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By Herbert Clark Hoover, Lou Henry Hoover

THE third book has explained the various and manifold varieties of veins and stringers. This fourth book will deal with mining areas and the method of delimiting them, and will then pass on to the officials who are connected with mining affairs'. Now the miner, if the vein he has uncovered is to his liking, first of all goes to the Bergmeister to request to be granted a right to mine, this official's special function and office being to adjudicate in respect of the mines. And so to the first man who has discovered the vein the Bergmeister awards the head meer, and to others the remaining meers, in the order in which each makes his application. The size of a meer is measured by fathoms, which for miners are reckoned at six feet each. The length, in fact, is that of a man's extended arms and hands measured across his chest ; but different peoples assign to it different lengths,

Jan 1, 1950

By R. W. Raymond

The death of John Frederic Blandy, which occurred September 17, 1903, at Prescott, Arizona, terminated the earthly activity of one of the most active and able of the American mining engineers of the last generation. Mr. Blandy was born, April 24, 1833, at Newark, Delaware. His father was an Englishman, who had been in business in the island of Madeira, and had come thence to settle in the United States. At the age of eighteen, he was attached to the engineering field-corps of the Philadelphia & Reading Railroad; but, after a year of this service, he went to Germany, where he spent three years, entering in 1852 the Mining Academy at Freiberg, Saxony. Graduates of that institution need not be told that, at the period referred to, it held unique prominence in its special field, not only by reason of the great investigators and instructors, such as Cotta, Breithaupt, Weisbach, Plattner and Gaetschmann, who belonged to its faculty and brilliantly blended theory and practice in its work, but also because rival institutions were few. It cannot be fairly said that Freiberg has fallen below its ancient standard of excellence. Its chairs of instruction are still occupied by eminent men, worthy successors of the illustrious teachers who preceded them. But a host of technical academies, especially in this country, munificently equipped and efficiently conducted, have come into existence during the last half-century; and no one institution can ever hereafter claim the pre-eminence which the Freiberg Mining Academy once enjoyed. In those days, American mining engineers returning with satisfactory credentials from that school were sure of immediate employment.

Jan 1, 1904

By J. E. Lawver

On the basis of both laboratory and pilot-scale tests, a newly developed high-tension electrostatic process is technically and economically feasible for the production of iron ore superconcentrates containing 0.02 to 0.20% silica at iron recoveries of 85 to 90%. The process can be used to recover both a superconcentrate and a pellet-grade concentrate, from a feed containing middlings, and the system is not unduly upset from changes in feed structure and composition. The adverse affect of excess quantities of material finer than 30 microns, i.e., above 10% in quantity can be avoided by a desliming step. Finally, because of the cost of drying, the best feed for the process appears to be dry-ground ores as well as spiral, flotation, or magnetic concentrates.

Jan 1, 1970

By E. J. Whittenberger, F. N. Rhines

The formation of casting porosity is viewed as a nucleation and growth process with solidification shrinkage and gas precipitation as cooperative driving forces. Experimental evidence evaluating the individual contribution of each force confirms the major premise that microporosity is nucleated by gas precipitation. Additional data disclose the effects of the identity and quantity of gas, the temperature range of freezing, and the freezing rate upon the amount and distribution of porosity in light metal castings. POROSITY, as it commonly occurs in metal castings, has been ascribed to the contraction that accompanies the freezing of the metal, to the evolution of dissolved gases from the liquid during cooling and freezing, and, most frequently, to a combination of the two.'" "Pipe" formation is universally associated with solidification shrinkage; spherical "gas holes" are understood to be retained bubbles of gas; but the origin of microporosity, which usually exhibits an irregular or scalloped outline when viewed in cross-section, remains a subject of continuing debate.", ' The present research constitutes an endeavor to show what parts are played respectively by shrinkage and gas evolution in the initiation and growth of micropores and what factors determine their number, size, shape, and distribution. A preliminary outline of the mechanism of cavity formation in castings will serve to coordinate the experimental findings that will be reported and will at the same time provide a general theory of the origin of casting porosity. Basic to the mechanism of cavity formation that will be proposed are the following established facts: 1—that liquid metals and alloys contract gradually during cooling down to the freezing range, where a relatively large contraction, known as the "solidification shrinkage," takes place (exceptions in bismuth and gallium being noted);' 2—that the capacity of liquid metals and alloys for dissolving gases diminishes with cooling until, in the freezing interval, a large decrease takes place (various exceptions being noted and excluded from present consideration) ;.: and 3—that freezing proceeds counter to the direction of heat flow, the freezing front most commonly being composed of a system of tapering dendrite stalks and side arms which are coarser the lower the freezing rate and which protrude into the liquid for a distance that is greater the longer the freezing temperature interval of the alloy and the smaller the thermal gradient.' The mechanism by which voids are generated

Jan 1, 1953

On Friday, Jan. 17, the thirteenth impression of the Perkin Medal was presented to Dr. Frederick Gardner Cottrell, at a meeting of the New York Section of the Society of Chemical Industry, held at the Chemists' Club, in New York City. The presentation address was delivered by Dr. C. F. Chandler, Senior Past President of the Society. The medal was awarded for the recipient's work in the electrical precipitation of suspended particles in gases. Dr. Cottrell's career, which is so familiar to members of the Institute, was sketched by Dr. Chandler. He told at some length of the experiments leading up to the final solution of electrostatic precipitation, which has done so much to solve the problem of smelter smoke. The principal interest in Dr. Cottrell's speech of acceptance lay in his remarks about helium, the production of which has been so reduced in cost that it has practically supplanted the use of hydrogen for inflation purposes in war balloons. He said: "Two or three weeks after war was declared in 1917, Dr. R. B. Moore attended a meeting of the American Chemical Society in Kansas City. At the general session, Mr. Seibel of the University of Kansas, gave a paper on krypton and xenon in some of the natural gases of Kansas. At the end of his paper, he expressed regret that at such a time, when everyone was thinking of war problems, his paper was of a purely scientific nature and had no practical bearing on the war. Dr. Moore immediately got up and said that he did not agree with Mr. Seibel. The presence of helium in those wells could, and should, have a very practical bearing on the war, as this gas could be extracted in quantity from the natural gas and used for balloons and Zeppelins. He pointed out some of the natural advantages of helium over hydrogen, and quoted Sir William Ramsey's letter advocating the use of helium for airships. The general attitude of those present was one of scepticism, so he finally asked Dr. Cady for his opinion who stated that he believed-the thing could be done, but was very doubtful whether it could ever be made practical on account of the cost." Dr. Moore in a letter wrote: "That same day I talked to Dr. Parsons, who was present at the meeting and was returning to Washington almost immediately. I told him what had happened, and that I believed the matter should be taken up by the Bureau at once and presented to the War Department. He promised to do this as soon as he got to Washington; and I know that he did take the matter up with other Bureau officials." Dr. Cottrell continued in part: News of Ramsey's suggestions also reached this .country through other channels and eventually came to our attention. Professors Satterly and Patterson of the University of Toronto commenced experimentation of the subject Jan. 1, 1916. Col. G. A. Burrell, who headed the research department of the Gas Warfare Service at the American University, tells me that Cady's experiments had also suggested similar possibilities to him.

Jan 3, 1919

By W. M. McKewan

A large amount of work has been reported in the literature on reduction of cubes, spheres, or regularly shaped particles of iron ore. Previously, it has been difficult to evaluate these data because no equation has been developed that would yield one or more constants for comparison of overall reduction rates. Iron ore in the process of gaseous reduction is a complex system. The reduction takes place through the series Fe2O3-Fe304-Fe0-Fe. Edstrom and Bit-sianesl have reported that the gas-solid type of reaction was found only at the FeO-Fe interface and that the internal reduction proceeded by elementary diffusion of iron. Therefore, during reduction oxygen is essentially removed from the system only at the FeO-Fe interface. Kinetically, it is reasonable to consider iron ore in the process of reduction as a

Jan 1, 1959

By Don B. Shupe, John K. Berry

The handling and disposal of mine water is a much larger problem than is apparent at first glance. Many more tons of water are removed from underground coal mines in the United States each year than tons of coal. In the old anthracite region of Pennsylvania the average was around 32.7 t (36 st) of water for each ton of coal produced, while bituminous mines average about 4.5 or 5.4 t (5 or 6 st). Water encountered in the mines may come from several different sources. In mines with light cover and without a firm solid roof, rain may seep directly into the workings. This is also true of deeper mines where pillar falls have broken the roof to the surface. The top under creek beds is generally faulty and broken and water comes through the roof at this point. Deeper mines are frequently overlain by water-bearing strata and pillar breaks and faulty top can admit water, while places running to the dip often accumulate water which comes up through the bottom. In all cases, except where passing under a year-round stream, the amount of water made is usually pretty closely connected with the weather-more water during the rainy season, less in the dry, although the deeper a nine is, the longer it is before changes in rainfall are felt. Another source of water, not connected with seasonal changes, is old water, accumulated over a period of time in abandoned workings of the mine, or from flooded adjacent mines. Here the water filters through the coal, the parting, or comes up through cracks in the bottom. Similarly, core holes, drilled to prospect the property, can be a source of unexpected water and modern safety requirements for dust-allaying water at the working faces can turn a pleasant working area into a soggy mess over the weekend if the system is not properly maintained and operated. Why water must be disposed of is obvious. If allowed to accumulate, sooner or later the mine will fill up, or at least it will become "roofed" in low places, blocking ventilation and traffic. It must be controlled long before it reaches this stage. Water standing in the working faces is

Jan 1, 1981

By J. D. A. Morrow

THIS discussion relates to the distribution of coal under the direction of the U. S. Fuel Administration beginning Apr. 1, 1918. At that time a definite method of ' controlling and directing distribution was put into effect. Prior thereto, although some of the machinery utilized was in operation, especially in the few weeks immediately preceding Apr. 1, distribution had not been effectively and comprehensively organized. The writer was called to the Fuel. Administration by Dr. Garfield about the. first of February, 1918, to assume general direction of the distribution of coal for the Fuel Administration, to develop the general plans, and to obtain practical men to assist in this work and in carrying through the program finally devised. A study of the situation and conferences with the Fuel Administrator and leading men in the business made it plain that it would- he necessary to begin at the bottom, measure the undertaking, develop plans to meet the need thus shown, and build an organization to effect the distribution required. This work had to be done under war pressure in the midst of a bad coal shortage. The successful performance of such a task is always primarily a matter of putting competent men in the right places and giving, them the power and opportunity to function properly together. In the Distribution Division of the U. S. Fuel Administration, the men who were chiefly responsible for whipping plans into practical form and then for carrying out these plans were A. W. Calloway, of Baltimore, President of the Davis Coal & Coke Co., who served as the Director of Bituminous Coal Distribution; S. Lovell Yerkes, of Birmingham, Alabama, Secretary of the Grider Coal Sales Agency, who assumed general charge of distribution while the new plans and organization were being perfected and then became the Assistant Director of Bituminous Coal Distribution; Warren S. Blauvelt, of Detroit, who was Director of Coke Distribution; A. S. Learoyd of New York, Director of Anthracite Distribution, in connection with the Anthracite Committee, consisting of Joseph

Jan 3, 1919

By R. M. Asimow

Both smith1 and wells2 have shown that the dif-fusivity of carbon in austenite increases rapidly with increasing carbon concentration. Smith has shown, in addition, that part but not all of this increase can be attributed to the concentration dependence of the activity coefficient of carbon in austenite. From the work of Eshelby', it is known that, because of the image displacements, there is a uniform dilatation of the material in a body containing random centers of dilatation. It is thus tempting to explain the enhanced diffusivity as resulting from this apparent negative pressure caused by the interstitial carbon atoms.* That is, the activation free energy for diffusion is not directly a function of concentration if we consider that the alloy is subjected to a concentration-dependent pressure. To proceed with a quantitative solution, it is necessary to determine the activation volume AV for the diffusion process. An exact calculation of AV is quite a difficult problem and does not appear to have been solved as yet. A simpler procedure is to use the semiempirical, macroscopic theory of seyes' which relates the activation free energy AG to AV. Keyes has shown that for many types of diffusion processes the following relationship is valid Where p is the Gruneisen constant and x the compressibility. This relationship is based on the assumption that AG can be identified with strain-energy terms. In general there will also be contributions to AG due to a change in the energy of the valence electrons of the metal; thus the relation must be considered largely empirical. Surprisingly, for self-diffusion where it is well-known that the electronic contribution is quite important,' the Keyes relation works quite well for many systems. For interstitial diffusion where it might be expected that the relationship is on a firmer theoretical basis, the limited experimental data available is not in particularly good agreement as can be seen from Table I. However, it must be remembered that besides the uncertain basis of the Keyes formula there is considerable uncertainty in some of the experimental values of AV. The only real justification for using the Keyes formula in the present analysis is that it gives a result which satisfactorily solves the problem at hand and, further, there are no more reliable procedures for calculating AV available. The coefficient 3 in Eq. [I] is determined such that the room-temperature value for x is to be used. The activation entropy AS is estimated as 8.95 x 10"3 kcal per OK mole using the values in Table I1 and the Zener" relation AS = PAHIT, where p is a dimensionless thermal coefficient of Young's modulus which is to be evaluated at low values of T/T,, aH is the activation enthalpy, and T, is the melting temperature of the alloy. The resulting value of AG at 1000°C is 25.6 kcal per mole. The Gruneisen constant (p = 3cup/XC,), where p is the density, is evaluated from the room-temperature data in Table I1 after calculating C, from the relation. A value of p = 8.32 g per cu cm based on the value of a. in Table I is used. The result is C, = 5.0 x lo6 erg per g, H = 2.32, and AV = 3.41 cu cm per mole at 1000°C and infinite carbon dilution. It is assumed that the activation volume is not a function of carbon concentration. The theory could be refined to consider AV a function of concentration, but due to the uncertainties in the parameters there seems little justification for this. Carbon dissolved in austenite forms a nonideal solid solution, so that in writing an equation for. the diffusivity of carbon it is necessary to take into account the change in activity coefficient with concentration. The resulting equation is16

Jan 1, 1964

By Benjamin Talbot

The problem of segregation and cavities in steel ingots is a subject which has given and is still giving metallurgists, engineers, and operators matter for serious consideration. This question has come more into prominence lately in the United States, due largely to the desire of railroad engineers to secure a better rail than they have obtained ill the past, as the service they demand is increasing in severity; and no doubt manufacturers will be able to meet what is required of them. The rails here are as good as those made in other countries, but the conditions of service and the extremes of climate are more Revere and consequently more breakages occur. Various reasons have been advanced to explain why rails may not be as good in quality to-day as in the past. Some engineers consider that modern methods of manufacturing, designed chiefly to obtain large output, tend to reduce the standard of excellence of more deliberate methods. Others think that 4-ton ingots are worse than those of 2 tons. Again, it is stated that the 100-ton heat in one ladle is too large, and is a step in the wrong direction in casting. My experience upon the question of the size of the ingot is that in rolling rails of from 85-to 100-lb. sections, the range of ingot is only practically such that the difference in the size does not help in the question of segregation, cavities, or blow-holes. I call attention to two ingots from work done at Pencoyd, Pa., 16 years ago. These ingots were bottom-poured, cast at the same time from the same center-runner, the one being 20 by 24 in. and the other 13 by 16 in. in size. The steel was acid open-hearth, and contained C, 0.43; P, 0.062; S, 0.069 per cent. At the same place in each ingot where seg-

Jan 1, 1914

By W. A. Griffith

The fundamental principles and modern techniques of experimental planning and data analysis, applicable to any type of research, are particularly important in flotation experimentation. Since they constitute the modern science of experimentation, they should be among the working tools of any scientist, research engineer, or plant operator engaged in flotation investigates. This chapter is a review of these principles and techniques. Equipment and procedures for the actual conduct of experiments will not be discussed here since these subjects are well covered elsewhere in this volume. Neither will any attempt be made to impart a working knowledge of statistical methods of data analysis since this would be impossible in the space allotted, and many excellent texts are available to the diligent inestigator.1-4 The objective here is simply to interest the reader in the application of statistical techniques to flotation experimentation by illustrating their utility in situations frequently encountered, and to point out the principles of experimental planning necessary for their proper use. Any conscientious metallurgist engaged in flotation experimentation or operations is well aware of the inherent complexity of the flotation process, and of the often frustrating difficulties this introduces into experimentation. The raw materials normally treated by the process are complex both physi- cally and chemically, and often highly variable even when from the same source. The flotation process itself is characterized by a very large number of potentially important process variables. Many of these are beyond the con- trol of the metallurgist, and some cannot even be measured quantitatively with available instruments. Those which can be measured and controlled with reasonable precision often produce effects which are intricately interrelated. Not only are the variables many, but the physical and chemical mechanisms by which they function are imperfectly under stood. To compound the difficulty, experimental techniques are relatively crude. Controls are not very precise, and the human factor looms large in most flotation experiments. These situations lead inevitably to experimental data of a relatively low degree of precision or reproducibility. Some are inclined to think that these conditions are unique to flotation experimentation. They are not. The experimental problems met by the agronomist, the biologist, the social scientist, and others are equally complex. Investigators in these fields pioneered in the development of methods for handling just such situations by proper experimental planning and the application of statistical methods in the analysis of data. Their pioneering work has grown into a well established modern science of experimentation which has spread into every field of science. This science is based upon statistical

Jan 1, 1962

By H. I. Aaronson, H. A. Domian, G. M. Pound

Zener's two-parameter theory of the y a reaction in Fe-X alloys is extended to encornpass austenite-stabilizing as well as fewite-stabilizing elements, and is then cottzbitzed with statistical thermodynamic theories of Fe-C alloys to permit development of a ther-modynamic description of the proeutectoid fewite reaction in Fe-C-X alloys. Equilibrium tielines are calculated for tile a + y rep'on from experimental data and frort extrapolations of the y/y +a equilibrium surface. Sectzovs of the y/y + 0 surface are calculaled for the tzetastable sstuation LYL u-kich alloyrtg eleitzents do not partition betzseen azrstenite andfer-rite. The finding that the metastable y/a + y curves Lie close to their equilibriuwz counterparts when X = Si, .Vo, Co, Al, and Cu but well below them when X = A/ln or Ari pr-elides a thermodunamic explanation for the expcri1?7e?ztally obserted absence of partition during the proeutec toid ferrite reartlon in the fortner alloys and for the occurrence of partition at hzgher ternperatures in the latter alloys. Cotarison ofno- patitzoa free-energy changes and y/y i a curr,es in Fe-C-X alloys with the equilibrium 11al1es of these quantities in Fe-C alloys furnishes additional qualitative insight into the irqluence of allojling elements upon the kinetics of the proeutectoicl ferrite reaction. THE introduction of a substitutional alloying element, X, appreciably complicates calculation of the thermodynamics of the formation of proeutectoid ferrite from austenite. As noted in the preceding paper,' the positional entropy of the interstitial species is the principal component of the free energy of an interstitial solid solution with which theory has so far been able to deal. One would expect, however, that other components of the free energy of this type of solid solution may be significantly altered by the addition of a substitutional alloying element. Even if the assumptions are made, by analogy to the case of Fe-C alloys,' that changes in the positional entropy of carbon represent a significant part of the thermodynamic effects of an alloying element, and that the remaining effects can be taken into account by fitting the equations developed on this basis to experimental data on Fe-C-X phase diagrams or on the activities of carbon in alloyed austenite and ferrite, the experimental information available on either of these quantities is not yet sufficiently accurate or extensive, respectively, to make such an approach useful. An attempt made by Zener on the former basis to explain the effects of alloying elements on the thermodynamics of Fe-C alloys in terms of a temperature-independent "free-energy change" (actually enthalpy hane') required to transfer 1 mole of an alloying element from austenite to ferrite, in which the "free-energy change" was determined by fitting the theoretical relationships developed to Fe-C-X phase diagrams, thus proved inadequate in part because of deficiencies in the available ternary-phase-diagram data.= Other difficulties of a more fundamental nature, however, also indicated the desirability of a different approach to the problem.3y4y6 zener6 subsequently proposed that the free-energy change associated with y — a transformation in pure iron can be decomposed into magnetic and nonmagnetic components. Alloying elements were assumed to affect those components separately. One parameter was used to describe the quantitative effect exerted on each component. These parameters were evaluated from Ms (martensite-start) temperature data and from other experimental information usually either readily available or measurable with acceptable accuracy. Zener applied this treatment only to the calculation of Fe-X phase diagrams in which X is a ferrite-stabilizing element. In the present study, this treatment is extended to include austenite-stabilizing elements, and then combined with treatments previously considered for Fe-C alloys1 to permit calculation of the thermodynamic quantities of interest in the austenite - proeutectoid ferrite transformation in Fe-C-X alloys, where a number of representative, and commonly used alloying elements are chosen for X, including Si, Mn, Co, Mo, Al, Cr, and Cu. The results are used to explain important features of the partition of alloying elements between austenite and proeutectoid ferrite, as reported in a companion paper7 on the basis of electron-probe analysis, and to provide some additional understanding of the influence of alloying elements upon the kinetics of nucleation and growth of proeutectoid ferrite. Portions of this treatment6 have been clarified in the course of a review by Kaufman and Cohen.3 The consolidated summary of these developments with which this section is begun provides a basis for further clarification of the treatment, from which extension to include austenite- as well as ferrite-stabilizing elements is a natural consequence. The division of the free-energy change associated with the 7 - a transformation in pure iron, into two independent components is formally stated as:

Jan 1, 1967

By W. E. Keck

THE potential iron ores of Michigan can be classified from the stand-point of the predominant impurities into siliceous, sulphurous and phos-phorous ores. Research on the flotation of each of these classes of ore was carried out in the following Planner. The flotative properties of the valuable minerals of iron and of the worthless and deleterious ones were first determined under carefully controlled conditions. This information was then applied to synthetic mixtures of these minerals, which simulated the potential ores. Finally, data obtained during the two foregoing stages of the investigation were used in the flotation beneficiation of samples of the potential ores. Hematite is the most important mineral of iron in each of the above classes of iron ores. This paper deals with a study of that mineral in the very nearly, pure state. There are two varieties of the mineral-specular hematite and massive hematite. The latter is the principal variety, but the former is an Impor-tant mineral of iron in some of the potential ores. Because of this condi-tion, flotation research was performed with both varieties. This research consisted essentially of: (1) a survey of the literature on hematite flota-tion, (2) the preparation of pure massive hematite, (3) the preparation of pure specular hematite, (4) the; development of a laboratory procedure and (5) flotation experimentation. For the purpose of this discussion, the results of previous work on the flotative properties of hematite can be summarized as follows: Specular hematite has been readily floated with terpineol and sodium oleate or heptylic acid1. Further, hematite has been likewise floated with a pro-prietary frother and oleic acid or other soluble oils 2. Finally, lead nitrate, copper sulphate, silver nitrate, chromium nitrate, mercuric chloride, ferric

Jan 1, 1937

By H. Sherman

The general curtailment of activities, so marked in 1931, was continued and intensified in 1932 and although production was maintained at approximately the level of the previous year, 1932 was chiefly characterized by the virtual cessation of drilling in many of the proven fields, a further decline in wildcatting activities, particularly in the Maracaibo Basin, and the relinquishment of large blocks of unfavorably located acreage. A total of only 60 wells was completed during the year of which six were wildcats, while at the same time concessions aggregating approximately. 3,222,000 acres were renounced and reverted to the National Government. The maintenance of production at the previously established level was made possible through the large potential built up by drilling in previous years and by a gradual increase in pumping and gas-lift installations. Towards the end of the year there was a slight but perceptible tendency towards increased drilling in certain of the proven fields. Total production for the year came to 118,076,000 as compared to 118,418,000 bbl. for 1931, while exports amounted to 114,758,000 as against 116,683,000 bbl. in 1931. Table 1 shows production and exports and the average rate per day for the first half of 1932 as compared to the second half. Table 1.—Petroleum Production and Exports in 1932, Venezuela (Barrels of 42 Gallons) Production Rate per Day Export Rate per Day I January-June............ 61,943,000 1 390, 347 July-December.......... 56,133,000 305,071 50,788,000 276,022 Total.........,....... 118,076,000 322,612 114,758,000 313,546 During 1932 the number of active vessels comprising the Lake Maracaibo fleet of shallow-draft tankers was still further reduced, some being temporarily laid up and some transferred to service in other coun-

Jan 1, 1933

In 1934 the Southern Experiment Station of the U.S. Bureau of Mines in. cooperation with the University of Alabama began an investiga-tion of the availability of kyanite ores as a source of raw material for the manufacture of refractories. Under this program, gravity concentration and flotation tests have been made on two varieties of Georgia kyanite ore, mica schist and massive. Most of the attention has been directed to the mica schist ores, as they are more widely distributed and seem to offer greater economic possibilities than the massive ores. It is evident that the preparation of kyanite for use as a refractory material involves other considerations than the mere elimination of impurities. A concentration process that eliminates impurities satisfactorily may have to be followed by some additional treatment, since the final product must be of a coarse-ness and size ratio that will make it suitable for refractories manufacture. So far in the investigation at the Southern Experiment Station of the U.S. Bureau of Mines only the concentration problem has been considered, and this paper is intended as an interim report.

Jan 1, 1936

By Irving B. Cadoff, Ernest Levine

The crack formation and propagation in the single -phase Cu-4 pct Ag alloys were studied. The alloys were loaded in mercury to various stress levels, the mercury was removed, and the specimen examined for cracks. Cracks were found to develop below the fracture stress; the frequency of such cracks increased with increasing stress level. Some cracks were nmpropagative. Fracture in mercury was found to occur by the link-up of cracks formed at various stress levels rather than by the growth and propagation of a single crack. If the mercury environment is removed prior to a critical amount of crack formation, then continued loading results in ductile fracture. The appearance of the cracks at selected grain boundaries is related to the relative orientation of the boundaries, as are the propaga-tive characteristics of the crack. The mercury interaction appears to be one of lowering the strength of the metal-metal bonds in the high-stress area of the grain boundary. GRIFFITH'S microcrack theory1 proposed a critical crack size above which a crack in an elastic material grows with decreasing energy at a stress of From his theory it was proposed that the presence of a liquid tends to lower the surface energy of the microcrack faces2 leading to a decrease in the critical crack size necessary for spontaneous fracture propagation. stroh3 proposed that the stress concentration at a grain boundary due to pile-up may initiate a microcrack at the grain boundary. petch4 and Stroh5 evaluated the stress distribution at the head of a pile-up in a polycrystal-line material and deduced that the critical crack size and hence of is dependent on the grain size. Experimental verification of this dependence was found by petch6 for hydrogen embrittlement of steel. Studies in stress-corrosion cracking7 have provided a picture of fracture which shows that initial separations occur in a scattered, independent fashion in regions of high tensile stress. A minimum or threshold stress is necessary to produce a sufficient stress concentration to initiate frac- ture. These separations join up to form a crack. The extension of fracture is largely discontinuous and consists of a joining up of cracks. In recent worka evidence of this scattered crack network was found in a Cu-Ag alloy embrittled by mercury. For the Cu alloy-Hg couple, the crack path has also been found to be dependent on the orientation of adjacent grains, and with the addition of zinc to mercury a reduction in embrittlement along with a change in fracture morphology was found.9 In this present study, a mercury-dewetting method was used to observe crack initiation and fracture morphology when a Cu-4 pct Ag alloy is deformed in mercury and Hg-Zn solutions. PROCEDURE Specimens of Cu-4 pct Ag were prepared as in previous crack-path studies.' The specimens were heated at 770°C for 24 hr and water-quenched Tension tests using a table-model Instron were carried out in mercury and in various concentrations of Hg-Zn. Loading was in steps up to the fracture stress, with the load being removed and the specimen examined for surface cracks at each step. The specimens were dewetted after each load to permit examination of the surface structure and rewetted prior to continued loading. The specimens were wetted by electro polish ing in phosphoric acid, rinsing in alcohol, and then immersing in a pool of mercury. Dewetting was accomplished by flame heating the specimen for 30 sec in a vacuum. Some surface contamination was found, but not enough to obscure crack configurations and grain boundaries. RESULTS Fracture Characteristics in Mercury. Fig. 1 is a stress-strain curve showing the progressive step-wise loading of the specimen. As may be seen from the graph, the first position stopped at a is at a stress 5000 psi below the expected fracture stress of 25,000 psi. Examination of the specimen after removal of mercury showed only one crack. The appearance of this crack at a stress far below the fracture stress of this alloy in mercury did not affect the stress-strain curve in any manner. The specimen was then recoated with mercury and deformation was continued (curve b, Fig. 1) raising the stress by 4000 psi, and the same procedure re~eated. The initial crack was located and appeared as in Fig. 2 (crack lb). In this figure the crack is

Jan 1, 1964

By Paul J. Sirkegian

The problem of properly controlling the movements of underground trains in the Emma Nevada and Morris Brooks workings of the Consolidated Coppermines Corporation of Kimberly, Nev., became more complex as the rate of production increased. Ore from these mines, which are connected through a 7000-ft. single-track haulageway (Fig. I), is hoisted through the Emma Nevada shalt. All production to date has been from one level. Because of heavy ground, even on the main haulage horizon, experience has shown that it is necessary to have a minimum cross section in the drifts, thus making it impractical to have a double track system. In 1937, production was 3000 tons per day; in 1938 it was increased to 6000 tons per day and in 1940 to 9000 tons per day. Each increase necessitated a revision in the method of controlling the underground traffic. In 1937 the tramming signal system consisted of a few signal lights in the main haulage drift. These lights were two 100-watt bulbs in a metal box that had one green and one red lens on each side. The box was mounted on the underside of a drift cap timber and could be seen For a considerable distance. The lights were so arranged that all boxes showed either red or green at the same time and all were controlled by a magnetic contactor at the entrance to each lateral drift. When the lights showed green, the main haulage was clear of traffic and a train could enter it. As the motor entered the main haulage drift, the motorman pulled the cord of the magnetic contactor switch, thus changing all the main haulage lights to red, which indicated that no other train could use the main haulage until the first train had turned into a lateral drift. When a train left the main line, its motorman pulled the cord connected with the magnetic contactors, causing the haulage lights to show green again. This arrangement permitted only one train at a time to use the main haulage and thus limited the number of train trips per shift, but it was satisfactory when the ore handled was only 3000 tons per day. Second SystEM Installed With a gradual increase in production it became necessary to place a train dispatcher in charge of all trains. He controlled their movements orally, giving his orders direct or by mine phone, instructing them where to load, when to leave for the station and when to return. His objective was to group several trains traveling in the same direction. Because of the human element involved, some mistakes were made. The danger of a serious collision was always possible. There was a 90° turn and curve in the underground haulageway, therefore travel in this section was always dangerous if mistakes were made in directing traffic. To protect the train crew, particularly the rear switchman who rode the last car or caboose, a two-way push button and flash-signal system was installed on the

Jan 1, 1946

IN the decade beginning 1850, the development by William Kelly in I the U.S.A. and Henry Bessemer in England of the pneumatic method of refining pig iron, known as the Bessemer process, gave the world the first method of producing low-cost steel in large volumes. Briefly, the Bessemer process consists of blowing air through liquid blast furnace iron in a refractory-lined vessel known as a converter. The air enters the iron in the furnace bottom through tuyeres, and during its passage through the iron removes the carbon, manganese, and silicon by oxidation. The heat produced by oxidation is sufficient to raise the temperature of the liquid metal to normal steel casting temperatures and, in addition, to melt some scrap. In the 1860's, the open hearth process was introduced which in the early part of the twentieth century surpassed the Bessemer process in steel production. In the early 1870's, Thomas and Gilchrist discovered that phosphorus could also be removed if lime were added and the converter lined with basic refractory; the modification is known as the basic Bessemer process and is used in Europe. Bessemer steel usually contains between 0.010 and 0.020 per cent nitrogen and between 0.05 and 0.10 per cent phosphorus which influences the properties. Henry Bessemer,1 in 1856, recognized the possibility of using oxygen in the converter process, but the cost was prohibitive. This interest was associated with the theoretical balance of the Bessemer process. Experimental work' has indicated that bottom blowing with pure oxygen results in serious converter bottom and tuyere erosion. Dilution of the oxygen by steam has been observed to be an effective means of maintaining low-nitrogen content of the steel and at the same time reducing bottom and tuyere erosion. A further advantage is that the fume emission characteristic of Bessmer operation is reduced. The addition of steam to the oxygen, however, reduces scrap-melting capacity due to the endothermic reaction characteristics of steam. The possible advantages of refining methods for steel using high-purity oxygen have been recognized for over a hundred years, but the develop-

Jan 1, 1964

By R. C. Ku, R. G. Davies

The stress-strain behavior of Fe-C and Fe-Ni solid-solution alloys has been investigated at 25°C. It is found that the rate of solid-solution strengthening is dependent upon the strain at which the yield stress is measured, the macroyield stress being much more concentration-dependent than the microyield stress. In fact the addition of nickel does not lead to any increase in the microyield stress of iron. The primary effect of increasing the carbon or nickel content is to increase the slope of the stress-strain curve in the microyield region; this effect has been correlated, by means of transmission electron microscopy, with a decreased ability of the dislocations to cross-slip. It is concluded that the Mott-Nabarro theory is a good description of true solid-solution hardening in these and other iron-base alloys. A.LL theories of the solid-solution strengthening1-4 indicate that the flow stress of an alloy increases both with solute concentration and "misfit" between the solvent and solute atoms. The functional relationship between strength, solute concentration, C, and misfit depends upon the particular theory. Mott and Nabarro1,2 and Schoeck and Seeger3 both predict a linear increase in strength with concentration, while Fleischer4 indicates that the strength should be proportional to C1/2; there are in the literature experimental observations to support both these compositional dependencies.1'8 The experimental evidence used to support the theories is the change in macroscopic yield stress (strain, e, = 10-3) with composition. However, recent investigations have revealed that solid-solution strengthening in a Cu-Al single crystals7 and in Fe-V polycrystal-line" alloys depends upon the strain at which the flow stress is measured; a flow stress in the microplastic range (e = 10-6 to 10-5) is much less concentration-dependent than the macroyield stress. Since the theories of solid-solution strengthening are concerned in particular with the stress to move a dislocation in a dislocation-free matrix, they should only be compared with microyield-stress data; it will be shown that in a material deforming homogeneously the microyield stress (e = 10-6) is approximately the stress to move through the matrix those dislocations which have been nucleated by stress concentrations such as particles or grain boundary ledges.9-11 In contrast, the macro-yield stress is more complex in that it is affected by several phenomena: dislocation multiplication, dislocation interactions, and the ease of propagating slip across grain boundaries. For example, it is experimentally observed that when long-range order12'13 or solute effects10 restrict cross alip the grain boundary

Jan 1, 1967

By C. E. Westley, R. R. Beebe

Recent works by Plaksh et al.,1,2 Glembotsky,3 and others have renewed interest in the effects of oxidation on the surface activity of the sulfides. Since considerable supporting data are available on galena-potassium ethyl xanthate, this system is being studied at South Dakota School of Mines and Technology by contact angle measurement, using the technique of McGlashan and McLeod.4 The contact-angle method is well adapted to investigation of the influence of small amounts of oxygen on the establishment of a stable contact angle on galena in potassium ethyl xanthate solution. Samples of massive galena containing less than 0.001 pct Cu, 0.001 pct Ag, and 0.01 pct Zn are mounted in castable plastic and ground and polished manually in a glove box containing the desired proportions of oxygen and purified nitrogen. Oxygen and nitrogen contents of the test atmosphere are determined with an Orsatt analyzer. In this way a reproducible surface is created in contact with whatever oxygen concentration is desired. Water and all reagents are prepared and stored in the test atmosphere. An absorbent is used to control carbon dioxide that might be present. Final polishing is done with levigated alumina on a glass plate. The prepared sample is placed in the test solution and transferred to the contact angle apparatus in a sealed box, and the test is conducted while both sample and solution are maintained under a slight positive pressure of the test atmosphere. Table I gives the results of contact angle measurements made at various 02-Nz concentrations.5 Each value of contact angle is the average of at least six individual measurements made with different bubbles at different locations on the sample surface. A period of 20 to 25 min has been found by preliminary tests to be sufficient to permit develop- ment of maximum angle, and all measurements are made after at least this much time has elapsed. Exposure of prepared samples to pure water under the test atmosphere before exposure to the xanthate results in a small but measureable and consistent reduction in contact angle. This is particularly true in the oxygen-deficient atmospheres; for example, at 2.2 pct O2 such water contact reduces the average angle about 8" from that obtained by immediate testing in xanthate. The general trend of increasing contact angle with increasing oxygen concentration corresponds to the results of Plaksin et a12 The absence of diminish-ment of contact angle at very high oxygen concentration has been attributed to the high concentration of xanthate per unit of galena surface: At oxygen concentrations below 1 pct (the limit of accuracy of the Orsatt analyzer), no contact angle is obtained. Furthermore, no contact angle is obtained at any oxygen concentration in the absence of xanthate. This result seems to be in disagreement with those cited by Plaksin.1 Further work on the interaction of galena and potassium ethyl xanthate or a similar collector as influenced by oxygen is contemplated. The true nature of the interrelation is as yet unknown. For example, it is not known whether the governing oxygen reaction is with the mineral, with the reagent, or with both.

Jan 1, 1961