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By J. M. Dahl, L. H. Van Vlack

STAFF: Editor, Gerhard Derge Associate Editor, Paul G. Shewman Carnegie lnstitute of Technology Schenley Park Pittsburgh, Pa. 15213 Editorial Assistant, M. A. Redmerski Production Editor, Otto T. Johnson THE METALLURGICAL SOCIETY: Jack H. Scoff, President; Richard C. Cole, Post-President; Harold B. Emerick, President-Elect; Ralph L. Hennebach, Treasurer; Robert W. Shearman, Secretary; Donald A. Parks, Assistant Secretary; Leslie S. Wilcoxson, Assistant Secretary. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: R. E. Lund, Chairman; T. E. Dancy, H. B. Emerick, P. R. Gouwens, R. E. Grace, J. H. Jackson, H. H. Johnson, A. E. Lee, Jr., R. R. Nosh, R. D. Pehlke, and Paul Queneau. Review and selection of monuscripts is under the supervision of the following Publications Committees: Extractive Metollurgy Division: R. E. Grace, Chairman; G. M. Bell, D. W. Bridges, J. M. Cigon, G. W. Healy, T. A. Henrie, R. D. Holli-day, C. E. O'Neill, C. S. Sami s, A. W. Schlech-ten, and Charles Shull . Iron and Steel Division: R. D. Pehlke, Chairman; T. P. Floridis, Arnulf Muon, G. R. St. Pierre, E. T. Tuckdogon, L. H.Von Vlack, and J. M. Uys. Institute of Metals Division: H. H. Johnson, Jr., Chairman; J. B. Clark, Vice Chairman; M. R. Achter, G. F. Bolling, J. O. Brittain, G. P. Conard, II, L. A. Girifolco. G. T. Hahn, J.P. Hirth, L. Himmel, G. T. Horne, George Krauss, C. F. Leitton, Jr., J. D. Livingston, R. D. Monning, H. M. Otte, S. V. Radcliffe, R. E. Reed-Hill, H. C. Rogers, O. Sherby, M. T. Simnod, G. R. Speich, E. A. Steigerwold, R. A. Swolin, W. A. Tiller, W. R. Upthegrove, J. B. Wagner, Jr., Derek Walton, H. W. Weart, W. W. Webb, and D. WiIsdorf. Published monthly by the American lnstitute of Mining, Metollurgicol, and Petroleum Engineers, Inc., 345 East 47th Street, New York, N. Y. 10017. Telephone PLAZA 2-6800. Subscription $30 per year for non-AIME members in United States and North, South, and Central America; $32, foreign; $7.50 for AlME members. Single copies, $6.00, single copies foreign, $6.50. The AlME is not responsible for any statement mode or opinion expressed in its publications . . . Copyright 1965 by the American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. . . . Registered cable address, AlME New York . . . Indexed in Engineering Index, lndustrial Arts Index, and Chemical Abstracts . . Second class postage paid at New York, N. Y., and Ann Arbor, Mich. Volume 233, Number 1.

Jan 1, 1965

By G. B. Walker, S. J. Swainson, S. A. Falconer

DURING the past few years much interest and attention has been focused on a relatively new method of ore concentration, which utilizes the principles of sink and float and employs as the heavy medium a suspension in water of a finely ground solid, such as galena or ferrosilicon. Although a relatively recent development, much progress has already been made in applying heavy-media separation processes to a considerable number of ores. Eight plants in this country and abroad -are now treating approximately 10 million tons of ore annually by heavy-media separation (sink-float) processes, including lead-zinc, lead, iron, garnet, tin and tungsten. At the annual meeting of the A.I.M.E. in 1941, three interesting papers (unpublished) dealing with heavy-media separation (sink-float) processes of ore concentration as practiced in four commercial units in the United States were presented by Victor Rakowsky, Grover Holt, Elmer Isern and Robert Ammon. These papers gave an excellent exposition of the principles of sink and float, as well as the operating practice in two iron-ore-beneficiation plants, the Harrison and the Merritt, of Butler Brothers, in Minnesota; the Central mill of the Eagle Picher Mining and Smelting Co.; and the Mascot mill, of the American Zinc, Lead and Smelting Co. Augmented by pictorial descriptions and a working model demonstrating the processes, these papers evoked a great deal of interest and discussion. In fact, in reporting the high lights of the meeting in the April 1941 issue Of MINING AND METALLURGY, Professor Taggart made the statement that "preconcentration by heavy suspension was Miss A.I.M.E. 1941 so far as milling is concerned." Although to date the greatest application of heavy-media separation from the tonnage point of view has been for the treatment of lead, zinc and iron ores, these processes have a much wider field of usefulness. In this regard, it is to be noted that recently new heavy-media separation plants for treating cassiterite ore and garnet ore have been placed in successful operation. Moreover, numerous other types of ores have been found to respond well to these processes when tested on a semi-commercial scale, and it is expected that in the near future a considerable number of new plants will be erected. In view of the fact that heavy-media separation processes offer such attractive possibilities, particularly now, when the mining industry is being called on for an even larger production than ever before has been attempted, despite shortages of labor and supplies, it was felt that a description of some of the successful separations that have been worked out during the past year in the Ore Dressing Laboratory of the American Cyanamid Co. on a variety of ores of strategic importance would be of interest. The purpose of this paper, therefore, is to present the essential data relating to investigations of heavy-

Jan 1, 1943

By R. H. Wightman

The following paper describes current mining practices of the Riverside Cement Co. at its Crestmore plant, Riverside, California. For a number of years the Riverside Cement Co. obtained its raw materials by surface quarry operations but after these deposits were exhausted for equipment available at that time, the company started underground mining. Mine workings were begun in 1927 to 1930 for the recovery of limestone by block-caving methods. Geology The bed of limestone that is being worked is a metamorphosed and recrystallized limestone, which is generally white in color and from medium to coarsely crystalline. This bed is fissured by water courses that vary from minute cracks to large areas. The bed has also been cracked by intrusions along the footwall and hanging wall. These walls are coarse-grained, gray, quartz granodiorite. The strike of the deposit is north and south and it dips to the east at an angle of approximately 50°. The bed is approximately 1700 ft. long, 270 ft, thick at right angles to the dip at the middle of the deposit and tapers to a thickness of approximately 100 ft. at each end. Mining Methods The mine layout consists of four main levels with elevations as follows: 892 Collar of shaft. 800 Manway level used for ventilation, prospect purposes and as an entrance into the stopes. 700 Mining level where all material is extracted and on which are located the tapping grizzlies. This is the elevation from which all main cutoff stopes and undercutting work is started. 660 Haulage level where the limestone is drawn from transfer raises into the cars and is transported to the tipple by electric locomotives. 633 Level where all water is collected and which keeps the general water table below the working levels. A detailed description of the mine was given in U. S. Bureau of Mines Information Circular No. 6795, in June 1934. Current Block Development The first blocks to be caved were developed very much after the procedure followed in the copper mines of Arizona. This paper covers the ninth block to be caved. with a hard, tough rock like our limestone, it was found that some alterations in the development and control of dm, i, caving were. necessary to secure better crushing effect and provide more safety for such secondary blasting as is required. Sequence of Block Development 1. The fringes of the 800-ft. manway level are driven to confirm the diamond-drill information and serve to determine the final location and development required for the block (Fig. I).

Jan 1, 1946

By B. Chalmers, Stefan Wojciechowski

Rotary oscillation of the mold has been used to produce mechanical stirring of the melt during unidirectional solidification. Al-Cu alloys (1 to 4 wt pct Cu) were solidified to study the influence of alloy composition, temperature at which intensive cooling was initiated, and intensity of stirring on the temperature distribution in the sample, the resulting structure, and the copper microsegregation at the columnar to equiaxed transition. The Proposed explanation for the equiaxed solidification in stirred castings consists of the melting off of dendrite fragments, their partial remelting in hotter liquid, and the subsequent growth of the surviving part when the temperature of the melt is lowered. This may result in the formation of a crystal network, which can stop the growth of the columnar crystals and produce the equiaxed zone. It has long been known and many times affirmed that ultrasonic vibrations or relative motion of liquid and solid can significantly reduce the length of the columnar zone and refine the grains in the equiaxed zone in ingots and castings. Because of the technological importance of these phenomena many investigations have been conducted in which ultrasonic energy or mechanical vibration,1-6 electromagnetic stirring,7"10'17 magnetic stirring,"'12 or mechanical stirring13'14 were used to produce the relative liquid-solid motion. More recently, the question of the importance of natural (or thermal) convection has been raised.15-l7 Several possible mechanisms have been suggested.l,8,18-20 They can be divided into two main groups. The first group includes such nucleation hypotheses as nucleation frequency enhancement due to cavitation at the mold wall or other surfaces; cavita-tion in the body of the liquid resulting from the pressure wave, or an agglomeration mechanism, which involves the formation of nuclei by the accretion of subcritical nuclei. The second group considers the grain-refining action to be due to crystal multiplication phenomena such as the removal of the dendrite fragments by viscous forces or by a high-pressure cycle following cavitation or by a melting-off process. Sbme recent investigations give good experimental support to the melting-off proposa1.21-23 The purpose of the present study was to examine the effect of mechanical stirring during the unidirectional solidification on the structure of alloy samples and on the solidification variables. The motion of the liquid was produced by rotary oscillation of the mold around its vertical axis.

Jan 1, 1969

The German Kaiser is employing the keenest engineering talent of his own and allied empires in his attempt to defeat the world. American employers are paying engineers such attractive salaries that voluntary enlistments of high class technical men in the United-States Army, are below requirements. This deficiency is also probably due in part to the lack of proper information concerning the engineering branch of the service. Few civilians know that it is possible for them to perform in the Engineering Corps almost exactly the same kind of work as that in which they are now engaged. The best results in any organization are obtained only when the energy of every man in it is concentrated along the line for which he is best suited by natural ability, education, and training. It. is more important to have the right man in the right place in our Army, where lives of men are at stake, than it is in any business enterprise. The First Replace meat Regiment of Engineers was organized at Washington Barracks, D. C., on Dec. 14, 1917, with the express idea of accomplishing this. end. Its specific, purpose is to keep all engineering units of the Army at full enlistment strength during the period of this war. This regiment has not only the responsibility of finding men to fill depleted ranks, but it must also fit them to step into the work of trained, efficient and disciplined soldiers. The preliminary work of the recruit is first a thorough training in military drill, for the engineer soldier must be prepared to lay down his shovel and take up his rifle at any time. Infantry drills gradually give way to engineer work and more specific technical training. The. engineer soldiers must know how to tie knots and lashings, to build spar and truss bridges, to construct revetments, dig trenches, place wire entanglements, construct machine-gun emplacements, build pontoon bridges, and to construct roads: They must, also know the methods of demolition, sapping, and mining. Specialized training in lithography, zincography, surveying, mapping, photography, carpentry, blacksmithing, electricity, and machinery, are also given to those qualified for further training in any of these branches. Engineers are called upon to perform such a wide range of work that practically every man with any technical training or mechanical ability can find a place in this organization. Every male citizen in the United States who is physically fit, and between the ages of 18 and 21, and 31 and 40, is eligible to join the regiment by voluntary enlistment.

Jan 5, 1918

By F. W. Aul, R. C. Glenn

EXTRACTION techniques are of particular importance in determining size, shape an: crystal structure of particles smaller than l000Å in steels and other alloys. However, artifacts that can arise during the preparation of extraction replicas may lead to erroneous conclusions. The purpose of this note is to illustrate some of these artifacts and the misinformation that can result from their presence. An alloy of iron with 0.8 pct Cu was investigated in the following conditions: 1) Solution treated 3 days at 925°C in dry hydrogen and quenched in water. Aged in steps to precipitate copper, as follows: heated to 700°C, held 1 day; then furnace cooled to 50O°C, held 3 days; then furnace cooled to room temperature. 2) Solution treated 3 days at 925OC in dry hydrogen and furnace cooled to room temperature. 3) Solution treated 3 days at 925OC or 17 hr at 1100°C in dry hydrogen to dissolve all copper, then quenched in water. A normal parlodion dry-extraction technique was employed after etching the specimens with super picralP or with 2 pct nital. A wet-extraction method

Jan 1, 1962

By Faustino Roel

AMONG the problems confronting the mining engineer in Mexico in recent years, labor conflicts have come to occupy s prominent place. Each day they have become more serious and frequently have caused- the ruin of companies. It is therefore necessary for the engineer to understand the Federal Labor Law, the rights and obligations of companies and of their workmen, and the reasons for conflicts; to keep in mind the expense which may be caused companies; and to endeavor to avoid difficulties as far as possible. Our labor legislation is primarily to protect the workman and the constant tendency of the tribunals, including the Supreme Court of Justice, is to support the work- man in his demands against employer$, even at times granting him more than he asks, with no limit other than the economic capacity of the company to com-

Jan 1, 1937

While the production of this state has not realized the early hopes that this coal would replace eastern coal on the Pacific Coast, it has been steady though small. Nearly all of the tonnages given are from Goodyear's, The Coal Mines of the Western Coast of the U. s., a carefully com- piled and accurate account of the development of the industry along the Pacific. [ ]

Jan 1, 1942

By Joseph P. Hodgson

Since about 70 per cent. of the total cost of mining is due to underground work which is out of sight, it is essential that expenditures should be made here to the best advantage. A great many mistakes have been made which were expensive, but perhaps these have not even been detected by mine owners. In the future these may be minimized to some extent, especially if there is cooperative effort on the part of each employee. I have been interested in this subject for some years and have tried to deduce principles and methods. These have proved highly advantageous and may also be of help to others. Some corporations, like the United States Steel, and the Cleveland-Cliffs Iron Co., have done a great deal in this field by having stated meetings of their organizations, with the view to interchanging ideas among their men and educating them along the lines of concerted effort. Since no man knows all about the various branches of mining, it is advisable that frequent meetings of the operating department be held for the interchange of ideas and that all members of the organization have an opportunity to express themselves on the various subjects. It has often been found that in discussions between heads of departments, foremen and bosses, many valuable suggestions may be obtained which promote the best interests of the company. The method regarded as the most conducive to cooperative effort, and pursued by the organization, is to analyze and develop the different phases of various mining subjects at regular meetings. Nine Foremen's Dinners In the latter half of 1912, the Copper Queen Consolidated Mining Go. gave monthly dinners to the men in the operating departments. Those who attended were superintendents, foremen, shift bosses, engineers, geologists, and heads of all departments, making a total of about 75 men. After the dinner, lectures were given on subjects which pre-

Jan 1, 1917

By J. W. Cunningham, W. A. Tiller, D. H. Lane

The effect of ultrasonic vibrations on ingot solidification has been considered both theoretically and experimentally. The theoretical section elucidates the mechanisms by which the ultrasonic vibrations might refine the ingot structure. The experimental section describes a very efficient means of introducing the ultrasonic vibrations to the freezing interface. The application of this technique to the consumable-electrode arc melting process shows that the columnar mode of freezing may be effectively suppressed yielding an ingot structure consisting predominantly of equiaxed grains. The results support the contention that the ultrasonic vibrations increase the nucleation frequency in the layer of liquid adjacent to the freezing interface. CERTAIN structural characteristics of as-cast ingots are undesirable since they create considerable difficulty for subsequent processing and often produce defects in the finished product. These structural defects are illustrated in Fig. 1(a), and are: 1) planes of weakness where columnar grains growing from the different mold faces meet, 2) strength anisotropy due to the preferred orientation of the columnar grains and 3) inhomogeneity due to segregation at dendrite boundaries within the columnar grains and at the columnar grain boundaries. The type of ingot structure that eliminates 1) and 2) and diminishes 3) is the fine-grained equiaxed structure illustrated in Fig. 1(c). Many attempts have been made to produce the desirable ingot structure illustrated in Fig. 1(c) by inoculating, casting with varying superheats, vibrating or stirring, or by irradiation with ultrasonic vibrations. These attempts have met with various degrees of success, the ingots generally having the structure illustrated in Fig. 1(b). All four methods have been the subject of numerous investigations,1"4 the latter producing the most erratic behavior and inconsistent success. The method of ultrasonic irradiation during ingot solidification has shown considerable promise on small-scale ingots (diam 2 in.) but has not yet been successfully adapted to large-scale operation. The present paper considers the application of ultrasonic radiation to ingot solidification both theoretically and experimentally. The purpose of the paper is to elucidate the mechanism by which ultrasonic energy refines the ingot structure and to describe a method for producing the desirable ingot structure in both laboratory scale experiments and in ingots of commercial size. THEORY Conventional Casting—Before discussing the possible effects of ultrasonic radiation upon ingot structure let us first briefly review the reasons for the breakdown of columnar crystallization to equiaxed crystallization during ingot solidification. The following is a slightly oversimplified description. In the conventional method of casting, the alloy having a certain degree of superheat, T, is poured to fill a cold mold which is at room temperature, Tc,. Due to conduction of heat through the mold wall the outer rim of liquid metal cools rapidly to the liquidus temperature and begins to supercool. At some degree of supercooling, nuclei of solid form at random in this supercooled layer at the mold surface. The grains in this chill layer begin to grow inwards producing a solute build-up, thus lowering the freezing temperature at the interface as illustrated in Fig. 2. As growth proceeds, the temperature gradient in the solid conducts away not only the latent heat of fusion evolved during growth but it also conducts away some of the superheat of the melt so that the temperature

Jan 1, 1961

"The pumping of the underground water of the Butte mines is largely done from two central plants of the Anaconda Copper Mining Co. The mines of one part of the mining district are served by a modern and mechanically efficient underground plant at the High Ore mine, and the remaining part by a similar one at the Leonard mine. Properties not affiliated with the A. C. M. Co. have separate pumping plants, although in several instances that company handles the water of outside companies, under which arrangement costly single plants are dispensed with. An extensive system of underground crosscuts and drifts connects these mines to both the main pumping plants, so that either may receive the water from all the mines in case there should be a failure in the other to perform its designed service.Quintuple) vertical electric pumps, 7 inches by 12 inches each, of a capacity of 600 gals. per minute under a head of 1,203 feet, are installed at both the plants. Each pump is direct connected to two 150 h-p. motors using 2,300 volts, the motors being on top of the pumps.At the High Ore plant the power cable of 400,000 c. m. is placed in a nearby shaft, the cable at present being hung from the surface to the 2,200 level. From this cable feeders of 300,000 c. m. are laid in connecting crosscuts to the pumping station at the High Ore shaft.The Leonard motors use 440 volts. The practice of building the pumps with the motors on top requires stations with high roofs, but permits the operation of the pumps if they should be submerged by an unusual flow of water."

Jan 1, 1913

By Charles H. Fulton

IT is assumed that the word "college" for the present purpose signifies technical school or technical department of a college or university. About ten or fifteen years ago, and more recently in some instances the contact between the technical school and the industry, as represented by the operating companies, was very limited. The school made no effort to place its graduates in the industry and the graduate's first position was obtained by his own or his friends' efforts; the friend often was a professor. The industries, or the operating companies, seemingly had little interest in the training of the technical graduates they employed or in seeking to discover their personal characteristics and fitness for the work. In the public mind there was little relation between technical training and industry. Such training was in the field of education; industry was in the field of business; and the interrelationship was not a matter of common knowledge or concern.

Jan 1, 1929

By J. R. Thoenen

The Bureau of Mines has used various sizes of core barrels above 2 in. and below 10 in. in diameter to core manganese, potash, coal, brown iron ore and bauxite. The paper describes in some detail the methods and types of equipment used to obtain maximum sampling accuracy. Introduction On December 11, 1946, R. D. Longyear, in his capacity as Chairman of the Subcommittee on Exploration Drilling, wrote the author requesting him to prepare a paper presenting the collective ideas of engineers in the Bureau of Mines on the design, standardization and application of core barrels using diamonds or other hard cutting media for drilling holes larger than two inches and less than ten inches in diameter. In subsequent correspondence it was indicated that similar papers covering the experience of other government agencies would be solicited and all such papers received would be combined in a symposium on the subject for discussion at the March 1947 meeting of the Mining Methods Committee AIME. In soliciting such information from other Bureau engineers, it developed that most Bureau experience had been confined to standard core size, two inches or less in diameter, and that larger sizes had been used only for special purposes. It is hoped the data contained herein will be of help to other operators in solving problems encountered in the field. Acknowledgments This paper was made possible by the request of Lowell B. Moon, Chief, Mining Division, Bureau of Mines, to all Division engineers to send to the author any data they had on the subject. Engineers of the Mining Division contributing were: M. H. Kline, Chief, Raleigh Branch. Paul T. Allsman, Chief, Salt Lake City Branch. J. H. Hedges, Chief, Tucson Branch. C. H. Johnson, Chief, Rolla Branch. A. M. Evans, Mining Engineer, College Park Branch. Wing Agnew, Engineer in charge, Mount Weather, Virginia. Andrew Brown, Mining Engineer, Tus-caloosa Branch. In addition Albert L. Toenges, Supervising Engineer, Bituminous Coal Mining Section, Pittsburgh, contributed his experience in coring coal beds. The author's experience in the use of cores within the limits stated has been confined to the brown iron-ore work described by Brown and coring bauxite and clay in Arkansas. Design and Standardization of Core Barrels Bureau engineers are primarily interested in obtaining core that will best represent

Jan 1, 1949

By J. R. Thoenen

The Bureau of Mines has used various sizes of core barrels above 2 in. and below 10 in. in diameter to core manganese, potash, coal, brown iron ore and bauxite. The paper describes in some detail the methods and types of equipment used to obtain maximum sampling accuracy. Introduction On December 11, 1946, R. D. Longyear, in his capacity as Chairman of the Subcommittee on Exploration Drilling, wrote the author requesting him to prepare a paper presenting the collective ideas of engineers in the Bureau of Mines on the design, standardization and application of core barrels using diamonds or other hard cutting media for drilling holes larger than two inches and less than ten inches in diameter. In subsequent correspondence it was indicated that similar papers covering the experience of other government agencies would be solicited and all such papers received would be combined in a symposium on the subject for discussion at the March 1947 meeting of the Mining Methods Committee AIME. In soliciting such information from other Bureau engineers, it developed that most Bureau experience had been confined to standard core size, two inches or less in diameter, and that larger sizes had been used only for special purposes. It is hoped the data contained herein will be of help to other operators in solving problems encountered in the field. Acknowledgments This paper was made possible by the request of Lowell B. Moon, Chief, Mining Division, Bureau of Mines, to all Division engineers to send to the author any data they had on the subject. Engineers of the Mining Division contributing were: M. H. Kline, Chief, Raleigh Branch. Paul T. Allsman, Chief, Salt Lake City Branch. J. H. Hedges, Chief, Tucson Branch. C. H. Johnson, Chief, Rolla Branch. A. M. Evans, Mining Engineer, College Park Branch. Wing Agnew, Engineer in charge, Mount Weather, Virginia. Andrew Brown, Mining Engineer, Tus-caloosa Branch. In addition Albert L. Toenges, Supervising Engineer, Bituminous Coal Mining Section, Pittsburgh, contributed his experience in coring coal beds. The author's experience in the use of cores within the limits stated has been confined to the brown iron-ore work described by Brown and coring bauxite and clay in Arkansas. Design and Standardization of Core Barrels Bureau engineers are primarily interested in obtaining core that will best represent

Jan 1, 1949

By J. L. Swedlow, M. L. Williams

Two standard techniques for assessing fracture initiatlon in sheet specimens involve measurements of 1) the applied load of fracture which, via linear fuacture mechanics, is used to find the fracture tough/less SC (or SIC), and 2) the velative displacement of fracture of the opposite free faces of the crack (COD). In the past, the quantitative association between these two parameters has not been determined in detail, owing to the mathematical difficulties of computing. the stress and strain fields in the combined elasto-plastic flow near the crack. Using a numerical technique Irecently developed and applied to a 7075- TO' aluminum plane stress specimern, the two parameters noted have been determined and associated quantitatirely. CONSIDERABLE effort has been expended in selecting a rigorous yet practical manner for predicting fracture. The usual point of departure is the modified Griffith criterion in which the mechanism of energy dissipation is reflected in Sc (or SIC), the parameter of "fracture toughness". Sc. differs from the surface energy used by Griffith in perfectly brittle fracture in that it includes the effect of plastic flow in the vicinity of the crack tip. Because plastic flow alters the stresses and displacements predicted from the usual linear theory of fracture mechanics, and because analysis of the nonlinear stress-strain field has presented great obstacles: only estimates of several pertinent quantities have heretofore been available. Nevertheless, two parameters have often been measured experimentally althougll usually just at the point of fracture. These are the energy release rate, or fracture toughness 9, (or I,), and the crack-opening displacement (COD). Such observations have been used in connection with frarture criteria and have been most helpful in design, although their application requires care with respect to changes in geometrical configuration from that upon which the criteria were based 1,2 Recently, however, a reasonably accurate and comprehensive method for analyzing the elasto-plastic flow has been devised and applied to plane stress specimens having arbitrary octahedral stress-strain curves.3 It thus becomes feasible to compute, albeit numerically, both the fracture toughness and crack opening as functions of the applied tensile loading on a typical specimen geometry. As a result, it is now possible to associate these two parameters quantitatively, and thereby to associate data obtained by one method with data pertaining to the other. ELASTIC ANALYSIS For the case of linear elasticity, it is relatively easy to deduce the connection between various measures of crack deformation. Using, for example, the singularity analysis, it is found that the leading term of the Airy stress function x f°r symmetrically applied loadings on an isotropic medium is

Jan 1, 1968

By J. L. Byers

THE metals of the platinum group, ruthenium, rhodium, palladium, osmium, iridium and platinum, have certain characteristic effects on the structure and appearance of the cupellation bead. These effects are dependent not only on the particular member of the group present, but also on its concentration. The extent and quality of these effects, however, have not received investigation worthy of their importance. Bannister and Patching investigated the qualitative effects of some of these metals in 1913. This paper deals with a possible rapid qualitative and quantitative delineation of the effects exerted on the cupellation bead by the various metals in the platinum group. More particularly, the paper correlates quantitatively the presence of such metals with their characteristic structural and surface effects. Inasmuch as the various members of the group are more frequently associated with gold than with silver, the gold button will receive the greater consideration. The past two decades have seen a much greater interest manifested in this particular group of metals, because of the increased industrial demand for them. There has been a constantly growing need for assays that will not only express the silver and gold values but also indicate the presence of the other metals. If these indications could be used as quantitative criteria, their value would be greatly increased, because the methods of chemical analysis for the elements of the platinum group are lengthy, involved and unreliable except when the analysis is made by an expert and experienced rare-metal analyst. The materials for the X-ray diffraction examination of the different beads were prepared by filing and screening to -200 mesh, and were then rayed in a General Electric X-ray diffraction unit. The filed samples were treated magnetically in order to eliminate any possible steel particles. Sodium chloride and C.P. gold and silver were used as standard comparators.2 (See Table 1.)

Jan 1, 1932

By S. K. Asunmaa, W. D. English, N. A. Tiner, W. A. Cannon

This paper discusses the reaction of metal surfaces with fluorine. Fluorination reactions result in the formation of metal fluoride films which are "passive" toward further reaction of the metal with fluorine. These films are very adherent, and do not easily detach from the substrate metal by mechanical flexing or thermal shock. Exposure of passive films to a humid atmosphere produces hydrated metal fluorides which cause secondary fluorination reactions upon reexpo-sure of the metal surface to fluorine. The surface films formed range from 10 to 30A in thickness and they pow at the expense of surface oxide films. The apparent film formation is completed rapidly in 15 to 30 min on stainless steel and nickel surfaces. On copper and on Monel surfaces, the film at first grows rapidly, then increases slowly over an extended period of time. Passive films are formed at all fluorine pressures in the range from 0.1 to 1.4 atm at room temperature. ALL metals react when exposed to fluorine. These reactions generally produce surface films which consist of metal fluorides. The rate of reaction is largely determined by the extent to which these films are protective. Although there is an extensive literature concerning reactions of oxygen with metals, there are very few investigations reported concerning fluorine-metal reactions. Brown, Crabtree, and ~uncan' investigated the kinetics of the reaction of gaseous fluorine with copper metal which had been freshly reduced in hydrogen. The reaction rate was independent of pressure over the range from 6 to 60 torr. A logarithmic rate law was obeyed in the temperature range from 25" to 300" ~. There was some deviation at higher temperatures which could have been the onset of a parabolic law. The calculated film thicknesses ranged from about two molecular layers, 10A, for 5 hr exposure at room temperature to thirty-five molecular layers for 5 hr exposure at 200" . The authors concluded that no single mechanism could explain all the observations. O7Donnell and spatkowski2 studied the reaction of fluorine with copper at 450°C at pressures from lo to 133 torr. The reaction was found to be pressure -dependent and followed a logarithmic rate law. It was not entirely diffusion-controlled, and fluorine was thought to be the migrating species in the reaction. Miscellaneous metal-fluorine reactions were investigated by Haendler et ~1.~ Reaction products were identified but no rate data were determined. Air Prod- ucts and Chemicals, Inc., have conducted an investigation of reactions between fluorine and various metal powders at room temperature and 85° C. Fluoride film thickness as a function of time of exposure was reported on the assumption that the reaction takes place between fluorine and metal to form the normal metal fluoride. Surface areas of the powders were only estimated so the relative film thicknesses may not be exact. The data showed reaction rates which were generally logarithmic in character, the rate of film growth virtually ceasing after a few hours exposure time for some alloy powders. The effect of moisture on fluoride films was also investigated by measuring additional reaction with fluorine after exposure of passivated powders to atmosperic moisture. The fluorination of iron was studied by 0'~onnell~ at temperatures from 225" to 525" ~ and at pressures ranging from 20 to 200 torr. In all ranges, the reaction followed a logarithmic rate law and was dependent on the square root of the gas pressure. The author concluded that fluorine gas passes through pores in the film. As the film grows, the blocking of pores leads to a rapid decrease in reaction rate; hence a logarithmic rate law is observed. Jarry, Fischer, and Gunther' investigated the mechanism of the reaction of fluorine with nickel at about 600" to 700°C. On the basis of the metallographic examination of fluoride scales growing on the nickel and from separate radioautographic data, it was claimed that fluorine is the migrating species in the reaction. This is in sharp contrast to the growth of oxide films on nickel where it has been shown that nickel ions migrate through the scale to the gas-solid interface to react with oxygen. Few investigations have been reported of the reaction of fluorine with metal oxides. Such investigations should be of great significance for a better understanding of passivation in view of the ubiquitous oxide films on technical alloys. Haendler et al.3 studied the reaction of fluorine with oxides of copper, tin, titanium, zirconium, and vanadium. Copper (I) oxide reacted as follows in the temperature range 150" to 300"~: temperature above 300" ~ was required for the CuO to react to form additional copper fluoride. Ritter and smith7 also investigated the reaction of fluorine with copper (11) oxide. An oxide powder comprised of spherical particles with a fairly high surface area was reacted with fluorine, starting at room temperature and increasing to 100° C over a period of 3 or 4 hr. The initial reaction was slow until the fluoride film thickness reached about to or 15R at which time the reaction rate accelerated, then decreased again. Most of the kinetic data was obtained during this final phase of reaction. The authors conclude that the film grows slowly at first until the stresses developed in the distorted lattice are sufficient to rupture the initial

Jan 1, 1969

By AIME AIME

WILLIS McGERALD PEIRCE-"Jerry" to his host of friends, and on that account a hit of a puzzle to those who have known him only as "W. 14."-a native of Buffalo, educated at Penn State College, Illinois: and Yale universities, has bee11 associated throughout all of his professional career with the New Jersey Zinc Company. Jerry has served successively as investigator, section chief, and division chief in the research department of the company and has just been promoted to chief of research.

Jan 1, 1937

By J. E. Flinn, S. A. Duran

The steady-state creep behavior of poly crystalline cad mi inn was studied over a temperature range of (1.56 to 0.94 Tm. Two distinct mechanisms were found to occur over this temperature range. They were described by: where and represerqt the minimum strain rates corresponding to the low- and high-temperature regions, respectirely. The two regions of constant acti11ation energy were connected by a transition region where the strain rate was controlled by both mechanisms acting in parallel. At temperatures below a transition temperature of about 0.7 Tm the agreement between the activation energy value for creep and that for self-diffiision suggests a rate-controlling mechanism of dislocation climb. For cadwzium, steady-state creep at temperatures above 0. 7 Tm appears to be controlled by another mechanism, perhaps involving the behavior of dislocation jogs. FRENKEL et al.1 studied the high-temperature creep of polycrystalline cadmium and reported an activation energy of 21 kcal per mole for the 0.5 Tm < T < 0.8 Tm range. Based on observations of creep rate at only two temperatures, a value of 22.1 kcal per mole was determined by Medbury. These two investigations were for the purpose of showing agreement between the activation energy for creep and that for self-diffusion, reported3 as 18.2 and 19.1 kcal per mole, respectively, for diffusion parallel and perpendicular to the hexagonal axis. Gilman4 investigated prismatic glide in single crystals of cadmium over a higher-temperature range of 0.72 to 0.93 Tm, and found an activation energy of 29 kcal per mole. He also reported5 an activation energy higher than that of self-diffusion for prismatic glide in zinc single crystals deformed at temperatures near the melting point. This value was in good agreement with those found for an equivalent temperature range by Flinn and Munson6 and by Tegart and sherby7 for polycrystalline zinc. These two independent studies also disclosed at lower temperatures another value of activation energy near that for self-diffusion. It would be expected from the creep results on zinc and single-crystal cadmium that creep studies on polycrystalline cadmium, extended to temperatures near the melting point, might yield an activation-energy value higher than the 22 kcal per mole value found in earlier studies. The purpose of this paper is to report the steady-creep behavior of polycrystalline cadmium over a temperature range of approximately 0.5 to 0.9 Tm EXPERIMENTAL METHOD The cadmium used in this study was obtained in the form of as-cast rods, 0.5 in. diam, through the courtesy of the Bunker Hill Mining Co. The material was of 99.995 pct purity, as determined by spectro-chemical analysis. The creep specimens, which were 0.250 in. diam by 0.400 in. long and annealed at 300°C for 45 min to produce a stable average grain diameter 0.25 mm, were tested in compression using an apparatus similar to that described by Sherby.8 The specimen temperature was controlled to within ±0.5°C with the help of appropriate constant-temperature baths. The applied stress was maintained within 1.0 pct of the desired value by the additions of lead shot at fixed strain increments. No barreling was observed over the strains encountered during testing. Isothermal creep tests9 were used in the study with only a few differential temperature tests10 run for comparison purposes. Steady-state creep data were obtained over a temperature range of 60 to 287°C (0.56 to 0.94 Tm) at five stress levels ranging from 28.1 to 140.6 kg per sq cm. RESULTS The minimum or steady-state creep rate may be described by an equation of the following form:" where i is the minimum strain rate, S is the structure factor, F is a stress function, Qc is the energy of activation, T is the absolute temperature, and R is the gas constant. The minimum strain rates obtained in this study for cadmium were recorded on a semilogarithm plot as a function of the reciprocal absolute temperatures for the various stress levels, as shown in Fig. 1. This figure shows a characteristic transitional behavior" with a parallel interaction of two mechanisms. It is obvious that the activation energies corresponding to the individual processes are insensitive to stress because the curves are parallel. The discrete activation-energies values for the low- and high-temperature regions for the various stress levels are reported in Table I, and were determined by the least-mean-square method. For the low-temperature region, an activation energy of 20.7 ± 0.6 kcal per mole was obtained, and for the

Jan 1, 1967

By H. E. Hostetter

GROSSMANN&apos;S method1 for calculating the hardenability of steel from the composition and grain size has gained wide acceptance, and when properly used, has been well proved in practical application, both for estimating the hardenability of known compositions and for selecting compositions to meet known hardenability requirements. The Grossmann method uses as the criterion of hardenability the "ideal critical diameter," DI, which is the size round that will just harden to a structure of 50 per cent martensite at the center when given the theoretically fastest quench, or "ideal quench." The DI can be related to actual quenching practice if the severity of quench is known; or the DI can be correlated with hardenability as determined by the Jominy end-quench method.2 The effect on hardenability of each element present in a steel can be represented by a multiplying factor, the value of which depends on the amount of the element present and the degree of effectiveness of the particular element. (The value of the factor for a given carbon content varies with the grain size.) When the factors for all elements present in a steel have been determined from charts, they are multiplied, and the resultant product is the D, of the steel. The validity of Grossmann&apos;s scheme of multiplying factors has been confirmed in a number of other investigations.3 -6 It can be appreciated that a certain desired level of hardenability can be obtained by adding chromium, molybdenum, nickel and vanadium to a base composition containing carbon, manganese, silicon and the usual impurities. Many of the ranges of hardenability used commercially can be obtained by any of the foregoing alloying elements used singly in the base composition. The same hardenability levels also can be obtained through use of any of a great number of multiple element combinations of these alloying elements. In this report a method will be presented for determining what one combination is the most efficient (based on hardenability and cost of added alloy) for a given level of hardenability. It should not be assumed from the emphasis given to hardenability, that hardenability is the only criterion for the selection of an alloy composition. Such properties as the hot-working characteristics, machinability, carburizing characteristics, amount of distortion during quenching and the retention of austenite may be considerations of importance in many applications. However, hardenability is one of the most important properties of an alloy steel and one that must be considered in almost all cases involving heat-treatment by quenching. Therefore, a method for determining the lowest-cost alloy combination should be of considerable value. DETERMINATION OF MOST EFFICIENT COMBINATIONS For comparing the alloying elements on standards of cost and hardenability, it

Jan 1, 1945