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By T. W. Turk, S. A. Sass

The engineering design features of the Mercur Gold Project crushing, grinding, carbon-in-leach, bullion, reagent, and tailings disposal areas will be discussed in this paper. It presents a project overview and flowsheet along with selected design alternatives. During the engineering phase, major equipment and other features were selected to optimize design within site location and environmental constraints. The project team organization and procedures were adopted to accommodate multiple optimization studies while maintaining a tight engineering schedule.

Jan 1, 1985

By Charles Fettke

IN 1914, the officials of the Brundred Oil Corpn., faced with the problem of introducing new methods to increase production in the old and nearly depleted pools of Venango County, became interested in the Smith-Dunn (Marietta) process which was at that time being tried out in southeastern Ohio and which was already yielding very encouraging results. A license to use the process in Pennsylvania was secured from the owners of the patents. These patents were later declared invalid. The method was first used in Pennsylvania on a property consisting of about 434 acres, of which 300 are productive, at Hamilton Corners, 15 miles northeast of Oil City, in Cherry Tree and Oakland Townships, Venango County. The producing horizon is the First Sand of the Venango Group. A small oil pool was opened up in this vicinity in 1904. By July, 1916, when the compressed air was first introduced to restore pressure, the production had dropped to a point where it was no longer possible to continue profitable operation. From that time until March, 1927, over 100,000 bbl. of oil have been recovered from the tract. The property is being operated at present by the Brundred Oil Corpn. and Lux. The 1926 production, amounting to 10,650 bbl., was only 400 bbl. short of the maximum reached during any year of the 10-year period that the process has been in operation. Inasmuch as the Hamilton Corners pool is the first one in Pennsylvania in which the Marietta process was tried out, and the one in which it has been longest in continuous operation, considerable interest attaches to the results obtained. Through the courtesy of H. D. Brown and W. J: Brundred, officials of the Brundred Oil Corpn., all their data on this operation were made available to the writer in connection with an investigation of rejuvenation methods in the State for the Pennsylvania Geological Survey.

Jan 1, 1928

By B. H. Caudle, A. B. Dyes

In a recent publication' it was shown that wells with a free surface in a homogeneous gravity-drainage reservoir have a hyperbolic decline with index n '. This paper reports efforts to extend this theory to practical field cases. As a first step in making the extension, a large number of lease production curves from gravity-drainage fields in the stripper stage were fitted with the general hyperbolic decline equation, q/q, = 1/(1 + y) y and n in each case being determined by statistical methods. It was found that this equation is reliable for decline curve extrapolation for periods up to at least 25 years. The resrilts obtained were disturbing in the sense that values for the index, n, were often smaller than one, which fact leads to the prediction that a well would produce all infinite amount of oil in infinite time. A theoretical investigation based on the results of the previous paper provides a suitable explanation for these low values of n. It suggests that these are obtained if production occurs from two or more layers of diflerent permeabilitv and thicktress or two lnyers having different skin effects. It is predicted that as the more permeable layers are exhausted, the index of decline, n, will rise from a value smaller than 2, to n = 2. A practical method is given for fitting the general hyperbolic decline Eq. 6 to production decline data. When this method is used, the index of decline observed in gravity-drainage reservoirs in the stripper stage when wing only data over early years 01 decline usually agrees quite closely with that determined using data over 25 years or more. This indicates that the hyperbolic decline equation is reliable for predicting behavior of such reservoirs. A method is also suggested for taking into account any changes in the value of the index INTRODUCTION As a result of both experimental work with models and theoretical deductions, it was recently concluded' that wells having a free surface in a homogeneous reservoir producing by pure gravity drainage should have a hyperbolic decline with n = 2. The present report details efforts to extend this work on ideal homogeneous reservoirs to actual field cases. It should be remembered that both the previous work and the present extension are based on the assumption that the reservoir is at very low pressure, and hence, nearly all the potential available for driving fluid to the well is the gravity head. Attempts to apply conclusions of this study to reservoirs which have considerable pressures supplementing the gravity drive may lead to difficulty. WELLS WITH NO FREE SURFACE In a dipping gravity-drainage reservoir such as that shown in Fig. 1, some of the down-dip wells have no free surface. The previous study' showed that the up-dip wells, which have a free surface, should follow Eq. 1. The following approximate analysis, of a type which was justified experimentally for up-dip wells in the work just mentioned, leads to results for the down-dip wells.

By J. W. Dougherty, J. M. Douglas

THE Hollinger gold mine is in the Porcupine mining division, District of Cochrane, in the northern part of the Province of Ontario. The adjacent town of Timmins, with a population of 25,119, lies 490 miles by railway north of the city of Toronto. GEOLOGY The property is situated on the northwest limb of a major syncline, which pitches northeast at approximately 50°. The principal rocks of the Hollinger area are of pre-Cambrian age and consist of altered, schistose, Keewatin lava flows intruded by stocks of schistose, quartzfeldspar porphyry generally assigned to the Algoman period. The structure of the Keewatin series is extremely complex as a result of close folding and some faulting. The schistosity, trending north 70° east and dipping steeply to the southeast, is most highly developed along a subsidiary anticline in which the major porphyry bodies occur. The ore bodies, which exhibit three principal structures, consist of quartz veins and associated pyritized wall rock. Some lodes are composed of en echelon veins, others exhibit a main quartz body with branching stringers and a third consists of a single definite lead. Gold, in a coarse visible form, may be confined to quartz in some ore bodies but in others it is finely divided and is found not only in quartz but also associated with pyrite in the adjacent wall rock. In many veins the distribution of gold is such that there are several ore sections, separated by areas of low-grade material, in the same vein although its physical appearance remains unchanged. The veins form a very complex pattern in an ore zone which in places attains a length of 6000 ft. and a width of 4000 ft. They are most abundant in the Keewatin lavas in the neighborhood of the porphyry bodies. Few of the veins are persistent for long distances, though some

Jan 1, 1940

By H. Leslie Bullock

From aluminum to zirconium, the quantitative preponderance of quartz as a gangue material is well recognized. lf this material is to be efficiently removed, its variations must be understood. Variations with temperature are especially important. Too little attention has been given to the thermal polarization of quartz. Under closely controlled conditions, electrostatic upgrading is very reliable. For efficient separation, contact charges must be fostered and charges due to radiation, surface coatings, or thermal polarization avoided. This paper lists thermal transition points of quartz and shows their effect on actual separations. Simple separation tests with all factors except temperature held constant are recommended for determining transition points. With silica making up more than 27% of the earth's crust, its oxides comprising more than 59% of all igneous rocks, and quartz accounting for most of the main free oxides, the mining engineer is in constant contact with quartz, which may occur as a valuable mineral to be purified or, far more frequently, as a gangue material to be removed as completely and economically as possible. As a means of effecting such purification or removal, dry beneficiation is becoming more and more desirable owing to local water scarcities, wet waste disposal problems, or freezing conditions. One method that has been gaining particularly rapid acceptance is electrostatic beneficiation, or the separation of dry free-flowing materials by means of opposite surface charges, differences in potential, or differences in conductivity. Electrostatic beneficiation dates back to the 1870's, but only in recent years have newly developed methods and apparatus and a growing knowledge of solid-state physics widened the field for its economical application. Because the term "electrostatic beneficiation" has been rather loosely used in the literature, it has come to include both electrostatic and electrodynamic procedures. Attracting type separators, however, in which oper- ation is based on differences of surface charge or potential, are truly electrostatic, because the separation occurs in a substantially static field set up between oppositely charged surfaces. Separations with this type of equipment may occur at potentials as low as 1000 v and seldom require potentials as high as 30,000 v. In the new contact charge dielectric separators1 the variation in charge is produced by continuous contact and separation of the particles in the moving feed stream and these charges are fostered by the use of non-conducting support and feed surfaces and by handling the feed in the form of streams of appreciable depth. This favors uniformity of feed and allows higher production rates. The distinctive surface charge differences are set up on the separation of the particles according to Coehn's Law,2 which states that equal and opposite charges are generated on the separation of any two materials in contact and that the substance having the highest dielectric constant will be positively charged. The basic contact charge concept is reliable, but all electrical charges are transient and modified by the electrical conditions of the surroundings. Pyro-electric, photoelectric and radiant effects may modify or totally destroy the contact charges necessary for efficient separation, or contact with conducting surfaces may neutralize them. Such hostile conditions must be carefully guarded against, since they have led to many costly failures in the past. The most consistent difference in surface charges to insure good separation is produced by repeated uniform contact and separation of particles in the moving stream. The thickness of the feed stream possible with this method reduces the effect of contact with the supporting surfaces, but as some contact is inevitable, the best results may be assured by having the dielectric constants of the supporting surfaces between the dielectric constants of the substances to be separated. In general, the hard smooth surface of quartz makes it an ideal substance for electrostatic separation from most minerals. For instance, with calcite, starting with a feed containing 1.9% acid insolubles, one can produce a concentrate containing 0.30% acid insolubles with a tailings containing 21.7% acid insolubles and a yield of 92.8%. The color can be held at 92 or above and the tint at 1.7 or lower. Working with specularite iron ore, laboratory work has given a concentrate of 68.8% Fe., with an iron unit recovery of 96.7%. Excellent results are also in pros-

Jan 1, 1969

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) No. 544.-Mining engineer, 39 years of age, graduate E. M. with extensive experience in the United States, Canada and Spanish-speaking countries. Good organizer, energetic and resourceful. Experience covers mining and milling of gold, silver, lead, copper, zinc and tungsten. At present a Captain of Engineers, U. S. A., expecting to be released shortly. Open for engagement as manager, superintendent or examining engineer. Correspondence and personal interview solicited. No. 545.-Engineer and geologist, member, age 29 years, technical graduate and married. Six years' practical experience as surveyor, chief engineer and in exploration work in West, Southwest and Mexico. Speaks French and Spanish. Desires position with exploration company or as engineer and superintendent of small mine. Will be released from commission in United States Navy about February 1. No. 546.-For staff position-or manager. Member, married, graduate mining and metallurgical engineer, 18 years' experience in underground and metallurgical work on gold, silver, copper, lead and zinc ores. Details, references, and qualifications will be sent if requested, or may be seen at Institute office. Available immediately in United States or Canada. Would go reasonable distance for an interview if desired. No. 547.-Member, experienced in mine operating, engineering, general contracting and constructing. Technical graduate, mining engineer, married, age 38 years. Many years' practical experience while advancing through different positions to manager. Best of references and rating. Desires change. Position with future. Can obtain results. Salary commensurate with position. Available on short notice. No. 548.-Mining engineer, member, technical graduate, age 31, on military service since August, 1914, available after January 31. Best of references.

Jan 3, 1919

By Craig S. Hartley

An approximate expression is obtained for the energy of a closed dislocation loop in equi1ibriu)n with a constant net stress. The result obtained is valid for loops in isotropic or anisotropzc materials provided that they are suJficiently large that the energy per unit length of a segment of the loop can be approximated by that of an infinite straight dislocation tangent to the loop. It is shown that this approximation leads to very close agreement with a more rigorous calculation of the elastic energy of a circular glide loop. The Gibbs-Wulff Form, GWF, of a dislocation is the closed planar loop which has the smallest elastic self-energy of all possible loops having the same Burgers vector and enclosing a fixed area, A.' The energy of such a loop is related to the net resolved shear stress* required to expand the loop and to the stress required to activate a Frank-Read source.223 In the following sectiorls the problem of determining the form of the GWF is discussed and an approximate method for calculating its elastic self-energy is presented. It is demonstrated that the approximations employed lead to no serious errors when applied to a calculation of the elastic energy of a circular glide loop. This method is then used to obtain a closed form expression for the energy of GWFs in isotropic and anisotropic materials. THEORY Burton, Frank, and cabrera4 have proved that the relationship of the equilibrium shape of a two-dimensional array of atoms under the influence of the Gibbs free energy associated with unit length of its boundary, G(O), is that the polar plot of G(0) vs 0 is proportional to the pedal of the GWF.* The angle 0 is measured "The pedal of the polar graph ofG(0) vs0 is the envelope of tangents to the eraph.relative to some crystallographic reference direction. The difficulty in applying this result to a closed dislocation loop arises from the self-interaction of the loop. For a dislocation the energy analogous to G(0) is a function of the total configurati~n.~ Consequently the relation which determines the GWF is an integro-differential equation rather than the simple differen- tial equation which results when G(8) is a function of 0 alone. Mitchell and smialek3 and Brown~ have used the self-stress concept introduced by ~rown' to calculate the shapes of dislocations in equilibrium with an applied stress. In this approach the glide force on an element of the dislocation loop due to the interaction of the element with the rest of the loop is equated to the glide force exerted by the local applied stress. The shape of the loop is then adjusted so that the two forces above are equal at all points on the loop. It is possible to calculate the energies of such loops by noting that, for equilibrium with an applied stress, the energy is equal to pijbiAj (summation convention) where bi is the Burgers vector, p.. is the local net stress tensor, and Ai is a vector directed perpendicular to the plane of thd loop with magnitude equal to the area of the loop. Also Brown' has calculated the energy of a hypothetical polygonal GWF using the above technique and anisotropic elasticity. However, his indicated solution for the energy in the general case of an arbitrary GWF is only slightly less involved than an iterative solution of the integrodifferential equation referred to earlier. In the present work the approximation employed by DeWit and Koehler' is used to calculate the energy of a closed loop in equilibrium with an applied stress. That is, the energy of a loop segment, ds, is approximated by the product of ds and the energy per unit length of an infinite, straight dislocation in a cylinder coaxial with the tangent to the loop at the angular position of the segment. This is known as the "line tension" approximation. The inner cutoff radius of the elastic solution defines the core radius, while the outer cutoff radius is determined by some characteristic dimension of the loop. Actually, both of these radii vary with the edge-screw character of the segment. The effective core radius changes because of the orientation dependence of the Peierls width of a dislocation,8 and the outer radius should be the radial distance from the circumference of the loop to the center of symmetry of the area enclosed by the loop.g However, since the energy varies logarithmically with the ratio of these radii while depending directly on the effective elastic constants, only the effect of the latter is considered. This approximation also neglects the self-interaction of the loop segments. For small loops this will doubtless be extremely important, but for large glide loops produced by plastic deformation the self-interaction is not nearly so important in determining the energy of the loop. This point is illustrated by the following calculation of the energy of a circular loop. Consider a circular loop of radius R which lies in the XI - x, plane of an infinite isotropic continuum and whose Burgers vector makes an angle $ with xs. The first-order solution for the elastic self-energy is:'

Jan 1, 1970

By John C. Sawyer

A brief review is given to show that catastrophic oxidation of stainless steel in the presence of lead oxide is similar in many respects to catastrophic oxidation as caused by MoO3 and V2O5, Experimental data are presented to show that lead oxide accelerates the normal oxidation process of stainless steel by chemically altering the normally protective oxide film formed on the base metal. Data are given to show that similar reactions occur during oxidation of stainless steel in the presence of MOO3,and V2O5. THE mechanism by which pure metals oxidize at high temperatures has been the subject of intensive research for many years and much has been accomplished towards understanding the processes involved. The mechanisms by which alloys oxidize have also been investigated, but due partly to the fewer number of investigations and partly to the complexity of the oxide systems present, available knowledge is not as extensive as with pure metals. When oxidation processes are further complicated by atmospheres contaminated with sulfide, halide, or oxide vapors, the knowledge of fundamentals becomes meager or altogether lacking. Thus, it is not surprising to find that the catastrophic oxidation of stainless steels in metal oxide vapors of MOO, and V2O5 is not a well understood phenomenon despite the fact that a number of investigations have been undertaken. The literature in dealing with the subject of catastrophic oxidation is primarily concerned with the effects of MOO3 and V2O5, but does mention that other metal oxide vapors, one of which is lead oxide, appear to promote a similar type of accelerated oxidation. While this latter effect is virtually unknown, the deleterious effect of lead oxide is of considerable commercial importance, as it is believed to be one of the fundamental reasons for exhaust-valve failure in gasoline engines. For this reason studies have been in progress for many years attempting to better understand the mechanism involved. Modern exhaust-valve alloys"2containing 20 to 25 pct Cr plus nickel and/or manganese are in effect high-grade austenitic stainless steels exhibiting ex- cellent oxidation resistance in air at exhaust valve operating temperatures of 1100° to 1700°F; yet these same alloys are prone to corrode during engine service because of the conditions attending their operation. These conditions are such that the valves become coated with deposits of complex lead compounds mainly derived from gasoline additives of tetraethyllead, ethylene dibromide, and ethylene dichloride. Literature searches3-7 and discussions with various investigators show that considerable difference of opinion exists as to the nature of the lead-bearing deposits found on the surface of exhaust valves and the atmospheres to which they are subjected; yet, all seem to generally agree that corrosion, a gradual transformation of alloy to nonmetallic products of corrosion, is a consequence of the presence of lead compounds. This majority opinion seems to be substantiated by laboratory engine tests which show that corrosion does not occur to any appreciable extent when lead-free fuels are used. The first observations of catastrophic oxidation reported in the literature were probably made by pfeil,8 but it was Leslie and Fontana9 who undertook the first detailed study of the phenomenon. Their work was chiefly centered on the acceleration of oxidation which took place when stainless steels containing more than 3 pct Mo were heated in air with restricted circulation. These investigators reported that the presence of other oxides near the surface would further accelerate the rapid oxidation which occurred. While they recognized that the effect was attributable to the presence of molybdenum, it was Rathenau and Meijering" who emphasized the fact that the presence of molybdenum in the alloy was incidental to the presence of MOO3 vapor in the atmosphere surrounding the specimens. Evans,11 as well as Cunningham and Brasunas 12 studied similar

Jan 1, 1962

By C. S. Sivaramakrishnan, Manjit Singh, Rajendra Kumar

Regarding liquid nzetals structurally as a suspm-sion of clusters , having derivated solid-state coordination, in truly liquid atoms, the recently developed Kuvlar-Samarin technique of centrifuging- in liquid state enabled the determination of the cluster sizes inAl-Cu mid Pb-Sn systems. It is shown that the colutne fraction of the clusters does not exceed 9 pct and the energy of their formation in Al-Cu is about 5.5 kcal per g-atom and in Pb-Sn eutectic alloys about 25 kcal per y-atoni. STRUCTURAL investigations of liquid state have principally followed the following three courses: i) studies with X-ray, electron, or neutron diffraction; these investigations have shown that there is a certain amount of regularity in the structure of liquid metals which can be defined by a coordination number and that the structure is a derived function of that in the solid state; ii) thermodynamical investigations which are based on the concept of ideal behavior; these describe the liquid state in terms of free-energy values and other thermodynamic functions; although these investigations are of help in the study of the general effects of alloying, they do not provide any structural insight into the precise atomic distribution in liquid state; iii) measurements of surface tension and viscosity; although it is natural to expect that the viscosity is related to the structure in liquid state, these investigations have so far only provided information which can be used by the foundry technologists and has been little utilized in formulating models of the structure of liquid state. As it happens, investigators in the three groups have worked almost independently of each other and there is practically no structural correlation between the results of one group with those of another. The purpose of the present paper is to indicate that the experimentally measured parameters of these three groups of research are closely related to the structure in the liquid state. STRUCTURE OF LIQUID METALS Although atomic distribution in solid and gaseous states is rigorously known, that of the liquid state is only appreciated on the fringes. There is no universal model of atomic distribution in liquid state, but two diverse models are at present hotly contested. The first, largely expounded by ~ildebrand,' regards the liquids as condensed gas since many of their properties and much of their behavior can be adequately described by regarding them as fluids. The second mode12j3 considers that some form of near-solid as- sociation of large number of atoms exists in the liquid state. On the other hand, ~ernal' was able to predict rather precisely the radial distribution functions in liquids on the basis of statistical geometric approach which considered that liquids are "homogeneous, coherent, and essentially irregular assemblage of molecules containing no crystalline regions or holes large enough to admit another molecule". He introduced the concept of pseudonuclei in the otherwise random structure as aggregates of closely packed tetrahedra which gradually merge into irregularity and continually replace each other. To what extent the pseudonuclei can be regarded as regions of near-solid association is indefinite but Bernal suggested that the concept of pseudonuclei can be compromised with the latter model if the near-solid associations are regarded as extremely dense and not necessarily crystalline. The difficulty in projecting the structure of liquid metals arises because they exhibit duplicity of character as some of their properties are closer to those of crystalline solids and others to fluids. There is an increasing tendency to discuss the structure of liquid metals in terms of the second concept according to which the structure of liquid metals may be conceived as consisting of i) clusters of atoms where the aggregation is a close derivative of that in the crystalline state, ii) individual atoms which behave like true liquids in respect to degrees of freedom and iii) excess number of vacancies. It is noteworthy that the introduction of only 5 pct vacancies is sufficient to transform crystalline matter into the liquid state. At any instant of time thermodynamic equilibrium exists between i, ii, and iii, but the relative proportion of the clusters and random atoms is not known. That this is so can be appreciated by the fact that, when liquid metal is rapidly cooled, liquid state vacancies may condense in the form of dislocation loops and vacancies in excess of their equilibrium number in solid state. These dislocation loops have been observed in thin foils of aluminum prepared from rapid cooled aluminum. As temperature increases above melting point the number and volume fraction of clusters decrease but those of vacancies and random atoms increase. Clusters are transient in nature. In pure metals the cluster is an aggregation of the metal itself. In alloys, however, the nature of the cluster largely depends on the interaction between solvent and solute atoms. If the interaction between unlike atoms is greater than between like atoms: the clusters are then aggregates of unlike atoms. Examples of this kind of system are A1-Cu, Mg-Pb, and so forth, i.e., systems which exhibit negative departures from the Raoult's law. In systems where the interaction between unlike atoms is smaller than be-

Jan 1, 1968

By M. H. Childs, K. E. Merklin

Blast furnace feed specifications are being revolutionized because of the large increase in iron pellet production from low-grade ores of the Lake Superior region. Recent laboratory findings aimed at a better understanding of factors influencing the physical quality of pellets produced from taconite concentrates are reviewed. Tests for determining better product quality, the effects of additives, and production factors are discussed. The current revolution in specifications for blast furnace feed is typified to a great extent by the recent tremendous growth in iron ore pellet production from low grade ores of the Lake Superior region. Indeed, pellets are responsible, at least in part, for many of the stringent new requirements that are being placed on the suppliers of furnace raw materials. As the tonnage of pellets going to the steel mills increases, more and more attention is being turned to the detailed characteristics that make this product an ideal blast furnace feed. Control of quality in pellets is similar to that of any other product. A basic understanding of the factors that are encountered in their production, from the crude ore through to the finished product, is required, along with careful process supervision and frequent quality checks. Normally, chemical grade is not a problem. This usually can be controlled within the desired specifications by minor operating variations in the con- centrator. While future changes in requirements may result in the need for self-fluxing pellets1 or other chemical changes, today's quality demands center primarily around the physical characteristics of the pellets. It is in this area that many of the recent laboratory studies have proven helpful to the operating plants. A better understanding of the physical factors involved in pelletizing has provided the basis for a continuing program of quality improvement. Tigerschiold and Ilmoni2 and Cooke with various associates are responsible for the development of much of the basic understanding of the pelletiz-ing process. These earlier findings have served as a most useful background for this work. LABORATORY PROCEDURES Magnetite concentrates produced from eastern Mesabi Range magnetic taconites were used for all of the work reported herein. The sizing and chemical analysis of a random sample are shown in Table t Additives usually are mixed with the concentrates in taconite plants before pelletizing to improve the strength characteristics of the unfired balls. Ben-tonite, soda ash, and coal are in common use. The bentonite used in these studies was of the Wyoming sodium type; the soda ash was a standard commercia1 brand. Anthrafines were used where coal was called for. The procedure for making batches of balls at the Hibbing Laboratory is as follows: In an especially designed mulling equipment 2800 g of dry ore are mixed for 10 min with the desired additives. Water is added and mixing continued for 1 1/2 min. The charge is removed from the muller and put through a mechanical shredder to break down any lumps that may have formed. sixty previously formed seed balls are placed in the balling drum, which is in fact a 6 x 16-in. diam airplane tire turning at 53 Wm. Two thousand grams of the shredded concentrate and additive mix are fed by hand into the tire at a con-

Jan 1, 1961

By M. J. Marcinkowski, D. B. Crittenden, A. S. Sastri

A study co.mbining stress-strain .measurements in conjunction with transmission electron microscoPy has been made with near equiatomic Fe-Cr alloys which were aged for various times at 500°C. Associated with this aging is a marked increase in deformation twinning. The outstanding feature of these twins is that they generate stress fields sufficiently great so as to give rise to spontaneous dislocation loop nucleation nearly normal to the propagating twin. This observation is in agreement with the theoretically predicted elongation of the stress field of a dislocation Perpendicular to its direction of motion as it moves near the speed of sound. Dislocation loop nucleation is more difficult in the longer aged alloys so that this energy absorption mechanism is not effective in hindering twin propagation. Since crack nucleation can readily occur near the tip of a twin, the aged alloys become extremely brittle when deformed in tension. Iron-chromium alloys in the vicinity of the equiatomic compositions become severely embrittled when aged at about 500°C. Fisher et 01.' have shown that this embrittlement is related to the decomposition of the original random Fe-Cr solid solution into a chromium-rich and an iron-rich phase. In addition, Mar-cinkowski et a1.' have shown that twinning becomes an increasingly more important mode of deformation as the aging time is increased. These results have been recently corroborated by the transmission electron microscopy study of Mima and amauchi . The Fe-Cr alloy thus seems ideal for verifying the predictions made in Parts I4 and 115 of this investigation where the behavior of large static or blocked twins and those of large dynamic or propagating twins, respectively, were investigated numerically. It was thus decided to measure the stress-strain curves generated by embrittled alloys that were aged for various times and to examine sections by transmission electron microscopy. EXPERIMENTAL PROCEDURE Electrolytic iron and electrolytic chromium were vacuum-melted and poured into ingot form. The composition of the resulting alloy was found to contain 46.0 wt pct Cr (47.8 at. pct), the remainder being iron. The resulting ingot was swaged above 850°C into 0.250-and 0.400-in.-diam rounds. Compression samples of 0.250 in. diam and 0.400 in. long were cut from the smaller-diameter rounds. These samples were then sealed in evacuated quartz tubes and annealed for 30 min at 1150°C to produce a uniform and equiaxed grain size of mean diameter equal to 1.73 mm. They in turn were rapidly quenched from 850°C so as to preserve the condition of random solid-solution characteristic of the elevated temperature. The samples were then aged for various times up to 300 hr at 500°C in a massive Pb-Bi alloy bath. The samples were next polished and tested in compression at room temperature as described in Ref. 6 using an Instron tensile testing machine. The strain rate used was 0.05 in. per in. per min. The remaining larger round was converted into compression specimens of 0.325 in. diam and 0.500 in. long. This larger diameter enabled wafers of sufficient size to be prepared for examination by trans-mission electron microscopy techniques after subjecting them to a suitable strain. Foil preparation is described in some detail in Ref. 6. All foils were examined in a type HU-11A Hitachi electron microscope operating at 100 kv. RESULTS AND DISCUSSION Fig. 1 shows the effect of aging at 500°C on the room-temperature stress-strain curves of the FeCr alloys. For greater clarity the origin of each curve has been displaced upward. The same origin has been used for both the 0 and the 0.1 curves. It is apparent that with increased aging times a sharp drop in load is observed at the yield stress which becomes more pronounced as aging proceeds. A loud sonic burst accompanies this drop and subsequent metallographic examination shows the sample to contain numerous twins. For intermediate aging times, a number of smaller twin bursts follow the initial large one. The total plastic strain associated with the twinning mode of deformation can be obtained by adding up the contributions AE~ from all i twin bursts, i.e., £,¦££,-, in the manner illustrated schematically in Fig. 2. The contraction of the specimen, as measured from the strip chart of the Instron, after suitably correcting for the elasticity of the machine, was converted into true strain using the assumption that there was no volume change and that the sample remained cylindrical. The dashed lines are all drawn parallel to the

Jan 1, 1970

By C. G. Dunn

MANY investigations have been made concerning the nature of plastic deformation and recrystallization of metals either in the form of polycrystalline materials or in the form of single crystals. However, similar work on strip materials composed of large grains as thick as the strip and having a high degree of preferred crystal orientation has not been carried out extensively. Such materials are ideal not only for studying changes in single crystals under conditions where neighboring grains exert their influences but also for obtaining the, complete change in orientation of a grain or group of grains during the course of plastic deformation and subsequent recrystallization. It is well known that first-order twins in the form of Neumann bands may be produced during the plastic deformation of ferrite crystals, particularly silicon ferrite crystals.1-3 Furthermore, it is believe that high-stress regions exist in the vicinity of these bands4a and it has been said that these banded regions would be active in recrystallization processes.5 Evidence to that effect in silicon ferrite had already been presented with photomicrographs showing recrystallization among Neumann bands during the early stages of recrystallization.5,6 Similar evidence has been published for nonferrous metals.5 Merging of fine parallel deformation bands during annealing to form twin bands of ordinary appearance in alpha brass has been offered not only as evidence of an active role being played by mechanical twins but also as evidence that such twins existed prior to recrystallization.5 Proof that such new structures are actually first-order twins, or even twins at all, must be considered inadequate except for those cases where X-ray or optical data have been obtained to confirm the necessary orientation relationship.7,8 A. B. Greninger has obtained excellent iliustrations of annealing twins in alpha irons Since his material was previously deformed by sharp hammering, a process that generally induces Neumann bands, the existence of twins following annealing might suggest that they grew from mechanical twins. In connection with transformation twins in alpha iron, Greninger reported that grains containing. three twin orientations occurred rarely and none occurred with three sets of well-developed bands.9 The work at the Pittsfield Works Laboratory on silicon ferrite in the form of large-grained strip steel deformed a small amount and annealed to partially recrystallize the grains indicates that the deformation and recrystallization processes that lead to annealing twins involve more complex processes than the formation of Neumann bands and the growth of such bands. Some groups of annealing twins are obtained which contain not only three well-developed twin structures, but also contain more than one order of twins. It is also shown, in one case, that an interrelated group of twins did not arise within one single parent grain and, furthermore, orientations of grains in the group

Jan 1, 1944

AT THE beginning of December, the Lausanne Con-ference was in session. The representatives of the United States declared the American position. The representatives of Russia were received and were heard. The Turks appeared at this conference in the attitude of victors, dictating terms. The British refused to surrender Mosul, and December thus ended with this question unsettled. Early in the month the premiers of the principal powers met in London for the discussion of the German reparations question, the temporary agreement expiring on. Jan. 15, 1923. On Dec. 11 the Conference adjourned without getting anywhere, and at the end of December prospects looked more hopeless than ever. The premiers are to meet again on Jan. 2, 1923. The interruption of the London conference was followed by the intimation of early participation of the United States in European affairs in the practical way of a large loan to Germany. These intimations, ema-nating from Washington, appear to have been in the nature of trial balloons. They showed that the wind was unfavorable, the bankers not considering conditions suitable for the flotation of such a loan. British statisticians are puzzled by the fact that the trade returns of Great Britain show a greater turnover in the volume of goods during the first 11 months of 1922 than in 1920, although the rate of labor employ-ment in 1920 was nearly 100 per cent. and in 1922 only about 86 per cent., with an economic situation admit-tedly so bad as to be alarming. The British Parliament was convened under the premiership of Bonar Law. One of its first acts was confirmation of the constitution of the Irish Free State. Civil war in Ireland continued. Poland, like most of the other countries of Europe, is torn between socialism and conservatism, with the former party at present predominant. Early in December, Gabriel Narutowicz, an engineer but a radical, was elected president. On Dec: 14 he entered office and-on Dec. 16 he was assassinated.

Jan 1, 1923

By Bernard York, John J. Reed

Mine opening stability was investigated by loading model openings to failure. Eight-inch plaster blocks were cast with small uniform section openings passing through the centers. After curing, the models were jacketed and loaded hydrostatically in a closed vessel. Opening size, shape, and orientation were varied to determine how these factors influence opening stability. THE investigation described in this paper is a continuation of a project begun in 1946 by Bernard York and W. E. Bush. .The experimental method used in the investigation involves the hydrostatic loading of a model mine opening to failure. Most investigators agree that this loading closely approaches actual conditions in very deep mines. The conditions are further idealized by using an essentially isotropic model material. The experiments consist of casting 8-in. plaster cubes, or 8-in. diam cylinders 8-in. long, having a relatively small uniform section hole passing through their centers. After thorough drying, the models are jacketed in a flexible plastic bag and loaded hydrostatically with water in a closed vessel. At about 300 to 500 lb per sq in. pressure the central opening fails. The fracture pattern resulting from opening failure is studied in a plane normal to the longitudinal axis of the opening. The model block is sawed through its center after loading to expose this plane and to eliminate the possibility of end effect. By changing

Jan 1, 1954

By A. V. Bradshaw, R. I. L. Guthrie

The behavior of large bubbles in the size range 4 to 25 cm3, rising through molten silver, has been studied. It was found that rising velocities were equivalent to those in aqueous systems of low viscosity. Mass transfer coefficients for oxygen bubbles dissolving in silver were found to be 0.036 ± 0.007 cm sec-1, being close to those predicted for transfer through the front surface of the spherical cap bubble only. It is suggested that the surface active nature of oxygen in silver could account for the relatively low coefficients obtained. MANY metallurgical processes involve interactions between gas bubbles and liquids. Examples include the removal of carbon monoxide in Open Hearth Steelmak-ing, the removal of sulfur by blowing air through copper matte during converting, and the removal of hydrogen from steel during vacuum degassing or inert gas flushing. The steps involved in such refining processes include; transport of the dissolved species to the bubble interface, adsorption and chemical reaction of the species at the interface, desorption of product molecules from the interface, and transport of product gas into the bulk gas phase of the bubble. It has been concluded1 that all the interfacial steps involved proceed so rapidly at steelmaking temperatures that transport of the solutes, present in the metal, become the important rate controlling factors provided nucleation phenomena are not restrictive. The O-Ag system was chosen for the investigation into gas bubble-molten metal interactions due to the relatively high solubility of oxygen that enables rates of oxygen transfer to be measured from changes in bubble volume. Other advantages of this system include the absence of a stable oxide phase at an oxygen pressure of 1 atm and the relatively low melting point of the metal which permits the use of a metallic container, providing that it is resistant to oxidation. In those metallurgical processes where bubbles have an important influence, bubble volumes are usually greater than 5 cm3. For this reason the present study relates specifically to single large bubbles of oxygen rising in silver. These bubbles adopt the characteristic spherical cap shape similar to that shown in Fig. 1 for a 30 cc bubble rising in water. After an initial investigation to determine the velocities of inert (nitrogen) bubbles rising in molten silver, experiments were carried out with oxygen and the rates of mass transfer between the oxygen bubbles and the silver were measured. EXPERIMENTAL Apparatus. The apparatus, Fig. 2, for containing molten silver, was constructed from "Nimonic 75" Alloy (75 pet Ni, 20 pet Cr, 5 pet Fe, Mn) and provided for the release of single bubbles from an hemispherical cup, situated at the bottom of the column. The cup was turned by translating the rotation of the drive shaft through 90 deg. This was accomplished by the use of a bevelled gear system, and a smooth drive was provided by the lubricating action of the silver on the gears. Since reliable high temperature seals at 1000°C were found to be impracticable, the filling and drive shaft tubes were extended outside the 3.5 kw resistance wire tube furnace, where connections were made using easily accessible O-ring seals. The apparatus remained gas tight to the atmosphere at pressure differentials far in excess of those used. The filling tube was connected via a small bore tube to the differential pressure transducer. Gas could be bubbled into the inverted cup from two i-in. tubes which passed down the inside of the column to preheat the gas. The temperature of the silver was maintained at 1020°C during all experiments. Measurement of Bubble Volume. In order to calculate mass transfer rates, it was necessary to obtain a continuous record of the bubble's volume during its passage through the column of molten silver. The method adopted for measuring the bubble volume involved closing off the top gas space to the atmosphere prior to each experiment, and recording the variation in gage pressure of this space during the formation and rise of the bubble. Since any change in bubble volume results in an equal change in top space volume, Boyles Gas Law may be applied (for isothermal con-

Jan 1, 1970

By Sidney Siegel, J. Gardner Brooks, Irvin R. Kramer

IN 1942 Grossmann1 proposed that the hardenability of a steel may be calculated from its chemical composition by considering the base hardenability associated with its carbon content and grain size and multiplying this base by factors for each element present. Since Grossmann's original publication, several investigators2-5 have reexamined the multiplying factors for the individual elements and in general have found that the multiplying principle is valid. However, some of the individual factor curves developed have been in poor agreement. Inasmuch as the carbon-factor curve obtained by Grossmann was dependent [ ] upon the factors for all the other alloying elements present in the steel, it logically followed that his results were in need of correction in the light of the new data available for manganese, silicon, and the other alloying elements. Furthermore, in order to avoid the possibility that errors in the manganese, silicon, or other curves might influence the carbon-factor curve, investigation of iron-carbon alloys containing little or no manganese and silicon was necessary. That the effect of carbon on hardenability was greater than indicated by Grossmann is shown by a comparison of the diameters of completely hardened rounds of iron-carbon alloys with the ideal critical diameter calculated from Grossmann's factors. These alloys have a greater hardenability in a hite quench than predicted by Grossmann's factors for an infinite quench (Table I). [ ] Among the other important variables that were in need of further investigation were the effect of deoxidation practice on the grain-size correction curves and the effect of stable carbide-forming elements on the depth of hardening. Most of the work by Kramer, Hafner, and Toleman4 was done on silicon-killed steels. It was not known whether Grossmann's grain-size correction curves, deter- mined on aluminum-killed steels, was valid when applied to steels with different deoxidation practice. More data on the

Jan 1, 1946

By Jacob T. Wainwright

AS a means for increasing the efficiency in modern blast-furnaces by supplying to them blast of a much higher temperature than is now possible, the writer offers as a suggestion a modification in the construction of regenerative hot-blast stoves. Stated briefly, the plan proposed is to pre-heat both the gas and the air for its combustion in a manner similar to that generally adopted in Siemens openhearth furnaces. After thus carrying the temperature of the stove to a point much higher than that common in hot-hlast stoves, the cold blast passes through it. Without entering into the details relating to the reversing valves and the system of flues, the general plan may be outlined as follows, referring to the accompanying drawings: The valves are so placed in heating up the stove that the blast-furnace gas enters at B, Fig. 1, and the cold air for combustion at A. Ascending in flues, F and E, respectively, combustible gas and air meet and mix in the combustion-chamber, I. Flowing through K, they descend through the flues, G and H, escaping through the chimney. In this manner the walls of the combustion. chambers, I and L, are highly heated, and the right-hand side of the stove is carried to a higher temperature. By reversing the valves, blast-furnace gas enters at C and cold air for combustion at D. Both are pre-heated in their ascent through the flues, G and H. They burn in the combustion-chamber, L, and the hot gases of combustion, flowing through K, I, E and F to A and B, heat the left-hand side of the stove. In this manner the stove is carried to a temperature greater than that of those now generally in use, in which air and gas are burned without preliminary pre-heating. In the plan proposed, that side of the stove will, of course, be relatively cooler through which cold air and furnace-gas last passed in its ascent to its combustion-chamber. After having sufficiently heated the stove in the manner outlined, the cold blast is admitted through all the flues, A, B, C and D. It ascends through the highly-heated regenerative material to the chambers at the top and descends through the flue, P, Fig. 2 (dotted

Jan 1, 1889

By C. E. Birchenall, J. R. Stubbles

ThE equilibrium between lead, lead sulfide (PbS), and atmospheres of H2 and H2S has been determined previously by Jellinek and Deubel,' and SudO.' Blbem and Kroger3,4 used Jellinek's data to calculate the sulfur dissociation pressures of PbS crystals (of

Jan 1, 1960

By R. V. Ramani, Robert Stefanko

The more stringent ventilation requirements of the 1969 Act have created a greater need for improved network analyses. More air is required at the last open crosscut (9000 cfm) and for the first time a minimum quantity is specified for the face (3000 cfm). Severe restrictions are placed on both belt and track haulage, and the intake air cannot contain more than 2 mg per cu m of respirable dust, to be reduced to 1 mg later. Larger tonnage and longer life mines are the trend today, necessitating multiple fans and shafts. Yet relatively little engineering goes into designing the mine ventilation system. In this paper a ventilation system is designed for a typical Pittsburgh block system, manual calculations are made and then checked by a computer solution. The computer is the ideal tool to try out proposed changes on paper to insure that the entire mine is properly ventilated and no costly adjustments need be made by dumping air. While it is theoretically possible to solve complex ventilation network problems by hand, it is not practical to do so because of the tremendous man-hours required and the many opportunities for errors. Thus the digital computer is indispensible to the ventilation engineer and newer improved ventilation programs are being developed to more realistically model mine ventilation networks. Suggested ventilation changes to comply with the new regulations are also critically evaluated.

Jan 1, 1973

By A. H. Larson, L. G. Twidwell

The influence which Au, Ag, Sb, Bi, Sn, and Cu have, both individually and collectively, on the activity coefficient of sulfur in liquid lead at 600"C zuas studied by circulating a H2S-Hz gas wlixture over a specific lead alloy until equilibrium was attained. Subsequently, the H2S concentration in the equilibrium gas mixture and sulfur concentration in the condensed phase were deterruined. The elements gold, silver, and antinzony (above 8 at. pct) increased the activity coefficient of sulfur. Bismuth had no apparent effect. Tin (above 3 at. pct) and copper decreased the coefficient. The influence of an individual element, i, on sulfur is best reported as the interaction parameter, riS, which is defined as The values o these first-order interaction zus are: ESzu = —55.0. These interaction parameters are used to predict the activity coefficient of sulfur in six fouv-component alloys and one seven-component alloy. Comparisons are made with direct experimental determinations. INTERACTIONS in dilute solution have been studied by many investigators. Most of the experimental work has been confined to solute-solvent interactions in simple binary systems and solute-solute interactions in ternary systems. Dealy and pehlke"~ have summarized the available literature on activity coefficients at infinite dilution in nonferrous binary alloys and have calculated from published data the values for interaction parameters in dilute nonferrous alloys. Interaction parameters are a convenient means of summarizing the effect of one solute species on another in a given solvent. Only a few investigators have studied interactions of the nonmetallic element sulfur in a metallic solvent. They are as follows: Rosenqvist,~ sulfur in silver; Rosenqvist and Cox,4 sulfur in steel; chipman, sulfur in alloy steels; Alcock and Richardson,% ulfur in copper alloys; Cheng and Alcock,' sulfur in iron, cobalt, and nickel; Cheng and ~lcock,' sulfur in lead and tin. The only reported work on the Pb-S system in the dilute-solution region is that of Cheng and Alcock.' Their investigation involved a study of the solubility of sulfur in liquid lead over the temperature range 500" to 680°C. The results may be summarized by the following relationship: S (dissolved in lead) + Pb(1) = PbS(s) log at. %S = -3388/T + 3.511 Experimentally, it was found that Henry's law was valid up to the solubility limit of sulfur in lead, i.e., at 600°C up to 0.43 pct. Their investigation did not include the study of sulfur in lead alloys. More accurate calculations could be made in smelting and refining systems if activity coefficients of solute species could be accurately predicted in complex solutions. One of the objectives of this study was to compare the experimental data with the values calculated from the equations derived from models for dilute solutions proposed by wagner9 and Alcock and Richardson. A temperature of 600°C was chosen as the experimental temperature to attain reasonable reaction rates and to minimize volatilization of the condensed phase. EXPERIMENTAL Materials. The Pb, Au, Ag, Sb, Bi, Sn, and Cu used for preparation of the alloys were American Smelting and Refining Co. research-grade materials. All were 99.999+ pct purity except the antimony and tin which were 99.99+ pct. The initial alloys prepared for this study consisted of twenty-one binary alloys, eleven ternary alloys, and one six-component alloy. The constituent elements were mixed for each desired alloy and were placed in a crucible machined from spectrographically pure graphite. The crucible was placed in a vycor tube which was evacuated with a vacuum pump and gettered by titanium sponge at 800°C for 8 to 12 hr. After the gettering was completed, the chamber containing the titanium was sealed and removed. The remaining sample chamber was placed in a tube furnace at 800°C for 2 hr and quenched in cold water. The final operation consisted of homogenization of the alloy for 1 to 2 weeks at a temperature just below the solidus for the individual system. The resulting master alloys were sectioned into small pieces and a random choice made for individual equilibrations. Cobalt sulfide (Cogs8) used to control the gas atmosphere in the circulation system was prepared by passing dried HzS for 24 hr over a Co-S mixture heated to 700°C in a tube furnace. This material was then mixed with cobalt metal to give a two-phase mixture which, when heated in hydrogen to a particular temperature, produced a desired H2S/H2 gas atmosphere in the circulation system. A Cu2S-Cu mixture also used in this study was prepared in a comparable manner. Apparatus for Equilibrium Measurements. The experimental technique of this study required apparatus

Jan 1, 1967