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By D. S. Sanders, E. W. Witcomb

FLOTATION tests, from which the flowsheet for the concentrator was determined, were made in a pilot mill at Chuquicamata and later comparative testing of full size flotation cells was done at the Andes Copper Mining Co. concentrator in Potrerillos. The principal sulphide copper mineral is chalcocite with varying amounts of covellite, enargite, and chalcopyrite. The oxidized portion is principally antlerite, a green basic copper sulphate. The gangue minerals include quartz, sericite, pyrite, feldspars and kaolin. Chuquicamata pit ores have proved to be hard grinding. The results of the flotation and metallurgical work prove that good extraction and concentrate grade can be obtained under a rather wide range of conditions. Metallurgy In general the metallurgy of the ore requires a fairly close control of the grind to the primary rougher flotation and of the regrind of the primary rougher concentrate before cleaning. Regrinding is necessary to reduce the insoluble content of the final concentrate since a large part of the middling combinations are between the copper and silica minerals. The alkalinity of the pulps can vary between wide limits and control of the percent solids gives the desired grind. Alkalinity Control Arroyo Salado water is supplied to the concentrator head tanks. It contains about 5000 ppm of salts but test work shows no deleterious effect. Actually this water permits a decrease of as much as 1 lb of lime per ton of ore as compared to San Pedro water, which is used for leaching oxide ore. About one quarter of the water flow through the concentrator will be new water from the reservoir. The remainder will be reclaimed from the thickeners. For primary grinding and rougher flotation, new and reclaimed water are combined in the head tanks. To avoid erratic results, only new water is used in the regrind system. Milk of lime is added to the rod mill feed chute to obtain the maximum benefit of mixing with the ore. This protects the equipment from corrosion due to entrained acids and soluble copper salts. Lime consumption is 3 to 5 lb per ton of ore. Grinding and Flotation The six bin gates over each belt feeder are opened in controlled combination and sequence to keep a live bed of ore in the bin to prevent arching and to obtain mixing. The milk of lime added ahead of the rod mill is regulated to suit rougher flotation requirements. The primary promoter reagent, Aerofloat 238, is added to the 10-mesh discharge of the rod mill as it is laundered to the ball mill scoop box. The classifier overflow is regulated to produce a grind of about 12 to 15 pct +65 mesh and 60 pct -200 mesh. A secondary promoter Z-4 (aml zanthate) and the pine oil frother are added in the overflow launder where a pH of 10 to 11 is maintained. Comparatively heavy beds of froth on the

Jan 1, 1952

By Gerhard Derge

THE extension of metallurgical control of steelmaking processes has always made it desirable to have some quick method for determining the oxygen content of molten steel. To meet the practical demands of the steel industry, this method must also be simple enough so that the sampling can be done by the regular furnace crew. This requirement was kept in mind continually in the work to be described. An oxygen value is required for proper control, whether it be of a rimming steel or of a fully killed steel. However, two factors have discouraged the development of such direct methods: I. The reaction C + FeO -+ Fe + CO is rapid enough to make the correct sampling of the bath a difficult problem. The most generally accepted means of circumventing this difficulty have been the aluminum-killed bomb test of McCutcheon and Rautio1 and the aluminum-killed spoon test of Herty.2 The theory of these tests is that all of the oxygen in the iron is converted to A1203, which can then be determined by chemical methods. Even when simplified so that the analysis is made by a measurement of turbidity, this method is too slow to be used in routine control. Furthermore, the results obtained have never been entirely satisfactory, and some of the reasons for this will be discussed later in this paper. 2. The ordinary chemical methods of analysis for oxygen in steel are not reliable. The only analysis that seems to possess sufficient dependability to be of value is vacuum fusion,3 and the apparatus and technique developed for this have been too complex and slow for routine work. INDIRECT METHODS Indirect methods of estimating the oxygen have been resorted to in mill practice. Generally these depend upon the chemical equilibria involved. The oxygen in the bath is related to other components in the slag or metal that can be analyzed more readily. These methods have many difficulties in common. Steelmaking processes involve a complicated set of interrelated reactions, all of which tend to approach equilibrium at varying rates. The degree to which any particular equilibrium is approached, is not , well established. Moreover, a proper use of theoretical equilibrium constants requires a more extensive knowledge of the activities of the reactants than we now have. This is well illustrated by the irregularities observed when trying to determine the oxygen in the metal by its ratio to the iron oxide in the slag. Equilibrium relations may be used more readily if they are evaluated by plant experience, but the extent of approach to equilibrium remains an undetermined variable and lack of an entirely satisfactory means of determining oxygen for the calibration is felt keenly. For example, the statistical analysis of the relation between carbon and oxygen4 5 illustrates that even in a single plant wide variations exist under normal conditions of operation. Nevertheless, this is one of the best methods now

Jan 1, 1943

By E. P. Dahlberg, R. E. Reed-Hill

On the assumption that stress or strain relaxation occurs as the result of a thermally activated process, equations are derived relating to tensile experiments that give the strain as a function of the time under the condition of constant stress, and the stress as a function of the time for constant strain. It is demonstrated that if the strain-rate equation i = previously proPosed by Kuhlmann., is used as a starting point, then the relaxation of strain at constant stress may be expressed by the equation c = (-RT/(Y) 1tz tanh (t + is the strain capable of being relaxed at any given instant. Similarly, it is shown that the relaxation of stress at constant strain may be given by a = (-RT/B) In tanh (t + t0)/27, where a is the instantaneois value of the relaxable stress. The fact that these relationships reduce to well-known empirical equations at both large and small values of the stress Or strain is also shozcn. The present theory is shown to agree well with experimental data obtained from tensile elastic aftereffect experiments on a zirconium specimen prestrained at 77 k as to make it strongly anelastic. It is also demonstrated that elastic aftereffect data obtained using torsional specimens ?,Lay agree reasonably well with the equation derived for the case of tension. RELAXATION experiments are often employed as a means of studying metallic deformation mechanisms.' The simplest and most commonly employed techniques involve stress relaxation at constant strain and strain relaxation at constant stress. In general, however, investigations of this nature have been seriously handicapped in the past by a lack of suitable equations giving the time dependence of the relaxing variable over an interval that extends from small strains up into the region where internal-friction experiments become strain-amplitude dependent. This paper presents a derivation of such a set of equations for the case where the time-dependent part of the strain is anelastic or recoverable and the specimens are loaded in simple tension. The relaxation of strain under the condition of constant stress will be considered first. Let us assume that strain relaxation occurs as the result of a reversible thermally activated process that occurs at a number of relaxation centers lying in an elastic matrix. Then, following Kuhlmann,2 we may express the rate of strain relaxation as follows: where C is the strain rate, AFx the free energy of activation of the process controlling strain relaxation, a, the effective or average resolved stress at the relaxation centers, u an activation volume, R the universal gas constant, T the absolute temperature, > a factor with dimensions of a volume that accounts for the strain contribution of a successful operation of a unit process, N the number of relaxation centers per unit volume, and v the Debye frequency. The first term on the right of Eq. [I] represents a strain rate in the direction favored by the stress, while the second term represents the rate in the opposite direction. It is implied in Eq. [I.] that both F and v are symmetrical with respect to the two basic directions of operation of a relaxation process. Eq. [I] may also be written where and S and Q are the activation entropy and activation energy, respectively, of the relaxation process. In the following, A will be considered a constant. This is compatible with a set of experimental conditions where the relaxation rate is controlled by a single basic reversible process in which it may be assumed that the temperature dependence of the product ?Nv is negligible in comparison with the temperature variation of the exponential term. It is also implied that v, 7, and N do not depend strongly on a, . In deriving a relationship for the strain as a function of the time from her equation, equivalent to Eq. [2], Kuhlmann2 chose to consider only the limiting cases where the time was either very small or very large. It will now be shown that it is possible to integrate Eq. [2] to obtain a single equation valid over a wide range of strains if the concept of relaxable strain is introduced. The use of this quantity, which is the difference between the instantaneous value of the strain and the value of the strain at complete relaxation, represents the primary point of departure of the present theory from that of earlier workers. Let us express the effective stress at the relaxation centers in terms of strain. For this purpose we may use the following equation derived by zener3 for the case of strain relaxation at slip bands: where M? and M are the relaxed and unrelaxed moduli respectively, go the applied constant tensile stress, and m an average orientation factor that takes account of the fact that a,, the effective stress at the relaxation center, may not be a tensile stress (i.e., a

Jan 1, 1967

By G. C. Gardner

A new correlation of blast penetration in model and operating blast furnaces is presented which overcomes objections to prevzous correlations. It is shown that the tuyere diameter is only of small importance in determining the magnitude of the penetration. The data from operating furnaces correlate satisfactorily with the data from models whose cross section is a segment of a circle. A bubble-shaped gas space called a "raceway" normally exists in front of the nose of a blastfurnace tuyere. The periphery or "wall" of the raceway is well defined and is composed of densely packed charge particles. The blast. issuing as a jet from the tuyere, entrains gas from the raceway, in the usual manner of a jet, as it flows to the opposing wall. There it divides and flows back around the walls to be entrained once more. The blast must, of course, eventually leave the raceway and pass up through the charge column, but before it does it may, on the average, make several circuits of the kind described and in doing so it carries with it charge particles, which, because of their fast and circulating motion, suggested the name of "raceway". A fuller description of the raceway may be found elsewhere."' Here it is only necessary to mention, in addition, the measurement which characterizes its size. If an iron bar is pushed through the opened peepsight of a tuyere, .as far as it will go with ease, it will be stopped by the relatively impenetrable opposing raceway wall arid the distance that the bar has been pushed from the tuyere nose is called the "penetration". This measurement may be of practical importance and has; been the subject, with considerable success, of several attempts at correlation with other variables2-5 as stated in the next section. There is still, however, a serious objection to the most recent correlation,3 which is overcome by the correlation proposed in this paper. It will be shown that the objection is not trivial, in that the new correlation will attribute considerably different importance to the variables affecting the magnitude of the penetration. The data to be treated were made available by Wagstaff and are the same as those used in his correlation. They include measurements taken on small models, in which a cold air blast was used and no combustion occurred, and they also include data from operating blast furnaces at Wheeling and Fairless. The information from the blast furnaces will be shown to be in substantial agreement with those models whose plan views are segments of a circle and which are thus like segments of a blast furnace. First, Wagstaff's most recent correlation3 will be discussed and the objection will be given. Then the new correlation will be developed and its implications considered. CORRELATION OF J. B. WAGSTAFF Wagstaff's correlation is where and D — the penetration D,-the internal tuyere diameter V —the blast velocity in the tuyere

Jan 1, 1961

By H. Eyring, J. W. Fredrickson

Many theories have been advanced to explain the phenomena of elastic and plastic deformation. The object of this report is to present a mechanism for deformation, not radically differing from existing theories, but embodying.certain principles and concepts of these theories. This proposed theory cannot be the complete answer to the age-old problem of deformation but it is believed that it will be a step further in the proper direction. The plastic properties of solids have recently been reviewed by Seitz and Read.' ZenerZ has reviewed and correlated the existing work on the anelasticity of metals. With these and others3'4'5 resent theories of deformation are well-known. Of the many theories now extant, those receiving most attention have been proffered by Griffith,6 Becker,l Smekal,8 Polanyilg Orowanlo and Taylor.'' Although differing quite widely in details, these theories are based more or less on a common principle of flaws or dislocations that exist in the crystal lattice. The effect of stress concentrations surrounding a flaw or crack has been treated most recently by Fisher and Hollomon.12 The various authors differ as to the exact nature of the flaws or dislocations, the causes of their appearance, or the manner in which they initiate slip. All of the theories agree that the number of dislocations increases with progressing deformation. It is universally agreed that the shearing process is not a simple gliding of ideally perfect atomic lattice planes. It is also agreed that the "macroscopic" process of gliding, or slip, is brought about by the spreading of a large number of locally initiated "glide steps" through the whole crystal. The occurrence of these "glide steps" is closely related to the presence of some kind of deviations from the "ideal" lattice structure, even in the undeformed crystal. These deviations are overcome ''one at a time," in a manner of speaking, due to some stress-concentrating effect.13 Proposed Theory Many solids show a continuously increasing deformation if subjected to a constant load of suitable magnitude in an extended range of temperature for a sufficient time. This deformation, or flow, may be said to be due, in general, to the tendency of the atoms or molecules in an elastically stressed body to readjust themselves in such a way that if the deformation were kept constant, a release of stress would take place. If rupture does not occur, this process of relaxation causes the rate of flow to obtain a final constant value, as shown in the curve (Fig I) obtained by Taylor and Quinney.14 In this state the release of stress by relaxation exactly counterbalances the increase due to the elastic strain on the test pieces.

Jan 1, 1949

By J. C. McCarthy, J. B. Stone

At Fresnillo a series of veins that has yielded very large quantities of silver and other metals has been developed over a length of 6500 ft. and to a depth of over 3000 ft. In the course of this work striking changes in the mineralogy and metal content of the principal veins have been disclosed and are well illustrated by assay data and ore reserve calculations. This paper describes those changes and suggests their bearing on theories of ore deposition. Location The Fresnillo mines and the adjacent city of Fresnillo are in the central part of the state of Zacatecas, 35 miles northwest of the capitol city of Zacatecas, once a great silver-mining center whose total production is said to place it fourth in. the world. Another famous old silver district, Sombre-rete, lies northwest of Fresnillo. Fresnillo is connected by a 5-mile branch with Fresnillo On on the Mexican National Railways line from Juarez to Mexico City. Lying near the southwestern edge of the central plateau of Mexico, Fresnillo is Surrounded by a semi-arid rolling plain from which rise widely scattered low hills. One of these is Proano hill, an inconspicuous elevation rising barely 300 ft. above the plain, but in and around Proano hill are the Fresnillo mines, and it is marked now by a great gash cut by glory-hole mining. According to an account written in 1834 by Francisco Garcia, then Governor of the state of Zacatecas, Fresnillo was discovered in 1554, and a presidio was established there in 1568 to protect travelers on the road between zacatecas and sombreretea Little is known of the earliest mining at Fresnillo, which seemingly began soon after its discovery, but by piecing together various accounts, it appears that mines there were working in 1717 and were notably active in 1751 under an administrator named Murguia, who left detailed notes describing them. In I757, however, the mines became inactive because of dificulties with creditors and no doubt also because of increasing water troubles, and they remained abandoned until 1830. In 1830 the mines at Fresnillo became the property of the State of Zacatecas because the interest of Governor Garcia had been aroused by the long disregarded notes of Murguia. Under Garcia's energetic leadership the mines were reopened, and silver production began in 1832 in spite of serious difliculties, including abnormal rains and an epidemic of cholera. In 1835 English capital was sought to allow installation of steam-driven is pumps at the two principal shafts and to build the great hacienda de beneficio (the present Proano hacienda). The company formed in 1835 (Cia. Zacatecano-Mexicana) operated successfully until 1872, when its career was brought to an end by the political and economic disturbances

Jan 1, 1949

By J. C. McCarthy, J. B. Stone

At Fresnillo a series of veins that has yielded very large quantities of silver and other metals has been developed over a length of 6500 ft. and to a depth of over 3000 ft. In the course of this work striking changes in the mineralogy and metal content of the principal veins have been disclosed and are well illustrated by assay data and ore reserve calculations. This paper describes those changes and suggests their bearing on theories of ore deposition. Location The Fresnillo mines and the adjacent city of Fresnillo are in the central part of the state of Zacatecas, 35 miles northwest of the capitol city of Zacatecas, once a great silver-mining center whose total production is said to place it fourth in. the world. Another famous old silver district, Sombre-rete, lies northwest of Fresnillo. Fresnillo is connected by a 5-mile branch with Fresnillo On on the Mexican National Railways line from Juarez to Mexico City. Lying near the southwestern edge of the central plateau of Mexico, Fresnillo is Surrounded by a semi-arid rolling plain from which rise widely scattered low hills. One of these is Proano hill, an inconspicuous elevation rising barely 300 ft. above the plain, but in and around Proano hill are the Fresnillo mines, and it is marked now by a great gash cut by glory-hole mining. According to an account written in 1834 by Francisco Garcia, then Governor of the state of Zacatecas, Fresnillo was discovered in 1554, and a presidio was established there in 1568 to protect travelers on the road between zacatecas and sombreretea Little is known of the earliest mining at Fresnillo, which seemingly began soon after its discovery, but by piecing together various accounts, it appears that mines there were working in 1717 and were notably active in 1751 under an administrator named Murguia, who left detailed notes describing them. In I757, however, the mines became inactive because of dificulties with creditors and no doubt also because of increasing water troubles, and they remained abandoned until 1830. In 1830 the mines at Fresnillo became the property of the State of Zacatecas because the interest of Governor Garcia had been aroused by the long disregarded notes of Murguia. Under Garcia's energetic leadership the mines were reopened, and silver production began in 1832 in spite of serious difliculties, including abnormal rains and an epidemic of cholera. In 1835 English capital was sought to allow installation of steam-driven is pumps at the two principal shafts and to build the great hacienda de beneficio (the present Proano hacienda). The company formed in 1835 (Cia. Zacatecano-Mexicana) operated successfully until 1872, when its career was brought to an end by the political and economic disturbances

Jan 1, 1949

R.. B. T. KILIANI, New York, N. Y.-I do not care to discuss Mr. Taggart's paper in the light of theory, as that has been very well done by Prof. Bell,1 but I should like to criticize some of his conclusions, in the light of actual operating practice at plants all over the country. 1. Mr. Taggart's first conclusion is that in crushing average ore, the character of the gangue has little effect on the efficiency of the mill. This, I believe, is not in accordance with the usual practice, since in crushing a hard ore the capacity will be much reduced below what it would be with a softer ore, while the power consumed will be practically independent of the character of the ore, being proportional only, to the load of ore and balls in the mill. 2. Mr. Taggart's second criticism is that the Hardinge mill is not suitable for grinding soft, tough material. In answer to this I might mention that the mill is being used for grinding tough, dnctile material, such as metallic aluminum, and also for grinding licorice root. 3. He says that the ball-mill works more efficiently on material of intermediate size, say 1/2 to 3/4 in., than on either coarser or finer feed.. This is true as to coarser feed. For the most efficient work, I believe that a ball-mill should be fed with material not coarser than 1 1/2 in.; it' will handle material up to 3 and even 4 in., but the reduction from 3 or 4 in. to 1 1/2 in. can be done much more cheaply and efficiently by rolls or disk crushers than in the ball-mill. 4. As to Mr. Taggart's fourth conclusion, that a greater ratio of reduction can be expected with feed of an intermediate size than with a coarse feed, I have not enough information to express an opinion. 5. His next conclusion is that steel balls are much more efficient crushing media than pebbles. Steel balls are undoubtedly more efficient for crushing coarse feed. On fine material they are also more efficient as to tons per horsepower crushed to 10-mesh, but on fine material I think it will be found that flint pebbles are cheaper than cast-iron balls, per ton of ore, although there will be a saving in power per ton by using cast iron instead of flint. The increased cost of crushing with cast iron will be due to the higher cost of iron at the present time. 6. Mr. Taggart's sixth conclusion coincides with present practice, that steel balls will grind as fine or finer than pebbles when working on the same feed.

Jan 1, 1918

By A. Heim, M. Gondouin

Invasion experiments were run on Berea sandstone cores to get laboratory measurements of resistivity and saturation profiles characteristic of water and oil sands invaded by mud filtrate. Injection rates were as low as 1.13 cm/D, and the cores were 30 to 36 in. long, cut parallel to the bedding planes. In the water-sand case, the resistivity profiles revealed the existence of an extensive transition zone between flushed and uncontaminated zones. In the linear geometry of the experiment, the width of the transition zone increased as the square root of the injected fluid volume. For the oil-sand case the core was prepared by displacing the formation water with kerosene to minimum water saturation. During the subsequent invasion experiment. oil saturation was measured directly by means of an oil-soluble radioactive tracer, and resistivity profiles along the core were taken at the same time. These data were interpreted in terms of an oil-water front, followed by a formation water bank, a zone of mixed waters, and finally, invaded mud filtrate near the borehole. Micro-fingering and capillarity seemed to affect considerably the resistivity profiles observed in the invaded oil-sand experiment. Beyond the regular conductive annulus or "low zone", it was found that a resistive "anti-annulus" could also be formed. As a result of these experiments, some simplified invasion profiles have been accepted and are being used in Grand Slam* interpretations. INTRODUCTION The importance of the mud filtrate-invaded zone in interpreting electrical logs has long been recognized.',* In trying to account for its effect, only very simple models of the resistivity profiles in the radial direction from the borehole have been used. In fact, most log interpretation charts have been based on resistivity models consisiting of two media of uniform resistivity (R, and R,) abruptly separated at the diameter of invasion. Such a clean separation of the media of different resistivities seems unrealistic, since flushing may not be perfect and may vary with radial distance into the formation.3** The nature of the transition zone, when it is within the radius of investigation of the surveying devices, may affect the log readings. Campbell and Martin' verified that a conductive annulus containing a high percentage of formation water may be formed when mud filtrate invades an oil-bearing sand. Interpretations which are to include the effect of such an annulus require the addition to the model of a conductive zone located at the outer rim of the invaded zone.' Using the Buckley-Leverett relations,6 aturation profiles may be derived, from which resistivity profiles can be calculated. Results of such computations by K. S. Kunz and J. H. Moran were given in a paper by Dumanoir. Tixier and Martin,7 and led to the construction of log interpretation charts which were based on a representation with three media of resistivities R, R0 and R1. Fig. 1 shows a schematic representation of a resistivity profile which includes an annulus. Campbell and Martin realized that, during the invasion of an oil sand, both capillarity and mixing would contribute to rounding of the profile shown in Fig. 1. Capillarity tends to draw some of the formation water from the annulus into the uncontaminated (Rt) zone, whereas mixing of the mud filtrate with formation water of the

Jan 1, 1965

By S. A. Spachner

An analysis of the powder patterns of the omega transition phase in three binary titanium alloys containing 8 pct Cr, 13 pet Mo, and 15 pet V, respectively, showed that all could be indexed on an orthorhombic unit cell. The unit-cell dimensions were all quite similar. There is evidence for the occurrence of more than one transition phase in Ti-Cr and Ti-V alloys. FOLLOWING the discovery of a new brittle phase in certain titanium-chromium alloys by Frost, Parris, Hirsch, Doig, and Schwartz,' named ? by these investigators, much interest has developed concerning the identification of alloy systems in which this phase exists, kinetics of the transformation in such systems, and the crystal structure of the ? phases appearing. Omega has been found in alloys of titanium-manganese, titanium-molybdenum, titanium-iron,' and titanium-vanadium.' In the present work, a study was made of the powder patterns of the ? phase occurring in alloys of Ti-8Cr, Ti-13Mo and Ti-15V in an effort to obtain a basis of comparison for ? phases appearing in these different alloys. Comparison of Alloys for ?-Phases Two hundred mesh powders of Ti-8Cr, Ti-13Mo and Ti-15V were prepared. A portion of powder sufficient for three x-ray powder specimens was placed in a Vycor tube, evacuated to less than 0.1 µ pressure, filled with argon, and sealed. The tubes were then heated to 900°C, held at this temperature for 30 min, and water-quenched. Following this transformation to the ß phase, the specimens were quenched in lead or solder pots, held at the desired temperature for varying lengths of time and water-quenched. The heat-treatments used and the phases identified are listed in Table I. The intermediate water quench was used in lieu of direct downquenching from 900°C to the bath temperature desired to circumvent the possibility of transformation of the powder specimen from ß to (ß + a) while it was being moved from the homog-enization furnace to the lead bath. To check the possibility that upquenching to the bath temperature might bring into play a different mechanism than downquenching to this temperature, resistivity measurements were compared on Ti-8Cr rod specimens which were transformed isothermally at 400°C by downquenching from the solution-treatment temperature and those which were transformed at 400" C by upquenching ß specimens from room temperature. The results are shown in Fig. 1. No difference in transformation mechanism was noted. It soon became apparent that sufficiently detailed Debye-Scherrer photograms of the ? phase in the alloys which were to be used could not be obtained by the use of copper radiation. Although satisfactory photograms of ß and ß + a phases were obtained with this radiation, the ? phase appeared to exhibit mild fluorescence, making interplanar spacing computation virtually impossible. Molybdenum radiation appeared to offer promise in cutting down this fluorescent effect, the mass absorption of titanium for molybdenum radiation being 23.7 in contrast to 204 for copper radiation. The reduction in the accuracy in determining the location of the photo-gram lines caused by the shorter wave length of molybdenum characteristic radiation did not appear to be a significant factor. Utilizing a camera of 57.3 mm radius, best results were obtained for exposure times ranging between 30 and 40 hr. Tube potential

Jan 1, 1959

By S. Kado, G. Derge, L. Yang

Self-diffusion coefficients of silver in molten silver have been measured by means of the capillary-reservoir method in the temperature range 1002" to 1105°C. The results can be .represented by the equation D = (7.10 i 0.06) X 10-4 exp [(—8150 ± 1130)/RT]. The heat of activation agrees within the limit of experimental uncertainty with that for the viscous flow. The validity of the Eyring and the Stokes-Einstein equations are examined on the basis of the self-diffusion coefficients obtained and the known viscosity data of molten silver. MEASUREMENT of the self-diffusion coefficient of silver in molten silver was made in the temperature range 1275° to 1378°K, using the capillary-reservoir method and &"' as the radioactive tracer. The experimental arrangement is shown in Fig. 1. Silver of 99.99 pct purity (fine silver), was melted and degassed in vacuum in a graphite crucible situated inside a McDanel vacuum jacket. The crucible (4 in. tall and 1 in. ID) was protected both at the top and at the bottom with graphite shields and contained about 220 g of silver. The sample holder was a piece of graphite rod (1 in. long and 1/2 in. diam) with 4 capillaries drilled longitudinally into it. The holder was screwed onto a long graphite rod (12 in. long and 74 in. diam) which was connected to a steel disk hanging on a nylon string through a glass pulley. The steel disk kept the sample holder at the center of the McDanel tube and was heavy enough to overcome the buoyancy when the holder was lowered into the molten silver. By turning a handle connected to the pulley through a tapered glass joint, it was possible to raise or lower the sample holder without breaking the vacuum. Two such arrangements were constructed, sitting side by side in 2 Kanthal furnaces. One with non-radioactive silver in its crucible was used for the diffusion run and the other with radioactive silver in its crucible was used for filling the capillaries. To fill the capillaries with radioactive silver, the sample holder was degassed first and then lowered into the radioactive molten silver in vacuum. Purified argon gas was then admitted into the system to push the liquid silver into the capillaries. After cooling in argon, the filled capillaries were polished on emery paper to expose the top of the rod and used immediately as samples for the diffusion run which was carried out at the same temperature as that used for filling the capillaries. During the diffusion run, the samples were degassed in vacuum and lowered slowly into the nonradioactive molten silver before purified argon was admitted into the system. After a predetermined period of time, the samples were raised out of the melt and cooled in argon. The temperature of the melt was measured before and after the run with a chromel-alumel thermocouple inside a McDanel protection tube. Another chromel-alumel thermocouple attached to the outside wall of the McDanel vacuum jacket was used to indicate any fluctuation in the temperature of the furnace during the run, which was found to be less than ± 2°C for the longest run made (93 min). The temperature gradient inside the molten silver was found to be negligible. No significant difference was observed in the results obtained whether the melt was stagnant during the run or was stirred by raising and lowering the sample holder slowly a few times a minute for a distance of about 1/4 in. inside the melt.

Jan 1, 1959

By F. L. Robertson, C. H. Bacon, J. W. Till

A description is given of the development of a process for making low sulphur steel on furnaces fired with 2 1/2 pet sulphur oil. Slag and metal are analyzed at melt. Slag weight is estimated. A simple method for calculating necessary lime additions for making 0.025 and 0.035 pct sulphur steel is given. DURING the last 15 years John Summers & Sons have been confronted increasingly by the problem of producing a low sulphur steel from high sulphur materials. The principles adopted, the processes used, the data collected on a furnace specially set aside to study this problem, and speculation on future developments are dealt with in this paper. This study is limited to two melting shops which make sheet steel only, of the following analysis: C, 0.06 pct; Mn, 0.33; S, 0.04, 0.035, 0.03, and 0.025; and P, 0.02 and 0.015. All the processes described have reference to the manufacturing of this steel and are not necessarily applicable, without modification, to other steels. The raw materials used are given in Table I. Development of Process About 1934, Schenck's work on phosphorus was applied to frame quantitative rules for the removal of phosphorus, with great success. We could however, neither in our own work nor in the voluminous literature, find any assistance to frame quantitative furnace rules to remove sulphur. Perhaps, we should have persevered with Schenck's outstanding chapter on sulphur in The Physical Chemistry of Steelmaking, but we missed the importance of one (Ss) sentence on p. 478. "Evidently this ratio -------- is [S] the important quantity to be considered from the point of view of chemical reaction; it is clear that the sulphur content of the steel alone, as frequently given in the literature cannot suffice for judging the success of the reaction unless special details are given regarding the sulphur charge and the amount of slag."' We were not however very successful in getting values for Schenck's "n" that agreed with (S) arrived at by our direct analysis. [S] In addition to Schenck's work much attention was given to V value. The formula selected for V was: (SCaO) — 1.57 (2 P2O5) (S SiO2) After plotting many charges a curve was obtained, based upon the relationship between the percentage sulphur in the finished steel and V value, Fig. 1. For a long time this was used as standard with about a 60 to 70 pct success on producer-gas fired furnaces, if all uprising scrap was used and no bought scrap used. An inspection of this curve shows clearly that it is not a quantitative manufacturing process, and that it was not sure enough to go to the trouble and expense of doing stage analysis for P,O,,

Jan 1, 1952

By Samuel Storchheim

IT was noted that variations existed in the magnetic properties, namely, coercive force, He, and rema-nence, Br, of 18/8 stainless steel wires of the same analysis when these wires were given the same percentage of reductiori of area at different rates of reduction. In order to determine the extent of these variations, a program was initiated whereby commercial 302 and 304 stainless steels were drawn with a wide variation of speeds. Ultimate tensile strengths and specific resistances, as well as the Hc-BT measurements, were determined. If variations of considerable magnitude were found, it was thought that the knowledge accrued from the investigation could probably aid in determining the particular drawing speed required to obtain desired properties for a given specification for a particular analysis of wire. Drawing Procedure Two specimens (set I, No. 302 and No. 304), the chemical analyses of which are given in Table I, were drawn at different speeds, namely, 45 to 3900 ft per min, directly from 0.016 in. diam wire to 0.004 in. diam wire, a 93.7 pct reduction of area. To obtain this high percentage of reduction, the wire at 0.016 in. was softened by annealing at 1150°C. It was then strung in a No. 16CF variable speed Vaughn drawing unit and passed through 13 B.&S. gage dies of successively smaller diameter, as shown in the accompanying table. Following this step, several hundred feet of the wire was drawn, at a particular speed, through the dies and wound upon a spool. Once the sample of wire was drawn at the desired speed, the spool with the finished sample was removed, tagged for later identification, and an empty spool was placed in the machine. Another wire sample was drawn at a different speed, after making the necessary adjustments upon the Vaughn unit. At the greater speeds, several thousand feet of sample were drawn to insure that the wire to be used for testing would be uniform. This was done because the desired speed was not reached instantly; the wire taking a short while to attain the required drawing rate. All speed measurements were made by placing a tachometer against one of the machine's pulleys during the actual drawing of the specimens. 84.4 pct reduction of area. The 0.072 in. diameter wire was also annealed at 1150°C. The process of obtaining samples was the same as described above. The only difference between the two was that the rates involved were not as extensive, set II covering a range of 625 to 1150 ft per min. Tensile tests were carried out for the 0.004 in. diam wires on a horizontal Scott Tensile Tester, while tensile tests for the 0.028 in. diam wires were made on a vertical Scott Tensile Tester. Each value listed in the tables represented the average of five samples with a maximum deviation of approximately 3 pct among the samples. Resistance per foot of the wires was determined by use of standard bridges accurate to the nearest hundreth of an ohm for the 0.004 in. wire, and to the nearest thousandth of an ohm for the 0.028 in. wire. The resistances per foot were then converted to resistivities by use of the following equation: P = RxCM where R is the resistance per ft in ohms per ft; CM, the area in circular mils; and P, the resistivity in ohms—CM. The values listed in the tables likewise

Jan 1, 1952

By Arthur F. Taggart, Nathaniel Arbiter

The fact that the floatability of minerals with fatty-acid collectors changes as the pH of a pulp varies was utilized in the early days of flotation, when sulphuric acid was used with oleic acid to float sphalerite and galena. from gangues which themselves float with fatty acids in alkaline pulps. Gaudin1 showed that this difference in floatability is a regular function of the extent of the change in pH. The present paper offers an explanation of the phenomenon, and on the basis thereof sets up recommendations for control of soap-flotation operations. Experimental Parallelism between floatability of a mineral in a given environment and its contact angle in that environment is so well established,2 and the contact angle is so readily and rapidly measurable, that contact angles have been used throughout the experimental work to indicate relative floatability. Experiments comprised contact-angle measurements on a number of representative minerals and metals, and a variety of subsidiary tests designed to check and to amplify the contact-angle indications. Contact-angle measurements were made by the method described in detail by del Giudice.3 Sequence of procedure for determination of the points of Fig. I was: I. Polish specimen. Most specimens yielded zero contact angle after polishing; a few showed a slight "cling." Cling is characteristic of specimens that pit on polishing; it is due to a residue of organic contamination, originally on the particle surface, which persists in the pits. The cling did not change total contact angle after conditioning, and is not, therefore, additive in the upper part of the curves of Fig. I. It may have broadened the bases of the curves for the affected minerals slightly. 2. The specimen was next conditioned in soap solution for 5 minutes. 3. The conditioned particle was transferred, under conditions that precluded surface drying, to an aqueous solution of the pH desired and contact angle determined. 4. The particle was thereupon transferred, again without surface drying, to water. The confirmatory tests will be described at the places pertinent in the argument. Discussion of Results Gaudin and Vincent4 have shown that contact angles with heptoic acid as a collector decrease for a given specimen when the concentration of collector present falls below a certain value. A similar reduction in angle occurs with collector-conditioned particles that are visibly slime-coated, and varies roughly with the extent of coating. Since in the last case the reduction in angle is certainly due to reduction in the proportion of total conditioned mineral surface presented to the bubble, the authors believe that the same condition prevails in the first case cited, and that similar reduction in angle and floatability will occur whenever starvation quantities of collector are present, whether by design or by reason of excessive consumption.

Jan 1, 1943

By Nathaniel Arbiter, Arthur F. Taggart

The fact that the floatability of minerals with fatty-acid collectors changes as the pH of a pulp varies was utilized in the early days of flotation, when sulphuric acid was used with oleic acid to float sphalerite and galena. from gangues which themselves float with fatty acids in alkaline pulps. Gaudin1 showed that this difference in floatability is a regular function of the extent of the change in pH. The present paper offers an explanation of the phenomenon, and on the basis thereof sets up recommendations for control of soap-flotation operations. Experimental Parallelism between floatability of a mineral in a given environment and its contact angle in that environment is so well established,2 and the contact angle is so readily and rapidly measurable, that contact angles have been used throughout the experimental work to indicate relative floatability. Experiments comprised contact-angle measurements on a number of representative minerals and metals, and a variety of subsidiary tests designed to check and to amplify the contact-angle indications. Contact-angle measurements were made by the method described in detail by del Giudice.3 Sequence of procedure for determination of the points of Fig. I was: I. Polish specimen. Most specimens yielded zero contact angle after polishing; a few showed a slight "cling." Cling is characteristic of specimens that pit on polishing; it is due to a residue of organic contamination, originally on the particle surface, which persists in the pits. The cling did not change total contact angle after conditioning, and is not, therefore, additive in the upper part of the curves of Fig. I. It may have broadened the bases of the curves for the affected minerals slightly. 2. The specimen was next conditioned in soap solution for 5 minutes. 3. The conditioned particle was transferred, under conditions that precluded surface drying, to an aqueous solution of the pH desired and contact angle determined. 4. The particle was thereupon transferred, again without surface drying, to water. The confirmatory tests will be described at the places pertinent in the argument. Discussion of Results Gaudin and Vincent4 have shown that contact angles with heptoic acid as a collector decrease for a given specimen when the concentration of collector present falls below a certain value. A similar reduction in angle occurs with collector-conditioned particles that are visibly slime-coated, and varies roughly with the extent of coating. Since in the last case the reduction in angle is certainly due to reduction in the proportion of total conditioned mineral surface presented to the bubble, the authors believe that the same condition prevails in the first case cited, and that similar reduction in angle and floatability will occur whenever starvation quantities of collector are present, whether by design or by reason of excessive consumption.

Jan 1, 1943

By Konrad Stern

The terms asphalt and bitumen have been applied interchangeably, although incorrectly on occasion, for centuries to various bituminous materials that were found in nature. Native bituminous materials of only the solid types, deposits of which are found on or near the surface of the ground, together with the principal asphaltic type petroleum bitumens will be considered in this chapter. The international dictionary compiled by the "Permanent International Association of Road Congresses" still gives the full name as "Asphaltic Bitumen" but of recent years the word "Bitumen" has been recognized as most appropriate and is defined by the American Society for Testing Materials as follows: "Mixtures of hydrocarbons of natural or pyrogenous origin, or combinations of both, frequently accompanied by their nonmetallic derivatives, which may be gaseous, liquid, semisolid or solid and which are completely soluble in carbon disulfide." Asphaltic pyrobitumens, as defined by Abraham,2 is a species of pyrobitumen, including dark-colored, comparatively hard and nonvolatile solids; composed of hydrocarbons, substantially free from oxygenated bodies; sometimes associated with mineral matter, the nonmineral constituents being infusible and largely insoluble in carbon disulfide. Deposits of native bituminous materials are found scattered over the entire world, but many are relatively unimportant as far as commerce is concerned. No attempt has been made to cover all of the known deposits. The principal bituminous materials of commercial interest are: 1. Native asphalts, solid or semisolid, associated with mineral matter such as Trinidad Lake asphalt, Rock asphalt and Selenitza, Boeton and Iraq asphalts. 2. Native Asphaltites, such as gilsonite, grahamite and glance pitch, conspicuous by their hardness, brittleness and comparatively high softening point. 3. Asphaltic bitumens obtained from nonasphaltic, semi-asphaltic and asphaltic crude petroleum by distillation, blowing with air and the cracking of residual oils. 4. Asphaltic pyrobitumens of which wurtzilite and elaterite are of chief interest industrially as they depolymerize upon heating, becoming fusible and soluble in contrast to their original properties in these respects.2 5. Mineral waxes, such as ozokerite, characterized by their high crystallizable paraffine content. Native Lake Asphalt At Brighton situated in the southwestern part of the Island of Trinidad is one of the largest deposits of native asphalt in the world.3 The lake is oval in shape, covering an area of 114 acres and having a depth of 285 ft at its center. The material forming this deposit is an emulsion of water and bitumen with a suspension of mineral matter consisting of impalpably fine clay dispersed by nature in the asphalt, and small quantities of silica and vegetable matter. The entire mass of asphalt is in slow but constant motion as evidenced by the migration of islands of vegetation from one place to an-

Jan 1, 1960

By S. Feuerstein

THE influence of environment on the mechanical properties of metals has been extensively studied and documented.' Most investigations have dealt with an interaction between a particular environment and a specific metal surface and the concomitant change in bulk mechanical behavior. Typical contributing media are oxide and metal film:;, electrolytes, and other surface-active agents. In the last category fall controlled gaseous environs (i.e., pressure or vacuum). Most vacuum exposure experiments prior to 1963 were conducted at pressures s>10-6 torr and elevated temperatures, or in such a manner as to prolong the exposure (e.g., by stress-rupture, creep, and fatigue). Little attention has been given to vacuum environment effects on the mechanical behavior of metals subjected to simple uniaxial deformation at room temperature. Test times and temperatures were assumed too ineffective as far as bulk changes were concerned. Further, the contribution of surface effects to the bulk mechanical behavior of metals was considered minimal. Under vacuums of the order of 1.0- 8torr and higher, molecular densities and, consequently, the rate of monolayer formation are such that exposures from seconds to days would be required for complete gas coverage. Thus, atomically clean surfaces created under ultra-high vacuum could conceivably maintain their cleanliness for time intervals orders of magnitude greater than at higher pressures. The influence of this unusual type of environmental surface phenomenon on the short-term bulk mechanical behavior of aluminum was first observed by Krame and Podlaseck in 1963.' kin equivalent effect was reported for magnesium by Williams and Nelson.3 It was concluded from these studies2,3 that vacuum and, consequently, the monolayer formation rate of the oxide, were responsible for the described changes in flow behavior. The presence of an oxide layer impedes dis- I) EXPERIMENTAL DATA: MOLYBDENUM The tensile behavior of molybdenum was investigated by the author4-6 at ambient temperature over a range of pressures from 760 to 10-10 torr. These studies revealed that the flow behavior of the bulk specimens (0.200 in. diam by 2 in. gage length) was independent of pressure on sintered (0.062 mm grain size) and arc-cast polycrystals (0.012 to 0.149 mm grain sizes) and single crystals. Since the specimens were relatively large in size, it was assumed that any flow behavior effect would be surface-limited because of the short-term deformation procedure. Strain-rate-change experiments performed to determine the activation volumes for individual specimens at 760 to 10- 10 torr further indicated that the surface flow contribution was either minimal or zero, contrary to the findings of Shen el a1.7 on aluminum. Although the flow behaviors did not change, specimen ductility did change. For the sintered material at a strain rate of 4.2 x 10-4, specimen ductility was -9 pct higher at l0- 10 torr than at atmospheric pressure (dry nitrogen). A more comprehensive investigations on this same material revealed a distinct pressure dependence, Fig. 1. Intermediate and atmospheric pressure tests were obtained by backfilling the system from l0- 10 torr with extra dry, prepurified nitrogen. Other environments (air and purified argon) were also utilized for the 760 torr experiments; the results were essentially the same as those for dry nitrogen atmospheres. Departure from the fracture strain values obtained at 760 torr takes place in the vicinity of l0-6 torr, as indicated by the scatter band; a noticeable ductility increase is apparent at l0-8 and 10-10 torr.

Jan 1, 1970

By Nathaniel Arbiter, Arthur F. Taggart

THE fact that the floatability of minerals with fatty-acid collectors changes as the pH of a pulp varies was utilized in the early days of flotation, when sulphuric acid was used with oleic acid to float sphalerite and galena from gangues which themselves float with fatty acids in alkaline pulps. Gaudin1 showed that this difference in floatability is a regular function of the extent of the change in pH. The present paper offers an explanation of the phenomenon, and on the basis thereof sets up recommendations for control of soap-flotation operations. EXPERIMENTAL Parallelism between floatability of a mineral in a given environment and its contact angle in that environment is so well established,' and the contact angle is so readily and rapidly measurable, that contact angles have been used throughout the experimental work to indicate relative floatability. Experiments comprised contact-angle measurements on a number of representative minerals and metals, and a variety of subsidiary tests designed to check and to amplify the contact-angle indications. Contact-angle measurements were made by the method described in detail by del Giudice.3 Sequence of procedure for determination of the points of Fig. I was: 1. Polish specimen. Most specimens yielded zero contact angle after polishing; a few showed a slight "cling." Cling is characteristic of specimens that pit on polishing; it is due to a residue of organic contamination, originally on the particle surface, which persists in the pits. The cling did not change total contact angle after conditioning, and is not, therefore, additive in the upper part of the curves of Fig. I. It may have broadened the bases of the curves for the affected minerals slightly. 2. The specimen was next conditioned in soap solution for 5 minutes. 3. The conditioned particle was transferred, under conditions that precluded surface drying, to an aqueous solution of the pH desired and contact angle determined. 4. The particle was thereupon transferred, again without surface drying, to water. The confirmatory tests will be described at the places pertinent in the argument. DISCUSSION OF RESULTS Gaudin and Vincent4 have shown that contact angles with heptoic acid as a collector decrease for a given specimen when the concentration of collector present falls below a certain value. A similar reduction in angle occurs with collector-conditioned particles that are visibly slime-coated, and varies roughly with the extent of coating. Since in the last case the reduction in angle is certainly due to reduction in the proportion of total conditioned mineral surface presented to the bubble, the authors believe that the same condition prevails in the first case cited, and that similar reduction in angle and floatability will occur whenever starvation quantities of collector are present, whether

Jan 1, 1943

By H. D. Kessler, M. Hansen, R. J. Van Thyne

The phase diagram of the titanium-rich portion of the system Ti-Cr-Fe to 70 pct Ti was established by means of isothermal sections at 900°, 800°, 750°, 700°, 650°, 600°, and 550°C, using arc-cast alloys. An isotherm at 800°C was determined for the section bounded by Ti, TiFe2, and TiCr2. Micrographic analysis was employed as the principal method of investigation, supplemented by X-ray diffraction and incipient melting studies. A ternary eutectoid, ß ? a+ TiCr2 + TiFe, occurs at approximately 8 wt pct Cr, 13 wt pct Fe, and about 540°C. AMONG the first titanium-base alloys in commercial production were the Ti-Cr-Fe alloys. For this reason, the Materials Laboratory, Wright Air Development Center, sponsored an investigation of the system. No information on the constitution of the titanium-rich corner was available. Vogel and Wenderott studied titanium-poor ternary alloys.' As part of this program, the binary systems Ti-Cr and Ti-Fe have been determined previously by the authors.' Other investigators have also studied the binary systems Ti-Cr,3-7' Ti-Fe.³,8-10 Both of the binary systems are characterized by the eutectoid decomposition of the ß phase. Most of the effort of the present work has been concentrated on the titanium-rich corner with compositions of less than 30 pct total chromium and iron content. The determination of isothermal sections was the experimental approach used to obtain the ternary phase diagram. Vertical sections were used to check the consistency of the isothermal sections. While this investigation was in progress, a study of the Ti-Mo-Cr system at Armour Research Foundation disclosed the existence of a high temperature modification of TiCr2 above 1300 °C.11 This allotrope has a hexagonal structure of the MgZn2 type, iso-morphous with TiFe2, whereas the low temperature modification of TiCr2 is cubic," of the MgCu2 type. The existence of allotropy in TiCr2 of course means a more complicated set of phase relationships in this general region than if the phase were monomorphic, as was first assumed. Additional studies were made late in the investigation in order to clarify the part that the hexagonal TiCr2 phase plays in the ternary phase relationships. These will be discussed in a separate section. Because they are of greatest practical significance, the phase relationships in the titanium-rich corner will be presented first, omitting the equilibria involving the hexagonal modification of TiCr2 in an effort to simplify the presentation somewhat. Experimental Procedure Materials: The titanium used in the preparation of the alloys was iodide crystal bar (99.9 pct pure) produced by the New Jersey Zinc Co. High purity chromium and iron were obtained from the National Research Corp. Table I gives the analyses of these materials. Melting Practice: Over 100 alloy ingots weighing 10 to 20 g were melted in a nonconsumable electrode arc-melting furnace. As the techniques are identical to those reported previously,12,13 they will not be detailed here. The ingots were melted in the cavity of a copper melting block insert under a slight positive pressure of helium. No measurable hardness

Jan 1, 1954

By J. J. Van Nouhuys

THE economics of aerial survey and the technical processes by the aid of which vertical and oblique aerial photographs are turned into line maps showing the most profuse topographical detail such as contours, rivers, roads, plantations, habitations and cultivated lands do not concern us here. They have been ably and exhaustively described in the publi-cations of the British War Office, handbooks on surveying methods and on photogrammetry and in the South African mining, engineering and geological press. Suffice it to mention that for geological interpretation vertical photo-graphs are used on such scales as soon to 1/5,000 to 1/10,000, overlapping each other by 55 to 60 per cent in the direction of flight and some 10 to 20 per cent sideways on to the next sequence or strip. Through this duplication in the overlap the stereoscopic examination becomes possible. The standards by which monochrome aerial photographs are inter-preted can be grouped under the following headings: 1. Continuity.-The continuity of topographic relief not obtainable on the ground owing to the smallness of man relative to that relief. Here lies the greatest value of aerial survey with relation to geology. An immediate alignment can often be made of drainages running in different directions on each side of a hill; saddles and gorges in the mountainsides; abrupt termination of outcrop or indubitable signs of faulting. Most conclusive evidence is thus often obtained about faults which may be perfectly visible at one place on the ground but cannot elsewhere be identified because of decreased throw. Similarly, dikes can often be followed notwithstanding frequent interruption and disappearance under the soil. Scattered outcrop in scrub-covered or bush-covered country can be conveniently located and often correlated, with a large saving of time compared with field work. The same applies to geological contacts. Once these have been established at a few points on the ground, the intervening stretches can be drawn in.

Jan 1, 1937