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By R. W. Smith

It is well known that certain silicates such as the feldspars and beryl can be readily floated from quartz at a low pH value using a long chain cationic collector in the presence of a fluoride.1-3 However, the mechanism whereby the fluoride activates feldspars and beryl is not known. Indeed, only a few authors have even speculated about possible mechanisms.1,3,4 As a first approach to the problem, it is perhaps best to look closely at the interesting character of hydrofluoric acid and how it dissolves silica and silicic acid. Hydrofluoric acid, unlike hydrochloric acid, is a weak acid with a dissociation constant of about 3.53 x 10-4 at 25°C.5 The reason for the weak acidic character of HF lies in the very small size of the fluoride ion.6 The pKa value is 3.45 which means that at pH 3.45 half the HF is present in molecular form and half in ionic form. The anion present is probably HF2.-6 At pH values below the pKa value, molecular concentration increases rapidly at the expense of the HF2- anion. It is known that HF readily attacks glass, silicates, quartz and silicic acid. The equation usually cited pertaining to the first step in HF attack of silica is6-'

Jan 1, 1965

By E. F. Kingsbury

ONE of the well-known and important uses of the noble or precious metals has been for electrical contacts. In fact, the elements of this group, comprising gold, silver and. the six platinum metals, have been called "noble" because of their ability to resist heat and corrosion, properties which. were early found to be of importance in good contacts. Of these, platinum and its iridium alloys, palladium, and silver, have been extensively used. In recent years the electrical industry has been responsible for about one-eighth of the total consumption of the platinum metals in the United States. Information is not available as to what part of this one-eighth has been used for contacts but it is certainly an important one. SUBSTITUTES FOR PLATINUM During the past 20 years a considerable number of contact alloys have been proposed in the patent literature largely with the aim of more or less replacing platinum by gold or silver, and some of these alloys are finding increasingly widespread application as the reliability of their performance becomes established. From even the partial data at hand it appears that this substitution by the less precious metals has replaced at least one-half of the amount of platinum that the entire electrical industry would otherwise be consuming at the present time. While the subject is of considerable interest to the metallurgist it is even more so to the electrical engineer and it is surprising that the literature records no systematic and' comprehensive investigation along these lines. Practically all the scattered work on noble metal contacts has centered around platinum as a standard and has had two more or less distinct aims. One of these has been the replacement of platinum by cheaper materials, and the other, the development of materials of superior electrical performance. The merit, of a contact metal has been assumed to be dependent on its infusibility, and since the more precious metals have the higher melting points there has naturally been an association of the two qualities in the sense that the more precious were

Jan 1, 1928

By AIME AIME

MORE than thirty members of the Coal Division attended the Coal Land Valuations Round Table on Monday morning. Chairman Dilworth stated that the Committee had been appointed to take up the question and, after reading the list of members of the Committee, pointed out that the object of the meeting was to formulate a plan of action rather than to discuss any phases of valuation, per se. To this end he presented a tentative outline of points to be considered in the future by the Committee. After a lively discussion on the desirability of inclusion of some questions in the agenda of the Committee, the following outline was adopted :

Jan 1, 1931

By G. F. Loughlin

MORE than 20 years have passed since the publication of Lindgren and Ransome's report on the Cripple Creek District,1 which was made when the district was much more active and prosperous than in recent years. They concluded that the output of the district, which had reached its maximum of about $18,200,000 in 1900, would gradually decline, and their conclusion has been confirmed by records of subsequent production. Between 1905 and 1915 annual declines were partly compensated by encouraging increases, especially in 1908, 1914, and 1915; but a rapid continuous decline followed, due largely to the war and its after effects, until in 1922 the value of output was only slightly more than $4,000,000. It rose to nearly $5,000,000 in 1924, but declined again in 1925 and in 1926, when it was about $4,400,000, and represented ores mainly from deep levels in the Cresson and Portland mines. The profitable operations of these two mines were the principal factors leading to a study of ore at deep levels in the district by the U. S. Geological Survey in coopera-tion with the Colorado Metal Mining Fund. The principal reasons for Lindgren and Ransome's conclusion were three: (1) the greater cost and difficulty of deep exploration; (2) the decrease in the number of veins with increasing depth, and (3) the probability that the telluride ore, believed to have formed at comparatively low temperature, would not persist indefinitely -in depth. Operations since they made these statements have verified the first two, but call for some modification of the third. Rich telluride, ore is being mined at a profit in the Portland mine 3000 ft. below the present surface, or 5000 ft. below the original surface of the Cripple Creek volcano, as interpreted by Lindgren and Ransome. The question arises, therefore, as to the number and extent of such deep deposits, and the answer, so far as it can now be given, must be based mainly on structural data, supplemented by data on the processes of ore deposition. Presentation of these data based on a study of deep mines in the southeast quarter of the district, the only

Jan 1, 1927

By J. D. Ridge

The geologic setting and mineral relationships of seven European massive sulfide deposits that more or less conform to the bedding of the largely noncal-careous sedimentary rocks and/or bedded volcanics in which they are found are considered here. These orebodies consist largely of massive beds or lenses of sulfides usually surrounded by halos of disseminated sulfides and distorted by tectonic activity. The formations containing these deposits have been metamorphosed in varying degrees at times subsequent to their lithification. The ore-forming process is thought to be essentially volcanic, with the ore constituents being brought to the shallow-water site of deposition through tectonic fissures from magma chambers at depth as gases or relatively concentrated hydrother-mal solutions. Certain European ore deposits of base metal sulfide have previously been considered to be of hydro-thermal or magmatic origin, but today a number of European mining geologists consider them to be syngenetically produced. In an effort to provide American geologists with some idea of the reasons behind this change in thought, the geological settings of seven of these deposits have been studied. These are: Ldkken, Meggen, Rammelsberg, Ergani-Maden, Outokumpu, Boliden and Roros. These deposits lie in bedded rocks that have undergone metamorphism from causes not universally agreed upon; most of the formations were originally shales, and may have been intercalated with limey and occasionally quartzitic beds, volcanic tuff, agglomerate, extrusive lavas and usually basic intrusives. Deposits of the conformable type, however, are not confined to these rock types but may be in calcareous and associated igneous rocks or almost entirely in volcanics. These deposits may be closely associated in space with igneous rocks that, again, are usually basic types. Although the ages of the enclosing rocks range from mid-Precambrian (Boliden and Outokumpu) to Eocene (Ergani-Maden), the bulk of them are Paleozoic, with two (Meggen, and eammelsberg) being upper middle Devonian and two (LØkken and RØros) being Cambro-Ordovician. Geographically, two are in West Germany, four in Scandanavia and one in Turkey. Of the seven deposits, six are mined for copper, with three of these also producing zinc, and two lead; one is mined for zinc and minor lead. In the discussions of the seven conformable deposits that follow, I have attempted to present as uniform a treatment as their varying characters will permit. For each deposit, I have considered the stratigraphy of the area, its major structural characteristics, the form of the orebodies, their mineral content, and the origin of the ore. In the last of these subdivisions, I have presented only the viewpoint of those who believe the ores to have been formed by syngenetic processes, processes that went on at the same time as those which produced the beds that enclose the ores but that are not, in the deposits in question, thought to have been sedimentary in the strict sense of the term. The materials of which these orebodies are composed, it is suggested, did actually collect by falling through sea water to the floor of that portion of the sea in which they accumulated. The ore constituents, however, are believed by a considerable number of European geologists to have been added to the sea water from intratelluric sources, probably igneous magma chambers, as exhalations — hydrothermal solutions or volcanic gases. The effect of the encounter with sea water on these ejected gases or water-rich vapors was to precipitate their potentially solid constituents with great rapidity; they were deposited so quickly, in fact, that the amounj of normally accumulated mechanical or chemical sediment deposited over the same period of time was essentially negligible. The ores formed in this manner, however, are generally interbedded with normal sediments or with lava flows, or with any combination of these two types of rock-forming materials. Such departures as these deposits may have from their original mineral content and attitude are thought to be directly related to the degree of dynamic or static metamorphism that they may have undergone after their accumulation. I have not attempted here to present alternate hypotheses to that of so-called exhalative sedimentation although, of course, such exist and, in my

Jan 1, 1963

By H. S. Munroe

THE native copper of Lake Superior occurs in the form of fine grains and scales, disseminated in small percentage through the copper-bearing rock ; and in large and small masses, from a few pounds to several hundred tons in weight. Formerly the bulk of the copper came from the mines of Ontonagon and Keweenaw counties, producing mass copper. At present these mines furnish less than one-tenth of the total product, and fully one-half of this is from a single mine. The masses are usually found irregularly distributed in nearly vertical fissure veins, and require much dead work in sinking, drifting, and stoping for their development. The risk and expense attending the working of these mines have made them, with few exceptions, anything but profitable. * Read at the Montreal meeting, September, 1880.

Jan 1, 1880

By William G. Pariseau

The flexure of geologic strata, a phenomenon of interest to geologists and mining engineers alike, is examined as a sheet bending problem in Coulomb plasticity. Fonnulae for the distribution of stress, strain, and displacement increments; volume change; change in the length of the central surface; and power of dissipation, as well as for the neutral surface shift are given. Strains of any magnitude are considered. The analysis shows that deeply buried strata may bend and develop "tensile" cracks under generally compressive states of stress. It is also shown that bed separation and high capacity props are desirable in mechanized longwall mining, a result in keeping with operating experience. Although speculative at this time, the analysis provides a rational working hypothesis as regards the problem of strata flexure and control. | he purpose of this paper is to present an analysis of the flexure of geologic strata as a problem in the bending of a sheet of material failing in accordance with a Mohr-Coulomb criterion. The flexure of strata has an obvious academic interest to the geologist concerned with the mechanics of folding. It is of interest to the economic geologist as it relates to the structural control of certain types of ore deposits. It has an intimate association with mine subsidence phenomena, and is of concern to the mining engineer. Strata flexure is also the dominant feature of roof behavior about longwall workings. An improved understanding of strata flexure through a rational mechanical analysis thus appears desirable not only from the academic view but from the economic one as well. In the field, the most commonly observed feature of folding, subsidence, and longwall roof behavior is the permanent and therefore inelastic nature of the strata movement. Fig. 1 illustrates the physical disposition of strata in the vicinity of a longwall face. Inasmuch as most rocks (with the possible exception of certain evaporites) do not exhibit significant viscoelastic behavior, at least not over time spans of engineering interest, a plastic analysis is indicated. The analysis is meant to apply to strata whose deformation is dominantly that of bending such as might be expected in the remote roof about a longwall face.

Jan 1, 1970

By K. C. Strebig, C. W. Schultz, A. A. Selim

The effect of some organic additives in diamond drilling of quartzite was investigated in the laboratory. The drill was designed to measure the rate of penetration, the thrust, and the torque and to record each as a function of the distance drilled. A statistical plan was followed throughout the investigation and an equation representing the bit performance was derived from the mathematical theory of reliability. The drilling torque was found to increase with the use of additives while the sliding coefficient of friction and the wear coefficient decreased. The energy per unit volume consumed was found to increase with the use of additives. A hypothesis explaining the effects achieved with the additives is given. INTRODUCTION For some time researchers have attempted to increase drilling efficiency by adding certain agents to the flushing medium. Much of this interest is the result of the observations of Rehbinder, Shreiner and Zhigach1 They postulated that "...in processes for the mechanical destruction of solids, a region of increased crack formation is created in the deformed layers adjoining that surface of destruction, forming the predestmction zone. The surrounding medium (for example, a liquid) which wets a given solid will penetrate the embryo microcracks of the predestruc-tion zone. Increasing the molecular affinity of this liquid for the surface of the solid considerably facilitates the deformation and destruction by softening the solid in the zone of increased crack formation. In this manner, the hardness or strength of the deformed body is decreased by the influence of the penetration of the liquid into the predestraction zone." This is known as the "Rehbinder effect". Rehbinder's work has prompted many investigators to examine the effect of additives on the mechanical destruction of rocks. Engelmann, Terichow and Selim reported that the maximum penetration of the rock by a diamond point in a solution environment was at the isoelectric point of the solution.* Robinson reported that his results did not appear to support the theory of Rehbinder.3 Joris and .McLaren suggested that additives with surface tension lower than water will be more efficient in cooling the diamonds.4 Their effectiveness in removing the fine cuttings from the face of the bit will also improve the efficiency of the system. They reported an improvement in impregnated bit life and penetration rates with the use of soluble oil additives. In contrast, Long and Agnew, drilling with surface set bits, reported that lubricating agents increase bit temperature and wear.5 A significant change was reported6 in the mechanical properties of rock with polar additives. It was concluded that this change in the mechanical properties of the rock in the presence of the additive is due to the rock hydrophilic properties. Ethylene glycol, glycerine and anionic detergent were selected for this investigation because their surface tension is lower than that of water. The surface tension of these additives for the concentrations studied was 42 to 75 percent of the surface tension of water. A low surface tension additive would wet the surface of the diamonds more easily and hence would be more effective in cooling the diamonds. Another characteristic of these low surface tension additives is their effectiveness in removing the cuttings and preventing the flocculation of the formed particles in the drilling process. This article summarizes the results of an investigation performed at the laboratories of USBM, Twin Cities Mining Research Center. The objective of the investigation was to study the over-all effects of some organic additives on the performance of diamond impregnated bits in atmospheric drilling conditions only and not in downhole pressured conditions.

Jan 1, 1970

By Charles W. Goodale, William A. Akers

The treatment of silver-ores of too low a grade to justify either smelting or preliminary roasting, and yet not " free" enough to permit of raw amalgamation, has ever been a serious problem. As bearing upon it, the operations of the Combination Mining and Milling Company of Black Pine, Deer Lodge county, Montana, during the past year may not be without interest. It is not claimed that the process to be described is not susceptible of great improvement, nor is any claim of originality made for it; but its use is, as yet, not very general, and it seems to offer a means of profitably working the large class of partially-decomposed argentiferous ores which, by reason

Jan 1, 1890

By Robert F. Mehl

THIS essay is an attempt to present the elementary facts and ideas concerning the growth of crystals, especially of metals. Freezing, like all heterogeneous processes, is a process of nucleation and growth; it manifests itself in metallurgy primarily in the freezing of ingots. The preceding paper in this volume discusses nucleation; the paper to follow describes ingot solidification. The present paper will treat of the growth of nuclei to large crystals, embracing a long series of phenomena, many of which are familiar to metallurgists.† Crystal growth, it will be immediately noted, occurs not only in the freezing of metals, but in the freezing of all substances; and it is a prominent and familiar phenomenon in crystallization from solutions, aqueous or otherwise, and in crystallization from the vapor phase. It will be necessary to include such systems in this discussion, for so much of value to metallurgists has been learned from their study. Apart from this, so far as metals are concerned, it will be simpler to limit the discussion to the freezing of pure metals and of solid solutions. Other types of freezing-eutectic, peritectic, etc.-will be excluded, though they have much of interest and of importance. BASIC MECHANISM OF FREEZING Ideally, nucleation and growth processes can best be considered from the point of view of isothermal reaction and upon the assumption of random nucleation. In. such an ideal case, nuclei form at random, and at a characteristic rate either constant or changing with time, and grow to spherulites at a characteristic rate, constant or changing with time, Fig. I.. On the simplest assumption, the reaction rate-in this case the rate of freezing-is a resultant of these two component rates. The reaction rate equation may be written in terms of these two component rates. The formation of pearlite from austenite closely approaches this ideal case. The ideal case forms a very useful point of departure in considering real cases. Various factors of reality produce deviations from this assumed ideality. In freezing, the isotropic medium, the melt, passes to the anisotropic solid, the crystal. Crystals are lattices of atoms, and the unit cell is often referred to as a crystal unit. Rosenhain, many years ago, represented the nucleation and growth process on freezing in the manner shown in Fig. 2, feeling, intuitively, that there must be some crystal unit in crystal growth. It now appears that this may be true, though his picture requires much elaboration. The greatest deviation from ideality lies in the nonisothermal nature of the freezing process in metals. To approach this properly it should be recalled that many nonmetallic substances freeze slowly. Tammann, to whom we owe the classic approach, studied complex organic materials in which (as in the case of eutectoid steels at high

Jan 1, 1951

By Richard O. Carlson

Ions of p31 and B 11 were implanted in natural insulating diamond macles. The thin (-0.4µ) layers showed sheet resistances of 107 to 1011 ohm per sq and activation energies of 0.17 to 0.34 ev above room temperature. However, no Hall effect could be measured, indicating that mobilities were less than I to 10 sq cm per (v-sec). Such low mobilities may be due to excessive scattering due to radiation damage in the bombarded layer or to very high concentrations of active compensating impurities. Annealing did not materially change the room -temperature properties, but the temperature was limited to -800°C by surface graphitization, the latter process probably being accelerated by lattice damage in our diamonds arising from the ion bombardment. A weak n-type thermoelectric power was detected after p31 irradiation, but it cannot be presumed that we have made the phosphorus ions active as donors in diamond. The natural diamonds have a high and uncontrolled concentration of impurities and, when coupled with the radiation damage and graphitization problems, would appear to seriously limit the quality of semiconductor that we can presently achieve by ion implantation in diamond. ALTHOUGH diamonds are usually thought of as insulating in terms of their electrical conductivity, it was found about 15 years ago that natural semiconducting diamonds do occur rarely, and these were designated as type IIb diamonds. These p-type semiconducting diamonds were found to be dominated by an impurity level 0.37 ev from the valence band. Evidence today based on correlation of the concentration of acceptor states from Hall effect measurements with the impurity concentrations determined by neutron activation analysis point to aluminum as the dominant acceptor impurity.' The compensating donor is believed to be nitrogen, which has a donor level 1.6 ev above the valence band.' However, only a small fraction of the total nitrogen content in the diamond is electrically active. An infrared absorption band at 7.8 p and ultraviolet absorption near 4 ev have been associated with nitrogen, the former providing a quantitative measure of nitrogen content.3 The nitrogen content is -l020 cm-3 in insulating or type I diamonds, but is less than 10'' in natural semiconducting diamonds. Much of this nitrogen is distributed in platelets oriented in (100) planes and not atomically dispersed in the diamond lattice.4 Semiconducting diamonds have been deliberately formed by incorporating impurities into the graphite charge in the high-pressure apparatus used to form diamonds.5 These manufactured semiconducting diamonds are always p-type, and while some show the 0.37 ev level due to aluminum, most such samples have been ascribed to impurity banding effects.6 The best natural or manufactured semiconducting diamonds have hole mobilities near 1500 sq cm per (v-sec) at room temperature, and those with the 0.37-ev level can be analyzed to reveal an acceptor concentration of 3 to 8 X 1016 cm-3 and a donor concentration 3 to 10 times lower.' NO bulk n-type diamonds have ever been reported, but the electron mobility has been measured as 1900 sq cm per (v-sec) by irradiating a diamond with ultraviolet to excite electrons out of the deep nitrogen donor level or other levels.7 New hope for the formation of n-type diamond has emerged from the ion-implantation method whereby desired impurities are introduced into a crystal lattice by bombardment with a high-energy beam of the impurity ion. It was found in the case of silicon that the usual donors such as phosphorus and arsenic and acceptors such as boron and gallium could be implanted into silicon. Wentorf and arrow' produced semiconducting layers on diamonds by an ionic bombardment in a glow discharge at potentials of about 2 kv. The observed typeness from thermoelectric probing seemed to depend on the atmosphere gas (nitrogen, argon, or hydrogen) rather than on the electrode material, but the nature of the conduction process in the thin damaged surface layer is completely unknown. A Russian group under Vavilov has attempted high-energy ion implantation in natural diamonds using boron and lithium ions9 and later also phosphorus, aluminum, and carbon ions.10 Their papers claim n-type layers from lithium, phosphorus, and carbon implant and a p-type layer from boron and aluminum implant, though the methods of type determination are not described in detail. Under government contract support, the Ion Physics Corp. has studied ion implantation in several semiconductors. While the bulk of their study1' was devoted to the irradiation of silicon, they did carry out a short study on boron and phosphorus implantation into natural diamonds. They did observe surface conducting layers but did not determine the typeness of the layers. For our experiments, phosphorus and boron were chosen as the dopant ions because of their respective donor and acceptor behavior in germanium and silicon. Moreover, they are the lightest mass dopants of the shallow level donors and acceptors from columns 111 and V of the Periodic Table (excluding nitrogen which is already present in diamond), and will have the largest depth penetration into the diamond lattice. EXPERIMENTAL Diamonds. As the target diamonds for our ion implantation study, we chose commercially available macles, which are flat, twinned diamond crystals. By scanning through the stock of a wholesale distributor

Jan 1, 1970

By J. W. Pugh, J. D. Nisbet

THIS study of the ternary has been made as one phase of a metallurgical investigation which began nearly four years ago in the General Electric Company's Research Laboratory in Schenectady, N. Y. The objective of this program is the discovery of new metallurgical information which will lead to the development of better high-temperature materials. Combinations of the four pure base elements—iron, chromium, nickel, and cobalt—are being studied at the present time. It is essential in an investigation such as this to know as much as possible about the constitutional diagrams involved. The study of the iron-chromium-nickel system has been made to this end. Preliminary Explanation of Experimental Procedure: In all, fifty-five alloys at steps of 10 at. pct were made for the investigation of this ternary. Several ternary alloys in the chromium rich corner had to be omitted because their extreme brittleness made testing impractical. All alloys were vacuum melted with hydrogen reduction and centrifugally cast. The apparatus and technique of this process has been described in detail by Nisbet.1,2 The purity of the alloys prepared in this way is considered to be quite good. Impurities are listed as follows: Pct Carbon.............................0.02 Oxygen................................0.02 Nitrogen.........................0.005 Magnesium..................0.03-0.05 Sulphur...........................trace Hydrogen....................trace Phosphorous..................trace Silicon........................ trace After casting, all samples were given a homo-genization treatment which consisted of holding them for 15 hr at 1150°C (2100°F) and water quenching. Testing was begun with the samples in this condition. The tests employed in the study of this system were (1) dilatometer, (2) hardness versus aging temperature, (3) tensile strength and elongation versus temperature, (4) microstructure analysis, and (5) electrical resistance versus temperature. Dilatometer tests were made at the rather rapid heating rate of 1093°C (2000°F) in one hour on a Bristol-Rockwell type instrument. Hardness data were taken on specimens cooled from 204", 427", 649°, 760°, 871°, 982°, and 1093°C under conditions which are thought sufficient to bring the specimens to equilibrium in all but the cases of the very sluggish transformations. Electrical resistance data for several specimens were taken for both heating and cooling conditions in a vacuum furnace especially designed for this work by D. W. Bainbridge, formerly of this laboratory. Provisions were made for heating and cooling standard specimens at a constant rate, while autographic records of resistance and temperature were made simultaneously. Micrographs of all the alloys were made in the quenched condition. Some question may exist as to how such physical values as hardness, tensile strength, and elongation were interpreted to indicate a change in phase. Original data were recorded on physical property versus temperature graphs, each of which was made from the data of a single alloy (fig. la). From these, another series of graphs were plotted with the physical property as a function of composition for constant temperatures (fig. 1b). Sharp deviations in the slope of these composition versus hardness curves often indicate a change in phase. The example of fig. 1 will serve to describe this experimental technique. The plotting of a single point from graph "a" to graph "b," and finally to the phase diagram "c," is illustrated. The location of the point on graph "b" is indicated as point (1). If all the alloys of the A-B binary system were solid solutions at temperature X, the hardness in this curve would be expected to rise at a fairly even rate as A is diluted with B to a maximum at some intermediate value between A and B, as

Jan 1, 1951

By E. D. Levine

A study was made to delineate the dislocation mechanistns controlling prismatic and basal slip at low temperatu.ves in titanium containing approximately 100 ppm interstitial impurities. Mechanical tests were performed on single crystals prepared from electron-beam zone-refined crystal bar by a thermal cycling technique. Measurements were made of critical shear stress and activation volume as functions of temperature. The study revealed that, for prismatic slip, two overlapping thermally activated processes aye rate-controlling below 300°K. From absolute zero to 220°K, reasonable agreement is obtained between experiment and the mechanism which involves overcoming 01. the Peierl's stress by the formation of double kinks in dislocation lines lying in close-packed directions. Between 220°and 300°K prismatic slip is controlled by a difierent thermally activated process which is characterized by a stronger temperature dependence of critical shear stress. Above 300OK, prismatic slip is controlled by an athermal process. Basal slip is controlled by a thermally activated process between 195' and 400°K. An approximate analysis suggests that it is the Peierl's mechanism that is rate-controlling in this range. Below 195°K, the occurrence of mechanical twinning obscures the features of basal slip. Above '400 X, basal slip is controlled by an athermal process. TITANIUM, an hcp metal with a less-than-ideal axial ratio of 1.587, deforms primarily by {1010}( 1210) slip at low temperatures.'-3 The critical shear stress is strongly affected by the presence of interstitial impurities. For example, churchman3 reported that a decrease in the combined nitrogen plus oxygen content from 0.1 to 0.01 pct decreased the critical shear stress for prismatic slip from 9.19 to 1.4 kg per sq mm at room temperature. Basal slip, however, is less strongly affected by interstitials; Churchman's data for {0001}( 1210) slip show a smaller decrease in critical shear stress from 10.90 to 6.3 kg per sq mm at room temperature, for the same decrease in interstitial content. In the present study, an attempt has been made to delineate the dislocation mechanisms controlling prismatic and basal slip in titanium. In view of the strong effects that impurities may have on at least some of these mechanisms, experiments were performed on material of reasonably high purity, so that comparisons could be made with investigations on material of both lower and higher impurity contents. EXPERIMENTAL PROCEDURE Single crystals were prepared from 1/4-in.-diam electron-beam zone-refined crystal bar, furnished by Materials Research Corp. The analysis of the zone-refined material is given in Table I, indicating that the interstitial content is of the same order as the purer of the two materials investigated by Churchman. The Vickers diamond pyramid hardness number of this material was 85.6. This value agrees quite well with the correlation between hardness and interstitial content proposed by Ogden and Jaffee.4 On the basis of hardness, the material investigated in this study is, therefore, intermediate in purity between that studied by Churchman (Vpn = 97) and that studied by Spangler and Herman (Vpn = 62.4).5 Single crystals were grown by thermal cycling through the a-ß transformation. Two-in.-long by 1/2-in.-diam bars were heat-treated in vacuum for 4 hr at 1160°C. The temperature of the furnace was then lowered to 865°C, and the specimens were maintained at this temperature for 7 days. This procedure was repeated several times, resulting in the growth of individual crystals up to 14 in. in length. Specimens for testing in direct shear along either {l010}(1210) or {0001}(1210) were obtained by electrical-discharge machining. The specimens were in the form of cylinders 1/4 in. in diam by approximately 1/2 in. in length, with a reduced section 1/8 in. in diam and a in. in length. All specimens were electropol-ished subsequent to electrical-discharge machining. The ends of the test specimens were cemented in stainless-steel collars. Shear tests were conducted in an Instron Tensile Tester at various temperatures from 4.2° to 508°K. Measurements were made of critical shear stress and activation volume. The latter measurements were performed by measuring the change in flow stress upon cycling the strain rate between ?1 = 2.62 x 10-3 per sec and ?2 = 2.62 x 10-4 per sec. Activation volume, I)*, is defined as u* =ßkT [11

Jan 1, 1967

By Zay Jeffries

It has been known for centuries that iron and steel could be hardened by cold hammering and that the metal could be restored to the normal condition by heating to a red heat arid cooling, either rapidly or slowly with nearly pure iron, but slowly with steels containing considerable carbon. The art of tempering steels is also very old. When a medium- or high-carbon steel is quenched from a cherry-red heat, the hardness is increased; this hardness can be reduced by heating to various temperatures below the lower thermal critical point,, which is near 700" C. The present paper will not consider these old and well known changes in iron and steel below the thermal critical range but will confine itself to the more unusual changes, some of which have been studied recently. Stromeyer,1 for example, In 1886, reports that both working steel and heat treatment of steel in the blue-heat range arc highly injurious. Recently, however, some metallurgists believe that the straiglltening of warped steel forgings at a blue heat produces a beneficial effect on the metal2 The Engineering Division of the National Research Council has constituted a committee on Physical Changes in Iron and Steel below the Thermal Critical Range, which has the following personnel: K. R. -Abbott, H. C. Boynton, William Campbell, J. V. Emmons, F. B. Foley, H. J. French, H. M. Howe, Zay Jeffries (chairman), F. C. Langenberg, J. A. Mathews, P. D. Merica, A. H. Miller, J. H. Nelson, G. A. Reinhardt, W. E. Ruder, H. F. Wood. This committee is studying several aspects of the physical changes in iron and steel. The results, reported in the literature and obtained by recent experimentation, will be given; this will be followed by a general theoretical discussion of the more important

Jan 1, 1922

By Zay Jeffries

It has been known for centuries that iron and steel could be hardened by cold hammering and that the metal could be restored to the normal condition by heating to a red heat arid cooling, either rapidly or slowly with nearly pure iron, but slowly with steels containing considerable carbon. The art of tempering steels is also very old. When a medium- or high-carbon steel is quenched from a cherry-red heat, the hardness is increased; this hardness can be reduced by heating to various temperatures below the lower thermal critical point,, which is near 700" C. The present paper will not consider these old and well known changes in iron and steel below the thermal critical range but will confine itself to the more unusual changes, some of which have been studied recently. Stromeyer,1 for example, In 1886, reports that both working steel and heat treatment of steel in the blue-heat range arc highly injurious. Recently, however, some metallurgists believe that the straiglltening of warped steel forgings at a blue heat produces a beneficial effect on the metal2 The Engineering Division of the National Research Council has constituted a committee on Physical Changes in Iron and Steel below the Thermal Critical Range, which has the following personnel: K. R. -Abbott, H. C. Boynton, William Campbell, J. V. Emmons, F. B. Foley, H. J. French, H. M. Howe, Zay Jeffries (chairman), F. C. Langenberg, J. A. Mathews, P. D. Merica, A. H. Miller, J. H. Nelson, G. A. Reinhardt, W. E. Ruder, H. F. Wood. This committee is studying several aspects of the physical changes in iron and steel. The results, reported in the literature and obtained by recent experimentation, will be given; this will be followed by a general theoretical discussion of the more important

Jan 1, 1922

By Laurence Pellier

Electron microscopical studies were made of the effect of sensitization at 1200oF on a Type-.104 stainless steel with high carbon and low nitrogen and oxygen contents, after solution annealing and after cold working. The loci of the carbide precipitates in the early stages of sensitization were followed in dry stripped plastic replicas. Some observations were made by direct electron transmission on thinned films. Intragranular dislocations showed a high degree of stability through the annealing necessary to produce sensitization. I HE present work was undertaken to determine the effect of sensitization, at 1200°F, for 1/2 hr, on the electron microstructure of a Type-304 stainless steel with high carbon, and low nitrogen and oxygen contents, after solution annealing and after cold working. Many electron microscopical studies of sensitization of 18-8 stainless steels have already been made. Most of them utilized extraction replicas, from which the morphology and composition of the precipitated carbides could be established.'-" ry stripped replicas were seldom used for such studies, although it was demonstrated that they are applicable, in general, to EurveYs of the general microstructure of many alloys' and, in particular, to the observation of precipitated carbides in austenitic stainless steels.3

Jan 1, 1963

By N. J. Sather

A detailed description is given of Bunker Hill's concentration process employed at the company's lead-zinc property in the Coeur d'Alene district, Idaho. The plant is equipped to process 3000 tpd of Pb-Zn ore. The history of the Bunker Hill mine dates back to Aug. 26, 1885, when Noah S. Kellogg found the outcrop of the Bunker Hill orebody on the hillside of Milo Gulch above the present town of Wardner, Idaho. A small concentrator was erected in 1886, and before the railroad came, the mine output was transported by mule teams to the head of navigation on Coeur d'Alene Lake. After ten years of production, an interest was purchased in the Tacoma smelter at Tacoma, Wash., to which the entire output was shipped. In 1916 and 1917, a modern lead smelting plant and refinery was erected, and a modern electrolytic zinc reduction plant was built in 1927-1928 by the Sullivan Mining Co. which was 50 pct owned (and now totally owned) by the Bunker Hill Co. The first concentrator, a 100-tpd capacity plant, was built in 1886 near the Reed Tunnel in Wardner. The treatment consisted simply of crushing ore to 2 in. and then to 1/2 in. through rolls in closed circuit with a bucket elevator and trommel screen. The undersize was further sized in trommels to 10 mm and 3 mm. Oversize from the latter was treated in Hartz jigs. The 3 mm undersize was classified in crude hydraulic classifiers furnishing sands to sand jigs, the overflow being dewatered in a long V tank which supplied sands to a Cornish buddle and to Frue vanners. The concentrates were of excellent grade, old records showing assays of 69 pct lead and 29 oz. of silver per ton. Tailings were high inasmuch as the provision for treating the slimes was inadequate. Since the erection of the first mill, the Bunker Hill plant has gone through many changes and improvements. In succeeding years, the flowsheet was enlarged somewhat with Huntington and Chilean mills, vanners, tables, ball mills, and flotation cells being progressively added. In the transition period to the present day practice, the object was not only to improve the equipment for better mechanical performance, but to add new equipment whenever practicable so as to improve both grade and recovery of the product at a lower cost. For the modern plant and flow-sheet, see Figs. 1 and 2. The history of flotation at Bunker Hill dates back to 1913 when experimental work was done in a cell in which the pulp was circulated through a centrifugal pump set outside the cell and discharged against a baffle in the cell. The cell was built with a spitzkasten, and the quiet zone in the latter tended to let the froth break down before it got to the overflow weir. To remedy this situation, a belt drag with light metal flights was arranged for drawing off the froth over a ramp in each cell. Recovery of lead was not as high as present day practice, but was so much better than the vanners that the cells were multiplied gradually to eight cell units. The mill men called them mud hens. Flow between the cells was controlled by a weir, which determined the pulp level in each cell. These early machines were called Bunker Hill machines. The tailings were later treated in pneumatic scavenger flotation machines in a series, producing concentrates for retreatment in the Bunker Hill cleaners as well as the final tailings. This system of flotation served with minor changes until the Fahrenwald machine was developed at Bunker Hill during the period from 1921 to 1925. In 1925, the Fahrenwald flotation machine gradually replaced the Bunker Hill machine, although the Hearing pneumatic scavengers for retreatment of the tailings from the Fahrenwald machines were retained in the lead section until 1928. The use of the Hearing pneumatic machine for cleaning the rougher concentrates was begun in 1924. In 1941, plans were made for remodeling and modernizing the concentrator, the goal being a modern concentrator employing the latest equipment and milling practices. The old wooden building was to be replaced by a steel and concrete structure. Shortly after preliminary work got under way, the United States entered World War II and the demands for metals increased. To meet this requirement, the management decided to increase the capacity of the concentrator to 1800 tpd. This was accomplished in record time by the construction and operation of a sink-float plant. Installation of this plant was the first step in the general plan for modernization. In 1947 the concentrator (including the sink-float plant) was enlarged to handle 3000 tpd. Milling operations today are at the rate of 2300 tpd, five days per week. During 1959, 453,000 tons of ore was beneficiated. The Bunker Hill concentrator is in three sections: the crushing plant, a 3000-ton capacity storage bin, and the concentrator building. The crushing plant is of wood design with a gunnite coating on the exterior.

Jan 1, 1961

By M. D. Curran

AS applied to coal, the term processing is subject to many interpretations. To some it means preparation of coal for the market by mechanical means such as crushing, sizing, washing, or treating with oil or chemicals to eliminate dust or improve combustion quality. To others it means conversion of the coal to other commodities as in carbonization to produce coke and by- products, or to liquids by application of the hydrogenation process. I prefer to classify the various forms of mechanical treatment under the heading of beneficiation and apply the term processing to those methods of treatment that destroy the coal sub- stance through distillation or hydrogenation.

Jan 1, 1939

By B. W. Howlett, M. B. Bever, Somnath Misra

The heats of Formation of the compounds Sb2Se3, Bi2Se3, Sb2Te3, and Bi2Te3 and the heats of solution of tellurium and selenium in liquid bismuth have been measured in a liquid metal solution calorimeter. The heat capacities near the melting point, the heats of fusion, and the melting points of the two tellurides have been measured in a constant temperature gradient calorimeter. The thermo-dynamic quantities are interpreted in relation to the stability of the compounds and the nature of the solid-liquid transition. THE selenides and tellurides of several elements of Group VB of the periodic system are of interest because of their electronic properties. The compounds Sb2Se3, Bi2Se3, Sb2Te3, and Bi2Te3 are semi- conductors; they also have gained prominence in the fields of thermoelectricity and photoconductivity. However, little is known about their thermody-namic properties. As part of a research program on the thermo-dynamic properties of intermetallic compounds, the heats of formation of the compounds Sb2Se3, Bi2Se3, Sb2Te3, and Bi2Te3 were measured in a liquid metal solution calorimeter. The heat capacities near the melting point, the heats of fusion, and the melting points of the two tellurides were measured in a constant temperature gradient calorimeter. The results, in addition to their intrinsic interest as thermodynamic quantities, contribute to an understanding of the stability of the compounds and the nature of the solid-liquid transition. 1) EXPERIMENTAL 1.1) Materials. Samples of the compounds SbzSe3 and Bi2Se3 were prepared by melting the elements in stoichiometric proportions in evacuated Vycor capsules followed by quenchinn in water. They- were then annealed in vacuum for 12 hr at 550°C. A sample of Sb2Te3, consisting mainly of one large grain, supplied by the Lincoln Laboratory,

Jan 1, 1964

By A. A. Bauer, F. A. Rough, G. H. Beatty

AS a result of recent studies, the constitution of the zirconium-uranium system has been fairly well defined. A diagram for the system is shown in Fig. 1. However, both oxygen and nitrogen are known1-3 to have a pronounced effect on the limits of both ß- and e -phase regions. It has been shown that small amounts of oxygen severely constrict the compositional limits of these phase regions in the ternary zirconium-uranium-oxygen system. A previously published tentative diagram shown in Fig. 2 illustrates the ß-phase constriction resulting from oxygen additions. Generally, iodide zirconium has been used in constitutional studies of zirconium-uranium alloys. While this is the highest purity material available, cast iodide zirconium-uranium alloys will generally average from 200 to 300 ppm 0 and from 50 to 60 ppm N. Thus, while the constitution of the zirconium-uranium system is fairly well defined, it must be realized that this definition applies to alloys containing in the vicinity of 250 ppm 0 and 50 ppm N. The present investigation was undertaken to accurately determine the boundary between the ß-plus-P and ß phases at a single temperature in the binary zirconium-uranium system by quantitatively

Jan 1, 1959