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By S. P. Rothwell

ABOUT thirty miles north of, the city of Belleville (which is situated on a branch of Lake Ontario), and in the township of Marmora, Ontario,: there is found a. belt of gold-bearing quartz veins, which present geological, mineralogical, and economic features of great interest to the profession. The district in which these veins are found is characterized as a rolling country, with low rounded bills of syenitic granite, overlain on the flanks of the hills by Silurian limestones, which lie in nearly horizontal beds, and in some places are so fine in texture as to afford lithographic stone of a fair quality. The gold-bearing veins run north and south through this belt of syenitic granite, and are quartz-filled true fissures, with micaccous or talcoid slates forming the walls of and horses in the veins. This

Jan 1, 1881

By E. S. Leaver

THE presence of soluble base metals in precious-metal ores usually precludes cyanidation as the best method of treatment. The laboratory experiments described in this paper show the possibility of cyanidation of gold-silver ores containing less than 0.5 per cent. of cyanide-soluble copper and the effect of zinc in the cyanide solution. PART 1.-COPPER IN CYANIDATION The proposed process of cyanidation of precious-metal ores containing copper is based on the regeneration of about 80 per cent. of the cyanide used in the dissolution of the copper. The method of regeneration involves a combination of the sulfide and the acid precipitation of the copper and silver. The resultant solution is made alkaline with lime, and the gold is precipitated with zinc dust.

Jan 1, 1929

By G. Hasenfus, M. Karmis, G. Goodman

Surf ace subsidence is rapidly becoming an important environmental consideration of active as well as abandoned mining operations. The damages attributed to this phenomenon have been witnessed in both rural and urban areas and include land settlement and fracturing, structural damages to surface buildings or facilities and disruption or contamination of ground water supplies. The problem of mining subsidence has gained considerable emphasis in the Appalachian coalfield. The increased mining activity over the past few years and the particular topographic conditions, lithologic and structural environment, mining methods and hydrological patterns are all factors which have contributed to specific subsidence characteristics in this region. The objective of this paper is to discuss and review the most widely accepted methods of subsidence prediction above longwall as well as partial extraction systems in Appalachia. These include an accurate and easy to apply empirical method, which has been developed entirely from field information pertaining to the Appalachian coalfield and incorporates both geometrical and geological information of the panel in question. The second method is a development of influence functions and is founded on the zone area approach. Both methods, originally derived for longwall mining, have been expanded to include room and pillar applications and have been widely used by the mining industry in the Appalachian coalfield.

Jan 1, 1984

By E. De Golyer

The only known direct method of discovering oil deposits is by the drilling of test wells. Such exploration is always hazardous and generally very costly. The problem of the prospector, therefore, is one of selecting test sites that are favorably located and so to reduce the odds against his venture. Early in the history of the oil industry, it was realized that oil and gas deposits, other conditions being favor- able, were usually found in anticlinal types of structure. This very understandable and rational habit of occurrence furnished the first substantial clue to the prospector. Oil occurs in sedimentary rocks, and beds of such rocks are deposited originally in parallel planes. An anticline at the surface, therefore, could be accepted as an indication of an anticline in lower beds. Structural geology became the tool of the prospector, and by its use in the past two decades, the majority of the known important oil deposits of the world have been discovered. This is but an incomplete, and the simplest, statement of the problem. Nine-tenths and more of the important oil pools of the world belong to the great class of accumulations controlled by structural traps- anticlines, faulted structures, salt domes, etc.-but by

Jan 1, 1932

By E. H. Jr. Dix

OF all the alloying elements used in commercial aluminum alloys, copper stands out as by far the most important, and it is perhaps for this reason that the constitution of the aluminum-copper system has received the attention of a number of experimenters covering a period of approximately 20 years. It would be expected that during this time the equilibrium relations had been thoroughly and exactly worked out. In a general way this is true, but there is a surprising lack of agreement in the details of the high aluminum end of the diagram, particularly in regard to the solid solubility of copper in aluminum, which has been given variously as 2 per cent. to 5 per cent. at the eutectic temperature. The importance of this is much greater than might at first appear to one unfamiliar with modern commercial aluminum alloys. This is true because, with one exception, the susceptibility of the strong alloys to heat treatment depends, in part at least, upon the solid solubility relations of copper in aluminum. In 1919, Merica, Waltenberg, and Freeman1 published the first detailed information on these solubility relations. They found that the solubility of copper decreases with falling temperature from about 4 per cent. at 5.25° C. to about 1 per cent. at 300° C. and is apparently still diminishing at lower temperatures. In 1921 there was published a brief account of the results obtained in the National Physical Laboratory, Teddington, England.2 This laboratory, however, reported that 5 per cent. of copper is soluble in aluminum at 540° C., and that this amount decreases to about 3 per cent. at 20° C.

Jan 2, 1926

By P. E. Hopkins

Introduction and History IN speaking of the economic geology of southeastern Ontario, W. G. Miller and C. W. Knight' say that "there occurs in southeastern Ontario a variety of minerals and rocks of economic value, probably as great as in any district of like size on the North American continent. Some of these deposits, including marble and trap, are inexhaustible. Others, including talc and iron pyrites, have proved to be of considerable economic importance. From time to time, during the last 50 years, the following minerals and rocks have been mined or quarried with varying success: gold, iron pyrites, zinc blende, copper pyrites, galena, mispickel, magnetite, hematite, talc, actinolite, mica, marble, ophicalcite, feldspar; fluorite, apatite, corundum, graphite and sodalite. All of the economic materials, with the exception of fluorite, appear to be of pre-Cambrian age. The fluorite veins penetrate the Ordovician, Black River, limestone." Accompanying that report was an article by the writer on the Queensboro Pyrite Area which includes one of the two working pyrite properties in southeastern Ontario. In the present paper will be given a brief description' of all the known pyrite deposits in the area which may at some time possess an economic value, with fuller descriptions of the two working mines-The Canadian Sulphur Ore Co.'s mine near Queensboro, and the Nichols Chemical Co.'s property at Sulphide. The earliest mining of iron pyrites in Ontario was done in 1868 on the Billings property near Brockville. The mines were closed down in 1879 under the assumption that they were exhausted. Many other

Jan 8, 1916

By Dever Ashmead

ANTHRACITE was first mined in the Wyoming Valley and sold as an article of commerce in 1808. As some preparation has always been necessary to make it ready to burn, the preparation of anthracite must date back over a hundred years. Two vital factors have determined to a large extent the degree and method of anthracite preparation. These are, first, the character of the beds worked and the methods by which they were mined and, second, the equipment used and practices followed in the burning of the coal. It is not the intention here to go deeply into these phases of preparation as a paper of no mean length could be prepared on the history of either. Rather, the intention here is to point out the main considerations and to show the influence they have exerted on the preparation of anthracite. MINING METHODS AND THEIR RELATION TO PREPARATION In the beginning f the nineteenth century, the coal beds were virgin with the possible exception of some outcroppings that had been worked, to a slight extent, by the Indians. It is known that the American aborigines had a knowledge of the use of this fuel, because when the Wyoming Valley was purchased from them, in 1754, they mentioned the fact that, by selling the land, they would lose their coal.

Jan 9, 1921

By A. M. Sarem, J. M. Campbell

Molecular refraction is introduced as a new and improved third parameter for prediction of the PVT behavior of hydrocarbon systems. This parameter, characterizing the complex as well as the pure hydrocarbon systems (1) is a direct measure of London dispersion forces which affect the PVT behavior; (2) can be measured directly, accurately and easily for complex as well as pure hydrocarbon systems; (3) varies significantly between the reference substances thus allowing accurate interpolation of PVT properties; and (4) has a fundamentally sound basis. Molal average molecular refraction was used with the pseudocritical mixing rule proposed by Leland and Mueller to predict the molal volume of liquid and vapor for 84 published data points on nC4-nCI0, Cl-nC5, Cl-nC4-nC10 systems in the region of coexisting vapor-liquid and at the critical point. The same technique was applied to predict the densities of liquid hydrocarbon mixtures in the two-phase and single-phase regions near the critical point for seven different systems each having different properties of the heptanes-plus fraction, but all simulating the fluids of either gas-condensate or volatile oil reservoirs. A modification of the Leland-Mueller mixing rule for the determination of pseudocritical properties is also presented which yields more accurate liquid density predictions than the original form when used with the proposed third parameter. INTRODUCTION The PVT behavior of multicomponent systems has received widespread attention in the literature in recent years. A large portion of the reported work has stemmed from attempts to overcome the inherent difficulties encountered when using the standard compressibility-factor chart which shows 2 as a function of reduced temperature T, and and reduced pressure p,. This chart assumes that z, is constant for all systems. The error in this assumption is not pronounced for pipeline-type gases high in methane and low in heavy ends, particularly when contained at moderate pressures. For such gases the error in the calculated z is usually less than 2 to 3 per cent. However, the reliability of this approach becomes somewhat nebulous for gas condensate and volatile oil systems at high pressure. One logical approach has been to recognize the variation of 2,. This idea was first suggested by Meissner and Seferianl and used by Lyderson, Greenkorn and Hougen2 to prepare extensive tables of thermodynamic properties. Other third parameters have been proposed by Stockmeyer, Kihara, Riedel, Lightfoot, Bloomer and Pitzer. These were tested by Satter and Campbel13 for many gas mixtures and it was shown that they were inter-related. All of these third parameters have a common fault — they cannot be directly evaluated for the heptanes-plus fraction. Consequently, one necessary requisite of an improved method for predicting the density of multicomponent hydrocarbon systems, was development of a third parameter that could be evaluated for that fraction. PREVIOUS MULTICOMPONENT DENSITY PREDICTION METHODS Sage and Lacey4 suggested a method of using partial molal volumes for computing the density of hydrocarbon gas mixture for pressures to 3,000 psi. In this technique, they approximate the complex multicomponent gaseous mixtures by a quarternary system of methane, ethane, propane and butane. Sage, Hicks and Lacey5 suggest a method of using partial molal volumes for computing the density of hydrocarbon liquids. The results agree within 3 per cent of the experimental values. However, the composition range is limited to about 10 per cent by weight of methane. Consequently, this correlation does not cover the low-molecular-weight liquid similar to natural gasoline and high-pressure gas condensates.

Jan 1, 1966

By George Moore

IN spite of many investigations of the occlusion of hydrogen in iron, the nature of the process and the reasons for the accompanying effects upon the metal are still open questions. This is in large part due to three causes: (1) the difficulty of obtaining iron of adequate purity as starting material; (2) the occurrence of allotropic transformations, which compli-cate the effects; and (3) the fact that the body-centered cubic modifica-tion does not lend itself readily to crystallographic investigation. The present paper attempts a critical review and correlation of the somewhat scattered and disconnected existing observations, and an experimental determination of the extent to which the conclusions that appear to follow from these are applicable to iron of really high purity, studied under well-defined conditions.

Jan 1, 1939

By AIME AIME

CLYDE WILLIAMS, after graduating from the University of Utah as a chemical engineer, worked for a time in western mills and smelters. He then joined the U. S. Bureau of Mines and during the World War studied Ordnance Department and Navy problems on ferroalloys and alloy steels at the Cornell University laboratories. Later, as superintendent of the Northwest Experiment Station of the Bureau, he was active in electric furnace and ore reduction work. Clyde then went to South America and surveyed the iron and fuel resources of the Argentine. Returning, he became chief metallurgist of the Columbia Steel Corp., of

Jan 1, 1936

By Takashi Katsura, Avnulf Muan

Equilibrium relations in the system FeO-Fe2O3 Cr2O3 have been determined at 1300°C at oxygen pressures ranging from that of air (0.21 atm) to 1.5 x 10-11 atm. The following oxide phases have stable equilibrium existence under these conditions : a sesquioxide solid solution with corundum-type structure (approximate composition Fe2O3-Cr2O3); a ternary solid solution with spinel-type structure (approximate composition FeO Fe2O3-FeO Cr2O3) and a ternary wüstite solid solution with periclase-type structure and compositions approaching FeO. The metal phase occurring in equilibrium with oxide phase(s) at the lowest oxygen pressures used in the present investigation is almost pure iron. The extent of solid-solution areas and the location of oxygen isobars have been determined. ThE system Fe-Cr-O has attracted a great deal of interest among metallurgists as well as ceramists and geochemists. Metallurgists have studied the system because of its importance in deoxidation equilibria, ceramists because of its importance in basic brick technology, and geochemists because of its importance for an understanding of natural chromite deposits. Chen and chipman1 investigated the Cr-O equilibrium in liquid iron at 1595°C in atmospheres of known oxygen pressures (controlled H2O/H2 ratios). The main purpose of their work was to determine the stability range of the iron-chromite phase. Hilty et al.2 studied oxide phases in equilibrium with liquid Fe-Cr alloys at 1550°, 1600°, and 1650°C. They reported the existence of two previously unknown oxide phases, one a distorted spinel with composition intermediate between FeO Cr203 and Cr3O4, the other Cr3O4 with tetragonal structure. They also sketched diagrams showing the inferred liqui-dus surface and the inferred 1600°C isothermal section for the system Fe-Cr-O. Koch et al3 studied oxide inclusions in Fe-Cr alloys and also observed the distorted spinel phase reported by Hilty et al. Richards and white4 as well as Woodhouse and White5 investigated spinel-sesquioxide equilibria in the system Fe-Cr-O in air in the temperature range of 1420" to 1650°C, and Muan and Somiya6 delineated approximate phase relations in the system in air from 1400" to 2050°C. The present study was carried out at a constant temperature of 1300° C and at oxygen pressures ranging from 0.21 atm (air) to 1.5 x 10-11 atm. The chosen temperature is high enough to permit equilibrium to be attained within a reasonable period of time within most composition areas of the system, and still low enough to permit use of experimental methods which give highly accurate and reliable results. These methods are described in detail in the following. I) EXPERIMENTAL METHODS 1) General Procedures. Two different experimental methods were used in the present investigation: quenching and thermogravimetry. In the quenching method, oxide samples were heated at chosen temperature and chosen oxygen pressure until equilibrium was attained among gas and condensed phases. The samples were then quenched rapidly to room temperature and the phases present determined by X-ray and microscopic examination. Total compositions were determined by chemical analysis after quenching. In the thermogravimetric method, pellets of oxide mixtures were suspended by a thin platinum wire from one beam of an analytical balance, and the weight changes were recorded as a function of oxygen pressure at constant temperature. The data thus obtained were used to locate oxygen isobars. The courses of the latter curves reflect changes in phase assemblages and serve to supplement the observations made by the quenching technique. 2) Materials. Analytical-grade Fe2O3 and Cr2O3 were used as starting materials. Each oxide was first heated separately in air at 1000°C for several hours. Mixtures of desired ratios of the two oxides were then prepared. Each mixture was finely ground and mixed, and heated at 1250" to 1300°C in air for 2 hr, ground and mixed again and heated at the same temperature for 5 to 24 hr, depending on the Cr2O3 content of the mixture. A homogeneous sesquioxide solid solution between the two end members resulted from this treatment. A Part of some of the sesquioxide samples thus prepared was heated for 2 to 3 hr at 1300°C and oxygen pressures of 10-7 or 1.5 x 10-11 atm. Reduced samples (either iron chromite

Jan 1, 1964

By John D. Wiebmer

Lignite Development in North Dakota is a "shotgun wedding" according to former state senator Robert L. Stroup-the unwilling groom (North Dakota) is being led to the altar by the nation's demand for increased coal production. The state's attorney general, Allen I. Olson, reacts to the situation this way: "We have no specific coal policy. We plan to keep the whole matter down to a dull roar and drag our feet until we see how we fit into the national energy picture." But despite a state administration labeled as "cautiously negative" toward resource development, North Dakota has experienced a twofold increase in annual lignite production within the last two years. And within the next four years, three more mine additions will double the state's output again.

Jan 8, 1977

By T. R. Braithwaite

The brief comments made in this chapter deal mainly with shaft sinking, but don't assume that freezing techniques apply only to shaft sinking. They can be used on tunnel work, on such things as liquid gas storage in sediment, and I think you will probably see other applications for it as we go along. The method was first developed in 1883 and was used to sink shallow shafts through water-bearing overburden in Germany and in England. One of the early shafts was in Germany and was sunk by freezing to 310-ft depth. The project required 17 months for drilling, roughly 5 1/2 months for freezing, and another 7 months for sinking, giving an average progress of 10 ½ fpm. Fortunately there have been numerous improvements and new developments in this technique through the years. With equipment and techniques available today, we can take a 20-ft-diam shaft down through 2000 ft of water-saturated overburden and the time schedule runs roughly 4 months for site preparation, freeze-hole drilling, installing the casings, and setting up the plant; 4 ½ months for freezing; and 6 months for excavating and installing permanent linings. This gives a progress rate of about 140 fpm, on average. I might qualify that a little in that the special linings that are required for some formations can affect the time. If it's straightforward sinking where one can use a heavy concrete lining, up to 630-640 fpm may be achieved in a shaft; but with special cast-iron tubbing or types like that, 5 fpd is pretty good progress, so the lining does affect the time. The freezing method is used mainly for sinking shafts through unstable water-bearing formations which cannot be grouted either effectively or economically and which are too deep to enclose in pile casing. Even with overburden, grouting methods available today can handle roughly 100 lb water pressure; in the range of, say, 100 to 150 ft from the surface, it's very often best to grout 40 or 50 ft. You normally drive a pile casing and go through it. Below that range, freezing is very often the economical

Jan 1, 1970

By C. H. Herty

AN earlier paper on absorption of sulfur by the slag in the basic open-hearth furnace included a brief discussion of the absorption of sulfur during the melting period. The data available at that time showed that the amount of sulfur absorbed by the melting scrap was proportional to the sulfur content of the furnace gases, and the following statement was made: "The conclusion may be drawn from these results that if a gas entirely free from sulfur were used during the melting, any iron in direct contact with the gases would be completely, or nearly completely, desulfurized before it reached the bath proper." The experimental work discussed herein deals with absorption of sulfur by the melting scrap when fuels with both high and low-sulfur content were used. Before taking up the experimental work let us consider the process as a whole as to the "flow" of sulfur. The input of sulfur occurs in: 1, the hot metal charged; 2, the scrap; 3, the stone or lime charged; 4, the ores charged; and 5, the gas. Sulfur goes out of the furnace in the steel, the slag and the gas. The distribution of sulfur in the furnace depends on the sulfur concentration in each of these materials and on the equilibrium conditions between them.

Jan 1, 1926

By H. H. Lowry

SCIENCE attracts the attention and interest of an individual or an industry in general only in proportion to the apparent direct application to its immediate welfare or benefit. Engineering accomplishments, as applied science, therefore receive more recognition than the scientific discoveries on which they are based. Even self-evident truth needs endless repetition before recognition: engineering as applied science cannot advance beyond the science on which it is founded. Scientific research, and discovery, is sometimes forced by the limitations recognized by those active in its development for the use of society and industry and sometimes results from an apparently superficially illogical curiosity about natural phenomena. Research has received inadequate support except in industries born in the laboratory, the chemical and electrical industries, from which many lessons might well be drawn by their elder associates. The rapid growth of these industries has been largely due to close cooperation of scientists and engineers. Most rapid advance is made when the research worker and the engineer keep in close touch with each other's ideas and problems. Many of the developments of modern industry are based on dis-coveries buried for years in scientific journals because the "time was not ripe" at their discovery. The situation with regard to utilization of coal is quite the opposite. The fundamental facts in regard to the scientific aspects of the problem of developing the energy from coal are scarcely known. The engineer, without much scientific cooperation, has accom-plished much in increasing the number of kilowatt-hours per pound of coal from 0.31 in 1919 to 0.69 in 1934, in increasing the 1000 gross ton-miles of freight hauled from 6.1 to 8.3 per ton of coal in the same period, in fuel economy in production of coke, and in developing the production of motor fuel in Germany and England by hydrogenation of coal. This lack of scientific research on the utilization of our most important natural resource, coal, has been due undoubtedly in large part to the reluctance of investigators to study the interrelationships involved in, the complicated processes in which coal is used. These complexities are made

Jan 1, 1936

ANY suitable characterization of the Utah Copper enterprise (now the Utah Copper Division of Kennecott Copper Corporation) involves the use of superlatives. If comparative records were compiled, after the fashion of baseball, the big opencut mine at Bingham Canyon, Utah, undoubtedly would hold dozens of championships in the mining world. For example, a few can be set down as follows: (1) The mine is the biggest man-made hole (excavation) in the crust of the earth! At the end of 1955 the total quantity of material moved (ore and overburden) was 1,673,000,000 tons or approximately 800,000,000 cubic yards. This is about3% times the yardage of earth moved in the original digging of the Panama Canal. It exceeds by fifty per cent the quantity dug in the justly famous Hull-Rust Mahoning open-pit iron mine on the Mesabi Range in Minnesota. (2) It holds first place among the mines of the world as to aggregate tonnage of ore mined and milled (734,000,000 tons at the end of 1955). (3) It holds first place among the mines of the world as to the aggregate quantity of metal produced (13,047,000,000 Ib- 6,523,500 tons-of refined copper). This is more than the actual production of all the mines in the United States during the eight-year period 1948 to 1955 inclusive. (4) In 1943, Utah established these world records: Tons of ore milled in a 24-hr day.. ................. 108,000 Tons of ore and waste moved in a 24-hr day.. ....... 235,000 Tons of ore milled in one month. ................... 3,074,000 Tons of ore milled in a year. ....................... 35,375,000 Pounds of copper produced in a year……….. 639,0000,000

Jan 1, 1957

By G. L. F. Powell

g samples of Cu-20 wt pct Ag alloy have been mdercooled to a maximum of 197°C by melting under a slag of commercial soda-lime glass in a vitreous silica crucible. No grain refinement of the primary copper was observed in samples undercooled to the maximum of 197°C. When the samples contained a small amount of oxygen, the copper dendrites were partially recrystallized at undercoolings greater than 97°C. In previous papers'-3 reporting the grain structure of undercooled silver and copper, it was observed that grain refinement was dependent on both undercooling and oxygen content. Grain refinement occurred in undercooled silver when the degree of undercooling exceeded the range 153" to 175"C, while in Ag-0 alloys (0.12 wt pct) fine equiaxed grains were exhibited when undercooling was greater than 50°C. Similarly, copper samples undercooled as much as 208°C displayed fan-shaped growth from a single nucleation site, while the grain structure of Cu-O alloys (0.08 wt pct) was fine and equiaxed at undercoolings larger than 150°C. Thus the presence of oxygen greatly reduced the undercooling at which grain refinement occurred. It was also observed that the change in grain size resulted from recrystallization and was not due to an enhanced nucleation rate in the liquid-solid transformation. It is possible that the influence of oxygen on recrystallization is due primarily to its presence as a solute element. walker4,' reported that, although a grain size change did not occur in pure nickel until the undercooling exceeded 150°C, small grains were observed in samples of Ni-Cu alloy solidified at small and large degrees of undercooling. Jackson et al.6 suggested that the fine grained structure of the Ni-Cu alloy resulted from the melting off of dendrite arms during recalescence. This remelting process may occur in alloys as a result of segregation during freezing which causes a variation in liquidus temperature from point to point within a dendrite. It was therefore decided to undercool copper with a metallic alloying element to ascertain whether the presence of a metallic solute would have a similar effect to oxygen in inducing grain refinement. A Cu-Ag alloy was chosen, since both metals had been shown to behave similarly on undercooling. The alloy Cu-20 wt pct Ag was selected since the eutectic constituent outlines the initial growth form of the primary copper, so that the as-frozen grain structure is not obscured if subsequent recrystallization occurs. This paper describes the results of undercooling experiments carried out with Cu-20 pct Ag samples undercooled to a maximum of 197°C and the effect of oxygen content on the grain structure of the undercooled samples. EXPERIMENTAL Melting was carried out in a small cylindrical resistance furnace using "fine" silver granulate and oxygen-free high conductivity copper. The procedure adopted was to melt the required quantity of silver in air in a clean vitreous silica crucible for approximately 15 min, freeze, and add granulated commercial soda-lime glass to form a complete surface slag cover, after which the sample was melted and frozen several times to reduce the oxygen content. The glass slag cover was approximately 3 in. thick. Pieces of copper (=50 g) were added to the crucible until the required quantity to make 350-g samples of alloy had been charged. Each piece was added quickly to the crucible which was held at a temperature slightly above the melting point of silver. The piece was quickly pushed beneath the glass to minimize oxidation and any oxide coating usually decomposed before the piece had settled down into the silver. After the full quantity of copper had been added, the melt was stirred with a silica rod to hasten homogenization and a Pt/Pt 13 pct Rh thermocouple enclosed in a vitreous silica sheath inserted for temperature measurement. Heating and cooling curves were recorded on a potentiometric chart recorder fitted with a zero suppression unit. The milli-voltage range of the recorder was adjusted so that temperatures could be read to 1°C. Heating and cooling curves were taken every hour until three consecutive readings gave the same solidus-liquidus range, consistent with the solidus-liquidus range for this alloy composition by reference to Hansen and Anderko.7 Metallographic examination of samples frozen at this stage, failed to show any variation in composition from bottom to top of the ingot. Consequently, it was considered that the melt was homogeneous at this stage and undercooling experiments were then car-

Jan 1, 1970

By E. P. Pfleider, D. H. Yardley

Layers of magnetic taconite of above average magnetic iron content extend down dip on the Mesabi Range to depths beyond the reach of open pit mining. A selected layer with thickness of 75 to 100 ft underlies many square miles. Such a selected layer can provide over 50 million tons of recoverable concentratc per square mile, at lower concentration ratios than in the present open pit taconite operations. The system contemplated would consist of large scale underground quarrying by a lane and pillar method. Working heights would be 60 to 100 ft; room widths, 50 to 75 ft; and productivity targets, about 40 tons per man-shift. The most critical problems would he roof control and blasthole drilling. The successful operation of large open pits and concentrating plants for treatment of magnetic taconites indicates that the basic techniques and economic problems of pellet production have been solved. The open pit reserves are large, but they are not necessarily available in sufficient quantity or quality to provide an adequate raw materials base for all potential producers. Furthermore, as the more easily available open pit crudes are used up, the pits will become deeper, stripping costs per ton of concentrate will increase, and recoveries will decrease as leaner crudes are utilized. The time will come when supplementary and replacement reserves of magnetic taconite will be required. One way these can be obtained is by underground mining of the down-dip extension of the Mesabi magnetic taconites, especially those layers averaging well over 25% recoverable iron. A key point in such a proposal is the possibility of realizing substantial savings by beneficiating an ore of 30% magnetic iron at 2.5 to 1 ratio of concentration. This contrasts with current practice in Mesabi commercial taconite plants, where the ore averages 22 to 25% magnetic Fe, with concentration ratios of about 3.0 when producing 61% Fe pellets. Two factors which favor the eventual development of underground taconite mining are: 1) the desirable physical structure and high grade of taconite pellets in general and 2) the improved engineering techniques in underground mining. Experience in large scale room and pillar mines demonstrates that, given strong rock strata immediately above a high grade mining

Jan 1, 1963

By Raymond Howe

SOME time ago,, a prominent engineer asked a representative of the firebrick industry to prepare a comprehensive paper on blast-furnace refractories. It was to have been the purpose of this paper to gather practical experiences from widely different sources, in the hope of determining what kind or kinds of firebrick were best adapted for certain uses. This engineer sent questionnaires to the large consumers of blast-furnace linings and stovebrick and received very detailed replies as to their experiences. These replies are conflicting, but, having been turned over to the writer, form the basis of this attempt to meet the request. Because of the impossibility of making final recommendations at this time, a few of the more interesting and commonly known methods of studying refractories are also discussed, as well as the more recent developments in this field. The first reply to, the questionnaire stated that good service was being secured from the linings. This satisfactory condition was attributed to the use of a very good distributor. The writer believed that manufacturers try to and do produce a good product and that the proper handling of equipment is of the utmost importance, if good results are to be secured. The type of bricks used was not mentioned. The second reply stated that good life was secured from the furnace linings, but that the writer had had soft-fired stovebrick crumble and, for that reason, preferred a hard-fired product for use in this position. The type of bricks used was not mentioned. The third reply stated that firebrick had crumbled from the mantle up; the cause was not known. The fourth reply stated that the stove linings were satisfactory. Hand-made furnace linings failed after 4 years' service so a steam-pressed lining was installed which was still good after 4 years of service. Consequently, a second steam-pressed lining was installed but this disintegrated at the top after the furnace had been in- blast 7 months. The firebrick manufacturer attributed this failure to the expansion of iron blocks that had been installed at the stock line to prevent erosion.

Jan 9, 1919

By J. Larsen-Badse

The resistance to dry sliding abrasion us been measured for some hardened and tempered carbon steels. The wear resistance, defined as the reciprocal of the volume loss per unit sliding distance, is found to vary linearly with the hardness of the abraded surface. The data fit two lines, one, of high slope, for the pure metals and for the annealed steels and another, of smaller slope, for the hardened and tempered carbon steels. A relationship is developed showing the alwasion resistance to be proportional to the hardness of the material and to en, where n is the exponent of work hardening. The values of n and of the hardness FOR most materials a high resistance to abrasion is generally associated with a high value of indentation hardness. Brine11 even used the abrasion resistance as a measure of hardness in an attempt at expanding the hardness range covered by his indentation-hardness test.' When comparing different types of materials there is, however, only a very general relation between abrasion resistance and hardness. Sample brittleness seems to contribute to the deviation from a direct relationship. In general, increased brittle- are those relating to the heavily deformed abraded surface. However, for materials having n constant or varying m a regular manner over a wide range of strailts, the wear resistance will also be a linear function of the bulk hardness of the material. For tempered steels containing a dispersion of cementite in ferrite the increase in wear resistance due to the dispersion is found to be a linear function of the volume fraction of Fe3C and of the reciprocal of the mean free ferrite path. This indicates indirectly that the yielding of this material, when it is already heavily deformed, follows the Orowan criterion. ness leads to decreased abrasion resistance.' When comparing materials in the same group, e.g., the metals, the spread is less. Kruschov found that the abrasion resistance of pure metals and of annealed steels is directly proportional to the hardness of the metal. For hardened and tempered steels he obtained another linear relationship, one of smaller slope and intersecting the line for the pure metals at the location of the data for the annealed steels. He also found that the abrasion resistance of cold-worked metals is independent of the degree of cold working. This shows, as he concluded, that the process of abrasion work hardens the metal in the surface region to a very high degree.

Jan 1, 1967