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By W. A. Anderson, R. F. Mehl

RECRYSTALLIZATION of cold-worked metals has long been known to proceed by a process of nucleation and growth.1 When a cold-worked metal is heated to a temperature at which recrystallization will ensue, nuclei of new grains, essentially strain-free, appear and grow. As the process proceeds, nuclei continue to appear and to grow, until the cold-worked matrix has been entirely consumed and recrystallization has been completed (Fig. I). Conducted isothermally, a measurement of the fraction of the matrix recrystallized plotted against time, yields an isothermal recrystallization curve, showing the time course of the recrystallization process (Fig. 2).2 Evidently, then, the rate of recrystallization is determined by the rate at which nuclei form and the rate at which they grow. The rate of nucleation N is the number of nuclei that form in unit time in unit volume of the unrecrystallized matrix, and the rate of growth G is the increase in radius of the recrystallized grain per unit time. In recent years attempts have been made to determine N and G as these vary with the well-recognized variables affecting recrystallization: time, temperature, degree of deformation, etc.' Such studies yield information that is more fundamental than that conveyed by the conventional recrystallization diagram,' since the rate of recrystallization is thus analyzed into its two component rates.2 Methods are now available by which N and G can be measured, and analytical expressions have been developed for the interrelationships among N, G, the isothermal recrystallization curve, and the final grain size, which greatly facilitate analysis.2-4 The application of these methods has been demonstrated recently for the recrystallization of silicon ferrite.2 Data on N and G in dependence upon the recognized recrystallization variables are, however, very fragmentary;* values of N and G have been determined for some metals, but the effect of temperature, which would yield the fundamentally important activation energies, has been too little studied. Thus far there has been no detailed study of the recrystallization of any one metal in terms of N and G over appreciable ranges of the variables time, temperature, degree of deformation, and original grain size. It is the purpose of the present paper to provide such a study, employing aluminum.

Jan 1, 1945

By W. O. Philbrook, H. E. Burner, F. S. Manning

The equation of continuity for the hydrogen reduction of hematite in a fixed bed of closely-sized particles is solved assuming a flat velocity profile, negligible temperature gradients, md negligible axial diffusion. A kinetic expression from the literature is used which assumes the reduction process is controlled at the oxide-metal interface. The integral fractional conversion is computed, and the importance of particle diameter, flow mte, temperature, bulk axial diffusion, and inter- and intra-particle mass trarnsfer is predicted. Comparison with experimental data suggests one or more additional undefined variable(s) is significant. Equipment modifications are suggested for fidture experimentcll work. WITH the increasing desire to "design" the ore feed of a blast furnace, it has become necessary to define more quantitatively the process variables and to evaluate the extent of their control upon the reduction process. The bulk of the work reported in the literature has centered about the reduction of single particles; however, the blast furnace process more closely resembles reduction of a fixed bed than that of single particles. To simplify this analysis, the isothermal reduction by hydrogen of a natural hematite in a fixed bed of closely-sized particles is examined. With appropriate modifications in the kinetic and flow rate expressions, the approach employed should be extensible to mixtures of carbon monoxide, hydrogen, and inert nitrogen, and to adi-abatic conditions, thus approaching the blast furnace process more closely. The fixed bed variables which are investigated in this study are particle diameter, flow rate, temperature, and bulk axial diffusion, as well as inter-and intra-particle mass transfer. Of particular interest is the effect of particle size upon fractional conversion for a bed operating under constant pressure drop. The constant pressure drop concept bears a close resemblance to the blast furnace process, where regions of larger particles may provide a greater permeability to divert most of the reducing gas flow from the regions of smaller ore particles. Under such conditions one would expect qualitatively that, for sufficiently small particle sizes where the flow rate is small and the total surface area is large, the reduction rate would be limited by the gas flow rate. Initially the gas entering the bed reacts very rapidly and the composition approaches the equilibrium conversion value a short distance from the reactor inlet. This concentration "wave-front" then moves up the bed as the flow of reducing gas is continued, leaving in its wake an ever increasing layer of reduced particles. Providing that the reducing gas leaves the bed at equilibrium concentrations, conversion is expected to increase with an increase in flow rate, and hence with an increase in particle diemater. Conversely, for sufficiently large particles the flow rate will be high but the surface area available for reaction will limit the reduction rate. Since the total surface area decreases with an increase in particle size, conversion, in this case, is expected to decrease as the particle diameter is increased. It is clear then that between these two extremes an optimum particle diameter must exist. THEORETICAL DEVELOPMENT Above the temperature where wiistite is stable (about 560°C) the reduction of hematite proceeds through the series Fe2O3/Fe3O4/FeO/Fe. On the basis of microstructural studies and earlier work, Edström1 has postulated a mechanism for the reduction of an ideal hematite lattice: 1) Iron phase formation at the boundary between wiistite, iron, and gas (for sufficiently porous iron). 2) Diffusion of iron across a wustite layer. 3) Phase boundary reaction of Fe3O4 to FeO. 4) Diffusion across a dense magnetite layer. 5) Phase-boundary reaction of Fe2O3 to Fe3O4. According to the mechanism postulated, gaseous reaction product has to be removed only at the boundaries between wüstite and iron or gas, the only possible exception being enveloped Fe3O4 specks. On this basis McKewan2,3 has proposed that one may consider the hematite reduction process as a simple two-phase system of oxide/metal. If, for FeO and Fe3O4 layers of negligible thickness, the hypothesis is made that the rate of formation of a

Jan 1, 1963

By M. V. Nevitt

THE Cr,O-type, or P-tungsten, structure having the space group (Oh2— Pm,n) is one of the most widely occurring structures found among the intermediate phases involving transition metals. Including the phases reported here for the first time, the total number of these A,B phases now known is 39. Greenfield and Beck' have correlated the lattice parameters of these phases with the Goldschmidt radius of the close-packed chains of A atoms. Laves' discussed the apparent size of the A and B atoms in this structure. Gel1er" proposed a scheme for reproducing the lattice constants of the phases by the use of a list of effective C.N. 12 radii for the component elements. Reported here is a survey of the A,B combinations which appeared favorable for the stability of the Cr,O-type phase but which, at the time the investigation was begun, either had not been reported upon or had conflicting reports as to the existence of the structure. Seventy systems were investigated, and 8 Cr,,O-type structures were found. Six of these also were reported by other investigators in the interval between the start of this investigation and its completion. This survey yielded information as to the influence of the relative sizes of the A and B atoms on the stability of the phase and, for the various families of Cr,O-type phases, the effects of the sizes of the A and B atoms on the lattice constant. Likewise, a somewhat clearer picture of the connection between the position of the A and B elements in the Periodic Table and their Cr,O-type phase-forming tendencies has become apparent. Experimental Procedure Alloys were prepared in the form of arc-melted 3-gram buttons in all cases where the vapor pressure of neither component was high enough to cause

Jan 1, 1959

By C. E. MacQuigg

In this paper it is impossible to more than touch on many of the commercial alloys of iron, chromium, and carbon, therefore the discussion is confined to the properties of some of the less well-known alloys with upwards of 20-per cent. chromium. The discussion has been based largely on the strictly engineering aspects of the alloys. Chromium has well-defined effects when added to the iron-carbon system. These effects depend on the amount of chromium added and on the composition of the iron-carbon alloy to which the addition is made, i.e. whether low- or high-carbon steel, cast iron, etc. In the case of the low-carbon steels, the chromium addition, when not in excess of several per cent., appears to exert an influence on the properties by its influence on the critical range. In the higher chromium alloys, the physical properties are influenced chiefly by the formation of new complexes, such as iron-chromium solid solutions and, with higher carbon contents, iron-chromium carbides of great hardness. Examination of the published data1 on the critical range phenomena of chromium-bearing steels up to several per cent. chromium indicates an agreement on the following points:

Jan 1, 1923

By C. E. MacQuigg

In this paper it is impossible to more than touch on many of the commercial alloys of iron, chromium, and carbon, therefore the discussion is confined to the properties of some of the less well-known alloys with upwards of 20-per cent. chromium. The discussion has been based largely on the strictly engineering aspects of the alloys. Chromium has well-defined effects when added to the iron-carbon system. These effects depend on the amount of chromium added and on the composition of the iron-carbon alloy to which the addition is made, i.e. whether low- or high-carbon steel, cast iron, etc. In the case of the low-carbon steels, the chromium addition, when not in excess of several per cent., appears to exert an influence on the properties by its influence on the critical range. In the higher chromium alloys, the physical properties are influenced chiefly by the formation of new complexes, such as iron-chromium solid solutions and, with higher carbon contents, iron-chromium carbides of great hardness. Examination of the published data1 on the critical range phenomena of chromium-bearing steels up to several per cent. chromium indicates an agreement on the following points:

Jan 1, 1923

By R. G. Ward, John Henderson

It has been shown1 that the observed density1-' of liquid iron silicates in contact with solid iron depends upon whether nitrogen or argon is used to protect the experimental system from oxidation. These densities have been measured by the maximum bubble-pressure method, in five different labora-

Jan 1, 1965

By James R. Cudworth, Joseph C. Mead

The Birmingham district of Alabama has utilized the slag from its blast furnaces consistently since the earliest development of the slag industry. Today there are producers of slag cement who started business in 1900, and who have, under a progressive policy, expanded the number of their products to meet present demands. There are producers of slag aggregates and other crushed slag products who have been successful for periods of over thirty years. There are at the present two companies, Cheney Lime and Cement Co. and the Southern Cement Co., manufacturing puzzolan cement; two companies, Birmingham Slag Co. and Woodstock Slag Co., making slag aggregates and by-products; one company, Tennessee Coal, Iron and Railway Co., a subsidiary of the U. S. Steel Corporation, producing ground open-hearth basic slag for soil conditioning. Two companies, the Sloss Sheffield Steel and Iron Co. and the Woodstock Slag Co., make slag concrete in ready-mix plants and one company, the Superock Company, manufactures fine and coarse slag aggregates under a new granulation process. NO Portland cement is made with slag as an ingredient, because dolomite is used so extensively as a blast-furnace flux that the magnesium content of the slag is excessive. Sources of Slag In the Birmingham district there are 22 blast furnaces, of which the majority are in blast. The present production is 165,000 tons of pig iron monthly; the production in 1935 was 1,297,960 gross tons1. There arc also two blast furnaces at Gadsden and one ferroalloy electric furnaee at Anniston. From these two sources is obtained slag to approximately 1.1 tons per ton of pig iron. History of Development of the Industry The history of the local utilization of slag as an industry probably starts with the Birmingharii Slag Cement Co. This company was

Jan 1, 1938

By A. G. Metcalfe, Koeneman

A study of the structure of chemically deposited nickel by Goldenstein, Rostoker, Scpssberger, and Gutzeit has been reported recently. In this work it was shown that the nickel deposit produced by the catalytic nickel-reduction process was an amorphous solid. Crystallization occurred at elevated temperatures when the original powder pattern which showed only a diffuse ring with a d-spacing of 2.01A became sharp, revealing nickel and nickel-phosphide lines. The phosphide was indexed provision%lly on a tetragonal lattice of parameters a = 9.01A and c = 4.42A, which is in reasonable agreement with the structure of Ni3P proposed by No-wotny and Henglein.3 The transformation from the amorphous to the solid state occurs abruptly (e.g., after 7 min holding at 400°C) with the evolution of considerably more than 1000 cal per gm-mole. A more detailed analysis of these effects requires a knowledge of the solubility of phosphorus in nickel. Konstanti-now3 mapped out the phase diagram in 1908 but did not determine the solid solubility. The eutectic was placed at 11 pct P and 880°C. The purity of typical catalytic nickel deposits is very high.' Spectrographic analysis for heavier elements showed only trace amounts of aluminum, calcium, iron, magnesium, lead, and silicon. The term "strace" is a qualitative definition for less than 0.1 pct and probably less than 0.01 pct. Analysis for the interstitial elements yielded 0.04 pct C, 0.0023 pct 0, 0.0005 pct N, and 0.0016 pct H. Some of this material with 7.5 pct P was used in the present work. EXPERIMENTAL METHODS Alloys were prepared from carbonyl-nickel shot and a master composition containing 7.5 pct P. Cold-crucible, nonconsumable-arc melting was used.

Jan 1, 1959

By Joseph C. Mead, James R. Cudworth

The Birmingham district of Alabama has utilized the slag from its blast furnaces consistently since the earliest development of the slag industry. Today there are producers of slag cement who started business in 1900, and who have, under a progressive policy, expanded the number of their products to meet present demands. There are producers of slag aggregates and other crushed slag products who have been successful for periods of over thirty years. There are at the present two companies, Cheney Lime and Cement Co. and the Southern Cement Co., manufacturing puzzolan cement; two companies, Birmingham Slag Co. and Woodstock Slag Co., making slag aggregates and by-products; one company, Tennessee Coal, Iron and Railway Co., a subsidiary of the U. S. Steel Corporation, producing ground open-hearth basic slag for soil conditioning. Two companies, the Sloss Sheffield Steel and Iron Co. and the Woodstock Slag Co., make slag concrete in ready-mix plants and one company, the Superock Company, manufactures fine and coarse slag aggregates under a new granulation process. NO Portland cement is made with slag as an ingredient, because dolomite is used so extensively as a blast-furnace flux that the magnesium content of the slag is excessive. Sources of Slag In the Birmingham district there are 22 blast furnaces, of which the majority are in blast. The present production is 165,000 tons of pig iron monthly; the production in 1935 was 1,297,960 gross tons1. There arc also two blast furnaces at Gadsden and one ferroalloy electric furnaee at Anniston. From these two sources is obtained slag to approximately 1.1 tons per ton of pig iron. History of Development of the Industry The history of the local utilization of slag as an industry probably starts with the Birmingharii Slag Cement Co. This company was

Jan 1, 1938

By W. H. Emmons

ALTHOUGH gold is one of the rarer metals, it is widely distributed; it is found on all of the continents and in each of the grand metallogenic provinces of the earth. It is prominent particularly in the shield areas of the earth; these areas have produced a large part of the world's lode gold and in most of them gold lodes are more important than the lodes of other metals. The Scandinavian shield is the only one that has not produced much gold. Nearly all of the world's gold has been derived from lodes and from sands and gravels where gold placers formed by the destruction of lodes. The gold derived from magmatic segregations, from pegmatites and from contact metamorphic deposits is quite subordinate to that derived from auriferous lodes. The lodes include all veins and related deposits that are formed by hot waters that move along fissures or other openings and that deposit vein matter in the fissures and by replacement of the country rocks along the fissures. All of the shield areas of the earth are characterized by large areas of granitic rocks including granitic gneisses, granodiorites and other acid intrusives which here are included in the general term "granite." The granites are intruded into schists, ancient lavas and other rocks which here are designated as the "invaded" rocks. The granites are parts of what once were great batholiths: that is, they are the remaining portions of great deep-seated bodies that slope outward, have very irregular roofs and so far as known have no floors but extend downward to great though unknown depths. Some of them are scores or hundreds of miles across and contain islands or "roof pendants" of the invaded rocks at places where the roofs of the batholiths were low-that is, where erosion has not yet completely unroofed the batholiths.

Jan 1, 1932

By L. G. Graper, E. L. Ramsey

THE present program of increased production of armament and lend-lease material for mechanized war has created a problem for the shops that must do the machining. They have naturally turned to the steel producers to provide them with a steel that can be accurately machined with the greatest possible speed. The adding of sulphur to steel as an aid to machinability has long been practiced; however, it may cause red shortness in rolling and may result in billets with seams and cracks, which must be removed before rolling can be continued. This conditioning of billets slows down production and' adds to the cost of making steel. Experience with various grades of sulphur steel made to different specifications has shown that Bessemer sulphur steels roll better than similar grades made in the open hearth, and also that low-carbon steels that are open or semikilled .as tapped roll better than completely deoxidized or killed steels. This has led to the belief that oxygen plays an important part in the rolling qualities of sulphur-bearing steels. It is generally held that the red shortness of sulphur steels is due to the low melting point of the sulphide compounds that separate out at the grain boundaries when the steel solidifies. At the rolling temperature of steel these sulphide compounds melt and cause cracking. ADDING SULPHUR AS A SULPHITE These difficulties can be avoided if sulphur is introduced into the steel by means of an anhydrous sulphite, such as sodium sulphite or sodium bisulphite, which-upon decomposition-forms sulphur dioxide. It is assumed that, in this case, the oxygen of the sulphur dioxide forms part of the sulphide inclusions in the steel, and raises their solidification temperature enough so that the formation in the steel of a low-melting eutectic is prevented. The result is the prevention of hot shortness and a more uniform distribution of inclusions. Fig. I shows photomicrographs of steels made with sulphur, while Fig. 2 illustrates the structure of steels made with sodium . bisulphite. These samples were cut from the steels as cast-that is, before rollingand were polished and lightly etched to bring out the grain boundaries. Fig. I shows that sulphide -inclusions segregate more or less at the grain boundaries, and it can be seen how the continuity of these low-melting inclusions would cause red shortness. Fig. z shows that the sulphide inclusions are more or less uniformly distributed throughout the matrix. This arrangement of inclusions has no apparent effect on the rolling qualities of a steel. This statement has been substantiated by the observation of the rolling of over 6000 tons of steel made with a sulphite addition. RESULTS As stated before, the sulphur dioxide-is added to steel by means of the decomposi-

Jan 1, 1942

By L. C. Brown, E. B. Hawbolt

The formation of grain boundary precipitates has been studied in Ag-5.64 wt pcl Al alloys at 688°C. Large-grain specinzerzs were used and the boundary misorientation measured by X-ray diffraction. At low-angle grain boundrrries Primary sideplates form. u)hile abore a 17-deg misorientation lenticular precipitates predominate. Growth of the lenticular precipitates was studied on individual grain boundaries using a statistical technique. The thickening and lengthening rates appeared to be independent of &apos;pain boundary misorientation, indicating that grain boundary diffusion was not significant in this system. The precipitates grew urith constant shape, with both the length and thickness increasing parabolically with time. The parabolic lengthening rates were unexpected since previous theory and experimerztal results had indicated linear growth. By approximating the shape of the precipitate to that of an oblate spheroid grouling with constant shape an equivalent diffusion coefficienl was calculated. The zlalue obtained was in good agreement with nleasurements obtained fron, diffusiorz couples. IF a single-phase alloy is heated or cooled to a temperature such that the phase becomes supersaturated, there is a tendency for a second phase to precipitate from it in order to remove the supersaturation. Precipitation takes place initially on grain boundaries due to preferred heterogeneous nucleation, but subsequently Widmans kitten plates may form in the grain interiors if the grain size and supersaturation are sufficient. The type of grain boundary precipitate formed depends on the nature of the boundary. Aaronson1 and clark2 have shown that grain boundary misorientation can be characterized by the simple parameter R, where and X, Y, and Z represent the minimum rotations about three orthogonal axes required to bring the two lattices forming the grain boundary into coincidence. The maximum value for R is 60 deg. In using this parameter the orientation of the grain boundary itself is, of course, neglected. However it was found in both Fe-si3 and A1-Ag2 that the precipitate shape depended only on the parameter R. Clark found that the vast majority of precipitates formed were allo-triomorphs— lens-shaped precipitates that grew along the grain boundaries. At low-angle boundaries, however, (R < 15 deg) Widmanstatten sideplates nucleated at the grain boundaries and grew into the adjacent grains. It has been reported that the rate of growth of grain boundary precipitates is controlled by diffusion within the supersaturated phase.&apos; The theories which have been developed for growth rates have assumed the diffusion coefficient constant over the composition range of the supersaturated phase. This is a fairly good approximation if the composition range involved is not large. Thickening rates have been calculated using the theory developed by Zener4 and by Frank5 for the growth of planar precipitates. A parabolic growth law

Jan 1, 1968

By Joseph P. Lyden

In the Picher field, structure made openings for the circulation of the mineralizing solutions by flexing, shearing, and fracturing the sedimentary beds. This structure is used with the spatial and genetic relationship of the ore minerals, sphalerite and galena, and the gangue minerals, dolomite and jasperoid, in prospecting for ore bodies.

Jan 12, 1950

By C. D. Wiseman

THE concept of alloying to increase the strength of metals originated during the bronze age. However, at the present time there is no single theory capable of explaining all of the observed strengthening effects of alloying elements on the mechanical properties. In general, it may be said that solid solutions are stronger than the pure metal and that the strengthening effect increases with increasing alloy content. Various theories for solution hardening have been proposed, the first of which was presented by Rosenhain who suggested that the alloying elements roughened the slip planes, thereby requiring a higher stress to initiate slip. Recent work by French and Hibbard2 confirmed Norbury&apos;s3 conclusion that those alloying elements which cause a greater change in lattice parameter have larger effects on hardness. However, a given change in lattice parameter produced by different alloying elements does not cause the same change in hardness. A further refinement was suggested by Dorn, Pietrokowski, and Tietz4 who considered differences in valence between the solute and solvent with the change in lattice parameter to explain the plastic properties of aluminum alloys. Allen, Schofield, and Tate5 further investigated the valency contribution to solution strengthening by testing some copper-base solid-solution alloys having constant electron densities. Tensile tests performed on these alloys gave identical stress-strain curves even though the atomic size effect, which varied by a factor of two, was neglected. The advent of dislocation theory6-8 provided a new and powerful tool capable of explaining many phenomena of plastic deformation and indicated new approaches to solution hardening. The basic con- cept of recent theories is that solution hardening is not due to stresses associated with randomly dispersed solute atoms, but rather to a nonuniform distribution of the solute. This conclusion was reached by consideration of the effective tension present on each dislocation line and the ability of a dislocation to pass an obstacle. cottrell suggested the possibility that the internal stresses due to randomly distributed solute atoms would offer essentially no resistance to the passage of dislocations. He reasoned that an edge dislocation may be considered as a rigid line discontinuity. As the dislocation moved through a crystal, the random stress fields would be equally distributed along its length. Since half of the stress fields would be acting to move the dislocation forward and the other half trying to move it back, the net effect on the dislocation would be zero. Thus the randomly distributed solute atoms would not contribute appreciably to solution strengthening. Mott and Nabarro10 considered the dislocation as a flexible, rather than a rigid, discontinuity. They obtained a simple model for a dislocation moving in a lattice having precipated particles, where the dislocation would actually bend around the obstacle until it would loop back onto itself to rejoin and then continue onward. Their work indicated that the minimum radius of curvature of the dislocation line, under the action of an external stress and in the region of an internal stress, would be such that the dislocation would be unable to pass through a matrix containing small closely spaced precipates by the looping process. The dislocations would tend to remain rather straight, approaching the condition of Cottrell&apos;s rigid dislocation. Hence, the strengthening must not be due to random solute atoms; however, it might be due to the concentration of atoms, either as clusters of like atoms or as short-range ordered regions, or to the concentration of solute atoms around dislocations. To date, four mechanisms of solution strength-

Jan 1, 1959

By Thomas C. Patton, Eric S. Cheney

L-D gold mine is 3 miles south of Wenatchee, central Washington. Recognition of locally mappable conglomerates, sandstones, and shales within the Paleocene (?) Swauk formation led to the discovery that the known epithermal gold mineraliza¬tion is limited to a previously unknown imbricate thrust zone of unknown displace¬ment cutting the open folds o f the area. Hypabyssal intrusions also are most nu¬merous along the trace of the thrust faults. Yakima basalt of Miocene age uncon¬formably overlies the Swauk formation, thrust faults, and the intrusions. The L-D mine is in a northwesterly trending imbricate fault block of nearly vertical strata. Microscopic native gold, electrum, and naumannite occur in quartz veins and as low¬grade disseminations in the well-silicified portions of arkosic sandstones. Fault gouge on the "footwall fissure" limits ore to the hanging-wall block of the fault. Epithermal mineralization and alteration are spatially related to the nearby intrusions. Right lateral north-south faults offset the ore a maximum of 300-400 ft along any one fault. From 1949 until January 1967, when the L-D mine closed, 1,036,572 dry tons of ore valued at $14,962,305 and averaging 0.396 oz Au per ton and 0.607 oz Ag per ton were mined. Recognition of the structural control of the mineralization and altera¬tion within the Swauk formation suggests several areas within and outside of the mine that warrant further exploration. For example, the high-angle faults, imbricate thrusts, and the intrusions of this area are on strike with similar features along the major Entiat fault zone 10 miles to the northwest. The L-D gold mine (previously called Squilchuck, Wenatchee, Golden King, Gold King, and Lovitt) is located in Squilchuck Canyon about three miles south of Wenatchee, Chelan County, Wash. (Fig. 1) on the eastern edge of the Cascade Mountains. The major stratigraphic unit in the area is the nonmarine early Tertiary Swauk formation, which is predominantly com¬posed of arkosic sandstone. The lack of laterally per¬sistent units and the paucity of outcrops heretofore have precluded all but the grossest subdivision of the Swauk.&apos; As a result, the true significance of the open folds in the Wenatchee area was not recognized, and although the geology within the mine was known, the structural setting of the mine was virtually unknown. During the present investigation, several locally map¬pable units were discovered within the Swauk which, in conjunction with mine maps, indicate an imbricate thrust zone. The epithermal gold mineralization, most of the hypabyssal intrusions, and the zones of hydrother¬mal alteration are located within or near this thrust zone. The purpose of this paper is to: (1) to describe this structural setting, rather than the detailed mine geology already presented by Lovitt and Skerl,2 and (2) to sug¬gest that from an exploration standpoint, this struc¬tural setting may be repeated in areas inside and outside of the mine area. Stratigraphy and Structure of the Swauk Formation General: The Swauk formation contains three distinct lithologies. Typical Swauk sandstone is gray on fresh surfaces, poorly sorted, weathers tan, and is cross¬bedded; it consists of 40-60% quartz, 20-40% feldspar, and up to 10% muscovite and biotite 9 The typical shale is gray to dark brown, very soft, and interbedded with silty sandstones; sharp contacts exist between the

Jan 1, 1972

By P. S. Rudman

Laves phases, AB2, are considered as Izerrzisub-stitutional solutions m1hich are defined by a one-for-truo replacement scheme. Atomic-size tnisfit is considered in terms of deviations of the ratio 2V°b/V°A from unity, where v° = atomic volume. A simple elastic model has been used to calculated deviations from "Vegard&apos;s law of atomic vol-umes". Comparison has been made between calculated and observed atomic-volume deviations fov 222 Laves phases. Agreement is generally very good although there ave some few exceptions which appear to be excusable in terms of electronic changes that ore beyond the scope of the present model. We can consider the formation of a binary sub-stitutional solution A-B from an A solvent as one-for-one replacements of A atoms by B atoms. As the atomic-size ratio deviates from unity, the solution becomes thermodynamically less stable and hence more restricted because of atomic-misfit strain energy. In accordance with our previously presented conclusion1 that the atomic volume, v, is in general the most appropriate measure of atomic size, the ideal size ratio for a binary sub-stitutional solution is vg/vA = 1. The Laves phases have been described by Berry and Raynor2 in terms of various stacking sequences of hexagonal layers of B atoms for the three structures MgZn2(C14), MgCu2(C15), and MgNi2(C36). To form the Laves phase of ideal composition AB, we start with complete hexagonal layers of B atoms in the appropriate stacking sequence and we remove, according to an appropriate scheme for each structure, two out of every four B atoms and replace the two removed atoms by one A atom. We thus might expect to find that the ideal size ratio for the Laves phases is 2v/B/ VA= 1. From this point of view, then, we call Laves phases hemi-substitutional solutions since we employ one-for-two replacements. By analogy with substitutional solutions we can expect for Laves phases that as the ratio 2VB/Va deviates from unity the phase occurrence will be more restricted. Laves3 has plotted the distribution of Laves phases as a function of the radius ratio, ?A/rB, and found that, while the distribution extended from 1.05 < rA/B < 1.50, the

Jan 1, 1965

By A. L. Mowry, John T. Norton

Isothermal sections of the pseudo-ternary carbide systems TiC-VC-ZrC, TaC-VC-ZrC, and NbC-VC-ZrC have been examined. The sections contain an inverted U shaped two-phase field whose maximum extent is 77 molecular pct for Tic, 64 pct for TaC, and 51 pct for NbC. lsoparametric lines were determined which show the curvature of the single-phase field and the direction of tie lines in the two-phase field. It was not possible to show any relationship between atom size and the extent of the two-phase field. REVIOUS work&apos; on the solubility relationship of several pairs of refractory cubic monocarbides from the group Tic, ZrC, VC, NbC, and TaC has shown that, with the exception of the system VC-ZrC, they all form continuous series of solid solutions. It was demonstrated that the limited solubility in the case of VC-ZrC system was primarily a question of the size factor, the size difference between vanadium and zirconium being greater than the limiting value of about 15 pet. It is interesting to consider the results of combining these isomorphous carbides in groups of three and to determine the isothermal section of the pseudo-ternary diagram at, for instance, 2000°C, a temperature that will assure an equilibrium structure in a reasonable length of time. In the ternary systems where the three pairs form complete solid solution series, it is probable that the isothermal ternary section would be a single- phase field, although this is not necessarily the case. However, if one pair of carbides has a very limited solubility, then there must be a two-phase field of some extent, and it is the purpose of the present work to examine the extension of this field and to determine if it can be related to the nature of the third carbide. This condition is fulfilled if the VC-ZrC pair, which has only limited solubility, is combined with Tic, TaC, or NbC. The relative sizes of the metal atoms undoubtedly play a role in the extent of the single-phase field, and the values obtained from the pure carbides, assuming close-packing between metal and carbon atoms and a carbon atom diameter of 1.54A, are

Jan 1, 1952

By E. S. Davenport

IT is indeed an honor and a responsibility to have been selected to present the thirty-fourth in this series of Henry Marion Howe lectures, established to perpetuate the memory of a great teacher and one of America&apos;s outstanding scientists. Previous Howe lecturers have established high standards for this annual AIME event. It has been my good fortune to have enjoyed close association with five of these former lecturers; namely, Bain, Grossmann, Johnston, Sosman, and Vilella, all of whom have been prominently identified with the research activities of the organization with which I am connected. Some years ago I had an opportunity to examine a letter written by Professor Howe in 1904. This document was particularly interesting to me since I never had the privilege of personal acquaintance with Professor Howe and do not recall even having seen him during his long and active career. In view of the fact that the letter dealt, to some extent, with matters related to the subject of today&apos;s lecture, I would like to quote briefly from it. The letter is datelined, "Bad Kissingen, June 11, 1904." The salutation reads, "Dear Bradley," which suggests that it was probably addressed to Bradley Stoughton, who, I believe, was working with Howe at Columbia University at that time. The letter reads, in part, as follows: "Austenite and Martensite. I have not examined what Osmond says in his new book. His former remarks about austenite I found very confusing, indeed unintelligible. I think we can reconcile matters well enough for the present by assuming that martensite is a transition step between austenite at one end and ferrite and cementite at the other. Above critical range for steel of 0 to 1.80 carbon, austenite is normal state; below Ar1, ferrite and cementite are normal." The letter then continues with a discussion of Osmond&apos;s ideas on metallographic nomenclature, particularly his use of the terms martensite, troostite, and sorbite, including the following pointed comment: "For common purposes it seems to me unwise to drag them in, and much simpler to confine ourselves to the end stages Austenite Ferrite plus Cementite Osmond does not really know his own mind— or does not clarify his ideas to others—as to nomenclature." Thus we see that, as far back as 1904, the transformation of austenite, and the products of that

Jan 1, 1958

By Carle Hayward

THE effect of copper on steel has been studied by numerous investigators. Before modern testing methods had been developed, blacksmiths noted red shortness in iron, the cause for which was ascribed to the presence of copper. Numerous papers have been published on the corrosion of steels containing various amounts of copper, and a few writers have discussed the effect of copper on the mechanical properties of steel. The purpose of the investigation described in the following paper was to obtain additional data on the mechanical properties of medium-carbon steel containing small quantities of copper. Among those who have published results of mechanical tests on copper steels are Ball,1 who states that copper increases the tensile strength and &apos;hardness but lowers the elongation. Stead2 states that copper steels closely resemble nickel steels containing equivalent percentages of nickel,, as regards tensile strength, resistance to shock, corrosion and hardness. Wigham 5 found that copper in small amounts had no injurious effect on steel. Breuil4 found that with 1 per cent. carbon, copper lessened the brittleness of steel and in low-carbon steel it increased the tensile strength and lowered the ductility slightly. H. H. Campbell 5 states that copper up to 0.25 per cent. slightly raises the elastic limit, elongation and reduction of area.

Jan 1, 1918

By J. E. Lawver, J. L. Wright, H. R. Kokat

Mesabi semitaconite and oxidized taconite ores that cannot be concentrated by froth flotation can be rendered amenable to flotation through partial concentration in a high-in tensity wet magnetic separator. Since 1964, a method for accomplishing this precon-centration has been under development at the Minnesota Mines Experiment Station, where several hundred tons of ore have been successfully processed. This paper is an analysis of the performance of the separators used at the Station. At present the United States is producing about 85 million tons of iron ore a year, and nearly 55 million tons of this comes from Minnesota. Nearly half of Minnesota&apos;s production is in the form of magnetite taconite pellets —the remainder being wash ore and gravity concentrates. As the demands of the blast furnace operators become more stringent - and they are becoming more so yearly — these demands are met by improved iron ore beneficiation technology. Furthermore, there is no doubt that as magnetite taconite, gravity ores, and wash ores are exhausted, new processes will be developed to produce a product comparable to magnetite taconite pellets from Minnesota&apos;s vast reserves of oxidized taconite and semitaconite. The magnetite taconite ores are rather easily bene-ficiated by conventional, low-intensity (500- to 1400-gauss) magnetic separators, followed, in some plants, by froth flotation of the magnetic concentrates.

Jan 1, 1969