Search Documents

By H. A. Schwartz, W. Kenneth Bock

In this paper it is shown that when the tensile strength of a given steel in various states of heat-treatment is plotted against its elongation, a straight line results. The equation of this straight line can be computed with considerable accuracy from its chemical composition. The appropriate equations are given. The logarithm of the slope of the tensile-strength locus is shown to be proportional to the cumulative effect of the total alloy addition and the vosition of the line to be directly proportional to the cumulative effect of the alloy content. It is further pointed out that heat-treatment is more effective than composition in determining yield ratio. The latter enters mainly by its effect on hardenability, which is briefly discussed. Reduction of area and Brinell number are given some incidental attention. The data are applicable only to steels that have been normalized and/or quenched. The steels, if normalized, may or may not have been tempered. If quenched they must have been tempered at or above 4oo°C. (75o°F.). Introduction Cast steels vary in composition and frequently are used in various states of heat-treatment. It is obviously important to be able to predict the compositions that might accompany specific engineering properties by suitable selection of heat-treatments. For cast steels, which are of necessity produced heat by heat in accordance with the particular requirements of the castings to be poured, there has been, happily, much less tendency to standardization than for rolled products, whose destination is not necessarily known when particular ingots are made or rolled. It is of distinct advantage to the steel foundry-men to be able to make steel of given properties, using alloys that can be recovered from scrap, or most conveniently or cheaply bought, rather than a particular formula adopted in the interest of standardization. The heat-treatment appropriate to securing a given result in a given steel is well known to be closely related to composition. For example, molybdenum steels are not much softened by tempering except at rather high temperatures. Highly alloyed steels are "air-hardening," and on cooling in air behave like carbon steels that have been quenched. With these matters, we do not concern ourselves in this paper, although we recognize their importance. The entire picture evidently will be very complex and can be brought within accurate understanding only if our knowledge of test results can be coordinated in terms of general principles.

Jan 1, 1944

By R. A. L. Black, J. E. Jennings

The problems of slope stability in open cast mines are examined. A criterion, the instantaneous stripping ratio, is suggested for use in the design of pit slopes and as an index of control at all stages of the exploitation of the orebody. This criterion may also be related to safety and to the maximizing of profits. Two approaches to safe design of slopes, one from the point of view of soil mechanics and the other from the point of view of rock mechanics, are described and critically compared. The effect on slope stability of the regional tectonic stress field is discussed. Explanation is given of the application of the Terzaghi effective stress concept to problems in both soil and rock environments, including possible effects when borehole deformation techniques are used to measure stresses in rock in situ. A company embarking on open cast mining is faced with two basic questions: 1) will the venture be profitable and 2) can it be carried out with safety? The two questions are obviously interrelated because both depend upon the slope angles adopted for the pit. The cost of open cast mining depends largely upon the stripping ratio, defined as the volume of overburden that must be removed to the volume of ore recovered. The steeper the slope angles, the more favorable the stripping ratio, but the stability of the slopes, and therefore the safety of men and materials in the pit, require that the angles be made relatively flat. Consequently, the design depends upon a compromise: the slopes must be steep enough to result in economical mining and flat enough to ensure safety. Today there is a world trend towards deeper mining by open cast methods. This is mainly due to the higher cost of underground mining and the lower cost of open excavation resulting from the introduction of large modern earth and rock-moving machinery. Deeper open cast mining has led to a very great increase in the volumes of wasted overburden, and much thought is being given to the considerable economic benefits which would result if pit slopes could be made steeper by even one or two degrees. The result has been an increasing interest in research into slope stability problems in the expectation that the application of scientific principles will provide solutions leading both to economies and to more predictable operation of the mines. In at least four places, the U.S., Australia, Western Germany and Southern Africa, comprehensive investigations are at present in progress, and it is the object of this paper to review some of the more important aspects of these programs. RELATION BETWEEN ECONOMY OF OPERATION AND SLOPE ANGLES The main object of any industrial enterprise in a free economy is to make a profit. In mining, where profits must be made from a wasting capital asset, a further definition of the profit motive is imposed, namely that the economic aim should be to maximize the total possible profit. But since profits deferred for a number of years are not as valuable as profits that are immediately available, it is usual to discount deferred profits at some rate of interest which reflects their current or present value in the hands of the investor. Thus, in mining the logical aim can be defined more closely still: to maximize the present value of the total future profits. In commercial terms the present value represents the market value of the operation as a going concern. Many factors enter into the forecast of current and future profits. They include the volume of production, the price of the salable product and the cost of production. Current profits can be estimated with reasonable accuracy by the operating engineers; but it is the task of economists and management to assess future trends in the mineral markets and in the economy as a whole, and together with the engineers, they can then estimate the future cost and profitability of the mining operations. In open cast mining, the rate of ore production once decided on remains a virtually constant factor unless a major change in the capital structure of the mine is made. But one factor over which the operator has a considerable measure of control is the ratio of the volume of ore mined to the volume of waste over-

Jan 1, 1963

By Ancel St. John

Defects in the interior of metal objects are troublesome to both manufacturer and user. For the former, they frequently increase manufacturing cost through the rejection of material when defects appear after considerable work has been done. For the latter, they often cause damage to equipment, personal injury, or loss of life when a part, which has passed all inspections and has been put in service, gives way because of a hidden flaw. Methods of testing that locate such flaws without subjecting the specimen to possible, if not actual, destl-uction are few; x-ray examination, whether fluoroscopic or radiographic, is one. Hitherto, however, x-ray examination has been restricted to objects of nearly uniform thickness and regular outline; the inspection of such articles as those shown in Fig. 1 has been inconvenient and unsatisfactory. This figure represents a group of 5/16-in. hexagonal-head machine bolts,

Jan 1, 1923

By Ancel St. John

Defects in the interior of metal objects are troublesome to both manufacturer and user. For the former, they frequently increase manufacturing cost through the rejection of material when defects appear after considerable work has been done. For the latter, they often cause damage to equipment, personal injury, or loss of life when a part, which has passed all inspections and has been put in service, gives way because of a hidden flaw. Methods of testing that locate such flaws without subjecting the specimen to possible, if not actual, destl-uction are few; x-ray examination, whether fluoroscopic or radiographic, is one. Hitherto, however, x-ray examination has been restricted to objects of nearly uniform thickness and regular outline; the inspection of such articles as those shown in Fig. 1 has been inconvenient and unsatisfactory. This figure represents a group of 5/16-in. hexagonal-head machine bolts,

Jan 1, 1923

By M. S. Burton, G. V. Smith, A. Rosen

The kinetics of re crystallization and the effect of recovery on recrystallization of pure iron were investigated within the temperature range of 517" to 632 OC. Grain growth and activation energies were also studied. Two stages can be distinguished during recrystallization; the first is gvowth-controlled and the second is nucleation-controlled. The extent to which the first stage succeeds before the second stage begins depends on both temperature of recrystallization and temperature of recovery. The softening of cold-worked metals and alloys due to transformation of the deformed crystals to strain-free equiaxed grains during annealing is well-known, and early inestiators established that recrystallization kinetics is strongly influenced by minute quantities of impurities. Generally, it is believed that impurities decrease the rate of recrystallization and the rate of grain growth. To understand the basic phenomena of recrystallization, investigations should be on pure materials. Most of the research on high-purity materials has been on metals having the fee Bcc materials, and especially high-purity iron, have been studied only in recent years. It is known that recovery may influence recrystalliation;" however, no general description of the influence, applicable to all materials, has been presented. This paper presents results of a study of the recrystallization kinetics of high-purity iron, after 60 pct cold deformation by drawing, with particular reference to the influence of recovery on the rates of recrystallization and grain growth. From observations of these rates, conclusions are drawn concerning nucleation. MATERIAL AND EXPERIMENTAL PROCEDURE Preparation of Material. High-purity iron, prepared by zone refining of vacuum-melted electroiytic iron at Battelle Memorial Institute under sponsorship of the American Iron and Steel Institute, was used in this study. Table I gives the reported chemical analysis of the material, taken at a point near the last molten zone and thereby rep- resenting the maximum impurity level for the entire bar. Prismatic specimens, approximately 10 x 10 X 50 mm, were sawed from the 50-mm-diam bar, perpendicular to the zone-refining direction, and turned to cylindrical shape. These specimens were sealed in quartz capsules under vacuum, approximately 10"e mm Hg, austenitized at 930° C for 15 min, slowly cooled, removed from the capsules, and cold-worked in air by swaging to approximately 20-pct reduction of area. The encapsulating, austenitizing, and swaging operations were repeated two additional times, after which the samples were encapsulated, austenitized, and cold-drawn to 60-pct reduction of area. A further vacuum anneal at 630°C for 120 min and cold drawing to 60-pct reduction of area produced wire 2.8 mm in diameter. The drawn wire was electropolished to remove deformed material on the surface, after which it was sawed into 4-mm-long specimens for the recrystallization study. Microscopical examination before the final cold reduction revealed equiaxed grain structure with very fine grains in a thin layer near the surfaces of the specimen and nearly uniform ASTM 3-4 grain size in the center. Recrystallization Heat Treatment. a) Direct Recrystallization of Cold-Worked The 60 pct cold drawn iron specimens were recrystallized at five temperatures, 517, 556, 590°, 612, and 632C, in a lead bath covered with graphite (the temperature was controlled to 1°C). Specimens were treated for twelve different times at each temperature, and all were water-quenched after heat &eatment. b) Recrystallization Following Preliminary Recovery Heat Treatment. After cold working, specimens were sealed into quartz capsules under vacuum, 105 mm Hg, and recovery-annealed at 362", 400", and 440°C for 20 hr prior to recrystallization. No evidence of recrystallization was found

Jan 1, 1964

By Edward B. Durham

The refinery at the San Francisco Mint takes the bullion purchased by the receiving department, and carrying Illore than 200 parts of precious metals in 1,000, or, in mint parlance, over 200 fine, and separates and refines the various metals contained therein, using electrolytic processes exclusively. Bullion containing silver is treated in cells charged with a nitric electrolyte. These cells produce fine silver and leave a residue rich in gold. The residue from the silver-cells, together with crude gold-bullion, is treated in cells having a chloride electrolyte. These produce fine gold and leave a residue containing silver chloride. The latter is reduced to the metallic state with zinc and is then treated in the silver-cells. The various waste solutions and the wash-waters, after being freed from the bulk of their precious metals, still contain copper and other metals. These are removed by scrap-iron, and are then treated in the copper-cells, having a sulphate electrolyte. These cells produce pure copper, and collect a residue containing lead, some gold and silver, and all the metals of the platinum gronp that were in the bullion. This residue is relatively small, and is melted into bars and stored until suEcient accumulates to warrant treating it for platinum, etc. The refinery occupies three large and three small rooms. The large ones are, a melting-room, 30 by 34 ft.; a cell-room, 39 by 46 ft.; and a wash-room, 30 by 33 ft. The small rooms are used as foreman's osce, laboratory, and , re- spectively. The methods here described are those in use in December, 1909, when notes for the present paper were taken.

Jan 1, 1912

By J. H. Nelson

An outline survey of the economic outlook for the United States export trade in petroleum products resolves itself broadly into two general divisions; first, a consideration of our present position in this trade, and second, a discussion of the visible factors which promise to affect appreciable changes in the immediate future in that trade. The United States PetRoleum Exports of majoR Petroleum Products 1925, 1926 and 1927

Jan 1, 1928

By Samuel B. Christy

" The man is always greater than his work." The training of the men who are to develop the mineral resources of the world is the most important problem connected with mining engineering. It becomes ever more important to civilization as the mineral wealth of the earth approaches exhaustion. I have therefore decided to consider a few of the more important problems arising in the training of the mining engineer, and especially those arising in America. , The Peculiar Nature of Mineral Wealth. Mining and Agriculture are the two fundamental arts. Without the latter our existence would be precarious; without the former, our civilization impossible. Agriculture furnishes that regular supply of food and raiment which leads to the growth of large communities in which cultivated leisure first becomes possible; while mining furnishes the metallic thread from which is woven that complex fabric we call civilization. But in these two arts the conditions for success are widely different. Most of the crops that the farmer reaps may be harvested year after year, and the proper fertilizers being added, he may continue the annual harvest indefinitely, while, as a result of cultivation, his farm becomes yearly more valuable. But the crop the miner reaps can be harvested but once in the history of the race. Our mineral wealth has taken unknown ages to mature in the bosom of the earth. The ripened fruit can be plucked but once. There are no fertilizers for worked-out mines. It never pays to work over a mine that has been

Jan 1, 1906

By R. A. Fitch, J. D. Griffith

A performance calculation method was used in conjunction with experimental studies to develop means of predicting and interpreting miscible floods and to explore possible methods. of improving their efficiency. The calculation method is based upon the division of reservoirs into multiple independent zones or strata. Comparison was made with some experimental floods and with a field project to obtain some measure of the applicability of the method. Two aspects of miscible flooding were considered: (I) the displacement of a miscible front through a reservoir, and (2) the distribution and utilization of the solvent volume injected to maintain miscibility. Calculations and experihental observations indicate that alternate gas-water injection behind a miscible front significantly improves miscible flood performance, both within a single stratum and in a multistrata reservoir. Calculations were made on the extent to which miscibiliry is maintained by a given solvent volume in a stratified reservoir. Two alternate criteria for determining the optimum volume of solvent for injection are discussed. The preinjection of a small volume of water ahead of the solvent is suggested as a method of obtaining more efficient utilization of solvent. Calculations and experiments were made to investigate the effects of water preinjection. INTRODUCTION Miscible fluid displacement as a possible means of recovering oil has been the subject of extensive research and numerous field tests over the past several years. This work has brought out both favorable and unfavorable features of the miscible recovery methods. Many tests have shown that a miscible fluid can displace all of the oil contacted, leaving no high residual oil saturation, as is characteristic of immiscible displacements. The miscible methods have proven dificult to control, however, as evidenced by early breakthrough of the displacing fluid and poor sweep efficiency in several field projects. It became apparent early in the investigation of miscible displacement that the development of improved techniques and better methods of control would be required to extend the range of applicability to any significant portion of our petroleum reservoirs. The purpose of this study was to consider the problem of designing miscible floods to obtain better performance. A performance calculation was used in conjunction with experimental studies to develop means of predicting and interpreting miscible floods and to explore possible methods of improving their efficiency. Two aspects of miscible floods were considered separately in this study and the results are presented in two parts. The first part concerns the manner in which the miscible front is displaced through the reservoir. In these calculations the condition of miscibility between the reservoir oil and the displacing fluid is assumed. In the second portion the distribution and utilization of the preinjected solvent in maintaining rniscibility is considered. This portion dealing with solvent utilization applies only to the enriched gas or LPG slug processes. CALCULATION METHOD AND EXPERIMENTAL STUDIES COMPUTATIONAL MODEL The calculations for expected reservoir performance are based upon the multi-strata concept of reservoir properties. The method assumes multiple, independent strata (no crossflow between strata) and explicitly includes variations in patterns, injectivity, areal sweep and displacement efficiency. Lateral variation in permeability within the strata (for example, directional permeability) may be considered in the calculations, provided the variations are similar in all strata. The calculations based on this model furnish the rates of injection and rates of production of both oil and the displacing fluid for the composite system of strata. To carry out calculations on the mathematical model described, information is required on the performance of the displacement process under consideration in a single stratum element of the pattern to be used. In particular, for a given pattern and displacement process, data are required relating injectivity and composition of the produced stream to the volume of fluid injected. Data on the variations in areal sweep must also be available if it is desired to track the areal sweeps in the multi-strata model. These data may be obtained from experimental work such as model studies or other suitable methods. This representation of reservoir properties is, of course, an approximation and may be inappropriate in some cases. But the representation is not an arbitrary one since most oil reservoirs are essentially successive layers of sediment with the net producing pay zone often comprising but a fraction of the gross formation thickness. The fact that permeabilities measured in the vertical direction are frequently but a fraction of the horizontal permeability adds some evidence to the validity of this model. This type cal-

Jan 1, 1965

By Allan J. Clark

It is nearly three years since the metallurgy of the Homestake ore was discussed with considerable thoroughness, in a paper1 read before the Institution of .Mining and Metallurgy. Certain changes have been made in this period which are perhaps of sufficient interest to justify a brief description, and it is chiefly with such details and miscellanies that this paper will deal. In the circumstances, a certain amount of repetition is inevitable, but matter treated of in the former paper will be referred to here only when it is necessary for the sake of coherency. For full descriptions of equipment and technique, the former paper should be consulted. The mineralized slates and schists which constitute the ore vary considerably in composition, but the unoxidized ore, perhaps constituting the major part of the reserves, contains either chlorite or hornblende (cummingtonite), with quartz, carbonates of lime, magnesia and iron, and arsenopyrite, pyrite, and pyrrhotite. Ferrous minerals predominate, and this fact has been an important factor in determining the metallurgical treatment. With one or two exceptions the minerals noted are of relatively high specific gravity, and the ore as a whole is exceptionally heavy, many determinations giving an average specific gravity of 3.00. This high specific gravity presents one decided advantage, when the cost of treatment is compared with operations elsewhere, in that the ton, almost universally the basic unit, represents a volume probably less by 10 per cent. than that of many gold ores. On the other hand, this high gravity renders more difficult the discharge of pulp from mortars, its distribution on amalgam tables, and its transportation in launders. In the same way, as attesting the usual balance of such variations of different ores, it may be noted that the needle-like fibers of hornblende (cummingtonite), interlacing throughout the mass, render the ore more difficult to crush than would be anticipated, but on the other hand assist

Jan 1, 1916

By T. A. Rickard

Our Transactions contain two notable papers descriptive of the stamp-milling practice of the Black Hills and of Grass Valley, namely, the elaborate and complete treatise of Prof. H. 0. Hofman, on " Gold-Milling in the Black Hills,"" and the paper describing the North Star mill, by E. R. Abadie, its superintendent. Having visited and examined the stampmills of both localities, I venture to offer here such comment as more recent information or a different point of view has suggested.†

Jan 1, 1896

By J. V. Gluck

In the present paper," as in earlier publications, V1'2"1 the authors present experimentally obtained relations for the free energy of solution of oxygen in various metals as a function of temperature. The relations are linear and given in slope-intercept form. The authors give values for the "probable error" of the slope and intercept, citing Birge's method17 for obtaining these quantities. Birge discussed these methods as early as the period 1929-32.25726 In Ref. 25 the probable error is defined as "the numerical value which the true error is as likely to exceed as not", i.e., 50 pct probability. Ref. 26 is even more detailed and includes a lengthy discussion of the applicability of the Gaussian distribution to experimental data. However, the use of the "probable error" has come under some question. For example, Ezekiel'~ states that "the use of the probable error tends to make the results appear rather more accurate than the standard error". Moroney28 stated (in 1951) that "the term 'probable error' was used in former times to denote 0.67450 (50 pct confidence using the normal distribution)....the term, a poor one, is now very much obsolescent. It has been said that 'it is neither an error nor probable' ". Bennett and Franklin in 1954" in discussing statistical confidence levels mentioned that "the customary use of the 5 and 1 pct levels is not completely a matter of chance; these levels probably represent a balance between the desire to be correct and the desire to be specific. Also in most people's minds the borderline between something that could possibly happen and something that is not likely to happen is somewhere in this region. Certainly 5 or 1 pct confidence limits are to be preferred to limits such as the 'probable error' which has only a 50/50 chance of including the correct value." It may readily be seen that the 95 pct confidence level, which is given by 1.960 (assuming large sample size), thus corresponds to approximately three times the "probable error". Indeed, limits of one standard deviation correspond only to about 68 pct probability. Even if we triple the tolerances given by the authors in the equations of their Table 111, the deviations do not become excessive and would not detract from their excellent results. It could then be said with a high degree of confidence (95%) that the precision of the slope and intercept values is about *3-5 percent of their absolute levels rather than the 1-2 percent implied in Table 111. This is then compatible with an earlier suggestion of Gokcen~' of a probable accuracy of 5 pct in dissolved oxygen measurements by the technique employed. Alternatively, the authors could have

Jan 1, 1967

By W. Francis

OF THE methods that have been used for studying the chemical composition of coal, attack by reagents has not, in general, yielded much information. Most of the reagents used have been strong oxidants such as nitric acid or Schulze's solution. The use of a milder oxidizing agent, such as air at low temperatures, enables progressive changes in the character of the coal substance to be studied and thus helps toward an understanding of its constitution. British bituminous coals frequently have a banded structure. These bands (of four types) can be separated one from another and have been found to possess markedly different chemical characteristics, even when taken from contiguous portions of the same lump coal. It has been found convenient to give each of the ingredients of banded coal a distinctive name, more or less descriptive of its appearance, and the study of the chemistry of bituminous "coal" in England has resolved itself into a study of each ingredient separately. . The coal chosen for this work was taken from the Top Hard seam at East Kirkby colliery, Nottinghamshire, a detailed chemical analysis of which has been recorded by Baranov and Francis.1 The banded structure was well marked and the bands could readily be separated. The research was confined to the brilliant vitreous bands (vitrain), the dull hard bands (durain) and the "sooty partings" (fusain); for previous work had shown that the fourth type, to which the name clarain has been given, is intermediate in character, chemically, between vitrain and durain.

Jan 3, 1925

By J. T. Norton, N. J. Grant, I. S., Servi

Coarse grained high purity aluminum was tested in creep at temperatures of 400° to 1200°F to develop subgrain structures. Measurements of subgrain size, distribution, and rotation were made from X-ray diffraction patterns. Subgrain size and distribution were checked metallographically and the size was compared with average slip band spacing. The slip family was determined for several specimens. THE interest and research recently evident abroad in the role of subgrain formation and polygon-ization as a contribution to the creep of metals at elevated temperatures is deserving of greater attention in this country. Such metallic subgrains can be defined as macroblocks existing within the grains. The general observation has been that the macro-blocks which belong to the same grain have a maximum difference in orientation of a few degrees. In spite of the considerable amount of work that has been done since Jenkins and Mellorl observed the "division of existing crystals into smaller units when deformation occurs at an annealing temperature," the subject of subgrain formation is only now receiving truly active discussion and investigation. The existence of subgrains has been revealed by metallographic methods, as in the work of Jenkins and Mellor,1 and by X-ray methods, first applied to this problem by Homes.' Hirst3 and Calnan and Burns4 applied the back-reflection Laue technique to the study of coarse grained specimens. Wood et al.5 and Greenough and Smith' examined the ring obtained with a back-reflection camera for the study of fine grained specimens. In addition to the above, the transmission technique was used by Wood.6 A special technique was developed by Guinier and Tennevin8 in order to improve the resolution. Metallographically, the subgrains have been observed directly on the surface of deformed specimens by Wood et al.,3 or have been made evident on repolished surfaces by applying a suitable etching reagent. The latter technique, first suggested by Lacombe and Beaujard,9 was then improved by Wyon and Crussard.10 Subgrains can be formed in single crystals after small amounts of bending followed by heating after this cold work, or during deformation at elevated temperatures. The first phenomenon was analyzed by Cahn11 for the simple case of pure bending followed by annealing. Cahn suggested a mechanism of subgrain formation based on the dislocation theory and called this phenomenon "polygonization." He extended this mechanism to the more complex case of local bending, such as the bending which may occur when a polycrystalline specimen is deformed in tension. Cahn's suggestion was later found quite consistent with the results obtained by Dunn and Daniels." An explanation has been presented recently regarding the formation of subgrains during deformation at elevated temperatures by Chang and Grant.'" In general, there are two schools of thought on the subject. One, according to Wood et al.,5 is that subgrain formation is a mechanism of deformation which is operative under certain conditions in the same way that the slip process is the mechanism of deformation which is operative under other conditions. The boundaries between the subgrains undergo a viscous flow which contributes substantially to the deformation of the material. The second, according to Cahn,13 Wyon and Crussard,10 and Chang and Grant,18 is that subgrain formation is the effect of simultaneous deformation and annealing and is,

Jan 1, 1953

THE composition and quality of finished steel depend upon selection and proportioning of the raw materials of the charge as well as upon control of furnace practice. This chapter deals only with the raw materials of the basic open-hearth process that are important in determining the composition of the steel or slag. They are the metallic charge, oxygen-bearing materials, fluxes, alloying and deoxidizing additions, and certain refractory materials used for maintenance of bottoms. Other refractories, which may affect the slag composition, are discussed in Chapter 3. Wide variations are possible in the type and composition of charged materials but certain limiting relations among the elements of the charge must be observed. Since the process consists essentially of refining by the oxidation of undesired dements, a balance must be established between the sources of oxygen and the elements in the charge that are subject to oxidation (see Chapters 2 and 7). For example, if it is desired to use a high ratio of blast-furnace hot metal to scrap, it is necessary to add an oxygen-bearing material such as ore or mill scale to eliminate the excess carbon and silicon that are present in the hot metal. An example of the opposite extreme is the use of a metallic charge composed entirely of steel scrap. With this type of charge, it is common practice to substitute burnt lime for limestone as a flux and to charge some carbonaceous material such as coke to avoid an excess of oxygen in relation to the elements of the charge that are subject to oxidation. Elements such as copper and nickel, which are not oxidized or eliminated by, any other reaction, may be introduced into the charge only to the extent to which they are permissible in the finished steel. An example of adjustment of the charge for elements of this type is found in the use of steel scrap high in copper. In this case, metallic components of the charge other than the scrap should be low in copper, or a sufficiently high ratio of pig iron to scrap should be charged to dilute the copper from the

Jan 1, 1951

By P. B. Bucky

IN previous publications1 it was shown that a scalar model of any weighty structure, where the stresses produced are mainly due to gravita-tional forces, will behave similarly to its prototype if the model and proto-type material are the same arid the model is placed in a centrifugal field of force (substituted for the gravitational field) which has been increased in the same proportion as the linear model scale is decreased. This principle is now being applied to a study of the behavior of mine structures in an attempt to determine the laws that control them. The importance of using models as a means of solving mining problems has been discussed previously, yet it may be well to reiterate here that this method of research and type of solution have been productive of far-reaching results in other engineering fields, notably those of hydraulics and aerodynamics. Model research is a comparatively cheap and time-saving method of checking practical experience. Up to the present time the best guide to what will happen underground has been the judgment of the man who has observed most and been longest acquainted with the local conditions. His experimental work underground is limited by the elements of cost, time and danger, while failure is seldom permissible. In a model, as in a test tube, all elements that affect the solution of a problem are under definite control. Each element may be varied independently at will and its effects noted. Experimental work on a small-scale model may there¬fore be performed at a comparatively small expenditure of time and money, instead of on a full scale in the mine, where the cost, time, and danger elements are necessarily great. The experiments described in this paper are to be considered as part of a progress report and a continuation of Technical Paper 425. One object of the research program is to make each experiment point the way for further research on that particular phase of the general problem. The results and conclusions presented here are therefore not to be considered as final, but are to be interpreted as

Jan 1, 1933

By W. E. Keck

THE flotative properties of the principal minerals in Michigan's potential iron ores have been investigated to develop methods of bene-ficiation for the ores. One of these minerals, magnetite, is of considerable importance as a source of iron. Study of its flotation was similar to that of hematite1, another iron mineral in these potential ores. The present research consisted essentially of: (1) a survey of the literature on mag-netite flotation, (2) the preparation of pure magnetite, (3) the develop-ment of laboratory procedure and (4) flotation experimentation. Literature an Magnetite Flotation.-For the purpose of this discussion, the results of previous work on the flotation of magnetite can be sum-marized as follows. The mineral has been floated with pine oil2, and it has also been separated from synthetic mixtures with silicates by the use of the same reagent2. Magnetite and apatite in iron-ore slimes have been separated by flotation of apatite with sodium palmitate3. These data were utilized in the present investigation. Preparation of Magnetite.-The pure mineral was prepared from the magnetic-separator concentrate of an iron ore (obtained from the Wither-bee Sherman Corporation, Port Henry, N. Y.). This concentrate was slowly comminuted with laboratory rolls and pulverizer to pass 65 mesh and was then tabled several times. Tabling yielded a relatively coarse magnetite concentrate, tailing and slimes. The two latter materials were rejected insofar as the present work is concerned, and treatment of the magnetite (table concentrate) was continued by separating it into -65 + 200 and -200-mesh sizes. Separation of the sizes was made by first dry screening and then wet screening. The -200-mesh material was rejected to eliminate possible introduction of error into flotation

Jan 1, 1937

By J. J. Pye, J. B. Drew

The surface-diffusion coefficients of Ni63 diffusing on low-index planes of nickel single crystals have been measured over the temperature range from 400° to 1000°C using a precision autoradio-gvaphic technique. The activation energy for sur -face diffusion appears to he the same on the {111}, {110), and (100) planes and amounts to -0.60 ev. This is in good agreement with the value (-0.62 ev) reported for (111) planes obtained by mass-transport techniques. In an earlier paper, the authors have reported self surface-diffusion coefficients on silver.' In that work, a deviation of the diffusion coefficients from linearity in the Arrhenius plot was observed at high temperatures. This effect was attributed to a loss of tracer atoms into the bulk by volume diffusion. The purpose of the present work was to extend the technique developed to the nickel surface-diffusion system up to the point where volume diffusion would come into play. The nickel system especially lends itself to this technique due to the high efficiency of the isotope in darkening the film and the large absorption of the weak radiation (0.063 mev /3- particle of the trapped tracer atoms. The diffusion coefficients and ictivation energy for different orientations on nickel can also be compared with a report published by Blakely and Mykura 2 where a mass-transfer technique was used. This paper reports the self surface diffusion of nickel on the low-index planes over a wide temperature range using a precision autoradiographic technique. EXPERIMENTAL PROCEDURE The experiment is similar to that described in the earlier publication consisting of a radioactive needle as a source resting on a flat, smooth, chemically polished surface annealed in a dynamic dry-hydrogen atmosphere. The needle is held snugly on the surface by a holder fabricated from commercially pure nickel. The point source is made by grinding down a small-diameter nickel rod until a tip of approximately 0.1 mm radius is formed. It is then etched and the needle tip plated with the radioactive isotope Ni63. Nickel single crystals were used whose main impurities were spectrographically determined as Co 0.05, Fe 0.007, C 0.005, and S 0.003 pct. The surfaces, oriented to within 1/2 deg of the low-index planes, were carefully mechanically polished and etched in a 50-30-10-10 hot solution of acetic, nitric, sulfuric, and phosphoric acids giving a smooth polished surface. The crystals were then washed in distilled water and alcohol. Annealing temperatures ranged from 400° to 1000°C with a furnace arrangement in which the crystals could be brought up to temperature in times short compared to diffusing times. The temperature was maintained constant to ±10°C. In the temperature range investigated, the ratio of the surface-diffusion coefficient to the volume-diffusion coefficient (Ds/Du) was 105 or more and the mean bulk-penetration values, calculated from literature values of volume-diffusion coefficients,3 were on the order of 10-5 cm. After the diffusion anneal, the sintered needle is removed, and both the radius of the needle point and spot left on the crystal face are measured. The crystal is then placed on photographic film. Diffusion profiles are obtained by scanning the film with a recording microdensitometer which has a slit width of 10µ. DISCUSSION AND RESULTS The experimental conditions are such that the source strength and needle radius are essentially constant and the time is adjusted such that the mean bulk penetration is small. An exactly analogous heat-flow problem has been considered by Carslaw and Jaeger4 and the solution can be written in integral form as:

Jan 1, 1964

By Robert F. Shurtz

When an ore deposit is evaluated on the basis of core sampling, questions always arise as to how much weight should be given the various sample grades and how the deposit should be divided into specific volumes assigned to corresponding grades. For a tabular deposit it is customary to use the so- called zone-of-influence. This zone is usually de- fined as the polygon in the plane of the deposit having corners halfway between a given core drill intersection and each of the nearest neighboring intersections. The volume of the ore in this polygon is assigned the analysis obtained from the drill core taken at the intersection. In massive or irregular deposits, volumes of various shapes may be defined with respect to the locations of drill core samples. These volumes may be regarded as three-dimensional zones-of-influence; the theory involved in assigning the values of the central analyses to the ore in the volumes is the same as that used in the case of a tabular deposit. The zone-of-influence method was used in evaluating one of the magnesite deposits at Gabbs, Nev.1-3

Jan 10, 1959

By A. E. Wheeler, H. Y. Eagle

The copper industry in the Province of Katanga, in the Belgian Congo, which is now controlled and operated by the Union Minére du Haut Katanga, had its inception many years ago in the vision of a Scotsman, Robert Williams, now Sir Robert Williams, Baronet. He it was who personally negotiated the mineral concession with King Leopold of Belgium, sent in the prospecting parties who located most of the present mines of the company, later arranged for the Belgian participation from which the present company was formed, and has been its active mentor ever since. The idea back of his efforts was the establishment of an industry on the Congo-Zambezi divide, of sufficient importance to draw up to it the head of the Cape to Cairo Railroad, the dream of Sir Cecil Rhodes, and the consummation of which he had left as a legacy to Mr. Williams, his successor. The reports of the prospecting expeditions showed that copper in profitable quantity was there, but many difficulties lay in the way of the establishment of the infant industry. The isolated location of the mines, various tribal wars, the Boer War, and many other factors contributed to making progress very slow. However, in spite of these difficulties the railroad was finally built and a blast-furnace plant erected at Lubumbashi, near Elisabethville, the capital of the Province. Operations of this plant were started in 1911, treating high-grade oxidized ores and producing pig copper by a reducing smelting. Production has been continuous since that time and the company has grown so that at present it ranks as the largest individual copper producer in the industry. It is a fitting monument to the foresight, optimism and driving force of its founder, and the progressive policies of his Belgian colleagues. In January, 1914, the Union Miniere du Haut Katanga engaged as its consulting engineer, Archer E. Wheeler, metallurgical engineer, at that time general superintendent of the Great Falls plant of the Anaconda Copper Mining Co. Mr. Wheeler was commissioned by the Board of Directors to proceed into Katanga, and make all necessary investigations to enable him to report on a comprehensive development program, and to recommend a scheme of treatment particularly for their low grade

Jan 1, 1934