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By L. J. Erck, T. E. Ban

A discussion of laboratory procedures used to determine pellet quality and to simulate handling and firing conditions. Strength-temperature relationships in pelletizing; effect of chemical additives on agglomeration; and crushing, abrasion, and impact resistance of the pelletized products are discussed with respect to five different iron ore concentrates. IN most routine experimental work on products and processes, method:; of operation and product evaluation are established from accurately controlled laboratory tests. With particular emphasis on the pelletization of fine iron ore concentrates, standardized procedures of laboratory production and product testing have been established at Cleveland-Cliffs Iron Co. Research Laboratory at Ishpeming, Mich. A program of this nature was used for investigating the agglomeration characteristics of various iron ore concentrates. The factors which control the process were studied and subsequently controlled for these investigations. Pelletizing as applied to iron ore agglomeration involves the preparation of spheroidal masses from a fine moist concentrate, followed by high-tempera-ture firing to produce a final product. The preparation of moist spherorids is generally designated as balling. This produces the so-called green pellets or balls. After, these have been fired they are called pellets. Balling is accomplished by rolling moist concentrates in a revolving drum until small spheroids form by a snow-balling action. These balls are then heated in a shaft furnace, or a modification of this device, to a temperature high enough to cause agglomeration within the individual balls while they descend countercurrent to hot oxidizing gases. By this process the lour strength balls are converted through various chemical and physical-chemical processes into hard pellets. With correct balling and firing, the pellets are strong, resist abrasive action and handling treatments, and provide a suitable blast furnace and open hearth feed. In 1950 Tigerschiold and Ilmoni developed a working hypothesis to explain the formation and stability of green pellets.' Their work was presented on the basis of geologists' discoveries concerning the soil-water system and C. V. Firth's early postulates of green pellet formation.' Fundamental reactions oc-curing within fired pellets have been described by Cooke and Ban, who showed the microstructure changes caused by different firing temperatures." All these investigators have provided scientific clarifications of agglomeration by the pelletizing process and have opened avenues for greater development. Mineral grain growth and ceramic bond formation are the two basic phenomena imparting coherency to particles within a fired pellet of iron ore. Each of these is established by the transfer of thermal energy to the mineral particles. Grain growth mechanisms are chiefly physical reactions wherein smaller particles consolidate into larger ones, with resulting decrease in surface energy conforming with the second law of thermodynamics. Ceramic bond formation is a chemical reaction usually between basic and acid metallic oxides of the gangue and ore minerals. CaO, MgO, A1203, and FeO of Fe3O4, react in varying proportions with SiO, or Fe2O3, to form a great series of compounds or amorphous solid solutions. These product bond iron mineral particles together by a bridging action or by direct reaction with the surfaces of the particles. The result of the grain growth-ceramic bond formations is a consolidated, coherent compact of gangue and iron minerals formerly held together by much weaker bonds of interstitial water and forces common to dry, unconsolidated particles.4 With respect to iron ore agglomeration, these high temperature bonding reactions have been described by Schwartz, who referred to the bonds in sinters," and by Cooke and Ban, who referred to the bonds in fired pellets." The extent of the bonding phenomena and the consequent strength of fired pellets is governed by

Jan 1, 1954

By J. Mackintosh Bell

In the numerous districts subsidiary to Cobalt, and carrying mineral deposits similar in character to that world-famous mining camp, the most interesting recent developments have occurred in South Lorrain. The district, the center of which lies about 16 miles southeast of Cobalt, was the scene of a rush in 1907 but, in spite of the success of the Wett-lauffer mine, the locality soon lost its popularity, largely on account of the unsavory early history of the Keeley mine. In recent years, following the successful development of this property by the London operators, who acquired it from the liquidator of the original company, and the later conspicuous progress made on the properties of the Mining Corporation contiguous to the Keeley on the north, the district has again come into prominence and, at present, is doing much toward maintaining the gradually declining production of Cobalt itself. Apart from the Mining Corporation of Canada and the Keeley Silver Mines Limited, the principal concerns now operating in South Lorrain are the Lorrain Consolidated, the Trout Lake Mines (operated by English interests associated with the Mining Corporation) and the Canadian Lorrain Silver Mines (operated by the Huronian Belt Co., of London). A number of minor prospects are also active. The Wettlaufer and Currie, on both of which considerable work was done some years ago, are now closed. TOPOGRAPHY AND GENERAL GEOLOGY The topography of the South Lorrain area is rather more rugged than that of the vicinity of Cobalt, but the local relief, relatively speaking, is not great. Numerous lakes and streams lend a certain picturesqueness to a landscape, which is not entirely marred by the absence, from the valleys and hillsides, of the splendid bush that formerly clothed them but which has been swept away by forest fires. The geology of the locality is simple, in a lithological sense, but rather complicated structurally. The oldest rocks are Keewatin greenstones

Jan 1, 1924

By A. P. Woods, J. A. Elias, A. J. Heckler

A method is described by whichX-ray pole figures and axis density figures may be plotted automatically. The X-ray data are obtained using a Siemens texture gonionleter and the Schulz reflection method. Composite sampling methods are used to obtain a full quadrant of the pole figure. The contour lines of the pole figure and axis density figures are drawn using a computer-controlled x-y plotter. The computer program used to draw the contours was obtained from ZBM. POLE figures used to describe crystallographic orientations of poly crystalline sheet materials are usually plotted manually from X-ray diffraction output in the form of a strip chart recording of the intensity distribution of a given crystallographic pole in physical space. Today's computers and associated plotting equipment now make it possible to plot pole figures and axis density figures automatically. Inverse pole figures have been determined by mathematically "inverting" X-ray pole figure data.'-' In general, these methods require complicated, time-consuming numerical calculations. A more economical but less accurate method is to determine the axis densities of low-index crystallographic poles using an X-ray diffractometer. When these axis densities are plotted in a unit stereographic triangle contour lines can be drawn to represent the axis density distribution. This can now be done automatically. Computers were used to plot pole figures by a method developed by Holland, Engler, and powers.' In their method intensity ratios based on a random standard sample were obtained from a strip chart recording, and the stereographic (x, y) coordinates of these ratios were determined by a computer. Symbols characteristic of different intensity ratio levels were then plotted using an automatic x, y plotter and intensity contours were drawn manually. The present paper describes a method by which pole figures and axis density figures have been automatically plotted from digital data obtained from a Siemens X-ray unit. Plotting was accomplished using an IBM 1620 computer and a Calcomp 563 digital plotter. COMPUTER PROGRAM The computer program was obtained from IBM Systems Reference Library, No. 1620-CS-05X, and was designed to plot contour maps from randomly distributed data. It consists of a set of twelve separate subprograms, four of which were used in this work. The program takes a given distribution of data points and by a numerical method determines the values at mesh points of a square grid system superimposed over the input data. The output data from this program is in a form suitable for input to the contour plotting program. A smoothing program is also available which calculates new mesh point values from a continuous function fitted to neighboring mesh points. The degree of smoothing depends on the number of points around a given grid point which are used to adjust or smooth the grid value. The contour plotting program is designed to allow the user to specify the interval, scale, and annotation of the contours to be plotted. EXPERIMENTAL PROCEDURE Pole Figure Data Points. Diffracted X-ray intensities were determined using a Siemens texture goniometer and the schulzs reflection method. Due to geometric

Jan 1, 1968

By James W. Neill

Discussion of the paper of H. 0. Hofman, presented at the Canal Zone meeting, November, 1910, and printed in Bulletin No. 42, June, 1910, pp. 473 to 497. JAMES W. NEILL, Pasadena, Cal. (communication to the Secretary *) :-Professor Hofman's paper brings the art up to . date. As I was one of the pioneers in this business, I beg to give the following incomplete data regarding my efforts in this line. In the year 1883, while I was in charge of the smelting-operations at Mine La Motte, Mo., there was at the concentrator an unusually large production of a middle product, locally called "iron," which carried considerable values in nickel and cobalt, and which it was desirable, for this reason, to treat by itself. The works could not spare a furnace for the purpose; and to handle this product I improvised a "roast-hearth " from an old " lead-hearth." This was a small cast-iron furnace of the usual construction, about 2 by 4 ft. in dimensions, with a hollow cast-iron back, through which the wind circulated before entering the tuyeres. I had a cast-iron grate made to fit this hearth, and placed it flush with the lip, or apron, and above the tuyeres. On this grate, which had round holes about 0.25 in. in diameter, and a total surface of about 20 by 40 in., I roasted the nickeliferous pyrite product; starting the fire with kindling, then adding charcoal, and then gradually feeding the sulphides with a shovel, so as to cover the fire, choke down blow-holes, and get an even bed. Blast at a pressure of 3 or 4 oz. was supplied by a fail-blower. When a cake of roasted material had formed, it was removed with a steel bar, or fork, to the lip of the furnace, and thence into a wheel-barrow.. The fine material which had remained unmelted, but very hot, on top of the cake would promptly ignite when the cake was broken up and removed. The fire would then be covered with fresh material and * Received Aug. 29, 1910.

Apr 1, 1911

By M. B. Yung

The Fu Chuan district lies near the eastern boundary of Kwang Si province in Southern China and is connected with the coast by the West river and its branches.

Jan 1, 1915

By W. A. Clark, E. H. Dresser

ORE from the Minnesota iron ranges is transported from the mines to the loading docks on Lake Superior over four different railways: the Great Northern, Northern Pacific, Soo Line, and Duluth, Missabe and Iron Range, with hauls varying from 60 to 110 miles. For this service a large amount of specialized equipment is used. The steel ore cars are of the hopper type, 24 ft. long, to dump into alternate pockets of the docks, these pockets being 12 ft. long to correspond with the 12 or 24-ft. spacing of the boat hatches. The more recently con-

Jan 1, 1941

By R. R. Sayers

TWO serious hazards from coal dust confront the bituminous-coal miner- -a physical or safety hazard and a physiological or health hazard. The first threatens the miner with loss of life from coal-dint explosions, and the second with loss of health and earning capacity from inhaling large quantities of the dust. Studies by the Bureau of Mines have shown that coal dust, except some grades of anthracite dust, is capable of initiating an explosion when no explosive gas is present and that its property of extending or propagating an explosion has been responsible for nearly all the widespread explosions that have occurred in bituminous mines in the United States in the present century. For years many mining people believed that low-volatile coal dust was not explosive but not only is it explosive but if the source of ignition is intense, it is as explosive as the dust of many high-volatile coals because the war is creating increased pressure for greater coal production and because of the trend toward greater mechanization in mines, explosion and health hazards from coal dust are likely !n increase considerably.

Jan 1, 1943

By R. H. Tien

This paper presents an analytical solution of the problem of freezing of a semi-infinite slab with constant surface temperature; in this analysis accoz~nt is taken of the heat evolution during the solid-state transformations in the frozen skin. The regions where transformations occur are treated as plane isothermal heat sources; i.e., the rates of transformations are assumed to be infinite. In the model considered, three plane heat sources are assumed to be present in the frozen solid. The solution yields the temperature distribution in the solid, the rates of movement of the heat sources , and the rate of movement of the solidification front. It is shown that, although the sum of the heats of transformations in the solid is about 20 or 43 pct of the heat of fusion of iron or manganese, respectively, the effect of the heat evolution in solid-state transformations on the rate of solidification is insignzficant. IN several recent mathematical studies of solidification of liquid metals'-3 no account was taken of the heat evolution accompanying the solid-state transformations. In the case of, for example, steel, there are several phase transformations 6 -y, y -a, and the magnetic transformation. Whether or not a significant error is introduced into the mathematical simulation of solidification processes by the omission of the heat effects associated with these phase transformations is not known. The purpose of the present study is to investigate the effect of these phase transformations on the temperature distribution and the rate of solidification based solely on the heat transfer point of view. That is, for the sake of simplicity, freezing of a pure metal with solid-state transformations will be considered. The mathematical model which represents the present problem includes four moving heat sources representing freezing and phase transformations, 6— y — a — ferromagnetic. The thermal properties such as conductivity and specific heat, and so forth, are different from one phase to the other. But they are considered to be uniform over any particular phase. The usual Fourier heat flow law is employed. The concept of conservation of energy is applied at every heat source in order to estimate their rate of movement. The temperature distribution in the solid and the positions where transformations occur are expressed analytically in terms of error function solutions and four coefficients which are determined from four nonlinear algebraic equations. These coefficients can be calculated either by trial and error or by any numerical method. MATHEMATICAL ANALYSIS Fig. 1 is a schematic diagram showing the zones of different phases 1, 2, 3, and 4 in the solidified portion of a semi-infinite pure liquid metal. The heat is subtracted from the system at x = 0 which is maintained

Jan 1, 1968

By S. S. Solomons, V. H. Tillmann, L. Smaniotto

INTRODUCTION The Zinc Corporation, Limited and New Broken Hill Consolidated Limited (ZC/NBHC) mines are situated at Broken Hill, New South Wales, Australia (refer Fig. 1). Both companies are wholly owned subsidiaries of Australian Mining and Smelting Limited (AM&S). Annual production from both mines is 2.3 million tonnes of lead, silver and zinc ore mined by a variety of underground methods. From 1911 to 1968, conventional overhand cut and fill stoping (both open and square set timber) was used almost exclusively, though some trials with shrinkage and sublevel stoping were undertaken. The trial stopes used short holes in conparison with today's sublevel open stopes. Mechanised cut and fill methods with regular rockbolt support were introduced in the early 1960's and undercut and fill stoping replaced square set timber stoping for pillar extraction in the late 1960's. Since 1968, increasing emphasis has been placed on longhole open stoping (LHOS) although some areas of the orebodies are comrnrnitted to the abovemehtioned methods since existing stope development makes it impracticable to change. In 1979, approximately half the total production was mined by LHDS and it is expected that the LHOS proportion will increase in the future. A vertical crater retreat method of longhole mining has also been successfully introduced to replace the undercut and fill stoping of some pillars and it is expected that this stoping method will be used in some future primary ore extraction. This paper reviews the progress of LHOS technology at ZC/NBHC with emphasis on the stope planning and design process and the importance of rock mechanics applications. The objective has been to maximise the primary extraction of the orebody giving due consideration to stability and safety. This has led to the design of a novel sloped wall longhole stoping method which should eliminate the formation of pillars by mining the orebody in a "continuous" manner incorporating a sloped sand interface between the blocks of ore being mined and the previously mined sandfilled stope. The expected results include the complete extract of the orebody without the formation of pillars and with minimal dilution of ore with sandfill. The evolution of the method can be best illustrated by following the mining progress of the relatively new Southern 'B1 Lode orebody at the NBHC mine. GEOLOGY Southern '8' Lode is the southern extension of the 'Bt Lode orebody, which is currently being mined further to the north in ZC/NBHC (refer Fig. 2). The ore block being developed and stoped extends for a vertical height of 90 metres from No. 17 level down to approximately ten metres above No. 19 level. The ore minerals are sphalerite and galena with the zinc:lead ratio averaging approximately 3:l with a minor amount of silver associated with the galena. There is a sharp contact between the ore and the country rock on the footwall and keel, while the hanging wall gradates into medium and low grade material. The gangue is primarily quartz together with garnet, biotite, feldspar, gahnite, sericite and minor apatite. In various horizons within the orebody, grey feldspar, quartz and garnet pegmatites occur as stratiform layers. The ore and country rock are competent with some inconpetent boundaries.

Jan 1, 1981

By B. B. Kunkle

The history of this refinery has been one of expansion. It now has the capacity to produce 240,000 tons of cathodes annually. A general flowsheet and descriptions of the plant layout, operations involved, and equipment used at one of the world's largest and most modern electrolytic copper refineries are presented. THE El Paso copper refinery of Phelps Dodge Refining Corp. was originally constructed by the Nichols Copper Co., in association with Phelps Dodge Corp. and the Calumet & Arizona Mining Co., in order to refine anode copper produced at the smelters of the two latter companies. Initial production was obtained from the plant in January 1930 and its annual refining capacity was 100,000 tons of anodes. In order to keep pace with Phelps Dodge Corp.'s increasing copper production in the Southwest, it became necessary in 1937 to increase the El Paso plant's refining capacity to 160,000 tons of cathodes annually. This was accomplished by adding two sections to the electrolytic tank house, increasing the number of anodes placed in each commercial electrolytic tank from 33 to 37, and making changes in the dc circuits which made it possible to put three generators on each of the two circuits instead of two, thus increasing the amperage on each circuit from 10,000 to 14,800 amp. The capacity of the two furnaces from which refined shapes were cast was increased by raising the sidedoor bays on the furnaces 6 in. An increase of 70 pct in the productive capacity of Phelps Dodge Corp.s Morenci Branch in 1942 again made it necessary to expand refining capacity. In order to accomplish this, Defense Plant Corp. set up a project to increase the capacity of the El Paso plant to 240,000 tons of cathodes annually. This project consisted of enlarging the tank house approximately 50 pct, the construction of another wire- bar furnace, and corresponding increases in other departments where necessary. The engineering work on this expansion was begun in March 1942. Actual construction was under way by August 1942, and the work was completed by March 1944. These additional facilities were purchased from Defense Plant Corp. by Phelps Dodge Refining Corp. in August 1949. The plant is in El Paso about eight miies east of the center of the city and near Highway 80 and the main lines of the Southern Pacific and Texas & New Orleans railroads. The plant site covers approximately 494 acres of company-owned land that is ideally adapted for its use, being well-drained sandy soil and having enough slope so that a minimum amount of excavation was required when the plant was constructed. There is still ample room on the plant site for any future plant expansion. The plant is constructed on four different ground levels and so arranged that the unrefined copper is unloaded on the highest level at the north side of the plant and the refined copper is shipped out from the lowest level on the south side of the plant. The receiving or unloading platform, weighing and sampling rooms, main floor of the tank house, acid and condensate storage tanks, and the slimes and copper sulphate plants are on the first or highest level. The tank house basement, yard scales, charging and furnace bays, balloon flue and stack, brick-storage building, substation and power house, boiler feedwater treating plant and pump house, water storage tanks, and change houses are on the second level. This second level also contains ample yard area for setting-up furnace charges, and for storage of custom scrap, cathodes, scrap anodes, blister, coke, and poles. The casting wheels, inspection conveyors, cathode shears, wire-bar scalping machine, slag

Jan 1, 1952

By Emil Gathmann

Through wide experience at numerous mills in the United States I have found that there is a decided difference of opinion among the producers of steel as to what constitutes commercially sound steel. Some metallurgists insist upon having, for certain grades of steel, a so-called "open steel," i.e., one which contains numerous blowholes of varying sizes, and consequently but little volume of true pipe, although a central intermittent shrinkage cavity often extends well down into the ingot. Such blowholes and pipe are expected to weld up during rolling or forging, because their surfaces are not oxidized. Even if this be admitted, included slag particles and a high degree of segregation are bound to be present in the product of such ingots. Blowholes are the result of an oxidized heat, and all heats, unless made or finished in the electric furnace, are oxidized more or less. Subsequent deoxidation, or rather degasification, either in the ladle or in the mold, or in both, is necessary to reduce or prevent blowholes. As is well known, a greater yield of billets or sheets is secured from the ingot by allowing the formation of blowholes, but this is undoubtedly obtained at the expense of the quality of the product. Decided segregation of carbon, phosphorus, and sulphur, as well as small included slag particles, undoubtedly exists throughout the greater portion of all so-called open steel, and cannot be removed by cropping. The first requisite for sound, homogeneous steel ingots and blooms is therefore, in my opinion, so to treat the steel in the furnace, ladle, and mold that "piping" steel is produced. The line of demarcation between harmful and so-called "harmless" blowholes is practically impossible to define. Is it not, therefore, the better and safer practice to use means for the elimination of blowholes and correspondingly reduce the segregation and allow the formation of a well-defined shrinkage cavity or pipe at the upper end of the ingot? With the relatively cheap deoxidizers available at the present time, e.g., ferro-silicon, aluminum and titanium, there is no commercial reason why all steel should not be thoroughly degasified. A degasified steel being provided, the method of freezing or solidifying the liquid steel into an ingot, and the subsequent working into blooms and thence into various products, is of great importance in reducing the crop or scrap portion of the steel, due to segregation and pipe. How to ac-

Jan 1, 1916

By K. C. Sclater, B. R. Stephenson

Recent progress in oil-recovery methods has brought into prominence gas-energy relations in oil sands. The greater the effort made to utilize this gas-energy relationship to the best advantage in oil recovery, the greater becomes the need for more precise information concerning physical conditions as they actually exist in an oil well. The intelligent use of gas-oil ratios when considering production efficiency has been the subject of much recent discussion. It has been stressed that the pressure as well as the volume of gas must be known when considering the efficiency of a producing well on an energy basis. When methods of production are compared on an energy basis it implies a knowledge of pressure, temperature and physical properties of the fluids at the bottom of the well. In questions concerning gas-lift and the pressure control of wells usually there is a wide variance of opinion among engineers when energy relations come up for discussion. Perhaps this difference f opinion can be traced to erroneous assumptions made with regard to the physical conditions existing within the well. If erroneous assumptions are made it follows that computations based on these assumptions will give results which also will be in error. That erroneous assumptions are made is not to be wondered at because when handling a fluid composed of gas and oil, we are dealing with a complexity of hydrocarbon components each varying to some degree in physical and chemical properties. This means that the physical state of the gas and oil will depend not only on temperature and pressure but that it will be influenced also by the relative amounts of the various hydrocarbon components present. If water is present the problem becomes still more complicated. From these considerations alone it would appear that we can well afford to give some thought to devising more positive methods or means for obtaining data on physical conditions within the well rather than depend entirely on computations from casinghead data. If these data

Jan 1, 1929

By J. A. Danko, C. D. Pears, L. D. Schmidt, J. P. McGee

This paper describes a pilot plant built on the campus of West Virginia University by the Federal Bureau of Mines station at Morgantown, West Virginia, for gasifying pulverized coal in a mixture of oxygen and steam at pressures in the gasifier up to 450 psig. The work upon which this report is based was done under a cooperative agreement between the Bureau of Mines and the West Virginia University. The goal of Bureau of Mines work at Morgantown is development of a low-cost process for producing mixtures of carbon monoxide and hydrogen for the modified Fischer-Tropsch synthetic-fuel plants, which may be shifted to produce hydrogen for coal-hydrogenation plants. Gasification with oxygen offers the inducement that the gas may be generated at the pressure at which the gas will be utilized in a gas-synthesis plant. Since the optimum pressure for the synthesis appears to be about 400 psig, the gas should be produced at approximately 450 psig to take care of pressure drops in the purification train and control valves. If the gas is generated at the pressure of utilization, only the oxygen need be compressed, not the raw synthesis gas. This means a saving in power of 5 hp per hour per 1000 cu ft (CO + H2), which is approximately a saving of 4 cents per gallon of gasoline. For example, consider a commercial plant generating 18,000,000 standard cubic feet per hour of raw gas that would produce approximately 10,000bbl of liquid product per stream-day. Assume that this gas would be 85 pd CO + H2 and that the oxygen required would be 320 cu ft per 1000 cu ft of CO + H2. The following estimate is based on a commercial centrifugal compressor. If the 18,000,000 std cu ft per hour of synthesis gas is compressed to 450 psig with 74 pd efficiency, 107,000 hp is required for compression. If the synthesis gas is generated at 450 psig pressure, only

Jan 1, 1953

By Elmars Ence, Harold Margolin

A. J. Goldak and J. Gordon Parr (University of Alberta) —While we appreciate the difficulties involved in any investigation of this system, and we wish to congratulate the authors on their comprehensive efforts, there are several aspects of their paper that are not clear to us. 1) If the 6 phase is, in fact, isomorphous with Ti3Sn, it should not be designated Ti,Al. An 4B structure cannot be isomorphous with an ordered structure of the DO type. Anderko et al.' suggested that the structure be called Ti3A1, and we believe this to be a more reasonable designation. The confusion is compounded when the authors designate the phase Ti3Al—yet the composition limits of this phase (according to their diagram) are approximately Ti,A1 and Ti,Al. Further, while Pietro-kowsky is said to have pointed out that the structure of the 6 phase is isomorphous with Ti3Sn, we understand that this was only a suggestion that was not confirmed. Margolin and Ence do not appear to have presented any evidence to support the suggested isomorphism. 2) In referring to the precipitation observed microscopically during the initial breakdown of high A1 a during quenching, the authors state that "such precipitation is not likely to be detected by Debye-Scherrer techniques". We suspect that if the precipitate was visible by optical microscopy, it must have at least one dimension of the order of 1 or greater, and would therefore be readily detected by diffraction techniques. 3) The authors state: "The basis for this suggestion (that 6 forms peritectically P + L—6) is the observation that the ,'3 + 6 and 6 phase fields were

Jan 1, 1962

By W. A. Tiller

The unidirectional freezing of a semiinfinite liquid from one end has been treated by calculating the solute and temperature distributions in the liquid and solid phases with time, when the solid-liquid interface advances at a rate proportional to (time)lt2. The nucleation probability for new grain formation is calculated as a function of the constitutional and thermal properties of the alloy, the pouring conditions and the catalytic efficiency of the nucleating agents. The transition from columnar crystal formation to equiaxed crystal formation is assumed to occur at a critical nucleation frequency for a particular alloy and the quantitative dependence of the ratio (columnar zone length/equiaxed zone length) upon the freezing conditions has been predicted. The effects of (i) fluid flow in the liquid, (ii) heat transfer through a mold wall, and (iii) a finite ingot length, have been explicitly tveated as departures from ideality. These departures from ideality are found to have very important consequences on the ingot stmcture. In Part I&apos; of this series, a qualitative description of the general ingot structure was developed. The factors that determine i) the ratio of the equiaxed zone length to columnar zone length and ii) the grain sizes in these zones, were discussed. In the present paper, topic (i) will be treated quantitatively, and it is intended that topic (ii) will be treated quantitatively in Part 111. The complete treatment has been split in this manner for ease of development and coherency of presentation. The treatments are quite mathematical in nature and, although some of the conclusions to Part 11 depend upon the treatment presented in Part 111, it was felt that the intended audience would find the material more readable and more useful in its present form. To this same end, it seems worthwhile to reiterate some of the qualitative aspects of grain nucleation during ingot solidification before embarking on the mathematical description. QUALITATIVE ANALYSIS In the conventional method of casting, a liquid alloy with a certain degree of superheat is poured into a mold. The outer rim of liquid metal cools rapidly to the liquidus temperature of the alloy and begins to undercool. As the degree of undercooling increases, nuclei of solid begin to form in this chill layer, this nucleation being catalyzed by certain heterogeneous particles in the liquid. The grains in the chill layer which are generally of random orientation, begin to grow inwards because of heat conduction through the mold. The grains usually develop a columnar shape since the frequency of nucleation of new grains in the liquid ahead of the advancing interface is generally insufficient to seriously impede the growth of the original grains. Due to the slow diffusion rate of solute in the liquid, a solute distribution is formed in the liquid adjacent to the interface which is either an excess or a depletion if the partition coefficient, ko, of the solute is < 1 or > 1, respectively. Thus, the liquidus temperature of the liquid adjacent to the interface is a function of position. The actual temperature in the liquid is also a function of position and the temperature gradient at the interface decreases as the interface moves away from the mold wall. Since the rate of advance of the interface decreases with time, the equilibrium temperature distributions and the actual temperature distributions as a function of interface position, X, can be illustrated as in Fig. 1. Thus, a region of liquid may exist in which the actual temperature is below the liquidus temperature. This liquid is contitutionally supercooled and therefore unstable with respect to the nucleation of new grains. Now, since the supercooling in Fig. 1 increases as the interface moves further away from the mold wall, the nucleation rate of new grains will increase. When the nuclea-

Jan 1, 1962

By Paul J. Fopiano

SOME relationships between the flow characteristics of iron single crystals of 99.9 pct purity and the behavior of imperfections have been investigated. X-ray rocking-curve measurements and etch-pit counts were made as a function of plastic strain, and compared to the stress-strain curve obtained on a modified Polyani tensile machine. Crystals grown from rolled strips of vacuum-melted iron by the strain-anneal method1 had a high preference for a (110) longitudinal direction and a (211) face normal. The tensile specimens were prepared from 2 by i by 0.040 in. single crystals having a gage area of 3 by \ in. Rocking-curve measurements were carried out with a highly perfect germanium monochromating crystal in which the dazz spacing was matched to that of the dZl1 in the ir0n.l Well-collimated CuKal radiation was used throughout. These procedures practically eliminated errors due to geometrical and wavelength resolution. Inasmuch as the rocking-curve half breadth may vary markedly from point to point in the specimen being irradiated, the crystals were strained in place by mounting a hydraulic loading device on the double-crystal spectrometer. The rocking curves were taken after each increment of strain in the unloaded condition, since no observable difference was found in the rocking-curves between the loaded and unloaded states. The rocking-curve half breadths of the as-grown specimens were in the range 90 to 120 sec of arc when the beam irradiated an area of about -£ by -& in. on the specimen. DeMarco and weiss3 have shown that, for a well-colli- mated X-ray beam, irradiating about 10"! sq in. of the very same material, half breadths within 10 pct of the Darwin natural half breadth were observed. Since the rocking-curve specimens were stressed by the load-unload technique, the strain achieved at any given stress depended on the time of holding because of low-temperature creep. Fig. 1 shows the rocking-curve half breadth (also area/peak height) as a function of plastic strain for a relatively short holding time (2 to 5 min) at each stress level. For strains less than 0.1 pct the rocking-curve breadth is essentially constant; it is only for larger strains that there occurs a significant increase in this breadth. Where the holding times at each stress level were longer (by well over an order of magnitude) there occurs a significant increase in the rocking-curve breadth only after plastic strains of the order of 0.6 pct had been introduced into the specimen. This observation is related to the time dependence of creep phenomena and emphasizes the difficulty in comparing data obtained by two such different straining methods. Etch-pit results were obtained using a 2 pct nital etch on specimens strained in the range of 0 to 1 pct. Prior to etching, all specimens were annealed for 3 hr at 150°C, the carbon content being sufficient to decorate the dislocations for strains of at least 1 p~t.~ The data points were all taken from parts of the same single crystal which had been strained with short holding times at stress in increments of strain of the order of tenths of 1 pct. The (211) plane is particularly difficult to etch-pit in vacuum-melted iron and therefore it is felt that these values are as much as an order of magnitude low. Fig. 2 shows the etch-pit density as a function of plastic strain. The smooth curve passing through the data points is not meant to infer a quantitative correlation with the rocking-curve data. What is of interest, however, is the change in etch-pit density in the region of 0.2 pct plastic strain. The first three increments in strain (points 2,3, and 4) did not produce a measurable change in the etch-pit density while subsequent increments did produce a measurable change. While the absolute values of these results do not appear to be cor-

Jan 1, 1967

By E. J. Ripling

A NY mechanism proposed to explain hydrogen embrittlement in titanium and its alloys must, of course, be consistent with the experimental data that characterize this embrittlement. Unfortunately, however, the mechanical behavior of hydrogen-bearing titanium, at least a-ß titanium, has not been unequivocally defined. Lenning, Craighead, and Jaffee have clearly shown that hydrogen cmbrittles a-titanium by elevating its transition temperature, probably as the result of the formation of titanium hydrides. Therefore, in these alloys, hydrogen acts like at least one other interstitial contaminant, namely, nitrogen.&apos; On the other hand, ß-titanium has been shown by these same investigators to tolerate very large amounts of hydrogen without suffering severe mechanical damage.2 Mixing these two phases, however, to form the most important class of commercial alloys, the a-ß alloys, again results in severe hydrogen embrittlement, although the mechanism by which the embrittlement is produced is not of the same type as that which causes brittleness in a alloys. Ductility damage due to hydrogen increases as the strain rate is reduced in a-ß alloys, while embrittlement in a alloys increases as the strain rate is increased, since the latter is a transition temperature behavior. Steel, like the a-ß alloys, becomes more hydrogen sensitive at slow strain rates, suggesting that the mechanism producing the embrittlement in these two metals is similar. Brown and Baldwin&apos; described the hydrogen-produced ductility depression in steel as a function of testing temperature and strain rate by defining the slope of the two surfaces that produced the depression in a three dimensional chart, Fig. 1. One of these surfaces was given by the equations (de/de)4 > 0 (de/dT) < 0 [1] while the other was defined by the pair of equations Surfaces of the type given by Eq. 1 are suggested in two ways. One is an embrittlement mechanism wherein the diffusion rate of hydrogen is competitive with the rate at which the material is being deformed, as suggested by the planar pressure theory of Zapffe and his co-workers.&apos; The other is the diffusion controlled extension of Orowan&apos;s theory on delayed fracture in glass by Petch and Stables.&apos;&apos; Surfaces of the type given by Eq. 2 are also compatible with a mechanism of pressure build up in voids, according to de Kazinczy,&apos; since the solubility of hydrogen in the metal increases with testing temperature so that as the temperature is raised, the pressure in the voids is reduced. Kotfila and Erbin recently presented some data on the dependence of ductility on testing temperature and strain rate for the a-ß 3 pet Mn complex alloy at four different hydrogen levels.H Although data were presented for only three testing temperatures at three different strain rates, their results indicated that surfaces of the types defined in Eqs. 1 and 2 are produced in the alloy when the hydrogen level is sufficiently high—200 and 300 ppm—Fig. 2. Jaffee and his co-workers presented data on a number of different a-ß alloys which indicated the existence of surfaces of the type described by Eq. 2, but the ductility recovery at low temperatures as given by Eq. 1 was not found." In an attempt to aid in crystallizing this description of the ductility dependence of hydrogen-bearing a-ß alloys, tests were conducted by the author on a-ß titanium 140A with three different hydrogen contents. The tensile properties of two as-received rods and one vacuum annealed rod* were obtained over a range of testing temperatures and strain rates as shown in Figs. 3 and 4. Hydrogen analyses were made by the Battelle Memorial Institute on four pieces of the rod whose properties are shown as solid circles in Fig. 4. The hydrogen content of these pieces, taken at widely spaced intervals within the rod, were 280, 270, 289, and 270 ppm, indicating that the hydrogen content within a single as-received rod was quite uniform. One of the broken test pieces whose properties are shown in Fig. 3 as solid circles was also analyzed, and found to have a hydrogen content of 310 ppm. The analyses obtained on two of the vacuum annealed specimens were 92 and 170 ppm.

Jan 1, 1957

By K. G. Kreider, J. H. Brophy, J. Wulff

The technology of nickel-activated sintering of tungsten powder has been successfully applied to the densification of plasma-sprayed tungsten. Nickel was added by infiltration in a zinc solution followed by evaporation of the solvent. After sintering one hour at 1300°C density 95 pct of theoretical and transverse rupture strength of 74,000 psi were obtained. Shrinkage was found to be anisotropic and the mechanism of densification was comparable to that found in the nickel-activated sintering of tungsten powder. 1 HE use of a plasma spray gun for the fabrication of massive tungsten parts has become increasingly interesting. Applications now exist where a deposit in the as-sprayed condition is satisfactory. However, these deposits are generally characterized by a lamellar anisotropic microstructure containing 15 pct porosity of which, typically, two-thirds is open to the surface. Mechanically, the as-sprayed deposits fail at relatively low stress levels with a biscuit-like fracture. As a result of these problems the possibility of improving structure and strength by sintering treatments subsequent to spraying is particularly attractive. Preferably this sintering treatment should be adaptable to large bodies of sprayed metal. The similarity between the as-sprayed tungsten structure and that of a powder compact suggests that the relatively low-temperature activated sintering technique1 might be profitably employed in the densification of plasma-sprayed tungsten. It was the purpose of the present investigation to develop a technique for introducing the nickel-activating agent into the sprayed structure, to evaluate the amount and mechanism of densification obtained as a function of time and temperature, and to obtain an indication of the relative strength before and after sintering. EXPERIMENTAL PROCEDURE Powder used for spraying was purchased from the Wah Chang Corp. in several size fractions ranging from an average size of 4 to 150 . These powders were sized further for an explicit study of the influence of average feed size on densification. All powders were dried at 200°C before use. Spraying was accomplished with a Plasma Flame unit manufactured by Thermal Dynamics Corp. Several modifications of the unit were helpful in conducting the investigation. A variable speed auger feed mechanism coupled with the carrier gas mecha nism facilitated the use of fine particle sizes. A coil of ten turns of copper tubing in series with the arc power and concentrically would around the nozzle improved nozzle life and extended the range of operating currents available. The function of the auxiliary coil was to cause the arc to spin and to prevent impingement at only one point in the nozzle. Normally air sprayed deposits were made with an arc maintained at 400 amp at 50 to 70 v. The arc was blown by a gas mixture containing from 5 pct H, 95 pct N for the finest powder feed sizes ranging to 20 pct H, 80 pct N for the coarsest size. The flow rate was maintained at 100 cu ft per hr NTP through a nozzle of 0.25 in. ID. When apraying in air, the powder stream was directed toward an aluminum substrate for ease of mechanical removal of the deposit. The substrate was cooled by diverting the plasma flame with an air jet, and a second jet was directed on the deposit surface. In this configuration a gun-to-work distance of 2 to 3 in. was found to be satisfactory. Fig. 1 represents a typical as-sprayed deposit micro-structure. Laboratory studies of protective atmosphere spraying were carried out in cylindrical chamber 8 in. in diam by 18 in. in length. In operating the nozzle attached to such a chamber, particular care was required to avoid nozzle burn out due to reduced gas flow. The structure and density of the chamber sprayed deposits varied over wide ranges depending on substrate temperature. For the purposes of this investigation, flat deposits were made approximately 2 in. sq by 3/8 in. thick. From these deposits individual samples were cut an ground to a rectangular shape typically 1 1/2 in. by 1/8 in. sq such that the long dimension was perpendicular to the spraying direction. For the study of shrinkage anisotropy deposits up to one inch thick were produced. From these, rectangular samples were cut having a longer dimension parallel to the spraying axis. Prior to the addition of activating agent, the samples were deoxidized in hydrogen at 800°C for 20 min. No detectable dimensional or microstructural change was observed after this treatment. The addition of nickel was accomplished by infil-

Jan 1, 1963

By Ferdinand S. Ruttmann

The Tilly Foster iron-mine is situated in the southeastern part of Putnam County, New York, about fifty miles north of New York City, on the line of the New York City and Northern Railroad. There are a number of deposits of magnetite scattered throughout the county, the most important being those known as the Tilly Foster, the Mahopac, and the deposits of the Croton Magnetic Ore Company. (See the paper of Mr. Wendt, Transactions, xiii., 478.)

Jan 1, 1887

New York Meets first Wednesday after first Tuesday of each month. DAVID H. BROWNE, Chairman. JOHN H. JANEWAY, Vice-Chairman. F. E. PIERCE, Secretary, 35 Nassau St., New York, N. Y. P. A. MOSMAN, Treasurer. LEWIS W. FRANCIS. BENJAMIN B. LAWRENCE. Boston Meets first Monday of each winter month. HENRY L. SMYTH, Chairman. ALFRED C. LANE, Vice-Chairman. HENRY A. WENT WORTH,. Secretary-Treasurer, 60 India St., Boston, Mass. A. H. EUSTIS. F. G. STANTIAL. Columbia Holds four sessions during year. Annual meeting in September or October. FRANK A. ROSS, Chairman. RUSH J. WHITE, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. FREDERIC KEFFER. - FRANCIS A. THOMSON.

Jan 12, 1915