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By J. A. Cahill, A. D. Kirshenbaum

Using an alumina or zirconia crucible with an alumina sinker or a molybdenum sinker coated with zirconium dioxide, the density of liquid iron was determined by the immersed-sinker method over the temperature range of 1800" to 2500°K. The density, with respect to temperature, is ex-Dressed by the equation Dg/cm = 8.523 - 8.358 X 10 T'K The molar Volumes and thermal coefficients of expansion were calculated. Iron, upon me1ting, was found to expand 3.5 pct. A basic knowledge of the physical properties of materials at high temperatures is becoming increasingly important. A check of the literature shows, that in spite of the importance of iron, very few measurements have been made of its physical properties in the liquid state. Density measurements have been made by Benedicks and his collaborators1g using the method of balanced columns, by Desch and smith4 using the immersed sinker method with an alumina sinker, by Lucas using the maximum bubble method5 and by Stott and endall' who used an alumina pyknometer. In the method of balanced columns, the difference in level of molten iron in two arms of a U-tube, together with the corresponding difference of pressure had to be measured. The formation of gas bubbles in one or both arms was a great source of error. These values are very erratic. They vary from 6.83 to 7.45 g per cm3 at the melting point (1805"~) and from 6.45 to 7.15 g per cm3 at 1890°K. Stott and Rendall determined the density at 1837"K, with a reproducibility of *0.2 pct. They used an alumina pyknometer fired to 1973°K. The vessel was filled in a vacuum furnace by immersion in the liquid metal. When thermal equilibrium was attained, the pyknometer was withdrawn, cooled, the ingot removed and then weighed. The chief disadvantage of the method was the difficulty of inserting the pyknometer without cracking it. The authors have been able to determine the density of liquid iron from its melting point up to 2500°K, by using the immersed-sinker method, with A1203 or ZrOz crucibles and A1203 or molybdenum sinkers coated with Zr02, Fig. 1. EXPERIMENTAL Apparatus. In these studies the source of heat was the carbon tube resistance furnace with an argon atmosphere described previously.7 Experimental runs were made using either Ala3 or ZrOz crucibles. The sinkers used were 1) pure A1a3 and 2) molybdenum coated with ZrOz. The crucible, 2 1/8 in. in diam and 3 in. high, was centered in the furnace on an Ala3 of Zr02 pedestal. The sinker, 1/2 in. in diam and 1 1/2 in. long, together with a counter weight, was suspended from an analytical balance into the melt by a molybdenum wire. Procedure. The procedure, as described previously,' consisted in measuring the weight loss of the sinker in the liquid iron while determining simultaneously the liquid iron temperature by means

Jan 1, 1962

By David L. Holt

The contribution of grain boundary shear to total elongation, CS/E&apos;, has been measured in an Al-Zn eu-tectoid alloy that was quenched from above the invariant temperature, then annealed at 250° C to a grain size of&apos; 1.8 p. At 250°C, ks/E&apos; is low at both high and low strain rates, but reaches a maximum, estimated as 60 pct at an intermediate rate of 5 X 10 per rnin. Rate sensitivity, as measured by the index m = a log a/a log E&apos;, follows the same trend, and furthermore the maximum values of m and -cur at approximately the same strain rate. This result, combined with the metallographic observation that boundary migration enhances boundary shearing, is interpreted as supporting a previous suggestion that the high rate sensitivity characterizing super-plasticity is the result of combined boundary shearing and migration. It is suggested that the latter event relieves stress concentrations at triple points, and smoothes boundaries so that stress is governed largely by a viscous boundary shear. GrAIN boundary shear has been considered in relation to superplasticity in several recent papers.&apos; The problem has been to explain the high strain rate sensitivity of flow stress, and the variation of rate sensitivity with strain rate (E&apos;) and grain size (L). The requirements for superplasticity, small L and high T, suggest the reasonableness of an approach to high rate sensitivity involving grain boundary shear. Further support came from experiments on the A1-Cu eutectic alloy,&apos; where it was found that strain rate sensitivity of cast material annealed to produce an equiaxed, micron-size grain is always low; taking as an index of rate sensitivity m = a log a/a log <, m < 0.3. However, m in hot-worked alloy of comparable grain size can be as high as 0.7. In the cast and annealed material, each phase is a single crystal, the only boundaries are interphase boundaries, and it is, consequently, geometrically impossible for boundary shear to contribute to deformation in any major way. Other observations (for hot-worked material) were a-L at constant (low) strain rates and indications that the rate of recrystallization was enhanced as strain rate increased. As a result of this work, it was proposed that high rate sensitivity arises from a deformation mode of boundary shear associated with boundary migration. Migration serves to relieve stress concentrations at triple points, and smoothes boundaries so that they assume properties of fluid films. On the other hand, the low rate sensitivity observed at high and low strain rates reflects deformation of bulk material. Measurement of the variation of grain boundary shear with strain rate and m have not yet been made. Such measurements are important, especially in view of a proposal, differing in detail from the above, that high m arises merely from a transition between a grain boundary shear mode of deformation at low rates to a transgranular mode at high rates.2&apos;4 In the present work, the contribution of boundary shear to total deformation is measured and in addition metallographic observations are made on surfaces of deformed specimens to look at the interaction between boundary shear and migration. The Al-Zn eutectoid alloy was chosen for its homogeneous, fine-grained structure, which is obtained readily without hot-working. It has also been the subject of a previous phenom-enologically directed study. EXPERIMENTAL Material. Compression specimens, cross section 4 by + in., length \ in., were machined from a sand-cast ingot of composition 77.5 wt pct Zn, 22.5 wt pct Al. (The melt was prepared from 99.9 pct Zn and 99.99 pct Al.) After homogenization at 375°C for 50 hr, the specimens were quenched in brine and removed before the heat evolution that accompanies de -composition of the high-temperature phase.5&apos;6 The resulting microstructure, see Fig. l(a), was too fine for grain boundary sliding to be easily studied; coarser structures were obtained by annealing for various times at 2 50°C. Annealing was terminated by a brine quench. Final average intercept lengths between all grain boundaries (both interphase and those lying in a phase), L, were: 0.5 p [annealed for 15 min, Fig. (a)], 0.8, 1.1, and 1.8 p [Fig. l(b)l. Testing Procedure. An Instron machine was used for most of the compressive deformation. Tests were of two types: those in which crosshead velocity was changed in steps to measure m as a function of strain rate15 and tests at constant velocity to a fixed (engineering) strain of -0.2 (20 pct). Stress reached a steady-state value (a) which was plotted, on a logarithmic scale, against log strain rate (E&apos;). An alternate and equivalent evaluation of m was to take the slope of the log o vs log 6 curve. Time at temperature before testing was 15 min. Strain rates covered by the Instron (4 x lo-&apos; to 4 x 10&apos; per min) were insufficient; at a higher rate of 5 x lo2 per min a gas-operated testing machine was used, the gas driving a piston to compress the specimen at a controlled velocity.&apos; To obtain points on the log a vs log E&apos; curve at low rates, specimens were compressed by a dead weight. strain rate was an average value computed by dividing strain at the end of test by loading time. In some tests strain was measured at fractions of the loading time; creep rate was found to be reasonably constant.

Jan 1, 1969

By Henry Sturgis Drinker, Rossiter W. Raymond

Jan 1, 1914

By T. L. Joseph

THE committee appointed to investigate the application of oxygenated air to the blast&apos; furnace believes, after a careful study of the problem, that this enriched air will increase hearth temperature, tonnage, flexibility of operation, and quality of pig iron made, and that fuel consumption will be decreased. These improvements are supported by theoretical evidence; but a practical trial of the process is necessary to establish more definitely the magnitude of benefits realized. The commercial application, however, may profitably be preceded by a test on a smaller scale. A small furnace will, in general, respond to the enriched air in the same way as a commercial furnace and the magnitude of the benefits to be gained from varying additions of oxygen can be fairly well established at relatively little expense. A new experimental furnace, being built jointly by the Bureau of Mines and the University of Minnesota, at Minneapolis, will have a capacity of about 6 tons and will riot require more than 700 cu. ft. of natural air per minute. Its hearth is 36 in. in diameter and its height about 32 ft. Enough oxygen to enrich the blast to the extent recommended by the committee can be obtained from a small oxygen unit. It might even be cheaper to perform preliminary experiments with tanks of oxygen obtained from regular, dealers. A procedure in making the test that suggests itself is to start with operation on normal air; then to use blast, enriched in several steps. Systematic temperature measurements of the tuyeres, slag, and metal would reveal any changes in hearth temperature. When these changes become large enough, the burden may be gradually increased to just within the breaking point and the furnace brought back to normal, if possible, by the addition of oxygen. Such a test would show what might be expected in the way of a decrease in fuel consumption and the time taken to "straighten up" the furnace by means of oxygen. The new furnace at Minneapolis is so equipped that the furnace process can be observed from the stock line to the iron notch. We have been taking gas samples at various elevations in the furnace to study combustibility of the fuel and the reducing power of the gas. If either of these is affected by removing inert nitrogen, the change can easily be measured.

Jan 11, 1924

By O. B. Hopkins

There was no noteworthy development in the oil industry in Peru during 1933 and all activities were restricted to the producing fields. The output of the country increased above that of previous years but there still remained a substantial shut-in production at the close of the year. The total production during 1933 is estimated at 13,259,891 bbl., of which the International Petroleum Co., Ltd. contributed 11,205,-362 bbl. A relatively small amount of new drilling was undertaken during the year. The International completed only one new well although a number of the old producers were reworked and deepened. Comments on Tables There are four oil districts in Peru, as shown in Table 1, although only three of these are now being operated. The exhausted Pirin field was abandoned eight years ago. La Brea-Parinus.—The La Brett-Parinas fields are on the property of the International Petruleum Co., Ltd. in the westernmost part of Peru. These fields include a number of producing districts that are defined by complex fault blocks associated with anticlinal folds. Data covering all the items listed in the table are not available on these fields but can perhaps be supplied in part in the future. Lobitos and Restin.—These two fields belong to the Lobitos Oilfields Limited and are near the coast, 10 to 20 miles north of the La Brea-Parinas fields. According to the Department of Mines and Petroleum of Peru, 311 wells at Lobitos and 197 at Restin had been drilled to the end of 1927. Since that date there has been enough drilling to increase moderately these figures. The depth of wells is not available but it is believed that their average depth is slightly greater than in the La Brea-Parinas area. The productive horizons are of Eocene age. zorritos.—The Zorritos field is the northernmost in Peru and is operated by the Establecimiento Industrial de Petroleo de Zorritos. The field is on the coast about 70 miles north of Lobitos. The number of wells drilled in this field to the end of 1927 was 343, according to the Department of Mines and Petroleum of Peru. The depths of these wells are reported to range from 300 to 700 ft. The largest wells do not produce

Jan 1, 1934

T. A. Rickard, Denver, Colorado: The observations made by the author concerning the treatment of gold-bearing ores, deal with the subject only briefly and in a general way; but, coming from an authority, they invite comment. In stating the fact that a " finely-divided condition " is a necessary characteristic of ores containing free gold, the author must be refer ring to those mining districts only with which he himself is ac quainted. The statement would not be true of certain gold-mining regions in America and Australia. The ores of some Californian mines and the mill-stuff treated at certain of the mills of Clunes and Ballarat in Australia, and of Otago in New Zealand, contain the gold in a free but in a coarse state. Moreover, "reduction to fine sand and flour" is not required by certain ores, even though the gold be in a finely-divided condition. In such cases the gold becomes de tached from the quartz before the gangue has been pulverized into particles as small as those in which the gold occurs. The dry-crushing of free-milling gold-ores is onknown in the new mining regions of the world. It is not clear whether the author has in mind any European district in which such a process is in actual use. If he has, a description of the method and the results obtained would be very valuable. Dry-crushing is, other things being equal, twice as slow and twice as expensive as wet-crushing. In the case of free-milling gold-quartz it serves no purpose, since such ore does not carry sulphides which contain any large percentage of value, and which, by being slimed, may carry away part of that value. The dry-crushing of a free-milling gold-quartz would be considered an absurdity by an American metallurgist. If the ore contain "free gold only," why submit it to a further treatment, such as concentration, after its passage over the amalga mating-plate ? What does the author propose to concentrate ? Again, why anticipate the treatment of tailings by the McArthur Forrest, or some other process ? The satisfaction felt by a mill-man in saving gold by a subsequent treatment of the tailings from his mill appears to me to be like that of the man who shoots at a rabbit,

Jan 1, 1894

By J. H. Jackson, P. D. Frost, C. H. Lorig, L. W. Eastwood, A. C. Loonam

It is well known that for equal weights of material, thin sections of the lighter structural alloys are more resistant to buckling under a compressive stress than thin sections of more dense material. Therefore, structural parts having the same resistance to buckling stresses are generally lightest when they are made of magnesium alloys. Consequently, there is considerable interest in the development of strong alloys having densities equal to or lower than that of magnesium and strength-weight ratios equivalent to those of the strongest aluminum alloys. The development of commercial magnesium-base alloys has been very successful, and their importance among materials in the structural field has been amply demonstrated. However, an even wider structural application of magnesium alloys might be effected if improvements could be made in the cold rollability and cold-forming characteristics. Such improvements, along with production of less directionality in properties. could be effected if the hexagonal close-packed lattice of present alloys could be replaced with a cubic lattice. In 1942, a project, having as its objective the improvement of some of the characteristics of commercial magnesium-base alloys, was initiated at Battelle Memorial Institute under the sponsorship of the Mathieson Chemical Corporation. At that time, one of the authors,* then Chief Metallurgist for the Mathieson Chemical Corporation, postulated that the addition of lithium to magnesium in sufficient quantities to change the crystal structure of the resultant alloy from a hexagonal to a body-centered cubic lattice should produce a magnesium-rich alloy which would have the desired improvements in cold-working characteristics with less directionality in properties. To test this view, a series of alloys was made and was found to have many of the attributes that were predicted. The view that magnesium-lithium alloys were of structural interest was also held by others. In 1943 and 1945, Dean and Andersonl,² obtained patents on magnesium-base alloys containing from about 1 to 10 pct lithium, from about 2 to about 10 pct manganese, and the balance substantially all magnesium; and on magnesium-base alloys containing from about 1 pct to about 10 pct lithium, from about 2 to about 10 pct manganese, from about 0.5 to 2 pct silver, and the balance substantially all magnesium. They noted that an alloy containing 83 pct magnesium, 10 pct manganese, 5 pct lithium, and 2 pct silver could be cold rolled by any of the usual methods and that this alloy was considerably harder and stronger than most other magnesium-base alloys heretofore available. In 1945, Hume-Rothery, et al.,3 predicted that magnesium-lithium base alloys should be soft and ductile and that such compositions, to which was added a third element for the purpose of producing a precipitation-hardening type of alloy, should be ductile, strong, and lighter than magnesium itself. Hume-Rothery investigated the binary magnesium-lithium and ternary magnesium-lithium-silver equilibrium relations and criticized the existing equilibrium diagrams. The binary magnesium-lithium equilibrium diagram has also been investigated by Grube, Von Zeppelin, and Bumm, Henry and Cordiano, Sal&apos;dau and Shamrai, Hof-mann,&apos; and Shamrai.8 The work of most investigators agreed with that of Grube, whose constitution diagram is shown in Fig 1. From the standpoint of development of structural alloys, the room-temperature equilibrium relations are of great interest. An examination of Fig 1 reveals that, from 0 to 5.7 pct lithium, the existing phase is alpha, which is a solution of lithium in hexagonal magnesium. The boundary between the alpha, and alpha plus beta regions, occurs at a Mg/Li of 16.5, corresponding to 5.7 pct lithium by weight. Between 5.7 pct and 10.3 pct lithium, there exists a mixture of the alpha phase (lithium dissolved in hexagonal magnesium) and the beta phase (magnesium dissolved in body-centered-cubic lithium). The boundary of the alpha plus beta and beta regions occurs at a Mg/Li of 8.7, corresponding to a lithium composition of 10.3 pct. Much of the work described here was directed toward obtaining an alloy made up of a large proportion, or entirely, of the body-centered-cubic beta structure. In his early work, Loonam found that specimens of lithium-bearing alloys were very malleable. Ingots of alloys prepared at that time were extruded to 3/8-in. diam bars, and the mechanical properties and the effects of heat treatment were then determined. These data are given in Table 1. The outstanding ductility of the alloys, combined with their moderately high strength, evoked considerable interest.

Jan 1, 1950

By ANDREW CARNEGIE

Although the noble building provided in New York City by Mr. Carnegie for the United Engineering Society has been pushed to about half-completion, the ceremony of laying its corner-stone was not performed until Tuesday afternoon, May 8, 1906. The stone lies just back of the southeast corner of the building, on the north side-of West 39th Street. Among those present were Mr. and Mrs. Carnegie, Miss Whitfield, the sister of Mrs. Carnegie, Ralph W. Pope, Secretary of the Institute of Electrical Engineers, Frederick R. Hutton, Secretary of the. Society of Mechanical Engineers, Rossiter W. Raymond, Secretary of the Institute of Mining Engineers, Charles H. Haswell, the first Chief Engineer of the United States Navy (1836-1851), now in his ninety-seventh year, John Fritz, of the Bethlehem Steel Company, William H. Fletcher, President of the Engineers&apos; Club, E. E. Olcott, President of United Engineering Society, and other interested friends. After an inspection of the interior of the building, the group formed about the corner-stone, which had been draped with the American flag. The exercises were opened by Mr. Olcott, who appropriately welcomed Mr. Carnegie, and briefly expressed the essential value of the building, saying, in part " The societies to be housed underneath this roof have as their aim the pre¬serving and putting in tangible form of the records of scientific accomplishments so as to avoid the repetition of mistakes. The possibility of finding the records of these results all at one center, so near the great Public Library of our city, will be an inestimable advantage to all professions. It is an occasion of no ordinary moment, therefore, when we can welcome Mr. Carnegie and have him lay for us the corner-stone of this great building which his liberality has provided." Mr. Carnegie responded in happy vein, thanking the committee for their greeting, and expressing his pleasure. in being able to do what he had done to further so worthy a cause. Among other things, he said

May 1, 1906

By P. G. Shewmon

Radioactive MgZA has been used to study the rate of self-diffusion in oriented single crystals of magnesium in the temperature range 468O to 635OC. The diffusion coefficients parallel and perpendicular to the c-axis are: Dl, = 1.0 exp (—32,200IRT) cm2 per sec and Dl = 1.5 exp (—32,500IR T) cm Qer sec. The ratio Dl/Dll was found to vary from 1.13 at 468 to 1.24 at 575 C. Assuming a vacancy mechanism, an explanation of this aniso-tropy of diffusion follows from a consideration of the difference in the saddle points for diffusion in and out of the basal plane. RECENT discovery of radioactive Mg2"&apos;-&apos; has made possible the study of self-diffusion in magnesium. The experimental procedure and the results of a study of diffusion in polycrystalline magnesium have been described in an earlier paper.V he present work is an application of the same techniques to the study of self-diffusion in oriented single crystals of magnesium. In the general diffusion problem the diffusion coefficient is a second order tensor relating the two vectors, the diffusion flux, and the concentration gradient. In a hexagonal lattice, such as magnesium, the complete determination of the diffusion coefficient D as a function of direction in the lattice requires a knowledge of D,, and D,, i.e., the diffusion coefficients parallel and perpendicular to the c-axis, respectively. It can be proven quite generally that in a hexagonal lattice D is independent of direction in the basal plane, and that out of the basal plane it varies with 0, the angle between the c-axis and the direction of diffusion, according to the equation D(B) = D,,cos2B + D,sin2B. [I] The proof of Eq. 1 depends only upon the symmetry elements of the hexagonal lattice and upon the transformation properties of a second order tensor." Therefore, Eq. 1 holds for any mechanism of diffusion and any c/a ratio. Experimental Procedure The experimental procedure used with polycrystalline specimens can be briefly outlined as follows. Radioactive Mg" was produced by bombarding a NaCl crystal with 350 mev protons and was chemically separated from the target as MgO. The Mg" was then vapor deposited on a specially cleaned magnesium specimen by heating the MgO on a tantalum ribbon in a vacuum. During the diffusion treatment, oxidation and vapor loss of the radioactive material were minimized by annealing the samples in pairs with the active faces in contact, each pair being inside a magnesium container, which was in turn surrounded by an argon atmosphere in a sealed Pyrex tube. The distance-activity profiles were obtained by measuring the activity of thin sections cut parallel to the original interface with a lathe. The only technique which was peculiar to this work was the preparation and orientation of the single crystal specimens. The single crystals used in this work were grown by E. C. Burke of the Dow Chemical Co., using a modified Bridgman method, in which the furnace and specimen were stationary while the temperature gradient moved.&apos; In growing these crystals the starting material was distilled magnesium, the crucibles were machined from Acheson electrode graphite, and the furnace atmosphere was tank argon. The crystals were grown from sublimed magnesium with the following analysis: 0.0002 pct Al, 0.0017 pct Fe, 0.0009 pct Mn, 0.0001 pct Ni, 0.0006 pct Pb, and less than 0.01 pct Ca, 0.0001 pct Cu, 0.001 pct Si, 0.001 pct Sn, and 0.02 pct Zn. The two crystals used were roughly lh in. diam and eight in. long. The c-axis made angles of about 7" and 78", respectively, with the specimen axes. If the values of D obtained by the use of these two crystals are taken equal to D,, and D,, respectively, the error introduced by this assumption is less than 1 pct. This can be shown by combining Eq. 1, the identity sin% + cos&apos;8 = 1, and the experimental fact that DJDn in magnesium was always less than 1.25.

Jan 1, 1957

By J. Chipman, N. J. Grant, H. L. Bishop, H. N. Lander

Data of several studies on the equilibrium between molten iron and open hearth-type slags have been combined to determine some of the chemical reactions involved in steel-making. Effects of slag composition and temperature on the iron oxide activity, distribution of sulfur between slag and metal, and the carbon content of the metal are discussed. Also, an overall reaction for the equilibrium between sulfur and oxygen is presented. DURING the past 15 years, a number of significant equilibrium studies have been carried out between liquid iron and simple basic and acid slags in an effort to throw light on the chemical reactions involved in steelmaking. This paper is a summary of the experimental reports on investigations which have been conducted at the Massachusetts Institute of Technology, and of related work in other laboratories. The investigations summarized in this paper include the works of Fetters and Chipman1 and Taylor and Chipman,&apos; which dealt with simple slags that are similar to those found in the open hearth. The sulfur determinations of the slag-metal tests of Fetters and Chipman as reported by Grant and Chip-man" are included. Also, the investigations by Win-kler and Chipman&apos; and Grant and ChipmanQ f more complex slag systems are included in this summary. The experimental procedure is described in detail in each of these papers and will not be discussed. Since the previous reports have been somewhat independent, it is desirable to review and combine the data of the various investigations to determine, as accurately as possible, the reactions in the slag-metal systems of the open hearth. It is the object of this report to present the combined data in such a way as to enhance their utility and applicability. Oxidizing Power of Slags of the System (CaO+MgO)-Si0,-FeO in Equilibrium with Carbon-Free lron The slags selected to determine the iron oxide activity in equilibrium with pure liquid iron were those containing less than 2 pct each of P,O,, MnO, or A1,0, on a weight percentage basis. The method used to calculate activities of iron oxide in liquid slags was that developed by Taylor and Chipman.&apos; The solubility of oxygen in molten carbon-free iron under pure iron oxide slags can be expressed by the following eauation —6320 log (pctO)-------------— + 2.734 [1] where T is the absolute temperature. The oxygen solubility values as determined from Eq. 1 were used throughout this study to calculate the iron oxide activity. The iron oxide activities of slags of various iron oxide contents are plotted in Fig. 1 as a function of the basicity, which is defined as the ratio (pct CaO + pct MgO)/pct SiO,, and are based on molecular percentage values of the components. The percent (FeO), is the total iron content in the slag calculated to FeO. Fig. 1 shows that as the basicity increases at constant mol pct (FeO),, the iron oxide activity increases rapidly and reaches a plateau which extends on the basicity scale from about 1.3 to 2.3; the iron oxide activity then decreases rapidly until a basicity of about 3.0 is reached, where it tends to level off. The solid portions of the curves represent the experimental data of Fetters and Chipman and Win-kler and Chipman. Their experimental heats were made in magnesia crucibles, and hence the slags were saturated with magnesia. The broken lines on the left represent the experimental data of Taylor and Chipman, who used a rotating crucible. In general, these slags contained less than 3 pct MgO. The absence of data for slags containing less than about 40 mol pct (FeO), and basicity ratios greater than about 2.5 made it necessary to calculate curves using ionic concepts of slags. The broken lines on the right, which disregard the solubility limits of di and tricalcium silicate and lime, were obtained by following the treatment of Flood and Grjotheim,"

Jan 1, 1957

By W. J. Moore, E. M. Swiggard, H. Shenker

Beryllium is the most soluble of the double-acceptor impurities in germanium; the solubility is at least 1 x 10 19 atoms cm3. Photoconductive, optical, and electrical measurements were made on a set of Ge:Be samples grown without other intentionally added imp~ivities. The excited-states spectrum of beryllium in germanium was determined both in zero field and in magnetic fields up to 30 kc. It was found that the absorption 0-f lines in the vicinity of the G line increased markedly with increasing magnetic field. The ioniza-tion energy of neutral beryllium in germanium was determined to be 24.3 * 0.1 mez: using the excited-states spectrum. An infrared detector using a Ge:Be element was found to have a normalized detectivity D* (50 p, 1000 cps, 1 cps) of 9 X ldO cm-~ps"~-w-&apos;. The Ge:Be sambles exhibited low-field breakdown and inibzirity band conduction effects at low temperatures. WHILE the properties of most dopants in germanium have been thoroughly investigated, the properties of beryllium in germanium have had relatively little attention. Much of the work that has been done&apos; has been concerned with the properties of singly ionized beryllium in germanium. The purpose of the present work was to determine the photoconductive and electrical properties of beryllium-doped germanium (Ge:~e) with a small concentration of other electrically active impurities. Ge:Be is of special interest since beryllium is the most soluble of the known double-acceptor impurities in germanium. MATERIALS PREPARATION A set of &:Be crystals with beryllium concentrations between 5 x 1013 and 1x 10&apos;&apos; cmm3 and without other intentionally added impurities was grown in a hydrogen atmosphere by the horizontal zone-refining techniques described by Swiggard and Shenker.2 The segregation coefficient of beryllium in germanium was found to be about 0.07 and its maximum solubility was found to be greater than 1 x 10&apos;&apos; atoms cm-3 which is in agreement with previous results.&apos; Most of the crystals were found to have a small net concentration of shallow acceptors; for example, a crystal having a beryllium concentration of 1.1 X 1016 cm-3 was found to have a net concentration of shallow acceptors of less than 1.5 X 1013 cm-3. Ingots designed to have a beryllium concentration of 1 x 1017 cm-3 or less exhibited a loss of electrically active beryllium. That is, the beryllium concentration was lower than expected and the decrease of the beryllium concentration along the length of the ingot was much larger than expected. It is hypothesized that this effect is due to the oxidation of the beryllium by the residual oxygen in the system. This effect is similar to but not as severe as the effect observed with boron in germani~m.3, 4 OPTICAL ABSORPTION SPECTRUM The excited-states spectrum of neutral beryllium atoms in germanium was studied by measuring the infrared optical absorption spectrum. A typical spectrum is shown in Fig. 1; the labeling of the absorption lines follows that of Fisher and Fan.* The spacings between the observed lines and the D line are nearly equal to the corresponding spacings for the other ac -ceptors in germanium.5-7 By the use of the theoretical result67&apos; that the neutral impurity ionization energy is 2.53 mev larger than the energy of the D line, the ionization energy of neutral beryllium in germanium was determined to be 24.3 * 0.1 mev at 4.2"K. This method yields a more precise value of the impurity ionization energy than the usual Hall effect method.&apos; The absorption spectrum of Ge:Be was also measured as a function of magnetic field using a magnetic field parallel to the incident radiation and using unpolarized radiation. A typical spectrum taken at 30 kG is shown in Fig. 2. An unexpected observation is that the absorption of the lines in the vicinity of the G line (there is a strong possibility that some of these lines may be associated with lines other than the G line) increases with magnetic field. RESISTIVITY AND HALL DATA Measurements of Hall voltage vs temperature were made on several of the samples. The thermal activa-

Jan 1, 1968

By R. G. Treuting

Germanium single crystals strained in tension at 600°C slip on the {Ill} plane and, macroscopically at least, in the <110> direction. Deformation is in homogeneous: various localized rotations are observed, as is a banding consistent with secondary slip banding. The structure after deformation is polygonized with a domain size of about 2x1O-3 cm. In relaxation tests, an incubation period prior to flow is observed, of duration inversely related to temperature and applied stress. Under continuous loading, there is a sharp first yield point. A critical resolved shear stress therefore must be cited with respect both to temperature and to rate of loading. At 600°C, when loading proceeds at 2900 psi per min, it is 1310 psi. The yield point phenomenon is suggestive of Cottrell&apos;s solute atom atmosphere theory and five points of qualitative agreement with this theory are found. PLASTICITY of germanium at elevated temperatures has been reported by Gallagher,&apos; who ascribed it to slip on {Ill) planes and described some associated effects. Preliminary experiments with single crystals of silicon and germanium loaded as simple beams confirmed {ill) as the slip plane of both materials.V his was demonstrated by the standard technique employing traces on two surfaces of known angle on a deformed crystal of known orientation.3 These experiments did not fix the slip direction, since more than one glide system operated. Uniaxial tensile straining is preferred for this purpose in order to restrict slip to one predominant system and to provide an unequivocal determination of the orientation change with respect to the stress axis. Experimental Method Specimens were diamond-sawed from germanium crystals containing about 5x10-5 wt pct Sb prepared by the zone-leveling process described by Pfann and Olsen;4 these specimens measured about 81/2 in. long, 0.20 in. wide, and were of various thicknesses from 0.035 to 0.060 in. Prior to testing, a specimen was coated over 1 in. or more of length at each end with Apiezon wax, chemically polished (in a solution of 15 ml HF, 25 ml HNO,, 15 ml CH3COOH, and 3 to 4 drops Br2), and dewaxed in warm xylene. A brief re-etching after scribing through a complete wax coating with vernier dividers provided gage marks at 0.200 in. intervals on the polished surface. A specimen with grips soft soldered to the ends was passed through the furnace tube and the grips pinned to the tensile machine in series with a stress gage. The Schopper testing machine is best described by reference to the illustration on p. 107 of Schmid and Boas5 and is operated with the pendulum arm locked, fixing the upper head. Load is applied through the screw-driven lower head, manually or by reduced speed motor. The furnace is 21/2 in. long surrounding a 4x7/16 in. ID quartz tube and was positioned about the specimen to permit free motion. The inert or reducing atmosphere required was sufficiently provided by a flow of helium introduced at the center of the furnace tube, with the tube ends loosely plugged with asbestos paper. Surface corrosion was slight. The stress gage employs a Be-Cu strip with SR-4 units incorporated in a simple bridge network with provision for balancing and calibrating. The bridge output on loading is fed through a Leeds and North-rup dc amplifier to a Speedomax 10 mv recorder, and calibration is obtained by dead loading. Experiments of two types have been conducted. Most have been in relaxation at constant elongation. One stress-strain curve has been taken with the machine continuously driven. Following extension of a specimen, Laue X-ray photographs were taken to obtain the orientation change between deformed and undeformed regions, recorded on a single film by translating the specimen in a plane normal to the beam between exposures. Sequences of such multiple exposures were made on some specimens to include the entire orientation range on one film. Slip Direction To obtain a maximum orientation change with a single slip system, crystals of very closely <110> axial orientation were used. The classic determination of slip direction rests on establishing that direc-

Jan 1, 1956

By Walter A. Backofen, Donald H. Avery

Intense primary and cross-slip traces were observed in easy glide on Cu: 6 pct-A1 single crystals deformed in tension. A mechanism of cooperative source operation is developed which recognizes that both the applied stress and that resolved from dislocation arrays contribute to the stress on a source. By considering the stress from arrays, the activation of secondary systems in easy glide and the difference in appearance of slip markings on pure and solid-solution crystals are explained. Furthermore the cross-slip system is predicted to be second favored during easy glide for a large range of orientations. FROM many studies of easy glide in fcc metal crystals, a pattern of observations has developed which still requires full explanation. In pure copper, aluminum, and silver, the easy-glide, slip traces are fine and uniform with steps 50 to 100A on the primary* system.1-4 Yet it has not been at all clear why slip in the pure materials should occur in this way. On the contrary, one might expect, with simple slip and a low hardening rate, that the weakest sources on the primary system would operate extensively to produce strong slip traces. In a brass, however, intense slip steps up to 0.5 are found on both primary and cross-slip system4,6-9 seeger10 has pointed out that in a material of low stacking-fault energy such as a brass, extensive easy-glide cross-slip could not be thermally activated, but rather must originate on the cross-slip plane. In further explanation, the wilsdorfs4 and seeger10 noted that only the cross-slip system would not harden differently than the primary, whatever the latent hardening tendencies of other systems; therefore, in brass, which exhibits high latent hardening, the cross-slip is the only secondary system which could be expected to operate extensively, once it became active. The explanation of how the cross-slip system, on which the applied stress is low, becomes activated has been related, in a nonspecific way, to pileups by Hirsch11 and Honeycombe.l2 In the work to be described, deformation traces on solid-solution Cu: 6 pct A1 single crvstals were studied with conventional light microscopy and a mechanism proposed to explain both the observed activation of secondary systems in easy glide and the difference in appearance of slip markings on pure and solid-solution crystals. EXPERIMENTAL In preparing the Cu-A1 single crystals, rectangular bars approximately 0.4 in. by 0.4 in. by 6 in. were first machined from ingots made by vacuum melting copper of 99.999 pct and aluminum of 99.99 pct purity. They were then packed in powdered graphite and the crystals grown in a modified Bridgman apparatus at a rate of 5 mm per hr under an atmosphere of purified nitrogen. Crystal perfection as indicated by Laue back-reflection spots was good except for the last inch to freeze, which was discarded. Orientations so determined are shown in Fig. 1. Tensile specimens with a reduced gage section were obtained by masking the ends with electrical tape and chemically polishing in a solution of 20 pct HNO3, 24 pct HAc, 52 pct H3PO4, 2 pct Hcl, and 2 pct H20 at room temperature.13 Finally, the specimens were electropolished in a 30 pct ortho-phosphoric acid bath at 12 v. Tensile deformation was performed in an Instron testing machine at a strain rate of approximately 1 pct per min. During easy glide, extensive cross-slip was observed with all crystals, in spite of the low Schmid factor on this system, and in no case was any other secondary trace encountered. A certain sequence of slip-line development was associated with the extension. At yielding, intense primary traces passing completely through the crystal developed at some point on the gage section, generally near the grips; weak cross-slip traces also appeared, extending from the primary traces into the adjacent undeformed crystal, Fig. 2. Further extension led to primary traces adjacent to the first-formed and connecting with those of the cross-

Jan 1, 1963

By H. W. Schull

The Alligator Ridge gold deposits are located in northwest White Pine County at the southwest end of Alligator Ridge. Alligator Ridge is on the west side of Long Valley in the range of hills that separates Long and Newark valleys. The nearest population center is Ely, about 113 km (70 miles) to the southeast. Access to the Alligator Ridge gold mine from Ely is via US Highway 50 and the Long Valley Ruby Marsh Road. The latitude and longitude is approximately 39° 45&apos; north and 116° 30&apos; west. The Alligator Ridge gold deposits occur in the lower 61 m (200 ft) of the Mississippian-Devonian Pilot Shale formation, a laminated calcareous carbonaceous siltstone. The gold deposits contain carbonaceous, oxide, and jasperoid type gold ore. For more details on the geologic features of the deposits, see Schull, Sutherland, and Ilchik (in press). The discovery story of Alligator Ridge began in the spring of 1976 when the areas mapped as jasperoid on the 1:250,000 scale geologic map of White Pine County (Hose and Blake, 1976) were examined and sampled. Seventeen samples, about 23 kg (50 lb), were collected from an area about 0.65 km2 (0.25 sq mile). Of these 17 samples 10 reported atomic absorption values of less than 0. 1 ppm Au and 7 reported values in the 0.1 to 1.0 ppm Au range. In June of 1976 20 lode claims were staked to claim the area of the rock chip sampling. The claims&apos; end and side center lines were used as a grid for soil sampling. Sample stations were 91 m (300 ft) apart and sample lines were 229 m (750 ft) apart. The samples were sieved to - 180 µm (- 80 mesh). Out of 99 soil samples, seven samples reported Au values in the 0.1 to 1.0 ppm range. Of the seven auriferous samples, five were located over the jasperoid outcrops previously sampled; one over unmineralized Pilot Shale a few hundred m (ft) downslope from some Au-bearing jasperoid; and one from a 15 x 15 m (50 x 50 ft) talus outcrop area of hitherto unnoticed mineralized Pilot Shale. Subsequent sampling, mapping and drilling would show that this 15 X 15 m (50 x 50 ft) outcrop area was the top of the Vantage 1 ore body, about 1.27 Mt (1,400,000 st) of over 3 g/0.9 t (0.11 oz/st) Au. Late in the summer of 1976 about 30 more 1.4 to 2.2 kg (3 to 5 lb) rock chip samples were collected in the course of preliminary geologic mapping. This mapping and sampling showed that the gold-bearing jasperoids occurred at the contact between the Pilot Shale and the underlying Devils Gate Limestone. Rock chip samples of 0.1 ppm Au or greater were restricted to the jasperoids and the mineralized outcrop area of Pilot Shale located by the soil sample survey. Rock chip samples from the area of mineralized Pilot Shale were in the 3 to 5 ppm Au range. Activity resumed in the summer of 1977 with a more detailed soil geochemical survey. The jasperoid areas were defined as large geochemical gold anomalies of values greater than 0.1 ppm and locally greater than 0.2 ppm Au. Soil samples from the area of mineralized Pilot Shale outlined a greater than 0.1 ppm gold anomaly 61 x 152 m (200 x 500 ft) in size. Further geologic mapping showed that elsewhere, even where bleached and silicified, the Pilot Shale areas were geochemically very low in gold (less than 0.1 ppm Au). In November, 1977 twelve rotary percussion drill holes were drilled to test the gold-bearing jasperoid areas and the mineralized Pilot Shale area. Drilling of the jasperoid areas showed that the jasperoids gave way at shallow depths [less than 24 m (80 ft)] to unmineralized unaltered Devils Gate Limestone. A five hole cross pattern was drilled to test the area of mineralized Pilot Shale. Four of the five holes re-

Jan 1, 1985

By D. Turnbull, R. E. Cech

EXPERIMENTAL studies of precipitation of iron from solid solution in copper by Gordon and Cohen 1, Bitter and Kaufmann 2 and Smith 3 revealed that the precipitate particles were initially paramagnetic but could be changed to a ferromagnetic

Jan 1, 1955

By N. A. Gjostein

The self-diffusion coefficient D, for a surface near the (100) plane in copper was determined by means of the Mullins theory of thermal grooving, and was found to obey the Arrhenius relationship, and Do = 6.5 x 10&apos; sq cm per sec. Suppression of surface diffusion by chemisorbed impurities encounters difliculties as a satisfactory explanation for the large Q, and Do. Instead, a model is presented which indicates that Q,, as determined by a mass-transport technique, may involve both the energy needed to form an adsorbed atom from a ledge in the surface as well as that for the movement of the adsorbed atom.; LITERATURE reviews1-3 indicate that the mechanism of self-diffusion on metal surfaces is not clearly understood. The lack of experimental data on the temperature variation of the surface self-diffusion coefficient DJ has contributed greatly to this situation. Radioactive tracer techniques4-rn have been used to measure Ds, but for many years only Nicker-son and Parker8 had determined (for polycrystalline silver) an activation energy B, and a frequency factor Do for the surface self-diffusion process. Even in this case, a mechanism could not be clearly inferred because it was suspeted7 that a contribution from volume diffusion was not taken into account by the investigators. Some later work by Li and parkere on polycrystalline gold, in which they obtained essentially the same results as for silver and in which volume diffusion could be accounted for, seems to invalidate this criticism. In 1957, Mullins10&apos;11 developed the theory for the thermal grooving process. This advance has opened a new and promising technique for measuring the surface self-diffusion coefficient Ds. Recognizing that a thermal groove may form by several different mass transport processes, Mullins first consideredlo the cases where a) the groove forms by evaporation and condensation or b) by diffusion along the groove surface, in either case, in a system where a metal surface is in contact with only its dilute vapor phase. In a later paper," he extended the treatment to cases where the groove forms by volume diffusion into c) the solid phase or d) by mass transport through a passive gaseous phase at 1 atm pressure. The time dependence of the groove dimensions and the shape of the groove profiles predicted by Mullins&apos; treat-

Jan 1, 1962

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&apos;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)&apos;, and the time-dependent stresses thus created may be investigated by means of Terzaghi&apos;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 Ralph Hultgren

IN solid solutions atoms of differing sizes occupy the same crystalline lattice, requiring that some of them be compressed and others expanded. The energy involved has been called misfit strain energy and is an important concept of crystal chemistry. If the atomic sizes and elastic constants of interatomic bonds are known, the misfit energy may be calculated,&apos; provided certain simplifying assumptions are allowable. Usually, isotropic crystals are assumed and interatomic distances are taken to be the statistical average determined from X-ray diffraction. Such calculations yield values of the misfit energy of the order of 1 or 2 kcal per atom in alloys such as Au-Cu at compositions of 50 atomic pct. However, evidence has accumulated in recent times that atoms change their sizes with composition of alloys, implying electronic rearrangement of the bonds. The size changes have been found particularly by application of the X-ray method developed by Warren, Averbach, and Roberts.&apos; Thus, Averbach, Flinn, and Cohen3 determined radii in Au-Cu alloys. Oriani4 showed that these new radii led to a calculated misfit energy in disordered AuCu, which was decreased from the values calculated by the usual theory more than twenty-fold, to only 80 cal per g atom. Thermodynamic calculations from the phase diagram5 also show misfit energy to be no more than a few hundred calories per g atom in this alloy. The question of what electronic rearrangements are possible therefore becomes compelling in estimating misfit energy. In the following pages the results of certain calculations on the AuCu tetragonal superlattice are submitted. Conclusions drawn from these should be applicable in large degree to disordered solid solutions. As in all ordered states, bonding distances in the superlattice are individually known, rather than being merely average distances as found from lattice constants of disordered states. Moreover, only the Au-Au and Cu-Cu distances are strained; the elastic constants of these are known in the elementary state. In the usual calculation it is necessary to assume elastic constants for Au-Cu bonds. Misfit energy has thus been calculable without the need of many simplifying assumptions usually made. It is still assumed that equilibrium bond lengths and elastic properties of the bonds are the same in the alloy as in the pure metals. As previously discussed, this is probably not correct. Also assumed is that the bonds are not affected by strain of neighboring bonds. A calculation of Young&apos;s modulus from compressibility data shows this to be far from true; extensive electronic rearrangements take place. It would seem that misfit energy cannot be calculated from elasticity data for the elements. The usual methods may, however, give an upper limit which is often much higher than the true value. The question of electronic rearrangement is, of course, a complex one. Pauling&apos;s theory gives a simple, approximate treatment of the relation between type of bond and bond distance. This has been applied with some success to the Au-Cu system, as will be shown in a later section. Misfit Energy in Au-Cu Alloys Hume-Rothery and Raynor6 discuss the Au-CU system as a type example of strain energy. The gold atom is 12.8 pct larger in diameter than the copper atom, near the size factor limit beyond which solid solubility is severely restricted. They therefore consider the misfit energy to be large, a conclusion for which they believe they find evidence in the phase diagram. Gold and copper are completely miscible in the solid state, but the alloy has a minimum melting point at an intermediate composition. From this Hume-Rothery and Raynor conclude that the strain energy is nearly large enough to prevent miscibility; the phase diagram tends toward a eutec-tic type. In Ag-Cu, which has almost identical size relationships, solid miscibility is quite limited; whereas in Au-Ag, where atomic sizes are nearly the same, there is complete miscibility without a minimum in the melting point. From their arguments the heat of formation of Au-Cu would be expected to be endothermic or only slightly exothermic, that of Ag-Cu to be endothermic, and that of Au-Ag to be exothermic. Deviations, from Ve-gard&apos;s law of additivity of atomic radii support these conclusions, since Au-Cu and Ag-Cu both have pronounced positive deviations, and Au-Ag has a negative deviation. Nevertheless, Au-Cu alloys form exothermically; indeed, considerably more exothermically than Au-Ag, Table I. Hence, strain energy must be much less important in this case than Hume-Rothery and Raynor have supposed.

Jan 1, 1958

By R. F. Nielsen, D. E. Menzie

The object of this study was to determine if crude oil could be produced successfully by a process of crude oil vaporization using carbon dioxide repressuring. This process appears to have application to highly fractured formations where the major oil content of the reservoir is contained in the non-fractured porosity with little associated permeability. Crude oil was introduced into the windowed cell and carbon dioxide was charged to the cell at the desired pressure. A vapor space was formed above the oil, and the crude oil-carbon dioxide mixture was allowed to come to equilibrium. The vapor phase was removed and the vaporized oil collected as condensate. Samples of all produced and unproduced fluids were analyzed. Tests were also performed to evaluate the amount of vaporized oil that can he produced by rocking from a high to a lower pressure. The carbon dioxide repressuring process was applied to a sand-filled cell to investigate the performance in a porous medium. A test was performed to evaluate how the condensate recovery changes as the size of the gas cap in contact with the oil changes. INTRODUCTION This study has been directed toward a relatively new process of vaporization of crude oil designed to increase ultimate production of hydrocarbons through the application of carbon dioxide to an oil reservoir. Suggested advantages of carbon dioxide repressuring of a petroleum reservoir are: (1) reduction in viscosity of liquid hydrocarbons due to the solubility of carbon dioxide in crude oil, (2) swelling of the reservoir oil into a larger liquid-oil volume with a resulting increase in production and decrease in residual oil saturation due to an increase in the relative permeability to oil, (3) displacement of more stock-tank oil from the reservoir since the residual liquid is a swelled crude oil, and (4) gasification of some of the hydrocarbons into a carbon dioxide-hydrocarbon vapor mixture. Balanced against these advantages are several detrimental factors which must be evaluated; i.e., high compression costs and corrosion of well equipment and flow lines. Some of the more outstanding contributions to the study of carbon dioxide injection have been reviewed in order to furnish a basis for a continuation of research pertaining to this method. The literature reviewed1-8 has been limited to that dealing with carbon dioxide repressuring processes or with carbon dioxide-crude oil-natural gas phase behavior. Articles relating to carbonated water injection and literature published on the use of low pressure carbon dioxide gas injection in water flooding have not been included in this study. In 1941 Pirson5 suggested the high pressure injection of carbon dioxide into a partially depleted reservoir for the purpose of causing the reservoir oil to vaporize and thus produce the oil as a vapor along with the carbon dioxide gas. By reducing the pressure on this produced mixture of hydrocarbons and carbon dioxide at the surface, it was proposed to separate the hydrocarbons from the carrier gas. He theorized that essentially all the oil in a reservoir could be produced by simply injecting enough carbon dioxide to vaporize the residual oil. This present investigation deals with the vaporization of a crude oil by carbon dioxide, the molecular weight and gravity of the vaporized oil product and the characteristics of the residual oil after several repressuring cycles with carbon dioxide. An attempt is made to evaluate the merits of a vaporization process for the crude oil rather than a flow process where the oil recovery is determined by relative permeability considerations. Such a vaporization of crude oil by carbon dioxide repressuring appears to have possible use in a highly fractured formation where the major oil content of the reservoir is contained in the non-fractured porosity with little permeability. The carbon dioxide flows into the fractures, contacts the crude oil in the matrix and vaporizes part of the crude oil; this vaporized oil is produced and recovered and the carbon dioxide is reinjected again. The specific problem of this study is to attempt to answer this question; Can crude oil be produced successfully (technically, but without economic considerations) from a petroleum reservoir by a process of vaporization of the crude oil by carbon dioxide repressuring? DEFINITION OF TERMS AS APPLIED IN THIS STUDY Carbon Dioxide Contact: One cycle in which carbon dioxide was injected and bled off. Condensate: The hydrocarbon liquid which was condensed out of the mixture of hydrocarbon-carbon dioxide vapor upon reduction of the pressure of the vapor. Hydrocarbons Produced (HCP): All the hydrocarbon!, which were vaporized by the carbon dioxide repressuring process and were removed from the cell during any specific cycle or carbon dioxide contact. Hydrocarbons Unproduced (HCU): All the hydrocarbons which were not vaporized by the carbon dioxide

By P. Shahinian, H. H. Smith, M. R. Achter

Crack growth rates are measured at elevated temperature in a resonant fatigue machine from vibration frequency decreases calibrated in terms of crack depth. Crack growth rates in Type 316 stainless steel at 500º and 800°C show a sharp increase with oxygen pressure in an intermediate pressure range and little or no change at high and low pressures. At 500°c, I torr of oxygen reduces the fatigue life by almost a factor of 100 in comparison to that in vacuum and raises the growth rate of shallow cracks by the same At At 800°C the effects are smaller. Changes in slope in the crack growth rate curves are discussed in terms of a model in which rates of surface production and of surface coverage by gas are compared. The use of a calculation method in which the surface exposure time is equal to X/v, where x is the interatomic spacing and v is the growth rate, makes it possible to obtain order of magnitude agreement at 500°C between the observed pressure and the predicted pressure at these slope changes. At 800°C oxidation becomes a .factor and the data cannot be treated by simple adsorption theory. THE decrease in the fatigue life of metals as a function of gas pressure usually follows a stepped curve with virtually all of the decrease concentrated in a sharp drop in a transition zone at intermediate pressures and little or no change at low and high ranges. A number of models, differing in the details of the mechanism, have been offered to explain the shape of the curve. Measurements of crack growth in aluminum as a function of gas pressure by Bradshaw and Wheeler&apos; and Hordon2 demonstrated opportunities for quantitative comparison to evaluate the proposed models. Since comparable data were lacking at high temperatures, in the present work rates of crack propagation were measured in Type 316 stainless steel at 500" and 800°C as a function of oxygen pressure. Choice of this material was dictated by two considerations; it is stiff enough at these elevated temperatures to resonate with the regenerative drive on our fatigue machine and it is known to display a large effect of environment. A new method of calculation is described to predict the gas pressure at the critical point. EXPERIMENTAL PROCEDURE Because of the difficulty of measuring crack depths directly at high temperatures, an indirect method was developed based on the decrease in the resonant frequency with the growth of a crack. A reversed bending, constant amplitude fatigue machine, described previously,3 vibrates a specimen at its resonant frequency, automatically records any changes in it and shuts itself off after it has reached a preset value of frequency decrease. The record of frequency change is used to determine the rate of crack growth. Sheet type specimens of Type 316 stainless steel, Fig. 1, incorporated a sharp, shallow notch to localize the formation of a single crack. After machining, they were annealed in a vacuum of l0-6 torr either at 1066" (lot A) or 871°C (lot B) and then electropolished in an acetic-chromic acid solution. Bending strains were measured at 500" and 800°C by an optical technique4 and reported as total strain without correction for the notch. At 500°C, the 0.141 pct strain was 0.085 pct elastic and the remainder plastic. At 800°C the 0.062 pct strain was all elastic. To convert frequency decrease to crack length, calibration curves were obtained by interrupting the vibration at stated intervals of frequency decrease. The crack depth was measured microscopically at a magnification of X400 and reported as the average of the measurement on each edge. Some specimens were sectioned for crack measurement while others were returned to the machine and fatigued further. There was good agreement between the two methods. Before beginning the vibration, the vacuum chamber was first evacuated cold to 1 x 1O-6 torr, then heated to the operating temperature and held there until the pressure was again reduced to 1 x10-6 torr at which time oxygen was introduced to the desired pressure. In this investigation the vibration frequency was nominally 10 cps and a decrease of 0.6 cps was taken as the failure point. The choice of the frequency decrease to represent failure has no appreciable effect on the fatigue life because the crack is growing very fast at this point.

Jan 1, 1970