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By G. E. Steudel

The study of the possibility of effecting a lower cost in the manufacture of pig iron reveals the importance of the ever present question of slag chemistry and volume. Factors that determine slag chemistry and volume are the impurities in the ore available, the ash-sulphur content of the coke, and a flux material necessary to promote removal of sulphur. Of these, the ores present by far the major source of impurities and what may prove to be the lowest practical slag volume with desired chemistry in one locality may be considered low or high in some other center of iron manufacture. The Chicago district is not only blessed with ores of high quality, but with excellent coke and flux materials as well. It is the intent of this paper to discuss slag problems at the South Works only, where burdens consist of Mesabi ores, Michigan stone, and coke ranging from 7 to 9 per cent ash and containing an average of 0.57 per cent sulphur. Early in the development of modern blast-furnace practice, the consideration of slags was secondary to the many adjustments of mechanical difficulties, such as furnace lines, stock distribution, stove design for obtaining higher blast temperatures, improved chemical segregation and size of raw materials. Furnace operators, after making these improvements, turned their attention to the study of other refinements in practice, of which slag chemistry appeared to be the most important. It is only within the last two decades that operators have become familiar with the various aspects of slag compositions. The industry, while rather slow in its recognition, is indebted to such investigators as Rankin,1 Wright,1 Feild,2 Royster,2 McCaffery,3 Kinney,4 Holbrook,5 and Joseph,5 whose researches concerning the elimination of sulphur within the blast furnace and the effect of slag composition upon melting point, viscosity, and desulphurizing power have established criteria for the selection of slags of the requisite quality. Large slag volumes result in higher coke consumption and cost of disposal. Any attempt to lower slag quantity must be accomplished

Jan 1, 1940

By G. E. Steudel

The study of the possibility of effecting a lower cost in the manufacture of pig iron reveals the importance of the ever present question of slag chemistry and volume. Factors that determine slag chemistry and volume are the impurities in the ore available, the ash-sulphur content of the coke, and a flux material necessary to promote removal of sulphur. Of these, the ores present by far the major source of impurities and what may prove to be the lowest practical slag volume with desired chemistry in one locality may be considered low or high in some other center of iron manufacture. The Chicago district is not only blessed with ores of high quality, but with excellent coke and flux materials as well. It is the intent of this paper to discuss slag problems at the South Works only, where burdens consist of Mesabi ores, Michigan stone, and coke ranging from 7 to 9 per cent ash and containing an average of 0.57 per cent sulphur. Early in the development of modern blast-furnace practice, the consideration of slags was secondary to the many adjustments of mechanical difficulties, such as furnace lines, stock distribution, stove design for obtaining higher blast temperatures, improved chemical segregation and size of raw materials. Furnace operators, after making these improvements, turned their attention to the study of other refinements in practice, of which slag chemistry appeared to be the most important. It is only within the last two decades that operators have become familiar with the various aspects of slag compositions. The industry, while rather slow in its recognition, is indebted to such investigators as Rankin,1 Wright,1 Feild,2 Royster,2 McCaffery,3 Kinney,4 Holbrook,5 and Joseph,5 whose researches concerning the elimination of sulphur within the blast furnace and the effect of slag composition upon melting point, viscosity, and desulphurizing power have established criteria for the selection of slags of the requisite quality. Large slag volumes result in higher coke consumption and cost of disposal. Any attempt to lower slag quantity must be accomplished

Jan 1, 1940

By Samuel G. Lasky

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

By Samuel G. Lasky

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

By Samuel G. Lasky

The writer has been interested in determining the mineralogic dis-t,ribut.ion of silver in the base-metal ore of thc Ground Hog mine of the Asarco Mining Co. in the Central mining district of New Mexico.' This ore consists of a varitextured mixture of sphalerite, chalcopyrite, galena and pyrite in a quartz gangue. The average ore contains 14 per cent of zinc, 9.5 per cent of lead, 5 per cent of copper, and 10 oz. of silver per ton. Generally it is accepted that the silver in ores of this type, in which no definite silver minerals can be recognized, is contained in the base-metal minerals. Published assays of pure mineral specimens from many districts show that each of the base-metal minerals contributes in some degree to the total silver content of the ores, and to determine the proportionate amount contributed by each mineral in any specific ore it has been the practice to assay selected specimens of each mineral, the purity of which has been determined microscopically. There being no such assays available for the Ground Hog ore, and it being impracticable to have enough of them made to give average results, the writer resorted to a mathematical attack upon composite assays of large quantities of ore and concentrates. Surprising results were obtained, and it is the threefold purpose of this paper to present these results, to describe the mathematical method used, and to point out the value of using this method even when assays of pure specimens are available. Value of the Mathematical Method The obvious way of attacking the problem would be to separate cleanly large quantities of ore into its component minerals and then to determine the average silver content of each mineral by assay of representative samples. Since an absolutely clean separation is not feasible, it has been the practice, as mentioned above, to assay pure specimens of the different minerals. No one will contend seriously that the silver content of a base-metal mineral is constant throughout any particular deposit, and it will

Jan 1, 1935

By Charles Y. Clayton

Cast-steel runners, while not interesting from a commercial standpoint, furnish valuable material for microscopic study. Folcyl found not only the usual ingot structure, but zones of Widmannstättian structure, which he explains as due to differential crystallization. The writer, in examining nickel-steel runners, found a type of pro-eutectoid ferrite that is unusual and most probably new. The runner in question was 8.75 cm. (3.5 in.) in diameter and analyzed at its center 2.69 per cent. nickel and 0.350 per cent. carbe a and at its edge 2.62 per cent. nickel and 0.359 per cent. carbon. Th macrostruc-ture, which is the usual type, is shown in Figs. 1 and 2, which are a cross-section and the longitudinal surface, respectively. Slight segregat'ion of ferrite can be seen near the center of the segment and at other points near the edges of polyhedral grains. Stead's reagent brings out the dendritic structure within the grains as shown in Figs. 3 and 4. This texture is what would be expected of such a steel. Figs. 5 to 10 show the peculiar swirls of pro-eutectoid ferrite, the finding of which prompted this paper. These swirls, or eddies, if such a term can be applied, occur in all parts of the runner and in all parts of the individual grains. The upper left-hand figure shows this ferrite at a grain boundary; the middle left-hand figure shows the inner portion of a grain; and the lower left-hand figure shows these swirls at the edge of a grain which is also the outer edge of the runner. Straight-lined ferrite associated with swirls is found in the areas of Figs. 11 and 12. The texture of the carbon-bearing constituent of the runner is shown to some extent in Fig. 12, the pearlite being very fine or sorbitic. Higher magnification does not bring out any new features either in the peculiar ferrite or in the pearlite. Figs. 13 and 14, at 240 diameters, show the curved and straight-lined ferrite.

Jan 1, 1922

By Charles Y. Clayton

Cast-steel runners, while not interesting from a commercial standpoint, furnish valuable material for microscopic study. Folcyl found not only the usual ingot structure, but zones of Widmannstättian structure, which he explains as due to differential crystallization. The writer, in examining nickel-steel runners, found a type of pro-eutectoid ferrite that is unusual and most probably new. The runner in question was 8.75 cm. (3.5 in.) in diameter and analyzed at its center 2.69 per cent. nickel and 0.350 per cent. carbe a and at its edge 2.62 per cent. nickel and 0.359 per cent. carbon. Th macrostruc-ture, which is the usual type, is shown in Figs. 1 and 2, which are a cross-section and the longitudinal surface, respectively. Slight segregat'ion of ferrite can be seen near the center of the segment and at other points near the edges of polyhedral grains. Stead's reagent brings out the dendritic structure within the grains as shown in Figs. 3 and 4. This texture is what would be expected of such a steel. Figs. 5 to 10 show the peculiar swirls of pro-eutectoid ferrite, the finding of which prompted this paper. These swirls, or eddies, if such a term can be applied, occur in all parts of the runner and in all parts of the individual grains. The upper left-hand figure shows this ferrite at a grain boundary; the middle left-hand figure shows the inner portion of a grain; and the lower left-hand figure shows these swirls at the edge of a grain which is also the outer edge of the runner. Straight-lined ferrite associated with swirls is found in the areas of Figs. 11 and 12. The texture of the carbon-bearing constituent of the runner is shown to some extent in Fig. 12, the pearlite being very fine or sorbitic. Higher magnification does not bring out any new features either in the peculiar ferrite or in the pearlite. Figs. 13 and 14, at 240 diameters, show the curved and straight-lined ferrite.

Jan 1, 1922

By John Henry Harden

This shaft, located in the northern anthracite coal-field about 2300 feet southwest from the court-house at Wilkes-Barre, in the County of Luzerne, Pa., is the property of the Lehigh & WilkesBarre Coal Company. The sinking and cribbing to the solid rock (see isometrical view on Plate IX) was conducted by Mr. W. W. Kenrick. Dimensions of the earthwork to the foundation of the cribbing, 51' 2" long, 17' 4" wide, 31' deep. Total amount of excavation in cubic yards, 998.5. Dimensions within the permanent cribbing, 45' 4" long, 11' 16" wide, 31' deep, divided into six parts by buttons 8" x 12", each division, 7' x 11' 6". Permanent cribbing 12" x 12"; temporary cribbing 8" x 10" ; backing, 3" thick ; clay puddle to exclude surface water, 12" thick; conductors, 8" x 5"; lining, 1" thick from top to bottom of the shaft. In the latter part of the year 1871, Mr. H. Murray & Son contracted with the company for the continuation of the work at the rate of four hundred dollars per yard in depth, to a point 100 feet below the Hillman seam of coal; for the succeeding 100 feet the price to be increased twenty-five dollars per yard, and so on until the bottom rock of the Baltimore seam of coal was found. The size of the shaft within the cribbing timbers is 45 feet 4 inches by 11 feet 6 inches, having six divisions of equal dimensions, 7 feet by 11 feet 6 inches, giving room for what is known as the "standard diamond " car, whose capacity when level full is 100 cubic feet, but when loaded by the miner 4 inches above the top contains 112 cubic feet." Two divisions of this shaft are intended for hoisting coal from the Hillman seam, two from the Baltimore seam, one for ventilation, and one for pumps. The works were planned for two pairs of direct-acting, high-pressure engines, twenty-four boilers, and for an estimated output of 2500 tons of coal per day from the two seams.

By D. A. Bailey, F. L. Kadey

During recent years, expanded perlite has found extensive use in a wide variety of commercial applications. Specifications for a range of uses call for aggregates having different physical properties and requiring various types of processing. The mitre scopic examination of expanded aggregates in specially prepared thin sections has yielded important information regarding internal structure and can be a useful aid in evaluation of the product. Perlite is an acid volcanic glass containing from 2 to 5 pct combined water. When crushed and rapidly raised to a temperature of 1500° to 2100°F, the volatilization of the combined water, coincident with softening of the siliceous glass, causes the particles to expand or pop. Expansion of perlite to densities as low as 1-1/2 lb per cu ft has been achieved, although the normal range is from about 2.5 to 10 lb per cu ft. Low-density materials of this nature have found application in cryogenic insula- tions, insulating tile and board, plaster and lightweight concrete, soil conditioners, filter aids after comminution, and a host of other uses. The expansion of perlite may be controlled by a number of variables. Some of these are ore milling, furnace design, expanding temperature, use of preheating techniques, screen size distribution, and feed rate of the crude. For the specific intended uses, the art of perlite expanding has developed to the point that much is known about the effect of these variables on the end product. The requirements, however, for an aggregate to be used in plaster are different from those for an expanded perlite to be used in lightweight concrete or for cryogenics. In the study of perlite, many practical questions remain unanswered. One of the most important is, "why do some perlites make hard aggregates while others cannot resist crushing or compaction?" The usual tests and methods for evaluation of nonmetallic substances have been tried and have contributed their share to our knowledge. But chemical analyses, compaction resistance tests, screen analysis, etc., will reveal only a limited amount of information. The answers to these complex questions may well be found in an examination of the intemal structure of the expanded particle. Such questions and the ex-

Jan 1, 1962

By E. P. Pfleider, O. Rellensmann

For many years mine surveyors and exploration engineers have sought an accurate means of transferring meridian underground by using the gyro-compass. These efforts have generally failed, either because they were inaccurate or because the size and cost of the unit were prohibitive. During the past ten years, however, great strides have been made. Autonetics in California has developed a comparatively light-weight (100-lb) gyro-theodolite, and the Institute for Mine Surveying at Clausthal Mining Academy in Germany has developed an instrument that is accurate to within 20" to 30" of arc. Concurrently, Minneapolis-Honeywell has produced an astounding gyro, the size of a salt shaker, that weighs less than 0.5 lb and compares favorably in performance with the 50-lb gyros of conventional design. This unit, designed for missile guidance, should be adaptable for surveying small boreholes. Given the proper interest and approach from the engineering fraternity, excellent gyrocompasses could probably be available for accurate underground survey work at nominal cost within the next three years. Principles of the Gyro-Compass: The gyrocompass, used for 50 years as a navigational instrument in ships and aircraft, senses the turning axis of the earth and points out true polar north. It does this by employing the earth's rotation, the force of gravity, and the precession characteristics of a gyro. For further details the reader is referred to several excellent publications'"3 covering the principles and application of the gyroscope. The heart of the gyro-compass is the gyroscope, or rapidly spinning wheel, which rigidly maintains its angular orientation in inertial space. Free gyros employ universal joints to allow the wheel axle to maintain its rigid spatial orientation independent of base motion disturbances. Free gyros are independent of the earth's turning and are not north-seeking. Only as they might be initially oriented parallel to the earth's turning axis could any north indication be obtained. In practice, the free gyro tends to drift off its set position and lose its accuracy. The Sperry-Sun Well Surveying Co. instrument (5M in O. D.) is of this free gyro type. It is counterbalanced, however, against the rotational effects of the earth, so that orientation of the spinning axis will be maintained throughout the survey.

Jan 1, 1960

By John Birkinbine

(New Haven 'Meeting, February, 1909.) AWAKENED public interest in efforts to conserve natural resources will certainly be appreciated by the members of the American Institute of Mining Engineers, and a discussion upon conservation may well form a part of one of the Institute meetings, for the records of papers and discussions which appear in the 38 volumes of its Transactions are replete with evidence of effort's in this direction. Every process which reduces the fuel consumed or the power applied per unit of product; every utilization of waste material, or employment of that formerly rejected, to obtain something of value ; every feature of construction or operation which lessens the labor required or increases the output per employee, is an advance in the direction of true conservation. This may not appear from the records of late conferences or from published articles, in which the effort seems to be concentrated upon reducing the consumption and presenting to the people of the country estimates of exhaustion of natural resources. I rejoice in the awakening of public interest in a matter so important for the present and future welfare of our nation; I appreciate the possibility of much good following conferences of the Governors and delegates from various States and from national societies; and I recognize the interdependence, not only of different States, but of contiguous nations. In fact, the marvelous development of transportation by land and by water, and the decreasing rates at which commodities can be moved great distances, have in many cases practically obliterated geographical boundaries, and nearly every country on the globe can either market its product in other lands or draw upon them for raw or manufactured materials ; hence, conservation is an international subject.

Apr 1, 1909

By R. A. Vandermeer, J. C. Ogle

The preferred crystallographic orientations (texture) developed in randomly oriented, poly crystalline niobium during rolling were studied by means of X-ray diflraction techniques. The evolution of texture at both the surface and center regions of the rolled strip was carefully examined as a function of increasing defamation throughout the range 43 to 99.5 pct reduction in thickness. Certain aspects of the center texture development in niobium are in agreement with the predictions of a theory by Dillamore and Roberts, but others cannot be explained by the theory in its present form. Above 87 pct reduction by rolling, a distinctly different texture appeared in the surface layers which was unlike the center texture. The present results are compared with previous results obtained from other bcc metals and alloys. RANDOMLY oriented, poly crystalline metal aggregates when plastically deformed to a sufficiently large extent develop preferred orientations or textures. In a recent review article, Dillamore and Roberts1 pointed out that the nature of the developed texture may be influenced by a large number of variables. These include both material variables such as crystal structure and composition and treatment variables such as stress system, amount of deformation, deformation temperature, strain rate, prior thermal-mechanical history, and so forth. From a practical point of view, the control of preferred orientation may often be important for the successful fabrication of metals into usable components. During the past few decades many experiments have been devoted to the study of deformation textures. This work, however, has been confined in large part to metals and alloys that have an fcc crystal lattice. By comparison, bcc metals and alloys have received much less attention, and consequently our understanding of preferred orientations in these materials is only shallow. This state of affairs worsens when it is realized that almost all of our present howledge about this class of materials derives from studies on irons and steels.' The bcc refractory metals, which are relative newcomers to the industrial world, have, on the other hand, been given at best only passing glances in the area of texture development. Our understanding of the evolution of preferred orientations in bcc metals can only remain fairly limited until systematic studies of metals and alloys other than the irons and steels have been carried out and the influence of the many variables has been determined. To that end a program was initiated to investigate in detail texture development in niobium. The present paper reports some of the results of this study. Textures were determined at both the center and surface of strips rolled variously to as much as 99.5 pct reduction in thickness at subzero temperatures. Emphasis in this paper is on texture description and on texture evolution during rolling to progressively heavier deformation. EXPERIMENTAL PROCEDURE The niobium was purchased from the Wah Chang Corp. as a 3-in.-diam electron-beam-melted billet. Chemical analysis indicated the impurities to be less than 300 ppm Ta, 40 ppm C, 10 ppm H, 170 ppm 0, and 110 ppm N. All other impurities were below the limits of detection by spectrochemical analysis. This large-grained billet was fabricated into specimen stock so that a fine-grained randomly oriented grain structure resulted. This was accomplished in three deformation steps alternated with recrystalli-zation anneals of 1 hr at 1200°C in a vacuum of low 10"6 Torr range after each deformation step. The first step was to alternately compress the billet 10 to 20 pct in each of three orthogonal directions. The second step was to compress in only two directions 90 deg apart to produce a 2-in.-sq bar. The final step was to roll this bar 50 pct to give a 1-in. by 2-in. cross section. After the final anneal, metallo-graphic examination showed the material to have an average grain size equivalent to ASTM No. 5 at 100 times (i.e., 0.065 in. diam). Specimens cut from the center and edges of this bar gave no indication of detectable preferred orientation when examined by X-ray diffraction. Samples 1.5 in. long, either 0.625 or 0.750 in. wide, and approximately 0.400 in. thick were machined from this fabricated ingot. The surfaces corresponding to the rolling planes were ground so as to be parallel. The samples were chemically polished in a solution of 60 pct nitric acid and 40 pct hydrofluoric acid (48 pct solution) prior to rolling to remove any cold work introduced in the machining operations. Rolling was accomplished with a 2-high hand-operated laboratory rolling mill that had 2.72-in.-diam rolls. Prior to operation, the rolls were polished with 600 grit paper, cleaned with acetone, and then soaked in a container of liquid nitrogen for several hours. The samples were also soaked in liquid nitrogen prior to rolling and were recooled between each pass. While some slight heating of the samples occurred during rolling, this procedure maintained the sample temperature well below 0°C at all times. The samples were rolled unidirectionally, and the rolling plane surfaces were not inverted during any phase of the operation. The draft per pass averaged between 0.010 to 0.012 in. After 96 or 97 pct reduction the draft was reduced to 0.001 to 0.002 in. per pass. Samples were rolled to various reductions in thickness between 43 and 99.5 pct.

Jan 1, 1969

By AIME AIME

HARVEY MUDD, mining engineer and distinguished citizen, has achieved that balance between professional and civic activities for which many of us strive but few attain. His able direction of mining operations is known to many Institute members but perhaps few know that he was in 1936 recipient of the annual award given by the City of Los Angeles to that citizen who contributed the most valuable and unselfish service to the community. Mr. Mudd was born in Leadville,

Jan 1, 1944

By M. Deighton, R. N. Parkins

The metals Cd, ,Wg-, Sn, TI, Zn, and Zr reach a peak hardness after a criticfir1 deformation by rolling- and then soften with fwther rolling-, thereby exhibiting wovk softening. Optical metallography on Cd, Mg, and Zn shows that work softening is accompanied by a change in grain size occurring during deformation. The creep of zinc from -1l° to +60°C at stresses in the range of 7.9 to 17.3 kg per sq mm is given by € = e0 -t- Bt + Kt +at6. The third and second rate constcints are related by the equation a = K~ K6 and their stress and temperature dependence can be represented by the equations K = A, . exp - (u, - Bu)/kT. A model based upon the stress activated glide of sub-boundaries is proposed which qualitatively accounts for the metallog-raphic observations. Expressions, which are in reasonable quantitative agreement with the ex-pe~inzental observations, are derived for the creep of zinc. THE term "work softening" has been used previously by Polakowski1 and by Cottrell and stokes2 to describe phenomena where further strain of a deformed material leads to a decrease in flow stress. In both cases, however, the conditions were changed for the second straining. Here, the term "work softening" is intended to refer to a decrease in flow stress after continued straining in the same direction at the same temperature: work softening is the antithesis of "work hardening". Work softening of zinc was reported by chadwick3 and in discussion of that paper Jenkins4 indicated that cadmium also work softens. More recently work softening has been reported5 in two magnesium alloys, -99.5 pct Mg. Chadwick found that the hardness, 0.2 pct Proof Stress and the UTS of electrolytic zinc all increased with progressive cold reductions up to 30 pct and then progressively decreased with further rolling. Gay and Kelly6 used a back-reflection X-ray technique to study the effect of cold rolling zinc and found that although deformations greater than 2 to 5 pct reduction in thickness produced some recrystallized grains, deformations greater than 40 pct caused com-plete spontaneous recrystallization. At deformations greater than 60 pct the material was found to consist solely of recrystallized grains, -20 pm diam, the size of which decreased with increasing reduction and was much less than the initial grain size of the annealed material (-300 pm diam). Similar results were also reported for cadmium, tin, and lead.6 Gay, Hirsch, and Kelly' suggest that these experiments indicate recrys-tallization takes place when the dislocation density exceeds a certain value. However, no measurements of MATERIALS AND EXPERIMENTAL PROCEDURE The purity of the metals used in this work is indicated by the following figures: Zn (99.99); Cd (99.94); Mg (99.95); T1 (99.99). The zirconium was iodide crys tal bar with a probable purity of about 98 pct. The metals were obtained in the form of 0.25 in. thick strip or 0.425 in. diam rod by various fabrication methods and then annealed to ensure complete re-crystallization. Hardness-deformation curves were obtained at room temperature by rolling 4 in. thick strip under conditions which left a surface adequate for diamond pyramid hardness tests immediately after rolling. The hardness was taken as the niean of five impressions made using a 5 kg load and the time elapsing between rolling and making the last impression never exceeded 5 min. The zinc specimens for creep testing were from 3 by 3 by 4 in. cast slabs which were rolled to 0.10 in. thickness starting at 350°C and finishing cold. The resulting strip was cut into pieces 1 in. wide and annealed in batches. With suitable choices of annealing temperature between 100" arid 400°C five different grain sizes varying from 4.54 x 10' to 3.03 x l05 grains per sq cm (530 to 20 um diam) were obtained. Creep tests were done in compression using a sub-press, based on a design after Ford,8 in which the strip is compressed between dies 0.100 in. wide under conditions of plane strain. Since there is no lateral spread of the material, the area of contact between the dies and strip remains constant throughout the test and the application of a constant load, using the load maintaining device of a hydraulic testing machine, resulted in a constant stress. Covering the dies with strips of P.T.F.E. reduced frictional effects to a minimum. The creep strain was obtained by measuring the travel of the crosshead of the testing machine to a sensitivity of 0.1 pct reduction in thickness. The complete subpress assembly was contained in a steel box and for tests above the ambient this was filled with liquid paraffin and heated electrically. Temperatures below the ambient were obtained with a cooling mixture of acetone and solid carbon dioxide in the box. The liquids were stirred and the temperature of the specimen, which was controlled to ±0.5"C dur-ing a test, was measured by a thermocouple placed near the dies. Compression testing of cylindrical specimens was also carried out in the subpress using hardened flat discs separated from the test material by P.T.F.E. sheets which obviated barrelling of the specimens. Various initial strain rates were supplied by the hydraulic testing machine, and the deformation was measured by a clock dial gage resting on the cross-

Jan 1, 1970

By Frederick Laist

I AM APPRECIATIVE of the honor you have done me in electing me to membership in your Society. I value the contacts with men of imagination and ideals which this implies. I am grateful for the recognition of such small contributions as I may have made, or helped to make, to the vast fund of scientific and engineering knowledge. We like to think, as we grow older, that our lives have not been purely parasitical, and that through our efforts some forward step, however small, has been taken toward improving conditions under which we live and do our work. In these days of industrial depression, we hear much criticism of our "machine age." Modern engineering, mass production, the complexity of our lives, all come in for some share of blame. The farmer is said to have been spoiled by the tractor and the gang plow, the factory worker has become a slave of the assembly conveyor, the scientific worker is no longer free but has sacrificed much of his individuality to the research organization of which he is a part. We wonder whether our work as engineers has been worth while and whether our striving after more efficient ways of doing things has been a curse to mankind rather than the boon we thought we were conferring.

Jan 1, 1932

By C. M. White

CITIZENSHIP is a rather abstract subject on which a great deal could be said-a subject on which a great deal is said -and still one which too many of us seldom think about and seldom work at. Too many of us engineers and business men have but a vague idea of citizenship. We think that if we go to the polls on election day and obey the laws scrupulously, with the exception of an occasional traffic violation, we are pretty good citizens and are doing our duty by our city, state, and nation. But when you think it over, that's a very passive observance of the important right of counting oneself a citizen of a country. There is nothing very positive in that attitude. There is nothing that indicates that we have sufficient interest to really go out and do a job for the -welfare of our country, forgetting any personal advantages or inconveniences that might arise. In other words, this type of voting-on-election- day, law-abiding citizenship does not keep us awake a single minute; it does not take any particular thought or require the expenditure of any time or energy.

Jan 1, 1939

By AIME AIME

THE fall meeting of the Petroleum Division, held at Tulsa, Okla., on Oct. 11 to 14, devoted two days to technical sessions and two to field excursions. A representative attendance of 250 to 300 engineers and operating officials engaged in oil production marked the sessions and paid close attention throughout to a notable series of highly technical papers. Restricted as the program was to consideration of production problems only, the time proved too short for discussion or even the presentation of the 20 papers submitted. Much informing and pertinent discussion none the less took place, and the sentiment was general to the effect that the meeting was one of the best ever held by the Division. The meetings were held in the auditorium of the Municipal building and local arrangements were well looked after by the Mid-Continent Section of the Institute and the Oil and Gas Association. The combination of the three organizations served to bring together engineers and operators most usefully. F. Julius Fohs, chairman of the Division, presided at the sessions on Monday. Tuesday morning John M. Lovejoy of the local section took over this responsibility in the absence of T. E. Swigart, who was detained in California. The afternoon session was presided over by A. G. Heggam of the Oil and Gas Association and the Tuesday evening banquet by W. C. Franklin of the same organization.

Jan 1, 1926

By J. F. Abel, F. T. Lee

Subsidence is controlled by a complex com¬bination of mining and geologic factors. For example, a compilation of worldwide data shows that, as the percentage of shale in the overlying rock mass decreases and the amount of sandstone increases, the angle of draw (and the area affected by subsidence) decreases. Limestone in the over¬burden appears to cause a more than twofold decrease in the angle of draw compared to a like amount of sandstone. Increased amounts of sandstone were accompanied by a greater surface subsidence relative to the mining height. The total thickness of overburden did not appear to influence the subsidence magnitude above super-critical panels. The greater the thickness extracted, the smaller percentage of that thickness shows up at the surface as subsidence. The greater the percent of the seam extracted, the greater the subsidence reaching the surface. The maximum subsidence above room-and-pillar panels de¬pends on the pillar height and minimum width as well as the other factors listed.

Jan 1, 1984

By John W. Langley

In the summer of 1888 it was the fortune of the writer to present the subject of the desirability of establishing a set of samples of steel, which should be analyzed with extreme care, in order that they might become standards to which scientific and commercial analyses of iron and steel could be subsequently referred; also, that greater uniformity in the results of analyses might be brought about, since these standards would bear towards analytical methods somewhat the position which the original units of weight and length, the gramme and meter, or the pound and yard, preserved in Paris, London, and Washington, do to the mechanical arts. The plan met with hearty co-operation, with the result that com mittees were appointed in Sweden, Germany, France, England, and America, to receive the material and to see that the necessary au alyses were executed. In England, the British Association for the Advancement of Science appointed a committee, which subsequently published a plan

Jan 1, 1891