Search Documents

By J. Visman

FOR more than 25 years evaluations of coal cleaning units have appeared in many publications, and during this time considerable progress has been made in developing the theory and techniques of calculating washery results. A variety of characteristics have been defined over the years, many receiving general recognition during the first post-war Coal Preparation Conference in Paris in 1950. Coal preparation has become a science, and the approach to preparation problems is being revolutionized. Formerly, for example, if a coal operator wanted to know the performance of a given cleaning unit for a particular grade of his run-of-mine, he either shipped a carload to the manufacturer for a test run or relied on a report of a test carried out on a coal similar to the one he intended to clean. In modern practice the expensive, time-consuming test work generally can be avoided if the washability curves of the coal in question and the error curve of the cleaner are known. Normally a guarantee can be given on the strength of this information. General acceptance of modern standards has thus reduced the need for pilot-scale models of existing types of coal cleaners. Needless to say, the method requires exhaustive and accurate information on the cleaning unit and on all the additional circumstances affecting its results, in- formation that ultimately can be secured only from actual tests made in the laboratory or in the washery.

Jan 10, 1954

By Stanley M. Moos, Richard Addison

Introduction The Pueblo Viejo gold-silver mine, located in the Dominican Republic, started production in early 1974 processing ores averaging 4 g/t gold and 20 g/t silver at a rate of 7.25 kt/d. The ore milled is a silicified siltstone with average work index of about 8 that occurs as an extensive oxide capping of a primary sulfide ore body. The sulfide ores are refractory to conventional treatment process and extensive research work is now in progress to develop a treatment process for them. The ore deposit has a long history, having been mined by the indigenous Arawak Indians for some time in the early sixteenth century prior to the arrival of the Spanish, and then by the Spaniards. In the early 1950s, Italian engineers attempted to process the sulfide ores. Mining by the Indians and Spanish was abandoned because of low grade and little coarse gold in the oxide ores and by the Italians because of the refractory nature of the sulfide ore. In 1969, Rosario Resources geologists discovered that there existed sufficient reserves of oxide ore for a viable mining operation and the plant was designed, built, and brought into production.

Jan 1, 1981

By C. W. Spencer, F. N. Rhines, R. J. Knight

Ametallographic study has been made of the peritectoid transformation as it occurs in two Ag-A1 alloys, containing 6.0 and 6.9 wt pct Al, respectively. After equilibrating at 475°C, these alloys were transformed isothermally just below the peritectoid temperature which lies at about 450°C.1-3 Peritectoid transformation in this alloy system consists in the reaction of a and 5 to form µ. The crystal structures of the a, µ, and 5 phases have been determined as face-centered-cubic, 6 manganese, and hexagonal-close-packed, respectively. At the peritectoid temperature their equilibrium compositions are approximately 5.85, 7.02, and 7.24 wt pct (19.92, 23.2, and 23.8 atomic pct) aluminum."" The transformation might be expected to occur principally at the interface between the a and 5, but such is not the case. Instead, the major part of the transformation occurs by the direct (and perhaps initially diffusionless) conversion of 5 to µ. The composition range of the forming µ nearly overlaps that of the parent at the temperature of transformation" so that little, if any, composition change is required. Transformation proceeds by the nucleation of µ at points upon the external surface of the sample and sweeps through the 5 phase, leaving the a initially almost undisturbed. Subsequently, the a phase participates in the transformation by being partly or totally converted to µ. Specimens approximately 1/4 x 1/4 x 1/16 in. were cut from cast ingots, previously equilibrated 68 hr at 588°C. The specimens were held for 3 hr at

Jan 1, 1958

The presentation of the John Fritz Medal to Professor Henry M. Hone will take place in the auditorium of the Engineering Societies? Building, 29 West 39t,h Street, New York, at 8:30 o'clock on the evening, of May 10. It is hoped that many members of the Institute will be able to attend this ceremony, and the committee desires to make special mention of the fact that ladies are cordially invited to be present.

Jan 5, 1917

By Arthur F. Wendt

Within the last few years the production of iron, and of the metals generally, by a given furnace-plant, has been largely increased, in many instances trebled. Iron-furnaces exceeding one hundred tons' capacity per diem are now the rule in new constructions. Copper and lead-furnaces smelting from 60 to 100 tons of ore per day are common. With this greatly augmented product, the life of furnace-linings has been diminished, and recourse has been had to various cooling devices for prolonging the life of such liuings. The object of this paper is to call the attention of the profession to an arrangement recently patented by the writer. The common course of projecting water against the exterior of the brickwork of a furnace has been in a large measure abandoned by our most progressive managers. All have recognized the danger of this proceeding, especially when applied to the crucible of a furnace below the line of the tuyeres. Cast-iron water-jackets, with wroughtiron pipes for circulating the cooling-water, have replaced the cruder methods. In iron-smelting the use of such jackets has been confined to the crucible and the space around the tuyeres; and it has been the custom to support the jackets on the brickwork of the furnace. But the erosion of the brickwork below tuyere-jackets allows them to sag, and often displaces the alignment of the tuyeres and leads to other annoyances. The principle of construction adopted by the writer to remedy this and other evils, is to use a thin fire-brick lining (not over nine inches) from the tuyeres up to the bosh, to back this lining with wrought-iron or steel water-jackets, hung from the mantel-ring, and thus to carry the whole weight of the furnace and its filling upon the supporting pillars. The crucible proper is lined with three or four thicknesses of fire-brick on the sides, and not less than forty-eight inches in the bottom. It is supported on independent pillars, and is practically an independent structure. It could even be placed on wheels and made removable, were there any adequate advantage to be gained by such an arrangement.

Jan 1, 1885

Because common salt, sodium chloride, is necessary to all animal and much plant life, it is probably the most widely used of all mineral commodities, except for water. Nevertheless, of the total salt consumed, only 7% is used for food, including animal food. Two-thirds of the total is used as chemical raw material, principally for making such basic chemicals as chlorine, caustic soda, and soda ash. Other uses are for road thawing (16%) and water softening. Some 162.5 million tons of salt were used, worldwide, in 1972 (Table 15.4F.1). Production is from bedded salt deposits, salt domes, and evaporation of brines, including solar evaporation of seawater. Production is worldwide from at least 20 countries, of which the United States, China, USSR, the United Kingdom, and West Germany are the leaders. Consumption increases about 7 % annually. Reserves are plentiful: Other important sodium salts are soda ash (sodium carbonate) and salt cake (sodium sulfate). Soda ash comes mainly from the Solvay process (70% ) , which uses salt, limestone, and ammonia as raw materials. A large and growing portion of United States production is from mining large bedded deposits of trona, a natural hydrated sodium carbonate and bicarbonate found in Wyoming, and from brine evaporation in California. Soda ash is used for glassmaking, phenol, soap, detergents, and bleaches. Half of the United States salt cake used is a byproduct from rayon manufacturing. The other half comes from brines and playa lakes in California, Texas, and Wyoming. Salt cake is used mainly for papermaking. ACKNOWLEDGMENT Appreciation is expressed to William B. Dickson, president, Salt Institute. [ ]

Jan 1, 1976

Annual Meeting, Philadelphia May, 1873 THE Institute assembled in the room of the Board of Trade, Mercantile Library Building, on Tuesday evening, May 20th, at 8 o'clock P.M, Hon. W. D. Kelley made an address of welcome to the Institute, which was responded to by President Raymond. The Council reported, through the President, that the Institute had during the past year, held three meetings, in New York, Pittsburgh, and Boston. Thirty-nine papers of great professional value had been read, and sixty-nine members and twenty-four associates added to the Institute. The finances of the Institute were in good condition, the report of the Treasurer, Mr. T. D. Rand, showing a balance on hand of $1569.74. The report was accepted. Prof. L. Gruner, of Paris, France, and Prof. Peter von Tunner, of Leoben, Austria, having been proposed by ten members of the Institute, and approved by the Council, were unanimously elected honorary members. The Council reported the names of the following gentlemen, with recommendation for election as members or associates. They were unanimously elected. *Barker, Prof. G. F., - Philadelphia, Pa. †Chalfant, John W., - Pittsburgh, Pa. *Crawford, John J., - Philadelphia, Pa. *Crasius, O. H., - Columbus, Ohio. †Dibble, Theo. Hoyt, - Pottsville, Pa. †Everson, John, - Pittsburgh, Pa. †Field, Robt. P., - Philadelphia, Pa. *Fisher, F. A., - Bristol, Tenn. *Fleming, W. E., - Pioche, Nev. *Harden, E. B, - Philadelphia, Pa. *Harding, G. E., - New York. †Hartshorne, J., - Philadelphia, Pa. †Haupt, H., Jr., - Philadelphia, Pa. * Members. † Associates.

Jan 1, 1874

By M. E. Glicksman, G. S. Ansel

It has been shown by Walton and Chalmers,&apos; that the mechanism of the development of solidification textures in castings involves the preferential growth of dendrites along certain crystallographic directions as determined by the influence of prevailing heat-transfer conditions. Specifically, this growth is parallel to the direction of heat flow. The purpose of the present investigation was to determine the applicability of this mechanism to: 1) commercially pure aluminum (99.75 pct) solidified to coarse columnar crystals, 2) an aluminum-silicon casting alloy (5.25 Si, 0.38 Fe, 0.02 Cu, 0.10 Ti, 0.002 S) cast to a fine-grained structure under complex and reproducible heat transfer conditions. PROCEDURE AND RESULTS 1) Specimen Preparation—Using a technique similar to that employed by Northcott and Thomas,2 samples were melted in the directional solidification mold, Fig. 1, by heating the entire assembly to 670° C. The mold was then end cooled using a water jet. From considerations of harmonic analysis, the likely distribution of isotherm normals encountered by the growing crystals is shown in Fig. 1. 2) Orientation Analysis—The pure aluminum sample froze to large columnar crystals, nucleated close to the metal diaphragm, with the growth direction parallel to the mold axis. Using the back-reflection Laue technique, the growth direction of these crystals was determined to be a <100>, which coincided within 53 deg to the mold axis. Metallographic examination of the relatively fine-grained aluminum-silicon sample revealed a dendritic mode of growth having its primary dendrite arms along isotherm normals. Back-reflection Debye-Scherrer patterns, taken with the specimen rotating about its cylinder axis, yielded rings displaying symmetrical arcing, thus proving that the sample did, indeed, possess the solidification texture inferred from the preliminary metallographic examination. To determine the extent and orientation of the texture in the aluminum-silicon alloy, a density distribution of the (111) poles of the sample was plotted using the transmission Debge-Scherrer

Jan 1, 1960

By Edward Keller

In a paper, " A Study of the Elimination of Impurities from Copper-Mattes, etc.," presented to the Institute at the Atlantic City meeting, February, 1898, I gave certain figures which I called the relative slaggability in refining copper. In that paper* will be found the following pertaining to this subject: Relative Slaggability in Refining Converter-Copper. Cu. Pb. Bi. Sb. As. Se, Te. 1 129.5 1.13 7.30 5.22 0.81 and Relative Slaggability in Refining Electrolytic Copper. Cu. Pb. Sb. As. 1 41 9.97 7.13 Since there is a, possibility of misinterpretation of the above values, the following supplementary information may seem justified in explanation. As the contents of impurities in the unrefined or crude copper were unknown, the contents of the refined copper were substituted therefor, merely in order to obtain the two series of figures for comparison. These figures are higher than they would be had I been able to take the correct ones for the unrefined copper. The high figure, 129.5, for lead, in the case of converter-copper, means simply that more lead was slagged from the crude copper than remained in the refined copper; or, in definite values, that to 1 per cent. of copper slagged, the ratio of the lead gone into the slag and the lead remaining in the refined copper is 129.5 : 100. It is possible to approximate the true slaggability much more closely by adding the quantities of impurities in the refined copper to those in the slag, thus obtaining values for the crude copper in which the amounts volatilized are ignored (the latter

Jan 1, 1901

By C. Goldberg, R. H. Wynne

WHEN using an optical goniometer to determine crystal orientation&apos; it is advantageous to use a preferential etchant so that the etch pits have plane faces which are parallel to crystallographic planes, all of which are of the same "form." "Westinghouse Silver Etch" (WAg), a preferential etch for germanium, is made up as follows: 40 ml of 49.7 pct hydrofluoric acid, 20 ml of 70.7 pct nitric acid, and 40 ml of distilled water containing 2.0 g of silver nitrate. Examination of metallographs of WAg etched surfaces (Fig. 1, for example) indicates that, regardless of crystal orientation, the faces of the etch pits are (111) surfaces. Optical goniometer examination of these WAg etched surfaces also indicates that the faces of the etch pits are (111) surfaces, i.e., all bright reflections are from (111) planes. When using an optical goniometer of the type described by Barrett,&apos; not only (111) reflections from a WAg etched germanium surface but also other reflections of lower intensity will be observed. These latter reflections can cause confusion. We have used an optical goniometer made from a war surplus astrocompass and a galvanometer lamp. The reflections are observed by using the goniometer in a darkened room and letting the reflected light be in- cident upon a piece of white paper. The resulting decrease of goniometer sensitivity enables (111) reflections only to be observed. This in turn permits the crystal orientation to be determined in a matter of minutes, since only two measurements are necessary. The authors wish to acknowledge the help received from R. E. Davis who assisted in making the metallographs and aided the authors in the interpretation of the metallographs.

Jan 1, 1954

By E. W. Steele

IN THE copper-casting department of a modern electrolytic copper refinery there are two kinds of casting furnaces: the first, or anode furnace for casting crude copper into anodes for electrolysis; the second, or refined-copper furnace for casting the cathodes resulting from electrolysis into market shapes, such as ingots, wire bars, and cakes. Both furnaces are reverberatories of practically the same general design and are operated intermittently, putting through a charge normally in 24 hours. The treatment of the copper in both furnaces is similar, in so far that oxidation followed by skimming and reduction (poling) is carried on in both; but in the refined-copper furnace, the work must be done with greater care and it is of extreme importance that not the slightest trace of impurity be introduced into the copper. The furnaces usually hold from 150 to 300 tons of molten copper, which constitutes the daily charge. Except in the case of furnaces in the Lake district, where the concentrates from native-copper ores are charged through the roof, the furnaces are charged through the side doors by charging machines similar to those used in open-hearth steel practice. In 1916, at the Perth Amboy plant, of the American Smelting & Refining Co., located at Maurer, N. J., a study was made of the possibility of firing the copper refinery furnaces with pulverized coal instead of by hand. The proposed method possessed obvious advantages over hand firing and coal was a much cheaper fuel than oil at that time. It was realized, however, that there were several objections to its use, the principal ones being the liability of increasing the sulfur content of the refined copper, and the additional slag that might be produced from the ash. The increase of the sulfur content of the refined copper was the more serious, as more than 0.002 per cent. sulfur is objectionable. In the case of the slag, any increase would be expensive as the copper in this slag would have to pass again through the entire smelting and refining process.

Jan 3, 1925

By A. D. LeClaire

This paper claims to provide a description of diffusion processes in solids which is said to be a reformulation of Fick&apos;s Laws and therefore, presumably, is supposed to be as general as those laws. In fact, it appears to provide no more than an atomic model of a rather restricted type leading even to results in conflict with experiment. The restriction lies in the assumption, carried throughout the paper, that even in a chemical gradient the jump frequency i of an atom of species i is a function only of the composition on the plane from which it jumps, i.e., ?i = ?i(cl, c2 ...). This means that atom jumps in opposite directions from a site would occur with equal probability. There would then be no tendency for atoms to migrate preferentially in one direction along the gradient, so the model is incapable of accommodating the well established phenomenon of atom drift in a chemical gradient.10-" A more general model that does not suffer this difficulty was discussed in a paper13 I wrote in 1958, and the results therein already contain as a special case those given by Dr. DeHoff. The simplest sufficiently general assumption is to suppose that ?i is a function ?i(a1 a2,...; wl, w2, ..-) of the concentration aj and ? ?j at the site from which and to which, respectively, a jump is made. Any such function can always be expressed as a function of the sum and difference of its arguments. Thus d is the jump distance and g a geometrical constant. Obviously this is zero, i.e., no drift, if ??ri/??j = 0. X is written in this form, revealing two components of the total drift, because it can be shown that only the second component, depending on ??&apos;i/???(?j -aj), actually contributes to the net diffusion flux Ji. This component can be shown,13 by a straightforward ther-modynamic transcription, to be responsible for the so called "thermodynamic factor" in the Darken approximation for a chemical diffusion coefficient is the activity coefficient of i. Because the jump rate ?i in DeHoff&apos;s approximation has no dependence on the concentration gradient it does not seem possible to derive the Darken equation from his Eq. [6] without the further rather arbitrary assumption that ?i = const ri. It is to be noted too that the author&apos;s derivation of Eq. [12] is only valid when ?i is in fact a function only of the cj at the plane from which the atom jumps—for only then is ci?i a unique function of position and therefore of A. Author&apos;s Reply R. T. DeHoff I am indebted to Dr. LeClaire for his penetrating discussion of my paper, "A Reformulation of Fick&apos;s First Law". I concede that it does appear initially that the relationship presented in my paper could be derived from the detail atomic model of random walk and atom drift presented in Dr. LeClaire&apos;s approach. However, there are some important differences in concept and viewpoint which deserve further amplification. Dr. LeClaire&apos;s description is penetrating, detailed, and fundamental. His approach describes an extremely complex phenomenon, the displacement of atoms in a multicomponent gradient, at a sophisticated level. For precisely these reasons, his analysis has not proved to be useful for experimental studies that have practical objectives. For example, in order to obtain the information required to complete the analysis of the jump frequency distribution in a ternary system, the following series of experiments would, I believe, be required: 1) chemical (gradient) experiments, covering the composition range;

Jan 1, 1970

By AIME AIME

To accompanying photograph of the plant of the Beattie Gold Miner Limited, at Duparquet,. Quebec, is taken from the east and shows the open-pit from which the ore is taken during the summer. The buildings on the level ground above the open-pit are the change rooms, steel shop hoist building, compressor building, machine shop, warehouse, carpenter shop, and oil house. The main five-compartment shaft is shown west of the hoist building. The crusher plant adjoins the headframe and a long conveyor transports the fine ore

Jan 1, 1936

H. 0. HOFMAN, Boston, Mass (written discussion*).-The paper by Mr.. Pyne gives clear evidence of the difficulties the metallurgist is likely to encounter when he tries to recover in the blast furnace the metal from old chromite lining used as a refractory material in the copper reverberatory furnace. It appears that chromite cannot be fluxed at temperatures which usually prevail in copper blast furnaces. This calls to mind the freezing-point curve drawn by M. Simonis1 of mixtures of chromite and kaolinite. The chromite used in the experiments contained 52.9 per cent. Cr203, 22.6 FeO, 4.8 AI203, 9.6 Si02, .10.1-MgO; FIG. 1. the kaolinite was clay from Zettlitz with 98.5 per cent. clay-substance: The accompanying curve shows that the eutectic mixture with 35 per cent. kaolinite and 65 per cent. chromite freezes at Seger cone No. 15 (1435° C.), while kaolinite fuses at cone No. 35 (1770° C.) and chromite at cone No. 42 (2000° C.). The curve indicates that the difficulty in the blast furnace can be overcome by having at the smelting zone a temperature much higher than is usual in copper smelting; a charge composition similar to that prevailing at the Mansfeld copper smeltery -which gives with 23 per cent. coke a, slag of the composition Si02, .49.09; .(FeMg)0, 5.58; (CaMg)0, 16.02; A1203,-16.02-might flux and fuse chromite.

Jan 3, 1918

By L. W. WALLACE

IN an engineering fashion we have made an assay of the engineering profession, using as a. sample the engineers listed in "Who&apos;s Who in America" (1928-1929). We are aware that some will say it is an unfair sample; that it came from the best mine. This is readily admitted, with this qualification: that all engineers and architects by virtue of their training and experience have been freed of most of the dross to which mankind is heir. They are -a selected group to begin with, having all the potentialities those in the sample possess. We are also aware that some will say a part of those included in the sample are not engineers. Our answer to that criticism is this: An engineer is no less an engineer because for the time being he is president of a bank, a university, an opera company, or a hotel company. Moreover, he is no less an engineer because he is a governor of a commonwealth, a United States senator, a member of the Cabinet, or the President of the United States.

Jan 1, 1929

By S. S. Shen, M. J. Pool, P. J. Spencer, J. R. Guadagno

VERY few thermodynamic data are available for rare-earth alloys, partly because of the difficulties of obtaining the metals in sufficiently pure form and also because of their comparative scarcity up to the present time. The rare earths form a very interesting series in the periodic table in view of the progressive filling of their 4f subvalence electron shell and would be expected to provide useful information with regard to alloying characteristics of transition elements. It has been found in recent calorimetric investigations that the heats of solution of a number of the rare-earth metals in liquid tin are highly exothermic.1-4 Exceptionally strong bonding between rare-earth and tin atoms is clearly indicated in the liquid solutions. Continued thermodynamic studies of the behavior of rare earths in solution could thus contribute a great deal to present theoretical knowledge of alloying behavior and would yield an insight into bonding of a strength hitherto unencountered in liquid alloys. The determination of the heats of solution of the pure components in liquid tin is an essential preliminary to calorimetric work of this nature. Heats of solution of praseodymium, neodymium, and samarium in liquid tin at 750" &apos; and the heats of mixing of Pr-Nd solid solutions&apos; have already been determined in this laboratory. The present investigations with lanthanum continue the study of rare-earth elements. Details of the construction and operation of the liquid metal solution calorimeter used in this work have been published previously by Pool and Peluso and no further description will be given here. The lanthanum used in heat of solution determinations was supplied by Lunex who quoted the purity as 99.9 pct. Their detailed analysis of the material is given in Table I. Samples of 0.0003 to 0.0005 g-atom were used for each run and great care was taken to remove all surface oxide prior to weighing. The samples were stored at all other times in a beaker of oil to prevent their otherwise rapid oxidation. The compounds LaSn (Cudu, L1P type structure) and La&, (structure not classified) were prepared from the appropriate quantities of the two pure components by arc melting under a purified argon atmosphere and once again great precautions were taken to avoid any subsequent oxidation of the specimens. Although no structural examination of the compounds was made, the consistency of thermodynarnic measurements carried out on twenty or so individual samples of each indicates that the compounds were in fact homogeneous, single phase alloys. Samples of the compounds consisting of 0.0003 to 0.002 moles were used in the calorimetric measurements. A solvent bath consisting of approximately 80 g of 99.9 pct pure Sn was used for each series of runs and its heat capacity was determined at regular intervals throughout the experiments using pure tin or tungsten calibration samples. Measurements were made of the heat of solution of lanthanum in liquid tin at 725", 750C, and 775°K and at compositions up to 2.21, 4.76, and 5.25 at. pct La at the three temperatures respectively. In every case, the heat of solution of lanthanum remained constant at its limiting value, within experimental limits, up to the highest lanthanum concentration investigated. Since no change in was observed, it was concluded that the liquid/liquid + LaSn, phase boundary had not been

Jan 1, 1969

By T. H. Alden, H. W. Schadler

The strain rate dependence of the flow stress of the eutectoid Zn-Al alloy has been determined as a function of mechanical processing, microstructure, and temperature. The best superplastic properties result from the ultrafine, equiaxed structure produced by solution treatment and isothermal transformation at 0°C. Lamellar structures produced by isothermal transformation and coarse equiaxed structures produced by annealing also exhibit strain rate sensitivity in excess of 0.5, but at higher stresses and lower strain rates than the finest structure. Solution treatment and isothermal transformation eliminate the effect of prior processing history. Small composition variations in the binary alloy do not influence the mechanical properties. Below the eutectoid transformation temperature (.275C) increasing temperature lowers the flow stress at all strain rates. The data do not favor any of the present proposals for the mechanism of superplastic flow. ALLOYS of zinc and aluminum, near the eutectoid composition, have been investigated for: 1) the flow stress-strain rate and elongation behavior,1, 2) the transformation kinetics,3 and 3) structure,3"5 but the structure sensitivity of the mechanical properties is poorly understood. Using a near eutectoid alloy water-quenched from 380°C, Backofen et aL2 estab- high and increases with increasing strain rate. They found a correlation between strain rate sensitivity and tensile elongation as expected from the increased resistance to necking that a high strain rate sensitivity provides.296 The large elongation at high strain rates is attractive for metal forming. Since most other superplastic alloys7-l3 do not show high strain rate sensitivity at such a high strain rate (for the exception see Ref. 12) there is the possibility of a unique deformation mechanism for this alloy. The sensitivity of the mechanical properties of the eutectoid alloy to thermal history1 suggests a structure sensitivity that has not been demonstrated. Gar-wood and Hopkins3 identified a lamellar product for material transformed between 200" and 260°C. The size of the lamellae decreased with decreasing temperature. They also demonstrated that an unresolved transformation product formed below 200°C. A granular two-phase material was resolved for specimens quenched to below 150°C by Mitbauer and sauerwald4 who observed coarsening of the structure after annealing. The role of grain boundaries in superplastic deformation is suggested by the strong effect of grain refinement in encouraging this phenomenon at high strain rateS7-11, 13 and is emphasized in several proposals about rnechanism7, 8, 12 and in a theory14 of high-temperature deformation. Alden8 showed metallographic evidence that grain boundary sliding is occurring extensively at strain rates where m is large but less at high strain rates where normal plasticity is observed. Holt and Backofen10 have shown that sliding also oc-

Jan 1, 1969

By A. L. Holley

IN order to put sufficient work on steel ingots for rails, they must be reduced from about 12 inches square. As this cannot be done at one heat, they are first drawn down to about 7 inches square, and then reheated and rolled into rails. This first reduction or " blooming," is usually done in this country in a 30-inch 3-high rolling-mill, with movable rolls, so as to get several reductions in each set of grooves. The first of these mills has been running at the Troy Steel-works above a year, with great success. Another at the Cambria Iron-

Jan 1, 1873

By F. Clerf

BLAST-FURNACE practice in France is determined more or less by the character of the ores used. Some French ores are siliceous and others are calcareous, therefore by proper burdening a self-fluxing mix can be used. This is not always clone, as, for instance, at the Caen furnaces of the Société Métallurgique de Normandie, where the Soumont ore of Normandy is used, which is a carbonate. This ore is crushed and calcined at the mines, yielding a product that is porous and well sized for blast-furnace consumption. The lines of the Caen furnaces are given in Fig. 1. Originally these furnaces had 16 tuyeres; six are plucked and these tuyeres are set in the lower part of the bosh. Operating data on these furnaces are given in Table 1.

Jan 1, 1937

By Walter Crafts, C. M. Offenhauer

In a previous study of the carbide phase of chromium steels, it was shown that chromium carbide (Cr7C3) is 2 more stable carbide than cementite (Fe3C) at tempering temperatures above about 500°C. in quenched steels containing from about I to 7.5 per cent chromium. Below this temperature the carbide phase was found to consist of cementite in all of the steels examined. In the present investigation it was found that a similar change in the carbide phase takes place in molybdenum and in chromium-molybdenum steels at approximately the same tempering temperatures. The approximate ranges of occurrence of the alloy carbides Cr7C3, Cr4C, and Mo2C have been determined in steels containing up to 5 per cent chromium, I per cent molybdenum and 0.60 per cent carbon. The experimental steels were made in small high-frequency furnaces from Armco ingot iron, low-carbon ferrochromium and calcium molybdate and were poured into 2-in. ingots, which were forged to I-in. round bars. Sections of the bars were heated to the carbide-solution temperature and cooled rapidly to induce austenite transformation at relatively low temperatures. The steels were subject to some segregation, therefore comparatively high temperatures were necessary to dissolve all of the carbides. The microstructure of the quenched specimens was examined to verify the belief that the carbides had been dissolved, and also to determine the nature of the nonmartensitic structure of incompletely hardened steels. Ferrite and pseudo-martensite were present in some of the specimens, but all specimens were quenched at such a rate that pearlite was not formed, in order to ensure the formation of the carbides at temperatures lower than about 500°C. It had been found previously1 that in chromium steels the chromium carbide could be produced by transformation of austenite in the pearlite range above 500°C., and, in order to start the tempering treatment with the carbide present as cementite, the absence of pearlite was considered to be essential. The specimens were tempered for 64 hr. to permit the formation of the stable carbide. After tempering, the specimens were submitted to microscopic and X-ray examination. The carbides were separated either electrolytically in a 5 per cent HCl electrolyte or with an acidified copper-potassium chloride solution. The crystal structure of the carbide phases was determined by the Debye-Scherrer type of X-ray patterns. The X-ray patterns obtained from specimens near the boundaries between two types of carbides were generally weak and diffuse as compared with the other patterns. For this reason, and because the more soluble components may be masked, the boundaries between the phases could not be determined precisely. However, the X-ray analysis of electrolytically separated carbides has given consistently reproducible results

Jan 1, 1943