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By L. D. Hall, S. J. Rothman

DIFFUSION coefficients of RaD (PD) and RaE (Bi) in a Bi-0.255 atomic pct Pb alloy have been measured by the methods outlined in a previous paper.' The following changes were made in the experimental procedures: the bath was made up of about 400 to 500 g Bi; and no correction was made for the volume change of bismuth on melting. The data are presented in Table I and Fig. 1. A least-squares analysis of the data yielded D = (0.120 t 0.09) exp ( -9680 + 1070/RT) D- (0.0465 0.001) exp (-8100 + 466/RT). Statistical analysis of the data indicated that the activation energies are significantly different at the 50 pct level, but not at the 75 pct level, while the D values are significantly different at the 97.5 pct level, but not at the 99 pct level. The differences are thus not as clear-cut as they were for lead. However, bismuth diffuses faster than lead in high bismuth alloys as well as in lead. The high activation energies, more than twice the value calculated from viscosities, are in good agreement with the results of Grace and Derge.' No data were obtained at higher temperatures because of gas bubble formation in the capillary. Acknowledgments This work was supported by the Office of Ordinance Research under contract DA-04-200-ORD-178. The authors thank 0. P. Vieria and M. Volpe for help in the experimental work.

Jan 1, 1957

Dr. Healy's paper presents a concise state-of-the-art description of mechanistic, thermodynamic models available today for design, interpretation, and trouble-shooting flocculation processes and problems. Coagulation by manipulation of inorganic electrolyte concentrations is controlled largely by adjustment of electrostatic repulsive forces, guided by well understood theory. For simple solids in simple electrolytes, existing models are capable of predicting the influence of potential determining ion and one dominant, non-reacting, symmetrical electrolyte concentration on floc stability quantitatively. Concentration changes required to coagulate and disperse can be estimated. Convenient, easily understood means are available for summarizing the effects of key variables, (e.g., pH, ionic strength) on dispersion stability, and estimating tolerance to unintentional changes (Matijevic coagulation domain diagrams). These models have not been developed to the point that mixed unsymmetrical electrolytes can be easily handled. They are capable of describing two- solid heterocoagulation, but not “n-solid” heterocoagulation. In combination with recently developed computer codes for simultaneous computation of solution equilibria, ion exchange and electrical double layer properties (1,2), these models .should be capable of describing simple clay coagulation systems. This has not been done. Models developed for polymer flocculation are valuable interpretive tools, have some qualitative predictive value, but are less potent in quantitative needs. Most real systems probably involve more than one mechanism of floc stabilization. Little has been done toward developing combined models, even in the simplest systems.

Jan 1, 1979

By W. D. BRENNAN

FOR a considerable number of years past, there has been a shortage of experienced coal miners at the coal mine of the Phelps-Dodge Corp. This is probably due, to some extent, to the mines being so far south of the main western coal producing regions, so that experienced men secure employment before reaching this point. These mines are at Dawson, New Mexico, which is in Colfax County, near the Colorado line. The district is known as the Raton field, and the seam being worked is known as the Raton or Blossburg seam. The mines operated are Nos. 1 to 6, 8 and 9. The daily out- put at the present time, with restricted operations, is about 4000 tons, but the daily capacity is about 5500 tons. The mines are so grouped that the coal is dumped over four tipples. The mines are about twenty-five years old and extend as much as three miles under ground; they are all drift openings, with trolley, storage battery, and mule haulage. At the same time that the shortage of miners existed there was a surplus of common labor seeking employment. We learned that the Copper Queen. Branch of Phelps Dodge Corp. conducted a training school in one of its mines which had worked out very satisfactorily, and thus gained the idea of attempting such a school in the coal mines at Dawson.

Jan 1, 1929

By Henry Mulryan

Diatoms are microscopic aquatic plants of the order Bacillariaceae. They are unicellular plants with skelctons made up of amorphous opaline silica. The skeletons show highly ornate, complicated geometrical designs. Diatoms live in water virtually everywhere. They are found in clean sea water, brackish water, and fresh-water lakes and ponds. When conditions are right, diatoms propagate by subdivision in huge numbers. Alkalinity, temperature, and the presence of high concentrations of silica in the water largely control diatom life. When the diatoms die the skeletons drop to the bottom of their habitat to form oozes of varying thicknesses. Diatomites Diatomite, or diatomaceous earth, is composed essentially of the siliceous remains of the diatoms, although other organic skeletons are also present, especially in sea-water deposits where radiolaria, sponges and silico-flagellates are common. Impurities are generally carbonaceous material, fine-grained silt, volcanic ash and dust, and occasional coarse grains of sand. Diatomites are marine, brackish, or fresh-water, depending upon types of diatoms and their method of deposition. Diatoms More than 8000 species of diatoms have been named and classified. Some are definitely classified as to their habitat; some are so well recognized as to their living conditions that they can be stated to be diagnostic types, and when encountered in a deposit determine the origin of the deposit. Some of the commoner types of diatoms found in the freshwater diatomites on the Pacific Coast are: Cymbella lanceolata Agardh Fragilaria virescens Ralfs Encyonema prostratum Ralfs Diatoma vulgare Dory Surirella biseriata Brebison Eunotia major Ehrenberg Amphipleura pellucida Kützing Stictodiscus niagarac Ehrenberg Gomphonema geminatum Lynberg Melosira granulata Ehrenberg Epithemia turgida Kützing

Jan 1, 1942

By Henry Mulryan

Diatoms are microscopic aquatic plants of the order Bacillariaceae. They are unicellular plants with skelctons made up of amorphous opaline silica. The skeletons show highly ornate, complicated geometrical designs. Diatoms live in water virtually everywhere. They are found in clean sea water, brackish water, and fresh-water lakes and ponds. When conditions are right, diatoms propagate by subdivision in huge numbers. Alkalinity, temperature, and the presence of high concentrations of silica in the water largely control diatom life. When the diatoms die the skeletons drop to the bottom of their habitat to form oozes of varying thicknesses. Diatomites Diatomite, or diatomaceous earth, is composed essentially of the siliceous remains of the diatoms, although other organic skeletons are also present, especially in sea-water deposits where radiolaria, sponges and silico-flagellates are common. Impurities are generally carbonaceous material, fine-grained silt, volcanic ash and dust, and occasional coarse grains of sand. Diatomites are marine, brackish, or fresh-water, depending upon types of diatoms and their method of deposition. Diatoms More than 8000 species of diatoms have been named and classified. Some are definitely classified as to their habitat; some are so well recognized as to their living conditions that they can be stated to be diagnostic types, and when encountered in a deposit determine the origin of the deposit. Some of the commoner types of diatoms found in the freshwater diatomites on the Pacific Coast are: Cymbella lanceolata Agardh Fragilaria virescens Ralfs Encyonema prostratum Ralfs Diatoma vulgare Dory Surirella biseriata Brebison Eunotia major Ehrenberg Amphipleura pellucida Kützing Stictodiscus niagarac Ehrenberg Gomphonema geminatum Lynberg Melosira granulata Ehrenberg Epithemia turgida Kützing

Jan 1, 1942

By L. W. Casteel, E. A. Jones

MINING the lead deposits of Southeast east Missouri has reached a high stage of technical development dictated by the scattered occurrences of low-grade ore through favorable horizons in the Bonne Terre formation. The rock-breaking, handling, and related practices described here have evolved as the best way of mining these particular deposits. These methods are applied in the production of about 19,000 tons of lead ore per operating day from four mines in Southeast Missouri. Development drilling Drifts 10 ft wide and either 8 or 9 ft high are driven in this district on contract. Miners are guaranteed standard wages plus a bonus on the footage advanced, if earned. Labor, fuse, caps, wire, and dynamite used are charged against the contract. Normally the cycle of operations in drifting is performed by a two-man crew, a motor operator and a shovel operator who first load out the rock broken by the preceding shift. The drift crew then sets up two vertical column and mounts the drills. Cleveland HC-10's are used which have a steel lug integral with the cylinder for connection with the air feed. All drilling in drifts is wet. Air pressure is 85 to 100 lb at the face. From 28 to 32 holes are drilled per swing in a pyramid cut. Cut holes

Jan 1, 1947

By J. H. Waxweiler, L. C. Ikenberry, R. J. Bendure

Carbon which is present as insoluble carbides in austenitic stainless steels can be measured quantitatively by dissolving the steel in iodine-methanol and analyzing the residue for carbon. Severe sen-sitization was observed in Type 302 due to precipitation of only 0.003 pet carbon. Both cold work and the presence of delta ferrite caused a marked acceleration in rate of carbide precipitation. Carbide precipitation rates in 17-7 PH were stzulied for the austenite conditioning and also the aging heat treatment. CARBON and its compounds exercise a major influence on the properties of stainless steels and their response to thermal treatment. Sensitization in 18-8 type stainless steels has been the subject of numerous investigations throughout the years. Bain, Aborn, and utherford," and Binder, Brown, Frankss all studied the effects of heating austenitic stainless steels in the temperature range of 1000° to 1500°F. The primary purpose of most of these studies was the investigation of susceptibility to in-tergranular attack in acids due to these sensitizing heat treatments. Intergranular precipitation of carbides was always associated with intergranular attack but it was recognized2 that severe attack could occur with but minute quantities of precipitated carbide. Mahla and ielsen utilized the electron microscope to make a significant contribution in illustrating the appearance and method of growth of chromium carbides during sensitizing heat treatments. However, as they stated, their studies of residues could not be used to obtain a quantitative measurement of the amount of carbon which was actually precipitated. The aim of the present investigation was to devise a relatively fast, simple method for the quantitative measurement of carbides in stainless steel. EXPERIMENTAL WORK The initial investigations were made to determine the best means of separating carbides from the matrix. A number of dissolving media were tried using both chemical and electrolytic attack. Qualitative examination of the extracted residues by X-ray diffraction indicated that solution in iodine-methanol would furnish a good means of separation. Consequently, further work was pursued along this line. The method is quite simple. The sample in the form of millings or nibblings is dissolved in iodine-methanol solution at room temperature (6-g iodine, 25-ml methanol per g of sample). The insoluble residue containing the carbides is separated by suction filtration through an ultra-fine glass filter disc. This is a very fine filter medium that will retain particles as small as 0.1 to 0.2 p in diameter. After washing with methanol and drying, the filter disc and residue are placed in a conventional combustion carbon-tube furnace and the carbon determined gravimetrically. Using this technique it was found that reproducible insoluble carbon values were obtained. However, since such small amounts of insoluble carbon were obtained on Type 302 after sensitizatipn at 1250°F and 1500°F, the values were confirmed by a second method. In the second method the sample was dissolved with copper potassium chloride and filtered through a millipore paper. This treatment dissolves the matrix but leaves undissolved practically all of the carbon irrespective of how it is present in the steel. The amount of insoluble carbon present as chromium carbide is determined by calculation from the analysis of the residue for chromium and iron. The derivation of the formula used for this calculation is discussed later. The values obtained by the indirect copper-potassium-chloride method were in agreement with those obtained by the iodine-methano1 method. See Table I. It should be pointed out that the sensitivity of the direct combustion method is not too high when the amount of carbide present is small. This is due primarily to inherent blanks and to analytical errors such as weighing. For this reason it cannot be stated with any degree of certainty that there is a significant difference between values of 0.002 and 0.005 pct. Having confirmed that the iodine-methanol extraction gave a quantitative measurement of the precipitated carbides in Type 302, exploratory tests were conducted on Armco 17-7 PH stainless steel. Samples from commercial Heat 54807 were solution annealed at 2000°F, water quenched and heated at 1250" and 1500°F, and water quenched. The analysis of Heat 54808 is as follows:

Jan 1, 1962

By G. D. Cremer, J. J. Cordiano

Aluminum powder is a well-known article of commerce and in various forms has been marketed widely for use in paint, for pyrotechnic purposes and for exothermic mixtures. For a number of reasons, however, aluminum powder has not been employed extensively in powder metallurgy, although a great many proposals along this line have been offered. Aluminum and alumiuum-alloy powders oxidize readily upon exposure to air and the thin film of oxide (or hydroxide) thus formed is highly refractory, in that ordinary gaseous reducing agents such as hydrogen or carbon monoxide do not reduce the oxide to metal at temperatures below the melting point of aluminum. It has been thought that the presence of these films of oxide on aluminum particles would interfere markedly in powder metallurgical work and a number of suggestions have been made, either for preventing the formation of the film through the production of the powders in inert or reducing atmospheres, or for the removal of the oxide by means of powerful reducing agents, including "nascent" or atomic hydrogen released from metal hydrides. A second and more serious difficulty in the use of aluminum and aluminum-alloy powders in powder metallurgy resides in the fact that during compression such powders tend to adhere or cold-weld to the die walls, thus interfering with the formation and ejection of a compact. A third difficulty, which has been encountered only with aluminum-alloy powders, is their hardness when compared with elemental aluminum. Certain of these powders are susceptible to age-hardening, which further hinders the formation of strong green compacts. These conditions are particularly true of atomized aluminum-alloy powders. Even in the annealed condition, plastic deformation of alloy powders under pressure is low when compared with unalloyed powders. This fact, coupled with the lower corrosion resistance of the alloy powders. is probably the significant factor in our failure to obtain strong sintered pieces. Methods of Puoducing the Powder Many methods have been proposed for manufacture of aluminum powder, only a few of which are used commercially. Several of the more important processes include: (I) atomization of the molten metal; (2) mechanical pulverization and other types of comminution; and (3) graining, in which molten aluminum is stirred during freezing. For pigment and certain pyrotechnic uses aluminum flake powder is desirable, because of its greater proportion of surface to volume; and large quantities of such material are made by a procedure that involves stamping or ball milling. In making flake intended for use as pigment,

Jan 1, 1943

By G. D. Cremer, J. J. Cordiano

Aluminum powder is a well-known article of commerce and in various forms has been marketed widely for use in paint, for pyrotechnic purposes and for exothermic mixtures. For a number of reasons, however, aluminum powder has not been employed extensively in powder metallurgy, although a great many proposals along this line have been offered. Aluminum and alumiuum-alloy powders oxidize readily upon exposure to air and the thin film of oxide (or hydroxide) thus formed is highly refractory, in that ordinary gaseous reducing agents such as hydrogen or carbon monoxide do not reduce the oxide to metal at temperatures below the melting point of aluminum. It has been thought that the presence of these films of oxide on aluminum particles would interfere markedly in powder metallurgical work and a number of suggestions have been made, either for preventing the formation of the film through the production of the powders in inert or reducing atmospheres, or for the removal of the oxide by means of powerful reducing agents, including "nascent" or atomic hydrogen released from metal hydrides. A second and more serious difficulty in the use of aluminum and aluminum-alloy powders in powder metallurgy resides in the fact that during compression such powders tend to adhere or cold-weld to the die walls, thus interfering with the formation and ejection of a compact. A third difficulty, which has been encountered only with aluminum-alloy powders, is their hardness when compared with elemental aluminum. Certain of these powders are susceptible to age-hardening, which further hinders the formation of strong green compacts. These conditions are particularly true of atomized aluminum-alloy powders. Even in the annealed condition, plastic deformation of alloy powders under pressure is low when compared with unalloyed powders. This fact, coupled with the lower corrosion resistance of the alloy powders. is probably the significant factor in our failure to obtain strong sintered pieces. Methods of Puoducing the Powder Many methods have been proposed for manufacture of aluminum powder, only a few of which are used commercially. Several of the more important processes include: (I) atomization of the molten metal; (2) mechanical pulverization and other types of comminution; and (3) graining, in which molten aluminum is stirred during freezing. For pigment and certain pyrotechnic uses aluminum flake powder is desirable, because of its greater proportion of surface to volume; and large quantities of such material are made by a procedure that involves stamping or ball milling. In making flake intended for use as pigment,

Jan 1, 1943

By K. E. Gray, M. S. Seth

Equations of elasticity for transversely isotropic, axisymmetric, homogeneous, porous media exhibiting pore fluid pressure were formulated. Using an analogy between thermal and porous body stresses, it was shown that the solution for a transversely isotropic porous body may be obtained by incorporating body forces and the stresses due to a boundary load into the corresponding solution for the thermal stress problem. Equations of elasticity ad the thermal analogy method were used to determine transient horizontal, tangential, and vertical stresses and radial displacement in a semi-infinite cylindrical region when either a constant pressure or a constant rate of flow is maintained at the wellbore. The vertical and tangential displacements are zero from the conditions of the problem. A numerical analysis was made of the solutions obtained by using a digital computer to determine the relative influence of each system variable. Considering rock as a porous body with internal fluid pressure generally gives results significantly different than considering the rock to be nonporous; the directional character of rocks leads to significant differences as compared to results based upon the common assumption of isotropy. Stress gradients are high near the wellbore but die out away from the well. Radial stresses are compressive or neutral, whereas tangential stresses are tensile, neutral or compressive, depending upon the boundary conditions and physical properties of the system Vertical stresses are compressive for an unbounded system. For constant wellbore injection rate, the vertical stress is proportional to the rate of fluid injection and decreases with time, whereas the radial and tangential stresses increase with time. At a given location, the radial displacement generally is very dependent upon time. INTRODUCTION A realistic appraisal of the state of stress in subsurface rock formations would be of considerable interest and use to the petroleum industry. For example, knowing the state of stress in proximity to a wellbore would be of fundamental importance in designing a fracturing operation or, more important, of clearly understanding the conditions necessary to produce rock failure of desired dimensions and geometry. Understanding conditions necessary for rock failure at the wellbore would also be of utility in a preventive sense. For example, borehole stability is an important consideration for many rock formations, and knowledge of the stress state at and near the wellbore under conditions of substantial pressure gradient due to fluid flow would be of great value. When fluid flows through a porous body which is initially at some uniform stress level, the following forces generate stresses at any point in the body. (1) Forces due to nonuniform pressure distribution. With increasing pressure the elements of a body are compressed. Such compression cannot proceed freely in a continuum when the pressure is not uniform throughout, and thus, stresses due to flow of fluid are set up. (2) Pore fluid pressure. This gives rise to normal stresses whose value at any point is the product of areal porosity and the fluid pressure. Although the fluid exerts uniform pressure, the stresses it creates in an anisotropic body may not be the same in all directions since the areal porosity in an anisotropic porous body is a direction-dependent quantity. This consideration leads to the concept of directional porosity. (3) Body Forces. The flow of the moving fluid imparts a force to the rock matrix, the magnitude of which depends upon the pressure

Jan 1, 1969

By A. E. Wraith, N. J. Petch, J. D. Embury, E. S. Wright

The two most important parameters controlling the fracture behavior of a solid are its intrinsic properties, e.g.,grain size, and the operative stress system. The latter may be modified in laminates by the presence of weak interfaces. This is studied in notch-impact tests on a mode1 system of mild steel laminates containing a variety of interfaces. The effect of these is evaluated in terms of the ductile/cleavage transition. Two laminate geometries are distinguished, here called "crack-arrester " and "crack-divider". In both, cleavage is inhibited. This arises because of relaxation of a state of triaxial tension. In the crack-avrester laminates, cleavage initiated at a notch is confined to the layer containing the notch. In crack-cliuider laminates, a thick specimen behaves as the Sum of a number of thinner ones. Additional benefit may derive from improved intritnsic propevties of- the lanlinate layers arising from greater deformation in their manufacture. It has long been recognized that the two most important parameters controlling the fracture behavior of solids are their intrinsic properties (e.g., grain size friction stress,3 distribution of second phase particles4) and the operative stress system under which fracture occurs. In solids that show a ductile/cleavage transition, cleavage is favored by the presence of a notch. This is because triaxial tensions, generated by the localized plastic constraint at the notch, are operative when fracture occurs.= Anything that suppresses these triaxial tensions will be unfavorable to cleavage. Such suppression may possibly occur in laminates containing weak interfaces and the purpose of the present paper is to explore this possibility. Two basic laminate geometries, here termed "crack-avrester" and "cvack-divider", are examined. They are illustrated in Fig. 1. With the crack-arrester laminates, there is the possibility that, when the fracture crack approaches the interface, this, if weak, may delaminate due to the tensile stress acting parallel to the plane of the crack.= If this happens, energy will be used in delamination, the crack will be completely blunted, and the triaxial tension associated with the crack will be relaxed. To fracture the second portion of the laminate, crack reinitiation will be necessary and, because of the relaxation of the triaxial tension, this reinitiation will occur under conditions of nearly uniaxial tension, which are unfavorable to cleavage. Thus there is the possibility of cleavage suppression in the second and subsequent subunits of a crack-arrester laminate. With the crack-divider geometry, there is again the possibility of delamination at the interfaces. This will divide the crack into a series of cracks propagating through the individual laminate subunits. If these are sufficiently thin, the triaxial tension will be relaxed towards a state of biaxial tension in each of them. Thus, with the crack-divider laminates, there is again the possibility of cleavage inhibition. In the present work, these possibilities are explored using a notched impact test on mild steel laminates bonded with soft solder, silver solder or copper. Even if delamination does not occur, it is still possible that cleavage may be inhibited in laminates. With the crack-arrester geometry, the cleavage crack in the first layer may be blunted and arrested by plastic deformation in the laminate bond, if this is ductile. Partial relaxation of the stress transmitted ahead of the crack into the second layer will then result and this will reduce the significance of this stress in the fracture of the second layer. With the crack-divider geometry, there cannot be much effect in the absence of delamination unless a large amount of energy is absorbed in rupturing the ductile material. EXPERIMENTAL DETAILS The composition of the mild steel (wt pet) was: 0.04 C, 0.29 Mn, 0.01 Si, 0.006 P, 0.008 S. "As-received" plate was annealed for 2 hr at 900°C and slowly cooled to give a grain size of 0.04 mm. The laminates were made by brazing or soldering together mild steel plates 8 by 3 in. by various thicknesses. These were obtained from the annealed plate by machining, so that the intrinsic material properties were .kept constant. Laminates containing two to six steel layers were studied using standard Charpy V-notch specimens cut from the bonded plates. Standard homogeneous specimens from the annealed plate and subsize ones from the laminate components

Jan 1, 1968

By O. J. Malacarne, D. G. Millenbruch

The use of a series of thickeners for washing of the slime fraction of a leached ore is not uncommon in the uranium industry; however, few ore processing mills have used a thickener circuit for washing leached total ore. The common practice is to wash the sand fraction in classifiers and the slime fraction only in thickeners. At the Uravan mill of Union Carbide Nuclear Co., a total ore acid leach is employed to extract uranium values from sandstone ores. These leached ores are then washed at a nominal rate of from 1000 to 1300 tpd in a series of washing thickeners. A typical screen analysis of the ore being washed in these thickeners is: 25 pct, -200 mesh; 3 pct, +35 mesh; and about 1 pct, +14 mesh. The amount of slimes (-200 mesh) will vary from 20 to 30 pct as the mill receives ore from 150 different mines. The washing liquor is acidic, from a pH of about 2 in the first thickener to 0.6 pH in the last thickener and, of course, all acid duty equipment must be used. The Uravan mill of Union Carbide Nuclear Co. is located in Montrose County, Colo. and is physically located on a canyon wall along the San Miguel River. The thickeners referred to in this paper are located on top of the mesa above the canyon. For purposes of identification, these thickeners are numbered 1 through 8 from south to north. GENERAL DESCRIPTION OF CIRCUIT The circuit utilized consists of eight wooden fir tanks, 60-ft diam by 12-ft deep, set in a line and staggered in elevation by approximately 3 ft. The washing water flows through the thickeners by gravity, while the ore pulp is pumped uphill from thickener to thickener. Adequate piping and pumping capacity are available so that any of the thickeners can be bypassed in the circuit. All the controls for the

Jan 1, 1962

By John McDonald

THIS report is a continuation of an earlier one with a similar title,1 to which the reader is referred for such details of procedure as do not appear here. A brief summary will be given of the objects and methods of the research at this time. It was pointed out in the previous paper that properties of magnesium alloys, as re-ported by different workers, often differ. This was thought to be due to differences in the preparation of the specimens tested. The ideal way to compare alloys would be to prepare each of them in so many ways that reasonable assurance would exist that the best properties of each alloy had been developed. The alloys would then be com-pared on the basis of these properties. The treatment actually given the alloys of these studies is necessarily a compromise with completeness. Nevertheless, enough treatments have been given so that a con-siderable degree of assurance exists that the properties obtained are representative of the alloy as such, and not merely of the manner in which it was worked and heat-treated.

Jan 1, 1940

By Walter Rose

In a recent technical note, Owen Thornton&apos; suggests that wetting liquid relative permeability may be derived from the relationship: where Pd/Pc is the ratio of displacement pressure to capillary pressure at the wetting liquid satdration Sw, and I is the resistivity index at this saturation. Thornton shows that this expression gives values for relative permeability in good agreement with those experimentally determined by Leverett. We have recently developed another expression for krw which seems preferable to Equation 1 since it requires fewer experimental data for its verification. This equation may be derived in the following manner. Making use of the analogy between mass transfer of fluid in a porous medium and electrical conductivity through the fluid in the same medium, we can postulate a hydraulic formation resistivity factor analogous to an electrical formation resistivity factor. From Poiseuille&apos;s Law the resistivity to flow in a tube of radius R is of the form 8u/R², where is the viscosity of the fluid. Similarly7 the resistivity to flow in a porous medium of the same dimensions as the tube is given by D&apos;Arcy&apos;s Law as where k is the permeability of the medium. The hydraulic formation resistivity factor, Ff, is thus the quotient of these two resistivities, or: But permeability is defined by the KO-zeny equation as: where: r is the average pore radius of the porous medium, L. is the average tortuous length of the average pore, + is the porosity, and L is the bed length. This gives Fr as a function of the (La/L) .-.-.tortuosity ratio and porosity, or in explicit form: where: T = (La/L)&apos;, and N is the number of pores of radius, r, which will be found in any cross sectional area, x R&apos;. That is, N = R²/r². It will be clear from the foregoing considerations that the hydraulic formation fat. tor should be dependent on the value of R which in every case must be arbitrarily selected. By analogy, the hydrauiic formation factor, Fcf, characterizing the porous medium at Sw<1,will be given by: R² NT. where ke is the effective wetting liquid permeability obtaining at Sw<l, and Te is the square of the (Las/L) ratio defined by Thornton. Therefore, the hydraulic resistivity index, If, is: However, Thrnton gives I as: and it follows that: Equation 2, when checked against the data of wyckoff and Botset² and some of the Morse et al data³, gives comparisons as shown at the bottom of this page. Computations based on Leverett&apos;s data, quoted by Thorntaon, gives computed krw values somewhat lower than the experimental values. Moreover, other instances can be cited where we find that neither Equation 1 nor Equa tion 2 is checked by experimental data. The work of Botset&apos; on the Nichols Buff sandstone and Morse et a1 on oil wetted Bradford sandstone are such instances. A reason for these discrepancies may lie in the fact that if both Equations 1 and 2 are presumed always to give accurate values for krw, it follows that PC = Pd/Sw". Such an expression, it is well known, is too simple to describe accurately the capillary pressure behavior of all porous media. However, it is believed that a particular advantage resides on the use of Equation 2, since it is not dependent for its utility on a knowledge of the capillary pressures obtaining in dynamic flow svsterns. No practical technique for measuring the capillary pressures characterizing the fluid distributions in dynamic flow systems has yet been proposed. Acknowledgment is given to Dr. Paul D. Foote, executive vice-president of the Gulf Research and Development Company, for permission to publish this note. 1. Owen F. Thornton, "A Note on the Valuation of Relative Permeability," J. Pet. Tech., 1:7, Section 1, July, 1949. 2. R. D. Wyckoff arid H. G. Botset, "The Flow of Gas-Liquid Mixtures through Porous Media," Physics, 7:325-345, 1936. 3. R. A. Morse, P: L. Terwilliger, .and S. T. Yuster, "Relative Permeability Measurements of Small Core Samples," Oil and Gas J., 46:109-125, Aug. 23, 1947. 4. H. G. Botset, "Flow of Gas-Liquid Mixtures Through Consolidated Sand," Trans. AIME, 136:91, 1940.

Jan 1, 1949

By Walter Rose

In a recent technical note, Owen Thornton&apos; suggests that wetting liquid relative permeability may be derived from the relationship: where Pd/Pc is the ratio of displacement pressure to capillary pressure at the wetting liquid satdration Sw, and I is the resistivity index at this saturation. Thornton shows that this expression gives values for relative permeability in good agreement with those experimentally determined by Leverett. We have recently developed another expression for krw which seems preferable to Equation 1 since it requires fewer experimental data for its verification. This equation may be derived in the following manner. Making use of the analogy between mass transfer of fluid in a porous medium and electrical conductivity through the fluid in the same medium, we can postulate a hydraulic formation resistivity factor analogous to an electrical formation resistivity factor. From Poiseuille&apos;s Law the resistivity to flow in a tube of radius R is of the form 8u/R², where is the viscosity of the fluid. Similarly7 the resistivity to flow in a porous medium of the same dimensions as the tube is given by D&apos;Arcy&apos;s Law as where k is the permeability of the medium. The hydraulic formation resistivity factor, Ff, is thus the quotient of these two resistivities, or: But permeability is defined by the KO-zeny equation as: where: r is the average pore radius of the porous medium, L. is the average tortuous length of the average pore, + is the porosity, and L is the bed length. This gives Fr as a function of the (La/L) .-.-.tortuosity ratio and porosity, or in explicit form: where: T = (La/L)&apos;, and N is the number of pores of radius, r, which will be found in any cross sectional area, x R&apos;. That is, N = R²/r². It will be clear from the foregoing considerations that the hydraulic formation fat. tor should be dependent on the value of R which in every case must be arbitrarily selected. By analogy, the hydrauiic formation factor, Fcf, characterizing the porous medium at Sw<1,will be given by: R² NT. where ke is the effective wetting liquid permeability obtaining at Sw<l, and Te is the square of the (Las/L) ratio defined by Thornton. Therefore, the hydraulic resistivity index, If, is: However, Thrnton gives I as: and it follows that: Equation 2, when checked against the data of wyckoff and Botset² and some of the Morse et al data³, gives comparisons as shown at the bottom of this page. Computations based on Leverett&apos;s data, quoted by Thorntaon, gives computed krw values somewhat lower than the experimental values. Moreover, other instances can be cited where we find that neither Equation 1 nor Equa tion 2 is checked by experimental data. The work of Botset&apos; on the Nichols Buff sandstone and Morse et a1 on oil wetted Bradford sandstone are such instances. A reason for these discrepancies may lie in the fact that if both Equations 1 and 2 are presumed always to give accurate values for krw, it follows that PC = Pd/Sw". Such an expression, it is well known, is too simple to describe accurately the capillary pressure behavior of all porous media. However, it is believed that a particular advantage resides on the use of Equation 2, since it is not dependent for its utility on a knowledge of the capillary pressures obtaining in dynamic flow svsterns. No practical technique for measuring the capillary pressures characterizing the fluid distributions in dynamic flow systems has yet been proposed. Acknowledgment is given to Dr. Paul D. Foote, executive vice-president of the Gulf Research and Development Company, for permission to publish this note. 1. Owen F. Thornton, "A Note on the Valuation of Relative Permeability," J. Pet. Tech., 1:7, Section 1, July, 1949. 2. R. D. Wyckoff arid H. G. Botset, "The Flow of Gas-Liquid Mixtures through Porous Media," Physics, 7:325-345, 1936. 3. R. A. Morse, P: L. Terwilliger, .and S. T. Yuster, "Relative Permeability Measurements of Small Core Samples," Oil and Gas J., 46:109-125, Aug. 23, 1947. 4. H. G. Botset, "Flow of Gas-Liquid Mixtures Through Consolidated Sand," Trans. AIME, 136:91, 1940.

Jan 1, 1949

By M. Cohen, W. J. Harris

The recent application of lineal analysislt2 to the austenite-martensite reaction has made possible a quantitative study of the kinetics of this transformation during rapid cooling. Martensite range curves can thus be constructed to portray the onset of the reaction at Ma and its subsequent progress as a function of temperature down to and below the ambient. It now seems in order to investigate other aspects of the martensite transformation, using this quantitative method of approach. One of the least understood characteristics of the austenite-martensite reaction is that of stabilization which has been defined by Troiano and Greninger3 as &apos;la lowering of Ma, resulting from aging, without change in chemical composition of the parent solid solution." In other words, if the hardening quench is arrested at a predetermined subcritical temperature (TA) for a sufficient period of time, more austenite may be retained at a given lower Or reference temperature (Tr) than if the steel had been cooled directly and rapidly to Tr in the first place. For the purposes of the work at hand, the extent of stabilization produced by the isothermal treatment at Th is measured explicitly in terms of the excess austenite (6) that exists in the steel at T,, over and above the amount that is normally present after direct quenching to T,. T, is conveniently taken to be room temperature, but this choice is not essential and is sometimes undesirable. The holding temperature (TA) may be above or below M,, and still cause stabilization depending upon the themistry of the austenite. stabilization has been found to occur in the presence of bainite4 and of martensite6,6,7,8 as well as in the absence of either,g The phe-nomenon of stabilization is not concerned with (and may even be obscured by) ferrite formation or any other type of phase change occurring at T~ that alters the chemistry of the remaining austenite. Such a structural change would obviously influence the martensite transformation during subscquent cooling. Stabilization, however, is more subtle; it appears to manifest itself without detectable variation of the austenite composition, whether in the presence or absence of transformation products. There are relatively few direct references to stabilization in the literature. The stabilizing effect of room temperature aging and tempering on the subzero transformation of retained austenite has been clearly shown in plain carbon,6,8 low alloy6s7.8 and high alloy tool steels.10&apos;5 ssa- with the as-hardened steel, the degree of stabilization increases with tempering time and temperature through

Jan 1, 1949

By F. C. Hull

The grain size of a metal or alloy is one of the most important factors determining its properties. In steels, for example, grain size affects hardenability, toughness and machinability; in brasses, grain size is related to hardness and deep-drawing quality. In the field of heat-resistant alloys, grain size has a marked effect on ductility, creep and endurance strength. In order to determine these effects, as well as to control the properties of materials, many accurate and rapid measurements of grain size must be made. This paper presents a new and improved method for the estimation of grain size. Usual Methods OF EvaluatiNg Grain Size A frequetly used method of estimating grain size is that of comparing the image of a polished and etched specimen on the ground-glass screen of a metallographic microscope with standard grain-size charts. Several types of standards are available for use with different classes of microstructures. Geometric Grids.—The Metals Handbook&apos; has a series of hexagonal grids ranging in size from ASTM No. I to 8. Idealized Grain Networks.—Idealized grain.boundary networks for ASTM grain sizes I to 8 are included in the American Society for Testing Materials Tentative Standard E 19 - 39 T, standard Micrographs & Metals Handbook and ASTM Tentative Standard E19-3gT contain micrographs of hypo-eutectoid and hypereutectoid steels ranging in grain size from No. I to 8. The grain size of annealed brass (diameter of the average grain in millimeters) is obtained by comparison with 10 micrographs of varying. grain size in ASTM Tentative Standard E 2-39 T. A handicap to accurate evaluation of grain size by this method is the fact that it is difficult to compare photographs in a dimly lighted room with the image on the ground-glass screen, or, if the general illumination is increased so that the printed standards may be clearly seen, the contrast of the image of the unknown is decreased. It is easier to estimate grain size by comparing a micrograph of the unknown with the grain-size standards. However, photographing every specimen on which the grain size is desired is too costly in time and materials to be practicable. For hardened steels, the Shepherd or Jernkontoret fracture grain-size standards are very accurate and useful, but this method obviously cannot be applied to ductile alloys such as brass, stainless steels and austenitic heat-resistant alloys. Jeffries&apos; method for grain-size measurements consists of counting the number

Jan 1, 1948

By F. C. Hull

The grain size of a metal or alloy is one of the most important factors determining its properties. In steels, for example, grain size affects hardenability, toughness and machinability; in brasses, grain size is related to hardness and deep-drawing quality. In the field of heat-resistant alloys, grain size has a marked effect on ductility, creep and endurance strength. In order to determine these effects, as well as to control the properties of materials, many accurate and rapid measurements of grain size must be made. This paper presents a new and improved method for the estimation of grain size. Usual Methods OF EvaluatiNg Grain Size A frequetly used method of estimating grain size is that of comparing the image of a polished and etched specimen on the ground-glass screen of a metallographic microscope with standard grain-size charts. Several types of standards are available for use with different classes of microstructures. Geometric Grids.—The Metals Handbook&apos; has a series of hexagonal grids ranging in size from ASTM No. I to 8. Idealized Grain Networks.—Idealized grain.boundary networks for ASTM grain sizes I to 8 are included in the American Society for Testing Materials Tentative Standard E 19 - 39 T, standard Micrographs & Metals Handbook and ASTM Tentative Standard E19-3gT contain micrographs of hypo-eutectoid and hypereutectoid steels ranging in grain size from No. I to 8. The grain size of annealed brass (diameter of the average grain in millimeters) is obtained by comparison with 10 micrographs of varying. grain size in ASTM Tentative Standard E 2-39 T. A handicap to accurate evaluation of grain size by this method is the fact that it is difficult to compare photographs in a dimly lighted room with the image on the ground-glass screen, or, if the general illumination is increased so that the printed standards may be clearly seen, the contrast of the image of the unknown is decreased. It is easier to estimate grain size by comparing a micrograph of the unknown with the grain-size standards. However, photographing every specimen on which the grain size is desired is too costly in time and materials to be practicable. For hardened steels, the Shepherd or Jernkontoret fracture grain-size standards are very accurate and useful, but this method obviously cannot be applied to ductile alloys such as brass, stainless steels and austenitic heat-resistant alloys. Jeffries&apos; method for grain-size measurements consists of counting the number

Jan 1, 1948

By P. W. Bridgman

DURING the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their, desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer layers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in. the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at, first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 2, 1920

By R. W. Newcomb

THE constancy of calibration, and to a great extent the life, of a thermoelement is dependent on the suitability of the primary protecting tube in which the wires are mounted, particularly when used at high temperatures. An ideal thermocouple protecting tube would be com-posed of materials that would not contaminate the thermoelement wires contained in it-one that would remain absolutely gas-tight ,it all temperatures of usage, that will not be attacked by gases, or other surrounding agencies, that is not destroyed by heat, that withstands sudden and extreme temperature changes, that affords a high degree of mechanical protection and does not deform at high temperatures, that is a good heat conductor and obtainable in small diameters so as to keep down lag factors. It has not yet been possible to produce tubes of any known mate-rials that will meet all of these conditions. In selecting protecting tubes, therefore, one should be chosen the characteristics of which best fit it to the particular conditions of usage. Frequently conditions are such that two tubes have to be used, a primary gas-tight protecting tube inside of a secondary protecting tube, because certain agencies will attack the primary gas-tight tube unless it is guarded by the outside tube.

Jan 9, 1919