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By N. B. Gray, R. V. Culver, W. S. Boundy, N. W. Stump

The kinetics of sulfation of single crystals of lead sulfide to lead sulfate have been studied between 969" and 1073°K in gas atmospheres of known composition using a thermobalance technique. The data are described by an equation derived on the basis that diffusion outward through the Product layer is the major controlling step. The rate of sulfation is linearly related to the logarithm of the sulfur trioxide partial DESPITE its industrial significance the oxidation of lead sulfide has received limited attention. The oxidation reactions have been studied using beds, briquettes, single crystals, or thin films of lead sulfide. Lead oxide and lead sulfate (PbSO,) were formed when Mclntoshl and Gardner2 roasted beds of galena pressure and the temperature coefficient of reaction is 40 ± 5 kcal per g mole. Gold marker experiments show that the sulfate layer grows by outward movement of ions through the sulfate layer. Initially the PbSO, adheres to the PbS but later forms an irnpewious spheroidal envelope; PbS vaporizes and pb2' ions diffuse through the envelope to react at the external surface. in air at temperatures up to 800°C. In a more extensive investigation, Tchizhykov3 obtained Pb, PbO, and PbS04 in accordance with Eqs. [1] to [4], when a bed of -200 mesh galena was oxidized in O2-N2 mixtures at 700° to 900°C.

Jan 1, 1968

By Nicholas J. Palethorpe

BACKGROUND Before addressing the above topic in any detail, it is pertinent to provide some background on Australia for those people who have not been there or who have a limited knowledge of our continent. Australia is approximately the size of the continental U.S.A. (excluding Alaska) covering an area of approximately 7 million square kilometres. It has a very dry climate which has led to a concentration of people in major cities scattered around the continents perimeter. Australia's population is currently approximately 15 million. Of the work force of 6.3 million, 72% work in tertiary industries, 20.2% in manufacture, 6.5% in agriculture and 1.3% in mining. Agriculture accounts for 46% of exports, mining for 31% and manufacturing for 23,. Economic activity is based on:- Agriculture This is capital intensive and covers extensive areas and is reliant on low cost farming. A.range of foods and fibres are produced with over 70% of production being exported. Such products are of course subject to the usual vagaries of world market demand and market access, particularly in regard to the operation of trade blocks such as the E.E.C. Mineral Resources A wide range of minerals and an abundance of iron ore, coal, gas and uranium resources provide an increasing volume of exports. However, Autralia's oil resources at present only supply approximately 70% of local requirements. Industry This is diverse and encompasses the processing of agricultural products and mineral ores as well as helping to supply the consumer and capital goods needs of the whole community. However, the small scale of local markets, the geographic isolation of Australia and relatively high wage costs have limited the scale of Australia's industry. Advanced technology has overcome some of these difficulties and high tariff and import quotas protect local producers from the full force of international competition. In 1980/81 Australia's Gross Domestic Product amounted to $130 billion with approximately 24% of this being devoted to investment. In the past decade Australia has experienced inflation rates ranging from 5% to 17% and only modest real growth rates ranging from 0.4% to 5% per annum. We have also experienced, as have many other industrialised nations, continuing wage and price increases. Unemployment presently stands at 6%. MINERAL DEVELOPMENT As the above figures indicate, Australia's continuing prosperity is very dependent on the mineral and agricultrual sectors of our economy. The dependence on these sectors is highlighted by the table below which indicates our position in a global context. [Australian Production of Minerals in a World Context Western World % Total Western World Position Mineral Production 1980 1st Rutile 75 Ilmenite 31 Zircon 70 Bauxite 36 Iron Ore 11 Tungsten 14 2nd Lead (Conc.) 15 3rd Manganese Ore 14 Brown Coal 11 (1979) Zinc (Conc.) 10 4thSilver (Conc.) 10 Nickel 6 5th Tin (Conc.) 5 6th Black Coal 5 Gold 2 Source: Mining Annual Review 1981] The total value of all mineral and fuel exports in 1980/81 is estimated at $5.9 billion. This prominence in the world mineral production has largely been achieved in the last 15 - 20 years. In fact, in the early 1960's, Australia had only 2 major mining export centres, Broken Hill in New South Wales and Mt. Isa in Queensland. This growth is highlighted by the fact that in 1963, for example, we exported only 9 tonnes of iron ore and less than 4 million tonnes of coal. In 1980/81 we exported 75m. tonnes ',of iron ore (valued at $1,117m.) and 47m. tonnes of coal valued at $1,965m.). The growth in our mineral industry has come about because of a number of factors. Abundance of Mineral Resources We are particularly well endowed with mineral resources, as indicated below.

Jan 1, 1982

By G. Birkbeck, T. C. Wells

Pearlite morphology in three commercially produced, low-carbon steels has been studied using optical and electron microscopy. A reduction in the cooling rate from 600° to 6°C per hr increased the interlamellar spacing but had little effect on pearlite content. The form of the lamellae was also assessed in terms of a new parameter, the ratio of lamellae length to interhmellar spacing. The variation of this parameter with cooling rate depended on steel composition. For each steel, it would appear that an optimum cooling rate exists at which lamellar pearlite can be produced to the greatest extent, though not necessarily the same extent in different steels. PeARLITE morphology depends principally on steel composition, prior austenite grain size, and either cooling rate or isothermal transformation temperature. Alloying with manganese,'" fine grain size,374 and slow cooling rates reduce the likelihood that a well-developed lamellar structure will be produced. Instead, imperfect structures usually consisting of partly globular carbides are formed in a ferrite matrix. Such structures have been described as granular.1,2,5 degenerate,6 or semi4-pearlite. Manganese additions also progressively lower the eutectoid temperature and the carbon concentration at the eutectoid so so that, for a given carbon content. the pearlite fraction is increased as manganese is added. While the effects of manganese are understood in a general way, quantitative studies of pearlite morphology have been carried out mainly on steels of eutectoid composition;9 little quantitative data is available for low-carbon steels. Certain anomalies exist in the behavior of steels containing -1.5 pct Mn, however. The pearlite morphology in niobium-treated steel differs from that which is generally accepted as typical of low-carbon/manganese steels in that a reasonably well developed lamellar structure is sometimes observed. In the present work, the effects of changes in cooling rate from 600° to 6°C per hr on the pearlite morphology in three commercially produced, low-carbon steels have been studied by both optical and electron microscopy. I) MATERIALS The steels were of the following types: 1) 0.1 pct C, 0.4 pct Mn steel (En 2, a composition similar to specification SAE 1010); 2) niobium-treated, 0.2 pct C, 1 1/2 pct Mn steel (BS 968:1962); 3) silicon-killed 0.2 pct C, 1 1/2 pct Mn steel (En 144, a composition similar to SAE 1320). The chemical analysis for each steel is given in Table I. To facilitate the comparison of pearlite morphology in the three steels, steels 1 and 3 (which were obtained as 1/2-in. plate and 1-in.-diam bar, respectively) were hot-rolled in the laboratory to $ in. thickness, finishing at around 850°C. The BS 968:1962 was received as 1/8-in. plate finished at 885°C and was not further worked. Specimens from each steel were heat-treated in vacuo at 950°C for 1 hr and cooled at rates of 600°, 60°, and 6°C per hr. 11) EXPERIMENTAL Pearlite contents were determined by point counting (500 points) on longitudinal sections mechanically polished and etched in 2 pct nital. Pearlite morphology is usually considered in terms of interlamellar spacing. For pearlite colonies randomly distributed in space and having a true, constant interlamellar spacing So Pellissier et al.9 determined the distribution curve for the apparent spacings of the lamellae on a random section plane. The areal fraction fs of the pearlite colonies occupied by apparent spacings up to a limiting value S is given by:

Jan 1, 1969

By Hokuichiro Ohmachi

INTRODUCTION Metallic minerals have been formed only through complex geologic processes which took place at certain stages of the earth's histrory. Their concentration, abundance, and distribution are, therefore, restricted geologically, and very small in global scale. Ore is a mineral deposit or mineral concentration from which metals can be economically extracted by the contemporaneous technology. By this definition, several factors should be considered before any mineral deposit is regarded as an ore. The grade of mineral concentration and the scale of the reserve are most important. Demand for the metal and its price are the other factors. Advancement of technology in mining and extraction are also vital. Copper, for example, is now commonly extracted from the ores containing less than 0.3% of the metal. However, in the 1700's the common minerable grade was about 13%, and in the 1900's between 5 to 2.5%. This decrease in minerable grade is a function of not only the demand for copper, but also technological progress in mining and metal extraction in this case. Availability of ores has recently been subject to political factors, which were not the primary concern in the past. The petroleum of the Middle East is the prominent example. The metallic minerals are classified into three categories. The first one is the minerals free from these factors mentioned above. Iron and manganese belong to this category. The second category include aluminum, copper, nickel, cobalt, titanium, lead and zinc. These metals can be provided by the future progress in technology which enables the use of lower grade deposits. The third one represents the metals whose occurrence is geologically limited, and, thus, subject to the political factors. Niobium and tantalium are the example. In this article, I discuss these minerals in detail to give an outline of the factors which brought their concentration, distribution and availability. SELECTED MINERAL CONCENTRATIONS Iron Major iron ore deposits are the features of the relics of ancient continental crusts. They are found in all the continents where the Precambrian rocks expose. They do not occur in the oldest rocks (3,000my old) nor in the youngest ones (600my old). They are sedimentary rocks, normally, exhibiting alternations of bands of iron oxides (magnetite and hematite) or iron silicates (especially greenalite), and bands of silica, variously described as jasper, quartzite and chert. The best known banded iron ore deposits exist in the Lake Superior region of the North America, and their distribution extends at intervals to Labrador of Canada. Other examples occur in the U.S.S.R. Brazil, Venezela, India, the mainland China, and southern and western Africa (Liberia and Guines) (Table 1). Recently large deposits have been discovered in the Hammersley region of the western Australia, and northern and central region of Brazil. These ore deposits were originally formed in shallow seas where simple but abundant life existed. After the deposition, enrichment processes , related to tropical weathering, have brought about wholesale removal of silica to produce the deposits of best quality. Ores with 50-60% iron represent the best products in the Precambrian fields. Since local reserves of this high grade ores approach to exhaustion, benefication processes have been used effectively to upgrade much leaner ores (for example, taconite with 20-25% iron in Minesota, U.S.A.). There are two other types of iron deposits. Ironstone, a sedimentary rock containing goethite, chamosite and siderite, first appeared in early Paleozoic times in the stratigraphic record, and reached its Zenith in the Jurassic. Similar bedded iron deposits are found in the belt from the Cleveland Hills to Oxford in England, and in the "minette" oolitic ores of Alsace-Lorraine in Luxenburg and France. The iron content of these ironstones seldom exceed 30%, but they usually contain calcite and are self-fluxing. They also have phosphorous as undesirable impurity. Because of the grade and impurities, they require more fuel than the Precambrian ores. The third type of iron ore is associated with igneous activity and consists of magnetite and some hematite, and apatite. This deposit is believed to be a product of magmatic differenciation. It occurs in Kiruna of Arctic Sweden. The iron ore, therefore, present no global shortage problem. They extend to considerable depths. Their concentration is largest among the metals. If low grades were treated, the resource can be stepped up much substantially. Manganese Manganese is a ferro--alloy metal, thus, essential to the manufacture of sound steel. Manganese comes from manganese oxide and silicate ores. Many minerals contain manganese, but only a few oxides, silicates, and, in some places, carbonates (rhodecrosite) are mined as ore. Types of manganese deposits are bedded, massive,

Jan 1, 1982

By W. W. Vaughn, R. H. Barnett, E. E. Wilson

Soon after the search for uranium ores on the Colorado Plateau began in earnest, thousands of feet of drill core ranging from 1 1/8 to 2 1/8 in. diam became available for study. Although significant advances had been made in the technique of quantitative gamma-ray borehole logging, instrumentation was in the development stage, and complete reliance could not be placed on gamma-ray logs alone to interpret quantitatively the meaning of radioactivity in a drillhole. A method that would be faster than chemical analysis and still give reproducible and reliable results for various drill core sizes was desirable to provide additional information on the enormous footage of drill core being accumulated. A solid phosphor scintillation drill core scanner was designed and constructed. Basically the instrument was developed to measure radiation from a drill core which would not be clearly recorded by a gamma-ray logger using a Geiger tube as the sensitive element. Such data would be beneficial in constructing isorad maps to delineate ore-bearing zones. A calibration in the range 0.01 to 0.1 pct eU.,O, was provided; above 0.1 pct eU3O8 gamma-ray logs were available and were being used to calculate grade and tonnage of ore reserves. The core scanner, however, has been used to estimate equivalent uranium content of ore-grade materials containing as much as 2.2 pct eU3O8 with an accuracy of ± 10 pct, the sample being in the form of a BX drill core. Actually, an apparent calibration of eU3O8 vs counts per unit time is a straight line with a slope that is a function of the sensitive element and the geometry of the counting assembly. A true calibration that will show the expected departure from a straight line is due principally to the random nature of the pulse from a radiation source and the nonlinearity of the electron circuitry. Design and Construction: Three methods of detecting radioactivity were considered and applied in developing the core scanner now in use: 1) the Geiger tube, 2) liquid scintillation phosphors, and 3) solid scintillation phosphors. The desired sensitivity and long-term drift characteristics needed for this operation could be attained only by using solid scintillation phosphors. All three methods are discussed. Before scintillation counters were common, nine beta-gamma sensitive Geiger tubes 7/8 in. diam by 12 in. long were used, arranged to surround the drill core with tube axes parallel to the axis of the core. This arrangement of Geiger tubes was en- closed in a lead shield 1 in. thick, and provision was made to slide a 6-ft length of drill core manually into the counting chamber, one foot at a time. A count for each segment was taken with a scaler while the core remained stationary. The equivalent uranium content of the different sections of drill core could then be estimated with the aid of a calibration curve of counts per unit time vs percent equivalent uranium (eU). In rare cases the effects of the radioactivity concentrated in small areas within the core introduced errors in the readings made with the Geiger tube arrangement owing to the geometry of the measurement. The variability of counting rate due to a localized concentration of radioactivity in a spot in the wall of a drill core is illustrated in Fig. 1. This effect and the inherent low efficiency of the Geiger tube were considered major disadvantages of this counting arrangement. When liquid scintillation phosphors became available the core scanner in Fig. 2 was constructed to make a more accurate measurement of the equivalent uranium content of a sample. This instrument contains about 4 liters of liquid phosphor in a stainless steel coaxial cylinder 1 ft long, with inner and outer walls 0.060 in. and 0.125 in. thick, respectively. Four end-window type photomulti-plier tube with cathodes of 2 in. diam, immersed in the solution at right angles to the axis of the core, were used to observe light flashes in the phosphor. The liquid phosphor offered equal sensitivity to radiation originating at any point in the enclosure and represented geometrically the optimum in design. However, providing a semi-permanent leak-proof seal between the glass envelope of the phototube and the metal walls of the container proved to be a serious problem in constructing the equipment. The most effective seals were especially machined O-rings from sections of large tygon tubing. The tygon took a permanent set owing to cold flow characteristics and in most cases sealed completely. The light absorption characteristics of the liquid phosphor changed gradually with time, and after one month the counting rate had decreased to half the original value. The most sensitive liquid phosphor tested proved to be a solution containing 4 g of 2.5-diphenyloxazole and 0.01 g of 2-(1-naphthy1)-5-phenyloxazole per liter of toluene. With fresh solution in the chamber and with all photomultiplier tubes operating in parallel, the counting rate contributed by any one of the four photomultiplier tubes was about 85 pct of the counting rate from a single tube operated individually. From these observations it was concluded that owing to coincident loss and light attenuation within the liquid phosphor, the apparent sensitivity could not have been materially increased by additional phototubes. However, this approach to core

Jan 1, 1960

By K. S. Lane

The problem of stability of slopes in reservoirs is one of real interest in civil engineering. The problem is whether the valley walls will remain stable or whether they are likely to slide as conditions are changed by storage of water in the reservoir. If major slides are indicated, as on the walls of relatively steep canyons, one must estimate whether they will be so located and of sufficient size as to interfere with operation of the reservoir-as by blocking the outlets, or by displacing sufficient water to over-top the dam in a huge wave. Some cases involve problems in soil mechanics for slides in earth or weaker rock; other locations need the assistance of rock mechanics for slides in harder rock. While this is not a new problem, attention has recently been focused on its importance by the hugh landslide into the Vaiont reservoir in 1963, which claimed the lives of over 2000 people and forced abandonment of the dam and powerhouse. VAIONT RESERVOIR SLIDE Fig. 1 shows Vaiont Dam in Italy which is a double curvature arch, 875 ft high, located on a tributary of the Piave River, north and west of Venice. When completed in 1960 it was the highest arch dam in the world. In 1960 a sizable landslide (some 700,000 cu yd) occurred on the left abutment a short distance above the dam. Following this, the reservoir was held down for construction of a by-pass tunnel through the right valley wall to insure connection with the upper end of the reservoir in event of further slides. In October 1963 a giant landslide occurred on the left valley wall, over a width of some 14 miles (see Fig. 2). Over 300 million cu yd slid into the reservoir, displacing the water and forming a hige wave 700 ft above the top of the dam as it hit the opposite, or right, wall of the valley. The wave then passed some 500 ft over top of the dam, followed down the tortuous winding canyon and debouched into the

Jan 1, 1967

By G. W. Elger, H. E. Bell, J. E. Tress, J. B. Wright

This paper describes laboratory techniques and subsequent results of US Bureau of Mines (USBM) research to produce chlorination-grade feed- stock from an abundant, low-grade, domestic, rock ilmenite ore. The research is part of the Bureau effort to devise technology that may help decrease US dependence on imported raw materials. A rock ilmenite containing about 46 wt % TiO2 was smelted in an electric arc furnace with coke, wood-chips, and Na2CO3 to separate most of the iron as pig iron and to form a low-iron, titanium-enriched slug. The slug was ground, pelletized, oxidized, and then sulfated with mixtures of SO2 and air in a continuous 4.5- to 9.1-kg/h (10- to 20-lb per hour) apparatus at 1023° to 122J0 K (1380° to 1740° F). The sulfated slug, containing 60% to 65% TiOb, was reground and leached in water at ambient temperature to decrease the combined levels of the troublesome calcium, magnesium, and manganese impurities from 7.0 to 1.7 wt 70. The final product was upgraded to about 8.4 wt % TiO2. This material is potentially suitable for chlorination in a fluidized bed reactor. The most favorable results were achieved with leached slug sulfated at a feed rate of 4.5 kg/h (10 lb per hour) and at temperatures of 1073° to 1123° K (1470° to 1560' F).

Jan 1, 1986

By Robert E. Bush, E. S. Mardock

The objective of this paper is to present practical methods of applying radioactivity logs to problems of interest both to those engaged in evaluating fundamental reservoir data as well as to those engaged in subsurface structural work. The basic theories underlying the operation of radioactivity logging methods are briefly discussed along with some of the problems arising in the interpretation of the log. Relative methods of quantitative interpretation are described, with a discussion of relative reference lines and specific examples are given showing the application of these relative quantitative interpretation methods. To show the variation of the methods described, specimen wells penetrating formations widely divergent in point of geologic age were selected to demonstrate the application. A relative reference line is determined for the Neutron Curve and by comparison to known petrophysical data such as porosities from diamond cores, a direct quantitative relationship is developed. The application of this relative calibration curve to logs of unknown wells will permit a reasonably accurate determination of porosity in limestone and dolomite formations. Specific examples are given showing the application of these relative methods of interpretation to logs of the Smackover limestone in Louisiana, the Edwards limestone and dolomites of South Texas, and Permian dolomites of West Texas. Radioactivity logs have been used extensively by the petroleum industry for a number of years and recognition of their value has grown steadily, not only as tools to aid in the solution of specific stratigraphic problems, but also as potential sources of the basic data necessary for the estimation of net pay and reserves. The value of radioactivity logs for stratigraphic work has been pointed out in the literature,1,2,4,5,6 and now has long been recognized by the industry, but the quantitative application of the logs has advanced but little beyond the stage of a strong conviction that radioactivity logging curves will some day provide the information on such important quantities as the porosity and the liquid saturation of the formations. During the past few years the staffs of the Lane-Wells Company and Well Surveys, Incorporated, have devoted a great deal of time, thought, and experimentation to the relationships existing between radioactivity curves and the lithologic conditions encountered, and this paper is, in a manner of' speaking, intended as a progress report of this work and includes suggestions which the authors have found useful in the interpretation of radioactivity logs. The section on theory is not intended as a complete exposition of the physical processes involved, but rather as a brief introduction to the reader of these processes so that he may acquire a better understanding of the behavior of the radioactivity curves under the varied conditions encountered in normal well logging. Three relative methods for using neutron logs for the quantitative estimation of porosity in limestone or dolomite are presented. These methods are based on the comparison of logs and porosity data from wells in Louisiana, South Texas, West Texas, and New Mexico. These areas were selected because not only were there more core data available from these areas but also the majority of these data were from limestone or dolomitic zones. The correlation between core data and logs is simpler for limestones and dolomites than it is for sandstones due to the fact that sandstones are more complex than limestones and differ more widely among themselves as to composition of cementing materials, siltiness, etc. When data applicable to the various types of sandstones are available, the authors hope to present a discussion similar to this paper covering sandstones or possibly a more general discussion covering all types of reservoir rocks. The relative methods for estimating porosity which are presented in this paper fall short of the absolute method sought. However, these methods possess the advantage that they can be applied to almost any neutron log as long as the range of application is held within the limits imposed by the local lithologic conditions which prevailed during calibration, i.e., these methods are for short range application only. THE THEORETICAL BASIS FOR RADIOACTIVITY LOGGING The two redioactivity logging curves commercially available today are the

Jan 1, 1950

By George C. Branner

STATE geological surveys have had an interesting development in this country. They first appeared more than a hundred years ago. The fact that they have persisted and are now an important part of most state governments indicates the basic need for state departments con-cerned with mineral problems. The number of state surveys in 1941 (43) is at an all-time high, as is the aggre¬gate appropriation for their support for the fiscal year 1940-'41 ($1,600,708). The first surveys, those of North and South Carolina (see Fig. 1), made their appearance in 1820-'30, but neither survived that period. During the next two decades surveys were created in twenty states, but only three survived. In fact, it was not until the decade 1900-'10, when eighteen surveys were created and only five abolished, that these agencies became firmly established.

Jan 1, 1941

By H. M. Varner

Under sponsorship of the US Bureau of Mines and the Department of Energy, a new type of rotary rock drill was developed by The Bendix Corp. Originally developed for the production of holes for the installation of longer than seam height roof bolts, the flexible drill is a useful tool for many drilling applications. It allows hands-off or remote production of holes for increased drilling speed and greater operator safety in any strata suitable for rotary drilling. This paper discusses various applications and experience for the flexible drill system in coal, metal/nonmetal mining, and for civil engineering uses. Manual, remote control, and automatic roof bolter modules are also discussed.

Jan 1, 1984

By J. G. Bartram

Jan 1, 1934

By Reno Sales

INTRODUCTION. THE geology of Butte possesses especial interest on account of the magnitude of the ore deposits, their extraordinary richness and persistence in depth. Since its discovery in the early 60's the district .has yielded, in round numbers, 6,000,000,000 lb. of copper, 260,000,000 oz. of silver, 1,250,000 oz. of gold, and a large but not definitely known number of pounds of zinc. This enormous metal production has been derived from an ore tonnage estimated roughly at 65,000,000 tons. At the present day, most of the important mine shafts have reached a depth of. 2,400 ft., while several are more than 3,000 ft., deep. At these-great depths rich bodies of copper ore are being exploited, showing no diminution in metal content as compared with the ores of the higher levels. The present (1913) daily rate of production is approximately 14,000 tons, of which 13,250 tons may be regarded as copper ore, although a small percentage of this is minable only because of the presence of

Jan 8, 1913

By Nicholas J. Grant, David S. Bloom

An investigation of the Cr-Ni system has revealed that there exists a eutectoid transformation at about 1180°C. 'The transformation in chromium implied by the eutectoid reaction was detected at about 100°C below its melting point. Associated with the eutectoid transformation, a metastable transition structure has been found. THE Cr-Ni phase diagram is shown in current literature to be a simple eutectic system in which the high chromium end of the diagram is incompletely determined, Fig. 1. The last investigation of this system was undertaken in 1936.' Because of limitations in metal purity, especially of chromium, and temperature measuring techniques, the diagram should be accepted with some reservations, as was indicated by Hansen.V or examwle.-, the wresence of the compound Cr²Ni, with a tetragonal structure," remains unverified and incompatible with the simple eutectic diagram. The work reported here began because of discrepancies that appeared in experimental studies in the binary alloys Cr-Ni and in the ternary system Cr-Mo-Ni. The existing binary Cr-Ni diagram failed to provide a complete explanation of observations made by microscope, X-ray, and thermal analyses. Experimental Methods The materials employed were of a higher degree of purity than were available to previous investigators. The Mond nickel used had a nominal purity of 99.87 pct, while the electrolytic chromium analyzed 99.03 pct with the major impurity being 0.5 to 0.7 pct oxygen with some iron. All alloys were melted in a vacuum furnace to remove dissolved gases, sufficient carbon was added to the charge to combine with all the oxygen as CO. Final analysis determined the carbon as about 0.02 pct and the oxygen around 0.06 pct or slightly more. Stabilized zirconia crucibles and thermocouple protection tips were used throughout and contributed no detectable impurity to the melts, as long as the oxygen in the chromium was kept low. Heats averaged about 250 g, which permitted about 2 in. of the thermocouple protection tips to be submerged. The temperature drop across the thermocouple protection tip was determined to be about 3°C, a minor source of error. The alloys, after removal from the vacuum furnace, were placed in a furnace operating in a purified argon atmosphere for the thermal analyses. An- nealed wolfram-molybdenum thermocouples provided the primary means of temperature determination, though a Pt-Pt-10 pct Rh couple was employed for a check when possible. A sensitive, high-speed Leeds and Northrup Speedomax recording potentiometer indicated the thermocouple output. X-ray diffraction patterns were obtained primarily on a Norelco unit, which permitted diffraction angles only up to 45" (28 = 90"). In general, either rotated or stationary solid samples were used, because it later evolved that many samples were susceptible to transformation resulting from the cold working involved in pulverizing. It was also noted that rotating a sample sometimes suppressed weak lines, so, usually, samples were not rotated. Later a high temperature camera was adapted for use at temperatures up to 1400 °C on the Norelco unit utilizing both solid and powdered samples. Unless otherwise noted, all X-ray patterns were made with a chromium tube and a vanadium filter. Further-

Jan 1, 1952

By Walter R. Hibbard, Harold Margolin

DURING preliminary tests on the aging of a Cu-plus 5 pct Ag alloy,' a specimen which had been overaged 24 hr at 550°C was annealed in a nitrogen-hydrogen atmosphere first for 2 hr and then for an additional 28 hr at 600°C. After each anneal the specimen was cooled to room temperature in about ½ hr and X-ray photograms were made. The first film, Fig. la, revealed two sets of copper-base lines, one intense and corresponding to the parameter at 550°C, the other fainter and shifted away from the beam, corresponding to the larger parameter at 600°C (see arrows). The 30-hr film, Fig. lb, revealed the same two sets of copper-base lines with a reversal of intensity. In neither case do the copper lines form a broad band which would be indicative of a range of compositions. This phenomenon is thus a "discontinuous" type of solution. A similar phenomenon was observed in a Ag-rich Cu-Ag alloy.' Finlay and Hibbard9 have suggested that directional rather than random solution of precipitate occurs in some alloys. Conceivably, for Cu-Ag alloys, the matrix-transition-precipitate precipitation sequence is reversible for the re-solution of the precipitate caused by rapidly raising the annealing temperature of an overaged specimen. A copper-base transition structure supersaturated with solute might be formed around the precipitate as it dissolves, thus obviating the necessity for a gradually changing solute composition of the matrix. The solute atoms then might be transferred rapidly and locally from the transition to the matrix phase in the proper amount and at the proper location to obtain directly the new ex- panded solid solution. The theory implies a minimum of diEusion of solute in the matrix (i.e., no significant range of matrix composition) and possibly suggests that the composition of the transition structure will vary with the conditions of re-solution. A transition copper phase found in aged Cu-Ag alloys1 might fulfill this function. Evidence regarding this suggestion could be obtained in Cu-Ag alloys by overaging a specimen until no trace of the expanded copper lattice is present and then subjecting the specimen to a retrogression treatment. Re-appearance of the transition copper phase would confirm the theory. Additional details could be secured by varying both aging and retrogression temperatures. References 'H. Margolin and W. R. Hibbard, Jr.: Effect of Ternary Additions on the Age Hardening of a Copper-Silver Alloy. Trans. AIME (1951) 191, p. 174; Journal of Metals (Feb. 1951) TP 3002E. 2 W. Ageew, M. Hansen, and G. Sachs: Decomposition and Changes in Properties of Super-saturated Silver-Copper Alloys. Ztsch. Physik (1930) 66, p. 350. 3W. L. Finlay and W. R. Hibbard, Jr.: Some Effects of Applied Stresses on Precipitation Phenomena. Trans. AIME (1949) 180, p. 255; Metals Technology (Sept.

Jan 1, 1952

By R. T. Hukki

IT is no great exaggeration to say that present grinding practice and economics are largely determined by lining design. A record of outstanding liner wear can be achieved with any liner surface pattern that will positively lock the outer layer or layers of grinding media. With no slippage, lining wear is bound to be slight. At the same time, popular practice calls for tumbling loads of about 50 pct of mill volume to obtain maximum grinding capacity. Innumerable parallel grinding investigations have verified that optimum speed for such a mill lies within 70 to 85 pct of theoretical critical speed. If the mill is speeded up to 100 pct of critical, little or no grinding can be accomplished. Earlier Work on Supercritical Grinding: First investigations concerning grinding at supercritical speeds seem to be very old. Remarkable work on the subject has been performed by White,&apos; and his experiments have been described and summarized by Richards.&apos; White&apos;s contributions seem to have passed unnoticed by Fahrenwald,2,3 whose extensive experiments have been well presented, yet apparently very little appreciated. Additional work on grinding at supercritical speed has been reported, e.g., by Lewenson and Tscherny,&apos; USSR; Anselm and Grunder,&apos;, Germany: and Rose and Evans." Great Britain. Subcritical and Supercritical Speeds: In the formula of the critical speed given in the textbooks of mineral dressing, no factor indicating the coefficient of friction is generally included. If this factor = 1.0, which is equivalent to grinding conditions in a mill provided with heavily ribbed lining, the formula of the critical speed holds as such and grinding is possible at subcritical speeds only. In a mill equipped with a smooth or relatively smooth lining, the numerical value of the friction factor in the denominator of the formula becomes <1.0, indicating that grinding at supercritical speeds should be possible in such mills. It has been recently shown by the author&apos; that a wide supercritical speed range will become available for grinding—and especially for fine grinding—if the basic conditions within the mill have been selected properly. Mathematical analysis of mill dynamics at supercritical speeds&apos; has indicated that the mill speed may be increased if: 1) total mass of grinding medium decreases, 2) mass of the individual grinding piece increases, and 3) the coefficient of friction between the outer layer of medium and the mill lining decreases. It is obvious that the mass of the individual grinding piece will be affected by its shape and by its specific gravity. The coefficient of friction decreases with: 1) increasing smoothness of liner surface, 2) increasing roundness of the grinding piece, 3) increasing fineness of material to be ground, 4) decreasing pulp density, and 5) decreasing hardness (abrasiveness) of the mineral to be ground. In a mill equipped with heavily ribbed lining, practically no size reduction will take place between the lining and the outer layer of tumbling medium, because slippage is prevented. In the overwhelming majority of today&apos;s mills the grinding accomplished is by virtue of cataracting and/or cascading media with some action within the tumbling charge. Sub-critical speeds only can be applied. In grate-type or peripheral discharge mills equipped with a smooth lining a tumbling load of any kind of common medium occupying about 50 pct of mill volume will behave in such a way that practically no slippage will take place. This has been verified in experiments run by the author in the laboratory and in pilot plant mills&apos; equipped with smooth lining. Again, the operation is limited to the subcritical range. In a mill with a smooth lining, grinding will be possible either at subcritical speeds or within a wide supercritical speed range as soon as the basic requirements for a desired speed are fulfilled. In a mill operated at supercritical speed, any point on the liner surface proceeds at a speed greater than that indicated by the formula of the critical speed, while any grinding piece situated in the outer layer of the medium against the lining proceeds in the same direction at a speed less than that indicated by the critical speed. This speed difference produces a very effective attrition grinding zone between the liner surface and the outer layer of the medium. The share of attrition grinding of the total grinding accomplished increases rapidly with increasing speed in the supercritical speed range. The smooth surface of the mill lining may be well illustrated by the surface of a bucking board. The outer ball layer may be similarly represented by the lower surface of a muller. If the bucking board, the material to be ground, and the muller all proceed in the same direction at the same speed, no grinding will result. This is the general situation in the mills of today. If, however, the muller is pulled with respect to the board, moving or stationary, grinding will be accomplished effectively. Although grinding in today&apos;s mills is primarily the result of cataracting and/or cascading media, the principal place of grinding at high supercritical speeds will be the attrition zone.&apos; In the mineral dressing laboratory of the State Institute for Technical Research. Helsinki, Finland, large quantities of different ores have been ground in a pilot plant ball mill (3x3 ft) at a top speed about 230 pct of the critical. With the same mill, theoretical investigations concerning the grinding characteristics of ball mills equipped with a smooth lining have been carried out up to the speed of 313 pct&apos; of the critical. With a smaller mill, the grinding characteristics with a variety of grinding media have been investigated at speeds up to 2000 pct of the

Jan 1, 1959

By C. Ernest Birchenall, Robert F. Mehl

APPLICATION of diffusion laws in the customary form to experimental studies in binary metallic solid solutions has shown the diffusion coefficient to vary with concentration for all systems investigated. The factors determining this variation have not been ascertained. However, the question of whether the diffusion coefficient would become a constant, independent of concentration throughout a single phase if the concentration gradient in the diffusion equation were replaced by an activity gradient has been an attractive subject for speculation. Wagner1 derived an expression for the force acting on a diffusing particle in terms of the chemical potential. This was also the approach chosen by Jost2 in his monograph. From a somewhat different point of view, Eyring3 and his co-workers have used activity gradients when dealing with diffusion in concentrated nonideal solutions. The only actual test with experimental data is that given by Darken,4 though this is more qualitative than quantitative. Many others opposed the application in any way of thermodynamic concepts to kinetic phenomena, including diffusion processes. A rigorous examination of this principle requires good data expressing the relationship between activity and concentration for solid solutions for which reliable diffusion work has been done. The literature provides such information only for the interstitial solution of carbon in gamma iron (austenite) and for the substitutional copper-zinc solutions (alpha brass). Activity data for carbon in austenite at 800°C and 1000°C are available from the recent work of Smiths on the equilibrium of hydrogen-methane and carbon monoxide-carbon dioxide mixtures with gamma iron. Combining these with the diffusion studies of Wells and Mehl6 makes possible a quantitative test for this interstitial solid solution. The vapor-pressure determinations for zinc over brass by Hargreaves7 allowed the calculation of activities in this system over a wide range of temperatures and concentrations. Extensive investigation of diffusion in this substitutional solid solution has been carried out by Rhines and Mehl.8 ACTIVITIES IN BRASS9 If the vapor phase of zinc is assumed to behave as an ideal gas, any solid or liquid solutions that are in equilibrium with the same partial pressure of zinc at the same temperature have the same thermodynamic activity of zinc. In order to assign a numerical value to the activity azn, it is necessary to choose some standard reference state to which an activity value of unity is arbitrarily assigned. It is customary to choose the liquid or solid state of the pure material. Then azn is defined numerically by azn = Pza/Pzn° [I]

Jan 1, 1947

By Nicholas J. Grant, Ulf Kalling, John Chipman

THE operation of a blast furnace is dependent to an important extent upon the sulphur content of materials charged and the desired limit of sulphur in the product. It has long been known that the blast furnace is the most efficient tool for desulphurization in common use and that this efficiency is associated with the strongly reducing conditions of the hearth and is enhanced by increased basicity and fluidity of the slag. The chemical reactions of desulphurization may be studied from the viewpoint of the ratio of the process or of the final equilibrium conditions. Both kinds of studies contribute to an understanding of the process and both are included here. A simple measure of the desulphurization power of a slag is given by the ratio: Pct sulphur in slag (Pet S) Pct sulphur in metal [Pct S] This ratio was used by Holbrook and Joseph&apos;,&apos; to measure relative desulphurizing powers under controlled laboratory conditions. It was also used by Hatch and Chipman3 as a measure of the equilibrium distribution. For the latter purpose it would be preferable to employ thermodynamic activities rather than percentages, but until very recently this has been impossible for lack of data. Now, thanks to the work of Morris and Williams and Morris and Buehl," the effects of carbon and silicon upon the activity of sulphur in the metal are known. The confirmation of this work and its extension to include the effects of other elements by Sherman and Chipman and by Rosenqvist and Cox&apos; make it possible to calculate the activity of sulphur in pig iron of any composition. Hence it is now possible to use data on the equilibrium distribution of sulphur to find its activity in the liquid slag and to approach an ultimate solution of the thermodynamic aspects of the problem. The rate of transfer of sulphur from metal to slag is the problem of major industrial importance and indeed the principal need for equilibrium data has been as a necessary adjunct to the kinetic studies. The rate of approach to equilibrium under laboratory conditions seems slow compared to the requirements of industrial practice, and it is clear that further laboratory studies of rates are needed. In the research reported below, the items which were investigated were the following: I—The role of mechanical stirring on the approach to equilibrium. 2—The role of MgO in desulphurization as compared to CaO. 3—The role of MnO in desulphurization. 4— The limiting reactions which constitute the slow steps in desulphurization. Experimental Procedure The experimental set-up and procedure previously described by Hatch and Chipman" were essentially followed with several small modifications. The graphite crucible containing the slag and metal charge was altered to provide considerably more active stirring and mixing of the slag and metal in the carbon monoxide atmosphere. For this purpose the crucible was machined to provide two deep cylindrical wells which were interconnected at top and bottom as shown in Fig. 1. A graphite screw with a flat thread and of shallow pitch (4 threads per in.) spinning at 600 to 800 rpm was used to lift the slag and metal over the partition between the two wells and throw them over into the second well, where the metal settled through the slag into the reservoir at the bottom. It was possible to see actual particles of slag and metal being thrown over the partition. In this respect, the stirring was more vigorous than used in the work of Hatch and Chipman. A charge of 400 g of wash metal was first melted, and 20 g of FeS was then added to yield a bath containing 1.65 pct S. Immediately 400 g of slag (as pure mixed oxides) was added and fused. The slag was generally fused in 1 hr * 10 min. Within 30 to 45 min after melting, the temperature was adjusted to 1525"C, and the first slag and metal samples were taken. The slag was picked up on the end of a cold Armco iron rod, whereas the metal was sucked into a silica tube. The wash metal composition was (in percent): 4.29 C; 0.022 S; 0.021 P; 0.38 Si. The slags used were of four fixed starting compositions covering a wide range of acid-base ratios shown in Table I. Deliberate variations in MgO were made in these slags to check the role of MgO in blast-furnace desulphurization. Changes due to additions and reactions were followed by analysis of samples. Additions of Mn and MnO were made to most of the heats to note the role of Mn and MnO on desulphurization. Three heats (62 through 64) were made in an open pot induction crucible (graphite) using a

Jan 1, 1952

By D. R. Hay, E. Scala

Electrotransport has been superimposed on the rate-limiling- step in zone refining which is the impurity diffusion through the liquid at the solid/liquid interface. The efficiency of zone refining is increased and relative resistivity ratios (P300°k/P4 2°K) he increased by 50 pel in tungsten for a given number of posses using- the electrotransport field-aided method. The effiect of zotze refining in the presence of an electric field on the relative resistivity ratio is examined as a function of its intensity and polarity. THE effect of electrodiffusion on the effective distribution coefficient of zone refining has been discussed by Pfann and Wagner.&apos; Control of the distribution coefficient in zone refining is of twofold interest. A distribution coefficient of unity can be increased or decreased, making possible the transfer of some previously inseparable solutes. The general efficiency of zone refining can also be increased. In the conventional zone-refining process impurities are removed by their retention in the molten zone and subsequent deposition at the end of the rod after a complete passage of the zone. In higher-melting-point systems a second mechanism may also operate, the volatilization of impurities from the molten zone. It has been suggested by schadler2 that, in refractory metals, vacuum distillation plays the predominant role in purification. In Koo&apos;s results,3 the resistivity ratio decreased beyond a zone-refined length of 6 in. from the starting end, indicating that some purification does in fact occur by true zone-refining action. Hay and scala4 showed that the degree of purity as measured by the relative resistivity ratio method depends on the square root of time in the molten zone (number of passes) and thus appears to be limited by diffusion in the boundary layer at the solidifying interface assuming good mixing in the body of the molten zone where a linear rate would prevail. The final concentration of impurities in electron-beam floating-zone purification depends very much on the operating conditions and results obtained by various investigators2,3,5 are difficult to correlate. The diameter of the starting material, operating vacuum, and rate of traverse are among the factors to be considered. There are, nevertheless, some general observations to be obtained from the literature. Lawley5 reviewed the literature up to 1962 and concluded that the major contaminants generally remaining in tungsten after electron-beam zone refining are molybdenum and carbon. Molybdenum due to its high melting point and distribution coefficient of nearly unity would be expected to be difficult to remove by either volatilization or zone refining. Carbon is not only a common contaminant in vacuum systems, but is also very difficult to remove by conventional vacuum melting. even with vacuums of 10-7 mm Hg. For each of those impurities removed by zone refining the equation of Pfann and Wagner may be applied: It relates the effective distribution coefficient k to a superimposed driving force which accelerates the solute away from the interface with a terminal velocity L" and to the more conventional zone-refining parameters; v = rate of traverse, t = thickness of the diffusion layer at the solidifying interface, D = diffusivity of the solute in the molten zone, and ko = equilibrium distribution coefficient of the impurity.

Jan 1, 1965

Aalde, Kaare, (S&apos;40) Box 827, Socorro, N. M. Aase, Glenn D., (S&apos;40) Engr. Experiment Sta., Univ. of Utah, Salt Lake City, Utah. Abadesco, Enrique A., (S&apos;39) Student. College of Engrg., Univ- of the Philippines, Manila, P. 1. Abbott, John L., (S&apos;40) Met. Engr., Engr. Trainee. Wright Aeronantical Corp., Paterson, N. .J. Abbott, Robert H., (S&apos;42). Agricultural & Mech. College of Texas, College Sta., Tex. Abreu, Ovidio M., (S&apos;38) Dept. of Geol., Compauia Cousulidada de Petroleo, Caracas, Venezuela. Acomb, Allen, (S&apos;41) 3921 Chestnut St., New Or¬ leans, La. Adam, Howard W., (S&apos;41) Montana School of Mines, Butte, Mont. Adams, Charles E., (S&apos;42) Uuiv. of California, Los Angeles, Calif. Adams, Charles W., (S&apos;39) Student, Michigan Col¬ lege of Min. & Tech., Houghton, Mich. Adams, H. Travis, (S&apos;39) 310 South 5th St., Bur¬ bank, Calif. Adams, John W., (S&apos;42) Univ. of Texas, Austin, Tex. Adams, Rob L., (S&apos;40) Lt., B. 0. C. No. 12, Fort Sill, Okla. Adamson, Charles R., (S&apos;41) Uuiv. of Utah, Salt Lake City, Utah.

Jan 1, 1942

Jan 1, 1908