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By Leendert de Witte, Fred J. Radd

In many areas caring failures can be directly related to electrical currents observed in the casings. It is the thesis of this paper that the observed casing currents are mainly due to electrochemical potentials of the type in evidence on spontaneous potential curves of electrical logs. The general nature of these potentials are discussed and an equivalent circuit is given for current and potential distributions around open holes. The casing forms a short circuit to these potentials and tends to average the effects of local cells. The case of casing corrosion opposite the Dakota water sands in the salt-mud area of Kansas is discussed anil used us a qualitative, illustration of the relation between SP's and casing currents. A method of quantitative derivation of casing current distribution frorn electric log SP curves, using linear transform theory, is described and results are compared with a measured current profile. The effects of hydrogen over-potentials at the cathodic portions of the pipe are considered and some laboratory data are given in support of conclusions regarding the over-1.01tuge.s. INTRODUCTION To date an appreciable amount of work has been done on the measurement of oil well casing currents and on the correlation of the anodic portions of the current profiles with corrosive casing failures. Speculations on the origin of the casing currents have, however, remained rather vague; and although almost every plausible cause has been mentioned, there is to the writers' knowledge no clear-cut expose' on the details of the causes of the corrosive currents in the literature. A study of current surveys and casing failures in the N.W. Burnett field, Ellis County. Kan.. indicated the probability that concentration cell emf's between the Wellington salt section and the relatively fresh waters in the Dakota sands were a major cause of the corrosion currents. A more general concept evolved upon analysis of the severe corrosive conditions in the Pleistocene sands in the Ventura Avenue and San Miguelito fields in California. In this area no major variations in the salt content of the formation waters occur and yet large casing currents are observed. An explanation is found in the fact that the local spontaneous potentials which are set up due to concentration contrast between the drilling fluid and the connate water are short circuited when casing is set. The very conductive path through the casing increases the magnitude of the currents and has the tendency to average local sources over fairly large intervals. Current will flow between the sections that are predominently shaly and the sections that are mostly sandy. At the places where the current leaves the pipe, corrosive attack will occur. This same phenomenon will be present wherever unprotected pipe is set through sections that show large SP kicks on the electric logs over reasonably thick interval~. GENERAL- NATURE OF THE SPONTANEOUS POTENTIALS When a sequence of sedimentary rocks is penetrated by a drill hole filled with a mud which has a different salt concentration from that in the formation waters, various types of electrochemical potentials are established between the formations and different parts of the mud column. Opposite clean sand sections. a simple liquid-liquid junction potential will be observed; while opposite argillaccous formations, a membrane potential, often referred to as shale potential, will be established. The first quantitative analysis of these emf's in terms of liquid junction and membrane potentials is due to Wyllie.1

Jan 1, 1956

By H. R. Spedden, A. M. Gaudin, M. P. Corriveau

A preliminary study of silver ion adsorption by sphalerite in ion exchange column with influent electrolyte marked with radiosilver is described. Rapid ion exchange occurs at first followed by slow reaction controlled perhaps by solid state diffusion. One experiment with radiocopper instead of radiosilver is reported briefly. IT has been known for many years that sphalerite is floated after it has been activated by a metallic cation, particularly copper.' The activation of sphalerite by copper is known to be an exchange of an atom of copper for an atom of zinc at the surface of the sphalerite.2,3 It has been estimated from various guesses of the available mineral surface that the depth of the copper-bearing coating is of the order of thickness of one atom. However, the exact mechanism of the activation process is unknown. A number of metals other than copper act in the same general manner."' " In particular, it has been known that silver replaces zinc at the surface of sphalerite. As copper is usually divalent, whereas silver is monovalent, it may well be assumed that there are differences, perhaps major differences, in the detailed scheme of activation by these two cations. Furthermore, since silver has unusual photoelectric properties and may be a contributor to the fluorescence of sphalerite, a study of its activating mechanism might open up some interesting avenues for exploring these other phenomena. The choice of silver as an activator of sphalerite was suggested also by the fact that its radioactive tracer, silver 110, is particularly convenient in that it has a long half-life and is energetic enough to permit counting through a counter window. The experimental technique selected, therefore, included the preparation of solutions of silver nitrate con- taining a proportion of active silver nitrate sufficient to give convenient counting data. In further considering the method to be used, a desirable choice seemed the use of batch experimentation in which a given solution was allowed to act on a certain lot of mineral for a given length of time at a given temperature, this period of mutual reaction being followed by analyses of the separated solid and solution. But an alternative method seemed more attractive. This is the method now so familiar to the users of ion-exchange resins, which was first made famous by the Russian chromatographer, Tswett.6-8 It consists in forming the mineral into a porous column through which the solution is allowed to flow at a constant rate. The usual method of allowing a batch of solid to react with solution is the equivalent of a single plate distillation operation while the chromatographic or ion-exchange column is a multiple-plate method—the multiplicity of the plates being represented by the reciprocal of the rate of flow of solution through the column. It seemed to us that the chromatographic method had such

Jan 1, 1952

By James P. Kimball

Sulphur is always present in mineral coal of every variety. In the oxidized state it may exist as sulphuric acid in combination with a base. In the unoxidized state it exists in combination with iron as bisulphide of iron. It is also supposed by some chemists to exist in unknown combinations with the organic elements of the coal. This supposition requires the demonstration as a fact that certain coals yield more sulphur than what may exist in a free state, or what belongs to recognized combinations, not only with the accompanying iron but with other inorganic bases abundantly occurring in coals, but which unfortunately are very rarely estimated. This practically as well as theoretically important question it is at present impossible to decide, simply for want of available thorough ultimate coal analyses including the ash. Such analyses, at the best imperfect, are luborious and intricate, and therefore seldom made, the much simpler proximate analyses, so-called, being resorted to by most chemists for technical purposes, and commonly substituted for more scientific work even in the laboratories of government surveys. And it is unfortunate enough that few ultimate analyses are extended to the composition of the ash, much less to its relation to the original constitution of the coal. Sulphur chiefly occurs in most coals in the form of yellow pyrites (pyrite) and white pyrites (marcasite), both minerals, characterized by differences in crystalline form and in physical properties as well as in color, but having the same chemical composition (FeS2). No coal is entirely free from one or both of these dimorphous forms of bisulphide of iron. It may be disseminated through the mass so as to be invisible, in plates or scales between the laminæ of the coal, or in conspicuous segregations or nodules, sometimes of considerable dimensions. Coals greatly differ as to the proportion of sulphur which they contain. They also differ as to the relative proportion in which its several forms of combination occur. Such qualitative and qnantitative disparities arc scarcely, if at all, more marked in separate coal seams of a uniform type than in different parts of one and the same coal seam, whether it be considered locally as constituted of several

Jan 1, 1880

By M. L. Fuller

DURING the last several years many papers have appeared dealing with the structure of highly polished metal surfaces. The awakening of interest in this subject is due to the applicability of the electron diffrac-tion technique to the study of surfaces. The original theory of Beilby1 considered the surface of polished metals as of the nature of a super-cooled liquid or a vitreous, amorphous solid. The electron diffraction effects from polished metals have been interpreted by many to be a direct experimental proof of the correctness of the Beilby theory. This inter-pretation has been strongly opposed by others, so that at the present time the subject is in an uncertain and controversial state. In the present paper new, and hitherto unpublished, electron diffrac-tion effects from polished zinc are described. These observations indicate that the polished surface of zinc is crystalline.

Jan 1, 1938

By Frederick N. Rhines, Robert F. Mehl

IT has been shown elsewhere1 that the data on the rates of diffusion in solid metals are fragmentary and in many cases unacceptable. As a result, relatively little is known concerning the factors determining rates of diffusion and the variations in these rates with temperature. The first form of Fick's law (equation 1 below), ‡ in which the diffusion coefficient D is assumed invariant with composition, has been recognized for many years as only an approximation. The differential equation representing the second form of Fick's law (equation 4 below) has only recently been integrated by Matano,2 and unfortunately only in cases where a full diffusion-penetration curve (concentration-distance curve) has been obtained can the Matano solution be applied. The proper analysis of diffusion data is thus confined to the data of Grube and Zedele and of Zedele.§ These data are essentially for one temperature alone and do not furnish any information on the variation of the activation heat of diffusion, Q, with concentration: no information exists on the variation of Q with concentration within a singles olid solution field. 11 Much of the argument concerning the properties of metals that determine D and Q has been drawn from data in which variations of the quantities with concentration are unknown, for these data have been taken from experiments that could not furnish this information. Speculation concerning the properties of metals that may be effective in determining D and Q on the basis of data in which the chosen D and Q values are averages over wide concentration ranges of values at particular concentrations, ranges often of 100 per cent, is likely not to be fruitful.

Jan 1, 1938

By H. G. Doll

A new logging method, called induction logging, is described; it measures the conductivity, or resistivity, of the strata traversed by a bore hole. The apparatus, which is briefly described, comprises a coil system coupled with the ground by induction, so that there is no need for direct contact with the mud, or with the formations. For that reason, the method is particularly useful in oil base mud, and it was first applied to that case. A discussion concerning the respective contribution of each region of ground in the vicinity of the coil system is given. Through the concept of a geometrical factor, it is demonstrated that the total signal, which measures the apparent conductivity, is the summation of the partial products — geometrical factor by conductivity — for the different regions of the ground under consideration. It is thus possible to establish, for each type of coil arangement, investigation characteristic as well as departure curves and correction charts for beds of various thicknesses. This should greatly facilitate the quantative interpretation of the field logs, even in cases where such interpretation would have been difficult on electric logs taken with electrodes. It is also shown that focussing combinations of coils can be used, which give, directly on the recorded log, a value close to the true conductivity, even for fairly thin beds, thus eliminating in most cases the need for corrections. These focussing systems also give a sharper definition of the boundaries between successive strain.

Jan 1, 1949

By H. G. Doll

A new logging method, called induction logging, is described; it measures the conductivity, or resistivity, of the strata traversed by a bore hole. The apparatus, which is briefly described, comprises a coil system coupled with the ground by induction, so that there is no need for direct contact with the mud, or with the formations. For that reason, the method is particularly useful in oil base mud, and it was first applied to that case. A discussion concerning the respective contribution of each region of ground in the vicinity of the coil system is given. Through the concept of a geometrical factor, it is demonstrated that the total signal, which measures the apparent conductivity, is the summation of the partial products — geometrical factor by conductivity — for the different regions of the ground under consideration. It is thus possible to establish, for each type of coil arangement, investigation characteristic as well as departure curves and correction charts for beds of various thicknesses. This should greatly facilitate the quantative interpretation of the field logs, even in cases where such interpretation would have been difficult on electric logs taken with electrodes. It is also shown that focussing combinations of coils can be used, which give, directly on the recorded log, a value close to the true conductivity, even for fairly thin beds, thus eliminating in most cases the need for corrections. These focussing systems also give a sharper definition of the boundaries between successive strain.

Jan 1, 1949

By G. P. Gladis, R. H. Atkinson

Palladium has been used for jewelry for many years, particularly in conjunction with gold. This use increased in amount during the war, as palladium and gold were only moderately used for war purposes while demands for platinum and some of the other members of the platinum group were so great that their use in jewelry was prohibited. Palladium hardened with a small percentage of ruthenium has the necessary technical properties and appearance for good jewelry, and it is sufficiently rare to be desirable for luxury items—at least I00 times as rare as gold. Although both visual and spectro-photometric examination demonstrated that the color of Palladium was almost the same as that of platinum, a few jewelers found the surface of palladium, even after some polishing, rather dark in areas that had been repeatedly heated during the soldering necessary to assemble certain types of handmade ornaments. This phenomenon is not to be confused with the thin, bluish oxide film that can be produced by heating in air over the range 400' to 800°C., as that film is easily reduced by dipping in warm 5 per cent formic acid or in warm methanol. It was suspected that the difficulty arose from heating in atmospheres that were alternately oxidizing and reducing, as Wise and Vines1 had found that this opened the grain boundaries of palladium and palladium-silver alloys in the same manner as in pure silver, as reported by Martin and Parker.2 This damage is caused by the reaction between oxygen in solid solution in the metal, acquired when heated under oxidizing conditions, and hydrogen diffusing in from subsequent heating under reducing conditions; the steam cannot diffuse out and therefore builds up sufficient pressure to disrupt the metal near the surface. Copper and various other metals can be damaged similarly, but platinum is nearly immune; therefore the problem was new to the platinum jeweler. Sulphur in the fuel gas also can cause trouble but did not appear to be dominant in the present instance. Metallographic examination of both pure palladium and ruthenium-palladium showed that the usual torch using oxygen and city gas as normally operated did in fact cause the surface and subsurface damage that had been observed, and also disclosed that a reducing flame caused more damage than an oxidizing flame and was very damaging even in the absence of any intentional swing in atmosphere from oxidizing to reducing (Fig. 7); besides the surface damage, there was serious loss of ductility. A full explanation of the mechanism of attack is not evident at the moment, but may be allied to the attack that occurs on heating catalytically active metals in nonequilibrium atmospheres.

Jan 1, 1946

By G. P. Gladis, R. H. Atkinson

Palladium has been used for jewelry for many years, particularly in conjunction with gold. This use increased in amount during the war, as palladium and gold were only moderately used for war purposes while demands for platinum and some of the other members of the platinum group were so great that their use in jewelry was prohibited. Palladium hardened with a small percentage of ruthenium has the necessary technical properties and appearance for good jewelry, and it is sufficiently rare to be desirable for luxury items—at least I00 times as rare as gold. Although both visual and spectro-photometric examination demonstrated that the color of Palladium was almost the same as that of platinum, a few jewelers found the surface of palladium, even after some polishing, rather dark in areas that had been repeatedly heated during the soldering necessary to assemble certain types of handmade ornaments. This phenomenon is not to be confused with the thin, bluish oxide film that can be produced by heating in air over the range 400' to 800°C., as that film is easily reduced by dipping in warm 5 per cent formic acid or in warm methanol. It was suspected that the difficulty arose from heating in atmospheres that were alternately oxidizing and reducing, as Wise and Vines1 had found that this opened the grain boundaries of palladium and palladium-silver alloys in the same manner as in pure silver, as reported by Martin and Parker.2 This damage is caused by the reaction between oxygen in solid solution in the metal, acquired when heated under oxidizing conditions, and hydrogen diffusing in from subsequent heating under reducing conditions; the steam cannot diffuse out and therefore builds up sufficient pressure to disrupt the metal near the surface. Copper and various other metals can be damaged similarly, but platinum is nearly immune; therefore the problem was new to the platinum jeweler. Sulphur in the fuel gas also can cause trouble but did not appear to be dominant in the present instance. Metallographic examination of both pure palladium and ruthenium-palladium showed that the usual torch using oxygen and city gas as normally operated did in fact cause the surface and subsurface damage that had been observed, and also disclosed that a reducing flame caused more damage than an oxidizing flame and was very damaging even in the absence of any intentional swing in atmosphere from oxidizing to reducing (Fig. 7); besides the surface damage, there was serious loss of ductility. A full explanation of the mechanism of attack is not evident at the moment, but may be allied to the attack that occurs on heating catalytically active metals in nonequilibrium atmospheres.

Jan 1, 1946

By R. M. Sellwood

The No. 4 I.S.F. Smelter Complex at the Avonmouth Works of Imperial Smelting Corporation (N.S.C.) Limited commenced operation at the beginning of 1968. The furnace rating is 120,000 tons zinc and 40,000 tons lead per annum. Zinc and lead concentrates are unloaded onto a 1,000 tons per hour capacity conveyor belt and automatically weighed and sampled before receipt into a 48,000 ton capacity raw material store. Distribution is by a reversible boom stacker into 16 x 3,000 ton bays and recovery is by a front end loader. Materials are fed to 16 proportioning bins for feeding via continuous weigh feeders to a 132 square metre effective updraught area sinter machine with a material flow rate of 240 tons per hour over the machine. The required quantity of output lump sinter at up to 800ºC is fed to 2 x 600 ton storage bins on the I.S.F. plant. By-product SO2 rich gas is fed to a conventional wet gas single stream acid plant rated at 600 tons per day utilizing a dry N.T.P. gas volume of 100,000 cubic metres per hour. The hot sinter and preheated coke (800ºC) are automatically neighed and charged to a 27.3m2 shaft area I.S.F. fitted with 2 x 5.5 m. wide lead splash condensers. Grade 4 zinc is tapped and transferred to the zinc refinery. Conventional type lead bullion and slag are tapped from the bottom of the furnace through a separation forehearth. The refinery consists of 6 lead and 3 cadmium columns to produce some 52,000 tons per annum of S.H.G. metal. S.H.G. metal and Grade 4 metal is cast into various shapes as required.

Jan 1, 1970

By E. A. Gulbransen, W. S. Wysong

THE behavior of tungsten and its surface oxides in oxidizing and reducing atmospheres and in high vacua at elevated temperatures is a question of considerable technical importance. The use of tungsten as a metal or as an important component in alloys in high temperature oxidizing atmospheres has been limited because of the unprotective nature of its oxide film and the volatility of its oxide. This paper will present results of a microbalance study1,2 of the following problems: (I) the oxidation behavior in the temperature range of 25 to 550°C (2) the reduction with pure hydrogen of thin oxide films formed on tungsten, and (3) the volatility of thin oxide films on tungsten. Tungsten is an interesting metal to study for the following reasons: (1) although the oxide to metal volume ratio is greater than one, the oxide is not considered protective, (2) the metal readily oxidizes at temperatures from 300° to 550°C (3) the oxides W02 and WO3 are reduced at temperatures as low as 500°C. by hydrogen, and (4) the oxide W02 is volatile at temperatures from 800 to 1100°C. LITERATURE The oxidation of tungsten in its thin film range has not been studied critically. In the thick film range Dunn3 has made the only systematic study. He found the oxidation rate to obey the parabolic rate law in the temperature range of 700 to 900°C. The temperature variation of the oxidation rate constant was found to follow an exponential law of the Arrhenius type. An inflection was noticed in the temperature plot of the rate law constant at 850 to 900°C. This was attributed to a phase change in the oxides. Scheil4 has studied the oxidation rate at 500 and 700°C over long periods of time and found a linear rate law. This result was interpreted as evidence for the presence of a nonprotective film. Pilling and Bedworth5 analyses of the oxide volume to metal volume ratio would indicate that a compact protective film should form. McAdam and Geil6 have studied the oxidation of tungsten in the thin film range using the interference color method. A parabolic rate law was found. Their curves showed that tungsten oxidizes faster than nickel but more slowly than iron. The lattice structures found in the oxidation of tungsten surfaces have been studied by Hickman and Gulbransen.7 They have reported that W03 is the stable oxide in contact with the metallic substrate up to approximately 600°C while W02 forms first at 700°C. Hägg and Magneli8 have recently reported a study of the lattice structures observed in the tungsten oxides using the X-ray diffraction method. In addition to an a-phase W03 and a d-phase W02, they reported the existence of two new phases. A ß' phase, homogeneous between

Jan 1, 1947

By Welton J. Crook

Unless present, in considerable praportion, metals of the precious-metal group—other than gold and silver—are not readily detected by the methods of fire assaying usually applied to ores and metallurgical products. Platinum, when present in small quantity, will ordinarily be reported as silver unless special methods of parting are used. Other elements occurring in the gold itself are all fluxed and slagged in the assay operation and if analyses are made on bullions the melting and slagging operations to which the bullion has been subjected may eliminate most of the associated elements. On the other hand, the analysis of precipitate from the cyanide treatment of gold ores may reveal the presence of many unexpected elements, such as tungsten and molybdenum. It is uncertain, however, whether many of the elements present in the precipitate are derived from the ore gangue or from the gold itself. No very general survey of the distribution of metallic elements in gold seems to have been made. Rose and Newman,l in connection with the composition of native gold, say in part as follows: Gold is occasionally found alloyed with copper and sometimes also with iron, bismuth, lead, mercury, tin, antimony, palladium or rhodium. Rhodium gold from Mexico was found to be of the specific gravity 15.5 to 16.8 and contained 34 to 43 per cent of rhodium. The native alloy of palladium, gold, and silver from Porpez contains 85.98 per cent of gold, 9.85 per cent palladium and 4.17 per cent silver. Mal-donitk, from Victoria, contains gold 64.5 per cent, bismuth 35.5 per cent (Louis). Dana2 says that native gold is usually alloyed with silver in varying amounts, and that sometimes it also contains traces of copper and iron. Rare varieties contain palladium, rhodium and bismuth. Other authors, for instance Zeigler3 and Clark,4 give similar information. Most references on the subject agree that ordinary native golds contain, in common, the elements silver, copper and iron. After completion of the work of which this paper is a record, the conclusion is reached that all ordinary native gold probably does contain these elements and, although in certain cases other elements may be found to be present, that it is difficult to

Jan 1, 1943

By Welton J. Crook

Unless present, in considerable praportion, metals of the precious-metal group—other than gold and silver—are not readily detected by the methods of fire assaying usually applied to ores and metallurgical products. Platinum, when present in small quantity, will ordinarily be reported as silver unless special methods of parting are used. Other elements occurring in the gold itself are all fluxed and slagged in the assay operation and if analyses are made on bullions the melting and slagging operations to which the bullion has been subjected may eliminate most of the associated elements. On the other hand, the analysis of precipitate from the cyanide treatment of gold ores may reveal the presence of many unexpected elements, such as tungsten and molybdenum. It is uncertain, however, whether many of the elements present in the precipitate are derived from the ore gangue or from the gold itself. No very general survey of the distribution of metallic elements in gold seems to have been made. Rose and Newman,l in connection with the composition of native gold, say in part as follows: Gold is occasionally found alloyed with copper and sometimes also with iron, bismuth, lead, mercury, tin, antimony, palladium or rhodium. Rhodium gold from Mexico was found to be of the specific gravity 15.5 to 16.8 and contained 34 to 43 per cent of rhodium. The native alloy of palladium, gold, and silver from Porpez contains 85.98 per cent of gold, 9.85 per cent palladium and 4.17 per cent silver. Mal-donitk, from Victoria, contains gold 64.5 per cent, bismuth 35.5 per cent (Louis). Dana2 says that native gold is usually alloyed with silver in varying amounts, and that sometimes it also contains traces of copper and iron. Rare varieties contain palladium, rhodium and bismuth. Other authors, for instance Zeigler3 and Clark,4 give similar information. Most references on the subject agree that ordinary native golds contain, in common, the elements silver, copper and iron. After completion of the work of which this paper is a record, the conclusion is reached that all ordinary native gold probably does contain these elements and, although in certain cases other elements may be found to be present, that it is difficult to

Jan 1, 1943

By H. E. Nold

ThE raw materials of the ceramic industry are mostly clays. This raw material is ground, water is added and the mixture pugged into a moist, plastic, rather stiff mass. From this mass the desired units of manufacture are made (bricks, hollow building tile, sewer pipe, etc.). These units are dried; then placed in kilns and heated until the desired degree of vitrification is obtained. For firing ceramic ware, two distinct types of kilns are used; namely, periodic and continuous tunnel. Periodic Kilns Periodic kilns are those ordinarily seen in a brick plant. They are either round or rectangular. The raw, dried, formed ware is piled or set in the kilns to depths frequently exceeding 10 ft. The kiln is heated until the ware is matured, then gradually cooled sufficiently to allow men to remove the ware; then the cycle is repeated. The time duration of the cycle may be more than two weeks. In order that heat can be distributed uniformly throughout the pile or setting, the units are placed so as to leave open spaces or flues throughout the pile for the passage of the hot gases. Each kiln is provided with a number of fireboxes (usually 10 or 12) spaced equally in the outside wall. The fireboxes may be equipped with flat or inclined grate bars or they may have no grates at all (dead bottom). Down-draft kilns are most used. In these the hot gaseous products of combustion from the fireboxes are deflected upward by bag walls just inside the fire zone. From the top of the kiln the gases are drawn down through the setting, off through holes in the kiln bottom, and conducted to a stack or stacks. In up-draft kilns the fireboxes are usually set somewhat lower. The hot gases are drawn inward and upward through the ware and pass off from the top. Up-draft kilns find their greatest use in the firing of common brick. In either case the problem is to maintain, as nearly as possible,

Jan 1, 1934

By Norman Weiss

IF we were to measure progress this year in terms of large new mills and discoveries of fundamental significance we should certainly be disappointed. Outside of the uranium field there was little of a spectacular nature. San Manuel and Reserve completed their first year of operation; Erie approached readiness; the Toquepala project in southern Peru broke ground and gained speed. Important mill enlargements occurred at Inspiration, Anaconda, Ray, and Climax Molybdenum. A 3000-ton copper concentrator was completed at Pima, near Tucson. The Republic Mill of Marquette Iron Mining Co. started up in April. Abroad, the great developments in the African Copper Belt can be likened to the rapid growth of the porphyry coppers in this country. Fundamental research was confined nearly entirely to iron ore flotation and recovery of metal values from leach solutions, particularly uranium. The large number of review articles this year reflected a desire to take stock and consolidate past gains before taking the next bold steps. Undoubtedly a shortage of competent young engineers and technicians is stunting the natural growth of theoretical investigation in the field of minerals beneficiation, as well as the conversion of ideas into action. We find our small stock of talented young scientists concentrated in a few centers of erudition because there are not enough to diffuse through the industry. It is safe to say that among mine administrators and managers there is more interest in the education, training, and welfare of the young engineer than ever before.

Jan 2, 1957

By F. E. Jaumot, R. L. Smith

Self-diffusion in zinc has been used as an instrument for comparison of the absorption and sectioning techniques as a means of studying diffusion. Single crystal as well as poly-crystal samples were used asanda the temperature range of diffusion extended from 200° to 415°C. For temperatures above 200°C, the data indicate that the results obtained from the absorption technique agree with those obtained from the sectioning technique. The effect on the values of the diffusion coefficient of electroplating vs evaporation as a means of applying the tracer was investigated and no significant difference observed. It was found that an excess or deficiency of tracer did not materially affect the results obtained from the sectioning technique, but invariably caused errors with the absorption technique. NEARLY all self-diffusion experiments and many alloy diffusion experiments have employed radioisotopes as the instrument for following the diffusion. Of the various techniques in which radioisotopes are applicable, the two most widely used are the sectioning and absorption techniques. In the former, the diffusion coefficient is obtained from a curve of log concentration vs the square of the mean penetration depth. In the latter, the diffusion coefficient is calculated from a knowledge of the decrease in activity at the surface after diffusion. In spite of the importance of knowing the reliability of the diffusion data and the widespread use of these two techniques, they had not been directly compared experimentally on the same samples. Thus, such a comparison was worthwhile. The specific system chosen for this comparison was the self-diffusion of zinc, since the metal was readily obtainable in high purity, single crystals were easily grown, and the anisotropic features of the diffusion added an additional factor of interest to the comparison. Self-diffusion in both single and polycrystals was investigated, since the possibility existed that grain boundaries and grain boundary diffusion might produce different effects for the different techniques. Also, the effects of electroplating vs evaporation as a means of applying the radioactive tracer, and the effects of applying an excess or deficiency of tracer material were studied. The general experimental procedures and the mathematical analyses of both techniques have been described previously in some detail, and only those points essential to an understanding of the present work will be discussed here. The mathematical analysis of the sectioning data requires only a knowledge of the solution of Fick's equation. where C,, is the initial concentration, C is the concentration at depth x, D is the diffusion coefficient, and p is the absorption coefficient of the solvent metal for the radiation from the solute. Having obtained F from the experiment, the value of z can be read from a plot of F vs In z, and D can then be calculated if is known. The necessity of knowing the absorption coefficient causes most of the criticism of the absorption technique. It is very difficult to measure accurately under the conditions existing in the diffusion experiment, but it is absolutely necessary, as will be indicated briefly later. Portions of this problem have been discussed in detail elsewhere." The difficulties involved in the measurement of the absorption coefficient arise from three principle factors: the physical characteristics of the absorber, the geometry, and complex radiation spectra. The first two are heavily dependent upon the third. If

Jan 1, 1957

By H. E. McKinstry

MOVEMENT on a fracture of irregular shape can cause local widening of the fissure and thereby offer freer channelways for circulation of ore-depositing solutions. This influence, coupled with large areas of wall rock available for reacting with ore solutions in brecciated and shattered ground can account for locally active deposition of metals and the resulting ore shoots. Such irregularities in the fracture system may be caused by local variations in the strength of rocks and by pre-existing lines of weakness, especially if these stand at favorable angles to certain components of the fracturing stress. Therefore correct interpretation of the mechanics of fracturing should permit deductions as to structurally favorable places on unexplored portions of the vein system. INTRODUCTION IT has long been recognized that movement on a curved or irregular fault surface is capable of separating the walls in certain portions of the fault, but until very recent years the importance of this mechanism as a factor in localizing ore shoots has escaped proper recognition. A short time ago W. H. Newhouse' presented a careful analytical study of displacements and their corresponding open spaces. For reasons that will be discussed later, it frequently happens that portions of the vein which are favorably oriented are not merely wider but also richer than the average. In many cases the widening with its accompanying richness coincides with very minor changes in the dip or strike of the vein, irregularities that commonly escape notice unless the vein is mapped in detail and a careful geometrical analysis made. While the relationship between the width of the vein and the changes in dip or strike has been recognized as a matter of observation, the irregularities have been accepted as more or less the result of accident. There has been very little effort except in isolated cases to find out the causes of these changes in dip or strike. Yet it is clear that if the causes can be recognized and expressed in terms of geologic structure the geologist will know where to look for repetitions of these favorable conditions either on extensions of the same vein or on adjoining veins. Any lack of understanding of the causes is due to the limitations of our ability to interpret our observations and not to the sheer capriciousness of

Jan 1, 1941

By C. A. Zapffe

BOTH the foundryman and the theoretical metallurgist are now generally agreed that the anomalous "rising" or "bleeding" of certain ferrous castings of killed metal is primarily attributable to hydrogen. How and why the phenomenon occurs, however, have not been made clear. The following discussion is intended to harmonize foundry experience with metallurgical theory so that the foundryman may possibly improve his ability to prognosticate whether a certain casting may bleed or not. BLEEDING, RISING, AND PIPING The "rising" to be discussed here is not to be confused with the action in rimming ingots as a result of the carbon-oxygen reaction, although a conclusion will be drawn that may apply to the art of controlling the rimming action. Only killed metal is considered, which includes both steels and irons. In Fig. I, three killed, chill-cast ingots are shown: a porous ingot whose evolution of gas during late stages of solidification has ejected metal through the top; an ingot in which moderate gas evolution during solidification has lifted the mushy central metal, i.e., it has "risen"; and, third, a sound ingot with good piping characteristics. The first type is referred to as "bleeding," and generally infers that a solid skin had first formed through which the liquid metal later erupted. There is no fundamental distinction between bleeding and rising in reference to killed metal.* POROSITY Hydrogen appears as a cause of bleeding because the gas evolution simultaneously leaves a porosity of a type traceable to hydrogen. Twenty years ago, Melmoth1 noted that killed steel that rose unexpectedly in the mold, if returned while liquid to the furnace and heated further under a reducing lime slag, would again rise in the mold; but that if the ingot were allowed to solidify and was then remelted no rising occurred. A critical quantity of the responsible gas is therefore removed by the rising action. Melmoth associated rising with high silicon (0.7 to 0.9 per cent) and concluded that silicon increased gas absorption. Because silicon is a strong deoxidizer, oxygen must, therefore, be eliminated from consideration of the three common gases in steel-oxygen, nitrogen, and hydrogen. Butterworth2 later decided that pinhole porosity was caused by gases dissolved in the metal and that hydrogen was obtained from steam in the mold. Allen's classical work on copper castings,3 soon followed by

Jan 1, 1942

By Robert F. Mehl, Gerhard Derge

The gamma-alpha transformation in iron and iron-rich alloys is of such practical and theoretical importance that many papers have been published upon the subject relating to critical temperatures, transformation rates and accompanying property changes. Although crystallo-graphic studies are of less immediate practical usefulness, the opportunities which these offer to furnish data on the basic atomic movements which characterize the transformation are not to be neglected1. The early work on the crystallography of this transformation has been reviewed in the fourth paper of this series2; since then several important papers have appeared. Our present knowledge may be briefly summarized as follows. Kurdjumow and Sachs, working with a 1.4 per cent carbon steel3, established the orientation relationships subsisting between the face-centered gamma and the metastable tetragonal lattices in freshly quenched martensite, and between the face-centered gamma and the body-centered alpha lattices in tempered martensite. The orientation relationship observed in the latter case may be stated in terms of planes and directions observed to lie parallel in the two lattices: {111} ?//{110}a [110] ?// [111]a (This notation is used throughout as the most descriptive means of expressing the fact that any (111) plane of the gamma phase may be parallel to any (110) plane of the alpha phase, and that a [110] direction in a particular (111)? plane is parallel to a [Ill] direction in the corresponding (110)a plane.) From these relationships the atomic movements that transform the gamma lattice into the alpha may be inferred. In the present experiment these may be considered as consisting primarily in a shear of the atoms parallel to the {111} planes in [110]? Directions

Jan 1, 1937

By E. S. Davenport, R. J. Hafsten, R. A. Grange

The influence of austenite grain size upon the hardenability of steel is now fairly well understood; for a given austenite, increasing the grain size increases the depth of hardening, and, since the latter is related to the fundamental transformation behavior of austenite, it follows that austenite decomposition must, in general, be retarded by increasing grain size. To date, very little quantitative information bearing directly on the effect of austenite grain size upon the progress and result of isothermal transformation has been published. Davenport and Bain,' and Zimmerman, Aborn and Bain2 have shown that the transformation is definitely relarded in hypereutectoid plain carbon steels at temperatures near and above the upper region of rapid transformation (Ar') when the austenite grains are increased in size. More recently, Griffiths. Pfeil and Allen3 investigated the effect of a series of different heating (austenitizing) temperatures upon the progress of isothermal transformation at 1245°F. (675°C.) and 745ºF. (395°C.) in a medium carbon, low-alloy steel; while they reported no measurements of the austenite grain size, their results suggest that increase in grain size retards austenite transformation at 1245ºF. (675°C), but has no appreciable effect at 745°F (395°C.). The present paper deals with the results of a study of the isothermal transformation of austenite in a single commercial alloy steel in which a fine-grained or a coarsegrained state was induced by appropriate selection of austenitizing temperature. The data are presented in the form of isothermal transformation diagrams, which clearly show that coarsening the grains lessens the rate of transformation of austenite to proeutectoid ferrite and pearlite—that is, at temperature levels above about 1000°F. (540°C.)—but is without significant effect at lower temperatures where the transformation product is bainite or martensite. It is to he presumed that the foregoing statement would be valid, at least in principle, for many other grades of steel; it confirms again that the mechanism of transformation to a pearlitic structure is fundamentally different from that to an acicular structure. A number of related observations were made, which seem to throw some light on the transformation process as it takes place in alloy steels, particularly at temperature levels in the vicinity of 1000ºF. (540°C.), where the transition from lamellar to acicular structures occurs. These data are discussed briefly in the belief that they may lead to a clearer understanding of this aspect of the subject. Material and Experimental Procedure The material investigated was a cornmercial grade of S.A.E. 4140 steel, the composition of which was as follows: 0.37 per cent C, 0.77 per cent Mn, 0.98 per cent Cr and 0.21 per cent Mo. It was hot-rolled to a 1 1/8-in. round bar and normalized by air-cooling from 1800°F. (980°C.).

Jan 1, 1941