Search Documents

By J. L. Walter

Tungsten ingots with and without small amounts of aluminum, silicon, and potassium were prepared by conventional powder-metallurgy techniques and hot-rolled to 0.001-in.-thick sheet. The ingots were rolled three different ways: I) initially cross-rolled, then straight-rolled; 2) straight-rolled, and 3) straig-ht-rolled, then cross-rolled. Total reductions were 99.8 pct. Samples of the sheet were annealed, in vacuo, at temperatures from 1200" to 2200°C. Substructures and textures were determined by transmission electron microscopy and X-ray diffraction. The doping agents were found to form particles of mullite (Al,Si,O,,) which, on rolling., appear to form strings of particles aligned parallel to the rolling direction. These strings of purticles are associated with an increase in the recrystal-lizution temperature from 1400°C for undoped sheet ThE addition of small amounts of aluminum, silicon, and potassium to tungsten has a profound effect on the grain structure of drawn and recrystallized wire.'" The grains generally do not occupy the entire cross section of the wire and have lengths many times the wire diameter. The grain boundaries are, in general, nearly parallel to the wire axis and have long ''fingers" projecting one into the other as may be seen in Fig. 1, a longitudinal section of recrystallized doped wire. When unsuitable additions or no additions are made or the wire is not sufficiently reduced during draw- to 2000°C for doped sheet. The particles also limit lateral grain growth while allowing growth parallel to the rolling direction. This results in the formation by primary re crystallization of large highly elongated grains of specific preferred orientation. The undoped sheet recrystallized to small equiaxed gains. The preferred orientations of the large grains were determined from axis density plots to be (113) (691). (0i3) (362), (116) (304) types for the initially cross-rolled then straight rolled material. These orientations are similar to the orientations of the large elongated grains in doped and heavily drawn tungsten wire. The nucleation of the large grains appears to occur by recovery of certain of the polygonized regions of specific orientation, followed by strain-induced boundary migration.

Jan 1, 1968

By W. J. Reagan

MANY factors enter into the manufacture of basic open-hearth steel of high quality. Perhaps the two most important are temperature and the iron oxide content of the metal. If we can control these two factors we can essentially control basic open-hearth practice. SOURCE AND EFFECT OF IRON OXIDE Earlier investigators, especially Herty and his associates, have shown that iron oxide is introduced into the open-hearth furnace in four ways:1 1. - By oxidation of the scrap by furnace gases. 2. By decomposition of the limestone. 3. By oxidation of the iron oxide in the slag by furnace gases. 4. By direct addition of iron ore to the charge. We also know that the speed of operation of an open-hearth furnace depends, for a given charge and given combustion conditions, on the rate at which iron oxide will diffuse from the slag into the metal. The rate of diffusion depends upon a number of variables, such as iron oxide content of the slag, slag viscosity, etc., which also depend upon the amount of iron oxide in the metal, amount of carbon present, temperature, and so forth. For a given carbon and a given temperature, the iron oxide content of the metal is in proportion to the iron oxide content of the slag. This fact can be easily verified by analysis of slag samples taken as described by Herty.2 It is preferable to take these samples just before deoxidation. In killing the steel samples with aluminum it is desirable to use aluminum rod of 99 per cent purity; ordinary commercial aluminum rod with a purity of approximately 92 per cent is not satisfactory. In drilling these samples it is also essential to take the largest amount of drillings possible. This gives more accurate results because it eliminates spotty segregation of Al203.

Jan 1, 1932

By Dorsey Hager, G. W. McPherson

The rapid increase of water troubles in the Mid-Continent oil fields is causing much alarm. Troubles occur at Towanda, Eldorado, Augusta, Cushing, Blackwell, and Healdton, although they had not been acute in the Mid-Continent field until about two years ago, when the unusual conditions in the deeper oil fields were first encountered. California faced the same situation, but, thanks to aggressive measures, has largely overcome the dangers. The following analysis of water trouble may throw some light on the subject and be of assistance in solving the problems involved. Water Troutles Classified The presence of water in large quantities in oil sands has the following results: 1. Diminishes oil production. 2. Diminishes casing-head gasoline production: (a) By curtailing the gas flow. (b) By making the use of vacuum pumps unsuccessful. 3. Increases lifting costs: (a) By making it necessary to pump large quantities of water, which requires a fast motion and long stroke (third hole). (b) By requiring the use of compressors for air lift. (c) By causing break-downs and delays due to the high speed necessary to pump water. (d) By making it necessary to treat "cut" or emulsified oil. Oil production is seriously curtailed by the presence of large quantities of water. Lease records show that wells are shut down 40 to 60 per cent, of the pumping time where serious water trouble occurs. While a small quantity of salt water may cut the paraffine and keep the oil moving, several hundred feet, or a hole full of water, effectually "kills" the oil and gas. The quick return of wells to production, once the water is shut off, shows how wells have been affected. The killing of gas sands

Jan 1, 1920

By C. C. Singleterry, D. L. Katz

The critical phenomena have been studied during the past century but our knowledge of the critical temperatures and pressures of complex hydrocarbon mixtures still is very limited. The critical temperatures and pressures of pure substances have been examined in large numbers120 and in great detail.11.17 No experimental determinations of the critical phenomena have been reported on such complex hydrocarbon systems as a reservoir fluid. The critical temperature is defined by Taylor18 as follows: "there is some temperature for each gas above which the gas cannot be liquefied. This temperature is called the critical temperature." The critical pressure of a pure substance is the vapor pressure at the critical temperature. It should be noted that these definitions refer to a given substance in the pure state and do not mean that the pure substance cannot be liquefied in the presence of a second constituent. The normal procedure for obtaining the critical temperature of a substance is to heat it in a glass tube 1,20 under pressure until the meniscus between the liquid and vapor phase disappears, although other methods, especially for mixtures, have been used.13,14 However, when considering oil and gas reservoirs, it is more enlightening to consider a critical phenomenon that occurs when a mixture of oil and gas are compressed at a reservoir temperature until the meniscus disappears because the two phases become equal in composition. This conception, along with erroneous applications of the definition of the critical phenomena of a pure substance to that pure substance when it is part of a complex mixture, has caused confusion even among persons familiar with the classical theories. The purpose of this paper is to discuss the critical phenomena of pure substances and mixtures and to report experimental data on a mixture of

Jan 1, 1939

By C. C. Singleterry, D. L. Katz

The critical phenomena have been studied during the past century but our knowledge of the critical temperatures and pressures of complex hydrocarbon mixtures still is very limited. The critical temperatures and pressures of pure substances have been examined in large numbers120 and in great detail.11.17 No experimental determinations of the critical phenomena have been reported on such complex hydrocarbon systems as a reservoir fluid. The critical temperature is defined by Taylor18 as follows: "there is some temperature for each gas above which the gas cannot be liquefied. This temperature is called the critical temperature." The critical pressure of a pure substance is the vapor pressure at the critical temperature. It should be noted that these definitions refer to a given substance in the pure state and do not mean that the pure substance cannot be liquefied in the presence of a second constituent. The normal procedure for obtaining the critical temperature of a substance is to heat it in a glass tube 1,20 under pressure until the meniscus between the liquid and vapor phase disappears, although other methods, especially for mixtures, have been used.13,14 However, when considering oil and gas reservoirs, it is more enlightening to consider a critical phenomenon that occurs when a mixture of oil and gas are compressed at a reservoir temperature until the meniscus disappears because the two phases become equal in composition. This conception, along with erroneous applications of the definition of the critical phenomena of a pure substance to that pure substance when it is part of a complex mixture, has caused confusion even among persons familiar with the classical theories. The purpose of this paper is to discuss the critical phenomena of pure substances and mixtures and to report experimental data on a mixture of

Jan 1, 1939

By Will Coghill

As the title indicates, this paper treats of the degree of liberation of minerals after grinding. To obtain the supporting data a "tool" not commonly used by metallurgists has been employed. It is the "heavy solution." The advantages gained through its use are shown. Actual ores were employed in order to make the study concrete. The selection was somewhat incidental and happened to embrace the red iron ores of Alabama. So, any reader interested in these ores will find some of their properties described. The red ores constituted the material examined and a somewhat new adaptation of heavy solutions was the tool of examination. If either the ores or the tool interest the reader these notes may be of some value. The writer's chief interest was in the rate of liberation of locked grains. Ores are generally ground preparatory to concentration and as long as the concentrators make suitable products the effectiveness of the grinding is likely to be unquestioned. But when suitable products are difficult to make, an investigation becomes imperative. In such a case a dissection of the ore might be made to find the cause of the trouble. Such a condition of unsuitable products exists in the low-grade red iron ores of Alabama. They are difficult to concentrate. To be sure it might be said that the concentration of iron ores is a new thing and that the ore-dressing methods are undeveloped, but a glance at the industry reveals an abundance of methods and devices for almost all imaginable conditions. Concentrating machinery has not taken a part in this investigation; the use of it would have been only machinery testing, and should never precede the ore testing which consists of such methods as herein outlined. When the properties of the ores have been gleaned the machinery may be used more effectively.

Jan 12, 1926

By H. W. McCue, Henry Rogatz

Oil.—In the Texas Panhandle, 502 oil wells were drilled during the year 1940, with a total daily initial production of 139,187 bb1.—that is, 137 more oil wells drilled than in the previous year, with an increase in total daily initial production of 8219 bbl. The total daily potential of the field on Dec. 31, 1940, as determined by the Texas Railroad Commission, was 1,375,502 bbl., an increase of 30,825 bbl. over the previous year. On Dec. 31,1940, a daily allowable of 85,050 bbl., which was a decrease of 35 per cent over 1939, was assigned to the field to be produced from 4788 wells. The total amount of oil produced for the year was 26,788,590 bbl., making a cumulative total of 378,960,728 bbl. during the past 19 years. No new oil-producing acreage was discovered. Gas.—During the year, 92 gas wells were drilled, having a combined open flow of 2,402,900.000 CU. ft.; that is, 6 more than the number of wells drilled in 1939, with an increase in the open flow of 204,900,000 cu. ft. per day. The gas production for the year was 670,435,112,000 CU. ft., and the total gas removed from thc ground during

Jan 1, 1941

By M. J. Salkind

In discussing the possible contribution of plastic deformation to neck growth during sintering, Wilson and Shewmon State that Lenel, Ansell, Salkind, and Early34, 35 concluded that dislocation flow is the rate-controlling process in sintering under zero external load. The experiments cited34, 35 were done with applied external loads, and the conclusions were that the same kinetics could be controlling sintering due to the force of gravity with no additional applied load. The effect of gravity on sintering behavior was previously cited.34, 31 In addition, Wilson and Shewmon argue that the conclusions of Refs. 34 and 35 are doubtful because the strain rate is proportional to stress for plastic flow. This assumption is true only for certain kinds of plastic flow such as Nabarro-Herring Microcree38 As Early, Lenel, and Ansell point out3' plastic flow, based upon dislocation movement, can exhibit strain rates which exhibit a power law relationship to the applied stress.39, 40 Wilson and Shewmon also doubt the results of Refs. 34 and 35 because the stresses in the necks are too small for x/a > 0.1. This is true, and the experiments described in Refs. 34 and 35 were done for small values of %/a. The conclusion was that plastic flow by dislocation movement was important during the early stages of sintering when x/a is small.

Jan 1, 1968

By Henry Rogatz, H. W. McCue

Oil.—In the Texas Panhandle, 502 oil wells were drilled during the year 1940, with a total daily initial production of 139,187 bb1.—that is, 137 more oil wells drilled than in the previous year, with an increase in total daily initial production of 8219 bbl. The total daily potential of the field on Dec. 31, 1940, as determined by the Texas Railroad Commission, was 1,375,502 bbl., an increase of 30,825 bbl. over the previous year. On Dec. 31,1940, a daily allowable of 85,050 bbl., which was a decrease of 35 per cent over 1939, was assigned to the field to be produced from 4788 wells. The total amount of oil produced for the year was 26,788,590 bbl., making a cumulative total of 378,960,728 bbl. during the past 19 years. No new oil-producing acreage was discovered. Gas.—During the year, 92 gas wells were drilled, having a combined open flow of 2,402,900.000 CU. ft.; that is, 6 more than the number of wells drilled in 1939, with an increase in the open flow of 204,900,000 cu. ft. per day. The gas production for the year was 670,435,112,000 CU. ft., and the total gas removed from thc ground during

Jan 1, 1941

By C. W. Spencer, B. F. Addis, G. H. Bishop, C. A. Steidel

STUDIES of the inter granular attack of metals by liquids have generally been confined to polycrys-talline specimens. This note reports the results of preliminary studies of the penetration of bismuth-rich Ni-Bi liquids into oriented bicrystal specimens of nickel. It is found that isothermal penetration follows a parabolic rate law and shows a definite anisatropy with respect to direction on the grain boundary surface. Nickel bicrystals containing < 100> tilt boundaries were grown using the Czochralski method. Relative misorientation of the parent crystals was controlled to ± 1deg. The boundaries are straight in the growth direction, i.e., the common <100>, and generally straight in the transverse direction, as shown in Fig. 1. The starting material, Inco HPM grade nickel was contained in a recrystallized alumina crucible and maintained under argon. Bicrystals typically contain 30 ppm C, less than 10 ppm S, O, N, and 50 ppm residual metallics, principally iron and silicon. Specimens, as schematically illustrated in Fig. l(c),were cut from bicrystal ingots using a thin water-cooled abrasive wheel. To insure removal of all residual strain, which accelerates the penetration, specimens were round through 600 grit silicon-carbide, chemically polished, and annealed for 4 hr at 1375°C under argon. The procedure described by Cheney et al.1 for exposing specimens to

Jan 1, 1962

By S. A. Allison, N. P. Finkelstein

After a brief consideration of the properties of zinc sulfide minerals, their flotation characteristics, and their reactions with thiol collectors, the literature on the activation of the minerals by cupric ion, their deactivation by cyanide, and their depression is reviewed in detail. The distinction between deactivation and depression is stressed. The contradictions in the published results and theories are discussed and attempts are made to resolve them. It is concluded that, whereas all aspects of the subject require further investigation, the study of depression is most likely to yield benefits in practice.

Jan 1, 1976

By N. Brown, J. Washburn, E. R. Parker

MOST previous quantitative work on creep of single crystals has been concerned primarily with developing empirical equations for the creep curve. Although the equations used by Cottrell and Aytekin¹ and Tyndall² represented the data quite well, it was often necessary to use different values of the constants for different specimens even though they were apparently tested under identical conditions. In the course of previous work on the effect of surface coatings on creep of zinc single crystals," it was found that equal resolved shear stress frequently did not produce equal creep rates in different specimens. The work of Chalmers&apos; in the very

Jan 1, 1954

By R. Haynes

ON the basis of compositional changes of a phase observed in a eutectoid Cu-Al alloy1 it has been suggested that mechanisms for the decomposition of the ß phase proposed by earlier workers2-5 were incorrect. These data are reinterpreted in conjunction with lattice parameter data obtained on an alloy containing 12.2 pet Al, whose isothermal transformations have been reported elsewhere.5 The a Lattice Parameters of a 12.2 Pet A1-Cu Alloy—~iffraction patterns of completely transformed specimens were obtained in a back reflection camera using copper Ka radiation. Lattice parameters of

Jan 1, 1959

By J. S. Rinehart, W. C. Maurer

The mechanics of impact crater formation in rock, particularly sandstone, has been sutdied, the velocity range being approximately that normally associated with oilwell gun perforators. The bullets were small steel spheres having diameters of 3/16, 9/32 and 7/16 in; impact velocities ranged from 300 to 7,000 ft/sec. The craters have two distinct parts — a cylindrical hole (or burrow) with a diameter the same as that of the impacting sphere, and a wide-angle cup comprising most of the volume of the crater. The burrow is fornred as material in front of the projectile is crushed and pushed aside, forming a cylindrical hole surrounded by a high-density zone. The clip forms as fractures are initiated in front of the projectile and propagate along logarithmic spirals, approximaling maximum shear trajectories, to the free surface of the rock. A most significant observation (made for the first time) was that, below the base of the cup in one type of sandstone, there are a group of similar fractures, not extending to the surface, which are spaced uniformly a few millimeters apart. Each fracture follows roughly the contour of the base of the cup and appears to require a certain threshold impulse to initiate it. These fractures comprise a relatively high fraction of the total, newly exposed surface area. The volume of the material removed by crushing varies as the first power of the impact velocity and the volume removed by fracturing, as the second power of the impact velocity. Penetration varies linearly with the impact velocity and is inversely proportional to the specific acoustic resistance of the target material, the proportionality constant being dependent upon the shape of the projectile. INTRODUCTION Yield of oil from a producing well is frequently enhanced by firing bullets and shaped charges through the well casing into the oil-bearing rock, forming craters and fractures from which oil can flow more readily. The purpose of this investigation has been to develop a better understanding of the mechanics of impact crater formation in rock, particularly sandstone, the velocity range being approximately that normally associated with oilwell gun perforators. FORCES OPERATIVE DURING IMPACT When a projectile moving at considerable velocity strikes a- massive target such as oil-bearing sandstone, intense and complex transient stress situations develop within both the projectile and the rock or sandstone against which it is striking. Usually the struck rock fails, the missile or projectile penetrating into the rock to some depth where it comes to rest or is forcibly ejected from its burrow by expansion of a plug of target material compressed in front of it. When the impact velocity is very high, the projectile itself may fail, breaking apart or becoming distorted; this situation is not considered here, the discussion being limited to nondeforming projectiles. Many experimental studies&apos;.&apos; have been carried out to determine the nature of the mechanics of crater formation and the salient features of the forces coming into play, some of the earliest studies being the French Army experiments performed at Metz between 1835 and 1845.&apos; The stratagem in most instances has been to make a post-mortem examination of the crater, measuring volume and depth of penetration and deducing force relationships from these observations rather than performing the more difficult (usually almost impossible) feat of measuring stresses during penetration. In many materials, the force acting during penetration of the projectile is found to be the sum of two components—(1) a constant force, independent of the velocity, representing some inherent strength of the target material; and (2) a component, proportional to the square of the velocity, representing inertial forces. For such materials, the average force per unit area acting on the projectile at any instant while it is in motion and being decelerated may be written F/A = a + bv2 . . . (1) where v is the velocity of the projectile at that instant, A is the cross-sectional area of the penetrating projectile taken normal to its trajectory, and a and b are constants which are dependent upon the target material and the shape of the projectile. It follows that the total penetration s is given by .........(2) where v, is the velocity of the projectile when it just strikes the target. Values of a and b for spherical projectiles impacting in a loose sand-gravel mixture and compacted earth were obtained in the Metz experiments. For sand-gravel, a and b are 620 psi and 0.0115 (psi) (ft/sec)&apos;, respectively; and for compacted earthworks, a and b are 432 psi and 0.0008 (psi) (ft/sec)&apos;. Figs 1 and 2

E. E. Russell Tratman, New York City (communication to the Secretary): Mr. Glenn&apos;s paper brings up again the question of the part played by coal-dust in colliery-explosions. In the discussion of Sir Frederick Abel&apos;s paper on " Accidents in Mines," read before the Institution of Civil Engineers,? much was said about the dangerous properties of coal-dust, and several instances were given of the successful use of a spray of water, water and compressed air, or exhaust-steam from an engine, to keep the mine SUEciently damp to prevent the formation of dust clouds. Methods of preventing shots from blowing out; of using water cartridges to prevent flame ; and of using lime cartridges, wedges and other means of breaking down the coal were also discussed. Mr. Emerson Bainbridge referred to the explosive termed " roburite " (ammonium nitrate and

Jan 1, 1895

By Archibald Macmartin

THE Königin-Marien-Hütte is the only works in Germany where the Bessemer process is carried on by the direct method. The Besserner plant there, is arranged after the true English type, and the only resemblance to the Swedish mode of procedure is the dispensing with the use of spiegeleisen at the end of the "blow." In a new department of the establishment, started within three years, each of the converters is turned by means of a very neat and compact reversible engine, the steel shaft of which is an endless screw, which turns against the oblique cogs of a large wheel attached to the shaft of the vessel. An advantage which this arrangement possesses over the ordinary English hydraulic arrangement, is the fact that the endless screw suffices to turn the vessel, in either direction, any number of complete revolutions; while even the latest American improvements, so clearly explained to us by Mr. Holley at the opening session of this meeting, do not secure even one complete revolution without changing the angle of inclination of the hydraulic piston. In the endless screw arrangement, there being no limit to the working of the motor in either direction (no return-stroke necessary), the vessel can always, unless outside reasons demand the contrary, be turned around to any desired position by the shortest cut, whether backwards or forwards. Also, the diameter of the cog-wheel attached to the vessel can be made sufficiently great to avoid all unevenness of motion. In the old department the motive-power still continues to be hydraulic. If reports be true, the new department produces spiegelized steel, for the manufacture of all-steel rails. But the old department is still,&apos; as from the beginning, devoted to the production by the direct method of steel for steel-headed rails. The most remarkable fact connected with this direct steel is the ease with which it welds to the iron&apos; of the rail-packets, although no borax or other fluxing agent is used to facilitate the welding. It is very rarely that an exception occurs, and an ingot or a charge is discarded by the rail-mill. The mixture of pig-iron used for the production of this steel is melted in cupolas of very interesting construction (not to be de

Jan 1, 1874

By J. C. Yannopoulos, N. J. Themelis

Ah electronic thermogravirnetric balance was used to measure the veductioiz rule o single cirpric oxide particles suspended in a stream of hydrogen. Very jzne thermocouples embedded in lie center and at the surface of the sphere recorded the variation of terw perature during reduction. In contrast to iron oxide reduction, where in most instances the rate of interface reactiokl is controlling, the heat- and mass-transfer phenotnena play a predolrinant role in the reduction of cupric oxide. The correlation of experitnental data or tnass lransfev lhrough the boundary layer at Reynolds nunlber 0-4 50 was as jollocs: ThE reduction of cupric oxide by hydrogen is represented by the equation: It is a highly exothermic reaction and the amount of heat released varies only slightly with temperature (-21,430 cal per g-mole at 400°C). Most of the published studies on this system have been conducted at temperatures in the range of 34 to 280c.l-&apos; The concensus of opinion has been that at temperatures below 200°C the reaction is preceded by an induction period during which there is very little or no reduction. The length of this period diminishes as the temperature of the reaction is increased1l5 and aseawa found that at 280°C reduction starts practically immediately when the oxide is exposed to hydrogen gas. The existence of an induction, or incubation, period has led experimenters to believe that the reduction of CuO by hydrogen is catalyzed by metallic copper.&apos; Boldurev and rmolaev found that mechanical additions of powdered copper to oxide did not affect its reduction, although metallic copper produced during the reduction seemed to have a catalytic effect. At least three other authors2&apos;5&apos;7 have reported that addition of copper had no effect on the rate of reduction. Pease and alor&apos; observed that water vapor had a strong inhibiting effect on the reduction at 1503C, but its effect was greatly diminished at 200 C. Pavlychenko and Rubinchik5 studied this reaction at 159 to 235 C and found that, once the reaction had been initiated, there was no inhibiting effect due to the introduction of water in the hydrogen stream; at temperatures above 183°C there was no inhibiting effect due to water vapor, either before or during reaction. The same authors noted that the rate of reduction was independent of pressure in the range of 200 to 700 mm Hg. aseawa investigated the kinetics of the CuO-Hz system at 160 to 280°C and estimated the apparent activation energy at 14,000 cal per g-mole. A similar value (13,500 1200 cal per g-mole) was reported by ond&apos; in the temperature range 148 to 216°C. Bond also reported that there was no incubation period and that water vapor had no inhibiting effect on reduction at temperatures above 190 C. The above studies have been conducted at temperatures below 280°C and the physical configuration of the system under investigation has not been defined adequately. However, it is well-known that the mechanism of gas-solid reactions depends on a number of in series physical and chemical rate prcesses.&apos;&apos; It is, therefore, essential to include among the experimental factors the geometry of the solid system and the mass-transport characteristics of the reducing gas. Scott studied the reduction of packed beds of cupric oxide cylinders by Hz-He streams of very low hydrogen concentrations at temperatures 400 to 600 C, pressure of 10 to 30 atm, and gas velocity from 0.18 to 5.8 ft per sec (3 < Rep < 30). The reduction rate was found to be mainly controlled by diffusion through the boundary layer and through the pores of the reduced copper phase. The following correlation was proposed: Scott in an earlier work studied the reduction of fixed beds of cupric oxide wire and found that the rate of flow of the gas stream through the bed had a controlling effect on the rate of reduction. The same mass-transfer phenomenon was observed by Bond and clark13 on a similar reduction system. The analogy between mass and heat transfer through the boundary layer which exists between a solid surface and the bulk stream stems from the similarity of the differential equations representing these phenomena

Jan 1, 1967

By J. E. Hilliard, J. W. Cahn

calculation has been made of the standard deviations to be expected in the measurement of volume fractions by areal analysis, lineal analysis and four point-counting Procedures. The effect of experimetztal errors is not included. Our conclusion is that a point count using a two-dimensional grid will be the most efficient method of volume fraction analvsis providing the grid spacing IS coarse enough. The predicted standard deviation for such an analysis is shown to he in good agreement with that determined experimentally. A metallurgist wishing to estimate a structural property by means of quantitative metallography is often faced with a choice between several different procedures. In such a case, he will naturally wish to know: a) Which procedure is the most efficient in the sense of requiring the least effort for a given precision? b) For a given procedure, what are the conditions for maximum efficiency? c) Under these conditions, how many measurements are required to attain a given precision? It is our aim in this paper to provide at least partial answers to these queries as they relate to the estimation of volume fractions from measurements on a random two-dimensional section of an opaque specimen. The commonly used techniques1,2 for volume-fraction analyses are based on one or more of the following principles: i) For an areal or Delesse3 analysis: That the areal fraction of a three-dimensional feature intercepted by a random plane provides an unbiased estimate of the volume fraction of that feature. ii) For a lineal or Rosiwal4 analysis: That the fractional intercept on a line passing at random through a two-or three-dimensional feature provides an unbiased estimate of, respectively, the areal or volume fraction of that feature. iii) For a point-count analysis: That the fractional number of randomly or regularly dispersed points falling within the boundaries of a two-dimensional feature on a plane, or within the boundaries of a three-dimensional feature in a volume, provides an unbiased estimate of, respectively, the areal or volume fraction of that feature. The absence of bias referred to in these principles does not, of course, imply that the results of an analysis will be free of error, but only that the expected result is equal to the true one. Application of the foregoing principles provide the following six possible experimental procedures: a) An Areal Analysis—This involves the measurement with a planimeter (or other means) of the area of a constitutent intercepted by the plane of polish b) A Two-Dimensional Random Point Count—Apos-sible experimental procedure for this analysis is to superimpose a sheet of transparent graph paper on a micrograph, and then use a table of random numbers to select coordinates for the points. c) A Two-Dimensiotuzl Systematic Point Count-Similar to b) except that the points are distributed in a prescribed manner, usually at the corners of a lattice superimposed on a micrograph or the screen of a projection microscope. d)A Lineal Analysis—A measurement of the fractional line length intercepted. It is usually performed by traversing the specimen under the cross hairs of a microscope and recording the distance travelled in each constituent. e) 4 One-Dimensional Random-Point Count— This could be performed by traversing the specimen with stops at random intervals to identify the constituent then present under the cross hairs. f) A One-Dimensionul Systematic Point Count— Similar to e) except that the traverse is stopped at prescribed (usually equal) intervals. It will be noted that the point-counting procedures b) and c) can be regarded as methods of estimating the areal fraction. Similarly, e) and f) are indirect methods of making a lineal analysis. All of the six procedures described above involve at least one stage of sampling. Thus, quite apart from any experimental errors, there will always be a statistical uncertainty associated with the final results. It is with the calculation of this uncertainty that we will be concerned. To avoid unnecessary repetition, the statistical relationships that will be used in the calculations are collected together in the appendix. For a fuller discussion reference should be made to one of the many textbooks5,6 on statistics. For symbols relating to the specimen structure we will follow as far as possible the terminology used by Smith and Guttman.7

Jan 1, 1962

By J. S. Kirkaldy, R. C. Dorward

The solubilities of copper and gold in silicon and germanium have been determined by equilibration of the solid semiconductors with coexisting liquidus phases. The experimental results were combined with estimated activity coefficients of the liquidus alloys to determine the following partial molar enthalpies and excess entropies of solution for the systems: Solubility measurements were also carried out below the eutectic temperature of the copper-silicon system. The partial molar enthalpy and excess entropy of copper in silicon with respect to Cu3Si were determined to be 40.2 ±0.5 kcal per mole and 9.7 i 0.5 cal per mole — OK, respectively. It has been dentonstrated that nu-cleation and growth of intermediate compounds are retarded in copper-silicon diffusion couples. This points out the dangers of determining equilibrium solubilities by dijjusion methods. THE thermodynamic requirement for equilibrium between contiguous phases at constant pressure and temperature is that the chemical potential of each component be constant throughout the system. Equating expressions for the chemical potential of solute, component 2 say, in two phases, alpha and beta, gives

Jan 1, 1969

By Bruce A. Kennedy, Richard M. Stewart

Slope stability has now become a practical tool in the design and operation of open pits. The selection of slope angles is a critical decision that can have far-reaching effects on the accumulated cash flow and the overall profitability of a mining project. Slope failures can now be dealt with in a number of ways. Two methods - the total removal and the partial unloading of a failing zone-have been practiced for many years. However, with the refinement of monitoring techniques, open pits can now learn to live with a slide and even turn a potential loss into a gain. There are various techniques, such as presplit blasting, drainage systems, and artificial stabilization, which can be applied immediately in an existing open pit to improve the stability of the pit slopes. The technology of slope stability will play an important part in the future mining of low grade, previously marginal orebodies, which will have to be exploited if the mineral needs of the world are to be met.

Jan 1, 1971