Search Documents

By R. Simon

The sources of energy dissipation for concentrated loadings on rock are considered in an attempt to account for the experimentally measured magnitude of the work required to break out a unit volume of rock from the free surface of an essentially semi-infinite medium. It is concluded that most of this work probably represents the elastic strain energy developed by the loading in a much larger volume of rock beneath the loaded region than the volume of the rock fragment broken out to the side of the loaded region. This strain energy is largely dissipated in the form of stress waves generated by the high rate of unloading produced by the propagating cracks. The energies associated with the formation of the new surfaces of the cracks and with the stress waves generated directly by the loading process are computed to be negligibly small. Possibilities for improving the utilization of energy to drill rod. subject to the geometrical limitations imposed by down-hole operation, are discussed. It is pointed out that any such possible improvements would probably have to be differential ones, since each rock configuration of more favorabIe loading geometry that can be created down the hole is accompanied by a complementary configuration of less favorable loading geometry. INTRODUCTION Dislodging each cubic inch of rock from the bottom of the hole by the action of a bit requires the expenditure of an amount of energy that varies from approximately 5,000 in.-lb to approximately 100,000 in.-lb, depending on the hardness of the rock, or, more technically, upon its fragmentation strength.1 In this paper we will discuss (I) why the energy expended in drilling is so large, (2) what happens to this energy upon completion of the drilling process, and (3) what are the possibilities for reducing the magnitude of the energy required to drill rock. DETERMINATION OF ROCK DRILLING ENERGY The volume of rock removed per unit time from the bottom of a hole of diameter D is evidently (7/4)D2R, where R is the rate of penetration of the bit. If P is the rate at which work is done by the bit on the rock at the bottom of the hole, the energy required to break out a unit volume of rock is given by: Ev =(4/p) P/D2R............(i) For rotary drilling, of either the rolling-cone or drag-bit varicty, P = 2pLN, where L is the torque resistance to rotation at the bottom of the hole and N is the rate of rotation of the bit. L is essentially the same as the torque measured at the rotary table only when drilling in shallow holes. The energies expended in rotating the drill string against the frictional resistance of the walls of the hole and and against the viscous drag of the drilling fluid are extraneous to the subject under consideration, although these may be much greater in magnitude than E, when drilling in a deep hole. For percussion drilling, P = fE where f is the percussion frequency and E is the work done on the rock per impact. The latter quantity can be both computed and measured for a percussion drilling machine. 2 (Under satisfactory drilling conditions, defined in terms of ranges of numerical values of certain dimensionless parameters, E is only 30 to 50 per cent less than the impact energy of the striker.2) Alternatively, E, may be measured directly by dropping chisels shaped like bit edges, backed by rigid weights, onto the surfaces of laboratory rock samples of effectively semi-infinite extent. Under these circumstances, essentially all of the impact energy is converted to work done on the rock, and the relationships among volume of rock broken out, chisel shape, impact energy and indexing distances can be obtained.3 The values of the energy required to break out a unit volume of rock under favorable circumstances are substantially in agreement for rotary drilling, percussion drilling and drop testing at atmospheric pressure. The energy per unit volume is a quantity of the order of magnitude of roughly twice the com-pressive strength of the rock as measured by a uniaxial loading test. The phrase "order of magnitude" in this paper means from about 1/3 as much to 3 times as much; i.e., the energy per unit volume may range from roughly the same up to several times

TO metallurgists generally, Arthur S. Dwight is no stranger even to those who do not know him personally. He is one of those contributors to technical progress whose names will go down to posterity because of their being attached to a successful machine or process, such as Dorr, Hardinge, or Marcy, or Wedge, MacDougall, or Herreshoff. The roasting and sintering method and equipment developed by Colonel Dwight and his associate, the late Richard L. Lloyd, may be found in lead smelters throughout the world, and also in many metallurgical works dealing with other ores, including those of iron. It is ordinarily used to desulphurize and agglomerate fine ores for subsequent smelting. Colonel Dwight's citation as James Douglas Medalist reads: "For his contributions to the art of smelting nonferrous ores; and particularly for his pioneer work in developing equipment and technique for sintering such ores and metallurgical products." The medal was awarded at the last Annual Meeting of the A.I.M.E. but unfortunately the medalist was unable to leave Florida at the time to receive it in person.

Jan 1, 1942

NEW MEMBERS The following list comprises the names of those persons who became members during the period July 10, 1919, to August 10, 1919. BALL, C. LEONARD.. Cons. Engr., Suffern Co., Inc., 135 Broadway, New York, N. Y. BARRY, CHARLES W Box 502, Idaho Springs, Colo. BATTLE, JOEL ALLAN, JR., Min. Engr., U.S. Bureau of Mines, Room 2114, Interior Bldg., Washington., D. C. BEER, GUIDO, Compagnia. Italian, Dir Bronzi Speciali, C. I., B. S. La Direzione, Italy. BITLER, WILLIAM F., Management of Coal Properties, The Provident Life & Trust Co. of Philadelphia, 409 Chestnut St., Philadelphia, Pa. BLOOM, SETH W., Chief Engr,, Northwestern Min. & Exchange Co., 130 E. Sribner Ave., Du Bois, Pa. BOYDELL, W. Guy B., Min. Engr., Tul Mi Chung Mine, Care Seoul Min. Co. Whang Hai Do, Chosen. Korea. BRYAN, RUSSELL R.., Met., Sunnyside Min. & Mill. Co., Eureka, San Juan Co., Colo. CHIAPELLA, STEPHEN EUGENE 323 W. 30th St., Los Angeles, Cal. CONWAY, EDMUND JOHN, Exploration Engr., Granhy Consolidated Min., Smelt & Power Co., Ltd., Anyox, B. C., Canada. DEMOREST, DANA J Prof. of Met., The Ohio State Univ., Columbus, Ohio. EIDEMILLER, H. N., Geol., Benjamin C. Neely, Min. Lands & Leases, Crystal Falls, Mich.

Jan 9, 1919

NEW MEMBERS The following list comprises the names of those persons who became members during the period June 10, 1919, to July 10, 1919. ANDERSON, JOHN EDWARD, Min. Engr., Lehigh Valley Coal Co., 121 N. Laurel St., Hazleton, Pa. BENBOW, B. L., Mgr., Cleveland Wire Division, National Lamp Works, General Electric Co., 1770 E. 45th St., Cleveland, Ohio. BLAIR, CHARLES S., Geol., Tennessee Coal, Iron & R. R. Co., Birmingham, Ala. BOLAND, FRED L., Chief Draftsman, Mine Dept., Chile Exploration Co., Chuquicamata, Chile, South America. COLLIER, OTTO L., Civil & Min. Engr., Secretary, Ernest M. Merrill Engrg. Co., Mullens, Wyoming Co., W. Va. DELAMATER, GEORGE RICHMOND, Asst. Supt:, By-product. Coke Oven Dept., Steelton Plant, Bethlehem Steel Co., Steelton, Pa. DOELL, WILLIAM R Chief Engr., Mahuomen Iron .Co., Crosby, Minn. ENDO, SHINZO 365 Komagome Shimmeicho, Hongo, Tokio, Japan. EVANS, CHARLES E., Chief Draftsman, American Smelt. & Refin. Co., Murray, Utah. FISCHER, OSCAR A 62S First National Bank Bldg., Denver, Colo. FISHER, GEORGE KINGSBURY, Met. Engr 47 Baker St., Saranac Lake, N. Y. FRAZEE, VERNE, Min. Engr Moweaqua, Ill. FURNICHI, ROKUZO, Supt. of Min. Dept., Besshi Copper Mine, Baron Sumitomo Co. Ehime Japan

Jan 8, 1919

By E. N. Doyle

Since the mid-1930's a number of plants, using the principles of heavy media separation, have been installed throughout the world. In cases involving lead, zinc or lead-zinc ores the reasons for the choice of this type of beneficiation process have fallen into four major categories: A) The economic recovery of additional distinctly separate products, such as dolomite limestone at the Mascot Plant (1) of the American Zinc Co., and the ferrosilicon produced by St. Joseph Lead Company. (2) B) The elimination of a large portion of run-of-the-mine ore prior to grinding and flotation, to allow increased throughput with low capital cost. Examples of this approach are the Levante and Ponente plants of the Montevecchio Company in Italy (3) and the frequent choice of the Sink-Float process by the Penarroya Company of Paris. C) The processing of a sedimentary deposit, in which the valuable mineral is contained in the matrix separating the boulders, as was the case at the St. Joseph Lead Company plant at Haydon Creek (4) and also at Bunker Hill Mining and Smelting, Kellogg, Idaho. D) The simplification of Around support programs in mines by allowing greater freedom of action in the extractive pattern. An example of this choice is Cominco’s Sullivan plant which came into being as part of an extensive proposal to update the mining, crushing, transportation, grinding and beneficiation processes. (5)

Jan 1, 1970

THE following employment items ore made available to AIME members on a nonprofit basis by the Engineering Societies Personnel Service, Inc., operating in cooperation with the Four Founder Societies. Local offices of the Personnel Service ore at 8 W. 40th St., New York 18; 100 Farnsworth Ave., Detroit; 57 Post St., Son Francisco; 84 E. Randolph St., Chicago 1. Applicants should address all mail to the proper key numbers in care of the New York office and include 6c in stamps for forwarding and returning application. The applicant agrees, if. placed in a position by means of the Service, to pay the placement fee listed by the Service. AIME members may secure a weekly bulletin of positions available for $3.50 a quarter, $12 a year. MEN AVAILABLE Graduate Mining Engineer, 31, married. Six years' engineering experience, mining and construction, U. S. A. and Alaska. Underground metal mining, production, development, geology, mine engineering. Engineering on airfield construction, earthwork, location work, mapping, topography, road location; office work. Commercial pilot license. Desires position mining or construction. Available 45 days. Prefer Latin America. M-676-477-E-8-San Francisco. Mining Engineer, 42, married, one child. Fourteen years' mining with much supervisory experience in developing and operating metal mines; also mine safety engineering. Familiar with many large and small mines in the western U. S. and Mexico. Excellent references. M-677.345-E-1¬San Francisco.

Jan 1, 1952

By Luther M. Krupp

A 3 ½ -mile asphalt mixed mat haulage road joins American Smelting & Refining Co.'s El Tiro copper pit northwest of Tucson and its Silver Bell mill. Two-axle trucks operate continuously over the road- way but the asphalt top shows none of the wash- board wear usually seen on dirt haulage roads during use by heavy vehicles. The following data cover construction of this road, and results of its use by Asarco and Isbell Construction Co., the road's builder.

Jan 11, 1958

By Franklin Allison

THE influence of cobalt and nickel on the properties of steel might be readily expected to be very similar. The two elements occupy close and somewhat unusual positions in the periodic table, their chemical behavior and compounds are so completely analogous and their various physical properties, including the ferro-magnetic characteristic, show such a remarkable correspondence, that there is no doubt of a strong resemblance existing between these two metals. However, the variety of, properties that are obtained from steel is due, largely to the fact that the element iron possesses allotropic forms. Alloying elements that affect these allotropic forms, or alter the nature of the allotropic changes, exert a profound influence on the resulting steel. In the case of nickel and cobalt, although these elements are very similar chemically and physically, it is found that they differ distinctly in their individual effects on the critical points of iron. Both nickel and cobalt form a series of homogeneous solid solutions with iron at temperatures above 1800° F. The difference in their behavior does not occur until changes begin to take place in the solid state below this temperature. An inspection of the respective thermal equilibrium diagrams at the lower temperatures makes the opposite effects of nickel and cobalt clearly evident.

Jan 3, 1927

By Leo Horvitz

PETROLEUM and natural gas are composed principally of the saturated hydrocarbons ranging from methane, the lightest, to nonvolatile liquids and solids containing approximately thirty-five carbon atoms. A technique for locating buried accumulations of these hydrocarbons before drilling obviously requires that some of the hydrocarbons leave the deposit and migrate toward the surface of the earth where they may be detected in their original form. Earliest attempts to link near surface hydrocarbons to petroleum at depth were apparently made by Laubmeyer1 in Germany and by Sokolov2 in Russia. These investigators collected samples of soil air from boreholes one to two meters deep and analyzed them for traces of hydrocarbons. They found that soil air over producing areas is richer in these constituents than is soil air over barren areas.

Jan 12, 1954

By L. F. Engle, M. A. Hewedi

SUMMARY Initial interest in using solutions of ammonium salts to leach native copper was documented in notes from an AIME meeting in 1871; By 1916-1917, application of the NH3-CO2-H2O system to recover nonferrous metals attained commercial significance, when it was used as a process for copper recovery by Kennecott Copper Corporation and Calumet & Hecla Mining Company. The Caron work in the early 1920s, Freeport Sulphur Company’s achievements leaching Cuban laterites during World War II, out- standing accomplishments in both eastern and western Canada, recovery of manganese related to the work of Dean -- all serve as landmarks as this One Century Review surveys a base for future technology. Current emphasis on compatibility of metals-producing systems with the need to meet environmental protection criteria provides special encouragement to researchers and engineers to find accept- able ways of recovering metals. The ever-present demand of management to design, build and operate facilities on a profitable basis provides additional impetus to apply information from the technical literature to that need. Examination of the general approach to this paper will reveal much that is firm and positive with respect to empirical results -- extractions, recoveries, amenability to familiar proven equipment and materials of construction common to the industry. Although there are many references, there are gaps in the basic scientific data that if filled could lead to even more usefulness; the paper attempts to indicate where further information is needed.

Jan 1, 1973

ALABAMA Anniston. Carrington, F. G. Ashland.-Herr, I. Auburn.-Brown, R. L. Bessemer.-Abbott, C. E. Dobbs, G. G. Ferguson, V. Salmon, H. S. Schaber, C. F. Birmingham.-Adams, J. H. Aldrich, T. H. Aldrich, T. H., Jr. Allen, A. W. Ball, E. M. Bonnyman, J. Bowron, J. Bush, M. W. Crawford, G. G. Crockard, F. H.

Jan 1, 1917

By David A. Summers, Clark R. Barker, Marian Mazurkiewicz

In May 1975 the U.S. Bureau of Mines contracted with the University of Missouri-Rolla, Rock Mechanics and Explosives Research Center to develop a Hydrominer modification to a longwall shearer unit, wherein the rotating pick-laced drums and connecting gear drives are replaced by a water jet cutting ahead. The concept of the water jet cutting head is based on using the high localized energy of the water jets to isolate a slice of coal by cutting a slot under, at the back of, and at the top of the web. The plow blade of the head then advances into the cut and wedges the coal cantilever over onto the conveyor [(Fig. 1)]. There were several potential advantages foreseen for the system; perhaps the most significant were the elimination of coal dust from the working area and the ability, with a variation in nozzle geometry, to cut webs of greater depth with a small increase in haulage horsepower. The University initially designed the head, based on experiments carried out in the laboratory, under an earlier Bureau of Mines contract. The experiments showed that it was more advantageous to work at a pressure of 68.9 mPa (10,000 psi) with an estimated flow rate of 3.15 X 10 - 8 m3/s (50 gpm) than go to the higher pressures and lower flow rates which have been advocated elsewhere.

Jan 1, 1979

By R. E. Ogilvie, J. I. Goldstein

The a and y solubility limits in the Fe-Ni phase diagram have been redetermined at temperatures above 500°C. Both a diffusion-couple and a quench and anneal technique were used. The solubility limits were measured with an electron-probe micro-analyzer. The nickel concentration at the phase boundary is increased below 700°C and the a solid-solubility range is much larger than had been previously measured. The solubility limits are also extrapolated to 300°C. It is suggested that the solubility of nickel in a FeNi reaches a maximum in the temperature interval 400o to 500°C. THE equilibrium diagram has been of great use in the field of meteoritics, where the phase relations between kamacite (a) and taenite (?) in metallic meteorites can be described by means of the Fe-Ni diagram. The study of metallic meteorites by electron-probe microanalysis has cast some doubt on the accuracy of the presently available Fe-Ni diagrams.1, 2 Recent thermodynamic studies of the Fe-Ni system also suggest that the diagram may be in error.3 For these reasons the high-temperature (800o to 500°C) part of the diagram was redetermined. INTRODUCTION The currently accepted Fe-Ni diagram is that of Owen and Liu.4 Above 910°C, there is a region of complete solid solubility, ? (fee). Below 910°C, the a (bee) phase is stable in pure iron. The effect of increasing amounts of nickel is to stabilize the y phase. The phases that form when Fe-Ni alloys are heated or cooled bear little relation to the equilibrium diagram. If an alloy is cooled from the y state and held at a temperature within the a + y field, no evidence has been found for the occurrence of the y - a transformation.5 If the alloy is cooled to low enough temperatures the y phase breaks down into a supersaturated bee phase called a2. In fact, in alloys over 27 pet Ni the y phase is retained at room temperature.6 The a, phase has the same composition as the original y. The temperature at which a2 forms, the M, temperature, has been determined experimentally.' A state of equilibrium can be approached by cooling below M, to form a2 and then reheating the alloy into the two-phase region of the diagram. The y phase will then begin to precipitate out of the a2 phase and grow. The growth of the phase, however, is quite slow. Using the interdiffusion coefficients -Da of Goldstein et al.,8 it is estimated that it takes about 1 year to grow a 10-µ-wide region of ? at 700°C in a 5 pet Ni alloy. Owen and Liu4 used the technique just described to form the equilibrium phases. The phases present were determined by means of X-ray analysis. The accuracy of their diagram depends on the number of alloys available near the phase boundary at a given temperature. In this study two different techniques were used to determine the a/a + ? and ?/a + ? solubility limits. The inherent accuracy of both techniques was greatly improved over that used by previous investigators because the phase-boundary compositions were measured with an electron-probe microanalyzer. PROCEDURE The two methods used to determine the Fe-Ni diagram are the diffusion couple (D.C.) and the quench-and-anneal (Q.+A.) techniques. In the first method, diffusion couples whose diffusion path goes through a two-phase region of the phase diagram were used. A description of the technique used for making the diffusion couples has been described in a previous paper.' After the diffusion treatment a discontinuity in the resultant concentration vs distance profile was measured. The nickel concentrations in the a and ? phases at the interface of the discontinuity are the solubility limits of the a and ? phases in the phase diagram at the diffusion temperature. If the interface com-

Jan 1, 1965

By Pei-Yung Huang, C. R. Hayward

In order to understand more fully the actual state of copper lost in copper reverberatory slags, a systematic study on the various reactions between certain metallurgically important copper compounds and synthetic copper reverberatory slags was undertaken by the authors in the Massachusetts Institute of Technology from 1942 to 1945.1 This paper, being only a part of the work completed, is published first because it furnishes the first experimental evidence of the formation of copper ferrite from reactions between cuprous oxide and copper reverberatory slags. Choice of Slag Composition The choice of the composition of the synthetic reverberatory slags to be used was much deliberated. Commercial copper reverberatory slags, neglecting minor constituents, avcrage :2,3 45 to 47 pct FeO; 38 to 42 pct SiO2; 5 to 6 pct CaO; 5 to 6 pct A12O3. Since the ternary system CaO-FeO-SiO2 has been much more thoroughly studied4 and is much simpler than the quaternary system CaO-FeO-SiO2-Al2O3, it was decided to use calcium oxide only instead of calcium oxide and alumina in the synthesis of the slags. Fortunately the composition of the average copper reverberatory slag with calcium oxide substituted for alumina lies in the region of the phase diagram clarified by the investigators. A survey of the phase diagram (Fig I) suggested two compositions: (I) the composition near the invariant point S, which is made up of 46 pct ferrous oxide, 37 pct silica and 17 pct calcium oxide; (2) the composition near the invariant point K with 45.5 pct ferrous oxide, 43 pct silica and 11.5 pct calcium oxide. Composition S has the advantage that the percentages of ferrous oxide and of silica almost exactly coincide with those of the average reverberatory slags, and that of the lowest melting point (1093º ± 3ºC) in the whole ternary system. The calcium oxide content, however, obviously is high. Since we have already substituted calcium oxide for alumina, and since calcium oxide is more basic than alumina, the fulfil- slag is decidedly too basic. Composition K has a slightly higher melting point (1150O + 3OC) and a higher silica content, but this is preferred because the slag is saturated with respect to tri-dymite and thus should not corrode siliceous refractories. Besides, it is less basic than composition S. The filial slag composition, therefore, was chosen to

Jan 1, 1949

Executive ROBERT E. TALLY, Chairman WILLIAM H. BASSETT JOHN A. MATHEWS LOUIS S. CATES EDGAR RICKARD Finance H. A. GUESS HENRY KRUMB, Chairman H. G. MOULTON Admissions ERLE V. DAVELER, Chairman GEORGE D. BARRON H. K. MASTERS JOHN M. LOVEJOY P. A. MOSMAN Alternates E. L. ESTABROOK C. E. MEISSNER J. A. SINGMASTER FRED H. KAY

Jan 1, 1929

Executive ROBERT E. TALLY, Chairman WILLIAM H BASSETT JOHN A. MATHEWS Louis S. CATER EDGAR RICHARD Finance HENRY KRUMB, Chairman H A GUESS H G. MOULTON Admissions ERLE V. DAVELER, Chairman GEORGE D BARRON H K MASTERS JOHN M. LOVEJOY P. A.-MOSMAN Alternates E. L. ESTABROOK C. E MEISSNER J. A. SINGMASTER FRED H. KAY

Jan 1, 1923

By J. F. Smith, J. R. Ogren, N. J. Magnani

The uapor pressrcres of magnesium over binary alloys of magnesium with twelve of the yare-earth eletnetzts have been measured by the Knudsen effuion method in the temperature range 675° to 910°K. These vapor-pressure measurments were combined with data concerning the tevtrlitzul magnesium solubility and the vapor pressure of pure magnesinm to evaluale the standuvd free energies of pluase jormation. These free-etzergy values indicate that the CsCl structures of the heacy rave earths tend to be somewhat less stable than those of the light rare earths. This dif-]eying- behaviov covrelates with differences which have been obsevz~ed in other alloy systetns wherein a phuse appeurs, disappeavs, or changes crystal stvucture as the atomic number of the rare-earth com-ponent is changed. This behauior also appears to correlate with the struclurul rariations within the rare-earth elements themselves, and it is speculated that cariations in the spatial extent of the 4f orbitals are responsihle. STUDIES of the phase relationships and crystal structures in the binary systems between rare-earth metals (lanthanons) and magnesium are extensive but far from complete. However, the currently available information1-10 does produce a rather interesting pattern. This is illustrated in Table I. If one excludes europium and ytterbium from consideration because of their generally atypical behavior, it can be seen from the table that the phase relationships in the magnesium-rich regions show a distinctly different pattern for the lighter lanthanons as compared to the heavier lanthanons. For the lighter lanthanons, LnMg2 phases occur from lanthanum to gadolinium with the cubic MgCu2 structure, LnMg3 phases occur from lanthanum to terbium with the BiLi3 structure, and magnesium-rich phases occur from lanthanum to gadolinium with stoi-chiometries between Ln5Mg42 and LnMg12. In contrast, for the heavier lanthanons, those LnMg2 structures which have been examined have the hexagonal MgZn2 structure, LnMg3 phases have not been observed beyond terbium, and the magnesium-rich phases occur with the a manganese structure near a stoichiometry of Ln5MgZ4. The heavy lanthanon-magnesium systems thus appear to be analogous to the Y-Mg system""2 wherein YMg has the CsCl structure, YMg2 has the MgZn2 structure, and the region Y4Mgz5-Y5Mg24 has the a manganese structure, and no other intermediate phases are observed. Similarity in alloying behavior between yttrium and the heavy lanthanons occurs commonly, and on this basis it seems likely that LnMg2 phases will be found with the MgZn2 structure in the binary systems of dysprosium, thulium, and lutetium with magnesium when the appropriate investigations are made. In the case of the magnesium-rich phases of the lighter lanthanons, only the Ce-Mg phase relationships have been investigated thoroughly and in detail, and until similar investigations are made for the other systems there will remain questions as to which magnesium-rich stoichiometries represent equilibrium phases and what systematic variations occur in the sequence from lanthanum to gadolinium. Thus the data in Table I show that only the LnMg phases occur with the same crystallographic structure throughout the sequence from lanthanum to lutetium. It was speculated that the relative stability of these LnMg phases might vary from one lanthanon to the next in such a way as to presage the differences which occur among the more magnesium-rich lanthanon-magnesium phases. On this basis the present investigation of the thermodynamics of phase formation was Gndertaken for the LnMg phases. PROCEDURE AND RESULTS A generalized phase diagram for the lanthanon-rich portion of a lanthanon-magnesium alloy system is shown in Fig. 1 where ß represents a high-temperature bcc

Jan 1, 1968

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 H. D. Merchant

NUMEROUS publications have examined hot hardness of metals and alloys. Some have studied creep in long-time hardness tests, few of which, however, were tested under a spherical indentor. 1-3 The results of Mulhearn and Tabor&apos; indicate a parabolic-type creep for indium and lead, whereas Moore and Tabor2 how a logarithmic-type creep for indium. Similar semilog relationships between hardness and time have been found by Goffard and wheeler3 for magnesium, aluminum, and their alloys. In this note, the elevated-temperature hardness of some complex alloys, shown in Table I, was examined to discover whether any basic information about the deformation behavior of the alloys could be obtained. One of the alloys, H-13 alloy steel, was tested for short-time creep tests to examine the hardness-time relationship at various temperatures. A standard Brinell Hardness Tester, mounted with an appropriate furnace and 99 pct A12O3 poly-crystalline indentor, was employed for the purpose. The alloys were tested at temperatures from room to 1400°F for 30 sec under 1500-kg load. The creep studies were conducted for about 8500 sec at 7l°, 500°, 1000°, and 1200°F. For constants A and B, a relationship of the type H = Aexp(-BT) [ll was obtained for all alloys between hardness, H, and temperature, T. In the semilogarithmic plot, the data points for each alloy were arranged into two groups, each group on a straight line with a specific set of A and B values. These results are in agreement with many such observations on hot hardness, notably those of Westbrook for pure metals,4 The thermal softening coefficient, B, and transition temperature, Tt, for various alloys are shown in Table I. The change in slope around the transition temperature suggests an apparent change in the mechanism of deformation, probably from the shear (below Tt) to the diffusion type of mechanism. At the temperatures above Tt, for constants A&apos; and B, a relationship of the type was obtained between H and T, Fig. 1. The nature of the equation, where R is gas constant, suggests the possibility of a thermally activated mechanism of deformation above Tt. The constant B&apos; may hence be defined as the apparent activation energy of indentation. The B&apos; values of various alloys are shown in Table I. A plot of B vs B&apos; gives a curvilinear relation shown in Fig. 2. The indentation-creep data for H-13 alloy steel is shown in Fig. 3. At 71" and 500°F, the creep initially follows the logarithmic time law. However, the indentation size stabilizes after 7 sec at 71°F, and after 10 sec at 500°F. Further increase in loading time has no effect on indentation size. The creep of 1000° and 1200°F follows the logarithmic time law for the first 1000 sec, after which the

Jan 1, 1964

By W. J. Keep

Cast-iron, or pig-iron, is iron which contains all the carbon that it could absorb during its reduction in the blast-furnace. As is well-known to chemists, carbon exists in cast-iron in two distinct forms. In chemical union, as "combined" carbon, it cannot be discerned, except as it may increase the whiteness of the fracture, in so-called white iron, or carburetted iron (sp. gr. about 7.72). Carbon mechanically mixed with the iron as graphite is visible, varying in color from gray to black, while the fracture of the iron, according to the color and amount of graphite it contains, ranges from a light to a very dark gray. The specific gravity of graphitic iron is about 7.40. Silicon in cast-iron is evidently to some extent combined with the iron and the carbon ; but whether it exists also in a form corresponding with graphitic carbon, mechanically mixed with the remaining mass, is a question still in dispute, which we have not in this paper endeavored to answer. It has been the opinion of many writers on metallurgy, and many foundry men, that silicon is in every way injurious to cast-iron. Yet

Jan 1, 1889