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By F. W. Luerssen, J. F. Elliott

F LUSHING the early slag from a stationary open Fhearth having a high percentage of hot metal in its charge is necessary in order to remove silica from the system. The flush slag is strongly oxidizing and is somewhat acidic. It has, however, considerable capacity to extract phosphorus from the bath and it also removes considerable manganese. It seems probable that factors which control the distribution of phosphorus and manganese between slag and metal in the refining period also should be dominant in the flush and postflush periods. Several studies, as summarized elsewhere,1,2 support the viewpoint that conditions closely approaching equilibrium for these elements are rather readily established during the refining period. Over the years these studies have repeatedly demonstrated that 1—high slag v01ume, 2—low bath and slag temperature, 3—basic slag, and 4—strongly oxidizing slag favor rapid elimination of phosphorus from the bath to the slag. They also show that the following conditions favor retention of manganese in the bath: 1—low slag volume, 2—high bath and slag temperature, 3— basic slag, and 4—minimum oxidizing power of slag. When it is considered that the flush slag often carries as high as 75 pct of the manganese charged and only 25 to 60 pct of the phosphorus charged, it is evident that in removing silica much manganese is sacrificed but phosphorus removal is far from conplete. Because of overriding circumstances, this is accepted in most operations and actually it is considered to be inevitable. This may account for the fact that little attention has been paid to conditions affecting the elimination of phosphorus and manganese in the flush slag. A recent study of the behavior of various charge oxides has developed considerable information on the flush and postflush periods. Because the data are felt to be of general interest, they have been brought together and Presented in this paper. The object is to show the various factors in the flush and postflush periods which influence elimination of phosphorus and manganese. Physical Conditions During and After Flushing Physical conditions existing during the flush vary from plant to plant, from shop to shop, from furnace to furnace, and even from heat to heat. They are strongly influenced by the physical and chemical character of the charge oxide which is ordinarily necessary to provide sufficient oxidizing power early in the heat. Invariably the period is characterized by a vigorous reaction between the principal re-actants: the hot metal being added and the charge oxide. During the flush, it is probable that the slag acts to some extent as an oxidizer; but, because of the critical influence of the behavior of the charge oxid'e on flushing action, it seems apparent that the oxide itself is the dominant oxidizer. Fig. 1 shows the course of two heats which were selected as being typical of the group studied. Heat A was charged with 55 pet hot metal, based on the total metallics charged, and heat B had 57 pct hot metal. As indicated in Table I and Fig. 1, the melt-down slag, which is not usually voluminous and which is principally FeO, expands greatly in volume and will show rather high levels of SiO2, MnO, and P2O5 very soon after the beginning of the hot metal addition. Simultaneously, large volumes of CO are liberated which cause violent mixing of slag and metal. It is of interest to note that the time required to bring carbon down to a low level is very much longer than that required for the removal of silicon, manganese, or phosphorus. At the end of flush, carbon in the bath is still approximately 2 pct. When strongly reducing hot metal is brought into contact with strongly oxidizing conditions within the furnace! it is probable that the rate of mass transfer to the slag (and atmosphere) of silicon, manganese, phosphorus, and carbon initially depends principally on the rates at which the two participating phases are brought into contact That is, it depends on the nature of the various reactions. Later in the flush period, when the scrap is virtually all dissolved and the action of the bath has settled down to a steady and somewhat gentle boil, it is likely that other factors, such as the transfer of oxygen across the slag-metal interface, become dominant. The temperature of the slag-metal system is far from uniform. Heat is being driven by the flame down through the slag. Bubbling and surging of the metal also frequently brings portions of the bath in contact with the flame. At areas of contact between the ore and liquid metal, or slag and liquid metal, the oxidizing reactions generate much heat. On the other hand, scrap is being melted which tends to absorb large quantities of heat. Because the liquid bath is high in carbon, the steel scrap is brought into solution rapidly. This can proceed at a rather low temperature; and until much of the scrap has been taken into solution, the bath temperature would not be expected to increase appreciably. Consideration of these factors leads to the conclusion that during the flush period the slag should be rather hot and the bath relatively cold. Both observation and temperature measurements bear this out. Experimental Data The extended program of charge oxide evaluation permitted study of the widely varying conditions existing during the flushing period. Slag and metal analyses and bath temperatures reported herein (Tables I and 11) were obtained toward the latter portion of the work. Four different types of charge oxide, sinter, two types of hydraulic cement-bonded soft ores, and a pyrobonded agglomerate were used in the study. Although the heats reported were from only one 205 ton furnace, they show variations in flush slag analyses all the way from 25 pct FeO, which is typical with the use of a hard natural charge ore, to 45 pct FeO which resulted when a very poorly agglomerated fine ore was used. The physical behavior of the flushes showed a correspondingly wide variation from well controlled reactions to violent surges following periods of inac-

Jan 1, 1956

By C. E. Birchenall, G. Derge

IN studying the kinetics of slag-metal reactions, it has become increasingly apparent that a complete knowledge of all aspects of interface phenomena will be required to clarify these processes adequately. A part of the data required for all oxidizing slags used in the refining of impure iron to steel is the rate of exchange of iron between the slag and metal phases. The simplest equilibrium of this type is that between liquid iron and iron silicate slag when both phases are equilibrated with the silica crucible containing them. In this study, the exchange of iron between the two liquid phases has been measured by using radioactive Fe as tracer. The observed high exchange rate indicates the ease with which such interfaces may be crossed in refining processes. The experiments required for this study involved relatively minor and normal modifications of well established techniques. Melting was accomplished by induction heating in heavy walled, fused silica, rotating crucibles." Rotation was used to minimize dilution of the slag by crucible erosion. The melting stock was ingot iron. Slags were prefused in iron crucibles using chemically pure grade oxide reagents. The special conditions applying to the active iron additions will be described for individual experiments. Suitable precautions were observed with regard to protection against radiation hazards.' Identification of Activity This particular study was initiated several years ago, but held in abeyance because the radioactive iron available at that time contained a foreign activity which concentrated in the slag so as to mask the iron activity and render the results unin-terpretable. With the benefit of experiences from other studies, radioiron of suitable purity can now be prepared. As received from the Isotope Div. of A.E.C., the unit appears to contain Fe + Fe50 and a high activity cobalt. The cobalt and iron are separated by repeated ether extractions, and the purified iron stored for sufficient time for the Fe'7 44 day half-life) to decay to negligible activity, leaving only Fe as the active isotope. This was confirmed by the absorption curves for slag and metal samples from heat No. 1. In Fig. 1 the experimentally measured points for the absorption curves of slag and metal are fitted by the calculated slope of 5.8 mg per sq cm in aluminum, which corresponds to the Mn K doublet emission resulting from the capture of an orbital electron of Fe" by the nucleus. This shows that the radioactive species are the same in both slag and metal and identifies it as Fe55 Description of Individual Heats For the first heat, the radioactive iron was contained in the prefused slag. The active Fe55 had been precipitated with carrier and was added as Fe2O3 during fusion in the iron crucible. The charge of 500 grams of ingot iron was melted, the protective iron sleeve added, rotation started, and a prefused, inactive slag was added to allow the system to approach equilibrium. After about 5 min at temperature, the wash slag was skimmed and the active slag added. Initial slag and metal samples were taken as soon as the slag was molten. Additional samples were taken at indicated intervals thereafter. Slag samples were dipped with a small iron spoon and metal samples were sucked into 1/4 in. ID silica tubes. The slag and metal samples were pulverized and mounted for radioactive counting. The slag samples were analyzed chemically for FeO. Temperature was read after the last slag sample by immersion of a Pt-Pt-Rh thermocouple protected by a fused silica sheath. Since no significant variation of rate with temperature was observed

Jan 1, 1954

By D. C. Hilty, W. Crafts

L. S. Darken—Laboratory investigation of deoxidizing and other steelmaking reactions is usually centered, at least first, on the determination of the equilibrium or equilibria involved. This seems a reasonable procedure since equilibrium, if attained, depends only on composition, temperature, and pressure; hence conclusions derived from data on small experimental quantities are applicable to a heat of steel providing eauilibrium is attained in both cases. A knowledge of equilibrium serves as a useful framework even though we may know that practical conditions do not correspond to complete equilibrium. On the other hand, nonequilibrium or rate phenomena depend on a wider variety of conditions and are more difficult to interpret; conclusions applicable to laboratory conditions may or may not apply to larger scale phenomena. Hence the attainment or nonattainment of true equilibrium in the experiments here reported is of critical importance in evaluating their significance. Since some of the statements in this paper and in the closely related preceding one (on aluminum deoxidation) imply some doubt on this matter, I should first like to ask the authors whether their conditions are intended and believed to represent equilibrium. I should like to point out three considerations which seem to cast considerable doubt on the achievement of equilibrium, at least of the particular equilibrium under consideration. 1. In the experiments on manganese deoxidation the authors point out that they could not maintain the manganese-oxide slag on top of the metal in their rotating crucible, and hence they substantially dispensed with this slag. This leads to serious trouble in the interpretation of the results, for any equilibrium is, of course, a particular specific equilibrium—in this case Mn + O = MnO The experimental deletion of the upper layer of manganese oxide means that if equilibrium is attained at all it is attained between the metal and the MnO which has soaked into or adhered to the crucible (under the metal) and has dissolved substantial amounts of the crucible material including impurities. These impurities may constitute a significant portion of the slag by virtue of the small total amount of slag, even though the crucible is relatively pure. Hence there would seem to be a strong presumption that the equilibrium (if attained) involves not a pure MnO (or MnO — FeO) slag but one saturated with alumina and containing perhaps considerable impurities which substantially lower the concentration and activity of MnO, causing the above reaction to proceed to the right further than it would in the absence of alumina and impurities. Hence it is not surprising that manganese here appears as a better deoxidizer than found by other investigators. The present results may represent equilibrium with a slag of unknown composition which seems unlikely to be particularly related to plant experience. 2. The curves representing the observed silicon deoxidation (figs. 3, 4, and 5) are all drawn with a discontinuity in slope at about 0.02 pct oxygen. This point is interpreted as corresponding to the three-phase equilibrium, metal, slag, solid silica. The type of construction shown in these figures (though apparently fitting the data) is contrary to a fundamental principle of heterogeneous equilibrium as pertains to the construction of phase diagrams. According to this principle, the two solubility curves (each of the two portions of the curves in figs. 3, 4, and 5) must intersect in such manner that their (metastable) extensions must lie outside the homogeneous field rather than inside as in these figures. In other words, the "point" in these curves should be aimed in the opposite direction, if it is to be interpreted as corresponding to the three-phase equilibrium. The construction adopted is in violation of the second law of thermodynamics. This matter is discussed in detail in several texts and also by Lipson and Wilson.&apos;" The same criticism applies to the later figures representing conditions for manganese additions. The occurrence of this discontinuity or break at 0.02 pct oxygen casts further doubt on its interpretation. The earlier investigation of this system by Korber and Oelsen is in substantial agreement with the several recent findings of Chipman and coworkers that the oxygen content of iron in equilibrium with silica and silica-saturated iron oxide slag is about one third to one half that (0.24 pct at 1600") of iron saturated with pure iron oxide; thus there seems reliable evidence that iron saturated with silica and iron silicate slag at 1600" contains about 0.1 pct oxygen, or certainly much more than the 0.02 pct proposed in this paper. 3. In the quarternary system iron-silicon-manganese-oxygen one of the equilibria involved may be written 2 Mn + SiO2 (solid) = 2 MnO <slag> + Si The activity of SiO, is constant (if equilibrium is attained) by virtue of its presence as a substantially pure solid. At not too low metallic manganese content, the activity of MnO in the slag is constant by virtue of the fact that the slag is substantially pure manganese silicate saturated with silica and hence of constant composition. Thus the equilibrium constant for the above reaction is asi/a2Mn. Barring unanticipated large changes in the activity coefficients, the equilibrium constant may be adequately approximated for the composition range covered as [% Si]/[% Mn]2. Thus a plot of log [% Mn] against log [% Si] would be expected to be linear with a slope of one half as found by Kijrber and Oelsen. In the present investigation the slope (shown in fig. 15) is found to be one. It is difficult to believe that this finding represents a correct equilibrium determination, since it is at odds both with prior experimental investigation and with. theory. In view of the above points it seems that, although this paper reports many interesting findings, there is room for considerable skepticism as to the attainment of equilibrium and as to the conclusions drawn. N. A. Gokcen—The authors consider that Si% x O2% product is constant. This product is a function of the asi X a0 activity of Si02. The true constant is -------------. If the asio2 slags of this investigation were always saturated with SiO2 then Si% X O2% product would be constant,

Jan 1, 1951

By A. H. Cottrel

SINCE metallurgy exists to provide strong, tough, engineering materials it must inevitably be perpetually concerned with the problem of brittle-ness. The steel-making industry was created because chemically unrefined iron is brittle. The steel-working and alloy-steel industries exist partly because hardness and ductility are mutually exclusive qualities in structurally unrefined steel. Yet, in spite of these immense industries, the brittle failure of steel ships hulls, bridges, pressure vessels, and pipelines, is still a contemporary problem. In fact, brittleness is a normal property of most solids, including metals and alloys, at low temperatures. Only face-centred cubic metals are commonly ductile at the lowest temperatures, and even here exceptions are known.&apos;," Expensive are-melting processes. under inert gases or vacuum, have been developed to overcome brittleness in titanium, zirconium, columbium. and molybdenum. Polycrystal-line zinc, magnesium, and uranium have little ductility at room temperature. Beryllium, chromium, and tungsten have even less; similarly for antimony, bismuth, germanium, silicon, intermetallic compounds, and metallic carbides, nitrides, silicides, and borides. Oxides and other ceramics would be ideal creep-resistant materials but for their extreme brittleness when cold, and great efforts have been made to overcome this problem by mixing ceramics with metals. In fact, the traditional use of the name metallurgy for what is really the science of engineering materials is a recognition that most non-metallic solids have so far been precluded, by their extreme brittleness, from use as major structural materials in mechanical engineering. Most of what we know about brittleness in metals has come from studies of structural steel, and it is this material that shall mainly be considered. The things we have learned from it have a wider application, at least to other body-centred cubic transition metals, although the extent to which similar ideas can be applied to hexagonal metals and other materials is not yet clear. Fracture and Plastic Deformation The theoretical breaking strength of an ideal solid, about E/10 where E is Young&apos;s modulus, has been approached reasonably closely in experiments on fibres. But large specimens break at much lower stresses. For example, brittle cracks in large structural steel assemblies have been observed to spread catastrophically at speeds of 6000 ft per sec under stresses of about 10,000 psi, i.e. about E/3000. There are two sources of weakness; stress concentrations, and chemical agents in grain boundaries or on crack faces that lower the surface energy y of the material. Although we shall deal mainly only with the first of these, much of the discussion is also applicable to the second when different values of y are used. Griffith&apos;s well-known formula p = [ 2Ey/p(1 - v2)c]1/2 [1] gives the smallest tensile stress p able to propagate an atomically sharp surface crack of length c or interior crack of length 2c through a thick plate (compared with c) of elastically isotropic material of

Jan 1, 1959

By Walter C. Lawson

THE primary objective in laying track in panel sections is to reduce the number of track laborers required. This is possible because the work is mechanized. Moreover, because the work is mechanized and each of the operations needs only a few men, and each is self-contained, the work can be carried on at night as well as in daylight; therefore, the method provides a means of preparing tracks on more than one shift. The laying of tracks in open pits and quarries in panel sections is not new but new methods have been made possible by the introduction of new types of equipment. The purpose of this paper is to describe the methods that are followed in&apos; the Morenci open pit. GENERAL MINING OPERATIONS Full-scale ore production at Morenci is about 50,000 tons daily. The normal yearly output of ore and waste is 32,000,000 tons, of which 30,000,000 tons is handled by rail haulage. This requires the building of approximately 47 miles of loading and other temporary tracks during a 12 months&apos; period (Fig I). Broken ore and waste, is loaded., into 90-ton capacity dump cars with 5-cu-yd full-revolving electric shovels. Shovel banks are uniformly 50 ft high:. They are blasted- with churn drill holes, and the broken material from a blast is loaded out with two shovel cuts, the first one being called (locally) the "splatter" cut and the second one the "clean-up" or "face-up" cut. When a shovel is making its clean-up cut, the loading track is about 70 ft from the toe of the bank and, under normal conditions, a bank is blasted against it without removing the track. It is thus evident that each track is used for two shovel cuts before relocation is necessary, inasmuch as a single position serves for both the clean-up cut prior to blasting and for the splatter cut following the blast. The normal advance of a solid bench by a single blast is 40 ft (Fig 2). PREPARATION OF PANEL GRADE In preparation of panel grades bulldozers and rooters are used for the bulk of the work and an auto-patrol road grader for the final stage. At Morenci, bulldozers have always been used for track-grade preparation, but before the introduction of the other two types of equipment grades were uneven and irregular at best, and always necessitated a big gang of track laborers to hand-block under the ties with rocks after a track was laid into place. High blocking also made poor track because of instability and caused frequent derailments. Under these conditions derailments were generally bad as re-railing became difficult. Much track was torn up and many ties broken in the process. The inadequacy of the hand-blocked track, together with the inefficiency of hand blocking, constantly pointed to the desirability of reducing the amount of labor required, so various means were tried to improve conditions, such as wood

Jan 1, 1947

By Edgar Dunn

PART I.-DETERMINATION OF GASES IN SMELTER FLUES. IN 1907, upon arriving in Anaconda to take up work in the testing department of the Washoe Reduction Works, the. following problem was met at the car step, so to speak: complete and. exact analysis of gases, not only at the stack, but also in all departmental flues. Taken up to employ time not otherwise needed for regular testing department work, instructions were extremely liberal for a commercial plant, to the effect that accuracy should not be sacrificed to speed. In December, 1907, the work was temporarily transferred to the Great Falls Smelter, and some of the methods here given were there worked out. Differences in smelting operations at Great Falls and Anaconda, however, necessitated further investigations and the development of a new method for S03 determinations at the latter plant, where work was resumed in July, 1908, and completed about a year later. At the time of inception of the work, data (not only on percentages, but even on methods) were found to be meager in the extreme, for one or the other of two reasons: either entire lack of experiment at a large proportion of smelters, or disinclination on the part of the managements to divulge data of any description pertaining to either results or methods. In making determinations of gaseous constituents of flues, two methods are open to consideration: 1, the drawing out of a sample, and collection of the same as a whole, to be removed to the laboratory for later analysis; and 2, the absorption in situ on the flue of one certain constituent, disregarding others for the time being, or perhaps combining two or three in one determination. The first is generally the more rapid, but it is also the more inaccurate, method of analysis, even with special type absorption apparatus, being the more largely subject to error, both of reading, and also because of leakage during complicated manipulation in the laboratory. The amount used for analysis must also, because of limit of container, be small for the first method, and an average gas is very seldom obtained, necessitating for a fair average result a large number of determinations. Consequently, when we balance the time spent in a dozen determinations of short-time samples as against the time employed in making two or three long-time determinations of various constituents in situ, we are not so certain in our statement as to the relative speed of the two methods. Moreover, the method of analysis in the laboratory of 100 cc. of flue gas is satisfactory only when constituents thus determined are present in considerable quantity, results being simply approximate when determining such compounds as sulphur dioxide, sulphur trioxide, carbon monoxide and dioxide, and arsenic trioxide and water vapor, none of which are carried in all smelter flues in amounts in excess of (or even approaching) 1 per cent by volume. Special condi-

Jan 8, 1913

By P. R. Sperry, M. L. Holzworth, P. A. Beck

The basic work of Z. Jeffries 1,2,3 has long ago established the main features of grain growth in the presence of a dispersed second phase. Working with sintered specimens of initially fine grained tungsten, to which various amounts of thoria had been added, Jeffries found that grain growth was inhibited, that is, practically prevented, up to a certain annealing temperature. When this temperature, which increased with the thoria content, was exceeded, extremely large grains developed abruptly from the fine grained matrix. such a a temperature" was later found by Gross-mann~3,14 in certain types of steel, while ~~i~ showed15 that in other steels grain growth was gradual, without inhibition and abrupt coarsening. Later work demonstrated the connection between coarsening and aluminum additions. The viewpoint that the direct cause of inhibition and coarsening in aluminum killed steels is a fine dispersion of aluminum oxide21 appears to be held quite generally, although some doubts have been voiced even very recently, 20 In steels with Ti additions the titanium carbide phase is considered responsible for the inhibition effects found.20 The coarsening temperature increases with the titanium content. That coarsening may occur, as a result of, certain heat treatments, even in low carboil rimmed sheet steel, was shown by Samuels. He also detected coarsening in a steel ingot of similar composition, after giving it the same heat treatment as that used by him for the sheet material. In this instance the identity of the inhibiting phase has not been determined. However, Tangerding found23 that even the few small carbide particles, which occur in carbonyl iron, have a very marked inhibitive effect. As a result of an oxidizing anneal at 850°C, large grains begin to form at the surface of the carbonyl iron specimen, and gradually grow inward as the subsurface oxidation of the carbide particles progresses and eliminates the obstruction. The carbide particles Can be removed also by annealing in hydrogen, with similar results. But if the oxidizing anneal of 10 hr at 850°C in air is followed between in hydrogen for 75 hr at the Same temperature, grain growth is more hibition usually the whole specimen is transformed into a single crystal (approx. 1.5 cm X 5 cm). The reversed procedure, that is, hydrogen annealing followed by oxidizing annealing leads to smaller grains. Tangerding arrived at the logical conclusion that there must have been in his specimens some additional obstruction to grain growth hibition from a minor impurity, other than carbon. It seems likely that this obstruction was caused by an oxide formed during the oxidizing anneal and gradually reduced rtain the subsequent hydrogen-annealing. Other instances of grain growth inhibition of varying severity, associated with a dispersed second phase, have been described by several authors. Notable examples: lead with 0.06 pet Cu or Ni,24 cartridge brass with 0.12 pct Cr,25 or with up to 0.15

Jan 1, 1949

By J. F. Abel

It can be concluded that rock mechanics instrumentation, geologic mapping, and operations research in combination will produce an accurate estimate of tunnel support requirements for establishing a steel-set load prediction model. This estimate can be used to increase safety and to reduce tunneling costs. Unnecessary supports can be eliminated; overloaded or insufficient supports can be replaced on a more scientific basis than previously possible. Only a limited number of measurements are required to develop a steel set load prediction model. The results of this study can be applied generally; but, every tunnel must be considered as a separate problem. The construction and geologic variables which were found to be significant in the prediction of rock loads in this tunnel were: steel section modulus, set blocking points, percentage of alteration, relative degree of faulting, relative water condition, distance to the nearest fault, and average joint spacing. INTRODUCTION A combined engineering geology and rock mechanics program was performed throughout the Straight Creek tunnel pilot bore in Colorado in order to develop a technique for estimation of steel tunnel support loads. The technique involves the construction of a statistical model from measured steel set loads, geologic and construction factors. The aim of the investigation was to produce a set of charts, based on these factors, which could be used by a trained man equipped with a hand lens and measuring tape, to specify a safe and economical steel size and set spacing. In order to be of practical value the measured parameters had to be rapidly measurable and capable of quantification. It was apparent from the beginning that quantitative values for many of the geologic factors would have to be arbitrary. It was impossible to ascertain in advance which of the readily determi-nable geologic and construction factors significantly affect steel set loading. As the investigation progressed the number of observations was systematically reduced in order to determine the minimum amount of data which would be necessary for a significant mathematical model. This paper presents an analysis of all the variables measured at each instrumented steel set. The statistical significance of the measured variables was determined. On the basis of this determination, a mathematical model was constructed and charts were prepared to select and space the steel tunnel supports at any given point in the tunnel. Once the effect of geologic and construction factors on set loading is sufficiently established, it is possible to exert close control over the selection of steel tunnel support size and spacing. The magnitude of this rock mechanics program can be appreciated when it is known that there were 44 instrumentation stations for which steel set loads were measured. For each of these sets there were three construction variables recorded, and nine geologic parameters determined (Table I). A rough approximation of the cost for both the collection and reduction of the data would be $50,000. This is in addition to the cost of geologic mapping.

Jan 1, 1967

By Stanley J. LeFond, Langtry E. Lynd

Elemental titanium has become famous as a space age metal, because of its high strength/ weight ratio and resistance to corrosion. However, the major use is in the form of titanium dioxide pigment, which because of its whiteness, high refractive index, and resulting light-scattering ability, is unequaled for whitening paints, paper, rubber, plastics, and other materials. A relatively minor use is in welding rod coatings, in the form of the mineral rutile. United States consumption of titanium dioxide in concentrates for these applications in 1982 was as follows: pigments, 630,000 st; titanium metal, 31,000 st; and welding rod coatings, 5,000 st. The only commercially important titanium ore minerals at the present time are ilmenite and its alteration products, and rutile. Titanium was discovered by Gregor in 1790, as a white oxide which he recovered from menaccanite, a variety of ilmenite occurring as a black sand near Falmouth, Cornwall. Barksdale (1966) stated that the fundamental chemical reactions on which the present day titanium industry is based were known before 1800, although it was not until 1918 that these pigments were available commercially on the American market. Pings (1972) outlined the early history of the titanium industry in the United States, referring to the work of Guise (1964) and others: Mining of titanium minerals in the United States began sometime between 1880 and 1900, in Chester County, Pennsylvania. Small quantities of rutile were also produced during that time in North Carolina and Georgia. In 1901 rutile was mined from a deposit near Roseland, VA, and was used in making titanium chemicals and for coloring ceramics. Ilmenite in the deposit was produced as a separate item in 1913, and rutile and ilmenite were obtained from this deposit through 1921. The mining of titanium bearing beach sands began in 1916 near Mineral City and Pablo Beach, FL, for the purpose of making titanium tetrachloride to be used in tracer bullets, flares, and smokescreens. The titanium pigment industry was founded in 1918. By 1928 a large part of the domestic production of rutile, ilmenite, and zircon came from Florida. However production ceased in 1929 in Florida with the mining of newly discovered deposits in Virginia which were mined until 1968. The discovery of new deposits in Florida, and the development of better mining and concentrating methods for low-grade sands, led to a return of activities in this area. The large deposits near Tahawus, NY. were brought into production in 1942 by National Lead Co. (now NL Industries, Inc.), and by 1949 this company was the leading producer of ilmenite in the world. In 1948 the extensive deposits of ilmenite and ilmenite-bearing iron ores were discovered in eastern Quebec. The large Trail Ridge sand deposit in Florida was discovered by E. I. du Pont de Nemours & Co., Inc. geologists in cooperation with the US

Jan 1, 1983

By G. O. Hiers

IN 1948 in the United States, 184,300 tons of lead was fabricated as coverings for electric power and communication cables. Such covering generally is called "sheathing" for the principal lengths of the cables, while the short lead encasements of the joints are called "sleeves." For the purpose of this paper, both lead sheathing and lead sleeving can fittingly be called lead tubing. In the United States in the same year, 34,262 tons of lead was consumed in making extruded lead pipes. Such pipe is employed frequently for water or chemical solution conveyance with gage pressures up to 100 psi. Consequently, the walls are thicker in ratio to diameter than is the case with the cable sheaths. For this discussion, lead pipes can be thought of as tubes or tubing. About 19 centuries ago, the Romans produced metallic lead of about 99.9 pct purity. Evidently this was cast in flat sheets of Y8-in. thickness, for instance. Such sheet of 10-ft lengths was bent around a removable core producing a tube somewhat oval in cross-section and with a typical internal diameter of, say, 3 in. This method of production necessitated a seam or longitudinal joint evidently made by casting the seam metal adherently. The seam metal, as analyzed recently, contains about 1 ½ pct Sn. Blow pipes were said to have been employed when the joint was made. Specimens of such pipe were found both in Italy and in the British Isles. It is believed the pipes conveyed water for drinking purposes and for baths. Numerous specimens are still in existence in a good state of preservation, due to lead&apos;s usual inertness in air or water. According to Claude E. Pearson,1 there were various stages in the evolution of lead extrusion presses for making tubes: I. First press by Joseph Bramah, 1797. 2-First successful press by Thomas Burr, 1820. 3-First bridge die press, J. and C. Hanson, 1837. In 1845, Wheatston and Crooke made the first lead sheathed electric cable. Flat lead strip was wound spirally around the insulated conductor. Overlapping edges of lead were soldered. Early cables were also made by pulling insulated conductors into 50-ft lengths of lead tube. Borel in France, and Wesselau are credited with devising the first presses for extruding lead sheaths directly on cables in 1879. In the United States, Eaton, in 188o, and Roberston, in 1885, introduced new presses of improved design. Following Cunningham&apos;s original idea of making lead traps and. bends in 1873, the presses apparently were improved and made successfully soon thereafter. Between the years 1930 and 1940, two continuous extrusion presses for lead were developed abroad. One apparently was originated by Dunsheath and made by the Henley Telegraph Works Co. The other was developed by the Pirelli-General Cable Co. CURRENT PRODUCTION In addition to the several descriptive chapters on lead extrusion in Pearson&apos;s book, the Metals Handbook2 recently described pipe, sheath, and collapsible tube production. The latter is by impact extrusion.

Jan 1, 1951

By Gerald Edmunds

Castings of pure metals and many alloys usually have a coarse-grained structure characterized by long columnar grains throughout the main body of the casting. Frequently, the surface exhibits finer, sometimes nearly equiaxed grains, and such grains may also compose other parts of the casting. This paper deals .primarily with determinations of the grain-orientation textures of the columnar and surface grains of polycrystalline zinc castings. It includes some results upon a cadmium casting and a magnesium casting. A hypothesis is developed to account for the observations on columnar grains and to use as a basis for predicting orientations in other cast metals. A general description of the position of the columnar grains in castings is that their long axes are approximately parallel to the direction of the thermal gradient during crystallization. Thus, in cylindrical castings the columnar grain axes tend to be radial, and in large flat castings where most of the cooling is through one or both of the large mold surfaces they tend to be perpendicular to the mold surfaces. At the edges and corners the direction of heat flow and therefore the position of the grains is more cornplex. Actually observation shows that even in castings made in flat molds the cooling seems to be somewhat irregular, since columnar grains tend to emanate from certain areas of the cooling surface, indicating that thermal contact was better there than in neighboring areas. The nucleus from which a columnar grain grows may be so oriented that its direction of maximum growth rate does not coincide with the direction of the thermal gradient. In this case the long axis of the grain probably assumes an intermediate position. Notwithstanding these minor irregularities, the situation does exist that the long axes of the columnar grains are generally disposed approximately perpendicular to the mold surface. Schmid and Wassermanl and Nix and Schmid2 have determined the orientation texture of columnar grains in castings of several cubic, tetragonal, hexagonal close-packed and rhombohedra1 metals. For zinc and cadmium, they report the basal plane to be parallel to the columnar grain axes, with no preference for any particular direction in this plane to coincide with the grain axes. This texture, termed a ring fiber texture,3 is uncommon in metals; zinc and cadmium are the only ones reported to exhibit it. Generally, it is stated, a simpler texture exists in which a principal, though not necessarily the most closely packed, crystallographic direction is parallel to the direction of heat flow. In cast magnesium (also hexagonal close packed) they report a digonal axis I, [100] direction, parallel to the direction of heat flow. The writer is not aware of any other orientation-texture determinations on cast polycrystalline hexagonal metals. In view of the observations reported in the present paper it is of interest also to note that Nix and Schmid stated that a

Jan 1, 1941

By Gerald Edmunds

Castings of pure metals and many alloys usually have a coarse-grained structure characterized by long columnar grains throughout the main body of the casting. Frequently, the surface exhibits finer, sometimes nearly equiaxed grains, and such grains may also compose other parts of the casting. This paper deals .primarily with determinations of the grain-orientation textures of the columnar and surface grains of polycrystalline zinc castings. It includes some results upon a cadmium casting and a magnesium casting. A hypothesis is developed to account for the observations on columnar grains and to use as a basis for predicting orientations in other cast metals. A general description of the position of the columnar grains in castings is that their long axes are approximately parallel to the direction of the thermal gradient during crystallization. Thus, in cylindrical castings the columnar grain axes tend to be radial, and in large flat castings where most of the cooling is through one or both of the large mold surfaces they tend to be perpendicular to the mold surfaces. At the edges and corners the direction of heat flow and therefore the position of the grains is more cornplex. Actually observation shows that even in castings made in flat molds the cooling seems to be somewhat irregular, since columnar grains tend to emanate from certain areas of the cooling surface, indicating that thermal contact was better there than in neighboring areas. The nucleus from which a columnar grain grows may be so oriented that its direction of maximum growth rate does not coincide with the direction of the thermal gradient. In this case the long axis of the grain probably assumes an intermediate position. Notwithstanding these minor irregularities, the situation does exist that the long axes of the columnar grains are generally disposed approximately perpendicular to the mold surface. Schmid and Wassermanl and Nix and Schmid2 have determined the orientation texture of columnar grains in castings of several cubic, tetragonal, hexagonal close-packed and rhombohedra1 metals. For zinc and cadmium, they report the basal plane to be parallel to the columnar grain axes, with no preference for any particular direction in this plane to coincide with the grain axes. This texture, termed a ring fiber texture,3 is uncommon in metals; zinc and cadmium are the only ones reported to exhibit it. Generally, it is stated, a simpler texture exists in which a principal, though not necessarily the most closely packed, crystallographic direction is parallel to the direction of heat flow. In cast magnesium (also hexagonal close packed) they report a digonal axis I, [100] direction, parallel to the direction of heat flow. The writer is not aware of any other orientation-texture determinations on cast polycrystalline hexagonal metals. In view of the observations reported in the present paper it is of interest also to note that Nix and Schmid stated that a

Jan 1, 1941

By Walter C. Lawson

The primary objective in laying track in panel sections is to reduce the number of track laborers required. This is possible because the work is mechanized. Moreover, because the work is mechanized and each of the operations needs only a few men, and each is self-contained, the work can be carried on at night as well as in daylight; therefore, the method provides a means of preparing tracks on more than one shift. The laying of tracks in open pits and quarries in panel sections is not new but new methods have been made possible by the introduction of new types of equipment. The purpose of this paper is to describe the methods that are followed in the Morenci open pit. General Mining Operations Full-scale ore production at Morenci is about 50,000 tons daily. The normal yearly output of ore and waste is 32,000,000 tons, of which 30,000,000 tons is handled by rail haulage. This requires the building of approximately 47 miles of loading and other temporary tracks during a 12 months&apos; period (Fig I). Broken ore and waste is loaded into 90-ton capacity dump cars with 5-cu-yd full-revolving electric shovels. Shovel banks are uniformly 50 ft high. They are blasted with churn drill holes and the broken material from a blast is loaded out with two shovel cuts, the first one being called (locally) the "splatter" cut and the second one the "clean-up" or "face-up" cut. When a shovel is making its clean-up cut, the loading track is about 70 ft from the toe of the bank and, under normal conditions, a bank is blasted against it without removing the track. It is thus evident that each track is used for two shovel cuts before relocation is necessary, inasmuch as a single position serves for both the clean-up cut prior to blasting and for the splatter cut following the blast. The normal advance of a solid bench by a single blast is 40 ft (Fig 2). Preparation OF Panel Grade In preparation of panel grades bulldozers and rooters are used for the bulk of the work and an auto-patrol road grader for the final stage. At Morenci, bulldozers have always been used for track-grade preparation, but before the introduction of the other two types of equipment grades were uneven and irregular at best, and always necessitated a big gang of track laborers to hand-block under the ties with rocks after a track was laid into place. High blocking also made poor track because of instability and caused frequent derailments. Under these conditions derailments were generally bad as re-railing became difficult. Much track was torn up and many tics broken in the process. The inadequacy of the hand-blocked track, together with the inefficiency of hand blocking, constantly pointed, to the desirability of reducing the amount of labor required, so various means were tried to improve conditions, such as wood

Jan 1, 1949

By C. H. Hewitt, J. T. Morgan

The Fry cocurrent in situ combustion project was carried out in a 3.3-acre portion of a lenticular body of Robinson sandstone of Lower Pennsylvanian age. This particular sand body is about 12,000 ft long and 3,500 ft wide; it varies in thickness from 0 to 55 ft, trends northeast-southwest, and occurs at depths between 880 and 936 ft. The reservoir is made lip of three distinct types of sandstone, each having characteristic reservoir properties. (See Table I.) Textural gradients, sedimentary structures, erosional basal contact, absence of marine fossils, and geometry of the sand body all indicate that the sandstone is of fluvial origin and part of an extensive complex of river-deposited sedirnents. Geographically oriented cores reveal that the direction of depositing currents was to the southwest, parallel with the sand-body trend. Directions of maximum pernleability also parallel the northeast-southwest trend. The layered nature of the sandstone reservoir and its directional properties have controlled the areal distribution of produced gas, the ignition behavior, and the vertical profile and horizontal extent of the conbustion zone. INTRODUCTION This paper is the first of a series of three papers that describe Marathon Oil Co.&apos;s Fry in situ combustion test. This first paper contains the results of a detailed study of the geology and reservoir characteristics of the Robinson sandstone reservoir in which the Fry test was conducted. The second and third parts of this series report on the field operations&apos; and performance. The geologic work reiated to cores cut through the combustion zone, and to the effect of reservoir properties on the combustion process is included in the third paper.&apos; GEOLOGIC STUDY OF THE FRY RESERVOIR The close spacing of continuous cores in the Fry combustion site provided an unusual opportunity to study the details of distribution of lithology and reservoir properties within a petroleum reservoir. The objectives of the study were: 1. To determine the distribution of rock types within the Robinson sandstone in the Fry area; 2. To determine the relationship of porosity and permeability to rock properties and establish the distribution and homogeneity of reservoir properties; 3. To determine the origin of the Robinson reservoirs so that attempts could be made to predict the size, shape, distribution, extent and continuity of Robinson reservoirs; and 4. To determine what effects, if any, the reservoir rocks might have on the combustion process, so that the process might be better evaluated. AVAILABLE MATERIALS Continuous cores were cut from 14 wells in the vicinity of the Fry site. Ten of the cores are from within the 3.3-acre pattern; six of the 10 were cut prior to combustion, and four were cut through the combustion zone. Cores from the Emma Fry No. 15, Wampler 0-2 and Fry B wells (Figs. 1, 2 and 9) were geographically oriented by the Eastman Oil Well Survey Co. Maps, electric

Jan 1, 1966

By J. L. Bruce, G. W. Nicolson

THE country rock of the Mavrovouni mine of the Cyprus Mines Corp. is hydrothermally altered, disintegrated pillow lava, with very little tensile strength ("short" ground). In places, especially when wet, it is heavy ground, though not extremely heavy except where movement has been caused by underlying or nearby stoping operations. Damage by caving from roof or sides of galleries is not sudden but progressively faster when the size of the cave increases as a result of the fall of small pieces. CEMENT AND CONCRETE LININGS During early operations, galleries in the country rock were supported by customary mine-timbering methods. Available timber, however, was of poor quality and of relatively high price, and replacements were frequent and expensive. Furthermore, the massive sulphide ore bodies required large volumes of fresh air for ventilation and cooling, and it was therefore desirable to provide smooth-lined galleries with low resistance for the introduction of air to the ore bodies. It was also desirable to eliminate hazards of fire in shafts and underground workings insofar as this would be practical. Cement and concrete were relatively cheap, and plans for using these in support of shafts, underground galleries, raises, and chutes, were developed steadily. Circular shafts with diameters ranging from 10 to 15 ft were adopted for all permanent shafts and airways. In places these were lined with concrete poured behind sectional pressed-steel forms especially constructed for this purpose. In other places, they were lined with precast-concrete blocks. It was found that such precast concrete of good quality could be produced on mass production scale and delivered at the mine from most favorable point of manufacture, at a cost of about 25 cents per cubic foot of concrete. This refers to prewar costs. As the use of concrete blocks in circular lined galleries was developed, it was found that there were very great advantages in the reduction of air resistance as compared with customary timber supports. After best methods had been developed, it was found that breakage and replacements were extraordinarily low, averaging only about 1 ½ pct per year during a period of about 15 years. Furthermore, it has been possible to reclaim for re-use a very large percentage of the concrete blocks from abandoned galleries. During the history of the operations precast-concrete blocks have been used for lining shafts, raises, ore chutes, galleries, and shaft stations, ranging from 3 to 16 ft id. The thickness of lining has varied from 5 to 10 in.; with I2 in. thickness in a few cases. Junctions of two galleries at angles ranging from about 30 to 60° are usually made of poured concrete behind sectional forms, or of a combination of poured concrete and precast blocks. In nearly all cases it has been found advisable to make the point of the wedge at the junction, of

Jan 1, 1947

By Robert E. Green, T. Hinton

Expressions are derived for tke orientation factors appearing in the Grana to -Lucke theory of dislocation damping, for fcc crystals. The factors are given as functions of the elastic constants, the direction cosines of the specimen axis, atld the direction cosines of the particle displacemeizts, for darnping due to dislocation motion on each of the twelve possible slip systems as ixell as lor simultaneous dislocation rnotion on all twelve systems. RECENTLY Green&apos; has outlined the general procedure for calculation of the modes of wave propagation in a single crystal possessing a given crystallo-graphic orientation. In addition he has suggested how the results of such calculations along with calculations of the resolved shear-stress factors for slip enable the orientation-dependent factors (orientation factors) appearing in the Granato-Lucke theory of dislocation damping to be calculated. However, reen&apos; assumed that the maximum stress on dislocations was in the direction of the particle displacement of the elastic wave giving rise to the dislocation damping. The present cal&apos;culations show that this is an oversimplified approach appropriate only to special cases of high crystallographic symmetry. The exact calculation of stress on the dislocations can only be obtained by resolving the nine components of stress associated with the elastic wave into the appropriate slip direction and then summing. In this paper the general expressions for orientation factors are derived for fcc crystals in terms of the elastic constants, the direction cosines of the particle displacements, and the direction cosines of the specimen axis, bearing in mind the point mentioned above. Equations are presented which give the orientation factors for damping due to dislocation motion on each of the twelve possible slip systems as well as for simultaneous dislocation motion on all twelve systems arising from elastic-wave propagation. These orientation factors are appropriate to attenuation measurements made by the pulse-echo technique, where the elastic wave is a traveling wave. They will be compared with those for the case of a standing wave as derived by Granato and Lucke which are appropriate to measurements of internal friction by the resonance technique. The expressions for the orientation factors are compared with the five values given by insruch,&apos; based on unpublished work of Granato and Liicke, for positions of highest symmetry in the stereographic triangle. The various equations derived for modes of wave propagation and orientation factors have been evaluated for the case of aluminum crystals at 1-deg intervals throughout the stereographic triangle. These results will be presented in the form of contour diagrams in a subsequent paper3 and their relevance to ultrasonic measurements discussed. ORIENTATION FACTORS The coordinate system used for the calculations is shown in Fig. 1 and all specimen axes are taken to lie in the shaded standard triangle. The twelve slip systems are indexed according to Table I. Following the suggestion of lers, we may define the orientation factor Ok in the Granato-Liicke theory5 by the equation

Jan 1, 1967

By David R. Mitchell

THIS paper is limited primarily to a description of dry coal-cleaning processes in which air currents are used to effectuate a separation between coal and refuse. Processes depending mainly on differences in the coefficient of friction, resilience and shape are not described unless the use of air is necessary for the proper functioning of the process. The air cleaning of coal is of primary importance to the coal industry of the United States. From figures presented in the 1941 edition Mechannual,1 it is estimated that at least 12 million tons of bituminous coal was cleaned in the United States during 1940 by machines using air as the separating medium. One of the current problems confronting the coal-preparation engineer is the dry cleaning of small sizes and slacks. Progress in machine development for the cleaning of small sizes has been slow in recent years in the United States of America; it has been much more rapid in Britain and on the European continent. This paper does not attempt an exhaustive survey of all these developments, and only machines and processes that have found considerable commercial application are cited. Further, no critical analysis has been made of the theory involved in the separation of coal from refuse by processes using air as the separating medium other than that necessary for an understanding of particular machine designs and applications. HISTORICAL SUMMARY The possibility of using air for the separation of coal from refuse was recognized early by mining men and many attempts were made to develop commercial machines. The ingenuity of the early experimenters is to be marveled at in view of their lack of knowledge of the theoretical principles involved. As in other arts, practice has largely preceded theory. Yet, science and practice play a game of leap frog, now one ahead, then the other; the careful experimenter governs his efforts along practical lines by adapting his experiments to the limits prescribed by scientific laws. By first studying developments and the theory involved, it is not only possible to adapt processes to new uses but also to reduce materially operating cost and to build larger units without costly failures. Although many inventors have applied for patents for separating minerals by the use of air currents, the literature in regard to coal is meager. Berrisford2 describes briefly some of the early attempts to clean coal without the use of water. Several of the examples cited by him are reproduced herein. Fig. I shows a machine used for grinding and sizing, in which rollers running in a pan with a perforated bottom and fan opening on the side crushed the coal, which was then carried by the air currents to a settling chamber. The heaviest particles dropped out first and the light ones farthest away, as shown. In the year 1864, a machine was made that could be used as a sizer or to separate dirt from coal with a sized feed (Fig. 2).

Jan 1, 1942

By C. C. Wright, R. J. Day

ALTHOUGH data on the exact tonnage of recoverable coal silt are not known, the quantity produced in 1943 was estimated to be over five million tons for the anthracite region of Pennsylvania alone. Since that time the recovery of the No. 5 buck- wheat size previously included in silt estimates has increased greatly thus reducing the total silt tonnage. As a compensating factor, however, the methods of recovering silt previously escaping into the rivers and streams have been markedly improved so that the net figure may not have changed materially. Comparable estimates for bituminous coal are lacking, but undoubtedly the silt represents a significant tonnage. With the trend toward increased wet cleaning of the smaller sizes of bituminous coal, it is to be expected that even greater quantities of silt will be available in the future. The raw silt from anthracite collieries usually contains a high mineral matter content, but technological developments in fine coal cleaning have been making rapid advances and it appears probable that more extensive use of these methods will be employed in the near future. Bituminous coal silt in many instances contains a similar high mineral matter content. As with anthracite silt, however, the cleaning of this material, where necessary, appears both technologically and economically feasible. With a view to upgrading the size and value of silt, considerable laboratory and pilot plant work has been conducted by a number of organizations on what is commonly known as pelletization. Actually the process is one of extrusion in which the moist silt is extruded from a die in the form of rods, which usually break into relatively short lengths-a few inches long-as they fall from the die. Fig I is a photograph of some extruded 3/8-in. diam pellets and of the anthracite silt from which they were produced. This technique of producing larger sized material from fines is by no means new, having been used extensively by the industrial carbon and clay industries for years.&apos; The application of the process to coal silt appears, however, to be relatively new. The first major program of investigation dates back only to July 1945, when a group of engineers representing the Anthracite Institute, The Pennsylvania State College and the J. F. Pritchard and Co. conducted preliminary tests on the extrusion of anthracite silt at the Floridin Co. plant at Warren, Pa. Since that time these three organizations-individually, together, and in co- operation with other interested groups- have actively pursued work on various phases of the problem. Much of the early history and details of the laboratory and pilot plant work by the Anthracite Institute, has been reported by Mulcey and Eckerd.2 It is the purpose of this paper to report additional information on the process, especially with respect to the factors influencing the quality and use properties of the product, and the current develop

Jan 1, 1948

By A. A. Watts, R. I. Jaffee, F. C. Holden, H. R. Ogden

Hypoeutectoid Ti-Cu alloys are responsive to heat treatment, and considerable variation of mechanical properties may be produced by transformation of the ß phase. Control of cooling rate, isothermal transformation, or quench tempering determine the transformation structure and properties. The transformation products are similar to those of carbon steel. THE equilibrium diagram for the Ti-Cu system has been studied by various investigators, and the most recent diagram is that determined by Jou-kainen, Grant, and Floe.&apos; The titanium-rich portion of this diagram is reproduced in Fig. 1. The alloy compositions and annealing temperatures used in this work are shown. The Ti-Cu alloys containing up to 17 wt pct Cu are representative of an active eutectoid alloy system. Joukainen et a1.l have stated that ß phase cannot be retained on quenching and this has been confirmed in the present work. The similarity between the Ti-Cu system and the Fe-C system is evident and, as will be shown later, many of the transformation products appear to have similar microstructures. Heat treatments in this program were designed to produce the structures of primary interest for study and determination of mechanical properties. Experimental Procedures Preparation of Alloys: Five ½ lb ingots, ranging in composition from 0.8 to 6.83 pct Cu, were prepared by double arc melting in an atmosphere of high purity argon. Titanium melting stock was obtained from high purity iodide titanium, and copper additions were made from copper wire clippings. Segregation was reduced by inversion melting, in which the once-melted ingots were inverted in the crucible and remelted. The double-melted ingots were forged at 1600°F to ¾ in. diam rods, with both heating and forging operations being carried out in air. Surface scale was removed by grit blasting and grinding, after which the forgings were vacuum annealed at 900°C. The alloys then were swaged to ¾ in. diam rod at 750°C and test specimens were cut from this material. The vacuum annealing operation was to remove dissolved hydrogen, which is commonly present in the iodide titanium as-received. Although vacuum fusion analyses were not obtained for all these alloys, past experience indicates that the 6 hr treatment with a limiting pressure of 10- to 10-5 mm of Hg is sufficient to reduce the hydrogen level to 10 to 30 ppm. Vacuum fusion analysis of the 0.8 pct Cu alloy showed 19 ppm of hydrogen. In addition to the five hypoeutectoid alloys, three 15 g ingots were prepared with nominal copper additions of 9, 10, and 11 pct. Fabrication procedures were similar, except that these alloys were rolled to 0.040 in. sheet. Microstructure specimens only were obtained. Table I shows analyzed compositions and fabrication temperatures for these alloys. Heat Treatments: All heat treatments were made in potentiometer-controlled, resistance-wound tube

Jan 1, 1956

By David R. Mitchell

This paper is limited primarily to a description of dry coal-cleaning processes in which air currents are used to effectuate a separation between coal and refuse. Processes depending mainly on differences in the coefficient of friction, resilience and shape are not described unless the use of air is necessary for the proper functioning of the process. The air cleaning of coal is of primary importance to the coal industry of the United States. From figures presented in the 1941 edition Mechannual, it is estimated that at least 12 million tons of bituminous coal was cleaned in the United States during 1940 by machines using air as the separating medium. One of the current problems confronting the coal-preparation engineer is the dry cleaning of small sizes and slacks. Progress in machine development for the cleaning of small sizes has been slow in recent years in the United States of America; it has been much more rapid in Britain and on the European continent. This paper does not attempt an exhaustive survey of all these developments, and only machines and processes that have found considerable commercial application are cited. Further, no critical analysis has been made of the theory involved in the separation of coal from refuse by processes using air as the separating medium other than that necessary for an understanding of particular machine designs and applications. The possibility of using air for the separation of coal from refuse was recognized early by mining men and many attempts were made to develop commercial machines. The ingenuity of the early experimenters is to be marveled at in view of their lack of knowledge of the theoretical principles involved. As in other arts, practice has largely preceded theory. Yet, science and practice play a game of leap frog, now one ahead, then the other; the careful experimenmenter governs his efforts along practical lines by adapting his experiments to the limits prescribed by scientific laws. By first studying developments and the theory involved, it is not only possible to adapt processes to new uses but also to reduce materially operating cost and to build larger units without costly failures. Although many inventors have applied for patents for separating minerals by the use of air currents, the literature in regard to coal is meager. Berrisford2 describes briefly some of the early attempts to clean coal without the use of water. Several of the examples cited by him are reproduced herein. Fig. I shows a machine used for grinding and; izing, in which rollers running in a pan with a perforated bottom and fan opening on the side crushed the coal, which was then carried by the air currents to a settling chamber. The heaviest particles dropped out first and the light ones farthest away, as shown. In the year 1864, a machine was made that could be used as a sizer or to separate dirt from coal with a sized feed (Fig. 2).

Jan 1, 1942