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By F. R. Morral, K. T. Aust

The preferred orientation and earing characteristics of ZS aluminum were studied. An empirical correlation was obtained relating earing behavior and variation of mechanical properties for face-centered cubic metals. Strain-ratio mecsurements for ZS were found to be in good agreement with Hill's theory of plastic anisotropy. DIRECTIONALITY in sheet metals may be revealed by earing in a cupping test, or by the variation of mechanical properties of tensile specimens taken at different angles to the rolling direction. However, no simple correlation appears to exist between earing and variation in mechanical properties in metals and alloys studied.1-5 Aluminum of commercial purity (known as 2S, with a specified minimum of 99.0 pct Al) cast by the direct casting process was chosen in the present investigation since ears at 45° or 0°, 90° can readily be obtained. Preferred orientation is often the principal cause of uneven metal flow, such as earing, and variation in mechanical properties. Consequently, the preferred orientation characteristics of 2s aluminum were initially studied using both X-ray diffraction and micrographic techniques. The variation of mechanical properties with angle to the rolling direction was next determined in an effort to clarify the apparent lack of correlation of earing behavior with mechanical properties for face-centered cubic metals. Strain-ratio*5,8 measurements were finally conducted to determine first, if the maximum values of the strain ratio occurred at the earing positions, and second, if Hill's theory of plastic anisotropy7 is applicable to other face-centered cubic metals such as aluminum. Detailed treatments, working, and heat treating are not given in this paper since this study is not concerned with the methods to produce earing, but to correlate earing with other properties and characteristics of the material. The percentage of earing was measured using the formula specified by the x—Y Aluminum Association, -------- X 100 = pct earing, where x is the height of the ear and y is the height of the valley from the bottom of the cup. Preferred Orientation Characteristics of 2S X-ray Studies: Beck and coworkers8 have determined that the rolling texture of 2s after 95 pct cold reduction may be approximately described by four equivalent ideal orientations near (123) [121]. Also, the recrystallization or annealing texture of 2s aluminum consists of four components of the (123) [l21] type, retained from the rolling texture, and of a (100) [001] or cube texture component." Fig. 1 illustrates the typical appearance of deep drawn earing cups with the corresponding X-ray diffraction patterns. The X-ray patterns were taken with copper radiation using the structure-integrating method'" in which the specimen is scanned during the X-ray exposure. The rolling direction was vertical and the rolling plane was perpendicular to the horizontal X-ray beam. It was found that an increase in the retained rolling texture component resulted in a greater 45" ear height, while an increase in the recrystallization texture component (i.e., cube texture) caused greater 0°, 90° earing. X-ray diffraction studies of 2s cold rolled to final thickness followed by a final anneal have shown that the rolling texture, and also the retained component of the rolling texture after annealing, are increased with greater cold-rolling reduction. The preferred orientation characteristics of 2s sheets given an intermediate anneal between cold rolling followed by a final anneal were found to depend on the position of the intermediate anneal during cold rolling. For instance, three identical samples of 2s homogenized ingot, each 1 in. thick, were given the following cold-rolling and annealing treatments: 1—50 pct reduction, intermediate anneal, 96 pct reduction to 0.020 in. and a final anneal; 2—75 pct reduction, intermediate anneal, 92 pct reduction to 0.020 in. and a final anneal; and 3—90 pct reduction, intermediate anneal, 80 pct reduction to 0.020 in. and a final anneal. The intermediate and final annealing treatments consisted of a 70°F per hr heating rate, held 6 hr at 800°F and air cooled. Typical X-ray patterns after each of these treatments are shown in Fig. 2. It was evident that after treatment 1, the retained rolling texture component predominated; after treatment 2, the retained roll-

Jan 1, 1954

F. W. Gordon, Philadelphia, Pa.: There can be no objection to the use of cross-compound blowing-engines; and when they are condensing they are susceptible of great range of duty with slight loss in efficiency. By those who have use for the full heat of the waste gases, this type of engine is advantageous; but many furnaces are not so located. The pig-iron is their finished product, and the gases are to be employed only for furnace-use. In this case simple engines are preferable, being less expensive and having less parts to take care of. These reasons determined the introduction of the engines, a sketch of which is distributed at this session. There are three of these engines to furnish blast for two furnaces, for a make of abont 250 tons per day, using 75 per cent. anthracite and 85 per cent. magnetic ores; and they are expected to blow up to twenty pounds pressure per square inch. For blast-furnaces I prefer the single to the coupled engine, except

Jan 1, 1894

By J. L. Gillson

In this past year of our Institute's life, February 1960 to February 1961, we had some major problems to face, as did our members, since businesses in which they were engaged were feeling the recession. The major problems confronting us during this past year were: 1) Financing the new Engineering Center. 2) Keeping our three almost autonomous societies working together and toward a stronger AIME. 3) Cooperation with other engineering societies the Functional Plan. 4) Licensing and registration, and the Model Law. 5) The reorganization of the Council of Section Delegates. 6) Combatting the slump in the appeal of engineering to the young students.

Jan 4, 1961

By Gerald Edmunds

CASTINGS of pure metals and many alloys usually have a coarse-grained structure characterized by long columnar grains throughout the main body of the casting. Frequently, the surface exhibits finer, some-times nearly equiaxed grains, and such grains may also compose other parts of the casting. This paper deals primarily with determinations of the grain-orientation textures of the columnar and surface grains of polycrystalline zinc castings. It includes some results upon a cadmium casting and a magnesium casting. A hypothesis is devel-oped to account for the observations on columnar grains and to use as a basis for predicting orientations in other cast metals. A general description of the position of the columnar grains in castings is that their long axes are approximately parallel to the direction of the thermal gradient during crystallization. Thus, in cylindrical castings the columnar grain axes tend to be radial, and in large flat castings where most of the cooling is through one or both of the large mold surfaces they tend to be perpendicular to the mold surfaces. At the edges and corners the direction of heat flow and there-fore the position of the grains is more com-plex. Actually observation shows that even in castings made in flat molds the cooling seems to be somewhat irregular, since columnar grains tend to emanate from certain areas of the cooling surface, indicat-ing that thermal contact was better there than in neighboring areas.

Jan 1, 1940

By L. A. Weitzenkamp, N. M. Bashara

A study of the electrical conductivity of gold films less than 200 in thickness indicates a negative temperature coefficient of resistance and a thermal actiuatlon energy of less than 0.25 ev. The films consist of discrete metal islands of linear dimensions from a few angstroms to 1000A. Films were able to withstand applied fields up to 60,000 v per cm before breakdown occurred. A model for the conduction mechanism is proposed which involtes a Potential barrier due to work junction, irriage forces , and an electrostatic potential arising from separating an electron from a neutral island leaving behind a positively charged metal island. Activation energies of less than 0.25 ev ave consistent with this model, which includes a tunneling andor Thermal mechanism for conduction between the separate metal islands. An apparent satuvation effect in conductivity at high fields is observed experimentally. The saturation effect may be explained by the influence of the electrostatic contribution to the potential barriers for the transition through several islands adjacent to the original island which was activated to give up an electron. The proposed model gives Poor quantitative agyeement for the intermal electrical field between islands. ThIS paper will relate the structure of discontinuous metal films to the electrical properties and will emphasize the following topics: 1) the relation of the conduction mechanism to particle size and a comparison of particle size from electrical measurements with electron-microscope studies; 2) the saturation of the conductivity at high electric fields; and finally, 3) a comparison between the external field applied and the apparent field between particles. che- latter comparison points to a need for a modification in the model for the conduction mechanism first proposed by orter' and expanded by Neugebauer and webb2 which will be dealt with in the discussion. The paper is based on results on gold films on glass microscope slides. The clms were vacuum-evaporated and were about lOOA thick, thickness being measured by interferometry. It has been observed that metal films of this thickness do not exhibit bulk metallic conduction. Films thinner than some critical thiclmess, depending upon substrate temperature and other factors, have conductivities which increase with increasing temperature with thermal activation energies of less than 0.25 ev. Electron-microscope studies3 have shown that these films consist of discrete metal islands having linear dimnsions from a few angstroms to approximately 1000A. When the metal is being vacuum-deposited on the substrate, islands on the order of a few angstroms appear first. As the deposition continues the islands may tend to agglomerate into larger particles and may eventually grow together into a continuous film,3''' In our tests the conductivity of the gold films was found to be about ten orders of magnitude less than the bulk conductivity of gold. When oxygen was introduced into the test chamber the conductivity decreased by a factor of about one-third. This can be related to an increase in work function for gold caused by adsorption of oxygen, as reported by Oullet and Rideal.s Exposure to an atmosphere of water vapor caused an increase in conductivity by a factor of 2 or 3 when a low field was applied. When the films were exposed to water vapor under a high field the conductivity increased by as much as two orders of magnitude. The activation energies measured were much less than the work function for gold, 0.25 ev or less, with the smaller activation energies observed for thicker films. It will be shown that the activation energy is a function of particle size and spacing. In general the model for the potential between metal islands would include the effective work function, the image force, the applied field, and an electrostatic term. The electrostatic contribution arises from the potential required to separate an electron from a conducting sphere. According to Neugebauer and webb2 the maximum potential due to the field and the electrostatic term only is

Jan 1, 1967

By George W. Maynard

In the biographical notice of Thomas F. Witherbee, published in.Bulletin NO. 32, August, 1909 (p. xxv), it is said that "he is believed to have been the first manager in America to use the chemical laboratory for the purpose of controlling the regular running of the blast-furnace." Since the year is not given, I cannot decide as to Mr. Witherbee's priority; but the statement leads me to contribute a bit of history, showing an early departure from the " rule-of-thumb " blast-furnace work to the employment of a chemist. In the autumn of 1868 the department of mining and metallurgy was established at the Rensselaer Polytechnic Institute. In connection with the assay-department a laboratory was equipped for making general commercial analyses. In January, 1869, Alexander L. Holley, the manager and builder of the Bessemer plant at the Rensselaer Works of John A. Griswold & Co., the first plant erected in the United States under the Bessemer patents, began to send me samples

Jan 1, 1911

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

Solid-solubility limits at 1500°, l000q and 500°C for carbon, nitrogen, and oxygen in high-purity tantalum were determined by X-ray lattice-parameter methods. For carbon, the solubility was found to be 0.17 at. pct at 1500°C, and less than 0.07 at. pct at 1000°C. A nitrogen solubility of 3.70 at. pct at 1500° C decreases linearly with temperature to 2.75 at. pct at 1000°C, and 1.8 at. pct at 500°C. In the case of oxygen, the solubility was found to be 3.65 at. pct at 1500°C, 2.95 at. pct at 1000°C, and 2.5 at. pct at 500°C. The phases Ta2C, the low-temperature modification of Ta205, and Ta,N of unknown composition but which has a superlattice structure based upon the original bcc tantalum lattice have been identified as the initial precipitates in the respective systems. Metallographic methods were employed to verify the X-ray analyses. The etching behavior of Ta is discussed in terms of lattice i?rzperfections and precipitate phases. The excellent fabricability, high melting point, and nuclear properties of tantalum are responsible for interest in this refractory metal. Data on the solid solubility of the interstitial elements (oxygen, nitrogen, and carbon) in tantalum and on the precipitate phases are somewhat limited. The significant contributions are discussed below. Because the purity of electron-beam melted tantalum (only recently available) is considerably higher than that used in previous studies, the present investigation was initiated. Gebhardt et all-3 have investigated the tantalum-oxygen and tantalum-nitrogen systems with particular reference to the changes in physical properties and to the rates of reaction between these gases and the metal. The solubility of oxygen in tantalum was reported2 to be 3.7 at. pet at 1500°, 2.3 at. pet at 100O°C, and 1.4 at. pct at 750°C. Schonberg4 reported that several oxide phases (Ta40, Ta,O, TaO and Ta,05) exist while X-ray studies by Gebhardtl showed only two oxides, Ta,05 and an unidentified phase which was associated with a platelet-type precipitate. La-gergren and Magneli,' however, questioned the existence of compounds other than the two allotropic modifications of Ta,05 for the tantalum-oxygen system. In the case of nitrogen, the solubility was estab- lished by Gebhardt3 to be of the order of 7 at. pct at 1800°c. The solubility was reported to decrease rapidly with temperature, and, although no limits were established, a precipitate phase was observed by Gebhardt except when the high-nitrogen specimens were cooled very rapidly from the reaction temperature of 1800c. He reported the initial precipitate phase to be a tetragonal distortion of the bcc tantalum lattice while Schonberg6 reported the phase lowest in nitrogen Jo be a cubic super-lattice with a cell size of 10.11 A. Two other nitride phases, Ta,N and TaN, were reported; these appear to be isomor-phous with the carbides of tantalum. The tantalum-carbon system was investigated by Ellinger7 and by Lesser and Braurer. Two compounds, Ta,C and TaC, were reported to exist, each with a range of composition. The solubility of carbon in tantalum was found to be practically nil at all temperatures. Thus, of the interstitial elements which are present in small amounts in high-purity tantalum, carbon might be expected to form precipitates. The present investigation was initiated to obtain additional data on the solid-solubility limits of these interstitials at 1500°, 1000°, and 500' with particular emphasis on the distribution and the identification of the precipitate phases. EXPERIMENTAL WORK AND RESULTS In the present investigations of the solid solubility and of the precipitate phases in the systems tantalum-nitrogen, -oxygen, and -carbon, high-purity tantalum was reacted with high-purity gases, homogenized at 1800°c, and annealed at and quenched from 1500°, 1000,

Jan 1, 1962

By John H. G. Monypenny

The range of chromium content of stainless steel is, in most cases, included in the limits 11 to 14 per cent., or the middle part of the range, 9 to 16 per cent., specified by the discoverer. For some time after the steel was produced commercially, the carbon content was about 0.3 to 0.4 per cent. and occasionally higher; only rarely was material with 0.25 per cent. carbon or less produced. The reason for this is obvious from the nature of the alloys of chromium available for making such steels; as the lowest carbon content generally available was about 1 per cent., and this in conjunction with a chromium content of about 60 per cent., the production of a 12-per cent. chromium steel with less than 0.25 to 0.30 per cent. carbon was impossible. The advent, on a reasonable commercial scale, of carbonless ferrochromium has modified this condition, however, so that for the last three years stainless material containing 0.1 per cent. or less carbon and the normal amount of chromium has been on the market. As far as the author is aware, the material was first made on a commercial scale by the firm with which he is associated in June, 1920, when a 5- or 6-ton cast of material containing 0.07 per cent. carbon and 11.7 per cent. chromium was made and cast into 12-in. ingots. The necessity for using a totally different raw material, carbonless ferrochromium, instead of the ordinary low-carbon ferro (0.6 to 1.0 per cent. carbon) has led to the idea that stainless iron is a quite distinct product and quite different from stainless steel. While this may be true from a commercial aspect, it is wrong metallurgically. The name stainless iron is unfortunate as the material is a very mild stainless steel and forms the lowest carbon member of a series of steels of continuously varying content which are, in many respccts, the counterpart of the series of ordinary carbon steels ranging from "dead soft" to tool steels. In an article on stainless steel in the Journal of the Society of Chemical Industry, November, 1920, the author said "Just as in the far-off days 'steel' was regarded as a hard product of iron, and little or no attempt was made to grade it into harder or softer varieties, so at present stainless

Jan 1, 1924

By John H. G. Monypenny

The range of chromium content of stainless steel is, in most cases, included in the limits 11 to 14 per cent., or the middle part of the range, 9 to 16 per cent., specified by the discoverer. For some time after the steel was produced commercially, the carbon content was about 0.3 to 0.4 per cent. and occasionally higher; only rarely was material with 0.25 per cent. carbon or less produced. The reason for this is obvious from the nature of the alloys of chromium available for making such steels; as the lowest carbon content generally available was about 1 per cent., and this in conjunction with a chromium content of about 60 per cent., the production of a 12-per cent. chromium steel with less than 0.25 to 0.30 per cent. carbon was impossible. The advent, on a reasonable commercial scale, of carbonless ferrochromium has modified this condition, however, so that for the last three years stainless material containing 0.1 per cent. or less carbon and the normal amount of chromium has been on the market. As far as the author is aware, the material was first made on a commercial scale by the firm with which he is associated in June, 1920, when a 5- or 6-ton cast of material containing 0.07 per cent. carbon and 11.7 per cent. chromium was made and cast into 12-in. ingots. The necessity for using a totally different raw material, carbonless ferrochromium, instead of the ordinary low-carbon ferro (0.6 to 1.0 per cent. carbon) has led to the idea that stainless iron is a quite distinct product and quite different from stainless steel. While this may be true from a commercial aspect, it is wrong metallurgically. The name stainless iron is unfortunate as the material is a very mild stainless steel and forms the lowest carbon member of a series of steels of continuously varying content which are, in many respccts, the counterpart of the series of ordinary carbon steels ranging from "dead soft" to tool steels. In an article on stainless steel in the Journal of the Society of Chemical Industry, November, 1920, the author said "Just as in the far-off days 'steel' was regarded as a hard product of iron, and little or no attempt was made to grade it into harder or softer varieties, so at present stainless

Jan 1, 1924

By Mark Alling

INTRODUCTION A FEW years ago, gravel mining in the ancient river beds of Sierra county was the principal industry of the county. Operating drift mines were very numerous and many large hydraulic mines were in action. Eventually the State laws put an end to hydraulic mining, it being claimed that the silt carried down the streams to the valleys filled the rivers and caused winter floods, which were damaging to the surrounding farms. The ancient river deposits which could easily be found were, in the course of 40 years, worked out or practically so. The prohibition of hydraulic mining was a severe blow to the industry in general. The deposits were not developed and the gravel-mining industry practically stood still for many years. In Sierra county, nearly all the hydraulic mines were at the points where the ancient channels were exposed to view by reason of the modern stream erosion, or, in the miner's language, where the channels "enter" or "break out of" the ridges. The claims covering them also covered large areas in which were long segments of lava-capped channels, suitable for drift mines, and the points being hydraulicked were usually the controlling points of attack. Men who have followed hydraulic mining for any length of time seldom are content to work a drift mine. Knowing the great value of their deposits and feeling that they had been robbed by the State, these men have stubbornly held to their claims. The gold that is carried in these gravel channel deposits is more or less scattered throughout the depth and width of the deposit; the percentage that can be recovered by the process of drifting ranges from 50 to 75 per cent. of the total. In hydraulicking, practically all of the deposit is put through the sluices, and as the cost per cubic yard is only about 10 per cent. of the cost of drifting, the deposits, if classed as hydraulic mines, are much more valuable than if classed as drift mines; hence the old timers have held their claims (now worthless as hydraulic mines) at prices which the drift-mining industry could not stand; and such mines

Jan 7, 1914

By C. N. Kravig

STANDARD raises at Homestake are 150 ft long. Raises of more than 150 ft, driven with the use of a cage and hoist, are considered long raises- some have been driven more than 900 ft. Long raises have eliminated the need for access drifts on each level when transfer and ventilation raises are driven. These timbered cage raises, 7x9 ft in cross section, include a rock compartment and a combination cage, pipe, and manway compartment. To prevent excessive weight on the timbers, 10x10-in. bearing beams are cemented into hitches cut in the rock at 150-ft intervals. The beams also hold back timber movement caused by daily drawing of rock through the rock compartment.

Jan 6, 1957

By A. R. Powell

Four, general methods have been used in the study of the decomposition of coal. The first has been directed toward the processes of coal formation, the second has been by means of microscopic studies, the third from the data of destructive distillation, and the fourth has made use of various solvents. Applying these methods to the sulfur of coal, it has been found that the organic sulfur of plant and animal life enters into the formation of coal and remains in organic combination in the final product. The inorganic sulfur is almost entirely combined as iron pyrites and marcasite. The infiltration of hydrogen-sulfide waters is doubtless a large factor in these combinations. Sulfates are found in very small quantities except where free oxygen has entered the coal strata. The mechanical mixing of detritus with the early coal material is another source of sulfur. In this case the sulfur is distributed in microscopic particles throughout the mass. In destructive distillation, a part off the sulfur comes off as hydrogen sulfide and various thiophen compounds, but this furnishes little information as to the nature of the sulfur compounds in the coal itself. The use of solvents has given valuable data concerning the sulfur compounds in coal. Fremy1 and later E. Guignet2 noted the action of alkaline solutions on coal after treatment with nitric acid and Anderson and Roberts3 showed' the presence of large quantities of organic' sulfur in the extract so obtained. In a study of the phenol extract of coal, Parr and Hadley4 found organic sulfur in the soluble organic material. These investigations proved the presence of organic sulfur in coal in addition to the inorganic forms, such as iron pyrites and sulfates. T. M. Drown5

Jan 9, 1919

By I. E. Puddington

The property of surface tension in liquids is said to have been known to Leonardo de Vinci in about 1500. Approximately'300 years later Thomas Young and others provided the ground rules relating surface tension to the wetting of solids and to the pressure drop across curved surfaces. In retrospect it seems remarkable that more than 100 additonal years were required for substantial technological use to be made of the-information. Thus super critical and freeze drying to avoid shrinkage of finely divided solids have only seen industrial use since the 1930's and doubtless additional possible applications will be equally slow in finding concurrence of conditions to make them attractive economically. The use of a second liquid phase that preferentially wets ,a suspended solid as a flocculant for that solid was pointed out in 1943 (1). Combining this phenomenon with mechanical energy to alter the morphology of the flocs or with surface chemistry to utilize it in the selective flocculation in mixed solids required more than an additional decade. A major stimulant in advancing surface energy based technology 'of suspensions was the report by D. I. Stock in 1952 (2) that mechanical agitation of a dry suspension of barium sulphate in benzene produced dense microspheres of the solid with highly desirable sedimentation characteristics. Investigation of this observation revealed that it resulted from small quantities of water in the system and mechanistically the phenomenon was identical with that reported in 1943.withthe addition of mechanical packing (3). Here then was a base from which to separate more efficiently suspended solids, to make small spheres from powders, to separate selected components from mixtures of finely divided solids or to break emulsions. Each of these possible branches of technology has been slow in developing on other than an experimental scale although considerable

Jan 1, 1979

By Bradley Stoughton, M. Miyake

The importance of magnesium alloys as engineering materials has increased rapidly in the past few years. The most important properties of magnesium alloys are their lightness and strength, which result in their extensive use in aircraft and automobile construction. Recent progress in the metallurgy of magneaium seems to offer hope of the production of the pure metal at a reasonable cost. The use of magnesium would doubtless increase greatly if it could be produced at a cost comparable with that of aluminum. A preliminary survey of the magnesium-base alloys shows that the most promising from a practical standpoint are magnesium-aluminum and magnesium-zinc as binary alloys, and magnesium-zinc-aluminum as ternary alloys. The research reported in this paper is a preliminary study of binary magnesium-aluminum and magnesium-zinc alloys, as an introduction to a series of further investigations. Magnesium-aluminum System The magnesium-aluminum system was first studied by Boudouard,1 who merely determined the liquidus. An accepted constitutional diagram was given by Grube,2 who found a compound A13Mg4 (melting point = 462.7" C.) and two eutectics at 35 per cent. magnesium (451.6° C.) and at 68 per cent. magnesium (440" C.) Between the first eutectic and the compound a solid solution exists. This diagram was checked or supplemented by Pécheux,3 Broniewski,4 Eger,5 Schirmeister,6 Voge17

Jan 1, 1926

By P. R. Bradley

The property of the Alaska Juneau Gold Mining Co., covering the Juneau gold belt for over a mile in length, consists of 136 claims and 24 mill sites; these are near Juneau, Alaska, in what is known as the Harris mining district. Gold was discovered in the district in 1880, by Richard T. Harris and Joseph Juneau, who had been prompted to explore the section by rumors they had heard among the Indians. Gold was first found on the beach at the mouth of Gold Creek and further search revealed the lode deposits in the Silver Bow basin, about two miles inland. The lode locations made immediately thereafter constitute the principal area of the Alaska Juneau group of claims. Gradually news of the strike spread and, during the late eighties, Silver Bow basin became a substantial producer of gold, both from placer work and from quartz milling. Numerous small mills of various types were erected to crush high-grade float and stringers gouged to shallow depths. Placer mining gradually ceased and the pioneer milling operations gave way to larger and better mills, which in time were the predecessors of the two large mills built by the Alaska Gastineau Co. and the Alaska Juneau Co. on the shores of Gastineau Channel. This evolution from arrastres to small mechanical mills, thence to the two large-capacity mills on Gastineau Channel, although a natural sequence of events, had a most important bearing on the development of the district. Knowledge of the character, extent, and value of the ore deposits gained by these early operations could not have been acquired otherwise. Spencer shows1 that the early mills were: Arrastres in 1881-82-83-84-85-86-88; a 5-stamp mill in 1882; a "newly devised grinding mill" in 1884; two Huntington mills in 1886; a 10-stamp mill in 1889; a revolving Dodge mill in 1890; a 5-stamp mill in 1891; and a 20-stamp mill in 1893. He also estimates the gold production to the end of 1893 as $1,000,000 from lode mining and $1,250,000 from placer mining. No estimate can

Jan 1, 1925

Upon the recommendation of its Technical Committee, The Com-pressed Air Society has adopted the following definitions of, certain terms. Displacement.-The displacement of an air compressor is the volume displaced by the net area of the compressor piston. Capacity.-The capacity should be expressed in cubic feet per minute, and is the actual amount of air compressed and delivered, expressed in terms of free air at intake temperature and at the pressure of dry air at the suction. Volumetric Efficiency.-Volumetric efficiency is the ratio of the capacity to the displacement of the compressor, all as defined above. Compression Efficiency.-Compression efficiency is the ratio of the work required to compress isothermally all the air delivered by an air compressor to the work actually clone within the compressor cylinder, as shown by indicator cards, and may he expressed is the product of the volumetric efficiency (the intake pressure and the hyperbolic logarithm of the ratio of compression), all divided by the indicated mean effective pressure within the air cylinder or cylinders.

Jan 8, 1918

By W. E. Rice

The ceramic industry has to do with forming or molding articles of clay, and imparting to them their characteristic properties of permanence, strength and color by subjecting them to heat treatment in kilns. This heat treatment is commonly known as "firing" or "burning." The art of firing clay ware antedates the industrial use of coal; hence wood was the fuel first used, and the earliest kilns were built to burn wood. The majority of the clay ware produced today is fired in periodic kilns that are essentially enlarged structures similar to the earliest enclosed kilns; a kiln consists of a large chamber 16 to 32 ft. dia. (or rectangular) in which the ware is charged and fired either in direct contact with flame or hot gases from the fuel, or in saggers which shield the ware from direct contact with the gases. The fuel is burned in a number of small furnaces built in the thick wall that encloses the chamber; these furnaces are from 16 to 36 in. wide and from 3 to 5 ft. long; some of them have horizontal or sloping grates, but many have no grates; the last are called "dead-bottom" furnaces. The temperature necessary to mature the charge in the kiln varies for different clays; for some it is as low as 1800°, and for others as high as 2700" F. Wood was an ideal fuel for the low temperatures that were used in early kilns; it burns freely and produces a long, clean flame, which promotes uniform distribution of the heat in the kiln; it does not coke and so restrict the passage of air through the fuel bed; the ash does not melt in the fuel bed to form clinker; and the ash that is carried into the chamber and deposited on the charge does not contain iron and sulfur to discolor the clay. The extent of the ceramic industry now precludes the general use of wood in kilns, so that today this industry is one of the large users of bituminous coal, burning more than eight million tons annually in kilns. Manufacturing plants usually are at or near the source of clay, with deposits of coal suitable for kilns occurring near the clay. The cost of coal is the largest single item of expense in the manufacture of clay ware, and, because all coals are not equally suitable for the process, the careful selection of coal is important. In this selection the desidera-

Jan 1, 1932

By John F. Elliott, Robert D. Pehlke

The rate of reaction of nitrogen with liquid iron and with binary alloys of iron and Al, Cb, Cr, Ni, O, S, Si, and W were measured. The surface active elements, oxygen and sulfur, decrease the rate markedly. The other alloying elements have very little effect on the rate except when they function as deoxidizers, The rates of absorption and de-sorption were found to be equal. Several possible reaction mechanisms which may control the rate are considered. In order to describe completely the behavior of nitrogen in steelmaking processes, the mechanisms of mass transfer between the gaseous and liquid phases, nitrogen and iron, respectively, must be understood. A kinetic study to determine the nature of these mass transfer processes was undertaken, and the results of that investigation are presented in this paper. Specifically, the study was directed toward determining the influence of alloying elements on the rates at which pure nitrogen gas at constant pressure is absorbed and desorbed by liquid iron solutions: A previous paper1 reported measurements of the equilibrium solubility of nitrogen in liquid binary iron alloys. The experimental data are presented and discussed first and then several possible rate limiting mechanisms are considered. PREVIOUS RESEARCH The results of several investigations on the rate of absorption of nitrogen by liquid iron and iron alloys have been reported.2-14 There is little agreement on the rate coefficients among these studies because of the influence of geometry on the experimental system and of the purity of the liquid iron. The rate was found to be influenced by alloying content for the binary liquid iron systems: Fe-Al,2 Fe-C,4,6 Fe-Cr,4,5,8 Fe-Mn,5 Fe-Ni,5,8 Fe-O,9,10 Fe-O,9,10 and Fe-Si.2,6,7,11 Several investigators12"15 have reported that the rate of nitrogen absorption is increased in a reducing gas mixture and decreased in an oxidizing atmosphere. A mechanism for the retardation by oxygen of the absorption of nitrogen has been described by Naeser18 as the formation of an iron oxide film at the gas-metal interface. The film slows the absorption rate until it disolves in the metal, thus permitting nitrogen to enter the liquid iron. Karwat17 discussed the influence of oxygen in terms of the formation of gaseous molecules of nitrous oxide which represent a higher energy form than the nitrogen and oxygen or the oxidizing gas and consequently constitute an energy barrier for the process. Fischer and Hoffmann10 showed that the oxygen markedly reduces the rate of absorption of nitrogen, the rate constant being one order of magnitude smaller in liquid iron containing 0.15 to 0.24 pct 0 as compared to that in melts containing 0.001 to 0.02 pct 0. Although Chipman and Murphy2 reported that the rate of absorption of nitrogen in liquid iron was essentially independent of temperature, Eklund3 found that the rate increases strongly with increasing temperature as did Kootz4 and Saito.5,6 Karnaukhov and Morozov7 also reported a large temperature coefficient, but related it to increased stirring at higher power inputs in an inductively heated system. All of the authors above have treated their results assuming that the reaction is diffusion controlled, that the surface reaction is in equilibrium with nitrogen gas, and that a "first order" reaction takes place. Karnaukhov and Morozov7 and Humbert; who studied the rate of absorption in a closed system by observing pressure changes in the system as a function of time, concluded that their results best fit a diffusion-type analysis. This was further verified by von Bogdandy, Dick, and stranski18 and Fischer and Hoffmann10 who found the initial rate of

Jan 1, 1963

By Roswell Johnson

To know the rate of decline of oil wells is very important, yet ordinarily we are prevented from getting this rate because the oil from several wells is put into one or a few tanks as soon as the wells have been connected to the power. The object of doing this is economy of tanks, pipes, labor and accounting. FIG. 1. But we are making a great sacrifice for this small economy. The advantages of the individual records are that we would know better: 1. When the well has ceased to be profitable. 2. When a well has gotten into bad condition. 3. The real record of the yield per acre and the rate of decline of the wells. The lease total is too mixed as to age of the wells for existing records to have much significance. To obtain such individual well records and more accurate logs are the great desiderata of satisfactory management of oil properties. 4. Which wells show the slowest decline-information which is valuable in locating new wells or purchasing adjoining leases.

Jan 6, 1917

By James A. Roberson

THE mechanical behavior of molybdenum has become a matter of considerable interest in recent years because it has a reasonably high strength at high temperatures. Various aspects of its fatigue behavior have been investigated previously,1-3 and the results can be summarized as follows. Recrys-tallized molybdenum exhibits a fatigue limit which decreases continuously with increasing temperature. The ratio of fatigue-limit stress to ultimate tensile stress is high (0.6 to 0.8) and reasonably constant. The present work was undertaken to determine the effect of variations in environment on the fatigue of molybdenum stressed in fully reversed axial tension compression. In order to provide a basis to which these data could be compared, a complementary series of fatigue tests were made in vacuum. All of the specimens used were made from one mill lot of unalloyed molybdenum which had been vacuum-arc melted, worked down to 1-in.-diam bar, re-crystallized, then warm-worked to 5/8 in. diam. The interstitial content by weight was as follows: C—0.022 pet, 02-0.0026 pet, Hz-0.0001 pet, and N20.0002 pct. The average grain diameter in the transverse direction was about 0.035 mm, and the average grain length was about 0.15 mm. Typical tensile-test data are shown in Table I. None of the specimens tested exhibited an upper yield point.

Jan 1, 1965