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By Lloyd Pollish, Robert N. Breckenridge

SUCCESS in any underground mining operation is determined by accessibility of the orebody, which in turn is dependent upon maintenance of passage- ways to the mining zones and temporary support of the voids caused by extraction of ore. This is accomplished by one or a combination of the following methods: timbering, back-filling, pillaring, or, more recently, rock bolting. Timbering has usually been the principal means of maintaining these underground openings necessary for mining operations. Timber, however, does not prevent ground movement beyond the scope of localized sloughing, which is indicated by the gradual failing of the timber itself. Besides this, timbering has always been a costly process, and with the decline of available supplies of timber close to the mining areas, mining men have constantly sought other methods of controlling ground.

Jan 7, 1954

By C. B. Foraker

THE Magma mine, of the Magma Copper Co., at Superior, Pinal County, Arizona, is 68 miles east of Phoenix and 21 miles west of Miami, Arizona, on highway U. S. 180. TEMPERATURES AND UNDERGROUND WATERS Surface Temperatures.-The average surface dry-bulb temperature at Superior is 72.4°; wet-bulb, 57.4°; with an indicated relative humidity of 38 per cent. The average yearly rainfall from 1921 to 1936, inclusive, was 18.74 in. The maximum condition of the atmosphere is in June, July and August, and the minimum is in January and February. The surface temperatures, of course, influence the temperatures of the down-cast shafts; however, the variation between winter and summer causes a difference of only 2° to 3° in the stopes and working places that are not close to the intake shafts. Average atmospheric conditions are shown in Fig. 1. Rock Temperatures.-Rock temperatures on the deeper levels of tile mine are as follows: LEVEL DEGREES LEVEL DEGREES 2000 109 3200 127 2250 112.5 3400 130 2550 116 3600 134 2800 120 3800 137 3000 124 4000 140 There appears to be no difference in rock temperature for any particu-lar horizon of the various formations or in the vein. Water encountered is always the same temperature as the rock from which it flows, and for this reason it is thought that the water is heated by the rock; not the rock by the water. The country rock apparently has been heated by the various intrusions, perhaps the vein itself, and has not yet had time to cool off. The geothermal gradient (Fig. 2) as indicated by the rock tem-peratures given above is 1 1/2 ° per 100 feet.

Jan 1, 1938

By V. A. Josendal, J. W. Wilson, B. B. Sandiford

Two radioactive tracers have been tested as a means of determining core saturation in multiphase flow studies. Cesium chloride was tried as a water-phase tracer, but complications in its use in low permeability cores resulted from sorption of cesium by the core or water-wet pads. IodoI3'ben-zene proved very satisfactory as an oil-phase tracer. The synthesis of iodobenzene from the sodium iodide as received from Oak Ridge is simple and direct. The tracer is insoluble in water and there was no evidence of sorption by any of the core materials used. use of the method to determine saturation profiles during capillary and dynamic desaturations and relative permeability measurements on oil-water and oil-gas systems is described. Comparisons of the dynamic and capillary methods of relative permeability determination were made using the tracer to check core saturation and saturation distribution. Other experiments are also described in which mobility of the oil phase at various saturations was measured by displacing labeled oil by flowing inactive oil. Similar experiments were made using water labeled with cesium 134. INTRODUCTION To be fundamentally sound. any laboratory method of determining relative permeability must meet, among others, the following requirements: (1) the core saturation between the pressure taps must be uniform, and (2) there must be uniform pressure difference between the phases in the region between the pressure taps. In practice it may eventually be shown that appreciable departure from either or both of these conditions may be permitted without introducing sensible error. but the magnitude of such error remains to be established. There is need then for methods of saturation determina- tion which will determine the saturation profile in a core as well as the overall average saturation given by the gravimetric or material balance methods usually employed. Methods which have received consideration include resistivity, X-ray absorption, gamma ray absorption, neutron diffraction, and radioactive tracers. The resistivity method has use in the determination of profile, but needs checking by independent means.' The X-ray method has been used successfully, but requires elaborate equipment and calibration.23 4 At present gamma ray absorption is practical only for very large cores. The neutron methodo does not appear adaptable to measurement of saturation variations in short cores since it is a scattering method. Russell, Morgan and Muskat' employed radiovanadium in a study of the mobility of interstitial water. Coomber and Tiratsook used radioiodine as an oil-phase tracer and measured profiles in unconsolidated sand packs. ADVANTAGES OF RADIOACTIVITY METHOD A thorough discussion of the theory of radioactive tracers and the technique of using them to study the movement of fluids in sands is given by Coomber and Tiratsoos and need not be detailed here. The method requires less equipment than the X-ray method; the counting problem is similar, but the generation and regulation of the radiation, which is a major problem in the X-ray method, is not required in the radioactivity method. In the X-ray method it is customary to add up to 20 per cent of absorber, usually an iodine compound, to the phase to be labeled. while in the radioactivity method a mere trace is sufficient. A possible disadvantage of the radioactivity method is that a disproportionate amount of the activity comes from the portion of the core nearest the counter, whereas the X-ray gives a true average saturation in the region traversed by the beam. 011 the other hand, this characteristic of the radioactivity method renders it peculiarly adaptable to study of certain types of radial variations in saturation. As with the X-ray method, a tracer may be added to either the oil or water-phase. An oil-phase tracer is more generally useful. however. since it permits work on oil and gas in the

Jan 1, 1952

By H. J. Gluiskoter

The chlorine content of the coals in the Illinois Basin ranges from 0.00% to more than 0.60%. The chlorine content of the Herrin (No. 6) Coal has been mapped on a regional scale and, in general, increases with the depth of the coal. The depth-chlorine correlation exists because the coal is in apparent equilibrium with the composition of the ground water associated with it, and the salinity of the ground water generally increases with depth. At least part of the chlorine can be easily removed from the coal in the laboratory. In a natural weathering experiment, chlorine values decreased markedly during an 8-week period. Results to date indicate that none of the coals studied has a sufficiently high chlorine content to make it unusable in high-temperature steam boilers, although special steps may be necessary in the preparation or utilization of some of the highest chlorine coals. Investigations into the occurrence and distribution of chlorine in Illinois coals have been in progress at the Illinois State Geological Survey for over 35 years. Since 1948, chlorine analyses of face channel samples and of drill core samples of coal have been made routinely. The increased interest in chlorine and alkalies in coal in the U.S. followed that in Europe, where power plants during World War II were called upon to produce at higher levels than previously and with less down time for maintenance. Higher steam temperatures were reached, resulting in increases in the amount of fouling of external heating surfaces and in corrosion of boiler tubes when high chlorine coals were used. Early studies of the problem showed that coals with high chlorine content were more likely than those low in chlorine to cause difficulties in installations fired with powdered fuel. Crossleyl reported that the first rule of thumb developed for British coals was that coals considered to be high in chlorine (more than 0.30%) caused the most trouble, those intermediate in chlorine content (0.15% to 0.30%) were less likely to cause difficulties and those low in chlorine (less than 0.15%) generally were not associated with alkali bonded deposits and corrosion. However, this relatively simple picture was not adequate to characterize the difficulties that could be expected during the utilization of a large number of coals and Crossley1 developed another scheme for assessing the chances of superheater corrosion. This scheme took into consideration the observation that coals high in sulfur as well as chlorine are more likely to cause corrosion and fouling than coals low in sulfur and high in chlorine. Crossley also considered the ash content. When two coals had the same chlorine and sulfur contents, the one with the greater amount of ash would be the less likely to cause difficulties. Knowing only the amount of chlorine in a coal obviously will not give all the answers. Indeed, the significance of the chlorine content has been much discussed and it has been suggested that perhaps the total alkalies are a better indicator of possible troubles. The observation that the deposits that form

Jan 1, 1968

By Paul T. Allsman, E. W. Newman

Trenching, sampling, and core drilling in Stillwater and Sweetgrass Counties, Mont., by the Bureau of Mines have delimited over 5,000,000 tons of chromite ore containing more than 20 per cent chromic oxide. The Benbow and Mouat-Sampson mines have been developed and are fully equipped for mining and milling 500 tons and 2000 tons a day, respectively. Introduction The Montana chromite deposits were the first to be explored under the Strategic Minerals Act of 1939. In June of that year, the Bureau of Mines started exploration by trenching, test pitting, sampling and diamond drilling, and completed the project in March 1943. The U. S. Geological Survey cooperated by mapping the geology and logging the cores. The project was to determine the extent and grade of the chromite ore and to indicate sufficient reserves to justify development and exploitation of the deposits for the national emergency. Exploration has indicated that the district contains the largest and most important reserve of chromite ore in the United States. The Benbow and Mouat-Sampson mines have been developed and a 500-ton concentrating mill has been constructed on the Benhow property and a 2000-ton mill on the Mouat-Sampson property. Concentrates were produced from the Benbow mill three months after the attack on Pearl Harbor, when the nation's major chromite supplies from foreign sources were cut off. History It has been known for 50 to 60 years that some chromite deposits existed in an east-west belt along the north escarpment of the Beartooth Mountains about 25 miles north of Yellowstone Park, but nothing was known of their size and extent until the war demand of 1917 and 1918 stimulated the search. In those years two properties in the Stillwater region were actively developed, but no shipments were made. The Benbow property was located in 1918 by a local group. The property comprised seven claims along the strike at the east end of the belt. An adit was driven several hundred feet on the Eclipse claim. The seven claims were sold to the Chromium Products Corporation of Livingston, Mont., and were subsequently patented. In 1929, an eastern group obtained an option, installed some equipment, and erected several log cabins. The "crash" in the market in 1929 caused the operators to drop their lease, and the property remained inactive until 1939, when the Bureau of Mines began its exploration. Fourteen claims were located on the Boulder River in 1918 and subsequently patented by the U. S. Chrome Corporation.

Jan 1, 1949

By Paul T. Allsman, E. W. Newman

Trenching, sampling, and core drilling in Stillwater and Sweetgrass Counties, Mont., by the Bureau of Mines have delimited over 5,000,000 tons of chromite ore containing more than 20 per cent chromic oxide. The Benbow and Mouat-Sampson mines have been developed and are fully equipped for mining and milling 500 tons and 2000 tons a day, respectively. Introduction The Montana chromite deposits were the first to be explored under the Strategic Minerals Act of 1939. In June of that year, the Bureau of Mines started exploration by trenching, test pitting, sampling and diamond drilling, and completed the project in March 1943. The U. S. Geological Survey cooperated by mapping the geology and logging the cores. The project was to determine the extent and grade of the chromite ore and to indicate sufficient reserves to justify development and exploitation of the deposits for the national emergency. Exploration has indicated that the district contains the largest and most important reserve of chromite ore in the United States. The Benbow and Mouat-Sampson mines have been developed and a 500-ton concentrating mill has been constructed on the Benhow property and a 2000-ton mill on the Mouat-Sampson property. Concentrates were produced from the Benbow mill three months after the attack on Pearl Harbor, when the nation's major chromite supplies from foreign sources were cut off. History It has been known for 50 to 60 years that some chromite deposits existed in an east-west belt along the north escarpment of the Beartooth Mountains about 25 miles north of Yellowstone Park, but nothing was known of their size and extent until the war demand of 1917 and 1918 stimulated the search. In those years two properties in the Stillwater region were actively developed, but no shipments were made. The Benbow property was located in 1918 by a local group. The property comprised seven claims along the strike at the east end of the belt. An adit was driven several hundred feet on the Eclipse claim. The seven claims were sold to the Chromium Products Corporation of Livingston, Mont., and were subsequently patented. In 1929, an eastern group obtained an option, installed some equipment, and erected several log cabins. The "crash" in the market in 1929 caused the operators to drop their lease, and the property remained inactive until 1939, when the Bureau of Mines began its exploration. Fourteen claims were located on the Boulder River in 1918 and subsequently patented by the U. S. Chrome Corporation.

Jan 1, 1949

By John Hall

THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 1 1/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. I this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions. .

Jan 7, 1913

By A. S. Richardson

THE conditions that make necessary the mechanical ventilation of the Butte mines of the Anaconda Copper Mining Co. are due to a number of causes, all of which are incidental to the depth at which mining operations are now carried on. The main object to be accomplished, of course, is the reduction of the temperature and humidity of the air in the working places. Ventilation fans, both surface and underground, have been used for many years, but increasing depth has made the problem much more difficult. Further improvement in both ventilation equipment and methods, therefore, became necessary; and it is the purpose of this paper to describe the work planned and done under the improvement program. The mines of the district have been frequently described in various technical publications, so a description is unnecessary here. From a mine-ventilation viewpoint, compared with coal-mine ventilation systems, the problem is complicated by the fact that the workings to be ventilated are situated on a large number of steeply dipping veins which frequently intersect and are faulted, and also by the fact that the extent, or existence, of orebodies is not definitely known in advance of actual development work. For these reasons ventilation work cannot be planned in advance of actual operations, nor can such regular systems of ventilation as are used in working the more uniform and continuous bodies of coal be developed. When operations are conducted at a normal rate, about 10,000 miners are employed on two shifts, so that about 5000 men will be underground at one time. But as ventilation is necessary to reduce high temperature and humidity due, mainly, to natural causes, the quantity of air per man per minute is not a governing consideration in determining ventilation requirements. Most important among the numerous sources of heat and humidity in the mines are : heat generated during decay of mine timber; heat and humidity given off by mine rock and water; heat generated by oxidation of sulfide minerals; heat given off by electrical equipment; heat generated by mine fires (in certain localities).

Jan 2, 1922

By S. J. Green, R. D. Perkins

Little data exists on the high strain rate behavior of geologic materials. Uniaxial stress tests by Kumar1 and by Serdengecti and Boozer2 present some results to strain rates in the range 10 to 103 per sec. The two references cited are the only ones the authors found for high strain rates. Techniques for experiments at high strain rates are not well developed and, in general, leave questions with respect to interpretation of data when the material behaves in a brittle manner. The most reliable data at very high strain rates (104 to 106 per sec) are found in some recent flat-plate work3-5 where experimenters have impacted one plate into another, thereby creating a uniaxial strain loading. The standard uniaxial stress-strain curves cannot be obtained directly from these tests; however, yield (or fracture) may be studied by measuring the "elastic" wave magnitude. These data then may be compared to uniaxial stress data by resorting to some preassumed yield/fracture criteria. Even with the most liberal interpretation of existing data, little can be said of the effects of high strain rate on stiffness, yield/fracture, and post-fracture behavior of geologic materials. It is the purpose of this work to begin to add to the understanding. The data presented here are intended to provide material information for use in calculating the response of geologic materials to high rate deformations. These data can be applied directly to determine parameters such as the elastic modulus and Poisson ratio as a function of stress. Furthermore, these data can be used to derive an understanding of yield/fracture and the effect of rate on the yield/fracture surface. The work presented is a first step, and is

Jan 1, 1972

By Albert Sauveur

This paper explains the possibility of using advantageously a boiling solution of sodium picrate to reveal dendritic segregation in steel. The mechanism of the action of the reagent is described. The failure of manganese alone to produce persistent dendritic segregation is also considered. IRON, like other metals, solidifies through the formation of dendritic crystals; iron alloys forming solid solutions, like other solid solutions, solidify likewise through the formation of dendritic crystals. The alloying elements or impurities as well as the inclusions segregate generally in the interstices, or "fillings," between the axes and branches of the dendrites; that is, in the portions last to solidify. This results in dendritic segregation or heterogeneity, which is generally persistent and makes possible the revelation of the dendritic crystallization of the metal through the selective action of a suitable etching reagent.1 For this purpose, a cupric solution, such as Le Chatelier's, is generally used, copper being deposited on the pure, or relatively pure, ferrite present in the axes while the fillings remain free, or relatively free., from copper deposition. The dendritic structure, formed on solidification in a steel containing 0.50 per cent. carbon, 0.37 per cent. manganese, 0.12 per cent. silicon, 0.07 per cent. sulfur, and 0.035 per cent. phosphorus is shown, after treatment with Le Chatelier reagent, in Fig. 1 under a magnification of 8 diameters. Commercial steel always contains inclusions of manganese sulfide, which are located in the fillings of the dendrites. Comstock has shown that boiling sodium picrate imparts a dark coloration to these inclusions. We find that this reagent likewise reveals dendritic segregations in commercial steel, as shown in Fig. 2, under a magnification of 8 diameters, which represents the same spot as that shown in Fig. 1. The fillings

Jan 2, 1924

By P. R. Gage, R. W. Bartlett

At high temperatues and reduced oxygen pressuves, molybdenum silicicles oxidize to form SiO(g) vathev than a passivating SiO2 film. This is a sevious problem for low-pressure applications of sili-cide-coated rejvactory tnetals. As oxiclalion pvoceeds, the higher oxidntion potential of silicon initially suppresses oxidation of molybdenum and silicon is depleted near the surface. Eventually, silicon depletion causes secondary passivation (SiO2) mid an active to passiue transition in oxidntion behavior at moderately low pressures. At very low pressures, silicon depletion continues until steady-state oxidation of both silicon and rnolyhdenum can proceed at rates propovtional to their initial stoicliiorrzetvies. Ohsel-vations of 'oxidatiou-rate belzcriliov at temperatures from 1101° to 1700°C and oxygen pressures from 10-7 to 1 at in were made using thermogravimetn'c, X-ray diffraction, and elect?*on-rtric?ro/,vobe techniqrres. The experimental results are in good agreement with calculated lirnits for the various types of behavior that were based on tlievtnochernicnl atzd dffusion rate data for the Mo-Si system. A protective oxide film normally forms during the oxidation of elemental silicon. However, at elevated temperatures and reduced pressures this film is not present and oxidation is rapid. wagnerl has shown that this behavior occurs because SiO(g) is more stable than SiO2. The behavior of the silicides at high temperatures is similar but more complicated. Molybdenum and several silicide compounds are involved and the chemical activity of silicon, or the equivalent silicon vapor pressure, can vary considerably in these phases. Also, diffusion in the silicides resulting from reactions in which a higher silicide is reduced to a lower silicide, or molybdenum containing dissolved silicon, must be considered. EXPERIMENTAL AND ANALYTICAL METHODS Isothermal oxidation experiments were conducted using hot-pressed MoSi2 and Mo5Si3 wafers. Each experiment was conducted at a fixed oxygen pressure by controlling the flow of oxygen in and out of the furnace chamber. Most of the experiments were conducted in a molybdenum-wound tube furnace. Special construction features, including use of a high-purity dense A12O3 refractory tube, permitted operation in high vacuum to 1500°C. Higher temperatures could be obtained at higher working pressures and with a sacrifice of tube lifetime. Temperature was measured with three Pt 6 pct Rh/Pt 30 pct Rh thermocouples and controlled with a proportional controller. Weight changes were monitored with a quartz spring balance. The few experiments, at higher temperatures and low pressures, were conducted in a cold wall vacuum chamber using induction heating with direct susceptance of the sample. Because of the variable levitation effect of the induction coil on the sample, weight changes could not be monitored continuously in these experiments. All samples representing both experimental methods were weighed before and after oxidiation and examined with a microscope and analyzed by X-ray diffraction. The analytical treatment assumes equilibrium at interfaces and uses existing thermodynamic data. For convenience, equilibria are expressed as chemical potentials or as vapor pressures of the gases involved. The resulting differences in equilibrium vapor pressure between adjacent interfaces and between the surface and external atmosphere drive diffusion processes in the solid and gas boundary film, respectively. These diffusion processes govern the rate of oxidation. A bibliography of the sources of thermochemical data for the reactions pertinent to the Mo-Si-O system is given in Table I. Reactions are listed with the sources of free-energy data referenced. Since all of these reactions involve one or more gas species, usually oxygen, a plot of the product-gas chemical potential, -RT In Pg, vs absolute temperature for each reaction is given in Fig. 1. These curves can be used to determine equilibrium vapor pressures or to compare the stability of different compounds in the various gases: O2, Si, SiO, and Moo3,. The data of Table I and Fig. 1 were used to determine the analytical results presented in this paper. EXPERIMENTAL RESULTS The weight changes for three MoSi, samples oxidized at 1500°C are plotted against time in Fig. 2. The treatments were identical except for the indicated variance of oxygen pressure and each curve represents one of three characteristic types of behavior that were observed. The upper curve is an example of passive oxidation, which is defined as

Jan 1, 1965

By R. S. Wagner, C. E. Miller, H. Brown

A dc field was applied to liquid BI-Sx or Au-Ge alloys of eutectic composition. The liquid alloys were kept at a temperature slightly above the eutectic. The concentration changes due to electrodijfusion are large enough to cause nuclcation and growth of the primary phases at the respective electrodes. Nearly complete separation of Bi-Sn eutectic was obtained as well as substantial separation of Au-Ge eutectic. The effect of an electric field on the solute distrihn-tion was itluestignted itt tlirectiortally solidified rods of a dilute Bi-Sn (0.5 al. pc,t Bi) alloy. Field-freezing was carried out in small-diameter cupillay tubes to avoid cotuectice mixing -of the liquid. The relative sollcte corzcentratioi, Cs/Co , was rneusred by n radioac1il.e tracer netlod. Cs/Co can be made both largev than unity or srialler than the equilibiuwz distvibrrlion c.oejyicienl, k, , oiler a substattiul portion of the soliclifi&apos;erl rocls. A direct current, passed through a liquid-metal solution, can cause substantial concentration changes by electrodiffusion. The magnitude of the change depends on the difference in ionic mobilities of the atomic species in solution. Electrodiffusion has been studied in many binary and ternary liquid alloys.&apos;y2 It was found that the rate of material transport decreases with time for a constant applied field, as a concentration gradient is established in the solution. A steady-state concentration profile is achieved when electro-diffusion is compensated by chemical diffusion. This may seem to limit the use of electrodif fusion for metallurgical application. However, a way of utilizing the effect of electrodiffusion is to combine it with crystallization or controlled freezing. rakin was first to propose this as a new method of separating metal alloys of eutectic composition at temperatures slightly above the eutectic temperature. It was possible by this method to separate Bi-Sn and Bi-Cd eutectics into their component phases. Angus et al discussed the possibility that the effective distribution coefficient, keff, could be varied by proper application of an electric field during solidification. The combination of electrodiffusion and solidification, called field-freezing, was discussed in detail by Pfann and aner. It was shown that field-freezing can be used as a crystal-growth process, an efficient method for eutectic separation, and a new means of changing the effective distribution coefficient. k,ff, beyond the usual range of ko < k,ff < 1. The liquid layer adjacent to the solid-liquid interface can be either increased or depleted in solute due to

Jan 1, 1967

By P. B. Bucky

IN previous publications1 it was shown that a scalar model of any weighty structure, where the stresses produced are mainly due to gravita-tional forces, will behave similarly to its prototype if the model and proto-type material are the same arid the model is placed in a centrifugal field of force (substituted for the gravitational field) which has been increased in the same proportion as the linear model scale is decreased. This principle is now being applied to a study of the behavior of mine structures in an attempt to determine the laws that control them. The importance of using models as a means of solving mining problems has been discussed previously, yet it may be well to reiterate here that this method of research and type of solution have been productive of far-reaching results in other engineering fields, notably those of hydraulics and aerodynamics. Model research is a comparatively cheap and time-saving method of checking practical experience. Up to the present time the best guide to what will happen underground has been the judgment of the man who has observed most and been longest acquainted with the local conditions. His experimental work underground is limited by the elements of cost, time and danger, while failure is seldom permissible. In a model, as in a test tube, all elements that affect the solution of a problem are under definite control. Each element may be varied independently at will and its effects noted. Experimental work on a small-scale model may there¬fore be performed at a comparatively small expenditure of time and money, instead of on a full scale in the mine, where the cost, time, and danger elements are necessarily great. The experiments described in this paper are to be considered as part of a progress report and a continuation of Technical Paper 425. One object of the research program is to make each experiment point the way for further research on that particular phase of the general problem. The results and conclusions presented here are therefore not to be considered as final, but are to be interpreted as

Jan 1, 1933

By W. G. Pfann

Under certain conditions, a molten zone can be made to move through a solid by impressing a stationary temperature gradient across the solid. This phenomenon can be utilized in fabricating semiconductive devices, growing single crystals, joining, boring fine holes in solids, measuring diffusivities in liquids, small scale alloying, and purification. Fundamentals and exemplary applications are outlined. ANEW aspect of the travel of a molten zone through a solid is considered in this paper. Whereas, in previously described zone melting techniques,&apos;-&apos; zones were usually caused to move by changing the position or temperature of a heat source, in the present technique a zone is made to move by impressing a temperature gradient across it. For example, a thin layer of molten A1-Si alloy, sandwiched between two silicon slabs having a temperature gradient normal to the layer, will travel through the hotter slab. One feature of temperature gradient zone melting, as this technique will be called here, is that zones of unusually small dimensions can be maintained. This leads to such diverse uses as have been listed in the abstract. In this paper fundamentals of the movement of a molten zone in a temperature gradient, and some practical applications thereof, are outlined. Assumptions The movement of a molten zone through a solid body of solvent substance in which a temperature gradient exists will be discussed. The length of the zone will be its dimension in the direction of motion. The direction of the temperature gradient will be toward the region of higher temperature. To be considered is a binary or higher order solute-solvent system in which the concentration of solute in the molten zone is sufficient to produce a lowering of the freezing temperature of the solvent which is at least of the order of the temperature range impressed on the charge. While we discuss primarily molten zones in a solid matrix, the principles are applicable to solid or vaporous zones in a solid matrix, a requirement being that the diffusivity in the zone be substantially greater than in the matrix. Diffusion of solute into the surrounding solid will be assumed negligible. In general, its presence will not basically alter the conclusions to be drawn. For illustration, a system represented by the partial constitutional diagram of Fig. la will be discussed, in which k, the distribution coefficient defined in the figure, is constant and less than unity. However, the technique is applicable to any solute- solvent system in which one component lowers the melting point of another component. Movement of a Molten Zone in a Temperature Gradient Consider, in the system AB of Fig. 1, where B is designated the solute and A the solvent, the effect of sandwiching a thin layer of solid B between blocks of solid A and placing the whole in a temperature gradient such that the temperature of the layer is above the lowest melting temperature of the system. Surrounded by an excess of A, the layer will dissolve A, becoming molten, and expand in length." As so- lution of A continues, at both interfaces, the mean solute concentration in the zone will move to the right in Fig. la, until at temperature T, the liquid at the cooler interface reaches the liquidus concentration C,. Solution of A thereupon ceases because the liquid T1 is saturated with A. The liquid at the hotter end of the zone, being at temperature T2, is not saturated with A at concentration C1. Hence solution of A continues there and concentration C2 is approached. A concentration gradient therefore is set up in the zone, causing A to diffuse toward the cool end and B toward the hot end. As a result, the liquid at the cool interface becomes supersaturated and a layer of crystalline A containing concentration kc, of B in solid solution freezes. Since a source of A

Jan 1, 1956

L. D. Ricketts, New York, N. Y.-In recent years the metallurgical field of the copper industry has expanded greatly, the copper ores have become lean and diverse in character, and we are obliged to treat such ores on a very large scale. On the commercial side, the operating and consulting staffs of ,the great mining companies have been enlarged and organized, and no great capital expenditure is decided upon until it has been investigated and recommended by a highly organized force of specialists as a committee. I believe that in the scientific field and in the most valuable proceedings of our various societies the old idea of one-man point of view and one-man treatment of principle and detail together has been. splendidly developed and should continue, but for the advancement of our art we should deliberately discuss subjects among ourselves in order to do away with the idiosyncrasies of the individual and to gain a composite view representing the best thought of many men. In the development of new ideas leading to the introduction of new methods, the societies could enlarge their present great field of usefulness if such discussion be had, and in my opinion further great good could be done if a number of men of different qualifications and experience would join in preparing a joint book, each dealing with his particular problem, but consulting the other men. In this way individualism would be preserved and various processes would be described, and if properly reviewed the paper would be palpably capable of analysis, and the student would have at his command the associated efforts of a group of qualified engineers.

Jan 4, 1915

By Charles D. Borror, George K. Foster

The Jeffrey mine of the Canadian Johns-Manville Co., Limited, is in the town of Asbestos, situated approximately 100 miles northeast of Montreal and about the same distance southwest of Quebec, in Richmond County, Quebec. Mining operations were started in 1881 on outcrops on a hill, as a side-hill cut, followed by a second and third cut. This development was the forerunner of the present large open-pit operations, the mine now ranking as the largest open-pit asbestos mine in the world. Operations were first carried on by hand, then by horsepower and later by stem cableways. By 1924 the derrick spans, 2000 ft. or more long, became unwieldy. To overcome this, and also to eliminate hand labor as much as possible, steam shovels and railroad haulage were introduced. The steam shovels were replaced in 1928 by larger electric shovels of the full-revolving type. The Ore Body The ore body is a serpentinized peri-dotite rock mass. The chrysotile fibers form a network of veins throughout, varying from microscopic width to two or more inches measured across the veins (Fig. I). These veins may be continuous for a few or many feet; they may increase or decrease in width within a few feet. The veins in which the fibers occur per- pendicular to the veins are known as cross fiber. Those in which the fibers lay parallel to the veins are known as slip fiber. The cross fibers are of better quality, and more in demand. The majority of the fiber

Jan 1, 1948

By George K. Foster, Charles D. Borror

The Jeffrey mine of the Canadian Johns-Manville Co., Limited, is in the town of Asbestos, situated approximately 100 miles northeast of Montreal and about the same distance southwest of Quebec, in Richmond County, Quebec. Mining operations were started in 1881 on outcrops on a hill, as a side-hill cut, followed by a second and third cut. This development was the forerunner of the present large open-pit operations, the mine now ranking as the largest open-pit asbestos mine in the world. Operations were first carried on by hand, then by horsepower and later by stem cableways. By 1924 the derrick spans, 2000 ft. or more long, became unwieldy. To overcome this, and also to eliminate hand labor as much as possible, steam shovels and railroad haulage were introduced. The steam shovels were replaced in 1928 by larger electric shovels of the full-revolving type. The Ore Body The ore body is a serpentinized peri-dotite rock mass. The chrysotile fibers form a network of veins throughout, varying from microscopic width to two or more inches measured across the veins (Fig. I). These veins may be continuous for a few or many feet; they may increase or decrease in width within a few feet. The veins in which the fibers occur per- pendicular to the veins are known as cross fiber. Those in which the fibers lay parallel to the veins are known as slip fiber. The cross fibers are of better quality, and more in demand. The majority of the fiber

Jan 1, 1948

By M. M. Neale

The pottery department has been aptly described as the "heart of the zinc plant," md every operator of a horizontal-retort plant is acquainted with the fact that good retort practice is the keystone of the smelting process. Since retorts and condensers are clay products, it is obvious that improvements in other branches of the ceramic industry should be observed for possible adoption in the pottery process for zinc smelting. Deaeration of clay bodies is one of the improvements that have become fully, established in many brick and pottery plants. Our investigation of a number of these installations always yielded the same answer—improved practice. Improvement in workability, elimination of laminations, less porosity, greater wet and dry strength, were among the claims put forth for this process. All of these features are exceedingly desirable characteristics in the manufacture of a zinc retort. A preliminary test, which involved truck transportation of deaired slugs over a relatively long distance, did show the value of many of these characteristics in forming the retort. Results from the standpoint of , longer retort life in the smelting furnace were not outstanding. The idea lay dormant for several years but was revived again in 1940, when it was decided to make whatever changes were necessary in the equipment for pottery manufacture to fully demonstrate the process. A number of the manu- facturers of machinery for clay work were asked to submit proposals, and the plan finally adopted was extremely simple and economical. Machine FOR DeaeRRATING Selection of the &apos;&apos;Straight-line&apos;&apos; principle for conversion of the "Wettengel" pug mill to a &apos;&apos;vacuum-extrusion" machine preserved some usable parts of the original equipment, such as the drive mechanism, and main shaft. The converted machine consists of a feed hopper, a compression and shredding zone, a vacuum chamber, and an extrusion barrel, as shown in Fig. I. In operation the clay mix travels from the feed hopper into the compression zone, where it is compressed and finally forced around the tapered cone into the vacuum chamber. As it enters this chamber the clay body is shredded into thin plates, for exFosure to the vacuum. The shredder consists of a hub mounted on the main shaft, to which are bolted segmental sections, each of which carries shredder knives. The compression zone and extrusion barrel function as seals for the vacuum chamber and the shredded clay mix is agitated thoroughly during its exposure to the vacuum. A vacuum pump, equipped with a 3-hp. motor, is attached to this chamber, and maintains 25 to 26 in. vacuum during operation of the mill. Changes in Practice Prior to the adoption of the deaeration process, our standard pottery practice called for double mixing in the combination 7

Jan 1, 1944

By S. E. Maddigan

MANY experimental and theoretical investigations have been made on the processes involved in annealing and recrystallization of metals. Most of these, however, have treated the time element as constant and heat-treatments used have been for relatively short times. Aside from the early work by Carpenter and Elam,1 the few that have investigated the effect of time on the processes have usually done so for fairly short time periods. During recent years the growing interest in long-time creep properties of metals and alloys under stress has made increasingly important a better knowledge of the recrystallization during prolonged heating. The recrystallization temperature of 70-30 brass given by Clark and White2 in 1932 was somewhat above 400°F. (204°C.) but under 500° (260°C.), whereas in our laboratory recrystallization has been observed in creep specimens at 204°C, the lowest temperature of Clark and White&apos;s range. Since the creep properties are quite different above and below the recrystallization temperature, erroneous conclusions can readily be drawn by the application of short-time recrystallization data to creep problems. It was thus considered of both practical and theoretical value to make long-time annealing studies near the minimum recrystallization temperature. In this way useful additions could be made to data on recrystallization temperatures and, since the reactions in this range are relatively slow, additional insight could be obtained into the factors involved in annealing. Several comprehensive reviews of recrystallization processes have been written,3-5 therefore only a brief review of the generally accepted facts will be given here.

Jan 1, 1940

By A. Goldberg, T. E. Tietz, J. E. Dorn

INTRODUCTION THE concept that the flow stress for plastic deformation of metals in the work hardening range is a function of the instantaneous values of the strain, strain rate and test temperature was promulgated by Ludwick1 many years ago. This thought has been more or less a guiding principle throughout the immediate period of development and growth of mechanical metallurgy. It has been tacitly assumed or knowingly applied to many investigations on the plastic behavior of metals. Spurred by the theoretical interest and practical importance of the plastic behavior of metals, many investigators have attempted to determine empirical, semi-empirical, and theoretical equations2-18 relating the flow stress with the strain, strain rate, and temperature. Although the applications of such equations have been extensive, the experimental verification of the existence of a mechanical equation of state is weak. Furthermore, some of the available evidence on plastic flow appears to suggest that no simple functional relation between stress, strain-rate, strain and temperature can exist. The mechanical equation of state demands that [a = a(e, E, T)[I]] Where o = true stress = load/instantaneous area e = true strain = In Instantaneous gauge lengths initial gauge length e = true strain rate T = temperature] This formulation implies that [da] is an exact differential. Therefore the flow stress (o) is a function of the instantaneous values of the strain (e) the strain rate (e) and the temperature (T), independent of the previous mechanical or thermal history. Having reached a certain strain, strain rate, and temperature, by any path whatsoever, a definite and fixed value of the flow stress should be obtained. One check on the validity of the mechanical equation of state is easily obtained. Consider the following three tests on the stress-strain curve at constant temperature: [A. Strain at rate [ei] B. Strain at rate i2 C. Strain at rate [Ei] to [ei] and continue test at i2] A graphical representation of possible results of such tests are shown in Fig I. If, for strains greater than [el], test (C) data coincide exactly with the data from test (B), as shown in Fig Ia, a limited verification of the mechanical equation of state is obtained for the range of strain rates from [ii] to [e2]. But if the data from test (C) differ from those of (B) beyond strain [el] where the strain rate is changed from [e,] to [€2i] the mechanical equation of state is not

Jan 1, 1948