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By R. J. Borg, C. E. Birchenall

Vapor pressures of eight compositions of Mg-Cd have been determined by the Knudsen effusion technique. Measurements are made at several temperatures for each alloy and the results interpolated to a common temperature for the calculation of the activities. It is not possible to obtain values for the partial molar enthalpies because of the narrow temperature range spanned by the measurements. The results show less precision than those obtained for pure Cd which are also reborted. These alloys are extremely susceptible to corrosion which provides a possible explanation for the lack of precision. Nevertheless, the values of the activity are in good agreement with the results of electromotive force measurements previously reported for the Mg-Cd system. MAGNESIUM and cadmium are mutually soluble in all proportions in the solid state and form a single phase which has the hexagonal close-packed structure. X-ray investigations of this system1,2 have revealed a rapid variation in the relative dimensions of the unit cell occurring at approximately 50 at. pct. The rate of change of the c/a ratio with composition increases markedly for alloys containing more than 50 at. pct Cd. The purpose of this investigation was to determine the activity of Cd in the neighborhood of 50 at. pct and to discover whether or not the thermo-dynamic properties undergo a similar rapid change. The activities are calculated from vapor pressure data obtained by the Knudsen effusion method. Unfortunately the precision of the data from which the thermodynamic values are calculated is insufficient to establish unequivocally a departure from the normal trend. The results are reported primarily because they substantiate the only previously reported activity measurements3 and because they include values for pure Cd which in contrast to those of the alloys show excellent precision. The Cd-Mg system is known to contain several ordered phases. However, this investigation was made at temperatures considerably above the transition temperatures, and the alloys may be regarded as nearly random solid solutions. EXPERIMENTAL Apparatus—The effusion cells are machined from solid tantalum rod. The lids consist of threaded, flanged rings of tantalum onto which are welded shallow cups of 4 mil molybdenum foil. The orifice, which is located at its center, is made by grinding off a small dimple produced with a sharpened punch. Such an orifice has been mounted in plastic, sectioned, and the thickness of the orifice edge measured in a microscope. The maximum thickness is 0.00016 in., and the Clausing factor is consequently equated to unity. The area of the orifice is determined by tracing its projection on the screen of the metallograph at a known magnification and measuring the area of the tracing with a planimeter. Excellent temperature control is achieved with a 4 by 18-in. alundum core, gradient-wound, furnace

Jan 1, 1960

By H. J. Rahilly

Mine fires, in the Butte district, have been a source of trouble and expense for the past thirty years, for while the actual fire area in most of the mines has been comparatively small, the handling of the gas has generally been a much larger problem than the actual putting out of the fire. The chief causes of these fires have been: Defective electrical equipment, incendiarism or carelessness, and spontaneous combustion. While fires from the first two causes have been numerous, they have generally been discovered and extinguished before they became very serious. Spontaneous combustion has been the cause of most of the large fires. Sufficient heat has been generated by ground movement, high rock temperatures, and decomposition to set fire to inflammable materials (tarred ropes, canvas, dry timber, manure, and hay) left in the gobs some years ago. Also, the heat resulting from the oxidation of the fine broken sulfide ore is sometimes sufficient to set fire to the timbers. In 1906, a fire was discovered on the 1100-ft. level of the Minnie Healy mine about 400 ft. (122 m.) west of the Minnie Healy shaft, which presumably originated, in one of the upper levels, from spontaneous combustion. The fire was walled off by concrete bulkheads and a pillar of ground 100 ft. (30 m.) thick was left below and mining resumed underneath. During subsequent operations, this pillar became cracked and broken and the fire passed into the new workings. It travelled downward and spread rapidly until, in 1917, it had become necessary to wall off portions of the Tramway, Leonard, and West Colusa mines on the 1300, 1400, 1500, 1600, 1800, 1900, and 2000-ft. levels, and the tops of the 2200-ft. raises were sealed. The fire area now consists roughly of a block 1000 by 1200 ft. and from the 600-ft. to the 2200-ft. level. This block is composed largely of a series of parallel northwest-southeast nearly vertical veins and stringers that form a large orebody, with no well-defined walls but badly fractured and faulted, and known locally as "horsetail ore." These veins, or orebodies, are mined by the square-set or the rill method.

Jan 1, 1923

By H. J. Rahilly

Mine fires, in the Butte district, have been a source of trouble and expense for the past thirty years, for while the actual fire area in most of the mines has been comparatively small, the handling of the gas has generally been a much larger problem than the actual putting out of the fire. The chief causes of these fires have been: Defective electrical equipment, incendiarism or carelessness, and spontaneous combustion. While fires from the first two causes have been numerous, they have generally been discovered and extinguished before they became very serious. Spontaneous combustion has been the cause of most of the large fires. Sufficient heat has been generated by ground movement, high rock temperatures, and decomposition to set fire to inflammable materials (tarred ropes, canvas, dry timber, manure, and hay) left in the gobs some years ago. Also, the heat resulting from the oxidation of the fine broken sulfide ore is sometimes sufficient to set fire to the timbers. In 1906, a fire was discovered on the 1100-ft. level of the Minnie Healy mine about 400 ft. (122 m.) west of the Minnie Healy shaft, which presumably originated, in one of the upper levels, from spontaneous combustion. The fire was walled off by concrete bulkheads and a pillar of ground 100 ft. (30 m.) thick was left below and mining resumed underneath. During subsequent operations, this pillar became cracked and broken and the fire passed into the new workings. It travelled downward and spread rapidly until, in 1917, it had become necessary to wall off portions of the Tramway, Leonard, and West Colusa mines on the 1300, 1400, 1500, 1600, 1800, 1900, and 2000-ft. levels, and the tops of the 2200-ft. raises were sealed. The fire area now consists roughly of a block 1000 by 1200 ft. and from the 600-ft. to the 2200-ft. level. This block is composed largely of a series of parallel northwest-southeast nearly vertical veins and stringers that form a large orebody, with no well-defined walls but badly fractured and faulted, and known locally as "horsetail ore." These veins, or orebodies, are mined by the square-set or the rill method.

Jan 1, 1923

By E. A. Holbrook

AT the meeting of the Committee on Engineering A Education of the Institute at the New York meeting last February, it was brought out that the number of men graduating in mining engineering from our colleges at the present time is not sufficient to meet the ordinary needs of the mineral industries. Following the meeting, Samuel S. Wyer, consulting engineer of the Fuel-Power Transportation Educational Foundation of Columbus, Ohio, prepared a pamphlet called "Mining Engineering's Appeal to High School Seniors." Under the auspices of this Foundation the pamphlet is being sent to every high school in the United States. The pamphlet does not in any way paint glowing word pictures of the profession; rather it is a statement of the importance of mining engineering in our present-day civilization, together with the requirements in young men who are looking forward to an engineering career.

Jan 1, 1930

By Manuel Valerio Ortega

This Mexican amalgamation-process, invented in 1557, at Pachuca, by Bartolome de Medina, has been widely discussed in America and Europe, but thus far there is no universal agreement as to all the chemical reactions involved. Having been, after many trials, the first to succeed in effecting the amalgamation of silver-ores by the same mechanical means, but doing without one of the chemical substances which had been considered indispensable in the practice of 300 Sears, I am led to offer these notes as a contribution to the discovery of an exact theory concerning the patio process. My treatment for silver- and gold-ores being protected by letters-patent in this country, the United States, France, Peru, Bolivia and Chile, I may speak freely concerning its materials and manipulation. I. Patio-Amalgamation. The ore extracted from the mine is sorted by pepenadores, who break the large pieces with hammers, rejecting those which contain no ore, set aside the very rich to be smelted, and deliver the rest to be crushed and pulverized for direct amalgamation in the patio. The broken lumps, of about fist-size, are first ground in Chilean mills, and then reduced, in arrastras or tahonas, to fine slime. After the lama or slime has acquired a suitable consistency by the evaporation, through the sun's heat, of a part of the water which it contained, it is spread upon the patio or amalgamating-floor, where it is mixed with 5 or 6 per cent. of common salt. The next day a certain amount (depending upon

Jan 1, 1902

By Sukune Takenouchi

Porphyry copper deposits in the southwestern Pacific region differ in some points of geologic features from those of the United States. The deposits distribute along old or active island arcs and are generally younger in age (1-16 m.y. B.P.). In Japan, however, no typical porphyry copper deposits are yet reported, though the geological situation of Japanese islands is similar to that of the southwestern Pacific. Fluid inclusions in some porphyry copper deposits In the southwestern Pacific region and those in igneous rocks genetically related to the ore deposits In Japan have been studied, and the genesis of ore-forming fluids from igneous rocks are discussed. From the results, the possibility of finding porphyry copper-type mineralization in Japan are considered.

Jan 1, 1976

By G. Venturello, C. Antonione, G. Della Gatta

Results from work on the effect of inferstitials on recovery and recrystallization of' very pure iron (99.995 pet) doped with nilrogen up to 400 ppm are reported. Nitrided specimens were obtained by heating the iron in a static atmosphere of NH3 + H2. The samples were cold-rolled 80 pet, subjected to a series of isochronal and isothermal anneals, and submitted to examination by X-rays, micrographs, and hardness tests. Small additions of nitrogen show a strong effect in reducing recovery of' the mechanical properties of high-purity iron. At the temperatures of. the experiments, this effect proved greater than in the case of carbon. At 400°C pure iron recovers more than 50 pet of the total hardness increase, carburized iron vecovers 25 pet, and nitrided iron only 10 pet. On the other hand. the addition of nitrogen has, similarly to carbon, a very small effect on recrystallization; the effect is, however, slightly higher than that of carbon. When the concentration Of nitrogen is above the solubility limit in a iron at the temperattue of the experiments, an increase in the frequency of nu -cleation is also observed. THE object of the present work is to improve knowledge on the effect of interstitials both on recovery and on primary recrystallization of pure iron. In fact. at present there are no available data on the effect of nitrogen on high-purity iron. The only work which at present can be somewhat related to this problem is a work of Leak et al.1 in which grain boundary internal friction at high temperature in the presence of increasing amounts of nitrogen is studied by a torsion pendulum. The present work is a continuation of a previous one2 on the effects of carbon. EXPERIMENTAL PART Preparation of the Material. Pure iron was prepared following the same methods used in the pre- vious work2 and was nitrided using controlled quantities of ammonia in an apparatus similar to that used for carburizing. The apparatus consists essentially of a gas-tight quartz tube containing the specimens. The tube, maintained at constant pressure by means of a mercury seal, is placed in a resistance furnace. For nitriding, the NH3 + H2 atmosphere with a suitable concentration of NH3 was introduced into the tube, which had been previously carefully evacuated and degassed by heating at 600°C. The hydrogen used was carefully purified by passing it through a palladium filter. The ammonia required was prepared with the following reaction: CaO + 2NH4CI —CaCl2 + H2O + 2NH3 by heating the mixture of CaO and NH4C1 in a glass flask and then collecting the ammonia in a graduated Hempel burette. For each nitriding program a given amount of NH3 prepared by this method was introduced together with the H2 into the tube previously evacuated. Nitriding of the sample was then performed at 570°C for 48 hr. After this, to ensure a homogeneous distribution of nitrogen, the samples were further heated for 72 hr at 800°C. With this method which uses a static nitriding atmosphere, carefully controlled conditions of purity are obtained. Contrarily, with the conventional continuous-flow methods, using large quantities of circulating gas, there is a greater risk of introducing impurities into the samples. Furthermore, the required nitrogen concentration in the specimen is easily predetermined and obtained. A plot of the relation observed between the initial concentration of NH3 in the gas and the quantity of nitrogen introduced into the iron samples is given in Fig. 1. The data refer to samples of 1.2-mm thickness and to the nitriding conditions previously described. Furthermore, as a comparison, the data relative to two 0.5-mm-thick samples are reported. The presence of a reservoir in the cold zone of the reaction bulb made possible the gradual dissociation of ammonia on the sample in the hot zone. Internal-friction methods were used to determine the content of nitrogen dissolved in the iron samples. Some analyses were also carried out with chemical methods. The following table, Table I, shows a comparison of data obtained with chemical and internal-friction methods. The correspondence between chemical methods and internal-friction

Jan 1, 1964

By Francis A Thomson

Montana Bureau of Mines and Geology, Montana School of Mines, Butte, Mont Francis A Thomson, President. The Bureau of Mines and Geology was formerly known as the Bureau of Mines and Metallurgy. A list of publications will be sent upon request¬ A series of six Bulletins and five Memoirs liave been issued by tlie Bureau, as well as several miscellaneous contributions Where the price is not indicated in tlie following selected list of those publications which are now available, the publications are presumably distributed gratis: Bulletin 3, Mechanical ore sampling in Montana, by H B Pulsifer (1920); 6, Geology and ore deposits of Bannack and Argenta, Montana, by P. J Slienon, 50 cents, Memoir 1, The Kevin-Sunburst and otlier oil and gas fields of the Sweetgrass Arcli, by E S Perry (1929), 2, Natural gas in Montana, by E S Perry (in preparation), 4, Tlie geologic structures of western Montana, by C H Clapp and others (in preparation), 5, Placer mining possibilities in Montana, by O A Dingman (1932).

Jan 1, 1933

By R. Stickler, A. Vinckier

An optical and electron microscope study was made on a commercial 302 stainless steel heat treated for massive carbide precipitation. Convincirg evidence was obtained that the grain boundary precipitate does not grow away from the grain boundary into the matrix, but grows as a network of large thin dendrites in between the grains. IN austenitic stainless steels the carbon in supersaturated solution precipitates when the steel is heated in the temperature range 450" to 1000°C. During such heat treatments the chromium-rich carbide occurs primarily at the grain boundaries and has adverse effects on the corrosion resistance and low-temperature ductility of the material. It has been shown that the morphology of the precipitated particles differs widely depending on the time and temperature of the heat treatment, the nature of the boundary, the misfit between the grains, and so forth.1"5 It was assumed by Mahla et al.,' Streicher,' and Mc Nutt' that the carbide particles which nucleate in the grain boundary grow in various geometric or dendritic forms away from the boundary into the matrix. However, Kinzel,' Hatwell et a, and Plateau et aL4 found that the particles nucleate in the grain boundary and grow as a network of thin dendrites in the grain boundary interface. We have made a comprehensive studyg of the precipitation occurring in a commercial 302 austenitic stainless steel heat treated for times ranging from 0.15 to 1500 hr at various temperatures from 480" to 1065"~. This study was made to elucidate the influence of heat treatments on both the mechanical and the corrosion properties of this steel. Part of this investigation which is pertinent to the morphology of the grain boundary carbides referred to above is separately reported here. We found that the particles which nucleated in the boundaries grew in the interface of these boundaries, thus supporting the viewpoints of Kinzel,' Hatwell et al.,3 and Plateau et al.4 Furthermore, when carbide particles nucleated in the matrix very close to the boundaries, they possessed a morphology distinctively different from the particles growing in the grain boundaries. MATERIAL A study of metallographic samples and of fracture surfaces of a 302 stainless steel is reported in this paper. The composition and heat treatments are listed in Table I. Polished and etched samples were examined und813r the optical microscope, and carbon extraction replicas of etched micrographic samples and various fracture surfaces3'8'9 were examined under the electron microscope. RESULTS AND DISCUSSION A representative optical micrograph of the 302 steel, condition A, is shown in Fig. l(a). Particles can be seen on the grain boundaries but no traces can be found of particles which grow from the grain boundaries into the matrix. A carbon extraction replica of this sample shows numerous large thin dendrites, Fig. l(b). The lateral dimension of such carbide particles vary up to 100 p, and their thickness estimated from the amoun! of electron penetration i:; between 500 and 1000A. Such large dendrites are extracted from almost all grain boundaries and, if they had grown into the grains, they would definitely be revealed by etching traces in the matrix, Fig. l(a). The reason why these large dendrites on the extraction replica appear to be grown into the grain is due to the mechanism of the extraction replica process. Thus, these dendrites are supported by the carbon replica film only at the edges originally along the grain boundary trace A-A, Fig. l(b), in the polished metal section and have subsequently fallen over onto the carbon replica film during handling. Although such dendrites generally fall only to one particular side of the grain boundary trace, one finds occasionally that parts of a dendrite have fallen to both sides, as shown in Fig. l(b). Further evidence for the growth of carbide in the grain boundary can be obtained from the appearance of fracture surfaces. A small impact specimen of the 302 steel, condition A, was broken at liquid nitrogen temperature. The fracture path follows the

Jan 1, 1962

By D. G. Westlake

Alloys of poly crystalline Nb-H have been tensile tested at 77" and 120°K after slow-cooling and after quenching from room temperature. A rationale has been developed to explain the effect of cooling rate on ductility in terms of microstructure. The inferior ductility of the slow-cooled alloys in this temperature range can be attributed to the precipitation of coarse hydride particles that fracture in the early stages of plastic deformation. Quenching Produced much smaller hydride particles and a decreased tendency for initia-tion and popagation of cracks. Prismatic dislocation loops, punched into the matrix of quenched alloys, eliminate the yield point and may Play some role in the low temperature ductility of the quenched alloys. The difference in ductility between quenched and slow-cooled V-H alloys was even greater than that observed in the N b-H alloys. It is well known that the ductility of Nb-H and V-H alloys decreases with increasing hydrogen concentra-tion and with decreasing temperature.1-l1 The follow-ing are some of the numerous mechanisms that have been adopted in attempts to explain these observations: 1) hydrogen-dislocation interarction,4'6 2) lowering of the crack surface energy by adsorbed hydrogen,9'10 3) localized lowering of the niobium bond strength,9 and 4) exertion of pressure inside voids by molecular hydrogen.6 A recent study1' indicates that, in some way, the embrittlement is related to the precipitation of a hydrogen-rich phase, because embrittlement and hydrogen solubility have the same temperature dependence. Most of the investigators observed that at very low temperatures there was a return of the ductility. Thus, hydrogenated niobium and vanadium may be said to exhibit a low temperature ductility minimum."1'8'9 It has been reasoned by most observers that diffusion is required for the embrittlement mechanism to be operative, and that as hydrogen becomes immobile at very low temperatures, the ductility increases. This investigation of the mechanical behavior of Nb-H al-loys under various conditions is an attempt to gain a better understanding of the low temperature ductility minimum. EXPERIMENTAL Tensile specimens, with gage length dimensions 20 by 3 mm, were machined from sheet stock" and both faces were ground on wet 600 grit Sic paper to obtain a final thickness of 0.5 mm. Annealing as described earlier12 resulted in average grain diameters of 0.3 mm. The recrystallized niobium tensile specimens were electropolished in 90 parts H2S04, 10 parts HF (48.9 pct) by volume, at 287°K and 30 v. Hydrogen, which may have been present in the starting material and/or added during specimen preparation, was removed by annealing at 1073°K in a dynamic vacuum of 2 X 10-6 torr. Hydrogenated specimens (1.15 at. pct H) were prepared by reaction with a known quantity of pure hydrogen (obtained by thermal decomposition of UH3) at 1073oK, followed by cooling at the rate of 100" per hr. These were vacuum encapsulated, homogenized at 573°K for 3 to 5 hr, and furnace-cooled. Tensile tests were conducted on an Instron machine at a strain rate of 4 x l0-5 per sec. The gripping device was such that the specimen was positioned below the crosshead. Thus, subambient test temperatures could be obtained by immersion of the device in a cooling bath of either liquid nitrogen or Freon-12. The temperature of the Freon-12 was controlled within ± 0.1°K of the desired temperature by automatically monitoring the flow of liquid nitrogen through a copper coil in the bath. Slow-cooling to 77°K was accomplished as follows. The testing device was surrounded by a rubber jacket, open at the top and with small holes in the bottom. Liquid nitrogen, brought up to the bottom of the jacket, entered the holes and vaporized quickly. The temperature was monitored at the specimen with a copper-constantan thermocouple, and a constant cooling rate of 2 deg per min was easily achieved by controlling the level of the liquid nitrogen outside the jacket. RESULTS AND DISCUSSION Low Temperature Ductility Minimum. Resistometric studies of both Nb-H12 and V-H13 indicated that at tem-peratures less than 150°K, virtually all of the hydrogen

Jan 1, 1970

By M. S. NORTH

IT may be a far cry from the days of the old horse whim, and it is relatively a long way back to hand production in factories. Modern machinery has made possible deep shaft-sinking, newer methods have increased the recovery of mineral. Technically, excavating and ore dressing have advanced as has mass production and its many ramifications in the manufacture of commercial product. To those of the mining industry who would have us believe that mining and manufacturing are totally different enterprises, it can be said that certain differences do exist. These differences rather than being fundamental are the result of adhering to past practices which were possibly sound years ago but do not measure up today. Differences in managerial control, sales, and distribution, cost finding, etc., are often so pronounced that efforts to compare or contrast are almost futile.

Jan 1, 1930

By AIME AIME

AN entirely new type of classifier is being put on the market by The Dorr Co., following three years of development and the experimental use of thirty machines of the improvement design in various parts of the world. It is known as the Multizone classifier. Compared with the older type the lower or overflow end has been decked over and is surmounted by one or more circular overflow columns. Feed is introduced near the middle of the machine and passes downward and under a vertical baffle, then along the underside of the deck to the base of the overflow columns. Under the baffle there is a restricted turbulent zone of high pulp velocity which holds the fine and critical size particles in suspension, preventing

Jan 1, 1937

(Members are urged to send in for this. column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at the Institute headquarters during the period Sept. 10, 1916 to Oct. 10, 1916. Arthur K. Adams, Chanaral, Chile. C. F. Moore, Salt Lake City, Utah. Hiram W. Belnap, Washington, D. C. L. D. Moore, Providence, R. I. E. A. Bridgman, Seattle, Wash. George A. Morrison, Chicago, Ill. D. W. Buckly, Wallace, Idaho. Pablo Ortega, Havana, Cuba. G. L. Carlisle, Jr., New York, N. Y. L. W. Paige, New York, N. Y. Ernest H. A. Cohen, Johannesburg, So. Africa. Charles Petzel, New York N. Y. A. Faison Dixon, Camp Rio de Oro, Venezuela. C. A. Pierce, Patagonia, Arizona. Charles E. Dutton, Goldfield, Nev. W. E. Pomeroy, El Paso, Texas. D.-F. Hewitt, Washington, D. C. George S. Rice, Washington, D. C. . James E. Howard, Washington, D. C. G. J. Schofield, Seattle, Wash. A. 0. Ihlseng, Joplin, Mo. Warren D. Thompson, New York, N. Y. I. Ishikawa, Niagara Falls, N. Y. M. M. Valerius, Tulsa; Okla. Montrose L. Lee, New York, N. Y. G. B. Waterhouse, Buffalo, N. Y. V. H. McNutt, Billings, Mont. Joel H. Watkins Washington, D. C. Benjamin L. Miller, So. Bethlehem, Pa. H. P. Wherry, Chicago, Ill. Arthur K. Adams has left for Chile, where he will act as geologist for the Andes Copper Co., a subsidiary of the Anaconda copper company.

Jan 10, 1916

By H. T. Clark, S. Feigenbaum

The importance of measuring the temperature of molten steel in the open-hearth furnace has been recognized for many years. Poor temperature control may be costly to steelmaking operations and lead to a lowered quality of the steel. Low or excessive temperatures may shorten the life of the furnace, ladles and molds. Rates of reactions in the furnace and efficiencies of deoxidizers are known to change materially with a change in the temperature of the metal and slag. Ladle skulls and mold and stool stickers cause steel to be scrapped instead of being converted into useful products. Finally, the structure, segregation and surface condition of ingots are affected by the teeming temperature. Mill investigations of the effect of bath temperature upon steelmaking operations have been largely qualitative in character, based upon observations by practical melting men. The physical chemist has used the empirical information available and has reached reasonable and useful conclusions with respect to the various melting processes. The introduction of a reliable direct-reading pyrometer will permit accurate quantitative evaluation of the effects of temperature and should furnish a more rational basis for study of the thermochemistry of steelmaking. The problem is not merely one of making a small numbcr of temperature measurements in the open-hearth furnace. This has been done by several methods to a * Assistant Manager, Research and Development, Jones and Laughlin Steel Corporation, Pittsburgh, Pennsylvania. Issued as T.P. 2031 in MEtals Technology, June 1946; also in Open Hearth Proc., 1946. † Open-hearth Metallurgist, Jones and 1aughlin Steel Corporation, Aliquippa. Pennsylvania. degree of precision that was apparently satisfactory. Considerable effort by a number of investigators has been directed rather to the development of an open-hearth bath pyrometer that would be both accurate and practical for routine measurements. To be practical, the pyrometer should be inexpensive to operate; that is, the installation, operating and maintenance costs should be exceeded by the tangible benefits to the open-hearth operator. Temperatures from 2800' to 3100°F. are. encountered in the open-hearth furnace. The surface of the molten metal is covered by several inches of slag, which prevents direct observation of the metal surface for optical or radiation measurements. Both slag and metal are highly reactive at these temperatures and will attack to a greater or lesser extent any material immersed in them. Adequate protectioil of thermocouples, which of necessity must be brought to the temperature of the bath, has generally resulted in a large, heavy assembly made up of brittle materials, unsuited for handling on the open-hearth floor. The life of the equipment was short and maintenance was an important consideration. Earlier Work Any of a number of Physical Properties of liquid steel could conceivably be used a a basis for temperature measurement. Efforts to the present time, however, have been confined largely to measuring either the thermal electromotive force generated between two dissimilar materials immersed in the steel or the intensity of radiation from the surface of the steel. These

Jan 1, 1947

By H. T. Clark, S. Feigenbaum

The importance of measuring the temperature of molten steel in the open-hearth furnace has been recognized for many years. Poor temperature control may be costly to steelmaking operations and lead to a lowered quality of the steel. Low or excessive temperatures may shorten the life of the furnace, ladles and molds. Rates of reactions in the furnace and efficiencies of deoxidizers are known to change materially with a change in the temperature of the metal and slag. Ladle skulls and mold and stool stickers cause steel to be scrapped instead of being converted into useful products. Finally, the structure, segregation and surface condition of ingots are affected by the teeming temperature. Mill investigations of the effect of bath temperature upon steelmaking operations have been largely qualitative in character, based upon observations by practical melting men. The physical chemist has used the empirical information available and has reached reasonable and useful conclusions with respect to the various melting processes. The introduction of a reliable direct-reading pyrometer will permit accurate quantitative evaluation of the effects of temperature and should furnish a more rational basis for study of the thermochemistry of steelmaking. The problem is not merely one of making a small numbcr of temperature measurements in the open-hearth furnace. This has been done by several methods to a * Assistant Manager, Research and Development, Jones and Laughlin Steel Corporation, Pittsburgh, Pennsylvania. Issued as T.P. 2031 in MEtals Technology, June 1946; also in Open Hearth Proc., 1946. † Open-hearth Metallurgist, Jones and 1aughlin Steel Corporation, Aliquippa. Pennsylvania. degree of precision that was apparently satisfactory. Considerable effort by a number of investigators has been directed rather to the development of an open-hearth bath pyrometer that would be both accurate and practical for routine measurements. To be practical, the pyrometer should be inexpensive to operate; that is, the installation, operating and maintenance costs should be exceeded by the tangible benefits to the open-hearth operator. Temperatures from 2800' to 3100°F. are. encountered in the open-hearth furnace. The surface of the molten metal is covered by several inches of slag, which prevents direct observation of the metal surface for optical or radiation measurements. Both slag and metal are highly reactive at these temperatures and will attack to a greater or lesser extent any material immersed in them. Adequate protectioil of thermocouples, which of necessity must be brought to the temperature of the bath, has generally resulted in a large, heavy assembly made up of brittle materials, unsuited for handling on the open-hearth floor. The life of the equipment was short and maintenance was an important consideration. Earlier Work Any of a number of Physical Properties of liquid steel could conceivably be used a a basis for temperature measurement. Efforts to the present time, however, have been confined largely to measuring either the thermal electromotive force generated between two dissimilar materials immersed in the steel or the intensity of radiation from the surface of the steel. These

Jan 1, 1947

Iron and steel lire subjects that will receive the attention clue them at the meeting in. St. Louis. Within the past 2 years the smelting of iron ore on a large scale has been started in the St. Louis area, and the blast furnaces are in full operation. Ore is being received. from the Lake Superior region, in large barges .brought clown the Mississippi River. Firebrick, for the lining of the furnaces, is made in the. St. Louis district to a greater extent than elsewhere in the country. At this meeting, there will probably be a discussion of the possibilities of the increase of manganese production in this country, and of improved methods of using it in steel manufacture.

Jan 10, 1917

By Donald H. Yardley, A. Aly Selim

An economic simulation model was developed to predict the amount of copper recovered from copper oxide deposits, and the cost of producing it as a function of the deposit parameters. The economic simulation model includes programs for fragmentation design and cost, copper extraction, solution distribution and recovery, effluent solution cut-off grade, and financial analysis. Cost and price indices were also developed to evaluate the economic feasibility of in situ leaching operations as a function of their starting date. Application of the models to various hypothetical properties having the same area and different ore thickness shows that the effluent solution cut-off grade does not vary with the ore thickness nor with its grade. The percent of copper recovery is, however, shown to increase with the increase in the ore thickness and is independent of the ore grade. It is also shown that while the profit per unit of extracted copper increases with the increase in ore grade or ore thickness, the rate of return on total investment does not show any correlation.

Jan 1, 1979

By I. Fatt

A recently developed system for measuring electrical resistivity of liquids without use of electrodes offers some interesting possibilities in electric logging technology. The equipment as supplied by the manufacturer is satisfactory for continuous mud logging on a drilling rig or for measuring mud or filtrate resistivity in the laboratory. A simple modification of the commercially available instrument makes it suitable for measuring resistivity of core samples in the laboratory. The continuous measurement of mud resistivity on a drilling rig is a convenient means for detecting mixing of formation water with the drilling mud. Such information is useful to the geologist, the mud engineer and the logging engineer. However, continuous mud resistivity logging by conventional electrode-type resistivity cells is beset with difficulties. The mud, sand and rock chips abrade the electrodes, thereby changing the cell constant and eventually destroying the cell. Also, additives and crude oil in the mud may poison the electrodes by coating them with a nonconductive material. An electrode-type resistivity cell. therefore, may give erroneous readings under certain conditions. Electric logging companies circumvent the electrode poisoning problem by using a four-electrode resistivity cell for measurement of mud resistivity. In this cell, change in electrode area does not change the cell constant. However, the four-electrode cell is difficult to adapt for continuous reading and does not solve completely the problem of electrode abrasion by the sand and cuttings in the mud. The measurement of electric logging parameters on core samples in the laboratory encounters some of the same problems discussed in connection with mud logging. Ideally, the electrical resistivity of a core sample should be measured by placing platinum black electrodes in direct contact with the plane ends of a cylindrical or rectangular sample. Platinum black electrodes however, are much too fragile and easily abraded to be brought in contact with a rock sample. Also, oil or other constituents in the fluid contained in the sample will poison platinum black. In practice, gold-plated brass electrodes, in an AC bridge circuit operating at about 1,000 cps, are used for routine core analysis. For more precise work in research studies, a four-electrode scheme is used.',' Preparation of the samples for the four-electrode method is much too involved for routine core analysis. An apparatus for measuring resistivity of liquids without use of electrodes was described by Guthrie and Boys3 in 1879. They suspended a beaker, containing the electrolyte, by a torsion wire and rotated a set of permanent bar magnets around the vessel. The eddy currents induced in the electrolyte reacted against the rotating magnetic field to develop a torque, which was measured as a deflection of the torsion wire. In 1879 this method could not be made precise or convenient because of the lack of strong permanent magnets. The writer described a very greatly improved apparatus similar to that of Guthrie and Boys, but it was not suitable for continuous measurements or core samples.' Many electrodeless resistivity devices using radio frequency current are described in the literature.5, 6 These generally are suitable only for noting the end-point in a chemical titration. They do not measure resistivity, instead measuring a complex quantity which includes the dielectric constant and the magnetic permeability. The first description of the apparatus to be discussed in this paper was given by Relis.7 Improvements and modifications are described by Fielden,s Gupta and Hills,> and Eichholz and Bettens.10 DESCRIPTION OF APPARATUS The apparatus used in this study is based on the principle that the solution under measurement can form a loop coupling two transformer coils, as shown in Fig. 1. For a fixed AC voltage applied across Coil A, the voltage appearing across Coil B is a function of the resistance of the liquid-filled loop. The details of the voltage generating and measuring circuits are given in Refs. 7, 8, 9 and 10. A block diagram of the equipment is given in Fig. 7. Special features worth mentioning are the operating frequency of 18,000 cps and the automatic temperature compensation which results in the given resistivity readings being automatically correlated to 25°C. The liquid loop supplied by the manufacturer, shown in Figs. 1 and 2, was modified for use in core analysis (Fig. 3). The core sample under test is substituted for a section of the original loop. As shown in Fig. 3, the unit accepts only plastic-mounted cylindrical core specimens. A Hassler-type sleeve easily can be designed for the unit if unmounted cores are to be measured. EXPERIMENTAL PROCEDURE MUD LOGGING A simulated mud line was set up in the laboratory.

By Freeman Bishop

Having obviously cleared the way for fast confirmation by the Senate Interior Committee, the Administration recently named Elburt F. Osborn, vice president of Penn State University, as director of the Bureau of Mines. Interior Committee Chairman Henry M. Jackson (D of Wash.) has moved hearings on the nomination right along, forecasting that they will end in a confirmation. Dr. Osborn not only made a good impression on the Committee, he also made it amply clear that he would be the boss of his job and have right-hand aides to help straighten out conflicts stemming from recently enacted health and safety regulations for miners. Mining engineers in the field hope this clarification can come soon. They are frankly fed up with local, state, regional and national overlapping of restrictions.

Jan 1, 1970

By H. M. FRENCH

ARC welding can be defined as a process whereby two A pieces of metal are brought together, heated to a molten state by the heat of an electric arc, and fused into one piece. There are several kinds of arc welding: the metallic arc, the carbon arc, the atomic hydrogen arc and the shielded arc methods. A short description of each, together with its major applications, will serve to distinguish between them. Metallic arc welding involves an arc drawn between a metal electrode and the material to be welded, called the work or the "parent metal." It may be further subdivided into hand and automatic welding, depending on whether the electrode is fed to the arc by hand or by motor drive. This form of arc welding can be applied to most welding operations. Exceptions to its use consist of applications where very thin metals are to be welded; where it is desired to join the work with- out adding metal; or where extreme ductility may be required:

Jan 1, 1930