Search Documents

By C. H. Mahoney, P. E. LeGrand, A. L. Tarr

MAGNESIUM, it is now generally realized, differs in some important aspects from most other structural metals, not excepting even its close neighbors, the aluminum-base alloys. This is particularly true with respect to the effects of elevated temperatures on the two light metals when in the molten state. Aluminum, on the one hand, should not be raised above its melting point any higher than is absolutely necessary if one is to avoid danger of gas absorption and a tendency toward grain growth in the resultant casting.1 Magnesium alloys, in sharp contrast, actually benefit by being heated to temperatures considerably above their melting point. It is a commonly accepted practice to establish the desired fine grain in the industrial magnesium alloys of the aluminum-bearing group by raising the temperature of the melt after the refining treatment to some 25e C (482°F.) above the melting range. To recall briefly the typical practice for magnesium alloys, the molten metal is refined by fluxing at about 730° C. (1350 F.), and after the melt has been covered with a suitable flux, the temperature is raised to between 870°C. (1600°F.) and 930°C. (I700°F.). It is then cooled as quickly as possible to the casting temperature. This superheating, as it is called, results in a fine-grained cast metal structure which has superior mechanical properties, enhanced amenability to solution heat-treatment, and better machinability than cast metal that has not been superheated. The minimum temperature of superheating varies to some extent with the composition of the alloys to be treated and usually increases with the percentage of magnesium in alloys containing the same constituent metals.2 It should be noted that the grain-refining effect of superheating is markedly apparent only in connection with the alloys containing aluminum as an alloying constituent-the binary alloy containing r.5 per cent manganese, for example, is not refined in grain to any noticeable extent by a superheating effort. While the phenomenon of superheating is well known in the magnesium industry, the mechanism of the process has remained a mystery. During the superheating cycle something occurs that forces a fine grain upon the solidifying metal. The process has been controlled in an empirical manner, and occasionally, especially on large-scale melts, and for no apparent cause, no grain refinement is obtained from a superheating treatment. Only a few papers of importance have been published on the subject. Of these, one of the most helpful is the paper by Achenbach, Nipper and Piwowarski,3 which gives considerable data concerning the effect of superheating on various properties such as fluidity, shrinkage and hot crack formation, as well as grain size, and a discussion without any definite conclusions on the theoretical aspects of superheating. A short article by Murphy, Wells and

Jan 1, 1945

By Max Y. Seaton

THE scope of this paper will be limited to finished materials that contain a large preponderance (around 80 per cent or more) of magnesium oxide. The large and commercially important production of refractory dolomite and modified dolomites is not discussed here, and the production of magnesium basic carbonate for use as a heat insulator is barely mentioned. The discussion is confined mainly to magnesias produced in comparatively great quantity by direct processing of naturally occurring raw materials and hence excludes secondary or highly purified products such as pharmaceutical products or U.S.P. light and heavy calcined magnesias of commerce. NOMENCLATURE The nomenclature of the magnesia products that will be discussed is somewhat confusing, in that it is customary in the trade to designate as "calcined magnesite" the materials that result from the calcining of magnesite to temperatures that remove the contained carbon dioxide. The finished product, therefore, is not magnesite at all but simply a more or less pure magnesium oxide or magnesia. Furthermore, partly for statistical and partly for commercial reasons, it has been customary, during recent years, to classify as "calcined magnesite" products that result from the heat-treatment of magnesium hydroxide precipitated from magnesium-containing brines; products that, obviously, have no relationship whatever to magnesite. In the listing of magnesia-containing materials, tonnages of which are regularly reported by the Bureau of Mines, reports ordinarily are made under two headings: "caustic calcined" magnesite, in which all of the varieties of products treated at relatively low temperatures are lumped; and "dead-burned" magnesite, in which are included both high-purity and low-purity, and particularly both high-iron and low-iron, materials that have been so heat-treated that the magnesium oxide occurs predominantly as crystalline periclase-materials used almost entirely for refractory purposes. In 1940 the apparent domestic consumption of "caustic calcined" magnesite was approximately 17,000 tons, about 95 per cent of which was produced in this country. The apparent consumption of "dead-burned" magnesite was approximately 172,000 tons, some 82 per cent of which was domestically produced. In both total quantity and percentage of material produced within the United States, these figures are record highs for many years past. UTILIZATION As indicated by these figures, the major tonnage outlet for magnesia is the refractories industry, in which magnesia is employed principally in three ways: (I) as dead-burned grain magnesite for the construction and maintenance of the hearths or bottoms of basic open-hearth furnaces; (2) in the form of refractory magnesite bricks and shapes; and (3) as a chemical

Jan 1, 1942

By John Mullen

Impingers TWO types of midget impinger apparatus are used at Climax. The Mine Safety Appliances Company's midget impinger (MSA) and the Climax Molybdenum Company's midget impinger (CMC) (Fig. I). The Leiman Brother's No. 25, positive displacement pump is used in the CMC impinger instead of the four-cylinder radial pump that is used in the MSA impinger. With the MSA apparatus it is possible to obtain the proper vacuum by adjusting the needle valve on the vacuum chamber, while with the CMC impinger the proper vacuum is obtained by varying the rate at which the pump is cranked. The Leiman Brother's No. 25 pump is built to displace 0.1 cu. ft. of air per min. when operated at 145 r.p.m. In the CMC impinger this pump is so geared that the required crank speed is approximately 59 r.p.m. Both types of impinger apparatus are equipped with a water gauge mounted on top of the case and they are calibrated and operated in reference to the gauge. The MSA impinger flasks and nozzles are used with both types. Calibrating Impingers A calibrated precision Sargent wet-test meter (Fig. 2) is used in calibrating the impinger apparatus. The apparatus is set up as for taking a sample in the field, except that the hose from the outlet side of the meter is attached to the impinger nozzle. One revolution of the large hand of the meter indicates 0.1 cu. ft. of air displaced. The impinger pump is cranked for one minute, therefore, at a rate that will cause the large hand of the meter to make one revolution. The gauge reading is noted, then the impinger is cranked at this rate for 10 min. and is checked for error. If the meter indicates that more or less than I cu. ft. of air has been displaced, the impinger must be cranked—ither slower or faster according to the error—for another 10 min. and again checked for error. This operation is repeated until the proper gauge reading for a sampling rate of 0.1 cu. ft. per min. has been determined. This gauge reading is used in all sampling operations until the impinger is again calibrated. An impinger is calibrated at least twice each week. MlCROPROJECTOR A Bausch and Lomb model B micro-projector is used (Fig. 3). It consists of a substantial metal base supporting the light source and a microscope. Illumination is provided by a Bausch and Lomb 4.5-amp. arc lamp with mechanical feed. A glass water cell filled with a heat-absorbing and color-filter solution is placed between the arc lamp and the microscope. Two types of solution have been found satisfactory— a 2 per cent solution of copper sulphate or a 2 per cent solution of picric acid and distilled water. This percentage may be varied to give the desired color to the light reflected upon the screen. Any standard microscope may be used. A Bausch and Lomb microscope with

Jan 1, 1946

By J. R. Hauber, N. R. Borch

A study uras made on the creep behavior of cast and extruded SR grade beryllium. It is shown that, for stresses below about 1000 psi in the temperature range 760" to 85o° c, the creep behatior is nearly exactly described by the Nabarro-Herring mechanism. The activation energy is apparently that for self-diffusion, 42 2 kcal per mole, below 1000 psi, but it rises to 88.6' kcal per mole at higher stresses. The slress exponent is 4.5 at the higher stresses. Tertiary creep in this material is clearly related to void formation apparently caused by grain boundary sliding. BERYLLIUM is becoming an increasingly important technological material. A search of the literature has revealed a lack of fundamental studies on the creep of beryllium. This investigation was therefore undertaken to gain insight into the creep behavior of this material. EXPERIMENTAL PROCEDURE Tensile creep samples were prepared from cast and extruded SR grade beryllium. The vendor's chemical analysis of the beryllium tested is shown in Table I. The test specimens were machined as shown in Fig. 1 from i -in.-diam rods. The machined creep specimens were annealed to remove surface damage and to establish a variation in grain size. The heat treatments and their resulting grain diameters are shown in Table 11. The average grain diameters were determined by the intercept method. True average grain diameters were estimated by multiplying the measured average grain diameters by 1.5.' The creep tests were performed at temperatures from 700" to 850°C in a vacuum of 105 Torr or better in a tantalum-element resistance furnace. Loads were applied by an Instron testing machine such that the stress was held constant to within 20 psi. The test temperature was measured by thermocouples on the sample. With one exception the deviation from the desired test temperature was 2"C, and in that case the deviation was 4"C. Elongations were measured by an extensometer within the vacuum chamber which was fastened to the creep specimens at the grooves in the grip ends, as shown in Fig. 1. The precision of measurement of elongation was 1 X loe4 in. The creep tests were begun only after thermal equilibrium had been established in the sample and the extensometer to insure that there was no strain rate component due to transient thermal effects. Two kinds of creep experiments were performed. First, at constant grain size, the effects of varying stress and temperature were studied. In the second set of experiments, the temperature was held constant and the grain size was varied. The activation energy for creep was determined by varying the temperature at constant stress, as described by orn, during the first set of experiments. The variable grain size experiments revealed that creep at low stress apparently occurred by the abarro-errin' mechanism. In all of the creep tests, the stress was held constant only until sufficient strain had occurred to accurately determine the creep rate. The stress was then raised to a new value and the new creep rate determined. This process was reported until tertiary creep occurred. In this manner several data points were obtained from each specimen. The assumption was made that the structure was not changing appreciably between the incremental stress levels. This was verified by reducing stresses to previously tested levels and comparing the creep rates with the creep rates obtained at the lower strains. The re-producibility was within experimental error over strains on the order of 1 pct. EXPERIMENTAL RESULTS A typical series of creep tests is shown in Fig. 2. Primary creep was not observed in any test. Transient creep, which we define as creep rates that are nonlinear with time, was not observed for any change in stress except where tertiary creep occurred. The absence of both primary and transient creep has been previously reported for hot-pressed powder beryllium.= The data for the creep behavior at constant grain size are summarized in Fig. 3. The data show two distinctly different stress dependencies. At stresses below about 1000 psi, in the equation:

Jan 1, 1969

By C. D. Hall

This paper may be divided into two main parts: (1) analysis and data to show that Eq. 6 adequately correlates the authors' experimental data, and (2) the assertion that Eq. 20 "should permit scale-up with data taken from one pipe diameter for Newtonian, inelastic non-Newtonian, and viscoelastic fluids, such as dilute polymer fracturing fluids, which produce considerable pressure reductions." The authors might well recommend that this broad grouping of fluid types could be correlated by using Eq. 6 (requiring data from at least two pipe diameters). On the other hand, Eq. 20 is only shown to be adequate for conditions within the range of the present data set. Specifically, predictions by Eq. 20 for diameter scale-up to casing sizes would give larger deviations than implied in Table 2, and scale-up for some other fluids that give large drag reduction could be grossly in error. The description of a class of fluids "which produce a diameter family of straight parallel lines on a log (d?p/4L) vs log (8 v/d) plot. . ." defines a necessary condition for using Eq. 6; i.e., that s shall be constant for each fluid. The proposal that Eq. 20 is applicable to turbulent flow of such fluids is equivalent to saying that the spacing of these parallel lines, with A being constant, will be found to correspond to m = -1.20 for all such fluids. Table 1 shows the values of m derived from data on 16 non-Newtonian fluids. The key statement of this paper is that the diameter exponents "do not vary significantly from . . . -1.20." In statistical terms, this says that the m value for each fluid, which was obtained from all the measurements made on that fluid. has not been shown to be different from the arithmetic mean of the m values for the 16 fluids tested. This implies that the group mean, -1.20, is a more reliable value to use for an individual fluid than is the m value derived from the data on that fluid alone. No statistical test is described to support the key statement that the diameter exponents do not vary significantly from -1.20. Such a test would have to take into account that each individual m value is shown to correlate the pressure gradients for its fluid, with only about 3 percent standard deviation over the diameter range covered. That is, the m value is not the result of a single independent measurement. Thus, it would not be sufficient, or valid, to compare the deviation of one of the m values with the variance of the 16 values of m about their mean. An alternative interpretation of the key statement is that the diameter exponents do not vary appreciably from -1.20; i.e., that using -1.20 does not cause serious inaccuracy. Table 2 seems to be offered in support of such an assertion. However, such a statistical treatment (1) is unnecessary and (2) cannot lead to any valid scale-up generalization. The amount of error introduced by using a 1"wrong" value of diameter exponent — i.e., -1.20 instead of m — is determined by Eq. 6. The ratio of the pressures predicted by Eqs. 6 and 20 for scale-up from ds in small pipe to d, in casing is The pressure for 30-percent calcium carbonate slurry (m = -1.112) in 10-in. ID pipe would be predicted 30 percent higher by Eq. 6 than by Eq. 20, if based on tests in 0.5-in. ID pipe. The data set tested in Table 2 represents only a limited sample of pipe diameters (ratio of about 4:l) out of the population of diameters that would

Jan 1, 1970

By Nicasio del Castillo

INTRODUCTION The tax structure of foreign mining investment into the United States has a significant impact on the financing and the profitability of the operation. For these reasons, it is critical for the foreign investor to develop and implement a well planned tax strategy that will enable its venture to: (1) reduce its U.S. income tax liability (2) lower U.S. withholding taxes when funds are transferred from the United States, and (3) decrease or defer home country taxation on its U.S. earnings ALTERNATIVE FORMS OF INVESTMENT A threshold business and tax consideration is the form in which the investment is to be made. The most common alternatives include: forming or acquiring a U.S. mining corporation, directly establishing a branch mining operation, or entering into a joint venture or partnership with a U.S. mining company. U.S. Corporations The most common structure through which foreign mining companies engage in business in the United States is to form a U.S. mining corporation. Forming a U.S. Corporation. If the investor decides to establish a new U.S. corporation the organization is relatively simple. No distinctions are made in the United States between "public" and "private" forms of incorporation. Minimum share capital is not usually required and share capital may consist of shares with no par value. Since corporate law is the responsibility of the individual states, the foreign investor must choose a state in which to incorporate. If appreciated mining property is transferred to a corporation solely in exchange for stock or securities in that corporation, and the transferors have control of the corporation (defined as at least 80 percent of all voting shares and at least 80 percent of all other shares) immediately after the exchange, no gain or loss will be recognized. However, if the transferors receive cash or other mining properties in addition to stock, any resulting gain may, in certain situations, be taxed to the extent of the cash and the fair market value of other property received. Acquiring an Existing U.S. Corporation. Acquiring an existing U.S. mining corporation is not as straight-forward as forming a corporation. This alternative may be accomplished through either a stock or an asset acquisition. Generally, with a stock acquisition the purchaser inherits all of the business and tax attributes of the former mining corporation. If the investor is able to acquire mining assets, however, the purchaser will usually be able to avoid any unknown or hidden liabilities that could be attached to an existing corporation. Another principal advantage in acquiring assets is that the purchase price may be directly allocated to the acquired mines or other mineral-related assets with the result that the assets' depreciable base may be increased. Assuming the domestic seller and the foreign purchaser can agree, it is generally advisable to allocate the purchase price in the sales agreement to specific individual assets. From the foreign investor's standpoint, it is preferable to allocate the purchase price to depreciable assets such as buildings and equipment versus an allocation to mineral land holdings or intangibles such as goodwill, which are generally not depreciable. It is not uncommon, however, for a seller mining company being acquired to insist for tax reasons that the investor purchase shares rather than assets. If the foreign

Jan 1, 1985

By B. H. Kear

Clustering of slip bands in different systems has been observed in both ordered and disordered Cu3Au crystals compressed in the <110> orientation. Certain features of the slip band patterns are explained in terms of reactions between dislocations with Burgers vectors at 120 deg; in a few rare cases, the slip band evidence suggests that the Products of such reactions form diffuse tilt boundaries between the differently slipped regions of the crystal, similar to the known behavior of ionic crystals, but not nearly so well defined. WHEN crystals with orientations favorable for multiple slip undergo plastic deformation, slip may occur in different systems in localized regions, so that clusters of slip bands are developed. This phenomenon has been observed in fee1-4 metals and also in ionic crystals having the sodium chloride structure.5-8 In the ionic crystals, the boundaries formed between the differently slipped regions of the crystal assume characteristic orientations and are associated with macroscopic tilts that are plainly visible on the sides of the crystal. Recently, this interesting feature was explained in terms of the formation of diffuse low-angle boundaries as a result of interactions between families of glide dislocations in the different systems meeting in the boundaries.9 This paper describes an attempt to obtain similar evidence for boundary formation in an fee crystal. The alloy Cu3Au was chosen for the present study simply because this material is currently being used in a general study of differences in deformation behavior of the ordered and disordered phases of this alloy, which will be described elsewhere. EXPERIMENTAL PROCEDURE The two specially oriented compression specimens used in the present study were prepared from a melt-grown single crystal by careful cutting, grinding and polishing. The finished specimens were about 6 mm by 2 mm in cross section by 6 mm tall, with their ends parallel to (101) and sides parallel to (111) and (121); the broad faces of the specimens were made parallel to (711). Both specimens were annealed in an evacuated quartz tube at 850oC for several hours, slowly cooled to 500°c, and then quenched into water in order to obtain the disordered state for the alloy. One of the specimens was partially ordered (with S- 0.8) by reannealing at 350oC for 100 hr. After these annealing treatments, both of the specimens were electropolished. 10 Finally, the specimens were compressed in the [loll orientation and their stress-strain curves were recorded. The deformation was carried out in increments of a few percent strain. At each stage in the deformation the specimens were unloaded, removed from the compression jig, and examined optically for slip bands. Before reloading, the specimens were repolished, so that the observed slip band patterns were characteristic of a particular stage in the deformation. EXPERIMENTAL RESULTS Fig. 1 show!; the stress-strain curves for the ordered and disordered specimens and also indicates the stages 1, 2, and 3 where the deformation was interrupted for examination of slip bands. The curves show marked differences in flow stress and in work hardening rate in the two specimens, as observed by previous workers.11,12 Also, it was found, in agreemement with the observations of Taoka and Sakata,&apos;3 that the plastically deformed disordered alloy showed the characteristic coarse slip bands of alloys, whereas the ordered alloy exhibited a fine slip band structure similar to that of pure metals. Slip Band Observations. In what follows, the description of the slip band patterns, with accom-

Jan 1, 1962

By S. L. Couling, D. J-P. Adenis

i2) twinning in poly crystalline magnesium does not usually occur homogeneously but is concentrated in localized regions or bands inclined at about 45 deg to the stress axis. These bands of twinning are in many ways similar to the Luders bands seen in mild steel alzd Al-Mg alloys. Within a hand the percentage of the volume twinned may approach 100 with no twinning outside the band. Bands are not produced in specimens of grain size a3 x 10-= in. or in samples deformed at temperatures 300°F. Annealing of heavily twinned regions leads to re crystallization textures markedly different from those found in the starting material. The exact preferred orientation appears to depend on the starting grain size, the amount of compres-sive strain and the manner in which it is introduced. MAGNESIUM, with its hexagonal crystal structure, deforms plastically at room temperature by a variety of deformation mechanisms, one of the most important of which is (1012) twinning. In single crystals such twinning occurs on compression parallel to the basal plane or tension perpendicular to it. In wrought polycrystalline magnesium, such as rolled sheet, the preferred orientation is such that almost all the grains have their basal planes nearly parallel to the sheet surface. Therefore, if sheet material is deformed by cold rolling or by tension in the plane of the sheet, deformation of the grains by (1012) twinning is not favored. On the other hand, twins form readily on compression parallel to the plane of the sheet as in a compression test, on the compression side of a bent sample, or at the outer rim of a drawn cup. The first part of this paper deals with the morphology of (1012) twinning in polycrystalline magnesium. Some aspects of this subject were covered by Barrett and ~aller.&apos; Of direct bearing on the work to be reported here are the comments of Jetter&apos; in discussion to Ref. 1. He shows that Mg + 1.5 pct Mn alloy sheet when bent about a transverse axis develops a pattern of transverse bands on the surface of compression. A longitudinal section through the sheet shows that the bands are wedge-shaped and inclined to the rolling direction. The bands were identified as "outcrops of regions in which deformation is localized as the result of the reorientation brought about by (1012) twinning". The second part of the paper treats the recrys-tallization texture of the specimens twinned by compression. Magnesium deformed and then annealed generally recrystallizes with no change in orientation.1&apos;3&apos;4 This statement is true provided that the amount of (1012) twinning occurring during deformation is small. In an isolated observation, Anse15 has shown that, when deformation produces much (1072) twinning, annealing causes new maxima to appear in the pole figure. The second part of the paper elaborates on this point. I) MATERIALS AND PROCEDURES All of the experimental work to be reported was done using the commercial sheet and plate alloy AZ31B (nominal composition: 3 pct Al, 1 pct Zn, 0.4 pct Mn, balance magnesium). This alloy is available commercially in two tempers, -0 (fully annealed) and -H24 (partially annealed), and specimens of both tempers were used in various experiments. The average grain. diameter (AGD) for -0 temper 0.125-in. sheet is about 0.5 x 10- in.; where material of larger grain size was desired, anneals at elevated temperature were used to grow the grains. compression tests were made on a screw-driven "hard" machine. The specimens were clamped in a

Jan 1, 1964

It is interesting to note that during the period that has elapsed since the Institute&apos;s formation, wood charcoal, anthracite and bituminous coal, as well as beehive and by-product coke, have been used as blast-furnace fuels, that the reign of supremacy of each fuel was associated with specific periods, and that each successive era was marked by a production of pig iron greater in quantity than the one it followed (Fig 1). The transition of the manufacture of blast-furnace iron from charcoal to anthracite and then to beehive coke, and ultimately to by-product coke, is a reflection of the economic limitations of each fuel coupled with availability sufficient to meet the increased demands of each succeeding decade. It is a pattern that has been followed almost without exception in the history of pig iron in every country. CHARCOAL Colonial production of iron relied exclusively on wood char- coal as a fuel, and the iron industry of this count recognizes the important role played by this fuel. Charcoal iron has been available to consumers since the beginning of the organized iron industry in America in 1645, by John Winthrop at Saugus, Mass.,1 and although its greatest use antedates the formation of the Institute, it is still used to some extent. Until about 1840 nearly all of the pig iron manufactured in the United States was made with charcoal, and it continued as a principal smelting fuel until 1855.2 After that time, more pig iron was produced with other fuels, despite the fact that

Jan 1, 1948

By B. L. Averbach, M. Cohen

Many hardened steels contain significant quantities of retained austenite even in cases where the carbon and alloy contents are low. In fact austenite has been detected in plain carbon steels containing as little as 0.50 pct carbon.1 Although the austenite may not be visible metallographically it causes definite dilatometric and magnetic effects during subsequent tempering or sub-atmospheric coo1ing.l,2,3 Therefore if the reactions which hardened steels undergo during later treatment are to be understood in quantitative fashion it is most essential to have some kind of absolute analysis for the austenite content in hardened steels. Once this analysis has been made, the austenite transformations can be followed precisely by observing such sensitive phenomena as changes in length or in magnetization but the latter techniques can only determine differences in the amount of retained austenite and usually an independent method must be found to put these differences on an absolute basis. In certain instances the microscope can be used advantageously to determine the percentage of retained austenite. The quenched sample is tempered to "darken" the martensite with minimum decomposition of the coexisting austenite, and then is polished and etched in the usual fashion. If the austenite is clearly distinguishable from the tempered martensite and other possible constituents its volume percentage can be measured quantitatively by point counting or lineal analysis.4 Such microscopic methods, however, depend on the etch being sufficiently discriminatory. In fairly coarse structures, if the austenite content is greater than 10-15 pct, there is probably little smearing of the etch, and point counting or lineal analysis seems to be quite accurate. On the other hand if the structure is difficult to resolve, as in commercially treated fine-grained . steels which contain less than 10-15 pct retained austenite, the latter may be completely obliterated by the dark etching martensite or it may appear disproportionately low as the interfaces between the two constituents become difficult to distinguish. Another disadvantage of the metallographic method is the need for "darkening" the martensite and hence the determination cannot be applied to as-hardened steels. The required tempering may spoil the structure for other tests or may even remove a small part of the austenite which is being sought. X ray methods hold more promise for covering the range under 15 pct retained austenite. Although austenite and martensite in the hardened steel may be chemically identical, their crystal structures and lattice parameters differ, and the intensity of an austenite diffraction line is some continuous function of the percentage of re-

Jan 1, 1949

By Frederick Laist

THE ore from the Butte mines of the Anaconda company is quite siliceous; that is, it contains considerably less iron than is needed for the fluxing of the silica. The direct smelting of this ore, therefore, requires the addition of considerable fluxing material. The only flux available in sufficient quantity at Anaconda is limestone containing no metallic minerals. This necessarily makes the direct smelting of the ore so expensive that it is more profitable to subject the ore to a preliminary treatment by concentration. However, as the losses in the concentrator were very high, compared with the losses in the blast furnaces, it was found, by calculation, more profitable to send ores containing more than a given percentage of copper to the blast furnaces, in spite of the higher costs of treatment. The dividing point was dependent on various factors, the chief of which was the prevailing market price of -copper. It was customary, therefore, to segregate the ore as mined into two classes. Ore in the first class generally contained 5 per cent. or over of copper;: this was sent directly to the blast-furnace department. Second-class ore contained less than 5 per cent. of copper, and averaged around 3 per cent.; it went to the concentrating department. With the introduction of the flotation process, it was found possible to maintain an average recovery, as concentrates, of 96 per cent. At the same time, the cost of reverberatory smelting was very materially decreased by the use of pulverized coal. These two changes in practice made the blast furnaces unable to compete with the reverberatory furnaces on a cost basis. The distinction between first-.and second-class ore was therefore abandoned, and the ore was treated by concentration. Obviously, on ores as high in iron as the Butte ores, the concentrator, produces a product that is self-fluxing; in fact, it is possible to produce a

Jan 1, 1920

By Falih Ergunalp

REGULAR production of chrome in Turkey started in 1860 with the operation of the Bursa deposits (5, Fig. I). Others were discovered at Makri, near Fethiye (3, Fig. I). For 33 years Turkey remained the principal source of this mineral. While new discoveries were coming in elsewhere, Turkey&apos;s output declined until 1921, as a result of four successive wars, which ruined the economics of the country. In 1927 a revival came with the production of 18,000 tons. In that year the Société Minière de Fethiye was formed. This company now operates mines in the Vilayets of Aydin, Denizli, Burdur and Mentese, and it has reached a maximum production of between 80,000 and 90,000 tons annually. The Turkish output therefore increased from 29,000 tons in 1930 to 55,000 tons in 1931; and to 119,009 tons in 1934. The second phase in the increase in chrome production in Turkey came about in 1935, when the Government decided to reorganize and control the mineral industry of the country according to the principles of "government control" of the present regime. Up to that time the mineral resources of the country had been exploited by private concerns. In 1935, the M.T.A. (Maden Tetkik ve Arama) Institute (Institute of Mining Research and Geological Survey) was established by the Government to do the geological and geophysical survey work and discover new mineral resources for the country. Before the establishment of the M.T.A. Institute, the chief chrome-producing region was Fethiye (3 and 4, Fig. I). As a result of the extensive work of this bureau, many new chrome deposits have been discovered and are now in production. The operational field of the mineral industry was given to Eti Bank, another Government-sponsored and Government-controlled establishment. Eti Bank gradually took over the exploitation of existing mines by purchasing them from privately operated companies. Attention was first given to the Zonguldak collieries and to the different chrome deposits scattered over the country. The Guleman mines (14, Fig. 1) were developed and put in operation in 1936. Since then the bulk of Turkish chrome output has come from this mine, which yields the highest grade ore in the world (averaging 52 per cent Cr2O3). In 1939, the recently discovered chrome deposits to the north of Eskisehir went into production, yielding ore having a Cr2O3 content of 51 to 52 per cent. Today, more than ever, the efforts of both the M.T.A. Institute and the Eti Bank are concentrated on finding new deposits and placing them in operation. There are still many promising regions of the country that merit systematic surveying and prospecting for chrome ores. Thus it is probable that Turkey will continue to make noteworthy progress in chrome output. As the annual chrome production of

Jan 1, 1944

&apos;T. C. MERRIMAN, New Haven, Conn. (written discussion *).-This most interesting paper gives much carefully obtained and valuable data. However, there are two points in connection with the commercial application of such data that might possibly be a source of trouble and mis-understanding. In the first place, the examination of thin sections of annealed brass, subjected to standard Brinell test.(500 kg. on a 10-mm. diameter ball) at thicknesses from 0.075 to 0.150 in. (1.9 to 3.8 mm.) indicates that cold work has been performed on the specimen during the application of the load sufficient to extend way through the section, and have the hardness of the metal affected by the backing. If the usual steel support is used, this effect is very evident. If a piece of soft brass is used as a support, there is an indentation in the surface of the support accompanied by a bulge on the under side of the tested specimen opposite the impression made by the 10-mm. ball. The result is that Brinell specifications (governmental or otherwise) on stock for a certain purpose may not be fair in all cases, since manufacturers, owing to differences in equipment, etc., may not all use precisely the thickness and conditions of stock on which the Brinell specifications were based. This would mean that the government Brinell specification might not give them the temper of stock best suited for their manufacturing methods. The concluding paragraph of this paper, stating that "the hardness of cartridge brass may be determined with greater accuracy by the Brinell hardness measurement than by attempting to judge it from the grain size" appears to be in line with the movement of the last year or so among brass manufacturers toward substitution of the Brinell test for microscopic examination as an acceptance test on cartridge brass. The statement may he strictly true that the Brinell test is the best test for hardness, but it is not, as the statement might readily be construed, a sufficient test of suitable condition. For instance, some cartridge brass might accidentally have been overheated to a point where it would be distinctly unsafe to use for the manufacture of small arms cases and then be so rolled (reduction 3 to 5 per cent.) as to pass perfectly proper Brinell specifications. Under such conditions the microscope would reveal its unsuitability where the Brinell test had failed so to do.

Jan 4, 1919

By W. A. White

UNDERCLAY squeeze is the plastic flowing of underclay below coal pillars into mined-out entries and rooms. Squeezes may be caused either by wet mine conditions where the moisture is taken up by the clay—making it more plastic—or by the presence of certain clay minerals, such as mont-morillonite, which are plastic when there is enough natural moisture. Under either condition, sufficient stress will cause the underclay to flow. Squeezes may fill an entry or room within several hours, or it may be several months before movement stops. Squeeze areas commonly cover hundreds or thousands of square yards. The Coal Div. of the Illinois State Geological Survey has collected samples of underclays from various mines and from cores drilled by coal companies in the state. From these samples natural moisture content, particle size and particle size distribution, and clay mineralogy are determined. Data from samples collected from the underclay below Herrin (No. 6) coal in the Lumaghi Coal Co. mine near Collinsville, Ill., are used in this report to clarify points in the discussion. Data from samples taken from other mines lead to the same conclusions. A generalized geological section for the area is given in Table I. The underclay below coal No. 6 ranges from a few inches to 3 or 4 ft thick. The upper 6 to 18 in. are noncalcareous; the lower part becomes more calcareous with depth. Limestone nodules become larger with depth, almost grading into the limestone below. In areas where the clay is nearly absent the limestone may thicken to take its place; thus they may complement each other in thickness. There are two types of squeeze areas in a mine. In one type up to 3 or 4 ft of underclay lie in what appears to be a depression in the limestone underneath. This is suggested by a rim surrounding the squeeze area where the underclay is thin and the limestone lies within a few inches of the coal. In the second type the underclay of the squeeze area is surrounded by underclay of similar thicknesses which does not squeeze. Test Methods: Natural moisture content, particle size and particle size distribution, and clay mineralogy were determined by the following methods: Natural moisture is the moisture content a clay contains in its natural environment, expressed in percentage of the weight of ovendried clay (110°C or 230°F). To obtain the natural moisture content, given in Table 11, the clay samples were sealed in containers as soon as the samples were taken in the mines. Particle size and particle size distribution were determined by the pipette method,&apos; and the data were plotted as cumulative curves, Fig. 1, on semi-logarithmic paper. Particle size was plotted on the logarithmic scale and percentage on the arithmetic scale. The quartiles (diameters that correspond to frequencies of 25 and 75 pct) and medians (diameters that correspond to the frequency of 50 pct) of the samples were determined from these curves. The clay minerals were identified from the data obtained by differential thermal&apos; and X-ray powder" techniques. The differential thermal analyses were made on the whole samples, whereas the X-ray analyses were made on fractions of less than 2p. Data and Discussion Moisture Content: After the sealed jars had stood for 24 hr, those that contained squeeze samples had perspired, so that droplets of water had accumulated on the insides of the jars. Table II shows the moisture in the clay after it had perspired for 24 hr. (This perspiring was not noted in samples from nonsqueeze areas.) After perspiration one of the squeeze samples still had a higher moisture content than the samples that did not squeeze. Clay Mineralogy: The thermal analysis, Figs. 2 and 3, indicates that the clay minerals are chiefly micaceous in type; the low-temperature endothermal

Jan 1, 1957

By Dale A. Vaughan, Oliver M. Stewart, Charles M. Schwartz

A. U. Seybolt (General Electric Research Laboratory)—The authors should be commended for adding some important information to our knowledge of the solubility of interstitial elements in metals. It is becoming increasingly evident that the effect of even traces of such elements have very far-reaching effects upon the mechanical properties of the body centered cubic metals. Those who have worked in this area know that the accurate determination of the small solid solubility limits in systems of the type reported by the authors is a quite difficult task, and it is therefore not surprising that frequently the results of different workers are not in agreement. It is instructive, and usually helpful, to plot the solubility results on log weight or atomic percent -1/T coordinates to find out if a straight line is obtained. A straight line is expected because in systems displaying solubilities of the order of 1 to 3 at. pet or less, Henry&apos;s law is usually obeyed—or at least well enough obeyed so that the deviation from linearity is not very appreciable. If Henry&apos;s law is obeyed, one canthen use the Van&apos;t Hoff Equation in the form In N = ?H/RT + C, where N is mole fraction, at. pet, or wt pet for small values, and AH is the partial molal heat of solution of the solute. R and T have the usual significance, and C is an integration constant. If one plots the reported nitrogen solubility values as indicated above, the three points fall reasonably well on a straight line. The oxygen values for the two upper temperatures fall very closely to the nitrogen values as shown in the authors&apos; Fig. 15. However, the value at 500°C departs widely from the straight line established by the data at 1500" and 1000°C. It is, of course, true that one cannot place too much emphasis on the significance of a line established by only three points, but in the absence of reasons for anticipating deviations, data exhibiting wide departures from linearity should at least be examined closely. Fig. 16 shows the log at. pct -1/T plots for the authors Ta-O and Ta-Ndata including a solid circle point at 500°C and 1.8 at. pet for Ta-O, which is simply extrapolated from the two higher temperature points. In addition, the data of R. P. Elliott9 for Nb-O are shown. These points were picked off his curve and are not very exact, but as can be seen they line up well on a straight line. It is interesting, and probably significant, that the slope of Elliott&apos;s results is not far from those of Vaughn, et al. This is probably to be expected because one would anticipate that the partial molal heats of solution of oxyten in these two very similar metals should be not too far apart. AH for Ta-O is about -1900 cal per mol, while for Nb-O it is near -2300 cal per mol. Hence, this lends some support to the thesis that the point at 500°C for Ta-O is much too high. The data of Gebhardt and Preisedanz10 are also plotted, and it is seen that their data while lying on a linear plot, have an appreciably steeper slope. The possible reasons for this will not be discussed here except to point out that their pressure-composition data show anomalies which suggest that they may have been dealing with a different equilibrium from that being discussed. There is another consideration which would also suggest that the solubility at 500°C is lower than shown. The solubility values were obtained by the classic method of first establishing a lattice parameter-composition curve. This the authors did, and there is probably little doubt that it is quite accurate. Such a plot is generally almost error-free because it has a self-correcting feature in that any deviation from linearity makes a data point immediately suspect, and subject to confirmation. Unfortunately, this is not true with respect to the actual solubility values. These are obtained ordinarily by taking an alloy containing more solute than is soluble at some temperature and then thermally

Jan 1, 1962

By Kefton H. Teague

Olivine is a mineral containing a mixture of forsterite (Mg2SiO4) and fayalite (Fe2SiO4) in solid solution. The name olivine was first applied by Werner in 1790 (Hunter, 1941) because of the olive-green color of the mineral. Olivine is the principal component of the rock dunite, which itself is a member of the peridotite group of ultrabasic igneous rocks. European uses of the terms olivine and dunite are somewhat different than US usage. In commerce European usage defines dunite as containing 36 to 42% MgO, 36 to 39% SiO2, and loss on ignition of approximately 10%. The term olivine is used to designate a material containing approximately 85% forsterite, with a chemical composition of approximately 45 to 50% MgO, 40 to 43% Si02, 5 to 8% Fe2O3, and ignition loss of 1 to 2%. Uses The principal use of olivine is in various applications involving hot metal. Table I shows the best estimate available as to the amount of olivine consumed by various industries worldwide. In excess of 90% of world uses involve hot metal, with approximately 75% as a slag conditioner in the blast furnace production of pig iron. Approximately 15% of total olivine usage is as a special foundry sand in mold making for the brass, aluminum, magnesium, and manganese steel foundries (Schaller, 1957, 1958; Snyder, 1957; Anon., 1977). Olivine was first used as an industrial mineral in the early 1930s for a refractory material (Anon., 1970; Hunter, 1941). As a refractory raw material, olivine was first introduced in the United States as hand-cobbed, selected, shaped blocks of crude olivine. This use met with limited success. More recently, finely ground olivine blended with MgO and pressed into bricks, which are then fired, has found use in glass tank furnaces and open-hearth furnaces. Ramming or gunning mixes for basic furnace linings also utilize olivine. Olivine has been used in ladle linings with varied success. In Europe, substantial tonnages of olivine are utilized in refractory brick for night storage heaters (Anon., 1970). A limited amount of olivine has been used in the past as a fertilizer (magnesium source) and has been fused with rock phosphate to produce a magnesium phosphate as a plant food. The relatively high magnesia (MgO) content of olivine also attracted attention to it as a potential source of both magnesium compounds and as a source of metallic magnesium (Bengston, 1956; Hunter, 1941). The use of olivine as an additive in the blast furnace is relatively new, having been developed during the last decade. J.W. Currier (Private communication, 1978) describes the behavior of olivine in the blast furnace as follows: Olivine (Mg, Fe2, Si04) represents a unique lime-free source of magnesia and silica as a blast furnace charge component. Only recently has the magnesia-rich mineral been recognized as beneficial cleaner for blast furnace experiencing the problems associated with excessive alkali inputs and/or low coke stabilities. For some time it has been known that alkalis tend to recycle and accumulate in blast furnaces. In the high temperature region of volatilization the elemental alkalis formed attack the integrity of the graphite structure. This alkali attachment is enhanced when poor coke is used. Higher in the furnace stack volatile alkali cyanides condense and oxidize. This accumulation of alkalis tends to agglomerate the burden materials, producing scabs and scaffolds. These structures not only inhibit the downward movement of burden materials and the upward passage of wind, but also lead to erratic furnace performance

Jan 1, 1983

By M. W. Legatski, D. L. Katz

The best currently available description of the longitudinal mixing properties of a porous medium is an equation of the form which relates the effective longitudinal dispersion coefficient Dp to the molecular diffusion coefficient Do, the electrical resistivity factor F, the porosity <f> and a Peclet number. If the parameters dpa and m are determined for a porous medium of known porosity and electrical resistivity factor, then a dispersion coefficient may be estimated for a given flow rate and a given gas pair. A new method, featuring on-line gas analysis by thermal conductivity and on-line data reduction by analog computation, was developed and used to determine these mixing parameters for eight naturally occurring sandstones and two dolomite samples. The exponent m of the above equation was found to vary between 1.0 and 1.5. The characteristic length dpa in the above equation was found to vary between 0.25 and 1.9 cm, with an average value of 0.4 cm for sandstones. Measurements were made on two cores in which paraffin wax had been deposited by evaporation from a pentane solution. They indicated that the presence of an immobile phase such as connate water could increase the dispersion coefficients significantly. INTRODUCTION While the petroleum and chemical industries have studied the mixing of miscible liquids flowing in consolidated porous media and of miscible gases flowing in unconsolidated porous media, relatively little data have been presented to describe the mixing of gases flowing through consolidated porous media. Such data are of particular interest to the gas storage industry. For instance, the U. S. Bureau of Mines is storing large quantities of a rich helium-nitrogen gas in contact with a natural gas in a dolomite reservoir. Since the rich gas occupies only 15 percent of the total reservoir volume, it is essential that the extent of rich gas-natural gas mixing be predicted and understood as a function of rock properties, pressure and rate of movement. This investigation was concerned only with the determination of longitudinal dispersion coefficients. It is understood that a transverse dispersion coefficient, which characterizes mixing perpendicular to the direction of flow, may be an order of magnitude less than the coefficient characterizing mixing in the direction of bulk flow.5719 It should also be recognized that the use of any dispersion coefficient is in itself a simplification. It is necessary to assume that mixing in a porous medium may be characterized by the equation for flow in a single direction. A number of authors1 l8,19 have pursued the mixing problem, not in terms of the so-called "dispersion model" described by Eq. 1, but in terms of a "mixing cell model". This model supposes that a porous medium is constructed of a large number of small mixing chambers and that the concentration of the diffusing component within each mixing chamber is uniform. Fick&apos;s law (Eq. 1) assumes that there is no gross by-passing of one fluid by another, and that there are not stagnant pockets of gas in the system under consideration as discussed by Coats and Smith.8 These assumptions are not always valid for flow through porous media and it is important to recognize the limitations upon Eq. 1. The most serious limitation upon the assumption of Fick&apos;s law mixing in a porous medium is

By Marie L. V. Gayler

Without diffusion taking place in liquid metals and alloys, no castings could be made; it is therefore the most important factor affecting the structure of metals. Diffusion involves the interchange of atoms, a process which takes place during the life history of an ingot. In the liquid, atoms are in a state of high thermal agitation, but this thermal vibration is reduced in amplitude with falling temperature. When solidification sets in, the atoms arrange themselves on an ordered space lattice and the changes in structure which take place in the solid are due to the interchange of atoms on this space lattice. The rate of atomic interchange—e.g., of diffusion—is most rapid at temperatures close to the melting point and decelerates as the temperature is lowered. At room temperature, the rate of diffusion is practically negligible in most alloys, and any change in structure can only be brought about by using methods which will accelerate the rate of diffusion. The rate of diffusion depends on three factors (I) temperature; (2) concentration gradient and (3) activation energy. The growth of grains and particles in the solid alloy also depend on these factors and are therefore intimately associated with diffusion. The rate of homogenization in a cast alloy depends on several factors, such as: (I) rate of solidification, which involves grain and particle size which, in their turn, depend on diffusion: (2) the nature of the constituents; (3) the temperature interval between the melting point of the metal or alloy and the temperature at which it is being heat-treated. It is well known that coarse, cast structures are extremely difficult—if possible— to homogenize, and the finer the grain size and particle size, the more readily solid solution will take place. The rate of diffusion depends, also, largely on the nature of the constituents; for instance, copper and magnesium form solid solutions with aluminum quite readily but nickel and iron do not; neither do certain intermetallic compounds, such as alpha and beta FeSi. Furthermore, the actual formation of intermetallic compounds may be a very slow process, particularly when they are formed in the solid state as equilibrium products. For example, BFeSi is formed in the solid as the result of the reaction aFeSi + A1 —+ PFeSi. The particles of aFeSi become surrounded with a reaction ring of PFeSi. This layer is formed as the result of diffusion of atoms taking place between the aluminum matrix and aFeSi. As the amount of aFeSi surrounding the core of aFeSi increases the concentration gradient becomes low and so the rate of diffusion of atoms also decreases until it practically ceases. This occurs after a comparatively thin layer of ßFeSi has been formed. It follows that when intermetallic compounds of this type are formed in the solid, as the result of diffusion, it is generally impossible ever to attain equilibrium, since the forma-

Jan 1, 1944

By George W. Crawford, W. P. Aycock, E. W. Hough

Forty oilfield brines have been examined so far by a polarographic technique new in petroleum engineering called the "tensatnmetric method" by the team of biochemists who perfected its use in their field. Samples of brine were obtained from various oil fields in which the wells were known to be producing fluid from oil productive zones in well-known geologic formations. Most of the reservoirs from which the samples were obtained are believed to have an active water drive under the prevailing conditions of operation. The 40 samples represent brines produced front 16 different formations of various geologic ages. Graphs have been prepared of the data obtained in the testing of each sample, and the distinctive waife-like curves so obtained are characterized by reproducible profiles, called "response curves." Careful comparison of the response curves of salt water coming from different fields producing from the same geologic formation reveals that the curves are similar. The response curves of salt water coming from productive zones of different geologic formations are characteristically different. Preliminary work offers the further hope that response curves of an oilfield brine indigenous to a particular oil-bearing formation and hence representative of a particular geologic environment, such as deposit-ional and all subsequent morphological conditions, may be of value in reservoir engineering in the interpretation of surface and interfacial phenomena. For example, the wettability of the rock matrix and more specifically, the classification of productive oil-bearing strata as hydrophyllic or hydrophobic may be determinable. However, many more brines must be examined and the resulting response curves analyzed in comparison to known causal phenornena before this objective is achieved. INTRODUCTION One of the perennial moot questions in the literature of petroleum engineering is whether the reservoir rock is oil- or water-wet. Possibly an answer to this question could come from a careful examination of oilfield brines. None of the conventional methods of examining brines (chemical analysis, pH and electrical conductivity measurements, and the like) answer the question. Careful analysis of reservoir behavior observed in the exploitation of oil fields, particularly in the application of fluid injection, has been fruitful to the extent that a few reservoirs are believed to be properly classified. Physical chemistry suggests the behavior of reservoir brine and rock may be due to something in the brine in small amount. The ever increasing development and modification of theory in the general field of surface and interfacial chemistry has, and is, contributing to a better understanding of the problem, particularly as theory is verified by data. The work herein reported was begun in 1953 by Hough and Roebuck 1,2 who employed a new form of alternating current polarography, i.e., tensammetry, developed by Breyer, et a13,4 and who studied eight oilfield brines in adapting tensammetry to petroleum engineering needs. THEORY AND DEFINITIONS Tensammetry is a new technique of inquiry into surface phenomena. Specifically, a weak alternating current voltage is superimposed upon the direct current voltage applied to a dropping mercury electrode in contact with an electrolyte containing a small amount of a surfactant. The resultant alternating current can be measured and provides the experimental data for this new area of research. Under the influence of the direct current voltage, polar molecules arrange themselves in a double layer at the electrode. This double layer may be compared to a variable condenser, the capacitance of which is a function of the imposed direct current voltage. The direct current voltage determines the degree of adsorption of the surface active molecule on the electrode. Whenever the molecules are strongly adsorbed on the electrode, the capacitance of the double layer is low and the alternating current through the cell is low. Desorption occurs at some values of the direct current voltage, and at these voltages the capacitance of the double layer is high, resulting in an increase in the alternating current through the cell. The direct current

Jan 1, 1958

By C. G. Dunn

WITH respect to theories of recrystallization in metals plastically deformed, it has been said that the present status of this subject is far from satisfactory.1 It may also be said that before any mechanism of recrystallization for metals and alloys can be set forth in a satisfactory manner, there must be made available considerable data on orientation changes that occur during the deformation and recrystallization processes. Although extensive data have been published on recrystallization in single crystals and in polycrystalline specimens, more results of a type that can be classified according to simple orientation changes would be desirable in this complex field. It might even be said that before classifications are made according to types of orientation changes, it may be possible to classify a considerable amount of data into certain kinds of orientation states if groups of common or nearly common orientation occur. Methods for computing the probability of occurrence for various types of groups have been published2 and it has been pointed out in particular that it should be possible to analyze orientation data for high-order twin relationships between old and new grains even when agreement is not at all exact. In this connection, work on recrystallization in silicon ferrite reported in a paper concerned with complex groups of annealing twins&apos; indicated that some data were consistent with primary nucleation occurring according to a second-order or a third-order twin transformation. However, further work in this latter direction was definitely needed. It is, therefore, the purpose of the present paper to report data and analyses for primary nucleation in silicon ferrite following small deformations that have been carried out at the Pittsfield Works&apos; Laboratory of the General Electric Co. Analyses have been made with the aid of standard groups of twins that are reported elsewhere .4 PREPARATION OF SPECIMENS AND EXPERIMENTAL PROCEDURE The material used in the present investigation was taken&apos; from the same heat of steel as that used in a prior report.3 The finished strip in both cases was made by the Allegheny-Ludlum Steel Corporation according to methods that produce a high degree of preferred crystal orientation. Samples with large grains had the following composition: 3.45 per cent Si, 0.003 C, 0.008 P, 0.020 S, 0.075 Mn, 0.031 Al and 0.072 Cu. Thickness of specimens was 0.012 inches. Plastic deformation was produced by cold-rolling the samples on a mill with

Jan 1, 1945