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By A. J. Lena, M. F. Hawkes

Changes in hardness, tensile properties, microstructure, electrical resistance, and X-ray diffraction effects indicate that lattice strains are necessary for the embrittlement of ferritic stainless steels when heated for relatively short times at 475°C (885°F). It is suggested that 475°C (885°F) embrittlement is due to the accelerated formation of an intermediate stage in the formation of s under the influence of these strains. FERRITIC stainless steels (low carbon alloys of iron with more than 15 pct Cr) are subject to two forms of embrittlement when heated in the temperature range of 375° to 750°C. The embrittlement which occurs after long time heating between 565" and 750°C is well understood; it is caused by the precipitation of the hard, brittle s phase. Sigma is an intermetallic compound of approximate equi-atomic composition with an extended range of formation in Fe-Cr alloys. The maximum temperature at which this form of embrittlement can occur is dependent upon chromium content; and is approximately 620°C for a 17 pct Cr steel and 730°C for a 27 pct Cr steel. The other form of embrittlement occurs after relatively short heating periods in the range of 375" to 565°C; in the higher chromium steels, hours may be sufficient as compared to months for s embrittlement. This phenomenon is not at all well understood and several controversial theories have been proposed. The rate and intensity of embrittlement increase with increasing chromium content but the maximum rate occurs at 475°C re-gardless of chromium content. As a result of this, the phenomenon has been termed 475°C (885°F) embrittlement. The effect of 475°C embrittlement on the properties of ferritic stainless steels has been thoroughly reviewed by Heger.1 The embrittlement causes a pronounced decrease in room temperature impact strength and ductility, a large increase in hardness and tensile strength, and a decrease in electrical resistivity and corrosion resistance. Microstructural changes accompanying embrittlement are minor and difficult to interpret with a general grain darkening, appearance of a lamellar precipitate, grain boundary widening, and precipitation along ferrite veins having been reported at various times. With the exception of reported line broadening, X-ray diffraction studies by conventional Debye analysis of solid samples have been of little value. BY making use of electron diffraction methods, Fisher, Dulis, and Car-roll' have recently shown the existence of a chromi-um-rich, body-centered cubic phase in 27 pct Cr steels which had been aged at 482°C (900°F) for as long as four years. Two types of theories have been advanced to account for the embrittlement. The first of these requires the precipitation of a phase not inherent in the Fe-Cr system with various investigators suggesting a carbide,3 nitride,3 phosphide,4 or oxide." Theories of this type have difficulty accounting for the influence of alloying elements on the embrittlement and for the facts that a minimum chromium content is necessary for embrittlement and the intensity of embrittlement increases with increasing chromium content. The second type of theory that has been proposed relates 475°C embrittlement to s phase formation which is inherent in the Fe-Cr system. An assumption of this kind can adequately explain the influence of alloying elements, for they exert an effect on 475°C embrittlement similar to that on s phase for-mation as can be seen in Table I. The minimum chromium content is essentially the same for both phenomena and it has been shown12,13 that s is a stable phase in the embrittling temperature range. In addition, it has been reported14,15 that pure alloys embrittle to the same extent as commercial type alloys. There are, however, several factors which have prevented complete acceptance of a s phase theory. Foremost of these is that the embrittlement can be removed by reheating for short time periods above 600°C, which in the higher chromium steels is within the stable s region. No s has ever been observed after one of these curing treatments, nor has any s been found as a result of embrittlement at 475°C. In addition, the simple precipitation of s cannot explain the time-temperature relationships for reactions between 350°and 750°C. This behavior is shown schematically in Fig. 1. Newell 16 and Ried-rich and Loib4 have shown that 475°C embrittlement follows a C-type curve as illustrated, while Short-

Jan 1, 1955

By Edward Halse

Normal banded structure,* exhibiting bands or layers of mineral symmetrically arranged from the sides to the center of the vein, appears to be by no means common in the Republic of Mexico. When the bands of quartz form interlocking crystals in the center (" comb-structure "), the evidence that the filling has taken place in an open space is complete. This also applies in the case of any mineral the fibers of which are perpendicular to the walls, and which presents here and there, in a central line, cavities or vugs lined with crystals (geodes); but it does not follow that the whole width of the banded vein represents that of the original open fissure. The opening and filling may have been slow and gradual processes, advancing

Jan 1, 1902

By Subhas G. Malghan

The response of feldspar flotation to tallow diamine dioleate collector in the presence of sulfuric acid is studied using batch flotation experiments. Application of this nonhydrofluoric acid (non-HF) reagent system in the flotation of mineralogically and chemically different feldspar ores is compared with that of the conventional hydrofluoric acid system. The dependence of flotation recovery and concentrate grade on feed particle size distribution, conditioning time, pulp density, and pH, combined variation of collector and acid addition rates, sodium hydroxide concentration in the collector solution, and initial pulp pH Prior to conditioning is studied. The results have been discussed in relation to applicability of the non-HF system to plant trials, and the nature of the collector adsorption in the selective flotation of feldspar.

Jan 1, 1982

By G. E. Archie

THE usefulness of the electrical resistivity log in determining reservoir characteristics is governed largely by: (I) the accuracy with which the true resistivity of the formation can be determined; (2) the scope of detailed data concerning the relation of resistivity measurements to formation characteristics; (3) the available information concerning the conductivity of connate or formation waters; (4) the extent of geologic knowledge regarding probable changes in facies within given horizons, both vertically and laterally, particularly in relation to the resultant effect on the electrical properties of the reservoir. Simple examples are given in the following pages to illustrate the use of resistivity logs in the solution of some problems dealing with oil and gas reservoirs. From the available information, it is apparent that much care must be exercised in applying to more complicated cases the methods suggested. It should be remembered that the equations given are not precise and represent only approximate relationships. It is believed, however, that under favorable conditions their application falls within useful limits of accuracy.

Jan 1, 1942

By K. U. Snowden, J. N. Greenwood

CRACKS which form in lead exposed to fluctuating stress frequently follow a rectangular pattern. It is well known that under ordinary atmospheric conditions these cracks are intercrystalline. On the other hand after fabrication the crystal grains in lead are in general irregular polygons. The observed facts appear to be mutually contradictory. Re-examination of some lead failures has confirmed that the rectangular cracks are intercrystal- line. It follows therefore that under fluctuating stress some of the grains lose their irregular outlines and become approximately regular polygons of cubic type. G. R. Gohn and W. C. Ellis* suggest that this is due to recrystallization during the life of the part, in such a way that the new grain boundaries are aligned at 45 deg to the longitudinal strain prior to the formation of the fatigue crack. Experiments at Baillieu Laboratory—Some recent experiments carried out in the Baillieu Laboratory in conjunction with the Broken Hill Associated Smelters have thrown some light on this transition. A test piece of pure lead was polished chemically

Jan 1, 1959

By C. H. Mathewson

BERYLLIUM, magnesium, zinc and cadmium, together with mercury, constitute a coherent sub-group of the periodic system and these metals, excepting mercury; have been studied in sufficient detail by the new X-ray diffraction methods to prove their common adherence to the hexagonal close-packed type of crystal structure with a progressive increase in axial ratio as we pass through the group from beryllium to cadmium. The first four columns of Table 1 summarize the data on crystal structure of these metals reported in the International Critical Tables.1 The last two columns are based on results obtained in the present investigation. TABLE 1.-Lattice Constants and Twinning Law of the Be-Cd Group of Hexagonal Metals Dimensions of Unit Axial Cell, A Ratio Description of Twinning Element a° c° (c°/a°) Composition Axis Plane Beryllium 2.28(3) 3.60(7) 1.58 {1012} Probably 1 {1012} Magnesium 3.22 5.23 1.621 ,1 {1012} Zinc 2.65(7) 4.94(8 1.86(2) 11012 } 1 {1012) Cadmium 2.98 5.63 1.88(5) {1012} Probably 1 {1012} Twinning has often been observed in zinc and cadmium. The general aspects of this twinning are abundantly illustrated by photomicrographs, diagrams, etc., in the papers by Romig, and Mathewson and Phillips reported to this Institute in 1927.2. A determination of the composition

Jan 1, 1928

By P. T. Gallagher, W. A. Oates

THE partial excess entropy of interstitial solutes in metals, SXS , has usually been interpreted as being principally vibrational ever since the initial statistical treatment of hydrogen in metals by Fowler and Smith-ells. The vibrational entropy is considered being due to the optical modes of the light interstitial atom. Little attention has been given to the magnitudes of the values of SXS'. Leiser and Witte2 and Ebisuzaki and O'Keeffe3 have noted that for hydrogen in metals Si is approximately constant for different metals. On the other hand if it is assumed that the interstitial solute is an isotopic defect then, as shown by McLellan, SXS should vary from metal to metal as follows: where S is the standard entropy of the solvent and Mi, M, are the masses of the interstitial and solvent atoms. respectively. Fair agreement with this equation was found for oxygen in silver and nitrogen in iron4 and for carbon in iron.= Ln a subsequent analysis of metal- hdrogen systems McLellan' found a variation of $' from metal to metal but not in a manner expected from the isotopic impurity equation. However, a possible correlation between the energy of solution, Ei, and sf was noted. Similar correlations have been noted for certain dilute substitutional solid Solutions 7, 8 and recently Kubaschewski 9 has demonstrated a correlation between integral heats and ex-

Jan 1, 1970

By J. D. Edwards, C. S. Taylor, A. S. Russell

Solubilities and densities are reported for alumina hydrates in NaOH solutions under the conditions of the Bayer process employed to purify alumina for aluminum production. The equilibrium constants for reactions to form A102- accurately correlate the effects of NaOH concentration on the solubilities; the temperature coefficients of the equilibria lead to heats of solution of 7.34, 4.76, and 5.24 kcal for the a trihydrate, a monohydrate, and ß trihydrate, respectively. Moderate calcination does not change the solubility of the a trihydrate but increases that of the a monohydrate. At solution temperatures above 100°C, the trihydrates transform rapidly to a monohydrate. Hydro-thermally produced a monohydrate is the stable phase above 20°C. CORNERSTONE of the aluminum industry, the Bayer process for alumina production is based on the difference in solubility of hydrated alumina in NaOH solutions between 170" and 40°C. Solubilities and densities in this system were determined thirty years ago by M. Tosterudl under the direction of J. D. Edwards and C. S. Taylor. The solubility data, which still appear more concordant than those in the literature, are employed to sort out the complex equilibria in this system. The nomenclature for the alumina hydrates is that presented in The Aluminum Industry' and more recently summarized in Alumina Properties.3 a trihydrate is the purified phase analogous to gibbsite, a monohydrate is similarly akin to boehmite, and ß trihydrate is sometimes known as bayerite. Literature Goudriaan4 reviewed the early literature on alumina in NaOH solutions and presented data on the solubility at 30°C of several forms. The gel precipitated from aluminum sulphate or chloride with ammonia and dried at 130" to 140°C had the highest solubility but was unstable, its solubility being cut to one-tenth on standing in NaOH. The solubility of the gel was decreased one-third on calcination at 300" to 400°C, while that of the gel transformed in NaOH at room temperature to a crystalline trihydrate was unchanged on calcination. The preparation produced by slow hydrolysis of sodium aluminate solution with CO, in the air gave solubilities in rough agreement with later values for a trihydrate. The solubility of this form was increased slightly by the calcination. Fricke and Jucaitis5 extended the work to 30" and 60°C with a trihydrate. They also gave solubilities for ß trihydrate (bayerite b), although the residue belonging to the left branch of the solubility curve corresponded to a trihydrate. The residues at high NaOH concentrations were mono and trisodium aluminates, the latter being 3Na2O . AL2O3 • 6H2O. Solubilities of a trihydrate at 95°C and of a monohydrate at 150" and 200 °C come from the work of Magarchak.6 a trihydrate transformed to a monohydrate above 95°C. A few measurements on the solubility at 25°C of an alumina trihydrate prepared by slow hydrolysis of NaAIO, solutions were presented by Sprauer and pearce.? Their analyses showed the monosodium aluminate to have the composition Na2O.Al2O3-2.5H2O.

Jan 1, 1956

By J. M. Hodge, M. A. Orehoski

tions to which it will be subjected, and this premise is probably the most important reason for hardenability control. However, the criterion of hardenability [ ] ture after quenching should consist wholly of martensite; and that transformation of austenite to intermediate-temperature products during quenching will have a deleterious effect upon the physical properties, particularly the toughness, of the tempered material. This implies that, in order to obtain the optimum physical properties from a given steel, its "hardenability" should be high enough to suppress all transformation except that to martensite under the heating and quenching condi- IT is now generally conceded that if a steel is to develop optimum physical properties in the conventionally quenched and tempered condition, the microstruc- [ ] that at present is most widely accepted and used is based on a microstructure of 50 per cent martensite. This criterion, which was suggested by Grossmann,1 does have considerable justification. It may be readily measured by a fracture or etch test and, since it represents the point at which the hardness is changing most rapidly with variations in cooling rate, it may be determined empirically from a hardness-depth curve by determining the point of steepest slope (the inflection point. Furthermore, in plain carbon steels or in steers of low hardenability, the difference in hardenability expressed in

Jan 1, 1945

By Hans Lundberg

In order to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. For its operation, electrical prospecting mainly depends on the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1). The good conductor, chalcopyrite, in the poor conductor, schist, thus attracts the current and deflects the normal flow far outside the conduct-

Jan 1, 1929

E. A. HOLBROOK,*Urbana, Ill.-To those who have followed the development of powdered coal two questions often occur. First, as to the moisture in the coal. In Illinois we recognize that the bituminous coals contain about 12 to 15 per cent. of what we call "contained moisture," that is, the moisture is present in the coal although this may appear absolutely dry and dusty. In addition, the surface moisture may be present in any amount. I would like to ask what is the relative effect of these two forms of moisture upon the work of pulverizing. Does Mr. Collins refer to the contained moisture or to the surface moisture in estimating the degree to which the coal must be dried? H. R. COLLINS.-In the lignite coals, of which this country possesses a great deal and is beginning to develop them to considerable extent, the "contained" or "combined" moisture does not .trouble us; we have no difficulty in reducing lignites to a high degree of fineness. But when dealing with bituminous, sub-bituminous, or semi-bituminous, we, prefer to reduce the combined moisture as well as the hydroscopic moisture as far as possible. We have recently put into operation, at a plant, furnaces and boilers consuming the lignite from northern New Mexico, which contains between 4 and 5 per cent. moisture as we pulverize and burn it. The evaporating efficiencies under the boilers have been so remarkable that we wish to check the results half a dozen times before quoting them. We have also just started two boilers at the Garfield smelter, and have obtained the same high efficiencies.

Jan 11, 1918

By H. W. Immolz

The Palo Pinto limestone pools of Jones and Shackelford Counties were defined and almost fully developed during the year. A new Palo Pinto limestone pool was apparently discovered when the K. B. Nowels NO. 1 Pardue, S.F.I. and W. survey, south central Haskell County, was completed for a small well in Palo Pinto limestonc at 3395 to 3421 feet. In Haskell County, Amerada Petroleum Corporation's C. J. Kleiner, J. M. Cass survey, drilled to the Ellenburger with a total depth of 5607 ft., where it was abandoned. A Bluff Creek sand field of undetermined size was discovered by the Fain-McGaha No. 1 Dawson-Conway, P. G. Holcomb survey, which was chompleted for 37 bbl. at 1496 feet. The Cook field was extended by the Roeser-Pendleton B-113 Cook in sec. 113, E.T.R.R. Co. survey, the well being completed for 510 bbl. from Cook sand encountered at 1545 to 1568 feet. Several shallow pools of minor importancc mere also discovered in Shackelford County during the year. In Jones County the Lewis and the Steffens fields, in block 15, T. and P.R.R. Co. survey, were further developed during the year but the limits of the Steffens field were not definitely defined. The most, important discovery in Jones County was the Guitar field, where most of the wells that had been producing from the Cook sand were deepened to the Hope limestone, a new producing horizon. In Taylor County, the Bowles field, see. 28, B.A.L. survey, was defined arid proved to he of minor importance. The Goldsboro and Novice area, ill northwest Coleman County, continued to hold considerable interest because of the developments near the town of Novice, where new Ieases continued to be opened for production. Nolan County was placed in the ranks of the producing counties when the S. B. Owens No. 1 Tipton, sec. 43, block 19, T. and P.R.R. Co. survey,

Jan 1, 1940

By H. W. Immolz

The Palo Pinto limestone pools of Jones and Shackelford Counties were defined and almost fully developed during the year. A new Palo Pinto limestone pool was apparently discovered when the K. B. Nowels NO. 1 Pardue, S.F.I. and W. survey, south central Haskell County, was completed for a small well in Palo Pinto limestonc at 3395 to 3421 feet. In Haskell County, Amerada Petroleum Corporation's C. J. Kleiner, J. M. Cass survey, drilled to the Ellenburger with a total depth of 5607 ft., where it was abandoned. A Bluff Creek sand field of undetermined size was discovered by the Fain-McGaha No. 1 Dawson-Conway, P. G. Holcomb survey, which was chompleted for 37 bbl. at 1496 feet. The Cook field was extended by the Roeser-Pendleton B-113 Cook in sec. 113, E.T.R.R. Co. survey, the well being completed for 510 bbl. from Cook sand encountered at 1545 to 1568 feet. Several shallow pools of minor importancc mere also discovered in Shackelford County during the year. In Jones County the Lewis and the Steffens fields, in block 15, T. and P.R.R. Co. survey, were further developed during the year but the limits of the Steffens field were not definitely defined. The most, important discovery in Jones County was the Guitar field, where most of the wells that had been producing from the Cook sand were deepened to the Hope limestone, a new producing horizon. In Taylor County, the Bowles field, see. 28, B.A.L. survey, was defined arid proved to he of minor importance. The Goldsboro and Novice area, ill northwest Coleman County, continued to hold considerable interest because of the developments near the town of Novice, where new Ieases continued to be opened for production. Nolan County was placed in the ranks of the producing counties when the S. B. Owens No. 1 Tipton, sec. 43, block 19, T. and P.R.R. Co. survey,

Jan 1, 1940

By F. E. Steigert, A. H. Geisler

THE permanent magnet alloy comol, which contains 17 pct Mo, 12 pct Co, balance Fe, exhibits a precipitation reaction analogous to that at the iron end of the binary Fe-Mo system. The equilibrium precipitate, (P,), has a structure isomorphous with Fe,Mo, which is rhombohedra1 with parameters a = 8.97A and a = 3038.6&apos; according to the work of Arnfelt and Westgren.&apos; In the ternary alloy the parameters are a = 8.87A and a = 31°0.5&apos;. Oscillating crystal patterns of a single matrix crystal, M, in which P, was precipitated by slow cooling from 1300°C, showed that the orientation relationship of the two lattices is as follows: (110)P3 // (110)* (111)p3 // (110)m There are crystallites of P, in 12 different orientations in a single crystal of the parent solid solution. Microscopic examination shows that the crystallites are generally plate-like with their lateral dimensions parallel to (110) matrix planes. When precipitation in a supersaturated alloy quenched from 1300°C progressed isothermally at temperatures between 600" to 800°C, the evolution of the P, structure could be traced. Diffuse diffraction effects in Laue patterns provided early evidence of the precipitation process. Analyses of these by a previously described technique2 showed that they corresponded to rod-like elements parallel to <110> matrix directions in reciprocal space. With further aging to promote growth of the precipitate, the rod-like elements contracted to points in reciprocal space for normal Bragg reflection from the precipitate as shown by the left diagram in Fig. 1. Thus the diffuse scattering was attributed to the small thickness of the plate-like particles which was inadequate for sharp diffraction. When the precipitate particles were first thick enough to give normal diffraction their structure was different from that of the equilibrium precipitate, P,. The first structure, P1, presumably is a coherent transition struc-

Jan 1, 1952

By Floyd Kelley

THE literature of the last decade is rich with information relating to the cause and means of control of grain growth in pure metals, but is deficient concerning the role diffusion plays in grain growth, although during this period many new products that depend on diffusion for their properties and success have been developed. Among these are cementation products, produced by calorizing, chromizing, and carbonizing, or by mixing, pressing, and sintering powdered metals such as Syke&apos;s iron-molybdenum die material, Genelite, and Elcon Metal (copper, tungsten) etc. This is a fertile field for new developments, but before it can be util-ized to the fullest extent there must be a thorough investigation of the processes by which diffusion and grain growth take place. Grain growth plays no small part in the process and certainly the physical properties of these products depend largely on the grain size and state of equilibrium produced. The field of investigation does not end here, but may be extended to the effect of diffusion on impurities, segregations and dendrites in the broad field of ferrous and non-ferrous metallurgy. A number of years ago the author investigated several of these cases and noted, with striking regularity, the pronounced effect of diffusion in promoting recrystallization and grain growth. An example of this phenomenon is given in his paper on chromizing1 which contained photomicrographs of large radial or columnar crystals produced by diffusion of chromium in the solid state. Another manifestation of this effect was discussed by Austen,2 who showed the part hydrogen plays in the decarburization of steel and the effect of diffusion upon the grain structure.

Jan 1, 1928

By A. S. Koster, G. D. Rieck

X-ray experiments were carried out to show the occurrence of cylindrical texture in drawn tungsten wire. Only a small amount of (110) (110) cylindrical texture could he found in wires of intermediate thickness, i.e., of about 1.5 mm diameter. DRAWN wires of tungsten and other bcc metals like iron and molybdenum show a well-established (110) fiber texture. Now it might be conceivable that in drawing radial stresses remove the randomness of the crystallites around the [110} axis, thus giving a fiber texture of higher symmetry. In the resulting so-called cylindrical textures a specified plane normal coincides with the radius of the wire. Several authors discuss the occurrence of cylindrical textures in bcc metals. ~ieck&apos; found no cylindrical texture in drawn tungsten wires of 165 n diameter. Leber~ states that in tungsten wires of 3 mm diameter a cylindrical {100)(110) texture is developed, which is gradually converted to a normal fiber texture by subsequent drawing. He also reported a definite cylindrical texture at the surface of iron wires. Peck and Thomas3 observed a nonuniform mode of deformation of the grains in transverse sections of heavily drawn tungsten and iron wires. According to Bhandary and cullity4 a swaged iron wire has neither a perfect (110) fiber texture nor a perfect {100}(110) cylindrical texture. It is clear that the concept of cylindrical texture in bcc metals still lacks a firm experimental basis. Leber&apos;s eviden~e,~ which seems to be the strongest, rests upon qualitative interpretation of photographs. The appearance of the 110 and 200 lines on the photograph of 3-mm wire, however, can be very well attributed5 to a normal ( 110) fiber texture superimposed on random background; our Fig. 1, giving a Debye-Scherrer diagram of etched tungsten wire of 180 p, is free of cylindrical texture according to all authors, but is quite similar to Leber&apos;s diagram. It was therefore decided to use a different method of X-ray texture determination on tungsten wires of diameters where cylindrical textures may be expected.

Jan 1, 1965

By P. W. Bridgman

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

Jan 1, 1922

By C. H. Herty, J. L. Keats

In the literature on the elimination of metalloids in basic open-hearth practice, there are a great many heats recorded in which excellent data on changes in slag and metal composition during refining are given, but in almost all of these heats either temperature data or weights and analysis of charge are unrecorded and observations on the physical characteristics of the slag are almost always lacking. With these points in mind, a test heat was made in which as complete data as possible on all the factors that affect the elimination of metalloids were obtained. The Test Heat The test heat was made in a standard 100-ton stationary furnace at the Lackawanna Steel Co., Lackawanna, N. Y., on January 17, 1922. The Charge—Scrap.—The scrap consisted entirely of rail-heat butts, selected from a number of heats made the week before the test. The average analysis of the scrap was calculated from the analysis of these heats and from the weight of scrap from each heat. Pig Iron.—Two ladles of pig iron were used in the charge and two samples were taken from each ladle as it was poured into the furnace. These four samples were composited for the average pig-iron sample. Other Materials.—Weights of dolomite, ore and spar were obtained by weighing a quantity of each just before the test and weighing the amount of each left after the heat was completed. The limestone. was weighed on the charging pans. Coal for recarburizing, ferromanganese, ferro-silicon and aluminum were weighed out as used. All these materials were carefully sampled before the test was begun. Coal consumption at the producers was obtained by getting the average capacity of the hoppers that fed the producers, and then counting the number of hoppers of coal used during the course of the heat. Products Steel.—The steel made was rolled into billets, the rolling properties being very satisfactory. The weight of steel was obtained by taking a

Jan 1, 1926

By P. W. Bridgman

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

Jan 1, 1922

By Edgar R. Kendall

A KNOWLEDGE of the fundamental principles of locating, sampling, testing and evaluating materials is essential in prospecting for mineral aggregates. In this discussion, mineral aggregates will be considered sand, gravel, crushed stone and slag that are used as materials of construction. The quantity of mineral aggregates produced in the United States during the year 1935 for such purposes was roughly 165,000,000 tons, about 60 per cent of which was sand and gravel, 37 per cent crushed stone and 3 per cent crushed slag. The total value of this material was approximately $100,000,000. It is apparent therefore that the prospecting for suitable mineral aggregates is of considerable economic importance. In prospecting for mineral aggregates, the methods employed are the same whether the organization is large or small. In the large organization there may be available geologists for locating sources of supply, a land acquisition department to arrange for the necessary options or permits, engineers to do the sampling, a laboratory for testing, and a board of consulting materials engineers to make the final selection. Even small organizations must follow the same general procedure, though the responsibility for the selection of aggregates may rest with one man, who may or may not be an engineer, but who must depend entirely upon his own judgment. LOCATING THE SUPPLY The initial step in prospecting for mineral aggregates is the locating of suitable, adequate and economic sources of supply for the project in mind. Commercial plants in the vicinity should be investigated and a survey made of the existing structures that have been built of aggregates from these sources. If the structures are rather old and show no signs of deterioration, it is fairly good evidence that the aggregate is satisfactory. If materials of the proper quality can be obtained from commercial sources in sufficient quantity, and delivered to the job economically, it

Jan 1, 1939