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By G. D. Rieck, M. M. P. Janssen

Chemical diffusion coefficients and heats of activation for diffusion in the NizAh fy), NiAl (6), and Ni3A1 (E) intermetallic phases and the solid solution of aluminum in nickel (( phase) were calculated from layer growth experiments. No finite diffusion coefficient for the NiAl3 ((3) inter metallic phase could be calculated. The values of the diffusion coefficients are dependent both on the method of calculation and the type of diffusion couple. The heat of activation for diffusion in the y phase was found to be 47 kcal per mole in the temperature range oj 428" to 610°C. Heats of activation of 41, 12, and 48 kcal per mole were found for diffusion in the 6, E, and ( phases, respectively , in the temperature range of 655" to 1000°C. Experiments with markers in the diffusion zone demonstrate a very pronounced Kirkendall effect. It appears that only aluminum atoms take an active part in the diffusion process during the formation of the 0 and y phases at temperatures of about 600°C. During the formation of the 6, E, and < phases at higher temperatures only nickel atoms are moving. It is suggested that the great stability of the intermetallic compounds in the Ni-A1 system governs the Kirkendall effect. SOME factors controlling layer growth during inter-diffusion in the Ni-A1 system (phase diagram, see Fig. 1) were studied by Castleman and Seig1e.l&apos;~ They found the NiA1, ((3) and NiAl3 (y) intermetallic compounds to appear in the diffusion zone of Ni-A1 couples at annealing temperatures of 400" to 625°C; the NiAl (6) and Ni3A1 (E) intermetallic compounds appeared in y-Ni couples at annealing temperatures of 800" to 1050°C. These authors carefully examined metallographically Ni-A1 couples after 340 hr annealing at 600°C. Besides the (3 and y phases they found very thin layers of the 6 and E phases. ~n~erman~ and Castleman and Froot4 observed a much more rapid growth of the 5 and E phases at 600°C in Ni-A1 couples in case a crack was present at the /3-A1 interface. Numerous layer thickness measurements carried out by Castleman and Seigle on the y phase prove that the layer growth of this phase obeys the parabolic law after a certain transient period. From this they concluded that the layer growth of the y phase is controlled by volume diffusion. The growth of the 13, 6, and E phases appeared to be volume-diffusion-controlled also. The authors estimated that at 600°C and at atmospheric pressure Dp was 1.8 x lo-"ll sq cm per sec, D, 9.1 x 10" ™ sq cm per sec, Qp 27 kcal per mole, and Qy 31 kcal per mole. The present work was carried out to obtain more quantitative data about the kinetics of growth of the phases of the Ni-A1 system and the reactions that occur during the formation of these phases. Because in this system the diffusion process results in the formation of several distinct intermetallic compounds, the current term reaction diffusion is used in the title of this paper. In order to obtain layers of the fl phase compound of uniform thickness, a new technique for preparing diffusion couples was developed. The kinetics of growth of the y phase in 6-Al, E-Al, and Ni-A1 diffusion couples was studied at different temperatures. The kinetics of growth of the 6, c, and ( phases in Ni-y, Ni-6, and Ni-c diffusion couples was also studied at different temperatures. The calculation of the diffusion coefficients Dp and Dy by Castleman and Seigle are critically considered in this paper; by means of a revised method of calculation more reliable val-ues of , and Dg were found. These values are in good agreement with the values of the diffusion coefficients obtained by the method of Boltzmann-Matano. From the temperature dependence of the diffusion coefficients the heats of activation for diffusion were calculated by means of an Arrhenius-type equation. The investigation of the Kirkendall effect has been used to obtain information about the ratio of the intrinsic diffusion coefficients of the separate atoms5 and the mechanism of diffusion. Moreover porosity as a result of a distinct Kirkendall effect would be of practical importance in connection with the bonding of diffusion coatings. The analyses of the diffusion couples were carried out by metallographic methods. The values of the concentrations at the phase boundaries and the concentration profile in each of the phases, which are needed for the calculation of diffusion coefficients, were obtained by electron-pro be X-ray microanalysis. EXPERIMENTAL PROCEDURE A) Materials for Diffusion Couples. The intermetallic compounds 6 (50 at. pct Ni) and E (74 at. pct Ni) were prepared from the pure metals by high-frequency induction melting in argon atmosphere. Use was made of aluminum wire (99.99 wt pct Al) and nickel sheet (99.95 wt pct Ni). The 6 and E phase melts and the nickel shiet (thickness 0.1 and 0.5 mm) used for preparing diffusion couples were annealed for 64 hr at 1200°~ for homogenization and grain coarsening (final crystal size 1 to 3 mm). composition and homogeneity of the intermetallic compounds were checked by mi-crohardness measurements and X-ray diffraction. From the 6 and E phase melts discs of 0.5 mm thickness were prepared by means of a water-cooled rotat-

Jan 1, 1968

By B. K. Larkin, H. R. Bailey

One of the most complicated and potentially one of the most promising secondary recovery methods is that of underground combustion. A number of field tests1,2,3 have been performed recently, apparently indicating that the underground combustion process is technically feasible. Relatively little has been published concerning laboratory or theoretical investigations of the underground combustion process. A few results of laboratory tube runs have been published4,5 and these data are valuable in understanding the process. The tube run data also emphasize the complexity of the thermal recovery process. Under various conditions, problems in heat transfer, multiphase fluid flow and combustion rates arise. For example, at low temperatures the combustion process proceeds so slowly that the front cannot be propagated. It is a problem in heat transfer to predict what injection rate of air is necessary to sustain combustion in a particular reservoir. Certain fluid flow aspects of underground combustion have been studied by Wilson, et a13. In the development of some of the flow equations, assumptions of adiabatic combustion were made. Vogel and Krueger1 have devised an analog model of the heat conduction process for a constant temperature cylindrical source moving radially outward in a homogeneous conducting medium. Jenkins and Ramey7, in a discussion of the Vogel and Krueger paper, present an analytical solution of a heat conduction problem related to problems considered by Vogel and Krueger. In the present paper an idealized model of the heat conduction problem is considered, which is more general than the model of Vogel and Krueger or Jenkins and Ramey. In particular, initial well heating, vertical heat losses and arbitrary frontal velocities are included. Equations for the temperature are obtained in terms of integrals. These integrals have been evaluated numerically for the case of frontal movement corresponding to a constant air injection rate and the case of constant frontal velocity. These results are presented graphically. From these graphs one may estimate conditions under which nearly adiabatic temperatures are obtained. The application of these results requires some knowledge of reservoir thermal properties, combustion rates and residual fuel content. Assuming no vertical losses it is possible to obtain explicit evaluations of these integrals in the linear con- stant velocity case and in the radial case corresponding to a constant air injection rate. PRESENTATION OF RESULTS The geometry of the radial system is illustrated in Fig. 1 where the reservoir is represented as a slab of thickness h. By making an energy balance for an infinitesimal volume, one obtains the following equation. T= x T+F(z.r).........(1) where F (z,r) =HWv1/pc (r-r1), if z h/2 = 0, if z >h/2 . In Eq. 1, V- represents the Laplacian operator and 8 is the Dirac delta function. Eq. 1 is the well-known diff-sion equation with a source term and may be applied to a linear system. For example, if the source is moving in the direction of the x axis, then the argument of the delta function is x - 1,. In deriving Eq. 1 the following approximations were made concerning the actual combustion process: (1) all heat transfer is by conduction in a homogeneous medium, (2) the formations bounding the reservoir have the same thermal properties as the reservoir, (3) the combustion fuel is consumed instantaneously as the front arrives, (4) there is a constant fuel concentration

By D. S. Tannhauser, I. Bransky

Measurements of the electrical conductivity, the thermal electromotive force, and the deviation from stoichiometry by thermogravimetry were made on ferrous oxide (wüstite) single crystals as well as on poly-crystalline samples in the temperature range of -900" to 1330°C. In the region defined by T 2 1000°C and 1.05 5 O/Fe 5 1.10 the electrical conductivity was shown to be proportional to the sixth root of- the oxygen partial pressure and to be linearly dependent on the deviation from stoichiometry. The absolute Seebeck coefficient of single and polycrystalline wüstite was shown to be independent of temperature in the above region and a p to n transition of the Seebeck coefficient was observed at O/Fe = 1.09 in polycrystalline wüstite. Analysis of the results showed that the predominant defects in wüstite in the above region were doubly ionized cation vacancies. The analysis also ruled out the existence of complexes of the type postulated by Roth, except that below 1000°C there is some evidence of &apos;association of defects. Of the three oxides of iron (FeO, Fe3O4, Fe2O3) only FeO (wüstite) can exist within a wide range of the ratio O/Fe. This has been shown by several investigations of the phase diagram using for instance chemical analysis of quenched samples&apos;-4 or thermogravimetric measurements. 5,8 Darken and Gurry&apos;s1 data for example in the temper- ature range 1100o to 1400°C show that the lowest O/Fe ratio obtainable for FeOl +. is about 1.045 and that the existence range extends to O/Fe = 1.20 at 1400oC. On the basis of detailed analysis of thermogravimetric measurements made by Vallet and Raccah6 the existence of three varieties of wüstite at elevated temperatures was suggested by these authors and by Kleman. It is well-established that wüstite has a NaCl structure with vacant cation sites.3, 8 From a neutron-diffraction study of wüstite samples quenched to room temperature Roth9 concluded that defects in wüstite are mostly complexes composed of two cation vacancies and one interstitial cation in a tetrahedral site. The atomic arrangement in the vicinity of such a defect is similar to that in magnetite, where each occupied tetrahedral site is surrounded by four vacant octahedral positions disposed at the corners of a tetrahedron, so arranged that each vacancy is shared by two tetrahedral cations. Thus there is an average of two vacancies per interstitial. Recent X-ray diffraction measurements made by Smuts10 on quenched wüstite samples confirmed the results of Roth&apos;s neutron-diffraction experiments. Roth&apos;s model of defects in FeO can be regarded as a solid solution of Fe3O4 in FeO; salmon1&apos; used this defect model to calculate the activity of Fe3O1 in FeO at high temperature and claimed good agreement with the results obtained experimentally by Darken and Gurry.&apos; Each missing cation in wüstite is accompanied by two trivalent cations, thus preserving charge neutrality. The "holes" which differentiate between the Fe 2+ and Fe3&apos; states of the ions in octahedral positions can overcome the attractive field of the cation vacancies, and are then free to move through the crystal as charge carriers. A similar picture holds for COO, NiO, andMnO.l2, 13 Localization of the charge carriers in transition

Jan 1, 1968

By Lawrence H. Van Vlack, Otto K. Riegger, Gerald I. Madden

The microstructural variations of periclase (MgO) in the presence of oxide liquids are examined under the steelmaking variables of: 1) temperature, 2) liquid composition, and 3) FeO additions under different oxidation levels. Attention is given to the distribution of the phases, both liquid and solid, and to the growth of individual crystalline grains. Silicate liquids penetrate more extensively between individual periclase grains than do liquids containing high percentages of Fe2O3 Higher MgO solubilities in the liquid and lower MgO contents of the solid favor more rapid grain growth. The presence of a second solid phase reduces the periclase grain growth rate and increases the amount of the solid-to-solid contact within the oxide microstructures at high temperatures. The service suitability of a refractory depends on many factors. Two are of major importance and include 1) the thermal resistance to melting, and 2) the mechanical resistance to loads at service temperatures. Neither is a simple consequence of the service temperatures because service conditions will alter compositions, produce partial melting, and induee phase changes. Consequently, the equilibrium phase relationships have been rather thoroughly studied and give a knowledge of the thermal resistance to melting, but do not give full information about the mechanical properties because two refractories with the same types and quantities of phase may have different microstructures. Although variations of microstructures with time, temperature, and composition have been subjects for extensive investigation in metals, only a limited amount of comparable microstructural work has been performed for refractory materials.&apos; This study was an attempt to evaluate some of the consequences of service parameters upon the microstructures of refractories so that bases may be established for the analyzing of high temperature mechanical properties. Periclase (MgO) was chosen as the refractory oxide; variables included those which are encountered under steelmaking conditions such as 1) temperature, 2) liquid composition, and 3) FeO additions under various oxidation levels. Specific attention was given to the distribution of the phases, both liquid and solid, and to the growth of individual crystalline grains. The most closely related work on microstructures of polyphase materials is that of Van Vlack and Rieg-ger2 on the microstructure of magnesiowüstite [(Mg,Fe)O] in the presence of silica. In that work which pertained to solid solutions with less than 40 pct MgO, most of the quantitative work was performed on FeO microstructures. The chief conclusions concerning these relatively low-melting oxide solids were as follows: 1) the rate of crystalline grain growth is inversely proportional to the grain diameter, 2) grain growth proceeds more rapidly at higher temperatures but is slightly retarded by additional liquid content, and 3) a Silicate-containing liquid penetrates as a film between the individual magnesiowüstite grains independent of time, temperature, amount of liquid, or the MgO/ FeO ratio. The above observations are in contrast to prior work3 on the microstructure of silica in the presence of iron oxide-containing liquids where the liquid does not penetrate as a complete film between solid grains. The phase relationships for the compositions of the present work are shown in Fig. 1 which is a summary of the work of several investigators.4 Of importance is the fact that CaO forms a more stable structure with SiO2 and Al2O3 than do either MgO or FeO. The oxygen potential has little effect on periclase unless iron oxide is also present. The iron oxide is ferrous at moderately low oxygen levels, changing to ferric as the Oxygen potential is increased so the spinels, magnetite, and magesioferrite are formed.5 These two phases are relatively stable in air at steelmaking temperatures. I) EXPERIMENTAL PROCEDURE ractory were made with reagent grade Oxides. The magnesium oxide used was 99 pct MgO after ignition, and the iron oxide raw material had a minimum content of 99 pet Fe2O3. The CaO, SiO2, and A12O3 were also reagent grade raw materials. After mixing, the required compositions were pressed into pellets at a minimum pressure of 5000 psi to insure compaction of the raw materials and prevent excess void content. A silicon carbide element tube furnace was used with thermocouple control for sin-

Jan 1, 1963

By H. E. Searle, Robert J. McKay, O. B. J. Fraser

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.&apos;&apos; This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929

By Robert J. McKay, O. B. J. Fraser, H. E. Searle

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.&apos;&apos; This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929

By M. S. Burton, J. E. Ritter

The sessile-drop technique was employed to study the effect of atmosphere and alloy additions of titanium and chromium on the surface tension and contact angle of nickel on sapphire substrates at 1500oC. Shear tests were conducted on the solidified sessile drops. The liquid-gas surface tension of pure nickel on sapphire was found to be 1747 ergs per sq cm, with a contact angle of 109.6 deg. The surface tension and contact angle were not affected significantly by the four atmospheres, vacuum, impure argon, pure argon, and pure hydrogen. Small additions of titanium and chromium decreased the contact angle and for the same alloy content, contact angles were lower in pure argon than in pure hydrogen. On the basis of shear-test results , the most probable cause for adhesion in the Ni-Al2O system is the formation of NiO:Al2O3 spinel at the interface; in the titanium alloy-Al2O3 system adhesion is thought to be due to a mechanical interlocking effect; in the chromium alloy-Al2O3 system adhesion is believed to be the result of solid-solution formation involving Cr2O3 and Al2O3 at the interface. In the last few years there has been considerable interest in reinforcing metals with ceramic whiskers. It has been postulated that, by reinforcing nickel with sapphire whiskers, high-temperature strengths su- perior to those of the best current nickel alloys can be achieved.&apos; To fabricate a whisker-metal composite having optimum density and strength, understanding of wettability and adherence in the system is of prime importance. Although there has been some previous research in this a a need for further studies has been cited4-8 to understand better the effects of impurities, alloys additions, and atmosphere on the wetting and bonding of metals to metal oxides. The purpose of this research was to investigate the factors involved in the wetting and adherence of nickel/nickel alloys to sapphire (single-crystal a Al2O3). Sessile-drop experiments were conducted in vacuum, impure argon, pure argon, and pure hydrogen, to determine the effect of atmosphere on the contact angle of the metals on sapphire, and the liquid-gas surface tension of pure nickel. The solidified sessile drops were sheared from the sapphire substrate to measure the bond strength between the metal and ceramic. The alloy additions chosen were titanium and chromium since both enhance the wetting of nickel on sapphire.2, 3c Also, titanium is commonly used when brazing metal-to-ceramic seals to improve adherence. Since chromium forms an oxide that is completely soluble in sapphire, it was thought that the oxide could serve as a transition phase to promote bonding between the Ni-Cr alloy and sapphire. I) EXPERIMENTAL APPARATUS AND PROCEDURE The sessile-drop apparatus was a horizontal furnace, with an induction-heated, cylindrical molybdenum susceptor in a water-cooled Pyrex chamber. This apparatus was patterned after that of Williams and Nielsen.7 A flat Pyrex window at each end of the furnace allowed temperature measurements to be made at one

Jan 1, 1968

By K. E. Barrett

Exxon owns a uranium mill and holds two mining leases in Live Oak County, Texas, about halfway between San Antonio and Corpus Christi. The properties make up the Felder Uranium Operations which was reopened earlier this year. Exxon held an oil, gas, and other minerals lease on the J. C. Felder tract, which was adjacent to a relatively shallow uranium discovery by Susquehanna-Western, Inc. on the Marrs-McLean lease immediately south of the Felder property. Drilling in 1967 and 1968 confirmed the presence of reduced uranium mineralization in the basal sand unit of the Oakville formation on the Felder tract, which formed the major part of the roll-front deposit. In 1969 Exxon and Susquehanna-Western, Inc. entered into a sale and purchase agreement which provided for Susquehanna to mine and process Felder ore and purchase recovered uranium. Susquehanna moved an alkaline-leach mill from Wyoming, erected it on the Ray Point property, and placed it into operation late in 1970. Susquehanna mined and processed ore from the Felder and McLean properties through March 1973. Susquehanna ceased operations in March 1973. Exxon then acquired the mill and mill property. Exxon also purchased the mineral rights to the McLean lease, re-negotiated a mining lease for that property, and carried out shut-down programs for the mining and mill areas in the fall of 1973. The project was put on a standby basis until late 1973, when Exxon initiated mine feasibility studies for the project. MINE PLANNING EVALUATION The feasibility study for reopening the Felder Project began in late 1975 and was not completed until late 1976. I will discuss several areas of the feasibility study that required additional work prior to making the decision to renew operations. Ore Reserves Preparations for estimating the ore reserves began with the re-evaluation of more than 1500 natural radioactivity logs from exploration and pre-development drilling that had been completed on the property. These gamma ray logs of non-core rotary drill holes were the principal source of data used in making the estimate. Chemical assays of cores from the deposit were also used in the reserve determination. Electric resistivity and self-potential logs were made along with the gamma ray log. In December 1975 an additional core drilling project was undertaken to confirm the in-place density and radiometric equilibrium characteristics of the ore deposits. Comparison of chemical assays of cores with the U308 values calculated from the logs showed that the unoxidized ores were in radiometric equilibrium. In contrast, cores from anomalies occurring in near surface, weathered, and oxidized zones were in radiometric disequilibrium. Several important decisions were made in developing a mine plan or schedule of production from the Felder and McLean ore bodies. Disposal of Produced Mine Water: The ore bodies of the Felder Uranium Project occur at a point below the ground water table. The ore zones to be mined must first be dewatered to allow removal of mineralized material. In the open pit operations, this is accomplished by maintaining a perimeter ditch around the periphery of the open pit, allowing the interior of the pit to drain and collect into a sump and be pumped from the mine. In addition to anticipated water production from future mining operations, approximately 200M gallons of water was contained in three open pits left from prior mining operations. In two of these existing pits, the water was to be removed and disposed to allow for planned backfilling of waste material into these pits. The third pit would also have to be drained to allow continued mining of an area left from the prior operations. Essentially no ground water information was available for this area. The only data available was water production history from Susquehanna&apos;s mining operation. Two water wells were drilled early in 1976 on the Felder lease for use in obtaining hydrological data. A long term draw-down test was performed by pumping one water well and measuring water level drawdown in both the pumped well and the observation well. From these data, values for permeability and storage coefficient were calculated. These data were then used in modeling the aquifer to allow calculation of water influx into the mining area versus time. Once a schedule of water production, including the stored volume in the existing pits was calculated, alternate solutions for disposal were evaluated. The first system evaluated was a series of deep injection wells. The wells were designed to inject at a depth of approximately 3500 feet. Again very little information concerning reservoir characteristics of the receiving sand units was known. Using assumed values for reservoir permeability and storage coefficients, an injection well system was designed to allow for disposal of produced mine water. The biggest

Jan 1, 1979

By Wm. B. Price

The work of Leon Guillet concerning the effect of nickel on the structural properties of brass is checked. The best value for the coefficient of equivalence t, that is, the amount of zinc replaced by 1 per cent. of nickel, is shown to be-1.1 per cent. The best hot- and cold-working nickel silvers, varying in nickel content between the limits of 4 and 18 per cent., are tabulated and plotted diagrammatically. Also, some data are given showing a comparison between the physical properties of a hot- and cold-working low copper-nickel silver, and a commercial cold-working nickel silver containing approximately 8 per cent. more copper. THIS investigation of low copper-nickel silvers was undertaken to check the work of Leon Guillet on special brasses and to determine, more accurately, the effect of the addition of nickel on the microstructure of the binary alloys of copper and zinc. It was hoped that the results could be successfully applied to the practical production of low copper-nickel silvers. To explain the results of his investigations on special brasses, Leon Guillet evolved his conception of "fictitious compositions." He states,1 in his general conclusions, that on the introduction of a small amount of a third metal to a copper-zinc alloy, it enters into solid solution with the normal constituents up to saturation, but by so doing it brings the ternary alloy into a state microscopically equivalent to a binary copper-zinc alloy of fictitious composition, and physically more nearly like the latter than the brass containing copper-zinc in the ratio actually present. The physical properties of the ternary alloy, when compared to the same properties of an actual brass of the fictitious composition, are modified by the natural properties of the third element. Beyond the point of saturation, a special constituent appears and the above generalization no longer holds.

Jan 2, 1924

By Michel Dagbert

"This paper illustrates the different ways grade-tonnage curves can be generated f or a mineral deposit. It emphasizes systematic discrepancies between reality, estimates and actual production according to different estimation methods and grade control programs. It does not offer a universal solution to the prediction of grade-tonnage curves. Hopefully, it will inspire caution to mineral economists who use estimated grade and tonnage data in the establishment of an optimum cut-off grade for a mining operation.IntroductionThe value of a mineral development venture often depends on a grade-tonnage curve. Statistics can help. The idea is to divide mentally the orebody into small blocks called selective mining units or SMUs. A SMU is an idealized version of the quantity of rock the grade of which will be tested against the cut-off at the time of mining. It could be as small as a truck load or a shovel load in very selective operations like some uranium mines where radiometric probing of each truck or car is performed. More typically, in an open pit operation, it will be the smallest zone flagged as ore from blast hole data, e.g. a 5 m by 5 m by 10m block, if blast holes are on a 5 m grid and bench height is 10m. Having defined the SMUs, the grade-tonnage curve determination amounts to evaluating the grade distribution of all the SMUs that can be mined in the depo sit. If we know this distribution we simply apply the cut-off to it and we get the number of SMUs above the cut-off (i.e. ore tonnage) and their average grade. .Assessment of the grade distribution of SMUs from exploration drill hole data is not an easy exercise and much has been published on the subject (David, 1972; Marechal , 1972; Huijbregts, 1975; Marechal, 1975; Guibal and Touffait, 1982). In this paper, we use a gold mine example to illustrate the influence of SMU size on the results. With the same example we also show that ""common-sense"" methods of grade-tonnage curve determination can sometimes be misleading."

Jan 1, 1987

FOR some time past keen interest has been shown in both America and South Africa in the mining drill-steel problem. This interest has extended to Australian mining fields, and Australian drill users, ever desirous of increasing efficiency, are vigorously attacking the problem. The writer has recently been engaged in the investigation of the problem on two of ,the biggest mining fields in Australia, and has formed very definite conclusions concerning the causes of many drill-steel casualties. He puts these views forward in the hope that they may be of interest to, both drill manufacturers and drill users. The subject is here dealt with mainly from the aspect of the properties of the steel and the modifications of these properties whensubjected to various manipulations. It is generally admitted that the drilling machine has greatly increased in power and efficiency during recent years, and the consequence is that the machine is demanding better service from the steel. This is being impressed on the drill users by an increase in steel casualties. This fact has led many mining people to the view that the machine has developed so rapidly that the steel maker has not been able to keep pace, and that consequently the steel isfailing by fatigue 0:1; so-called crystallization. This view is rather depressing. The writer, on the other hand, is inclined to discountenance fatigue as a serious factor under good normal working conditions where the steel is carefully manufactured and supplied to the user under suitable structural and sound conditions, and has subsequently received kind treatment at the hands of the drill sharpener and the drill user.It is not reasonable to attribute failures to fatigue until it has definitely been proved that the steel is fundamentally sound and is in the best structural condition to resist the stresses it is called upon to withstand, and, this being so, that all fundamental principles of...

Jan 1, 1923

By VAN. H. MANNING

During the nine years that have elapsed since the Bureau of Mines was established in 1910, the work of the bureau has included many investigations that have proved of high value to the Nation. Eleven mining experiment stations established by act of Congress have greatly increased the bureau's usefulness; being situated in the mining fields, these stations are closely in touch with industrial needs, and the results of their research and educational work are more directly available to those engaged in the mining, metallurgical, and mineral industries. In the United States mining is second in importance to agriculture only. The Federal Government annually appropriates large sums in the interest of agriculture, whereas the appropriations for mining are relatively small. But the nation-wide popularity of Government assistance to agriculture should not overshadow the need of Federal assistance to the mineral industry. With scientific management farms can be made to produce indefinitely without any depletion of the potential resources of the soil, but the mineral wealth of a country is a fixed quantity, and every year's production brings nearer its ulti- mate exhaustion. As the deposits of the richer or more readily available ores, espe- cially those in the West, have been depleted, development of methods for mining and treating the leaner or more inaccessible ores has lagged, so that meeting the increasing demands for certain metals is becoming more and more difficult. In some branches of mining the small inde- pendent operator is greatly handicapped. He has to rely on custom mills and smelters for the profit or loss of his product, and because of relatively inefficient methods of milling or smelting he may receive no return for much of the ore he mines. Even though the small operator thinks he knows of improved methods of obtaining the metals from the ores, he can not afford to install the necessary machinery or to carry on experiments that may or may not prove successful. In view of the increasing need of metals and the impossibility of renewing the ore supplies, efforts should be directed toward developing the most economical and efficient methods in mining and metal- lurgy. The great mining companies carry on independent research work, some of them on a large scale; but as such work is usually undertaken for gainful purposes, these companies do not feel under any obligation to give the results of their investigations to the world. Clearly the solution of the difficulty is to place in the mining districts trained mining and metallurgical engineers who will investigate and solve the problems for the benefit of the whole industry. It is with this purpose in view that experiment stations of the Bureau of Mines have been established to investigate economy, efficiency, and safety in mining, and to make public the results of the investigations. The Federal Government can be of most help in developing the mineral resources of the country when its forces are brought in direct contact with these resources. Mining is as old as civilization, but only within a generation has this country busied itself with any other problem of mining than the amount of mineral products that could be put upon the market. Little concern was felt if much of the metal in an ore was wasted, if the miner lived in unsanitary surround- ings and died of preventable disease, or if accidents occurred fre- quently and from causes that could easily be controlled. Now we realize that the waste of any resource is inexcusable. The mineral wealth of the country can be mined but once. The task before the Nation is to recover as much metal as possible from the ore in the ground, and to do this in the most economical way without waste of human life. This task is of such magnitude as to warrant aid from the Government through experiment stations. In its efforts to make the work of these stations of most benefit to the mineral industry the Bureau of Mines seeks the cooperation of State authorities, of mine operators, of miners' organizations, and of every person interested. These experiment stations also serve an educational purpose. Gen- erally speaking, mining is not a preferred occupation. The miner should have reason to take greater interest in his work; he should feel that the experiments the Government is making affect him vitally by enabling him to increase his production and by making his work safer. The mine operator should realize that the Government stands ready to aid him, and he should know that he can bring his own problems to a Government organization that is trained and equipped to solve them. The surest method of accomplishing these results is to carry the work of the Bureau of Mines into the mining regions through the establishment of experiment stations easily accessible both to the mine operator and to the miner. Many miners in this country do not read English, but they can understand motion pictures of mining methods; they can learn how lives can be saved in case of accident; and they can appreciate the larger results gained by modern methods and equipment. In every

Jan 1, 1919

By Rachel S. Prudhomme, Michael L. Jeremic

"The consolidation of mine backfill by free zing is a concept which has been under study in the mining engineering laboratories at Laurentian University during the past three years. The proposed underground application of freezing involves the artificial freezing of in-situ backfill by means of a refrigerated brine solution which would be circulated through a circuit off freeze pipes. The most interesting findings to date are: (I) The uniaxial compressive strength off frozen fill is considerably higher than that of cemented fill in a ratio of 20:1 (aggregate to cement), and (2) load deformation characteristics of the frozen fill suggest that a higher ice content results in more brittle failure and that samples which have initially failed can still support up 10 one-half the ultimate load without additional failure.Although at this early stage a derailed economic analysis of the procedure has not been possible, a general evaluation of the costs involved suggests that the method could be competitive with the hydraulic placement of cemented backfill. Results obtained from laboratory investigations indicate that the freezing of backfill is a structurally feasible option .IntroductionGround consolidation by freezing is based on the principle of transformation o f water contained in an aggregate-slurry into ice, which act s as a binding agent between the bulk particles, and which results in the transformation of a granular soil into a ""rock -type"" material. The abrasive nature of the particles enhance s the strength o f the ice by providing internal friction. As a result of this internal friction, the chances of plastic flow of the frozen mass when in a loaded condition are reduced(1). T he strength of a frozen aggregate is al so dependent on the grain shape of the aggregate particles which may or may not promote particle interlocking(2) and on the temperature since, below the freezing point of the water/aggregate mixture, the strength of the frozen mass increase s with decreasing temperatures.In the shaft sinking industry, artificial freezing of loose , unconsolidated soils has been in practice for several decades. Shafts for Saskatchewan &apos;s potash industry have been sun k to depths of 3000 feet by employing artificial freezing to stabilize the Blairmore Formation(3). The common procedure for freezing ground for shaft sinking is summarized as follows(4,5): I) 150 mm diameter bore holes spaced on 1.5 m centres are drilled in a circular pattern with a radius of 1.5 m outside the periphery of the proposed shaft."

Jan 1, 1985

By E. Teghtsoonian, E. M. Schulson

The tensile behavior of bcc ordered P&apos; AuZn single crystals (CsCl structure) has been investigated under varying conditions of temperature, composition, and orientation. Between -0.2 and 0.4 T, multi-stage hardening occurs fm stoichiometric and nonstoichio-metric crystals oriented near the middle of the primary stereographic triangle. At higher and lower temperatures, parabolic type hardening occurs, followed by work - softening at the higher temperatwes. Deviations from stoichiometry give rise to increased flow stresses. Multi-stage hardening was observed for most orientations, except along the [loll-[lll] boundary and near the [001] corner of the stereo -graphic triangle, where parabolic type hardening occurs. Along two slip systems, (hk0)[001] and (, operate simultaneously while in the [001] comer, slip occurs mainly on the system. Electron microscopy of deformed crystals revealed bundles of edge dislocations forming walls approximately Perpendicular to the glide plane. In general the plasticity of 4&apos; AuZn closely resembles the plasticity of bcc crystals. In recent years, considerable interest has arisen concerning the mechanical properties of the CsCl type intermetallic compounds Ag Mg,&apos;- Fe co,&apos; and Ni Al.&apos;-&apos; The compound P&apos;AuZn is structurally similar. It has a low and congruent melting point of 725"~,&apos;" remains ordered up to the melting point,16 and pos-esses a range of solid solubility from 47.5 to 52.0 at. pct Au at room temperature.15 The present paper reports the results of an investigation on the general tensile behavior of material in single crystal form. Some dislocation configurations characteristic of the deformed state are also reported. The results of a detailed study of the slip geometry in AuZn are presented in a separate paper.17 PROCEDURE Alloy preparation, crystal growing techniques, and the procedure followed in selecting specimens of minimum composition variation are reported elsewhere.17 Dumb-bell shaped tensile specimens were prepared by carefully machining single crystals in a jewellers&apos; lathe to a gage length of 0.80 in. and diam of 0.090 in. Back-reflection Laue X-ray patterns and room temperature tensile tests revealed that machining damage could be eliminated by electrochemically polishing 0.005 in. from the machined surface followed by annealing at 300°C for 1 hr. Specimens were polished in fresh 5 pct KCN solution (40°C, 12 v). Experiments were performed by gripping specimens in a self-aligning pin-chuck and threaded collet system, then straining in a floor model Instron tensile machine. All tests were performed in duplicate. Experimental variables included temperature, composition, and orientation. Unless otherwise stated the strain rate was 2.5 x 10"3 per sec. Liquid testing environments included nitrogen (WOK), nitrogen cooled petroleum ether (133" to 293"K), and silicone oil (293" to 488°K). Resolved shear stress-shear strain curves were electronically computed from autographically recorded load-elongation curves. Stress and strain were resolved on the macroscopic noncrystallographic (hkO) [001] system operative under the specific test conditions of temperature, strain rate, and orientation reported earlier.17 RESULTS The temperature dependence of the work-hardening curves is shown in Fig. 1 for gold-rich crystals of 51.0 at. pct Au oriented near the center of the stereo-graphic triangle. Over the range of intermediate temperatures from -200" to 400°K, they are very similar to those classically observed for fcc metals (reviewed by Nabarro et al.).&apos;&apos; The beginning of deformation is characterized by a region of decreasing hardening rate, stage 0, which is followed by a region of low linear hardening, stage I, and then a region of higher linear hardening, stage 11. At the higher temperatures, stage 111 is observed, a region of decreasing hardening rate. Over the intermediate temperature range, the extent of stage 0 and of the slow transition between stages I and I1 decreases with increasing temperature. Total ductility is large, often greater than 300 pct shear. As the temperature is either increased or decreased, the extent of stage I is decreased, giving rise to parabolic type flow and reduced ductility. Similar temperature effects have been reported for bcc ~r~stals.~~-~~ Below -14O°K, hardening is terminated in brittle fracture while above -400°K. initial hardening is followed first by work-softening and then by chisel-edge type ductile fracture. Stoichiometric (50.0 at. pct Au) and Zn-rich (51.0 at. pct Zn) crystals were also tested from 77" to -500°K. The effect of composition on the flow behavior is illus-

Jan 1, 1970

By F. V. Lene, E. J. Westerman

The recrystallization behaviors of two extruded and cold-drawn experimental sintered aluminum powder alloys, containing 1.75 and 3.0 pct Al2O3 by weight, were compared with that of extruded and cold-drawn commercially pure alumirzum. The kinetics of recrystallization of the alloys are described semiquantitatively. For the alloy containing 1.75 pct A l203 the rates of nucleation and of growth were also semiquantitatively determined. THE most striking property of aluminum alloys strengthened by a dispersion of Al2O3, the so-called SAP alloys, is their stability at elevated temperatures. One of the manifestations of this stability is their resistance to recrystallization after they have been cold worked. Most of the commercial grades of either the Swiss SAP or of Alcoa&apos;s Aluminum Powder Metallurgy Products have not been recrys-tallized after cold working, even when they are heated for a long time at a temperature near the aluminum melting point. Lenel, however, observed that the dispersion strengthened aluminum alloys with a larger spacing between the oxide particles than that of most commercial grades would recrys-tallize.1 It appeared to be of interest to further investigate the mode and kinetics of recrystallization of these alloys, and to compare their recrystallization behavior with that of commercially pure aluminum. Because homogeneous deformation of these SAP alloys in tension did not provide sufficient cold work to induce recrystallization, they were cold worked by wire drawing; the nonuniformity of this deformation unavoidably complicated the interpretation of the recrystallization studies. EXPERIMENTAL DETAILS Extrusions—Two types of sintered aluminum powder extrusions were used in this study. One type, designated AT-400, was produced from Reynolds atomized aluminum powder consisting of spherical particles averaging 3µ in diam and containing 1.75 wt pct of Al2O3. This powder was very similar to the R3M powder from which extrusions were previously prepared with an average spacing of 0.9µ between oxide particles.2 The second type, designated MD 2100, was produced from Metals Disintegrating Co. flake powder containing 3.0 wt pct of Al2O3, with an average flake thickness of 0.8µ. The average spacing between oxide platelets in MD 2100 extru- sions was 0.45µ.2 Powder compacts of 3/4-in. diam were extruded at 1000°F into 0.097-in. diam (AT-400) and 0.093-in. diam (MD 2100) wires by methods previously described.3 In order to compare the recrystallization behavior of sintered aluminum powder extrusions with that of wrought commercially pure aluminum 3/4 in. rod stock of 1100 F aluminum was extruded at 1000°F into 0.102-in. diam wire. Wire Drawing—Tungsten carbide dies were used for the AT-400 and 1100 F alloys. They had an included angle of about 15 deg and reduced the wire area approximately 7 pct per pass. Steel dies with an included angle of 11 to 13 deg and an average reduction per pass of 10 pct were used for drawing the MD 2100 alloy, because drawing this alloy through the carbide dies produced overdrawing defects. Heat Treatment—The cold-drawn wires were cut into small samples, and the deformed ends were etched off. The samples were each wrapped tightly in a single layer of aluminum foil, and individually isothermally annealed in a lead bath. Metallography—The modes and kinetics of recrystallization were determined by metallography. Mounted and polished specimens were anodized in a solution of 1.8 pct HBF4;4 examination under polarized light clearly revealed their grain structures. The recrystallized grains were generally much larger than those of the unrecrystallized matrix, and could clearly be distinguished because they alternated between maximum and minimum light reflection when the microscope stage was rotated, while the unrecrystallized matrix had a comparatively homogeneous "salt and pepper" structure. The fractional recrystallized volumes of the dispersion hardened alloy wires were determined by cutting and weighing of recrystallized and total transverse areas on photomicrographs. The recrystallized grains in the 1100 F alloy were too small to be cut out individually; therefore a combination of cutting and lineal analysis was used in this case. RESULTS AND DISCUSSION Modes of Recrystallization—The modes of recrystallization of the three alloys varied widely. In the 1100 F alloy nucleation and growth started in the region midway between the center and the surface;

Jan 1, 1961

By Charles T. Steuart, Richard B. Berg

Tripoli and the related mineral commodities such as micro- crystalline silica have been mined for more than 100 years for their abrasive properties. Although abrasive and buffing compound markets are still very important, within the last 15 years the filler and extender markets in paint, plastics, rubber, adhesives, and sealants have increased substantially. Tripoli or microcrystalline silica consists almost entirely of very small quartz crystals, many less than one micrometer in length. Material mined from different districts differs in crystal shape, grain size, and texture of the rock, all of which influence markets. Most US deposits are now mined by surface methods, and both air floated and micronized products are marketed. Deposits of tripoli now mined in the United States occur in chert-bearing Paleozoic limestone in the central part of the country with producing districts in southern Illinois, central Arkansas, and eastern Oklahoma. Although deposits within each district are confined to specific formations and extend laterally within those formations, individual bodies form minable deposits that are typically several hectares in areal extent. Tripoli is white to cream to rose and characterized by high porosity and ease of disaggregation. DEFINITIONS Tripoli In the United States, tripoli was first used to describe the fine-grained, easily disaggregated material from Seneca, MO, be- cause of its similarity to a rock from the Tripoli region of North Africa (Hovey, 1894). The North African rock is actually diatomaceous earth, a material that is similar in appearance to the rock from Seneca, but is of entirely different origin having formed by the accumulation of siliceous remains of microscopic marine or fresh- water animals. Tripoli is best defined as a very fine-grained, generally porous rock that consists of microcrystalline quartz, typically formed by the alteration of a chert-bearing limestone. Tripolite A term used to describe a rock from the vicinity of Tripoli in North Africa which is diatomaceous earth (Quirk and Bates, 1978) Microcrystalline Silica Microcrystalline silica is the same material as tripoli, but the distinction between the use of these two names is dictated largely by convention and markets. Material produced from southern I1linois deposits and used in white pigment and filler applications is generally referred to as microcrystalline silica, whereas that used in abrasive applications, both from the Illinois district and from other states, is commonly called tripoli. Amorphous Silica Amorphous silica, a term formerly used to describe the material produced from the deposits in southern Illinois, is now replaced by the term microcrystalline silica. Amorphous silica came into use when even optical methods for the identification of very fine- grained quartz were not widely available and the Illinois product, composed of quartz grains too small to be seen with the unaided eye, was thought to consist of amorphous silica. The Illinois material is clearly crystalline quartz, as shown by X-ray diffraction analysis and scanning electron microscopy (Fig. 1). Novaculite Although originally used to describe a rock suitable for the manufacture of whetstones, novaculite is now defined more generally " - as a homogeneous, mostly white or light colored rock, translucent on thin edges, with a waxy or dull luster, and almost entirely composed of microcrystalline quartz" (Steuart et al., 1983). The more compact rock mined in central Arkansas from the Arkansas Novaculite is referred to as novaculite, whereas the more porous rock is referred to as tripoli. Rottenstone The commodity rottenstone is sometimes included within the general mineral commodity category of tripoli. Rottenstone is mined in Northumberland County in eastern Pennsvlvania and formed by the weathering of a siliceous shale of Devonian age (Faill, 1979, Berkheiser, private communication, 1991). This material is used as a filler and extender, but is apparently unlike tripoli both in origin and physical properties. Spiculite Spiculite is a rock consisting of siliceous sponge spicules having formed by the removal by solution of the carbonate matrix of a spicule-bearing limestone. Spiculite has been mined in Texas and, because it resembles tripoli in several aspects, is included in the discussion of deposits.

Jan 1, 1994

By John F. Elliott, John P. Hager

The standard free energies of formation of the lowest stable sulfides of chromium, molybdenum, and tungsten in equilibrium with the corresponding metal hazle been determined by reacting the sulfide and metal with H2(g)/H2S(g) mixtures. The reaction is A method for estimating the standard ~nolav entropies and standard entropies of formation at 298°K of the sul-fides of refractory metals is presented. The standard free energies of formation of the lowest sulfides of the metals in group VIa of the periodic table are probably best determined with the reaction* is known with greater accuracy than is that property for any other sulfur-bearing compound or solution which might serve as a reference phase to establish the chemical potential of sulfur for the essential re- However, there still remain significant problems to the use of Reaction [I] in studying these sulfides. First, the equilibrium gas ratios (Ph2S/PH2) are very small, and with the most stable sulfides in the series the ratios tend to be at the limit of the range for precise chemical analysis (10-4); and second, the reaction rate for the formation or reduction of these sulfides appears to be relatively slow. A primary reason for the latter problem is that the gas phase near the equilibrium concentration has very little capacity for transport of sulfur. It is to be noted that the thermo-dynamic properties obtained from the experimental results by Eq. [I] apply for 1 g-atom of sulfur in the metal-saturated compound even though the exact composition of the compound has not been determined. The work reported here is a study of the standard free energies of formation of the lowest sulfides of chromium, molybdenum, and tungsten, and of copper, by Reaction [I]. In planning the experimental program, it was decided that the technique that has been used previously3"&apos; could be used with modification and that an improved analytical method was needed for determining H2S in the gas phase. THE EXPERIMENT The once-through flow of gas was selected in preference to recirculating the gas, a) because of the low sulfur capacity of the gas, b) because of the relatively slow rate of reaction and the danger of the

Jan 1, 1968

By D. D. Dunlop, J. R. Welker

The growing interest in the use of CO, in crude oil recovery increases the need for data on the effect of CO, on hydrocarbon physical properties. Data are presented on the solubility of CO, in various dead oils, the swelling changes in CO2-oil solutions and the effect of CO, on dead oil viscosity. This latter property shows the most pronounced effect, with viscosity reductions up to 98 per cent of the uncarbonated viscosities. An empirical method of estimating the viscosity of carbonated oils is presented. The apparatus and procedures used are described in sufficient detail to allow others to make similar studies. INTRODUCTION The effect of dissolved carbon dioxide on the swelling and viscosity reduction of specific hydrocarbon oils has been observed and recorded by a number of investigators.&apos;- me object of this paper is to offer a means of predicting these effects for crude oils free from natural gas, using the dead state viscosity and gravity of the crude oils. The CO, solubility and swelling of numerous crude oils were determined in a visual cell at various pressure levels. The viscosity of the oils carbonated to various pressure levels was then determined by measuring the pressure drop across a capillary tube. From these data, the physical properties were correlated empirically. The resulting correlations allow the prediction of CO, solubility, swelling and viscosity reduction if the dead state gravity and viscosity of the oils are known. SOLUBILITY AND SWELLING MEASUREMENT EQUIPMENT AND PROCEDURE A high pressure visual cell was installed in a constant temperature cabinet. A test gauge was attached at the top of the cell for pressure measurement, and a line was run through the cabinet wall to a wet test meter which was used for volumetric measurement of the gas. The first step in making a test run was to put the oil in the cell up to a level about half to two-thirds of the total volume. This required about 50 to 65 ml of oil. carbon dioxide was then bubbled up through the oil for a time during which the pressure of CO2 in the cell was kept above 800 psia. Saturation of the oil with CO2 at this pressure and ambient temperature was confirmed by slowly bleeding CO2 through a valve to the atmosphere. If the oil was completely saturated with CO2, bubbles of gas would form in the oil at the first small decrease in pressure. If the oil was under-saturated, no bubbles formed until the pressure was decreased to the saturation pressure existing in the oil. If this saturation pressure was lower than that desired, more CO2 was bubbled through the oil until the desired level was reached. After saturation at ambient temperature was completed, the cabinet temperature was adjusted to the desired level and the cell was allowed to reach temperature equilibrium. After temperature equilibrium was reached, the pressure was again decreased slightly, and the oil again checked for full CO2 saturation at the cell pressure. The pressure now had changed because of the difference in solubility of the CO, in the oil at higher temperatures and the expansion of CO2 as the temperature increased. The outlet tube from the cell was then connected to the wet test meter and the CO2 was allowed to flow slowly out of the cell and through the wet test meter at ambient temperature and pressure. The water in the wet test meter had previously been saturated with CO2 at ambient temperature and pressure by allowing CO2 to flow continuously through it lor a period of several hours. The gas flow was stopped at several pressures during the run and the cell was allowed to come to equilibrium; this made possible the measurement of solubility and swelling data at the intermediate pressures. The volume of the oil in the cell was recorded at each of the equilibrium pressures in order to obtain swelling data. DATA AND RESULTS The solubility of CO2 in the oil was calculated by the relationship V — V, where R. = solubility of CO, in crude oil, cubic feet of CO, measured at 60F and 1.0 atm/ bbl of dead state oil at the temperature under which solubility was measured, V, = volume of gas released from the cell between the saturation pressure and zero pressure, corrected to 60F and 1.0 atm, cu ft, V, = volume of CO: contained in the gas space above the oil, corrected to 60F and 1.0 atm, cu ft, and V, = volume of the dead oil in the cell in bbl at the temperature of the run. The volumetric data of Sage and Lacey&apos; were used to calculate V., from the volume of CO2 at high pressures. The swelling factor was calculated as where V, is the volume of the C0,-

By Fritz Kleiner, Walter Meintrup

On Nov. 4, 1981 A/S Sydvaranger&apos;s 1-kt/h (1,100-stph) wet-process, iron ore ball mill completed its first four months of uninterrupted, full-load operation in Kirkenes, Norway. This 6.5-m-diam (21-ft-diam) mill is driven by a gearless ring or wraparound 8.1-MW (10,860-hp) motor at 13.1 rpm-a first of a kind in this segment of industry. This article examines reasons for selecting this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes the installation in Norway. History For almost a decade, good operating experiences have been gained with 28 gearless ring motor drives in the cement industry, driving 2.5 to 4-m-diam (8.2 to 13-ft-diam) tube mills with drive powers ranging from about 3-4 MW (4,000 - 8,000 hp). Why then did the mineral ore processing industry hesitate until 1980 to adopt this successful concept for similar applications on ball, semiautogenous, and autogenous mills? There are a number of good reasons in the eyes of conservative mill builders and operators, the most commonly cited ones are: • No operating experience in this segment of specialized industry. • More severe environmental conditions in the wet ore grinding process. • An indifferent attitude of mill builders and electric motor manufacturers towards new drive technologies. • Limited confidence in solid-state power supply systems, such as frequency converters of the required size. There have been and still are numerous problems associated with low-speed geared mill drives of any kind, especially with individual motor/gear sizes approaching or exceeding about 4 MW (5,360 hp). Every mill builder knows about them, but operators learn to accept them as inevitable. The Decision to Change Three things combined to break this technological stalemate: the courage and progressive spirit of one major iron ore processor in Scandinavia, the cooperation of three experienced manufacturers, and an unusual application problem that could not be solved by any conventional approach. The last factor was surely the decisive one, but the first one does not come as a surprise either. The Swedes near Kiruna and the Norwegians around Kirkenes are experienced ore miners and processors, and much credit goes to them for technological breakthroughs in the industry. At A/S Sydvaranger in Kirkenes, above the Polar circle at about the latitude of Alaska&apos;s northern tip, the existing grinding facilities, with a total of 14 100 to 240-t/h (110 to 264-stph) ball mills, can not be expanded. Nevertheless, to increase mill throughput, only installing a larger mill in place of an existing smaller one was a practical alternative. For this replacement, the owners set requirements that seemed impossible to meet: • The old 100-t/h (110-stph) ball mill should be replaced with a new ball mill with 10 times the rated throughput, without significantly impairing the operation of the remaining mills, and without significantly changing the mill building. • The new mill should have a variable-speed drive to ultimately optimize the grinding process by means of a closed-loop process¬computer-controlled grinding cycle, and to minimize the specific energy consumption. • Availability, efficiency, and life expectancy of all new components must be higher than those being replaced. • Inrush-current and harmonic loads on the rather weak electric supply line must be minimized to ensure safe plant operation. All old ball mills at A/S Sydvaranger are the geared type, using single synchronous and wound-rotor, slow-speed motors with ring-and-pinion gears. Operators are familiar with the limitations and problems associated with such drives, and they are aware that the following items become major concerns when drive powers are drastically increased: • Gears are subject to wear and tear, require frequent maintenance, and eventual replacement of major parts. • Gears are sensitive to misalignment, overload, and thermal distortion, limiting their useful life. • On dual or quadruple drives, load-sharing and torque oscillations between motors can be a major reason for concern. • At these speeds, ring-and-pinion gears reach their torque transmission capabilities altogether at around 4 MW (5,360 hp) per motor/pinion. To obtain the desired variable-speed performance of the new drive, the only practical and economical conventional solution would have been a frequency-controlled, low- or medium-speed dual motor drive with about 8 MW (10,720 hp) of power. This, however, was not feasible because of limited floor space. Therefore, bids were solicited for the alternative drive method, the gearless ring motor. General Considerations Why are such large mills considered? After all, one could avoid all the problems by simply staying with smaller mill unit sizes. Under competitive pressures of free markets, however, grinding efficiencies and specific energy consumption become key factors in selecting new equipment. Specific energy consumption of ball mills decreases with increas-

Jan 9, 1982

By S. A. Lever, R. Hultgren

The solidus is usually the least satisfactorily determined portion of a phase diagram. Cooling curves, which succeed well with the liquidus, show the solidus inaccurately or not at all because of segregation which occurs during freezing. Heating curves of carefully homogenized alloys might be expected to indicate accurately the solidus, but they are seldom used. Dynamic methods involving heating or cooling are never completely satisfactory because of uncertainty as to whether equilibrium is attained. A static method in which the specimen may be allowed hours, days, or even weeks to attain equilibrium is to be preferred. In a static method a solid solution, for example, is first made thoroughly homogeneous, then heated to successively higher temperatures. After sufficient time at each temperature to assure equilibrium, some property is measured which should alter strikingly when melting begins. Microscopic examination can be used to detect the beginning of melting, but the method is tedious since the specimen must be quenched, sectioned, polished, and etched before each examination. Of all the physical properties which change on melting, electrical resistance is probably the most satisfactory to measure. The measurement may be made while the specimen is at temperature without damage to the specimen. It may be repeated indefinitely to ascertain when equilibrium has been achieved. Measurements may be made on a single specimen over the whole range of temperature. Most metals approximately double their resistance on melting. Since an accuracy of a few tenths of a percent is easy to achieve, the method is highly sensitive to the beginning of melting. In spite of these advantages, which have been perceived for a long time,l,2 a reasonable search of the literature has failed to reveal a single case in which the method has been satisfactorily applied in practice to the determination of solidus temperatures. The use of electrical resistance measurements appears to have been confined in practice to changes in the solid state. In the work described in the following pages we have applied the electrical resistance method to the solidus of the lead-tin system. We have found the method to be convenient, reproducible, and highly sensitive. We chose the lead-tin system because it leads to few technical difficulties. Furthermore, a number of determinations of solidus have been made in this system by various methods and results could be checked against them. However, all published results are not in good agreement with one another, so this work should help in determining the solidus more precisely. The Lead-tin Diagram Because of its commercial importance, there have been numerous investigations of the lead-tin diagram. The results of the most recent work on the solidus are indicated in Fig 7, as well as the results of the present work. The works of Honda and Abe3 and of Stockdale4 agree fairly well with each other and with the present work. Jeffery&apos;s5 data indicate the solidus to be about 50°C lower. Honda and Abe3 used differential thermal analysis on both heating and cooling cycles. Stockdale4 used the microscopic method and also differential heating curves. Stockdale&apos;s results were about 4" higher than those of Honda and Abe at low tin contents and lower at higher tin contents. These results also agree with those of Rosen-hain and Tucker.= Jeffery5 used electrical resistance measurements of the alloy as it was being heated or cooled. Apparently he did not attain equilibrium as his results are about 40°C lower than those of Stockdale4 or Honda and Abe.3 MATERIALS AND METHODS The lead and tin used were of high purity. They were supplied by the American Smelting and Refining Co., who gave the following analyses: Lead: silver, 0.0016 oz per ton; copper, 0.0008 pct; cadmium, 0.0007 pct; zinc, 0.0002 pct; arsenic, 0.0003 pct; antimony, 0.0002 pct; bismuth, 0.0005 pct; tin, 0.0001 pct; iron, 0.0020 pct; lead (by difference), 99.995 pct. Tin: antimony, 0.037 pct; arsenic, 0.020 pct; bismuth, 0.004 pct; cadmium, trace; copper, 0.025 pct; iron, 0.004 pct; lead, 0.020 pct; nickel and cobalt, 0.005 pct; silver, 0.0005 pct; sulphur, 0.005 pct; tin (by .-difference). 99.88 pct. One hundred grams of metal with the desired proportions of lead and tin was weighed out to the nearest one-tenth of a milligram. The mixture was placed in a silica crucible, covered with charcoal, and melted in a reducing atmosphere in a gas-fired furnace. The alloy was well stirred. Chemical analysis of two of the alloys checked closely with the weighed portions. The compositions of the remainder of the alloys were taken directly from the weighings, without chemical analysis.

Jan 1, 1950