Search Documents

By R. W. Fountain, John Chipman

The solubility of nitrogen in Fe-B alloys (0.001 to 0.91 pet B) is determined by the Sieverts' technique for temperatures of 950° to 1150°C. The activity coefficient of nitrogen is decreased by boron. The three-phase equilibrium between ? iron, BN, and gas is established and also the four-phase equilibrium between iron, BN, Fe2B, and gas. The above equilibria are calculated for a iron. The relation of these data to hardenability and strain aging of boron-treated steels is discussed. BORON additions are known to enhanbe the hardenability of heat-treatable steels and to assist in the control of strain aging in sheet steel for deep drawing. The increase in hardenability is explained by the theory that adsorption of boron on austenite grain boundaries reduces their free energy and thus retards ferrite and upper bainite nucleation.l,2 Digges and Reinhart3 have shown that the full effectiveness of boron in commercial steels is achieved only when strong nitride formers such as titanium and zirconium are also present. The influence of nitrogen on eliminating the boron contribution to hardenability was also demonstrated by Shyne and Morgan.4 These workers prepared Ni-Mo steels containing either nitrogen or boron or nitrogen plus boron. The nitrogen-plus-boron steels showed the lowest hardenability which was attributed to the presence of stable nucleating particles, presumably nitride. Morgan and Shyne5-7 have shown that boron in the amount of 0.007 pet will completely eliminate strain aging due to nitrogen in low-carbon, open-hearth steels. In addition, by proper control of the boron additions, a rimming steel can be produced. Since the effectiveness of boron on hardenability and eliminating strain aging is influenced by the amount and distribution of the nitrogen in the steel, the present study was. undertaken to determine the influence of boron on the solubility of nitrogen in iron. EXPERIMENTAL PROCEDURE The solubility of nitrogen in Fe-B alloys was measured by the method of Sieverts, which consists of determining the amount of gas dissolved by the metal in a constant volume system. The apparatus employed in this investigation and the experimental details have beendescribed previously.B AMcLeodgage was added to the apparatus to allow measurements at very low pressures. The alloys were melted at reduced pressure in a basic-lined induction furnace using electrolytic iron and ferroboron. Ferroboron was added after the primary deoxidation of the iron with carbon. Since it was difficult to attain a constant low level of oxygen by this procedure, silicon was added after the carbon deoxidation and prior to the ferr obor on addition. The alloys were castas 2-in. sq ingots, heated in argon at 1050loC, and forged to 1/4-in. plate. After forging, 1116 in. was machined from each side of the plate to remove any possible contamination, and it was then cold-rolled to 0.010-in. sheet. The sheet was cut into approximately 1/4-in. squares and pickled in an inhibited H2SO4 solution to ensure a clean surface. In the case of the boron alloys, a hydrogen treatment could not be used for surface cleaning because boron losses resulted. The composition of the alloys is given in Table I. For a solubility determination, a 75-g sample was inserted in a quartz tube and sealed in place in the apparatus. The entire system was evacuated at room temperature and leak tested for 24 hr. If no leaks were observed, the system was heated to the temperature of measurement and again leak tested for 24 hr. If no leaks were detected, the hot volume and solubility determinations were begun. The hot volume was determined at a constant temperature for each run by admitting successive amounts of argon and recording pressure vs volume, which, in all cases, resulted in a straightline relationship. The argon was then removed and the procedure repeated with nitrogen. Successive additions were made until the desired nitrogen content of the metal and equilibrium pressure of the system were obtained. The

Jan 1, 1962

By T&apos Ke, ing-sui

NUMEROUS investigators have observed that internal friction accompanies cold-working of metals and the effect of annealing is to reduce this internal friction.1,2 However, - most of the experiments were made at high stress amplitudes and the principal purpose was to study the increase of internal friction as a result of the applied cyclic stress during measurement. In order to study the internal friction introduced by cold-working applied prior to the measurement, the stress level applied during the measurement of internal friction must be sufficiently small. The results of measurement are significant and can be used for a base of comparison only when the applied cyclic stress is so small that the internal friction is independent of stress amplitude. Internal friction of cold-worked metals under small stress level has been studied by a number of workers8 -" he internal friction was measured around room temperature with a frequency of vibration of the order of kilocycles per second. The purpose of this paper is to report a study of the change of internal friction when severely cold-worked aluminum was annealed at successively higher temperatures until it was completely recrys-tallized. The measurements of internal friction were made over a range of temperature extending from room temperature up to the temperature of prior anneal. The frequency of vibrations used was about one cycle per second. The apparatus used for the internal friction measurements to be reported in this paper was a torsion pendulum with the specimen in wire form as the suspension fiber. The description of this apparatus and the method of measurement have been previously given.7,8 The applied stress was sufficiently small SO that the magnitude of internal friction is independent of stress level at each temperature range concerned. Corresponding to this stress the maximum shearing strain on the surface of the specimen is of the order of l0-5 and lower. The in- ternal friction (Q-1) is reported as 1/p times the logarithmic decrement. Internal Friction Versus Temperature of Anneal: Fig. 1 shows the internal friction measurements performed upon 99.991 pct aluminum subjected to 95 pct reduction in area. The final diameter of the wire is 0.033 in. This figure gives a general survey of the effect of temperature of anneal and of temperature of measurement. The internal friction of the cold-worked specimen was first measured at room temperature. It was then annealed at 50°C for one hour and the internal friction measured at 50°C and at room temperature. The same wire was successively annealed at higher temperatures for one hour and measurements were taken at the annealing temperatures and lower temperatures as before. Such a procedure was followed in order to stabilize the internal friction at the temperature of measurement so that during the measurement which generally takes about half a minute, there is no detectable change in internal friction. This series of measurements .was made up to 450°C. After each annealing a short test piece of the specimen, which had received the same past thermal and mechanical treatments, was taken out for metallographic examination. It is seen from fig. 1 that up to the annealing temperature of 250°C we have the following observations: for any given temperature of measurement, the internal friction is lower the higher the temperature of prior anneal. When the annealing temperature is 290°C or higher, the internal friction at the annealing temperature drops abruptly to a value which is much smaller than that for the previous curve. Metallographic examinations showed that the recrystallization of the specimen was completed after the annealing at 290°C. Fig. 1 shows that, as far as internal friction is concerned, there is no abrupt transition between the processes of recovery and recrystallization. Averbach has also reached the conclusion that recovery may be a process analogous to recrystallization on the basis of X ray extinction measurements in brass." The effect of annealing temperature upon the internal friction at room temperature is shown by curve I of fig. 2. In this figure the internal friction at room temperature was plotted as a function of annealing temperature. It is seen that the internal friction decreases rapidly at first with an increase

Jan 1, 1951

By R. J. Stoehr, F. Howell

Since the ore mined in the Grants-Ambrosia Lake uranium area is taken from a water-saturated sandstone formation, part of the milling operation includes a drying process. The authors discuss the merits and disadvantages of two methods: natural drying and mechanical gas-fired drying; operating and cost data are included. In the Grants-Ambrosia Lake uranium area, approximately 7000 tons of ore are mined each day from a water-saturated sandstone formation. This ore is sampled and treated at four separate milling operations. Prior to the design and initial construction of the milling facilities, very little was known as to the physical properties of the ore which would be handled in the sampling and crushing facilities at the mills. All four mills initially were constructed without ore-drying facilities. As mining proceeded, it was determined that, even after drying the ore in place by use of drainage development underground, the moisture content of the ore as hoisted averaged approximately 18 pct. Actually, some of the mines produced ores which resembled cream-of-wheat in character and had a moisture content in excess of 24 pct. Each of the four mills had a differently designed sampling and crushing plant; therefore, the moisture content of the ores had varying adverse effects upon the operation of the plants. It was determined after some experience that most of the sampling and crushing facilities could not economically handle ore if the moisture content was greater than 10 pct—one operator considers 12 pct moisture as a maximum. In all of the plants, moisture content over 8 pct increases costs to some extent. In addition to the added sampling and crushing costs, some of the mills were located 15 to 20 miles from the mines and the high moisture content of the ores increased the haulage costs from the mine to the mill. It was generally conceded that it was necessary to employ some method to reduce the moisture content of the ore prior to sampling. Several methods were considered: 1) natural drying at the mine site, 2) mechanical gas-fired drying at the mill site, 3) mechanical gas-fired drying at the mine site, 4) radiant heating on concrete clabs, and 5) infrared shed drying. After preliminary investigation all possibilities but natural drying and mechanical gas-fired drying at the mill site were eliminated. NATURAL DRYING A cooperative feasibility study was conducted on the natural drying method. This study indicated the following: 1) During summer months May through September, ore piled 4-ft deep would dry from +20 to +10 pct HzO in 30 days with no mechanical turning. 2) In the first four days after piling a reduction of 5 to 7 pct total moisture content was accomplished by drainage and absorption of the water into the underlying ground on which the ore was piled, providing the ground surface absorption rates approached 10 gal per sq ft per day. After the first four days the decrease of moisture caused by drainage was practically nonexistent. 3) In the summer months drying by evaporation amounted to approximately 0.1 pct decrease in total moisture per day and mechanical turning of the ore could increase this as much as three times. 4) Climatic conditions of the area indicated that: a) Air temperatures averaged 64' May, June, July, August, September; 41" October, November, December, March, April; 31" January, February. b) Average rain fall was 10 in. with 40 pct of this occurring during July and August. c) Only on very rare occasions were there over five consecutive days with below freezing temperatures. d) The annual evaporation rate was approximately 75 in. On the basis of this study, two of the mill operations decided to attempt to meet the moisture specifications by natural drying supplemented by mechanical turning. The other two operations decided upon rotary gas-fired drying at the mill site. The natural drying method has been quite successful in practice. The ore running approximately 18 pct moisture is trucked from the head frame and piled in rows about 6 ft wide, 3 1/2 ft deep, 5 feet apart during the months of May through September. In approximately 30 days this ore will

Jan 1, 1961

By J. W. Leomrd, B. A. Donahue

Results of research are presented examining the extent to which the analytical characteristics of the relatively distinct coal bands from a variety of coal seams can be related to each other. This paper dis-cusses an approach for developing a practical coal petrographic quality control program based on conventional analyses, most of which is part of the standard A.S.T.M. procedure. The work is a final follow-up to Part I of this series which was prepared by the authors as an approach to applying conventional coal petrography to single coal seams. Recent published work by the authors entitled Petrography for Coal Mining and Coal Prepration: Part I dealt with interrelating various chemical and physical properties of coal1 measured using conventional analyses made on distinct petrographic bands taken from single coal seams. Since most coal production facilities process coal from a single coal seam or from very closely related coal seams in the same area,2 emphasis on interrelating the properties within a single seam appeared appropriate. The distinct petrographic bands were analyzed on the assumption that such differentiated data would be more representative of a heterogeneous coal seam than the single analytical value commonly used to characterize each property of an entire seam.34 Effort was directed at demonstrating the extent to which the interrelated chemical and physical properties 5,6 could be developed into nomographs or petrographic standardization graphs. Thus, one analysis, determined on a series of petrographic fractions separated from a single sample, was used to estimate numerous other properties in each fraction by referring to the previously established petrographic standardization graphs. This conventional approach to coal petrography was undertaken as a suggested feasible means by which a few coal analyses could be employed to develope a more penetrating knowledge of the properties of coal from any given seam in order to monitor more extensively its performance at the point of utilization. Such procedures can support development of the type of in- formation commonly sought through automated testing and through the use of computers.7 The broad knowledge which can be developed through these procedures is intended for application in the generation of an analytical profile or broad characterization of coal. These estimates were not intended as replacements for individual coal analytical tests. In this expanded second part of the research program, distinct petrographic bands from nine coal seams in the Central Appalachian Region were physically and chemically analyzed to elucidate the extent to which this concept of conventional petrography could be broadened for application to numerous coal seams. In presenting this second phase of work, the relationships developed are presented individually and not in a connecting series of nomographs or petrographic standardization graphs as in the previous work, thus leaving open the combinations of possibilities to individual interpretation and application. MATERIAL AND EXPERIMENTAL WORK Nine coal seams, representing a wide range of rank, from the Central Appalachian coal fields were used in this study. The distinct petrographic bands from the Kittanning, Pond Creek, Jawbone, Tiller, Poca-hontas No. 3, No. 2 Gas, Eagle, Winifrede, and Pittsburgh coal seams were separated by carefully removing a portion of each band at the face of the seam. The following were determined: ash, sulfur, free swelling index, heating value, bulk specific gravity, volatile matter, Hardgrove Grindability Index, and Gieseler Plastometer measurements. Determinations, where procedures were available, were carried out using ASTM standard procedures.8 Bulk specific gravity was determined using a kerosene volume displacement procedure modified from a method applied by Headlee and McClelland of the West Virginia Geological survey,9 Those bands with a bulk specific gravity greater than 1.60, which is generally above the practical specific gravity cleaning range of bituminous coals, were excluded and no analyses were performed. Much of the initial organization of this second phase of work was developed through the extensive use of a computerized statistical monitoring program (see Ref. 4). However, in order to achieve the closest possible interpretation of results, the final organization of data proceeded mainly from exhaustive trial

Jan 1, 1968

By Robert D. Pehlke, Robert G. Blossey

The solubility of nitrogen in liquid iron alloys containing chromium and nickel has been measured in the temperature range 1550° to 1700°C at nitrogen pressures to 1 ah. The solubility surface has been determined for the iron corner of the liquid metallic ternary to 21 pct Cr and 11 pct Ni. The nitrogen solubility increases markedly with increasing chromium concentration. The effect of nickel and the bilinear effect of chromium and nickel are less pronounced. The solubility data are presented, and interaction coefficients are determined from them. THE solubility of nitrogen has been determined in liquid Fe-Cr-Ni binary and ternary alloys. The work in this laboratory has been directed toward a relatively limited composition range, that is to 20 pct Cr and 10 pct Ni. Humbert and Elliott1 studied the entire ternary; but their investigation was, understandably, limited in this region. The region considered here is of the greatest commercial interest. Knowledge of the solubility in these alloys is important for accurate control of the nitrogen levels in various stainless alloys. Also, the solution behavior is of theoretical interest because of its deviations from ideal dilute solution rules at moderate chromium levels. The nitrogen solubility in the iron binaries has been reviewed extensively by Pehlke and Elliott,2 particularly with respect to the dilute solution interaction parameters. More recently, there has been some interest in accurate descriptions of solute interactions in non-dilute solutions. Most of the investigators have adopted a power series fit to accommodate any non-linearity of the data. The Taylor series expansion is adopted here, using Scimar's notation3 for the interaction coefficients. An alternate method, instead of requiring higher-order expansions, is to restrict the range of the composition variables. A planar solubility surface may be fitted to the data and its range of validity determined. If the axes of this region are displaced from the usual origin—the solvent pure iron—a change in standard state is required for the solution reaction. The standard state for nitrogen in iron is commonly taken as the hypothetical 1 wt pct solution of nitrogen in pure iron. However, for an alloy of appreciable solute concentration, e.g., 13 pct Cr or 18 pct Cr-8 pct Ni, it would be convenient to use that base composition as the solvent and redefine the solution reaction in terms of that particular solvent. A brief derivation follows, defining the free energy of solution in an alloy solvent. Following the treatment by Darken and Gurry,4 for a nitrogen pressure of 1 atm: N (pure component) = N (1 wt pct in solvent) [l] AG=RT ln100/ wt pct N in solvent Taking this reaction for an alloy solvent less the same reaction for a pure iron solvent the relation between nitrogen in pure iron and an alloy is: N (1 wt pct in Fe) = N (1 wt pct in alloy) [2] AG = RT[ln(wt pct N in Fe) - ln(wt pct N in alloy)] Adding ½ N2(g) to each side and subtracting N (1 wt pct in Fe) = ½N2(g), the total free energy for solution of nitrogen in an alloy, referred to nitrogen at infinite dilution, is given by: ½N2 (g) = N (wt pct in alloy) L3] AG°3 = -RT ln(wt pct N in alloy )PN =1 atm Interaction parameters have their usual meaning when ?G°/RT is differentiated with respect to the proper composition coordinate. If desired, the dilute alloy treatment may be utilized with the new reference composition as the solvent. This has. indeed, been done by Small and pehlke5 in their analysis of nitrogen solution in liquid 18-8 alloys. The Sieverts' technique was used for this investigation on an apparatus previously described.6 The materials used in this program were: Ferrovac-E iron, 99.95 pct, Crucible Steel Co.: chromium, 99.95 pct, Union Carbide Metals Co.; nickel, 99.9 pct, International Nickel Co. Recrystallized alumina crucibles were used with no evidence of crucible-melt reaction. RESULTS The locations of the ternary compositions investigated are shown in Fig. 1. The data of Turnock7 and small8 have been alluded to in other papers.5'6 There were no departures from Sieverts' law observed for

Jan 1, 1969

By Elton A. Youngberg

The Holden mine operated by the Chelan Division of the Howe Sound Co. is on the east slope of the Cascade Range in north central Washington on the south slope of Railroad Creek valley at an elevation of 3500 ft. The mine may be reached by a 40 mile boat trip from the town of Chelan which is at the southern tip of Lake Chelan, to Lucerne at the mouth of Railroad Creek and an 11. mile bus ride up Railroad Creek to Holden. A11 freight and concentrate is moved over this route to Chelan Falls on the Columbia River which is on the railroad four miles below the town of Chelan. The mine is now producing 2000 tons of gold, copper, and zinc ore per day which is treated in the Holden mill. Gold-copper and zinc concentrates are made, the first of which is shipped to Tacoma, Wash., and the latter to Kellogg, Idaho, for smelting. Ore is broken by long-hole blasting using the Noranda system which has been modified to meet local conditions. Until recently, blastholes have been drilled by diamond drills. Now a partial substitution of percussion drill holes, drilled with tungsten carbide insert bits, is being made. Geology The ore body occurs as a replacement deposit in a highly metamorphosed series of sedimentary rocks, mainly gneiss and schists, in a shear zone several hundred feet in width and of undetermined length. Commercial ore has been found in mineable widths of 25 to 100 ft for approximately 2500 ft along its strike. The commercial minerals are chalcopyrite, sphalerite, and gold. During the period of mineralization considerable silicifica-tion took place giving the ore an abrasive drilling characteristic. Following the period of mineralization, numerous dikes were introduced into the ore body. The earlier ones were of granite composition having a width of a few inches up to 80 ft. These were followed by much younger, fine grained basic dikes which usually do not exceed 2 ft in width. Development of Percussion Blasthole Drilling Equipment Test work with the 1½-in. tungsten carbide bit was carried on in development headings for several months early in 1947. The short life of the bits, because of gauge loss caused by the abrasive nature of the rock, prevented its adoption for this use. However fast drilling speed and ability to drill a long uniform hole suggested its use for drilling blastholes in competition with diamond drills as diamond costs were steadily increasing and exper-ienced drillers were difficult to obtain. The 1½-in. bit was the largest available at the time initial test work was started with sectional steel. The 1½-in. hole limited the diameter of the steel thread and coupling which could be used. Type F couplings were first used but because of the small thread section excessive breakage of the steel was experienced. Type H couplings were tried next. In order to use this coupling which is 15/8 in. in outside diameter, it was reduced to 1 3/8 in. giving 1/8 in. clearance between the coupling and the hole. Rod breakage at the thread was substantially reduced but some coupling breakage was experienced, however the overall performance was considered satisfactory (see Fig 1 for illustration of coupling and thread). Early test work with the 1½ in. bit indicated machines of piston diameters larger than 255 in. would cause inserts to loosen or break. It was found however that the additional weight of the sectional steel cushioned the blow enough to prevent bit failures when 3-in. Leyners were used. Rods used with the 1½-in. bits were 7/8 in. q. o. for sectional steel and 1 in. q. o. for all chuck pieces. In May 1948, 2-in. tungsten carbide bits became available and test work was immediately started. The 2-in. hole approximated the AX (1 15/16 in.) diamond drill hole which was being used exclusively for blastholes and permitted their substitution for diamond drill holes in a ring without alteration of pattern, burden, or explosives. The 2-in. bit also gave room in the hole for larger couplings and permitted the use of heavier rods and 3½-in. machines, increasing the

Jan 1, 1950

By A. G. Guy

Thermodynamic activity rather than chemical composition is basic to the analysis of diffusion. This is the essential conclusion reached by Darken1-3 and by Birchenall and Mehl.4 If so, it is reasonable to expect that diffusion calculations should be carried out using activities. This paper will illustrate a method of employing activities in analyzing interstitial diffusion. For interstitial diffusion (of carbon in iron and probably generally) the diffusion of the solvent atoms, volume changes, and other such complexities not explicitly provided for in the usual diffusion equations cause a negligible error of the order of 1 pct. Therefore it is relatively easy to test the validity of an analysis based on activities in the instance of interstitial diffusion. The mathematical treatment of the more complex substitutional diffusion could be simplified once the adequacy of the activity method had been established for substitutional diffusion. Thus the present work has the purpose not only of providing a superior analysis of interstitial diffusion but also of indicating a possible approach to the more important question of an adequate treatment of substitutional diffusion. Development of the Diffusion Equation Although activities are convenient quantities to determine experimentally, they are derived from the more fundamental fugacities.9 Possible confusion in using activities can be avoided by basing equations involving their use on the relationship, dP = -D1d/ax dt [I] where, dP = the number of grams of solute crossing one cm2 in the time dt sec. D, = the diffusion constant for use with fugacities; it is assumed to be constant at a given temperature, and has units of secs. f = the fugacity of the solute in the solid solution; the units are those of pressure, dynes per cm2. x = the distance in cm. Eq 1 can be considered to be the basic form of the first Fick Law for one-dimensional diffusion. In order to convert Eq 1 into an equation involving activities, a choice of a standard or reference fugacity, f°, must be made: then. a = f [2] where a is the activity corresponding to the fugacity f. However, the value of a is also determined by the relation, a = a\c [3] where a is the activity coefficient and c is the concentration. For a given value of a (such as a = 1) it is evident that the units used for expressing concentration will affect the numerical value of a corresponding to a given amount of carbon dissolved in y-iron. Since weight per cent concentration is so widely used, this unit will be adopted as the standard in this paper. When the value off given by Eq 2 is substituted in Eq 1, the first Fick Law becomes, dP= -D,f°dl [4] Since D,f° is constant (at a given temperature), the second form of Fick's Law can be obtained in the usual manner, -dt D'f° dx [5] where c' is the concentration in g per cm3. In terms of weight per cent concentration, c, Eq 5 becomes, dc _ 100 d2a Tt = T /f w [6] where p is the density of the solid solution and will be assumed to be constant. In order to simplify Eq6, it is necessary to consider the standard state, f°. Standard states are chosen for convenience. There appears to be one especially convenient choice for the analysis of interstitial diffusion. If the activity coefficient, a, is set equal to unity at infinite dilution of the solute, 100 then — 100D1fl° is approximately equal P to the usual diffusion constant in dilute solutions. This is true since the activity, a, in Eq 6 can be replaced by the concentration, c, with little error in an infinitely dilute solution.* Here f1° is the standard fugacity necessary to achieve this standard state. It is proposed that a diffusion constant Da' be defined, Da1=100/pD1f1° [7] where A is the metal whose diffusion is * The second derivative of a is equal to the second derivative of c in dilute solution only if -da/dr- is. zero. Although theory does not require this condition, in the systems C in Fe, and Zn in Cu, dc is in fact found to be essentially zero.

Jan 1, 1950

By J. F. Smith, J. E. Davison

A value for the enthalpy of formation of z2 of -3.14 i 0.21 kcal per g-atom has been measured by the technique of acid solution calorimetry. This result is in quite good agreement with two earlier determinations by tin solution calorimetry and by direct reaction caloriinetry, and averaging of values determined from the three independent calorimetric techniques gives enhanced precision and accuracy with AHh8 (CaMgZ) = - 3.15 i 0.05 kcal per g-atom. For comparison with experimental data, values for the enthalpies of formation of CaMgz, SrMgz, and BaMgz of -9.8, -7.9, and -2.8 kcal per g-atom were estimated from a calculation based on the LVigizer-Seitz approximation as modified by Raimes for polyvalent elements. While complete quantitative accord between these calculated talues and available experimental data is lacking, nonetheless numerical accord is better than might be expected and, more importantly, parallel numerical trends are observed between experimental and calculated vnlues. WITHIN the past decade the enthalpy of formation of CaMg, has been determined a) from measurement of magnesium vapor pressures over binary Ca-Mg alloys,' b) by solution calorimetry with liquid tin as the solvent,' c) from measurement of hydrogen vapor pressures over ternary alloys of calcium, magnesium, and hydrogen,3 and d) by direct reaction alorimetr. The value from tin solution calorimetry is the most precise and is probably the most reliable, and this value is within the quoted uncertainties of the other three experimental results. The overall agreement among the four independent investigations is quite good, particularly so when the diversity of techniques is noted. On the basis of this agreement, CaMgz was chosen as a test material to evaluate the operation of a newly constructed apparatus for the determination of enthalpies of formation of intermetallic phases by acid solution calorimetry. This was believed to be a severe test because of the high chemical reactivity of both calcium and magnesium which reactivity presumably accounts for the fact that an early determination5 of the enthalpies of formation of Ca-Mg alloys by acid solution calorimetry yielded values significantly more negative than the four recent determinations. EXPERIMENTAL APPARATUS AND MATERIALS Experimental Apparatus. The enthalpy of formation of CaMg, was determined by measuring the difference between the heat evolved when dissolving the metallic compound and the heat evolved when dissolving equivalent amounts of unreacted metallic elements in hydro- chloric acid. This was done differentially with an apparatus consisting of twin calorimeters which were constructed to be as nearly identical as possible. The advantage of differential calorimetry is that systematic errors arising from the individual calorimeter design tend to cancel. A schematic representation of the apparatus is shown in Fig. 1. A dead air space around both calorimeters was provided by a large, thermally insulated jacket. Each calorimeter consisted of a 2-liter Dewar flask which was completely enclosed in a copper container. Each Dewar contained 1600 g of 2.5hr HCl to act as the solvent, and thermal effects resulting from solvent evaporation were minimized by covering the acid with 50 g of mineral oil. There was no detectable reaction between the acid and the mineral oil. Equivalent amounts of mechanical energy were added to the calorimeters through twin stirring rods which were driven at the same rpm by a single motor with the intent of the stirring being to maintain thermal equilibrium throughout the solvent. To calibrate the heat capacities of the calorimeters, known amounts of electrical energy could be added by passing measured voltages and currents for known times through submerged heaters, approximately 20 ohms, which were wound noninductively from Manganin wire. A 6-v storage battery was used as a power source, and a dummy heater was used as an exercise circuit to allow the battery to stabilize at a constant electromotive force before energizing one or the other of the calorimetric heaters. A type K-2 potentiometer was used to measure the potential drop across an energized heater while the current was determined from the potential drop across an external standard resistor. Times of energization were measured with an electric timer, and the electrical energy supplied to a heater

Jan 1, 1969

By C. G. Dunn, P. K. Koh

THE primary recrystallization texture in cold-rolled silicon iron, which is the matrix texture for developing the Goss texture or the cube-on-edge texture by secondary recrystallization at temperatures near 900°C,1-5,21 has not been adequately described. Thus from the present available information, it is not possible to explain satisfactorily both the grain-growth selectivity of the matrix and the often observed magnetic torque curve, which itself provides some information on the texture. Also lacking is information on the special annealing texture that develops in this material when the annealing temperature is 1200°C or higher and the rate of rise to temperature is extremely rapid. From the work of May and Turnbull5 and from unpublished work, it was known that isothermal annealing near 1200°C tends to reduce the extent of secondary recrystallization and that a much weaker cube-on-edge texture results if appreciable normal grain growth replaces secondary recrystallization. Koh and Dunn6,7 have obtained additional information on complex primary recrystallization textures from further studies made after normal grain growth. In these instances the initial textures were retained during normal grain growth. A similar result reasonably could be expected in the present study except for the presence of a grain growth ihibitor1-5,8,9.21 and its tendency to allow only a few grains to grow. However, any information on the orientations of grains in the special annealing texture, even if far from representative of the initial matrix texture, would provide useful information on the nature of the matrix texture. In the present texture study the method of Newkirk and Bruce,10 which is based on the methods of Geisler" and Schwartz, 12 is used to obtain a complete (110) pole figure of the primary recrystallization texture. The high-temperature annealing texture is determined simply from the orientations of a large number of selected grains. The kinetic nature of the process that produces the annealing texture is treated elsewhere13 and it is shown that a form of secondary recrystallization with a very high rate of nucleation occurs during rapid annealing at high temperatures. EXPERIMENTAL PROCEDURE Commercial 0.014-in. cold-rolled silicon iron strip (3.16 wt pct Si), prepared by two stages of cold rolling with an intermediate short anneal, was given a decarburizing 3-min anneal at 800°C. Me-tallographic studies indicated complete recrystallization. Short-time anneals at 900° C and at higher temperatures proved that secondary recrystallization had not begun at 800°C, in fact, the short additional anneals were still in the induction period of secondary recrystallization. A rapid rise to an annealing temperature of 1260°C (2300°F) was obtained in a BaC12and NaCl fused salt bath. The structures that resulted from anneals in the range 12- to 1000-sec duration were relatively finegrained, even though the growth was a form of exaggerated grain growth13 or secondary recrystallization with a high nucleation frequency.= Many of the grains were large enough for an X-ray study using a 5-mil X-ray beam. A transmission Laue Camera and an optical-mechanical stage for moving the grains into the X-ray beam were used. A total of 325 grains were X-rayed in this manner and the grain orientations determined. Complete (110) pole figures were obtained for the primary recrystallization texture using CoKa radiation at 30 kv in the back-reflection range, such as (220) for (110) poles, as described recently by Newkirk and Bruce.10 The low voltage serves to reduce the spurious white radiation to a minimum. A filter of 0.001-inch iron foil was located in front of the detector slit for transmission and in front of the beam slit for back reflection. A new and improved specimen holder extended the useful tilting angle range for transmission to 70 deg instead of 60 deg as previously reported.' A torque magnetometer was used to obtain the magnetic torque curves for a number of l-in. diam disk specimens. RESULTS The (110) pole figure of the material after recrystallization at 800°C is shown in Fig. 1. The positions of the pole concentrations are found to be

Jan 1, 1961

By David S. Bolin

INTRODUCTION This paper is directed toward those companies or individuals who may be considering the possibility of tin exploration or development projects in South America. Although tin deposits are known in many countries of Latin-America including Argentina, Peru, and Mexico, the majority of the deposits are located in Bolivia and Brazil. These two countries also account for virtually all the current production. Many factors affect the economic decisions related to mining and exploration projects in this region including the following: 1) Types of deposits 2) Anticipated size and grade of deposits 3) Deposit geometry and ore distribution as it affects the selection of a mining method 4) Metallurgical amenability 5) Governmental policies 6) Taxation 7) Anticipated capital and operating costs 8) Marketing costs This discussion will be directed toward each of these points. The majority of the presentation will be concentrated on Bolivia as this country is the principal producer in the region, however, the potential for further tin development in Brazil is excellent. Due to the remote and previously almost inaccessible location of the stanniferous districts of Brazil, little is known with respect to size and type of non-alluvial deposits which may exist in this vast country. TYPES OF DEPOSITS Two major types of deposits are currently being exploited in Bolivia; alluvial, and hard rock or lode deposits. Bolivia produces substantial tin from both types of deposit whereas virtually all Brazilian production to date has been from alluvial sources. Alluvial Deposits Brazil: The alluvial tin deposits of Brazil are located in river channels and flood plains adjacent to low mountain ranges. The terrain containing the tin placers is flat, marshy, and generally jungle covered. The major controls of alluvial cassiterite concentration are the ancient and present stream channels. The average tin concentration in the placers varies from 500 grams to approximately 1.0 kilograms per cubic meter. Tin reserves in the Rondonia field of Brazil have been estimated at 600,000 tons of fine tin. A bucketwheel suction dredge went into production in the Rondonia district in 1979, and four others have since been ordered. Several other gravel pump, and hand mining operations are also in production in this field. In addition to the Rondonia district, tin occurrences are known from Xingu, in Para state, and in the state of Minas Gerais. Bolivia: The alluvial deposits of Bolivia are somewhat more complex due to the variable geomorphology and abrupt topography. Conventional placer accumulations of cassiterite are found in many stream channels and intermontane basins surrounding the major lode tin producing regions. In addition to stream and valley placers, a group of deposits locally referred to as "Pallacos" or "Llamperas" which consist of colluvium, landslide debris and glacial moraine material, contain substantial tin reserves in some areas. The stream channel and intermontane basins contain the only deposits which are presently being exploited by mechanized methods. One dredge is working the stream channel below Cerro Rico de Potosi and another is operating in an intermontane basin southeast of the city of Oruro. Both of these dredges are operated by private companies. The average grade for these operations varies from 250 to 500 grams per cubic meter. The largest of the intermontane basin placers known at present is the Centenario deposit located adjacent to the Catavi lode deposit. This deposit contains approximately 170 million cubic meters of material with an average grade of about 150 grams per cubic meter. The "Pallacos" deposits are found on the slopes of mineralized areas and in glacial moraine. The mineralized material is generally completely unsorted, with tin and sometimes tungsten values distributed erratically throughout the entire mass. Most of these deposits are worked by small leasors or cooperatives; however, at least one mechanized washing plant is in operation southeast of Oruro. The size of these deposits may reach up to several million cubic yards. Grades are very erratic, but may range from 200 to 500 grams per cubic yard. In addition to the formal mining operations, virtually every drainage surrounding the major mines is being worked by independent' miners utilizing hand mining and jig or pan concentration. The aggregate production from these operations is substantial. The

Jan 1, 1982

By T. K. Perkins, L. R. Kern

A study of fluid mechanics, rupture of brittle materials and the theory of elastic deformation of rocks shows that, for a given formation, crack width is essentially controlled by fluid pressure drop in the fracture. Operating conditions which cause high pressure drop along the crack (such as high injection rate and viscous fluids) will result in relatively wide cracks. Conversely, operating conditions which cause low pressure drop (low injection rates and thin fluids) will result in relatively narrow cracks. Charts and equations have been derived which permit the estimation of fracture widths for a variety of flow conditions and for both horizontal and vertical fractures. INTRODUCTION There has been considerable speculation concerning the geometry of hydraulically created fractures in the earth's crust. One of the questions of practical importance is the width of fractures under dynamic conditions, i.e., while the fracture is being created and extended. Such width information could be used, for instance, to help estimate the area of a fracture generated under various conditions. Also, there has been a recent trend toward the use of large propping partiles.13, 15 Therefore is is desirable to know what factors can be varied in order to assure entry of the large particles into the fracture. There has been some work on fracture widths reported in the literature. In particular, there have been several Russian publications dealing with this sub-jeCt.1.31,3 These papers have dealt principally with the elastic theory and the application of this theory to hydraulic fractures. These studies have not led to an engineering method for estimating fracture widths under dynamic conditions. A recent paper3 has reviewed and summarized the Russian concepts. An earlier paper- from our laboratories also discussed the application of the elastic theory to hydraulic fractures. This first approach, based largely on photoelastic studies, has proved to be too simplified to accurately describe the fracturing process. However, these early thoughts have served as a guide during the development of more exact concepts. We would like to present in this paper our current concepts regarding fracture widths and some estimates of hydraulic fracture widths for several conditions. We believe that it is now possible to predict with fair accuracy the factors influencing fracture widths. Furthermore, the method of prediction has been reduced to a simple and convenient graphical or numerical calculation. CRACKS IN A BRITTLE, ELASTIC MATERIAL Many investigators2, 4, 30 have shown that competent rocks behave elastically over some range of stresses. Of course, if the tensile stress imposed upon a rock exceeds some limiting value, then the rock will fail in tension. In similar manner, there are some limiting shear stresses that can be imposed upon rocks. Hubbert and Willis11 have discussed the shear conditions which will lead to failure. Under moderate stress conditions (such as those likely to be encountered when hydraulically fracturing) and when stresses are rapidly applied, relatively, most rocks will fail in a brittle manner. Hence, for this discussion of hydraulic fractures in the earth's crust, we assume the rocks behave as brittle, elastic materials. Let us develop the discussion in the following way. (The following thoughts are applicable only to brittle materials.) 1. First we consider a brittle, elastic system. An energy balance will show the minimum pressure necessary to fracture rock, and from this pressure we calculate the minimum crack width resulting from extension of a hydraulic fracture. 2. Then we will show that, under ordinary fracturing conditions, fracture widths are appreciably greater than the minimum widths of extending fractures. In fact, we will find that crack width is controlled by fluid pressure drop in the fracture. 3. We will discuss pressure drops in fractures and resulting crack widths for various operating conditions and both vertical and horizontal fractures. 4. Finally, we will discuss the significance of these concepts, their relationship to fracturing pressures, etc. First, consider minimum fracture extension pressures. We can shed some light on this question by considering the theory proposed by Griffith7, 8 Yo explain the rupture of brittle, elastic materials. Griffith recognized that solid materials exhibit a surface energy8 (similar to surface tension in a liquid). The fundamental concept of the Griffith theory is that, when cracks spread without the application of external work (in the interior of an elastic medium which is stressed

By A. H. Daane, R. L. Myklebust

The yttrium-manganese system has been investigated by thermal, metallographic, and X-ray diffraction methods. There are three intermetallic compounds present: YMn2 which melts congruently, YMn4, which undergoes syntectic decomposition, and YMn,, which undergoes peritectic decomposition. The compound YMn4 is ferromagnetic at room temperature with a Curie temperature of 214°C. There are eutectics at 25.2, 60.9, and 82.0 wt pct Mn which melt at 878°, 1100°, and 1075°C, respectively. Crys-tallographic data are given for YMn4, and YMn12 . The terminal solid solubilities are low. In a general program of study of yttrium metal in this laboratory some alloy systems of this metal with elements of the first transition period have been examined. This work was originally instigated by experiences in cladding yttrium with jackets of some protective metals such as Inconel for high-temperature service in air.' In some cases a low-melting phase was observed to form between the Inconel and the yttrium resulting in failure of the samples. In characterizing this reaction, a survey was made of the systems of yttrium with chromium, manganese, iron and nickel,, and it was found that a eutectic was formed between these metals and yttrium on the yttrium-rich side of the system. This present study of the Y-Mn system was carried out to examine in more detail the alloying nature of yttrium, and to correlate trends that have been observed in previous related studies. It was observed by Voge13 that in the systems of lanthanum, cerium, and praseodymium with each of the metals in the first transition series, the tendency to form compounds diminished in the order nickel, cobalt, and iron while no compounds were formed with manganese, chromium, or titanium. Beaudry and Daane4 observed a similar behavior in the systems of yttrium with some members of the first transition series except that the tendency for compound formation was greater. Both the Y-Ti5 and Y-Cra systems consist of simple eutectics, while in the Y-Fe,7 Y-CO, and Y-Ni4 systems, there are four, eight, and nine compounds, respectively. In addition to the above trends, the similar atomic radii and electronegativities of yttrium and thorium invite a comparison between their alloying behaviors with a common element such as manganese. In crys- tallographic studies, Florio et al.' have identified three intermediate phases in this system which are ThMn2, Th6Mn23, and ThMn,,. Gschneidner and Waber10 have examined published information on alloy systems of the rare-earth metals and have correlated this information with current alloying theory. From their study, they predicted that the Y-Mn system would contain one intermetallic compound. On the basis of this prediction, the trend in the alloying behavior of yttrium with the elements of the first transition series and the alloying behavior of thorium with manganese, one might expect from one to three intermetallic compounds to form in the Y-Mn system. A consideration of Hume-Rothery's rules of alloying based on size-factor, electronegativity, and valency suggested a small terminal solubility and possible compound formation. The present study was undertaken to confirm these predictions of low terminal solid solubility and compound formation and to establish the general alloying behavior of yttrium with manganese. EXPERIMENTAL Materials. The manganese used in this investigation was obtained from the Foote Mineral Co. as electrolytic plates of 99.9 pct stated purity; the yttrium metal was prepared in this laboratory. Table I gives the analyses of these materials. For the solubility studies at the yttrium-rich end of the alloy system, distilled yttrium, whose major impurity was 200 ppm Ti, was used. Preparation of Alloys. The alloys were formed by comelting the two metals in an are-melting furnace under an atmosphere of argon. The buttons thus formed were inverted and remelted three to five times to promote homogeneity. Due to the high vapor pressure of manganese, it was assumed that the weight lost during are-melting was all manganese. This assumption was based on the very good agreement observed between calculated compositions and chemical analyses of several alloys. The compositions of the dilute alloys used for solid solu-

Jan 1, 1962

By J. K. Elliott, P. H. Kelly

Many engineering functions such as surface metering work and laboratory compressibility check points involve the use of liquid densities of light hydrocarbon mixtures at various pressures and temperatures. However, at the present time, no simple reliable method exists for determining density variation, particularly if the composition of the liquid is unknown. Consequently, a study was undertaken to develop and present a simple and accurate method of predicting density variation of a light hydrocarbon liquid with pressure and temperature, knowing only the density of the liquid at some condition. The experimental liquid compressibility data from API Project 37 by Sage and Lacey' have been considered to be accurate within 0.5 per cent and cover a wide range of pressure (14.7 to 10,000 psia), temperature (100" to 400°F) and molecular weight (up to 150). From these data, a set of liquid density curves, which relate density to pressure, temperature and molecular weight, was developed. These curves make it possible to predict density variation with pressure and temperature. Compared to extensive laboratory compressibility data on a complex, light hydrocarbon liquid, the use of the liquid density curves resulted in an average error of less than 0.5 per cent. Based on the results of this analysis, it is concluded that the set of liquid density curves developed from the data of Sage and Lacey provides an accurate and simple method for predicting the density variation of light hydrocarbon liquids when the density at some condition is known. These curves should be very helpful in many engineering calculations, particularly in the surface metering of light hydrocarbon liquids. INTRODUCTION Many situations arise in field and engineering laboratory work, such as reservoir engineering studies, check of experimentally determined laboratory data and orifice flow-meter formulas, where liquid density factors at various pressure-temperature conditions are required. Also, the need for accurate light hydrocarbon liquid information has become more important with the advent of miscible-type displacements for secondary recovery purposes in oilfield operations. Several reliable methods are available1 - "or determining the density of liquid hydrocarbons if the composition of the liquid is known. However, there is a definite lack of methods for accurately determining the variation of density when the composition of the liquid is unknown. The purpose of this study is to review the various methods for determining hydrocarbon liquid densities and to develop a simple and reliable method of determining variation in density of light hydrocarbon liquids with pressure and temperature when the compositio~n of the liquid is unknown. METHODS FOR DETERMINING DENSITY OF LIQUIDS OF KNOWN COMPOSITION Sage, Lacey and Hicks' have proposed a method to predict the density of light liquid hydrocarbons by using partial molal volumes. Data are available on experimentally developed partial liquid volumes of hydrocarbons over a rather limited range of temperature, pressure and composition. The partial mold volume method has proved satisfactory for determining the density of some hydrocarbon liquids when the composition is known. Within the range covered in the Sage, Lacey and Hicks1 data, the results agree within about 3 per cent of the experimental values. Hanson mentions the limitation of this method to a composition range of approximately 10 per cent by weight of methane, which will not allow this correction to cover most low molecular weight-light hydrocarbon liquids. Standing and Katz2 studied data on light hydrocarbon-liquid systems containing methane and ethane at high temperature and pressure and have presented a method for determining liquid densities, assuming additive volumes for all components less volatile than ethane and using apparent densities for methane and ethane. The compressibility and thermal-expansion curves used by Standing are based on assumptions that compressibility of a hydrocarbon liquid at temperatures below 300°F is a function of the liquid density at 60°F and that thermal expansion of the liquid is affected little by pressure. The information required to use this technique with an example problem is furnished by Standing.' Hanson eports an average error of - 0.5 per cent using the method of apparent densities in calculating liquid densities of several volatile hydrocarbon mixtures. However, as implied, the apparent density method is not applicable for liquid density calculations when the composition of the liquid is unknown. Watson- as presented a method

By K. Sallmann

Spurred by a variety of factors, coal flotation is making headway among the preparation plants of West Germany. The author gives some statistics on German coal flotation plants and information on the properties of the feed and quality of the derived products. Types of machines and reagents used, dewatering practices, tailings disposal, and thickening operations are covered. There is special emphasis on the many-sided problems that confront German coal preparation engineers. The coal mining industry of West Germany is concentrated in three coalfields: the first on the Ruhr and the Rhein rivers, the second on the Saar river, and the third near the frontier between Germany and the Netherlands, around the towns of Aachen and Erkelenz. The total run-of-mine production of these three coalfields amounts to 736,000 tpd which come from 145 collieries. There are 121 washeries, 43 of them with a flotation plant. The total throughput of these 43 washeries is 280,000 tpd, out of which 26,000 tons (9.3 pet of the washery feed coal) are cleaned by flotation. The capacity of the individual flotation plants varies within relatively wide limits, the average being 40 tph and the capacity of the largest flotation plant being 120 tph. During the last few years, the number and size of flotation plants have been steadily increasing, although flotation must be looked upon as an expensive and rather complex cleaning process. The considerations which have led to the widespread application of flotation may be summarized as follows: 1) In making coking coal, it is seldom possible to add uncleaned fines to the coke oven charge, as their ash content is too high. If, however, the ash content of the fines is reduced to a maximum of 7 or 8 pet, they can be admixed to the washed and crushed small sizes without difficulty. This means, naturally that revenue is increased since the price of coking fines is always higher than the price for dust or uncleaned wet fines. 2) To prevent silicosis and pneumoconiosis, water infusion and spraying of the coal are practiced much more today than ever before. As a result, moisture content of run-of-mine coal has markedly increased and the washery feed coal contains more and more slurry instead of dry dust. The price of slurry, how- ever, is very low, and in many cases it is impossible to sell filtered raw slurry with a moisture content of 20 to 25 pct and, at the same time, 20 to 25 pct of ash. Reduction of the ash content of these slurries improves the possibility of dewatering them and, in this way, also enhances the marketability of this product. 3) The new severe laws and regulations against pollution of air and rivers make it necessary to de-dust coal better than in the past and to reduce the quantity of the waste water from coal preparation plants and their solids content to a minimum. 4) Even if there were no compulsory reasons to clean the fines, flotation will often lead to an increase in the overall yield. Although not the only application, it appears that the treatment of coking fines is the primary field for the flotation process in coal preparation. It must not be overlooked, however, that a series of arguments may be advanced against flotation: 1) Flotation is an expensive process because, in addition to the cleaning operation itself, the dewatering of the froth and the disposal of the tailings is very costly. 2) Operation of a flotation plant requires well trained personnel. 3) Filtered froth has about a 20 pct moisture content and, therefore, if mixed with the cleaned small coal it causes an undesirable increase in water content of the coke oven charge. For this reason it is necessary to take additional measures for dewatering washed small coal and this, of course, entails additional expense. 4) Disposal of flotation tailings involves very difficult problems, particularly in the highly industrialized regions. An investigation covering 32 flotation plants of Western Germany shows the following composition and properties of their feed:

Jan 1, 1961

By Robert E. Green, P. W. Kingman

Application of a constant geometry compression test to single crystals of aluminum of selected diameters from 1/4 to 1/64 in. showed the presence of a diameter-dependmt size effect. The most pronounced effects were found in those crystals oriented for single slip, while for specimens possessing orientations in the comers of the standard stereographic triangle virtually no size effect was exhibited. The yield stress of the crystals oriented for single slip was found to increase with decrease in specimen diameter, while the strain-hardening rate was found to be lower for the smaller specimens. The experimental results are in general agreement with those of other investigators obtained from lensile tests on copper and aluminum crystals. THE earliest systematic investigation of a possible size effect on the plasticity of metals was that of no,' who in 1926 performed tensile tests on cylindrical aluminum single crystals with diameters of 3 to 8 mm. Ono concluded that the gross stress-strain curve did not show a diameter dependence, but that the resistance to slip for strains of 0.1 pet and less appeared higher for 3-mm-diam crystals than for larger sizes. Later studies of aluminum by Maddin et al2 tentatively concluded that a size effect exists, but the conclusions were again open to question because of inconsistencies in the experimental data. Wu and Smoluchowski3 had previously shown that the slip system activated in a single-crystal sheet specimen of aluminum is a function of the specimen cross section in the slip direction, but no stress-strain data were obtained. Subsequently Fleischer and Chalmers4 studied the effect of the length of the slip direction of the primary-slip system on the stress-strain curve by testing aluminum crystals with geometrically dissimilar cross sections. In the course of this investigation a size effect was indicated in rather large crystals; however, the number of these tests was small. Other investigators have indicated that a size effect in aluminum is appreciable only for diameters of 0.5 mm or less.5, 6 Size-effect studies have also been carried out on copper crystals, the most detailed being that of Suzuki et a1.7 who performed tensile tests on specimens of many diameters ranging from 2 to 0.12 mm. Suzuki found a strong size dependence in the easy-glide region, both the extent of the easy glide and the hardening rate in easy glide were size-dependent, and the size effect was found to be orientation-dependent. Suzuki's results are in agreement with the less extensive observations of Pater-sonB and those of Garstone et al.9 A size effect was found by Rebstock using tubular copper crystals.'0 Size effects have also been noted in a brass,6, 11 in cadmium,12'19 and in hexagonal crystals.14 All the previously cited works have been entirely concerned with the variation of specimen cross section. The effects of specimen length and the change of specimen geometry which results from using progressively thinner specimens while maintaining the same specimen length have been largely ignored. A theoretical discussion of the effects of specimen length and geometry has been given by Hauser and Jackson,15 who predict a grip effect on easy glide as a function of specimen geometry provided that the specimen dimensions are large compared with the spacing between the slip bands, and by Fleischer and Chalmers,18 whose analysis of grip effects resulting from lattice rotation predicts an increase in easy glide with an increase in specimen length. A study of size and geometry effects in aluminum crystals by Kitajima and shimba17 indicated increasing amounts of easy glide in specimens of increasing length and identical cross section, and nearly identical stress-strain curves for specimens of different sizes having constant length-to-diameter ratios. Since the present study is primarily concerned with diameter dependence, the following factors were taken into account: specimen material, specimen geometry, testing method, range of sizes to be tested, and possible influence of surface and volume effects. Aluminum was chosen because of the present lack of conclusive results and the seeming possibility of size effects at relatively large diameters, the

Jan 1, 1964

By J. Lohrenz, C. R. Clark, B. G. Bray

Procedures to calculate the viscosities of in situ reservoir gases and liquids from their composition have been developed and evaluated. Given a composition expressed in methane through heptanes-plus, hydrogen sulfide, nitrogen and carbon dioxide together with the molecular weight and specific gravity of the heptanes-plus fraction, the procedures are capable of calculating the viscosity of the gas or liquid at the desired temperature and pressure. The procedure for reservoir liquids was developed using the residual viscosity concept and the theory of corresponding states, and was evaluated by comparing experimental and calculated results for 260 different reservoir oils ranging from black to highly volatile. The average absolute deviation was 16 per cent. This is the first known procedure for calculating the viscosity of reservoir liquids from their compositions as normally available, i.e., including the heptanes-plus fraction. The procedure for reservoir gases uses a sequence of previously published correlations. Evaluation of the procedure was accomplished by comparison of 300 calculated and experimental viscosities for high-pressure gar mixtures in the literature. The average absolute deviation was 4 per cent. The calculations are useful for (I) determining viscosities in compositional material balance computations and (2) predicting the viscosity decrease which occurs when gases, LPG, or carbon dioxide dissolve in reservoir oils. INTRODUCTION Methods to predict viscosities of reservoir fluids from the normally available field-measured variables have been presented. Beal,1 Standing,2 and Chew and Connally3 orrelated oil viscosities with temperature, pressure, oil gravity and gas-oil ratio. Carr, Kobayashi, and Burrows4 and Katz et al.5 have presented correlations for reservoir gas viscosities as a function of temperature, pressure and gas gravity. Lie all intensive physical properties, viscosity is completely described by the following function: Eq. 1 simply states that viscosity is a function of pressure, temperature and composition. These previous correlations1- hay be viewed as modifications of Eq. 1, wherein one assumes more simple functions may be used. The assumptions are practical, because the composition is frequently not known. Further, the assumptions are sufficiently valid so that these correlations are frequently used for reservoir engineering computations. In compositional material balance"' computations, the compositions of the reservoir gases and oils are known. The calculation of the viscosities of these fluids using this composition information is required for a true and complete compositional material balance. For reservoir gases, Carr, Kobayashi and Burrows4 have presented a suitable compositional correlation. For reservoir oils, no correlation is available, and data from reservoir fluid analyses have been used7-9 for compositional material balance calculations.* From a theoretical point of view, this is entirely invalid. The reservoir fluid analysis, whether flash, differential, or other process, does not duplicate the compositions which occur during the actual reservoir depletion process, therefore the viscosities measured during reservoir fluid analysis are not those which occur in the reservoir. From a practical point of view, the "error" of using viscosities from reservoir fluid analysis is of varying and unknown significance. One can say qualitatively that the error is greatest where compositional effects are greatest, i.e., for volatile oil and gas condensate reservoirs and pressure maintenance operations. The first requirement to obtain a quantitative estimate of the significance of the error is to develop a reliable compositional correlation for the viscmities of reservoir oils. No such correlation has been available. Consistent with this requirement, the objective of this study was to develop a procedure to predict the viscosity of reservoir fluids from their compositions. Normally, the compositions of reservoir fluids are available expressed as mole fractions of hydrogen sulfide, nitrogen, carbon dioxide and the hydrocarbons methane through the heptane-plus fraction, with the average molecular weight and specific gravity of the latter. The final correlation was to use the composition in this form. While the more challenging objective of the study was the development of a correlation for the viscosities of reservoir oils, the viscosities of reservoir gases were also studied. The end result of the study was a procedure to calculate the viscosities of reservoir gases and liquids suitable

Jan 1, 1965

By W. W. Stephen, J. P. Walsted, W. J. Kroll

FOR the production of carbides, various furnace types are available, especially those using arc, resistance, and high-frequency heating. Selection of a specific means of heating depends primarily on the material to be treated and the physical properties of the carbide produced. In the present case, zirconium carbide had to be prepared on an industrial scale as a raw material for the production of anhydrous zirconium chloride. Considering that a rather expensive pure oxide was to be used, the arc-furnace treatment recommended for zircon sands in a previous publication' was ruled out because of the considerable volatilization and dust losses caused by the blast of the arc. For this reason, either high-frequency or resistance heating seemed to offer more promise. Since there was not enough capacity of the former available, resistance heating was chosen. It was first thought that the Acheson silicon carbide furnace would be suitable for the present purpose, but the voltage in such a furnace, in which the current passes through the batch, varies from 220 to 75 v from the start to the end of a run. This variation is so great that a special tap transformer would have been required. Trouble was also expected by local melting of the carbide. Pure zirconium carbide melts at about 3527°C, but the melting point is brought down to 2427°C, according to Agte,2 when an excess of 6 pct C is present in the carbide. This we found confirmed by experiments in a high-frequency furnace. Excess carbon is needed in the batch to obtain a complete reduction. Fusion of the charge would cause great difficulties in an Acheson-type furnace because of the good electrical conductivity of the carbide as compared with that of the loose batch. Also, fused carbide is much more difficult to chlorinate than the spongy product that can be made in the radiation furnace described below. It was apparent that, to obtain a good-qual-ity zirconium carbide, the heat input would have to be well-controlled. The hairpin-resistor principle seemed to offer possibilities in this regard, and a furnace of this type was therefore developed. The advantages of the hairpin-resistor radiation principle have been discussed in previous publications, and a split-tube graphite-resistor furnace," now increasingly used in various laboratories, as well as a centrifugal quartz melting furnace4 of this type, has demonstrated the usefulness of this heating method. The hairpin-heater element has the following definite advantages over a straight resistor of the type used, for instance, by Georges:5 Its resistance is four times greater; it can expand freely; it is sturdier because of the larger diameter, and it has a larger radiation surface; there are no hot contacts that might wear out or overheat; only one clamp is used which permits assembling all electrical leads at one side of the furnace, making the other sides easily accessible to the operator. The shorter element and its larger diameter permit greater concentration of heat. The furnace developed is shown in fig. 1. The box (I), made of 2 1/2-in. graphite plates, has inside dimensions of 23x17x16 in. It contains the briquet-ted batch (2). The box is embedded in lampblack (3) up to the cover plate. The cover plate contains an opening for the gas escape (4) and for the observation hole (5), which permits measuring the temperature with an optical pyrometer. The cover plate is embedded in charcoal (6). The lampblack is contained in the insulating brick lining (7), held in the 1/4-in. sheet steel box (8). The graphite box is set on two rows of triangular graphite bars (9). The hairpin-heater element (10), the dimensions of which are given below the main drawing, extends horizontally in the graphite chamber and radiates freely on the batch. A graphite tube (11) keeps the lampblack from falling into the slot. The split electrode, which in reality is turned 90" against the drawing, is so arranged that the slot is vertical. The water-cooled packing gland (12) is insulated by an airgap from the heater element. A thin pipe (13)

Jan 1, 1951

By W. W. Eckles

This paper is presented as a suniniary report of the use of well gas composition correlations obtained from mass spectrometer recordings as a means of identification and determination of reservoir continuity. Conventional methods for detecting composition differences are en-pensive, elaborate, and difficult to obtain. This excludes the use of extensive composition data for most applications. During recent years the mass spec-trometer has come into general use as an analytical tool in petroleum refineries. The use of mass spectrometer composition patterns ir~ characterizing or "finger-printing" the produced gas from a reservoir, presents a novel method for correlatitlg gas samples from well to well. The mass spectrometer provides a trace similar to an electric log. having peaks which represent the abuntlnnce of certaitz hydrocarbons in the well gas sample. Without going further into the detailed analysis the idea has been advanced that these traces or patterns could be used as a means of identifying a particular natural gas. This theory has proven to be essentially correct. The mass spectrometer pattern method is simple and cheap as COi?7pared to other standard methods. It greatly facilitates the solution of reservoir and geological problems in which correlation of well gas Com-positions is a factor. Specific field applications have been made. This paper concerns the results obtained in 465 individual gas analyses from 35 fields and 77 res- ervoirs. In a number of cases it has been found that such data have been extremely valuable in the determination of reservoir continuity. In at least one case, the method was a valuable contribution in tracing a reservoir from sand to sand in a coinplex fnulted field involving n11rnerous gas reservoirs. Field applications are presented to illustrate the possibilities of the method at the present stage of developnient and to stimulate the ernployrnent of this new approach by geologists and petroleum engineers in the industry. INTRODUCTION Identification of producing horizons and the determination of reservoir continuity are often a problem in those areas where dome structures and highly faulted sands are encountered. To complicate the picture further, there may be numerous sands, one on top of the other which dip and diverge in different directions. Even though it may be possible to develop some solutions to the preceding problems on the basis of the geological and reservoir data on hand. it is readily recognized that substantiating data based on independent methods would he extremely valuable. It has been found through field studies that correiation of well gas composition can be used to advantage in the geological and engineering study of a complex reservoir identification problem. METHOD FOR COMPARISON AND CORRELATION OF WELL GAS SAMPLES Since a large number of well gas samples are required in a gas identification or reservoir con- tinuity problem, it is necessary that a method of analysis be employed which can detect differences in composition readily and inexpensively. Although detection would be possible by means of low temperature fractional distillation (POD) analpsis, the method requires a relatively large sample and is comparatively slow and expensive to run. The mass spectrometer affords an inexpensive and precise analysis of small well gas samples taken at the surface which are about 1/300 as large as a POD sample. These samples can be obtained by regular field personnei and shipped to the spectrometer for analysis. It is, therefore, a practical approach to the problem. A typical record from the mass spectrometer is illustrated in Fig. I. The peaks on the record represent the abundance of ions produced from the different hydrocarbon molecules making up the gas sam-ple. In well gas comparisons only five peaks are employed, since the other peaks are formed from the same gas molecules and furnish no additional information. The five peaks used represent the abundance of methane, propane, ethane, butane and heavier, and oxygen. They are referred to respectively as the 16, 29, 30, 43, and 32 peaks. The oxygen peak is used to correct for air content in

Jan 1, 1958

By Jun Hino, P. G. Shewmon, P. A. Beck

THE investigations of Crussard,' of Guinier and Tennevin,' and of Dunn and Daniels," indicate that the subgrains formed in a cold worked and annealed metal are capable of growing at each other's expense during annealing, if the temperature of annealing is sufficiently high and the time is long enough. The results of Dunn and Daniels are particularly convincing in showing that subgrain growth is essentially the result of the free surface energy associated with the subboundaries. In subgrain growth, as in ordinary grain growth, energy is gained as a result of the decrease in total subboundary surface area per unit volume. Recently, Wood and Scrutton4 found that the rate of subgrain growth upon annealing increased very considerably, if simultaneously a creep strain was applied to the specimen at a low strain rate. Working with 99.98 pct pure fine-grained aluminum, these investigators found that the continuous X-ray diffraction back-reflection rings of material strained at room temperature remained continuous after heating for ten days at 250 °C. However, when heated at the same temperature under a stress of 1000 psi even for only three days, the formerly continuous X-ray diffraction rings broke up into numerous dots, which were fairly clearly separated from each other. The continuous X-ray diffraction rings were interpreted as indications of a very small subgrain size, not resolved by the X-ray diffraction method used. The breaking up of the continuous X-ray diffraction ring during annealing under stress was taken as an indication of a great increase in subgrain size, so that the individual subgrains could then be resolved. The effect of simultaneous strain at a low strain rate in accelerating subgrain growth, discovered by Wood and Scrutton and designated by them as "cell growth," is of fundamental importance. The experiments described in this note were carried out in order to confirm Wood and Scrutton's results by direct metallographic observation. Also, information was sought as to the minimum creep strain necessary to produce this effect. A fine grained high purity aluminum strip was prepared by alternate 33 pct rolling and annealing treatments for 1 hr at 350°C. Specimens cut from this strip were subjected to a relatively fast creep strain of 7.2 pct in 3.5 min at 300°C under a constant load initially corresponding to 1185 psi. The subgrains set up were large enough (about 0.015 to 0.03 mm) to be clearly observed (Fig. 1) at X200 magnification with polarized light, after electrolytic polishing and anodic etching, producing a fine oxide film." The corresponding X-ray diffraction pattern is shown in Fig. la. After the fast creep strain treatment a portion of the specimen was subjected to a creep strain of 8.3 pct in 44 hr at 350°C under a constant load initially corresponding to 320 psi. Another portion, annealed under the same conditions, but not strained, served as control specimen. The subgrain size of a typical area of the specimen annealed under strain and of the one annealed without strain is shown in Figs. 2 and 3 (X-ray diffraction patterns, Figs. 2a and 3a). Annealing without strain produced clearly observable subgrain growth (subgrain size: about 0.03 to 0.05 mm). The effect of simultaneous strain was to increase greatly the rate of subgrain growth (resulting in a subgrain size of approximately 0.05 to 0.13 mm), in accordance with Wood and Scrutton. In another experiment, the effect of the amount of simultaneous strain was studied. The initial subgrain structure was set up by fast creep, as described previously. The specimen was then heated at 350 °C under a constant load initially corresponding to 320 psi, as above, for 2.2 hr (0.24 pct strain), and 8.8 hr (0.58 pct strain). Comparison with the corresponding unstrained control specimens by means of X-ray diffraction showed that 0.58 pct strain definitely had an effect, but the effect of 0.24 pct strain was doubtful.

Jan 1, 1953

By D. Turnbull, J. H. Hollomon

THERE is a large body of evidence'" indicating that solidification during the liquid-solid transition is usually induced by heterogeneities present in the liquid. By dispersing liquid metals into small droplets, the impurities responsible for catalyzing solidification are isolated within a small number of these droplets. The effect of the foreign body therefore is restricted to a single drop by this technique. Thus upon cooling below the melting temperature, solidification is initiated by homogeneous nucleation in the majority of the droplets that do not contain impurities. In the case of solidification of liquid metals, the activation energy for nucleation is so great that its rate changes by orders of magnitude for a change in temperature of only several degrees centigrade.' Effectively homogeneous nucleation occurs at a critical temperature upon continuous cooling. Thus by microscopic observation of single particles during cooling, a temperature at which the rate of homogeneous nucleation becomes sensible can be determined.3 since at the temperatures at which nucleation occurs in the absence of impurities the rate of crystal growth is extremely rapid, the temperature at which the entire particle solidifies is very nearly the temperature at which the nucleation of the solidification occurs. Thus for liquids that freeze at high temperatures the onset of nucleation can be established by simply observing the temperature at which the marked heat evolution and increase in brightness of the particle occur. For liquids that freeze at lower temperatures the onset of nucleation can be determined by a rumpling and change in shape of the particle resulting from its solidification. The microscopic technique for observing the solidification of small particles has already been described." In earlier papers the nucleation of solidification of pure metals 5,6 and of alloy systems7 showing complete liquid and solid solubility have been described. In the present paper, the observations are extended to a simple eutectic system (Pb-Sn) where the possibility of the formation of two solid phases exists. Metals for the investigation were obtained from the American Smelting and Refining Co. in the form of pure lead and pure tin, 99.8 and 99.9 pct purity, respectively. An ingot of each of the pure metals was made into shot by heating the metals at a temperature about 50 °C in excess of the melting point and pouring the liquid slowly into a container of water at 15°C. Samples of the shotted pure metals were weighed out to make alloys containing 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, and 90 atomic pct Pb. Samples of each alloy were then melted in separate beakers. Each melt was poured through a pyrex funnel into a cylindrical mold (% in. ID). The casting solidified in 10 to 20 sec. The inside of the mold as well as the funnel through which the metal was poured were coated with graphite to eliminate adherence of the metal. Analyses were performed on some of the compositions and are given in Table I. The compositions also were checked for these samples and for those that were not analyzed by determining the spread between the liquidus and the solidus upon melting the small metal particles. These measurements agreed as well with the nominal compositions as the analyses listed above. Results The results of the supercooling experiments for the several alloys are summarized in Table II and plotted on the constitution diagram in Fig. 1. Data for the pure lead and pure tin were taken from earlier investigations. The values for the maximum supercooling of the several alloys are the average of several determinations on a number of drops of each alloy. The maximum value in any determination was within about 2 pct of the average. For the alloys containing from 20 to 60 atomic pct Sn, inclusive, two marked changes of the surface structure were observed upon cooling. At the higher temperature, after the first appearance of the solid phase it continued to grow slowly at a constant temperature and then stopped. At the lower temperature the alteration of surface structure was abrupt. For the alloys containing from 70 to 95 atomic pct Sn, inclusive, an abrupt change in surface structure was observed at a single critical temperature.

Jan 1, 1952