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By F. Fraas

ELECTROSTATIC methods are used to separate and concentrate or purify granular particles derived from ores or various synthetic and agricultural products. Compared with other separation methods that require many technological refinements, the electrostatic attraction of fibers, grass, and seeds to charged surfaces clan be accomplished under the most primitive circumstances, and the early development of this method of beneficiation seemed very promising. Precise application of the method to provide high selectivity, however, is a complex procedure, and interest in this method declined. During this period Mr. O. C. Ralston initiated a Bureau of Mines research program oil electrostatic separation. It is the purpose of thins publication to describe the development of the electrostatic method of particle separation from the early beginning to the present resurgence of interest. Most of the information for this description bas been derived from references, a few of which were not available for thorough review. Much information has been drawn from the investitions of the Bureau. Acknowledgments Mr. O. C. Ralston, former Chief metallurgist of the Bureau of Mines, began the research program on the subject and did research on the mils literature. Both Mr. Ralston and Mr. H. B. Johnson, former president of the Huff Electrostatic Separator Co., furnished patent references. A critical review by Mr. F. D. Lamb, Research director, and Mr. M. J. Spendlove, Supervisory metallurgist, Bureau of Mines, College Park Metallurgy Research Center, lifts been of much value in preparing this report.

Jan 1, 1962

By W. A. Krivsky, R. Schuhmann

Jan 1, 1962

By N. A. Gokcen, R. A. Dodd

Solubility of nitrogen in liquid iron-manganese system at 1550°C and one atmosphere pressure has been determined by a simple method. Results show that the solubility increases from 0.040 pct for pure iron to 1.41 pct for pure manganese. DETERMINATION of the solubility of gases in volatile metals. and alloys by the well-known Sievertsl method is unreliable. This is particularly true for the Fe-Mn system since Mn vaporizes readily from the alloys containing as little as 2 pct Mn, and, upon condensing on the cooler parts of the apparatus, it absorbs large amounts of nitrogen. Further, the condensing Mn vapor interferes with the usual method of temperature measurements with an optical pyrometer.

Jan 1, 1962

By H. I. Aaronson

THE TTT-curve for the beginning of transformation in hypoeutectoid steels containing appreciable amounts of relatively strong carbide-forming alloying elements often exhibits a "bay" at intermediate temperatures. In many of these steels, proeutectoid ferrite is the initial product of the decomposition of austenite not only at temperatures above the bay but also in an appreciable temperature range below the region of the bay. Hultgren has postulated that ferrite formed above the bay, termed "orthoferrite", contains the equilibrium concentration of alloying element at temperatures above the eutectoid range, and the extrapolated metastable equilibrium concentration at lower temperatures. The ferrite formed below the bay, on the other hand, termed "paraferrite", was assumed to inherit completely the bulk alloy content of the austenite without regard for the compositional requirements of equilibrium. As shown schematically in Fig. 1, the two types of ferrite were taken to have different Ae3 temperatures and different C-curves on a TTT-diagram. Their different kinetic behaviors were thus considered responsible for the bay in the TTT-curve for the proeutectoid ferrite reaction in this type of alloy steel.

Jan 1, 1962

By Wilhelm in der Schmitten

A necessary condition for a uniaxial stress distribution in compression testing is that the specimen end surfaces make full contact with the apparatus compression plates. In addition all compression surfaces must be machined perpendicularly to the loading axis. In general this condition is not sufficiently fulfilled in a simple apparatus. Therefore on application of the load the compression plate may first touch the specimen at one point only. This may cause crumbling of the specimen if the material under investigation is brittle (e.g., ionic crystals). It also precludes a precise study of the beginning of deformation as the effective cross sectional area is unknown. In addition a complex stress state is set up which renders quantitative work impossible, e.g., on dislocation density and arrangement as a function of stress. To overcome these difficulties a "self-adjusting" upper compression plate is required. A simple and reliable method of achieving this is shown in Fig. 1: A steel hemisphere is placed on the specimen. As soon as the compression plate (which no longer needs precise machining) makes contact with this hemisphere the load is uniformly distributed over the whole specimen surface, and a homogeneous uniaxial state of stress results. An advantage of the method is that the loading is always central, even when the specimen surface is not parallel to the compression plate (Fig. 1, dashed line). Therefore to a first approximation a uniaxial state of stress is maintained if the misorientation of the specimen end surface is small. Two typical stress strain curves of identically prepared sodium chloride crystals are shown in Fig. 2; curve 1 was taken without and curve II with the hemisphere under otherwise identical conditions. The improvement in the accuracy of defining the beginning of elastic and plastic deformation is clearly indicated. The writer wishes to thank the Deutsche Forschungsgemeinschaft for financial support, and Professor P. Haasen for providing facilities for this work.

Jan 1, 1962

By K. C. Dean

A flotation method was developed by the Bureau of Mines for concentrating pollucite, a cesium-aluminum-silicate mineral that may contain from 20 to 40 percent cesium oxide. Separation of the pollucite from three typical ores was achieved by froth flotation of the associated micas, feldspars, and other gangue minerals, using sulfuric and hydrofluoric acids and a cationic-type collector. A low-tenor, 8 percent cesium ore from Maine was upgraded to 20 percent cesium with recovery of 87 percent of the cesium. Relatively high- grade ores from Canada and Southern Rhodesia were beneficiated at lower ratios of concentration to 28 and 29 percent cesium content respectively with recovery of over 92 percent of the cesium. In addition to concentrating the cesium content of ores, the method also effectively separates cesium from sodium, potassium, and lithium, and in certain ores from rubidium. This is accomplished by selective froth flotation of the alkali metal-bearing gangue minerals such as lepidolite, other micas, and feldspars. Since the alkali metals, especially potassium and rubidium, are difficult to separate chemically or thermally from cesium to prepare high- purity cesium products, separation by physical mans is important.

Jan 1, 1962

By B. H. Bergstrom, J. J. Gilvarry

Previously the authors showed that the Gilvarry equation correctly describes the distribution of fragment size in single fracture, provided the exoclastic particles showing original surface of the specimen are removed from the distribution. In the present work this conclusion has been strengthened in two respects. First, it has been shown that the existence of two peaks in the differential distribution for the endoclastic particles, corresponding to the effect of surface and volume flaws in the interior of the specimen, can be demonstrated from the average of data for a large number of specimens. Second, it has been shown by means of a Coulter counter that data obtained from specimens fractured in gelatin display the behavior at fragment sizes approaching 1 p which is demanded by the limiting form of the Gilvarry equation in this case. In previous work, a rigorous derivation of the proper distribution function for fragment size in single fracture of a brittle solid has been given by Gilvarry,' based on a closely defined physical model and deduced strictly by the laws of probability. Experimental work has been reported by Gilvarry and Berg-str~m,~ confirming the theory in its broad outlines. Subsequently, Gilvarry and Bergstrom extended the theoretical discussion to include comminution and presented experimental data bearing on this point. They have described further experimental results for the case of single fracture recently. The experimental evidence regarding single fracture was rather convincing. However, it was based on only five specimens for which fragment sizes were determined by sieve analyses and three for which measurements in the finer sizes were made on a Coulter counter. The purpose of the present paper is to extend the experimental results as obtained by means of both sieve analyses and the Coulter technique. In the former case, sufficient specimens are included so that the average data should vield ac- curately the detailed behavior of the distribution function for the coarser fragment sizes. In the latter case, measurements for the finer sizes are reported which correspond to single fracture more closely than prior results and fill a lacuna left in the experimental verification. In addition, an extension of the theory given recently bGilvarry for the case of fracture of a two-dimensional solid will be outlined, and experimental results obtained by him will be discussed.6 THREE-DIMENSIONAL CASE Gilvarry' has shown that the Schuhmann size modulus is a measure, in a sense specified later, of the number of activated edge flaws in a specimen undergoing single fracture. Single fracture is defined as that resulting from a single instantaneous application of energy, such as the blow of a hammer whose motion is halted when fracture begins. Plural fracture consists of a short sequence of single fractures, as in a jaw or gyratory crusher; multiple fracture obtains when many applications of energy are made, as in a ball mill. The Griffith flaws associated with fracture of a specimen are flaws occurring within the volume of the body, on the new surfaces created within its interior and on the new edges (intersections of two surfaces) within the body. Fracture proceeds by activation of flaws in the volume of the specimen, in the fracture surfaces throughout its interior, and in the edges produced by intersection of fracture surfaces. If all the flaws and all groups of flaws are distributed at random, independently of other flaws or groups thereof, it has been shown by Gilvarry that the distribution function for fragment size has the form of a Poisson distribution. The fraction y, by weight or volume, passing a sieve of mesh size x is given by where k is an average spacing of activated edge flaws, j2 is an average amount of surface containing one activated surface flaw and i3 is an average volume corresponding to an activated volume flaw. The averages in question are referred to the mean dimension x of a fragment. On the basis of the theoretical

Jan 1, 1962

Jan 1, 1962

By W. D. Robertson, E. G. Grenier, V. F. Nole

The electrical, mechanical, and corrosion cracking properties of an age-hardenable Cu-Ni-Si alloy have been studied over a range of time, temperature, and deformation states for the purpose of determining the relationship between the properties and the structural state. The precifitate has been identi3ed as and the sites of preferred precipitation have been located by electron microscope studies of the structures developed by various combinations of heat treatment and plastic deformation. An extreme form of deformation banding has been observed in the aged alloy that results in high strain concentration in bands lying parallel to {111} planes. These bands are the structural paths along which transcrys-talline cracks propagate in the deformed alloy. The observations provide a basis for a general mechanism of transgranu-lar corrosion cracking of face-centered cubic alloys in terms of stacking fault probability. AMONG the age-hardening copper alloys the copper-nickel-silicon (Silnic Bronze) type is outstanding in exhibiting a high strength combined with a considerable capacity for cold working, a relatively high conductivity, and a low to negligible susceptibility to stress corrosion cracking. It is not a new alloy and it has been the subject of a number of investigations,1-5 which were made primarily to establish practical composition and heat treatment limits. The structural characteristics of the aging processes in this alloy have not previously been studied in detail. This particular investigation was undertaken to explore, in detail, and over a wide range of conditions, the properties obtainable by various combinations of working and heat treatment and to correlate structural changes with the observed mechanical, electrical and corrosion properties. MATERIAL AND PROCESSING Eight different commercial heats of the alloy were made and used in the investigation. The range of composition among the eight heats is shown in Table I. Billets, 8 by 24 in., were cast into water-cooled molds, extruded to 1.687-in. rod, and quenched in water after extrusion. Extruded material was rod rolled to 0.750 in., annealed at 1450° F for 2.5 hr, and quenched in water. Subsequent working operations were performed by tandem rolling to various sizes depending on the degree of reduction required. Final cold-working operations were performed by drawing to a uniform size of 0.187 in. diam and straightening by a roller straightening machine (Lewis). The combinations of heat treatment, working and aging that were investigated are summarized in Table 11; the various treatments were performed in the order given in each row of the table, and they will be subsequently identified by the symbols shown in the first column. SOLUTION TREATMENT All material investigated in the cold-worked condition, or cold worked prior to aging, was solution

Jan 1, 1962

By Sara Jane Boles

In recent years the interest in rare-earth compounds as refractory materials has exceeded the available literature on the subject. While some basic properties, such as density and melting point, of the more readily available rare-earth compounds have been reported in the literature, relatively few papers can be found that deal comprehensively and primarily with high-temperature refractory properties and applications of rare-earth oxides, carbides, sulfides, and nitrides. Therefore, this bibliography has been pre-pared for the use of the ceramic industry as a guide for locating and utilizing the scattered and frequently fragmentary information available. The term "rare earths", as applied in the literature search for this bibliography, is understood to include the following elements: cerium, dysprosium, erbium, europium, gadolinium, holmium, lanthanum, lutetium, neodymium, praseodymium, samarium, terbium, thorium, thulium, uranium, and ytterbium. (On the periodic chart, these elements appear as numbers 57 through 60, 62 through 71, 90, and 92.) It is emphasized that many of the abstracts included are from papers in which the rare-earth compound or compounds are treated along with several other ceramic materials, are mentioned only secondarily, with primary interest placed on a more commonly used refractory material, or are used as part of a mixture of materials formed experimentally and reported on in the paper. As the better known rare-earth materials, such as the oxides of uranium, thorium, and cerium, appear more frequently in the literature, they also appear more frequently in this collection. Articles abstracted include only information on the basic properties that are of interest to the refractories investigator. References to crystal lattices and related topics are generally excluded from this publication. The temperature 1,500° C. has been set arbitrarily as the lower limit for reported data on thermal properties. However, because of the scarcity of information, some reports are included in which data are limited to those obtained at lower temperatures. Many of the articles abstracted include lists of references that will be of additional assistance in pursuing specific lines of investigation.

Jan 1, 1962

By G. H. Matheson, J. M. W. Mackenzie

The coal concentrates studied contained clay slimes which would not flocculate on the addition of a polymer flocculent alone. The mechanism of the flocculation process is interpreted on the basis of the flocculation of lyophobic colloids. The filtration rate characteristics are shown to deviate slightly from certain basic filtration equations. Cake moisture was shown to decrease with cake drying time and vacuum, and increase with cake thickness. Filtration is a commonly accepted method of dewa-tering the fine coal concentrates produced in coal cleaning operations. Dewatering of these concentrates, using drum or disc vacuum filters, usually presents few technical difficulties and will result in the production of a filter cake containing some 20 to 25 pct moisture. In many coal cleaning operations it is common practice to add flocculants to the coal concentrates prior to filtration to increase the filtration rate. The mechanism whereby flocculation increases filtration rate has been summarized by Gaudin,4 while Geer, et a15 have compared the effectiveness of starch and synthetic flocculants as filter aids for a variety of coal concentrates. Coal concentrates, containing appreciable quantities of expanding lattice clays of the montmorillonite-illite group, sometimes prove impossible to filter without flocculation of the pulp prior to filtration. The fine coal concentrates produced at the Newcastle washery of The Broken Hill Proprietary Co. Ltd. fall into this group. Coals mined in this district contain appreciable quantities of expanding lattice clays which break down in the washery circuit waters and, by processes of mechanical inclusion, contaminate the coal concentrate thickener feed. Despite the classifying action of this thickener, the underflow which is pumped to the filters contains sufficient clay slimes to render filtration of the unflocculated pulp impossible. Filtration leaf and plant tests were carried out to develop effective and economic flocculant combinations and to determine the filtration characteristics of the flocculated coal concentrates. The determination, by leaf testing, of the filtration characteristics, and the analysis of these characteristics in the light of the equations of Brown2 resulted in the successful trial operation of the filters in the Newcastle washq. Although the filtration characteristics are not entirely in agreement with the theoretical treatment of Brown, the equations developed made it possible to predict, from leaf tests, the effect in the plant filters of pulp density, form vacuum, and form time on filtration rate and filtrate volume. EXPERIMENTAL PROCEDURES The sample used for leaf testing was the coal concentrate thickener underflow, which in plant operations would form the feed to the two 12-disk Dorr-Oliver filters. The feed to the coal concentrate thickener comprises the undersize produced by dewatering the Diester table concentrate on 5-mm dewatering screens and the overflow produced by cycloning of the froth flotation concentrate. At the time of testing these filters were inoperative because of the difficulties in filtration, arising from contamination of the

Jan 1, 1962

By T. V. Philip, R. E. Lenhart

When commercial silicon iron sheets of varying magnetic quality are isothermally annealed at high temperatures, extremely large grains develop in the material having good magnetic properties. These grains are of the (110) [001] orientation and are formed by secondary recrystallization. The primary driving force for this secondary recrystallization is grain boundary free energy. For the secondary grains, activation energies of 103 kcal per mole for nucleation, and of 75.5 kcal per mole for growth, were obtained. The activation energy for nucleation of the secondary grains is consistent with a model involving redistribution of a precipitate acting as the primary grain growth inhibitor. SINGLY oriented silicon iron sheet was first produced in 1935.1 The material as commercially produced today has a very highly developed preferred orientation or texture; up to 95 pct of the grains are crystallographically oriented with their (110) planes in the plane of the sheet and their [loo] directions parallel to the rolling direction. This texture, usually written as (110) [00l], is referred to as the "GOSS" or the "cube-on-edge" texture. Because the magnetic properties of this material are superior to those of the nonoriented sheets in the direction of rolling, the oriented silicon iron has acquired tremendous industrial importance especially in the manufacture of transformer cores and other electrical equipment. The commercially produced material is essentially an iron-silicon alloy containing about 3 1/4 pct Si with minor impurities totaling less than 0.15 pct. The silicon steel heat is melted in the open hearth or electric furnace. The ingots are hot rolled, with or without being slabbed, to strips of 0.100 to 0.080 in. thickness. They are then cold reduced to an intermediate thickness, recrystallized, cold reduced to final thickness, decarburized, and finally annealed at a high temperature. During this high-temperature anneal, extremely large grains with the cube-on-edge texture are produced in the sheet. Several papers have appeared in the literature2-10 relating to the production of the Goss-textured material. Most of these describe the textures produced on cold rolling and on subsequent annealing of single crystal or polycrystalline silicon iron. May and Turnbull11,12 have recently shown the necessity of a second-phase dispersed impurity in the material for the production of the Goss texture. However, none of these papers describes in detail the nucleation and growth kinetics of the (110) [001] grains during the final high-temperature anneal.* The present work, therefore, is an attempt to understand the nucleation and growth kinetics of the cube-on-edge grains in the silicon iron sheet during the final high-temperature anneal.

Jan 1, 1962

By J P. Bolduc, P. E. Pelletier

Preceded by brief general considerations such as the development of the mining industry in. the Province of Quebec, the choice of plant location, the types of problems studied etc., the paper gives a complete description of this new research and treatment center for metallic, non-metallic and asbestos ores. Facilities for carrying out operations in the three sections of the plant -the sampling section, the ore treatment section and the asbestos section -are fully discussed as well as laboratory facilities for (a) the preliminary testing of ores prior to pilot plant treatment and (b) the grading and testing of asbestos fibre. AT THE beginning of the century, the annual value of the mineral production of the Province of Quebec stood at the $2,500,000 level. Twenty-five years later, it was just under $24,000,000. In 1950, half a century later, it was slightly in excess of $200,000,000. But in 1959, in the span of only nine years, it

Jan 1, 1962

By G. B. Craig, J. Rezek

The critical resolved shear stress of zone-refined zinc single crystals deformed in tension is found to increase with increasing amount of striation substructure. The increase in strength with numbers of striations can be accounted for by a dislocation pile-up mechanism. A somewhat different means of plotting stress-strain data is introduced which allows a more unambiguous choice of yield stress to be made. FEW systematic studies of the role played by mac-romosaic or striation-type substructure in the de- formation of high-purity metal single crystals grown from the melt have been reported. McGrath and Craig' found that striations increased the critical resolved shear stress of zone-refined aluminum crystals, postulating a dislocation blockage by the striations as the strengthening mechanism. Lauri-ente and Pond2 found that, as the etch pit density increased in aluminum crystals grown from the melt, the critical resolved shear stress also increased. Fleischer and Chalmers3 also found changes in the critical resolved shear stress of aluminum crystals grown from the melt at varying rates, but could not be certain whether an increase of strength with rate was due to a higher concentration of impurity in the gage length or to an increase in the number of small-angled boundaries. An early work by Hibbard4 indicated that copper crystals containing lineage boundaries were stronger than those free from this type of imperfection.

Jan 1, 1962

By R. J. Wasilewski

Electrical resistivity variation with temperature was measured on a series of alloys containting up to 33 at. pct of oxygen over the range 77° to1500°K. The resistivity behavior is highly anomalous and itzconsistent with simple metallic conduction. Both composition and temperature-depended resistivity singularities were observed. A few experiments carried out on Ti-N and Zr-O alloys indicate the presence of similar anomalies. These observations, together with the published data on effects of substi-tutional alloying on the resistiuity of titanium, suggest that the anomalies are inhevent in the electron structure of this group oj metals. The existence of two-band conduction, and a significant shift of bands relative to each other with temperature and/or the electron concentration are suggested. CONSIDERABLE advances have been made in recent years in the alloy theory of simple metals. Very little, however, is known about the bonding in transition metals and their alloys.&apos; Titanium, with its relatively few electrons, may be expected to show simpler alloying behavior than the more complex transition elements. Its alloys with the interstitial elements appear particularly attractive in an investigation of bonding characteristics because of a) the simple nature of the solute elements, b) the remarkable similarity between the equiatomic structures Tic, TiN, and TiO, and c) the extensive solid solubility ranges of oxygen and nitrogen in a titanium reported.2,3 The Ti-O system was chosen for the most extensive investigation because of the relative ease of preparation of suitable specimens. Since the main object of the work was to obtain data on the bonding and its changes on alloying, electron-sensitive properties were primarily investigated. The present work describes the investigation on the electrical resistivity-temperature-oxygen content relationships. A few experiments were also carried out at selected compositions in the Ti-N and Zr-O systems. EXPERIMENTAL Materials and Method. Polycrystalline specimens were prepared in the form of hairpin strips some 50 by 5 by 0.15 to 0.50 mm by direct metal-gas reaction. This was carried out by controlled oxidation followed by a homogenizing anneal at a higher temperature. All the test specimens were fully homogenized as judged from the uniform microstructure and microhardness. To avoid preferred orientation, each strip specimen was annealed in the ß range prior to the oxidation, this procedure assuring random orientation in the strip;4 hence any texture resulting from the oxidation reaction itself affected all the specimens to a similar extent. Titanium used was of high purity (66 DPN, 10 Kg load; major impurities 0,-43G ppm, N,-70 ppm, C-25 ppm, Fe-14G ppm). The solute content of the alloys was determined by weighing, after the reaction with a known amount of oxygen. The specimens in which the discrepancy between the volumetric and gravimetric measurements exceeded 2 pct (or 0.2 mg for the low oxygen alloys) were rejected. The mean between the two measurements was then taken as the oxygen content of the alloy. Check analyses showed no measurable nitrogen contamination. All oxygen contents are given in atomic percent. Zr-O alloys were prepared in identical manner from hafnium-free crystal bar metal, cold-rolled to strip 0.25 mm thick. Ti-N alloys required very long reaction times at the maximum temperature available (1250°C). In order, therefore, to detect possible oxygen contamination, duplicate specimens were reacted in every experimental run, and one of these was analyzed both for oxygen (vacuum fusion) and for nitrogen (Kjeldahl). Only the specimens in which the check analysis showed < 1000 ppm O were then used for resistivity investigation. Since only relatively high nitrogen alloys (7.1 at. pct; i.e., 2 wt pct N,) were investigated, this oxygen contamination was considered permissible. Dc resistance was measured by the four-probe method as previously described.= The temperature was determined with a calibrated thermocouple placed in the center of the specimen hairpin. The errors in the specimen resistance values thus obtained were estimated at 1 pct due almost exclusively to the finite thickness of the potential wires and the consequent uncertainty as regards the true resistance length of the specimen. For the calculation of the specific resistance, however, no dimensional measurements could be carried out on most of the

Jan 1, 1962

By J. F. Butler

Boron nitride, BN, has been identified in boron low-carbon steels by means of light microscopy, electron microscopy and diffraction, and chemical analysis. This boron nitride is responsible for strain aging suppression in these steels through the removal of nitrogen from solution; however, small oxidizing potentials which result in deboronization In the austenitic temperature range also result in boron nitride decomposition and the subsequent occurrence of nitrogen strain aging. THE addition of boron to low-carbon steels is an effective means of eliminating the detrimental effects of strain aging;&apos;,&apos; however, the mechanism by which boron suppresses strain aging has not been established. In studying the effect of heat treatment on the strain aging of boron low-carbon steels, Butler3 found that no detectable nitrogen was present in the ferrite solid solution after various heat treatments even though the total nitrogen analyses of the steels were 0.003 pct N. Apparently the function of boron in suppressing strain aging is the removal of nitrogen from solution to form a relatively stable second phase. A clue to the identity of this phase was found by Speight4 who extracted from an aluminum-killed boron steel an acid insoluble residue which contained boron and nitrogen in proportions corresponding to the compound, BN. Shyne and Morgan5 found that the addition of nitrogen to a hardenable boron steel lowered its hardenability in a manner which suggest-d the presence of nucleating particles (presumably BN) even at high austenitizing temperatures. Although this indirect evidence for the presence of boron nitride in boron steels has been found, the compound was not identified metallographically as a separate phase in these steels. Because boron has an affinity for oxygen comparable to that of silicon,5 boron steels must be thoroughly killed with aluminum in order to prevent the reaction of boron with oxygen.7 The affinity of boron for oxygen also is demonstrated through the ease of deboronization of a boron steel in an oxidizing atmosphere. Digges, Irish, and Carwile8 found that a mixture of wet natural gas and air caused both deboronixation and decarburization of a boron steel at 1900°F. The boron content rose at the surface of the steel due to the formation of boron oxide. Shyne and Morgan9 encountered deboronization at much lower oxygen potentials; loss of boron occurred in steels treated at 1750o F under argon purified to 0.0014 pct 0, even though decarburization did not occur. Boron oxide, B2O3, is much more stable than the nitride, BN, as is indicated by the standard free energies of formation at 980oC: -235 kcal per mol of B2O3 (liquid) and -28 kcal per mol of BN (crystal). It is evident that the oxygen potential must be kept low in the presence of BN in order to prevent its decomposition and the subsequent formation of B2O3&apos; The purpose of the work described in this paper was to identify the nitride phase responsible for the removal of nitrogen from solution and to study its stability under oxidizing conditions. IDENTIFICATION OF BN In order to identify the phase containing boron and nitrogen, several alloys high in boron and nitrogen were made up in a small vacuum furnace. In alloys 3 and 4, Table I, electrolytic iron was used as a charge material. Boron additions were made in the form of 18 pct B ferro-boron after the iron was molten. In the case of alloy 3, the charge was solidified at this point; for alloy 4, nitrogen at 1 atm pressure was admitted over the melt before it was

Jan 1, 1962

By H. R. Ogden

The notch sensitivity of titanium alloys is affected by impurity content, microstructure, and heat treatment. Using notch tensile properties to evaluate notch sensitivity, three commercial titanium-base alloys were investigated over the temperature range of -320o to 390°F. The alloys studied were Ti-5Al-2.5Sn, Ti-6Al-4V, and Ti-2Fe-2Cr-2Mo. Six interstitial levels were studied for each alloy in four mi-crostmctural conditions. The ff- 0 alloys were studied in both the annealed and heat-treated condition. All tests were conducted using 1/4-in. diam round tensile samples. The notched samples had a 50 pct notch with a notch sharpness (a/r) of 53, corresponding to Kt 6.3. Notch sensitivity was increased by increased interstitial content, low temperature, and acicular-type microstructures. The heat-treated, high-interstitial content - 13 alloys were more notch sensitive than the same alloys in the annealed condition. In addition, minima in the notch tensile-temperature curves were observed at temperatures near 32°F. These minima became more pronounced with increasing interstitial content. 1 HE increaseduse of titanium alloys in high strength applications at subzero temperatures requires that a better under standing of the low-temperature behavior of the alloys be obtained. At low temperatures, metals generally exhibit increased strength with lowered ductility and tohness. Notch sensitivity and the factors which influence it become more important as the strength level is increased and the temperature is decreased. Some of the factor s which affect notch sensitivity in ti- tanium alloys are composition, interstitial content, microstructure, and heat-treatment condition. In this paper, the results of a study of these variables on the notch sensitivity of three titanium alloys at temperatures from —320o to 390o are reported. The notch geometry selected for this program was chosen to provide a severe test of notch sensitivity. The ability of the metal to flow without initiating fracture under these severe conditions is reflected in the notch-strength values. Since notch strength is, in part, determined by the constraint exerted by the combined tensile stresses, the behavior of notch specimens reflects the properties of the material under combined stresses. For example, a material with a high notch-unnotch strength ratio may be expected to withstand the biaxial stresses encountered in a pressure vessel better than a material with a low ratio of notch-unnotch strengths. This implies that maximum strength alone is not a sufficient criterion for applications of this type. It further may be concluded that the various conditions that promote poor notch behavior also will affect adversely the performance of materials under combined stresses. In the alloys studied, these included low temperatures, high interstitial levels, and hasformed microstructures. EXPERIMENTAL PROCEDURES Three alloys, Ti-5Al-2.5Sn, Ti-6Al-4V, and Ti-2Fe-2Cr-2Mo, were purchased from commercial producers as 2-in.-dam rod stock. Oxygen and nitrogen were added to these alloys by remelting to obtain a variety of interstitial contents as shown in Table I. In order to Compensate for the much more potent strengthening effect of nitrogen compared with oxygen, an oxygen equivalent content is used to describe the total oxygen plus nitrogen contents studied. It has been suggested previously1 thatnitro-gen is approximately twice as effective in strengthening as oxygen, and carbon, to the extent it is in so-

Jan 1, 1962

By W. V. Kotlensky, H. E. Martens

In an earlier communication, Ref. 1, the authors presented the tensile properties and the changes in crystal structure and microstructure for pyrolytic graphite tested at 2750°C. It was suggested that changes in the structure may have an effect on the tensile properties of this material. Accordingly, tensile tests were run on a series of specimens, from one block of pyrolytic graphite, some of which were hot-worked by being strained at 2750°C, others of which were tested in the as-deposited condition. According to the manufacturer, General Electric Co., the polycrystalline material was deposited at 2100°C on a substrate of synthetic graphite by decomposition of a dilute natural gas mixture. The as-deposited material had a density of approximately 2.19 g per cc, and as shown in Fig. 1 had a structure of medium size growth cones which were regenera-tively nucleated. All specimens had a gage section 0.75 in. long by 0.06 in. wide by 0.1 in. thick with the thickness direction perpendicular to the basal planes. The testing method and equipment used have been previously described, Ref. 2 and 3. For both the hot-working and the testing the load was applied parallel to the basal planes; a cross-head speed of 1.5 x l04 in, per sec was used. All heating was done in an atmosphere of bottled helium.

Jan 1, 1962

By Paul Meadows

This Bureau of Mines report presents operating practices and results of pressure maintenance and secondary recovery by water injection or by water injection supplemented by gas injection. Particular emphasis is placed on the results of water injection, which is the principal oil-recovery method employed in projects covered by this report. No attempt is made to study gas-injection projects or operations that are considered water-disposal projects. Also, this report does not include water-injection projects that have not been in operation long enough to evaluate results. Figure 1 is a map of north Louisiana showing the geographical locations of the projects included in this report. Most of the data used in this study were supplied by unit operators, operating companies, and the Louisiana Department of Conservation. Reservoir information and recovery data are generally those supplied by the operators, but include revisions where deemed necessary.

Jan 1, 1962

By Joseph H. Bilbrey

COBALT is a silvery gray metal which closely resembles nickel in appearance and properties although it is somewhat harder and more brittle. It is rather widely disseminated and is estimated to make up about 0.001 percent of the earth&apos;s crust as compared to 0.020 percent for nickel. Cobalt, one of the four ferromagnetic elements, is used for many magnetic applications. It is oxidation resistant, a property which when coupled with its moderately high melting point of 1,495° C., makes it useful in high-temperature applications. Although cobalt had been used by man as a coloring agent for glass and other ceramic products for 4,000 years, it was not isolated as a metal until 1742 and not established as an element until some 40 years later. Early in the 20th century, cobalt began to be used in alloys, and soon these applications displaced ceramics as the major consumer of cobalt. The use of cobalt in alloys gave considerable stimulus to production, and the world output of cobalt increased rapidly, rising from 400 tons in 1920 to 1,400 tons in 1930 and 5,500 tons in 1940. With the advent of the jet plane in the mid 1940&apos;s and the consequent increased need for cobalt-bearing high-temperature alloys, cobalt production again increased, reaching 7,900 tons in 1950. The increased demand for cobalt during the Korean war coupled with a large demand for stockpiling caused world production to more than double within the next 10 years, reaching a peak of 17,300 tons in 1959.

Jan 1, 1962