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By D. J. McAdam

Results of investigation of corrosion-fatigue of metals at the U. S. Naval Engineering Experiment Station have been presented by the author in four papers.1, 2, 3, 4 In those papers references were given to the work of Haigh in 1917.5 The investigation at Annapolis included a variety of ferrous and non-ferrous alloys. The experiments showed that even slight corrosion simultaneous with fatigue may cause failure at stresses far below the ordinary endurance limit. The experiments also showed that, for most metals, severe stressless corrosion prior to fatigue is much less damaging than even slight corrosion simultaneous with fatigue. The term "corrosion-fatigue" was restricted to mean the simultaneous action of corrosion and fatigue. The combined effect of corrosion followed by fatigue was called "prior-corrosion fatigue." A stress-cycle graph representing corrosion-fatigue is a curve approaching a horizontal asymptote, the ordinate of which may be called a "corrosion-fatigue limit." To avoid confusion in later discussion, the term "endurance limit" will be restricted to mean the fatigue limit obtained by tests in air with specimens as free as possible from stress concentration and from corrosion. The cndursnce limit as thus obtained presumably represents an inherent property of the metal.

Jan 1, 1929

By P. A. Young

The historical background of on-strand cooling is given, together with a resume of recent practical developments. Laboratory test procedures are then considered in detail, for both productivity and quality parameters, with particular reference to the design of the Ravenscraig No 3 machine (Scotland). A heat transfer model is presented for a porous sinter with propagating cracks. The influence of cooling/sintering area ratio, sinter strength, granulometry, return fines, coke consumption and FeO levels are examined in relation to economics. A detailed comparison of capital and running costs for two different strands, designed for identical duties, but with off or on-strand cooling, is then given.

Jan 1, 1977

By George C. Fryburg

The oxidation of platinum at high temperatures (above 800°C) is controlled by boundary-layer diffusion, except at the lowest pressures. The rate of oxidation is determined by the rate of diffusion of oxide through the boundary layer away from the platinum. This is in contrast to the situation in tungsten and molybdenum oxidation, where the rate is controlled largely by the diffusion of oxygen through the boundary layer towards the metal. The difference in mechanism is a consequence of the much lower rate of oxidation of platinum. Evidence is presented that supports this mechanism for the oxidation of platinum. SOME years ago we reported1 a study of the oxidation of platinum in ordinary oxygen in the temperature region above 800°C, where the oxide is volatile. All the data available up to that time had been obtained with platinum crucibles or plates heated in tube furnaces. The results were widely variant and highly dependent on the flow rate of gas through the furnace: the faster the gas flow rate, the higher the measured oxidation rate. These results indicated to us2 that reaction equilibrium was being approached in the furnace and that the rate was diffusion limited. To minimize these effects, we employed1 electrically heated ribbons placed in a cooled bulb. We were primarily interested in the low-pressure region, but some experiments were performed at pressures up to 1 atm. We found a peculiar pressure dependency which was explained on the basis that the rate of oxidation was proportional to the pressure at all pressures, but that with increasing pressure an increasing fraction of the volatilizing oxide was back-reflected to the ribbon by the surrounding gas molecules. The oxide molecules are not stable at the temperature of the platinum and are decomposed on impact, the platinum being re-deposited on the specimen. Because of the limitations of space, this explanation was offered summarily without detailed support. Recently, Jaffee and associates3, 4 have suggested that the pressure dependency of our data up to 0.5 torr could be explained on the basis of a Langmuir-type adsorption of molecular oxygen followed by dissociation. Since the correct explanation of the effect of pressure on the oxidation rate is a necessary requirement to the development of the basic mechanism of the oxidation reaction, we felt that the back-reflection theory should be presented in more detail. This is the object of the present paper. RESULTS AND DISCUSSION A typical set of results showing the pressure dependency of the oxidation reaction is presented in Fig. 1, where we have plotted, on logarithmic scales, the rate of oxidation, R, vs the pressure, p. For comparison some results of Krier and Jaffee4 and of Raub and plate5 are also shown. These data were taken at atmospheric pressure using furnaces. The effect of reaction equilibrium within the furnace is apparent from the much smaller values that these observers obtained: Raub and Plate In O2 found a rate of 3.1 µg cm-2 hr-1 compared to our value of

Jan 1, 1965

By G. L. Oldright, T. B. Brighton, C. M. Dice

The base bullion from the lead blast furnace contains varying amounts of the impurities left in the smelter feed by the concentrator, regardless of the method of smelter operation. These impurities may be held in part in mechanical suspension rather than being present as true alloys. However, usually there is little free space in the crucible in which to separate these drosses before the bullion is taken from the lead well. When such a dross is melted in a laboratory crucible and allowed to cool, the products obtained are lead bullion, speiss, and matte in well separated layers. Typical analyses of layers are: Analyses. Per Cent Element Bullion Speiss Matte Pb.............................................. 92.0 41.2 38.3 Cu.............................................. 2.4 36.3 40.6 As............................................... 4.0 16.5 4.3 Sb............................................... 0.7 0.2 0.4 S................................................ 0.6 1.9 13.1 Fe............................................... 0.0 0.0 0.0 Totals......................................... 99.7 96.1 96.7 The absence of iron in these products drossed from the blast-furnace bullion proves that the impurities for the greater part are not simply finely divided blast-furnace speiss or matte that has been dissolved or dispersed in the lead, but are held in solution by the liquid metal and rise to its surface as infusible compounds when the temperature of the bath is lowered. In general, the drosses made locally are metal sulphides and arsenides and not oxidized compounds. The large content of metallic lead also does not seem to be retained because of oxidized compounds

Jan 1, 1937

By E. P. Klier, Jane Jellison

The course of the transformations on cooling in a series of Cu-A1 alloys has been followed by means of thermal analysis, X-ray diffraction, and optical metallogrAphy. Specimen size was found to have a pronounced effect on the time of completion of the pearlite transformation due to modification in the unmber of nuclei. The ordeving transformation zvas observed for all cooling rates for all alloys studied, and is considered insuppvessible. At intermediate cooling' rates, a transitional struchire for 011 alloy compositions and based ox the bainite reaction was observed. The alloys of aluminum and copper possess a eu-tectoidal region at from about 9.4 to 16 pct Al. Above the critical temperature, the disordered bcc phase, 0, is stable. At subcritical temperatures, the 0 phase decomposes under equilibrium conditions into the stable phases, a and y,. At the eutectoid composition, these phases develop a lamellar pearlite structure, in appearance much like that found in steels. During rapid quenching from supercritical temperatures, the diffusion processes required for the formation of the equilibrium phases are suppressed, and the 0 transforms to an acicular martensitic phase, designated B or y' depending on the aluminum content, or to a mixture of the two. Early investigators of this system concentrated on determining the equilibrium phase diagram, ''' the structure of the equilibrium phases,3 and later the isothermal decomposition of the 0 phase at subcritical temperatures, or the decomposition of the martensite on tempering. Other work which treated the nonequilibrium transformations concentrated largely on the martensite transformations and the structure of the b and y' phases.15"17 Since the pearlite and martensite transformations in this system resemble those in steels, the one being formed by nucleation and growth of adjacent lamellae of the equilibrium phases, and the other by a diffusionless, shear-type transformation, the present study has been undertaken to investigate the structures formed on continuous cooling, with the objective of constructing cooling transformation diagrams analogous to those derived for alloy steel systems. In particular it was desired to determine whether parallels between the A1-Cu and iron-iron carbide systems on continuous cooling extended to encompass the intermediate phase, namely the bainite structures, which form by a combined martensitic-diffusion mechanism,'' but which are supersaturated with respect to the equilibrium phase upon which their crystal structure is based. To this end the transformations in representative alloys of the Cu-A1 B eutectoid system have been followed, using the methods of thermal analysis, X-ray diffraction, and optical microscopy. EXPERIMENTAL PROCEDURE Materials. The materials tested were those used by Klier and Grmko 5 in their study of the isothermal decomposition of these alloys. The alloys were melted in graphite crucibles and chill-cast into 5 by 2 by 1/4 in. ingots. The ingots were then hot-rolled to sheets 1/8, 1/16, and 1/32 in. thick. The compositions are given in Table I. Specimen Preparation. Specimens for thermal analysis were in the form of small squares approximately 1/4 in. on a side. For the 11.9 and 13.5 Al-Cu alloys, the sheet thickness was 1/16 in. and for the 10.5 A1-Cu alloy the 1/32-in. sheet was used. One lead of a chromel-alumel thermocouple was spot-welded to either face of the square with the specimen itself thus forming the hot junction of the thermocouple. Specimens for X-ray analysis were prepared as filings from martensitic sheet stock and were sealed in glass ampoules under 1/2 atm of argon. Metallographic examination of the powder specimens was carried out on a portion of the heat-treated filings mounted in lucite. All specimens were examined metallographic ally after etching

Jan 1, 1965

By Chandler Morse

RENEWABLE VS. NONRENEWABLE NATURAL RESOURCES Nonrenewable resources, such as minerals, are the inevitable center of attention in discussions of depletion and exhaustion. Nevertheless, it may well be proper to regard some nonrenewable resources as not subject to exhaustion, and renewable resources may sometimes be treated as if they were finite stocks. Thus, the availability of nonrenewable resources is not and probably never will be known completely Chap. 2.5A, and therefore is not subject to firm predictions concerning exhaustibility. Moreover, because exploration and discovery are more or less continuous processes it is often appropriate to regard mineral supplies as flows, and to treat the estimated reserves as working capital, an inventory, continually depleted by use and augmented by discoveries.23 The aggregate economically exploitable stocks of a given mineral are seldom estimated (or estimatable) with precision, as Chap. 2.5A shows, and even when they are, forecasts concerning years of remaining life can be and often are falsified by changes in one or more of the multidimensional conditions of supply and demand; or the productive services formerly derived from an exhausted stock may continue to provided without material impairment by one or more substitutes b Conversely, the renewable resources are all subject to depletion when the rate of use exceeds the natural or induced rate of replenishment, and cases of exhaustion or near exhaustion, as through soil erosion, overcuttmg of forest lands, and overfishing, are rather common c Where exhaustion is a clear possibility the resource may either be exploited on a consciously adopted "sustainable yield" basis or be treated as an exhausting asset." In some cases, conscious treatment

Jan 1, 1976

By A. F. van Everdingen

The pressure drop in a well per unit rate of flow is conrolled by the resistance of the formation, the viscosity of the fluid. and the additional resistance concentrated around the well bore resulting from the drilling and completion technique employed and, perhaps, from the production practices used. The pressure drop caused by this additional resistance is defined in this paper as the skin effect. denoted by the symbol S. This skin effect considerably detracts from a well's capacity to produce. Methods are given to determine quantitatively (a) the value of S, (b) the final build-up pressure, and (c) the product of average permeability times the thickness of the producing formation. INTRODUCTION Equations which relate the pressure in a well producing from a homogeneous formation with pressures existing at various distances around the well are generally used within the industry. The relation ii quite simple when the fluid flowing is assumed to be incompressible. It becomes somewhat more complicated when the flowing fluid is considered compressible so that the duration of the flow can he considered. In each case the major portion of the pressure drop occurs close to the well bore. However analyses of pressure build-up curves indicate that the pressure drop in the vicinity of the well bore is greater than that computed from these equations using the known, physical characteristics of the formation and the fluids. In order to explain there excessive drops it is necessary to assume that permeability of the formation at and near the well bore is substantially reduced as a result of drilling. completion and, perhaps. production practice. This possibility has been recognized in the literature. A method to compute the pressure drop due to a reduction of the permeability of the formation near the well bore. which is designated as the skin effect. S, is given in the following paragraphs. To start, equations normally used to describe flow in the vicinity of a well are given without considering this effect. These equations then are modified to include the effect of a skin on the pressure behavior. Finally a method is given to estimate the effect of the skin on the pressure and production behavior of a well. PRESSURE EQUATIONS Incompressible Fluid Flow If p is defined as the flowing pressure in a well of radius the pressure at distance r from the well has been shown to be:" The total pressure drop between the drainage boundary, and the well bore is given by These equations are valid only if the flow towards the well occurs in a horizontal homogeneous medium and the fluids are incompressible. The assumptions imply that all fluid taken from the well enters the system at r a condition rarely encountered in practice. Compressible Fluid Flow, Steady State A more realistic equation is obtained if it is assumed that the compressibility, c, of the flowing fluids is small and has a constant value over the pressure range encountered. After the well has been producing for some time so that its rate has become constant and steady state is reached, the pressures throughout the drainage area are falling by the same amount per unit of time, and the pressure differences between a point in the drainage area and the well are constant. When these conditions are met. the rate of production, q, from a well is equal to where dp/dt is the pressure drop per unit time. The fluid flowing at a distance from the center of the well is equal to From the last equation and from Darcy's law it can be shown that The equation holds for a depletion-type reservoir of radius drained by a well located in its center, provided the compressibility of the fluid per unit pressure drop is small and constant, and no fluid moves across the boundary Compressible Fluid Flow — Nonsteady State Table 111 of reference (5) shows the relationship between the pressure at the well bore and the reduced time, The pressure-drop function, p represents the drop below the original reservoir pressure, p caused by unit rate of production for several values of R, the ratio of drainage boundary radius to well radius, r In most reservoirs the values of approach infinity. and under these conditions the values of p shown in Table I of reference (5) can be used where p then signifies the difference between the pressure in the well and the prevailing reservoir pressure per unit rate of flow. The total pressure drop below prevailing reservoir pressure amounts to where the factor converts the cumulative pressure drop per unit rate of production to cumulative pressure drop for actual rate. q. For values of T > 100 the P function may be written (equation VI-15 of reference 5) as Using the time conversion the difference in pressure between reservoir and well becomes If values for the physical constants of the formation and the fluids are inserted, it is found that T exceeds 100 after a few seconds of production (or closed-in time), so that the approximation becomes valid almost at once. A simple relation between the pressure in the well and in the reservoir can also be derived by considering the well as a point source"" '" instead of a unit circle source, that is, by using Lord Kelvin's solution instead of the unit circle source

Jan 1, 1953

NORTH AMERICA ALASKA Anchorage.-Strandberg, H. Tuck, R. Coal Creek.-Moore, E. G. Spencer, W. W. College.-Hance, J. H. Henricksen, R. Henton, H. M. Comet.-Albertson, F. E. Cordova.-O'Neill, W. A. Douglas.-Cahill, W. E. Fairbanks.-Crawford, J. D. Earling, R., B. Fowler. D. A.

Jan 1, 1937

By C. W. Mac Gregor

THE observation of the flow layers, or Lüders' lines, produced in mild steel when it is stressed into the plastic range often provides considerable useful information for the study of the fundamental mechanism of the plastic flow of metals. It is a commonly observed fact that as soon as the upper yield point in a mild-steel tensile-test bar is passed, an unstable condition develops in the equilibrium, the load on the testing machine drops and if the surface of the bar contains a thin mill scale, the latter begins to flake off rapidly along certain "lines." These "lines" are in reality traces of wedge-shaped flow layers and are formed by the inter-section of the surface of slip and the surface of the bar. The average plane of the flow layer itself has been found by various experimenters to be inclined at an angle of approximately 45° to the axis of the test bar. In a body of more complicated shape stressed in possibly a different man-ner, the tangent planes to the flow layers at each point seem in many cases to be inclined at an angle of about 45° to the principal stress direc-tions at the point. As examples of the latter may be mentioned the logarithmic spirals obtained when a rivet hole is punched in a thin plate, or when a tube is subjected to internal pressure only, etc. Hence if the flow layers are observed from an experiment, the shear-stress trajectories -the curves indicating the directions of the maximum shearing stresses in the body-may then be approximately determined. Since the latter curves form an orthogonal family inclined at 45° to the principal stress directions, the family of principal stress trajectories, or the curves indicating the directions of the principal stresses, may be thus obtained. Although the discontinuous type of stress-strain curve at the yield point is commonly observed with test bars of mild steel, more recent experiments have shown that this is by no means the only material exhibiting this interesting phenomenon. A similar effect has been observed in zinc and cadmium crystals, by Becker and Orowan;1 in duralumin and other aluminum alloys, by Dawidenkow, 2 Elm,3 Fell, and others; in copper and copper-alloy crystals, by Elam;5 in brass by Elam;5 in brass wires by deForest;6 in higher carbon steels, tungsten steel, and

Jan 1, 1939

By Frederick N. Rhines

Pure copper that has been allowed to oxidize at an elevated temperature in the air is found to be covered with two distinguishable layers of oxide scale. The outer of these, which is very thin, is composed of cuprie oxide, while the inner layer, comprising the bulk of the scale, is made up chiefly of cuprous oxide (Fig, la). If a small quantity of an alloying element, such as silicon, is present in the copper, silica particles are found disseminated through the cuprous oxide, deposited most abundantly near the metal surface, and, in addition, silica particles occur to a limited depth within the copper itself (Fig. 1b). It is this inner layer, composetl of oxide particles precipitated in a matrix of metallic copper, that is known as the "subscale" or the zone of internal oxidation. Under a low oxygen pressure it is possible to produce the subscale without the formation of external layers of copper oxides, thus leaving the metal surface bright and apparently clean while oxidation has occurred, in fact, to a considerable depth within the metal (Fig. 2). Although little is yet known in a detailed way of the mechanism of internal oxidation, the general nature of the process is evident. By virtue of the considerable solubility of oxygen in copper,' it is possible to bring the alloying element in contact with oxygen within the metallic solid solution. If the oxide of the alloying element is more stable than cuprous oxide, the foreign oxide may form and, since most oxides are relatively insoluble in copper, it will not long remain in solution, but mill separate as a precipitate. As the metallic solute is exhausted in the zone of precipitation, oxygen that is constantly being supplied at the surface diffuses farther into the alloy and thus produces an ever-thickening shell of subscale. The distribution of the reacting elements in the subscale and adjoining zones must be somewhat as indicated in Fig. 3. The conditions requisite to internal oxidation to be anticipated are thus: (I) a solubility of oxygen in the alloy, (2) the ability of oxygen to diffuse at an appreciable rate into the alloy, (3) the possibility of the

Jan 1, 1940

By Frederick N. Rhines

Pure copper that has been allowed to oxidize at an elevated temperature in the air is found to be covered with two distinguishable layers of oxide scale. The outer of these, which is very thin, is composed of cuprie oxide, while the inner layer, comprising the bulk of the scale, is made up chiefly of cuprous oxide (Fig, la). If a small quantity of an alloying element, such as silicon, is present in the copper, silica particles are found disseminated through the cuprous oxide, deposited most abundantly near the metal surface, and, in addition, silica particles occur to a limited depth within the copper itself (Fig. 1b). It is this inner layer, composetl of oxide particles precipitated in a matrix of metallic copper, that is known as the "subscale" or the zone of internal oxidation. Under a low oxygen pressure it is possible to produce the subscale without the formation of external layers of copper oxides, thus leaving the metal surface bright and apparently clean while oxidation has occurred, in fact, to a considerable depth within the metal (Fig. 2). Although little is yet known in a detailed way of the mechanism of internal oxidation, the general nature of the process is evident. By virtue of the considerable solubility of oxygen in copper,' it is possible to bring the alloying element in contact with oxygen within the metallic solid solution. If the oxide of the alloying element is more stable than cuprous oxide, the foreign oxide may form and, since most oxides are relatively insoluble in copper, it will not long remain in solution, but mill separate as a precipitate. As the metallic solute is exhausted in the zone of precipitation, oxygen that is constantly being supplied at the surface diffuses farther into the alloy and thus produces an ever-thickening shell of subscale. The distribution of the reacting elements in the subscale and adjoining zones must be somewhat as indicated in Fig. 3. The conditions requisite to internal oxidation to be anticipated are thus: (I) a solubility of oxygen in the alloy, (2) the ability of oxygen to diffuse at an appreciable rate into the alloy, (3) the possibility of the

Jan 1, 1940

By L. F. Mondolfo, B. E. Sundquist

The crystallographic orientation relationships resulting when lead is nucleated from the liquid by Ni, Cu, Ag, and Ge were determined. For each nucleating agent several definite orientatioz relationships were found. These relationships seemed to be controlled by good symmetry relations and low crystallographic disregistry between mating planes. For any given nucleating agent the under colling for nucleation was found fairly constant and independent of the orientation relationship and consequent disregistry. It was also found that, upon re melting and refreezing the Pb, the orientation relationship was changed. These findings prove that crystallographic disregistry is not the controlling factor in heterogeneous nucleation from the liquid. The results of this investigation tend to confirm the theory presented in a preceding paper that heterogeneous nucleation starts with the formation of an adsorbed layer of nucleated metal on the nucleat-ing impurity. Evidence is given that cavities in the nucleating agent act as centers of nucleation. IT has long been known' that solid extraneous particles are active in catalyzing phase transformations that occur in a system, particularly condensation and crystallization. It is well established that these heterogeneities act as catalysts by providing surfaces upon which nuclei of the precipitating phase can form with activation energies smaller than those required for homogeneous nucleation. Numerous investigations have shown that in this process of heterogeneous nucleation: a) the nucleus forms with one, or several, definite crystallographic orientation relationships with the nucleating phase2-4 and b) that there is a small range of undercoolings or super saturations characteristic of the nucleation of a given solid on a given Substrate.5-10 Turnbull and vonnegut11 have developed a theory based on theories developed by Volmer12 and Turn-bull and Fisher1= for heterogeneous nucleation from gases and liquids, that relates the super saturation or undercooling required for nucleation to the dis-registry between the lattices of the nucleus and the nucleating agent. This theory predicts that nucleation should occur with the orientation relationship between the nucleus and nucleating agent that minimizes the disregistry. Further, it predicts that the undercooling or super saturation necessary for nucleation should be a function of the disregistry. Numerous investigations have dealt with the orientation relationships resulting from the condensation of vapors onto crystalline solid substrates2,3 and a few with the nucleation of one phase by a second phase in solidification4,14. Others have dealt with the supersaturation8-10 and undercooling5-7 associated with nucleation in condensation and solidification respectively. However, there is virtually no report that gives both of these factors for the same system. In this investigation a study was made of the undercoolings and orientation relationships resulting when Pb is nucleated from the liquid by Ni, Cu, Ag, and Ge. It was the purpose of this investigation to check the Turnbull-Vonnegut theory, i.e., the importance of crystallographic disregistry between nucleating catalyst and nucleated metal. The results indicate that disregistry is not an important factor in nucleation and that the nucleation process is probably somewhat more complex than current theories suggest. EXPERMENTAL PROCEDURE Small single crystals of nickel, copper, silver, and germanium were prepared from materials of four to five nines purity, and the Pb used was also 99.999+ pet pure. Cu and Ag single crystals were prepared by sealing small chips of Cu or Ag in an evacuated quartz capsule and heating the capsule at 2000°F for 1 hr before cooling. Nickel crystals of 200 diam were also prepared in evacuated quartz capsules, but melting was done by heating the capsules in an oxy-acetylene flame for a few minutes. These spheres were invariably polycrystalline so

Jan 1, 1962

By Frederick M. Becket, Russell Franks

In a recent article,l which described the softening effect of columbium in plain high-chromium steels, the authors stated that their investigations had shown columbium to be also a particularly valuable inhibitor of intergranular corrosion in steels of the 18 per cent chromium, 8 per cent nickel type. It is the purpose of the present paper to record some of the results obtained through the introduction of columbium to the austenitic chromium-nickel steels. The damaging effects of this type of corrosion have become so widely known as to restrict considerably the applications of the steels under consideration, and therefore there is little question of the importance of the goal to be attained. Numerous contributions concerning the susceptibility of the austenitic chromium-nickel steels to intergranular corrosion have appeared during the past few years, and among others who have dealt constructively with the subject are such well-known authors as Strauss and Houdremont of Germany, Hatfield of England, and Bain in the United States. Different theories have been propounded as to the cause of intergranular corrosion, and various remedial measures have been proposed, the majority of which involve the use of addition agents. Titanium is the addition agent at present most generally employed, as suggested by Houdremont and modified as described by Bain, Aborn and Rutherford. Little has been published on the effects of holding these steels for long periods at the relatively lower temperatures in the presence of corroding media, and the effects have mot been fully realized by producer and consumer.

Jan 1, 1934

[Abad. Leopoldo F., Min. Engr., Div. of Mines, Bureau of Science Manila, P. 1. '28 Abadilla, Quirico A., Geol., Lago Pet. Corp Box 172, Maracaibo, Venezuela. '20 Abarquez, Ramon F., Met., Bureau of Science Manila, P. I. '24 Abbey, Robert Graham, Student, Case School of Applied Science Cleveland, Ohio. '21 Abbott, A. N., Mines Supt.. Mazapil Copper Co,, Ltd Concepcion del Oro, Zac,, Mexico. '28 Abbott, Clarence E., Mgr,, Mines & Quarries, Tenn, Coal, Iron & R. R. Co., 1242 Brown Marx Bldg,, Birmingham, Ala. '04]

Jan 1, 1928

By E. T. Turkdogan, P. Grieveson

Experimental results are presented for the rate of solution of nitrogen in a iron in the temperature range 750° to 873°C and in 6 iron in the temperature range 1410° to 1470°C. It is shown that the rate controlling process is diffusion of nitrogen into the iron. The diffusiting of nitrogen in a and 6 iron is derived from the results, and the temperature dependence of the diffusivity is represented by the equation D = 7.8 x e- 18,900/RT sq cm per sec. The solubility of nitrogen in a and 6 iron, in equilibrium with 1 atm pressure of nitrogen, has been measured. Using these results and other available data, it is found that the variation of the logarithm of nitrogen solubility with the reciprocal of absolute temperature is nonlinear. In an Appendix, some results of Darken and Smith are presented for the rate of solution of nitrogen in iron using ammonia + hyidrogen mixtures. These data also support the view that diffudsion of nitrogen in iron is the rate-controlling process when ammonia + hydrogen mixtures are used. A considerable effort has been made to obtain data on the solubility1-5 and diffusivity of nitrogen in a iron6-l2 because an understanding of the effect of nitrogen on the properties of steel must be based on an accurate knowledge of the properties of nitrogen in pure iron. However, no information is available concerning the kinetics of solution of nitrogen in a and 6 iron. Recently the authors13 have investigated the rate-controlling mechanism operating in the kinetics of solution of nitrogen in y iron. This study was directed to determine the rate-controlling processes for similar reactions with a and 6 iron as well as to establish values for the solubility of nitrogen in equilibrium with nitrogen gas in a and a iron. EXPERIMENTAL The procedure used in experiments to determine the rate of solution in cylindrical iron rods was the same as that described in a previous communication.13 Ferrovac E grade iron used in all experiments contained the following impurities in weight percent: C, 0.005; Mn, 0.001; P, 0.002; S, 0.006; Si, 0.006; Ni, 0.025; Cr, 0.002; V, 0.004; W, 0.02; Mo, 0.01; Cu, 0.001; Co, 0.01; 0, 0.007. After cleaning the surface, the iron rods were treated in an atmosphere of purified hydrogen for 17 hr before the reacting gas was introduced for known experimental times. After quenching, the samples were sectioned radially and analyzed for nitrogen. In addition to experiments using rods, iron foils were used in the measurements of solution rates of nitrogen in a iron. The foils of two different thicknesses were prepared by cold rolling Ferrovac E grade iron cylindrical rod to 0.051 and 0.152 cm. Foil samples were used in a rectangular form 5 cm long and 1.25 cm wide. The specimens were thoroughly cleaned of surface oxide with fine emery cloth and degreased with carbon tetrachloride immediately before entry into the furnace. The experimental procedure was the same as that used in the study with rods. At the completion of an experiment, the foil samples of the nitrogenized iron were analyzed for nitrogen after discarding 0.3 cm from the perimeter of the specimen. Iron foils were nitrogenized and denitrogenized in the a and 6 range with a gas mixture of 95 pct N and 5 pct H for times varying from 5 min to 2 hr. Results obtained for the average composition of nitrogen in iron for these experiments are presented in Fig. 1. Prior to the denitrogenization experiments, the samples were saturated with nitrogen at 1000°C and 0.67 atm N, giving a uniform nitrogen concentration of 0.0204 pct. According to the known a-y phase boundary in the Fe-N system,14 this composition lies within the ferrite region at temperatures 750" to 850°C. Use of this initial nitrogen content insured that reaction occurred between the gas and a single solid phase, a iron. Examples of the results for the mean concentrations of nitrogen in cylindrical iron rods, 0.356 cm radius for both the a and 6 ranges are given in Fig. 2. Typical examples of the results obtained for the radial distributions of nitrogen in rods are presented in Fig. 3. It appears that the results for radial distributions can be extrapolated to constant surface compositions which agree with the equi-

Jan 1, 1964

By Waldemar Lindgren

I. Introduction............790 II. Geological Feature*:........793 The Gold-Bearing Fissure- Veins........793 Contact Melamorphic Deposits.........798 Classification According to Age........ 799 Introduction...........799 Pre-Cambrian Deposits.........800 Cretaceous Veins of the Pacific Coast...... 801 Late Cretaceous or Early Tertiary Deposits (Central Belt).. 802 Tertiary Deposits..........804 Conclusions,...........808 III. Detailed Descriptions:.........811 United Stater...811 Alaska.. ..812 Arizona,..814 California ..816 Colorado .. ..818 Idaho...823 Montana...825 Nevada...829 New Mexico,..........831 Oregon...833 South Dakota..834 Utah...836 Washington.. 837 Wyoming..838 Appalachian States..........839 British North America..........840 Mexico ....843 I. Introduction. The precious metals. gold and silver. are the basis of the monetary systems of the world. It is. therefore. natural arid inevitable that widespread interest should be manifested in their

Jan 1, 1903

By J. A. Church

I. Early Furnaces,......423 11. Experiments with the HIgh-Shaft FURnace,..... 426 III. ExperMents wIth the Wide FURnace,..429 IV. ExperEentS with Extreme BOSH,... 43.2 V. Survival of the 56 by 180 IN. Furnace,.434 VI. Recent ExpeEiments,.....436 VII. SUMMary,........438 I. Early Furnaces. Copper blast-furnace construction in America has long recognized a general standard in the rectangular water-jacketed shaft with separate forehearth. The details, however, and especially those relating to shaft dimensions, have had to meet a great variety of conditions, and show no uniformity whatever. Selecting a few of the present day Western plants, we find furnace lengths varying from 12.5 to 87 ft., widths at tuyere level from 42 to 84 in., and heights above tuyeres from 5 ft. 4 in. to 22 ft. 4 in.; and comparing present designs with those of the past, we meet contrasts no less striking. Unlike its transverse section, the length of a furnace has come to depend rather on the size of unit desired than on the requirements of smelting; and if the question of length be ignored, several of the various existing designs can be grouped together on the basis of a common transverse section. This section, having a width at tuyere level of 56 in. and a height above tuyeres of 18 ft., was developed at Great Falls, and the story of its development contains some interesting features. Ground was broken for the Great Falls works in the spring of 1891. About a year later, the concentrator was able to begin operation, followed within the next few months by the Brueckner, reverberatory, and converter departments, and in April, 1893, by the first blast fur-

Jan 1, 1914

By A. H. Geisler, J. H. Keeler

Preferred orientations in rolled and annealed titanium sheets were determined by the Geiger counter spectrometer X-ray diffraction technique. Five annealing textures dependent upon the temperature range of annealing were found, and in order of increasing annealing temperature pendent upon the temperature range are: 1—a deformation like texture, 2—a rotated inorder a-recrystallization temperature texture, 3-a retained u-recrysraIlization texture, on annealing at lower temperatures of the ß-region, 4—a transformation texture based on recrystallized a and predicted by the Burgers' relationship, and 5—a ,ß-cube texture. These results are examined in terms of current theories of recrystallization textures. UMEROUS investigators have described the tex- ture obtained by cold rolling the hexagonal metals, titanium, zirconium, and beryllium, which have c/a ratios less than that of ideal packing, 1.633. The basal planes are rotated out of the rolling plane, about the rolling direction, so that the basal poles are tilted toward the transverse direction as shown schematically in Fig. la. In all instances but one,' it was also reported that the [1010] direction was parallel to the rolling direction (see Fig. lb). Hot rolling has been reported as causing a similar tilt of the basal poles in the transverse direction (see Fig. la) and causing the [1010] direction also to be parallel to the rolling direction as shown schematically in Fig. lb. Annealing after deformation does not appreciably change the tilt of the basal poles in the transverse direction." Beryllium2-7 continues to have the [1010] direction in the rolling direction after annealing, and similar observations for titanium and zirconium' . have been reported for annealing at fairly low temperatures, again as in Fig. lb. At higher annealing temperatures, however, the recrystallized grains of titanium" and zirconium have an orientation such that the [1120] direction is approximately in the rolling direction, although the basal poles are still inclined in the transverse direction. Figs. la and lc show the resulting orientations schematically. This change in orientation has been described as a nominally ±30° rotation of the hexagonal crystallites about the basal poles of the cold rolled texture and is apparent from the results which are summarized in Table I for investigations with the X-ray diffraction technique employing film. The angles y, , and ß are indicated in Fig. 2 which represents the stereographic projection of (1070) poles for the mean orientation of a pole figure. Texture determinations for titanium using the Geiger counter spectrometer have provided similar results except that in some instances additional components of the texture were proposed, as shown by the summary of data in the upper half of Table 11. On the other hand, the spectrometer technique, when applied to zirconium,* has revealed a splitting Recently completed studies of the textures of annealed zirconium", show zirconium to possess textures very similar to those reported here for titanium. Therefore, much of this discussion will include zirconium by virtue of its close similarity to titanium in pref erred orientations. of the intense areas of the pole figure for samples annealed at 600°C. This splitting could be described by a 7" rotation of the tilt axis about the normal to the rolling plane. Such a splitting for the annealed texture relative to the cold rolled texture was not observed in other determinations for either zirconium or titanium using the less sensitive film X-ray methoe and makes the relationship between the two types of texture more complex than the simple rotation about the (0001) pole based on film work. The more precise investigations on zirconium permit the descriptions in the lower part of Table 11, which show that the texture depends quantitatively on the temperature of annealing. When zirconium is annealed at temperatures up to 400°C, the texture is similar to the cold rolled texture, while annealing in the range 500" to 900°C produces a texture which is only approximately described as [11%] in the rolling direction. More precisely described results for zirconium show that the two types of splitting ( 1—about an axis in the rolling plane through an angle given in the second column in Table II and 2—about the normal to the rolling plane through an angle given in the third column of Table 11) depend on annealing temperature. The [1120 is the rolling direction only when the annealing temperature is in the vicinity of 900°C

Jan 1, 1957

By M. L. Holzworth, Philip R. Sperry, Paul A. Beck

INTRODUCTION THE basic work of Z. Jeffries1,2,3 has long ago established the main features of grain growth in the presence of a dispersed second phase. Working with sintered specimens of initially fine grained tungsten, to which various amounts of thoria have been added, Jeffries found that grain growth was inhabited, that is, practically prevented, up to a certain annealing temperature. When this temperature, which increased with the thoria content, was exceeded, extremely large grains developed abruptly from the fine grained matrix. Such a "coarsening temperature" was later found by Gross mann13,14 in certain types of steel, while Bain showed" that in other steels grain growth was gradual, without inhibition and abrupt coarsening. Later work16,17,18,19,21 demonstrated the connection between coarsening and aluminum additions. The viewpoint that the direct cause of inhibition and coarsening in aluminum killed steels is a fine dispersion of aluminum oxide21 appears to be held quite generally, although some doubts have been voiced even very recently.20 In steels with Ti additions the titanium carbide phase is considered responsible for the inhibition effects found.20 The coarsening temperature increases, with the titanium content. That coarsening may occur, as a result of certain heat treatments, even in low carbon rimmed sheet steel, was shown by Samuels,22 He also detected coarsening in a steel ingot of similar composition, after giving it the same heat treatment as that used by him for the sheet material, In this instance the identity of the inhibiting phase has not been determined, However, Tangerding found 23 that even the few small carbide particles, which occur in carbonyl iron, have a very marked inhibitive effect. As a result of an oxidizing anneal at 850°C, large grains begin to form at the surface of the carbonyl iron specimen, and gradually grow inward as the subsurface oxidation of the carbide particles progresses and eliminates the obstruction, The carbide particles can be removed also by annealing in hydrogen, with similar results. But if the oxidizing anneal of 10 hr at 850°C in air, is followed by annealing in hydrogen for 75 hr at the same temperature, grain growth is more spectacular; usually the whole specimen is transformed into a single crystal (approx. 1,5 cm X 5 cm). The reversed procedure, that is, hydrogen annealing followed by oxidizing annealing leads to smaller grains. Tangerding arrived at the logical conclusion that there must have been in his specimens some additional obstruction to grain growth resulting from a minor impurity, other than carbon. It seems likely that this obstruction was caused by an oxide formed during the oxidizing anneal and gradually reduced during the subsequent hydrogen-annealing. Other instances of grain growth inhibition of varying severity, associated with a dispersed second phase, have been described by several authors. Notable examples: lead with 0.06 pct Cu or Ni,24 cartridge brass with 0.12 pct Cr,25 or with up to 0.15

Jan 1, 1948

By William H. Spice

Exploratory drilling in South Central Texas for the year 1944 showed a marked increase over that of 1943 and resulted in a similar increase in new fields discovered. In this area, which comprises the 30 counties included in district No. I, Oil and Gas Division, Railroad Commission of Texas,? 61 exploratory wells were drilled during 1944 as compared with 29 exploratory wells drilled during 1943, or an increase of over 100 per cent. Three new oil fields, two new gas fields and one gas-distillate field were discovered during the year, as compared with one new oil field and one new gas field discovered during 1943. These new fields were the result of exploratory drilling throughout the district along the Wilcox trend and the deeper Edwards lime trend, which was started during the previous year. The Wilcox trend yielded the new Loma iilta-Wilcox oil field and the San Caja gas-* tlistillate field, both in McMullen County. The Charlotte field, in Atascosa County, was discovered along the deeper Edwards lime trend. These three discoveries were of considerable importance and subsequent development should indicate the desirability of continued exploration along these trends. The other three discoveries, United oil field in Guadalupe County, Pederson gas field in Milam County and Van Cleve gas field in Zavalla County, were of minor importance. Charlotte Field, Atascosa County, was discovered by the Humble Oil and Refining Company's No. 3 Pruitt, completcd on Aug. 9, 1944, flowing 176 bbl. per day, 3/16-in. choke, 710 lb. tubing, 475 lb. casing pressures, 37.7º A.P.I. gravity, from the top of the Edwards lime from 6917 to 6923 ft. Two oil wells were completed during the year in this field. This discovery is 14 miles southwest of the same company's Imogene field, also producing from the Edwards lime but with considerable difference in reservoir characteristics. The discovery of this field is the result of surface geology and subsequent seismograph survey of the area. Loma Alta-Wilcox Field, McMullen County, was discovered by the Atlantic Refining Company's No. I Atkinson, completed on June I, 1944, flowing 102 bbl. per day, 9/64-in. choke, 1900 lb. tubing pressure, 37º A.P.I. gravity, from Wilcox sand from 6866 to 6869 ft. after being drilled to a total depth of 7185 ft. This discovery is the result of subsurface geology and an extensive seismograph survey of the entire area. Sun Caja Field, McMullen County, was discovered by Edwin M. Jones No. 2-C Ezzell, completed on June 2, 1944 as a dual completion in the Wilcox sands, flowing 1,740,000 cu. ft. gas with 53 bbl. distillate, 1/4-in. choke, 2035 lb. tubing pressure, 53.2º A.P.I. gravity, from sand 6416 to 6453 ft. and flowing 2,000,000 cu. ft. of gas with 127 bbl. distillate, 1/4-in. choke, 2500 lb. tubing pressure, 50º A.P.I. gravity, from sand 6889 to 6916 ft., after being drilled to a total depth of 7264 ft. Three gas-distillate wells were completed during

Jan 1, 1945