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By F. C. Kelley, L. L. Wyman

In order to clarify and amplify the existing data concerning the action of the cementing material in cemented tungsten carbide alloys, the authors have initiated this investigation of the entire range of cobalt-tungsten carbide alloys. Inasmuch as the ultimate objective is relative to what actually goes on during the sintering of cemented tungsten carbide materials, this work was necessarily restricted to heat treatments similar to those used in actual production of these materials. In the course of numerous experiments, the authors have noted several conditions that indicated that there was a solubility to be considered. Among these factors are the following: 1. Many of the alloys showed a much larger amount of binding constituent to be present than could possibly be accounted for by the cobalt content. 2. In many areas, grains of the carbide constituent are much larger than the particles of carbide originally added. In addition, these grains are of very regular contour. 2a. In samples of cemented tungsten carbide which had been fused in the atomic hydrogen torch in the presence of excess binder constituent, immense grains are formed, and their shapes are very regular. This is also true when the cemented tungsten carbide of 13 per cent. Co content is fused alone in the atomic hydrogen torch. Contrary to general expectation, chemical analysis of this material, after fusion in the atomic hydrogen torch, checks the analysis of unfused material. 3. In making the cemented tungsten carbide materials by the process of exerting the pressure at the time of heating a certain portion of the ' contents squeezed out of the mold. Chemical analysis has shown that this material contains approximately 12 to 20 per cent. of tungsten. The microstructure shows a cored dendritic structure interlaced with eutectic network, and some graphite, as shown in Fig. 1. 4. Thermal analysis of these materials has consistently indicated an arrest point close to 1350" C.

Jan 1, 1931

By G. O. Hiers

THE object of the experiments reported in this paper is to determine the eutectic composition of copper and tin and to determine the location of the part of the liquidus line immediately above the eutectic composition in copper. Three methods were used in the investigation: (1) the method of dissolving copper in a bath of molten tin at constant temperature, with the idea that when the bath was saturated with copper its copper content, by analysis, together with the temperature at which the saturation took place would locate a point on the liquidus line (2) the method of the differential cooling curves, and (3) the method of microscopic examination. This paper is principally concerned with the results of the last two methods mentioned. The results of the first method, that of dissolving copper in molten tin, did not agree with the .results of Miller,1 by the same method, nor with the results of other investigators by other methods, nor yet with the results of the cooling-¬curve experiments and microscopic examination reported here.

Jan 1, 1929

By J. N. Hobstetter

It is widely believed that the nucleation of phase transformations in solid metals is accomplished by some type of local atomic fluctuations in the parent phase which arise from spoutaneous difiusion in the metal or alloy system. Under appropriate conditions, these fluctuations are believed to be stable in the sense that the free energy of the entire system is lowered if the fluctuations, or nuclei, grow. Under other conditions they are thought to be unstable in the sense that the free energy is lowered if they redissolve. The criterion for stability is usually taken as the size of the fluctuation. This view has been rationalized by Beckerl in terms of the free energy released by the volume of the nucleus and the free energy associated with the formation of a new surface surrounding the nucleus. The qualitative result of this reasoning is shown in Fig I where the changes in free energy for the surface and volume effects are plotted together with their sum against the radius of the nucleus. There is evidently always a critical size r, beyond which the release of free energy which is proportional to the volume always dominates the increase of free energy which is proportional to the surface area. Borelius2 has also attempted to rationalize the stability criterion for binary alloys, but in terms of the internal concentration of the fluctuations. He has found that, if surface energies are entirely ignored, the fluctuation must still reach a critical concentration if it is to become stable and avoid subsequent dilution. Although the Borelius theory fails to predict many observed nucleation phenomena such as the vanishing of the nucleation rate at the critical temperature, the major premise must certainly be valid. In this paper a reconciliation of the Becker and Borelius views is made by means of a search for nuclei which are at once stable with respect to both size and internal concentration. The increase in free energy per mole accompanying the formation of a nucleus which is just stable, AF., is independent of the path whereby the nucleus is brought into being. It is thus appropriate to seek critical nuclear attributes without reference to the fluctuation mechanism. The rate of nucleation, however, cannot be treated without a detailed understanding of the exact fluctuation process which produces stable nuclei. In this and succeeding papers the purpose will be to find the size, shape and internal concentration of the stable nucleus which is formed with a minimum increase in free energy in a wide variety of systems. The Nature of the Nucleus It is necessary ti have rather detailed knowledge of the nature of a nucleus if AF, is to be computed. Fortunately, enough facts are known or suspected about the nucleus to make possible a detailed analysis. X ray diffraction studies have shown

Jan 1, 1949

By Paul A. Taylor

MUCH information concerning pegmatites which was thought to be true a few years ago has been proved false, and what is now actually known about some pegmatites is not true of many others. The erratic and seemingly unpredictable structure and variable composition of this class of mineral deposits has been widely emphasized. Even parts of the same pegmatite body exhibit marked differences in texture, mineral composition, width, and attitude. Constructive geological thinking in respect to pegmatites now aims to establish general laws rather than to stress the confusing diversity of features having no special economic significance. Substantial progress has been made in classifying different types of these deposits according to general features, internal structure, mineralogy, and origin. In some cases it has even been possible to block out tonnage reserves in advance of mining. It is still easy, however, to make highly erroneous predictions after a preliminary examination of a pegmatite prospect. Pegmatites are important to the economic well being of the country and to its military security. They furnish virtually all the feldspar, strategic mica, beryl, columbium, tantalum, and caesium utilized in the United States, as well as sundry other minerals and significant amounts of lithium and rare earth minerals and gems. With the exception of vermiculite, occasional ilmenite-rutile, and perhaps soda-lime feldspar and garnet deposits, basic pegmatites are of little economic importance. Consequently in this paper, as in common parlance, the term pegmatite generally relates to coarsegrained acidic rocks or what is aptly called giant granite. Available data indicating the size and importance of the production and trade in specified pegmatite minerals are summarized in Table I. Geological Features Much of the latest thinking on the economic geology of pegmatites is now available in a 115-page monograph' by a group of experts who participated with geologists of the Federal Geological Survey in the widespread wartime investigations. Doubtless the most significant feature of the monograph is indicated by the title, The Internal Structure of Pegmatites, but it also contains a vast amount of other new information and includes the assimilated concepts of many earlier writers, whose works are given in a comprehensive list of references. The shape, size, attitude, and continuity of many pegmatite bodies is controlled by the structure of the older rocks in which they occur. If the older rocks are easily penetrated, e.g., biotite schist, most of the pegmatites in a given district will be found outside the parent granite mass as exterior pegmatites. Marginal pegmatites are more prevalent if the older rocks are massive, unsheared, and sparingly jointed. Networks of pegmatites are abundant in highly-jointed rocks. In strongly foliated schists the bodies are usually lenticular, whereas in highly-folded areas they assume tear drop, pipe or pod-like, bow-shaped, or sinuous forms. Jahns2 recognizes five major shape classes: l—dikes, sills, pipes, and elongate pods; 2— dikes, sills, pipes, and pods with bends, protuberances, or other irregularities; 3-—trough-or scoop-shaped bodies with or without complicating branches; 4—bodies with the form of an inverted trough or scoop; and 5—other bodies, including combinations of the above and miscellaneous shapes. Many pegmatite deposits are scarcely big enough to be recognizable as such. Most of them, in fact, are small tabular deposits less than 4 in. wide and usually without economic concentrations of minerals. On the other hand, some pegmatites are more than a mile long and over 500 ft wide. The ratios of length to breadth range from 1 : 1 to 1 : 100. Although the vertical dimension bears no invariable relationship to strike length, tabular deposits or large lenses are often symmetrical enough to show nearly as much continuity down dip as in their horizontal extension, and some pipes or pods are amazingly persistent in the vertical plane. Small pegmatites often string along a fairly definite trend line; in a given district major bodies may lie roughly parallel, and where only a few of them do not, the erratically disposed bodies generally differ in composition from those conforming to the regular pattern. This does not apply, however, in all districts. Characteristically, pegmatite veins pinch and swell or split into branches. When they pinch out entirely it is often possible to find a new body by prospecting the extension of the strike or dip, but the chances of finding a hidden deposit are ordinarily too uncertain to justify much subsurface prospecting. Diamond drilling may yield valuable information as to the continuity of known deposits whose upper portions are well-exposed. Some deposits, in fact, can be proved up for hundreds of feet by surface trenching and then intersected by drill holes at various depths like any other vein-like deposit. Others twist and branch, apparently defying all efforts to explore them short of actual mining.

Jan 1, 1954

By O. E. Kiessling

THIS announcement of the topics relating to production control, which the Committee hopes to have discussed at the February meeting, supplements the preliminary announcement published in the November number of MINING AND METALLURGY. In the previous article, the writer indicated the kaleide-scopic nature of the questions involved in obtaining better coordination in industry, and that, as a matter of practical expediency, the discussion in February would be limited to the more obvious difficulties in industry which need attention and to those questions which the Committee thinks would be of greatest interest to members of the Institute. But while practical considerations necessitate limiting the program, free discussion of all phases of the subject is urged by 'the Committee. In a preliminary consideration of the production control problem, there loom up two questions which have to be faced: (1) First, there is the question of the extra industrial capacity necessary to meet demand during the ordinary fluctuations of business, commonly characterized as `the "business cycle." Anyone who tries to formulate a program pertaining to productive capacity must decide whether he wishes to discuss the control of business cycles. While this question may eventually lend itself to treatment, the Committee does not feel that it can be considered at present with much profit. (2) The second question arises from the existence of over-stimulated capacity above and beyond peak demands in boom times. Discussion of this topic, it is felt, would be most fruitful. How to prevent capacity from being over-stimulated to an extent beyond any hope of possible demand is a

Jan 1, 1929

By W. E. Forsythe

WHEN measuring ordinary temperatures, the instrument is generally placed in very close contact with the body the temperature of which is desired. However, if the temperature of the source is continually raised, a point is soon reached where no known substance will, in general, remain constant in any of its temperature-measuring properties if placed in direct contact with the source. Also, it is occasionally necessary to measure the temperature of a source that 'is so small or so situated that it would be very hard to bring the measuring instrument into direct contact with the source. When these conditions exist, advantage is taken of the well-known fact that all bodies, when at sufficiently high temperatures, send out radiation in amounts readily measurable. This radiation has been found to be related to the temperature. The temperatures of very hot bodies have probably always been judged by the color, or the brightness, of the light given off. With practice, one can estimate probably within 50° to 100° C. of the correct value. However, if judgment is left to the eye alone, very much larger errors are sometimes made, due to

Jan 9, 1919

By Reinhardt Thiessen

IN THE general study of coal, all evidence points in the one direction -that coals had their origin in a manner analogous to that of peat. The best method of studying coal, whether it concerns its chemistry, composition, or physical condition, is to study peat. The essentials in a study of peat are a knowledge of the chemistry of plants, knowledge of decay and of the transformation process of plant-substances into peat. A number of facts must be emphasized, namely, (1) peat is formed under wet conditions only; (2) plants grow in the place where peat is formed; (3) all the plant substances go into the bog; and (4) all the plant substances are subjected to a series of phases of decay which are (a) in the air completely above the water level but in relatively moist conditions; (b) above the water level, but covered by debris; and (c) completely submerged by both water and debris.

Jan 3, 1925

By Robert W. Elayer

In August 1973, Fluor Utah, Inc. was awarded a contract by the Office of Coal Research (now part of the Energy Research and Development Administration), Department of the Interior, for the examination of the unique problems of large-scale surface coal mining to supply coal conversion complexes. The project consists of two phases: (I) data base development and organization and the formulation of a mathematical computer modeling system for surface mining; and (II) computer manipulation of the data base in accordance with the model to formulate several typical preliminary mine and preparation plant designs. Phase I is scheduled for completion by the end of July 1975 and Phase II is scheduled to be complete by the end of January 1977. This paper briefly discusses the effort for only one aspect of this project-the foundation for geologic modeling developed in Phase I. The Phase I task of geologic modeling can be broken down into two subtasks: (1) identify areas containing sufficient resources of surface-minable coal to support at least one large-scale mining complex, and (2) characterize the coal deposits in these areas for computer storage and retrieval. Identification of Resource Regions The basic production design criteria for large-scale surface mining, as stated in the contract, is the production of 75,000 tpd, or more, of bituminous coal. Based on a constant total Btu delivered to the preparation plant, daily production requirements for the different coals are as follows: Bituminous Coal 75,000 tons Subbituminous Coal 99,500 tons Lignite 143,500 tons Although surface mining on this scale is presently non-existent, it is deemed that future operations, in order to meet the increased energy demands, will have to look forward to much larger scale mining complexes. These tonnage requirements are meant to be used only for the delineation of general areas suitable for large-scale surface mining, termed "Strippable Coal Resource Regions." They were determined largely from the latest complete detailed coal resource estimates of the U.S. Bureau of Mines. Nine strippable coal resource regions, containing over 100 billion tons of strippable coal resources, were identified [(see Fig. 1)]. The delineation of these regions was based entirely upon estimates of surface-minable coal resources and the production design criteria for large-scale surface mining. If surface-mined coal was combined with underground production, or if smaller production rates were specified, then other areas which were omitted here would be included in the regions. Changing the outline of the regions, however, would not add any new mining situations to be studied in Phase II. Characterization of Coal Deposits The second subtask involved the general characterization of the coal deposits contained in the strippable coal resource regions. The geological information gathered

Jan 1, 1976

By H. A. Hoffman

Competition from an all-flotation plant, with demonstrated economies and efficiencies, plus a change in smelting contract and introduction of improved cyclones lead to conversion from gravity-flotation. Detailed descriptions are given of equipment installed and procedures used at St. Joseph Lead's Federal mill. Future plans include further quality control by instrumentation in all aspects of the mill operation. Also planned are improvements in materials handling systems. Competitive conditions will continue to dictate improvements and changes in the mill flowsheet. The advent of all-flotation mills in the Lead Belt was introduced by the Indian Creek mill in late 1953. This modern and efficient plant then became a pattern for the other mills in this area to re-evaluate their circuits in an effort to develop flowsheets that would improve operating conditions and metallurgy. The Indian Creek mill demonstrated that all-flotation would require considerably less operating and maintenance labor than the combination of tabling and flotation that was common in the Lead Belt at that time. Two significant changes occurred in recent years to allow all-flotation to be seriously considered in other Lead Belt mills. One was a change in the smelting contract which did not require gravity concentrate. Another was the development of cyclones which provided classification of the flotation feed in a very small space. Since the Federal mill was the largest concentrating plant in the Lead Belt it was felt that the greatest savings could be made by investigating the all-flotation possibilities at this mill. Interest was stimulated by the milling and ore dressing Depts. to determine if this mill would be converted without undue cost, provided the metallurgy could be improved. Accordingly, laboratory tests were initiated to learn what metallurgical benefit could be derived. Numerous tests were run which indicated that grinding to all-flotation would improve the tailing by as much as 0.02 pct Pb. This was quite significant when multiplied by the tonnage of ore treated. Projecting the added cost of power for extra grinding and flotation, and the additional flotation reagents required, plus additional new equipment that would have to be purchased, it would still add up to a considerable saving. The all-flotation mill would reduce man power by some 30 pct, and make a metallurgical improvement. Operating costs could be reduced bv 2$ per ton. The metallurgical improvement would amount to 4$ per ton, for a total of 6$ per ton of ore milled. An estimate of the cost of the conversion was set at $250,000. With the savings as estimated this could be paid off in about two years. On paper it therefore seemed attractive enough to justify a mill test. MILL TESTING One section of the Federal mill was made available for use as a separate test circuit. Cyclones and density controllers were borrowed from the Viburnum and Indian Creek mills. Denver flotation cells were obtained from the Desloge mill that was then shut down. Two 10-cell groups of Fagergren flotation machines, consisting of eight roughers and two cleaners in each bank, were segregated from the remainder of the plant. The 9x12-ft rod mill was continued as a primary grinding mill. The two 6%x12-ft mills on this section were converted from rods to balls, and the speed increased to 22.0 rpm. Cyclones were installed to close the circuit of these ball mills. The ground pulp from each of the ball mills was fed separately to its own bank of flotation cells so that two completely separated test circuits could be run in parallel. This test circuit operated on a three-shift basis from Dec. 22, 1959 to Mar. 21, 1960. The first few weeks were occupied in developing conditions for proper metallurgy and trouble-free operations. Results were rather erratic but as the ore dressing laboratory and the mill operators became more familiar with conditions they were able to obtain expected results, which could be duplicated day after day. The last five weeks of testing indicated the best results and are tabulated in Table I. During the first two weeks a Denver unit cell was used on No. 1 flotation circuit. Even though it recovered almost one half of

Jan 1, 1962

By Edward Steidle

NOTHING stands still. We go forward or backward. As a distinct group of educators, our immediate concern is with the preparation of young men and women for participation in the mineral industries on a professional basis. I am going to have the temerity to state emphatically that for a long time as a whole we have remained in a static position. We are now confronted with the choice of advancement or retrogression. We are still in a position to make a choice and our ultimate fate will depend upon the course of action we elect to follow. Wars always have been great catalysts and social and scientific advancements mature under military stimulus in a fraction of the time normally consumed. We are now in the midst of a conflict whose duration or final effects cannot be estimated. However, the record already demonstrates that this war as never before is a mineral war in which incentive, strategy, and outcome are directly related to the distribution and utilization of minerals. The inevitable result is a drain upon our resources now reflected in our record production and a growing public consciousness of the importance of minerals in the role of human affairs. It is evident that we must seek new mineral frontiers beyond the borders of the United States and take every other precaution to forestall a "have-not" position in the world.

Jan 1, 1943

By PAUL AUDIBERT

THE downward trend of metal prices seems to act something like a reagent that precipitates selfishness in most business men's hearts; in the same way the upward trend precipitates altruism. Operators do not say: "I continue working my mine without curtailment because I can afford the present prices while my neighbor cannot and thus will give me way." They say: "I continue working my mine because 1 consider it a service for consumers. They will get better prices on a free market. Any curtail¬ment would be an attempt to raise prices artificially, that is to say, bad economics." Copper producers have learned how fallacious is such an opinion. It perhaps was not fallacious in olden times when all mines were worked on a small scale even if operating on a big deposit. At that time the supply and demand law played fair. When prices were too low and profits were vanishing for many mines, they would. shut at once, then little by little the metal scarcity would induce prices to climb up again; finally these prices would reach the point when it became profitable to again work the closed mines. Re-opening and shutting down mines was then a normal custom. Workers and operators weakly deplored this unstability, but there was nothing effective they could, do about it.

Jan 1, 1931

Elected Died 1895 *ABBOTT, AI ATTHUR 1908 1882 *ABBOTT, ARTHUR V 1906 1905 * ABE, MASAYOSHI 1909 1903 * ADAMS, CHARLES C. 1905 1906 * ADAMS, JOHN C. 1913 1905 * ADAMS, WILLAMS 1909 1903 * ADAMS, W. EDWARDS 1910 1884 *ADDY, MATTHEW 1896 1906 * AFFLECK, WILLIAM A. 1911 1889 * AKERS, WILLIAMS A. 1906 1905 * ALABASTER, RUPPERT C. 1911 1899 * ALBERGER, LOUIS R. 1911 1894 *ALLEN R B 1896 1905 * ALLEN, R. SCOTT 1906 1874 * AMIOT, H. 1892 1886 *AMSLER, CARL 1894 1898 ** ANDRSON, JOHN W 1905 1895 *ÅNGSTROM, CARL 1901 1887 * ARCHBALD, JAMES 1910 1900 * ARLETT, GEORGE H 1906 1895 *ARMSTRONG, JOHN F 1898 1882 *ARNOLDS, HUGO 1886 1875 *ASHBURNER, CHARLES A 1889 1872 *ASIIBURNER, WILLIAM 1887 1883 *ATKINS, C M , JR 1885

Jan 1, 1917

Philip Argall, Denver Col. (communication to the Secretary): Dr. Raymond claims (Trans., xxiii., 560)) that my statement (p. 557) regarding the crystallization of iron "is beyond question incorrect." He says: "It is not even settled that vibration will crystallize iron under any conditions." While admitting that authorities differ on the possibility of cold crystallization of iron, I believe it is a settled and undisputed fact that vibration in the presence of heat will crystallize iron. Bloxam and Huntington say :* " Vibration assists 'in converting fibrous metal (iron) back into a crystalline state when heated, a lower temperature sufficing than in the absence of vibration." Mr. A. F. Hill, summing up a very exhaustive review upon the crystallization of iron and steel, pronounces against crystallization, but only at temperatures below 900' F. Mr. Howe, discussing ,the breakage of a 20-foot porter-bar with a crystalline fracture, suggests that it was attributable to heat, jointly with the jar. We see, then, that vibration of heated iron bars will induce crystallization and consequent change of structure. Referring to my statement, I wish to point out, that I was discussing the vibration of stamps arid should have said, "vibration under all such conditions," etc. That is, vibration attended with sharp blows, such as a stamp-stem is subjected to, will crystallize iron; yet I believe that intense vibration under any condition will

Jan 1, 1895

By A. W. H. Morris, G. H. Laurie, J. N. Pratt

Using- galvanic cells of the form Sn(liq)/Sn" (LiCl-KC1-SnCl,)/Sn-Ag (alloy), measurements have been made of relative thermodynamic properties of the a, C, E, and liquid phases of the Ag-Sn alloy system. Partial heats of solution of the components in the liquid alloys lzave also been observed by direct cal-orimetric measurement in an isoperibol calorimeter. The thermodynanzic quantities are disczlssed in relation to structural and other properties and the existence of anomalous minor fluctuations in the partial heats and entropies of solution in liquid alloys is tentatively suggested. In the course of a recent electro motive-force study of the thermodynamic properties of Sn-Ag-Pd liquids,' some measurements were also performed on the Ag-Sn binary system. Most previous thermodynamic studies of this system have been concerned with the liquid state. Measurements confined to the limiting heat of solution of silver in liquid tin have been made by many calorimetric workers2 while high-temperature calorimetric measurements of the heats of formation of the full range of liquid alloys are reported in the early work of Kawakami~ (1323°K) and more recently by Wittig and Gehrin~(1248°K). Electromotive-force studies on liquid alloys have been made by Yanko, Drake, and Hovorka' (606" to 686°K; 86 to 99.4 at. pct Sn) and by Frantik and Mc Donald' (900°K; 30 to 90 at. pct Sn). The only known measurements on the solid state are of heats of formation of the a, £, and c phases; these values were obtained using tin-solution calorimetry, at 723"K, by Kleppa,~ whose investigation also yielded heats of formation of liquid alloys containing more than 64 at. pct Sn. The present experiments on the Ag-Sn alloys include a re-examination of the liquid phase and, because of the dearth of free-energy data for the solid state, attempted measurements on the a, c, and E phases. The principal new feature of electromotive-force results obtained for the liquid phase was an indication of anomalous fluctuations in the partial heats and entropies of solution of tin at certain compositions. However, since the values for these thermodynamic quantities were determined from the temperature coefficients of cell potentials, which are commonly subject to considerable error, confirmation by calorimetric measurements was considered desirable. A detailed investigation of the partial heats of solution of the components in the binary liquids was made using a liquid metal solution calorimeter. I) GALVANIC CELL STUDIES a) Experimental Details. Measurements were made, as a function of alloy composition and temperature, of the potentials of reversible galvanic cells of the form: ~n(liq)/~n++/~n-Ag (solid or liquid alloy) Details of the apparatus and experimental techniques have been given elsewhere.' so that a brief account will suffice here. Molten salt, 58 mole pct LiC1-42 mole pct KC1, containing small amounts (1 to 2 mole pct) of stannous chloride was used as the electrolyte. The salts were dehydrated by pre-electrolysis and vacuum -drying techniques. Cells were established under an argon atmosphere by immersing tin and alloy electrodes in the molten salt contained in a large silica tube, heated in a vertical resistance furnace. The tube was sealed at the top by a head plate provided with openings permitting the simultaneous insertion of six electrodes, a central thermocouple sheath, and connections to vacuum and argon lines. Temperatures were controlled to *0.2"C over prolonged periods, with maximum variation over the electrodes at any time of 0.l°C. Temperatures were measured with a standardized Pt/13 pct Rh-Pt couple. The electromotive force of this and the cell potentials were measured on a Cambridge Vernier potentiometer and short-period galvanometer. Alloys were prepared from Pass "S" tin (99.999 pct) and Johnson-Matthey high-purity silver (99.999 pct) by melting in evacuated silica capsules and quenching in cold water. For liquid phase experiments, pieces of the resulting alloys were remelted into prepared silica electrode units, while solid electrodes were prepared by remelting into 3-mm bore tubing, inserting a cleaned molybdenum lead wire, and quenching to produce uniform rods about 3 cm in length, with soundly attached leads. In all cases remelting was done under an argon atmosphere. The solid electrodes were subsequently annealed in evacu ated silica tubes for 14 days at about 20°C below the solidus and quenched. Analyses showed that these techniques produced uniform electrodes with no significant change from weighed out compositions. b) Results and Discussion. Measurements were made on about forty alloys in the solid and liquid states, over varying ranges of temperature between 550" and 1050°K. Stable, mutually consistent, and reproducible electromotive-force data were obtained with most liquid alloys and these are shown in Fig. 1. Investigations were extended below the liquidus tem-

Jan 1, 1967

By S. A. Levy, J. D. Wood, J. F. Libsch

A study of the preparation and characteristics of a sevies of Fe-C-N alloys has been conducted. X-ray, microhardness, and metallographic data from a series of single-phase alloys produced by controlled nitriding of carburized foils are reported. The existence of a, y', and E carbonitride has been confirmed and it has been found that y' is the hardest of these three phases. These results have been used to interpret the structures observed in nitrided steels. ThIS paper represents the second phase of a three-part study concerning combined nitriding and induction hardening. The first part' reports the engineering properties (depth hardness, fatigue, corrosion, and tempering resistance) obtained when seven different steels were subjected to the combined surface hardening treatment. The present paper concerns the nature of a series of single-phase alloys prepared by controlled nitriding of carburized foils. The objective was to simulate the various layers present in the as-nitrided steels. A third paper will report data concerning induction hardening of the foils and will attempt to set forth a mechanism for the high hardness obtained with the combined treatment. Studies of nitriding generally fall into three categories. The first were performed with bars using conventional nitriding procedures, thus yielding a nitrogen gradient and a series of phase layers near the surface.2-6 Such studies were complicated by the presence of the nitrogen gradient, for it was difficult to correlate microhardness and X-ray data with chemical composition. There were always complications due to penetration of the X-ray beam which yielded data influenced by underlying layers. Similar difficulty was experienced in taking hardness readings on a tapered specimen or in isolating various layers by machining. A second group of investigations was primarily concerned with establishment of regions in the Fe-N7,9,10 or the Fe-C-N phase diagram.8 These were performed with powder specimens which were nitrided in am-monia-hydrogen mixtures to produce a series of single-phase specimens. Unfortunately, the powder specimens were not amenable to either microstruc-ture or microhardness study. The third was essentially a compromise of the first two. Bose and Hawkes," using 0.005-in.-thick iron foils, were able to obtain microhardness, microstruc-ture, composition, and X-ray data on Fe-N alloys of eutectoid composition by equilibration in ammonia-hydrogen mixtures at 1290°F. To obtain a better understanding of the nitriding process and the characteristics of the phases in ni-trided plain carbon steels, the present investigation was undertaken. The investigation was patterned after that of Bose and Hawkes with the exception that nitriding was performed at 930°F (below the eutectoid temperature), as in the case of conventional nitriding. In addition to gaining some understanding of the source of high hardness of nitrided and induction-hardened steels, found in a previous study,' this investigation was concerned with the possibility of controlling the phases present in a nitrided case through the use of ammonia-hydrogen mixtures. Knowledge of the properties of each phase and the conditions necessary for its production could make it possible to avoid undesirable surface layers in nitriding. EXPERIMENTAL PROCEDURE Specimen Preparation. A specimen thickness of 0.005 in. was selected to insure that a uniform nitrogen concentration could be obtained in a reasonable length of time by equilibration in an ammonia-hydro-gen atmosphere. The starting material was a vacuum-cast ingot of pure iron, the major impurities of which were: C, 0.003 pct; 0, 0.014 pct; S, 0.004 pct; N, 0.003 pct.* 'Compositions are quoted as weight percent except as noted. The ingot was heated to 1500°F in a nitrogen atmosphere and forged to a slab 0.25 in. thick. The material was then reduced to 0.005 in. by alternately cold rolling and annealing in a nitrogen atmosphere at 1600°F. This material was divided into five groups of specimens which, after carburizing, yielded the following carbon contents: 0.003, 0.28, 0.36, 0.46, and 0.74 pct C. The carburizing was performed by the Leeds and Northrup Research Laboratories, using a controlled "carburizing potential" which yielded a uniform carbon concentration throughout the cross section.

Jan 1, 1970

By M. R. Moharam

The well-known formulae of screening efficiency and circulating load calculations in closed crushing circuits were exploited to achieve graphical estimation of these parameters. Three basic charts were proposed and constructed. The first one is for the regular closed circuits where the new feed goes to the crusher. The second is for the reverse closed circuits in which the new feed reported to the screen is free of screen undersize particles. The third chart controls the reverse circuits when they are receiving new incoming feeds containing undersize material. Compound circuits were also reanalyzed and a concept of equivalent simple circuit was introduced to enable graphical manipulation of these complex circuits with the help of the aforementioned charts

Jan 1, 1982

By John N. Hobstetter

IT is widely believed that the nucleation of phase transformations in solid metals is accomplished by some type of local atomic fluctuations in the parent phase which arise from spontaneous diffusion in the metal or alloy system. Under appropriate conditions, these fluctuations are believed to be stable in the sense that the free energy of the entire system is lowered if the fluctuations, or nuclei, grow,' Under other conditions they are thought to be unstable in the sense that the free energy is lowered if they redissolve. The criterion for stability is usually taken as the size of the fluctuation. This view has been rationalized by Becker1 in terms of the free energy released by the volume of the nucleus and the free energy associated with the formation of a new surface surrounding the nucleus. The qualitative result of this reasoning is shown in Fig I where the changes in free energy for the surface and volume effects are plotted together with their sum against the radius of the nucleus. There is evidently always a critical size r. beyond which the release of free energy which is proportional to the volume always dominates the increase of free energy which is proportional to the surface area. Borelius2 has also attempted to rationalize the stability criterion for binary alloys, but in terms of the internal concentration of the fluctuations. He has found that, if surface energies are entirely ignored, the fluctuation must still reach a critical concentration if it is to become stable and avoid subsequent dilution. Although the Borelius theory fails to predict many observed nucleation phenomena such as the vanishing of the nucleation rate at the critical temperature, the major premise must certainly be valid. In this paper a reconciliation of the Becker and Borelius views is made by means of a search for nuclei which are at once stable with respect to both size and internal concentration, The increase in free energy per mole accompanying the formation of a nucleus which is just stable, ?fe, is independent of the path whereby the nucleus is brought into being. It is thus appropriate to seek critical nuclear attributes without reference to the fluctuation mechanism. The rate of nucleation, however, cannot be treated without a detailed understanding of the exact fluctuation process which produces stable nuclei. In this and succeeding papers the purpose will be to find the size, shape and internal concentration of the stable nucleus which is formed with a minimum increase in free energy in a wide variety of systems. THE NATURE OF THE NUCLEUS It is necessary to have rather detailed knowledge of the nature of a nucleus if ?Fe is to be computed. Fortunately, enough facts are known or suspected about the nucleus to make possible a detailed analysis. X ray diffraction studies have shown3

Jan 1, 1948

The members of the Institute have probably seen in the daily papers notices of the plans of the Secretary of the Navy to. form an Advisory Board to assist the Government to make available the latest inventive genius of the country. Secretary Daniels has appointed Mr. Thomas A. Edison Chairman of this Advisory Board and has officially invited the Institute to secure the selection of two of its members to serve. on this Board. The Secretary in his letter states: "I feel that the work your Institute has done has been such as to give it the right to be in a way officially represented, and the Navy Department desires in this way to testify to its own appreciation of the splendid work for our country that your Institute has done. I have the emphatic approval of Mr. Edison, and he agrees entirely with me that your Institute should he represented in this way and that no better method of getting the kind of men we need could be devised." The invitation of the Secretary of the Navy has been officially accepted and steps have been taken to nominate the two members. Since the Constitution provides for no meeting of the Board of Directors until September, and as Secretary Daniels urged early action, the matter was discussed at a special meeting of the Executive Committee of the Institute, at which were present as many members of the Board of Directors as were in New York City at the time. Invitations were also extended to other members of the Institute who happened to be in the vicinity. At this meeting it was decided to submit the matter by a special letter-ballot to the Board of Directors and in doing so to suggest or nominate five members of the Institute, accompanying this nomination with the statement that the Directors might vote for two of the members so nominated or for any other members of the Institute not so nominated. It was voted at this meeting that it. was the sense of those present that in view of the fact that this committee was an advisory one the type of men to be chosen should be men of administrative or executive ability, cap-

Jan 9, 1915

By N. Arbiter, C. C. Harris

In 1961, a research program started at Columbia into the mechanical aspects of flotation,* and certain ends are now in view. The purpose of this note is to explain these tentative conclusions in the hope of stimulating discussion and eliciting new data, especially industrial data, with which to test the views expressed. The variables presently under consideration are impeller rotational speed, N, volumetric air rate, Q, and impeller diameter, D, the latter being the parameter chosen to designate cell size. The most favorable *The latest work 1 references all previous publications. chemical environment is not under discussion since the procedures for establishing it are better understood than those for optimizing N and Q by virtue of a longer history of more intensive investigation. THE GRADE AND RECOVERY SURFACES With a given ore, chemical treatment, and flotation machine, both grade, G, and recovery, R, are functions of N and Q. The GNQ and RNQ relationships are best viewed in terms of three-dimensional surfaces (Fig. 1) which are experimentally determinate.2 TO maintain grade at an acceptably high level, it is necessary for N and Q to lie within certain limits, and similarly with recovery. However, the ranges of N and Q for grade on the one hand and recovery on the other are rarely the same. Selecting the single N

Jan 1, 1970

By William J. Coulter

WITHIN the past thirty years the United States has been involved in two tragic, vicious, and costly world wars. To make the world safe for democracy was the reason given for our participation, but the confusion and misunderstanding that prevails all over the world today suggests that war is not the proper approach to the attainment of that utopia. These conflicts were conceived and prosecuted by nations far advanced in civilization and culture. Their best manhood was sacrificed, a staggering tax burden was saddled on their peoples, huge financial losses were incurred, destruction of property was appalling, and cultural and peaceful scientific advancement received a setback that may require centuries to retrieve. Therefore, some basis is established for the conclusion that progress in the past fifty years has been most outstanding in the development of instruments used for death and destruction, and that progress in this direction between the two World Wars would indicate that the next war will go far toward total destruction of world civilization.

Jan 1, 1946