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By J. S. Kirkaldy, D. G. Fedak

The extra degree of freedonz introduced by a second independetzt concentration in a tenzary system gives rise to the possibility of unstable planar phase interfaces in semi-infinite diffision layer couples. Diffusion paths which pass continuously in and out of too-phase regions of the phase diagram but which are not coincident with tie-lines give rise to super saturated zones which may be either adjacent to or isolated from planar phase interfaces, with corresponding nonisolated or isolated precipitates. Nonisolated precipitates are equivalent to morphological development of the interface. Selected couples in the ternary systems Fe-Ni-Cr and Cu-Zn-Sn have been examined nzetallographically and ifz the latter case both isolated and uo~zisolated precipitates have been observed. The diffusion path in one of the couples showing interface morphological developtnent has been examitled using electron probe microanalysis. IGNORING the spurious effects of preferential grain boundary diffusion and anisotropic crystal growth7 it can be unequivocally stated that it is impossible for a binary isothermal diffusion couple constructed of two unsaturated phases to sustain a nonplanar phase interface. Consider for demonstrative purposes the schematic phase diagram of Fig. l(a). Given an initial flat phase interface, semi-infinite boundary conditions and the internal boundary condition fixed by the constitution diagram, xB = xB(T), the unique solution of the diffusion equation requires a persistent flat interface. No other solution is possible. If, however, we anticipate the involvement of surface tension, then the internal boundary condition must be written xB = xB (T,Y) where r is the radius of curvature of a hypothetical nonplanar interface. The introduction of a new parameter such as r can be equivalent to the release of an internal constraint, so that a stable nonplanar interface may be possible after all. Consider a perturbation to the interface as indicated in Fig. 1(b). According to the Ostwald-Freundlich equation: which is applicable to a system of this constitution, the solubility of A in the matrix ß ,xB (Y), at a point of curvature r is given by where Va is the molar volume of the a-phase, R is the gas constant, and a is the interfacial tension. Since the right hand side is positive, xB(r) >xB cm, as indicated in Figs. 1(a) and 1(c). Accordingly, the perturbation will carry the interface concentration in a direction which is opposite to that which would sustain local equilibrium. Such a perturbation is necessarily moderated and the system is returned to its initial condition. This result is general for all binary couples since we can regard an interfacial perturbation as an attempt to precipitate within un-

Jan 1, 1962

By D. L. King, B. A. Schepman

A number of unique thickener mechanism designs with the operating results achieved in various installations are discussed. These unusual designs include new types of raking arms, lifting devices, and feed-wells employed to obtain higher underflow densities and minimum operator control or improved overflow clarity. Several installations of large thickeners in which the underflow lines pass upward through the center to eliminate tunnels are reviewed. The location of the lines and pumps with the maintenance and operating records are included. Several types of automatic lifting device controls are used to provide storage in the thickener. Some of the installations employing underflow density controls are achieving excellent operating results. Thickeners or sedimentation basins are used in minerals beneficiation plants for three basic purposes. These are 1) Concentration, or to raise the density of a liquid-solids slurry. 2) Clarification, or removal of finely divided solids from a slurry. 3) Hydroseparation, or removal of a specific fraction of solids from a slurry. The concepts that control the size and configuration of basins used for these purposes are different. Likewise, different equipment is properly employed to accomplish these various objectives. The pattern of liquid and solids flow in the clarification zone of a sedimentation basin used for thickening or raising the density of a pulp normally is not critical. That is, the solids normally will drop or plunge to the bottom quite readily, and the liquid separates itself from these solids so as to overflow the basin in a relatively clear condition. When clarification or removal of finely divided particles is to be accomplished, the flow patterns in the basin are extremely important. The velocity of the incoming stream must be dissipated and the liquid flow distributed ]In the tank so that the feed is not divided into streams that flow directly to the overflow carrying the fine:ly divided solids that are to be removed. Similarly, the configuration of the arms that provide the raking and thickening of the pulp is not as important in basins primarily devoted to clarification. In thickening, the design of the arms and the manner in which the pulp is moved or worked, can contribute appreciably to the thickening process and achievement of a higher density underflow. THICKENING As the grade oi ore bodies throughout the world generally decreases, and chemical processes, hydro-metallurgy, and other more refined methods of minerals beneficiation are required, problems in thickening become more acute. Difficult operating conditions, previously encountered only occasionally in thickening metallurgical slurries, or clarifying process streams in the mill, are now the rule rather than the exception. Fig. 1 illustrates some of the different types of raking arms that are successfully achieving the desired goals in pulp thickening. The conventional raking arms consist of a relatively simple truss with the blades attached to the bottom chords. This design provides proper Concentration of many 'normal' slurries. A modificaiion of this design as shown in the center is being used with excellent results on large thickener basins where it is desirable to have a

Jan 1, 1962

By John J. Reed

Great strides have been made during the past few years in the field of rock mechanics, and steps have been taken to implement our newly acquired knowledge to advance the mining industry and improve the lot of the miner. This article is a summary of the latest progress in those areas of rock mechanics indicated by the subtitles. Let's look at these new tools for mining men. GROUND STABILITY DETERMINATIONS Much valuable information in the field of rock mechanics can be obtained by relatively simple, inexpensive measurements and observations, and this kind of investigation can be classed under the general heading of "Ground Stability Determinations." The instrumentation involved in this type of work is relatively simple and inexpensive, and its operation is not difficult to understand.1,2 Precise deformation measurements accurate to a few thousandths of an inch are very helpful in detecting stope convergence, pillar compression, floor heave, etc. Such measurements recorded over a period of weeks and months will detect and forwarn against failure of the overall mine structure long before any other visual evidence can be observed. Such advance warning then permits the introduction of sufficient artificial support in time to do some good. Instead of precise measurements which must be made with a special instrument, sensitive warning lights can be used which will flash red upon sensing movements as small as .002 or .003 in. These devices are well received by miners, and very practical under noisy conditions. High precision is important tit this area, but in large openings, engineer's tapes plus machinists scales reading to .01 in. may be sufficient. Uniform tensioning of the tape is of course essential. Long term, precise measurements have shown repeatedly that opening convergence lends to be slow and uniform except when accelerated to sudden large displacements by blasting, rock bursts or other sudden large scale failures. It is interesting to note that measurements in South Africa in very deep mines have shown 40% of the closure was footwall rise, and only 60% was hanging-wall sag.

Jan 4, 1962

By P. Shahinian, J. Weertman

Minimum creep rates of nickel samples were measured in the stress region of 2.5x107 to 2.8xl0 dyne per sq cm and the temperature region of 400° to 1100°C. The creep rate seems to be proportional to (stress) at stresses below 7x10H dyne per sq cm. The activation energy of creep is approximately 65,000 cal per mol. IN a recent theory' of steady-state creep which is based on Mott's dislocation climb mechanism, the following creep equation was derived for creep in polycrystalline metals (if where K is creep rate, Q the activation energy of self-diffusion, S the entropy of activation of self-diffusion, L' the grain size, L the subgrain size, b the length of the Burgers' vector of a dislocation, u the shear modulus, u the stress, a the critical shear stress, M the density of active Frank-Read sources, v the vibrational frequency of a vacancy, and kT has its usual meaning. This equation predicts a creep rate which depends on the stress through a power law at low stresses. At high stresses the creep rate increases much more rapidly with stress. The theory breaks down for stresses great enough that the inequality holds true. It was the purpose of the present in-

Jan 1, 1957

By C. H. Jr. Herty

ALMOST every metallurgist who has given the Howe Memorial Lecture has had a personal contact with the distinguished gentleman to whose honor this hour is devoted. Unfortunately for me, such personal contacts were not possible. However, in the preparation of a thesis on the open-hearth process, one of my earliest tasks was to make a survey of the literature, and it was from Professor Howe's Metallurgy of Iron and Steel that I drew a number of references to previous work which formed the foundation for my reading. In his volume there is such a complete exposition of the then current thought on the subject of slags and on their role in the elimination of phosphorus from steel that I feel no hesitation in discussing in this Howe Lecture the subject of "Slag Control." In the present era of close specification, the drive for uniformity of product, and the close inspection of the product and of the cost sheet, the utmost efforts must be made to control the steelmaking variables to the best advantage of the steel producer. One of the major variables is the slag in the furnace and its effect upon the composition and quality of the metal. What advantages are to be gained from slag control? In the broad sense the advantages must be tremendous, because the very foundations of good steel melting are based on "shaping up" the slag to a point where, with proper temperature, the heat is ready for the final additions. Every melter works toward these ends through his experience with innumerable heats of steel. The elimination of undesirable constituents such as phosphorus and sulphur is entirely a matter of slag composition and physical nature, a point well known for over half a century. The role played by the slag in assisting in proper heat transfer from roof and flame to the steel has been equally well known. In more recent years there has come the problem of oxygen control in the more accurate gaug-ing of additions for making high-grade rimmed steel for the new strip mills, and in the deoxidizing additions for grain-size control and cleanli-ness of forging steels, both carbon and alloy. In this problem the oxidiz-ing characteristics of the slag are of prime importance.

Jan 1, 1940

By W. M. Peirce, R. K. Waring

Zinc of high purity offers definite advantages in certain fields. A process by which zinc of 99.99 + per cent purity is produced by pyro-metallurgical methods is described in this paper. The process consists of a fractional distillation following the primary reduction; this fractional distillation employs the principles of rectification for the separation of lead and other high-boiling impurities and cadmium and other low-boiling impurities. Theoretical Considerations Involved in Production of High-purity Zinc by Distillation Fractional distillation, fractional condensation, and rectification are recognized methods of separating mixtures of liquids. In the field of organic liquids these methods are widely used but not commonly to effect as complete a separation of liquids as is done in the problem under consideration. Zinc boils at 905" C., cadmium at 778" C. and lead at about 1620" C. Zinc may contain from several hundredths of one per cent to over one per cent each of cadmium and lead, and the problem is to reduce these impurities to a few thousandths of one per cent. For lead and zinc, the spread in boiling points is substantial, 715° C., while for zinc and cadmium it is only 127" C. The basic limitation of any separation by distillation may be found from the relation between the equilibrium composition of the vapor and the liquid for all mixtures of the two substances involved. If a mixture of constant boiling point is found, or if a stable compound that vaporizes without dissociation occurs, there is a definite theoretical limit to the degree of separation that is possible when operating at atmospheric pressure with respect to that mixture. Otherwise, any degree of separation is theoretically possible. The equilibrium composition of vapor in contact with liquid mixtures of zinc and cadmiurn at the boiling point has been determined experi-

Jan 1, 1937

By L. A. Walker

DURING the past twelve years the underground shaft of the United States mine at Bingham has been sunk an additional 2000 ft. with stations and pockets cut every 200 ft. without interrupting the mining of 600 tons of ore per day and the advancing of 1500 ft. of development per month. Following is a brief description of the way the joint work is conducted. The vertical underground shaft is a three-compartment shaft with outside dimensions of 6 ft. 4 in. by 15 ft. 6 in., and inside dimensions for each compartment of 4 ft. 2 in. by 4 ft. 8 in. The manway compartment of the main shaft is used as the hoisting compartment in sinking operations; it is partially lined with 2 by 12-in, lagging and a bucket is used without guides or crosshead. Preparatory work includes the placing of a bulkhead in the manway compartment, 60 ft. above the lowest station or level, the installation of a hoist, a head sheave, a fleet sheave, a-signal system, air and water lines, and a trap door for handling waste.

Jan 1, 1937

The meeting of the Institute at St. Louis brought together many members of the Women's Auxiliary, and Mrs. Philip N. Moore, who was nominated as the Director for the St. Louis Section, took the occasion formally to inaugurate the organization in that district. A meeting was held at the Planters Hotel, anti after discussion as to, the aims and objects of the. Auxiliary, officers were nominated for the' Section; the meeting then adjourned for two days, to he resumed in Joplin.. Here a very successful meeting was held, at which the Vice-Chairman, Secretary, and Treasurer were elected. A great deal of interest was arouse under the able directorship of Mrs. Moore the St. Louis Section is likely to become a large and active organization. The president of the Women's Auxiliary, in opening the meetings, told the ladies present of the inauguration of-the-Society in February, 1917, and of the work which had been accomplished up to date. She told how the Society devotes itself to patriotic and humanitarian work along lines acceptable and interesting to the Mining Engineer, standing always alongside and behind the men of the profession. The Central Welfare Committee of the organization has three Sub-Committees: Foreign Relief, Emergency, and Americanization, and under one or other of those heads most of the work of the' Society has been done. Mr. Hoover was responsible for the inception of the Foreign Relief Committee, as its first work was the collection of funds for the supplementary meals for the Belgian Children. Under the energetic administration of Mrs. H. Knox, this sub-committee raised $12,100 in the period between the February meeting and the Declaration of war by the United States, when our government took over the entire duty of feeding starving Belgium. The organization of the Belgian Relief Committee, as it was styled, still remains, but the members are now asked to take up the question of relief in France. The President, Mrs. S. J. Jennings suggested at the St. Louis meetings that one way of working for the foreign relief alight be that all the members of the Auxiliary should, during the period of the war, forego all giving' and receiving of Christmas presents, except those they have been accustomed to give to the poor or in charity, and those they would give to the men in the services of the United States; that the money usually spent on the Christmas gifts should be put into a fund to be sent abroad for the fatherless children of France, as a gift from the families of the Institute. A good deal of discussion followed this proposal, as some of the ladies felt that children should have their Christmas gifts as usual. The Director of the Section emphasized the truth that the Christmas spirit was the .spirit of giving and sacrifice, and that no sacri-

Jan 1, 1918

By H. A. Kuhn

THE Pittsburg coal field in western Pennsylvania, is conceded to be the most important in the world. To measure its importance it is necessary to understand the extent of its service in the various industries of the country. Probably 90 per cent. of the pig iron manufactured in the United States up to the present time has been made by using coke manufactured from the Pittsburg coal seam in western Pennsylvania. This coal field is the foundation on which the city of Pittsburg rests and is the reason for the great growth of the iron industry in the Pittsburg district. Iron ore is brought to this district, not because Pittsburgh is a. natural location, over other locations, for the iron and steel industry-as its position places the manufacturer at the mercy of the railroads-but the ore is brought 1,100 miles to meet the fuel. It can be said that the illuminating-gas industry in the United States has used this coal exclusively to the same extent that the pig-iron maker has used it. It may be also said that 20 to 25 per cent. of the fuel used on railroads in the United States conies from this coal field. The Pittsburg coal field is unquestionably the center of the industrial population of the United States, for in addition to the industries of the district and those closely adjoining, it has tributary to it all the cities and industries along the Great Lakes and practically all of Canada with the exception of the extreme western and eastern ends. It supplies the industries and population west of Duluth and Superior many hundreds of miles. This coal is floated down the Ohio and Mississippi rivers, supplying the towns en route, and is delivered in New Orleans, a distance of 2,200 miles, for approximately SO to 90 c. per ton transportation cost. It is delivered on the docks of Superior and Duluth at a cost of transportation 50 c. a ton less than the cost of transporting the same coal from Pittsburg to a local consumer in Philadelphia. With other Appalachian coals it has large markets east and along the seaboard, especially for byproduct-coke making and the illuminating-gas industry. It is considered the premier railroad fuel of the world on account of the fact that this coal in a given-sized locomotive will probably haul more cars than any other coal in the

Jan 10, 1914

Rossiter Worthington Raymond, Ph.D., LL. D-1840 to 1918.-Dr. Rossiter W. Raymond, Past President, Honorary Member and Secretary Emeritus, died suddenly of heart failure at his home, 123 Henry'St., Brooklyn, N. Y., on the evening of Tuesday, Dec. 31, 1918. He was one of the founders of the Institute and its second President. A Memorial 'Service will be held on Monday afternoon, Feb. 17. James Douglas.- The Institute suffered a second very severe loss by the death of Dr. James Douglas, Honorary Member, Past President (having served as President for two years), and in three separate respects the greatest benefactor of the Institute: first, in raising funds by volun¬tary subscription and his own personal gifts to pay the Institute's share of the money owed on the land on which the Engineering Societies Build¬ing now stands; second, as original donor to Engineering Societies Library; and third, by his bequest of $100,000 for the maintenance of the library of the American Institute of Mining Engineers. A resolution regarding the death of Dr. Douglas was passed by the Board of Directors and at the meeting of the Institute on Sept. 4, 1918, in Colorado, at which time a memorial service was held in the thea¬ter of the Hotel Broadmoor, attended by about 400 members and guests. A copy of the resolution was prepared and sent to the family. A bronze tablet is now being prepared and will be placed in the Members' Room and unveiled at the February meeting. A biography and portrait of Dr. Douglas was published in the September, 1918, Bulletin. There is also placed in the Engineering Societies Library an oil portrait of Dr. Douglas which had his own approval and was presented by him. American Institute of Metals.--During the Spring of the year, plans were completed with the American Institute of Metals whereby this society became the Institute of Metals Division of the American Insti¬tute of Mining Engineers. This body was a dignified aggregation of metallurgists which had been in existence for about 11 years. A bronze tablet commemorating the American Institute of Metals is now being placed in the Members' Room of the Institute, and during the year 1919 the Bulletin will bear the following title: "Bulletin of the American Institute of Mining Engineers, with which is consolidated the American Institute of Metals." Visits to Local Sections.-During the year President Jennings made visits to six of the Local Sections, on three of which occasions he was accompanied by the First Vice-president and the Secretary. First Vice-president Goodale made five visitations and the Secretary made eight.

Jan 1, 1923

By R. F. Mehl, B. Lustman

The formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.' It is necessary here only to cnumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type—i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained—the isothermal growth of the phase follows a simple parabolic equation: X2 = kt [i] where X is the thickness of the alloy layer, k thc reaction rate constant, and t the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such a plot has been considered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.$ In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varics with temperature according to the Arrhenius equation: k = Ae-Q/RT [2] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. Ali phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase.4 The reaction layers tend to have a

Jan 1, 1942

By R. F. Mehl, B. Lustman

The formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.' It is necessary here only to cnumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type—i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained—the isothermal growth of the phase follows a simple parabolic equation: X2 = kt [i] where X is the thickness of the alloy layer, k thc reaction rate constant, and t the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such a plot has been considered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.$ In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varics with temperature according to the Arrhenius equation: k = Ae-Q/RT [2] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. Ali phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase.4 The reaction layers tend to have a

Jan 1, 1942

By J. G. Y. Chow, S. B. McRickard

The tensi1e properties of Ferrovac iron have been studied from 4° to 300°K. The stress required for macroscopic yielding was found to he constant below approximately 50°K. The effect of mechanical twinning on this low -temperature stress plateau was investigated. The onset of twinning occurs in this iron between 130° and 150°K and depending on its previous thermal history the twinning-stress curue may drop below or remain above the vield-stress curves as the temperature is lowered. Twinning has been shown to initiate slip in quenclzed iron at low temperatures. In no instances, however, did the onset of twinning alter the continuity of the yield stress -tempwature curve. Our data shows that carbon inhibits twinning and slip at low tem-peratures. This observation nay be used to explain the ductile-to-brittle transition in iron. The effect of fast neutron irradiation on yielding and embrittlement in iron and Fe-C alloys is offered as supporting evidence for this viewpoint. THE mode of yielding in iron at low temperatures was studied in an attempt to find an expression based on a single mechanism to describe the thermal dependence of the yield stress of iron. There are two types of inflections observed in the variation of the yield stress with temperature in iron and Fe-C alloys. The first is associated with ductile behavior and consists of a region extending 50" to 100°K above absolute zero in which the yield stress is independent of temperature. The second is observed in more brittle materials such as Fe-C alloys and irradiated iron and consists of an abrupt discontinuity in the yield curve as the temperature is lowered through a ductile-to-brittle transition point. The temperature dependence of the yield stress for iron with four grain diameters as found in this study is shown in Fig. 1. To varying degrees all the curves appear to flatten or approach an asymptotic value as the temperature is lowered below 50°K. Several other investigators1,2 have observed a plateau in the yield stress of iron and steel at low temperatures and in 1956 Louat3 presented a theory which contained an explanation for this behavior. In a subsequent exchange with Erickson and Low4'5 who attributed the plateau to the onset of mechanical twinning Louat8 showed that twinning first occurs in iron and steel tested in tension at temperatures as high as 140°K which is well above the observed plateau in yield stress. Furthermore he pointed out that both twinning and slip are basically dislocation processes and that with modified parameters his original theory still applied when deformation is initiated by twinning. Variables which affect the ductile-to-brittle transition in iron are test temperature, strain rate, composition and grain size.7 LOW,8 Hahn et al.,9 and Hull10 have provided evidence which links brittle fracture at a given temperature with the specimen grain size and the onset of twinning. In fact, Hull equates the brittle fracture stress to the twinning stress. On the other hand brittle fracture has been observed in the absence of twinning and priestnerl1 has given a fracture criterion which is valid whether or not fracture is preceded by extensive twinning. The data presented here clarify the role of twinning in the low-temperature deformation of iron. Strong evidence is given that the amount and distribution of interstitial impurities such as carbon are of

Jan 1, 1965

By F. H. Wilson, R. M. Brick

With the papers of Palmer and Smith1 and of Burghoff and Bohlen,2 published in 1942, understanding of the problem of the development of ears on deep-drawn brass cups was brought to the point where, from a practical standpoint, producers of brass sheet could keep earing under control. However, these very practical results raised questions concerning the reasons for the observed behavior. Since plastic deformation is fundamentally a function of crystallographic slip, these reasons must be considered in the light of the textures to be found in the annealed sheet. Various attempts have been made. to interpret the mechanism of ear formation by correlation with the preferred orientation and the anisotropy of the sheet. However, none of these has satisfactorily explained why ears are usually found in the rolling and transverse directions for copper but at 45' to these directions for brass. This paper offers additional data on these two related subjects and has been divided into two sections The first section provides a survey of the recrystallization textures of brass as affected by annealing temperatures and prior reductions, and an account of the caring behavior which accompanies these textures. The second section reports new data on the anisotropy that accompanies a characteristic texture for brass and endeavors with partial success to establish the factors that account for the difference in earing behavior between copper and brass Earing BehavioR oF Brass Review of Textures The recrystallization texture of severely rolled brass was first reported by Bass and Glocker.3 The preferred orientation to which this texture, obtained from metal annealed at 500°C., was most akin was (II3)[I12] This texture has been confirmed by Bauer, von Göler and Sachs;4 Brick;' Brick, Martin and Angier;6 and Cook and Richards7 who, in general, used annealing temperatures under 500°C. Bass and Glocker3 also reported the recrystallization texture at 850°C. to be the same as at 500°C. They analyzed their textures by means of single photograms obtained with white radiation. The photo-grams for both temperatures are reproduced in their paper, and there is a strong similarity between the two. However, for the latter temperature, the number of spots registered on the film was remarkably large for the grain size to be expected, and the authors made no mention of using a technique that would integrate a large enough area of the specimen to produce so many spots. The only other attempt to determine textures resulting from high temperature

Jan 1, 1945

By S. Senderoff, D. E. Couch

A PROCESS for the electrolytic preparation of molybdenum from molten salts has been described previously. This previous work centered on electrowinning and electroplating characteristics of the process. In this paper the properties of the process as a refining medium are discussed. In producing metals from ores, it frequently has proven most economical to obtain a comparatively impure metal by smelting, and to purify the product by electro refining. Direct electrowinning from molten salts is rather difficult when a porous diaphragm is required in the process, as in the case of molybdenum, since satisfactory refractory materials for such a diaphragm in molten salts have not yet been developed. In electrorefining, however, a soluble anode is used. By suitable control of anode and cathode current densities, the lower-valent molybdenum compound used in the electrolyte is not oxidized, and a diaphragm is not needed, thus avoiding difficulties which are encountered with other electrowinning processes. Electrorefining may result from two different processes in the cell: Dissolution of the molybdenum and the less noble impurities with a separation of the more noble impurities as an anode sludge; the electrodeposition of molybdenum and the more noble metals at the cathode, leaving the less noble metals in the electrolyte. The amount of separation which occurs in each process is determined by the potential of the operating electrode and the relative concentration of the various species at (or in) that electrode. Since molybdenum has a comparatively noble position in the EMF series in molten alkali halides,2 most refining would be expected to occur at the cathode. In this work only the cathodic process was studied. The objective was to determine to what extent various metallic ions, if they dissolve from the anode or are otherwise introduced, were concentrated in the electrolyte. The necessary conditions for the separation of each and the limiting concentration which may be tolerated in the electrolyte for effective refining were studied. The deposits were chipped from the cathode and analyzed spectrochemically for metallic impurities. Besides determining the major contaminant, a general qualitative analysis was obtained to be sure that other metallic ions were kept at a very low level during each series of runs and to be sure that the baths were not being contaminated accidentally. Samples of the bath, for analysis, were taken at the temperature of operation so there was no chance of selective crystallization during cooling. In this way the ratio of molybdenum in the bath to the other metal could be determined readily. These data permitted a check on the anode efficiency and any volatilization that took place during the electrolysis. Experimental Apparatus—The apparatus as shown in Fig. 1 was used to determine the effect of the various foreign ions upon electrodeposited molybdenum. The entry chamber A allowed the cathodes to be removed without cooling the bath and without allowing oxygen or moisture to enter." The cathodes were made Prom 0.25-in. tungsten rods and were rotated during the electrolysis. The balloon in the lower arm B was inflated with helium after the cathode was drawn up into the upper section for removal. A new cathode was then placed into the entrance chamber A after which the chamber was flushed

Jan 1, 1959

By B. M. Larsen

A discussion based on three commercial furnace tests and electrical analogue calculations is presented. It shows that while regenerator efficiency is mainly dependent on loading or relative amount of heat exchange surface plus the heat transfer coefficients as effected by flow velocity, the actual air preheat temperature can be high or low, largely independent of regenerator efficiency, mainly due to the diluting or unbalancing effects of cold air leakage into various parts of the furnace system. THERE are many signs of a renewal of interest in the heat regeneration aspect of the open hearth process, among them being the recent paper by Marsh,' the introduction of auxiliary checkers in the stacks of the Isley furnace design, and a number of recent installations of two-pass checkers in new and old furnaces. However, there are also signs of yielding to the usual temptation of oversimplifying a problem. Faced with the job of obtaining better draft on a furnace, for example, a good designer always recognizes that focusing attention on some one factor, such as height of the stack or capacity of the exhaust fan, does not make his problem any easier; rather he must look at the whole system, including such items as valve resistances, bends in the flues, and flow resistance in the waste heat boiler; then he must make his design in relation to the available draft so as to avoid any serious bottleneck in the system. Yet this example is really much simpler than the problem of air preheating, and again, the latter problem is not really made easier by concentrating on air temperature in uptakes and on the more obvious methods for making this air as hot as possible. Also to be considered are such things as the total amount of air needed theoretically for complete combustion at any selected fuel rate, together with that needed for oxygen absorbed into the bath and for burning the combustible gases given out from the bath, plus some excess air. Furthermore, how does this total air requirement relate to the regenerator efficiency at various loadings? How much of the total air equivalent in stack gases will come from preheated air passed through the whole length of the incoming regenerator and how much from air leakage into various zones of the whole furnace system? Does the effect of leakage air differ depending on whether it leaks into the ingoing regenerator, the furnace above floor level, the outgoing regenerator, or the stack zone? Over a number of years we have in this Laboratory experimented with methods for measuring hot gas temperatures; we have measured, approximately, the efficiency of a few regenerators on commercial furnaces and we have developed an electrical analogue' for calculations of regenerator efficiency. The whole problem is too complex to cover in one paper even with a more complete background of data than we possess, but we can attempt here to clarify certain aspects in a general way, hoping to assist specific plant studies on individual furnaces. Some of our earlier experience has been incorporated into chaps. 4, 19, 20, and 21 in the book "Basic Open Hearth Steelmaking,"" and on the assumption that this text is available to most readers, this discussion has been shortened by references to that book. The most recent design of a flowing-gas thermocouple which we are now using for measurement

Jan 1, 1955

By H. A. Guess

Introduction. History and Production Statements. Southeast Missouri is the oldest of the large producing districts of the United States. The first recorded production from disseminated ores was in 1869, although for many years prior to that time lead had been milled from shallow pockets, and steady growth in production has been shown ever since, the greatest increases being during the past five years. The production by years for each of the operating companies from 1869 to 1907, inclusive, is given in Table I. In Table 11. is given the production by years from 1908 to 1912, inclusive, for the district as a whole, showing the tonnage of crude ore mined, yield in concentrates, average assay of concentrates; yield in metallic lead both per ton of crude ore and in total; also approximate value of the yearly production. It is interesting to note that the production for the 5-yr. period 1908 to 1912, inclusive, is practically equal to the total previous production, viz., the 39-yr. period 1869 to 1907, the summary being as follows:

Jan 1, 1915

By L. J. Ingvalson, Roy H. Miller

IN 1948, as part of a program to expand the copper tube mill facilities of the American Brass Co. plant at Kenosha, Wisconsin, plans were formulated to convert the 100 ton capacity anode casting furnace at the Great Falls, Montana plant of the Anaconda Co. to the production of 3 in. phosphor -ized billets. The furnace was rebuilt completely and construction was started on an addition to the building. Members of the Great Falls staff visited various billet casting plants to draw upon the experience of other producers of this type of casting. Many features of other plants were incorporated into the Great Falls plant but, in addition, many new designs were made and perfected to make the plant the most advanced of its type. Construction was begun in 1949, with the intention of having the plant in production in the early part of 1951. In January 1951, as the plant was being rushed to completion, the government placed restrictions on the production of copper tubing. As a result, work was halted and the plant lay idle for two years. Interest was reactivated in May 1953 with the lifting of restrictions on copper. Plans were laid to go into production in July and the first charge was taken out July 1, 1953. Basically the plant is designed to produce from cathode copper a 3 in. diam billet, 50 in. long. weighing 110 lb, and containing 0.013 to 0.036 pct P, at a rate of 150,000 Ib per operating day. These billets are to be pierced and drawn into tubing. Furnace The furnace is a 100 ton capacity reverberatory type, gas fired furnace; 21 ft long and 9 ft wide. Gas is introduced to the furnace through two 38 hole Mettler gas burners. These burners are of chrome nickel alloy with four jets per hole. The furnace is charged with cathodes from the Electrolytic Copper Refinery plus return scrap from the casting operation by means of a Wellman Seaver Morgan Co. 7,000 lb capacity charging machine. The charge crane has a 20 ft boom and fork peel provided with an air ram to push material off the peel. The machine travels on overhead tracks and can be moved in any direction. The boom can be raised and lowered and swung through an arc of 180". With well stacked units of 6,000 lb, an experienced operator can put the first charge into the furnace in 40 min. After charging, the steel framed silica brick charge door is put in place and sealed with clay. After melting and skimming off the slag, the copper is blown until an oxygen content of 0.40 pct is reached. The metal is then heated to 2180°F, covered with coke, and poled. Poling is continued until a 3 in. diam test billet, 8 in. long, shows a flat set. The oxygen content is usually 0.030 pct at this time. At the end of poling, a temperature of 2160" to 2180°F is desired. In the side of the furnace opposite the charging door is the taphole slot, extending 36 in. upward from the bottom of the furnace. It is 4½ in. wide at the outside face and widens to 9 in. at the inside face of the furnace. It is filled with a wet mixture of sand, fireclay, and crushed coal. Flow of metal

Jan 1, 1957

By R. H. Hiltz, R. W. Douglass

Large-grain specimens of iodide titanium prepared metal-lographically were stain etched using the technique of New York University as modified by Watertown Arsenal Laboratories. Orientations of grains showing an abnormal response to stain etching were determined by back-reflection X-ray techniques. X-ray results showed that a-titanium grains, oriented such that their basal planes were parallel to the polished surface, have a slower reactivity to stain etching than any other orientation. Grains oriented such that their basal planes made small angles with the polished surface exhibited reaction rates between that of the true basal orientation and the normal rate. As the angle with the surface increases the reactivity increases up to a maximum angle of 14 deg. Basal planes making an angle with the surface of greater than 14 deg show normal reactivity to stain etching. These data, plus work on polycrystalline specimens, indicate that the oxidation rate of titanium might be reduced by correct alignment of crystal planes. ThE earliest observed phenomenon in the micrography of titanium was the occurrence of a grains which exhibited no birefringency. Even though a titanium possesses a hexagonal-close-packed structure and should be optically anisotropic, it can appear optically isotropic, when the crystal is so oriented that its intersection with the polished surface is perpendicular to the axis of symmetry. During the develoment of color staining techniques for titanium: it was noted that the a phase did not stain uniformly. Staining of specimens of commercially pure titanium resulted in a micro-structure of blue-colored grains, among which were randomly oriented a few grains exhibiting colors between the initial yellow and the final blue color. Under polarized light, these off-colored grains appeared to be optically isotropic. More intense study with polarized light, however, showed only the yellow grains to be isotropic. The intermediate colored grains exhibited weak birefringency, which at first glance is not detectable due to the strong birefringency of the surrounding structure. Aminoff2 and Straumanis3 have previously shown that in zinc the basal orientation is less reactive than other orientations. Leidheiser4 showed the same thing to be true for the hexagonal-close -packed configuration of cobalt. Thus, it would appear that the basal-plane orientation is responsible for the abnormality in stained titanium. Later work by Leidheiser5 on cobalt has shown that other planes besides the basal plane exhibited reaction rates slower than the normal rate. Reported planes were the (100), the (1011) and several planes making small angles with the basal plane. The last observance appears not to be due to the reactivity of the reported plane but due to the reactivity of the basal plane which is very close to being parallel to the surface. There are, then, two possible explanations for the range of colors observed in stain-etched a titanium. Since extensive research on the effect of orientation on surface reaction has failed to provide any definite trend, these two explanations are not adequate in themselves. Planes showing the retarded reactivity differ not only for different crystal structures but for metals of the same crystal structure and even for different reactions of the same metal. Tragert,6 Leidheiser,7 Tammann,6 and wagner9 have shown copper to exhibit retarded reactivity on the (111) plane. However, Leidheiser10 has shown that under other conditions the retarded reactivity of copper is associated with the (100)

Jan 1, 1960

Report of the Secretary TO THE BOARD OF DIRECTORS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS Gentlemen:-To a Board of Directors keeping in as close touch with all of the affairs under their care as do the Board of Directors of the A. I. M. E., through their monthly meetings, a report of the year's progress is almost superfluous. To the members who read the monthly reports of. the Board Meetings and of the various activities of the Institute as published each month, a yearly report cannot carry much fresh information; yet for both it may be well, as is the custom, to glance over the field of our activities during the past year, and to make an estimate for the year to come. The beginning of 1924 was not propitious for the members of the mining profession, though tonnage production for 1923 had been high and the gross value higher than for several years. The margin of profit had been narrow, prospecting and development were limited, and many of our members were unemployed, or were working in other industries. Toward the end of the year, higher metal, prices were in sight. Old-time optimism began to grow, and it now brightens the outlook for 1925. An excellent barometer of the prosperity of the industry, and that of the Institute, for they go hand in hand, is the work of our Employment Bureau. During the past few months, the percentage of our members for whom openings have been found has been increasing to a marked extent, and many members who had fallen in arrears are placing themselves in good standing. The number of new members joining has remained about as it was in 1922 and 1923. The Directors have reason to congratulate themselves on the interest maintained during a dull period, for it is not humanly possible to take a keen interest in the technology of an industry when our hands and minds are not actively engaged in it Now, with a much brighter outlook, we can look forward to a year of increasing prosperity for the industry and for the Institute.

Jan 3, 1925