fail to show values for the fluorides of many important metals. In most cases this is because the entropy of the metallic fluoride is unknown. For preliminary calculations it is often useful to have available the best estimate of an unknown datum, rather than no information at all. With this in mind, Table I lists estimated standard free-energy values for a number of important metallic fluorides not included in Figs. 1 and 2. The values reported in Table I were, calculated by Brewer et al.13 and are based on estimated entropy values. The estimated uncertainty of the values for each fluoride were calculated from the uncertainty values given by Brewer1' for ?H°, and the entropy function.

Jan 1, 1952

By I. W. L. Finlay, H. R. Ogden, R. Jaffee, D. J. Maykuth

Aluminum has been found to be soluble in a titanium to about 26 pct, and to raise the temperature range of transformation from a to 8. Two intermediate phoses exist in the system, a new face-centered tetragonal phase, designated as 7, which occurs between 34 and 46 pct Al, and TiAI Metallographic and X-ray diffraction data were used to determine the diagram. ALUMINUM is one of the useful alloying additions for titanium-base alloys. It is an important constituent in two commercial alloys released in 1950, one containing 4 pct A1 and 4 pct Mn, and the other containing 3 pct A1 and 5 pct Cr as the metallic alloy content. It is probable that, in the future, other titanium alloys containing aluminum will be released. In the course of alloy development work, some of the features of the constitution of titanium-rich Ti-A1 alloys have been developed. These are described in the present paper. The only available information on the Ti-A1 system concerns the aluminum-rich end of the diagram. In summarizing the early work, Hansen' indicated that there is little solubility of titanium in aluminum, and that a two-phase region exists up to the intermediate compound, TiA1a (37.2 wt pct Ti), which has a congruent melting point at 1355°C. Fink' has reported that a peritectic reaction occurs at 665°C between the melt and TiA1³ to form the terminal solid solution of titanium in aluminum. The solubility of titanium in aluminum has been established at 0.24 pct at 510°C and is estimated to be between 1 and 1.5 pct at the peritectic temperature. No information has been published on the diagram above TiAl,, other than a statement- hat aluminum raises the a to ß transformation temperature of titanium. Materials and Preparation of Alloys Iodide-type titanium and high-purity aluminum were used in this investigation. Typical analyses of these materials are given in Table 1. Alloys were prepared by arc melting on a water-cooled copper hearth, using the techniques described previously for contamination-free melting.' Weight losses during melting were very low, ranging from 0 to 0.02 g in a 10 to 15 g charge, indicating that little or no loss of aluminum occurred during melting. This permitted the use of nominal compositions for these alloys. Alloy ingots containing from 0 to 7.5 pct A1 were rolled in air at 850°C to 0.040 in. sheet. Alloys containing from 7.5 to 16 pct A1 could only be rolled about 25 pct reduction at temperatures up to and including 1200°C. Alloys containing above 16 pct A1

Jan 1, 1952

MONTANA SECTION W. C. SIDERFIN, Chairman, OSCAR ROHN, Vice-Chairman, E. B. YOUNG, Secretary-Treasurer, 526, Hennesey Building, Butte, Mont. F. W. BACORN, C. D. DEMOND. The semi-annual meeting of the Montana Section was held at the Silver Bow Club, Butte, Montana, on Friday, Nov. 16, at 8 p. m.; this was a postponement of the regular October meeting because of conflict in date with the St. Louis meeting of the Institute. An informal dinner was served to 68 members and guests. After dinner, Chairman W. C. Siderfin called the meeting to order. The minutes of the annual meeting, of Feb. 2, 1917, and the special meeting of May 21, 1917, were read and approved. C. W. Goodale led the discussion with "Notes on the St. Louis Meeting." He was followed by J. H. Warner who spoke on " The Joplin and Miami Districts," and by J. L: Bruce, Alexander Leggatt, N. B. Braly, and E. B. Young, the latter speaking on the work of the War Minerals Committee; and on the Cosden Oil Refinery at West Tuba, Okla. R. H. Sales reviewed briefly the manganese situation. E. N. Norris presented a paper on "Fire Proofing of Mine Shafts by the Anaconda Copper Mining Co." This resulted in interesting discussion by C. L. Berrien, C. E. Nighman, N. B. Braly, W. B. Daly, B. H. Dunshee, and J. J. Carrigan. C. L. Berrien and C. E. Nighman presented their papers on "Fire Extinction by Hydraulic Filling." In view of the late hour, discussion was waived. The executive committee, by unanimous consent, decided to request written discussion of the above papers to be presented at the next meeting, in February. B. B. Thayer spoke interestingly on the work of the Naval Consulting Board, and referred to the arsenic situation. Spencer Miller, also a, member of the Naval Consulting Board, entertained the-meeting with a vivid description of the method of "Coaling Battleships at Sea." Robert Sticht of Tasmania, in a short talk, spoke feelingly of his relations with the United States. At a late hour adjournment ended a most successful and interesting meeting. E. B. YOUNG, Secretary.

Jan 1, 1918

By J. O. Edstrom, G. Bitsianes

Parabolic rate constants were determined for the formation of wiistite by the solid state reaction between magnetite and iron. The reaction was diffusion controlled and inert marker studies indicated that the mass transport through the wiistite layer was accomplished by means of iron migration. Relationships between rate constants and self-diffusivities are discussed. The transport capacity for iron through dense wustite layers was found to be sufficient to carry on reduction, even in gaseous reduction processes. REDUCTION of iron oxides has been the subject of many investigations. Most of the work, however, has been done on rather crude material and there have been difficulties in correlating the data on a quantitative basis. The reverse process of the oxidation of iron has been studied more thoroughly and usually by starting from the pure metal. As a result, the mechanisms of oxidation are now fairly well known.It has generally been found that the oxidation of metals follows the so-called parabolic 1aw;Q hat is, when the oxides are formed as dense layers, their thicknesses are proportional to the square root of the reaction time. This parabolic law follows directly from Fick's first law of diffusion The flux, J, is defined as the quantity of diffusing substance passing per unit time through unit area of a plane at right angles to the direction of diffusion. This flux is proportional to the concentration gradient of the diffusing substance, and the factor D, known as the diffusion coefficient, is introduced as the proportionality factor with dimensions of (length)'/time. If the flux is measured as the increase of thickness of the oxide layer (Ax) per unit time (t) and the assumption is made that the concentrations of the reactants at the phase boundaries of the layer are independent of time, Eq. 1 reduces to Integration of this expression yields the parabolic function ax = k . t. [31 The product of the diffusion coefficient and the concentration difference across the oxide layer is included in the constant k. When iron is exposed to a highly oxidizing atmosphere, the oxide phases are formed normally in a topochemical fashion, i.e., the interfaces between the phases maintain parallel positions to the original surface of the specimen. Above 570°C, the phases are orientated usually in the order of iron, wiistite, magnetite, and hematite, a condition in conformance with the requirements of the Fe-0 system. Below 570°C, the wiistite phase is unstable and has not been found as a normal constituent in the oxidation products of iron. There is a strong probability that continuous layers of the solid oxides are formed as the specific volumes of the phases increase in direct order from iron to hematite.' , ' Regarding mass transport through dense solid oxide layers, Wagner' has postulated that diffusion in oxides generally may be interpreted as migration processes of ions and electrons. There must be normally a concentration gradient across the growing oxide layer for diffusion to occur. This condition requires that there be deviations from the ideal stoi-chiometric composition of the oxide and accordingly deviations from the strict order of an ideal lattice. Such "lattice defects" include interstitial ions, cation and anion vacancies, quasi-free electrons, and electron holes and are decisive for all migration processes.' Cations, anions, and electrons all may have some mobility in the oxides but the movement of one of the particles generally far exceeds that of the others. Previous work', 1,2,7 has shown that during the oxidation of iron the migration through the wiistite layer, and probably also the magnetite layer, is confined to the movement of iron ions. Migration through hematite, however, has been found to take place by oxide ion movement. These behaviors are in direct agreement with the type of vacancies present in the respective oxides. Reduction of Iron Oxides The gaseous reduction of iron oxides, like the oxidation of iron, takes place in a topochemical fashion at distinct interfaces between the appearing phases."-'" Porosities might be expected in these reaction products, since their specific volumes are less than that of the starting material. Frank and van Der Merwe" have shown, however, that it is theoretically possible for nonporous layers to form if the degree of misfit in specific volume is less than about 15 pct. These aspects on porosity formation

Jan 1, 1956

THE TRANSACTIONS of the Institute for the early years display but Little interest in physical metallurgy-indeed, it is striking how thoroughly process metallurgy absorbed attention until quite recent years. The first volume carries no article that can be strictly described as physical metallurgy, unless one on the rolling and hammering of ingots be doubtfully so described. Nor does the second volume contribute more the interest then was in mining, and in production methods, both ferrous and nonferrous, with much attention to the new methods of making steel. The third volume records papers on: the condition of carbon in gray and white iron, a paper devoted to chemical rather than microscopic analysis; the annealing of spiegeleisen; phosphorus and carbon in iron and steel, similarly chemical. Much attention was given, and continued to be given for years, to the manufacture and behavior of rails. The question of the nature of steel appeared early (Vol. 11)-What is Steel, by A. L. Holley-where arguments on nomenclature were already active; and Holley also bemoans, in modern spirit, the Inadequate Union of Engineering Science and Art; Pearse wrote on cast iron for guns (reflecting again the ironic beneficence of war in metallurgy), and said that Captain Walbach was the first to insist on chemical analysis of gun irons; he quotes Major Wade's study of comparative hardness, using penetration hardness measurements (Brinell was to come later), and quotes the important Reports on the Strength and Other Properties of Metals for Cannon, by H. C. Baird, Philadelphia, 1855, in which the advanced state of tensile testing at the time is shown. Hewitt, in Vol V, comments upon the function played by technical schools and technical societies upon the growth of metal-

Jan 1, 1948

By R. D. Pehlke, J. V. Gluck

The limiting activity coefficient of zinc in a "binary " solvent has been described for several dilute ternary solutions by combining literature data from recent interaction studies in the terminal regions with thermodynamic data for the central regions. Results are discussed in terms of the Alcock and Richardson random solution model. The observed behavior agrees semiquantitatively with predictions using the model. RECENT efforts in the thermodynamics of dilute ternary liquid metallic solutions have been mainly concerned with the interactions between two dilute solutes, that is, the terminal region at an apex of the composition diagram.'-' A more general case is that of the behavior of a dilute solute over the full range of a ternary system, or, more specifically, the limiting activity of solute i as projected to the k-j binary side of the i-j-k composition triangle. An implication of this is that the interaction between i and j at the k apex should connect in some way to the interaction between i and k at the j apex. A model to characterize various types of expected behavior has been discussed by Alcock and Richardson.9,10 Such behavior can range from a simple linear relation for In yi over the 1-k binary to more complex curved relations which depend on various assumptions regarding the heat of solution in the j-k binary system and the presence or absence of clustering with solute i. Quantitative data to assess these concepts have been limited primarily to the cases of nonmetallic interstitial solutes in ferrous solutions. Alcock, Richardson, and various coworkers9-13 have discussed the behavior of oxygen, sulfur, silicon, or hydrogen in dilute solution over the range of iron + metal systems; however, the only data considered by them for substitutional nonferrous metallic solutions were the results of Elliott and Chipman concerning the activity of cadmium in the Pb + Sn, Pb + Bi, and Pb + Sb systems.9 These data were limited and did not cover the terminal regions in detail. An opportunity to extend the Alcock and Richardson considerations to the dilute solution of zinc in various "binary" solvents has been afforded by combining results of several of the recent investigations of ter-minal-region interactions with previous data from the literature for the same more concentrated solutions. RESULTS AND DISCUSSION The results of the analysis are shown in Figs. 1 to 5 where the log activity coefficient, (In yZn)xzn--o, is plotted vs the composition of the "binary" solvent. In these plots the end points are the values for In yzn in the appropriate binary solution with Bi, Pb, Sn, Cd, or In at the indicated temperature—usually 550°C (823°K). For the terminal regions the slopes were drawn using the first-order interaction parameters taken from various studies reported in the literature. The data points shown in the central regions were obtained by the short extrapolation to infinite dilution of the logarithm of the activity coefficient calculated from thermodynamic studies reported in the literature for the same systems. The sources of the data are indicated on each figure. Second-order effects were not considered. Reasonably smooth curves can be drawn to connect the central region with the terminal regions for the Zn-Pb + Bi system, Fig. 1, the Zn-Pb + Zn system, Fig. 1, and the Zn-Bi + Cd and Zn-Bi + Sn systems, Fig. 2. As shown in Fig. 2, where central region data are available from two independent investigations, the agreement is quite good. The Zn-Pb + Cd system does not appear to be as well behaved as the previous four, Fig. 3; however, this type of behavior has also been

Jan 1, 1970

By AIME AIME

IN RESPONSE to a request from the president- elect of the Institution of Civil Engineers of Great Britain, Mr. Calvin W. Rice, secretary of the American Society of Mechanical Engineers, prepared a brief history of the joint activities of engineering societies in the United States, from which we have taken the following facts. National Societies Our first joint activities were in collection with the celebration of the eightieth birthday of "Uncle John" Fritz in 1902, and it is of interest to note that two of the members of the original celebration committee, Messrk. . Ambrose Swasey and Jesse Merrick Smith, will be members of the official deputation to England in June. Mr. Rice, also,' was .a member, of the original committee.

Jan 1, 1921

By Willard P. Ward

SOME TIME in the year 1874 or 1875, I conceived the idea that spiegeleisen might be made -in a blast furnace from ores that were not carbonates, and which did not contain both manganese and iron in the same ore. Up to this time, such ores had formed the basis of all the spiegel that had been produced; and all the ferromanganese that was on the market before 1875 was made in crucibles, and cost about 00 per ton, for 80 per cent. Mn. I consulted the great steel metallurgist of the day, Alexander Holley, who listened attentively to what I had to say, and told me he did not think my plan was practical, so I abandoned it for the time being. But I was so stubborn that I could not get the notion out of my head. It seemed to me that a good metallurgist should be able to work the thing out in some way. I had already had some experience in smelting refractory lead ores in Utah, and was young and not lacking in self confidence, so after waiting a bit, I got Anton Eilers, the best all-around metallurgist I knew, and J. H. Bramwell, the best iron blast-furnace man I knew, both intimate friends of -mine, to come to my place in Bartow County, Georgia, and look over things. They remained for several days, and made all the examination they thought necessary; and they also advised me to give up the project, and either to keep the furnace running on car-wheel iron or to blow it out. After my talk with Holley, I improved my plant in several ways. I closed the top of the furnace, put in a hot-blast stove, a steam boiler and a Weimer blowing-engine which gave me blast enough, at a pressure high enough for all the requirements of, the furnace, and which I could bring up to a temperature of 600° to 700° F.

Jan 1, 1921

By Alexander Field

IN THE light of the experimental data on equilibrium for the reaction C + FeO = Fe + CO in molten steel recently obtained by Kinzel and I Egan,1 it is necessary to revise current theories regarding the nature of equilibrium between carbon and FeO in the basic open-hearth furnace. According to the measurements of these investigators the equilibrium constant m for the above reaction for a pressure of dissolved CO equal to 1 atm. is equal to 0.0005 at 1550° C., when concentrations of carbon and. FeO are expressed in percentages by weight. Their work also shows that, with the pressure of CO fixed at 1 atm., not only is the product of carbon and FeO constant, but carbon and FeO are each independently constant-a circumstance which might have been predicted from theoretical considerations. At 1550° C., carbon is constant at about 0.025 per cent. and FeO at about 0.020 per cent., with the pressure of dissolved -CO equal to 1 atm., the product of these two constants being equal to the originally mentioned constant of 0.0005. Available data on the dissolved FeO content of samples taken from the metal bath at practical slag-metal equilibrium prove that this FeO content is determined solely by temperature and the effective FeO content of the slag. The distribution constant r at 1550° C., as determined by Herty, Gaines, Larsen, Simkins, Geruso and Watkins2 is equal to 0.0086. A slag would have to contain 0.020/0.0086 = 2.3 per cent. effective FeO or less in order to prevent the metal from containing more dissolved FeO than that required for equilibrium with CO at 1 atm. pressure. Such low percentages of FeO are never found in basic open-hearth slags at the completion of a heat when rate of carbon drop has become practi-

Jan 1, 1930

By K. S. Milliken

NORMAN W. Lord&apos; has shown that the resultant impurity distribution after n zone passes is given by in the ingot section OSa<N—n, where a is the displacement in zone lengths, N is the ingot length in zone lengths, C,, is the initial uniform impurity concentration, k is the segregation constant = Ceoll C,,,,,,,, at equilibrium, and The foregoing expression is formidable in respect to computational labor. However, the triple sum can be reduced as follows is better if computing for only a single value of n. For k<l, it can be shown that this last equation is equivalent to The infinite series is useful only when k is small enough to force rapid convergence. In such cases, the absence of subtraction from unity has the definite advantage of preserving accuracy. Acknowledgments It is a pleasure to acknowledge stimulating correspondence with Dr. Howard Reiss of Bell Telephone Laboratories Inc. This note is published by permis-sion of the Deputy Minister, Dept. of Mines and Technical Surveys, Ottawa, Ont., Canada.

Jan 1, 1956

By Amitava Gangulee, Michael B. Bever

The order-disorder transition in Ag-Mg alloys in the range 17 to 26 at. pct Mg was investigated and some thermodynamic, electrical and mechanical properties of ordered Ag-Mg alloys were measured. A modification of the phase diagram is proposed on the basis of measured transition temperatures. The stability of the ordered structure is analyzed in terms of the quasichemical theory. Kinetic aspects of the order-disorder transition were also investigated. The energies of ordering at 273°K of Ag-Mg alloys were measured by liquid metal solution calorimetry. The electrical resistivities and the tensile Properties of the ordered alloys were measured. The exothermic energy of ordering increased with magnesium concentration up to the composition Ag3Mg; it is discussed in terms of the quasichemical theory. Pronounced order hardening was observed and can be explained by several strengthening mechanisms, which are particularly effective because of a change in crystal structure associated with the ordering transition. IN silver-rich solid solutions containing approximately 17 to 26 at. pct Mg, long- range ordering may occur during appropriate therma1 treatments. Clare-brough and Nicholas1 first detected such long-range order in the solid solution of composition Ag3Mg and suggested that the unit cell of the superlattice contained 256 atoms. x-ray2 and electron diffraction3 investigations confirmed the occurrence of long-range order, but indicated a shifted Ll2-type structure. On the basis of recent X-ray measurements the crystal structure of ordered Ag3Mg has been confirmed as type D023.4 The present paper is concerned with the order-disorder transition in silver-rich Ag-Mg solid solutions and some thermodynamic, electrical, and mechanical properties of the ordered alloys. The effects of short-range order on the properties of silver-rich solid solutions containing up to 26 at. pct Mg are discussed in a concurrent paper.5 1) EXPERIMENTAL PROCEDURES 1.1) Preparation of Specimens. Specimens of Ag-Mg alloys containing from 18 to 26 at. pct Mg were prepared in the form of 1.0-mm-diam wires as described in Section 1.1 of Ref. 5. Disordered specimens were prepared by annealing at 773°K for 1 hr and quenching into iced brine. Ordered specimens were prepared by annealing at 773°K for 1 hr and slowly cooling to room temperature over a period of 15 days. The specimens were stored at 78°K. 1.2) Resistivity Measurements. Electrical resistivi- ties were measured by a potentiometric method.&apos; Equilibrium values were obtained at several temperatures. The kinetics of ordering were investigated by following the time-dependent changes of the resistivity of initially disordered specimens during annealing. The specimens were enclosed in copper capsules and immersed in salt pots; the heating up was accelerated by injecting preheated helium into the capsules. 1.3) Calorimetry. The energies of ordering of the alloys were measured in a tin solution calorimeter as the difference between the heat effects of additions of completely ordered and disordered specimens of the same composition. The procedure and the method of calculation have been described.6 Magnesium was used for thermal compensation in most calorimetric runs in order to improve the accuracy.677 1.4) Mechanical Tests. Tensile tests were carried out with wire specimens at room temperature as described in Section 1.5 of Ref. 5. Microhardness measurements were also made.? 2) RESULTS AND DISCUSSION The characteristics of the order-disorder transition of silver-rich Ag-Mg solid solutions will be discussed first. Some thermodynamic, electrical, and mechanical properties of the ordered alloys will then be considered and compared with the corresponding properties of dis-disordered alloys. 2.1) The Order-Disorder Transition. 2.1.1) Thermodynamic and Structural Aspects. The transition temperatures Tt were determined from discontinuities in the slope of the equilibrium resistivity vs temperature curves. Normalized curves for three compositions are shown in Fig. 1. The transition temperature increases with the magnesium concentration and reaches a maximum at the stoichiometric composition Ag3Mg. The transition temperature of the alloy Ag3Mg was measured as 665° ± 2°K and compares with published values of 660°,1 663°,8 and 66°k.3 In the slopes of the resistivity vs temperature curves of alloys containing 22.2 and 22.5 at. pct Mg, discontinuities were observed at two temperatures. Such upper and lower discontinuities indicate a two-phase field. A modified form of the published phase diagram9 is shown in Fig. 2. A two-phase field was found only on the low-magnesium side of the composition Ag3Mg. On the high-magnesium side, the existence of a two-phase field could not be established because of insufficient resolution, but such a field must be present. This part of the phase diagram can be made complete by a eutec-toid-type reaction a = (a&apos; + ß). The existence of a boundary between the two-phase fields (a + ß) and (a&apos; + ß) is also in accord with published lattice parameters.3 The crystal structure of ordered Ag3Mg (type Do23)

Jan 1, 1969

By T. J. Smolik, Harman, D. W. Fuerstenau

By means of electrokinetic measurements, the surface properties of the aluminosilicate polymorphs (sillimanite, andalusite, and kyanite) and also mullite have been found to depend on the ratio of A10 bonds to SiO bonds in the surface. The Al-toSi ratio in the surface is dependent upon the crystal lographic properties of the mineral, which in turn determine coordination numbers of A1 and of Si, cleavage characteristics, and density of the various solids. Mullite with a greater bulk Al-toSi ratio has the highest zpc of the aluminosilicates. By treatment in dilute acids or by cycling between acidic and basic solutions, alumina is selectively dissolved from the surface of these orthosilicates. This shifts the apparent zpc to lower pH values as the fraction of SiO groups in the surface increases. Thus, surface properties can be altered by procedures that alter the A l-to-Si ratio in the surface. Flotation of these aluminosilicates results from electrostatic interaction of the collector ions with the mineral surfaces. As a result, flotation response shifts in accord with any shift in apparent zpc by pretreatment. Separation of minerals by flotation is based on differences in the physicochemical properties of their surfaces.&apos;-3 For many minerals, adsorption of flotation collectors results from their functioning as counter ions in the electrical double layer at solid-water interface. In such systems, separation depends on differences in the zero point of charge (zpc) of the various minerals. The zpc is defined as the concentration of potential determining ions in solution at which the surface is uncharged. The potential determining ions for inorganic oxide-water interfaces are hydrogen and hydroxyl.4,5 This work is concerned with the effects of crystal structure, composition, and surface preparation on the surface properties and flotation behavior of aluminosilicates. Differences resulting from crystal structure were studied by measuring electrokinetic potentials and determining the flotation behavior of three different aluminosilicate materials having the same chemical composition (Al2O3 SiO2), namely andalusite, kyanite, and sillimanite. Furthermore, the effect of the Al2O3-to-SiO2 ratio on flotation behavior and surface properties was investigated by including synthetic mullite, 3A12O3 .2SiO2. Gaudin and co-workers 6,7 have clearly shown how crystal structure determines the native floatability of certain minerals. Those solids in which the surface is comprised mainly of broken residual bonds possess naturally hydrophobic surfaces. It was found by Bakakin8 that for a number of oxidized lead minerals, differences in floatability were due to the distance of Pb atom from the surface. Only limited work has been done on relating electrical properties of surfaces to crystal structure and composition. Healy et. a1.9 found that the zero points of charge of various manganese dioxides ranged from about pH 1.5 to pH 7.5, and these differences in the zpc&apos;s were interpreted in terms of the atomic packing in the various crystals. The research presented here clearly shows that crystal structure and chemical composition do affect the surface properties of aluminosilicates and, in addition, that these effects can be altered by changing conditions under which the surfaces are prepared. CRYSTAL STRUCTURE OF THE ALUMINOSILICATES Sillimanite, andalusite, and kyanite are composed of regionally metamorphosed rocks differing mainly in degree of metamorphism. All three minerals have the same chemical composition, Al2O3 - SiO2, of which sillimanite is the high temperature polymorph and kyanite and andalusite the lower temperature polymorphs. Andalusite and sillimanite crystallize in the orthorhombic system while kyanite crystallizes in the triclinic system. The structure of these three minerals is essentially chains of aluminum-oxygen octahedra linked laterally by silicon and aluminum. The arrangement of these chains in the three minerals is shown in Fig. 1.l4

Jan 1, 1967

By Fred H. Poettmann

An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of the compressibility factor of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. Comparison of calculated results with field measured results were made on 20 dry gas wells from a given field and 11 distillate wells from different fields. The agreement between calculated and observed results is good. In addition to their use in the calculation of sandface pressures of flowing wells, the factors can be used in the direct calculation of the static bottom hole pressure of gas wells, the capacity of gas transmission lines, and in the calculation of the theoretical isothermal horsepower necessary to compress a natural gas. Examples demonstrating the use of various equations are given. INTRODUCTION Many of the equations used to calculate the sandface pressures of flowing gas wells from well head data do not take into consideration rigorously the deviation of the natural gas from ideal gas behavior. For low pressure wells this error is not serious. For high pressure wells flowing at high rates this error call be serious. Sandface pressures are used to determine the producing capacity of gas wells as shown in the U. S. Bureau of Mines&apos; Monograph 7.&apos; An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of compressibility of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. In addition to their use in the calculation of sandface pressures, these "factors" can also be used to give a direct solution in the calculation of the static bottom hole pressure of gas wells, the calculation of the capacity of gas transmission lines, and the calculation of the isothermal horsepower necessary to compress a gas. CALCULATION OF SANDFACE PRESSURE OF FLOWING GAS WELLS The starting point in the derivation of any specific flow equation is an energy balance on the fluid flowing between any two points in the system. This energy balance based on one pound of flowing fluid is expressed by the well known general flow equation: jp~- vdP+ Ah + -— + wt + r. = o . . (i) P, 2 g. where V = specific volume of flowing fluid in cu ft/lb P = pressure in Ib per sq ft ah = difference in height above datum plane in, ft ------ = kinetic energy change of one lb of flowing fluid, v equals velocity in ft/sec and g. = 32.174 Ws = Work done by fluid while in flow (similar to shaft work in driving a turbine) W, = Znergy losses due to the irreversibilities of the flowing fluid This equation contains no limiting assumptions and can be made the basis of any fluid flow relationship by limitations or substitutions. The energy units are usually expressed in term* of foot-pounds of energy per pound of mass. Considering the vertical flow of gas through tubing or annu-lus, the external work W, done by the gas is zero. Let us also assume that the value of the kinetic energy function is small and can be neglected. Equation (1) is reduced to: /P: VdP + Ah+Wt = 0 .......(2) Pi The energy loszes PI can be expressed in terms of the well known Fanning equatinn: 4/Lf: rf = —— ............(3) 2g,D where L = the integrated average velocity in ft/sec of vertical flow in a uniform flow string -~h = L v = the integrated average velocity in ft/sec / = dimensionless correlating function

Jan 1, 1951

By Fred H. Poettmann

An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of the compressibility factor of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. Comparison of calculated results with field measured results were made on 20 dry gas wells from a given field and 11 distillate wells from different fields. The agreement between calculated and observed results is good. In addition to their use in the calculation of sandface pressures of flowing wells, the factors can be used in the direct calculation of the static bottom hole pressure of gas wells, the capacity of gas transmission lines, and in the calculation of the theoretical isothermal horsepower necessary to compress a natural gas. Examples demonstrating the use of various equations are given. INTRODUCTION Many of the equations used to calculate the sandface pressures of flowing gas wells from well head data do not take into consideration rigorously the deviation of the natural gas from ideal gas behavior. For low pressure wells this error is not serious. For high pressure wells flowing at high rates this error call be serious. Sandface pressures are used to determine the producing capacity of gas wells as shown in the U. S. Bureau of Mines&apos; Monograph 7.&apos; An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of compressibility of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. In addition to their use in the calculation of sandface pressures, these "factors" can also be used to give a direct solution in the calculation of the static bottom hole pressure of gas wells, the calculation of the capacity of gas transmission lines, and the calculation of the isothermal horsepower necessary to compress a gas. CALCULATION OF SANDFACE PRESSURE OF FLOWING GAS WELLS The starting point in the derivation of any specific flow equation is an energy balance on the fluid flowing between any two points in the system. This energy balance based on one pound of flowing fluid is expressed by the well known general flow equation: jp~- vdP+ Ah + -— + wt + r. = o . . (i) P, 2 g. where V = specific volume of flowing fluid in cu ft/lb P = pressure in Ib per sq ft ah = difference in height above datum plane in, ft ------ = kinetic energy change of one lb of flowing fluid, v equals velocity in ft/sec and g. = 32.174 Ws = Work done by fluid while in flow (similar to shaft work in driving a turbine) W, = Znergy losses due to the irreversibilities of the flowing fluid This equation contains no limiting assumptions and can be made the basis of any fluid flow relationship by limitations or substitutions. The energy units are usually expressed in term* of foot-pounds of energy per pound of mass. Considering the vertical flow of gas through tubing or annu-lus, the external work W, done by the gas is zero. Let us also assume that the value of the kinetic energy function is small and can be neglected. Equation (1) is reduced to: /P: VdP + Ah+Wt = 0 .......(2) Pi The energy loszes PI can be expressed in terms of the well known Fanning equatinn: 4/Lf: rf = —— ............(3) 2g,D where L = the integrated average velocity in ft/sec of vertical flow in a uniform flow string -~h = L v = the integrated average velocity in ft/sec / = dimensionless correlating function

Jan 1, 1951

By R. H. Gautschi, F. C. Langenberg

Rare-earth additions were made to laboratory heats of Type 310 stainless to observe their effect on as-cast ingot structure, nitrogen and sulfur contents, and nonmetallic inclusions. Lanthanum had a grain-refining effect in 30-lb ingots, but results with 200-lb ingots were inconsistent. Cerium, lanthanum, and misch metal lowered the sulfur content when the sulfur exceeded 0.015 pct and the rare-earth addition was greater than 0.1 pct. The rare-eardh content in the metal dropped very rapidly within the first few minutes after the addition. The size, shape, and distribution of nonmetallic inclusions was not changed in 30-lb ingots, but changes were noticed in larger ingots. RARE-earth* additions have been made to austenitic Cr-Ni and Cr-Mn steels to improve their hot workability. The high alloy content of these steels often results in a considerable resistance to deformation and inherent hot shortness at rolling temperatures, particularly in larger ingots. Rare earths in the metallic, oxide, or halide form are usually added to the steel in the ladle after deoxidation although they can be added in the furnace prior to tap or in the molds during teeming. The literature- indicates that the effects of rare-earth treatments on these stainless steels are not consistent, and sometimes even contradictory. Since no mechanism has been presented which satisfactorily accounts for the claimed improvements, the effects of rare earths are a qualitative matter. The work described in this paper was initiated to expand the knowledge of the effects of rare-earth additions on melting variables such as ingot structure, chemical analysis, and nonmetallic inclusions. REVIEW OF LITERATURE Ingot Structure—Rare-earth additions to stainless steels have been reported to cause a change in primary ingot structure in that there are fewer coarse columnar grains. However, the results are inconsistent. While one investigation1 has shown a large reduction in coarse columnar crystals, another2 has been unable to observe this effect, particularly when small ingots were poured. Post and coworkers3 observed ingot structures for a number of years and found that the columnar type of structure is not definitely a cause of any particular trouble in rolling or hammering, provided the alloy is ductile. Knapp and Bolkcom4 found rare-earth additions to be quite effective in preventing grain coarsening in Type 310 stainless steel. Chemical Analysis—Many effects of rare-earth treatment on chemical analysis have been claimed in the literature. Russell5 observed that some sulfur is removed by rare-earth metals, and that a high initial sulfur content improved the efficiency of sulfur removal. Lillieqvist and Mickelson6 report that rare-earth treatment causes sulfur removal in basic open-hearth furnaces, but not in basic lined induction furnaces. Knapp and Bolkcom found no sulfur removal in acid open-hearth and acid electric furnaces, probably because the acid slag can not retain sul-fides. snellmann7 showed that sulfur could be lowered apprecfably with rare-earth additions; however, a sulfur reversion occurred with time. Langenberg and chipman8 studied the reaction CeS(s) = Ce(in Fe) + S(in Fe), and found the solubilit product [%Ce] [%S] equal to (1.5 + 0.5) X 10-3&apos;at 1600°C. Results in 17 Cr-9 Ni stainless were about the same as those in iron. Beaver2 treated chromium-nickel steels with 0.3 pct misch metal and observed some reduction in the oxygen content. He also noted an inconsistent but beneficial effect of rare earths when tramp elements were present in amounts sufficient to cause difficulty in hot working. It is not known whether rare earths reduce the content of the tramp elements or change the form in which these elements appear in the final structure. No quantitative data are available concerning a possible effect of rare-earth treatment on hydrogen and nitrogen contents. However, Schwartzbart and sheehan9 stated that additions of rare earths had no effect on impact properties when the nitrogen content was low (0.006 pct), but served to counteract the adverse effects of high nitrogen content (0.030 pct) on these properties. Knapp and Bolkcom4 analyzed open-hearth heats in the treated and untreated conditions and found the nitrogen content (0.006 pct) to be unaffected. These two results lead to the speculation that rare-earth additions can reduce the nitrogen content to a certain level. Decker and coworkers10 have observed that small amounts of boron or zirconium, picked up from magnesia or zirconia crucibles, increased high-tem-

Jan 1, 1961

By J. H. Wernick

IN a study of the rate of decomposition of %-in. cubes of limestone, dolomitic limestone, and dolomite in a sweeping nitrogen atmosphere, Joseph, Beatty, and Bitsianes&apos; found that the zone of calcination advanced at substantially a constant rate at a given temperature. The purpose of this paper is to show that their data indicate at least two processes occurring when the above carbonates decompose. It is suggested that there are two processes occurring consecutively, one the limiting process in a given temperature range and the other the limiting process over another temperature range. The data of Joseph and co-workers have been extended by use of the Arrhenius equation, Eq. 1, a relation beween the velocity constant k of a reaction and the absolute temperature T. d In k A &apos; dT Rr2 A is the activation energy in calories per mol (additional energy that must be added for an average molecule to react), and R is equal to 1.986 cal

Jan 1, 1955

By H. C. Burghard, F. R. Brotzen

Experiments were performed to determine the effects of mechanical vibrations on ordering in CuAu. The effects of 5, 10, and 15 kc vibrations were investigated over a range of ordering temperatures of 280° to 360°C. A decrease in the rate of ordering was observed at all frequencies and ordering temperatures. THE effects of mechanical vibrations on certain solid-state reactions have been noted by several investigators. In 1930, Mahoux&apos; reported a substantial increase in the case depth of a steel sample nitrided under the influence of mechanical vibrations over that of an unvibrated sample. Similarly, an accelerating effect of vibrations on the diffusion of chromium in steel was noted. Guillet, in the same year, confirmed the results of Mahoux. More recently Schenck and schmidtmann3 studied the effects of low-frequency, alternating loads on the diffusion of carbon in steel. The results of their experiments, conducted at 500 cycles per min and large strain, (0.2 pct), indicated an acceleration of the process. These workers also reported an increase in case depth of a sample vibrated at 430 kc during a carburizing treatment. Effects of high-frequency vibrations on solid-state reactions have also been investigated by Gudzoff and Gavze6 and Fairbanks and Dewez.7 The former reported an acceleration of the age-hardening process in aluminum alloys. The latter noted changes in the structure and mechanical properties of steel annealed under the influence of vibrations. On the other hand, Altenburg4 and Ehringer5 have given some theoretical reasons and experimental evidence as to the improbability of any effect of vibrations on diffusion. Comprehensive surveys of the effects of vibrations on metallurgical reactions are given by Hiedemann&apos; and Bergmann.9 None of the above investigations led to a physical description of the effects of mechanical vibrations on solid-state reactions. In the present study an attempt was made to gain an understanding of the influence of vibrations on nucleation and diffusion. The order-disorder transformation was chosen for investigation since its mechanism has been extensively discussed in the literature. Moreover, the progress of the transformation may be easily followed by observation of electrical resistance changes. EXPERIMENTAL PROCEDURE The specimens used for the experimental observation of ordering rates were prepared from 50 at. pct Cu-Au alloy wire.* Each specimen consisted of a 0.02-in. diam wire approximately 10 in. long to which two copper potential leads were silver soldered, 2 1/2 in. apart, near one end of the wire. A 1/8-in. diam by 1/4-in. long steel stub was silver soldered

Jan 1, 1960

By R. R. Harvey

Recent evidence has indicated that the films forming at crude oil-water interfaces are the result of naturally occurring su,rface-active components in the crude oil rather than oxidation products resulting from exposure of the oil to air. Since the presence of such films may strongly affect the displacement of oil from porous media, a knowledge of their composition and formatiorz is of fundamental importance. In this study, without the assumption of a specific mechanism, film formation is considered to involve the transfer of a weakly surface-active species in solution in the oil to the oil-water interface. The film gas law and the Gibbs adsorption equation may thus he applied to the system. The rigid films which form upon decrease of the oil-water interfacial area are considered a result of the very slow rate of re-solution of the film material into the oil. When the shrinkage of the interface is very rapid, the amount of film material leaving the interface is negligible, and the system may then be treated in the same manner as an insoluble film. The combination of these treatments leads to a new concept of the film factor in which it may he quantitatively related to the concentration of film-forming material at the interface. Suitable experiments can then yield the following information. 1. Original concentration of surface-active species in the oil. 2. The change of concentration with time. 3. Concentration of surface active species at the interface. 4. The change of this concentration with time. 5. Interfacial tension of the system at any time and its variation with time. 6. Equilibriunz concentrations for a given set of conditions. 7. Concentration requirements for solid film formation. 8. Molecular diameter of the adrorbed species. These calculations may be made solely from data taken from measurements on the original oil. While using the pendant drop method of interfacial tension measurement of crude oil-water systems, Bartell and Niederhauser&apos; remarked on the thin, transparent, pliable, solid films or membranes which were often formed at the interface between crude oil and water. As a result of their observations of these films, Bar-tell and Niederhauser concluded: 1. The films are formed by material from the oil adsorbed at the interface rather than by a reaction at the interface. 2. The adsorption of the film-forming material is a rather slow process. 3. There are good indications that the process is reversible; i.e., the film constituents may re-dissolve into the oil. 4. The film will spontaneously spread over any new surface formed. 5. The process of adsorption at the interface is accompanied by a decrease in the interfacial tension of the system. Although they had proved that film formation was not due to a reaction at the interface, Bartell and Niederhauser were unable to demonstrate conclusively whether these film-forming constituents were present in the original reservoir oil or whether they were formed as oxidation products after exposure of the oil to air. Recent evidence seems to point to their presence in the original oil. Although the true nature of the film-forming constituents is still uncertain, these conditions would be fulfilled by the assumption of the presence of a slightly soluble surface-active component in the original oil. This component would migrate to a freshly formed interface because it would thereby lower the free energy of the system. The component at the surface constitutes an expanded monolayer which would become compressed, upon retraction of drop, due to the slow rate of re-solution of the film components into the bulk of the oil. It is possible, by involved extraction processes, to separate or at least concentrate this film-forming fraction. However, using the assumptions made above, the technique of monolayer film study may be applied to reveal much of the nature of the adsorbing material without resorting to an actual separation of the film-forming constituents.