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By I. Cornet

With the greatly expanding use of magnesium during the war, it appeared necessary to the War Metallurgy Committee that the notch sensitivity of magnesium alloy extrusions be further investigated and the influence of various factors upon notch sensitivity be noted. Accordingly, the National Defense Research Committee of the Office of Scientific Research and Development placed a research contract with the University of California, supervised by the War Metallurgy Committee. The work discussed herein was done under "Restricted" Project NRC-21, reported in Dec. 1943~; it has been released for publica-tion by the O.S.R.D. Scope of the Investigation The notch sensitivity of various magnesium alloy extrusions was determined under axial tension, and also under several conditions of nonaxial tension. Hardness, grain size and other metallographic features were observed; stress-strain data were obtained, and the chemical compositions of the alloys were determined, in order to correlate these quantities with thc notch sensitivity. Notch sensitivity under axial tensile load was determined for a few specimens which had been cold worked to various degrees by tensile prestraining. Magnesium alloy extrusions studied included Dowmetal 0, X, J, and A(. For comparison, extrusions of aluminum alloy 24s-T, cast bars of aluminum alloy 122-T2, and cast bars of magnesium alloy C were also tested. The specified chemical composition of these alloys is given in Table I. All bars tested were within specification limits of composition. Investigation of thc tensile notch sensitivity of various magnesium alloy extrusions, under conditions of axial and eccentric load, showed little or no correlation with stress-strain or other conventional data. Since the many uncontrolled variables present might mask significant relationships, one alloy was selected for intensive study. Magnesium 0 alloy extrusions were subjected to experimental heat treatments, and the ,Changing hardness, tensile strength, microstructure, and notch sensitivity observed. Experimental Techniques and Procedures Tensile Testing Bars used for axial loading were machined with % in.- and with 34-in. minimum diam1 and included specimens with 60" V notches (Fig I and 2). Each V-notched specimen was roughed out carefully and then finished with a honed tool. These Y-notched bars were sampled frequently, sectioned, polished, and examined at 500 X magnification to control

Jan 1, 1949

By Henry Howe

W. E. RUDER, Schenectady, N. Y.-In 1913 I presented a paper before this society on Grain Growth, and at that time it seemed to me that the only explanation for grain growth was that of critical strain. I do not think I published the photographs at the time, but I made some experiments on the effect of stretching sheets of metal. This allowed for fairly accurate determinations of the amount of cold deformation, At the time I worked-with silicon steel because one could see the change in grain growth with the naked eye. I stretched about 10-samples from 0.5 per cent. to 10 per cent., and, after heating to 1,050° C., I found that the maximum grain growth occurred at about 2 ½ per cent. cold deformation. This I designated "the critical strain" for maximum grain growth. About a year ago I talked with Prof. Jeffries, who explained to me his ideas of grain growth. It occurred to me that it would be a very easy thing to check the strain hypothesis against the strain and temperature hypothesis, if we took a certain number of these strips, strained exactly alike and heated to different temperatures; in that case the maximum grain growth ought to appear at a different percentage of deformation for each temperature. These experiments showed that there was, as Mr. Jeffries shows in his present paper, a decrease in germinative temperature with increased cold deformation. The samples were stretched from ½ to 8 per cent. and heated for 10 hr. in hydrogen. Samples were introduced into a furnace previously heated to temperature. A maximum grain growth was obtained at 5 per cent. deformation, when heated to 750° C.; at 2 ½ per cent. when heated to 800' C.; at 1 1/4 per cent., if heated at 950°C.; and at 5/8 per cent.. when heated at 1,100° C. This shows very clearly that the germinative temperature decreases with the increase in cold deformation. The growth was very much more marked, however, at the high temperature, i.e., the grain grew more rapidly and attained a much larger size than at lower temperature. In considering the photographs (Fig. A) those along the lateral edges should be ignored because.

Jan 4, 1917

By D. L. Wood, J. H. Westbrook

The tensile behaviors of the CsCl structure compound AgMg are extensively documented in terms of strain, strain rate, temperature, composition, and metallurgical processing treatment. The observations lend themselves to presentation in terns of three regimes of deformation behavior; 1) low temperatures where deformation is primarily by slip; 2) intermediate temperatures where the deformation mode is also slip but with the detailed behavior dominated by dislocation interactions with solute atoms; 3) high temperatures where defomation is primarily by diffusion controlled processes. Of all the material groups of potential interest as high-temperature structural materials, the inter-metallics have been the least studied, particularly with respect to their mechanical behavior. Moreover, the application and processing of intermetallics for uses which exploit their often unique physical properties have been impeded by a lack of understanding of their mechanical properties. Previous work in this area* has been largely *For a recent review, see Westbrook.' exploratory, aimed on the one hand at the direct empirical development of materials of engineering utility and ,on the other at identification of the important parameters affecting the mechanical behavior of inter metallics. As a consequence, there has not been available, heretofore—for any inter-metallic—data, sufficient in extent or precision to provide an adequate phenomenological description of the effects of metallurgical variables on deformation behavior. Such documentation is prerequisite to intelligent application or processing design and is also necessary for testing present and future theoretical analyses of mechanical behavior. It was therefore an objective of the present investigation to document the deformation behavior of a simple ordered intermetallic over as wide a range as possible of all the usual metallurgical variables. The compound AgMg was chosen as the subject of this investigation because it met all of a group of desired criteria, namely: 1) congruent but moderate melting point; 2) simple crystal structure; 3) ordered structure persisting to the melting point; 4) broad solubilities for the component elements. The first and last criteria were expected to aid in the preparation of homogeneous single-phase specimens: the second and third to help simplify the

Jan 1, 1962

By I. Cornet

INTRODUCTION WITH the greatly expanding use of magnesium during the war, it appeared necessary to the War Metallurgy Committee that the notch sensitivity of magnesium alloy extrusions be further investigated and the influence of various factors upon notch sensitivity be noted. Accordingly, the National Defense Research Committee of the Office of Scientific Research and Development placed a research contract with the University of California, supervised by the War Metallurgy Committee. The work discussed herein was done under "Restricted" Project NRC-21, reported in Dec. 1943 1; it has been released for publication by the O.S.R.D. SCOPE OF THE INVESTIGATION The notch sensitivity of various magnesium alloy extrusions was determined under axial tension, and also under several conditions of nonaxial tension. Hardness, grain size and other metallographic features were observed; stress-strain data were obtained, and the chemical compositions of the alloys were determined, in order to correlate these quantities with the notch sensitivity. Notch sensitivity under axial tensile load was determined for a few specimens which had been cold worked to various degrees by tensile prestraining. Magnesium alloy extrusions studied included Dowmetal 0, X, J, and M. For comparison, extrusions of aluminum alloy 24S-T, cast bars of aluminum alloy I22-T2, and cast bars of magnesium alloy C were also tested, The specified chemical composition of these alloys is given in Table I. All bars tested were within specification limits of composition. Investigation of the tensile notch sensitivity of various magnesium alloy extrusions, under conditions of axial and eccentric load, showed little or no correlation with stress-strain or other conventional data. Since the many uncontrolled variables present might mask significant relationships, one alloy was selected for intensive study. Magnesium 0 alloy extrusions were subjected to experimental heat treatments, and the changing hardness, tensile strength, microstructure, and notch sensitivity observed. EXPERIMENTAL TECHNIQUES AND PROCEDURES Tensile Testing Bars used for axial loading were machined with 3/8 in.- and with 1/4-in. minimum diam, and included specimens with 6o° V notches (Fig I and 2). Each V-notched specimen was roughed out carefully and then finished with a honed tool. These V-notched bars were sampled frequently, sectioned, polished, and examined at 500 X magnification to control

Jan 1, 1948

By R. E. H. Pomeroy

THE statistical data given in this paper are taken from the actual performance of the No. 2 reverberatory furnace of the Nevada Consolidated Copper Co., Me Gill, Nev., for a period of four months, from April to July, 1914. The principal furnace dimensions are: Length, 132 ft. ½ in. at the skim-line level; average width, 18 ft., 10 in. at the skim-line level. The roof is 7 ft. above the skim-line level at the firing end. The average area in the uptake flue is 36 sq. ft., and the area above the skim line under the vulcatory arch is 24.3 sq. ft. Fig. 1 shows a diagrammatic plan and sectional elevation of this furnace. The furnace is equipped with two 400-b.h.p. Stirling waste-heat boilers set in parallel. California crude petroleum is used for fuel and has a specific gravity of 16.5° B., flashing in open test at 199° F. The oil is heated to about 200° F. in a steam heater before going to the burners, requiring about 9 b.h.p. per furnace day to heat it from the line temperature to the burning temperature. Measurement is made by oil meter, checked daily by reservoir readings. The oil is fed by gravity (34 lb. static pressure) to seven low-pressure blast burners of the Steptoe type (Fig. 2). The blast for these burners is supplied at about 40-oz. pressure by a motor-driven Connersville blower of 42 cu. ft. capacity per revolution. The air supplied by the blower through the burners for atomizing the oil amounts to about 10 per cent. of the theoretical air necessary for complete combustion of the oil. The remainder of the necessary air enters the furnace through the burner openings in the firing wall. No checker holes are provided, and the charge holes in the roof are equipped with slide gates and "dog houses? to minimize air leakages. The combustion of the fuel, as shown by gas analysis at the front of the furnace, is practically complete, the carbon monoxide in the gases being less than 0.5 per cent.

Jan 2, 1915

State of California, Division of Mines, Ferry bldg., San Francisco, Calif. Walter W. Bradley, State Mineralogist. A list of publications available will be sent upon request. Bulletin 77 is a list of publications complete from 1880 to 1917 and contains synopses It is sent free. Bulletin 105, California mineral production and directory of mineral producers for 1930, brings the complete list up to date, sent free on request The Division of Mines issues principally (1) A series of Reports, (2) Bulletins, (3) Preliminary Reports, and (4) maps. The Reports were first issued biennially, later annually, and for the past few years they have taken the form of quarterly reports. The yearly subscription price for the quarterly reports is $1, payable in advance Reports and separate chapters available are Report 2, First Biennial (1892), $1, 14 (1913-1914), Chapter on mines and mineral resources of Colusa, Glenn, Lake, Mann, Napa, Solano, Sonoma, and Yolo counties, 50 cents, 15 (1915?1916), Mines and mineral resources of Butte, Lassen, Modoc, Sutter and Tehama counties, 50 cents, and Mines and mineral resources of Monterey, San Benito, San Luis Obispo, Santa Barbara and Ventura counties, 65 cents, 16 (1917-1918), Nevada County, 75 cents, Plumas County, 50 cents, Sierra County, 50 cents; 17 (1920), Mining in California during 1920, $1 75, 18 (1922), Mining m California, chapters for Aug , Sept , Oct , Dec , free, 19 (1923), Mining in California, chapters for Jan , Feb , Mar, Sept , free, 20 (1924), Quarterly chapters on mining in California (except July, out of print), 25 cents, 21 (1925), Quarterly chapters containing county reports- Jan (Sarcramento, Monterey, Orange) 25 cents, April (Calaveras, Merced, San Joaquin, Stanislaus, Ventura), 25 cents, July (Del Norte, Humboldt, San Diego) 25 cents, Oct (Siskiyou, San Luis Obispo, Santa Barbara), 25 cents; 22 (1926), Quarterly county reports: Jan. (Santa Cruz, Trinity), 25 cents, April (Shasta, San Benito, Imperial), 25 cents, July (Mann, Sonoma) and Copper in California, 25 cents, Oct (El Dorado, Inyo) Minarets District, 25 cents, 23 (1927), Quarterly county reports- Jan (Contra Costa), 25 cents, April (Aniador, Solano) Bibliography of clay

Jan 1, 1933

By F. Keller, E. H. Dix

The desirable high strength and hardness of the heat-treated strong aluminum alloys result from two distinct structural changes: (1) the formation of a solid, solution by heating at the required temperature for a sufficient period, and the substantial retention of this solid solution by rapidly quenching; (2) precipitation of particles of constituent and coalescence to a critical size to produce maximum strength and hardness. In alloys of the duralumin type, that is, alloys containing both copper and magnesium silicide precipitation takes place at normal atmospheric temperature, whereas in alloys containing copper without magnesium silicide or magnesium silicide without copper, maximum properties are obtained only after an accelerated aging treatment consisting of heating for 15 to 20 hr. at temperatures of about 150" C. The mechanical properties of these alloys subsequent to quenching but prior to aging are ideal for forming operations. Unfortunately, however, the alloys of the duralumin type age very rapidly during the first 24 hr. and aging is substantially complete after four days. For severe forming, such as the heading of rivets, it is desirable that this be accomplished within ½ hr. or at the most 2 hr. after quenching. Alloys containing magnesium silicide without copper also age at normal temperatures but the aging is less rapid and the material can be satisfactorily worked within several weeks after quenching. Some slight aging of alloys containing copper alone also takes place at room temperature but it is unimportant from the standpoint of workability. Any method of retarding the aging at room temperature of the duralumin type of alloys would be of considerable advantage in that the period during which the material could be worked successfully would be lengthened. For instance, in aircraft plants it is customary to supply the workmen with small lots of rivets that should be used within ½ hr . after heat treatment. Such procedure has the obvious disadvantage of being uneconomical, and furthermore there is always the possibility that the workmen would use the rivets after the time limit had expired, or the supply being depleted might use some that had not been heat-

Jan 1, 1931

By Edward Steidle

It has been said that "the command of nature has been put into the hands of man before he knows how to command himself," and what we see about us gives particular emphasis to this observation. If this condition be granted, the vaunted boast of school and college, of the institution that had the training of this generation, and of its fathers, and of its grandfathers, the boast that education is a "preparation for life," stands exposed as a hollow claim, or as a ghastly, cynical conception of life, or else education has fallen far short of its intentions. It has been evident for some time that education was not meeting the fullest expectations of society. In recent years there has been a deal of speculation indulged in by both laity and faculty in regard to American education and American civilization, and some few and sporadic changes have been effected. Today, however, there is no longer time for mere hypothetical considerations; we are faced with certain definite facts and confronted with obvious conditions that will not wait for fine-spun theories. If educators do not put their house in order, someone else will do it for them. The trends in mineral industries education must be in harmony with this general realignment that is today visible on the educational horizon, and only as these trends are in conformity with this movement can they be called sound. Two questions, then, confront mineral industries educators: (1) What are the trends in mineral industries education, and (2) how do these trends correlate with the major educational movements of the day? Scope or Mineral Industries Education Before launching into these particulars, it might be well to define the scope of mineral industries education and to consider its present position. Mineral industries education embraces three main types of work: 1. Earth Sciences and Geography.—Geology, mineralogy, geography— courses basic to all mineral industries and to the humanities. 2. Mineral Engineering.—Mining, petroleum and natural gas—dealing with mineral producing industries. Application of earth sciences and all types of engineering to exploitation of natural mineral resources.

Jan 1, 1934

Magazine Advertising $ 62,564 83 Magazine Sales 3,591 44 Total 66,156 27 Dues, Arrears 7,032 88 Dues, Current 96,839 74 Dues, New Members 6,525 00 Dues, in advance 1,907 02 Initiation Fees 7,584 00 Sale of Transactions 3,909 03 Sale of Binding .. 7,845 05 Sale of Special Editions 338 20 Sale of Year Book 76 20 Sale of Pamphlets 1,189 06 Sale of Authors' Reprints 867 54 Miscellaneous Receipts 62 93 Interest on Bank Balances 1,712 89 Interest on General Reserve Fund 337 50 Interest on Life Membership Fund 557 84 Interest on James Douglas Library Fund 5,491 89 Total Receipts $208,433 04

Jan 1, 1923

YEAR OF r ELECTION 1913 FRANK DAWSON ADAMS Montreal, Canada 1921. WILLIAM CUTHBERT BLACKETT Sacriston, Durham, England 1923 GELASIO CAETANI Washington, D C 1920. HENRY STUROIS DRINKER Menon Station, Pa 1921. FERDINAND FOCH . Pans, France 1922. FEDERICO GIOLITTI Torino, Italy 1888. HATON DE LA GOUPILLIERE Paris, France. 1906. SIR ROBERT A. HADFIELD London, England 1921. FRANK WILLIAM HARBORD London, England 1921. HEINRICH O HOFMAN Cambridge, Mass 1917. HERBERT HOOVER .. Washington, D C. 1915 JAMES FURMAN KEMP New York, N. Y 1905. HENRI LECHATELIER Paris, France 1921. C. McDERMID London, England 1913 EZEQUIEL ORDONEZ Mexico City, Mexico 1909 ALEXANDRE POURCEL Paris, France 1911 ROBERT H RICHARDS Cambridge, Mass 1907. CHARLES D WALCOTT Washington, D C

Jan 1, 1923

YEAR OF ELECTION 1913 FRANK DAWSON ADAMS Montreal, Canada 1921 WILLIAM CUTHBERT BLACKETT Sacnston, Durham, England 1920 HENRY STURGIS DRINKER Merlon Station, Pa 1921 FERDINAND FOCH Paris, France 1922 FEDERICO GIOLITTI Torino, Ttaly 1888 HATON DE LA GOUPILLIERE Paris, France 1906 SIR ROBERT A HADFIELD London, England 1921 FRANK WILLIAM HARBORD London, England 1921 HEINRICH O HOFMAN Cambridge, Mass 1917 HERBERT HOOVER Stanford University, Cal 1919 ROBERT W HUNT Chicago, ILL 1915 JAMES' FURMAN KEMP New York, N Y 1905 HENRI LECHATELIER Paris, France 1921 C MCDERMID London, England 1913 EZEQUIEL ORDONEZ Mexico City, Mexico 1909 ALEXANDRE POURCEL Paris, France 1911 ROBERT H RICHARDS Boston, Mass 1906 JOHN E STEAD Middlesbrough, England 1907 CHARLES D WALCOTT Washington, D C

Jan 1, 1923

[YEAR OF ELECTION 1913. FRANK DAWSON ADAMS Montreal, Canada. 1921. WILLIAM CUTHBERT BLACKETT Sacriston, Durham, England. 1923. GELASIO CAETANI Washington, D. C. 1920. HENRY STURGIS DRINKER Merion Station, Pa. 1921. .FERDINAND FOCH Paris, France. 1922. FEDERICO GIOLITTI Torino, Italy. 1888. HATON DE LA GOUPILLIERE Paris, France. 1906. SIR ROBERT A. HADFIELD London, England. 1921. FRANK WILLIAM HARBORD London, England. 1921. HEINRICH O. HOFMAN Cambridge, Mass. 1917. HERBERT HOOVER Washington, D. C. 1915. JAMES FURMAN KEMP New York, N. Y. 1905. HENRI LECHATELIER Paris, France. 1921. C. MCDERMID London, England. 1913. EZEQUIEL ORDONEZ Mexico City, Mexico. 1909. ALEXANDRE POURCEL Paris, France. 1911. ROBERT H. RICHARDS Cambridge, Mass. 1907. CHARLES D. WALCOTT Washington, D. C.] [ ]

Jan 1, 1925

YEAR OF ELECTION 1913 FRANK DAWSON ADAMS Montreal, Canada 1921. WILLIAM CUTHBERT BLACKETT Sacriston, Durham, England 1923 GELASIO CAETANI Washington, D C 1920. HENRY STURGIS DRINKER Merion Station, Pa 1921 FERDINAND FOCH Paris, France 1922. FEDERICO GIOLITTI . Torino, Italy 1888. HATON DE LA GOUPILLIERE Paris, France 1906 SIR ROBERT A. HADFIELD London, England 1921. FRANK WILLIAM HARBORD London, England 1921. HEINRICH O HOFMAN Cambridge, Mass 1917 HERBERT HOOVER . Washington, D C 1915 JAMES FURMAN KEMP New York, N. Y 1905 HENRI LECHATELIER Paris, France 1921. C. McDERMID London, England 1913 EZEQUIEL ORDONEZ Mexico City, Mexico 1909 ALEXANDRE POURCEL Paris, France 1911 ROBERT H RICHARDS Cambridge, Mass 1907 CHARLES D WALCOTT Washington, D C

Jan 1, 1923

By W. R. Webster

SINCE the delivery of our paper on Some Comparative Properties of Tough-pitch and Phosphorized Copper,1 a new brand known as "oxygen-free high-conductivity copper" (brand OFHC) has become available to consumers. It was thought desirable to make a comparison between the properties of this material and those of the materials covered by our original paper and its discussion. FIG. 1.-CHARACTERISTIC ANNEALING CURVES OF VARIOUS TYPES OF COPPER. Preliminary tests had indicated some notable differences. A billet of oxygen-free high-conductivity copper was taken from regular production. A chemical analysis of the particular billet was not made, but the producer of the material has given as typical the analysis shown in Table 1. The

Jan 1, 1933

LARGEST known fluorspar deposits in the world are mined in southern Illinois (Hardin County), and northwestern Kentucky (Crittenden County). Colorado, New Mexico, Montana, and Utah are the principal western sources in the U. S. Rosiclare Fluorspar District Hardin County, Illinois The Rosiclare area is located in the southern part of Hardin County on the Ohio River where the Illinois Central Rd. branch line terminates and provides transportation. Fluorspar has been mined commercially in this area since 1870. Aluminum Co. of America and Rosiclare Lead & Fluorspar Co. are the two major producers in this area. Ozark-Mahoning Co. operates a concentrating plant in Rosiclare but the bulk of its ore is mined near the town of Cave-in-Rock.

Jan 1, 1958

By R. G. Knickerbocker

A most important research and development item on ferroalloys in the calendar year of 1949 was the increase of interest in the recovery of secondary manganese. Owing to the importance of manganese to the nation's welfare, it is Ferroalloys most necessary that all possible avenues of research and development on the recovery of this vital metal be investigated. The principal objective of this new development is to recover manganese from steel furnace slags. Steel furnace slags contain a total of approximately 772,000 tons of metallic manganese which is compared to the 680,000 tons of metallic manganese as ferromanganese that is estimated to be used by the steel industry, annually, at this time.

Jan 6, 1950

By Robert C. Berggren

THE hot-milling process for reconditioning rock-drill bits is not new. It has been employed by a few mines for years and in the past decade it has been widely adopted, as its advantages have become better known. Because of the extensive commercial development in England and Canada of machines to operate on this principle, general acceptance has been largely in the British possessions and until recently has been chiefly in the field of conventional steel. In the past two years there has been a definite trend toward hot-milling of detachable bits in Canada, [t] but only in the past year has any considerable attempt been made to build special machines for this type of work. Generally a machine designed for conventional steel has been used and special holders employed to manipulate the bit. As early as 1934 at least one operator in the United States had adapted hot-milling to conventional steel with a substantial saving in resharpening costs.1 Several other operators have taken it up but there has been no widespread adoption of the method in this country by users of conventional steel. This may be partly explained by the fact that until recently no American manufacturer produced this equipment and operators have been obliged to build their own hot-millers or import them. Several years ago a few machines were built in Seattle, Washington, and operated in some mines in the northwest, but, for reasons not generally known, the effort was abandoned. THE PROCESS Hot-milling performs the function of re-dressing the bit at a forging temperature of about 1650°F., by the removal of metal from the flutes with a milling cutter, followed by a similar cut from the bit gauge. Conventional bits are thus treated following the usual forging operation in a sharpener, and usually in the same heat.

Jan 1, 1940

By Duk-Won Park

The PSU/MVS program, one of the computer programs for ventilation network analysis most recently developed at The Pennsylvania State University, was applied to the analysis of modifications to an existing ventilation system for a coal mine located in southern West Virginia. The program is well designed and has diversified capabilities which allow the users to make decisions on the optimum size and number of fans, the location and number of airshafts, and the optimum operational procedures. The mine had 10 working faces, from which the average production rate was about 5900 tons of clean coal per day. Two vane-axial mine fans were used in parallel at a shaft, and both of them operated simultaneously. One additional shaft was in the final construction stage and it would be used in four months to alleviate the load for the existing fans and distribute intake air more evenly. The overall ventilation surveys, including the altimeter pressure survey and the air quantity survey, were carried out in the mine entries, shafts, slopes, and gob areas. Computations were made using the above-mentioned computer program on the present condition and after one additional fan was placed in operation at the new shaft. Also, recommendations were made on the air route and fan blade settings for the most economical and efficient ventilation system. Further studies were carried out to decide the proper period when the third air shaft would be required according to the long-term mining plan. Additional branches were added for the next 4 years of the production plan, and the ventilation conditions were tested at the end of each year. Numerous combinations of blade settings and modifications of air routes were tested. It was recommended that the third air shaft be added at the end of the third year so as not to experience fan stall.

Jan 1, 1982

By W. G. Pfann

The problem of forming points on wires that were from 0.002 in. to 0.010 in. in diam arose in the recent appearance of silicon and germanium point contact rectifiers as elements in microwave radar.' In these devices a pointed tungsten wire makes a delicate contact with the surface of a semiconductor. Because the quality of such rectifiers is largely determined by the nature of this contact, considerable attention has been given to the formation of the metal point. Reproducibility of contour and freedom from burrs and even microscopic irregularities are considered essential. The operations involved must be simple and rapid enough for mass production. Previously tungsten wircs had been provided with conical points by a grinding method which involved rotating a wire about its axis and causing it to bear at an oblique angle against a spinning abrasive disc. This was later complemented with an electrolytic polishing treatment which removed irregularities from the ground point and also rounded it off at the tip—a desirable feature. Finally, these operations were supplanted by the electrolytic pointing method described here. Mechanism of Point Formation The wires to be pointed are partially immersed in an electrolyte in a vertical position whereupon they are provided with smooth rounded points entirely by electrochemical action. The process is independent of the depths to which the wires penetrate the electrolyte because the points are formed at the surface level. It may be used to point a single wire or many of them simultaneously and is applicable to wires of different diameters within a limited range. Solution of the immersed portion of a tungsten wire is accomplished by making it the positive electrode in an electrolytic cell, as shown in Fig I. While the wire is maintained at constant voltage the current through the cell falls continuously, principally because of the decrease in wetted area which results from solution of the tungsten. This increase in resistance occurs in a reproducible manner and is used as a control in the process. As thc immersed portion of the wire dissolves, it remains cylindrical in shape except for the short section which is wetted by the meniscus. Here the rate of solution is lower and decreases as the top of the meniscus is approached. The result is the formation of a tapered section inside the meniscus. As solution continues, the cylindrical section either dissolves entirely or drops off just before complete solution, leaving only the taper which is now sharply pointed. Further action causes this point to become rounded and then quite blunt, until finally the end of the wire is almost plane. Fig 2 shows the stages in this development. Contour PF is most representative of those used in point contact rectifiers. Thus a variety of point

Jan 1, 1949

REPUBLIC STEEL CORP. and Armco Steel Corp. have joined in a $160,000,000 project for the production of iron ore from Taconite in the Lake Superior mining region. The two companies announced acquisition in equal shares of 100 pct ownership of the stock of Reserve Mining Co., which controls a vast deposit of magnetic Taconite iron ore on the eastern end of the Mesabi range in Minnesota. Through Reserve Mining the two companies will build a plant for manufacturing high grade ore from Taconite near Beaver Bay on the north shore of Lake Superior. The first announcement calls for about a $60,000,000 plant which will be built as soon as plans are completed and will have an annual capacity of about 2,500,000 tons of iron ore pellets. Longer range development plans call for future expansion of the plant to provide an annual capacity of 10,000,000 tons. This will amount to an additional investment of

Jan 10, 1950