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By William G. Kegel

Aside from having a usable product and good mining conditions, the greatest asset for a profitable coal mining organization is an effective mine maintenance program. The first step in acquiring this is the presence of good mechanics-men who have a desire to be mechanics and who want to know more about the design and control of the machines in their charge. The knowledge and ability to be found in a good mechanic is the result of ambition, curiosity, and determination. With these qualities as a start, the aspiring mechanic can launch his career if he begins learning all he can about mechanics, electricity, and hydraulics. The path is rough, but the goal is rewarding. Mining machinery probably absorbs as much or more abuse than any other heavy equipment in use today. And when one considers the conditions under which much of the repair work must be done, it can be seen that the mine operator needs the best of men and tools to perform the service. MOTORS AND POWER SUPPLY Mining machines, from their inception, have utilized the electric motor; and down through the years of mechanization, this power source has undergone many changes to better adapt it to the job. The first motors used were large, heavy-framed, open d-c motors (direct current), using a series or shunt winding. A motor having one or more field coils connected in series and themselves in series with the armature, is called a series motor (Fig. 1). The series motor had the advantage of quickly developing starting torque, and it was, and still is, the best motor for locomotive or shuttle car tramming service. The series motor, however, speeds up as the load is reduced and, if not properly controlled, can overspeed. The shunt motor, as its name implies, has one or more field coils in

Jan 1, 1973

By A. J. Lena, M. F. Hawkes

Changes in hardness, tensile properties, microstructure, electrical resistance, and X-ray diffraction effects indicate that lattice strains are necessary for the embrittlement of ferritic stainless steels when heated for relatively short times at 475°C (885°F). It is suggested that 475°C (885°F) embrittlement is due to the accelerated formation of an intermediate stage in the formation of s under the influence of these strains. FERRITIC stainless steels (low carbon alloys of iron with more than 15 pct Cr) are subject to two forms of embrittlement when heated in the temperature range of 375° to 750°C. The embrittlement which occurs after long time heating between 565" and 750°C is well understood; it is caused by the precipitation of the hard, brittle s phase. Sigma is an intermetallic compound of approximate equi-atomic composition with an extended range of formation in Fe-Cr alloys. The maximum temperature at which this form of embrittlement can occur is dependent upon chromium content; and is approximately 620°C for a 17 pct Cr steel and 730°C for a 27 pct Cr steel. The other form of embrittlement occurs after relatively short heating periods in the range of 375" to 565°C; in the higher chromium steels, hours may be sufficient as compared to months for s embrittlement. This phenomenon is not at all well understood and several controversial theories have been proposed. The rate and intensity of embrittlement increase with increasing chromium content but the maximum rate occurs at 475°C re-gardless of chromium content. As a result of this, the phenomenon has been termed 475°C (885°F) embrittlement. The effect of 475°C embrittlement on the properties of ferritic stainless steels has been thoroughly reviewed by Heger.1 The embrittlement causes a pronounced decrease in room temperature impact strength and ductility, a large increase in hardness and tensile strength, and a decrease in electrical resistivity and corrosion resistance. Microstructural changes accompanying embrittlement are minor and difficult to interpret with a general grain darkening, appearance of a lamellar precipitate, grain boundary widening, and precipitation along ferrite veins having been reported at various times. With the exception of reported line broadening, X-ray diffraction studies by conventional Debye analysis of solid samples have been of little value. BY making use of electron diffraction methods, Fisher, Dulis, and Car-roll' have recently shown the existence of a chromi-um-rich, body-centered cubic phase in 27 pct Cr steels which had been aged at 482°C (900°F) for as long as four years. Two types of theories have been advanced to account for the embrittlement. The first of these requires the precipitation of a phase not inherent in the Fe-Cr system with various investigators suggesting a carbide,3 nitride,3 phosphide,4 or oxide." Theories of this type have difficulty accounting for the influence of alloying elements on the embrittlement and for the facts that a minimum chromium content is necessary for embrittlement and the intensity of embrittlement increases with increasing chromium content. The second type of theory that has been proposed relates 475°C embrittlement to s phase formation which is inherent in the Fe-Cr system. An assumption of this kind can adequately explain the influence of alloying elements, for they exert an effect on 475°C embrittlement similar to that on s phase for-mation as can be seen in Table I. The minimum chromium content is essentially the same for both phenomena and it has been shown12,13 that s is a stable phase in the embrittling temperature range. In addition, it has been reported14,15 that pure alloys embrittle to the same extent as commercial type alloys. There are, however, several factors which have prevented complete acceptance of a s phase theory. Foremost of these is that the embrittlement can be removed by reheating for short time periods above 600°C, which in the higher chromium steels is within the stable s region. No s has ever been observed after one of these curing treatments, nor has any s been found as a result of embrittlement at 475°C. In addition, the simple precipitation of s cannot explain the time-temperature relationships for reactions between 350°and 750°C. This behavior is shown schematically in Fig. 1. Newell 16 and Ried-rich and Loib4 have shown that 475°C embrittlement follows a C-type curve as illustrated, while Short-

Jan 1, 1955

By L. S. Darken

IT has long been recognized that the driving force in an isothermal diffusion process may be regarded as the negative gradient of the chemical potential (partial molal free energy) of the diffusing substance. This equivalence is exactly analogous to the fact that a mechanical force is the negative gradient of the potential energy. Nernst1 in 1888 expressed these driving forces in terms of osmotic pressure, which is directly related to the chemical potential and free energy. The relationship between the diffusivity, mobility and activity coefficient of electrolytes in aqueous solution has been developed in great detail by Onsager and Fuoss2 with results which have recently been confirmed experimentally by Harped and Nuttall.3 This interpretation of the driving force in isothermal diffusion has been discussed earlier by the author 4.6 who pointed out4 that "for a system of more than two components it is no longer necessarily true that a given element tends to diffuse toward a region of lower concentration even within a single phase region"; departure from the behavior of an ideal solution may be so great that the concentration gradient and the chemical potential gradient, or activity gradient, may be of different sign, thus giving rise to "up hill" diffusion. Since, in the discussion of that paper,4 some skepticism as to the validity of this conclusion was expressed, it seemed desirable to adduce experimental evidence to support it. Evidence of such diffusion in nonmetallic systems has already been reported. For example, it was observed by Hartley11 in a series of experiments in which sodium chloride diffused from a saturated solution in about 5 pct acetone in water into a solution virtually free of salt but with essentially the same acetone concentration. Specifically, a wine glass containing crystalline salt and saturated solution was totally immersed in a large glass cylinder containing the acetone-water solution without salt; the difference in specific gravity was such as to prevent convection. Diffusion of salt was accompanied by a marked depletion 0f acetone in the wine glass; after 3 days the acetone concentration decreased from 5.37 pct at the top of the glass, where the salt concentration was low (0.93 pct), to 1.84 pct at the bottom where the salt concentration was high (21.64 pct). This "uphill" diffusion was found to be such that the partial pressure (activity) of acetone was essentially equalized throughout the system when a steady state gradient of sodium chloride was maintained. In order to demonstrate the existence of such diffusion in metals, a series of four weld-diffusion experiments was made. In these measurements pairs of steel of virtually the same carbon content, but differing markedly in alloy content, were welded at the end and held at 1050°C for about two weeks. Subsequent analysis showed that carbon had diffused so as to produce an inequality

Jan 1, 1948

By E. E. Donath

Application of the coal hydrogenation process for the production of chemicals is described. It has been estimated that a plant to produce 31,090 bbl per day of chemicals and fuels would cost $326,- 000,000. These products would consist of 6.1 pct by weight tar acids, 50.8 pct aroma tics, 16.4 pct LPG, and 26.7 pct gasoline. THE coal hydrogenation process is well known as a means for the production of liquid fuels from coal. In this paper the possibilities of the coal hydrogenation process as a source of chemical raw materials will be discussed. The recovery of chemicals from coal hydrogenation products necessitates some modifications and additions to the equipment used for the production of fuels. The conversion of coal into liquid fuels such as gasoline requires two steps: liquid phase and vapor phase hydrogenation. Intermediate oils obtained in the liquid phase contain oxygen and nitrogen compounds, especially aromatic compounds, since the coal itself is composed mainly of cyclic compounds. These oils are the raw material for the separation of high molecular weight aro-matics and of tar acids and tar bases. The relative amounts of heavy and middle oil—boiling above and below, e.g., 325°C—can be influenced by temperature, residence time, and catalyst of the liquid phase hydrogenation. In the vapor phase hydrogenation a solid bed catalyst is used to convert the intermediate oil from the liquid phase operation into hydrocarbons of the gasoline boiling range. Essentially pure hydrocarbons with a low content of sulphur, oxygen, nitrogen, and olefines are obtained. Depending mainly on the catalyst, the high ring compound content of the liquid phase oil can be preserved and gasoline rich in aromatics obtained. However, with other catalysts, these ring compounds can be split into gasoline with a high content of isoparaffins.' Again, depending on the operating conditions, products of varying boiling range can be obtained. Selection of catalyst and operating conditions therefore makes possible the production of different grades of motor fuel and also variations in the relative amounts of benzene, toluene, and xylene when aromatic hydrocarbons are produced. The schematic flowsheet, Fig. 1, shows the main steps of the coal hydrogenation process, and the product streams used for the recovery of chemicals are indicated. In the liquid phase hydrogenation stage, coal is made into a paste with recycle heavy oil. The coal paste is mixed with hydrogen and preheated at a pressure of 300 to 700 atm in heat exchangers and preheaters. The coal paste and hydrogen enter high pressure converters where the liquefaction of coal, conversion of the high boiling liquid materials initially obtained, into intermediate oils is performed at a temperature around 470°C. The reaction products enter the hot catchpot in which lower boiling oil vapors are separated from the residue containing unreacted coal, ash, and heavy oil. This residue, usually called H.O.L.D. (heavy oil let down), is processed to separate solid and liquid material. By thermal treatment of the residue, e.g., a coking process, distillate oil is obtained, which can be recycled as part of the pasting oil. This stream is rich in polynuclear aromatics and can be, and has been, used for the recovery of such material. The oil vapors and hydrogen from the hot catchpot are cooled in heat exchangers and a cooler, and the condensed oil is separated from the recycle hy-

Jan 1, 1953

By E. E. Donath

Application of the coal hydrogenation process for the production of chemicals is described. It has been estimated that a plant to produce 31,090 bbl per day of chemicals and fuels would cost $326,- 000,000. These products would consist of 6.1 pct by weight tar acids, 50.8 pct aroma tics, 16.4 pct LPG, and 26.7 pct gasoline. THE coal hydrogenation process is well known as a means for the production of liquid fuels from coal. In this paper the possibilities of the coal hydrogenation process as a source of chemical raw materials will be discussed. The recovery of chemicals from coal hydrogenation products necessitates some modifications and additions to the equipment used for the production of fuels. The conversion of coal into liquid fuels such as gasoline requires two steps: liquid phase and vapor phase hydrogenation. Intermediate oils obtained in the liquid phase contain oxygen and nitrogen compounds, especially aromatic compounds, since the coal itself is composed mainly of cyclic compounds. These oils are the raw material for the separation of high molecular weight aro-matics and of tar acids and tar bases. The relative amounts of heavy and middle oil—boiling above and below, e.g., 325°C—can be influenced by temperature, residence time, and catalyst of the liquid phase hydrogenation. In the vapor phase hydrogenation a solid bed catalyst is used to convert the intermediate oil from the liquid phase operation into hydrocarbons of the gasoline boiling range. Essentially pure hydrocarbons with a low content of sulphur, oxygen, nitrogen, and olefines are obtained. Depending mainly on the catalyst, the high ring compound content of the liquid phase oil can be preserved and gasoline rich in aromatics obtained. However, with other catalysts, these ring compounds can be split into gasoline with a high content of isoparaffins.' Again, depending on the operating conditions, products of varying boiling range can be obtained. Selection of catalyst and operating conditions therefore makes possible the production of different grades of motor fuel and also variations in the relative amounts of benzene, toluene, and xylene when aromatic hydrocarbons are produced. The schematic flowsheet, Fig. 1, shows the main steps of the coal hydrogenation process, and the product streams used for the recovery of chemicals are indicated. In the liquid phase hydrogenation stage, coal is made into a paste with recycle heavy oil. The coal paste is mixed with hydrogen and preheated at a pressure of 300 to 700 atm in heat exchangers and preheaters. The coal paste and hydrogen enter high pressure converters where the liquefaction of coal, conversion of the high boiling liquid materials initially obtained, into intermediate oils is performed at a temperature around 470°C. The reaction products enter the hot catchpot in which lower boiling oil vapors are separated from the residue containing unreacted coal, ash, and heavy oil. This residue, usually called H.O.L.D. (heavy oil let down), is processed to separate solid and liquid material. By thermal treatment of the residue, e.g., a coking process, distillate oil is obtained, which can be recycled as part of the pasting oil. This stream is rich in polynuclear aromatics and can be, and has been, used for the recovery of such material. The oil vapors and hydrogen from the hot catchpot are cooled in heat exchangers and a cooler, and the condensed oil is separated from the recycle hy-

Jan 1, 1953

By Arvid E. Anderson, Frank K. Cameron

The weathering of copper-bearing ores with the formation of a water soluble salt and the recovery of the metal by leaching and evaporation precipitation, are processes long known, which have at various times been utilized with more or less commercial success. It is commonly assumed that the technical principles involved are quite simple and their application to a particular case easy. If these assumptions were true, we should anticipate a long list of uniformly successful leaching operations, which is not the case, and one would be justified only in calling attention to either unique or peculiar features of any particular enterprise; whereas, in studying the problems of the recovery of copper from the old workings of the Ohio Copper Co. in the light of available descriptions of other leaching projects, we have not found the assistance hoped for to guide us to the best realization of our own opportunities. It appears desirable, therefore, to call attention to these guiding principles, together with a description of the facts of accomplishment. Justification lies in the fact that the leaching and precipitation of copper at the Ohio Copper Co. mine in Bingham Canyon, Utah, is successful. This success is measured by an average monthly production of 600,000 Ib. of copper at an average operating cost, to date, of 3.85 cents per pound at the company's workings, or 6.32 cents per pound after paying shipping and smelter charges on the finished copper. A total of 17,076,099 Ib. of copper had been shipped to the smelter from the beginning of operations, August, 1922, to April 1, 1925. Probably these results can be bettered with further study and realization of the factors involved and the devising of methods of meeting them. It is now an assured fact that the enterprise will have a relatively long and continuously profitable life and that its reserves will not, nor cannot, be suddenly and permanently depleted. It is particularly noteworthy that the financing of this enterprise has been entirely from its earnings. The few hundred dollars necessary for the first experiments and production were obtained by the sale of used, and no longer needed, equipment from a mill belonging to the company; and all funds since required throughout the growth and development of the enterprise, from a few troughs with a production of 2000

Jan 1, 1926

By H. C. Goodrich

AT THE Utah Copper mine, steam shovels were first used, in 1906, for the removal of overburden, and in June, 1907 for the mining of ore. Prior to 1907, the ore came from underground development work and from stoping. The use of the steam shovel gradually increased until 1914; since then all material, both overburden and ore, has been loaded by power shovels operating on the various benches of the mine. During FIG. 1.-SCENE OF UTAH COPPER MINE BEFORE OPEN-PIT MINING WAS BEGUN. these 19 years, there has been a great improvement in open-pit mining; largely in the use of equipment having greater capacity and dependableness. The history of the development of mechanical shovels and related equipment, as affecting the Utah Copper Co., would be interesting and would justify considerable space; but of greater interest at this time is the operation of the equipment now in use. The Utah Copper mine is in a great deposit of copper-bearing monzonite, which occurs as a prominent headland of the Oquirrh range of

Jan 9, 1925

By Donald R. Rathburn, Jung K. Mok

An historical review and a survey of current practice in the application of fine dry grinding in the iron ore industry are given. Both closed and open-circuit applications are reviewed, and the advantages, disadvantages, and process considerations for these two systems are discussed. The ground ore temperature rise, and the cool-ing of ground ore and mill ventilation are also discussed, along with the agglomerating characteristics of dry ground ore. Screening during the production of high-grade lump ore for blast-furnace burden, particularly from recently developed ore deposits in Australia, South America, and Africa, has resulted in large tonnages of fine iron ore. Certain owners have decided to stockpile these fines until some later date. Others have either sold these fines "as is" for agglomeration at the steel plant or have established their own pelletizing plants to produce a premium quality agglomerate. In almost all cases some grinding is required prior to pelletizing. Most of these ores occur in the weathered state which may result in difficulty in the thickening and/or filtering stages when ground in a wet system. The resulting filter cake would probably require partial drying to provide a product suitable for the subsequent balling operation; however the partial drying and subsequent material-handling steps often produce random agglomeration. Normally, these agglomerates will cause problems in the green ball formation process. Thus dry grinding has developed as a solution to this problem. Most of the dry iron ore grinding installations utilizing the standard-type rod or ball mill are grinding high-grade natural ores that do not require beneficiation. Although power consumed per ton of final product is 120% or greater in dry grinding as compared with wet grinding, the additional power required for dewatering and handling a wet ground product can easily exceed the initial power savings. Dry grinding of raw feed and clinker has been practiced in the cement industry for many decades but its major application to the iron ore industry has taken place only within the past ten years. The successful application of dry grinding to iron ore has required the solution of several unique design and operating problems. The purpose of this paper is to review recent developments in fine dry grinding of iron ore for pelletizing and to discuss the various designs and operating parameters involved.

Jan 1, 1971

By Robert E. Cuthbertson

IT is the purpose of this paper to describe in detail the laboratory development and mill application of an unusual combination of flotation reagents employed in the concentrator of the Climax Molybdenum Co., on the Continental Divide, near Leadville, Lake County, Colorado. This development originated in an ore-dressing research laboratory maintained by Climax at the experimental plant of the Colorado School of Mines, which is staffed by men directly employed by the Climax Molybdenum Co. Mill-scale testing of laboratory developments was supervised by a representative from the testing laboratory, working in close cooperation with the operating staff at the mill. General milling practice at Climax is ably described in a paper by E. J. Duggan,1 mill superintendent. Other aspects of the Climax project have been described in papers by W. J. Coulter,2 by Butler, Vanderwilt and Henderson3 by Allen Kissock,4 and by Leo H. Glanville.5 Consequently, this paper will be confined to the metallurgical aspects of recent reagent developments, avoiding, as much as possible, repetition of material covered in these earlier publications. BRIEF HISTORY OF REAGENT PRACTICE AT CLIMAX Prior to the year 1937, the only reagents employed at Climax for froth production and collecting action in the flotation of molybdenite were steam-distilled or destructively distilled pine oils. The only exceptions to this practice were brief periods of mill testing, when reagents of various types were tried on an experimental basis. None of these experimental runs was sufficiently encouraging to justify its continuation as regular practice. Sodium, cyanide has been employed since the very early days of milling at Climax as an inhibiting agent for control of pyrite and chalcopyrite. Alkaline reagents such as lime or soda ash have been used in recent years to minimize the detrimental effect of iron salts on flotation of molybdenite. The presence of these harmful salts is attributed to the decomposition of fine metallics abraded from liners and balls in the first stage of regrinding rougher concentrate. Flint pebbles are used in subsequent regrinding, since alkaline reagents are not entirely adequate to offset the inhibiting effect of iron salts as the grind becomes progressively finer and the grade of concentrate progressively higher. Climax metallurgists were familiar at an early date with the use of petroleum products such as kerosene and gas oil as promoters of flotation of molybdenite. Charles C. Oliver6 discussed the use of pine oil and kerosene as early as 1920, in connection with the milling practice at Dominion Molybdenite Co., Quebec. Never theless, the early attempts to apply this knowledge in the Climax concentrator were complete failures. In the light of recent experience, it may seem strange that the early mill tests with petroleum

Jan 1, 1944

By Charles Barrett

RECRYSTALLIZATION textures-the orientations of grains after recrys-tallization-have been studied extensively not only because of their metallurgical importance but also because of the information they yield regarding the atomic movements during recrystallization. Recrystallized grains must possess the same orientations as the submicroscopic nuclei from which they have grown, and thus they offer a direct road by which experimenters can penetrate the submicroscopic realm. Many perplexing results have come of these studies, but one of the most striking has been the apparent difference in behavior between single crystals and polycrystalline grains. For example, Burgers and Louwerse have shown' that when single crystals of aluminum are deformed by compression and are recrystallized (at 600° C.) the new grains appear with orientations that are different from the orientations of the deformed crystal in which they grew; but polycrystalline specimens, on the other hand, appear to have a [110] fiber texture both before and after recrystal-lization and thus to retain their texture during recrystallization. This apparent difference between the habits of single crystals and small grains is the subject of the first part of the present research and has been explained by findings reported herein. A similar situation appears to exist for aluminum when elongated or drawn into wires, for single crystals alter their orientation2,3 and polycrystalline wires retain their texture 4,1 6 upon recrystallization after elongation (at least with high-purity alumi-num), and it is possible that the explanation found in this paper for compression can be extended to cover elongation and other types of deformation as well. The second part of this paper deals with the theory of recrystallization textures. In the most successful theory for aluminum recrystallized after compression,1 much weight is given to the orientation of highly stressed nuclei in the deformed material. Taylor's "local distortions" are assumed to exist along the slip planes where displacement has occurred, consisting of fragments rotated in a specific way with reference to the slip plane and slip direction; namely, about an axis lying in the slip plane perpendicular to the slip direction. 1,7,8,9

Jan 1, 1940

By A. Kaufman

More than 3 trillion gal of water are used annually by the mineral industry. Of this, approximately 21/2 trillion gal are recirculated, the rest constituting intake water. The major users are natural gas processing plants and phosphate rock, sand and gravel, and iron ore producers. Water was used by the mineral industry for mining (6%), processing (64%), cooling and condensing (27%), and miscellaneous uses such as boiler feed and sanitary purposes (3%). Whereas total water use is dependent on the quantity of material processed and on the particular process requirements of an industry, recirculation is dependent on processing, as well as cooling and condensing requirements, quality of new water intake, and the necessity for treating new and discharged water. Consumed water, on the other hand, is dependent on the quantity of water recirculated, and temperature and humidity in the area. Based on this analysis, an increase in water use by the mineral industry of 21/2 times by 1985 is forecast. Wster intake, however, will only rise 62%, because of a substantial increase in recirculation. In one report of a special series concerning the water resources of the United States, the Senate Select Committee on National Water Resources, 87th Congress, estimated that water demand would double by 1980 and triple by 2000.' In view of the possible water deficiencies that might result from such expanded usage and the need for research guidance, the Bureau of Mines organized and carried out a statistical canvass of water use in the mineral industry for calendar year 1962. The data used in this paper, unless otherwise noted, are derived from that canvass.' The efforts in this paper are devoted toward summarization of the canvass and analysis of the data. SOME DEFINITIONS Intake: Water introduced from an external source for the first time into a given mine or plant regardless of quality. Intake water is also called new water, water withdrawn, or makeup water. Fresh Water: Water suitable for cooking and drinking. Saline Water: Water containing more than 1000 parts per million of dissolved solids. Contaminated Water: Water not suitable for domestic use, but excluding saline water. Recirculated Water: Water reused to conserve intake water. Solutions that are recycled primarily because of fixed metallurgical practices, such as copper leaching solutions containing sulfuric acid, are excluded. Gross Water Used: Recirculated water plus intake water. Also called total water used. Consumed Water: Water that is lost by evaporation, as well as water lost in product. Seepage and transferred water are not considered consumed. The use of either intake or recirculated water may result in consumption. However, because of difficulties in measuring consulmption, consumed water is defined as the residual between intake and water discharged from the mine or plant. Mineral Industry: For the purposes of this paper, mineral industry includes all metal and nonmetal surface and underground mines and their associated processing plants, as well as custom mills, coal washing plants and associated mines, petroleum and natural gas well drillers, natural gas processing plants, and secondary recovery operations. WATER USE IN THE MINERAL INDUSTRY Water used by the mineral industry constitutes a relatively minor fraction of the water withdrawn by all users. Data compiled by the U.S. Geological Survey in 1960 indicate that water withdrawals, exclusive of that used to generate hydropower, approximate 99 trillion gal annually.3 Our data indicate that water withdrawals by the mineral industry comprise only 1% of this total, or 2% of the water withdrawn by industrial users. Use by Industry: Water used by various mineral industries is shown in Table I. The table indicates that close to one-half of the gross water used by the mineral industry in 1962 was used by natural gas processing plants, followed by sand and gravel, phosphate rock, and iron ore producers. The largest aggregate users of water are also the largest users per dollar of product. For example, Fig. 1 shows that the natural gas processing and phosphate rock industries are very large users of water per dollar of product. Their recirculation per

Jan 1, 1968

By G. W. Leney

Iron ores occur in such a wide variety of forms that nearly every kind of prospecting, geological knowledge, and geophysical technique has some application in the search for them. The type of orebody that is considered desirable depends on political and economic considerations, on transportation and markets, on the characteristics of the orebody, on the metallurgy of the ore, and on its comparison with other available ores. In North America, materials that can be efficiently processed into high grade concentrates and pellets are now the object of most exploration work. These are usually shallow, relatively unoxidized, metamorphosed iron formations that are particularly suitable for geophysical methods of exploration. Magnetic surveys are used for the direct discovery of new orebodies, for mapping stratigraphy and structure, and at times to locate oxidized zones in magnetic iron formation. Gravity mapping provides supplementary information, indicates gross tonnages, is useful in regional studies, and can discover non-magnetic orebodies. Electrical methods have not been fully exploited but self-potential, resistivity, applied potential, electromagnetic and perhaps induced polarization surveys all have restricted but highly useful applications. The use of all geophysical techniques promises to increase as the number of exposed easily discoverable orebodies decreases. A high consumption of steel, and consequently of iron ore is the chief characteristic of an industrial society and this consumption has been increasing at an average rate of about 35% every ten years for the past century. To supply this demand, iron ores and iron bearing materials in a wide variety of forms have been exploited on every inhabited continent and in nearly every country. Nearly every kind of prospecting, geological knowledge and geophysical technique has some application in the search for them. The type of orebody that is con-

Jan 1, 1964

By Henry G. Granger, Edward B. Treville

The Republic of Colombia is the northernmost country of South America. Its northern coast line exteilds from the frontier of Costa Rica to that of Venezuela, on the Caribbean Sea. On the west it fronts on the Pacific Ocean, along the Panama Isthmus, and down to Ecuador. It is bounded on the south by Ecuador, Peru and Brazil, which latter country with Venezuela form its boundaries on the east. Its area exceeds 500,000 square miles. It is deemed unnecessary to give here a map of the country. Fig. 1, a map of the department of Antioquia, studied in connection with a good modern general map of Colombia, will explain itself. Fig. 1 contains also some of the region of the Cauca valley, described in this paper. Access.—The interior of Colombia is reached through the ports of Sabanilla and Cartagena on the Caribbean Sea, each of which places is connected with the Magdalena river by a short narrow-gauge railroad, running respectively to Barranquilla and Calamar. From these points lines of river-steamers serve the ports of the upper Magdalena, which they reach in journeys of a week to ten days. After leaving the steamer, a short railroad journey, followed by a long and tedious mule-ride, reaches the cities of Bogota and Medellin. Quibdo, at the head of the navigation of the Atrato, and its most important town, is connected by steamer-service with Cartagena, by canoe-routes with the various districts of the Choco, and by mule-road, at present well-nigh impassable, with the heart of Antioquia. On the western coast the port of Tumaco is a starting-point for canoe- and mule-travel to the southern part of the department of Cauca, while Buenaventura is the port of the central section of the valley of the Cauca,

Jan 1, 1899

By Ernst F. Eurich

Alexander Parkes patented in England in 1851-52-53 a process for desilvering lead by means of zinc, making use of the greater affinity of silver for zinc than for lead, discovered by Karsten in 1842. The efforts in England to develop it commercially were not particularly successful, nor was the attempted introduction into the United States. This last was not surprising, as it was about the beginning of our Civil War, and at that period there was very little lead-bullion produced in the United States and there was no field for the process here. There was at that time on Staten Island an establishment that pattisonized lead, probably from Rossie, N. Y., and Chester, Pa., and possibly some Spanish lead, but the production of lead-bullion in the Far West had not yet begun. In 1864, Edward Balbach, of Newark, N. J., patented in this country a process for desilvering lead by means of zinc, and in 1867 Edward Balbach, Jr., patented a " movable black-lead retort with a neck, placed in a furnace," for the purpose of distilling the alloy of zinc, lead, and the precious metals. A brief comparison of the Parkes and the Balbach processes is interesting. The Parkes process as practiced in England consisted in stirring into silver-bearing lead, melted in a kettle, from 1 to 2 per cent. of zinc, cooling, skimming the alloy of lead, zinc, and silver that rose to the surface, liquating it in an iron retort, distilling the residual rich alloy in fire-clay retorts, thus regaining the zinc, and refining the desilvered lead at a low heat in a shallow cast-iron pan that formed the hearth of a reverbera-tory furnace. If the lead was too impure, it was first softened

Jan 1, 1913

By E. Seidl

THE basic material for testing aluminum, copper and zinc is a cast metal, principally in the form of wire bars (Figs. 1 to 3) and plates for the produc- tion of sheets or strips, (Figs. 4 to 7). Experience has proved that the chemical and crystallographic proper-ties of such cast metal exercise a certain influence when it is being worked, which is usually done while the metal is hot. In a chemical sense the slight impurities, which even the purest industrial metal contains, have a disturbing effect. They settle either along the outside limits of granulation, as in the case of aluminum and copper, or else in the interior of the crystal, as in the case of zinc; but frequently are also found accumulating at certain points (formation of the blowholes and skin) (Fig. 7). The crystallographic character of the metals is either that of uniformly fine granulation, or else there occurs a certain distinct casting texture marked by sharply defined cooling conditions and consisting of crys-tals of a pronounced stalk-like or blade form. Since we generally distinguish between a crystal texture and a crystal structure, the term crystal texture is used here for the arrangement of the crystals relative to each other and their microscopic composition; crystallic structure is used to mean the radioscopically ascertain-able structure of the crystal. The influence of the impurities and of the crystalline character on the working of the metals has been fre-quently pointed out in practice as well as in science.

Jan 11, 1927

By Leonard Grimshaw

THE idea of bonding two dissimilar ferrous metals, and making use of both, is an old one. Tips have been brazed onto tool shanks for many years. The bonding of larger pieces to form whole bars and sheets has also been accomplished, but has received little attention in the technical literature, although a number of patents have been issued covering various methods for its accomplishment. There are three main motives behind the manufacture of composite steels. One is that the physical properties of one steel may supplement those of another; a useful, but at the same time, hard, brittle steel may be backed by a soft ductile one, or a stainless steel may be backed by a steel possessing greater strength. Another motive is direct lowering of cost; an expensive steel may be backed by a less expensive one, bringing down the cost of the piece as a whole. The third motive is an indirect lowering of cost, as when a useful steel is backed by a steel that is easier to machine, so that machining cost on a finished product is lowered considerably. Often more than one of these motives lead to a decision to use a com-posite steel.

Jan 1, 1936

By K. G. Davis, P. Fryzuk

A study has been made of the effect of undercooling on the grain structure and solute distribution in small ingots of pure bismuth and of a 100 ppm Ag in bismuth alloy. Autoradiographic evidence shows that in undercooled melts a network of dendrites is formed throughout the melt immediately after nu-cleation. At large undercoolings the dendrites are very thin and closely spaced. The origin of the observed grain morphology can be explained on the basis of information about the mode of solidification revealed by the impurity substructure. WHILE a great number of studies of nucleation in undercooled molten metals have been made, comparatively little attention has been given to the mode of solidification from melts with large undercool- ings. Colligan and Bayles1 and Walker2 have measured the rate of advance of the solid-liquid interface in undercooled nickel melts, but the morphology of the solidifying material remained a matter of speculation. Fehling and Scheil3 have described the grain structure in ingots formed from undercooled melts of nickel, palladium, and copper, and a series of Ni-Cu and Ni-Pd alloys. At small undercoolings, equiaxed structures are observed, the grain diameter tending to increase as the temperature of nucleation is lowered. At greater undercoolings, a columnar structure is developed, while with still further undercooling there is a smaller grain size incorporating rather coarse subgrains. All-bright and Colligan4 examined the grain structure shown by ingots solidified from melts of nickel and of Ni-Ag alloy at an undercooling of 105°C, and concluded that considerable grain growth had taken place after solidification. The object of the present work is to correlate the mode of solidification from undercooled melts with both the grain structure and impurity segregation, using tracers to examine the latter.

Jan 1, 1965

By W. R. Kanne, P. R. Strutt, R. A. Dodd

A study has been made of the creep behavior of ß-NiAl of stoichiometric composition in the temperature range 475" to 775°C. Single crystal tensile specimens were deformed under a constant applied load. From slip line studies and tensile axis rotations it was concluded that the crystals deformed by pencil-glide on (100) and (110) planes with a (100) slip direction. Electron microscope thin-film studies showed evidence for profuse cross-slip, and the dislocation Burgers vector was determined to be (100). There was no tendency for the dislocations to lie in definite slip planes, although a strong alignment of segments of edge dislocations was frequently seen. The activation energy for creep in the temperature range 475" and 775°C was judged to be much lower than that for creep at temperatures above 775°C. It is possible that the rate-controlling process is the thermally activated cross-slip of screw dislocations. In recent years considerable interest has developed in the possible use of high-melting-point intermediate phases for high-temperature applications necessitating good creep resistance. Ordered alloys such as Ni3A1, modified by alloying additions, have received particular attention, culminating in the recent development by Pratt and Whitney of single crystal turbine blades.' The intermediate phase NiAl has considerable theoretical interest from a creep standpoint because not only is it ordered up to the melting point (-1650°C at stoichiometry) but it contains a high concentration of structural vacancies on the aluminum-rich side of stoichiometry. These vacancies are known to exert a strengthening effect under some conditions,' but in addition they might be expected to affect high-temperature creep rates through dislocation climb. The present paper deals with the slip line and dislocation structures developed during creep of stoichiometric NiAl between 475" and 775C, and with possible attendant creep mechanisms. MATERIALS AND TEST TECHNIQUES NiAl ingots of stoichiometric composition were prepared by induction melting 99.996 pct A1 and 99.98 pct Ni (kindly provided by the Kaiser Aluminum Co. and the International Nickel Co., respectively) in 100 cc pure alumina crucibles in a helium atmosphere. No chemical melting flux was used in order to avoid con- tamination of the alloy. Each ingot was slowly direc-tionally solidified to avoid porosity and to produce very large grains up to 2 in. in length. In this way, ingots were obtained which were suitable for sectioning into single crystal creep specimens. Chemical analysis indicated that all alloys were within the range 49.6 0.3 at. pct Ni. For the present investigation, identical rectangular single crystal blanks were cut vertically from one particularly large crystal in an ingot using a series of three diamond cut-off wheels with appropriate spacers. Thus, all sliced crystals had the same orientation with the tensile axis parallel to the long side of the rectangle; the initial orientation of the tensile axis is shown as S, in Fig. 1. The blanks were homogenized at 1250 to 1300°C for 48 hr and subsequently cooled slowly to room temperature. A gage length of rectangular cross section and about 0.75 in. in length was prepared on each specimen using an electrolytic lathe and a dilute nitric/phosphoric acid electrolyte. The gage length cross section was 0.250 0.0005 in. by 0.040 ± 0.0005 in. Holes to accommodate tensile grips were electrolytically machined using a rotating acid jet. After creep testing, this same technique was used to cut discs for transmission electron microscopy. Thus, all shaping was done electrolytically, the only exception being that (122) sections were spark-machined from some speci-

Jan 1, 1970

New Members The following list comprises the names of those persons who became members during the period June 10, 1916, to July 10, 1916: ADAMS, WILLIAM S., Filtration Engr., Anaconda Copper Min. Co., 701 Cherry, Anaconda, Mont. ALLEY, JAMES E., Shift-boss.. .......... Belmont Milling Co., Tonopah, Nev. BADGLEY, CHARLES WELLING, Research Chemist, El Paso Smelting Works, El Paso. Tex. BALLENBERG, ADOLB G., Engr., porcupine Exploration Co., Ontonagon Co., Mich. BARKER, RALPH FEINER, Met.. ................ Garfield Smelt. Co., Garfield, Utah. BLOSSOM, EDWARD LUDLAM, Staff of Research Corpn., 63 Wall St., New York, N. Y. BROUGHTON, EUGENE HARDING, Experimental Engr., Copper Queen Cons. Min. Co., . - -. -- - Bisbee, Ariz. BURFORD, SAMUEL W., Genl. Mgr., Cleveland Mining Co., 223 West Third St., Joplin, Mo.

Jan 8, 1916

By J. Kucera, J. Vreštál

DIFFERENT authors1 ' have been engaged in meas-uring the vapor pressure of pure cobalt. The results of their measurements satisfy the expected temperature dependence of vapor pressure and are in mutual agreement, with the exception of the results by De Dyk Man and ~esmejanov.~ The latter authors, by using the effusion method, have achieved considerably higher values than other workers. By using the isotope exchange method they obtained much lower values than other authors. The determination of thermodynamic functions of the binary Ni-Co system was carried out, as far as we know, only by De Dyk Man and Nesmejanov.4 This determination was based on extremely low values of vapor pressure over pure cobalt obtained by the isotope exchange method. Therefore we considered it useful to repeat these measurements. Furthermore, the reliable values of thermodynamic functions should complement the migration characteristics, the inner magnetic field data obtained by Miissbauer effect measurements, specific heat data, and the K effect and positron annihilation characteristics that have been achieved for the Ni-Co system in the Institute of Metallurgy of the Czechoslovak Academy of Sciences in Brno.5-9 The measurements in this paper were performed by the isotope exchange method. In this method, as has been shown by analysis,10-'3 the vaporization rate, w, can be calculated from the relation w = k/1oSw [1] i0Sw) [1] where L, is the activity per unit mass of the source, S is the area of evaporation, k is the tangent at the point t = 0 to the curve giving the radioactivity de-pendence of the target vs annealing time, t, and wis the probability for the tracer atom condensation on the target surface. The value for cc. can be obtained from the equation w = a + 2P(l-a) [2] where P is Clausing's coefficient and a is the condensation coefficient. In the present work the cylinder shaped containers for annealing the samples were used, characterized by the ratio 1:d = 1.06. Here 1 is the length and d the diameter of the container. For this ratio P = 0.514 and w =0.5, and w is independent of the condensation coefficient. The vaporization rate is related to the vapor pressure p by the relation where R is the gas constant, T is the absolute temperature, and M is the molecular weight of the component investigated. Measurements of the vapor pressure of the i component over the pure metal, p!, and the alloy, pi, at the given temperature and composition enable one to calculate the thermodynamic activity of this component from the equation ai=pi/pi [4] is and the activity coefficient ri=ai/xi [5] xi where xi is the molar fraction of the investigated alloy component. EXPERIMENTAL Evaporization rate measurements were carried out with pure cobalt and eight different Ni-Co alloys, which were kindly delivered by the Centre National de Recherches Me'tallurgiques Liege, Belgium. The composition of the alloys is given in Table I. The cobalt used in these alloys contained the following impurities: 0.016 wt pct Fe, 0.014 wt pct Cu, 0.01 wt pct Mn. Other elements were present in much lower concentrations. From the melts, samples in the form of small cylinders of 12 mm in diam were ma-chined. The thickness of the targets and sources was 2.5 and 1.2 mm, respectively. The lower thickness of the sources was chosen to make their over-all ac-tivity as low as possible. Sources were activated in

Jan 1, 1970