Search Documents

By A. J. Heckler, J. A. Peterson

A capsule technique was successfully employed to investigate the effect of nickel on the activity of nitrogen in Fe-Ni-N austenite in the temperature range 600" to 1200°C. This technique consisted of equilibrating nitrogen among various Fe-Ni alloys within a sealed silica capsule. Nitrogen transfer among the specimens occurred by N, gas at 900°, lOOO? and 1200?C. Nitrogen gas pressures within the capsules were estimated to be as high as 22 atm. The activity coefficient of nitrogen, fN , in Fe-Ni-N austenite is adequately described by the linear interaction equation: log . wt pct Ni where the standard state is chosen such that fN = I as wt pct Napproaches zero in binary Fe-N. This relationship was determined over the temperature range 873" to 1473°K and for nickel contents of 0 to 35 wt pct. ALTHOUGH chemical thermodynamics of liquid iron alloys have been extensively studied, experimental data for the solid state are needed. These thermody-namic data will provide a basis for understanding phase transformations, precipitation reactions, metal-gas equilibria, and so forth. The interaction of sub-stitutional alloying elements with the interstitial elements is of particular interest. In this investigation the thermodynamic behavior of Fe-Ni-N austenite has been studied. The solubility of nitrogen gas in iron austenite is known to obey Sieverts&apos; law up to about 65 atm.1-6 In addition, the solubility of nitrogen in Fe-Ni austenite has been investigated5"8 using the classical method of equilibrating Fe-Ni alloys with nitrogen gas at 1 atm. A capsule technique similar to that used to study the activity of carbon in alloyed austeniteg&apos;&apos;&apos; was employed in the present work to determine the effect of nickel on the activity of nitrogen in Fe-Ni austenite over the temperature range 600" to 1200°C. EXPERIMENTAL PROCEDURE A series of Fe-Ni alloys up to 35 wt pct Ni was vacuum melted and cast into 1 by 3 by 6 in. ingots. Chemical analyses at the top and bottom of each ingot demonstrated that the ingots were homogeneous with respect to nickel content. The nickel contents are given in Table I. Additional chemical analyses showed that wt pct Si < 0.05, s < 0.01, C < 0.01, Al < 0.006, 0 < 0.004, Mn < 0.002, and P < 0.002. A 2 in. section of each ingot was cold rolled to 0.015 in. The material was then decarburized to a carbon content of less than 0.004 wt pct. A portion of the material of each nickel content was nitrided to various levels in a H2-NH3 gas atmosphere to provide a source of nitrogen during subsequent equilibration. The experimental technique consisted of equilibrating the series of Fe-Ni-N alloys in a partially evacuated sealed silica capsule at the temperature of interest. Both Vycor and quartz capsules were used. In general, the final equilibrium nitrogen content for each Fe-Ni alloy was approached from both higher and lower nitrogen levels. The criterion for establishing that equilibrium was attained was that the final nitrogen content for each Fe-Ni alloy was the same irrespective of the initial level. A schematic drawing of the sample configuration in a capsule is shown in Fig. 1. The samples were arranged so that there was a minimum of physical contact. The samples were also dusted with a fine, high purity alumina powder to help prevent sticking. Several different types of furnaces were used in this study. In each case, a thermocouple was placed immediately adjacent to the capsule during equilibration and the temperature was controlled to within *4?C of that reported. At each equilibration temperature, the following times were found to be more than sufficient to attain equilibrium: 600°C-250 hr, 900°C-150 hr, 1000°C-150 hr, and 1200°C-50 hr. After equilibration the capsules were quenched in water and the nitrogen contents of the specimens determined by a Strohlein analyzer. Analyses of samples after equilibration at 1000" and 1200°C showed no silicon pickup from the silica capsules. RESULTS AND DISCUSSION Transfer Mechanism. The mechanism by which nitrogen was transferred among specimens in an initially hydrogen flushed and partially evacuated capsule equilibrated at 1000°C was investigated. After equilibration the gas in the capsule was collected over water and an estimate of the pressure at temperature

Jan 1, 1970

By E. A. Almond

An attempt is made to explain the effect of stress on strain aging by examining the mechanism of yielding for a group of aged dislocations. The experimental results on which the theory is based indicate that a linear relationship develops between the aging stress and the discontinuous yield effect in a low carbon steel THE discontinuous yield effect that occurs in bcc metals after strain aging is usually explained by the interaction of interstitial atoms with individual dislocations. Attempts have been made to interpret the kinetics of strain aging in terms of interstitial segregation to nonrandom groups of dislocations1-3 but apart from Li&apos;s4 work little or no effort has been made to examine the effect of groups of aged dislocations on mechanical properties. It appears likely that such groups can be stabilized if a positive load is maintained on the specimen during aging5 and, furthermore, that the enhanced strain aging effect associated with aging under load might be due to the stability of these aged groups. The effects associated with this latter phenomenon have been described by Almond and Hull, Ref. 5, Figs. 2 and 3, and it is found that the upper yield stress, the lower yield stress, and the yield point elongation are increased by aging under load. The yield point elongation reaches a maximum value but the enhanced effect persists in the upper and lower yield stress values even after extended aging treatments when the general level of the flow stress curve rises. The flow stress, as measured at 8.5 pct total strain, however, is independent of aging stress. Almond and Hull5 showed that it was unlikely that the differences in mechanical properties could be caused by stress enhanced diffusion and they suggested that the effect was in some way associated with the different dislocation distributions that are obtained when specimens are aged with and without an applied stress. At that time no explanation was offered for the strengthening effect produced by stabilized dislocation distributions but additional tests have been performed to establish a quantitative relationship between aging stress and mechanical properties, and also to examine more closely the effect of varying the procedure for applying the aging stress. EXPERIMENTAL The material used was an iron wire containing 0.015 wt pct C, 0.002 wt pct N, and 0.006 wt pct 0. Tensile specimens with a 1 cm gage length and 0.08 cm diam were annealed at 850°C for 1 hr in vacuum to establish a grain diameter of 0.032 mm and then aged at 200°C for 24 hr. After this treatment the amount of carbon left in solution would be less than 10-4 wt pct, and ni- as aging time is increased. It is suggested that this observation, and effects that arise from varying the method of applying the aging stress, can be explained by a strengthening mechanism whereby dislocations are more difficult to move when they are aged in piled-up groups. trogen would be the main cause of strain aging. Tensile tests were performed in a hard beam machine at a constant crosshead speed of 0.02 cm per min and the specimen chamber was immersed in a temperature controlled silicone oil bath at 32" * 0.05"C. RESULTS All specimens were prestrained 5 pct before aging under stress and the results in Figs. 1 to 5 show the effect of aging time and aging stress on the following parameters ?UY = auy — ?F(5); i.e., the difference between the upper yield stress after aging,?uy, and the flow stress after prestraining 5 pct, ?f(5). ?LY = sly —sf(5); the difference between the lower yield stress after aging, ojy, and the flow stress after prestraining 5 pct. s8.5 = the flow stress at 8.5 pct total strain after aging at 5 pct strain. Varying the Loading Procedure. Three variations in the procedure for applying the aging stress were examined; i) After prestraining, the specimen was unloaded to a stress of 18 kg mm-2, aged at that stress, and then tested. ii) After prestraining, the specimen was unloaded to 2 kg mm-" then reloaded to 18 kg mm-&apos;, aged at that stress, and tested. iii) After prestraining, the specimen was unloaded to 18 kg mm-&apos;, aged at that stress, then unloaded to 2 kg mm- before testing. Specimens were unloaded or reloaded by decoupling a clutch in the drive transmission of the tensile machine. This enabled the crosshead to be driven manu-

Jan 1, 1970

By J. J. Jonas, G. Gagnon

SHG zinc was extruded in the temperature range 110" to 350°C and the strain rate range 0.05 to 5 sec-1 The strain rate/flow stress/temperature results were analyzed using a power sinh stress relationship. When temperature changes due to the heat of deformation and to heat losses are neglected, the exponent of the sinh function of the stress is 5.6, and the apparent activation energy of deformation is 28 kcal per mole. When these changes are taken into account, the exponent decreases to 4.7 and the activation energy to 23 + 2 kcal per mole. The corrected stress exponent and activation energy are in very good agreement with published values obtained from creep experiments, and suggest that the hot extrusion of zinc is controlled by a mechanism involving self-diffusion. When the extrusion and creep data are compared using a Zener-Hollomon parameter and either a sinh or an exponential stress term, an appreciable offset is observed, which may be due to the difference in impurity content. For a given set of extrusion conditions the ram speed, maximum pressure, and initial temperature can also be correlated using a Zener-Hollomon parameter and a sinh pressure term. THE deformation of metals at temperatures over about one-half the absolute melting temperature has been extensively studied at creep strain rates. By contrast, relatively little work has been carried out on the behavior of metals at hot working strain rates. Most of the latter investigations have been performed using simulative methods, such as hot torsion and hot compression, in which the friction conditions and temperature rise during deformation may differ appreciably from those existing under industrial conditions. Recently, however, Wong and Jonas1 used a scaled-down industrial process to determine the stress and temperature dependence of the strain rate during the extrusion of aluminum. In such tests, the effects of friction and adiabatic heating are closer to those produced in industrial operations. Also, with regard to the testing of materials of limited ductility such as zinc, hot compression and hot torsion do not permit the attainment of true strains as large as the deformations usually applied commercially. The present study was undertaken to investigate the extrusion behavior of Special High Grade (SHG) zinc. The detailed objectives were: 1) to establish the stress and temperature dependence of the strain rate with and without a consideration of adiabatic heating, 2) to study the pressure and temperature dependence of the ram speed, and 3) to investigate the microstruc- tural changes occurring during the deformation. The last aspect of the investigation will be covered in a separate paper. The treatment described below differs from that of Wong and Jonas in that the adiabatic temperature rise during deformation is taken into account, and the calculation of the mean equivalent strain rate is based on the redundant as well as on the homogeneous work. EXPERIMENTAL PROCEDURE Rods from two shipments of continuously cast SHG zinc* were used in the investigation. The composition *Supplied by courtesy of Cominco Ltd. range of the impurities present, as given by the supplier, was: Pb: 0.0013 to 0.0023 pct, Fe: 0.001 pct max Cd: 0.0001 to 0.0006 pct, Cu: 0.0002 to 0.0005 pct, Ti: 0.0001 pct max; thus, by balance, zinc valued from 99.9963 to 99.9966 pct. The as-received rods were machined into billets having a nominal diameter of 1.56 in. and a nominal length of 1½ in.; longer billets up to 4 in. in length, were also used to investigate special aspects. The as-machined rods were annealed at 400°C for 24 hr and slowly cooled. This treatment produced a columnar grain structure, with a grain size of about $ by 2½ cm which was appreciably larger than the as-cast one. A 150-ton, direct extrusion, vertical press was used. Ram displacement and force were recorded continuously against time. A constant flow control valve permitted the maintenance of a range of preselected ram speeds up to in. per sec. The selected speed was held constant, irrespective of the required force, as long as the load developed was below the maximum available. Strain gages were used to determine the force; the gages were calibrated before and after each testing period with a 200,000-lb capacity load cell. Further details of the experimental equipment can be found in Ref. 2. The billets were preheated for 90 min in the extrusion container, which was well insulated so as to minimize temperature gradients. This period was sufficient for the billet to reach a uniform temperature at all temperatures between 110" and 350°C. A square-shoulder die having a 0.290-in. diam central hole was used. The extrusion ratio was 30 to 1. This is equivalent to a reduction in area of 96.7 pct, an elongation of 2900 pct, and a true strain of 3.4. The ram speed was varied over two orders of magnitude from 0.0027 to 0.26 in. per sec. The ram was water-cooled during most of the tests, although some experiments were conducted with a preheated, uncooled ram. All extrusions were run without lubricant, which resulted in conditions of sticking friction. EXPERIMENTAL RESULTS Stress Dependence of the Strain Rate Neglecting Adiabatic Heating. The maximum force required to extrude is given in Table 1 for each of the five initial

Jan 1, 1970

By J. H. Bramwell

THE following experience in rebuilding a furnace crucible while in blast may not be wholly uninteresting to some, notwithstanding its purely practical character. Few are aware of the frequent calls made on a furnace manager&apos;s skill and ingenuity, to meet the irregularities which present themselves with kaleidoscopic variations in the operations of furnaces. Unfortunately the methods pursued in overcoming these practical difficulties are too seldom recorded, and much valuable information is lost that could not fail to be of value to many, and to none more so than the educated technical manager, with a limited practical experience, who, without a literature or record of any kind to refer to, finds himself, in times of emergency, dependent and looking for assistance from those whom it is his province to instruct and direct. With positive data, however, that like difficulties have been successfully overcome, he can confidently resort to similar expedients, with such modifications as the circumstances may demand in his particular case, and pull through seeming impossibilities in the face of ignorant prejudice. The Quinnimont Furnace (60 x 15 feet) had been in operation but two months, when it became necessary to draw the tuyeres out a distance of 18 inches, in order to give them a resting-place; the brickwork under them being completely cut away, so that after each

Jan 1, 1877

ABERDEEN, ESTHER, U. S. Geological Survey, Washington, D. C. ALLEN, VICTOR T., Director Geology Department, Institute of Technology, St. Louis University, St. Louis, Missouri. BATES, THOMAS F., Associate Professor of Mineralogy, Department of Earth Sciences, School of Mineral Industries, The Pennsylvania State College, State College, Pennsylvania. BOLGER, ROBERT C., Geologist, Pennsylvania Topographic and Geologic Survey, Harrisburg, Pennsylvania. BRIDGE, JOSIAH, U. S. Geological Survey, Washington, D. C. BURST, JOHN F., Geologist, Exploration and Production Research Division, Shell Oil Company, Houston, Texas. CAMPBELL, IAN, Executive Officer, Division of Geological Sciences, California Institute of Technology, Pasadena, California. FLINT, DELOS E., U. S. Geological Survey, Washington, D. C. FREDERICKSON, A. F., Associate Professor of Geology (Geochemistry), Washington University, St. Louis, Missouri. GLASS, HERBERT, Illinois State Geological Survey, Urbana, Illinois. GORDON, MACKENZIE JR., Geologist, U. S. Geological Survey, Washington, D. C. GRIM, RALPH E., Research Professor, Department of Geology, University of Illinois, Urbana, Illinois. HARDER, E. C., Aluminium Secretariat Limited, Montreal, Que., Canada.

Jan 1, 1952

By Hans Rumpf

INTRODUCTION Agglomeration is based on adhesion between particles. Production of agglomerates of specific strength, strain properties, size, porosity and structure necessitates the activation of the adhesive forces. To achieve this, it is important for us to know details of the various systems of adhesion. Reports on the work of our Institute for the investigation of systems of adhesion were published on various occasions. A reference to those publications is made in the following abstract, and the findings previously published are presented only to the extent necessary for a better understanding of more recent test results, or of changed ideas. 1. MECHANISMS OF ADHESION We must distinguish between various "mechanisms of adhesion". By "mechanism of adhesion" we understand the interaction between a particle and a substrate resulting from a clearly definable physical or physico-chemical process resulting in a definite mathematical interrelation- ship between the decisive variables.

Jan 1, 1977

By R. Venkateswar, G. C. Sresty

Size measurement is important in characterization of fine particles. Commonly employed size measurement techniques such as sieving, microscopy, and sedimentation are discussed in this paper. Operating principles, advantages and limitations of these techniques are discussed based on the published information and working knowledge with several of these instruments at the authors&apos; laboratories. A brief description of the recently developed equipment for fine particle characterization is also included. At the end of the paper, a rationale is presented for selection of the size analysis equipment based on specific requirements.

Jan 1, 1980

By H. J. Modi, P. L. De Bruyn

In recent years interest has been aroused in flotation rate studies both from a technical and a more practical aspect. With increasing fineness of grind becoming a necessity in treatment of low grade ores, differences in flotation rates of various size ranges will assume importance in the evaluation of overall recovery results. Theoretical analysis of flotation kinetics was initiated by Schuhmann, who sought to define flotation rate of a given mineral and specified size range in terms of certain physical variables of the flotation system. Using as a basis for his analysis the bubble- particle encounter hypothesis previously advanced by Gaudin, Schuhmann writes for the rate of flotation (R,) of particles of average size x, [ ]

Apr 1, 1956

By R. Hogg, F. F. Aplan, P. B. Bradley, M. F. Placha

Particle size distributions of the solids fraction in typical coal preparation plant black water have been evaluated. The carbonaceous and mineral fractions were found to have distinctly different size distributions: the mineral matter being significantly finer than the carbonaceous material in all cases. Based on analyses of 13 samples obtained from the Appalachian, mid-continent and western regions of the US, it was found that, on the average, 83% of the mineral particles but only 41 % of the coal particles were finer than 44 pm (325 mesh). Typically, the size distributions of the mineral matter fraction tend to be bimodal, probably due to the presence of relatively coarse quartz, calcite, pyrite, etc., together with much finer clay particles.

Jan 1, 1981

By L. P. Bayvel

The method of spectral transparency was investigated. A device for measuring particle sizes based on this method was developed, tested and applied. The device affords measurements of particle size distribution in the range from 0.1 to 4 µm. It proved possible to measure sizes not only of spherical particles but also of non- spherical ones. The spectral range in which it is necessary to determine transparency for particle size measurements was found.

Jan 1, 1980

By E. S. Porter

The techniques of particle-size measurement are of particular importance in the manufacture of portland cement. A range of sizes, from a close approximation to Fred C. Bond&apos;s "theoretical infinite" (represented by raw material in the quarry) to particles smaller than one micron is represented in the process. Moreover, similar size-reduction operations are performed on both natural and synthetic materials, the former relatively inactive in water and the latter quite reactive. This means that aqueous sedimentation systems for particle-size analysis are applicable only to some of the materials involved in the process. A brief review of the process should be useful to place the measurement techniques described here in perspective. (Fig.l) Raw materials are quarried, crushed and transported to storage at a maximum size usually of a few inches. Typical materials are limestone and clay or shale, with small amounts of other materials used to adjust the plant mix to the concentration of lime, silica, alumina and iron oxide required.

Jan 6, 1962

By Herbert H. Uhlig

A STUDY of passivity in chromium-iron alloys holds considerable interest, both because of the present-day practical importance of the stainless steels, and because of the scientific importance attached to the mechanism of their corrosion resistance. Upon the discovery of the passive chromium-iron alloys in 1912, it seemed logical to attribute the observed phenomenal corrosion resistance to a thin, continuous, protective reaction product on the surface. The product was thought to be Cr2O3 or a similar oxide containing both chromium and iron. This mechanism seemed likely in view of Michael Faraday&apos;s conjecture that passive iron is not reactive in concentrated nitric acid because of an oxide on the metal surface.† Since 1912, data have accumulated that permit a further exploration into the nature of passivity and provide a new approach to the problem. A summary of the facts lends considerable weight to a mechanism based not on physical protection of an oxide or similar compound, although such compounds may be present on the surface, but to a change in tendency of surface metal atoms to react chemically. This change in reaction tendency is ascribed to chemisorbed films that effectively satisfy residual valence forces of the metal surface, but do not appreciably disturb the positions of metal atoms in the lattice. In other words, formation of a new lattice such as that of an oxide is not a necessary condition for this type of passivity. The decreased reaction tendency of the metal by reason of chemisorbed films can thereby account for low reaction rates of the stainless steels in many media, as well as a noble galvanic potential as is observed. Substances capable of adsorbing on the stainless steels, and hence accompanying the property of passivity, are typically oxygen, nitrites or chromates, but are not in any sense limited to these. Other elements and compounds can also chemisorb, and therefore may also play a major part in the mechanism of passivity in specific media. The mechanism of passivity based on chemisorption or activated adsorption begins with the interpretation Langmuir proposed for his experiments concerning adsorbed oxygen on tungsten.1 He found that adsorbed oxygen was tightly bound, remaining on the tungsten surface above temperatures at which WO3 rapidly volatilizes. The oxygen in such a state did not readily react with hydrogen even at

Jan 1, 1947

By C. E. Williams

THE Iron and Steel Division, A.I.M.E., is unique in this country in that it serves all phases of the iron and steel industries. Through its publications, its meetings, and its sponsorship of new technical developments in the industries, it has proved of great value. The various technical committees of the Division are the nucleus around which this service can be developed. The Blast Furnace and Raw Materials Committee has done excellent work. The need for beneficiation of iron ores is increasing and the economics of this operation are developing more and more in favor of increased activities. Ores that are slightly undergrade should be concentrated up to grade to supplant the present practice of mixing with higher-grade ores to bring up the average composition. Marginal ores that are not now being mined, or that are being mined and piled for future use, should be concentrated. The development of the use of sinter in the blast furnace, because of the elimination of fines, the advantage of better sizing of the charge, the resulting reduction of coke consumption, and increased output of pig iron per furnace, will make concentration and sintering become practical ahead of its natural time.

Jan 1, 1936

By C. E. MacQuigg

BY and large the education of the engineer has been conservative and the reasons for this are obvious. Quite properly it has been a tradition of engineering education that facts and not fancies must be adhered to. Without a doubt, those men who formed the mold of our engineering philosophy as much as it is possible for such molds to be established-rightly held the highest standards of intellectual honesty. Fortunately, it was unthinkable to them to temporize with untried theories and naturally the men whom they trained as engineering educators carry this philosophy in turn to their students, thus handing down the tradition of stability.

Jan 1, 1943

By R. L. Doan

WHEN the Plutonium Project was started in the spring of 1942 there was no technology to produce uranium metal of the required purity. Not only was there no such metal available; no one knew how to make it or fabricate it after it was made. Since this time vast technical effort has been ex-pended in the atomic energy field. A short 15 years later the metallurgy of uranium is probably better known than that of any other metal, with the possible exception of steel. At the beginning of the 1942 drive to obtain pure uranium metal the most available raw material was black uranium oxide (U3O8) of about 92 pct purity from the Great Bear Lake region of Canada. It took only three months for the project chemists to develop a process for bringing the purity of this oxide up to 99+ pct and another three months for Mallinckrodt Chemical Co. of St. Louis to build the purification plant and get it into operation. In early summer of 1942 the purified brown oxide (UO2) started moving to the Metal Hydrides Co. in Beverly, Mass., and to the Westinghouse Research Laboratory in Bloomfield, N. J., both of which had been granted Government contracts to try to make pure uranium metal.

Jan 9, 1957

[ ]

Jan 1, 1946

[ ]

Jan 1, 1946

Institute of Metals - Iron and Steel - Mineral Industry - Industrial Minerals Year ?Division - Petroleum Division ? Division - Coal Division - Education Division -Division 1918 W M CORSE 1919 1920 W. H BASSETT 1921 1922 W B PRICE RALPH ARNOLD 1923 E DEGOLYER 1924 G K ELLIOTT 1925 F JULIUS FOHS 1926 PAUL D MERICA 1927 JOHN M LOvEJOY 1928 S SKOWRONSKI A W AMBROSE RALPH H SWEETSER

Jan 1, 1952

Year Institute of Metals ? Petroleum - Iron and Steel ? Coal ? Mineral Industry Education - Industrial Minerals 1918 W M CORSE 1919 1920 W H BASSETT 1921 1922 W B PRICE 1923 E DEGOLYER 1924 G K ELLIOTT 1925 F JULIUS FOHS 1926 PAUL D MERICA 1927 JOHN M LOVEJOY 1928 S SKOWRONSKI A W AMBROSE RALPH H SWEETSER 1929 J B UMPLEBY G B WATERHOLSE 1930 ZAY JEFFRIES C V MILLIKAN W J MACKENZIEHOWARD N EAVENSON 1931 SAM TOUR C E BEECHER F M BECKET 1932 C H MATHEWSON EARL OLIVER F N SPELLERTHOMAS G FEAR C H FULTON

Jan 1, 1952

Jan 1, 1929