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By Blake M. Loring, Robert A. Colton

MELTING procedures for most metals and alloys usually include some provision for the control of oxygen, since this element frequently has some undesirable effect on the properties of the metal or alloy concerned. In the melting of the various bronzes, this is especially true, since oxygen can be introduced into the melt in a number of ways, most of which are difficult to control. In making bronzes from virgin materials, oxygen is usually present in the commercial grades of copper used; electrolytic he refined copper ingots usually contain from 0.02 to 0.05 per cent oxygen. When ingot metal or scrap bronze is used in the charge, oxides are almost always present to some degree. Under certain melting conditions and in certain types of melting equipment the atmosphere over the metal may be highly oxidizing. This, of course, may be desirable in the melting practice used, but is certain to introduce appreciable amounts of oxygen into the melt, and that may not be entirely desirable. From the foundry viewpoint oxygen may have several harmful effects on bronzes. The formation of excessive amounts of oxides may produce drossy metal, which, in turn, means dirty castings and a potentially high rejection rate. It is claimed, too, that oxides in the metal may combine with hydrogen to form steam and thereby produce porosity in certain of the bronzes. The presence of certain refractory oxides, such as SnO2, may be undesirable from the viewpoint of making machining difficult, or as possible stress-raisers in the metal matrix. It is often said that excessive oxide present in the liquid metal makes the metal run sluggishly. Since it appears impractical to try to control the amount of oxygen introduced into the metal beyond taking the economical limit of precaution about charging dirty scrap, it would seem that control of the oxygen content of the liquid metal offers the most promising approach to this problem. This might be done by using slags, or covers, or by the use of some element or compound added to the melt to remove oxygen preferentially. Most aspects of this problem have been considered and considerable work has been done along these lines. A reconsideration of the problem is indicated, however, by the controversial nature of the evidence at hand, especially on the possibility of using a chemical deoxidizer to control the oxygen content of bronzes. CHOICE OF DEOXIDIZER The choice of the chemical agent selected as a deoxidizer would naturally depend first on the alloy in which it is to be used; in this particular case the alloy is Navy gun metal. In Table I are listed a group of elements that might be considered as

Jan 1, 1946

By S. J. Kidder, G. C. McCartney

THE Helen Mine, of the Algoma Steel Corporation, in the Michipicoten district, Ontario, Canada, has produced more than 6,240,290 tons of iron ore. Prior to and during World War I, 2,823,369 gross tons of brown ore were shipped, and from 1939 to the end of the 1944 season, 3,416,921 gross tons of siderite ore were produced from open-pit operations. Brief descriptions are given of the nature of the ore, the mining methods employed and the manner of treatment of the ore. Shipment of the finished product, known as Algoma sinter, is made to blast furnaces in both Canada and the United States. The iron-ore bodies-i.e., the oxide ores of the Old Helen and the siderite of the New Helen-are a part of a tabular shaped area of iron formation that extends over a length of more than 10,000 ft. and has a maximum width of 1000 ft. The ores are considered to be a product of introduction of iron-bearing material accompanied by replacement of the rocks already present. It is shown that introduction took place subsequent to the development of the major folded structures. It is believed the iron-bearing material emanated from an igneous source.

Jan 1, 1946

By R. W. Raymond

Richard Pennefather Rothwell, was born May 1, 1836, at Oxford, Upper Canada (now the province of Ontario). His father, Rev. John Rothwell, was a native of County Meath, Ireland, where the family (originally, no doubt, a Scottish one) still holds large estates, under a grant from William and Mary. John Rothwell was graduated at Trinity College, Dublin, and became a clergyman of the Established Church. He married Elizabeth Garnett, of Athearn Castle, Ireland, and subsequently came to Canada. It is said that he was a man of liberal views combined with sterling piety, an enthusiastic sportsman and yachtsman, and a pastor who refused for many years to accept any remuneration from his parishioners. After preliminary education, the subject of this sketch entered Trinity College, Toronto, with the intention of studying law; but a year later he resolved to become a civil engineer, and entered the Rensselaer Polytechnic Institute at Troy, N. Y., where he was graduated, with high standing, as civil engineer, in 1858. He then went to Paris, and entered the Imperial School of Mines, where, by reason of the proficiency he had already acquired in civil engineering, he was able to finish in two years and a half the full three-year course, and to take the degree of Engineer of Mines. In 1861 he took the "practical courses" in mining and ore-dressing at the Mining Academy of Freiberg, Saxony. After traveling in Italy, etc., he went in 1862 to London, where, for the purpose of familiarizing himself with business methods, he entered the offices of W. T. Henley, a manufacturer of wire

Jan 1, 1902

By B. O. Pickard

WITH more than a score of shafts and numerous stope openings to the surface, all inter-connected underground; with underground temperatures high, often exceeding 100° wet bulb; with an ore presenting a dust health-hazard; with certain rocks giving off inert gases; with an altitude of 6000 ft. above the sea level and a dry desert climate, the Tonopah mines offered an interesting, problem to the student of metal-mine ventilation. Tonopah is not an old mining district relatively speaking. It was discovered in 1900 and Tonopah soon was a boom camp. By 1910 the mines of this district had paid many millions of dollars in dividends. At the time of the 1921 ventilation study, mining had passed its peak of production and the operators were striving to reduce costs, to discover new ore bodies, and to attract desirable workmen. In 1925, the camp was operating on a still less prosperous basis, but the several managements had not relaxed in their efforts to keep the mines on a paying basis, neither had they lost their faith in the ability of the mines and the price of the silver to "come back." Early in the fall of 1921 the Bureau of Mines was invited by the mine operators at Tonopah, Nevada, to make a detailed study of the under-ground air conditions in the Tonopah silver district. D. Harrington,? who was then directly supervising the ventilation studies of the bureau, detailed district engineer B. 0. Pickard, mining engineer E. D. Gardner, surgeon C. E. Kindall, and petrographer H. Insley to carry on the study. G. S. Rice, as chief mining engineer of the Bureau of Mines, was in general charge of the work. Upon the completion of the study each operator was furnished a report on conditions in his mine.

Jan 2, 1927

By Donald W. Murphy, John Chipman

Recent developments in iron alloys containing nitrogen have indicated that this element may exert a considerable influence on the properties of the metal. This influence is not always in an undesirable direction and the indications are that nitrogen should be regarded as an alloying element, the amount of which should be subject to control, rather than as an inherently deleterious impurity. In controlling this element in liquid iron to the best advantage, it is necessary to have a reliable background of fundamental data pertaining to solubilities, rates of solution and chemical reactions of nitrogen in liquid iron. Obviously, the first step in such an investigation is the determination of the solubility of nitrogen in pure iron, and this has been the object of the experiments described in this paper. The solubility of nitrogen in solid iron has been measured by Jurich,' Sieverts,2 Martin,3 and Iwasé4 and the agreement among the first three inspires confidence in their results. No accurate determinations of its solubility in liquid iron have been recorded though several investigators have obtained approximate results. Strauss6 was able to introduce 0.03 to 0.04 per cent nitrogen into steel by the action of either ammonia or nitrogen on the liquid metal. This was accomplished by Eilender and

Jan 1, 1935

By John Chipman, Donald W. Murphy

Recent developments in iron alloys containing nitrogen have indicated that this element may exert a considerable influence on the properties of the metal. This influence is not always in an undesirable direction and the indications are that nitrogen should be regarded as an alloying element, the amount of which should be subject to control, rather than as an inherently deleterious impurity. In controlling this element in liquid iron to the best advantage, it is necessary to have a reliable background of fundamental data pertaining to solubilities, rates of solution and chemical reactions of nitrogen in liquid iron. Obviously, the first step in such an investigation is the determination of the solubility of nitrogen in pure iron, and this has been the object of the experiments described in this paper. The solubility of nitrogen in solid iron has been measured by Jurich,' Sieverts,2 Martin,3 and Iwasé4 and the agreement among the first three inspires confidence in their results. No accurate determinations of its solubility in liquid iron have been recorded though several investigators have obtained approximate results. Strauss6 was able to introduce 0.03 to 0.04 per cent nitrogen into steel by the action of either ammonia or nitrogen on the liquid metal. This was accomplished by Eilender and

Jan 1, 1935

By H. Schwartzbart, J. R. Low

Annealed, .Poly crystalline, low carbon steel exhibits a phenomenon known as the "yield point." If such a steel is loaded in tension, the load increases steadily with elastic strain, drops suddenly, fluctuates about some constant load value for a time and then rises with further strain. The load at which the sudden drop occurs is called the "upper yield point"; the load at which deformation proceeds at constant load is known as the "lower yield point"; the amount of elongation at constant load is termed the "yield point elongation." Deformation which occurs during the yield point elongation is heterogeneous in nature, deformed metal existing next to undeformed metal. The drop in load from the upper yield point is concurrent with the formation of a band of deformed metal which usually appears at a stress concentration such as a fillet and at an angle of approximately 45" with the direction of pull. As deformation proceeds during the yield point elongation, the deformed region grows until the entire specimen has been strained an amount equal to the strain in the first band. A phenomenon very often associated with the yield point is that of strain aging. Aging in steels may be of two types: quench aging, or precipitation hardening, and strain-aging. Strain aging differs from precipitation hardening in that if the metal is merely strained instead of given a solution anneal and quenched, it then undergoes changes in properties similar to those observed in quench aging. The yield point effect and strain aging are most markedly exhibited by low carbon steel, but have been observed in other alloys. Numerous explanations for the mechanisms of both phenomena have been advanced, but the evidence for the acceptance of any of the hypotheses is incomplete. One of the explanations of the yield point phenomenon frequently proposed is that there exists a honeycomb of grain boundary material that supports the load above the yield strength of the ferrite and that when this network ruptures, the ferrite flows with no increase in load. This notion was first advanced by Dalbyl in 1913 and has been since put forward in more concrete form by many investigators. The testing of this hypothesis was, in part, the object of the present investigation. Similarly, the mechanism by which strain aging occurs remains to be explained. Presumably, it is a precipitation hardening phenomenon similar to quench aging, the precipitation being initiated by strain. However, it is not known whether the process is a solution and precipitation effect or a change in solubility due to strain. One obvious method of determining whether or not the yield point is a grain boundary phenomenon is to determine if single crystals exhibit a yield point. Low and Gensamer2 have shown that carbon and nitrogen are responsible for the yield point and aging in steel and that these effects can be eliminated by the removal of these elements through wet hydrogen purification. Single crystals that have been grown in wet hydrogen treated material must then be recarburized or re-nitrided in order to evaluate the effect of grain boundaries. In the present investigation, single crystals of iron which had been annealed in wet hydrogen to remove the carbon and nitrogen were cut into two specimens having the same orientation with respect to the tension axis. Of these, one specimen was pulled in tension in the wet hydrogen treated state and the other was carburized or nitrided and tested similarly. All the crystals were examined for a yield-point and strain aging. The grain boundary hypothesis for the explanation of the yield point in steel has been tested only indirectly previously. Arrowsmith,3 Andrew and Lee,4 Edwards and Pfeil,5 Fell,6 Ludwik and Scheu,7 Winlock and Leiter8 and others found a decrease in proportional limit and yield point effect with an in-

Jan 1, 1950

By W. M. Wojcik, R. F. Kowal

Oxygen and sulfur distributions in commercial, 5-ton ingots of killed, medium carbon steel are described. Oxygen distribution is found to vary with deoxidation practice. Irregular distribution of oxygen within ingots makes necessary special precautions in sampling of rolled products for analysis of oxygen. Oxygen distribution is discussed in terms of recently published solidification concepts which had been successfully applied to simpler cases of segregation. These concepts have been found inadequate to explain observed oxygen distributions. Convective movements of the liquid metal, as determined by tracer elements, are shown to be capable of accounting for the observed distributions of oxygen. IN an effort to explore the origin of surface and subsurface imperfections in pierced steel products, a study of oxygen and sulfur segregation was made on ingots cast in open-top and hot-top molds. The results of our previous investigations1"3 have indicated the importance of the location and amount of oxide inclusions in an ingot. Inclusions close to the surface of the ingot have been found to contribute greatly to the formation of imperfections in the surface of finished products. This study of the effects of deoxidation and casting practice on segregation and the resulting oxygen distribution in ingots was initiated to determine the parameters controlling the location of inclusions in an ingot. Segregation of solute elements during solidification of low-melting binary alloys has been studied in the past.1, 5 Formation and growth of inclusions in iron melts have been studied under specific conditions."- In spite of these and other recent studies,10-12 segregation during solidification of commercial, killed steel ingots is not well understood. Consideration of solidification rates, of segregation during solidification of the chill, dendritic, and central zones, and of material balances for the segregated elements has indicated that a simplified theoretical solidification model is not adequate. However, the observed high oxygen contents in localized volumes of the dendritic zone can be rationalized if additional effects of convection currents in the ingots, precipitation, and rapid growth of new phases are considered. EXPERIMENTAL PROCEDURE Steelmaking and Processing. A group of nine killed. medium carbon steel heats having compositions listed in Table I have been studied. The deoxidation and mold practices used were varied to give a wide range of steel oxygen contents. The amounts of aluminum added to the ladle and the ingot casting practices (hot top and open top) were the main variables. The steel was made by a duplex practice in 160-ton tilting basic open-hearth furnaces. All nine heats were top-cast into 24 by 24 in. big end down, fluted molds, to a height between 60 and 76 in., using both open tops and exothermic hot tops. The deoxidation practice and the tapping and teeming details for each heat and ingot studied are given in Tables II and III, respectively. Hot-top practice is indicated by the letter H following the heat designation. Furnace and ladle temperatures were measured by standard disposable-tip, Pt/10 pet PtRh thermocouples. Teeming-stream temperatures were obtained as described by Samways et al.,13 by immersing a Pt/10 pet PtRh thermocouple, covered by a silica sheath, into the teeming stream under the nozzle. The output of this thermocouple was recorded with Leeds & Northrup Speedomax potentiometer. Calibration of the latter thermocouples was based on the freezing point of a pure iron/oxygen alloy (2795°F). The accumulated errors of measurements were within ±10°F. The thermocouple measurements were supplemented in this investigation by continuous recording of a ratioing, two-color pyrometer (Shawmeter), protected from smoke by a blast of clean air within the sighting tube, and calibrated to read with better than ±10°F accuracy. Following teeming of three heats, P, R, and T, tracer elements were added to the steel in the molds to obtain a record of the progress of solidification. As soon as the teeming stream was shut off, a 0.010-in.-thick steel can containing a mixture of crushed standard ferro-titanium and ferro-vanadium (0.05 pet of each alloy element) was plunged into the middle of the steel pool to a depth of 6 in. In about 30 sec no indication of the can or its contents remained. The surface of the open-top ingots solidified in 20 to 30 sec. A study of liquid metal movement and the precipitation of oxides was facilitated materially by use of the tracer technique as titanium has a low distribution coefficient between solid and liquid steel while vanadium has a high distribution coefficient.

Jan 1, 1965

By G. A. Croes, N. Schwarz

The dimensionless groups, to which the variables that govern the displacement of oil from reservoirs by liquids can be combined, are derived. Three types of displacement are considered, viz. cold-water drive, hot-water drive and solvent injection. The derivation of the dimerzsionless groups is carried out by means of the relevant basic equations (in-spectional analysis). The resulting sets of groups are afterwards completed by means of dimensional analysis. The form of the groups is given in such a way that they can be adapted to suit the various boundary conditions that are encountered in practice. The physical meaning of the groups is discussed. They have all been brought together on a chart, from which their mutual relation and their corresporzdence to related dimensionless groups in common use in other engineering sciences can be read off. The limitations of dimensionally scaled model experiments as a useful tool for studying liquid flow in porous media, as occurring in oil reservoirs, are discussed. The use of models to study fluid mechanics has an appeal for everyone endowed with natural curiosity. What active boy has not played with ship and airplane models, or crude models of dam and drainage systems Even in the most advanced technical engineering, such models play a fundamental and indispensable role. "And yet in few departments of the physical sciences is there a wider gap between theory and practice, between scientific knowledge and the state of art, than in the use of models to study hydrodynamic phenomena." Garrett Birkhoff1 INTRODUCTION Laboratory displacement experiments are extensively used to investigate, directly or indirectly, the production behavior of petroleum reservoirs. Such experiments are representative of the reservoirs as a whole, if they are carried out with models that are "properly scaled." The performance of oil reservoirs is governed by the values of a number of variables, which can be combined to dimensionless groups. Two general methods are available for the derivation of these groups. In the first of these, dimensional analysis, combination of the variables is done essentially by trial and error. Its only premise is knowledge of the complete set of relevant variables. In the second method, inspectional analysis, the dimensional homogeneity of the equations describing the behavior of the system to be studied is used. The resulting dimensionless groups can be divided into: (a) independent (variable) groups, such as dimensionless length, time, etc.; (b) dependent groups, giving the dimensionless form of the variables, such as recovery and pressure, that can, at least in principle, be measured during an experiment; (c) similarity groups, which are independent constant groups, such as ratio of length to height of the reservoir and ratio of

Jan 1, 1957

RUfUs J. Foster, Scranton, Pa. (communication to the Secretary*) :—In answer to one of the inquiries made of Mr. Conner, and as a matter of historical record, I beg to say that the idea of supporting the strata over worked-out areas in coalmines by flushing the openings full of culm originated and was put into actual practice by the late R. C. Luther, a former member of the Institute, at that time Chief Mining Engineer, and later General Manager, of the Philadelphia & Reading Coal & Iron Co. In the early 80's the Philadelphia & Reading Coal & Iron Co. purchased from Messrs. Hecksher & Co. the Eohinoor colliery, situated in the western part of the borough of Shenan-doah, Pa. On taking possession of the colliery the Philadelphia & Reading Coal & Iron Co. made a conlplete resurvey of the mine-workings, giving an absolutely correct map which showed not only the plan of the mine-workings, but also every improvement on the surface over the workings, and the marked features of the surface of the ground. Tidal elevations were shown at every eurvey-station in the mine and on the surface, so that, as is the case with all the maps of the company, contour-maps of either the surface or the bottom of any coal-seam, or geological cross-sections, could be constructed directly from the information on the mine-maps. In a cornparatively short time after the company took possession of the colliery, the workings which extended under the western portion of the borough of Shenandoah began to cause trouble and damage dwellings and other buildings in that section of the town. The lots in this section had been sold, in many cases, to individuals by the Gilbert & Shaefer Estate, owners of the coal-lands on which the colliery was located. In

Jan 1, 1912

By John B. Farish

This brief paper is designed to place on record some interesting occurrences, recently observed during an examination of the Golden Age Mine, in Boulder county, Colorado. Leaving the little village of Jamestown—or Jimtown, as it is more generally called—located in the canon of James creek, the road winds up a steep mountain composed of the coarse gray granite, with occasional belts of gneiss, common to all the mineral-bearing sections of Boulder county, to the summit of the front range of the Continental Divide. Here are located the mines known as the Golden Age and the Sentinel, the relative locations of which are shown in Fig. 1. The Golden Age location covers the outcrop of a quartz-porphyry dike, which cuts through the granite country-rock with a strike of about N. 70' E. This dike varies in width from a few feet, as at a point between the main shaft and the Hill shaft, to about 50 feet,

Jan 1, 1891

By W. B. Lewis, M. E. True, M. C. Leverett

Tars paper states the theory underlying the design of two kinds of dimensionally scaled models of parts of idealized oil fields. One of these simulates an oil well and its surrounding sand for a distance of 16 ft. radially from the well. The other model simulates linear flow through layered sands. Construction and operation of the models are described and typical data are given. The unique features in the design of the models are: (I) the treatment of the permeability-viscosity quotient as a single variable and (2) the use of previously reported experimentally developed relations between relative permeability and saturation and capillary pressure, saturation, porosity, perm ability and interfacial tension. The models at present simulate flow of oil and water only, through unconsolidated sands. They are superior to unscaled models, which may give rise to erroneous conclusions. The models are designed to study the desirability of various methods of sell completion and the effects of various factors on recovery of oil from layered sands.

Jan 1, 1942

By Thomas Leonard Watson

I. Historical. Barite has been mined for many years in various parts of Virginia, probably the earliest mining-operations being in Prince William county, within 600 ft. of the Fauquier county line, about 4 miles south of east from Catlett, a station on the Southern Railway. It is claimed that the mineral was mined here as early as 1845. Mining-operations in Campbell and Pittsylvania counties in the Piedmont region, and near Marion in Smyth county, in the southwest Virginia Valley region, were begun about 30 years ago. The mining and milling of barite on a commercial scale in Tazewell and Russell counties are more recent, and commenced about 15 years ago. II. Geographical and Geological Distribution. Barite occurs in many counties in the State, as shown in Fig. 1, but the industry has been confined to only a few of them. Its occurrence is noted in two of the three major divisions of the State—namely, the Piedmont region east of the Blue Ridge, and the Paleozoic area west of the Blue Ridge. In the Piedmont region the mineral has been mined in the following counties: Bedford, Campbell, Louisa, Prince William, and Pittsylvania. In the region west of the Blue Ridge, composed of Paleozoic sediments, barite has been mined in Montgomery, Russell, Smyth, and Tazewell counties. Of the counties mentioned, Bedford, Campbell, and Pittsylvania of the Piedmont region, and Russell, Smyth, and Tazewell of the Valley region, have been the principal producers. In 1906, operations were confined to five counties—Bedford, Louisa, Pittsylvania, Russell, and Tazewell—but in the first two counties named there was no production, the work being solely development.

Jan 1, 1908

By N. A. Ziegler

THE present publication is a continuation of the work on gas analysis, described in a paper presented before the Institute of Metals Division a year ago.1 While that paper was largely descriptive in character, dealing with the various parts of the apparatus and method of operations, the present one gives numerical data obtained as a result of a series of experiments with iron-carbon alloys. The apparatus and the methods applied are essentially the same as previously described, changes being only in minor details. Attention should be called to the fact that in the present work we are dealing with the gaseous mixtures obtained as a result of vacuum melting of various ferrous alloys. It should be understood that when the terms "degasified sample" and "products of degasification" are used, they refer to the sample remaining after the vacuum fusion of the alloy and the gaseous products removed therefrom, respectively. The writer does not wish to create the impression that the metallic products of this process are absolutely free from any gaseous elements, nor that the gases obtained are present as such in the original sample. These two points are not yet definitely known and are subjects for future investigation. The point, however, which has been established beyond doubt, is that all the gases dealt with come from the metallic charge and are present either in the charge as such, or are produced as a result of chemical reactions going on within the charge. The suggestion that the gases are due to the reactions between the metallic charge and the refractory materials has no valid basis.

Jan 1, 1929

By W. A. Griffith

The fundamental principles and modern techniques of experimental planning and data analysis, applicable to any type of research, are particularly important in flotation experimentation. Since they constitute the modern science of experimentation, they should be among the working tools of any scientist, research engineer, or plant operator engaged in flotation investigates. This chapter is a review of these principles and techniques. Equipment and procedures for the actual conduct of experiments will not be discussed here since these subjects are well covered elsewhere in this volume. Neither will any attempt be made to impart a working knowledge of statistical methods of data analysis since this would be impossible in the space allotted, and many excellent texts are available to the diligent inestigator.1-4 The objective here is simply to interest the reader in the application of statistical techniques to flotation experimentation by illustrating their utility in situations frequently encountered, and to point out the principles of experimental planning necessary for their proper use. Any conscientious metallurgist engaged in flotation experimentation or operations is well aware of the inherent complexity of the flotation process, and of the often frustrating difficulties this introduces into experimentation. The raw materials normally treated by the process are complex both physi- cally and chemically, and often highly variable even when from the same source. The flotation process itself is characterized by a very large number of potentially important process variables. Many of these are beyond the con- trol of the metallurgist, and some cannot even be measured quantitatively with available instruments. Those which can be measured and controlled with reasonable precision often produce effects which are intricately interrelated. Not only are the variables many, but the physical and chemical mechanisms by which they function are imperfectly under stood. To compound the difficulty, experimental techniques are relatively crude. Controls are not very precise, and the human factor looms large in most flotation experiments. These situations lead inevitably to experimental data of a relatively low degree of precision or reproducibility. Some are inclined to think that these conditions are unique to flotation experimentation. They are not. The experimental problems met by the agronomist, the biologist, the social scientist, and others are equally complex. Investigators in these fields pioneered in the development of methods for handling just such situations by proper experimental planning and the application of statistical methods in the analysis of data. Their pioneering work has grown into a well established modern science of experimentation which has spread into every field of science. This science is based upon statistical

Jan 1, 1962

By Terry Ramsey

INTRODUCTION The Cyprus Pima Mine is located 20 miles southwest of Tucson, Arizona and about fifty miles north of the Mexican border. The Cyprus Pima orebody was discovered in 1950. Feasibility studies were begun in 1952 employing underground development. Economic studies showed open pit operations to be feasible and stripping of overburden was begun in late 1955. The first ore was reached in October of 1956. A 3,000 tpd (tons per day) concentrator was completed and began operation January 1, 1957. From these beginnings, Cyprus Pima Mining Company has expanded into a plant processing approximately 54,000 to 56,000 tpd. Four expansions were required to bring the plant up to its present capacity. Each expansion incorporated what had been learned in previous operation of the plant. The first expansion was completed in August of 1963 doubling design capacity to 6,000 tpd. In reality, because of softer than average ore, capacity was closer to 8,000 tpd. Expansion II was completed in July 1966 bringing design capacity to 18,000 tpd. Expansion III followed immediately. Completed in the summer of 1967, this expansion increased the design capacity to 30,000 tpd. The actual dry tonnage of this portion of the operation in 1974 averaged 38,400 tpd, again, primarily as the result of treating softer than average ore. The latest expansion (Expansion IV), completed in December 1971 and utilizing a semi-autoge- nous grinding circuit, is located in a separate building (Mill II) approximately 200 yards southeast of the original mill (Mill I). Expansion IV was designed for 14,000 tpd, but after circuit modifications, averaged 16,500 tpd in 1974.

Jan 1, 1976

By G. G. Sarkar

SHARPNESS of separation and washing efficiency are often confused. The sharpness index indicates the precision of a washing unit; the washing efficiency takes into account not only the unit's precision but also the washability characteristics of raw coal and the near-gravity materials at the effective density of cut. A sound basis for evaluating the sharpness index is essential in comparing the sharpness of separation attained by different cleaning units. Sharpness Index and Related Criteria: Washing plant sharpness of separation has been well represented by Hancock's efficiency chart and Tromp's curve of migrated materials. Some useful coefficients derived from Tromp's curve-the error area, probable error, and imperfection value-have been widely used to measure sharpness of separation. These are defined in a number of papers presented at the first and second International Coal Preparation Conference held in Paris (1950) and Essen (1954).1-5 In evaluating the performance of a dense medium separator at four different gravities, Yancey and Greer6 observed that even with similar operating conditions and the same size grading of feed, the imperfection value of a washing plant varies through a greater range than the probable error. The present writer also observed the same type of anomalies in comparing the imperfection values of one plant which were determined under almost identical conditions. He therefore devised a graphical method to evaluate a washing unit's sharpness of separation and define it by a single coefficient, which is substantially independent of coal characteristics under normal operation of the unit. Unlike imperfection value, the new coefficient can be expressed on a percentage basis.

Jan 12, 1957

By J. J. Lillie

Sublevel stoping was first developed in the Michigan iron mines many years ago. Since that time this method, and modifications with long hole drilling, have been used in a number of non-ferrous mines and have been described in various papers and articles. With a few exceptions, the operations where sublevel methods have been applied are producers of large daily tonnages from ore bodies of considerable size. In selecting mining methods for small properties or relatively small detached ore bodies, sublevel methods often have been overlooked. The method has been used successfully in relatively small operations at Copper Canyon, Nevada, and, more recently, in mining small ore bodies at Darwin, Calif. As a result of this experience, we believe that a review of the general procedure, the advantages noted, and the results obtained will be of interest to many operators of relatively small mines. General Description Briefly, sublevel stoping consists of, first, driving sublevel drifts at predetermined vertical intervals through the length of the stope block; second, breaking an initial mining slot across the stope; third, driving crosscut benches from each sublevel by slabbing into the slot; and, fourth, breaking the ground between benches. Applicability Since this is an open stope method, it requires wall rock that will stand over reasonable stope lengths without caving or excessive slabbing. Ore must be moderately firm but need not be hard. The method is best adapted to steep dipping, tabular or lenticular ore bodies but may be applied to ore bodies of almost any shape if their vertical extent is appreciable. It can be used with dips that are too flat for successful shrinkage stopes and can be modified for use with slushers on dips below about 40". Initial mining at the Copper Canyon operation consisted of sublevel stopes for the wider ore sections and shrinkage stopes for the narrow sections where ore widths averaged about 15 ft. After some experience and a study of comparative results on completed stope blocks, sublevels were substituted for shrinkage stopes even in the narrow ore widths. Practical stope lengths depend upon the character of the walls and the continuity of values within the ore body. Where blocks of low grade or waste are included in the stoping limits, these areas can readily be left as pillars for intermediate wall support and longer stope lengths may be planned. Raises can be spotted in narrow or low grade areas and stope lengths adjusted accordingly. Stoping Details To illustrate stoping details, assume that we have an ore shoot 15 to 30 ft wide and about 200 ft long, with walls that would stand over a stope length of 80 to 90 ft (Fig1). PRELIMINARY DEVELOPMENT Preliminary development for sublevel stoping would be simple. A service raise is driven at about the center of the block and stope limits planned to leave a pillar around this raise. Sublevel drifts driven each way from this central raise will outline the

Jan 1, 1950

By J. C. Williams, M. J. Blackburn

MANY aspects of the formation of the metastable w phase in titanium-transition metal alloys have been described in several recent papers.1-4 These papers have reviewed earlier work on the w phase and have further defined most of the important features related to the formation of this phase, e.g-., its crystal structure, composition, and morphology. There are, however, several important points regarding formation of the w phase in titanium alloys which have been described in less detail. Two of these are the relationship between lattice misfit and w phase morphology and the influence of lattice misfit on the mode of formation of the equilibrium a phase. In this communi- cation we will present transmission electron microscopy results relevant to these two points. The alloys used in this study were prepared by non-consumable electrode arc melting, each 30-g button being remelted a minimum of twelve times. The alloy compositions we have studied are listed in Table I. Thin foils were prepared using standard techniques described elsewhere. Two distinct c' phase morphologies have been reported in earlier papers. The phase is ellipsoidal in the Ti-Mo3 and Ti-Nbl system and cubical in the Ti-V3 system. Results of the present study show that the w phase is also cubical in Ti-Mn, Ti-Fe, and Ti-Cr alloys as illustrated in Fig. l(b) to (d). Fig. l(a) shows the ellipsoidal morphology in Ti-MO3 for comparison purposes. It was suggested in an earlier paper3 that the w phase morphology may be controlled by the lat-

Jan 1, 1970

By D. C. Hilty, W. Crafts

Determination of the solubility of oxygen in iron containing silicon, or manganese, or both, has confirmed the earlier work on silicon, shown that manganese is more effective than expected, and has demonstrated that the combination of silicon and manganese is a much stronger deoxidizer than might have been inferred from their individual effects. SILICON and manganese are of primary impor-tance in the deoxidation of steel, and a study has been made at the Union Carbide and Carbon Research Laboratories, Inc. of the solubility of oxygen in iron in the presence of silicon and manganese, singly and in combination, as a basis for more effective control of inclusion formation. The investigation was carried out with the same equipment and experimental procedure that were used in the determination of the oxygen solubility of iron containing aluminum'. The heats were melted in a rotating crucible furnace under an argon atmosphere. Bath temperatures were controlled by platinum/platinum +10 pct rhodium thermocouples to attain equilibrium at 1550°, 1600°, and 1650°C, so that oxygen solubility isotherms were determined directly without requiring calculation from a temperature coefficient. A detailed description of the furnace and procedure is given in the paper on aluminum deoxidation1. Oxygen solubility in the presence of more than 0.10 pct silicon was found to approximate earlier determinations closely, but some deviation was observed at lower silicon contents. Manganese appeared to be more effective than had been anticipated. The combination of silicon and manganese lowered the solubility for oxygen markedy as compared with either silicon or manganese alone. Although the solubility for oxygen in the presence of both silicon and manganese represents only a part of the information needed to control inclusion formation, it suggests a partial explanation of the benefits of this combination that have been observed in practice. Manganese and Oxygen in Liquid Iron: The study of oxygen in iron in the presence of manganese was carried out in magnesia crucibles of the type furnished commercially for laboratory induction furnaces. Alumina crucibles were unsatisfactory, because the work on the aluminum-oxygen equilibria in iron' had shown that merely melting iron in an alumina crucible limited the solubility of oxygen to a level considerably below that anticipated for moderate concentrations of manganese. Silica crucibles appeared unsuitable because of the dangers of excessive fluxing by the melt. Moreover, as will be shown later, melting iron in a silica crucible also limits the oxygen content below that in equilibrium with

Jan 1, 1951