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By David Sinclair, Philip B. Bucky

The dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests. § None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their application in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I The Photoelastic Method The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution. General Explanation The stress at any point 0 in a structure (Fig. I), may be resolved into two components, P and Q, each a pure tension or compression, at right angles to each other, called principal stresses.' To fully identify the stress, the values of P and Q and their directions or angle F must be known.

Jan 1, 1940

By P. L. Weston, S. E. Khalafalla

A systematic study was made by the Bureau of Mines on the effect of so me hypothesized accelerators for the process of wustite reduction in carbon monoxide. When small concentrations of promoter materials in the order of 0.69 at. pct were added to the reducible charge, the rate of reduction to iron was increased. Promotion phenomenon prediction was made in light of a suyface reduction mechanism with the aid of Vol'kenshtein's effect regarding the propagation of crystal lattice disturbances by small amounts of relatively larger interstitial ions. The acceleration produced by a typical promotor, such as potassiunl, increases with protnoter concentration up to a maximum, beyond which the reduction rate decreases. Concentration for maximum promotion depends on the nature and physicochemical properties of the promoter. The extent of reduction rate enhancement is found to be directly proportional to the atomic volume and electronic charge of the additive. DESPITE the enormous volume of literature on iron oxide reduction, very little is reported concerning additive or impurity effects on this important metallurgical process. The beneficial effect bf calcium compound additions on the reducibility of iron oxide sinters has been reported by Tigerschiold,1 vor dem Esche,2 and Edstrom. Doi and Kasai~ found that the addition of lime or limestone to iron ores helps to break up any unreducible compounds, such as fayalite or ilmen-ite. and thus free the combined iron for reduction. Schenck et al. 5 suggested that the increased reduction rate obtained when adding lime could be accounted for by the instability of wustite in the presence of lime. Acid-base slagging reactions resulted in wustite disproportionation according to The dicalcium ferrite formed will yield iron and calcium oxide during reduction. Regenerated calcium oxide dissociates more wustite. This mechanism has been used by Seths and white7 to explain their experimental results. Recently, Strangway and ROSS' attributed the calcium carbonate acceleration of iron oxide agglomerate reduction to increased porosity, both initial as well as that developed during reduction. Aside from calcium carbonate, or oxide, no other promoter was noted in the literature, except for a brief mention by Barrett and woodg on the effect of sodium carbonate and aluminate as activators for the hydrogen reduction of magnetite at 600°C. The present investigation systematically studied a host of other promoters, including calcium and sodium, in an attempt to elucidate the mechanism by which promotion takes place and to fit the results into a simple chemical model. To attain this goal, the effect of promoter physical properties, such as atomic volume, electronic charge, and concentration are related to wustite reduction kinetics in this paper. Wustite reduction to iron, rather than the overall hematite reduction, was chosen since this reaction is known to be the slowest, and hence the rate-deter mining step for the overall iron oxide reduction process. EXPERIMENTAL PROCEDURE Raw Materials and Their Preparation. The pure or impregnated wustite pellets were prepared from minus 400-mesh chemically pure hematite powders. A known weight of hematite was thoroughly and uniformly mixed with a calculated weight of the additive. The mixed paste containing 35 wt pct water was gradually heated from 400" to 1200° C and fired at 1200°C for approximately 4 hr in an air atmosphere. After cooling, the sinter was pulverized to minus 100 mesh and pelletized into minus 4- plus 5-mesh spheres. Pellets were fired, similarly to the paste mix, air-cooled, sized, and stored. An appropriate weight of the charge (20 g) was placed in a zirconia reduction tube maintaining a uniform oxide bed height of 1 cm and a cross section of 7.1 sq cm for all of the test runs. The samples were supported in the vertical reaction tube by a bed of fragmented insulating firebrick plus 3- to 6-mesh alumina beads. The hematite was then transformed to wustite by reduction with a 30 pct CO2-70 pct CO gas mixture at 1000°C in a globar furnace. Complete conversion to wustite was ascertained by a continuous infrared gas analyzer recording the CO-CO2 content of the effluent gas until no carbon monoxide was absorbed from the inlet gas, and inlet-outlet gas analysis remained constant for 30 min. The wustite sample was then reduced with 100 pct CO at 100WC. From the recorded data, an initial rate of reduction was determined by the initial slope of the graph percent reduction vs time. In order to estimate the accuracy of the data, five separate determinations of the reduction curve of pure wustite, under otherwise identical conditions, were performed. The maximum deviation from the average reduction at 14 min amounted to 2 2 pct reduction. This deviation corresponds to 3.8 pct variation based on the percent reduction of the sample. Aiiy impurity effect below the limits of this maximum deviation was considered a spurious result. If the effect exceeded + 4 pct, then it was considered as a positive one. Considerable care was exercised in determining the initial rate from the slope of the initial segments of the curve. Each reduction curve was examined separately on large graph paper and the best tangent to the curve at zero time was drawn. The slope of this tangent was taken as a measure of the initial fractional reduction per minute. Although the time required to reach 50 pct reduction may be of special practical significance, initial rate measurements are invaluable in fundamental studies. These rates provide a measure of the process kinetics on the initial

Jan 1, 1968

The Elura Orebody consists of a number of parallel, vertically oriented pipe-like structures of pyrite-sphalerite-galena mineralization located at the core of a structural dome. Concentric zoning of the mineralization into an outer Siliceous, intermediate Pyritic and inner Pyrrhotitic Zone has been previously recognized and is used in routine geologic modelling of the lead, zinc and silver grades.Statistical analysis of the metal grade distribution in the orebody has confirmed the importance of the mineralogical zones in the understanding of grade trends. The gradational nature of intra-zone boundaries, especially those related to the subjective definition of the Siliceous Zone, are apparent in the statistics.

Jan 1, 1990

Real Time Monitoring of Cemented Paste Backfill Introduction Methods ?how to instrument a Long Hole stope Key Results from 2 case studies: barricade pressures and displacement, in-stope pressures Importance of Real Time Monitoring How binder, rise rate, cement content affect fence pressures

May 1, 2010

By A. C. Heath, E. H. Dix

THE importance of aluminum-silicon alloys in the light alloy field is now generally recognized. Where silicon was once considered detrimental to the properties of aluminum, useful alloys now contain as much as 13 per cent. Furthermore, silicon is present as an impurity in aluminum of even the purest grades. Iron is another important impurity in aluminum and like silicon is found in small quantities in the purest aluminum available today. The manner of occurrence of iron and silicon in commercially pure aluminum and many of its alloys exerts a very pronounced influence upon their properties. The effect of large quantities of iron in aluminum-silicon alloys is so detrimental that it has been found necessary to limit the allowable maximum percentage to as low a figure as is consistent with quantity production and satisfactory physical properties. The intimate relation existing between iron and silicon in aluminum and aluminum alloys makes necessary a more complete knowledge of this ternary system. This paper is divided into two principal parts, dealing respectively with aluminum-silicon solubility equilibria and the constitution of aluminum-iron-silicon alloys. PART I.-ALUMINUM-SILICON ALLOYS The early work on this system was largely confined to determining the general form of the diagram and in this respect the results are in good agreement. Briefly, aluminum and silicon form a simple eutectiferous series without compounds. Until recently the solid solubility of silicon in aluminum had not been accurately determined. Fraenkel1 (1908) stated that aluminum will retain 0.5 per cent. silicon in solid solution. Rosenhain, Archbutt and Hanson2 gave the maximum solubility as about 1.50 per cent. and added that "this solubility does not appear

Jan 1, 1928

By F. F. Craig

Many full-scale waterflooding operations are preceded by pilot floods, one purpose of which is to provide an estimate of recoverable oil. A laboratory model study was made to determine the influence of the producing wells' effective productivity on the oil recovery efficiency of single five-spot pilots, as well as single injection well pilot floods. The effective productivity is indicated by the value of Condition Ratio, defined as the actual well productivity to that of on undamaged and non-stimulated, normal-sized well in the same formation. The effects of initial gas satrcration and mubility ratio on recovery eficiency were also investigated in this model study. Model test results skowed that at favorable mobiliry ratios, a five-spot pilot flood can provide a direct quantitative estimate of the recoverable oil in the pilot area. If the pilot producer's Candition Ratio is 2.2 or more, upwards of 90 per cent of the recoverable oil in the pilot area is recovered from the inside producer, regqrdless of the mobility ratio or initial gas saturation. This Condition Ratio can be achieved with preyent fracturing techniques. Model studies also showed that over the range of imposed injection pressure differences and regional pressure gradients normally encountered in field operations, there was no effect on the recovery efficiency of a five-spot pilot waterflood. Model studies of single injection well pilot waterfloods showed that with no initial gas saturation, the total oil recovery at the offset producing wells can indicate the oil recovery possible by full-scale waterflooding. It is essential that the Condition Ratios of the offset wells be above 1.4. If an initial gas saturation exists prior to water injection, the recoverable oil cannot be directly evaluated by a single injection well pilot flood. However, the production per formance of such a flood can be used to provide information on volumetric sweep efficiency. INTRODUCTION Oil reservoirs are conlplex structures and cannot always be fully studied in the laboratory. Therefore, many operators consider it prudent to evaluate a waterflood prospect by means of a pilot flood. Pilot waterfloods generally involve one of two well arrangements: a single five-spot pilot waterflood, involving four injectors and an internal pilot producing well; and a single injection well pilot flood (sometimes called an inverted five-spot pilot) having one injector and four sur- rounding pilot producers. Some pilot floods are composed of multiple five-spot pilot patterns. To yield information applicable to field-wide performance, the pilot must be located in a representative portion of the reservoir. Pilot floods generally are conducted for one or more of the following reasons: (1) to determine whether water could be injected at desirably high rates, (2) to determine whether an oil bank or zone of increased oil saturation is formed by water injection, and (3) to estimate the oil recovery by waterflooding. Many of the early pilot water-floods were conducted for only the first two reasons. As soon as a buzz in oil production was obtained in the pilot, water injection was initiated throughout the entire lease or field. A number ot laboratory studies have been directed toward determining conditions under which a pilot flood could yield a quantitative estimate of the oil recovery possible by full-scale pattern flooding. One of the early studies of single five-spot pilot flooding' showed that well damage to the inside pilot producer could reduce the total amount of oil recovered. In a study of the single injection well pilot flood pattern,' the results indicated that if the model boundaries were no closer than a half-well spacing beyond the pilot pattern, the pilot performance in the laboratory is unaffected by these boundaries. In another study,? he effect of initial gas saturation and mobility ratio on the ratio of production to injection rate for various groupings of five-spot patterns was defined by mathematical and analog methods. In a study4 involving both potentiometric and flow model experiments at a mobiliry ratio of unity, four different pilot patterns were studied. These included a single five-spot, a single injection well pilot, a cluster of four single injection well pilots and six inverted five-spots. In this study the ratio of well diameter to the distance between injection and producing wells was held constant at 1:1000. The effect of the 7 ratio-—the ratio of the pressure drawdown at the producing wells to the pressure build-up at the injection wells on the pilot performance-was studied. The values of 7 ratio ranged from 0 to 0.34. Results showed that both the total oil recovery and the total fluid production from the pilot relative to the cumulative injection increased with increasing values of the 7 ratio. The effect of both the ratio of injection to producing rates and mobility ratio on the oil recovery performance of a liquid-saturated single five-spot pilot flood was studied in a series of flow model tests.5 Rate ratios ranged from one to four, and mobility rates ranged from 0.1 to 10. Resulls of these tests showed that at low rate ratios, the pilot producers may recover up to four times the recover-

Jan 1, 1966

By Harold Earle Cook

The purpose of this paper is to state briefly the inspection requirements of the Bureau of Ordnance, the specifications governing the inspection, and the physical and chemical properties of the steel used in the construction of ordnance for our Navy. It would be of interest to evoke discussion on points in these specifications which do not tend to insure the production of the very best material for the purpose intended. In other words, what requirements of our specifications are useless and also in what manner are our specifications deficient? It might be well at the start to answer the first criticism of this paper which will probably be made, and that is that the title does not agree with the subject matter. Considering metallographic work as covering only the macroscopic and microscopic examination of metals, this paper will have gone beyond the subject; but it is believed that a broader definition of metallography is that it is the study of the relation of the internal structure of metals and alloys to their composition and to their physical and other properties. The internal structure of steel is dependent on its physical and its chemical properties. These physical properties are dependent on the chemical composition and the mechanical and thermal treatment of the steel. So it seems that this subtitle would not be entirely necessary and that the title " Metallography of Steel for Ordnance Purposes" would cover a study, not only of what we can learn of macroscopic and microscopic examination, but broadly of the whole subject of the specifications, the fulfillment of the requirements of which produce the structural conditions revealed by macroscopic and microscopic examination. I will refer but briefly at the beginning to the microscope and its uses in our inspection. It is only very recently that the Bureau of Ordnancc has furnished certain of its inspection offices with a portable Tassin outfit for the microscopic examination of steel. Since that

Jan 1, 1916

By Michael W. Oakland

Weidlinger Associates was retained to evaluate the foundations supporting ten oil storage tanks at a tank farm on the east coast. The tanks were constructed over the site of a landfill which was underlain by deep organic deposits. The tanks were typically 48 ft. in height and ranged in diameter from 60 to 150 ft. The tanks were supported on both wood and steel pipe piles. After more than 35 years of service, an inspection found that up to 25 percent of the piles had separated from the mat foundation. The operations at the facility were temporarily stopped pending further investigation. Weidlinger developed comprehensive finite element models of the foundations for each tank and used random generators to conduct Monte Carlo simulations the range of scenarios of detached support conditions since it was not possible to survey all the piles below the tanks. To confirm the modeled performance and verify stability, each tank was also load tested using water with electronic instrumentation installed by Geo-Instruments. The instrumentation provided real time, web based monitoring during testing in areas which would otherwise be inaccessible during loading. Through inspection, complex modeling and sophisticated load testing, Weidlinger and Geo-Instruments were able to show that all but one of the tanks could safely be put back into service. This paper details the analysis, Monte Carlo simulations and instrumentation and load testing performed for this unique project.

Jan 1, 2009

By S. P. Jekielek

"This paper describes the automation of a mine hoist ore loading pocket using a programmable controller. It provides an introduction to programmable control, and outlines the various modes and operating sequences of the loading pocket. A comparison is made with previous equipment to illustrate the increased flexibility, reliability and diagnostic functions that are gained.IntroductionLoading pockets have evolved from a couple of manually operated air cylinders to entirely automated systems. Early pockets were usually formed in rock, with loading and discharging regulated by air-operated gate s. Interlocks, added to this arrangement, prevented simultaneous operation of the gates and ensured proper hoist position . As the loading pocket advanced, it was recognized that gravity feed posed problems, often becoming plugged or letting water run through into the shaft. A belt conveyor was employed, eliminating the se problems and resulting in greater loading control. Weighing the combination of transistorized logic modules, replaced many relay systems. This elimination of moving parts and contacts increased reliability and reduced maintenance costs.As semiconductor technology progressed, there were major breakthroughs in miniaturization and reliability, and as a result the programmable controller was introduced. Programmable controllers first appeared in the automotive industry in the late 1960's. A system controller was required to replace the large relay panels in operation at that time. The use of digital integrated circuitry enabled these programmable controllers to automate processes with hundreds of inputs and outputs. Advances in electronics reduced production costs , making controllers for smaller application s viable . This development is on-going, each generation introducing controllers with greater capabilities for a wider variety of systems. equipment was the next step in loading pocket development, and dependance on much of the manual control was reduced . The complete system was first automated using relay panels. Solid- state devices were later introduced, and static control,"

Jan 1, 1980

By Chas. Y. Clayton, Francis B. Foley, W. E. Remmers

DuRing the summer of 1919, the late Dr. Henry M. Howe, then Chairman of the Division of Engineering of the National Research Council, organized a committee to obtain a better insight into the behavior of carbon steels under the influence of various treatments by a proper control of the time and temperature factors. During part of 1919 and 1920, work in connection with this investigation was carried on at Dr. Howe's laboratory at Bedford Hills, N. Y. During 1921 there was an enforced hiatus in the work, occasioned by the illness which resulted in Dr. Howe's death in 1922. At that time one of the present authors compiled the results of the work which had been done and this was published in 1923.' Following the publication of this work, it seemed desirable to carry on in the same manner an investigation of steel of C 0.75 per cent., which steel had not been as fully treated as had the other steels of C 0.34 and 0.52 per cent., used in the published work. Furthermore, certain unusual results have been obtained in the treatment of C 0.52 per cent. steel by quenching and drawing, and repetition of this part of the work seemed advisable. This has been done during the past year at the School of Mines and Metallurgy of the University of Missouri at Rolla, Mo., by a cooperative undertaking of the School and the Bureau of Mines, working in conjunction with the Committee on Heat Treatment of Carbon Steels of the National Research Council. The present paper is a report of the results obtained in this work.

Jan 1, 1926

By M. W. Price, Joseph V. Mather, E. H. McCleary

"INTRODUCTION The asphyxiation or poisoning of workmen in underground mines by noxious gases from blasting in adjacent strip mines can be prevented.Considerable progress has been made in eliminating or reducing hazards to the health and safety of underground workmen in anthracite mines, but seldom does a year pass without reported cases of underground workmen being poisoned by the fumes from blasts of explosives in strip-mining operations. In the early days of the anthracite industry, the coal near the surface was only partly mined, and many small stumps of pillars and barrier pillars were left standing; these pillars are now being recovered by stripping. It has become necessary to give more consideration to the effects of blasting at strip mines upon the quality of the air in underground mines adjacent to stripping operations.Special precautions are taken by the .personnel of the Jeddo-Highland Coal Co., whose mines are near Jeddo, Luzerne County, and near Centralia in Columbia and Schuylkill Counties in the anthracite region of Pennsylvania, to prevent asphyxiation of workmen by carbon monoxide or other toxic gases resulting from blasting in strip mines. The procedures established by the Jeddo-Highland Coal Co., are given in this circular so that others may benefit thereby and thus avoid hazards to underground workmen where mining is carried on under similar circumstances."

May 1, 1949

By M. Semchyshen, A. P. Coldren, W. G. Scholz

A survey of the Fe-Mo-B system was made to determine the extent to which boron might affect the microstructure and strength properties of iron-rich Fe-Mo alloys. Seventeen vacuum-induc tion melted ingots were prepared with approximate mo-lybednum contents 01 2, 4, 9, and 19 wt pct and approximate boron contents of 5, 14,50, and 630 ppm by weight. Phases extracted from annealed specimens and identified by X-ray diffraction analysis included E Fe3MO2, Mo2FeB2, and an oxide hazling a diffraction pattern practically identical to that of MnFez04. Three types of alloy strengthening were observed: a) Fe-2 pct Mo-B alloys were hardenable by a bainitic-type transformtion of austenite to ferrile; b) Fe-4 pct Mo-B alloys were hardened by the solid-solution mechanism; and C) Fe-9 pct Mo-B and Fe-19 pct Mo-B alloys were hardened by precipitation of the E Fe3Moz phase. Boron was observed to have a very strong hardening effect in the Fe-2 pct Mo alloys and a mild strengthening effect on the 1200°F properties of the Fe-4 pct Mo alloys. In the Fe-9 pct Mo alloys there was no consistent effect of boron on strength at either room temperature or 1200° F. The Fe-19 pct Mo alloys were so brittle that meaningful tensile or creep-rupture data could not he obtained. No dispersion hardening from borides was recognized in any of the alloys. THE high-temperature properties of iron-rich Fe-Mo alloys were studied by Reiter and Hibbard.' They found that the strength of the alloys increased markedly as the molybdenum content was raised from 0 to 15.9 pct by weight. The authors explained the various degrees of strengthening in terms of a) solid-solution strengthening, b) strengthening from a martensitic-type transformation, and C) precipitation strengthening. The objective of the present investigation was to conduct a survey of the iron-rich portion of the Fe-Mo-B system to determine whether the beneficial effects of molybdenum on the strength of iron can be enhanced by the presence of boron. It was thought that perhaps fine dispersions of molybdenum- rich borides would be found which could improve the high-temperature strength of ferritic alloys beyond the strengths attainable by molybdenum additions alone. Also, it was considered worthwhile to study the effects of boron in alloys which are essentially free of carbon. Most, if not all, of our present knowledge about boron in high-temperature alloys pertains to alloys containing carbon and carbides. EXPERIMENTAL PROCEDURES Alloy Preparation. Seventeen 8-lb ingots were prepared from electrolytic Plastiron, unalloyed molybdenum chips, and boron powder by a vacuum-induction melting procedure employing hydrogen as the main deoxidizer. The alloys were melted in alumina crucibles using 35-lb melts, with each melt being split four ways to achieve varying boron contents within four Fe-Mo base compositions. The results of chemical analyses conducted on chips machined from the chilled ends of the ingots are presented in Table I. The boron analyses were performed by a spectrographic method utilizing primary standards prepared from boric acid. They indicated that in ingots to which no boron was

Jan 1, 1964

By R. F. Mehl, C. S. Barrett, A. H. Geisler

THE studies of the mechanism of precipitation and of the resulting property changes in aluminum-silver alloys1-3 have presented some new concepts of the aging reaction-concepts that may be fundamental in establishing a complete quantitative theory of age-hardening. With both aluminum-copper and aluminum-silver alloys, thin platelike aggregates form parallel to the Widmanstätten planes of precipitation.1,4 These platelets grow in lateral dimensions and in thickness with aging time until they are thick enough to produce an X-ray diffraction line pattern. Their structure is that of a transition lattice which is coherent with the matrix, since the atomic spacings in the matrix and the precipitate are the same on each side of their common interface.2,4 The equilibrium precipitate forms later from and at the expense of the transition lattice. Since age-hardening occurs during the formation and growth of the transition lattice, the major contributor to the hardening no doubt is the stress condition in the matrix resulting from the matrix holding the precipitate in the coherent condition. The development of these stresses also appears to be responsible for an increase in the electrical resistance superimposed on the normal decrease resulting from a change in the concentration of the matrix during aging.3 The two consecutive reactions constituting the aging process are accompanied by characteristic microstructural alterations. The initial precipitation process results in the formation of a Widmanstätten figure, while the later transformation of the transition lattice to the equilibrium lattice is accompanied by a coalescence, in the case of aluminum-copper alloys,5 and by the appearance of light areas at the grain boundaries with aluminum-silver alloys showing a structural rearrangement of matrix and precipitate.3 This latter reaction is similar microscopically to the so-called "discontinuous precipitation." Possibly discontinuous precipitation is a process that often if not always follows true precipitation of a coherent lattice and during which the transformation of the coherent transition lattice to the equilibrium lattice takes place accompanied by matrix recrystallization.3 EXPERIMENTAL PROCEDURE The alloys were made using 99.97 per cent Al or distilled magnesium, with

Jan 1, 1943

By E. H. Jr. Dix

DURING an investigation of high-strength manganese bronze by the Engineering Division of the Air Service, at McCook Field, Dayton, Ohio, particles of a "blue constituent" were noted in the microstructure of most of the bronzes examined. The constitution of the simple copper-zinc base alloy is still a matter of dispute in spite of the fact that the copper-zinc series is one of the oldest industrially important groups of alloys, and has received the early consideration of scientific research. The diagram, according to the most recent work,1 is shown in Fig. 1. The disputed questions involve the termination of the beta field and the line at 470° C. The earliest experimenter, Roberts-Austin, detected an arrest in some of his cooling curves at approximately this temperature and ascribed them to the formation of a eutectic; it has since been proved that there are no eutectics in this series. Shepherd2 was unable to detect any thermal arrests at this temperature; his diagram was essentially as shown in Fig. 1, except that the line at 470° C. was omitted and the beta phase carried down to normal temperatures. Later, Carpenter and Edwards,3 by a very painstaking research, definitely established the authenticity of the line but attributed it to the breakdown of the beta constituent into a eutectoid of alpha and gamma. Microscopic evidence of the formation of the eutectoid is doubtful and it seems more likely to be due to an allotropic change in the beta constituent as shown by Fig. 1. At least for practical purposes, it is more convenient to think of the structure of a 60-40 brass as a mixture of alpha and beta prime crystals rather than alpha plus an unresolvable eutectoid of "apparent beta" as it has often been called.

Jan 5, 1922

By Edward C. Jeffrey

The use of coke in metallurgy, to any important degree, dates from the middle of the 18th century. Its utilization came most opportunely for European civilization. The forests of Europe, except in the most remote and inaccessible regions, had been largely fed, in the form of charcoal, into the smelting furnaces. For a hundred years—the middle of the 17th to the middle of the 18th century—there .was a stationary condition of population corresponding to the exhaustion of European forests. This situation, which was particularly evident in Great Britain, was due to the fact that the forests had been depleted and the practical utilization of coke had not begun. The coking industry is essential for our metallurgical industries, which in turn are basal to healthy economic progress. But coke is of great importance, not only on its own account, but for its byproducts, which enter fundamentally into all the arts of peace and war. The dyestuff industry and the manufacture of explosives are intimately connected with one another, as was shown by the recent war. The subject of coking coal, therefore, is well worthy the serious attention both of practical industry and the scientific investigator. The most valuable coking coals, from the metallurgical standpoint, are derived from the coals of highest ranks. Coals, for example, that have a carbon ratio of from 70 to 80 per cent. yield the most valuable coke for the blast furnace. The difficulty of investigating these coals, however, is great, for they are rather friable and delicate and possess a high carbon content, which makes them difficult to manipulate. They present, on account of their high carbon content, a considerable degree of opacity when examined, in thin sections, under the microscope. The tenderness of structure and blackness of such high-grade coking coals as those of Connellsville and the Pocahontas region make them extremely difficult to investigate. Two of my colleagues, who are taking part in this discussion, will describe the valuable results that have been reached by studying coal by the methods of the mineralogist. Doctor White and Doctor Thiessen have studied the structure of coal as determined from thin sections that

Jan 1, 1925

IN this paper an attempt is made to describe the sluicing operations on the tin fields of north-eastern Tasmania. No claim is made to completeness, for much of the ground has already been covered, and nothing is to be gained by needless repetition. On this account some portions of the subject have obviously received but scanty attention in order that others may be rather more fully dealt with; for instance, figures referring to the accuracy of various methods of valuing alluvial deposits, particulars of efficiencies, and water duties on both overburden and drift; also, the system of recording water distribution, &c.The plans of the tin-streaming shed, sluice and feed·race, and overburden tail-race represent types of the most modern design.The principal alluvial deposits being worked at the present time are situated either in the ancient or modern bed of the Ringarooma river or its tributaries. This river flowed in a north-easterly direction, receiving numerous tributaries on either bank, and finally emptying into Boobyalla harbour. The most important of these tributaries, from a mining point of view, are the Cascade, Main creek, Weld and Frome rivers (which unite just before joining the modern Ringarooma), Wyniford river, and Bradshaw's...

Jan 1, 1911

By M. Viljoen

South Africa has produced more than a third of the total gold mined throughout history and remains a major although, until recently, no longer the largest producer of gold. South African gold production peaked in 1970 with an output of 1 000 t, a major component of the western world?s gold production, with the development of the country?s economy having been based largely on this mineral wealth. The costs and difficulties of increasingly deep-level mining, coupled with increasing labour costs and the low gold price until relatively recently, have seen production fall steadily since then, with the closure of many mines including those of the Central Rand Goldfield in the mid seventies. Thus in 1998, only 464 t were produced, with 342 tons being produced in 2004. In 2006, 275 tons of gold were produced and after more than 100 years was the last year as the world?s largest gold producer. In 2008 gold production was 221 tons, making South Africa the third largest gold producer after China (292 t) and the USA (234 t). Gold production would have been lower if it had not been for massive tailings dam retreatment operations that started in the late seventies, including in the Central Rand Goldfield. Mining of a remaining deep and lower grade shallow resources has now also become a major focus and has recently lead to a rebirth of reef mining on the Central Rand Goldfield.

Jan 1, 2009

By J. Chipman, T. Fuwa

The effects of various elements on the activity coefficient of carbon in liquid iron have been studied by two experimental methods: 1) equilibration with controlled mixtures of CO and CO2; 2) the solubility of graphite in the melt. Activity coefficient of C is increased by Al, Co, Cu, Ni, P, Si, S, and Srz. It is decreased by Cr, Cb, Mn, Mo, W, and V. THE thermodynamic properties of the iron-carbon binary system have now been fairly well established, although some uncertainty remains with respect to the exact location of some of the phase boundaries. The activity of carbon in ferrite and in austenite has been measured in the classic researches of R. P. smith' while similar measurements by Richardson and ~ennis, and by Rist and chipman3 have established the values of the activity of carbon in liquid iron up to 1760°C. On the other hand, our knowledge of the effects of alloying elements on the activity of carbon in dilute solutions is restricted to Smith's experiments on systems Fe-C-Mn and Fe-C-Si in the austenitic range and to some more recent experiments of schwarzman4 in the a range. In addition there have been a number of determinations of the effects of various elements on the solubility of graphite in liquid iron, and from these the corresponding effect in saturated solution may be obtained. The purpose of the present study was to extend the investigation of the liquid system to include the effects of alloying elements upon the activity coefficient of carbon, principally in dilute solutions. Equilibrium measurements were made on the reaction C + co, = 2 CO (g) The prepared mixture of CO and CO,, diluted with argon, flowed over the surface of the liquid metal which, after several hours' exposure to the gas, was quenched and anqlyzed. As in the earlier experiments, the principal experimental difficulty was in the deposition of carbon on the parts of the furnace at temperatures slightly below that of the metal bath. In order to minimize this difficulty, the ratio (Pco)2 /PCo2 was restricted to values not much higher than 100 atm, and correspondingly the carbon concentration in the metal seldom exceeded 0.30 pct. EXPERIMENTAL METHODS The method and apparatus were essentially the same as used by Rist and Chipman.3 The gaseous mixture consisting of highly purified CO, CO,, and argon, each controlled by a flowmeter, was led into the furnace and passed over the surface of the liquid-iron melt which was heated and stirred by high-frequency induction. One slight modification was made in that a molybdenum susceptor was placed outside the crucible for the sake of uniformity of temperature and to combat the tendency of carbon to precipitate on the crucible wall. Pure alumina crucibles approximately 25 mm ID were used. The charge consisting of about 30 g was made up of electrolytic iron, the alloying element to be added, and enough graphite to supply slightly more or less than the anticipated equilibrium carbon concentration. All metals used were of high purity. Metallic chromium, columbium, and vanadium were from special lots supplied by the Electro Metallurgical Co. Tin, copper, molybdenum, tungsten, cobalt, and nickel were of purest commercial grades. The electrolytic iron, after being cut to the proper size for charging, was prereduced by hydrogen at 850° to 1000°C to remove surface oxidation. The oxygen content of the reduced material was 0.002 pct. This treatment made it easy to control the carbon content of the initial melt. The charge was melted under the gas mixture to be used for the entire run. In some earlier melts the charge was melted under a stream of argon, but in this case some alumina was reduced from the crucible, and the aluminum thus absorbed in the melt was subsequently oxidized with the formation of a solid film of alumina on the surface of the melt. AS another safeguard against film formation, overheating of the bath was carefully avoided. All runs were made at a temperature of 1560°C. Under experimental conditions a charge of pure iron picked up 0.17 pct C in 3 hr and 0.23 pct C in 6 hr under an atmosphere for which the equilibrium concentration of carbon is 0.27. It is clear that the time required to reach equilibrium from an initially carbon-free melt would be very great. For this reason each experiment was started with a melt of known carbon concentration not far above or below the expected equilibrium value, and each melt was held at temperature for a period of at least 5 hr. Under such circumstances it was possible to chart the approach to equilibrium from both high-carbon and low-carbon materials. Temperature was controlled by frequent optical observation and adjustment and the metls were timed in such a way that the final 2 hr occurred during a time when electric power was steady; for example, 2 to 4 pm or after 11 pm. In melts containine volatile metals such as copper, tin, and mangane\e the time of holding was decreased somewhat in

Jan 1, 1960

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 Charles T. Malcomson

In the United States, improvements in methods of combustion have made possible the use of the smaller sizes of anthracite. This coal is now being reclaimed from the culm banks accumulated by the miners in the more prodigal years. To-day the freshly mined "slush" is segrega,ted and stored against the time when, through briquetting or some other means, it may be utilized as a commercial fuel. For many years Europe has achieved enviable results in the conservation of her small coal by briquetting. This profitable industry, first placed on a commercial basis in France in 1842, has grown to such magnitude that the production during 1913 exceeded 36,000,000 short tons. Briquets produced in Great Britain are used principally for steam purposes and the greater part of the output is either exported or taken by the Admiralty. On the Continent the briquets are sold in all branches of the coal trade. The French railways consume from 16 to 40 per cent. of their fuel in briquet form, and in Germany the lignite briquets (of which 20,000,000 tons were produced in 1913) are as familiar and interesting to the American traveler as the huge porcelain stoves in which they are burned. It is not strange, therefore, that aggressive and far-sighted promoters heralded this means of converting our ubiquitous coal waste into revenue. To the superficial student the briquetting process seemed so simple as to make success easy. It is for this reason principally that the path of the industry in America has been strewn with failures. The rash enthusiast had either not worked out the mechanical problems involved or had failed to grasp the local conditions under which the briquets must be made and sold. It may be confidently stated, however, that in spite of the many vicissitudes through which it has passed, coal briquetting is now an accomplished economic success in this country, and as a profitable adjunct to the coal industry it has come to stay. Several valuable contributions relating to coal briquetting are found in the Transactions. Charles Dorrance, Jr., has sketched briefly the history of the anthracite briquetting plants from the time of Loiseau's pioneer plant down to that of the Lehigh Coal & Navigation Co. at Lans-ford. Since then this phase of the industry has remained practically at

Jan 1, 1915