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By W. H. Bassett

Beads of metal frequently appear at the ends of cast-copper wire bars and on the sides of wedge cakes near the top. These are richer in cuprous-oxide than the rest of the casting. A micrographical study of these exudations has been made. It is suggested that the material is forced through the surface while the copper is solidifying. If not eliminated in process of manufacture, it shows on the finished polished sheet copper in patches differing in color from the main body of the sheet. FIGURES 1 to 4 show the copper exudations, at different magnifications, as they appear on the ends of cast wire bars, and on the sides, usually near the top, of wedge cakes. Sometimes the exudations are in fine "drops;" at other times, large masses of the material are found. Microscopic examination of the copper exudation indicates that it is high in oxide and of eutectic proportions. Because of the difficulty of securing a suitable sample, the protuberances have not been analyzed chemically; but the spectroscope shows no indication that there are any more metallic impurities present than in the balance of the copper. The lowest copper plus silver content of the coppers studied for this? paper was 99.914 per cent.; the highest, 99.966 per cent.; so the oxygen content of the whole casting would be well under 0.07 per cent.

Jan 2, 1926

By N. A. Rose, E. L. Spain

THIS study was undertaken primarily to determine the reasons for certain variations in the soundness of gravel aggregate taken from a number of widely separated points on the Tennessee River. Under laboratory tests, concrete made with these various aggregates in some cases exhibited marked differences in specific gravity crushing strength and durability. Gravel was studied in detail from Chattanooga to the mouth of the river and to a lesser extent from Chattanooga to Knoxville. The causes of variation were determined, and variational curves were constructed, which accurately predict the composition of aggregate at any point on the river and therefore its relative suitability for use in concrete. The aggregate at any point is suited for making sound concrete; the variance of suitability is due to varying percentages of sandstone and weathered material, which are less sound than other constituents. INTRODUCTION When it is stated that the aggregate from one point is inferior to that from another, it must not be construed to mean that the gravel is unfit for use. The classification upon which such aggregate ratings are based is largely arbitrary, thus inferiority or superiority is merely relative. Samples of gravel were selected from stockpiles at the dams of the Tennessee Valley Authority under construction, from the stockpiles of private companies along the river, and from samples taken by the gravel- exploration barge of the T. V. A. One hundred or more gravels of each size studied were selected at random by taking small handfulls while walking around the piles. These were separated according to the different mineral or rock constituents present, and the percentage of each constituent was obtained by counting. At least three such samples were taken from each size, and all checked with one another within a few per cent. The results were then averaged. In order to check on the accuracy of such sampling, a whole sample was taken from one point after the gravel was thoroughly mixed. The two methods gave approximately identical results. SOURCES AND TYPES OF MATERIALS The sources of gravel found in the Tennessee River are numerous and varied. The river itself traverses several geologic provinces, each

Jan 1, 1937

By H. H. Kellogg

Available high-fernperatzwe equilibrium measurements and other thermochernical data have been critically reciewed for sulfation reactions of the type: Recommended values for log K and ?Fo as junctions of temperature are given for thirty-six suck reactions involving twenty-six different metals. Methods of calculation and choice between conflict-ing data are discussed. SELECTIVE sulfation now enjoys a considerable renaissance as a metallurgical unit process due, in large part, to the available of the fluid-bed re- actor—a device capable of the close control of temperature and gas composition necessary for a successful sulfation process. An additional need, however, if sulfation chemistry is to be approached in a scientific manner, is a reliable body of data on the equilibrium and kinetics of sulfation reactions in simple and complex systems. This paper offers a critical review and compilation of equilibrium data on pure sulfates (simple systems). The last such review, by K. K. Kelley in 1935:30 has proven itself most useful, but the existence of many new data makes necessary a re-evaluation of the available information. METHODS OF CALCULATION For a simple sulfation reaction such as MS04(c) = MO(c) + SO3 [1] there are two approaches one may take toward establishing the value of ?Fo or K as a function of

Jan 1, 1964

By R. B. Adamson

The fatigue behauior of irradiated copper single crystals is compared to that of unirradiated crystals. Proton or electron irradiation did not substantially change the fatigue-lzj.e, fatigue-hardening-, or slip-line characteristics, while neutron irradiation did appear to alter these parameters. Postfatigue transrrzission electron microscopy did not reveal any marked structural differazces between irradiated and unirradiated specimens. Possible dislocatio~a mechanisnzs to explain the observed behavior are discussed. A LTHOUGH considerable work has been done to ascertain the effects of radiation on the tensile properties of metals (e.g., Refs. 1 and 2), little work of a basic nature has been reported on the effect of radiation on fatigue properties. Since it is known that fatigue properties are sensitive to conditions at the surface of the metal, it was felt that charged particle irradiation, whose penetration into metals is very small, might influence the fatigue behavior. To investigate this surface effect, irradiations with 10 mev protons and 1.5 mev electrons were conducted. The range of 10 mev protons in copper is about 0.236 mm; which is very small compared with the thickness of the specimens used (1.53 mm). The range of 1.5 mev electrons is somewhat larger, on the order of 0.665 mm.4 On the other hand, irradiation with reactor neutrons produces damage throughout the entire specimen, so neutron irradiation can be used to study the effects of bulk damage. The damage introduced by proton and neutron irradiation is expected to con!ist of large interstitial dislocation loops,5 tiny (<25A) vacancy loops," and/or various vacancy-rich regions called depleted zones.&apos; In the case of electron irradiation at about -173°C the damage is expected to consist of isolated Frenkel pairs.&apos; The effect of radiation damage on the fatigue properties of some engineering materials has been reported,g,10 but the results are not clear-cut or consistent. SPECIMEN PREPARATION Zone-refined copper was used to grow single crystals by a modified Bridgeman technique in an inert helium atmosphere. Using a seeding method, single crystals were obtained as bars about 6 in. long with a cross section of 3 by $ in. Immediately upon removal from the split-mold graphite boat in which they were grown, the very soft bars were embedded in a room-temperature setting plastic. They could then be cut into specimen lengths without introducing any long-range damage. Generally, four or five specimens plus one seed were obtained from each bar. The plastic material was dissolved away in acetone and the orientation of each sample was checked by the standard Laue X-ray

Jan 1, 1968

By J. E. Burke, A. M. Turkalo

IN 1923 Desch¹ pointed out that the grains in a metal which is anisotropic with respect to its thermal coefficient of expansion would contract differently upon cooling, and that the stresses developed might approximate the plastic strength of the metal. More recently Boas and Honeycombe2-5 studied the behavior of several metals upon thermal cycling and observed that the stresses developed in arlisotropic metals are great enough to produce slip lines in individual grains and a roughening of the specimen surface. This phenomenon they have named "thermal fatigue." The mechanism they propose involves essentially a kneading of the grains, the deformation being alternately in compression and tension in a given grain as the temperature is changed in one direction and then the other. The present work was undertaken to investigate the possibility that an additional mechanism might operate to produce plastic deformation during thermal cycling—a "thermal ratchet" that depends upon a combination of grain boundary flow to relax the stress that develops between differently oriented grains upon raising the temperature and transcrys-talline slip to relax the oppositely directed stress which develops on lowering the temperature. Thus, thermal cycling should produce a nonreversible distortion such that certain grains will change shape differently from their neighbors with a simultaneous displacement being produced at the grain boundary. Temperature Dependence of Grain Boundary and Grain Strength The critical resolved stress for the initiation of slip in metal grains is only mildly affected by temperature." For example, in cadmium it decreases from 0.15 to about 0.05 kg per sq mm when the temperature is increased from 20° to 458°K and further temperature increase causes little further decrease. On the other hand, the work of KG1 indicates that the grain boundaries behave in a viscous fashion that can be described8 by the expression: t = BVexp(Q/RT) [1] t is the shearing stress on the boundary; B, a constant; V, the flow rate at the boundary; Q, the activation energy for grain boundary flow; R, the gas law&apos;s constant; and T, the absolute temperature. Eq 1 indicates that the stress necessary to cause a given grain boundary flow rate, V, decreases rapidly with increasing temperature. The value of the constant B is such that at sufficiently low temperature and ordinary strain rates deformation will occur preferentially by slip rather than by grain boundary flow. There is considerable evidence to indicate Consider the bicrystal shown in Fig. 1. In grain 1 the slip plane lies 45 " to the boundary while in grain 2 the slip plane is 90" to the boundary. The coefficients of expansion of the grains in a direction parallel to the length of the crystal are a1 and a, with a, > a2 for the orientations shown. The sequence of events that can occur upon heating and cooling this specimen is illustrated schematically in Fig. 2. Initially there is assumed to be no stress in the specimen (A). Upon heating, grain 1 attempts to become longer than grain 2, but is constrained by grain 2. Thus grain 1 is loaded in compression and grain 2 is loaded in tension, and a shearing stress is present across the boundary (B). As the temperature is increased, the stress will build up, and finally grain 1 will be plastically deformed by slip, since the greater stress is resolved on its slip planes. Any further heating will result in more slip and the stress will remain constant until some temperature T* is reached where the stress can be relaxed by grain boundary flow.† At this relaxation temperature (C) a step will appear between grain 1 and grain 2. Further heating above T* will cause grain 1 to become relatively longer, but no stress will appear because the grain boundary is too weak to support the stress (D). Upon cooling again, at T* (E), the grain boundary will again be able to support a shearing stress, and upon cooling further, grain 1 will be loaded in tension and grain 2 in compression (F). When the decrease in temperature below T* is sufficient to impose the critical shear stress upon the slip plane of grain 1, it will be stretched by slip.

Jan 1, 1953

By R. D. Mollison, C. F. Fogarty

Sulfur is widely distributed in nature. It is present in the earth&apos;s crust, the ocean, the meteorites that come to us from cosmic space and in practically all animal and plant life. According to Clarke,9 the earth&apos;s crust contains 0.06 pct sulfur. Large quantities of free or combined sulfur are found in coal, natural gas and petroleum. Mineral waters contain sulfates and hydrogen sulfide. Sulfur is rather plentiful in the crust of the earth; however, only under special circumstances can it be produced profitably. Sulfur is one of the cheapest raw materials used by industry; and, therefore, the economic feasibility of a given deposit is strongly dictated by the law of supply and demand on local as well as world-wide levels. The forms which are commercially important are elemental sulfur or brimstone, and the sulfides such as pyrite (FeS2), pyrrhotite (FenSn+1), chalcocite (Cu2S), sphalerite (ZnS), and galena (PbS); the sulfates such as gypsum (CaSO4,2H2O), anhydrite (CaSO4), and kieserite (MgSO4,H2O). Elemental Sulfur Elemental sulfur is found in many localities, generally in solfataras and gypsum type deposits. The solfatara deposits are found commonly in the neighborhood of active or extinct volcanoes as in Italy, Japan and Chile, or fumaroles associated with mineral springs such as the Mammoth Hot Springs in Yellowstone Park. Here the sulfur is deposited in tufas or other porous host rocks. This type of sulfur deposit probably results from the oxidation of hydrogen sulfide or the reaction of hydrogen sulfide with sulfur dioxide. Most of the world&apos;s supply of elemental sulfur comes from the gypsum-type deposits. Here the mineral occurs as either crystalline or amorphous sulfur in sedimentary rocks in close association with gypsum and limestone. This association is characteristic and occurs in almost all the great gypsum beds of the world, although sulfur is not always present in quantities of economic importance. Various theories have been advanced to account for this association. Bischof5 suggested that the sulfur came from hydrogen sulfide which resulted from the reduction of calcium sulfate by carbon or methane in accordance with the following reactions: CaSO4 + 2C= CaS + 2CO2 CaS + C02+ H2O = CaCO3 + H2S CaSO4 + CH4= CaS + C02+ 2H20 2H2S + 02= 2H20 + 2S All of the sulfur-bearing domes on the Gulf Coast have calcium sulfate in great quantity in the cap. They all show the presence of hydrocarbons. The oxygen for the final reaction could have been supplied by circulating ground waters. The principal objection to this theory is that temperatures of 700° to 1000°C are needed to reduce the sulfate to sulfide with carbon compounds. The geologic evidence is that the temperature of the sulfur-bearing domes of Texas did not exceed 100°C. Proponents of the theory say that geologic time or a catalyst replaced temperature. According to another theory the sulfur in the salt domes is the result of bacterial action. Sulfate reducing bacteria have been detected in sulfur cores and in the formation water issuing from salt domes. It has, therefore, been suggested that these bacteria converted the sulfate to sulfide which subsequently was converted to elemental sulfur.

Jan 1, 1960

By Jerome Alexander

The object of this paper is to show that many of the important phenomena of metals and alloys are due to the facts that, at some stage, metals and alloys, or some of their constituents, are in a colloidal state and that a portion of the metal or alloy tends to remain in this state. The so-called amorphous phase in pure metals is an isocolloid, consisting of colloidal groups of metal molecules that may be dispersed in still more finely subdivided metal; these colloidal particles are not truly amorphous, but may consist, in part, if not entirely, of ultramicroscopic crystals; as a result the expressions amorphous phase and amorphous theory might he replaced by the expressions colloidal phase and colloidal theory. Any substance is in the colloidal state when the constituent particles consist of molecular or atomic groups, whose size varies approximately from about 100 down to about 5pp, that is from just below the limit of microscopic resolvability to the dimensions commonly ascribed to the larger molecules. Colloidality involves no assumption as to the shape, internal structure, or orientation of the colloidal particles; size alone is the critical factor. A colloidal system may therefore contain crystalline groups, or amorphous groups (non-crystalline, random or haphazard clusters), or a mixture of the two. All colloids consist of at least two phases, the subdivided substance, or dispersed phase, and the substance into which this is subdivided, the dispersion medium. It is not necessary that there be any chemical difference between the dispersed phase and the dispersion medium. As molecular forces are extremely powerful, their application may produce marked changes in the physical properties of metals. It is doubtful whether metal in the interior, especially of large masses, possesses the same properties as that on or near the surface, which alone is open to inspection.

Jan 1, 1921

By Arthur B. Yates

DIAMOND drilling has advanced and expanded during the past few years. Along with this increase there has been a marked trend to rely more and more upon drilling for the outlining of ore for reserve purposes. This is especially true underground, where men have not been available for opening up ore by crosscuts, drifts and raises. During the recent heavy call upon known ore reserves, more drilling has been done for exploration and it has become expedient to drill longer lateral holes from underground and deeper holes both from surface and from exploration headings in the mines. Furthermore, these deeper holes have to be drilled closely enough to warrant calculation of "probable" if not "proven" ore, from the results obtained therefrom. Interpretation of diamond-drill results has become more precise and reliable with the growing knowledge and understanding of the geologic structures that control the geometry of ore distribution, and this has broadened the field of usefulness of the drill. All of this has created a necessity and a demand for more accurate control of the hole as to direction, a more precise and reliable method of surveying for position, and a need for better and more complete core recovery, as well as larger cores, to provide an adequate sample. At depth the control becomes more difficult and, at the same time, more important. CONTROL A close study of drilling in various parts of the world for a period of more than 20 years has brought to light one definite rule, practically invariable; namely, that diamond-drill holes tend to deviate into a position normal to any structure existing in the rocks, such as bedding, schistosity, gneissosity, or even parting or jointing-even if the hole is started at almost any angle other than parallel with the structure. It also appears that the better developed the structure is, the more quickly will the hole get into a position perpendicular to it. It has often been said that there is a tendency for holes to "drift" in the direction of rotation. This is obviously untrue, for in a vertical hole the measure of deviation would depend upon the azimuth chosen as zero, and there is an infinite number of choices. It has been proved, however, that in homogeneous rocks there is a tendency for the hole to corkscrew, and that the direction of the spiral is the same as the direction of rotation. This may account for the belief that holes drift in that direction. Some tests have been made using right-hand and left-hand rods, and these show that no matter what the direction of rotation the hole will swing into a position perpendicular to the structure. Methods of Control The foregoing empirical rule may be used as an indirect method of control. If the prevailing structure is known, it may be advantageous to start the hole as nearly normal to it as possible, for the nearer the direction of the hole is to this ideal, the straighter it will remain. This, of course, is not always practical and in some cases is impossible. Usually such a

Jan 1, 1946

By C. S. Simons, G. Major-Marothy, M. A. K. Grice, D. A. Dahlstrom

The vacuum filter operating variables that influence cake moisture are discussed. The influence of temperature control, particularly through application of steam to the cake, is emphasized. Results of pilot plant studies on filtration of fine hematite concentrates are presented and discussed, and are shown to support the theoretically-derived conclusions. Results on fine magnetite concentrates are also used to support the argument. The relative merits of disc and drum filters from the standpoint of cake moisture are discussed. Moisture content has always been recognized as one of the most important properties of concentrates used as pellet plant feed. Most iron ore concentrates are produced by wet methods, and are finally de-watered on filters. Obviously, a real economic advantage accrues to the ability of control the moisture content of the filter cake within the range required for optimum pellet production. Another consideration, also, has been receiving increasing attention recently. Transoceanic shippers of concentrate cargoes are critically assessing the hazards of excess moisture. The nature and magnitude of these risks have been described, &apos; and it appears that their elimination may require that residual moisture be somewhat lower than the limit for proper pelletization. Coarse, very free-filtering materials, such as the products of spirals, are usually best handled on top-feed types of machines. The moisture content of the cake may be held at a specified value by proper design and operation, taking into account cake thickness, air-flow rate, and drainage time. Fine-grained concentrates, with which we will be concerned here, must be filtered on Drum or Agidisc machines. With many of these materials, it is possible, by proper design, to meet cake moisture requirements with a conventional filter station. The first installations to produce high-grade pellets from magnetic taconites fell in this class. In fact, the design criteria were developed in connection with operations of Reserve Mining Co. at Silver Bay, inn.,2 and these have been verified repeatedly in other mills. The trend today, however, is toward the production of more difficultly dewatered concentrates. This is due on the one hand to the increasing attention being given to non-magnetic ores, which tend to be far slimier, and therefore much more retentive of moisture, than the magnetites. On the other hand, the pressure to improve the grade of the magnetic ores is leading to finer grinds, which also are more difficult to dewater. In the latter case, the decision to improve grade in an existing operation by finer grinding for better liberation may lead to two unattractive alternatives: 1) substantially higher bentonite consumption, plus the risk of poorer quality pellets, from high cake moisture, or 2) installation of a thermal dryer. There is, however, a third alternative. In recent papers by two of the authors3,4 it was shown that for many materials a significant decrease in cake moisture can be obtained by applying live steam to the cake face during the drying part of the filter cycle. Further, this limited drying appears to have distinct economic advantages compared to thermal drying. It is the purpose of this paper to explore the third alternative. To do this, the results of an extensive pilot study of steam filtration of a hematite flotation concentrate will be critically examined. This study was sufficiently broad so that a number of alternate suggestions (besides steaming the cake) for reducing moisture content were tested, and comparative data for both Drum and Disc filters were obtained. The work was particularly interesting since the concentrate has a high Blaine surface, and is therefore particularly difficult to dewater to the levels required. FILTER CAKE MOISTURE The significant difference between concentrate filter cake as discharged from the filter, a cargo of that same filter cake during or after shipment, and a green ball formed from that filter cake is in the relative volume of voids, or porosity. In every case, the material is a collection of small solid particles held together by the cohesive forces of a liquid. The physical properties of the aggregate are determined by the

Jan 1, 1967

By S. A. Montague

Mica can claim a considerably greater importance than would be assumed from its comparatively small dollar volume, which came to about $37,000,000 for the United States industry as a whole in 1957. Mica is one of the strategic minerals. We must depend on imports from distant sources for virtually all of our requirements of high grade block and all of our mica splittings. Mica is essential and indispensable for vacuum tubes and high-performance condensers, two electronic components which are vital military necessities besides being nearly indispensable to civilization today. Composition and Properties Mica is the general name for a group of some nine different minerals, two of which, muscovite and phlogopite, are the minerals used by the mica industry as its raw material. Several of the other varieties are commercially useful-vermiculite, * used for heat insulation in expanded form, and lepidolite, used as an ore of lithium while the others-biotite, roscoelite lepidomelane, paragonite and zinnwaldite have little or no commercial importance. Biotite frequently occurs as an undesirable impurity in muscovite. Table 1 lists various properties and other data concerning muscovite and phlogopite. Chemically, mica is a complex silicate of sodium, potassium and aluminum. Most varieties of muscovite are higher in sodium, and of phlogopite in magnesium. There are no important uses of mica where the chemical analysis is important, except that in some uses of ground mica, the content of iron oxide present as an impurity must be kept to a very low limit. Muscovite occurs in a range of color from the so-called India "ruby" which is more closely a pinkish brown, to light and dark green, with numerous other intermediate shades. Ruby color is usually preferred by industry, especially in the better qualities. When split very thin the color in most [ ] micas disappears. Muscovite mica is frequently found containing black and red "stain" as a homogeneous part of the books or sheets. In most cases this stain or impurity is magnetite

Jan 1, 1960

By Paul A. Beck

While the recrystallization properties of most of the practically important metals are known in considerable detail, those of lead are still relatively little known in spite of some valuable contributions in recent years. This condition probably is due to the difficulties involved in applying the usual methods of investigation. The microscopic method of discriminating between the elongated deformed grains of the familiar lenticular shape and the equiaxed recrys-tallized grains is not successful with fully refined lead: lenticular grains cannot be seen under the microscope with any amount of deformation whatever. The probable cause of this phenomenon was recognized long ago. With large deformation the time of recrystallization at room temperaturc is shorter than the period of preparation of the specimen for microscopic examination; with small deformation the deformed grains arc not noticeably elongated in the first place. However, with small cleformation the migration of the grain boundaries can be observed. The only systematic investigations yet published on the recrystallization of lead, those by R. S. Russell, 1-3 make use of the conditions just described. Russell considered recrystallization completed when no further migration of boundaries could be observed. A serious objection to this method arises from the fact that there is no evidence to support the view that grain-boundary migration results only from recrystallization. If such migration does result from other sources after recrystallization is completed—after the deformed grains have been replaced by new unde-formed grains—the "time of recrystallization" as determined by Russell may be too long. Furthermore, the method is subject to the above.-mentioned limitation because of the unavoidable period of preparation of the sample. According to Russell, even with the fastest technique 5 min. clapsed before the deformed samples were ready for examination, and consequently no reearystallization time shorter than 5 min. could be measured. The lack of success in detecting the recrystallization of lead by the usual hardness or tensile tests is again caused by the time necessary for

Jan 1, 1940

By F. F. Sharpless

IT IS to be. read in Western newspapers that Hon. S. S. Arentz who introduced H. R. 7736, &apos;has repudiated it, that certain mining men in Utah and Nevada say that they will fight it "until hell freezes over." It is to be read in more temperate expressions that "the eminent engineers who drafted the bill exhibited a woeful misunderstanding of Western sentiment and opinion." Furthermore, it is averred that there is no need for revising the mining laws, that we have got along pretty well under the existing laws, etc. Such statements are so surprising in view of, the facts of record that it is hard to believe that the oppon-ents of the bill, who make them, are well informed, or that they represent general opinion. It will be useful therefore to review the record of the case. Our GOOD OLD MINING LAWS We have indeed got on well in our mining industry, but that has not been by virtue; of our good old mining laws. Rather has it been in spite of them. Ever since the Richmond-Eureka case in the &apos;70s there has been litigation arising from them. Early in the &apos;80s the apex law was discarded by common consent in Leadville, and it has been ignored in every district of flat-lying ore deposits ever since. The great mines of the present time are the porphyry copper deposits. At Bingham, Ely, Ray, Chino, Miami, Clifton and Ajo the apex law is simply inapplicable. A law that is inapplicable to the modern conditions of mining may be an old law, but it can not properly be characterized as a "good" law. For such reasons, and many others of weight, there has been a demand for revision of the mining laws; dat-ing ,back at least three decades. President Roosevelt appointed a commission to advise respecting the question, said commission comprising. Dr. James Douglas (chairman), John Hays Hammond, D: M. Barringer, Walter B: Devereux, and William B. Mather. This committee was unanimous on the following points:

Jan 1, 1922

By Frederick M. Becket, Russell Franks

WideSpread experimentation has been conducted in recent years to devise a means of preventing intergranular corrosion in austenitic chromium-nickel steels of the 18 per cent chromium-8 per cent nickel type. Additions of titanium to these steels have been used commercially to overcome this dificulty, as advocated by Krupp of Germany, and the latest literature reference concerning improved details of this method is the article by Bain, Aborn and Rutherford.&apos; Extensive work by the present authors has shown columbium also to be a particularly valuable agent for inhibiting intergranular corrosion. This paper does not deal with steels that are largely or wholly austenitic; it is limited to a discussion of the results obtained through the use of titanium and columbium in plain high-chromium steels. For many years titanium has been used commercially by some steelmakers as a cleanser, and to a lesser extent as a hardener, but then in greater percentages. The results of the work to be described disclose that titanium and columbium in proper Proportions act as effective softeners in the high-chromium steels. It is well known that chromium intensifies the hardening effect of carbon in steel; it imparts pronounced air-hardening properties within a rather wide range of chromium content; it provides increased ductility in steels of given strength and hardness; and it enhances resistance to corrosion and oxidation at elevated temperatures to a marked degree. However, in applications requiring a combination of some of these valuable properties great hardness is frequently a detriment rather than a merit. When the objective is a soft and ductile steel having optimurn corrosion resistance, the producer strives for a carbon content as low as commercially practicable. Despite these efforts some of the commercial high-chromium steels low in carbon present considerable difficulties during production, owing to their air-hardening properties, and in consequence the economic result is not favorable. A good example is found in the 5 to 6 per cent chromium steels employed chiefly in the oil-cracking industry. Sleels

Jan 1, 1934

By Arthur Taggart

FLOTATION of ores is a practical utilization of the energy that resides in the surfaces of solids and liquids. The best known manifestation of this energy is called surface tension; an equally important, though less apparent, phenomenon is adsorption. This paper reviews some of the recent investigations of these phenomena, and gives the results of certain experiments performed by the authors. Surface tension is a manifestation of energy having its seat at the bounding surface between the adjacent phases of a multiphase system. Thus, at the interface between a liquid and a gas, or between two immiscible liquids, or between a solid and a gas or a liquid, there are forces capable of doing work, their magnitude depending on the nature of the adjacent phases and the extent of the bounding area. These surface forces are inappreciable when the ratio of surface to volume of the adjacent phases is small, but they become powerful when this ratio becomes large, as it does when one of the phases is highly dispersed. Froth flotation, which consists in buoying solids heavier than water to the surface of water by means of gas bubbles, utilizes the force of surface tension to attach the solid particles to the gas bubbles and again to maintain the floating mass of bubbles as a more or less persistent froth at the surface of a pulp for a sufficiently long time to allow its removal. It follows from the second law of thermodynamics that the potential energy of a system in equilibrium is a minimum. Therefore a multiphase system, tending toward equilibrium, will arrange itself in such a way that the total energy of the interfaces will be the least possible. This end can be accomplished in two ways: by a change in shape that will reduce the interfacial area; by a change in the nature of the surface layer in

Jan 8, 1922

By Paul A. Beck

While the recrystallization properties of most of the practically important metals are known in considerable detail, those of lead are still relatively little known in spite of some valuable contributions in recent years. This condition probably is due to the difficulties involved in applying the usual methods of investigation. The microscopic method of discriminating between the elongated deformed grains of the familiar lenticular shape and the equiaxed recrys-tallized grains is not successful with fully refined lead: lenticular grains cannot be seen under the microscope with any amount of deformation whatever. The probable cause of this phenomenon was recognized long ago. With large deformation the time of recrystallization at room temperaturc is shorter than the period of preparation of the specimen for microscopic examination; with small deformation the deformed grains arc not noticeably elongated in the first place. However, with small cleformation the migration of the grain boundaries can be observed. The only systematic investigations yet published on the recrystallization of lead, those by R. S. Russell, 1-3 make use of the conditions just described. Russell considered recrystallization completed when no further migration of boundaries could be observed. A serious objection to this method arises from the fact that there is no evidence to support the view that grain-boundary migration results only from recrystallization. If such migration does result from other sources after recrystallization is completed—after the deformed grains have been replaced by new unde-formed grains—the "time of recrystallization" as determined by Russell may be too long. Furthermore, the method is subject to the above.-mentioned limitation because of the unavoidable period of preparation of the sample. According to Russell, even with the fastest technique 5 min. clapsed before the deformed samples were ready for examination, and consequently no reearystallization time shorter than 5 min. could be measured. The lack of success in detecting the recrystallization of lead by the usual hardness or tensile tests is again caused by the time necessary for

Jan 1, 1940

By F. Habashi

Conclusive evidence is given showing that the dissolution of gold in cyanide solution follows mainly the over-all equation A similar equation can also be written for the dissolution of silver. Theoretical derivation of the velocity equation for this reaction has been obtained, which describes quantitatively the experimental facts. The equation is as follows: where [CN-] and [O2] = the concentrations (in moles/ml) of cyanide and dissolved oxygen, respectively. DcN- and Do2 = the diffusion coefficients of cyanide and dissolved oxygen; 1.83 x 10-5 and 2.76 x 10-5 cm2 sec-1, respectively. A = the surface area of the metal in contact with the aqueous phase, in cm S = the thickness of the boundary layer; varies between 2 and 9 x 10-3 cm, depending on the speed and method of agitation. Rate being expressed in g. equiv. sec-1. INTRODUCTION During recent years a number of papers have been published on the kinetics of dissolution of gold and silver in cyanide solution.1,6 The authors agree that the rate of dissolution is diffusion-controlled, but disagree regarding the mechanism of the reaction. Some authors&apos;-3 support the Bodlander equations: The apparently conflicting results, when critically reviewed, are concordant and lead to the conclusion that the proper equation for the dissolution reaction should be only Eq. 1. This conclusion is based on the following facts: 1) For every 2.2 equivalents of metal dissolved one mole O2 was consumed. 2) For every 1 equivalent of metal dissolved, 2 moles of cyanide were consumed.&apos; 3) Hydrogen peroxide is formed during the dissolution of gold or silver, and for every 2.2 equivalents of metal dissolved, one mole H2O2 was produced.1,2 The fact that Kudryk and Kellogg4 did not detect H2O2 during the dissolution of gold should not throw doubt on the many affirmative reports of other investigators. Lund2 has shown that depending on the crystalline nature of the silver surface, (e.g. method of etching the sample) H2O2 may undergo catalytic decomposition heterogeneously according to: Further Kudryk and Kellogg4 carried out their experiments in the presence of 0.5% KC1 to achieve a greater electrolytic conductivity, and Matsudaira7 has shown that H2O2 is catalytically decomposed (homogeneously) in the presence of C1- ion in alkaline solution. 4) Experiments carried out by Boonstra8 and Lund2 showed that the dissolution of gold and silver respectively in KCN + H2O2 in the absence of oxygen was a slow process. Thus the reaction takes place to a minor extent only. Further kinetic studies showed that: 1) The rate of dissolution depends on the surface area of the metal in contact with the liquid phase, thus indicating that the process of dissolution is a heterogeneous process. 2) The rate of dissolution depends on the speed of stirring,5,6 thus indicating that the process is controlled by a physical phenomenon.

Jan 1, 1967

ALTHOUGH the open-hearth charge contributes CO, C02, H2, and water vapor to the combustion gases and absorbs oxygen from them, in the main the thermal effects in the melting charge and molten bath can be considered independently of those in fuel combustion; the latter then is regarded simply as the source of the net heat required to finish a heat of steel. First of all, it should be remembered that a large percentage of the heat supplied to the bath is furnished by oxidation of the various elements in the charge itself. If this charge consisted of 80 to 100 per cent of hot metal and the oxidation were accomplished by blowing in air or oxygen, as in the bessemer converter, the net heat absorption would be negative; that is, the bath would contribute part of the heat required to keep the melting chamber hot, in addition to that contained in the finished steel and slag. - In actual open-hearth practices, probably the nearest approach to this is in the duplex furnace, charged with bessemer-blown metal and some hot metal, where very little heat is required to complete the refining and nearly all the heat energy from fuel combustion is used to keep the roof and walls of the melting chamber up to around 2900 to 3000 F (1600 to 1650 C), so that the bath will not cool off during the refining. The other extreme is with all-cold charges containing around 80 per cent steel scrap and 20 per cent cast iron or cold pig iron, in which case a very large proportion of the heat in the bath at tap is supplied from the fuel combustion. THERMAL EFFECTS IN MELTING In a typical heat, the fuel furnishes about four million British thermal units per ton of steel produced. The heat required for the metallurgical processes is not easily defined in useful manner but it ranges downward from about one million Btu, depending not only on the charge but on the manner of calculation. In any event, this requirement appears small in comparison with the

Jan 1, 1951

By J. H. Nead, J. W. Halley

The new low-alloy high-strength steels are obviously here to stay. With 75 per cent higher yield strength and 50 per cent higher tensile strength than plain carbon structural steel, they permit 20 to 40 per cent weight savings and 10 per cent or more increase in pay load in the construction of railroad cars, buses, trucks, and a great variety of material-handling equipment. Their cost is low enough so that the extra cost of the new lighter construction over that with carbon steel offers an attractive self-liquidating investment; in some instances new construction with these low-alloy steels may even be as cheap as with plain carbon steel. A considerable and rapidly growing demand for the low-alloy steels has already sprung up. The many steel compositions that have appeared on the market lately18, 27, 28, 29, 30 to meet this demand would seem to indicate that no single composition is uniquely fitted for the purpose. However, no doubt some compositions are more suitable than others. The purpose of this study was, therefore, to compare the effects of the various alloying elements that might be used in the low-alloy steels in order to choose the metallurgically most logical composition, paying due regard, of course, to the economic aspects involved. Properties Desired in Low-alloy Steel A distinction between the new low-alloy steels and the common alloy steels is that the latter are generally used in the heat-treated (that is, quenched and tempered) conditions, whereas the new low-alloy steels are not only not heat-treated but are not susceptible to heat-treatment in the ordinary sense of the term. In this lies one of their chief advantages. Their properties can be obtained in the as-rolled, air-cooled, or annealed condition, just as with mild plain carbon structural steel. There is no need for heat-treating. Such steels can be readily formed hot or cold, and their properties are not appreciably changed by hot

Jan 1, 1936

By J. H. Nead, J. W. Halley

The new low-alloy high-strength steels are obviously here to stay. With 75 per cent higher yield strength and 50 per cent higher tensile strength than plain carbon structural steel, they permit 20 to 40 per cent weight savings and 10 per cent or more increase in pay load in the construction of railroad cars, buses, trucks, and a great variety of material-handling equipment. Their cost is low enough so that the extra cost of the new lighter construction over that with carbon steel offers an attractive self-liquidating investment; in some instances new construction with these low-alloy steels may even be as cheap as with plain carbon steel. A considerable and rapidly growing demand for the low-alloy steels has already sprung up. The many steel compositions that have appeared on the market lately18, 27, 28, 29, 30 to meet this demand would seem to indicate that no single composition is uniquely fitted for the purpose. However, no doubt some compositions are more suitable than others. The purpose of this study was, therefore, to compare the effects of the various alloying elements that might be used in the low-alloy steels in order to choose the metallurgically most logical composition, paying due regard, of course, to the economic aspects involved. Properties Desired in Low-alloy Steel A distinction between the new low-alloy steels and the common alloy steels is that the latter are generally used in the heat-treated (that is, quenched and tempered) conditions, whereas the new low-alloy steels are not only not heat-treated but are not susceptible to heat-treatment in the ordinary sense of the term. In this lies one of their chief advantages. Their properties can be obtained in the as-rolled, air-cooled, or annealed condition, just as with mild plain carbon structural steel. There is no need for heat-treating. Such steels can be readily formed hot or cold, and their properties are not appreciably changed by hot

Jan 1, 1936

By Hallet R. Robbins

Korea, the ancient" Hermit Kingdom," is a peninsula jutting out from the coast of eastern Asia. By the natives it is called " Chosen," nfhich, translated, means " Land of the Morning Calm." It lies between the Yellow sea and the Sea of Japan. On the north it is separated from Manchuria and the Russian province of Primorsk by the Yalu and Tiumen rivers; on the south the Korcan straits interpose a rough voyage of 120 nliles to the nearest point in Japan. The entire country is situated between the parallels of 34O and 42O N. latitude. The surface of the country is made up of successive ranges of ul~glaciated mountains, separated by narrow, fertile, and more or less densely populated, valleys. Through all the obscure centuries of its history, Korea has succeeded in maintaining a monastic seclusion, over which, from time immeniorial until the late Chino-Japanese war in 1894, China exercised a shadowy sovereignty. Although Korea had been forced into slight foreign contact previously, her first forcign treaty was signed with Japan in 1876. Under the restraining guardianship of China, the Japanese treaty bore but infiignificant innovations for Korea; but when, in 1883, a treaty was made with the United States, the first of the western nations, a decade after the American gunboats, under Commodore Rodgers and Lieutenant Schley, forced their may up the Salee river, Korea awoke from her sleep of 4,000 years. The Eorean peninsula suddenly became the arena where the enterprises and individuals of many foreign nations met in fiercest rivalry. Out of this struggle grew two singularly successful American enterprises, both of which have played an important part in developing the natural resources of the country. The first, and best known of these, is the Oriental Consolidated Mining Co., which was organized by Lcigh Hunt

Jan 1, 1909