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By R. L. Wilcox, M. L. Fuller

Owing to the nature of the die-casting process, fresllly cast alloys are undoubtedly not at equilibrium from the standpoint of alloy phase relationships. After casting, therefore, they tend to undergo phase changes, with the ultimate effeet of reaching a state of equilibrium at the aging temperature, beyond which no fnrther change takes place. This phase alteration undoubtedly is one of the primary causes of the changes in dimensions and physical properties that zinc-alloy die castings undergo during aging. It is planned to report on this problem in a series of papers of which this is the first. The writers have made a study of commercial zinc die-casting alloys over a period of several years, utilizing the X-ray diffraction technic of determining the phase composition changes in the alloys. Up to the present, two principal phase changes have been observed which are capable of causing dimensional changes: (I) the segregation of secondary constituents from the zinc-base solid solution and (2) the beta aluminum-zinc decomposition. The latter is the subject of the present paper and studies on the former will be reported upon at a future time. Scope of Study In the present investigation a special technic for the study of the beta phase in zinc-alloy die castings has been developed, making possible the determination of the period of existence of the beta phase after casting. The pure beta constituent and its decomposition have been studied in detail. The effect of magnesium and copper on the velocity of the decomposition is reported. The heat of decomposition, the eutectoid temperature arid the accompanying density change have been measured. The density change lias been calculated from data on crystal structure and the result thus obtained has been compared with the actual change.

Jan 1, 1935

By Waldemar Lindgren

The following pages present data accepted by many geochemists and geologists regarding the succession of minerals and the temperatures of formation in ore deposits affiliated with igneous rocks. They also present the individual views of the author on the composition of the solutions that were active and on the mode of deposition. He does not regard these views as speculations or hypotheses but as forming a well motivated and consistent theory. It is not certain, however, that all investigators will subscribe to them. Introduction The mining engineer may not always be interested in the field of stability and temperature of origin in the mineralogy of ore deposits, but he certainly is interested in the succession of minerals because this has a definite bearing on the understanding of the ores and on the best processes of extraction. It is proposed, therefore, to summarize in plain language the principal features of succession as shown in metallic ores. Chemical analyses of ores are always important, but the real knowledge of succession—sometimes called paragenesis-—of ores has been gained only in the last 20 years, by the study of polished sections. The study of hand specimens threw much light on the subject—as shown, for instance, by Breithaupt, whose "Paragenesis," written a hundred years ago, is still useful—but the results have been modified by our slowly gained understanding of the processes of replacement. Indications of Temperature Melting Points.—In the first place, a distinction must be made as to whether the ore is a product of magmatic consolidation, of pegmatitiza-tion or of hydrothermal activity. Most of the ores fall in the latter class. In any case, the melting points, although of importance, are not definite indications. In a magma the oxides and sulfides are likely to be among the earliest crystalline products (magnetite, ilmenite, zircon, corundum,

Jan 1, 1937

By E. Hornbogen

Discontinuous precipitation in a iron can occur by at least two different mechanisms. These mechanisms are compared, using observations made on an Fe-22 at. pct Zn alloy and an Fe-19.5 at. pct Mo alloy. In the Fe-Zn alloy, precipitation began on grain boundaries. These boundaries moved into the supersaturated solid solution, providing nucleation sites and an easy path for diffusion. The precipitated phase pew as lamellae, perpendicular to the PRECIPITATION reactions are called discontinuous if the nucleation of particles does not occur on individual sites in the supersaturated matrix.' In discontinuous precipitation, nucleation and growth occur on a reaction front that moves into the supersaturated solution and leaves a two-phase aggregate behind. The term cellular precipitation2 has also been used, but the term autocatalytic precipi- moving reaction front. The orientation of the depleted iron differed from that of the supersaturated iron. In the Fe-Mo alloy the growing precipitate particles apparently created dislocations in the growth front which served as nucleation sites. The precipitate grew on (110) planes of the iron, and growth occurred through volume diffision. The depleted iron retained the orientation of the supersaturated solid solution. tation seems to describe the nature of such reactions best. The basic effect of such a precipitation mechanism in a solid is that it is able to move or create sites that can catalyze nucleation. Such sites can be grain boundaries and dislocations. A mechanism of autocatalytic precipitation must, therefore, include some rational process by which a grain boundary may move into the supersaturated matrix or by which dislocations may be generated in front of the reaction. Discontinuous precipitation is always in competition with individual nucleation and growth of par-

Jan 1, 1963

By C. C. Furnas, T. L. Joseph

It is well known that particles of different sizes are not distributed evenly throughout the average charge in an iron blast furnace. Just how great the disparity in particle size in different parts of a single plane in a furnace may be is indicated by the results of some recent investiga-tion1,2 conducted by the Bureau of Mines on a furnace operating on Lake ores. The wide variations found in gas velocity, gas composition, and temperature from the periphery to the center of the upper charge column were caused by the great variation in particle size of the raw materials used and were also greatly influenced by the methods of charging. This paper summarizes the results of an investigation of the influence of different methods of charging and of the treatment of raw materials upon the size distribution of the solid particles in the blast furnace. A more complete report will appear later as a Bureau of Mines technical paper. Importance of Gas-solid Contact One of the authors has pointed out in a previous report? that the operation of the blast-furnace process is entirely dependent on contact between the gas stream and the solid particles in the stock. The gas stream carries the necessary heat as well as the carbon monoxide molecules that do the work of rednction. In the parts of the furnace in which there is little or no contact between the gas stream and the solids there can be little work of reduction. Obviously, the part of the apparatus that is not doing the work for which it is intended is inefficient; the ideal condition is one in which all portions of the stock column are

Jan 1, 1929

By R. A. Morgen

THE binary system lead-antimony has been the subject of compre-hensive investigations in these laboratories by Dean1 and his associates. The effect of a third constituent on this system, particularly on the lead-rich alloys in which dispersion hardening ,was found, has a commercial value as well as an academic interest. This paper covers the effect of the addition of copper, bismuth and tin, all of which are likely to be found in commercial lead-antimony alloys, and is divided into three parts, as follows: I. The System Lead-Antimony-Copper II. The System Lead-Antimony-Bismuth III. The Lead Corner of the System Lead-Antimony-Tin These three systems are of three different types, and hence may be considered as covering three general kinds of additions. Bismuth forms no compounds with either lead or antimony and forms solid solutions with both. Copper forms several compounds with antimony as well as solid solutions but with lead it forms a two liquid layer system and no appreciable solid solution. Tin is soluble in both lead and antimony in the solid state and also forms a compound with antimony. The effect of small amounts of bismuth on the lead-antimony alloys is small, having no appreciable effect on the solubility of antimony. The temperature of the solidus floor is lowered appreciably by the presence of bismuth, cutting down the range of heat treatment. Copper, on the other hand, due to compound formation, increases the apparent solubility of antimony. The excess antimony is tied up with the copper finally and so is not available for dispersion hardening. The net result of addition of small amounts of copper is to shift the dispersion hardening peak of the

Jan 1, 1927

By C. A. Stetefeldt

In my paper on "The Consumption of Fuel in the Taylor Gas-Producer Plants at the Aspen and Marsac Mills" (Trans., xxiii., 134), I mentioned that in the plant which I had designed for the Ontario mill, the gas-tubes were to be covered with thin, corrugated sheet-iron, over which a coating of asbestos-magnesia would be spread in order to effect a good insulation and keep the gas as hot as possible. At the Ontario mill, two Stetefeldt furnaces and two revolving driers are fired with gas. One furnace is connected with a Taylor producer of 5 feet diameter, and the other furnace and the two driers are heated by the gas from a Taylor producer of 7 feet diameter. In the latter case the gas-tubes are necessarily somewhat long, and the cleaning of them takes time. In order to prevent overheating of the tubes during that operation, it has been found advantageous not to provide them with an insulating covering. If a tube becomes red-hot at any place by the burning of soot, this is at once observed, and the tube is closed until it cools down. The tubes con-

Jan 1, 1895

By H. W. Kropholler, L. A. Cramer, E. T. Woodburn, J. C. A. Greene

A generalized mathematical structure is proposed whereby internal species mass flows within a flotation network are defined uniquely by a matrix of enhancement factors. An element of the enhancement factor matrix is defined as the ratio of the mass flow of that species leaving a given cell in the concentrate to the species mass flow leaving the same cell in the tailings. To predict the enhancement factors, knowledge of flotation kinetics effects is required. Recently experimental data has become available relating to the performance of industrial flotation circuits which indicate that the discrete or discrete-distributed kinetic schemes are capable of reasonably effective simulations. These simulations show the importance of including froth effects. The prediction of performance of networks from small-scale batch tests on flotation streams shows that the model for the froth phase used in the simulations does not scale-up well and that aeration effects are also difficult to predict. The network analysis should be useful in differential flotation of complex ores and it is disappointing-in this context that little information on the kinetics of activation and depression is available.

Jan 1, 1976

By R. E. Hook, R. L. McGaughey, A. M. Adair

The initial yielding characteristics of a vacuum-melted iron have been measured as a function of thertnal history after slow cooling or quenching from a 700°C recrystallizntion anneal. A thermal history favoring the segregation of interstitials to grairz boundaries results in a material having high values of upper and lower yield stress and long, irregutar Luders' plateaus, wheueas specimens treated to minimize grain boundary segregation have significantly lower values of these yielding characteristics. The struc- ture of typical grain boundary areas as revealed by electron transmission microscopy is consistent with these findings. The grain boundaries in iron are considered to be principally responsible for the release of dislocations during macroscopic yielding and it is suggested that strong locking results when a substantial amount of grain boundary segregution is present; it follows that weak locking results from a more random distribution of interstitials to grown in dislocations. RECENT years have seen an increased emphasis placed on a more quantitative study of the influence of grain boundaries on the yield behavior of bcc metals. The earlier picturk of dislocation pileups at grain boundaries building up a sufficient stress concentration to unlock dislocations in neighboring grains1

Jan 1, 1967

Geological Survey of Ohio, Columbus, Ohio. Wilbur Stout, State Geologist. A complete list of publications will be sent upon request The present Geological Survey of Ohio is the fourth organization of this kind in the state The first Survey issued two reports, dated 1838 (not now available), the second, from 1869 to 1888, issued two reports, 75 cents and $1, respectively, and five volumes on geology, $1.25 to $3 50. The third organization, 1890 to 1900, issued a report for 1890, $1, and vol. 7 (1893), $150 Since 1900 the present organization has issued a number of Bulletins, most of which deal with the geology of some part of the state, as follows: Bulletin 10, The Middle Devonian (1909), 25 cents, 14, Columbus Quadrangle (1911), 30 cents; 15, Devonian and Mississippian of northwestern Ohio (1912), $1; 17, Conemaugh Formation (1912), 60 cents, 22, The Dunkard Series (1920), 60 cents; 23, Camp Sherman Quadrangle (1921), 50 cents; 24, Wayne County (1921), 50 cents, 28, Columbiana County (1924), $1, 30, Delaware County (1926), 75 cents, 31, Vinton County (1927), $1; 35, Jefferson County (1930), $1. Other bulletins on Ohio geology and resources of most interest are.

Jan 1, 1933

By Byron W. Cheever

In my paper on the estimation of manganese, etc., presented at the Halifax meeting, in September, 1885 (Transactions, xiv., 372), I said that the colorimetric process "can never be made to give reliable results." This statement was based on the results of many trials made by my assistant, Mr. E. D. Campbell, and myself, following in our work the printed and oral directions of others, and such modifications as suggested themselves from time to time. The accuracy of the statement having been questioned, I have, since then, endeavored to find some method of conducting the operation which would give accurate results; I have also tried the methods used by five different chemists; and I am not able to bring the process within the limits of an exact method. While it can fairly be ranked with the colorimetric carbon-process, and can be used for checking the operations of a steel plant, yet it requires more care to obtain uniform results, and is liable to greater variations from slight causes than the carbon-process, and, in my judgment, is not a safe method to employ when exact results are sought.

Jan 1, 1887

By R. H. Ernst, H. R. Ogden, D. J. Maykuth

AT present, no theories exist which allow prediction of the effect of alloying additions on the thermoelectric properties of metals. Nevertheless, Battelle and others1 have observed that, at high temperatures, the peak thermal electromotive-force output (relative to a platinum standard) occurs with metals in Group VI of the Periodic Chart. The authors suspected that this peak was associated with the fact that maximum electronic bond stability is achieved with these metals which have six bonding electrons per atom. On the basis of current electron-concentration theory for transition metals and alloys:' it was surmised that the addition of valency electrons to metals of Groups IV and V (accomplished by the addition of metals from Groups VI, VII, or VIII) should progressively increase the thermoelectric-power output of the resulting alloys until an alloy composition is reached at which the number of valency electrons per atom is six. A further increase in the ratio of valency electrons per atom should then decrease the thermoelectric power. In contrast, the addition of bonding electrons to Group VI, VII, or VIII metals should decrease their thermoelectric power since the electron per atom

Jan 1, 1965

EUGENE MCAULIFFE, St. Louis, Mo. (written discussion*).-When we undertook the development of the Kathleen mine, near DuQuoin, certain features greatly influenced the construction and underground development. The country is very flat, so that the usual gravity yard movement of empty and loaded coal cars would entail a very heavy fill at the empty-car end of the tracks, with some form of car-pulling arrange-ment to move the loads where it was practically impossible to provide. a gravity movement. So the yard was made level, except for 1000 ft. (304 m.) under the two tipples, where the cars are moved by gravity and controlled under the main-shaft tipple by four Fairmont car retarders. Both tipples are spread sufficiently to admit of introducing a narrow-gage track and locomotive. One 18-ton locomotive is at present employed in moving empties clown to a point above the main-shaft tipple and the loads off the track scales clown into the storage yard; ultimately a 25-ton loco-motive will be employed on the loaded side of the tipple. This form of car movement and control will admit of handling empty and loaded cars

Jan 11, 1919

By F. Lynwood Garrison

As the specific gravity of low-carbon steel seems to be attracting considerable attention as a means of détermining the quality and value of the metal, I give here a few of the results of a long series of experiments recently made by me. The object of the experiments not requiring more than approximate correctness in the third place of decimals, the extreme precautions to obtain accuracy which are sometimes used in determining specific gravity were not observed. But each piece of metal was carefully cleaned to remove scale, rust, dirt, etc., thoroughly dried, and then weighed in air, all weighings being carefully repeated. The balance used was one of Troemner's finest, and sensitive to one-tenth of a milligram. Before weighing in distilled water, care was taken to remove, as far as possible, the air enclosed in the pores of the metal. The pieces of metal were suspended by means of fine silk thread, a correction of course being made for the weight of the silk. Care was taken that the water in which they were weighed should he always at the same level, and, as far as possible, at the same temperature.

Jan 1, 1887

CHARLES E. GUILLAUME,* .Sèvres, France written discussion?).-Referring top. 2052, experiments made at the end of the year 1884showed a remarkable agreement between the indications of various verre dur thermometers of which all the corrections had been determined with the greatest possible precision. The maximum deviations not attributable to the comparisons themselves were then about 0.002 to 0.003 degree. Much later, greater differences began to show. They were caused by the fact that the glassmaker-had modified the composition by adding to it a small quantity of lead. Efforts are now being made in France to obtain a regular, supply of glass made according to the old formula. The determination of the boiling point of sulfur made by Chappuis,1 444.5°, accords very well with the value noted on p. 2054. The International Committee of Weights and Measures and the General Conference have already considered the future abandonment of the hydrogen scale in favor of the thermodynamic scale. The hydro-gen scale appears to be, in their estimation, a transitory one, happily so closely approaching the final scale that no correction should be necessary for all measurements of temperature made during the last 30 years.

Jan 12, 1919

By L. H. Hart

Because of a widely recognized association between breccia pipes of one form or another and many important copper deposits, conditions under which breccia pipes develop have been of great scientific interest for many years. Since these phenomena first attracted attention, many theories have been advanced to explain their origin. This is not unexpected, since it is likely that they have been formed by and under a wide range of conditions. Moreover, the entire subject is confused by the fact that the term breccia pipe is applied to a wide variety of occurrences. To discuss any part of the subject intelligently, therefore, it is necessary to start with definitions of the terms used. In their discussion of the Toquepala deposit, Richard and Courtright have carefully defined the terms they have used in their presentation of a very logical geo- logical history of Toquepala breccias. This is a real contribution, as there is no reference in the literature known to the writer where the history of a series of breccia pipe epochs, confined essentially within one channelway, may be read with the degree of certainty that appears to be possible at Toquepala.

Jan 6, 1958

By J. Wayne Erickson

One of the major problems facing today's mining industry is how to manage people and control costs in the underground mine. It is a problem with a solution. Because of the concerted effort to find and mine minerals near the surface, open-pit mine opportunities for certain minerals are becoming more limited; the mining industry will eventually be forced to produce more and more from underground mines in order to obtain those resources necessary to sustain our civilization. Although much technical progress has been made towards solving problems associated with the underground mine, such as - mine design, ventilation, rock support, equipment, and blasting techniques, little has been written on managing mining personnel. Much of what is being taught and practiced today about human relations, motivation, incentives, etc., applies to the underground miner, but the uniqueness of his group dictates a different treatment from that associated with the typical construction worker or factory employee. The difference lies with the kind of man attracted to underground mining and his working environment. Anyone who has had the responsibility of managing an underground mine would agree it is a unique problem.

Jan 9, 1976

By Bruce T. Stanley

The concepts of ore reserve estimation at the Henderson mine are reviewed presenting a geostatistical approach and procedure as applied. Specific problems encountered are recapped and explained as to the nature and resolution thereof. The methodology and results are shown, along with an approximation of computer usage and capacities needed. The scope of the paper is to set forth an example of actual application, usage, and benefits realized from such a procedure. Local Conditions The Henderson molybdenite deposit is located in central Colorado about 69 kilometers west of Denver. The geology consists of a classic subvolcanic ryolite porphyry sequence with quartz-molybdenite mineralization occurring in an extensively fractured granite stock complex. Being assymetric and bilobate in section, the orebody measures approximately 300 meters thick and 600 meters by 1200 meters in plan. The orebody is sampled by means of underground drill holes which create an east-west fan pattern spaced roughly 60 meters apart in the north-south direction. Approximately 27,000 meters of drill hole assayed on 3.04-meter intervals were available for analysis. Recovery on the core is about 95 to 100 percent, thereby affording us with reliable data all prepared to the same standards.

Jan 1, 1977

H. A. BUEHLER, Rolla, Mo. -I consider the lead .and zinc deposits of the Mississippi Valley to be the result of descending waters. There are many features that we have not determined and yet when you see the general field relations, it seems to me that the cause and effect can be well explained by descending circulation. In the Joplin-Miami district, for instance, the ore deposits are connected with openings or with old cavity fillings which have a direct connection downward from the surface to practically 300 ft. In the Miami camp, in the western part of the field, some of the deepest orebodies are directly connected with water, channels; the same condition has been obvious and always present with the shallower ores. I speak of one deposit that I have examined more thoroughly than any other in that district, the Admiralty property, which contains large openings or caves at the deepest levels. It seems to me that waters which would pass upward through 1800 ft. of dolomite would be saturated with lime and magnesia so far as the carbon dioxide of those waters would dissolve them, and therefore, on

Jan 1, 1918

SINCE I told you in the preceding chapter how the potter's art is followed in practice, now in this following one I wish to tell you how mortar* and bricks are made, and how and to what purpose they were discovered, although I know you will answer that you know it, inasmuch as it is an art known not only to skillful men but also to the unskilled ones by whom it is practiced, and that bricks and mortar were made and always will be made for the purpose of building. This I admit, but probably everyone does not know it as you do, and you perhaps, do not know its beginnings, although I remember having told you of them. Wishing to repeat it better now I shall begin with long ago, so that both you and I may be better satisfied. Therefore I tell you that you should know that all the arts that men practice in the world have been learned by them either through the process of reasoning from the principles of natural phenomena, from the actions of animals, by chance, or when forced either by some necessity or

Jan 1, 1942

By Henry S. Brown, Jean E. Tilden

Pyrite, pyrrhotite, chalcopyrite, and sphalerite from deposits distributed within the Piedmont and Blue Ridge provinces of North Carolina and adjacent areas were examined by atomic absorption spectrophotometry for cobalt, nickel, manganese, lead, tin, chromium, molybdenum, and gold. The ore samples were also examined petrographically. Cobalt and nickel, in general, enter pyrite and pyrrhotite rather than chalcopyrite and sphalerite. Manganese generally enters sphalerite rather than the other phases where an alternative is possible. The presence of tin in sulfide minerals was noted in a group of deposits east of the known occurrences of tin oxide (cassiterite) in the Kings Mountain belt, which may indicate the presence of a more extensive tin belt in the southeastern Piedmont than was previously recognized. Pyrrhotite from a group of four deposits in Jackson and Clay Counties, North Carolina, differs from pyrrhotite from other Ducktown-type deposits in having cobalt/ nickel ratios less than one, finer grain sizes, and colloform texture. These differences suggest that that this group of deposits has had a history different from that of the other Ducktown-type deposits studied. No significant conclusions could be made based on the distribution of lead, chromium, molybdenum, or gold.

Jan 1, 1975