Search Documents

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 T. S. Hutchinson, C. E. Kemp

The bottom water drive analysis presented by Muskat has been extended to include fields with wider well spacings. Curves are presented from which volumetric sweepout, water-oil ratio, and rate relations may be calculated. The effects of non-unity ratios on sweepout eficiency and productivity decline have been studied by an approximate method. Also, the effect of gravity on volumetric sweepout has been approximated for a particurlar geometry. INTRODUCTION The purpose of this paper is to report work done in applying the analysis of bottom water drive reservoirs given by Muskat1 to a larger class of reservoirs, to extend this analysis to include the effects of gravity and non-unity mobility ratios in an approximate manner, and to investigate the rate of decline of productive capacity. The bottom water drive type reservoir is one where the oil is underlain by a water zone of sufficient thickness that water movement is essentially vertical. This system is defined in more detail in the appendix and a one well element is shown diagrammatically in Fig. 1. Muskat obtained solutions to the equations describing the volumetric displacement efficiency of idealized bottom water drive systems by assuming that gravity effects due to differences in density betwecn oil and water were negligible and that the mobilities of oil and water were the same. If either of these assumptions is not made, the complexity of the system makes an analytical solution well nigh impossible at the present stage of mathematical development. Coles and Stade' developed an approximation to consider these factors. The authors have refined approximations, starting with the same basic assumption, which should give a somewhat quantitative picture of bottom water drive performance when mobilities are not equal and the effects of gravity are not negligible. The results of these approximate calculations can then be used to obtain the decline in well productivity as the field is depleted.

Jan 1, 1957

By B. Yarar, J. Kaoma

[Introduction The critical surface tension of wetting of hydrophobic materials has been investigated extensively by Zisman et al. (1973) and relates the spreading of a liquid on a solid to the surface tension of this liquid. Thus, the Zisman ap¬proach shows that a plot of Cos 0 versus ?LV where, 0 is the contact angle and ?LV is the surface tension of that liquid in contact with its own vapor at equilibrium, produces a straight line which can be extrapolated to Cos 0 = 1. The intercept corresponds to a given ?LV, termed the critical surface tension of wetting. In instances, however, Cos 0 - ?LV plots show deviations from linearity. Alternative approaches have also included the plotting of adhesion tension (YLV COs 0) versus ?LV that can be interpreted in terms of critical surface tension data (Lucassen-Reynders, 1963). It has, on the other hand, been customary to correlate contact angle (0) with flotation data, although it is recognized that surface inhomogeneities and related contact angle hysteresis limit the interpretations pertaining to solid surface structures purely based on contact angle measurements. It is nonetheless true that 0 = 0, when the liquid is water, corresponds to a hydrophilic solid. Determination of ?c by contact angle measurements in conformity with the Zisman approach can encounter experimental difficulties, especially when solids are in a powder form. Following the reasoning that 0 = 0 corresponds to the hydrophilic state of a solid, froth flotation experiments can be expected to produce critical surface tension of wetting values for powders. The technique that consists of plotting recovery (% R) versus YLV data and extrapolating the linear part of the curve to % R = 0, has been described elsewhere (Yarar and Kaoma, 1984). This paper describes some of the results obtained by the extrapolation technique mentioned above, using various sulfide minerals. Experimental Materials Molybdenite (MoS2), sphalerite (ZnS), chalcopyrite (CuFeS2), chalcocite (Cu2S), and galena (PbS) were handsorted from massive samples and ground by mortar and pestle, and the -147 Fan fraction used in experiments; sulfur (S) was a C.P. Fisher Scientific Co. product. Method One gram powder samples were conditioned for three minutes in methanol-water solutions of predetermined surface tension values and the percents recovered by flotation using a Partridge-Smith Cell (Partridge and Smith, 1972), were plotted against each ?LV value. Results and Discussion The percent recovery versus ?LV for two naturally hydrophobic solids, i.e., natural molybdenite, MoS2 and sulfur are given in Fig. 1 where it is seen that ?c for sulfur is obtained as 31.5 mNm-1 whereas for MoS2, it is 26 mNm-1. Figure 1 also shows that the new flotation technique described, for estimating ?c is in good agreement with the Zisman method. Curves obtained by the same method for the minerals Cu2S, PbS, and ZnS are given in Fig. 2, where it is seen that for Cu2S, ZnS, and PbS, the extrapolation to % R = 0 produces ?c values of 36, 39, and 49 mNm-1, respectively. CuFeS2, on the other hand, gives a curve that does not permit such an extrapolation to obtain a ?c value with certainty. Nonetheless, treatment of the powder with 8.95 X 10-5 molar Na2S solution followed by washing with distilled water prior to flotation effects the curves as shown in the insert of Fig. 2. The type of curves given in Fig. 1 appear to be typical of hydrophobic solids as can also be observed in Fig. 3. The composition of solid and minute quantities of inclusions seem to play an important role as regards the surface properties of solids as reflected by the slope of the linear part of the % R - ?LV plot and thus the value of ?c obtained by this technique. For example, MoS2 of three different stoichiometric compositions produced the data given below. [MoS2MoS2.14Mo1.002S2 ?c mNm-126.029.031.0 dR/d?8.95.23.0]]

Jan 1, 1985

By Nathaniel Herz

PARTING of bullion before shipment to the mint had been considered by the Homestake Mining Co. at various times, but had never been attempted before 1933, be- cause the margin of profit appeared to be too small to warrant the complications in refining. When the gold standard was abandoned by the United States in the spring of 1933, however, parting of the bullion was decided upon. The method selected was the Miller or chlorine process, which consists of the passing of gaseous chlorine into a bath of molten bullion, converting all metals other than gold into chlorides, and remov-

Jan 1, 1935

By E. A. Anderson, M. L. Fuller

The copper-zinc phase equilibrium diagram has been the subject of many investigations. Until recently, however, the boundary of the terminal solid solution of copper in zinc (eta) has not been thoroughly investigated. This paper reports determinations of the solid solubility of copper in zinc at temperatures from 100' to 400' C., the course of the liquidus and solidus for the eta solid solution and determinations of the peritectic temperature and peritectic point for the reaction between epsilon and the melt to form eta. The liquidus of the eta phase was determined by thermal analysis and the solidus by the microscopical examination of specimens quenched from temperatures above and below the solidus. The temperature of the peritectic horizontal was obtained by thermal analysis and the composition at the peritectic point was determined by extrapolation of the solid solubility boundary of the eta phase to the peritectic horizontal. The solid solubility boundary of the eta solid solution was investigated very carefully. Particular care was used to achieve equilibrium in the alloys at each temperature selected. The X-ray, electrical conductivity and microscopical methods mere used in determining the solid solubility limits. The X-ray method measures the changes in the solvent lattice with increasing solute content and in this manner locates the composition of the alloy at which no further change in the solvent lattice takes place, the limit of solid solubility. The method of electrical conductivity measures the conductivity of the alloys of a graded series of compositions, whereby the solubility limit is indicated by a discontinuity in the conductivity-composition relationship. The microscopical method distinguishes, by direct inspection, between the homogeneous solid solution alloys and those having a secondary constituent in addition to the solid solution phase, and thus indicates from the examination of a series of alloys the solid solubility limit.

Jan 1, 1934

By Cyril Stanley Smith

THE art of metallography is mature and the forms in which various micro-constituents appear are well known. Investigations almost without end have disclosed the importance of the exact manner of distribution of phases on the physical properties and usefulness of an alloy. Surprisingly, however, relatively little attention has been paid to the forces that are responsible for the particular and varied spatial arrangements of grains and phases that are observed. Like the anatomist, the metallurgist has been more concerned with form and function than with origins. In this paper it is proposed to develop the simple concept that many microstructures result from an attempted approach to equilibrium between phase and grain interfaces whose surface tensions geometrically balance each other at the points and along the lines where they meet. From this follows a number of principles which may prove to be of interest to the metallographer and of practical use in explaining failures and in designing alloys for particular service. In general, the discussion will be limited to structures obtained after full annealing. The simple principles do not apply to structures resulting from Widmanstatten mechanisms in precipitation, or to other structures not in local equilibrium and in which lattice coherency is a determining factor. INTERFACIAL TENSION Much has been written by physical chemists about the free energy of surfaces, which manifests itself as a measurable surface tension. Two- and three-phase interfaces in fluids seek a condition of minimum energy and approach a geometrical configuration in which the various forces are in vectorial balance.* Measurement of the angles established between the interfaces when in equilibrium provides a quantitative value for the relative value of the surface forces involved. The case of two fluids meeting at the surface of a solid (of great importance in connection with the flotation of minerals) has often been studied, but there have been few investigations of the equally definite interface between two or more crystals of a single solid phase, or the more complex cases where crystal grains of more than one phase are involved. The principles are best illustrated by considering first the case of two and three immiscible liquids. If, as in Fig I, a liquid, 2, is dropped into a less dense liquid, I, it will form a sphere-if gravity and viscosity can be ignored-for in this shape the interface has the smallest possible area. If these two phases should together encounter a third phase in which they are both immiscible, the geometry will change to become that which gives the lowest total energy for all three interfaces. Thus, if the spherical drop of liquid, falling through r, eventually reaches the interface between liquids 3 and I (we are assuming that the density of 3 is greater than 2, and 2 than I), it will assume the shape of a lens, the angle

Jan 1, 1948

By H. F. A. Hergt, K. L. Sutherland, J. Rogers

In 1938 Ralston4 reviewed the many attempts to find a satisfactory collector for the separation of cassiterite from its ores and in 1944 Dean and Ambrose2 summarized some further attempts. Generally, soaps and amines are effective but nonselective collectors. We have discovered that reagents containing either the polar group — SO4- or — SO3- are excellent collectors for cassiterite and promise to be selective. The response to these reagents of cassiterite and of minerals commonly associated with it was studied, using the captive-bubble technique. Using these fundamental data, the practicability of separation and concentration of tin was investigated by flotation tests in a 2000-gram Denver cell. Experimental Methods Reagents All inorganic reagents were of Analar grade. The preparation and purification of sodium cetyl sulphate, cetyl trimethyl-ammonium bromide, laurylamine and cetylamine have been previously described.5 The other collectors were commercial surface-active agents, which were used without purification. Tests Captive-bubble Tests and Cylinder Flotation Tests have been previously de- scribed.5,10 The full lines shown in the figures relating solution composition to contact (flotation) distinguish solutions in which contact (flotation) is possible from those in which it is not. The curve is derived by successive approximation and the accuracy is ±0.2 pH units and ± 5 mg. per liter of collector or depressant. Solution compositions for which it was shown experimentally that contact or flotation is possible are marked by a circle, those for which it is not possible, by a cross, and those for which it is doubtful by a cross within a circle. It is assumed that at all other solution compositions within (without) the curve, contact or flotation is possible (not possible). After testing in the collector solution, the mineral was removed, washed, and tested by the captive-bubble method in water, or floated in a cylinder with frother only. In this way the composition of solutions in which a mineral was conditioned but in which properties of the collector solution prevented contact or flotation can be defined. The composition of solutions in which conditioning was possible lie between the full and broken curve, and the experimental results are indicated by a square. The curves show the limits of composition of solutions in which flotation in a cell would be possible but many factors other than those considered in these the determine recovery and grade of a given mineral in practice. Flotation Tests in 500 and 2000-gram Denver SUbmachines,—Melboume tap water, containing 12 parts calcium, 6 parts

Jan 1, 1947

By J. Rogers, H. F. A. Hergt, K. L. Sutherland

In 1938 Ralston4 reviewed the many attempts to find a satisfactory collector for the separation of cassiterite from its ores and in 1944 Dean and Ambrose2 summarized some further attempts. Generally, soaps and amines are effective but nonselective collectors. We have discovered that reagents containing either the polar group — SO4- or — SO3- are excellent collectors for cassiterite and promise to be selective. The response to these reagents of cassiterite and of minerals commonly associated with it was studied, using the captive-bubble technique. Using these fundamental data, the practicability of separation and concentration of tin was investigated by flotation tests in a 2000-gram Denver cell. Experimental Methods Reagents All inorganic reagents were of Analar grade. The preparation and purification of sodium cetyl sulphate, cetyl trimethyl-ammonium bromide, laurylamine and cetylamine have been previously described.5 The other collectors were commercial surface-active agents, which were used without purification. Tests Captive-bubble Tests and Cylinder Flotation Tests have been previously de- scribed.5,10 The full lines shown in the figures relating solution composition to contact (flotation) distinguish solutions in which contact (flotation) is possible from those in which it is not. The curve is derived by successive approximation and the accuracy is ±0.2 pH units and ± 5 mg. per liter of collector or depressant. Solution compositions for which it was shown experimentally that contact or flotation is possible are marked by a circle, those for which it is not possible, by a cross, and those for which it is doubtful by a cross within a circle. It is assumed that at all other solution compositions within (without) the curve, contact or flotation is possible (not possible). After testing in the collector solution, the mineral was removed, washed, and tested by the captive-bubble method in water, or floated in a cylinder with frother only. In this way the composition of solutions in which a mineral was conditioned but in which properties of the collector solution prevented contact or flotation can be defined. The composition of solutions in which conditioning was possible lie between the full and broken curve, and the experimental results are indicated by a square. The curves show the limits of composition of solutions in which flotation in a cell would be possible but many factors other than those considered in these the determine recovery and grade of a given mineral in practice. Flotation Tests in 500 and 2000-gram Denver SUbmachines,—Melboume tap water, containing 12 parts calcium, 6 parts

Jan 1, 1947

[Contents AH-Metal Mining and Industrial Minerals Pipeline Transportation of Phosphate. (Paper by I. S. Tillotson, R. B. Burt, and J. A. Barr, Transactions AIME, 193, 273; Mining Engineering. March 1952. Discussion by Howard Howie.) 1066 B-Minerals Beneficiation The Effect of Zinc Deleading Operations on Lead-Zinc Selectivity at the Parral and Santa Barbara Mines. (Paper by C. L. Boeke an G. C. Gunther, Transactions AIME, 193, 495; Mining Engineering. May 1952. Discussion by I. M. Symonds, L. H. Lange, Norman Weiss, H. S. Wildman, C. F. Zeuch, E. H. Crabtree.) 1067 Jaw Crusher Capacities, Blake and Single-Toggle or Overhead Eccentric Types. (Paper by D. H. Gieskieng, Transactions AIME, 190, 971; Mining Engineering. November 1951. Author s supplement.) 1069 Screened Ore Use for Fine Grinding at Lake Shore Mines. (Paper by Bunting S. Crocker, Transactions AIME, 193, 499; Mining Engineering. May 1952. Discussion by Fred C. Bond, J. Myers, Norman Weiss, Harlowe Hardinge, Oscar Johnson, L. E. Djingheuzian.) 1069 The Third Theory of Comminution. (Paper by Fred C. Bond, Transactions AIME, 193, 484; Mining Engineering. May 1952. Discussion by Milton C. Shaw and Donald R. Walker; R. J. Russell.)1071 Flotation Rates and Flotation Efficiency.t (Paper by Nathaniel Arbiter, Transactions AIME, 190, 791; Mining Engineering. September 1951. Discussion by Gregoire Gutzeit and Porter Clements.) 1074]

Jan 1, 1952

By E. S. Davenport, R. J. Hafsten, R. A. Grange

The influence of austenite grain size upon the hardenability of steel is now fairly well understood; for a given austenite, increasing the grain size increases the depth of hardening, and, since the latter is related to the fundamental transformation behavior of austenite, it follows that austenite decomposition must, in general, be retarded by increasing grain size. To date, very little quantitative information bearing directly on the effect of austenite grain size upon the progress and result of isothermal transformation has been published. Davenport and Bain,' and Zimmerman, Aborn and Bain2 have shown that the transformation is definitely relarded in hypereutectoid plain carbon steels at temperatures near and above the upper region of rapid transformation (Ar') when the austenite grains are increased in size. More recently, Griffiths. Pfeil and Allen3 investigated the effect of a series of different heating (austenitizing) temperatures upon the progress of isothermal transformation at 1245°F. (675°C.) and 745ºF. (395°C.) in a medium carbon, low-alloy steel; while they reported no measurements of the austenite grain size, their results suggest that increase in grain size retards austenite transformation at 1245ºF. (675°C), but has no appreciable effect at 745°F (395°C.). The present paper deals with the results of a study of the isothermal transformation of austenite in a single commercial alloy steel in which a fine-grained or a coarsegrained state was induced by appropriate selection of austenitizing temperature. The data are presented in the form of isothermal transformation diagrams, which clearly show that coarsening the grains lessens the rate of transformation of austenite to proeutectoid ferrite and pearlite—that is, at temperature levels above about 1000°F. (540°C.)—but is without significant effect at lower temperatures where the transformation product is bainite or martensite. It is to he presumed that the foregoing statement would be valid, at least in principle, for many other grades of steel; it confirms again that the mechanism of transformation to a pearlitic structure is fundamentally different from that to an acicular structure. A number of related observations were made, which seem to throw some light on the transformation process as it takes place in alloy steels, particularly at temperature levels in the vicinity of 1000ºF. (540°C.), where the transition from lamellar to acicular structures occurs. These data are discussed briefly in the belief that they may lead to a clearer understanding of this aspect of the subject. Material and Experimental Procedure The material investigated was a cornmercial grade of S.A.E. 4140 steel, the composition of which was as follows: 0.37 per cent C, 0.77 per cent Mn, 0.98 per cent Cr and 0.21 per cent Mo. It was hot-rolled to a 1 1/8-in. round bar and normalized by air-cooling from 1800°F. (980°C.).

Jan 1, 1941

By R. J. Hafsten, E. S. Davenport, R. A. Grange

The influence of austenite grain size upon the hardenability of steel is now fairly well understood; for a given austenite, increasing the grain size increases the depth of hardening, and, since the latter is related to the fundamental transformation behavior of austenite, it follows that austenite decomposition must, in general, be retarded by increasing grain size. To date, very little quantitative information bearing directly on the effect of austenite grain size upon the progress and result of isothermal transformation has been published. Davenport and Bain,' and Zimmerman, Aborn and Bain2 have shown that the transformation is definitely relarded in hypereutectoid plain carbon steels at temperatures near and above the upper region of rapid transformation (Ar') when the austenite grains are increased in size. More recently, Griffiths. Pfeil and Allen3 investigated the effect of a series of different heating (austenitizing) temperatures upon the progress of isothermal transformation at 1245°F. (675°C.) and 745ºF. (395°C.) in a medium carbon, low-alloy steel; while they reported no measurements of the austenite grain size, their results suggest that increase in grain size retards austenite transformation at 1245ºF. (675°C), but has no appreciable effect at 745°F (395°C.). The present paper deals with the results of a study of the isothermal transformation of austenite in a single commercial alloy steel in which a fine-grained or a coarsegrained state was induced by appropriate selection of austenitizing temperature. The data are presented in the form of isothermal transformation diagrams, which clearly show that coarsening the grains lessens the rate of transformation of austenite to proeutectoid ferrite and pearlite—that is, at temperature levels above about 1000°F. (540°C.)—but is without significant effect at lower temperatures where the transformation product is bainite or martensite. It is to he presumed that the foregoing statement would be valid, at least in principle, for many other grades of steel; it confirms again that the mechanism of transformation to a pearlitic structure is fundamentally different from that to an acicular structure. A number of related observations were made, which seem to throw some light on the transformation process as it takes place in alloy steels, particularly at temperature levels in the vicinity of 1000ºF. (540°C.), where the transition from lamellar to acicular structures occurs. These data are discussed briefly in the belief that they may lead to a clearer understanding of this aspect of the subject. Material and Experimental Procedure The material investigated was a cornmercial grade of S.A.E. 4140 steel, the composition of which was as follows: 0.37 per cent C, 0.77 per cent Mn, 0.98 per cent Cr and 0.21 per cent Mo. It was hot-rolled to a 1 1/8-in. round bar and normalized by air-cooling from 1800°F. (980°C.).

Jan 1, 1941

By Charles L. Mantell, Kurt Straler

The hydrogen reduction of Cr2O3 to chromium metal was found to be feasible at very low water-vapor concentrations, corresponding to dew points of -38° to -24°C, over a temperature range of 1130" to 1490°C. Hydrogen reduction under these conditions was predicted by the calculated equilibrium curves which also indicated that CrzOs is reduced directly to chromium without forming the intermediate oxide, CrO. This reduction path was confirmed by X-ray diffraction analysis. The percent reduction of Cr2O3 at each reaction temperature was constant with time, suggesting an inhibiting effect of water vapor. A small increase in the residual water-vapor concentration of a single temperature, 1490°C, strongly retarded the rate of reduction This effect was expressed by an empim'cal equation which indicated a direct relationship between "distance from equilibrium" and the rate of reduction. me effect of temperature over the range of 1130" to 1490°C was expressed in an Arvhenius plot of log rate vs reciprocal absolute temperature. From this curve the apparent enthalpy of activation was found to be 29,600 cal. Based on the hypothesis that the rate of reductiun is contvolled at the oxide-metal interface, an over-all rate equation consistent with the experimental data and the thery of absolute reaction rates was formulated. A simplification of this expression to an Arrhenius equation was justified by the overriding effect of temperature on the rate of reaction for the minimum water-vapor concentration range. MOST of the metals in Subgroup V1 of the periodic table can be prepared commercially by direct reduction of their oxides by hydrogen or carbon monoxide, at temperatures considerably below the melting points of both the metals and their oxides. Chromium is an exception, being generally reduced from its ore, Cr2O3 . FeO, by silicon in an electric arc furnace which operates above the melting point of the Fe-Cr alloy or above the melting point of chro- mium if a chromium oxide be the starting material. In reduction of chromium oxide by hydrogen, either reduction does not occur at all or the rate of reduction is extremely slow. Theoretical considerations based on the high, exothermic, free energy of formation of Cr2O3 compared to the oxides of the other Subgroup VI metals, molybdenum, tungsten, and uranium, would also suggest a slow rate of reaction and a high activation energy. Interest in the direct gaseous reduction of fine-powdered ores in fluidized beds was considered justification for examination of this reaction. In order to develop a basis for a continuing study of the commercial feasibility of the direct gaseous reduction of chromite, a study of the kinetics of the reduction of Cr2O3 with hydrogen was undertaken. To the authors' knowledge no accurate kinetic data for this reaction have been obtained. Neither has an activation energy been determined nor has an attempt been made to establish a mechanism of reaction. LITERATURE Maier10 compared the data of I. Y. Granaat,6 H. von Wartenburg and S. Aoyama, and G. Grube and M. Flad7 with that derived from calorimetric and ther-modynamic properties for the equilibria for the reduction of Cr2O3 with hydrogen. These results, plotted as the log of the equilibrium constant vs absolute temperature for the reduction of Cr2O3 and the intermediate oxide, CrO, to chromium, show agreement between the differently derived data. In both cases the equilibrium constants were extremely low. Maier showed that, over a temperature range of 1000° to 2000°K, Cr2O3 is more readily reducible than CrO. Granat assumed that CrO was preferentially formed from Cr2o3 above 1100°C. Grube and Flad's analysis of their reaction products in the 895" to 1000°C range indicated the coexistence of only Cr2O3 and chromium. The hydrogen reduction of the other Subgroup VI metals, molybdenum, tungsten, and uranium, shows that reduction of the higher oxide proceeds through all of the intermediate oxides before being reduced to the metal. Since evidence pointed to an anomaly in the reduction behavior of Cr2O3, the authors investigated the reduction path of Cr2Os.to chromium. This was done theoretically with more recently available free-energy data and experimentally by X-ray diffraction analysis. This work reinforces Maier's conclusion.

Jan 1, 1964

The volumes of Transactions, which are published annually, contain the list of officers, rules, etc., the Proceedings, and the papers revised for final publication. (In this revision, after the preliminary publication, authors are permitted to use the largest liberty; and the changes and additions made in papers are sometimes important. It should be borne in mind by those who study or quote a paper in the preliminary edition, that they may not have in that form the ultimate and deliberate expression of the author's views. It should be added, however, that in the majority of cases there are no important changes.) These volumes are for sale as follows, in paper covers:

Jan 1, 1917

By Samuel B. Christy

" The man is always greater than his work." The training of the men who are to develop the mineral resources of the world is the most important problem connected with mining engineering. It becomes ever more important to civilization as the mineral wealth of the earth approaches exhaustion. I have therefore decided to consider a few of the more important problems arising in the training of the mining engineer, and especially those arising in America. , The Peculiar Nature of Mineral Wealth. Mining and Agriculture are the two fundamental arts. Without the latter our existence would be precarious; without the former, our civilization impossible. Agriculture furnishes that regular supply of food and raiment which leads to the growth of large communities in which cultivated leisure first becomes possible; while mining furnishes the metallic thread from which is woven that complex fabric we call civilization. But in these two arts the conditions for success are widely different. Most of the crops that the farmer reaps may be harvested year after year, and the proper fertilizers being added, he may continue the annual harvest indefinitely, while, as a result of cultivation, his farm becomes yearly more valuable. But the crop the miner reaps can be harvested but once in the history of the race. Our mineral wealth has taken unknown ages to mature in the bosom of the earth. The ripened fruit can be plucked but once. There are no fertilizers for worked-out mines. It never pays to work over a mine that has been

Jan 1, 1906

By M. C. Manderson

Abstract-The sharp drop in world phosphate demand that took place in 1975, due to temporarily high prices, now seems to be reversing itself. And prices for both phosphate rock and phosphate fertilizers, which declined dramatically from their 1975 highs, now appear to be bottoming out. This recent price weakness has delayed new mining ventures that had previously been planned for completion by around 1980. While there is ample capacity to supply near-term rock needs, the stage seems to be emerging for a better supply-demand and price environment in the late 1970's and early 1980's.

Jan 1, 1978

By Albert Ledoux

SEVERAL years ago my firm was representing the Mt. Lyell Co. of Australia, which was shipping its blister copper to a refining works in the United States. After the contract had been running for many months, the superintendent of these works discovered that if water was poured upon the surface of the bars much of it would disappear into the interior through blow holes. -Some experiments made by him showed that this could be a considerable amount, so that copper which had been rained on before it was weighed, although the surface appeared dry, nevertheless would contain water. It had frequently occurred in our experience-as samp-lers that the drillings from a lot taken by boring would come out quite wet, and in some cases, indeed, water would drip into the sample pan placed below the bars, due to the fact that the drill had penetrated a cavity or cavities containing water, which presumably got into the cavities at the time the copper was water-cooled after casting, there being, perhaps, no outlet to the surface. So far as I know, until this discovery at the refining works, no. one had thought that rain could penetrate into the interior of blister copper; at least in any quantity sufficient to be considered.

Jan 10, 1922

By C. F. Smart

SINCE their comparatively recent development, the alloys of cadmium with silver and copper or nickel, and of cadmium with nickel alone, have been used somewhat extensively as liners for connecting rod bearings and main bearings of internal-combustion engines. In applications where, owing to high hearing loads and elevated operating temperatures, the life of hearings made from tin-hale or lead-base alloys has been undesirably short, cadmium alloys have demonstrated considerable advantage. In applications where, because of deflection of the crankshaft or bearing supports, copper-lead bearing metals have resulted in scored shafts, cadmium alloys have been operated successfully. The somewhat serious drawback to these alloys in hearing service has been that they, in common with copper-lead and certain lead alloys, are susceptible to corrosion in the presence of lubricants containing organic acids. These acids may be fatty acids (such as oleic acid) derived from animal or vegetable oils that sometimes have been compounded with engine lubricants, or they may be compounds of an acid nature developed by the oxidation of some petroleum oils under operating conditions. The result of such acid attack on hearings is illustrated by the photograph, Fig. 1. The petroleum oils that are most readily oxidized to a corrosive condition, and the operating conditions under which such oxidation most readily occurs, are now rather well known among the technical organizations of both the petroleum and automotive industries. While means have been developed for inhibiting petroleum oils against such acid formation, the knowledge that this condition may be encountered has been a factor in restricting the wider use of cadmium alloys as engine bearings. It has appeared, therefore, that their value and use would be enhanced if they could be made corrosion-resistant to a degree compatible with the most severe operating requirements. Investigation, undertaken with this in view, indicated that the addition of fractional percentages of the metal indium to the cadmium bearing

Jan 1, 1938

Jan 1, 1942

By S. H. Ash

More than 100 minerals are mined and processed in the U. S. Management and labor have negotiated wage-scale agreements that have balanced wages and affected cost of labor in such a manner that comparisons can be made of transportation costs. Transportation of materials underground has become of vital importance. This report describes underground haulage methods and equipment, presents cost analyses, and discusses future plans for underground transportation in metal mines. It does not cover hoisting in shafts or slopes by cage, skip, or cars. Advancements have been made by the metal mining industry in lowering transportation costs in several mines, making it possible to mine orebodies or portions of orebodies not considered economically recoverable a few years ago. Numerous reports have been written on transportation at metal mines; this report covers recent haulage at some representative mines throughout the U.S. The term metal mine is used to include all noncoal mines from which up-to-date information was obtainable.

Sep 1, 1956

By Archer E. Wheeler, Milo W. Krejci

The Boston & Montana Reduction Works at Great Falls, Mont., was formerly the reduction works of the Boston & Montana Consolidated Copper & Silver Mining Co., and continued as the reduction plant for the independent company until June 1, 1910, when the consolidation of a large number of the operating companies of Butte was effected. It then became merged in the Anaconda Copper Mining Co. as the Boston & Montana Reduction Department of the Anaconda Copper Mining Co. The history of copper converting at this plant, while not covering the entire period of the commercial use of the process in this country, does cover by far the larger part of it, and as the operation of and appliances for the process have undergone many changes during the time, it may, perhaps, be of some interest to put the record of these changes into permanent form. The plan followed in the preparation of this paper has been to give first a brief chronological record of the principal events and changes and then, even at the risk of some repetitions, to give more detaild accounts of some of these changes under separate headings. The headings for the complete paper are as follows: 1. General. Chronological Review. 10. Development of Different Classes 2. Mechanical Manipulation. of Converters After Class I. 3. Casting of Finished Copper. 11. Basic Lining. 4. Tamping of Linings. 12. Number and Size of Tuyeres. 5. Early Acid Linings. 13. Cast Copper Tuyeres. 6. Acid Linings With the Use of Ore. 14. Efficiency of Air. 7. Introduction of Flux Through the 15. Size of Converter Mouth. Tuyeres. 16. Height of Converter. 8. Bottom Blast. 17. Summary. 9. Disposal of Converter Slag, General Chronological Review. Ground was broken for the general concentrating and smelting plant in the spring of 1,891. The first departments to start operations were the concentrator in March, 1892, and the Brückner roasting and reverbera-tory smelting departments in April, 1892. The converter department

Jan 1, 1914