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By Frederick V. Lawrence

Broadly speaking, fluxes are substances which promote wetting and spreading or enhance the fluidity and manipulative properties of materials in joining, fusion, and smelting operations. The term most strictly applies to substances used to facilitate soldering and brazing; but in .he discussion which follows, the definition will be broadened to include materials used to promote fusion in arc welding and which aid in he smelting of metals. In each of the mentioned applications, the role of flux and its composition differs considerably; consequently n the discussion which follows, fluxes for soldering, brazing, arc welding, and smelting applications will be considered separately. Soldering and Brazing Fluxes Soldering and brazing are metallurgical joining processes in which a joint is formed using a filler metal of composition dissimilar to that of he joined pieces (base metal). The filler metal, older or braze, is always of lower melting point than the base metal. Consequently with these) recesses there is no melting of the base metal. The successful creation of the joint depends upon the wetting and spreading of the solder or braze around or throughout the joint. The obstacles to successful soldering and brazing are contaminants and tenacious oxide films on the metal surfaces. In soldering and brazing applications, fluxes act to remove and exclude oxides and other impurities from the joint. There is no fundamental difference between soldering and brazing. The distinction between them is made on the basis of temperature. Joining operations carried out at temperatures above 500°C are termed brazing. The higher temperatures used in brazing enable higher melting point filler metals to be used which generally provide stronger joints. The higher temperatures of brazing processes also require fluxes which are substantially different from those used in soldering and which will remain effective at high temperatures. Consequently the distinction between soldering and brazing can also be made on the basis of the fluxes used.

Jan 1, 1975

By H. I. Aaronson, C. Wells

THIS is a preliminary report on a detailed metal- lographic investigation of the bainite reaction in a plain carbon hypoeutectoid steel. In view of the current interest in the bainite reaction and of the controversies which still exist about even the basic phenomenology of this mode of transformation, it was considered desirable to present a summary of the more important results obtained to date prior to the completion of this investigation. The steel used contained 0.29 pct C, 0.76 pct Mn, 0.25 pct Si, 0.005 pct P, and 0.007 pct S. The alloy was homogenized for 48 hr at 1250°C. Individual specimens were then austenitized for 30 min at 1300°C and isothermally transformed for various times at temperatures above and within the bainite region, ranging from 775" through 500°C at intervals of 25°C. These specimens were carefully examined on a research metallograph; a few specimens of especial interest were also studied electron microscopically.' Bainite may be defined as the aggregate structure resulting from the precipitation of carbides from supersaturated ferrite which formed by nucleation and diffusion-limited growth. Two groups of experimental observations made during the present study provide support for this mechanism of the bainite reaction: 1—at 625°C, partial conversion of pro-eutectoid ferrite to bainite began after more than 99 pct of the austenite had decomposed and 2—the precipitation of bainitic carbides occurred only within the ferrite phase. The proeutectoid ferrite and the bainite reactions in the steel studied were found to be morphologically continuous. Following the classification scheme of Mehl and Dube,2 three principal morphologies of proeutectoid ferrite were identified in the temperature region (625" to 550°C) in which the two reactions blend—grain boundary allotriomorphs," * Grain boundary allotriomorphs are crystals which nucleate at and grow preferentially along matrix grain boundaries. Widmanstaetten side plates, and intragranular plates. Carbide precipitation converted these morphologies into their bainitic equivalents with increasing isothermal reaction time. Conversion took place more rapidly as the reaction temperature was reduced. The replacement of supersaturated ferrite by bainite, however, did not occur uniformly even within individual austenite grains and was noticeably incomplete at higher transformation temperatures, e.g., 625° to 575°C. The ferritic and bainitic forms of a given morphology thus were frequently found to coexist, often inextricably intermixed, in a given specimen. At 625" and 600°C, the conversion of ferrite to bainite was clearly seen to have occurred entirely by the nucleation of carbides at ferrite/ferrite boundaries, as shown in Fig. 1. The nature of the loci at which carbides formed at lower temperatures was often difficult to ascertain with a light microscope, although the alignment in rows of many of the carbides, illustrated in Fig. 2, suggested that nucleation had again occurred at grain boundaries or subboundaries within the ferrite. Application of the electron microscope confirmed this deduction for bainitic structures formed at these temperatures, as shown in Fig. 3. The dense black appearance of bainite formed at very low reaction temperatures in higher carbon steels3 indicates, however, that isolated lattice defects within ferrite crystals prob-

Jan 1, 1956

By L. S. Reid

THE study of the flow of oil and gas mixtures through oil-bearing formations has received special attention from the petroleum industry within the past few years, and has resulted in a series of research projects based upon various phases of the flow of heterogeneous fluids through porous media. Obviously, the low cost of producing oil during the flowing life of a well makes it desirable to obtain production by natural flow as long as possible and to effect a maximum recovery of oil and gas by the utilization of reservoir energy through efficient methods based upon a thorough knowledge of reservoir characteristics. Despite the extensive research that has been carried out, there is little information available on the behavior of oil and gas mixtures flowing through reservoir formations. This makes it impossible to predetermine the optimum operating condi-tions for flowing wells. A differential pressure must exist in the reservoir in order to induce flow toward the well. It is a well established fact that with homogeneous fluids the relation of pressure drop to linear distance traveled is a straight-line function as long as the flow is viscous. However, in regard to gas-saturated oils, a number of investigators1,3,4 have reported that the flow characteristics are materially altered as some of the lighter hydrocarbons are liberated from the oil to form gas while the fluid passes through the reservoir. Most of the work done has been concerned primarily with steady-state flow of liquid-gas mixtures. Cloud1 has studied the effects of saturating crude petroleum oils with various gases, together with the resultant pressure gradients under steady flow conditions, noting that unsaturated oils flowed faster and yet maintained lower pressure gradients than saturated oils.

Jan 1, 1938

By R. V. Ramani, R. D. Zigmond, R. L. Frantz

In this paper, a computer program for determining the capital and operating costs for coal preparation plants is described along with its applications. The logic of the computer program is based upon the results of a survey of existing preparation plants, operators, plant contractors, equipment manufacturers, and consulting firms. This survey provided information on plant performance, order-of-magnitude costs, and costing procedures. Additionally, an extensive cost data file for the major capital equipment in coal preparation plants has been developed. Using the washability data and the computer program out- puts, the cleaning costs per million Btu can be calculated. Details about the program and its applications can be found in a report by the authors (Zigmond et al., 1979).

Jan 1, 1983

By F. Milton Lewis, Roshan B. Bhappu, James L. Coburn

Part one of this article, published in the September 1976 issue of MINING ENGINEERING, described procedures for analytically evaluating the physical and chemical properties of an ore; it also described various types of equipment that are available to the minerals engineer for designing required comminution operations. Part Two of this article illustrates the practical application of these principles to the design of a sound comminution system for a known set of ore characteristics. This exercise is aimed at giving the young engineer a review of the methods and procedures that are available for designing comminution systems. To illustrate these methods, a large-tonnage porphyry copper ore body with the following characteristics is selected:

Jan 11, 1976

By Robert E. Thurmond, E. D. Spaulding, Walter E. Heinrichs

DISCOVERY of a commercial ore deposit has resulted from a program emphasizing geophysical techniques and concentrating upon exploration of alluvial-covered areas. United Geophysical Co. selected these areas as offering the best possibility of success, for here the surface evidence of ore deposits has been hidden from the eyes of prospector and geologist alike. Pima mining district, Pima County, Arizona, was selected for initial exploration. The project was successful in that a commercial ore deposit was discovered and proved through drilling and extensive underground development.

Jan 2, 1954

By K. A. Natarajan, I. Iwasaki

The meaning and the utility of redox potential (Eh) measurements in sulfide flotation systems are examined. Since some preliminary plant Eh and laboratory flotation data were available, experiments were made to establish the pH range at which a platinum electrode might be used for such measurements without much difficulty in aerated systems. Triangular wave voltammetry was used to study the surface conditions of the electrode immersed in pyrrhotite suspensions at different pH. The measured Eh both at the plant and the laboratory is interpreted in terms of the experimental water-oxygen line.

Jan 1, 1974

Jan 12, 1950

By Gordon M. Matheson, Charles V. Logie

The current state-of-the-art design of mine pillars can be grouped into empirical and numerical design techniques. Numerical design techniques are based on sophisticated computational techniques which analyze the stresses and strains through the interstices of a pillar. Empirical techniques are less exact, but have been widely used, particularly for coal mine pillar design, because of their ease of computation. Over the years numerous empirical equations have been proposed to calculate the ultimate strength of coal mine pillars. This paper presents a review of the various equations which are most frequently utilized and examines the fundamental assumptions, limitations and applicability of the design formulae. The review intends to provide the practicing mining engineer with an understanding of the assumptions and mathematical basis of each equation to aid in the selection of the criteria most applicable to his specific design problems. Recommendations are made of the empirical equations that are presently most acceptable for design.

Jan 1, 1983

Jan 1, 1922

By W. G. Whildin

This paper will be confined to a discussion of the methods in use in the property of the Lehigh Coal and Navigation Co. in the Panther Creek valley.

Jan 1, 1915

By W. A. Clark

THE production of sand in an oil well increases operating costs because of abnormal wear in subsurface equipment, the necessity for frequent cleanouts, and the need for a means of disposing of the sand. Moreover, removal of sand from the zone can bring about the creation of cavities from which bodies of formation, sand or shale, may slough into the hole, endangering the shutoff, impeding production or collapsing the liner. The procedure known as gravel packing is attracting attention as a means of controlling these factors and contributing to the productive life of a well. That gravel packing is now substantially beyond the preliminary stage on the Pacific Coast is reflected in the 191,000 bbl, of oil produced monthly by the 66 gravel-packed wells in 11 different producing sectors. REASONS FOR GRAVEL-PACKING Gravel packing, if properly carried out, can be expected to provide the following benefits: 1. Prevent the movement of sand and thus eliminate sand production and sand fills, and prevent the formation of cavities. 2. Provide a practical, relatively inexpensive, large-diameter hole, which will provide well-known theoretical advantages. 3. Support the walls of the hole by completely filling the space between the liner and the formation, regardless of its irregularities, and afford a support for liners. 4. Provide for more efficient pumping operations in wells by: (a) possibly utilizing the gravel as a gas trap in pumping gaseous fluids, (b). allowing deep submergence of the pump into the oil zone.

Jan 1, 1939

By Earl Chairman Oliver

The major development in stabilization of the oil industry during 1933 was the transition in the United States from state control to federal control in many of the functions that government is presumed to exercise. A brief review of the influences leading to that transition is given here to suggest its significance and to assist in forecasting its further development. Bitumens were known to the ancients and have been applied to minor uses since earliest historic times, but it was not until after the discovery of oil in considerable quantities near Titusville, Pennsylvania, in 1859 that it was made the basis of extensive commercial undertakings. In 1859 little was known about the origin of oil and gas, the nature of these deposits, and the physical laws that controlled their accumulation. Scientists soon began to study them, but 50 years or more of active oil-field development had elapsed before sufficient geological information had been accumulated to point the way toward efficient recovery of these products. In fact, only within the past five years has the function of reservoir energy become widely understood, yet it is a primary factor in oil recovery. discovery near Titusville, this infant industry has developed into an industrial giant. In complete ignorance of their destructive effect, wasteful development methods were initiated in Oil Creek and these became industrial habits. These habits in turn became oil and gas law. Under that law vast sums of money have been expended, rights have become vested and development methods fastened on a great industry that not only bring upon it periodic demoralization but cause ruthless destruction of the nation's reserves of these important natural resources. This is occurring in the midst of a petroleum era when oil is essential to the nation's security, its industrial supremacy, and the personal convenience of every citizen. Its conservation, therefore, has become a question of grave national concern. Conflict between PHysical Facts and Oil Law This destruction of an important natural resource and periodic demoralization of a vast industry can be halted only by readjusting oil

Jan 1, 1934

By Benjamin Webber

MANY of the auriferous placers of the arid Southwest differ widely from the standard types of stream and eluvial deposits of more humid regions, although exhibiting some of the features of each. This diver-gence in characteristics is of geological and economic importance and appears sufficient to warrant the consideration of these placers as a class distinct from both stream and eluvial deposits. It is hoped that the consideration of these auriferous gravels as a distinct type of deposit will facilitate recognition of morphological and economic features that might remain obscure if these deposits were viewed in the light of stream or eluvial placers whose type locality is a more humid environment. "Bajada placer" is proposed as the designation for this type of placer deposit. Bajada is the Spanish term for slope and is used locally in the Southwest to indicate the lower slope of a mountain range, the portion consisting of rock debris and standing at a much lower angle than the rock slope of the range proper. It has been used in a geologic sense by Schrader1 and others. The type locality of bajada placers is the Sonoran Desert,2 where they occur on the bajada or rock debris slope of desert ranges. Stream placers are represented in the Southwest, but most of them lie within the mountain topographic province, the Mexican Highlands2 section of, the Basin and Range physiographic province. Eluvial placers may occur in the mountainous semiarid Mexican Highlands but are almost unknown in the extremely arid Sonoran Desert, as mountain slopes are generally too steep to permit the accumulation of any considerable mantle of residual debris. Since their salient distinctions are almost wholly the result of formation under conditions of extreme aridity, bajada placers are largely confined to the Sonoran Desert, although a few occur in the adjacent Mexican High-lands. They may be modified by the action of ephemeral streams, in which case the placer gravels of these arroyas approach stream placers in type and habit of occurrence, but their relation to an arid environment and the bajada type is usually apparent.

Jan 1, 1935

By L. C. Skinner

THE Coal Hydrogenation Demonstration Plant at Louisiana, Missouri, was completed early in the year 1949. It has operated more or less continuously since completion except for the time required for making necessary inspections, repairs, and alterations between runs. Operations have included a short vapor-phase run on North Dakota lignite-tar distillate oil in 1949, followed in 1950 by four comparatively short exploratory liquid-phase runs and one vapor-phase run on Rock Springs [ ]

Jan 1, 1953

By Richard D. Call

Data obtained from development drilling provide the basic input for open pit mine planning and design. Development drilling is defined as delineation of the size, mineral content, and disposition of an ore body by drilling boreholes (Thrush, 1968). The objectives of development drilling are: ( 1 ) determining the geometry of the mineralization, ( 2 ) determining the grade and tonnage, , ( 3 ) obtaining samples for metallurgical testing, and ( 4 ) obtaining geotechnical data for mine design. To accomplish these objectives, an appropriate drilling plan must include the number of holes, the spacing and orientation of the holes, and a suitable data collection program. The data collection program covers sample collection, hole logging, and data presentation. This chapter will present some guidelines for development drilling and data collection techniques. The operational aspects of drilling will be covered in an- other chapter.

Jan 1, 1979

By B. L. Cusack, N. W. Stump

Selected technological developments applicable to lead and zinc mineral processing and changes in Australian concentration practices made since 1770 are reviewed. Laboratory and pilot plant studies of two new ores have been conducted since 1770. These have resulted in final flowsheet proposals which are described. New production capacity since IT0 has been based on plant expansion or the retreatment of oxidised tailings from plants operating pre-1940ts. Major developments in existing plants have come from the application of computer control to crushing, grinding and flotation and the installation of on-stream analysis systems. Flowsheet configurations have been altered in a number of plants. Selected research topics applicable to lead and zinc processing are also reviewed.

Jan 1, 1977

By Rollin Farmin

"SWELLING GROUND" delivers pressure on mine timbers that originates in expansion of the wall rock, whereas "heavy ground" delivers only gravitative pressure. Of the several possible causes considered, the swelling is attributed to the physical surface action of water on gouge and flaky rocks at the periphery of the mine opening.

Jan 1, 1944

By Albert F. J. Bordeaux

The following general survey of the character and present condition of the silver-mines of Mexico, though not offered as a detailed treatise, has been prepared with care, is believed to be generally up-to-date, and is offered as a summary which may be found useful by mining engineers. For several centuries Mexico has ranked first anlong the silver-producing countries. It is now second as a copper-producer, and seventh as a gold-producer, with a fast-increasing output every year. The total amount of capital invested in its mining- and smelting-works exceeds $250,000,000, while the value of the yearly metallic production is $160,000,000. There are more than 20,000 recorded mining properties. The silver-mines of Mexico represent deposits of three principal classes: (1) veins and stock-works in eruptive rocks; (2) fissure-veins crossing the crystalline schists, granite, diorite, etc.; and (3) veins and replacement-deposits in limestone. The true fissure-veins in some districts contain (in value) vol. xxr1x.—22

Jan 1, 1909

By J. E. Hilliard

It is proposed that shape anisotropy in the internal structure of materials be defined by distribution functions which specify what fraction of the total line length or boundary area lies in a given direction. Methods are descriibed for determinirg these distribution functions from measurements on sections through an opaque material. New derivations, that have certain advanifages over those given previously, are Provided for well-known expressions used in estinzating the total density of lineal or areal features. INCREASING attention is being given to the quantitative description of imicrostructures in metals and other materials. This interest stems from the recognition that the structure often provides a convenient half-way point between the properties on the one hand and the processing variables on the other. Such cross correlations become increasingly desirable as materials become more complex and the demands on them more stringent. One of the principal aims in structure analysis is therefore to find parameters that are readily measurable and specific enough to be correlated with other properties of the material. Certain properties, such as magnetic and mechani cal behavior, are strongly influenced by structural anisotropies; in order to relate such properties to the structure it is obviously necessary to have means of specifying and measuring the type and degree of anisotropy. For the determination of preferred orientations in crystal structure, X-ray diffraction methods are available and are widely used, but scant attention has been given to the estimation of anisotropy in the shape of grains and particles. It is the latter problem that will be considered in this paper. It is evident that shape anisotropy can be describe in terms of preferred orientations of lineal and area elements of the structure. It will be shown that these preferred orientations can, in turn, be specified by distribution functions that define what fraction of the total line length or boundary area lies in a given direction. Methods will be given for determining the distribution functions from measurements on sections through the structure. Even when the orientation distributions are of no interest per se, they still have an important bearing on the measurement of the total line length or boundary area by means of an intercept analysis. The treatment in terms of orientation distribution functions leads to new derivations, that have certain advantages of those given previously, for the well-known expressions used in estimating the total density of lineal or areal features. The treatment is divided into two main sections. The first deals with the orientation distribution of a two-dimensional array of lineal features such as occurs in the projected image of dislocations in electron transmission microscopy. The other section treats the estimation of the distribution of lineal and areal features dispersed in three dimensions.

Jan 1, 1962