Search Documents

By G. L. Schroeder

Investigations were conducted at two underground locations, foreman's room and 5702 area, of the Kermac Nuclear Fuels Corp. uranium mining installation, Ambrosia Lake, New Mexico. The rock environment is stratified sandstone. Pressures were varied from minus 0.4 an Hg to plus 3.8 cm Hg with respect to barometric pressure, and were maintained for periods ranging from several hours to 21 days. One cm Hg overpressure (-1.5% of normal barometric pressure) produced a 20-fold decrease in Rn flux into the foreman's room as compared to the Rn flux observed during dilution ventilation. The 5702 area experienced a 5-fold decrease in Rn flux for a similar overpressure. During 21 days of continuous 1 cm Hg overpressure in the 5702 area this reduced Rn flux was maintained. The smaller reduction in flux for the 5702 area results in part from the proximity of the foreman's room to a non-pressured area and the presence of an impermeable shale lens overlying the ceiling of the 5702 area. A 0.4 cm Hg underpressure of the 5702 area increased the Rn flux into the area by 3-fold over the non-pressured value. A barometric pressure influence on Rn flux into the mine and on air Rn concentrations in non-pressurd areas of the mine was measured. A falling barometric pressure causes an increase in the flux of interstitial gas into the mine; a rising barometric pressure decreases this flux. These effects are not seen in overpressured mine areas. Radon concentrations in rock interstices show, during overpressure, decreases of all locations monitored except in the immediate vicinity of the shale lens above the 5702 area ceiling. These reductions are the result of air flowing from the mine into the rock interstices under the influence of the pressure gradient induced by the overpressure. The relative humidity of the 5702 area was reduced after 2 days of 1 cm Hg overpressure from a pre-overpressure value of 96% to 81%. The control of harmful or noisesome gases which emanate into underground mining areas from surrounding rocks is often a costly necessity. In uranium (U) mines this problem is presented by the high interstitial concentrations of radon-222 (Rn), a radioactive noble gas of 3.82-day half-period, formed in the decay scheme of U238, and the relative ease with which this noble gas diffuses from its parent rock into the interstices of the rock and then to a working area. Long-term exposure to moderate concentrations of Rn (3000 µµc per 1) and its short-lived alpha-ray emitting daughter products, RaA (Po218) and RaC (po214), has been found to result in an increased incidence of bronchial carcinomaa2 The acceptable limit of Rn daughter products in a mine atmosphere is presently set at a concentration of short-lived radon daughters which would be in equilibrium with 100 ppc of Rn per 1 of air. Ventilation of mines is conventionally accomplished by continuously diluting the mine air with fresh air brought in by fan or natural convection from above ground surface. The diluted air is allowed to vent freely to the atmosphere. This process does nothing to retard the rate at which gases (including Rn) diffuse into the mine from surrounding rock. It merely reduces the concentrations of these gases within the mine. It is suggested that in a sufficiently permeable rock environment a slight pressurization of the mine air may induce air flow from the mine into the interstices of rock surrounding the mine. The convective flow of comparatively fresh air will reduce the concentration and the concentration gradient of undesirable gases in the rock interstices adjacent to the mine. Radon will diffuse counter-current to this convective flow at a rate proportional to its concentration gradient. In time, a steady state of convection and counter diffusion will be established. The Rn flux into the mine will never be reduced to zero, and will only asymptotically approach zero as the overpressure (and hence the convective velocity of purging air) approaches infinity. During 1963 and 1964, an investigation into the effect which such applied pressures have upon the Rn characteristics of a mine atmosphere was conducted at the Kermac Nuclear Fuels Corp. uranium mines, Ambrosia Lake (near Grants), New Mexico.

Jan 1, 1967

By A. G. Gilbert

Paradoxical is the word. The coal industry, despite reach- ing a 22-year high in production (590 million tons), has been tagged as having its back to the wall vis-a-vis its valiant attempts to quench the nation's still unabated craving for coal. What must be even more reassuring to the industry, infected once with rumors of a uranium takeover, is a nation's almost insatiable appetite for electricity. Between 1967 and the summer of 1970, utility stockpiles were being gobbled up, diminishing to 79% of the January 1968 level.

Jan 1, 1971

By Philip Bucky

THE term "longwall mining" is best known to coal men, although modifications of the method are continually being used in other fields. Longwall mining is of interest today because it makes for greater mecha-nization and better supervision at the working face, and therefore lower production costs and increased safety. It is an approach to the factory system of production, the high efficiency of which as compared to that in mines is well known. There is available an accumulation of experience regarding this work but coordination of experience is lacking and this series of experiments was undertaken to help serve this purpose. Model experiments were used for reasons of safety, cost and time, and because it has been previously shown1,2,3 that a scalar model built of the same material as the prototype will behave in a manner similar to that of the prototype, with time effects the same, if the effective weight of the model is increased in the same proportion as its linear dimensions are decreased. This is accomplished by substituting a centrifugal for the gravitational field; i.e., placing the model in a centrifuge and controlling the strength of the centrifugal field by varying the rate of rotation. Many factors affect the behavior of the geologic material overlying a bed, therefore results and conclusions contained in this paper apply only to the conditions presented herein.

Jan 1, 1938

By J. Gordon Parr, D. H. Polonis

The formation and subsequent decomposition of metastable phases in Ti-Ni alloys containing up to 11 pet (atomic) Ni have been studied. The decomposition of a completely retained ß phase and of a completely transformed 8 phase in a 6 pet alloy has been followed by X-ray diffraction and metallographic methods and by hardness determinations made during the process. The possible mechanisms of the reactions are discussed. PREVIOUS investigations of the Ti-Ni system have usually been limited to phase diagram studies; but little attention has been given to metastable phases and tempering processes. These are important, however, since equilibrium conditions are rarely achieved—nor, perhaps, are they desired—in practice. Up to the present time the available transformation data for titanium alloys appear to be restricted to isothermal transformation curves for selected binary and ternary systems. No quantitative studies have been made of the mechanism by which equilibrium is approached. Several independent investigations have been carried out to determine the Ti-Ni phase diagram. Early work by Wallbaum' and later by Long et al.' produced tentative phase diagrams which were not representative of true binary conditions, since the alloys were contaminated with oxygen and nitrogen. The most recent diagram (Fig. 1) is due to Margolin et al.," and a slight modification of the a + ß/ß boundary (shown dotted) has been proposed by McQuillan.' The structure of the phase Ti,Ni was shown by Duwez and Taylor" to be face-centered-cubic, with 96 atoms per structure cell. The formation of a martensitic ß phase (close-packed-hexagonal) in Ti-Ni alloys has generally been observed when specimens of low nickel content are rapidly cooled from the 0 (body-centered-cubic) range. Margolin et al. reported an increasing tendency for P to be retained in lump specimens as the nickel content increases. McQuillan' has studied the effect on the microstructure of delay time in quenching, and has reported the formation of pro- eutectoid a precipitate in a quenched hypoeutectoid alloy. In a previous study of Ti-Fe alloys," experiments were made on powder specimens produced by filing alloy ingots. Techniques were devised for the preparation and heat treatment of alloys, and X-ray diffraction methods were used both for structure determinations and phase ratio estimations. A similar approach has been made in this study of Ti-Ni alloys. Experimental Methods Ten alloys ranging from 0.25 pet to 18 pet Ni* * All compositions are in atomic percentages unless otherwise stated. were prepared from iodide titanium bar stock (hardness Rf 72) and Johnson-Matthey spectrographic standard nickel by levitation melting.' As a check

Jan 1, 1957

By J. A. Retty

HOLLINGER CONSOLIDATED GOLD MINES LTD., through two subsidiary companies, has the exclusive right to prospect in two contiguous areas in central Labrador. This paper presents the results of the mineral exploration that has been conducted in these areas to date. One of the subsidiaries of Hollinger. the Labrador Mining and Exploration Co. Ltd., under an agreement with the Newfoundland Commission of Government, holds an area of approximately 20,000 sq.mi., which comprises the western portion of Newfoundland-Labrador and includes the upper basins of the Hamilton and Naskaupi Rivers. (The main area of the deposits so far discovered may be located on a map at about 67° west longitude and 55° north latitude.) The other subsidiary of Hollinger, Hollinger North Shore Exploration Co. Ltd., has licensed from the Province of Quebec an area of approximately 3900 sq.mi. lying directly north of the Newfoundland-controlled area at the headwaters of the George, Whale, and Swampy Bay Rivers. The M. A. Hanna Co., large iron-ore operators of the Lake Superior region, are participating in the project. With the exception of the years 1940 and 1941, field work has been conducted in the Newfoundland area since 1936, and in the Quebec area since 1939. Hollinger assumed the management in 1942. The field base is at Hollinger Lake, some 300 miles north of the tidewater base at Seven Islands, Quebec, which, in turn, is just west of the mouth of the Moisie River, on the Gulf of St. Lawrence. Air transportation is used exclusively to service the operation.

Jan 1, 1945

By Herbert Clark Hoover, Lou Henry Hoover

PREVIOUSLY I have dealt with the methods of separating silver from copper. There now remains the portion which treats of solidified juices ; and whereas they might be considered as alien to things metallic, nevertheless, the reasons why they should not be separated from it I have explained in the second book. Solidified juices are either prepared from waters in which nature or art has infused them, or they are produced from the liquid juices themselves, or from stony minerals. Sagacious people, at first observing the waters of some lakes to be naturally full of juices which thickened on being dried up by the heat of the sun and thus became solidified juices, drew such waters into other places, or diverted them into low-lying places adjoining hills, so that the heat of the sun should likewise cause them to condense. Subsequently, because they observed that in this wise the solidified juices could be made only in summer, and then not in all countries, but only in hot and temperate regions in which it seldom rains in summer, they boiled them in vessels over a fire until they began to thicken. In this manner, at all times of the year, in all regions, even the coldest, solidified juices could be obtained from solutions of such juices, whether made by nature or by art. Afterward, when they saw juices drip from some roasted stones, they cooked these in pots in order to obtain solidified juices in this wise also. It is worth the trouble to learn the pro- portions and the methods by which these are made. I will therefore began with salt, which is made from water either salty by nature, or by the labour of man, or else from a solution of salt, or from lye, likewise salty. Water which is salty by nature, is condensed and converted into salt in salt-pits by the heat of the sun, or else by the heat of a fire in pans or pts or trenches. That which is made salty by art, is also condensed by fire and changed into salt. There should be as many salt-pits dug as the circumstance of the place permits, but there should not be more made than can be used, although we ought to make as much salt as we can sell. The depth of salt-pits should be moderate, and the bottom should be level, so that all the water is evaporated from the salt by the heat of the sun. The salt-pits should first be encrusted with salt, so that they may not suck up the water. The method of pouring or leading sea-water into salt-pits is very old, and is still in use in many places. The method is not less old, but less common, to pour well-water into salt-pits, as was done in Babylon, for which Pliny is the authority, and in Cappadocia, where they used not only well-water, but also spring-water. In all hot countries salt-water and lake-water are conducted, poured or carried into salt-pits, and, being dried by the heat of the sun, are converted into

Jan 1, 1950

By John Chipman, Theodore B. Winkler

IN order to understand more fully the complexities of the reactions occurring between the liquid steel and the slag in the basic open-hearth steelmaking furnace, investigations in this country and abroad have turned to laboratory equilibrium studies. This paper is one of a series of reports on investigations being conducted at the Massachusetts Institute of Technology. The experimental work was completed early in 1942. The slag systems found in the basic open hearth are very complex, being made up of at least eight major components and as many others whose effect might be classified as minor. The first two papers of the series, by Fetters and Chipman,l,2 as well as the paper by Taylor and Chipman,3 dealt with the simplest possible slag system that would resemble those found in the basic open hearth-the slag system consisting of CaO-MgO-SiO2-FeO. (Taylor's rotating induction furnace eliminated the necessity of contamination of the slag by MgO.) Having arrived at some reasonable conclusions regarding the physical chemistry of the reactions between molten iron and the simple slags at equilibrium, the next step was to investigate more complex slag systems. The major purpose of the present investigation was to determine what factors control the distribution of phosphorus between molten iron and the more complex basic slags at equilibrium, and to what extent these factors are influential. The slags used contained CaO, MgO, Si02, FeO, Fe203, P205, MnO, A1203 and CaF2, but not all of the slag samples contained all of these components at one time. REVIEW OF LITERATURE Although a number of interesting papers have been published on the subject of dephosphorization of an iron bath, there are as yet no results from laboratory studies that give thoroughly reliable information on the dephosphorization reaction. Even for the supposedly simple Fe-O-P system involving iron-phosphorus melts and iron oxide-iron phosphate slags, the experimental results are contradictory and no formulas have been established that adequately fit the equilibrium conditions. The Fe-O-P system has been studied by Schackmann and Brings4' von Samson-Himmelstjerna,5 Oelsen and Maetz,6 Bischof and Maurer,7 Diepschlag and Schürmann,8 and Herty,9 and the results of their investigations appear in Table I. A number of different equilibrium constants and distribution ratios

Jan 1, 1946

By P. Payson

INTERGRANULAR corrosion in corrosion-resistant chromium-nickel steels has been widely discussed in the last few years. So far as the author knows, nothing has been published which definitely shows that this tendency can be eliminated, although suggestions have been made that a remedy is possible if certain specifications are satisfied. Strauss, Schottky and Hinueber1 suggested an increase in chromium content to an extent that would prevent the impoverishment of chromium on carbide precipitation sufficient to cause impaired corrosion resistance in the matrix. Pilling2 suggested an increase in nickel, so that the stability of the austenite matrix would be increased. Aborn and Bain,3 say that "intergranular attack-may be eliminated by preventing carbide precipitation (e. g., by lowering the carbon content or somehow raising its solubility) or by precipitating it permanently under conditions which will not remove chromium from solid solution so drastically at any points." In a later paper Aborn and Bain4 state that many different metallic elements, tungsten, vanadium, copper, aluminum, molybdenum, titanium and zirconium, have been added in small per-centages to increase the stability of these alloys, but that it has been reported that according to the copper sulfate test these added elements act only to retard the intergranular corrosion, and that increased nickel and chromium contents have similar effects. Newell5 showed that the lower the quenching temperature before reheating, the less severe was the intergranular attack.

Jan 1, 1932

By R. B. G. Yeo

Pronounced isothermal martensite formation at room temperature was measured dilatometrically in a steel containing 0.01 pct C, 24.9 pct Ni, 0.26 pctAl, 2.58 pct Ti and 0.25 pct Cb. It is shown that martensite will form isothermally if stabilization of the austenite-martensite transformation is eliminated by removal of carbon. The decarburization of two iron-nickel alloys allows isothermal transformation to martensite to occur at temperatures above their athermal Ms temperatures. In an Fe-22.4 pct Ni alloy, at the 0.008 pct C level, the Ms temperature during air cooling is 85°F higher than that during- water quenching-. At the 0.15 pct C level this difference is reduced to only 5°F. The introduction of carbon causes stabilization during air cooling which lowers the Ms temperature virtually to the same level as determined during mate?. quenching. Thus in the 0.15 pct C alloy, the Ms temperature is almost independent of cooling rate. It is suggested that rival theories of martensite formation should be reexamined in alloys of sufficiently low carbon and nitrogen content to eliminate the complication of stabilization. The Ms temperature of a steel containing 0.01 pct C, 24.9 pct Ni, 0.26 pct Al, 1.58 pct Ti and 0.15 pct Cb, solution treated at 1500°F and air cooled as 1/8-in. diam specimens, was found to be 57 °F. 1 However, when held for several hours at room temperature the steel hardened slightly and became appreciably ferromagnetic. Isothermal transformation to martensite was first revealed by Kurdjumov and Maksimova2 in an iron-base alloy containing 0.6 pct C, 6.0 pct Mn and 2 pct Cu. Most of the other studies of isothermal martensite have also been confined to highly alloyed steels which transform at subzero temperatures; for instance, DasGupta and Lement, 3 Cech and Hollomon, 4 Machlin and Cohen,5 Shih, Averbach, and Cohen.6 Averbach and cohen7 noted a rapidly decaying volume increase at room temperature in a steel containing 1 pct C, 1.5 pct Cr and 0.2 pct V. cina8 and Marshall, Perry, and Harpster9 have described the isothermal transformation to martensite at room and subzero temperature in stainless steels. Kurdjumov10 has recently reviewed the subject, noting that the isothermal formation of martensite can be observed only in the temperature range somewhat below Ms or below -50°C. The isothermal formation of martensite may be characterized as follows: 1) It occurs in steels of widely different compositions, the main prerequisite being a low transformation temperature. 2) The transformation occurs by the formation of new plates and not by the growth of old ones. 3) The isothermal transformation is suppresed by stabilization during slow cooling or holding at temperatures near room temperature. However, the factors governing this mode of transformation are still not fully understood. The formation of martensite isothermally suggests an activated process. The early theories of martensite formation did, in fact, utilize classical nucleation concepts. Kurdjumov 11 first proposed the presence of thermally activated nuclei of different sizes and compositions which would grow if they reached critical size during cooling. This treatment was enlarged and developed quantitatively by Fisher, Holloman, and Turnbull12,13 and was later reviewed by the latter two authors.14 Fisher15 associates Ms with a nucleation rate of one per cc per sec. At slightly higher temperatures the nucleation rate is so low that isothermal formation of martensite is not observed in reasonable times. At slightly lower temperatures the nucleation rate is so high that it could not be suppressed by rapid cooling. By judicious use of parameters Fisher 16 was able to obtain good agreement between classical nucleation theory and the incubation times of martensite formation.4 However the application of these principles to martensite formation in iron-nickel alloys15 predicts that an alloy containing about 30 pct (31 at. pet) Ni would not transform. The presence of an Ms temperature at -223° C in an alloy containing 34.1 pct (33 at. pct) Ni led Kaufman and cohen17 to reject the hypothesis of homogeneous nucleation in favor of the reaction path theory originally proposed by Cohen, Machlin and Paranjpe.18 This theory conveniently explains the formation of martensite athermally but becomes labored when dealing with isothermal formation. Kaufman and cohen19 did explain the isothermal activation of embryos by assuming it to be a result of the expansion of their boundary dislocation loops but this treatment predicts an upper temperature limit of isothermal martensite formation.

Jan 1, 1962

By David Sinclair

THE dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests.§ None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their appli-cation in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I THE PHOTOELASTIC METHOD The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution.

Jan 1, 1940

By W. W. Norton

The gradually increasing proportion of sulphide ores which lead smelters of to-day are called upon to handle has caused the roasting problem to become one of ever greater importance. Mines have increased in depth, methods of concentration have improved, competition in the purchase of ores has become more keen and it has been clear that new and modern methods of eliminating sulphur must receive a large share of attention. We may look back a score of years or so and recall the old hand roasters, some of which turned out a finely divided roasted product, and others fashioned with a "fuse-box" wherein the roasted ore was slagged. Then came mechanical furnaces of several types, the Bruckner cylinder, the Brown-O'Harra, the Ropp, and others, all designed to cut out the cumbersome hand labor of the old reverberatories. Roasting costs were thereupon reduced and tonnages stimulated to a gratifying extent. However, it seems to have been early recognized that this very feature of a greater amount of roasted sulphide ore as compared with oxide ore brought with it a train of difficulties at the blast furnaces. The mechanically roasted ore was fine physically, the blast furnaces were choked and the troubles of the smelterman were not at an end. Then the Huntington-Heberlein pot system of roasting appeared upon the scene, and later on the Dwight-Lloyd machines were invented, and inasmuch as both of these processes were designed not only to roast the ore but to agglomerate it as well, it was apparent that distinct steps in advance had been achieved. At the Murray plant, modern up-to-date roasting practice is fully exemplified and there are now in successful operation roasting furnaces or devices of several sorts: namely, Godfrey revolving-hearth furnaces, Wedge multiple-hearth mechanical roasters, Dwight-Lloyd sintering machines, and Huntington-Heberlein pots. Godfrey and Wedge furnaces will properly handle material high in sulphur, say ores with 25, 30, and 35 per cent. of that element; D. & L. machines and H. & H. pots will positively not treat efficiently ores or mixtures containing anywhere near the sulphur content mentioned, but are confined to charges containing in the neighborhood of 15 or 18 per cent. In passing, it may also be explained that, so far as the knowledge of the writer goes, Godfrey and Wedge furnaces do not economically eliminate sulphur to an extent

Jan 1, 1915

By Samuel Hoyt

THE writer has long been interested in seeking an explanation of the upper heat effect in the copper-tin alloys over the a + ß range, first described in 1913. These notes are offered, not at all as the final explanation of this heat effect, but rather to indicate certain progress which has been made toward establishing what happens over this temperature interval. While working on the thermal analysis of the copper-rich kalchoids (copper-tin-zinc alloys), it was noted that those alloys containing major portions of tin and minor portions of zinc exhibited two marked heat effects, one at about 520° C. and the other at about 600° C., instead of the single effect which is generally observed in either of the two binary series. This matter was discussed with Dr. Guertler, who suggested that a heat effect at about 600° C. in the pure copper-tin alloys might be expected. This led to a more searching examination of the thermal critical points in the pure copper-tin alloys, with the result that a marked, although somewhat weak, heat effect was located at about 600°. Somewhat later, this upper heat effect was discussed with Dr. Burgess, and it was requested that the Bureau of Standards make heating and cooling curves of one of these alloys for the purpose of removing any possible doubt as to the actual presence of the heat effect. Results obtained by the Bureau are given in Plate I. In an earlier paper1 differential curves were published showing that the heat effect occurred at constant temperature over the a + ß range and increased in magnitude with the amount of a up to a point somewhat above 20 per cent. tin. No heat effect was noticed at this temperature in the eutectoid alloy. The existence of this heat effect seems to require a modification of the present copper-tin diagram in the a + ß field, and it has been the object of the work here presented to secure the evidence upon which such a change should be based.

Jan 12, 1918

By David P. Shoemaker, Clara B. Shoemaker

It has been shown for an important class of complex transition intermetallic compounds (a, P, R, 6, and p phases) characterized by "normal" coordination [CN12 (icosahedral), CN14, CN15, CN16/ that interatomic distances nay be calculated to a good approximation as the sum of characteristic atomic radii. Two radii, one for major ligands and one for minor ligmds, are specified for each atom, except in the case of CN12 where only a miaaor-ligand radius is specified. The same appears to be true of transition-metal phases of simpler struc-ture: Laves phases (CN12, CN16), and p-tungsten phases (CN12, CN14). In the case of known examples of the more complex phases, a simple rule is given which specifies these radii. However, only a fraction of the known examples of the simpler phases obey this rule closely. To include the latter phases the rule may be modified by considering the radii as linear functions of the weighted average of the Pauling CN12 radii of the two kinds of atonzs, with the radii weighted according to the over-all chemical composition of the alloy. With very few exceptions interatomic distances for both tlze complex and the simpler transition phases can b$ predicted with this modified rule to within 0.06A. ManY intermetallic compounds are known of composition A,By, in which A is a transition element to the left of the manganese column in the periodic table and B is a transition element in or to the right of it. Frequently the coordination numbers (CN) found in these compounds are CN12 (icosahedral), CN14, CN15, and CN16 (called "normal" coordinations by Frank and Kasperl). Well-known examples are the cubic and hexagonal Laves phases which have CN12 and CN16, and the 0-tungsten (CrsO) phases which have CN12 and CN14. In the more complicated (often ternary) phases, such as the a phase,2 the Beck phases p3 and R~, the 6 phase,5 and the p p atoms occur with CN12, CN14, CN15, and (except for a) CN16; in many cases several crystallographically independent atoms of one particular CN occur in the asymmetric unit. A large number of independent interatomic distances are found in these complicated phases, varying from 20 in the a phase to 94 in the 6 phase. These distances show a large spread; they vary, for example, from 2.358 to 3.278A in the 6 phase. In our analysis of these distances we found that in each of these compounds every atomic position can be characterized by either one or two radii. The CN12 positions are characterized by a single radius, The higher coordinated positions are characterized by two radii, namely: the CN14 positions by 4 in the direction of the twelve "5-coordinated" ligands3 (called 'minor" by Frank and Kasperl) and by r:, in the direction of the two "6-coordi-nated" ligands (called "major" by Frank and Kasper); the CN15 positions by r15 for the twelve minor and r:, for the three major ligands; the CN16 positions by rlE for the twelve minor and r:, for the four major ligands. We have expressed the experimentally determined interatomic distances in observational equations as the sums of the appropriate pairs of these characteristic radii and the value of these radii have been determined by the method of least Squares. Despite their wide range, the interatomic distances could then be predicted by the sums of these atomic radii with an average deviation in any one compound of 0.06A or less. The results are summarized in Table I. Inspection of the radii thus obtained shows that in the structures in Table I the radii (in A) are given to a first approximation by the simple relationship: Where CN is the coordination number (12, 14, 15, or 16), and A = 1 for major ligands and = 0 for minor ligands. The interaLomic distances can be predicted within about 0.1A by sums of these atomic radii. Another phase belonging in this group with CN12, 14, 15, and 16 is the y phase & B7, in which A is molybdenum or tungsten and B is iron or cobalt. Recently the M%C phase has been refinedE and the observed distances also agree well with those calculated with Eq. [I]. (In the original determination of the structure of W6FeV7 the F$(II)-W(II1) distance was erroneously given as 2.84A, but we have recalculated it fro? the published parameters and found it to b? 2.57i4, in good agreement with the value of 2.6A predicted with Eq. [I.].) Many binary transition alloys are known to crystallize with the simpler structures having "nor-

Jan 1, 1964

By W. E. Ruder

It has been pointed out by Stead1 that grains of considerable coarseness may be developed in steels containing from 3 to 5 per cent. of silicon, and in a previous paper2 the present author has shown that under the proper conditions of annealing single grains having an area of 50 sq. cm. may be obtained. It is the purpose of this paper to discuss in more detail the conditions promoting the growth of these grains, in the hope that the experiments described may throw some additional light upon the general problem of grain growth in metals. These silicon steels lend themselves particularly' well to such experiments because of the ease with which the change in structure may be followed and because of the fact that the effect of the carbon present is largely obliterated by the high percentage of silicon. This forms a solid solution with the iron, which acts very much like a pure metal. This alloy has been found to have but one critical point, viz., Ar2. This point, determined by Roberts-Austen for Hadfield's 4 per cent. Si alloy, was found to lie at 703" C. Vigouroux3, in working with pure Fe-Si alloys, finds this point to rise from 750" C. for 0.5 per cent. Si to 860" for 6 per cent. alloy, with a flat region in the curve from 3 to 4 per cent. Si. No accurate determination of this point has been undertaken by the present author, but it has been roughly determined to lie between 730" and 750:. In the preliminary experiments, some of which have been described in a previous paper, it was found that practically all of these steels, when annealed to 1,200" C. or higher, showed grains of comparatively large size. These grains varied in size, however, from about 4 sq. mm. to 50 sq. cm. (see Figs. 1 and 2) under the same conditions of anneal, and it was for the purpose of determining the cause of this difference in size that the experiments herein described were undertaken. From a preliminary study of the chemical composition of the specimens

Jan 1, 1914

By C. A. Stickels

In a recent paper, Held1 showed that rolling conditions can have a marked effect on the volume fraction of surface texture produced in low-carbon steel. This variation in rolling texture is reflected in the recrys-tallization texture and affects the plastic properties of the annealed sheet. The fact that roll friction can influence the surface deformation texture in iron and steel has been known for some time;'= but the magnitude of the effect has never been shown quite so clearly before. The analogous effect during wire drawing has been recognized for many year.4 Dillamore and Roberts5 examined surface textures in warm- and cold-rolled aluminum and copper. They found that when a surface texture was present it could be described as the interior texture rotated about the transverse sheet direction. The angle of rotation was a function of the type of lubrication, the amount of reduction per pass, and the temperature of rolling. The purpose of the present note is to show that surface textures in cold-rolled iron can also be described as interior textures rotated about the transverse sheet direction. Vacuum-melted electrolytic iron* was straight- rolled 90 pct at room temperature in a two-high rolling mill with 5-in.-diam rolls. Two rolling procedures were used: a) no lubrication with reductions of about 0.035 in. per pass, and b) heavy lubrication with lano-line and reductions of about 0.002 in. per pass. The final sheet thickness was 0.030 in. (110) pole figures were determined by transmission through specimens taken from the sheet surface and sheet midplane. The surface texture of the sheet cold-rolled according to procedure a is shown in Fig. l.* The shapes of the low-intensity contour lines indicate that the texture can be described as a partial fiber texture with a (110) fiber axis normal to the sheet. The approximate range of orientstions present is (011)[211] — (0ll)[100] — (011)[211]. This range of orientations is what one would obtain by rotating the interior texture 90 deg about the transverse sheet direction. The intensity of (110) and (222) reflections from planes parallel to the surface was measured after removing metal from the surface by chemical polishing. The surface texture here was confined to the outer

Jan 1, 1968

By E. C. Burke, W. R. Hibbard

Plastic deformation in magnesium single crystals was studied by tensile tests at room temperature utilizing an improved preparation and testing technique. Consistent critical resolved shear stress values for basal slip were obtained. The advent of pyramidal slip at room temperature was rationalized upon the basis of grip constraints. A bend-twinning hypothesis was advanced as an explanation of mechanical twinning which occurs as a complex stress-relief mechanism. INVESTIGATIONS of the plastic deformation of magnesium have been limited to the determination of the fundamental kinetics which may be summarized as follows: 1—Twinning on the {102).l 2— Slip on the (001) plane in the [loo] direction at room temperature.' 3—Slip on the {101) or {102) plane in the [loo] direction above 225°C." 4—Critical resolved shear stresses for basal slip in tension at room temperature of 83 g per sq mm with a variation from 57 to 127 g per sq mm." Bakarian' studied the compression of thin wafers of magnesium single crystals and classified the components of the deformation mechanisms as follows: 1—The Basal field: (001) at an angle of less than 20" to the compression surface. Fracture along {101} or slip on (001) followed by {101} fracture. 2—The prism field: (001) at an angle greater than 60" to the compression surface. Twinning on the {102) generally occurring during the early stages of loading, basal slip in the areas of original orientation and (001) slip within twins. 3—The central field: (001) at angles greater than 20" but less than 60" to the compression surface. Slip on the (001). 4—The critical resolved shearing stress for {101} slip above 225°C was 400 g per sq mm. Observations of mechanical twins in hexagonal close-packed metals have been summarized by numerous investigatorsb-' emphasizing a lateral or rotational atomic adjustment, in addition to the pure twinning shear, and the importance of reorienting the basal plane to a position more favorable for continued slip, rather than the resulting small dimensional changes. Criterion for the operative twinning planes has not been clearly established. Schmid and Boas hurmised that an energy condition related to the atom movements is the determining factor. MillerQ bserved that twinning stresses in zinc crystals decreased as the amount of prior deformation increased. Preparation of Specimens Magnesium single crystals % in. in diam x 8 in. long were grown from the melt under an argon atmosphere in a gradient furnace similar to that described by Jillson." Magnesium containing 0.018

Jan 1, 1953

By L. C. Graton

The federal taxes on incomes and excess profits are of course heavy. In 1917, the value of the mineral production of the United States was a little in excess of $5,000,000,000. The total of federal taxes for that year, for the mineral producing companies, as computed by themselves, amounts, according to tentative compilations, to about $207,000,000, and the total for the comprehensive group of mineral and metal industries to about $766,000,000, which figures represent respectively 9.5 per cent. and 35.1 per cent. of the total tax paid by all corporations. Because of greater complexities in applying the revenue laws to mineral properties than to most other industries, opportunity is afforded for wide differences of view. The taxes indicated above, therefore, are not final and may conceivably be very materially increased. For 1918, the taxes are expected to be still greater, but no compilations are yet available. Taxes at a high rate are to continue indefinitely. The subject is clearly of gravest import to the mining industry in particular. The Commissioner of Internal Revenue, who is charged by law with the administration and collection of the taxes, is determined that these functions shall be performed in a just and businesslike way. Fairness and finality are to be the chief objectives. In view of the peculiar conditions that attach to the tax program as applied to mines and other wasting industries, like oil, gas, and timber, the Commissioner has resorted to professional advice and assistance by manning a Sub-division of Natural Resources with competent engineers, brought in from the several industries, into whose hands he has placed for solution the technical questions involved. These engineers have a two-fold duty: (1) to devote to the solution of these problems their own knowledge and experience; (2) through their acquaintance with their respective industries, and with the men engaged in those industries, to focus upon these problems, by conferences and otherwise, the best opinion of the country. The principal object of this paper is to acquaint the mining profession with the attitude of the

Jan 1, 1923

By L. C. Graton

The federal taxes on incomes and excess profits are of course heavy. In 1917, the value of the mineral production of the United States was a little in excess of $5,000,000,000. The total of federal taxes for that year, for the mineral producing companies, as computed by themselves, amounts, according to tentative compilations, to about $207,000,000, and the total for the comprehensive group of mineral and metal industries to about $766,000,000, which figures represent respectively 9.5 per cent. and 35.1 per cent. of the total tax paid by all corporations. Because of greater complexities in applying the revenue laws to mineral properties than to most other industries, opportunity is afforded for wide differences of view. The taxes indicated above, therefore, are not final and may conceivably be very materially increased. For 1918, the taxes are expected to be still greater, but no compilations are yet available. Taxes at a high rate are to continue indefinitely. The subject is clearly of gravest import to the mining industry in particular. The Commissioner of Internal Revenue, who is charged by law with the administration and collection of the taxes, is determined that these functions shall be performed in a just and businesslike way. Fairness and finality are to be the chief objectives. In view of the peculiar conditions that attach to the tax program as applied to mines and other wasting industries, like oil, gas, and timber, the Commissioner has resorted to professional advice and assistance by manning a Sub-division of Natural Resources with competent engineers, brought in from the several industries, into whose hands he has placed for solution the technical questions involved. These engineers have a two-fold duty: (1) to devote to the solution of these problems their own knowledge and experience; (2) through their acquaintance with their respective industries, and with the men engaged in those industries, to focus upon these problems, by conferences and otherwise, the best opinion of the country. The principal object of this paper is to acquaint the mining profession with the attitude of the

Jan 1, 1923

By E. P. Klier, Taylor Lyman

THE structures formed when austenite is quenched to subcritical temperatures and allowed to transform isothermally have been the subject of intensive study since the work of Davenport and Bain.1 Isothermal transformation diagrams summarizing the results of many of these studies have become widely familiar to metallurgists. Of particular interest to metallographers are the dark-etching, acicular products of transformation formed by isothermal reaction below the temperature of maximum velocity of the austenite to pearlite reaction. These products, the bainite structures, can be formed in a wide variety of steels. However, the constitution of bainite is not well understood and divergent views have been expressed as to its mode of formation. In this investigation a combination of dilatometric, microscopic and X-ray methods has been brought to bear upon the problem in the hope of some elucidation of the bainite reaction as it occurs in hypoeutectoid steels. MECHANISM OF BAINITE FORMATION Davenport and Bain1 considered the mechanism of bainite formation to consist of two steps-an allotropic transformation followed by precipitation of carbide. The separation in time of the two processes was considered to be very slight in the upper temperature range and very marked at temperatures just above the martensite range. This concept has been restated by Vilella, Guellich and Bain2 in the form of a definition of the acicular mode of transformation as: The successive, abrupt formation of flat plates of supersaturated ferrite along certain crystallographic planes of the austenite grains; this supersaturated ferrite begins at once to reject carbide particles, (not lamellae), at a rate depending upon temperature. In effect, this is the acicular mode of transformation, even though the temperature be such as to limit the actual life of the quasi-martensite to millionths of a second. The investigation of isothermal decomposition of austenite in certain alloy steels (notably those containing chromium or molybdenum) has revealed that there may be a range of temperatures between the pearlite and bainite reactions in which the austenite decomposes at a relatively low rate.3-6 Further, it is characteristic that in the second region of fast reaction the decomposition of the austenite is incomplete by one reaction but goes to completion by a second reaction. These observations led Wever7 to a description of the bainite reaction as follows: I. The reaction takes place by initial precipitation of a martensitic intermediate structure. 2. In the upper temperature range this structure readily decomposes into ferrite and cementite. In the lower range carbon separates in an unknown form. 3. In the upper temperature range the precipitated carbide nucleates the precipitation

Jan 1, 1944

By J. W. H. Clare

An equilibrium isotherm at 550°C is given for ternary alloys rich in aluminum containing 0 to 15 wt pct Cr and 0 to 20 wt pct Mn. Phases encountered are: aluminum solid solution; stable temary compound G; and MnAl8,. In addition, a limited number of alloys were annealed at 450°C to check for differences from the 550°C isotherm. These experiments limited the composition of the G phase at 550°C and further experiments established that the G Dhase is not stable above 590 ± 1 °C. RAYNOR and Little1 established several equilibrium isotherms using aluminum-rich alloys containing up to 5 pct of the elements chromium and manganese. These isotherms showed that, in addition to an a solid solution and the two binary intermediate compounds 8 and MnAl6, a stable ternary compound ex-isted in the system. This phase was called the G phase because of its ghostly appearance in micro-sections. Little, Raynor, and Hume-Rothery2 found a similar phase in binary aluminum-manganese alloys and, as a result of their experiments, concluded that the G phase was a metastable phase existing in the aluminum-manganese system. This phase was stabilized by the addition of chromium. The constitutional work of Raynor and Little,' although showing the existence of the G phase in the aluminum-chromium-manganese system, did not establish precisely the composition limits of the phase or the temperature above which the phase became unstable and disappeared from the system. The work described in this paper was undertaken to provide this information. An examination of the previous work' showed that an isotherm at 550°C would provide the required data regarding composition in the shortest possible time, as the (a + G) phase field narrows considerably at higher temperatures. The same work showed that the G phase ceased to exist between 580° and 595°C. A more precise estimate of the transformation temperature would therefore be obtained by annealing selected alloys at successively higher temperatures beginning at 580°C. EXPERIMENTAL PROCEDURE 1) Materials Used—The experimental alloys were prepared from four master alloys containing 15.00 w pct Cr, 15.28 wt pct Cr, 19.80 wt pct Mn, and 19.38 wt pct Mn which were made from super-purity aluminum, electrolytic chromium, and electrolytic manganese. The aluminum was of 99.996 pct purity, the principal impurities being copper, iron, and silicon. The chromium and manganese were 99.9 pct pure, the principal impurities being antimony, calcium, and magnesium. 2) Preparation of the Experimental Alloys—The alloys were prepared in 20-g quantities by melting together the requisite amounts of master alloy and aluminum in an alumina-lined crucible and, after thorough stirring with an alumina rod, cast into a cold copper mold to give ingots 1/4 in. in diam and 3 in. in length.

Jan 1, 1960