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By R. T. Webber, R. B. Owen

The vapor phase deposition of molybdenum and tungsten from the hexacar-bonyls has been thoroughly investigated by Lander and Germerl, and shown to yield well-bonded coatings on a variety of hot metallic surfaces. They also demonstrated that chromium coatings2'3 could be similarly deposited, but did not investigate this metal extensively. Recently, conditions have been described by which this compound can be prepared in quantities sufficient for laboratory scale plating experiments, and it is the purpose of the present communication to outline the results of preliminary experiments upon the plating of chromium from its carbonyl. Apparatus and Technique The apparatus used in these experiments is shown in Fig I. At one end, connected by a short length of rubber tubing, is a Cenco Hypervac 20 pumping continuously. At the opposite end is a needle valve which allows a small stream of purified hydrogen to flow through the apparatus. Connected in series are a trap T1, maintained at the temperature of dry ice and acetone, the plating chamber, and two traps T² and T3 containing crystals of the carbonyl. T² is kept in a constant temperature bath (not shown), while T³ is at room temperature. Stopcock S6 allows the hydrogen flow to by-pass the carbonyl traps. A McLeod gauge is connected so that it can measure the pressure at the pump through Se, or the pressure at the plating chamber through S9 and S6. The standard (12 liter) volume connected by Sb is used to determine the volume included by S4, S6, SB, Slot the needle valve and the McLeod gauge. Knowledge of this volume allows calibration of the flow of hydrogen. The apparatus* is built entirely of pyrex, except for the needle valve, the rubber connection to the Hypervac, and the cover of the plating chamber. The plating chamber is water-jacketed, with a large brass top allowing insertion of the specimen to be plated. Set into the brass top is a ground glass stopper through which thermocouple leads are sealed. The thermocouple wires (pure Pt, and 87 pct Pt-13 pct Rh) serve the double purpose of measuring the specimen temperature and suspending it in the chamber. Surrounding the chamber is the coil of an induction heater, H. The apparatus is designed to allow variation of the following conditions: (I) the specimen temperature, from room temperature to about 1000°C, (2) the carbonyl vapor pressure, from 40 to 220 microns, and (3) the hydrogen flow. In several runs, 0.8 to 1.8 PCt of hydrogen sulfide was introuced through a needle valve that replaced S4. The vapor pressure of the carbonyl is

Jan 1, 1949

By B. M. Larsen, T. E. Brower

IN two previous papersl,2 dealing with the carbon-oxygen reaction, and the simultaneous content of each, in liquid steel in the furnace, we have made use of the quantity 0[O], defined as the excess oxygen beyond what would be in equilibrium with carbon then present if the pressure of carbon monoxide were I atm,; that is, if [C] X [O] is taken as 0.00222, 0[O] = [O] - 0,00222/[C] where [O] is the percentage of oxygen by weight as measured by the method described earlier.' This quantity 0[O] proves to be substantially independent of carbon content over the range 0.08 to 1.2 per cent, as well as of the basicity of the slag, and is nearly always within the limits 0.015 to 0.025 per cent when the bath is boiling normally and is in what we have termed a steady state. Apparently it must be at least about 0.014 per cent before boiling occurs; but this threshold value seems to depend upon the ease of bubble formation at the metal-hearth interface, hence upon the condition of the surface of the hearth. In any case, 0[O], on the average, changes considerably following any disturbance of the bath, as by addition of ore. The present paper deals with the average changes in ?[O] level following addition of Spiegel or crop ends, or after procedures to promote stirring, or by tapping of the steel from the furnace. The observations were made on a large number of commercial heats, and consequently are subject to the influence of various disturbing factors; the results have the compensating merit of showing the consistency obtainable under the limitations imposed by practical operation. VARIABILITY OF EXCESS OXYGEN IN NORMAL OPEN-HEARTH OPERATION The preceding general statements refer to the average value of ?[O] particularly in heats that are boiling actively; on individual heats, which are less active, there may be a variable time lag between the disturbance and its effect, which complicates the interpretation of what is going on. For instance, if in the normal refining process boiling is sluggish, the slag usually is gaining oxygen from the gas phase above it, or from added ore, faster than it is losing oxygen to the metal; yet when the bath starts to boil vigorously, the opposite condition may prevail for some time. The consequence of this lag is a variation of ?[O], the interpretation of which in a single heat may not be immediately obvious, This condition is illustrated in Figs. I and 2. In Fig, I, ?[O] at the beginning of the test period was near the lower limit of its usual range (dashed lines) in the steady state as a consequence of the lime boil, which had ended about as indicated. The bath is now cold, carbon drop is slow, and the first small ore feed causes only a small rise in 0[O]; as the temperature rises and as lime dissolves in the slag, and the bath becomes more active, the

Jan 1, 1946

By H. M. Hobart

This paper deals principally with investigations undertaken by the Welding Research Sub-committee of the Welding Committee of the Emergency Fleet Corporation. The general object of the investigations has been to extend the use of welding in the construction of merchant ships and, specifically, to provide a definite basis for obtaining the greatest economy and efficiency in employing welding in place of riveting in the construction of the hulls of such ships. Composition of_ Ship-plate Steel The chemical composition of the steel employed in such hull construction varies with the thickness of the plates. Through the courtesy of Mr. H. Jasper Cox, of Lloyd's Register of Shipping, the following information may be given concerning the kind of steel plate employed in American shipyards in 1918 for the hull construction of merchant ships. Lloyd's requirements do not relate to the chemical composition. They require a tensile strength of 58,000 lb. per sq. in. (40.75 kg. per sq. mm.) for their lower limit and 72,000 lb. per sq. in. (50.59 kg. per sq. mm.) for their upper limit. For the information of the Committee, Lloyd's obtained from their surveyors at various works data of the carbon content, which is as follows: Works Carbon Content for Plates 1/4 In. Thick 1 In. Thick A..................... 0.14 0.23 B..................... 0.14 0.25 C2.................. 0.19 0.25 D................. 0.20 0.30 E Upper limit..... 0.35 Lower limit..... 0 24 0.29 Upper limit,.... 0.25 0.30 Lower limit..... 0.21 0.27 Upper limit..... 0.25 0.35 Lower limit..... 0.22 0.28

Jan 1, 1920

By P. D. Merica, J. R. Freeman, R. G. Waltenberg

Contents Page Constitution of Commercial Aluminum.................. 4 Solubility of CuAl2 in Aluminum at Different Temperatures........ 9 Effect of Magnesium on Solubility of CuA12 in Aluminum ......... 15 Solubility of Mg4Al8 in Aluminum at Different Temperatures........ 15 Solubility of Metals and Metal Compounds in Aluminum.......... 20 Summary and Conclusions......................20 Aluminum and its alloys have been the subject of much investigation1 during recent years, in the course of which the principal features of the constitution of most of the binary alloy systems with aluminum have been determined. Except in the case of a few metals—silicon, bismuth, cadmium, lead, zinc, and tin—an aluminum-rich compound is formed in each binary system, which forms a eutectic with the aluminum or its solid solution with this compound: Thus such compounds as FeAla, CuA12, Mg4Al3, and NiAls are formed, which are found in aluminum-rich alloys of their respective series as eutectics with the aluminum solid solution. These compounds are, in all cases, hard and brittle and their presence affects profoundly the physical properties of the alloys in which they occur. Within the zinc-aluminum system a compound, Al2Zn,, is formed that decomposes at lower temperatures. Silicon and tin each form a simple eutectiferous series with aluminum; bismuth, lead, and cadmium are only partly miscible in the liquid state with it. The extent of the solubility in aluminum, in solid solution, of these compounds or of the elements themselves, in the case of those series in which compounds are not formed, is of the greatest importance in

Jan 1, 1921

By E. Hein, R. A. Dodd

The fatigue softening of prior strain-hardened poly crystalline copper has been determined by measuring changes inflow stress resulting from fatigue treatments. Tensile fatigue does not soften the metal, while the softening due to reversed stress fatigue depends on the extent to which fully reversed stressing is approached. True tensile fatigue is shown to be possible only in the case of long wire specimens. Annealing following fatiguing of strain-hardened metal shows that tensile fatigue is very effective in modifying normal recovery and recrys-tallization. OBSERVATIONS by Ludwik and Scheu,' Kenyon,' Polakowski and Palchoudhuri, Kemsley, and Broom and Ham,596 have shown beyond doubt that strain-hardened metals are softened by reversed-stress fatigue. To some extent the softening might be associated with a rearrangement of dislocations, but the results of Broom and Ham5 on the temperature dependency of the fatigue hardening of annealed copper, and those of McCammon and Rosenberg7 on the partial recovery at 100'C of fatigue-hardened copper suggest that point defects may be involved. Since lattice vacancies are the only species of point defect present in appreciable quantities in thermody-namic equilibrium, most attention has been accorded them in the various theories advanced to explain hardening and softening effects resulting from fatigue. Precise mechanisms remain uncertain, and while some effects may be due to single vacancies, defects arising from vacancy clusters may also contribute to the changes in properties. All types of plastic deformation result in point-defect formation, one frequently invoked formation mechanism involving the nonconservative motion of jogs formed by the intersection of, for example, mixed dislocations. But since fatigue deformation is thought to be a particularly effective way of forming point defects, additional mechanisms peculiar to fatigue must be sought. One possibility is that jogged loops contract during the unloading cycle to give rows of vacancies. A local high-vacancy concentration could conceivably promote polygonization and recovery by climb, and, therefore, could explain the fatigue softening of strain-hardened metals under appropriate conditions of temperature. Conversely, the experiments by Broom and Ham6 on the fatigue hardening of copper single crystals involving subsequent tensile testing of previously fatigued specimens, resulted in the observation of distinctly lowered yield points. This could be due to vacancy atmospheres associated with dislocations, possibly augmented by jogs on dislocations. In addition to the yield-point phenomenon, a post-yield hardening was observed, with a temperature-dependence resembling the friction-hardening of irradiated metals,9 this again suggesting a point-defect mechanism. An important development in this field has been the observation,10 by transmission electron microscopy, of high concentrations of prismatic loops in fatigued aluminum. By analogy with quenched aluminum filmso11 it seems certain that these loops originate in the collapse of vacancy clusters formed during deformation. Metals, such as copper, having a relatively low-stacking fault energy would tend to produce Frank sessile loops (in practice tetrahedral defects with stacking faults on all (111) planes) rather than the glissile prismatic loops observed in aluminum. The manner in which these various defects affect the different aspects of fatigue behavior has not yet been fully investigated. The present work was designed principally to indicate whether tensile fatigue gives rise to hardening and softening effects similar to those associated with reversed stress fatigue, and with the hope of providing additional information on the contribution of point defects to fatigue deformation. Despite the uncertain ty often associated with the interpretation of resistivity data, i.e., the relative contribution of stacking faults and other defects, such measurements are conveniently employed to study point defect pheno-

Jan 1, 1962

By Nathaniel Arbiter

THE separation of minerals by flotation can be regarded as a rate process, with the extraction of any one mineral determined by its flotation rate, and the grade of concentrate by the relative rates for all the minerals. So regarded, the significant variables for the process are those that control the rates. These variables are of two types, the first describing the ore and its physical and chemical treatment prior to flotation and the second characterizing the separation process in the cells. This paper will examine the variation in rates for a group of separations, will show that a simple rate law appears to govern, and will consider the relation of the control variables to the rates. The use of rate constants for evaluation of performance and efficiency will be discussed. Flotation involves the selective levitation of mineral and its transfer from cell to launder. The flotation rate is the rate of this transfer. It may be defined by the slope of a recovery-time curve for any cell in a bank, or at any time in batch operation. The objective in flotation rate study is an equation expressing the rate in terms of some measurable property of the pulp. This can be either the concentration of floatable mineral in weight per unit volume1,2 or a relative concentration, which will be a function of the recovery." A rate equation for an actual flotation pulp will contain at least two constants, both to be determined from the data. One of these, the initial concentration or proportion of floatable mineral, is not necessarily equal to the feed assay because of nonfloatable oversize or locked particles." The other, a rate constant, is a measure of proportionality between the rate and the pulp property on which the rate depends. The value of the rate constant will be determined by the values of all variables which control the process and will be changed by significant changes in any of them. It is, therefore, a direct measure of performance. Where recovery or grade change continuously with flotation time, the rate constant will be independent of time and will characterize the entire course of the separation. Development of Rate Equations Rate equations can be developed either by analysis of the mechanism of the process or by direct fitting of equations to recovery-time data. Sutherland's attempt by the first method' suggests that the effect of particle size variation on the rate complicates the derivation of a simple equation applicable to an ore pulp. A further problem with an ore is the concentrate grade requirement, which usually involves a variable rate of froth removal. Thus the final rate for any cell may depend on the froth character and froth height, as well as on the pulp composition. This does not imply that each cell cannot reach a steady state2 in which the rate will depend ultimately on pulp composition. The second method is the fitting of rate equations consistent with the necessary boundary conditions* to experimental recovery-time curves. On the assumption that under constant operating conditions the flotation rate is proportional to the actual or relative concentration of floatable mineral in the pulp, a generalized rate equation may be expressed as follows: Rate = Kcn [I] where K is the rate constant, c is some measure of the quantity of floatable mineral in the pulp at time t, and n is a positive number. In previous rate studies, the value of n has been taken as 1, either by direct assumption," or as a result of the hypothesis that bubble-particle collision is rate determining.' A first order equation results, which after integration in terms of cumulative recovery R, leads to Loge A/A-R = Kt [2] The quantity A is the maximum possible recovery with prolonged time under the conditions used. No conclusive proof for the validity of this equation in flotation has been advanced. The evidence cited in its support consists entirely in the demonstration that it appears to apply to a limited number of recovery-time curves."' It will be shown subsequently that this procedure is not sufficient to establish the order of a flotation rate equation. The possibility that the equation may be of higher order therefore requires examination. If, in particular, the exponent in eq 1 is assumed to be 2, then after integration there results R = A2Kt/1 + AKt [3] with K again a rate constant and A the maximum proportion of recoverable mineral. Eq 3 may be

Jan 1, 1952

By C. L. Dake

Chemistry of Iron Solution IRON is much more soluble in the ferrous than in the ferric form. Where, as in the case of the ferrous silicates and the sulphides, the iron is already in the ferrous form, it may go at once into solution and be removed, upon the breaking down of the parent rock. If in the ferric form, it must first be reduced; usually by the decay of organic matter, the demand of the decaying carbonaceous matter for oxygen being so great that the latter is abstracted from the ferric compounds and the iron is thereby reduced and rendered' soluble. The iron may go into solution as the sulphate, or in the presence of excess CO2 as ferrous carbonate. It is probably soluble as salts of the organic acids.1 Recent work indicates that these are important in the formation of bog ores.2 There is considerable variety of opinion concerning the behavior of these organic compounds.3 The secretions about the roots of plants and trees also cause the solution and removal of iron and a consequent bleaching of the soil.4 While the matter is not yet well understood, we can probably say definitely that the so-called organic acids are a group of colloids which possess slightly acid properties, and the salts of which are partly soluble

Jan 7, 1915

By Hertha Freche

THE diffusion of magnesium and silicon from the core into the high-purity coating of Alclad sheet is important commercially, and led to the use of a duplex product for the study of diffusion by means of spectro-graphic analysis of successive layers. It has been found that in the duplex materials the diffusion of magne-sium from an undersaturated aluminum-magnesium alloy into its high-purity aluminum coating is approximately of the same order of magnitude as the diffusion of silicon from a saturated aluminum-silicon alloy into its high-purity aluminum coating. However, if magnesium and silicon are both present in the alloy in the ratio of Mg2Si they appear to diffuse in the approximate ratio of this compound. Finally, if the alloy contains silicon in excess of the amount required by magnesium silicide, the amount of diffused silicon in the high-purity aluminum coating will also be in excess. The interdiffusion of metals in the solid state is of both scientific and technical interest, because it is helpful in the study of the alloy structure and in the solution of problems pertaining to the strength and surface condition of the fabricated product. W. C. Roberts-Austen1 carried out the first quantitative determination of the coefficient of diffusion of gold into lead. This classical experiment was followed by a series of investigations on the diffusion of metals and nonmetals in iron and steel and in nonferrous metals and alloys. Recently the diffusion of copper in coated strong aluminum alloys was investigated by A. Burkhardt2. This appeared to be the first published investigation on the diffusion of metals into aluminum.

Jan 1, 1936

By Wm. Reuben Webster

BRASS is an alloy of copper and zinc. The brasses (using this term to denote all useful proportions of the two constituents) are the most valuable and widely employed of all [ ] nonferrous alloys, because of their high resistance to ordinary corrosive agencies and the very wide range of properties that may be imparted to them by variations in the proportions of the constituents and by variations in mechanical treatment and heat-treatment. Fig. I shows the normal physical properties, as determined by standard tensile tests, of the series when in the annealed condition. Fig. 2 shows the effect of varying amounts of cold-working on an almost pure brass containing 70 per cent copper and 30 per cent zinc. Fig. 3 shows the effect of annealing at various temperatures on the same alloy. This effect is somewhat modi- [ ] fied by the degree of cold-working to which a brass has been subjected, as shown by Fig. 4. A fourth test, which is empirical, has been found useful because of its simplicity the hot hammer test. Samples 1/2 in. in diameter and 3/4 in. long are placed in a suitable furnace. These are withdrawn one at a time at successively higher temperatures and are subjected to the blow of a drop hammer weighing 50 lb. with a drop of 4 ft. The percentages of reduction in length of the cylinders are plotted against temperatures and give a comparative measure of plasticity at different temperatures. The results of this test on several

Jan 1, 1942

By I. M. Bernstein

The steady-state creep behaviov of zirconium and zivcaloy-2 was examined in the temperature vatlge 520° to 620°C A1 low stresses the creep rates were cimracterized by a linear stress dependence; at highev stresses the stress dependence was much more pronounced. Temnperature-cycling tests yielded values for the aclivation enevgy for creep. Various tlzeories were examined in the ligltt of- the experimental re-sults and it mas concluded that the low-stress creep behavior is the result of the stress-direcled diffusion of vacancies along gain boundaries. It has been observed,"&apos; usually under conditions of high temperature and low stress, that creep deformation can occur for which the steady-state creep rate is linearly dependent on the applied stress. For magnesium and certain magnesium alloys, Harris and ones&apos; and ones&apos; have argued that this type of creep occurs by mass transfer as a result of the stress-induced generation and migration of vacancies, along a gradient defined by the stress direction. Jones&apos; demonstrated that the rate-controlling diffusion path is sensitive to grain size and temperature, and that by suitable control of these variables creep could occur by vacancy diffusion either predominately along grain boundaries or through the lattice. Recently, Jones3 suggested from an examination of limited high-stress data for zircaloy-2, composition in Table I, that significant diffusion creep could occur at low stresses, at least between 375" and 500°C, controlled by grain boundary vacancy diffusion. This process could have an important implication in assessing the role of zirconium alloys as a structural or cladding material in certain classes of nuclear reactors, since it predicts creep deformation far in excess of any estimates based on extrapolating slip creep data from higher stress levels. If the diffusion creep process occurs it should be possible to describe the total steady-state creep rate of zirconium and its alloys as the sum of two terms, Eq. [I]; the first term relates to a slip creep process important at high stresses and which is manifested by a much more pronounced dependence of creep rate on stress4 than diffusion creep and the second to a process controlled by mass transfer,5&apos;6 dominant at low stresses: where A and BI are parameters which can depend on structure, Ql and Q2 are the activation energies for the particular creep process occurring, and n describes the sensitivity of the creep rate on stress. It is the purpose of this paper to present some direct experimental evidence in support of this view. It is recognized that other analytical approaches have been proposed to explain data of this kind and these will also be discussed. 1) EXPERIMENTAL PROCEDURE Flat creep specimens (gage length 1 by 0.25 by 0.02 in. approx) were prepared from cold-rolled, argon-remelted, crystal bar zirconium and cold-rolled commercial-grade zircaloy-2, the analyses of which are given in Table I. The specimens were annealed at a pressure of < 10-5 Torr at temperatures from 625" to 675°C for 2 hr and slow-cooled. This treatment produced stable grains of average size (defined here by the average linear intercept) of for zirconium and -4xin. (-10 p) for zircaloy-2. The specimens were tested in a dead load tensile creep rig. The stress was maintained constant by adjusting the applied load after approximately each 1 pct of strain. The specimen temperature was controlled to better than +1°C. This system had a small thermal lag, so that rapid temperature changes were possible. To minimize corrosion, the specimens were tested in high-purity (99.95 pct) argon, further dried,

Jan 1, 1968

By John Fulton

The Menominee range is one of the four great mining belts that flank the western prongs of Lake Superior. It has received its name from its location along the north side of the Menominee river, which at this place flows between the States of Michigan and Wisconsin. The term "range" is derived from the elevated ridge, extending in a westward direction, and along the southern flank of which the iron-ore mines are located. This range is some 200 to 300 feet high above the general level of the adjacent country, and is made prominent by its surroundings of low, swampy lands. Its whole length is about 27 miles, and it is intersected, at intervals along its course, by gaps which are threaded by streams. The geology of the Menominee range is peculiarly interesting. It is composed of three distinct groups of Hurouian rocks. The supporting group consists of light-colored limestone beds of a crystalline, siliceous character, called the "Norway limestone belt." The map, Fig. 1, and the section, Fig. 2, will give a general notion of the position and structure of the range. The properties shaded in the map are those of the Penn Iron Mining Company, which is the Michigan representative of the Cambria Iron Company of Johnstown, Pennsylvania. This belt is at least 1200 feet thick. It outcrops boldly at many localities along the range, especially north of the Norway, Quinnesec and Chapin mines. At Quinnesec it can be studied readily. The next, or Banking group, which is estimated at a thickness of 1000 feet, is called the Quinnesec ore-formation. It consists, in the portion next to the limestone, of siliceons or jasper slates, largely impregnated with iron oxide. These are succeeded by argillaceous hydro-mica black and flesh-colored slates. This formation embraces the deposits of the iron-ores. The third group consists of a series of dark gray, slaty or schistose beds, with occasional quartzose bands, having a thickness of 2000 feet. It is called the Lake Hanbury slate group.

Jan 1, 1888

By E. P. Pfleide, L. W. Gibbs. J. R. Gross

A method using computer techniques is described for the comparative evaluation of truck performance over any given haul road using readily obtainable manufacturers&apos; data. An additional computer program is utilized to calculate individual cycle times for each truck and shovel combination, fleet requirements for any desired production rate, and to estimate comparative costs. The introduction of a large number of variables into the program permits management to determine the critical system factors having the greatest bearing on costs. Thus, the method described can be used not only for analysis of needs for a new surface mine but for cost improvement in existing mines where changes in truck and shovel operations are contemplated. The systems analysis approach to the solution of problems in the mining industry is gaining in industry acceptance. This is a logical development in view of the fact that a mine constitutes one of the most dynamic systems of production. In contrast with a manufacturing plant, situated in a location selected through choice and utilizing a regulated source of quality controlled raw materials, the miner must go where the ore is and he is faced with ever changing physical conditions. He is subjected to the vagaries of nature, and he can never mine the same ore twice. What is systems engineering? There seems to be no concise and universally accepted definition of the term and its meaning is still fairly local. It deals largely with trade-offs of subsystem characteristics to achieve some desired result in an overall system. This concept of suboptimization can be explained by an example. If the objective of a mining company is to produce a certain quality ore at minimum cost, the optimum operation is not achieved by minimizing all costs, since all phases of mining are interrelated. Reduction of blasting costs might well increase loading, hauling, and crushing costs out of proportion to the resulting saving in explosives. Hence tradeoffs are necessary. It is evident then that an optimum system is achieved through a blending of suboptimal components which taken together yield the desired result. OBJECTIVE For our mathematical model we will assume the existence of a hypothetical new organization called Taconite Mining Co. (TMC). TMC has made an analysis of their orebody, their proposed operation, and

Jan 1, 1968

By John Chipman, Raymond L. Orr

Recently reported high -temperatlnre thermal data have been incorporated in a reuieu&apos; of the therinody-r~ar,zic propesties of iron. The recent data permit mot corlsisterlt and reliuble choices to be made for many of the pvoperties, resnlling in bettev eslablished tabrtlations of the thermodynamic functions. Values of Cp, h°t- - H°298. s°t - S2sa, and (G°T -H298/T are tabulated for -the solid and liquid phases of iron in both stable and melastable regions. Consistency of the tabulations has been maintained to the precision necessr~vg to yield the Gibbs energy change belween the bcc (a, 8) and fcc (y) phases of iron at temperatures pertinenl to alloy studies. THE importance of the metal iron has stimulated many investigations of its thermodynamic properties at elevated temperatures. Reviews and summaries of the data have appeared from time to time. Among these the 1951 paper of Darken and smith&apos; deserves highest recognition for the quality of its criticism and for the precision and thermodynamic consistency of its tabulations. These and the more recent table of Kaufman, Clougherty, and weiss2 reproduce the Gibbs energy of the (a, 6)--Y transformation with sufficient sensitivity for alloy studies. Other recent compilations of equal validity3-&apos; make no attempt to do this. Since this Gibbs energy change is not greater than 22 cal per g-atom over the temperature range 1100° to 1800°K, it is obviously desirable to tabulate values of (G°t - H298)/T to four places of decimals even though the absolute accuracy would not warrant such precision. The necessity for reconsideration of the problem is emphasized by the recent publication of several important researches on the enthalpy and heat capacity of iron. The older work is well-covered in the reviews cited and will be mentioned here only when actually employed in the tabulations. GAMMA IRON Transition temperatures are taken from the selec -tions of Elliott and Gleiser,5 based on the work of Boulanger7 and earlier workers. For the a-y (A3) transition at 1184°K we retain the value 215 cal per g-atom adopted by Darken and smith.&apos; It has received confirmation in the recent work of Dench and Kubaschewski,&apos; and of Braun8 using adiabatic calori-metry, and of Wallace, Sidles, and Danielson10 using a pulse heating technique. The enthalpy data of Olette and ferrier" and of Anderson and Hultgren12 at higher and lower temperatures may be extended to 1184°K to give the following values which are adjusted to the required value of ? 1184 Ha,1184 Ha 298 = 8030 cal per g-atom [11 hr,1184-ha298 = 8245 cal per g-atom [2]

Jan 1, 1968

By H. B. Pulsifer

.ABOut 1.5 varieties, or tnodifications, of the best rnagnesiurn available were prepared and subjected to etching tests, then examined for micro-structure. Of the 30-udd etching reagents that were tried, nearly half, mostly ammonium salts, etched the metal satisfactorily. The surfacing and etching of magnesium is shown to be a very simple and quick operation. The density and hardness of magnesium were determined. The most interesting new observations relate to the finding of the hexagonal etch figures, the crystal laminations, and the fact that the metal is plastic, cold, when restrained or quickly deformed. Under slowly applied pressule cold metal deforms slightly, then shears to fracture without plastic flow. The chief structural features of magnesium arc presented in two reduced photographs and 30 photomicrographs. Materials Tested There are only two sources in the United States from which new metal can be procured: the American Magnesium Corpn. and the Dow Chemical Co. No pronounced structural or property differences in the metals from these two companies were disclosed by the work of this investigation. The following materials were obtained from the manufacturers: 1. Massive crystals of distilled metal (American Magnesium Corpn.). 2. Rods of hot-extruded metal, ½-in. squares and 5/8-in. rounds (American Magnesium Corpn.). 3. Sheet magnesium, 0.005-in. thick (American Magnesium Corpn.). 4. Cast stick metal, 13/8-in. dia. (Dow Chemical Co.). 5. Magnesium-aluminum alloy, hot-rolled plate, ½-in. thick (American Magnesium Corpn.). From these materials, were prepared: 6. Sections from a furnace-cooled ingot made from clistilled crystal. 7. Cold-strained pieces from (6), (4) and (2). 8. Pieces cold-squeezed to fracture from (6), (4) and (2). 9. Hammer-struck pieces from (6), (4) and (2). 10. Steam-hammer struck pieces from (6), (4) and (2). 11. Sections from furnace-cooled ingot of the magnesium-aluminum alloy.

By C. D. Allman

Specifications for coal at the Grand Lake thermal electric station read in part: "Coal will be Rom Minto Bituminous (strip operation). Maximum lump 3x3x4 ft. Very corrosive, abrasive and when damp, sticky. Coal may consist of frozen lumps of coal, snow and ice." To maintain quality control it was necessary to develop an automatic sampling system capable of: 1) sampling from one 10-ton truckload every 1½ min; 2) permitting an operator to automatically take a sample from each truckload; 3) depositing the sample in a pre-selected container, one of a possible 10; and 4) performing the sampling operations in accordance with latest ASTM specifications for sampling coal with an ash content of 35%. This paper tells how these and other problems were resolved and describes the equipment used. The New Brunswick Electric Power Commission issued detailed specification No. 5351-5009 outlining the scope of work and general requirements for a mechanical coal handling system to be installed at the Commissions Grand Lake Generating Station. The thermal station is located at Newcastle Creek, some 40 miles east of Fredericton, N.B. Canada, on the shore of Grand Lake. This particular location is immediately adjacent to the Minto strip mining coal area of New Brunswick. Contained in the specifications, but not detailed specifically was an automatic coal sampling system. The system outlined, was to be designed and specified by the individual equipment tenderers. In conjunction with the Hardinge Co., the Barber-Greene Co. designed a sampling system which was contained in the general contract proposal. The system as designed originally, however, presented certain limitations to a continuous coal handling system and was ultimately changed. However, it was only through preliminary study and design that problems created by the specifications were determined, and these problems discussed and finally negotiated with the NBEPC engineering staff created the subsequent sampling system now being installed by Barber-Greene. It must be considered that where the original specifications did not detail the mechanical equipment, it was necessary to present a system which would correspond to the intent of specification and for which Barber-Greene would be responsible as to function, but remain in a competitive position with regard to the tender considered primarily on a price basis. The system now being installed, contains basically all the components which were detailed originally, with the exception of the holding bin arrangement, which was changed to allow a continuous operation of the entire coal handling system. SPECIFICATIONS The specifications covering the sampling system follow. 4.5 Sampler: An automatic sampling system shall be installed capable of sampling one-truck load of coal every 1½ min. When the coal is dumped into the receiving hopper, the operator shall push a button and the sampler shall automatically take a sample of that particular coal when it reaches the sampler. Then the sample taken shall be crushed and reduced in quantity to a workable sample and deposited in a pre-selected container, one of a possible ten. All samples and sampling operations shall be in accordance with the latest edition of ASTM designation 492 for sampling coal with an ash content of 35%. The coal for the initial sample shall have maximum sized lumps of about 3/4 in. and the final sample shall be adjustable from 2 to 5 lb per sample and capable of passing through a sieve with 1/8-in. diam openings. It should be noted that, because of the time delay between the time the sample is requested and when it is actually taken, the operator may call for one or two additional samples from different coal before the first sample is completely refined and in the final sample can. Coal is received from a number of different suppliers on the same day, therefore, the system shall be designed so that there is no possibility of mixing or contaminating the coal from the different suppliers. All coal rejected from the sample shall be returned to the main conveyor. All chutes, hoppers, etc. shall be designed in accordance with Section 4.6 of these specifications. 4.6 Chutes, Hoppers, etc. All chutes and hoppers

Jan 1, 1963

By Frank Firmstone

The material described below was made at Furnace No. 2, Longdale, Va., Oct. 28, 1907, during a sudden derangement of working, in the course of which the furnace became entirely bridged over and for some time no solid material whatever descended into the hearth. This caused the hearth to become so completely emptied that, at the tuyere-level, a pricker put in at one tuyere could be seen by looking in at the opposite one. The tap-hole was opened and the iron got out with some difficulty. It ran sluggishly, throwing many sparks, but was not too thick to run into the chill-molds. Naturally, the product was assumed to be white iron, which is almost always produced under similar circumstances; but on removal front the molds it proved to be very strong and tough, although full of blow-holes. Most of these blow-holes bad bright, unoxidized walls. The iron could be drilled by using a "special steel" drill, the drillings curling up similarly to those of steel. An analysis by P. W. Shimer of this unusual product gave: Si, 0.019; P, 0.228; S, 0,39; Mn, 0.042; C, 2.366; and graphite, 0:000 per cent. A cast of iron made just before the disturbance contained P, 0.98, and Mn, 1 per cent. The peculiar product seems to have been decarburized in the hearth and, at the same time, to have lost much phosphorus and manganese, either by the action of the blast in the empty hearth, or, more probably, by. contact with the cinder rich in iron which was formed at the time. Unfortunately, no specimen of the cinder was preserved, so its composition cannot be given. It seems very remarkable that, with the furnace in bad condition, the temperature should be high enough to keep such

Sep 1, 1908

By M. G. Benz, J. F. Elliott

The austenite solidus of the iron-carbon system has been determined using a series of diffusion couples, each of which consisted of a specimen of austenite held in contact with a melt saturated with austenite. After the equilibrium distribution of carbon had been established by diffusion at a specified temperature, i.e. the austenite specimen had become austenite of the solidus conzposition, the diffusion couple was cooled, sectioned and anazlyzed for carbon. The solidus was found to be a straight line: A revised iron-carbon temperature-composition diagram is presented, COMPOSITION has a marked effect on the temperature at which austenite begins to melt and the austenite solidus of the iron-carbon system describing this effect has been the subject of many investigations.1-10 The significant results of these investigations are presented in Fig. 1. The experimental methods and purity of the materials used in them are summarized in Table I. In plotting the data in Fig. 1 no attempt has been made to convert these results to the International Temperature Scale of 1948," except for the data of Adcock,5 as this conversion would do little to reduce the uncertainty that exists as to the position and shape of the solidus. A point of major concern in evaluating these data is that the alloys studied, except those used by Adcock, were not binary alloys of iron and carbon, Table I. Also, it would appear that several of the methods did not permit equilibrium to be established through the system being studied. All that can be said for the results of these investigations is that they indicate only approximately the location of the solidus with the uncertainty as to its location at 1 pct C being approximately 100°C. The current investigation was undertaken to provide reliable data by which the austenite solidus could be established. It was hoped that information on the liquidus also could be developed at the same time, but experimental limitations prevented this as austenite segregated from the liquid on cooling. After a careful study of possible experimental methods and extensive laboratory tests, it was decided that the use of a series of austenite-liquid diffusion couples would provide the most reliable results. This paper describes the method and its results and also includes a complete iron-carbon temperature-composition diagram based on what are considered to be the best available data. EXPERTMENTAL METHOD The diffusion couple used for this investigation consisted of a small cylindrical pellet of austenite held in contact, at a specified temperature, with a melt saturated with austenite. The composition of the cylindrical austenite pellet was chosen to be approximately 0.1 wt pct C less than the estimated

Jan 1, 1962

By Jed H. Mosgrove

Ventilation is the method of producing, conducting, and distributing a constant current of fresh air through mine workings and returning the impure air to the outside atmosphere. Without ventilation no operations are possible in an underground mine. Therefore it is the most important single phase of mining, one on which everything else depends. A good ventilation system, therefore, must be correctly designed, properly conducted as the workings advance, and continually checked to make sure it is functioning correctly. Good air is essential for men to comfortably and safely perform their work. It is also essential to dilute, render harmless, and sweep the mine of any explosive fumes and the gases that are released in varying degrees by all coal seams and the rock strata in which they are contained. GENERAL The body of air that is being moved through the mine, known as the ventilating current, must have a definite way to enter and leave the mine. In other words, there must be a definite intake and return. The main consideration is to get the proper amount of good quality air to the working faces where it is needed. Inasmuch as the mine is divided into sections with interconnecting corridors, known as entries, it is necessary that there be a proper means of conducting the air to the proper points. As a simple explanation of a mine, consider a long tube and think of it in terms of a mine entry ill which the air must pass. The tube must have at least two openings before air can travel through it and this is the same for coal mine entries. The problem in ventilation is to find some means that will cause the air in the tube to flow from one end to the other. The only possible way to do this is to cause greater pressure at one end of the tube than at the other. Air at the end with the greatest pressure would then, of course, flow to the en which has the least pressure. Mine

Jan 1, 1973

By O. M. Schaus

GRATIFYING progress continues towards the elimination of the hazards confronting health and safety in and about mines. Employers and employees are diligently co-operating. One of the outstanding movements towards this end is the National Safety Competition conducted by the U. S. Bureau of Mines. William W. Adams, of the Bureau, has stated that "Through 1936 there has passed by a dozen years of this National Safety Competition, as it started in 1925 with an enrollment of 210 mines and quarries in 28 states and 68 million man-hours of employment. For 1936 it covered 328 mines and quar-

Jan 1, 1938

By R. Rocca, M. B. Bever

THE adiabatic elastic deformation of a body is accompanied by a change in temperature. This phenomenon is known as the thermoelastic effect. Under adiabatic conditions the temperature of a metal bar is decreased by an elastic elongation and is increased by an elastic compression. All materials which elongate on heating behave in this manner. The sign of the thermoelastic temperature change is reversed for the few materials which have a negative coefficient of thermal expansion. The following equation for the thermoelastic effect can be derived from fundamental thermody-namic theorems, as shown in the Appendix: dT8 =-a1/cs T dss [1] Cs In this equation, T is the absolute temperature, S is the entropy, a, is the coefficient of linear thermal expansion, cs&apos; is the heat capacity per unit volume at constant stress and s is the stress (positive in tension). Eq 1 can be applied to small, but finite changes in stress in the following form: ?Ts =- a1/cs T?ss [2] The sign of the temperature change AT is opposite to that of the change in stress s for materials which have a positive coefficient of thermal expansion. Eq 2 has been verified for many different materials and stresses at room temperature. No previous publication appears to have been devoted to an in- vestigation of the thermoelastic effect over a range of temperatures. Review of Literature Lord Kelvin (W. Thomson) presented a general theory of the thermoelastic effect in 1851&apos; and later applied it to a solid, subject to an arbitrary system of stresses&apos;. His analysis was based on a cycle of isothermal and constant-strain transformations and led to Eq 2 above. Even today, one of the clearest expositions of the thermoelastic effect is found in Lord Kelvin&apos;s article on elasticity in the Ninth Edition of the Encyclopedia Britannica (1878). R. ROCCA, Junior Member, and M. B. BEVER, Member AIME, are Research Assistant in Metallurgy and Associate Professor of Metallurgy, respectiuely, Massachusetts Institute of Technology, Cambridge, Mass. AIME New York Meeting, Feb. 1950. TP 2760 E. Discussion (2 copies) may be sent to Transactions AIME before APT. 1, 1950, and is scheduled for publication Nov. 1950. Manuscript received Oct. 15, 1949.

Jan 1, 1951