Search Documents

By W. T. Hicks

The oxidation of CbO was studied by a gravimetric technique from 400° to 1200°C in oxygen. In this temperature range the oxidatiotz is characterized by an irlductive period of low oxidation rate, which becomes shorter as the temperature increases, followed by a rapid parabolic oxidation. The oxidation of CbO cannot be rate controlling in the oxidation of Cb metal in the temperature range, 800° to 1200°C. A thin optically inactive layer has been observed between the metal and Cb2O5 layer of Cb oxidized at 700°C or higher temperatures. Figs. 1(a) and 1(b) show the edge of a sample of Cb reacted to 50 pct of complete oxidation at 800°C. Fig. l(a) taken under bright field illumination shows a layer of oxide adhering to the unoxidized metal core. Fig l(b) taken under polarized light shows that this oxide layer is

Jan 1, 1962

By J. D. Prater, H. R. Spedden, E. E. Malouf

Application of research findings to the old art of leaching copper from copper-bearing mine waste has resulted in a significant contribution of copper to over-all copper production. For example, at the completion of the current expansion program at the Kennecott properties in the United States, copper produced from waste dump leaching will amount to about 25% of the total production, whereas formerly only 2% was derived from this source. This planned expansion of copper leaching focused attention on the problem of developing more efficient methods for the recovery of copper from greatly increased volumes of copper-bearing so1utions.l Detailed investigations made in laboratory pilot plant and plant tests for the recovery of copper from copper-bearing solutions have included electrowinning, solvent extraction, ion exchange and cementation with iron in launders, precipitation drums, activated launders, and precipitation cones. The results of these investigations have led to the development of a precipitation cone-type recovery system having advantages over older methods.

Jan 4, 1966

By E. J. Schmitz

The mining of the Triassic coals of the Richmond basin has been carried on, upon a larger or smaller scale, for more than a hundred years. Notwithstanding the close proximity of the field to a large city and to tide-water, assuring both a good home-market and cheap transportation, and notwithstanding the good quality of the fuel and the great thickness of the principal bed developed and worked, operations in this field have been conducted with but limited success. The basin comprises about 189 square miles, being from 24 to 31½ miles in length by 5½ to 10 miles in width. Not much more than one-tenth of this area has been explored in a practical and efficient way, and not over 1200 acres have been worked near and along the outcrops or edges of the coal. The practical mistakes which have been committed undoubtedly in a number of the mine-operations of the past, do not alone explain the unsatisfactory success and progress of the industry of this field ; nor can it be ascribed to the lack of local enterprise. Other reasons have to be looked for; and, as a principal one, the irregularity and the faulted conditions of the coal deposits must be pointed out. As a second cause, the indifference of the State government, which leaves the development of the field entirely to private enterprise, instead of aiding it by systematical and practical geological investigations, deserves to be mentioned. Nothing has been done by the State since the excellent work done more than fifty years ago by Professor Rogers, who could not at that time enter into the details of such

Jan 1, 1895

By Theodore H. Eyde

The Superior Oil Co. drilled two holes, 4720 and 5940 ft, respectively, using conventional oilfield rotary drilling equipment. The results indicated that large rotary drills can be adapted to mineral exploration purposes with few modifications. The principal advantages are: a large hole diameter, excellent samples of cuttings, a geolograph which is a constant drilling record, rapid penetration even in hard rocks, and the ability to use electric logs for measuring the properties of the rock being penetrated. The disadvantages are the high cost of mobilization, drilling, and oilfield service at remote locations. Though the oilfield sampling techniques are adequate for identifying lithology, improvements are necessary to obtain representative samples for analytical purposes. As deeper targets are explored, mineral exploration organizations will have to resort to rotary drilling.

Jan 1, 1975

Discussion of the paper of J. IV. GWINN, presented at the New York meeting, February, 1915, and printed in Bulletin No. 98, February, 1915, pp. 239 to 247. GIRARD B. ROSENBLATT, Salt Lake City, Utah (communication to the Secretary*).-The storage-battery locomotive certainly has its place in metal mining and I an) glad to note that it is now receiving the recognition that is its clue. It is, however, not a panacea for all conditions of mine haulage. There are places where it will not work to advantage and cannot compare with` the trolley-type locomotive in cost of operation or in cost of maintenance. On the one hand, there are places where it clearly outshines the trolley-type locomotive. Much depends on the headroom available in the drifts and on the condition of the roof. For short hauls with moderate-

Jan 5, 1915

By Joseph W. Richards

THIS method of briquetting flue-dust, or flue-dust mixed with fine ores, or, in a few exceptional cases, coke-dust, has come into large commercial use in Europe, and a small plant is already in operation in the United States. It promises to become of such great importance to the iron industry of the United States that the following description will certainly interest the majority of our pig-iron producers. Discovered in 1908, the process rests upon the observation of Dr. Schumacher that blast-furnace flue-dust, while possessing of itself no binding or cementing properties, acquires strong cementing properties if mixed with a very small amount of certain salt solutions, the amount of which is so small that the resulting cementation appears to be rather by catalytic action of the salts added than by the mass-action of such chemicals. To be more specific, fresh blast-furnace flue-dust mixed with from 5 to 10 per cent. of its weight of magnesium chloride or calcium chloride solution-that is to say, with from 0.25 to 2 per cent. of its weight of magnesium chloride or calcium chloride-acquires the property of setting within a short time, from 15 to 60 min., and forming a hard cemented briquette. Alkaline solutions appear to have no action such as described, and they even interfere, if present, with the action of the magnesium and calcium solutions. When treated in this way the flue-dust briquette sets very hard, apparently from pure excess of cementing- and setting-power. It is, therefore, possible to . mix with the flue-dust a considerable proportion of inert ore or like material, which has no setting-power by this process, and thus to make a compound briquette containing large quantities of ore mixed with flue-dust, but in which the flue-dust may be regarded as the cement or binding-material. A particularly strongly cementing flue-

May 1, 1912

By A. R. Orban, R. B. Engdahl, J. D. Hummell

The initial phase of a research program on smoke abatement from Bessemer converters is described. In work sponsored by the American Iron and Steel Institute, a 300-lb experimental Bessemer converter was assembled to simulate blowing conditions in a commercial vessel. Measurements of smoke and dust were also made in the field on a 30-ton commercial vessel. During normal blows the dust loading from the laboratory converter averaged 0.51 lb per 1000 lb of exhaust gas. This was similar to the exhaust-gas loading of a commercial vessel. The addition of hydrogen to the blast gas of the laboratory converter caused a decided decrease in smoke density. Smoke was also reduced markedly when methane or ammonia was added instead of hydrogen. The research is continuing on a bench-scale investigation of the mechanism of smoke formation in the converter process. DURING the past 2 years, on behalf of the American Iron and Steel Institute, Battelle has been conducting a research program on the control of emissions from pneumatic steelmaking processes. The objective of the research program is to discover a practical method for reducing to an unobjectionable level the emission of smoke and dust from Bessemer converters. PRELIMINARY INVESTIGATION Although conceivably some new collecting technique may be devised which would be economically practicable for cleaning Bessemer gases, no such system based on presently known principles seems feasible because of the extremely large volume of high-temperature gases involved. Hence, the research is being directed toward prevention of smoke formation at the source. A thorough review was first made of former work to determine the present status of the cleaning of converter gases. No published work was found on work done in the United States on collecting smoke or on preventing its formation in the bottom-blown, acid-Bessemer converter. In Europe, however, a number of investigations have been made on the basic-Bessemer converter. Kosmider, Neuhaus, and Kratzenstein1 conducted tests on a 20-ton converter to obtain characteristic data for dust removal and the utilization of waste heat. They concluded that because of the submicron size of the dust, special equipment would be necessary to clean the exhaust gases. Dehne2 conducted a large number of smoke-abatement experiments at Duisburg-Huckingen in a 36-ton Thomas converter discharging into a stack. A number of wet-scrubbing and dry collectors were tried unsuccessfully. A waste-heat boiler and electrostatic collector with necessary gas precleaners was felt to be the best solution for this particular plant. Meldau and Laufhutte3 determined that the particle size was all below 1 µ in the waste gas of a bottom-blown converter. Sel'kin and zadalya4 describe the use of oxygen-water mixtures injected into a molten bath in refining open-hearth steel. They claim that with use of oxygen-water mixtures the amount of dust formed was reduced between 33.3 and 20 pct of its previous level, and emission of brown smoke almost ceased. Pepperhoff and passov5 attempted unsuccessfully to find some correlation between the optical absorption of the smoke, the flame emission, and the composition of the metal in a Thomas converter in order to determine automatically the metallurgical state in the melt. In a recent U. S. Patent (NO. 2,831,762)' issued to two Austrian inventors, Kemmetmuller and Rinesch, the inventors claim a process for treating the exhaust gases from a converter. By their method the inventors claim that the exhaust gases from the converter are cooled immediately after leaving the converter to a degree that oxidation of the metal vapors and metal particles to form Fe2O3 is inhibited in the presence of surplus oxygen. Gledhill, Carnall, and sargent7 report on cleaning the gases from oxygen lancing of pig iron in the ladle. They claim the Pease-Anthony Venturi scrubber removed 99.5 + pct of the smoke, thereby reducing the concentration to 0.1 to 0.2 grain per cu ft, which resulted in a colorless stack gas after the evaporation of water. Fischer and wahlster8 developed a small basic converter and compared the metallurgical behavior of the blow with that of a large converter. Later work by Kosmider, Neuhaus, and Hardt9 on the use of steam for reduction of smoke from an oxygen-enriched converter confirmed that the cooling effect of steam is detrimental to production. From review of all of the published information on the subject, it was concluded that a practical solution to the smoke-elimination problem had not been found. Accordingly, it was deemed desirable to investigate the feasibility of preventing the initial formation of smoke in the converter.

Jan 1, 1961

By D. E. Thomas, C. E. Birchenall

ALTHOUGH Eoltzmann gave a mathematical solution for the diffusion equation (for planar diffusion in infinite 01. semi-infinite systems only) in 1894 allowing for variation of the diffusion coefficient with a change in concentration, it was not until 1933 that this solution was applied to an experimentally investigated metallic system. The calculation was carried out by Matano' on the data obtained by Grube and Jedele3 for the Cu-Ni system. Since that time concentration dependence of the diffusion coefficient has been demonstrated for many pairs of metals. However, the nature of this dependence has never been fully elucidated. Many investigators have suspected that these variations could be related to the thermodynamic properties of the solutions, one of the earliest explicit statements being contained in a discussion of irreversible transport processes by Onsager' in 1931. Development along these lines has been greatly retarded by the lack of reliable data on the variation of tliffusivity with concentration, the paucity of the thermodynamic data for the same systems at the same temperatures and compositions, and an incomplete understanding of the relation of the thermodynamic properties of the activated state for diffusion to the bulk thermodynamic properties. The last factor has been discussed by Fisher, Hollomon, and Turnbull.5 In many instances where data exist, it is difficult to know which are acceptable. This problem probably applies more strongly to diffusion data than to activity measurements. For instance, four sets of observers"-" have reported self-diffusion coefficients for copper. The average spread between extreme results is a factor of about four, though the individual sets of data are self-consistent to about 20 pct. Thus one or more factors are out of control, at least in these experiments, making estimates of internal error unreliable. The most reliable diffusion data in most systems have resulted from the use of welded couples with a plane interface from which layers for analysis are machined parallel to the interface after diffusion. The layers are analyzed, and the result is a graphical relation between distance and concentration, usually called the penetration curve. Given the same set of analytical data and distances and following the same procedure in computation, different observers will generally produce diffusion coefficients which vary appreciably, especially at the extremes of the concentration range. Experiments must be carefully designed so that the precision is good enough to answer a particular question unequivocally. In the first calculation of the dependence of the diffusion coefficient on concentration in the metallic solid solution Cu-Ni, Matano found that the coefficient was insensitive to concentration from 0 to 70 pct Cu, after which it rose more and more steeply to some undetermined value as pure copper was approached.' The same behavior was reported for Au-Ni, Au-Pd, and Au-Pt.* The data used were those of Grube and Jedele which were very good at the time, but are not considered particularly good by present standards. Furthermore, the method of calculation makes the ends of the diffusion coefficient-concentration curve unreliable. For better reliability, the high copper end of the curve has been checked by incremental couples, where the concentration spread is 67.7 to 100 atomic pct Cu. The implication of the curves calculated by Matano was that diffusion is very concentration sensitive in one dilute range of this completely isomorphous system and hardly at all in the other. Matano's result is confirmed. Later Wells and Mehll0 published data on diffusion in Fe-Ni at 1300°C, which represent a thorough test of the shape of the concentration dependence curve. They ran couples with the following ranges of nickel concentration: 0-25 pct, 1.9-20.1 pct, 0-20.1 pct, 20.1-41.8 pct, 0-99.4 pct, and 79.3-99.4 pct. Although the trend of the data indicates an S-shaped concentration dependence, their curve was drawn to the pattern set by Matano. Their original data have been recalculated for the 0-99.4 and 79.3-99.4 pct couples. Wells and Mehl's points and two independent recalculations from the raw data are plotted in Fig. 1. What appears to be the best curve is drawn through them. This curve shows little sensitivity to composition in both dilute ranges with a strong dependence at intermediate composi-tions.? Similar experiments on the Cu-Pd system are reported here at temperatures where solubility is unlimited. These lead to the same type of concentration dependence for the diffusion coefficients as was found upon recalculation of the data for the Fe-Ni system. Experimental Procedure Cu-Pd: The concentration dependence of the diffusion coefficient may be determined by the use of

Jan 1, 1953

By K. J. Anusavice, R. T. DeHoff, A. G. Guy, T. B. Lindemer

As one oi the approacizes to understanding multicorn-ponent dimsion, an expevinzental sturly is being jnade of tracer diffusion in the copper corner of the CLI-Ni-Zn syste?n, out to 30 at. pct each of nickel and zinc, and in the 150°C range oJ temperature just below tlze solidts te?rlperature. The reslts obtained using the Znm isotope are reported heve, while studies with nickel and copper isotopes are planned for a future paper. The fifteen alloys investigated were melted in sealed wear lubes, sroaged, homogenized, and then analyzed, using the conventional isotope-plating plus lathe- sectiorzing teclzniqlte. The data obtaiued show that the difJusion coeflcient of the zinc isotope increases titlz increase in zinc content, and decreases t'itlz incease in nickel content. The correlation xith solidus temperature is particularly strong. Diffirsiui-ties ranged fro u sq cm per sec nt tlze Iiigh-zinc, low-nickel compositions. The activation energy /or tracer diffusion ravied j.or 31.000 to 54,000 calper mole. It is now generally recognized that diffusion data and theories are needed for multicomponent systems, where extensive practical developments and even some theoretical studies have already been made. For example, much recent work on precipitation from solid solution has been concerned with ternary solid solutions such as A-M-Z' while Zener relaxation has been studied on Au-Ag-Zn alloys,' although adequate diffusion data are available for neither of these systems. Actually, the only ternary systems for which systematic diffusion studies have been begun, in addi- tion to the one reported here, are CO-i-cr3 and Cu-A-Au. Since the theory of multicomponent diffusion is still in the stage of active development5 it is important to distinguish the various kinds of diffusion data that can be determined. An oversimplified approach, widely used prior to 1950, was to determine the influence of a third element, such as nickel, on the diffusion behavior of a binary alloy, such as CU-Z. Later it was recognized7 that four diffusion coefficients can be used to describe ordinary interdiffusion in a ternary system, while as many as six coefficients may be required to include the Kirkendall effect. It is likely that the number of independent coefficients will be shown to be less than four and six, respectively, through the application of the thermodynamics of irreversible processes.5 The simplest type of diffusion in a multicomponent system is tracer diffusion, since each component is characterized by its own tracer-diffusion coefficient in an alloy of a given composition. Thus, in a ternary alloy there are three tracer-diffusion coefficients, each a function of composition and temperature. The present research program is a study of tracer diffusion in the copper corner of the Cu-Ni-Zn system out to 30 at. pct each of Ni and Zn in a 150°C range of temperature just below the solidus temperature. The

Jan 1, 1967

By Grafton M. Thrasher

For the proper discussion of this subject it is necessary to incorporate in this paper the substance of part of an article published by me in Metallurgical and Chemical Engineering for January, 1915. Several years ago, while I was chief chemist for a malleable-iron company, it occurred to me that the mere regulation of silicon was not sufficient to produce the desired degree of chill. But only after repeatedly encountering this fact in both open-hearth and air-furnace, as well as cupola metal, was I led to regard variation in the total carbon as the principal cause of disturbance; and I resolved to determine the total carbon as well as the silicon in every heat, and by a carefully prepared test piece to gauge the approximate degree of chill. The test piece selected was a round plug, 2 in. in diameter and 12 in. long, cast on end

Jan 1, 1916

By Richard H. Sillitoe

Gold is an important byproduct and, locally, coproduct of porphyry copper deposits, and possesses potential for discovery as the major metal in porphyry deposits in either island arcs or Cordilleran belts. Tungsten and tin occur as major components of several potentially bulk-minable porphyry deposits, as well as being byproducts from the Climax porphyry molybdenum deposit. Whereas porphyry tin systems are localized in Cordilleran back-arc settings, their tungsten counterparts appear to span a range of geotectonic settings, from Cordilleran principal arcs through back arcs to rifts. Although silver is a common byproduct of porphyry cop- per deposits, it tends to be preferentially concentrated with lead and zinc on the fringes of all types of porphyry deposits and/or as late-stage superpositions; the latter situation could be of some interest in the higher parts of porphyry systems. As byproducts, rhenium, uranium, platinoids, and magnetite are exploited occasionally, and rutile and the rare metals, such as tantalum and niobium, merit consideration.

Jan 1, 1983

By F. L. Ransome

The dike here described is exposed in the workings of the Wedge and Bachelor mines, on the southern side of Red Canon, north of the town of Ouray, Colorado. Its course is north 80° east, or nearly east and west, and it hades to the north about 10°. It rarely outcrops, and was nowhere seen at the surface near the mines. A specimen collected by Dr. A. C. Spencer about two miles to the westward, near the mouth of Red Creek, indicates, however, a probable exposure of the dike near this point. The Wedge and Bachelor mines lie in a nearly horizontal series of fine-grained, light-grey sandstones, alternating with beds of very fine-grained shale of the same color. The shale as encountered underground is unusually compact and massive, but weathers readily on exposure, and splits much after the manner of ordinary shale. When fresh it closely resembles some finely arenaceous limestones, but it does not effervesce with acids, and is eseentially a fine, indurated, siliceous silt. Near the surface, and near the top of the sedimentary series as

Jan 1, 1901

By L. W. McKeehan

Jan 1, 1934

By S. R. B. Cooke, H. S. Choi, I. Iwasaki

In magnetic taconite of the East Mesabi range, quartz, magnetite, and cummingtonite (OH}(Fe, Mg)(Si4O11)2) are the three major ore-forming minerals.' Fine grinding and magnetic separation of the taconite leads to a concentrate analyzing 64 to 65 pct Fe and 8 to 9 pct insoluble; the gangue content of the concentrate arising from the presence of locked magnetite-gangue particles, and of occluded gangue particles in magnetic floccules. To further upgrade such taconite concentrates, flotation appears to offer a particularly promising approach. To evaluate its effectiveness in separation, a knowledge of the flotation characteristics of each mineral comprising the concentrate becomes desirable. The floatability of magnetite and of quartz have already been reported in a previous paper,2 in which the flotation characteristics of the two minerals were correlated with the electrokinetic properties at the mineral-solution interfaces. Since cummingtonite has somewhat intermediate chemical composition between the above-named oxides, the electrokinetic and the flotation behavior of this mineral becomes of interest for both practical and fundamental reasons. In the present article the results of electrophoretic mobility measurements and of Hallimond tube flotation tests on cummingtonite are reported and are compared with those of quartz and magnetite. MATERIALS AND METHODS A sample of cummingtonite-rich taconite, received from the Mitchell pit, near Babbitt, Minn., was crushed and ground through 100 mesh, and the product was fractionated magnetically into three portions. First, a drum-type laboratory cobber was used to separate a highly magnetic portion, consisting mainly of free, but also containing locked, magnetite particles. The cobber tailing was then passed in two stages through a Franz isodynamic separator. The middle fraction was isolated, and, upon examination petrographically, was ascertained to be principally cummingtonite. The 100 to 150 mesh fraction of this sample was selected for the present study. It was cleaned by leaching briefly with hot, dilute HC1 and then by rinsing repeatedly with demineralized water. A ground and elutriated fraction of -5p cummingtonite was used for the electrophoretic measurements.

Jan 1, 1961

By J. L. Dumanoir, Maurice Martin

The induction-electrical log is a combination of a SP curve, a short normal curve, and an induction log; all three logs being recorded simultaneously in a single run. The spacing of the short normal is 16 in. The induction log is designated as 5FF40, which means that the sonde involves five coils and a focusing system, and that the distance between the main coils is 40 in. Examples of induction-electrical logs are shown in Figs. 13 and 15. The right-hand track contains the induction conductivity curve. The scale of this curve is linear with the units of conductivity, i.e., mhos/m or millimhos/m (mmhos/m), increasing from right to left. The same curve can be read in the reverse direction as a resistivity log, with a hyperbolic scale. In the middle track, the solid curve represents the short normal. (An amplified short normal is also shown in Fig. 15). The dotted curve is the resistivity curve of the induction log, i.e., the reciprocal of the conductivity curve, recorded with the same linear scale as the short normal. The SP is in the left-hand track. In this combination, the SP curve and the 16-in. normal are the essential correlation curves, as in the conventional electrical log. The induction log provides a more accurate and detailed record of formation boundaries than the conventional log, especially in hard rock territories. Furthermore, the induction-electrical log makes possible the determination of fluid content, particularly in thin beds—at least qualitatively and very often quantitatively. In such thin beds, because of the adverse effect of the adjacent formations, the responses of the conventional devices are generally doubtful and/or incom-plete. Another advantage of the new combination is that the induction log is little affected by the presence of thin hard streaks interbedded within the permeable sections, whereas such occurrences are the cause of serious distortions of the long normal and lateral curves. The evaluation of saturation from any resistivity log implies the knowledge of the true resistivity R, of the bed and of the resistivity R.. of the flushed zone, or at least of the ratio Rxo/Rc. With the induction-electrical log run in fresh mud, the 16-in. nor-mal has a smaller radius of investigation than the induction log, so that the former reads closer to R.. and the latter closer to Rt. Thus, it has been observed that the ratio of the 16-in. normal to the induction log readings can be used as a basis for the interpretation in terms of saturation, with the help of appropriate charts. The purpose of the present paper is essentially to explain this procedure and to provide the corresponding charts. On the other hand, when a formation is deeply invaded, the response of any log (in particular the induction log) depends upon the radial distribution of formation resistivities behind the wall of the hole, which itself is a function of the arrangement of the fluids saturating the formation pore spaces. This paper, accordingly, will begin with a schematic description of the distribution of fluids and resistivities in the invaded zone. Next, some essential characteristics of the induction log will be reviewed. Finally, the determination of the interpretation charts and their application will be explained. The discussion will be confined to the case of fresh muds, i.e., muds whose resistivity is at least five times as great as that of the formation waters. With the present equipment the induction log is not well adapted for logging in salty mud. The Laterolog and guard electrode log are at their best under conditions of low resistivity mud. Accordingly, when these tools were introduced a few years ago, the use of salty mud was recommended. Now, with the introduction of induction logging, spe-

Jan 1, 1958

By J. B. Cheatham, J. W. McEver

A laboratory investigation of the behavior of casing subjected to salt loading indicates that it is not economically feasible to design casing for the most severe situations of nonuniform loading. When the annulus is completely filled with cement, casing is subjected to a nearly uniform loading approximately equal to the overburden pressure, and, although the modes of failure may be different, the design of casing to withstand uniform salt pressure can be computed on the same basis as the design of casing to withstand fluid pressure. Failure of casing by nonuniform loading in inadequately cemented washed-out salt sections should be considered a cementing problem rather than a casing design problem. INTRODUCTION Casing failures in salt zones have created an interest in understanding the behavior of casing subjected to salt loading. The designer must know the magnitudes and types of loading to be expected from salt flow and he must be able to calculate the reaction of the casing to these loads. In the laboratory study reported in this paper, short-time experimental measurements of the load required to force steel cylinders into rock salt are used as a basis for computing the salt loading on casing. These results must be considered to be qualitative only since rock salt behaves differently under down-hole and atmospheric conditions and also may vary in strength at different locations. The beneficial effects of (1) cement around casing, (2) a liner cemented inside of casing, and (3) fluid pressure inside of casing in resisting casing failure are considered. ROCK SALT BEHAVIOR UNDER STRESS The effects of such factors as overburden loading, internal fluid pressure, and temperature on the flow of salt around cavities have been studied extensively at The U. of Texas. Brown, et al.1 have concluded that an opening in rock salt can reach a stable equilibrium if the formation stress is less than 3,000 psi and the temperature is less than 300°F. At higher temperatures and pressures an opening in salt can close completely. These results indicate that calculations based upon elastic and plastic equilibrium for an open hole in salt should be applied only at depths less than 3,000 ft. In most oil wells the tem- perature will be less than 300F in the salt sections, therefore no appreciable temperature effects are anticipated. Serata and Gloyna2 have reported an investigation of the structural stability of salt. .They assume that the major principal stress is due to the overburden. Other stresses can be superimposed if additional lateral pressures are known to be acting in a particular region. In the present analysis an isotropic state of stress is assumed to exist in the salt before the hole is drilled, since salt regions are generally at rest. This assumption is partially verified from formation breakdown pressure data taken during squeeze-cementing operations in salt. Experimental measurements of the elastic properties of rock salt indicate a value of 150,000 psi for Young's modulus and a value of approximately 0.5 for Poisson's ratio. A value of % for Poison's ratio with finite Young's modulus would indicate that the material was incompressible. Values ranging from 2,300 to 5,000 psi have been reporteda for the unconfined compressive strength of salt. These variations may be due to differences in the properties of the salt from different locations or at least partially to differences in testing techniques. Salt is very ductile, even under relatively low confining pressures. For example, in triaxial tests reported by Handin3 strains in excess of 20 to 30 per cent were obtained without fracture. When casing is cemented in a hole through a salt section, the casing must withstand a load from the formation if plastic flow of the salt is prevented. To determine the forces which salt can impose on casing, circular steel rods were forced into Hockley rocksalt with the longitudinal axis of the rods parallel to the surface of the salt. The force required to embed rods 0.2 to I in. in diameter and 1/2 to 1 in. long to a depth equal to the radius of the rods was found to be F/DL =28,700 psi (± 3,700 psi) , .... (1) where D is the diameter, and L is the length of the rod. CASING STRESSES Since an open borehole through salt at depths greater than 3,000 ft will tend to close, cemented casing which prevents closure of the hole will be subjected to a pressure approximately equal to the horizontal formation stress after a sufficiently long time. As a first approximation the horizontal stress can be assumed to be equal to the overburden pressure. This is in agreement with the suggestion by Texter4 that an adequate cement job can prevent plastic flow of salt and result in a pressure on the casing approximately equal to the overburden pressure. He also advocated drilling with fully saturated salt mud

Jan 1, 1965

By H. C. van Elst

Ultrahigh-speedphotographic and electronic meth-ods were applied to an investigation of details of brittle-fracture propagation in steel. The brittle fractures studied were obtained in steel plate with the aid of a Robertson apparatus. It was found that a brittle fracture proceeds by discrete steps ranging from 30 mm near the stop temperature to less than 2 mm at lower temperatures. The halting FROM prior metallographic observations of brittle fracture in steel' it could be concluded that the distribution of mechanical twins along a brittle fracture was similar to the distribution of mechanical twins induced by explosive deformation. It was therefore assumed that a running brittle fracture created stress waves, cf. Refs. 2-7. An emission of stress waves by a brittle fracture, however, seems only conceivable if the fracture propagates by discrete steps. For this reason a study of the details of times between successive steps drop in this tem-perature region from 20 usec to about 1 psec. The stepwise propagation mechanism is accompanied by an intermittent emission of stress waves of the order of 100 to 200 kg per sq mm. These stress waves seen1 to play an important role in the mechanism of brittle fracture as will be discussed. brittle-fracture propagation was undertaken to investigate the possible determination of the fracture steps and the emitted stress waves associated with the assumed mechanism. The more practical object of this work is the development of a test method for the determination of the ductile-brittle transition in small specimens. This has special advantages for the study of irradiation damage in steel. In this test method, which will be published in a following paper, the stress waves emitted by an actual brittle fracture are reproduced with explosive or electrical means and are then transmitted through small specimens at various temperatures. In the present paper only the results of the brittle-fracture study will be reported.

Jan 1, 1964

By Philip Drinker, R. M. Thomson

In the mining and metallurgical industries, numerous problems arise requiring determinations of solid and of liquid particles suspended in air. Frequently, these problems are of local interest and involve purely economic or operating difficulties; on the other hand, toxic effects from the inhalation or the ingestion of substances suspended in air may be a matter of concern. For checking up process improvements or for determining ventilation efficiencies in problems of this general nature, various methods have been proposed. .Although simpler methods are often satisfactory, precipitation combines several desirable features that other methods lack. This paper is, therefore, devoted to a discussion of portable alternating-current precipitators applicable to the quantitat,ive determination and microscopy of dusts, fumes, and smokes in air. Small particles suspended in gases, such as air, are referred to in the literature as aerosols or suspensoids. Of these terms, suspensoids appears to be preferable as being more nearly in keeping with words in everyday use. In problems involving air pollution by small particles—by suspensoids—it is convenient to distinguish three broad classes based on the size, the degree of dispersion, and the method by which the particles become suspended in the air. Dusts.—Particles or aggregates of particles, 150 to 1 micron in diameter, that are thrown into the air by mechanical agencies are termed dusts. Examples are silica; talc; cement; organic dusts such as hard rubber, starch, and cocoa; flocculated fume, and smoke products. Fumes.—Particles, 0.2 to 1 micron in diameter, formed from chemical or physicochemical reactions are known as fumes. Examples are ammonium chloride, lead and mercury, zinc and magnesium oxides, fogs, and acid mists. Smokes.—Particles, less than 0.3 micron in diameter, formed by incomplete combustion of carbonaceous and other substances are called smokes. Examples are the particles formed from burning tobacco, oil, tar, and gas.

Jan 1, 1925

By Philip McKenna

WHEN a new material becomes available to industry, it is useful to describe its properties as a guide to its most effective application; and when the new material may be produced in compositions having a series of graded properties, tests to select the combination of properties best adapted for various uses are helpful. The class of materials to be con-sidered in this paper are hard tool materials produced by processes of powder metallurgy from hard carbide constituents and various matrices of iron, nickel or cobalt, or alloys of them with tungsten, or tungsten and carbon. The customary use of carbide hard alloys is for metal-cutting tools; although wire-drawing dies, lathe centers, follow rests, grinding rests, burnishers, rolls, extrusion dies, measuring gauges and micrometers, and a number of other tools are also made with these hard alloys as the essen-tial wear-resisting parts. The properties and tests to be considered are those affecting these uses. In the development of tool, materials since the industrial revolution we have had carbon tool steels, Mushet steel, high-speed steels, stellites, and now cemented carbide compositions. For an understanding of the latter category of materials their properties and uses relative to the older and more familiar tool materials will be considered.

Jan 1, 1938

By Edgar C. Bain

Of the important phenomenon of the hardening of steel, Professor Sauveurl says: It would seem as if the methods used to date for the elucidation of this complex problem have yielded all they are capable of yielding and that further straining of these methods will only serve to confuse the issue, the point having been reached when this juggling, no matter how skilfully done, with allotropy, solid solutions, and strains is causing weariness without advancing the solution of the problem. The tendency of late has been to abandon the safer road of experimental facts and to enter the maze of excessive speculations, in which there is great danger of some becoming hopelessly lost. The conclusion seems warranted that new avenues of approach must be found if we are to obtain a correct answer to this apparent enigma. With some degree of fitness we may say this of other problems. It seems likely that one of the new avenues of approach to many metallo-graphic problems is the study of crystal structure, or more accurately, the atomic arrangement, by means of the x-ray spectrometer. The crystal structure of some materials has been carefully worked out by the mineralogist, but his methods are, in general, unsuited to commercial metals and a method that yields even better information is at hand as the result of work on the diffraction of x-rays by Laue and the Braggs2 and later by HullI3 St. John, and others. It should be understood that the contour of free crystals, which is the subject of measurements by the crystallographer, is the result of the atomic structure and, in general, bears a simple and obvious relation to it. The use of the x-ray spectrometer4 has been described frequently, so the procedure will not be given here.

Jan 1, 1923