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By E. O. Kirkendall

The investigation reported herein was undertaken to obtain data to supplement those presented in an earlier paper,l particularly for longer times at a higher temperature. This information may further develop our knowledge of the mechanism of diffusion in substitutional solid solutions. Diffusion of solute atoms interstitially dissolved is not difficult to visualize: it can take place without much disturbance of the solvent atoms. The mechanism of diffusion of solute atoms substitutionally dissolved is not so easily understood. Many theories have been advanced. Rosen-hain,2,3 Frenkel,4 Smekal,5 Langmuir,3,6 Steigman, Shockley and Nix,' and Johnson8 all proposed theories to explain diffusion. Langmuir's proposed mechanism consisted of a simple cyclic interchange of atoms involving an interchange in lattice positions of four or more atoms. This mechanism, accepted by the author at the time of his previous publication,1 and apparently quite generally accepted, required a net exchange in positions of both solute and solvent atoms in equal numbers. In other words, the rate of diffusion of the solvent and solute atoms would be the same. That this cyclic interchange in lattice positions of solute and solvent atoms in equal numbers is the only true mechanism of diffusion is denied by the evidence presented in this paper. Experimental Procedure This modification of similar procedure1 will be outlined briefly. The method consisted of the following steps: I. A pure Muntz metal (60.6 per cent Cu, 0.1 per cent total impurities) that was almost all beta brass at 780°C. was chosen. 2. The brass was turned between centers in a lathe to a diameter of 0.5965 inches. 3. After the brass was cleaned, it was electroplated with pure copper to a diameter of about one inch. 4. The sample was heated slowly to 400°C. under reduced pressure and held at that temperature for 4 hr. to remove occluded gases. It was then cooled to room temperature. 5. The sample was heated to 780°C. ± 3°C. and held at that temperature for different lengths of time; then quenched. Samples were cut off each time after quenching. Metallographic samples 1/4 in. thick were removed at I hr., 6 hr., 24 hr., 96 hr. and 701 hr. After 96 and 701 hr. samples of about I in. were removed for X-ray analysis. 6. The metallographic samples were polished on the cross section and photomicrographs were taken. 7. The I-in. samples were polished and etched on both ends. With the aid of a microscope each was carefully mounted in a four-jaw chuck in a lathe, so that they could be accurately bored for an arbor. 8. Turnings were taken for each X-ray sample. After each set of turnings, the sample was heated in an oil bath for about 1/2 hr. at 300°C. It was then etched in 25

Jan 1, 1942

By E. O. Kirkendall

The investigation reported herein was undertaken to obtain data to supplement those presented in an earlier paper,l particularly for longer times at a higher temperature. This information may further develop our knowledge of the mechanism of diffusion in substitutional solid solutions. Diffusion of solute atoms interstitially dissolved is not difficult to visualize: it can take place without much disturbance of the solvent atoms. The mechanism of diffusion of solute atoms substitutionally dissolved is not so easily understood. Many theories have been advanced. Rosen-hain,2,3 Frenkel,4 Smekal,5 Langmuir,3,6 Steigman, Shockley and Nix,' and Johnson8 all proposed theories to explain diffusion. Langmuir's proposed mechanism consisted of a simple cyclic interchange of atoms involving an interchange in lattice positions of four or more atoms. This mechanism, accepted by the author at the time of his previous publication,1 and apparently quite generally accepted, required a net exchange in positions of both solute and solvent atoms in equal numbers. In other words, the rate of diffusion of the solvent and solute atoms would be the same. That this cyclic interchange in lattice positions of solute and solvent atoms in equal numbers is the only true mechanism of diffusion is denied by the evidence presented in this paper. Experimental Procedure This modification of similar procedure1 will be outlined briefly. The method consisted of the following steps: I. A pure Muntz metal (60.6 per cent Cu, 0.1 per cent total impurities) that was almost all beta brass at 780°C. was chosen. 2. The brass was turned between centers in a lathe to a diameter of 0.5965 inches. 3. After the brass was cleaned, it was electroplated with pure copper to a diameter of about one inch. 4. The sample was heated slowly to 400°C. under reduced pressure and held at that temperature for 4 hr. to remove occluded gases. It was then cooled to room temperature. 5. The sample was heated to 780°C. ± 3°C. and held at that temperature for different lengths of time; then quenched. Samples were cut off each time after quenching. Metallographic samples 1/4 in. thick were removed at I hr., 6 hr., 24 hr., 96 hr. and 701 hr. After 96 and 701 hr. samples of about I in. were removed for X-ray analysis. 6. The metallographic samples were polished on the cross section and photomicrographs were taken. 7. The I-in. samples were polished and etched on both ends. With the aid of a microscope each was carefully mounted in a four-jaw chuck in a lathe, so that they could be accurately bored for an arbor. 8. Turnings were taken for each X-ray sample. After each set of turnings, the sample was heated in an oil bath for about 1/2 hr. at 300°C. It was then etched in 25

Jan 1, 1942

By E. J. Yoder, N. B. Aughenbaugh, R. B. Johnson

Mineral aggregates experience degradation during field and laboratory compaction. Reduction in the aggregate size is accomplished by abrasion of the particle edges and fracturing of individual pieces which have become overstressed. Little is known of the factors that govern the amount of breakdown experienced for a given situation. A field study was made of the factors affecting aggregate breakdown under compaction using three carbonate aggregates of different physical properties. The preliminary results indicate that rock type, compactive effort, gradation, and thickness of compactive layer are factors which exert the greatest influence. Mineral aggregates experience a mechanical breakdown of some of the aggregate pieces into smaller fragments during any compaction process, whether in the field or laboratory. This phenomenon occurs as abrasion of the sharp edges during movement and reorientation of the particles in densifying and/or as granulation and fracturing of those pieces which have become overstressed. Two types of aggregate breakdown occur in the field. These may be classed in a general category of aggregate degradation.* One occurs during the con- * Aggregate degradation has been defined in many different ways. For this paper it is considered as any breakdown of larger particles into smaller ones, whether mechanical or chemical. struction period and is related to the densification of the aggregate body from a loose state to a relatively dense mass by heavy compaction equipment. This type is almost entirely a mechanical action. The other occurs after the construction period when the roadway has been put into use. This in-service breakdown is; a different phenomenon from the breakdown during construction in the sense that it combines mechanical with chemical changes. Time becomes an important consideration that may cause subordinate factors in construction degradation to develop into principal ones for in-service breakdown. Breakdown of aggregates in service has been extensively studied by investigators from the northwestern

Jan 1, 1962

By H. A. Schwartz, Wolfram Ruff

The spheroidal form of the temper carbon nodules in malleable cast iron and of the graphite mottles of "mottled" cast iron suggests that in both all the graphite in a given mottle or nodule grew from a single center of crystallization or nucleus. $ There is, however, a distinct metallo-graphic difference between the mottle and the nodule; the area of mother metal impoverished in combined carbon by the crystallization of graphite in a mottle is practically coextensive with the ramifications of the graphite, while the impoverished zone of metal corresponding to a given nodule is always larger, and usually much larger, than the approximately spherical mass of graphite crystals forming the nodules. Furthermore, the mottle probably is formed during freezing and the nodule almost always at a considerably lower temperature. Assuming that the nodules or mottles can be used as a measure of the existing nuclei (capable of germination) we propose to record certain observations as to the graphitizing reaction in the light of the number and habits of growth of these nuclei. The present authors, in cooperation with others'-', have reported upon various cognate aspects of the problem. The fact that temper carbon is a mass of flakes and not a solid granule has become well recognized since the introduction of an improved polishing technique8, 9, 10 for cast iron. The problem of deriving from the circular planar intercepts of a mass of spheres of varying sizes their number and size distribution in space has also been satisfactorily solved12, 13 Growth of Nuclei in White Cast Iron It has already been shown1, 3 that the progress of graphitization with time is usual1y consistent with the assumption that nodules grow in size

Jan 1, 1936

By Wolfram Ruff, H. A. Schwartz

The spheroidal form of the temper carbon nodules in malleable cast iron and of the graphite mottles of "mottled" cast iron suggests that in both all the graphite in a given mottle or nodule grew from a single center of crystallization or nucleus. $ There is, however, a distinct metallo-graphic difference between the mottle and the nodule; the area of mother metal impoverished in combined carbon by the crystallization of graphite in a mottle is practically coextensive with the ramifications of the graphite, while the impoverished zone of metal corresponding to a given nodule is always larger, and usually much larger, than the approximately spherical mass of graphite crystals forming the nodules. Furthermore, the mottle probably is formed during freezing and the nodule almost always at a considerably lower temperature. Assuming that the nodules or mottles can be used as a measure of the existing nuclei (capable of germination) we propose to record certain observations as to the graphitizing reaction in the light of the number and habits of growth of these nuclei. The present authors, in cooperation with others'-', have reported upon various cognate aspects of the problem. The fact that temper carbon is a mass of flakes and not a solid granule has become well recognized since the introduction of an improved polishing technique8, 9, 10 for cast iron. The problem of deriving from the circular planar intercepts of a mass of spheres of varying sizes their number and size distribution in space has also been satisfactorily solved12, 13 Growth of Nuclei in White Cast Iron It has already been shown1, 3 that the progress of graphitization with time is usual1y consistent with the assumption that nodules grow in size

Jan 1, 1936

By G. Derge, Ling Yang, John Henderson

Self-diffusion coefficients of aluminum have been measured by the capillary reservoir technique in liquids of the CaO-SiO2-Al2O3 system containirg equimolar portions of CaO and SiO2, in the temperature range 1400o to 1520oC. For the melt containing 6.0 mole pct Al2O3 the results can be expressed by the equation D = [(4.3 * 0.3) x 104] exp [(-85,000 * 17,500)/RT]cm~sec-'; for the melt containing 12.5 mole pct Al2O3, by the equation D = (5.4 i 0.2) exp [(-60,000 * 10,00O)/RT] cm2sec-: A concept of the constitution of these melts has been developed which proposes that the ratios O/(Si +Al) and Al2 O3/CaO determine the dominant species present. In recent years considerable work has been done on the system CaO-SiO2-A12O3 with a view to elucidating the structure of liquids of this system. Conductivity,' electromotive force, 3 density,4 and activity5 measurements have all contributed to an understanding of the problem, but as yet there is no entirely satisfactory theory that can account for all the observed experimental results. In principle, measurements of self-diffusion coefficients should give further information which is not obtainable in other ways. Self-diffusion coefficients for calcium, silicon,6 and oxygen7 have been measured. The present investigation extends the series of self-diffusion coefficient measurements to include aluminum and develops a concept of constitution for liquids of this system which is compatible with all the observed experimental results. EXPERIMENTAL The technique used in the measurement of the self-diffusion coefficient of aluminum was the capillary-reservoir method,8 A126 being incorporated in the melt contained in the capillary and inactive aluminum in the reservoir melt. This method was chosen because it minimizes convection currents' in the diffusion zone. It has the further advantage that the boundary conditions are such that a slight modifica- tion of Anderson and saddington's8 solution of Fick's Law yields an equation which requires measurements only of the length and the initial and final average specific activities of the solidified melt within the capillary. where t is the diffusion time, Co is the average specific activity of the melt contained in the capillary at t = O, C is the average specific activity of the melt contained in the capillary at t = t, 1is the length of the capillary, and D is the self-diffusion coefficient. The equation is of somewhat different form than those previously applied to high temperature diffusion studies because the specific activity of the melt in the reservoir was negligible both before and after diffusion. The diffusion apparatus is shown schematically in Fig. 1. It consisted of a silicon carbide resistance furnace containing the inactive melt in a graphite crucible, internal dimensions 7/8 by 4 in., enclosed in a 1 1/4- by 1 1/2- by 30-in. McDanel tube. A 3/8-in. McDanel thermocouple sheath to which graphite radiation shields and a graphite protection tube were affixed, was used to hold the capillaries. By moving this sheath through a rubber seal at the top of the McDanel tube the capillaries could be lowered into or raised out of the melt. Temperature was measured with a Pt-Pt 13 pct Rh thermocouple which was calibrated periodically against a standard couple. The furnace temperature was controlled to ± 5°C through the thermocouple immersed in the melt. Temperature variation over the depth of the melt was less than ± 3°C. The inactive melts were prepared from pure native quartz, assaying better than 99.9 pct SiO2, A.R. grade A12O3 and A.R. grade CaCO,. The same quartz and CaCO3 were used in preparing the active melts, the

Jan 1, 1962

By Helmut Thielsch

During the last three decades a great many arguments have been presented on the subject of "mosaicJ' or "blockJJ structures of metals. Apparently because of insufficient evidence, the "block-structure" theories have never been widely understood among the physical metallurgists in this country, and most investigators among the few that have tried to demonstrate the existence of such an inner strutture Of crystals or grains have failed to recognize also the existence of a lamellar structure. Moreover, little thought has been given to justify the existence of such "lamellar" or "mosaic-block" structures on a theoretical basis. Since properties such as Plasticity; ferro-magnetism, hardness, diffusion, and others may be explained by structural faults in the lattice network of the crystals: the great importance of a more detailed knowledge of the structure within crystals or grains becomes now evident. Because Of the vast extent of the field Of submicroscopic structures, it shall be the purpose Of this paper only to review the more important of the results obtained by other investigators, especially in Germany, where a great deal of attention has been given to mosaic structure during the last three years. The origin of this mosaic patternt and effects of cold reduction and recrystallization will be shown in further studies later on. Imperfections in Crystals The many terms used in the literature to denote structural types of crystals are often not clearly defined. To clear up some of the confusion, the meaning of the more important terms will be given here. ideal, or perfect without any structural imperfections are called "ideal crystals,,or ''Perfect'' crystals,n meaning a Homogeneous interior structure of atoms, ions or molecules, as the case may be. In other words, at every point in the interior of the crystal exactly the same orientation of the crystallographic axes of the coordinate system would exist. The Surface of such a body, if etched with an appropriate etching reagent, would reflect light with perfect uniformity. Crystals of this type are almost nonexistent. Real Crystals.—L'Real crystals"' may contain various types of structural defects, which can be classified into: (I) lineage structure, (2) mosaic-block structure, (3) lamellar structure. The inhomogeneities many,in these groups mean that the orientation of the crystallographic aies will not be the same at every point within the interior of a crystal (or grain of a poly crystalline body). 'Perjecl Real Crystals.—The term "perfect real crystals " is generally used to describe crystals with minute structural or thermo-dynamical inhomogeneities. The former

Jan 1, 1946

By James A. Barr

THE writer's first experience with flotation was during World War I, in the beneficiation of Alabama graphite schist ores. One plant used a cone with a peripheral overflow; dried ore was distributed by a rotating disk onto the surface of the water. No reagents were added. The flake-graphite film floated along with some fine silica. Dewatering screens separated the flake. Naturally unit capacities were low but results were satisfactory. Minerals Separation mechanical flotation machines were used in another graphite mill. Pine oil was added directly to the head cells, with very good results. All the graphite concentrates from both types of flotation were carefully refined after drying by passing through burr mills, followed by very close sizing on sifters. In March 1927, the writer ran a very successful flotation test on minus 28-mesh, deslimed, Tennessee brown phosphate "sand,"[t] using a mechanical laboratory machine built in the shops of the Anaconda Copper Mining Co., through the courtesy of Ernest Klepetko. The machine was soon converted to a subaeration type, with improved results. This phosphate research program was greatly enlarged and led to the formation of the Phosphate Recovery Corporation. The development of nonmetallic flotation followed rapidly. The first flotation machine for beneficiation of phosphate was installed in January 1928, in a pilot mill, by International Minerals and Chemical Corporation, at Mulberry, Florida. These machines were Minerals Separation, 24-in., subaeration types, with weir control of pulp between cells. The sand bleeders were very small-about 1 ¼ -in. diameter. As the feed contained 15 to 25 per cent plus 28-mesh material, the cells choked up frequently. This was corrected by cutting a 2 by 6-in. bleeder opening above the impellers, at grid level, which short-circuited the coarse fractions directly into the feed of the next cell. The matter of size classification and grinding was a considerable problem, which does not come within the scope of this article. Because of the troubles noted above, cascade-type roughers were installed in the second flotation plant, built about 1930. Experimental cells had been tried in 1928. General plant layout is shown in Fig. I and details of the cascade construction in Fig. 2. The cascade installation in plant No. 2 gave good results and eliminated troubles due to choke-ups and coarse feed. The capacities and metallurgical results equaled those of the modified 24-in. Minerals Separation flotation machines in plant No. I The objections to the cascade installation are the floor space and mill height required. In 1939 an improved Minerals Separation machine was tested in parallel with the cascades. Extensive tests indicated

Jan 1, 1945

By P. W. Ramsey, G. L. Werley

THERE have been numerous examples in recent years of the similarity between aging behavior and diffusion behavior, where a plot of the logarithm of the aging rate versus the reciprocal of the absolute temperature yields an approximate straight line, analogous to a similar plot of the diffusion coefficient D (log D vs. 1/T). Austin and Rickettl have pointed out that this linear relationship holds empirically for the de- composition of austenite into pearlite and bainite in carbon steels, and Robertson' has shown similar trends in the aging of 24S-type aluminum alloys. Jenkins and Bucknall³ have also demonstrated the association between aging and diffusion rates for nickel-silicon-copper alloys. Jetter and Mehl,4 however, have shown that the maximum rate of dilation of a series of aluminum-silicon alloys does not show this linear relation and Mehl5 has pointed out that careful study of available knowledge indicates that "aging rates increase with temperature approximately exponentially, whereas D increases precisely exponentially." He further notes that "the rate of aging at a given temperature is the greater the lower the melting point of the alloy, which is also true for D." This paper describes the aging changes occurring in a zinc-25 pct manganese-15 pct copper-0.1 pct aluminum die casting alloy. It was found that this alloy does show this linear relationship and use was made of this relationship to estimate aging rates at low temperatures from data acquired at elevated temperatures. It should be noted that the aging reaction is being studied only indirectly, using changes in certain properties as criteria of the progress of the phenomenon. This alloy is purely an experimental one and is not available commercially. Zinc-Manganese-Copper System: The zinc-rich portion of the zinc-manganese-copper diagram which is of significance in the present work is quite uncertain. X ray examination of the alloy as die cast shows a phase similar to the epsilon phase (hexagonal close packed) of the copper-zinc system. All of the data accumulated indicate that the epsilon phase of the zinc-manganese-copper alloy is stable at high temperatures; that is, 500°C or above. Below this temperature a new phase is precipitated on annealing, and a decrease in specific volume occurs. At elevated temperatures this phase change occurs quite rapidly, while at room temperature the alloy has shown no change after several years. According to X ray data, this precipitated phase resembles the gamma phase (cubic) of the copper-zinc system, a hard and brittle structure. From examination of the microstructure and from X ray examination of the alloys annealed at

Jan 1, 1951

By Helmut Thielsch

During the last three decades a great many arguments have been presented on the subject of "mosaicJ' or "blockJJ structures of metals. Apparently because of insufficient evidence, the "block-structure" theories have never been widely understood among the physical metallurgists in this country, and most investigators among the few that have tried to demonstrate the existence of such an inner strutture Of crystals or grains have failed to recognize also the existence of a lamellar structure. Moreover, little thought has been given to justify the existence of such "lamellar" or "mosaic-block" structures on a theoretical basis. Since properties such as Plasticity; ferro-magnetism, hardness, diffusion, and others may be explained by structural faults in the lattice network of the crystals: the great importance of a more detailed knowledge of the structure within crystals or grains becomes now evident. Because Of the vast extent of the field Of submicroscopic structures, it shall be the purpose Of this paper only to review the more important of the results obtained by other investigators, especially in Germany, where a great deal of attention has been given to mosaic structure during the last three years. The origin of this mosaic patternt and effects of cold reduction and recrystallization will be shown in further studies later on. Imperfections in Crystals The many terms used in the literature to denote structural types of crystals are often not clearly defined. To clear up some of the confusion, the meaning of the more important terms will be given here. ideal, or perfect without any structural imperfections are called "ideal crystals,,or ''Perfect'' crystals,n meaning a Homogeneous interior structure of atoms, ions or molecules, as the case may be. In other words, at every point in the interior of the crystal exactly the same orientation of the crystallographic axes of the coordinate system would exist. The Surface of such a body, if etched with an appropriate etching reagent, would reflect light with perfect uniformity. Crystals of this type are almost nonexistent. Real Crystals.—L'Real crystals"' may contain various types of structural defects, which can be classified into: (I) lineage structure, (2) mosaic-block structure, (3) lamellar structure. The inhomogeneities many,in these groups mean that the orientation of the crystallographic aies will not be the same at every point within the interior of a crystal (or grain of a poly crystalline body). 'Perjecl Real Crystals.—The term "perfect real crystals " is generally used to describe crystals with minute structural or thermo-dynamical inhomogeneities. The former

Jan 1, 1946

By J. W. Marx, R. H. Langenheim

The authors are to he complimented for a timely presentation of useful information concerning application of heat to oil reservoirs to increase the rate and ultimate recovery of oil. The solution for heated area resulting from constant rate injection of a hot fluid, presented by the authors, and the fluid-flow analogy, solved by Carter,' are particularly interesting in that 110 restriction is placed on the direction of development of the heated area. It is not necessary that the heated area grow radially. Thus the solution could provide useful information for heat injection in any type of well pattern with any specified swept area data. However, it was assumed in the development that the heated region would remain at a constant clevatcd temperature. Vertical heat losses were computed on this basis. Physically. the assumption that the heated region will remain at a constant temperature (independent of distance from the injection point) appears to require that the heat injection medium be stcam, or other condensible gases near the boding point at injection pressure. If a hot liquid below the boiling point or a hot gas considerably above saturation temperature were used, the temperature of the heated region would decrease with distance from the injection well. Lauwerier2 has discussed this problem for a linear system. (See also Jenkins and Aronolsky; and McNiel and Nelson.') Thus, the authors' solution applies more nearly to steam injection than to hot water injection or hot, non-condensable gas injection. Assuming steam as the injection medium, it appears that steam would pass through the constant-temperature heated region and condense upon contact with the unheated sand. The tempcrature in the condensing region would probably be governed by the release of heat of vaporization required for phase equilibrium at the existing pressure distribution. Temperatures in the region would also be influenced by vaporization of hydrocarbon. Thus, it is doubtful that an expression for radial temperature distribution based on heat conduction only (such as the authors' Eq. 9) would have practical significance. As pointed out by Marx and Langenheim, the growth of the heated area under constant rate steam drive will eventually be limited economically by vertical heat loss. The possibility of continuing to move heat economically by cold water injection or by increasing the steam injection rate appears to be a very important consideration. (Movement of liquids away from the injection well should increase injectivity.) Fortunately, the solution presented by the authors may be generalized to thc case of a variable heat injection rate. The general solution is:

By AIME AIME

YALE UNIVERSITY looked like a top-notch school to "Bert" Phillips in spite of the belief that the college in the home town sometimes looks less attractive than a more distant campus. So Bert, a native of New Haven, earned his B.S., M.S., and Ph.D. degrees from Yale. Immediately after Yale days lie served as metallurgist of the Scovill Manufacturing Co., Waterbury, and then went to the Central Research Laboratories of the American Smelting and Refining Co. at Maurer, N. J., where since 1931 he has been superintendent of research. Bert has contributed to metallurgical literature many reports of studies on the constitution and the physical, metallurgy of copper and copper alloys as well as papers on general nonferrous physical metallurgy.

Jan 1, 1938

By C. S. Matthews, H. C. Lefkovits

Drilling progress is often delayed by sticking of the drill string. The development of preventive and remedial methods has been hampered by incomplete understanding of the sticking mechanism. A recent lahorntory investigation hns indicated that one type of sticking may be attributed to the difference in pressure between the borehole and formation. This paper shows, by means of soil mechanics, that the primary cause for differential pressure sticking is cessation of pipe movement, whereas diflerential pressre and stanrtding time determine the severity of the sticking. The analysis stresses the importance of using low-weight muds with low solids content and low water loss to alleviate diflerential pressure sticking and describes why packed hole drilling, long strings of drill collars, and a large deviation from the vertical are conducive to sticking. Finally, preventrve and remedial methods ore evaluated, and a theory is presented on the release of stuck pipe by spotting oil. INTRODUCTION Since drilling with long strings of oversize drill collars has become standard practice in many areas, the incidence and severity of the stuck pipe problem has increased. It has been noticed that in the majority of these cases the sticking could not possibly be attributed to key seating or caving of shales. It appeared that, due to the differential pressure between the mud column and the formation fluid, the collars were pressed into the wall and so became "wall stuck". Points to note about differential pressure sticking are: (1) sticking is restricted to the drill collars, (2) the collars become stuck opposite a permeable formation, (3) the sticking occurs after an interruption of pipe movement, (4) circulation, if interrupted, can be restarted after the sticking is noticed, and (5) no large amounts of cuttings are circulated out after restarting circulation. Helmick and Longleyl investigated pipe sticking by differential pressure in the laboratory and found an empirical relationship between the differential pressure, the sticking time and the required pull-out force. In this paper an explanation of the mechanism is given based on Terzaghi's theory of clay consolidation. A qualitative description is given in the following paragraphs while the derivation of fonnulas is given in Appendices. This paper is a first attempt to explain pressure differential sticking and many points will require additional theoretical and practical investigation before the problem can be fully understood. PRESSURE DIFFERENTIAL STICKING AS A CONSOLIDATION PROBLEM In any borehole, where the mud pressure is higher than that exerted by the formation fluids, a mud cake is formed opposite the permeable sections of the hole and a continuous flow of filtrate takes place from the mud, through the cake and into the formation. This radial flow pattern requires a certain distribution of the hydraulic and the effective (grain-to-grain) stresses inside the mud cake. Any quantitative or qualitative change in the external pressure conditions will produce a change in the flow pattern and, consequently, also in the internal stress distribution inside the cake. In view of the low permeability and the high compressibility of a clay mud cake, the adjustment of the internal stress distribution is slow and is accompanied by a change in volume. Time dependent stresses are thus created which gradually diminish as the new state of equilibrium between internal and external pressures is approached. Some 30 years ago, Terzaghi developed his "Theory of Consolidation" to account for the time-dependent stresses and settling of clay formations under the influence of external loads. He derived a differential equation by which the time-dependent hydraulic stress and the consolidation can be computed for any point inside the layer during the consolidation process. His theory is based on the assumption that the change in stress is solely due to a change in water content and it may only be applied to one-dimensional consolidation phenomena. Other investiga-tors5,10 have expanded his theory to include processes of more than one dimension. The difference between the external pressures on the mud cake before and after sticking is a qualitative one (isolation of part of the cake by the static contact with the drill collars after pipe movement has been stopped)', and the time-dependent stresses thus created may be investigated by means of Terzaghi's theory. By this analysis the changes in the nature of the contact surface between the drill collars and the mud cake during the sticking can be explained; and the friction force between the two may be computed as a function of the sticking time, the borehole dimensions and the mud cake characteristics.

By Robert H. Richards

This truly remarkable machine was built on a preliminary scale in May, 1895. The first full-sized table was built by Mr. A. R. Wilfley, and was used in his own mill in Kokomo Colo., in May, 1896. The first table sold for installation was placed in the Puzzle mill, Breckinridge, Summit county, Colo., in August, 1896. The mill enthusiasts at first hailed it as the cure for all the ills that flesh is heir to in the milling line. A little later it was found to make losses which were serious, and on this account the table succeeded only to a limited extent in displacing the vanners of the gold-mills. Still later, mill-men in a number of districts throughout the country made special studies of the faults of the machine, and devised a number of ways of grouping supplementary machines to overcome as far as possible the losses, and at the same time retain the benefit of the extraordinarily large capacity accompanied by the production of clean concentrates for which the machine has become so justly famous. I hope to make an exhibit of some of these methods in an appendix to my book on ore-dressing which is now in preparation. These experimenters have not written up the subject, and if they possess all the facts they have not given them out for the benefit of the mining profession at large. The object of this paper is to obtain the facts and to present them so clearly that their bearing can be seen by all. To this end two complete series of tests have been planned. One (the present paper), to study concentration of galena in presence of quartz; the other (to follow shortly), to study concentration of chalcopyrite in presence of quartz. Some authorities claim that the table does its best work when treating natural products; by this phrase I mean products which have been crushed to pass through a limiting

Jan 1, 1908

By Frank Speller

WE are here to honor again the memory of Henry Marion Howe, one of the foremost metallurgists of his time, and it is indeed a great privilege to be called upon by the Board of Directors of .this Institute to give the memorial address this year. Professor Howe started active investigation of corrosion of iron from a metallurgical standpoint in 1887, and made several important contribu-tions to the subject from 1895 to 1908.(1) ? The papers named in the bibliography are only a few of his valuable papers, but in all his works he sets a high standard of scientific accuracy, together with a clearness and power of expression rarely equaled in engineering literature. There-fore it seems appropriate on this occasion to review the work on corrosion of this distinguished gentleman and then endeavor to make a brief inventory of what has been accomplished since his time. Howe saw the beginning of the steel industry in America and before he died (May 14, 1922) witnessed it develop to a production of 45,000,000 tons per year. He was naturally very much interested in the infant industry and was quick to see the importance of the question of corrosion. It was my privilege to discuss the subject of corrosion frequently with Professor Howe at various times from 1905 to 1908; in this, as in other metallurgical problems, he sought the truth without bias and always insisted on proving an opinion or conclusion before accepting it. We should remember that when Howe started his investigation of corrosion, in 1887, steel was rapidly supplanting wrought iron. Certain papers in the early eighties (now forgotten) claiming much greater durability for wrought iron than for steel aroused Howe's interest. He could not reconcile the statement that steel was intrinsically and incurably less durable than wrought iron with the continued and widening use of steel,

Jan 1, 1934

By G. W. White

Over the past several years, the steady progress of gas lift from a mysterious art into a developing science has been traceable through the many fine papers that have appeared in Journal of Petroleum Technology. Consequently, this magazine has rightly become a standard for the serious students of gas lift all over the world. The following discussion is offered in a sincere attempt to accurately present certain topics covered in the subject paper in the light of acknowledged state of the art procedures. INSTALLATION DESIGN The first point to be questioned is the author's installation design, beginning with Eq. 6. The use of 1,200 psi in the spacing equation instead of the 1,275 psi noted as available seems, at first glance, to be a simple arithmetic error. Upon further examination, it appears evident that both this 75 psi plus the 100-psi safety factor must be subtracted from available kickoff pressure because of conditions imposed by the characteristics of the ASC valve (see Fig. B-1). Pressure-charged valve design is incorrectly penalized by spacing the first valve using only 1,100 psi. The use of such a high back-pressure makes it appear that a typical ASC installation would require no more valves than a comparable conventional valve installation. Using a value of 100-psi tree pressure, the well could be valved to 11,000 ft very conservatively with seven pressure-operated valves, but would still require 11 ASC valves. The use of 400-B/D spacing gradient for a 140-B/D rate is not an accepted practice using precharged valves. The author would have done well to note the advantages to be gained by reducing the 500-psi tree pressure, which is clearly explained by Beadle, Harlan and Brown.' In Step 1 of Part III of the continuous flow discussion, the author incorrectly applies the Poettmann and Carpenter curves.2 Item 2 is an incorrect statement. An excellent reference on this point is the paper by Baxen-dell and Thomas.' VALVE MECHANICS The next topic relates to the mechanics of precharged valves. Eq. 2 for the ASC valve can be used to describe the condition of equilibrium, wherein the valve is closed with opening pending. When this equation is used to determine relative values of casing, dome and tubing pressure with conditions approaching the transition value, some strange results are obtained. The following uses the author's symbols and values given on page 689. Fig. B-1 shows the condition that exists at the moment an ASC valve has been uncovered during the unloading process (Condition I). The obvious result is a locked condition. The basis for the curve is shown on the figure which includes 1,000 psig casing pressure to uncover the valve. If injection gas is not bled off the casing until the pressure is decreased by an amount exceeding the stabilizer discharging valve pressure, upward adjustment of the casing pressure is mandatory for the valve to open and unloading operations to continue. In Condition I the dome pressure exceeds the casing pressure by 20 psi, and the tubing pressure required to open the valve is 1,212 psig. This tubing pressure would not exist under the assumed conditions. In Condition I1 the casing pressure is increased to the dome pressure, and the tubing pressure required to open the valve is 1,102 psig. It is apparent that the casing pressure must be increased to a value exceeding the dome pressure before unloading operations could continue. In Condition I11 a maximum casing pressure of 100 psi (stabilizer charging valve set pressure) above the dome pressure is reached, and the tubing pressure required to open the valve is 549 psig. The author's statement after Eq. 5 that "the minimum tubing pressure required to open an ASC valve is equal to the casing pressure at depth less the transition pressure of the valve" is incorrect except for Condition I11 only. Otherwise, the equation is invalid.

Jan 1, 1965

"The Midvale. Plant of the United States Smelting, Refining and Mining Company, situated twelve miles south of Salt Lake City, consists of mills for concentrating lead-zinc ores and a custom lead smelter.The milling department includes a 475-ton gravity mill for ores from the United States Mines at Bingham, a 100-ton Huff electrostatic zinc plant and a 60-ton pilot flotation mill for differential separation of lead and zinc. The gravity mill and electro¬static plant are being replaced by a 600-ton differential flotation plant, now under con¬struction, for differential separation of lead, zinc and iron. This new mill will have cap¬acity for treating custom ores in addition to ores from the company's mines at Bingham.The smelting department is equipped to handle 1600 tons of charge per day through six blast furnaces, 48 inches by 160 inches at the tuyeres. All gases from both blast furnaces and roasters are filtered through baghouses, which remove the dust from the gases so effectively that even when the plant is running at full capacity no smoke can be seen coming out of the 450-foot brick stack handling rca2ter gases, nor out of the two shorter steel stacks which take the blast furnace gases. On this account the Midvale plant has come to be known as the ""smokeless smelter.""The blast furnace gases are filtered through 832 woolen bags, 33 feet 6 inches by 18 inches in diameter, and 1200 woolen bags, 28 feet by 12 inches in diameter."

Jan 1, 1925

By K. R. Van Horn, L. W. Kempf

Plastic deformation of most commercia1 metals within a sufficiently low temperature range results in profound changes in structure and properties, of which the causes and effects are not completely understood. One of these effects is the presence of internal residual stresses and strains, which ordinarily do not appear to require specific consideration in most structural applications but which may be quite undesirable in particular instances. For example, in heavy sections that require considerable machining before assembly, residual stresses may be undesirable because of the distortion they cause when their balance is disturbed by machining or otherwise. In addition, the distribution of stresses may be such that it acts in the same direction as the applied load, thus bringing about premature failure or reducing the load-carrying capacity of the member. One source of residual stress in metal structures is the plastic deformation that may occur during rapid cooling from relatively elevated temperatures, as in the cooling of a casting in the mold or the quenching of a heavy section from elevated temperatures during heat-treatment. These residual stresses are usually undesirable because their direction of operation and magnitude cannot be controlled well enough to permit utilization of the changes in properties of the metal that they may bring about. The most convenient manner of controlling such residual stress is by proper selection of the cooling rate or by reheating to a temperature at which plastic flow can take place, resulting in relief of the residual stresses and strains. Both of these methods of control, however, may cause a reduction in the optimum properties obtainable from the previous operation. A compromise must be struck, and if it is to result in the best possible combinations of properties, specific information must be available regarding the magnitude of the stresses and the rate at which they are affected by variations in cooling rate or in reheating temperature. The complete quantitative estimation of residual stress in complicated metal shapes is exceedingly difficult, if not impossible. In simple sections, however, relatively quantitative analysis may be applied and useful cstimations of stress distribution may be made. This paper is concerned largely with the rate of relief, upon reheating, of internal residual stress in simple aluminum-alloy structures. Since even with simple structures quantitative estimation of residual stresses is laborious and costly, an attempt was made to find other means of collecting data upon which commercial heat-treatments might be based. Incidentally, a few data were collected bearing on the problem of relaxation of aluminum alloys. Determination of Residual Stresses The magnitude and distribution of residual stresses in simple aluminum-alloy shapes rapidly cooled from elevated temperatures has been discussed in a previous paper.' Fig. I reproduces some of the data

Jan 1, 1942

By L. W. Kempf, K. R. Van Horn

Plastic deformation of most commercia1 metals within a sufficiently low temperature range results in profound changes in structure and properties, of which the causes and effects are not completely understood. One of these effects is the presence of internal residual stresses and strains, which ordinarily do not appear to require specific consideration in most structural applications but which may be quite undesirable in particular instances. For example, in heavy sections that require considerable machining before assembly, residual stresses may be undesirable because of the distortion they cause when their balance is disturbed by machining or otherwise. In addition, the distribution of stresses may be such that it acts in the same direction as the applied load, thus bringing about premature failure or reducing the load-carrying capacity of the member. One source of residual stress in metal structures is the plastic deformation that may occur during rapid cooling from relatively elevated temperatures, as in the cooling of a casting in the mold or the quenching of a heavy section from elevated temperatures during heat-treatment. These residual stresses are usually undesirable because their direction of operation and magnitude cannot be controlled well enough to permit utilization of the changes in properties of the metal that they may bring about. The most convenient manner of controlling such residual stress is by proper selection of the cooling rate or by reheating to a temperature at which plastic flow can take place, resulting in relief of the residual stresses and strains. Both of these methods of control, however, may cause a reduction in the optimum properties obtainable from the previous operation. A compromise must be struck, and if it is to result in the best possible combinations of properties, specific information must be available regarding the magnitude of the stresses and the rate at which they are affected by variations in cooling rate or in reheating temperature. The complete quantitative estimation of residual stress in complicated metal shapes is exceedingly difficult, if not impossible. In simple sections, however, relatively quantitative analysis may be applied and useful cstimations of stress distribution may be made. This paper is concerned largely with the rate of relief, upon reheating, of internal residual stress in simple aluminum-alloy structures. Since even with simple structures quantitative estimation of residual stresses is laborious and costly, an attempt was made to find other means of collecting data upon which commercial heat-treatments might be based. Incidentally, a few data were collected bearing on the problem of relaxation of aluminum alloys. Determination of Residual Stresses The magnitude and distribution of residual stresses in simple aluminum-alloy shapes rapidly cooled from elevated temperatures has been discussed in a previous paper.' Fig. I reproduces some of the data

Jan 1, 1942

By P. R. Sahm, T. V. Pruss, D. A. Gandolfo

Cb 3 Sn powders were hot-pressed to estahlish densi-fication conditions and assess the possible use of such compacts in multiphase structures with ceramic or magnetic inclusions. Superconducting transition temperatures, Tc, were measured as a function of powder particle size, pressing temperature, and second-phase admixtures. The highest transition temperatures were found in coarse powder (5 to 500 u) compacts and were only weakly depended on pressing temperatures up to 1200°C. Fine powders (below 5 p), however, both single-phase CbsSn and Cb3 Sn-composites, showed a stronger dependence on hot-pressing temperatures. While Al2 O3 phase admixtures did not affect T, much more, a Pronounced T, degradation was observed upon the addition of ferrimagnetic Fe2 Mno. 5 Zno.5 O4 powders. Likewise, critical current densities, Jc, at 4.2° K were lowered appreciably in the ferrite doped samples, whereas the neutral A1203 inclusiow gave slightly improved Jc values. MULTIPHASE structures in electronically active materials have recently gained in interest as pointed out by Galasso in a review article.' In superconductors the most widely reported group are eutectic alloys which have been mostly investigated with respect to the proximity effect.2"4 In addition, "artificial eu-tectics", for example in the form of mercury-vycor glass sponge5 or fine niobium wires imbedded in a copper matrix,= have been prepared to attain higher critical fields and critical current densities. The idea was to enhance flux pinning phenomena by second-phase inclusions or ho1es. 7 Flux pinning should also be possible by the introduction of insulator inclusions into a superconducting matrix. Ceramic-metal combinations are most easily produced by hot pressing (= pressure sintering), as it permits an almost unlimited selection of material combinations. Cb 3 Sn has been prepared by vapor phase growths or in the form of thin films. Large compacts must be sintered,1° however, and normally present difficulties. At temperatures below 1350°C insufficient densities are obtained and at higher temperatures the loss of tin due to dissociation upsets the stoichiometry. Hot pressing is a natural approach to circumvent the problems, since one can obtain satisfactory densities despite low sintering temperatures. This work was mostly concerned with establishing conditions to hot press Cb3 Sn and Cb3 Sn multiphase structures (= composites), because no data are presently available, and to evaluate these with respect to their transition temperatures. However, a few measurements on critical current densities were also carried out, in particular to assess the value of ferrimagnetic inclusions. I) EXPERIMENTAL PROCEDURE The experimental procedure involved the preparation of feed material and powders, hot pressing, and evaluation of the resulting ingots. As no attempts were made to synthesize Cb3Sn from the elements during hot pressing, feed material had to be produced. For this purpose, a stoichiometric Cb-Sn powder mixture was compacted into a 3-cm-diam ingot (80,000 psi) and then inserted into a quartz tube and evacuated. Rf heating was employed. Above the tin melting point (230°C) liquid tin was forced out of the ingot, but was pulled back by capillary action after approximately 0.5 hr of continuous pumping at 700°C. Thus, it appears that evacuation at this temperature caused desorption of impurity gas creating wetting surfaces which, later on, favored alloying at relatively low temperatures. After a presintering period of 17 hr at 800°C, the quartz tube was tipped off and sealed into another such larger-diameter tube which, in turn, was connected to a pump system. This configuration permitted a temperature treatment at 1400°C, carried out for 65 hr, without collapsing of the glass walls or unfavorable chemical interaction of Cb3Sn with the quartz. The resulting material was

Jan 1, 1969