Search Documents

By W. A. West

ONE who attempts to collect and classify equilibrium data from various iron-alloy systems is soon struck with the absence of any quantitative theory that can serve as a general background against which to compare and contrast results from different systems, at different temperatures, and with different concentrations. It is not necessary to wait for a perfect theory; investigation of divergences of theory from observation may prove of great value in acquiring understanding of the subject. For example, one has only to think of Raoult's law as applied to aqueous solutions. The equations developed by Zener1 represent an effort to provide such a quantitative theoretical background, and it is therefore desirable to subject this theory to such tests as can be applied. The present article is intended to be an application of available tests, and may thus be considered as a supplement to Zener's paper. It is assumed that this paper is available to the reader. The equations make it possible to calculate the effect on the equilibrium concentration of one alloying element due to the presence of one or more other elements. In particular they are intended to give, for alloy steels, the carbon concentrations in alpha and gamma phases in equilibrium with each other, and in gamma in equilibrium with cementite. They may, however, be modified for use for carbon-free alloys. A summary is given later of the equations used in analyzing the data in this paper, and the symbols are there defined. About 125 papers have been examined for experimental data suitable for this investigation. An effort was made to look up all available reports of ternary systems including iron and carbon, as well as similar systems of higher order. Supplementary material was also obtained from a number of binary systems. A few noncarbon ternary systems were also found to which these methods could be applied. A comparatively small proportion of the papers read provided usable material. In many systems the number of quantitative observations made in the iron-rich region is extremely small, and the smoothed curves to be found in most published phase diagrams are entirely useless for quantitative treatment. This opinion is confirmed by the authors of the series on Alloys of Iron Research, whose remarks show clearly that they have no illusions as to the accuracy of many diagrams that they present. A further difficulty arises from the fact that these equations apply only to rather low percentages of alloying elements. The result is that at the lowest concentrations, where the best agreement might be hoped for, the errors of observation become relatively very large. The experimental difficulties in measurements of this kind of equilibrium are, of course, an old story.

Jan 1, 1946

By C. G. Maier

COMMERCIAL processes of lead softening directly involve the behavior on fusion of mixtures of the oxides of antimony and lead, and the vapor pressures of these materials. Practically no quantitative data have been available for the discussion of lead softening from the point of view of the fundamental metallurgy of the process. The Pacific Experiment Station -of the United States Bureau of Mines, in cooperation with the University of California, in the course of its program of study of the fundamental properties of oxides and sulfides, recently made vapor pressure measurements upon the various forms of pure antimony trioxide.1 When these measurements were considered in connection with the softening and "fuming" furnaces which are often used for lead purification, an unexpectedly anomalous condition appeared. In brief, this anomaly consisted in the fact that in certain softening furnaces, where lead bullion of approximately 1 per cent antimony content was being treated at a temperature of approximately 1300° F., no appreciable volatilization of antimony occurred, there being produced only a "skim" containing from 15 to 20 per cent Sb, 65 to 60 per cent Pb, as mixed oxides. In the "fuming furnaces," where the temperature was only about 1400° F. and where an accumulation of "skims" from the primary softener was being treated with certain other antimony-containing materials, a considerable volatilization of antimony as oxide occurred; an "impure" skim of some 60 to 65 per cent Sb and 10 per cent Pb was also produced as mixed oxides. The latter material cannot be suitably treated in hearth-type or softener furnaces. The essential chemical difference between the first and second step is the customary use of some reducing material (such as petroleum coke) in the later operation. An obvious interpretation of the effect of coke in facilitating the fuming of the antimony is the supposition that the antimony may be reduced to metal, and volatilized as such. This supposition is improbable, however, when it is realized that a slight extrapolation of the vapor-

Jan 1, 1932

Jan 1, 1912

By L. J. Boucher

The beneficiation process at Northampton is described and reasons are given for installing a flotation plant. The economics of running the plant, the difficulties of operation, and subsequent remedial action are discussed.

Jan 3, 1953

By G. Almgren

Swedish cut-and-fill mines are described with regard to location, production volumes, and grades. Development goals (such as higher productivity and better working conditions) are presented, and different methods of development, such as mechanization, new layouts, etc., are discussed. Development methods are described with examples from drilling, loading, haulage, and rock mechanics. Special attention is paid to filling techniques. Figures are given for productivity and relative costs.

Jan 1, 1977

By R. W. Heckel, R. A. Tanzilli

Treatment of the finite, diffusion-controlled, two-phase, moving-interface homogenization problem has been carried out by numerical methods for a wide range of input parameters. Solutions have been obtained for planar, cylindrical, and spherical diffusion geometries. The effects of parameters such as the interdiffusion coefficients (concentration-independent) of- both phases, the concentrations (time-independent) of each phase at the interlace, mean composition, initial size of the dissolving- phase, and initial composition of- the two phases are considered. The results are displayed to show both the position of the interjace and the degree of homogenization (expressed in terms of concentration at the matrix phase symmetry boundary) as a function of diffusion time. Typical exaw~ples to which the results may be applied are discussed. A limited number of exact, closed-form solutions to the multiphase, diffusion-controlled, moving-interface problem exists in the literature, e.g., Refs. 1 to 7. The exact, closed-form solutions generally consider the outermost phases to be infinite in extent and also assume an interfacial velocity function. It is through use of such boundary conditions that closed-form solutions are readily obtained. An extensive literature also exists on numerical solutions to the mathematically analogous solidification problem, e.g., Refs. 8 to 12. In addition, a numerical solution involving mass transfer with spherical interfaces and infinite boundaries has recently been carried out.13 A practically important class of diffusion problems exists, however, in which the boundaries of each phase away from the interface are finite. For example the finite boundary condition arises when one sets up a model for analyzing the homogenization behavior of two-component powder compacts in two-phase systems or for studying the solution behavior of precipitates. Although exact, closed-form solutions have as yet not been found to this class of problems, solutions are possible using numerical methods. The purpose of this paper is twofold: 1) to describe a numerical method for treating the two-phase, diffusion-controlled, moving-interface problem involving finite boundaries with planar, cylindrical, and spherical interfaces; 2) to present the results of a parametric study which identifies the role played by each variable appearing in the analytical model. R. A. TANZlLLI,Student MemberAIME,onleaveofabsence from the General Electric Co., Re-entry Systems Department and A. W. HECKEL, Member AIME, are Graduate Student in Materials Engineering, and Professor, Department of Metallurgical Engineering, respectively, Drexel Institute of Technology, Philadelphia, Pa. Manuscript submitted May 6. 1968. IMD MATHEMATICAL MODEL The three geometries analyzed are shown in Fig. 1. For each configuration a symmetry element is shown, across whose boundaries the mass transfer is zero. Mean composition, C, and the characteristic solute-rich phase half-thickness (or radius), 1/2, are the independent variables while the characteristic symmetry element half-thickness, L/2 (measured from solute-rich phase center to the matrix phase plane of zero mass transfer), is a dependent variable. The symmetry element for a planar interface accurately represents a real diffusion situation involving the stacking of symmetry elements of constant size. Because cylindrical and spherical symmetry elements of constant size cannot be stacked to fill space, the meaning of the dimension, L/2, for these situations may be considered in terms of the following approximations: and where NA is the number of parallel cylindrical elements per unit area on a surface normal to the cylinder axes and Nv is the number of spherical elements per unit volume. The model consists of a solute-rich phase matrix phase composite of limited mutual solubility. The concentrations at the interface are assumed constant with time; no assumption of local equilibrium at the interface is necessary except for the case where the

Jan 1, 1969

COUNCIL OF SECTION DELEGATES Jack A. Criehton. Chairman Allen T. Cole. Vice Chairman M I. Signer, Secretary EXECUTIVE COMMITTEE W. C. Leonard, North Pacific W. K. Beck, Cleveland W. W. Leonard, Southwest Texas

Jan 1, 1952

By Leland L. Mink, Roy E. Williams, C. Daniel Kealy

The passage by Congress of Public Law 92-500 (the 1972 Water Pollution Control Act amendment) has placed a new emphasis on the need for methods to minimize the escape of water from tailings ponds. Presumably tailings pond seepage will fall under the jurisdiction of the act. This paper is designed to explain some of the problems caused by leakage from tailings ponds and to present a method by which leakage can be minimized if not eliminated. Ground-water pollution in one case studied by the authors results from leaching of old jig tailings that are intermixed with the upper part of a sand and gravel aquifer. Anomalous concentrations of zinc, lead, and cadmium occur in ground water and soil samples taken from the portion of the sand and gravel aquifer containing the old jig tailings. Analysis of water samples from a tailings pond located in the area indicates that the pond water is not the source of the heavy metal concentrations found in the down-gradient ground water. However, leakage from the pond and water from the pond's decant system combine with natural ground water to compound the problem by raising the water table into old jig tailings which cover the upper portion of the aquifer. The ground water which discharges from this aquifer causes a statistically significant decrease in the quality of the receiving stream water. The shallow ground water contains oxygen; therefore, corrective measures include lowering the water table to depths below the old jig tailings which cover the aquifer at ground level. This, in turn, implies elimination of ground-water recharge by subsurface leakage from the pond. A laboratory study and a mathematical model study have revealed that seepage from such ponds can be minimized by a carefully designed and managed peripheral tailings discharge system. The process involves maintaining the slime zone and the free-water surface near the center of the pond so that the slimes retard downward and semilateral movement of pond water. The free-water surface must not be allowed to extend out over the nonslime portion of the tailings during or after pond operation. Mathematical model output reveals that this method can hold the subsurface discharge rate to as little as 110 gpd per acre of pond water area. The technique should be applicable to any tailings pond system in which the loss via seepage of poor quality water must be minimized or where recharge of ground water by losses from a tailings pond must be minimized, regardless of the reason.

Jan 1, 1974

By L. A. Hanson

Jan 1, 1964

By J. W. Harden

APART from the merits of the respective systems of mining under conditions alike, there is much in the nature of the coal and the measures with which it is associated, to make that system which is successfully practiced in one locality ill adapted to that of another ; the structure of the coal itself, the roof, the floor, the depth and character of the overlying strata, each exercising more or less controlling influence. Again, in the highly bituminous districts, and with such as have caking coals, where the size of the coal as it comes off the face does not affect its value, as the very smallest of it may be utilized, and in the hard, the open and free-burning coals, in some of which the round only (large coal) is merchantable,

By Newell Alford

AT its meeting in the fall of 1937, the Executive Committee of the Coal Division considered the growing scarcity of young engineers entering coal mining with serious intentions. This scarcity was the cause of con-siderable alarm and a committee consisting of C. T. Hayden, E. A. Holbrook, C. E. Lawall and L. E. Young, with the writer as chairman, was appointed to gather factual data on the current trend. A questionnaire1 was designed and mailed to the heads of the 60 mineral technology schools listed by Prof. W. B. Plank in his article in September 1937.2 Replies were received from 46 institutions, not all from heads of coal-mining courses but all from men that at one time or another have had experience with some kind of coal-mining curricula and know current student impressions. Our committee is indebted to all of these gentlemen for their cooperation. Our committee hoped by this means to quickly reach the root of the trouble and make a set of comprehensive recommendations to the Coal Division for relieving the industry immediately from the growing dearth of youth who yearn for coal-mining careers, but the condition is more serious than at first diagnosed. We must now refer the question back to the Coal Division, with the recommendation that the Division get the industry's permission for still another major operation on its frame of mind. In addition to 10-year statistics on the first pay received by graduates in coal mining and other technical work, we requested enrollment data for 20 years from all schools with either mining engineering or mineral technology curricula. Nine leading questions were also plied, as shown in the Appendix. Every one of the answers was significant and inter-esting. Fortunately, we encountered positive frankness that was extremely helpful.

Jan 1, 1938

By J. B. Woodworth

Under the above title it is desired to bring to the attention of assayers a short-cut method which has been perfected by Mr. A. S. Warren, of Buffalo, and the writer; has been used several years at three " Lake copper " refineries in occasional alternation with the regular " combination," or a wet and fire," assay; and has proved more rapid, and rather more accurate than the latter on all refined copper—namely, the direct cupellation of the silver chloride (+gold) precipitate, without scorification. No claim of priority is made for this direct method, as it has suggested itself to many others, and was mentioned by Mr. Warren in the symposium of assayers' results brought together in 1895 by the Secretary," after the plan and suggestions of Dr. A. R. Ledoux.† Lately, this important subject of assaying copper-materials seems to have been re-opened for discussion. The shortening of time by 'the direct method is so considerable (nearly 20 minutes on a batch)—to say nothing of the saving

Jan 1, 1902

By G. R. Fitterer

Trends in slag composition in acid open hearth practice, particularly the variation in iron and manganese oxides during refining, are reviewed. A procedure which is currently being used to control the refining reactions is described and partially explained through slag phase diagram considerations. In addition, the ionic nature of these slags is considered and it is proposed that silica combines with the oxide ion and forms a series of complex silicate ions. The effect of basic oxides such as FeO, MnO, and CaO is apparently additive in furnishing the oxide ion for this purpose. IT is now possible to control192 the refining of steel in an acid open hearth furnace to a surprising degree. This control has been brought about through the knowledge and use of several facts and tests. These are: 1—A planned charge analysis based on a knowledge of the type of fuel, the bath depth, etc. 2—Knowledge and control of rate of fuel input as well as its method of atomization, if any. 3—Determination of the slag fluidity. 4—Bath temperatures (use of the Pt-Pt-Rh thermocouple). 5—Periodic determination of carbon content (use of the Carb-analyzer or Carbometer). Through the use of these control methods, a heat may be made to "melt-in" with or without residual manganese and silicon. The rate of refining or carbon elimination may be controlled accurately, and the desired tapping (or "go-ahead") carbon may be approached at a rapid or slow rate according to preference and type of steel being made. Thus operating time may be predetermined and greatly reduced. Further, all of the refining can be done without any ore or other oxidizing additions, and the heat may be brought to the desired tapping temperature simultaneously with the attainment of the desired carbon analysis. This control procedure is being used in most acid plants in the United States today and has been de- scribed.', ' Although the slag metal relations are sufficiently well known to control the heat as stated, yet it is possible to account for only about two-thirds' of the 0, which must have been used for the elimination of the carbon and other metalloids. Phase diagram studies' of the slags, slag weights, the metal particle theory,' ore additions, limestone additions, etc., may all be taken into consideration; yet, the mechanism of oxidation and source of all the oxygen remain to be explained. This paper reviews some of the principles upon which the control methods were based and proposes other possibilities regarding the unexplained phenomena. Old and New Acid Open Hearth Practice Some of the recent statements in the literature regarding acid open hearth operation are based on old heat data which are not typical of modern American practice. These old heat logs have been responsible for many misconceptions regarding the acid hearth practice and represent heats which do not coincide with modern methods. In recent years, American practice has been altered materially and these changes will be briefly described. Modern American Practice: A typical log of a modern American acid open hearth heat' is shown in Fig. 1 which indicates that the refining time was only two hours, during which the carbon was eliminated rapidly and the bath temperature increased at a fast rate. The manganese and silicon contents of the metal were essentially eliminated and their oxides had become constituent parts of the slag at the "melt-down" period. During the course of the heat, the MnO content of the slag remained practi-

Jan 1, 1954

By G. L. Oldright, Virgil Miller

It is well known, in metallurgical circles, though less recognized in the technical press, that there have been remarkable increases in the capacity of the blast furnace in the last five .years. In places this capacity has been almost doubled. This paper will brief the experimental work carried on during more than five years with the direct assistance of the technical staffs of three lead smelters treating three distinctive types of feed. The first is the custom smelter of the International Smelting and Refining Co. at Tooele, Utah1, with a multiplicity of ores; the second, the Kellogg, Idaho, smelter of the Bunker Hill and Sullivan Mining and Concentrating CO.2, treating an exceedingly rich lead charge, such as is now being made more and more as the practice of concentration is improved; and the third, the smelter at Trail, B. C., owned by the Consolidated Mining and Smelting Company of Canada, Limited3, which treats highly zinciferous charges and later recovers zinc from the slag. In comparing operations at these three smelters it must be clearly recognized that the objectives in smelting differ through differences in economics. Many operations are not, then, strictly comparable. There have also been decided improvements in operation since all of the smelters were examined, though this was but a relatively short time ago. The general factors that govern speed in smelting and the loss of metals in the smelters examined will be stressed. (For details of operation the reader is referred to the original papers.) This paper will then be an examination of the fundamentals of operating units in a search for improvements, and not a description of three great lead smelters. Capacity of Blast Furnace Assuming a well prepared and self-fluxing charge to start with, enough coke must be added: (1) to melt the charge, particularly the slag-forming

Jan 1, 1937

By Arthur Phillips, E. N. Skinner

DURING the course of an experimental program concerned with the hydrogen embrittlement of copper containing oxygen in concentrations within the solubility limits it became necessary to make a critical appraisal of the literature dealing with the solubility relationships of oxygen and solid copper. The latest determinations, and perhaps the only data obtained on "spectroscopically" pure copper, are those of Rhines and Mathewson1 who reported that the solid solubility increases from 0.007 per cent oxygen at 600°C. to about 0.015 per cent at 1050°C. Hanson, Marryat and Ford2 had previously placed the solubility limit at less than 0.009 per cent oxygen at 1000°C. and Allen and Street3 had suggested, on the basis of an unpublished research by T. Hewitt, not over 0.005 per cent oxygen at 500°C. In the introductory stages of the investigation indirect evidence accumulated to suggest that the solubility limits were significantly lower than those previously reported. For this reason it was deemed essential to clarify this point before proceeding with a program intended to establish a quantitative relationship between hydrogen embrittlement and oxygen concentrations positively known to be within the solid solution range. Furthermore, the increasing production and the highly selective applications of the commercial "oxygen-free" coppers inevitably direct attention to the practical necessity for exact knowledge regarding the effects of minute concentrations of the elements ordinarily found in the high-purity coppers now available. Of these elements oxygen occupies a unique position, not only by virtue of its specific effects on copper but more particularly in view of its important reactive tendencies toward the other impurities with which it is associated. Rhines and Mathewson considered several methods for measuring the solubility of oxygen and finally adopted the simple plan of saturating the specimens, obtained from redeposited cathode copper, by heating at the desired temperature in air. After the removal of surface oxide by mechanical and chemical means, the oxygen content was determined in the underlying metal. In general, this process of saturation, with a few modifications, was followed by the present writers. Although the procedure is direct and has obvious advantages, its effectiveness, unfortunately, is reduced by an excessive scaling of the copper, particularly at the higher temperatures. After saturation treatments above 900°C. the writers found that the specimens, necessarily rather thin in the original condition, consisted largely of scale and yielded too little metal for a satisfactory analytical sample. Furthermore, great difficulty was experienced in effecting complete removal of the scale. Needless to say, it is necessary to exercise extraordinary care in the preparation of the surface of the analytical sample in order to eliminate submicroscopic fragments of cuprous oxide which ordinarily are lodged in the crevasses and

Jan 1, 1941

By Rip Thompson

ALTHOUGH the metallurgical treatment for the Ophir Hill tailings was developed more than 20 years ago and in the interim a vast amount of experimental work was done with later-developed flotation rea-gents, it was found necessary to revert to the original oil reagents and their combina-tions with specific chemical reagents in order to obtain results of economic value. This is of especial interest because in present ore-treatment investigations later-developed flotation reagents are used almost exclusively and the coal-tar deriva-tives, except in certain patented reagents, are virtually neglected. These coal-tar oils and derivatives still have a definite field of application, especially in the treatment of some oxidized ores when modified sulphidi-zation is desirable. The Ophir Hill tailings deposit is in Ophir Canyon, Tooele County, Utah, about 55 miles southwest of Salt Lake City and 25 miles south of the Tooele smelter of the International Smelting and Refining Co. A road good for trucks leads directly from the Ophir mill to the smelter.

Jan 1, 1940

By Robert C. Edmiston

The measurement of temperatures in exploratory drill holes yields information on regional and local geothermal gradients and mean surface temperatures. This data may be beneficial to the mining geologist interested in the occurrence and oxidation of metallic sulfide minerals or to the mining engineer interested in subsurface temperatures or water movement. Additionally, the estimation of mean surface temperatures by the projection of thermal gradients to the ground surface provides data on which to evaluate infrared imagery as an exploration tool. Temperature measurements in 30 diamond drill holes in the Silver Bell mining district of Arizona show that a regional geothermal gradient of 2.45°C per 100 m increases to 3.03°C per 100 m near the ground surface. It is also found that an anomaly in the mean annual surface temperature of 0.5°C is associated with the shallow occurrence of disseminated sulfides. Changes in the geothermal gradient due to topography, water circulation, and formation changes also occur.

Jan 1, 1976

By G. H. Kennedy, H. E. Criner

CYCLONE thickeners are "hydraulic centrifuges" designed either to produce a maximum practical separation between the water and solids of a feed slurry or to classify the slurry solids according to particle settling rate. The possibilities of utilizing the thickener to "close" plant water circuits have been investigated. Since the thickener becomes an integral part of the plant water circuit when installed, the basic means by which the solids content of all circulating water systems must be controlled is reviewed. All coal not separated from the circulating water by means of dewatering screens or settling devices must be bled from the plant at the same rate as they are being fed or created by degradation. If this were not true, the circulated volume would finally be completely filled with solids. If the rate of bleed is low, the solids concentration in the bleed and circulating water generally will be high. To keep a reasonable circulating water concentration, large amounts of fresh water must be supplied and the bleed rate must be high. These conditions are usually undesirable because of the difficulty in securing fresh water, the loss of large quantities of coal, and the pollution of nearby streams. Thickeners are the primary stage in the separation of the water contained in the bleed from the coal. Since a thickener, when operating with reasonable efficiency, usually cannot be expected to deliver an underflow containing less than 50 pct water, secondary dewatering devices such as a slurry screen or vacuum filter must be used to separate additional water from the bleed. The surface area required by the filter or screen will be nearly proportional to the total water which must be handled, and therefore the thickener becomes necessary to hold down the original cost. The water separated from the coal is then returned to the plant circuit to maintain the water balance and thus becomes the source of fresh water. It is not necessary to return clear water to the plant to maintain control of the circulating water concentration. It is only necessary that the bleed dewatering devices remove coal in all sizes at a rate equal to that at which these sizes are entering the circulating water. However, practically speaking, in order to maintain low solids concentration, it is usually necessary that the thickener have good recovery characteristics on bituminous coals in those sizes down to 400-mesh. The thickener can remove the smaller sizes from the closed-circuit system at the "solids in" rate and prevent their "build up" in the circulating water as shown in Fig. 1. With the portion of the feed water going directly to the underflow, comes the very fine solids not concentrated by the cyclone. All the larger solids are removed from the feed and delivered in a concentrated condition at the underflow. To apply thickeners with some reasonable assurance that operating requirements will be met, it is necessary to know the rate at which solids of all sizes must be removed from the circulating water and to know the thickener characteristics. The required removal rate of fine solids not recovered by other dewatering devices may be estimated from the size distribution and tonnage of the plant feed with a reasonable allowance for degradation in the circulating water system. A more reliable estimate may be secured by sampling the plant bleed water during a constant load period.

Jan 1, 1952

By Kalanadh V. S. Sastry, D. W. Fuerstenau

Design and operation of a batch balling drum that can be used easily for experimental investigation of the balling or granulation behavior of particulate materials are described briefly. An experimental procedure for ascertaining the growth kinetics of iron ore concentrates or other particulate materials with this kind of apparatus is outlined.

Jan 1, 1972

By William Glenn

The taking of proper samples of crude ores seems to he less thoroughly understood, or less carefully practiced, than its impor tance requires. We all know how often we encounter the reports of very accurate assays and analyses, the weight of which as evidence wholly depends on the method of obtaining the sample, and is very probably nil, because there has been no proper sampling. Pissages might be cited from technical books, and from current technical literature (all the work of writers whom we delight to honor) to show that even among high scientific authorities there is too little acquaintance with the practical art of the sampler. There is no metallurgical or chemical establishment which does not frequently receive samples truly representing nothing. They consist usually of bits of ore, or what not, selected because they are worse or better than the average of what they are meant to represent. And they are worthless, no matter who made the selection. Where conscious choice is permitted to enter into the operation, a fair sample will not result, unless by a miracle. The work of sampling is often looked upon as within the realm of boys and of pensioners only. At least, though the manual labor be left to subordinates, the principles on which it is conducted and the safeguards with which it is surrounded are not unworthy of the study of experts; and experts should he ready to teach these principles and enforce them in practice. For exact sampling is the indispensable first step towards learning the value of any boxful, carload or shipload of ore. I propose to give a simple account of the method of sampling by hand, such as I have always pursued. There is nothing new about it. So far as I know, it is the immemorial old method, as old at least as Cornish copper-mining. Perhaps my fellow-members in the Institute may suggest improvements in it. If not, it will constitute a record in our Transactions to which laymen and beginners may be referred.

Jan 1, 1892