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By H. M. Howe

Page 1. Introduction............................514 2. Definitions.............................517 3. Brevity of the Heating........................517 I. THE HARDENING OF THE BORE..............517 4. The Hardening of the Bore.....................517 5. The Thickness of the Hardened Layer.................517 6. Martensitization..........................518 7. The Hardening Repetitive ......................519 8. The Temperature Cycle.......................519 9. The Hardened Layer is the Merged Layer............... 521 10. The Progressiveness of Merging....................521 11. The Progressive Thickening of the Hardened Layer from Round to Round. 523 12. Merging and Hardening are Cumulative................523 13. Three Additional Causes of the Progressive Thickening of the Hardened Layer 525 14. Progressive Roughening of the Bore..................525 15. Avoidance of an Endothermic Transformation.............525 16. Asymptotic Retardation of the Thickening of the Hardened Layer.....527 17. The Troostitic Layer........................ 529 18. The Usual Lack of Martensitic Markings................529 19. The Thickness of the Hardened Layer Should Increase with the Quantity of Heat Taken up by the Walls of the Bore.................530 20. The Decrease of the Thickness of the Hardened Layer from Breech to Muzsle 531 21. Phstic Deformation as a Contributory aCause of Hardening........531 22. In What Way May Plastic Deformation Hasten Hardening?....... 535 23. Possible Need of Coarsening.....................535 24. Carburization as a Cause of Hardening..........:.....536 25. Does Hardening Increase Erosion?..................-538 11. THE CRACKING OF THE BORE ...............539 26. Appearance of the Bore and Cracks in Elevation............539 27. The Cracks in Elevation in the Rear Ring...............539 28. The Cracks in Elevation in the Forward Ring.............540 29. The Copper Network in the Grooves.................540 30. The Cracking of the Lands......................541

Jan 1, 1918

By Michael Tenenbaum

Selected characteristics of nonmetallic phases were determined in low-carbon sheet steels which had been produced by various refining; deoxidizing, and casting procedures. The results showed little influence of the refining process on the quantity, distribution, size, and character of the nonmetallic phases. The quantity of inclusions was governed by the deoxidation procedures. While the mode of casting influenced the internal structure and the pattern of inclusion distribution, it had little effect on the quantity of nonmetallics. The vast majority of inclusions were under 30 µ in diam, and there was little change in size distribution during hot and cold rolling. The composition and structure of the inclusions were expained an the basis of known equilibrium phase diagrams for the appropriate systems. Additional work is needed to explain some of the observations of this paper. HENRY Marion Howe's contributions to the metallurgical profession include his many writings, the wisdom that he imparted to his students, and the inspiration that he gave to the many scholars, teachers, and industrialists who knew him personally. It was Professor Howe's intimate colleague, Albert Sauveur,1 who, in the first Howe Memorial Lecture, could have been speaking for the metallurgist of our generation as well as his own when he wrote, "...how many of us on the point of going astray were called back to the right path by Howe's guiding torch?" More than a quarter of a century later, Francis Foley,2 one of the last in the Howe Lecture series who worked directly with the great man, delivered the ultimate tribute, "...truth, in its time is so hard to identify." While Professor Howe strove to be right, "he was content if he provoked the reader to take the next step along the path to greater knowledge." Like so many of my predecessors, I sought guidance for this lecture by referring to Professor Howe's two classic texts, Metallurgy of steel,3 and Metallography of Steel and Cast Iron: the former book interpreting the facts as he saw them near the start of his career, and the latter—published 26 years later—pointing to many fertile fields for metallurgical investigation. Those of us who harvest the fruits of Henry Marion Howe's contributions to the metallurgical profession now look with wonder at the tremendous legacy he has provided. It is rewarding to study his writings and to recognize the anticipation of such aspects of modern ferrous metallurgy as: 1) Direct reduction 2) Steelmaking reactions 3) The approaches and benefits of degassing 4) Solidification mechanisms 5) Habits and behavior of nonmetallic inclusions 6) Recrystallization phenomena 7) Slip and slip propagation 8) Dislocations 9) Discontinuous deformation 10) Microscopic and macroscopic segregation

Jan 1, 1970

By Paul Billingsley

THE development of the North Lily ground, which lies in the East Tintic district, Utah,. about half a mile northwest of the famous Tintic Standard mine, was undertaken by the International Smelting Co. on purely geological reasoning. The geologic theory on which this work was based resulted from several years' intensive study of the East Tintic district by the geological department of the International Smelt-ing Co., who were, during this period, indebted to many for valuable suggestions that were adopted and became part, of the gradually maturing concept. For example, E. J. Raddatz, president of the Tintic Standard Mining Co., first called attention to the significance of rhyolite alteration; J. W. Wade, assistant manager, contributed greatly to our knowledge of the great Tintic Standard orebodies; and so on all along. the line. In short, the ultimate theory embodies the aggregate experience and thought of all those most familiar with the area in question. The problem in brief was this: is the Tintic Standard deposit an isolated occurrence of ore, or are other ore deposits to be found in the vicinity? If the latter is the case, where can these others be looked for? The difficulty of the problem lay in the fact that most of the area is covered by rhyolite; beneath which lies the limestone in which the orebodies occur; so that the available evidence as to the structure of the formations, and, their mineralization; is of the slightest. The sav-ing features of the case, by means of which it proved possible to solve the problem, are three in number first, the rhyolite is pre-mineral and hence has been exposed to alteration by the mineralizing agencies; second, certain persistent dikes and fissures are con-tinuous through the rhyolite into the limestone below; and third, the extensive underground workings of the Tintic Standard gave a good basis for study of the sub-rhyolite structure and the occurrence of ore. The rhyolite overlies the Tintic Standard orebodies, and over them shows a large patch of brownish altera-tion. This patch proves to be due to chloritization and sericitization, which has spread out from certain zones of dikes, pebble-dikes and fissures. The dikes are com-posed of a light fine-grained rock which has been altered to an aggregate of quartz, alunite, and magnetite. They can be traced southwest to a common center in Big Hill, the entire mass of which is composed of the same material. The pebble-dikes, which consist of a mass of rounded pebbles, mainly quartzite, in a matrix ranging from the same quartz-alunite-magnetite rock as above to almost pure vein quartz, are closely asso-ciated with these light dikes, but in general extend farther northeast. They thus represent a specialized phase of the intrusive action of which Big Hill is the center. The brown chloritized rhyolite, then, is an alteration product due, in all. probability, to emana-tions closely associated with this phase. Since it coin-cides geographically with the Tintic Standard area of highly altered limestone, with its many great ore-bodies, it has been concluded, that it is the expression in the rhyolite of activities which have also altered and mineralized' the underlying limestone.

Jan 4, 1927

By Walter E. Heinrichs

The following is a condensed version of an open letter addressed to Bil Gilbert of Sports Illustrated: Your article, "When a Law Fights a Law, Sports Illustrated. April 26, 1971, betrays considerable unfamiliarity with the subjects of ecology, social science, mining law and history. In a magazine as widely circulated as Sports Illustrated, an article of such a slanted nature misleads the general public.

Jan 1, 1971

By K. H. Heino

Two 200 T/da Lurgi Turbulent Layer fluid-bed roasters have been in operation at Canadian Electrolytic Zinc Limited since 1966. Zinc concentrate containing 52-54% Zn, 9-11% Fe,31-33% S is treated to produce calcine containing 60-62% Zn,10-12% Fe, .l-.3% S as sulphide and .8-1.2% S as sulphate. Each roaster train comprises a waste heat boiler, two cyclones in parallel and a two-field electrostatic precipitator. Distribution of calcine collected is 10-15 percent from bed overflow, 55-65 percent from boilers, 20-25 percent from cyclones and 2-6 percent from precipitators. A Monsanto designed contact plant produces acid at a rated capacity of 365 T/da (100% H2304 basis) from roaster gases diluted to 7.0-7.5% S02. The process steps are gas cleaning and cooling by weak acid scrubbing, acid mist removal in electrostatic precipitators, gas drying in 93.5-96.5% H2304, conversion of sulphur dioxide to sulphur trioxide in a four-pass converter containing vanadium pentoxide catalyst, and absorption of the sulphur trioxide in 98.1-98.3% H2S04. Product acid is 93.2% H2S04. Conversion efficiency is 97-98 percent and overall sulphur recovery from concentrate is 87-90 percent. The adjacent fertilizer plant has a capacity of 135 T/da of P205. The products are 54 percent phosphoric acid, run-of-pile triple superphosphate, and diammonium phosphate. The plant is of Ugine-Kuhlman design and consists of an air-cooled multiple tank reactor, a tilting pan filter, and a forced circultation vacuum evaporator. Triple superphosphate is made on a continuous belt and partially cured in a rotary dryer. Diammonium phosphate is produced by ammoniating phosphoric acid in a single stage reactor. The slurry of ammonium phosphate is granulated in a blunger and dried.

Jan 1, 1970

By Harry C. Gatos, Frank J. Bachner, Mario D. Banus

The portion of the Nb-Sn phase diagram between 75 and 79 at. pct Nb at temperatures near the liquidus has been investigated by melting alloys of known composition and examining the microstmc-tzlres resulting when these melts were quenched. The Nb-Sn samples were contained in magnesia sleeves, and were mounted in a high-pressure apparatus. It was shown that Nb3Sn me1ts by a peri-tectic decomposition and that the composition of the compound Nb3Sn at the peritectic horizontal lies between 77 and 78 at. pct Nb. Analysis of the phases present in the samples was accomplished by anodic staining techniques and an electron-microbeam analyzer. DURING the past several years a great deal of work has been devoted to the Nb-Sn system, and the bulk of this work has been primarily concerned with the intermetallic phase Nb3Sn. However, the melting characteristics of Nb3Sn have not been investigated because of the difficulty in maintaining known compositions due to tin losses by vaporization, and the added difficulty of containing Nb-Sn alloys without sample-container reaction at the high temperatures involved. This paper reports on the development of a technique for containing Nb-Sn alloys under pressure high enough to prevent tin losses at temperatures in excess of the liquidus. Using this technique, melts of known composition were made and a phase diagram near the liquidus is proposed based on the microstructures resulting when these melts were quenched. EXPERIMENTAL The Nb-Sn alloys weighing 0.7 g each were prepared in the form of cylinders. Niobium powder, -200, +325 mesh, and tin shavings with a minute amount of tin powder for a binder were mixed in the desired proportions and cold-pressed at 50,000 psi in a 0.150-in. die. This cylinder was then enclosed as shown in Fig. 1, and the entire arrangement mounted in a 2.6-in. pyrophyllite tetrahedron.' The desired temperatures (-2500°C) presented several problems in high-pressure container materials. Boron nitride, the usual sample holder, was found to react with niobium to form the nitride. However, MgO cans and plugs machined from refractory rods did not melt nor react with the sample. Thick tantalum contact disks were used to carry the large currents (~450 amps) to the graphite heater, since tantalum did not melt and had enough strength to prevent extrusion of the sample. It was further observed that the graphite heater and tantalum disks could not be in direct contact with the pyrophyllite because it melts and decomposes at these temperatures to kyanite and coesite (SiO2),2 the former reacting with graphite and the latter with tantalum to form the silicide. The use of a MgO outer sleeve

Jan 1, 1965

Coal Division Industrial Minerals Division Minerals Beneficiation Division Mining, Geology and Geophysics Division Established as a Society February 26, 1957 OFFICERS AND COMMITTEES J W Woomer, President A B Cummins, President-elect S D Michaelson, Past President C E Lawall, Eastern Regional Vice-President D W Scott, Central Regional Vice-President 3 D Forrester, Western Regional Vice-President R B Ladoo, Treasurer John Cameron Fox, Secretary

Jan 1, 1959

By O. T. Berge

Development and production from open cut mines continued its vigorous growth trend during the year 1968. Material handling and transportation were again exposed to the use of larger equipment with shovels, trucks and front end loaders leading the way. Highlights of World Mining Activities Africa: The Anglo American Corp. opened a new high-grade copper mine in Zambia during the year. In Angola, the Companhia Minera do Lobita planned a 3 million ton iron ore production for 1968 from new mines which will ultimately produce 5 million tons per year. A feasibility study of Bethlehem Steel Co., for the development of large high- grade iron ore reserves in Gabon, was in final stages of completion this year and Pickands Mather and Co. continued its investigation of iron ore deposits along the Ivory Coast.

Jan 2, 1969

By J. E. Breen, J. Weertman

The creep rate of polycrystalline tin was studied as a function of temperature and stress in constant stress experiments. The temperature was varied from room temperature to almost the melting point of tin. Activation energies were calculated from tests run at the same stress. It was found that on a log creep rate vs inverse temperature plot the experimental points did not fall on one straight line but on a line which changed its slope in the 90° to 160°C region. Two activation energies for the creep of tin can be calculated from the data: a value around 26,000 cal per mol at high temperatures and a value around 11,000 cal per mot at low temperatures. It is suggested that the discrepancies between the creep activation energies and those of self-diffusion can be accounted for if self-diffusion takes place predominately by Zener's ring mechanism rather than through vacancy or interstitial movement. SHERBY, Orr, and Dorn' and Dorn' have recently reviewed some of the data on high temperature creep of metals. -The data show that the activation energy of high temperature creep is approximately equal to the activation energy of self-diffusion. This same correlation has also been successfully made between the activation energy of grain boundary relaxation and that of self-diffusion.3,4 The metal tin does not fit into this simple picture. Its activation energies of self-diffusion differ appreciably from that of grain boundary relaxation and of creep. Fensham,5 from a precisely performed experiment, has determined that the activation energies of self-diffusion of tin are 10,500 and 5,900 cal per mol along the C and A axes, respectively. There are two energies because of the anisotropic nature of tin. Rotherham, Smith, and Greenough6 have shown that the grain boundary relaxation activation energy is 19,000 cal per mol (measurements made from room temperature to 100°C). Puttick and King7 found the same activation energy for grain boundary slip in bicrystals of tin (180° to 225°C region). Until recently, there was no high temperature large strain creep data on tin suitable for activation energy calculations. At rather small strains (up to 0.01), Tyte8 had made a series of measurements on tin from which activation energies can be calculated. In Fig. 1 are plotted some of his data on a log creep rate vs inverse temperature graph. It can be seen that Tyte's work indicates that at a relatively low temperature the activation energy is around 7,400 cal per mol but at higher temperatures the activation energy increases. Since Tyte measured the creep only for small strains, it is doubtful if a

Jan 1, 1956

By Walter W. Bradley

FOR a number of years up to the economic setback of the 1929-1931 period, the greatest proportional advances in the mineral industries in California were made among the substances in the nonmetallic groupings, particularly among the so-called industrial minerals and the salines. During the past year or two, although these have not regained the stride that marked their progress in the preceding decade, we can still record, -some new developments. California produces annually between 55 and' 60 different minerals on a commercial scale. Of these, some 40 to 45 comprise the "structural," "industrial," and "salines" materials as grouped in the reports of the State's Division of Mines. Barite-The barite deposits of California were described in Report

Jan 1, 1935

By C. H. Li, R. J. Stokes, T. L. Johnson

The effect of alumina particles on the nucleation and growth of cracks through a silver- chloride matrzx has been investigated. It has been found possible to promote fibrous cracking in dispersion-strengthened silver, chloride under notch-impact conditions at temperatures at which silver chloride alone cleaves brittlely The modification) of fracture beIzavzor is thought to be due to the relaxation of hydrostatrc stress beneath a notch by the nucleation of cavities near alumina particles. In recent years, composite or dispersion-strengthened materials have been studied primarily to understand their high resistance to plastic flow particularly at elevated temperatures. Dislocation models have been developed with which it is possible to deduce with fair success the effects of interparticle distance, particle size, temperature, upon yielding and creep behavior.l-4 Much less attention has been paid to the fracture behavior of these materials (with the notable exception of common structural steels) and little is known experimentally about the manner in which inclusions affect the nucleation and growth of cracks through a matrix. Nevertheless a beginning has been made in connection with fibrous cracking in ductile matrices where inclusions appear to play an essential ro1e.5-7 During the severe localized plastic deformation which accompanies necking in a tensile test, cavities are believed to develop at inclusions; these cavities subsequently grow and coalesce by plastic flow until separation is complete. It is of interest to consider whether inclusions can affect fracture behavior under loading conditions which restrict the plasticity of the matrix itself (for example, cleavage under conditions of a high imposed strain rate at low temperatures). It is particularly interesting to study these effects in a solid which shows a spectrum of behavior ranging from fully ductile to semi-brittle behavior. Such a solid is silver chloride whose mechanical behavior depends sensitively upon temperature and strain rate.'," The present paper is concerned with a study of the influence of inclusions (in the form of alumina particles) on the fracture behavior of silver chloride loaded uniaxially at low strain rates at room temper- ature and also under notch impact conditions over a wide range of temperature. In particular, it will be shown that the alumina particles can exert a startling effect on the ductile-brittle transition temperature of notched silver chloride and that the magnitude and nature of the effect depends upon both the quantity of alumina and the shape of the alumina particles. 1. EXPERIMENTAL PROCEDURE 1.1 Materials Used. Silver chloride powder of analytical reagent (AR) quality having an average particle size 6 was supplied by the Mallinckrodt Chemical Works (st. Louis, MO.). Acid washed 900 mesh alumina powder, designated A38-900, was supplied by the Norton Co. (Cambridge, Mass.). This powder was added to silver chloride in two forms: a) the as-received condition in which the individual particles were of random irregular shape; their statistical average size was 7; b) in a condition in which each particle was spherically shaped by a fusion technique. In this case, the statistical average particle size determined with the optical microscope was approximately the same (about 5p) but electron micrographic evidence indicated that many ultra fine particles were present in the spheroidized powder. 1.2 Preparation of Composite Materials. Silver chloride-alumina composites containing 2.5, 5, and 15 pct by volume of alumina were produced by the extrusion of mechanically mixed powders blended in a ball mill for 24 hr at room temperature. The mixtures were compacted at 50,000 psi at room temperature in the form of billets 3/4 in. in diameter and 1 in. long which were then extruded with a 16:l reduction ratio at 370°C through a radius-type steel die having a 5 deg lead-in angle. An extrusion temperature of 370°C was selected to ensure that all composites had sufficient plasticity to be extruded. Apart from this general requirement, the choice was arbitrary. 1.3 Microstructure of Composites. Attempts were made to check the distribution of alumina metallo-graphically by polishing transverse and longitudinal sections of the extruded rod. Specimens were wet-ground to 600 emery paper and lapped successively with 5 and 0.25-p grades of diamond paste. They were etched for 10 sec in 10 pct sodium thiosulfate solution and lightly polished in concentrated ammonium hydroxide. The most effective way to render the alumina particles and grain boundaries visible was to radiate the surface with intense white light to decorate the grain boundaries and the particle-matrix interfaces photolytically.

Jan 1, 1962

By J. G. Early, F. V. Lenel, G. S. Ansell

The isothermal shrinkage rates of copper-powder compacts were determined in the temperature range from 760o to 1060oC. The rates for compacts fabricated from a pure spherical copper powder were compared, on the one hand, with those fabricated from a spherical powder containing a dispersion of aluminum oxide in the copper matrix and, on the other hand, with those fabricated from a pure copper powder having irregularly shaped particles. The irregular copper-powder compacts shrank much faster than the spherical copper-powder compacts and these, in turn, shrank faster than dispersion -strengthened copper -powder compacts. The experiments were run under a small external load. By varying this load, the stress dependence of the isothermal shrinkage rate could be measured for compacts from spherical-copper powders. This stress dependence was found to be approximately proportional to the 4th (dispersion-strengthened alloys) or 4.5th (pure metals) power of the stress. It is concluded that the material-trans port mechanism is due to dislocation climb rather than to Herring-Naharro creep. In this investigation the isothermal shrinkage rates of compacts made of copper powder with an average particle size of 70 g in the temperature range from 780o to 1060°C were studied. The aim of the investigation was to determine the mechanism of material transport responsible for the shrinkage of these compacts. Since the phenomenon observed in this investigation was shrinkage of compacts at high temperatures, it will be necessary to consider all the material-transport mechanisms possible in sintering. It is unlikely that evaporation and condensation, surface diffusion, or even volume diffusion of vacancies, in which surfaces of small radius of curvature are vacancy sources and those of larger radius of curvature vacancy sinks, will materially contribute to a sintering process involving shrinkage, i.e., one in which the centers of adjacent particles move towards each other. The two principal mechanisms which were considered were the so-called Nabarro-Herring mechanism and a plastic deformation mechanism by dislocation movement. Both of these mechanisms were originally conceived to explain creep, i.e., the plastic deformation of metals at elevated temperatures under a constant applied stress. The shrinking of metal-powder compacts which was studied in this investigation can be readily treated as a creep process. This means that the shrinkage rates observed are considered as creep rates under the influence of an applied stress. It is true that the stresses in sintering experiments are generally not constant but decrease continually with time, but, by considering creep rates or shrinkage rates over a relatively short time interval, the small changes in stress during this time interval can generally be neglected. Nabarro-Herring microcreep is a high-temperature deformation mechanism which is caused by a diffusional flow of vacancies from boundaries under a tensile stress towards those under a compres-sive stress. Herring1 has shown that in this type of microcreep the strain rate e is proportional to the applied stress and follows an equation of the form ma, aexp(-Q/RT) [l| where <j is applied stress, Q is the activation energy for self-diffusion, R is the gas constant, and T is the absolute temperature This type of creep can explain the shrinkage of a porous compact. The surface of the pores are subjected to the tensile stress of surface tension, while the grain boundaries are under a compressive stress also due to surface tension. Vacancies diffuse from the pore surface through the lattice to the grain boundaries, where they are eliminated. In order to maintain vacancy equilibrium at the pore surface the vacancies leaving the region of the pore surface are replenished from the volume of the pore, which means that the pores shrink.

Jan 1, 1964

By Antoni Kidybinski

Mechanical properties of the nether roof rocks play a substantial role in maintenance of mine openings. On longwall faces too low strength is a cause of rock- falls which bring about delays in face advance, and hazard to the miners, while too high strength may result in over hanging of roof rocks in gobs, sometimes over a large area, initiating dynamic periodical pressures. Hence, efforts have been undertaken to develop methods of caveability evaluation for proper selection of roof control system and of longwall-face supports. DESCRIPTIVE CLASSIFICATIONS One of the basic qualitative criteria for classification of roof types with different caveability is the criterion of geological structure. The 26-stages scale worked out for conditions of Donetz Coalfield. USSR, by E.T. Proyavkin et al.(l) may be an example of that type of classification. This scale is presented graphically in Fig. 1. The first types of roofs according to this scale are easily caving immediately after exposure of a small surface, while the last be- long to the strongest roofs which over-hang in waste and require artificial fracturing. Observations and measurements carried out also in Donetz mines lead W.T. Davidyanc (2) to following classification: Class I - weak and densely bedded rocks very easily caving after each advance of supports. The roof subsidence over a waste edge is: [ ] where: h is roof subsidence, m M is thickness of the seam being mined, m S is width of an opening, m Class II - medium caveability and small main roof movements [ ] Class III - hardly breakable rocks, thicker beds with higher strength: caving by large blocks. After exposure of larger roof surfaces the movements of the main roof strata may affect an opening. [ ] Class IV - very hardly breakable rocks - thick, monolithic sandstones: they cause considerable difficulties in working with caving. [ ] Class V - thin-bedded rocks featured by the capacity of a smooth subsidence without disintegration into loose blocks with keeping contact between the particular blocks in a bed. In this classification mining with full roof caving is recommended for class I-III and only exceptionally for class IV. In many coal fields, qualitative and quantitative observations of roof rocks behavior have been carried out: as a result relations and characteristics found in certain mines are given. As an example, Kizielov Coalfield data in the USSR given by B.S. Vinokur (3) may be mentioned. In working thin pitching seams man- less system of undercutting the seam by means of rope saw is used there. The author separated four classes of roofs and gave, for every class, the empirical relation between the extracted area and the time of roof stability. The size of the stable area of exposed roof for particular classes is as follows: 120 to 150 m2 (1291 to 1614 ft2 ), 170 to 200 m2 (1829 to 2152 ft2), 250 to 280 m2 (2690 to 3013 ft2 ) and 350 to 400 m2 (3766 to 4300 ft ). For Kuznetz coalfield in the USSR the following classification of roofs was developed at the WIMI Institute in Leningrad: Class I - completely unstable: impact strength in- dex of rock f = up to 1.5 - the strip of roof 1.4 to 2.0 m (4.59 to 6.56 it) wide, exposed after shearer&apos;s cut holds stable during the time not longer than 5 min. Class II - low stability: f = 1.5 to 2.5 - the strip of roof 1.4 to 2.0 m (4.59 to 6.56 ft) wide and up to 4.0 m (13 it) long, exposed after shearer&apos;s cut holds stable during 5 to 20 min. Class III - medium stability: f = 2.51 to 3.5 - the strip of roof 1.4 to 2.0 m (4.59 to 6.56 it) wide and 4.0 to 25 m (13 to 82 ft) long, exposed after shearer&apos;s cut holds stable from 20 min. to 2 hours. Class IV - stable: f = 3.51 to 4.5 - the strip of roof 1.4 to 2.0 m (4.59 to 6.56 ft) wide and 25 m (82 it) long exposed after shearer&apos;s cut is stable during the time longer than 2 hours. Class V - entirely stable: f = over 4.5

Jan 1, 1982

Accessions AMERICAN ELECTROCHEMICAL SOCIETY, TRANSACTIONS, vol. 33. Bethlehem, Pa. 1918. AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS, BULLETIN, vol. 2. 1918. (Gift of the Association.) AMERICAN YEAR BOOK: 1915. Edit by Francis G. Wickware, New York. 1919. (Gift of D. Appleton & Co.) ANNUAIRE DE LA HOUILLE BLANCHE FRANCAISE. ` By M. Auguste Pawlowski. 2d year. 1918-1919. Paris. (Gift.) BLACK DIAMOND, Vol. 60, Jan.-June, 1918; vol. 61, July-Dec., .1918. (Gift.) Chicago. CANADIAN MINING INSTITUTE, TRANSACTIONS, vol. 21. 1918. Montreal, Quebec. COMPTES-RENDUS DE L&apos;ATHÉNÉE LOUISIANAIS, vol. 4, No. 3. (Gift of Wm. Beer.) EFFICIENCY OF NATURAL GAS AT Low PRESSURES. Abst. of testimony of Samuel S. Wyer before the Corporation Commission of Oklahoma, February 4, 1919. Printed by Empire Gas & Fuel Co., Kansas City, Mo. GEOLOGICAL. INSTITUTION OF THE UNIVERSITY OF UPSALA, BULLETIN. Edit. By Hj. Sjögren. vol. 14, 1917; vol. 15, 1916; vol. 13, pt. 2, 1916. (Gift.) HYDROGENATION OF OILS. Catalyzers and catalysis and the generation of hydrogen and oxygen. By Carleton Ellis. 2d edition. New York. 1919. (Purchase.) INSTITUTE OF METALS, JOURNAL, vol. 26. No. 2. Edited by G. Shaw Scott. London. 1918.

Jan 6, 1919

Discussion of the paper of R. J. COLONY, presented at the New York Meeting, February, 1921, and issued With MINING AND METALLURGY No. 169, January, 1921. R. J. COLONY (author&apos;s reply to discussion).-The work of Sosman and Merwin on the system lime-ferric oxide, mentioned by Mr. Rankin, was not overlooked. When studying portland cements and portland-cement clinkers petrographically, however, the lime-iron compound was difficult to correlate with the very definite dicalcium ferrite described by those investigators, which possesses such well-defined optical properties. In portland cements, the calcium ferrite (or ferrate?) is an indefinite, fuzzy, and generally amorphous, or apparently amorphous substance that is distributed interstitially with respect to the other grains, from which it was very difficult to derive any satisfactory results. For this reason, the writer, tentatively, chose to regard it as related to the aluminate, and assigned to it the composition 3CaO.Fe203, which may be incorrect, however, as Mr. Rankin suggests.

Jan 8, 1921

By Bert Sandell

MUCH has been said and written about the various uses of die-castings, their applications in the various industries and their advantages and disadvantages. Examination of this literature, however, fails to disclose any data concerning the effect of temperature upon any of the physical properties of die-casting alloys. The uses and applications of die castings are so numerous, and of such a varied nature, that far too lengthy a manuscript would be required to list all of them. Brief mention of some specific cases will suffice to illustrate the temperature ranges in which certain die castings function. Automobile hardware, such as hub caps, door handles, radiator caps, etc., can be used as one example. Castings of this type are constantly exposed to varying climatic conditions, temperatures ranging from below zero to upwards of 100° F. Refrigerator parts, such as ice-cube trays, etc., form another example. Approaching the other temperature extreme, we encounter conditions such as are found in kitchens in which oven-heat indicator parts, cooking utensils, waffle grids, etc., embody use of die castings, where temperatures as high as 500° F. are often met with. Because of this variation in service temperatures, it was felt necessary to ascertain the effect of these temperatures upon the physical properties of die-casting alloys. The Charpy impact test was chosen first because of its simplicity, and because of the fact that brittleness is more likely to be objectionable in die castings than hardness or other physical properties.

Jan 1, 1932

By GEORGE D. RAMSAY

WHEN the Ironton blast furnace of the Columbia Steel , Co. was first put into operation the iron ore was mined frol11 the deposit near Iron Springs, Utah. This is principally a hematite with 12 to 20 per cent of magnetite finely disseminated throughout the ore. It varies from a fairly soft broken rock structure to that which is hard and compact. In the broken form it will weigh about 150 lb. per cu. ft., and in place the density is approximately 250 lb. per cu. ft. The first ore received for the blast furnace was crushed so as to pass through approximately a 4-in. square opening screen. A typical screen test of this ore is shown in Table 1.

Jan 1, 1935

By S. E. Bronisz, R. E. Tate

s-plutonium samples possessing a strong growth texture have been produced by allowing them to transform under pressure from p to a. A fiber texture with [010] parallel to the pressure axis results. The textured samples are expected to be useful in determining the effects of crystallographic orientation on the physical properties of a plutonium, and initial results of measurements of resistivity and mechanical properties are described. THE crystal structure of a plutonium1 is mono-clinic, P21/m, and many of the metal&apos;s properties should reflect the crystallographic anisotropy. Unfortunately, it has not yet been possible to grow useful sizes of single crystals of a plutonium. Therefore, few of plutonium&apos;s orientation-sensitive properties have been determined as a function of crystallographic orientation. One way to gain information about at least some of the orientation-dependent properties is to study a highly textured sample. Such samples have been produced by cold rolling a plutonium,2 but they are necessarily very small in one dimension. We have now successfully used two other techniques to produce highly textured samples, not limited to small thicknesses. METHODS OF PRODUCING PREFERRED ORIENTATION The texture is produced by causing the plutonium to transform from ß to a while under pressure. It was observed by Gardner3 that applying a compres-sive load during the transformation resulted in the formation of columnar grains of a plutonium, and Cramer4 observed a similar structure in some diffusion couples rolled in the P phase. Neither of these workers, however, investigated the subject beyond these observations. The more flexible of the two methods developed is that of compressive loading. The technique is to enclose a sample of plutonium in a die assembly before applying the load. It is possible, of course, to dispense with the die and simply press the sample between two platens. In this case, however, the unrestrained sample deforms during the pressing, making it difficult to maintain the load and to control the final sample thickness. This compressive loading technique has been used on specimens ranging from 1/4 to 3 in. diameter, with height-to-diameter ratios ranging from 5 : l to 1:6. The procedure begins with loading the sample, a right cylinder of a plutonium, into the pressing die. Plastic deformation of the sample while it is being pressed is minimized by machining the sample so that its diameter is nearly the same as that of the die barrel. Then the loaded die assembly is placed in a vacuum pressing can that fits on a hydraulic press. After a vacuum is achieved the die assembly is heated to 180°C and equilibrated. The load is then applied and the specimen and die are allowed to cool to about 40° to 50°C before the pressure is removed. The resulting sample is composed of rod-shaped a -plutonium grains, the rod axes being parallel to the cylinder axis and the pressing direction. Photomicrographs of the oriented structure are shown in Fig. 1. Although most of the specimen is composed of grains whose rod axes are parallel to the cylinder axis, a thin, peripheral layer consists of rod-shaped grains whose rod axes are perpendicular to the cylinder axis. Presumably, the highly plastic nature of p plutonium leads to approximately hydrostatic conditions during the initial stages of the P — a transformation under pressure. At this time, the grains in the peripheral layer would have grown parallel to the local force direction. During the latter stages of the transformation, the accompanying volume contraction would have eliminated the radial forces, leaving only the axial force and resulting in the growth of the observed structure. The growth texture did not form without the application of pressure. Attempts were made to produce the texture by repeating the standard temperature cycle without

Jan 1, 1965

By Robert M. Grogan, James C. Bradbury

The Illinois-Kentucky mining district has, since 1880, accounted for 80 per cent of all U.S. production of fluorspar. The ore deposits are of two types: vein deposits formed by fissure fillings along faults and bedding-replacement deposits formed by the replacement of strata at certain favored stratigraphic positions along minor faults and fractures. Fluorite is the chief valuable mineral in the deposits. Sphalerite and galena commonly are present in small amounts but, in some ore bodies, may form a substantial part of the valuable constituents of the ore. Calcite is the chief gangue mineral; quartz and barite Exposed strata range from Devonian are present in various amounts. through Pennsylvanian in age. Igneous intrusive rocks occur as mafic dikes and sills and intrusive breccia dikes and plugs. Structurally, the district is situated on a generally northwest- trending arch that has been sliced into a series of long, narrow blocks by normal faults that trend northeastward. The structural The localization of the ore deposits by faults and fractures, the association of fluorite mineralization with intrusive breccias, and various lines of petrographic and geochemical evidence indicate that the fluorite-zinc-lead deposits were epigenetic and deposited by solutions emanating from a deep alkalic magma.

Jan 1, 1968

By Paul M. Tyler

ROUGHLY one-half the value of mineral products at mines or quarries must be spent for wages. In view of the steady increase in hourly wages that continued for several decades prior to the onslaught of the recent depression, it is perhaps surprising to discover that labor&apos;s share of the gross proceeds of the mining and quarrying industries of the United States declined to 46.8 per cent in 1929, compared with 52.2 per cent in 1919 and 53.2 per cent in 1909. The actual percentages vary in different branches of the industry and in different localities but the downward trend is unmistakable. For the period 1909 to 1919 it was quite marked in every industry and from 1919 to 1929 it was apparent in all but six: namely, gold and silver lode mining, placer gold mining, crude gypsum production, marble quarrying, asbestos production, and fluorspar Tninino mining

Jan 1, 1933