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HAVING previously shown you how ores are found and mined, and also how they are prepared and disposed for smelting, and then how the blast furnaces and other furnaces are made for purging their earthiness, all this would be as nothing if I did not proceed to show you the method of smelting them. Therefore, in the present chapter I wish to show you how you must proceed in this very important operation, telling you all I have seen and also how much work with this kind of blast furnace I have done or directed. For this reason I tell you first to take by weight or measure the quantity of ore that you wish to smelt and, particularly if it is a kind that contains silver, break it into small pieces about the size of [52v] beans. If the ore had previously needed evaporation by fire or cleaning by washing, you will have had this done well and have had it properly prepared by a master sorter or others. A layer of this is arranged on a bed of planks, bricks, or flat stones in front of the blast furnace and its companion is placed on top, then a quarter part of galena or a third if you can obtain it. Then an equal part of crushed iron slag or slag from the same or different ore is added. These materials are spread in layers one above the other. When the blast furnace has been constructed as taught above, correct in all its parts, and is full of well-kindled burning charcoal, then fill it up with charcoal and admit water to the bellows machine. When you see that it is well kindled again from this wind and that the flames begin to come out forcefully on top, work it down with a little rake and fill it up again. Then the pannier is filled with new charcoal, the blast furnace heaped full, and another basketful of the said composition of ore is also put on top. Proceed in this way, continually adding charcoal and ore as long as you have any, or as long as you wish to keep up the work, maintaining the blast furnace always full, or continuing in this way until the bottom of the blast furnace is filled with melted materials. Decide this by judgment, or by seeing through the mouth of the tuyère where the wind of the bellows enters that they are level with this. Then with an iron tool open the hole that was left as an outlet in front of the blast furnace and allow all the metal with its slag to run out. These two things, flowing through the chan-

Jan 1, 1942

By A. C. Fieldner, W. A. Selvig

Ash in coal has always becri regarded as an undesirable substance, as the heat content of a coal dccreases in direct proportion to its ash contcnt. It represents so much inert materid that has to be transported, handled when the coal is burned, and finally disposed of. W. R. Roberts, in an address bcfore the Engineers' Society of Western Pennsylvania, Pittsburgh, on Sept. 29, 1925, said that on an annual output of five hundred rnillion tons of coal, a reduction of 3 per cent. of ash means fifteen million tons of refusc and a decrcase of $30,000,000 in freight charges. Ash also often prevents effieient utilization of the coal through the formation of clinker causcd by the mcltirig of the ash constituents when subjected to heat. The mineral constituents of coal may be of such nature as to make the coal unsuited for speeifie uses as for instance, high-sulfur coal for making metallurgical coke. While the usual proximate analysis of coal gives the amount of ash, it gives no information as to the nature and coniposition of the ash nor of the minera1 constituents from which the ash is produced. For the efficient washing of coal to remove ash-forining constituents it is desirable to know the composition and distribution of the ash-fonning constituents. Obviously such information is also desirable for the most efficient utilization of coal. Nature and Composition of Coal Ash Coal ash may be defined as the inorganic residue remailning after cornplete ignitior of coal. It is dcrived from the mineral constituents of thc coal. The ash-forming constituents may be roughly classified as inherent impurities and extraneous impurities. The former are mixed intimately with the coal substance, and arc derived either from the original coal-forming material or from external sources such as sedimentation and preeipitation while the vegetal coal-forming plant remains accumulated. The latter are present in the coal bed as partings, bands or nodules of pyrite! slate, shale, calcit,e, bone, etc. These are formed either during the laying down of the coal bed, or subsequently. Flag-

Jan 1, 1927

By Alexander Coucoulas

FABRICATION of thin-film circuits deposited on glass substrates requires the formation of permanent electrical contacts. Since thin films are in the order of a few thousand angstroms thick and are deposited on nonconductive surfaces such as glass, new methods of lead attachment are being pursued in the microelectronics industry. Ultrasonic welding is being considered in thin-film technology since joining can be accomplished between a wide variety of dissimilar materials.l,' Ultrasonic welding is accomplished by a transducer-coupling-tip system which converts high-frequency electrical energy into mechanical vibrations and delivers it into the weld region. During the process the tip oscillates in a direction parallel to the surface of the weldments, inducing shear stresses in the work pieces which are clamped between the tip and anvil. Though the basic bonding mechanism is not clearly understood, it has been described as closely akin to friction welding. In the course of an investigation concerned with ultrasonic we!ding of aluminum wires to tantalum thin films (1400A) deposited on glass, low weld strengths were related to glass failure. Upon investigating this condition, an improved method of bonding was developed where the aluminum was held at a temperature where a minimum amount of strain hardening occurred during the introduction of ultrasonic energy. Experimental Procedure. Aluminum wires (0.015 in,) were bonded to tantalum thin films with an optimized set of welding parameters (power, time, clamping force) employing a commercial 100-w 60-kc ultrasonic welder. Forty-five degree shear-peel tests, where the lead is pulled at a 45-deg angle with respect to the substrate at 0.2 in. per min, produced a large variation from zero to the strength of the wire, Table I. Inspection of the weld region generally revealed: glass cracking before and after testing; the removal of glass nuggets from the substrate by the lead during testing, Table I; thin-film penetration. In an effort to improve the shear-peel strength, the aluminum between the tip and substrate was heated above ambient temperature through an argon gas media prior to and during welding with the same parameters employed above. With the addition of heat: wire deformation was increased; shear-peel tests all failed at the weld-wire junction, leaving the bonded portion undisturbed; no evidence of glass cracking or film penetration prior to or after testing was observed. In order to prevent failure at the weld-wire junction due to excessive wire deformation, 0.035-in. aluminum wires were welded to tantalum thin films with an optimized set of welding and heating parameters. As

Jan 1, 1967

By H. H. Kellogg

An invitation to address you on the occasion of the one-hundredth anniversary of AIME represents an honor, a challenge and an opportunity: an honor that you judge me worthy; a challenge that I present to you a picture of extractive metallurgy in the years ahead that contains some ideas of value; and finally, an opportunity for me to express some deeply felt beliefs about our profession and our industry. My topic concerns the technology of metal production in the future - the processes, new and old, that will be used to extract metals. The nature of these processes will be shaped by many forces - some technical, some economic, some political or social. A forecast of future technology must recognize the role of each of these forces, and I have endeavored to do this in the analysis that follows. In brief, my outline consists of an analysis of the forces (perhaps better called "problems") that will influence the future of our industry, followed by consideration of likely lines of technological development to meet them. Let me dwell for a moment on the nature of this industry and the profession that serves it. I have been engaged in the profession of extractive metallurgy - teaching, researching and consulting - for 30 years. I have always found the subject stimulating and rife with challenges of a scientific, engineering, economic and socio-political nature. It is a big subject - it encompasses most of the elements of periodic table; we measure the U. S. production of six metals in millions of tons per year; new plant costs range to $100 million and more. The supply of metals from our extractive plants plays an essential role in our modern industrial economy. We could do without DDT, or phosphate detergents or 300-page Sunday newspapers; we cannot do without a huge and increasing supply of metals. The Basic Goal of Extractive Metallurgy Understanding of some basic forces that shape this industry can be gained by consideration of the question: What determines the utility of metals to man? We think immediately of the inherent properties of metals - strength, ductility, electrical conductivity and so forth - but these tell only part of the story. Metal price and the available supply play equally

Jan 1, 1971

By R. E. Allen, A. C. Jephson

ELECTROLYTIC zinc plants of the American Smelting and Refining Co. are located adjacent to the present city limits of Corpus Christi, Texas. The original plant commenced operations during 1942, and is designed for the production of special high grade zinc from zinc sulfide concentrates.' Subsequent changes include the erection of an additional acid plant during 1950, and additions for increased generating and production capacity during 1951. New Electrolytic Plant—The new electrolytic plant is a separate unit erected for the treatment of densified fume produced at Asarco plants located in El Paso, Texas and Chihuahua, Mexico. Construction was completed and operation commenced during June, 1953. Decision for the erection of a separate plant for the treatment of densified fume is based on several factors. One of the principal reasons is the assurance of continued production rate of the original plant, which might have been jeopardized by combined treatment of calcine and fume. Of equal importance is the advantage of locating a plant on a site with adequate space for eventual expansion. General Description—The new plant for the treatment of densified fume consists of four main buildings for the following operations: storage and grinding of fume, leaching and purification, electrolyzing and casting, and rectifier units. Auxiliary buildings include a baghouse, reagent storage, and a lunch room. Leaching of ground fume with electrolyte from the cells is a batch type operation in tanks equipped with mechanical agitators and weightometers. Completed leaches are pressure filtered, the resultant residue being recovered for shipment to El Paso by conventional use of thickeners, drum type vacuum filters, and a direct-fired dryer. Filtrates from the filter section are purified in mechanically agitated tanks, filtered after completion through plate and frame presses, and then pumped to an evaporative type cooling tower. Solution discharged from the basin of the cooling tower is collected in storage tanks for use in the cells. The cool purified solutions are pumped as required from storage to the solution circuit for circulation of electrolyte through the cells. Except for the addition of purified feed solution and withdrawal of electrolyte for leaching, the circulating system for the cells is essentially a closed continuous circuit that includes the use of evaporative cooling towers for control of solution temperatures. Aluminum cathodes and Ag-Pb anodes are used for electrolysis, which is maintained at a current density of about 82 amp per sq ft. Cathode zinc produced is melted in a gas-fired reverberatory furnace and then cast into slabs on a straight line casting machine. Unloading and Storage—Fume produced by the Chihuahua plant is shipped in box cars, and fume by the El Paso plant in hopper bottom dump cars. Shipments as received are weighed on a 7 5-ton capacity railroad scale, sampled, and then moved over one of the two unloading hoppers with a car puller. The cars are then unloaded with mechanized equipment, a car scoop being used for unloading of box cars and a car shaker for the hopper bottom cars

Jan 1, 1958

By S. Leber, R. F. Hehemann

This investigation describes the kinetics of alloying in a (Cb-15 wt pct W. 5 wt pct Mo, 1 wt pct Zr) powder-metallurgy alloy. The degree of homogeneity obtained in hydrostatic ally pressed and vacuum-sintered samples is described by composition distributions resulting from analysis of X-ray dvfraction line profiles. Sintering variables and degvee of powder dispersion were evaluated. The utility of single-value parameters obtained from composition distributions is disaissed. The spatial distribution of composition, as revealed by anodically tinted metallographic sarrzples, was used to provide diffision models based on a concentric-sphere geometry. Diffusion equations developed from these models were found to be in general agreement with experimental results. The powder-metallurgy method for the production of refractory metal alloys has the ability to produce an inherently fine-grained, fabricable structure. The more general use of this method is inhibited, in part, by the presumed difficulty in obtaining homogeneity on a microscale. The degree of homogeneity therefore is an important, but usually neglected, variable in specifying the quality of a powder-metallurgy alloy. Convenient techniques for measuring the degree of homogeneity are now available,' and have been used to develop a model describing the process of alloying in a simple binary mixture.' In this investigation, the process of alloy formation has been studied in a more complex system. PROCEDURE The columbium-based F-48 mixture was prepared from the constituent powders shown in Table I. The particle sizes tabulated were provided by the vendors of the individual powders. Standard laboratory techniques utilizing a jar mill were employed for blending. The blended powders were hydro-pressed into 1-in. diam rods which were then sliced into thin discs for vacuum sintering. All samples were given a preliminary treatment at 1700°C for 2 hr. Varying degrees of homogeneity were obtained using additional treatments at higher temperatures. The degree of homogeneity obtained by a specific sintering treatment was evaluated metallographi-cally using the anodic-tinting technique described by olff,' and quantitatively by the analysis of X-ray diffraction line profiles using the X-ray diffraction technique developed by udman.' The diffraction technique is strictly valid only for binary systems. However, the relatively small difference between the lattice parameters of tungsten and molvbdenum when compared with columbium permitted the treatment of the complex composition of F-48 as a (W, Mo)-Cb pseudobinary. Calculations were weighted in accord with the W-Mo ratio in the F-48 composition. The contribution of the 1 pct Zr was ignored since it could not even be detected in the blended powder. Two factors are required to convert an X-ray line profile into a composition distribution. The variation of these factors with composition is shown in Fig. 1. Curve A was used to convert angular posi-

Jan 1, 1964

By J. E. Dorn, L. A. Shepard

LOW and Gensamer' demonstrated a number of years ago that the yield point phenomenon in mild steels was associated with the presence of fer-rite soluble carbon or nitrogen. More recently the yield phenomenon in body-centered-cubic metals containing interstitials was rationalized by Cottrell' in terms of a simple dislocation model. Interstitial atoms interact with dislocations in two ways; they cause not only local expansions but induce local tetragonality in the lattice. Consequently, interstitial~ interact with the hydrostatic tension and shear components of the stress about dislocations. They tend to migrate toward the expanded regions of edge dislocations and to assume sites that relieve the shear stresses of screw dislocations. Thus, a dislocation saturated with solute atoms constitutes a lower free energy state than that obtained when the dislocation threads through the average composition regions of the matrix. A greater stress will be required to separate the dislocation from its atmosphere than to move the dislocation through the matrix. This factor gives rise to the upper yield stress, which is required to unleash a series of dislocations in a localized region. This local yielding is propagated across the specimen to form a thin band of plastically deformed material known as a Lueder's band, making an angle of about 45" to the stress axis. Once the band has formed, deformation continues at the lower yield stress by the spreading of the Lueder's band in the direction of the applied stress. Undoubtedly the spreading of Lueder's bands at the lower yield stress is accomplished by the high stress concentrations at the band fronts, which serve to induce continued unlocking of new dislocations in advance of the migrating band fronts. Cottrell and Bilby have shown that the dependence of the yield point on temperature can be deduced by assuming that thermal fluctuations aid the stress in unlocking small dislocation loops from their solute atmospheres. Once a loop that exceeds a critical size has been nucleated, the entire locked diqlocation is released and can migrate. Fisher4 simplified this analysis by assuming that the locking forces were short range, so that if the dislocation loop were displaced only one Burgers vector from its atmosphere, it would be unlocked. Applying his model to the special case of delayed yielding under a constant stress of the order of the upper yield strength, he demonstrated that the delay time 7 for yielding should depend on stress and temperature according to where A and B are constants, G is the shear modulus, and u and T are the resolved shear stress and absolute temperature, respectively. Cottrell and Bilby, Fisher, and Fisher and Rogers' have shown that the above deductions are at least in qualitative harmony with the experimental facts. A number of investigators5-0 have shown that the yield point phenomenon can also be induced in sub-stitutional alloys of face-centered-cubic metals. In general such yield points are not as pronounced as those encountered in body-centered-cubic metals containing interstitials. The yield point phenomenon in these materials is usually enhanced by prestrain-ing at low temperatures and aging at intermediate temperatures. Undoubtedly the yield point phenomenon induced by strain aging substitutional alloys also results from locking of dislocations. But the locking of dislocations in substitutional alloys of face-centered-cubic metals differs somewhat from interstitial locking of dislocations in body-centered-cubic metals. Substitutional elements in face-centered-cubic lattices cause only radial displacements of the adjacent lattice points. Consequently, only the edge components of dislocations can be locked by the mechanism suggested by Cottrell. Additional locking, however, can be obtained by the Suzuki mcchanism.10 In face-centered-cubic metals, dislocations exhibit lower energies when they are present in the

Jan 1, 1957

By T. D. Yensen

AGING is a term that connotes a slow change in properties under ordinary operating conditions. It can be accelerated by increasing the temperature and by mechanical straining. The magnetic properties of iron and some of its alloys have for many years been known to be subject to such a change. But the cause of the change was not recognized until a few years ago after mechanical age-hardening in non-ferrous alloys of the "duralumin" type had been definitely shown, by means of solid solubility curves, changes in electrical resistance and microanalysis, to be caused by slow precipitation of one or more con-stituents from the solid solution. The similarity between the solid solubility curves of such alloys (Fig. 1) and those for iron-nitrogen (Fig. 2) and iron-carbon alloys (Fig. 3) below the Al transformation point suggested at once that magnetic aging of iron might be caused by a similar process; namely, by the slow precipitation of carbon and nitrogen in the form of Fe4N and Fe3C at ordinary temperatures because of a cooling rate that had been too rapid to permit complete precipitation according to equilibrium conditions. This suggestion has since been amply confirmed, particularly by the comprehensive work of Köster1 on the effect of nitrogen and carbon. Typical curves are shown in Fig. 4 for the relationship between aging temperature and coercive force. Previous to the establishment of the precipitation-hardening theory it was thought that the effect of nonmetallic elements like C, N, 0, etc., on the magnetic properties of iron was greatest when these elements were retained in solid solution, atomically dispersed throughout the interstitial spaces of the iron lattice2.

Jan 1, 1935

By G. Sachs, S. I. Liu

INTRODUCTION IN a previous investigation on the effects of repeated strains of large magnitude on the aluminum alloy 24ST, it was found that the reduction in ductility by straining in tension was partially restored by a subsequent compression.&apos; As illustrated by the dashed line in, Fig I,§ the ductility (EF) retained after prestraining in tension by a certain amount (EI) and measured in a subsequent tension test is represented by a straight line sloping down under 45°. If a compression of the same magnitude as the first tension is inserted (E2 - EI) between prestraining and final testing in tension, such a "balanced" tension-compression cycle yields a ductility considerably higher than that present after prestraining in tension only. . The results of these tests can be correlated with those of an investigation on the effects of prestraining in compression.2 As also shown in Fig I, the ductility in subsequent tensile tests decreased with compression, at a rate considerably slower than that after prestraining in tension. The above discussed testing conditions can be considered as special cases of a general straining cycle, consisting of first, straining in tension by an amount E1, subsequently straining in compression by an amount E2, and finally determining the retained ductility, Ef, in a tensile test. Prestraining in tension is then represented by E1 > o and E2 = o. Prestraining in compression is given by E1 = o and e2 < o. Balanced cyclic straining is defined. by the condition E1 > o and E2 = -El. In order to obtain further information on the effects of straining cycles consisting of tension and subsequent compression, further tests were made, varying both the tension strain, E1, and the compression strain, E2, within extreme limits; El varied between 0.06 and 0.28 and E2 between -0.008 and -0.60 approximately. Apparently, such tests have not been previously performed. They revealed phenomena which have not been recognized to date. The results of the investigation are herewith reported, without attempting to correlate them with internal processes within the metal structure. However, in order to assist in an analysis of this type, the results have been represented in various manners. In addition, further test data on the effects of prestraining by compression were provided by using specimens of various contours (notched specimens) in the subsequent tensile tests.

Jan 1, 1948

By Wayne E. Tuomi

The mining industry is faced with a pressing problem; that is, to develop more efficient methods of extraction, handling and upgrading-techniques that will do the job faster and better than ever before. New techniques require new machines, or applications of new and improved materials that can be used to modify and improve existing machine and equipment designs. The traditional approach has been to increase productivity by increasing equipment size. Prognostication indicates that the trend toward larger equipment sizes and capacities will continue as one answer to the challenge imposed by future increases in mineral demands. But what is the limit on the continued growth of equipment size? Until about 1930, there was a very definite limit-a limit imposed by the strength of the steels and the power plants then available. The equipment engineer had come to an impasse: even though it was easily possible, for instance, to triple the size of a bucket, it had become impractical to correspondingly enlarge the boom, the counterweight, and the power plant.

Jan 3, 1967

By S. H. Williston

IT is not often that bore hole surveys can be checked by actual civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bisbee, Ariz., drilled a 1245 ft, 8 in. diam, churn drill- hole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in- the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Be- cause of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results &apos; of doubtful value.

Jan 1, 1950

By M. B. Ramachandra Rao

The spontaneous polarization surveys dealt with in this paper were carried out near Guddadarangavvanahalli (lat. 14° 17&apos; N.; long. 76° 24&apos; E.) in Chitaldrug district, which forms part of the Chitaldrug schist belt. The occurrence of gold, copper, lead and antimony ores has been noticed for several years but efforts to exploit them have been unsuccessful, therefore some spontaneous polarization surveys were made in the hope of finding indications of workable ore bodies. The country examined has a rugged topography, with numerous hills on which there is little vegetation. The climate is generally dry, the average annual rainfall of the tract being about 25 in., of which 17 in. occurs during the southwest monsoon. The geological formations of the area pertain to an ancient schistose series known as the Dharwar system (Archean). Locally, the rock formations have been divided into three series1—the chloritic series (or the Chitaldrug formation), the clay series (or the G.R. formation) and the trap series (or the Jogimardi trap). The chloritic series includes a complex of altered ancient traps and volcanic agglomerates intermixed with some schists of sedimentary origin, all of which are highly metamorphosed. The lithological types of this series are mostly distinguishable as greenstone schists, calc-chloritic schists, slaty schists, ochery and calcareous mica-chlorite schists, with subordinate bands of secondary limestone. The clay series (G.R. formation) is made up of shaly and argillistic schists, litho-margic clays, sandstones and brecciated ferruginous quartzites. The Jogimardi trap is mostly of the nature of an epidiorite (hornblende diabase), which is distinctly intrusive in the form of large laccolithic and narrower dikelike masses. In addition to this trap, there are other minor intrusives such as the chalybitic trap, quartz porphyry and quartz reefs. The topographical and geological features of the area are noted on the map of Fig. I. The locations of some of the spontaneous polarization centers determined by the geophysical survey are indicated also. Method of Survey and Apparatus Employed The spontaneous polarization surveys were carried out in the manner recommended by the Imperial Geophysical Experimental Survey.2 Preliminary reconnaissance was first carried out along a series of parallel traverse lines that were laid out over the area. The Potential profiles obtained in these traverses were plotted* on a suitable scale and when any

Jan 1, 1946

By M. B. Ramachandra Rao

The spontaneous polarization surveys dealt with in this paper were carried out near Guddadarangavvanahalli (lat. 14° 17&apos; N.; long. 76° 24&apos; E.) in Chitaldrug district, which forms part of the Chitaldrug schist belt. The occurrence of gold, copper, lead and antimony ores has been noticed for several years but efforts to exploit them have been unsuccessful, therefore some spontaneous polarization surveys were made in the hope of finding indications of workable ore bodies. The country examined has a rugged topography, with numerous hills on which there is little vegetation. The climate is generally dry, the average annual rainfall of the tract being about 25 in., of which 17 in. occurs during the southwest monsoon. The geological formations of the area pertain to an ancient schistose series known as the Dharwar system (Archean). Locally, the rock formations have been divided into three series1—the chloritic series (or the Chitaldrug formation), the clay series (or the G.R. formation) and the trap series (or the Jogimardi trap). The chloritic series includes a complex of altered ancient traps and volcanic agglomerates intermixed with some schists of sedimentary origin, all of which are highly metamorphosed. The lithological types of this series are mostly distinguishable as greenstone schists, calc-chloritic schists, slaty schists, ochery and calcareous mica-chlorite schists, with subordinate bands of secondary limestone. The clay series (G.R. formation) is made up of shaly and argillistic schists, litho-margic clays, sandstones and brecciated ferruginous quartzites. The Jogimardi trap is mostly of the nature of an epidiorite (hornblende diabase), which is distinctly intrusive in the form of large laccolithic and narrower dikelike masses. In addition to this trap, there are other minor intrusives such as the chalybitic trap, quartz porphyry and quartz reefs. The topographical and geological features of the area are noted on the map of Fig. I. The locations of some of the spontaneous polarization centers determined by the geophysical survey are indicated also. Method of Survey and Apparatus Employed The spontaneous polarization surveys were carried out in the manner recommended by the Imperial Geophysical Experimental Survey.2 Preliminary reconnaissance was first carried out along a series of parallel traverse lines that were laid out over the area. The Potential profiles obtained in these traverses were plotted* on a suitable scale and when any

Jan 1, 1946

By T. M. Broderick

InveStIgations into the possibilities of economically mining and concentrating low-grade iron ores of the Lake Superior region are attracting increasing attention. Among the organizations that are carrying on the work are the United States Bureau of Mines, the State of Minnesota (which spends about $80,000 annually on problems of the iron and ferroalloy ores of Minnesota), and the State of Michigan (which spends about $10,000 annually of its iron-ore research). Several of the mining companies are also financing research. Of the states in the Lake Superior district, Minnesota has done most in iron-ore concentration. In 1930, thirty-seven concentrating plants were in operation on the Mesabi Range, beneficiating about one-third of the total ore shipped. About one-half of these plants reduced silica; the others reduced moisture or improved the structure of the ore.&apos; Research into the possibilities of magnetic concentration of the Eastern Mesabi magnetite ores indicates that vast tonnages of that ore may be utilized at a profit in the not distant future. Magnetic concentration has also been tried at Sellwood, Ontario, on the Moose Mountain deposit, and at the Berkshire mine in Wisconsin on the magnetic ores of the Western Gogebic Range. There have been few attempts to concentrate Michigan iron ores. In order to determine the possibilities of such concentration, iron-ore research has been carried on at the Michigan College of Mining and Technology for the past few years. After a general survey of the iron ores of the state, a program of more detailed experimentation was outlined, starting with work on the Ironwood formation of the Gogebic Range. The results of this research led to the belief that gravity methods will produce fairly satisfactory concentrates from the parts of the iron formation that are made up of comparatively thick alternating beds of rather high-grade ore and lean chert. About 85 per cent of the iron and steel produced in the United States comes from ores of the Lake Superior district. The reserves of direct

Jan 1, 1935

By T. M. Broderick

InveStIgations into the possibilities of economically mining and concentrating low-grade iron ores of the Lake Superior region are attracting increasing attention. Among the organizations that are carrying on the work are the United States Bureau of Mines, the State of Minnesota (which spends about $80,000 annually on problems of the iron and ferroalloy ores of Minnesota), and the State of Michigan (which spends about $10,000 annually of its iron-ore research). Several of the mining companies are also financing research. Of the states in the Lake Superior district, Minnesota has done most in iron-ore concentration. In 1930, thirty-seven concentrating plants were in operation on the Mesabi Range, beneficiating about one-third of the total ore shipped. About one-half of these plants reduced silica; the others reduced moisture or improved the structure of the ore.&apos; Research into the possibilities of magnetic concentration of the Eastern Mesabi magnetite ores indicates that vast tonnages of that ore may be utilized at a profit in the not distant future. Magnetic concentration has also been tried at Sellwood, Ontario, on the Moose Mountain deposit, and at the Berkshire mine in Wisconsin on the magnetic ores of the Western Gogebic Range. There have been few attempts to concentrate Michigan iron ores. In order to determine the possibilities of such concentration, iron-ore research has been carried on at the Michigan College of Mining and Technology for the past few years. After a general survey of the iron ores of the state, a program of more detailed experimentation was outlined, starting with work on the Ironwood formation of the Gogebic Range. The results of this research led to the belief that gravity methods will produce fairly satisfactory concentrates from the parts of the iron formation that are made up of comparatively thick alternating beds of rather high-grade ore and lean chert. About 85 per cent of the iron and steel produced in the United States comes from ores of the Lake Superior district. The reserves of direct

Jan 1, 1935

The Library of the above-named Societies is open from 9 A.M. to 10 P.M. on all week-clays, except holidays, from Sept. 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their tine in localities isolated from sources of information. To these the Library can render valuable service through correspondence; letters requesting information will receive special attention.. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information as to the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral natter will be saved, and the information will be sent more promptly and in more usable shape. The members of the Institute can he of service to the Library by forwarding copies of mining reports, maps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library freely, and assurance is given that most careful service will be rendered to them.

Jan 3, 1916

By H. Reiss

The zone-melting process in which redistribution of solute in a solid bar is effected by the passage of a molten zone is considered mathematically. Simple approximate techniques are developed for computing the manner in which redistribution occurs as molten zones continue to pass. The introduction of the "zone-melting flux" provides valuable insight into the nature of the phenomenon, as well as a central mathematical theme in terms of which the process can be discussed. Curves are presented for typical and general cases. AN extremely efficient purification technique was described recently by Pfann.1 Known as zone refining, it consisted of the slow passage of a series of molten zones, produced by external heaters, through a long solid ingot of the substance to be purified. Equations were given for the maximum separation attainable, and a numerical computation method was described for obtaining the concentration in the ingot after a given number of zone passes. The present paper offers an interpretation of the physical nature of zone melting in terms of a transport process in which formal diffusive and convec-tive flows occur. This interpretation, in addition to providing insight into the physical nature of the process, also provides a basis for its mathematical treatment. From this basis, useful equations are developed for the solute concentration in the ingot as a function of the number of zone passes. These are applicable particularly where large numbers of passes are necessary and where numerical computational methods might be laborious. All considerations will deal with the limiting form of the process, described by Pfann,&apos; in which: 1—Diffusion in the solid is considered negligible. 2—Mixing in the liquid is supposed, complete. 3—The distribution coefficient, k, measuring the ratio (at equilibrium) of solute concentration in the solid to that in the liquid is supposed, independent of composition. In general, this paper will be concerned with a bar of uniform (actually unit) cross section, ex- tending in the x-direction from x = 0 to x = L, where L may be infinite. Zone melting is a transport process, and as such must admit of interpretation in terms of a flux of transported quantity. However, the progress of operation is not measured in units of time but in terms of the number of completed zone passes. Consequently, the zone-melting flux will be a rate, per unit pass, rather than per unit time. The description of this flux and the examination of its properties is given below. Zone-Melting Flux Fig. 1 represents an intermediate stage of the nth pass. Concentration C is plotted against distance, x. The molten zone with its back at the point x and front at x + I moves in the direction indicated by the arrow. As it moves, it leaves behind the nth

Jan 1, 1955

Jan 1, 1924

By Philip D. Pearson

IN recent years, there have been many changes in mining operations in the Lake Superior district. To follow these trends on the Menominee Range of Michigan, information has been assembled from all of the iron mining operations in the area. There are 15 operating underground mines in the Iron River-Crystal Falls area of the Menominee Range. Within the past two years, two idle properties were re- opened and are now producing, and a third and fourth are being reopened. Also, there are two siliceous openpits operated by independent companies outside this immediate area. Six companies operate the underground mines, employing some 1850 employees. Table I shows pertinent facts about these properties.

Jan 4, 1951

The regular activities of the Institute are financed mainly by income derived from members&apos; dues, from advertising in MINING AND METALLURGY, and from the sale of publications to the public. In addition, collateral activities and special projects are financed each year by means of income from endowed funds controlled and administered by the Institute. In the aggregate, the amount of these endowments totals more than $637,000. An active effort is being made to increase the endowment funds of the Institute through a standing committee, of which Henry Krumb is Chairman, and of which the other members are: George D. Barron, Cleveland E. Dodge, John V. N. Dorr, Howard N. Eavenson, D. C. tackling, Harvey S. Mudd, Wallace E. Pratt, Milnor Roberts, and Wilfred Sykes. This committee believes that there exists a tremendous opportunity for the Institute to be of evergrowing service to the public, to the mineral industries, and to the &apos;profession. It welcomes suggestions as to names of men of means who are vitally interested in the mineral industries, and to whom the opportunity to make a contribution or bequest might appeal favorably if presented in the proper light.

Jan 1, 1946