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By D. J. DeLazaro, D. W. Levinson

Observations were made of the isothermal transformation and quench and reheat transformation characteristics of binary titanium alloys containing nominally 6 wt pct and 10 wt pct Mn at temperatures of 700°, 600°, 500°, and 400°C. A large change in electrical resistivity attends the beta to alpha transformation in these alloys. The correlation between the resistivity and microstructure provides a very sensitive means of following the transformation. IN a recent paper, Wyatt' determined the electrical resistivity of several grades of unalloyed titanium metal as a function of temperature. In addition to the expected discontinuity accompanying the a-B transformation, it was shown that s-Ti has a much larger temperature coefficient of resistance than 8. The result would be a very large change in resistivity attending ß?a: transformation if it were possible to retain the ß structure at room temperature in pure titanium. From these data, it was reasoned that this very large resistance change should accompany the decomposition of the ß phase in alloys in which the ß phase can be retained by quenching to room temperature from the ß field. This effect is illustrated schematically in Fig. 1. Binary Ti-Mn alloys containing more than 5 wt pct Mn can be quenched to retain ß from the ß field. While the ß phase would be expected to transform in these alloys to a + TiMn via a eutectoid reaction,' it has been observed that the eutectoid decomposition does not occur readily in hypoeutectoid alloys, but rather the decomposition of the ß occurs by rejection of proeutectoid a only." Thus, the resistivity should show a marked decrease, as the a: phase is rejected from ß and a study of the resistivity of solution treated and isothermally transformed or quenched and reheated alloys should provide an excellent means of establishing the transformation kinetics of these alloys at various temperatures. The usual metallographic method of determining the transformation temperature-time characteristics of alloys of this type is very satisfactory for deter- mining the time required to initiate the rejection of the a phase at temperatures relatively close to the ß/a: + ß boundary when the rejected a is coarse, and a typical Widmanstaetten structure is produced. The metallographic method is less satisfactory for this purpose at lower temperatures where a fine nodular decomposition product is observed and is very unsatisfactory for the determination of the time required to complete the transformation at any temperature. Accordingly, specimens were prepared for resistivity measurements in order to determine the transformation characteristics of the alloys.

Jan 1, 1955

By G. Gutzeit

An inner complex is a cyclic chemical structure containing an inorganic cation that is bound simultaneously to several atoms in a single organic molecule; on the one hand by means of ordinary valence bonds (electron exchange), on the other hand through the action of the electric field thus created, which satisfies the so-called secondary valences. The relative positions of the salt-forming and complex-forming groups are such that most frequently a four, five, or six-membered ring results through this double attachment of the cation.1-6 The formation of inner-complex ring systems depends not only upon the nature and suitable position of the salt-forming and complex-forming groups for ring closure, but, to a great extent, also on the nature of the metallic cation entering the reaction. This selective character of chelate-forming organic compounds is one of their most interesting and most valuable properties. As a matter of fact, the largest number of their practical applications is based upon their specificity.4,7-l3 Once a chelate compound is formed, its character is definitely "organic" in nature. In other words, its properties are conditioned to a much larger degree by the carbon chains or rings than by the metallic atom. Many inner complexes are soluble in nonpolar solvents such as benzene, paraffin oil or carbon tetrachloride, while the chelate-forming reagent before closure of the metal-organic ring is water soluble. (Example: copper complex of salicyl-aldoxime') It is obvious that such particular properties as those indicated above can be utilized whenever specificity and practically complete binding of inorganic ions into an undissociable complex are required. One of the well-known applications of chelate-forming compounds has been the development of specific reagents in analytical chemistry, creation of the spot-test method,4,14-16 and the application of the same principles to the contact print method for determining minerals." Chelate-forming Compounds as Collectors In the field of flotation, where selectivity is often a quality of paramount importance for the collector, various workers have lately attempted to apply their knowledge of specific organic analytical reagents to this purpose. A. C. Vivian18 has concentrated cassiterite by using ammonium nitrosophenylhydroxyl-amine (Cupferron) C6H5NO(=NONH4). Holmanl9 has tested dimethylglyoxime for the flotation of nickel oxide minerals, while deWitt has shown in a series of systematic experiments that alpha-diox-imes were generally selective collectors for nickel ores. Taurin NH2(CH2)2S03H has been proposed for the concentration Of Oxidized lead ores.19 Diphenylthio-carbazone

Jan 1, 1947

By J. Rogers, H. F. A. Hergt, K. L. Sutherland

IN 1938 Ralston4 reviewed the many attempts to find a satisfactory collector for the separation of cassiterite from its ores and in 1944 Dean and Ambrose2 summarized some further attempts. Generally, soaps and amines are effective but nonselective collectors. We have discovered that reagents containing either the polar group -SO4- or _S03- are excellent collectors for cassiterite and promise to be selective.1 The response to these reagents of cassiterite and of minerals commonly associated with it was studied, using the captive-bubble technique. Using these fundamental data, the practicability of separation and concentration of tin was investigated by flotation tests in a 2000gram Denver cell. EXPERIMENTAL METHODS Reagents All inorganic reagents were of Analar grade. The preparation and purification of sodium cetyl sulphate, cetyl trimethyl-ammonium bromide, laurylamine and cetylamine have been previously described.5 The other collectors were commercial surface-active agents, which were used without purification. Tests Captive-bubble Tests and Cylinder Flotation Tests have been previously described.5-10 The full lines shown in the figures relating solution composition to contact (flotation) distinguish solutions in which contact (flotation) is possible from those in which it is not. The curve is derived by successive approximation and the accuracy is ±0.2 pH units and ± 5 mg. per liter of collector or depressant. Solution compositions for which it was shown experimentally that contact or flotation is possible are marked by a circle, those for which it is not possible, by a cross, and those for which it is doubtful by a cross within a circle. It is assumed that at all other solution compositions within (without) the curve, contact or flotation is possible (not possible). After testing in the collector solution, the mineral was removed, washed, and tested by the captive-bubble method in water, or floated in a cylinder with frother only. In this way the composition of solutions in which a mineral was conditioned but in which properties of the collector solution prevented contact or flotation can be defined. The composition of solutions in which conditioning was possible lie between the full and broken curve, and the experimental results are indicated by a square. The curves show the limits of composition of solutions in which flotation in a cell would be possible but many factors other than those considered in these tests determine recovery and grade of a given mineral in practice. Flotation Tests in 500 and 2000-gram Denver Submachines.--Melbourne tap water, containing 12 parts calcium, 6 parts

Jan 1, 1947

By G. Gutzeit

An inner complex is a cyclic chemical structure containing an inorganic cation that is bound simultaneously to several atoms in a single organic molecule; on the one hand by means of ordinary valence bonds (electron exchange), on the other hand through the action of the electric field thus created, which satisfies the so-called secondary valences. The relative positions of the salt-forming and complex-forming groups are such that most frequently a four, five, or six-membered ring results through this double attachment of the cation.1-6 The formation of inner-complex ring systems depends not only upon the nature and suitable position of the salt-forming and complex-forming groups for ring closure, but, to a great extent, also on the nature of the metallic cation entering the reaction. This selective character of chelate-forming organic compounds is one of their most interesting and most valuable properties. As a matter of fact, the largest number of their practical applications is based upon their specificity.4,7-l3 Once a chelate compound is formed, its character is definitely "organic" in nature. In other words, its properties are conditioned to a much larger degree by the carbon chains or rings than by the metallic atom. Many inner complexes are soluble in nonpolar solvents such as benzene, paraffin oil or carbon tetrachloride, while the chelate-forming reagent before closure of the metal-organic ring is water soluble. (Example: copper complex of salicyl-aldoxime') It is obvious that such particular properties as those indicated above can be utilized whenever specificity and practically complete binding of inorganic ions into an undissociable complex are required. One of the well-known applications of chelate-forming compounds has been the development of specific reagents in analytical chemistry, creation of the spot-test method,4,14-16 and the application of the same principles to the contact print method for determining minerals." Chelate-forming Compounds as Collectors In the field of flotation, where selectivity is often a quality of paramount importance for the collector, various workers have lately attempted to apply their knowledge of specific organic analytical reagents to this purpose. A. C. Vivian18 has concentrated cassiterite by using ammonium nitrosophenylhydroxyl-amine (Cupferron) C6H5NO(=NONH4). Holmanl9 has tested dimethylglyoxime for the flotation of nickel oxide minerals, while deWitt has shown in a series of systematic experiments that alpha-diox-imes were generally selective collectors for nickel ores. Taurin NH2(CH2)2S03H has been proposed for the concentration Of Oxidized lead ores.19 Diphenylthio-carbazone

Jan 1, 1947

By J. R. Low, M. Gensamer

During the course of an investigation into the drawability of automobile-body sheet steel, it became apparent that certain advantages would be possessed by a deep-drawing steel with a very low yield strength, but almost normal tensile strength, provided a reduction in yield strength could be accomplished without sacrifice of ductility and fine grain size. It would also be desirable to have this steel free from strainaging; that is, free from the tendency for the yield point to return after it had been eliminated by straining. It was known that wet hydrogen treatment acted to eliminate aging, but as carried out by other investigators, at relatively high temperatures, this treatment resulted in grain coarsening. It has been established by some of the experiments reported in this paper that all of these objectives can be accomplished by treatment in wet hydrogen at a low temperature, in the neighborhood of 720°C. The time of treatment is relatively short (about 3 hr. to completion with 20-gauge sheet) if the water content of the hydrogen atmosphere is made fairly high, say almost 30 per cent by volume. At this temperature, the grain size remains fine in the time required. After this treatment sheet reduced the usual amount by cold-rolling has a grain size of about A.S.T.M. No. 7. The yield point is completely eliminated, and the yield strength is reduced to a very low value, in the neighborhood of 15,000 lb. per sq. in. The stress-strain curve departs gradually from the straight-line elastic part after the fashion of nonferrous deep-drawing alloys. This elimination of the yield point is accompanied by a very low indentation hardness; for example, 32 Rockwell B or even lower. There is no aging as measured by increase in the yield strength upon aging at room temperature or for 3 hr. at 200°C., after stretching about 10 per cent in tension. Tensile strength is only slightly less than the box-annealed sheet, seldom dropping much below 40,000 lb. per sq. in. Elongation is practically unchanged, or increased slightly. The term yield point, as here used, refers to the phenomenon of heterogeneous deformation occurring at a substantially constant load, observed principally in annealed low-carbon steels. If such a steel is loaded in tension, the load increases steadily with elastic strain, suddenly falls, fluctuates slightly about some constant value for a time and then begins to rise again as deformation proceeds. The maximum initial load before the sudden drop is generally called the "upper yield point"; the value of the load where deformation proceeds at a

Jan 1, 1943

By Robert A. Stansbury

Keeping development ahead of retreat mining is a problem which occurs nearly everywhere longwall mining is used in the United States. As improved equipment technology has allowed the application of longwall mining to more difficult mining conditions, and with higher retreat rates, the problem has become more critical. Many factors determine development speed, including roof and floor conditions, mining heights, seam heights, and the number of entries. In an effort to maximize the rate of development and production from development sections, U. S. Steel's Gary District has used five entry, three entry, four entry and is planning two entry development panels at its different mines. With the introduction of various types of shield supports, it is now possible to utilize longwall mining in higher coal over 3 meters (10 feet), lower coal under one meter, in difficult roof conditions, and with soft floor. Improved shearers of 300 KW (400 HP) and more make cutting heights over 3 meters (10 feet) possible, and off pan shearers and improved Gleithobel plows make cutting less than 1 meter (40 inches) seam height possible. Longwall mining under these conditions puts an added strain on the ability to develop panels as fast as they are retreated. Poor roof conditions require a substantial amount of additional roof support to ensure that roof control in the head and tall entries will not hinder longwall retreat. The additional measures of longer bolts, resin bolts, point anchor resin bolts, roof mats, roof trusses, steel or wood cross bars, and roof grouting all place an additional burden on man power, installation time, and cost on the mining cycle. Additional roof bolting on development can cut the potential mining rate in half, and any roof falls cause significant delays to mining. Timbers and cribs can restrict ventilation and require more entries. Soft floor conditions can greatly impede development through tramming difficulties with shuttle cars and roof bolters, time required for cleaning and repairing roadways, and maintenance difficulties on equipment. High coal sometimes requires rib support to be Installed during the mining cycle, further cutting the mining rate. Mining low seams requires that roof or floor be mined in the head and tail entries as well as the track or tractor roadway entry to provide clearance of the longwall equipment. Mining this rock slows down the mining rate because of the extra material being mined and the extra wear and tear on equipment. To a large degree these conditions effecting development speed cannot be controlled.

Jan 1, 1981

By J. E. Forciea, R. W. Salmi

Operating and research personnel at U.S. Steel's Pilotac concentrator have evolved specifications for magnetic separators suitable for use in beneficiation of Mesabi magnetic taconite. These specifications were developed as a result of investigations into the operating and metallurgical problems at the Pilotac concentrator over a period of some ten years. This paper discusses primary magnetic separator specifications, but much of the information is also pertinent to secondary and tertiary magnetic separators. Of particular significance is the proposal of a new basis for specifying the magnetic field which includes consideration of both field strength and field gradient. Other areas of discussion include flowsheet service, operating conditions such as drum speed and pulp level, tank configuration, magnet strength including field gradient, sleeve bearing design, designation of corrosion resistant materials and other details that result in a metallurgically efficient machine that has low repair and maintenance requirements. The mechanical and metallurgical design of magnetic separators at the Pilotac plant, Minnesota Ore Operations, United States Steel Corp. has progressed from the original single-stage, belt-type machines to the present multiple-stage, drum-type units, In ten years of operation, the plant operating and research personnel, in consultation with manufacturers, have made design changes to improve mechanical, electrical and magnetic features to meet process needs as flowsheet designs developed and to incorporate new permanent magnet materials as they became available. Separator specifications were an end result of this effort. The latest specifications which were developed for the Minnesota Ore Operations' plant were not all-inclusive listings; they covered only those points indicated by plant experience. For example, magnet pole piece design and dimensions were not stated. The manufacturers were given freedom to use any design as long as the field pattern was as specified. The selection of the items to be included in the specifications was undoubtedly influenced by particular conditions at Pilotac such as composition of plant water, concentration characteristics of the ore, repair and maintenance facilities available and the research programs that had been conducted. Only the developments leading to the specifications for a primary or "cobber" magnetic separator are presented in this paper. However, the same general concepts are used to specify secondary and tertiary separators. The areas of interest discussed include flowsheet service, tank configuration, magnet design, bearings, materials of construction, and some minor mechanical details. FLOWSHEET SERVICE The primary magnetic separators in the Pilotac Concentrator flowsheet are located after the first stage of grinding as shown in Fig. 1.

Jan 1, 1965

By R. H. Wightman

THE following paper describes current mining practices of the Riverside Cement Co. at its Crestmore plant, Riverside, California. For a number of years the Riverside Cement Co. obtained its raw materials by surface quarry operations but after these deposits were exhausted for equipment available at that time, the company started underground mining. Mine workings were begun in 1927 to 1930 for the recovery of limestone by block-caving methods. GEOLOGY The bed of limestone that is being worked is a metamorphosed and recrystallized limestone, which is generally white in color and from medium to coarsely crystalline. This bed is fissured by water courses that vary from minute cracks to large areas. The bed has also been cracked by intrusions along the footwall and hanging wall. These walls are coarse-grained, gray, quartz granodiorite. The strike of the deposit is north and south and it dips to the east at an angle of approximately 50º. The bed is approximately 1700 ft. long, 270 ft. thick at right angles to the dip at the middle of the deposit and tapers to a thickness of approximately 100 ft. at each end. MINING METHODS The mine layout consists of four main levels with elevations as follows: 892 Collar of shaft. 800 Manway level used for ventilation, prospect purposes and as an entrance into the stopes. 700 Mining level where all material is extracted and on which are located the tapping grizzlies. This is the elevation from which all main cutoff stopes and undercutting work is started. 660 Haulage level where the limestone is drawn from transfer raises into the cars and is transported to the tipple by electric locomotives. 633 Level where all water is collected and which keeps the general water table below the working levels. A detailed description of the mine was given in U. S. Bureau of Mines Information Circular No. 6795, in June 1934. Current Block Development The first blocks to be caved were developed very much after the procedure followed in the copper mines of Arizona. This paper covers the ninth block to be caved. With a hard, tough rock like our limestone, it was found that some alterations in the development and control of draw in caving were necessary to secure better crushing effect and provide more safety for such secondary blasting as is required. Sequence of Block Development I. The fringes of the 800-ft. manway level are driven to confirm the diamond drill information and serve to determine the final location and development required for the block (Fig. I).

Jan 1, 1944

By D. A. Woodford

A number of observations have now been reported where the steady-state creep rate is apparently linearly dependent on the applied stress at high temperature and low stresses. This results in a creep rate greater than that predicted by extrapolation of high-stress data and has obvious practical implications. However, some of these observations are open to question. For example, the analysis by Harris and Partridge17 of the data of Greenfield et a1.18 was dependent on strain rates which, according to the original authors, were too low to be measured. Dr. Bernstein appears to have demonstrated a linear stress dependence at low stresses in two zirconium alloys. There are, however, a number of discrepancies in his treatment of the data and the subsequent theoretical analysis which require clarification. 1) It is incorrectly stated that steady-state conditions are revealed by a slope of unity on a plot of log i vs log (time). This objection is trivial if the author meant to say a slope of zero, although it is unclear how subsequent extrapolation was made to determine the steady-state creep rates at low stresses for the zircaloy-2. If the plot used was actually log c vs log (time), it is unlikely that a slope of unity would represent a constant creep rate. A plot of log (c - co) vs log (time), where c0 is the extrapolated intercept sf the steady-state creep rate on the strain axis, would have a slope of unity during steady-state creep. However, eo cannot be determined unless is is already known. 2) The author chooses to interpret his results based on the equation: where A, and B, are structure-sensitive parameters, Ql and Q, are the activation energies for the particular creep process, and n describes the sensitivity of the creep rate on stress. The first term represents a slip creep process and the second a diffusion creep process. However, it is stated later that "two distinct processes acting in parallel are involved". Eq. [I] surely represents two processes in series since each reacts to the total applied stress and t, is the sum of the individual creep rates. If the processes are acting in parallel, then the effective stress in each would be less than the applied stress. The component stresses would be given by sl + s2 = a but it is not clear how the magnitude of either, or the corresponding stress exponent, could be determined.

Jan 1, 1969

By J. B. Darby

In an investigation of various equiatomic alloys of transition elements, Dwightl did not find evidence for the CsC1-type ordered structure in VMn. More recently waterstrat2 has reported the occurrence of this structure in the alloy his sample had been homogenized at 1150°C and subsequently reannealed at 725°C after crushing to powder. The purpose of this note is to confirm the existence of the CsC1-type ordered structure in VMn and to report a lattice parameter. An equiatomic alloy was prepared by arc-melting under an argon atmosphere vanadium and electrolytic manganese having a purity of at least 99.9 pet. The composition was obtained by charging an excess of manganese and monitoring the weight loss until the stoichiometric composition was achieved; the assumption that the loss during melting was due to the vaporization of manganese appears to be a valid one.' The calculated composition of the sample prepared was 49.85 at. pct V and 50.15 at. pct Mn. Specimens taken from the fractured as-cast buttons were wrapped in molybdenum foil and encapsulated in quartz capsules under vacuum; there was no evidence of a reaction between the alloy and foil. The X-ray patterns were obtained using filtered copper or chromium radiation with a Straumanis-type Debye-Scherrer camera having a diameter of 114.6 mm. The CrKa radiation is best suited for detecting the superlattice lines since it overcomes the slight difference in scattering powers of the components by making use of the anomalies in atomic scattering factor which occur when the frequency of the radiation is close to the characteristic absorption frequency of one of the elements.394 A specimen in the as-cast condition, as well as one which had been annealed for 1 week at 900°C and water-quenched, gave a diffraction pattern for the disordered bcc solid solution. However, when samples were homogenized at 900°C for 3 weeks followed by a subsequent anneal at 700°C for 6 to 7 weeks and then water-quenched or furnace-cooled, the (loo), (1111, and (210) Ka superlattice lines were observed in films taken with chromium radiation. An ao = 2.904 * 0.001 was determined by a Nelson-Riley extrapolation from a film taken with CuKa radiation. The author wishes to thank Mr. J. W. Downey and Mr. L. J. Norton for carrying out the experimental portion of this investigation. This work was performed at the Argonne National Laboratory under the auspices of the U.S. Atomic Energy Commission.

Jan 1, 1963

By Dan Crackel, G. G. Ramos, Mark Heisel

INTRODUCTION Feasibility studies indicated that a cratering type stoping method was best suited to the character of the first ore block at Carr Fork. This method known as vertical crater retreat (VCR) has since been modified to a combination cratering and deck blasting using VCR drop raises for initial undercut development . The modified form retains many of the advantages of VCR while allowing high tonnage production blasts which have offset many of the disadvantages. FIRST CONCEPTS AND PREMISES Geologic Considerations The Steep Highland Boy (SHB) skarn orebody, the first of several blocks being developed, is a steeply dipping 70° to 90° limb of a syncline, with a width averaging 25 m (82 ft). The bed has a consistent east-west strike length of over 400 m (1300 ft) and extends from the surface to depths of over 1000 m (3300 ft). The footwall is highly fractured quartzite and the hanging wall grades from garneti te to limes tone and hornfe 1s. Because of the limestone in the hanging wall, the hanging wall appears more competent than the footwall. The ore is garnetite with lenses of massive sulphide and magnetite. The quartzite footwall is highly fractured not only because of the bedding but also due to the folding and intrusion of the quartz monzonite. This irregular footwall outline of some stopes in- creases the likelihood of excessive dilution. The principal ore mineral is chalcopyrite with some bornite. The garnetite ore is quite variable in terms of compressive strength and drillability. In addition to the sulphide and magnetite lenses, it is transected by clay- altered dikes and major and minor north-east faults. TABLE (1) gives the range and mean strengths of the rocks. Investigating Mining Methods Initial consideration of a suitable mining method centered around maximum safety and efficiency with minimum potential dilution. The following major methods were considered and investigated. Cut and fill mining was eliminated because of low productivity, the cost and problems associated with providing fill, and the relatively unsafe nature of the method. Sublevel caving was rejected due to the unpredictable cavability of the waste and the geometry of the ore body. Conventional sublevel or blasthole methods require excessive development, as fan and ring drills are limited to efficient drilling in the 18 to 25 m range (60 to 80 ft). Mining downdip with equipment drilling small diameter holes would have required eight separate extraction/drill horizons with crosscuts and associated excavation in the main ore block. The use of down the hole (DTH) machines cap- able of drilling 165 m (6g in) diameter holes

Jan 1, 1981

By Roswell P. Angier, Herbert S. Kalish, Henry H. Hausner

POWDER metallurgical methods as applied to zirconium are of great interest because they permit not only the fabrication of parts directly to shape with a minimum loss of material but also the utilization of scrap, and the metal may be processed at temperatures well below the melting point. There are two difficulties involved in the melting of zirconium: 1—High vacuum is necessary for melting, and 2—zirconium reduces nearly all oxides so that it is difficult to find a suitable crucible material. The purest material, zirconium crystal bar, is expensive, and the methods of subsequent fabrication are limited. Cold rolling or extrusion of zirconium crystal bar is suitable for making certain shaped parts, but where melting is involved, the purity of the metal is invariably decreased, and a method of casting to a definite shape does not seem to be feasible. Where it is necessary to hot roll, zirconium must be covered with a steel or copper jacket to protect it from the air. This is necessarily a costly operation. Where annealing of zirconium is necessary it must be conducted in a high vacuum. In an investigation of powder metallurgical methods for zirconium, the zirconium powder used should be characterized by the following properties: 1— Highest degree of purity, 2—uniformity in particle shape and particle size distribution, 3—low compression ratio, and 4—satisfactory strength of the compacted powder (green strength). Zirconium powders have been made by two methods: By the reduction of zirconium tetrachloride (ZrC1,) with sodium,2' *•B "nd by the reduction of zirconium oxide with calcium and calcium chloride." The first method represents one of the earliest attempts to make pure zirconium metal, and the sintered product from this powder is extremely brittle. The second method of making zirconium powder is far more successful, but the powder made in this way has an extremely low apparent density and, therefore, a high compression ratio which makes it difficult to use it for powder metallurgical purposes. For these reasons the above-mentioned zirconium powders were not used in this investigation. To obtain sintered zirconium compacts of highest 'purity and good ductility, it was first necessary to produce a suitable powder. Pure zirconium has been made chiefly by two methods. The iodide method, from which the product is "crystal bar" zirconium, was developed first.'." By this purification process very soft, pure, and ductile zirconium metal can be produced. The second method, developed by the U. S. Bureau of Mines, is the reduction of zirconium chloride with magnesium." The sponge zirconium thus produced is also soft, pure, and ductile.

Jan 1, 1952

By Hans Neuberger

INTRODUCTION IN our everyday life, visual perception plays perhaps a more important role than any of the other senses with which we are equipped by nature. It is, therefore, quite understandable that the average person associates 'with the term "atmospheric pollution," clouds of dust, palls of smoke or deposits of soot, phenomena which are so familiar to the residents of industrial cities. On the other hand, "air" is usually considered the prototype of the invisible, of the intangible, and any suspensions in the air which do not conform to this concept, are regarded as foreign to the atmosphere and thus as "pollution." According to Webster, the term "pollution" implies uncleanness, impurity, in short, something undesirable. Although the scientist often accepts popular concepts, he is generally inclined to suspect that apparently "obvious" phenomena imply, literally, "more than meets the eye." To show that this suspicion is also justified with regard to atmospheric pollution, is the objective of this discussion. It will be shown that what seems foreign to the air at first sight, is by nature an integral part of it, and that the more important aspects of pollution generally escape attention. THE ATMOSPHERIC CONSTITUENTS We can distinguish two classes of atmospheric constituents: the permanent gases, chiefly nitrogen, oxygen, traces of argon, neon, and others, and the variable constituents which include water in its different states, carbon dioxide, ozone, and various suspensions, either in gaseous, liquid or solid form. These suspensions, known by the collective term "Aerosol,"20 will be considered in detail. DUST There are two general types of aerosols: the first type is represented by the socalled "neutral" particle 3, commonly known as dust and experienced by everyone, as it is the more conspicuous type of suspensions. . It often represents a special problem to the mining engineer, the mechanical engineer, the industrial engineer, and many other professional men. Dust consists of finely divided solids derived from weathering, drilling, handling and preparation of rocks and coal. Dust may also consist of organic or inorganic particles resulting from manufacture of a variety of products such as flour, rubber, lime and steel, from traffic on land be it on the highways, on rails or in city streets, from decomposed vegetation or from volcanic eruptions. Perhaps the most reviled member of this class of suspensions is the soot and fly ashes from coal fires and other combustion processes. The cosmic source of dust, namely the injection of meteoric matter into the atmosphere, is of minor significance because the concentration of particles is exceedingly small despite the relatively large mass of material invades the earth’s atmosphere from space

Jan 1, 1948

By R. S. Shoemaker, F. W. McQuiston

RECOVERY METHODS AS RELATED TO PROPERTIES OF SILVER ORES The earliest metallurgical process for treating silver ores was amalgamation with mercury which was in use in the early 1500's. Closely following was the development of the Patio process for treating ores at Pachuca, Mexico. Silver often occurs as the native metal and in deposits associated with other metals such as gold, copper, lead and zinc. Principal silver minerals include compounds of sulfur, antimony, arsenic, and copper. Silver chloride, and argentiferous galena are also prime sources. Native silver and the chloride characterize the oxide zone of most deposits. Native silver can be concentrated, amalgamated, or cyanided. Silver chloride rapidly dissolves in cyanide without oxygen. Oxidized silver ores containing the higher oxides of manganese are generally refractory to metallurgical treatment. A refractory compound of manganese and silver is formed, probably a manganite , which is insoluble in cyanide solutions. Argentite is the predominant silver mineral. Other important economic minerals are native silver, argentiferous galena, cerargyrite, pyrargyrite and tetrahedrite. Argentite dissolves slowly, the reaction being reversible requires an excess of cyanide. Argentite with disseminated fine grained gold occurring in quartz veins with minor amounts of chalcopyrite and galena may be cyanided directly after grinding, with high silver and gold recoveries. The flowsheet adapted to this type of ore is the Minas de San Luis, Tayoltita cyanide plant, which treats a high grade argentite silver ore containing gold. It is a standard cyanidation circuit but employs long periods of agitation contact for the high silver sulfide content ore. Lead-zinc base metal semi-oxidized- complex ores in pipes and chimneys are replacement deposits in limestone at El Mochito Mine, Honduras. Mineralization comprises galena, cerussite, anglesite, sphalerite, calamine, and smithsonite. The silver content of about 16 ounces occurs as native silver globs, wire and the mineral argentite. After flotation of lead and zinc concentrates, the tailings are cyanided for gold and silver recovery. The great Huelva pyritic copper deposits of Spain carry a little gold and silver. At Cerro Colorado, these metals were concentrated above the chalcocite zone into the so-labeled Mgossanu. This material with a content of 0.08-0.09 oz Au and 1.50 oz Ag per ton is amenable to cyanidation. See Cerro Colorado flowsheet. In southern Hidalgo, about 60 miles north of Mexico City, are the great silver--gold veins of one of the foremost silver mining districts of the world. Real del Monte, Pachuca. The mineralized area consists of flow rocks and intrusives. The oxidized ores carry pyrites with oxides of iron and manganese and other minerals, silver and gold. The first zone contains

Jan 1, 1975

By David R. Poirier

Activity data of carbon as a function of both temperature and composition throughout the stable austenite range is correlated by mearts of an equation derived from a quasi-chemical model. The carbon activity data of austmite for temperatures between 800° and 1200°C are utilized in conjunction with the activity of carbon calculated for the y solidus using the activity of carbon in liquid iron and published austenite-liquid equilibria. The results agree very well with Chip-man's correlation; however, a small difference in the activity of carbon in the high-temperature range of the austenite field is evident. Excellent agreement is found for the heat of solution of graphite in infinitely dilute austenite; from this study the value is 10,550 cal as compared with Chipman's value of 10,680 cal. AS part of a program to study microsegregation in dendritic solidification of ternary Fe-C-Cr alloys, it was desirable to be able to describe the equilibria between austenite and liquid iron in Fe-C-Cr alloys. In this regard, it was necessary to correlate existing data on the activity of carbon in Fe-C austenite as a function of both temperature and composition. At that time, Chipman's analysis1 of the thermodynamics of binary Fe-C austenite was not available. It will be shown that this study and Chipman's study agree rather well throughout the stable austenite range of temperature and composition; however, some small differences appear at temperatures greater than the eutectic temperature. Benz and Elliott 2 presented isoactivity lines for austenite superimposed on their revised Fe-C phase diagram. Using an expression from Darken and Gury 3 representing Smith's4 activity data between 800" and 1000°C, they found that the activities extrapolated above 1000°C to the solidus did not agree with the activities determined from the corresponding liquidus compositions. It is the purpose of the following argument to reconcile carbon activity data of austenite with the activity in liquid Fe-C alloys as determined by Rist and Chipman. 5 In addition, a simple analytical expression is sought for computational convenience. ACTIVITY DATA OF CARBON IN ZRON Fig. 1 shows the activity of carbon in Fe-C austenite as determined by Smith, 4 Schenck and Kaiser, 6 Scheil et a1.,7 and Bungardt et al.' The lines are merely drawn to separate the data into the respective isotherms. These data are inadequate to determine the activity of carbon at temperatures greater than 1200°C. The activity coefficient in Fe-C liquid alloys was assumed by Rist and chipmans to obey the following

Jan 1, 1969

By Irving M. Symonds

COMPAÑIA Minera de Peñoles, S. A., at its Avalos unit operates a lead-zinc concentrator having a capacity of about 600 short tons per day. Lead and zinc concentrates are made by flotation methods. The concentrator is at Terminal de Providencia, in the state of Zacatecas, some 70 miles south of Saltillo, Coahuila. The Peñoles-Avalos railroad operating between the plant and Estacion Avalos, a distance of 6 miles, makes connections with the Coahuila and Zacatecas railroad, which in turn connects with the Nacionales de Mexico at Saltillo. The three railroads are each of different gauge, requiring the transfer of all supplies and concentrates at each junction. The mill operates on company ores, on ores from leased mines, and as a custom mill. The custom business is very small. The lead concentrates are shipped to company smelters at Monterrey, Nuevo Leon and Torreón, Coahuila. Since the European war, all zinc concentrates have been shipped to the United States. ORE TREATED The major source of ore supply is a group of four mines owned or leased by the company, some three miles south of the mill in the mountains, from which the ore is delivered to the mill by a gravity aerial tramway. Custom ore comes in by rail. The ores occur in chimneys. The upper levels contained oxidized siliceous ores of lead, copper, silver and gold, with varying amounts of zinc. These ores were direct-smelted. In the first two years of operation a good deal of the tailing loss was caused by the oxidized content of the ores milled. Much of the ore in the transition zones between the oxides and sulphides was not mined. The ores now being milled are clean, hard sulphides in a limestone gangue, with only occasional contamination of oxides. The lead and zinc sulphides are of coarse structure and are freed even above flotation sizes. The galena is usually "steel" colored, easily and quickly floated. When there is any oxidation, it is usually on the coarsest crystals. The zinc minerals vary a good deal in color; a resin sphalerite predominates but there are varying shades of brown marmatites. On an average, the zinc sulphides contain 64 per cent zinc. The only common copper mineral is chalcopyrite. Little is known of the occurrence of gold and silver. Waste minerals are mainly limestone and pyrite, both of which are barren. The ores vary from 20 to 35 per cent pyrite. Mill heads for the year 1940 and the first eight months of 1941 are given in Table I. [ ]

Jan 1, 1942

By W. R. Opie

The object of this paper is to show the manner in which typical electrodeposits of hexagonal-close-packed metals—zinc, titanium, and zirconium—tend to form. The conditions of electrodeposi-tion markedly affect the nature of the deposits in regard to crystal size, orientation, and appearance. No attempt is made to correlate cell conditions with deposit quality but, rather, characteristic types of deposits were selected and a study made to show the relationship between outward appearance and crystal structure. The zinc deposits were made in aqueous electrolytes and the titanium and zirconium deposited from fused salt baths. ZINC deposits studied were made in the American Smelting and Refining Co.'s Central Research Laboratories. They were representative of bright, shiny, smooth deposits, which can be obtained by using proper current densities and electrolyte addition agents, and of deposits which are dull and tend to be nodular. Four deposits were selected which ranged from smooth and bright to very nodular and dull, and their classifications are shown in Table I. These were examined microscopically and were found to differ quite markedly in outward surface structure and in microstructure. The outward surface variation is illustrated in Figs. 1 to 4. At X50 the texture could be seen to progress from granular to platelike to smooth. The microstructures of the deposits' cross sections from starting sheet to outer surface are shown in Figs. 5 through 8. The dull nodular deposits (sample Nos. 1 and 2) show some tendency for acicular growth. The platelike sample (No. 3) shows tendency for columnar growth development and the smooth deposit (No. 4) has a well developed columnar structure. Back-reflection X-ray patterns of the deposit surfaces revealed some interesting information. The crystal orientation was random in all deposits except the smooth deposit. Fig. 9 is a typical back-reflection pattern of a nodular deposit. All planes are reflecting in the proper relative intensity. The pattern of the smooth deposit is shown in Fig. 10. The only planes which reflect are the (10.4). This series of planes is in the right position, with the FeKa radiation used, to satisfy the Bragg equation if the basal planes {00.1) are at right angles to the X-ray beam. The results were interpreted to mean that in the bright smooth deposit preferred orientation has occurred with the basal hexagonal planes oriented in the plane of the sheet but with all other planes randomly oriented around the c-axis.

Jan 1, 1957

By J. R. Long, E. T. Hayes, D. C. Root, R. S. Dean

The U. S. Bureau of Mines has recently reported on the development of a process for preparing pure ductile titanium in substantial quantities1 and on the physical properties that may be attained in the metal, when consolidated by powder metallurgy methods and fabricated by certain hot and cold-working procedures.2 The high physical properties (Table I), combined with excellent corrosion resistance and light weight, will lead no doubt to appropriatc applications of the metal. In any application, methods of joining will be of considerable importance. The relatively high activity of the metal toward the common gases raises the question of weldability and conditions that might be required for successful welding. Since hydrogen, oxygen, and nitrogen embrittle the metal, it should be protected from these gases at elevated temperatures. This was demonstrated by a few preliminary trials of arc, gas, and resistance welding. In these trials only the resistance method proved to be immediately- applicable. While atomic: hydrogen welding of titanium may be successful in some instances, a considerable amount of development work will be required to prove its worth. In addition, it would be suited only to small assemblies that could be heated subsequently in a high vacuum to remove embrittling hydrogen. Heli-are methods likewise would be limited to small assemblies, which could be completely protected by a helium atmosphere. It was quite apparent that titanium required more protection than was afforded by the normal flow of helium gas used for welding magnesium and aluminum. The hot metal is attacked by oxygen and nitrogen, and the rapid diffusion of the oxide into the metal prevents the formation of a protective coating and requires the helium atmosphere to be maintained until the weld has cooled nearly to room temperature. The preliminary work indicated that titanium could be successfully spot-welded without deterioration of the metal and that the microstructures of the welds were normal, exhibiting good bonding, and no oxidation. The high resistivity of titanium (53 microhms per cu. cm.) suggested that it would behave somewhat like stainless steel and allow considerable latitude in the several welding variables. The results reported here are intended to give a general picture of the effects of varying welding current, welding time, and tip pressure on single spot welds made on several different thicknesses of titanium sheet. The work was undertaken to demonstrate the feasibility of welding titanium rather than as an exhaustive study of spot welding. There are, therefore, a number of factors that will require further investigation to establish the specific controls required for actual applications.

Jan 1, 1947

By J. R. Long, R. S. Dean, D. C. Root, E. T. Hayes

The U. S. Bureau of Mines has recently reported on the development of a process for preparing pure ductile titanium in substantial quantities1 and on the physical properties that may be attained in the metal, when consolidated by powder metallurgy methods and fabricated by certain hot and cold-working procedures.2 The high physical properties (Table I), combined with excellent corrosion resistance and light weight, will lead no doubt to appropriatc applications of the metal. In any application, methods of joining will be of considerable importance. The relatively high activity of the metal toward the common gases raises the question of weldability and conditions that might be required for successful welding. Since hydrogen, oxygen, and nitrogen embrittle the metal, it should be protected from these gases at elevated temperatures. This was demonstrated by a few preliminary trials of arc, gas, and resistance welding. In these trials only the resistance method proved to be immediately- applicable. While atomic: hydrogen welding of titanium may be successful in some instances, a considerable amount of development work will be required to prove its worth. In addition, it would be suited only to small assemblies that could be heated subsequently in a high vacuum to remove embrittling hydrogen. Heli-are methods likewise would be limited to small assemblies, which could be completely protected by a helium atmosphere. It was quite apparent that titanium required more protection than was afforded by the normal flow of helium gas used for welding magnesium and aluminum. The hot metal is attacked by oxygen and nitrogen, and the rapid diffusion of the oxide into the metal prevents the formation of a protective coating and requires the helium atmosphere to be maintained until the weld has cooled nearly to room temperature. The preliminary work indicated that titanium could be successfully spot-welded without deterioration of the metal and that the microstructures of the welds were normal, exhibiting good bonding, and no oxidation. The high resistivity of titanium (53 microhms per cu. cm.) suggested that it would behave somewhat like stainless steel and allow considerable latitude in the several welding variables. The results reported here are intended to give a general picture of the effects of varying welding current, welding time, and tip pressure on single spot welds made on several different thicknesses of titanium sheet. The work was undertaken to demonstrate the feasibility of welding titanium rather than as an exhaustive study of spot welding. There are, therefore, a number of factors that will require further investigation to establish the specific controls required for actual applications.

Jan 1, 1947

By J. M. Hodge, H. M. Reichhold, R. D. Manning

The work reported in this paper represents the first of a series of investigations of the factors governing notch toughness in ferritic materials. This paper is concerned with two of these factors, namely, the effect of ferrite grain size, and the effect of an alloy content of 3.64 pct nickel. Every effort has been made to hold other variables constant in order to isolate the effects of these two. The compositions chosen for study were 0.02 pct carbon in order to eliminate the variable of carbide distribution, one steel being a plain carbon steel and the other alloyed with 3.64 pct nickel. Both steels were fully killed with silicon, without an aluminum addition, so that the variable of deoxidation practice was held constant. Finally, all samples were water quenched from 1200°F and tempered 24 hr at 300°F in order to hold the quench aging variable constant and to decrease the tendency for grain boundary carbide precipitation. The ferrite grain size was varied by heat treatment over the range of A.S.T.M. grain size numbers of about 2 to 6 in each steel so that the effect could be evaluated individually and the notch toughness of each steel could be compared at comparable ferrite grain sizes. Materials and Experimental Procedure MATERIALS The materials for this investigation were obtained from Battelle Memorial Institute as 250 Ib induction melts which were forged into 134 in. square bars and then rolled into 0.6 in. square bars. Both steels were deoxidized with silicon, the aluminum content being held to a minimum. Check analyses of these materials are shown in Table 1. HEAT TREATMENT FOR GRAIN SIZE The grain size was varied by varying both the cooling rate and the austeni- tizing temperatures. The heat treatments used and the corresponding grain size values are tabulated in Table 2. A semicontinuous network of grain boundary carbide was observed in the microstructure of both the plain carbon and nickel steels in the as rolled condition and an additional heat treatment was necessary to eliminate this variable. Therefore, all samples were water quenched from 1200°F and tempered 24 hr at 300°F as a final treatment before testing. This heat treatment served to eliminate to a great extent the grain boundary carbide network and to hold the quench aging effect constant. IMPACT TESTING Standard keyhole Charpy impact tests were machmed after heat treatment. A bath of acetone and dry ice was used for refrigeration of the samples down to temperatures of —94°F (—70°C) and a bath of either methyl-cyclohexane or isopentane, cooled by

Jan 1, 1950